Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications [1st ed.] 978-3-030-03504-4, 978-3-030-03505-1

Table of contents :
Front Matter ....Pages i-xv
General Data on Carbon Allotropes (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 1-8
Conventional Carbon Allotropes (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 9-33
Classic Carbon Nanostructures (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 35-109
Less-Common Carbon Nanostructures (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 111-302
Other Existing Carbon Forms (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 303-373
Predicted Carbon Forms (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 375-411
Coordination/Organometallic Compounds and Composites of Carbon Allotropes (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 413-575
Solubilization and Dispersion of Carbon Allotropes and Their Metal-Complex Composites (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 577-638
Carbon Allotropes in the Environment and Their Toxicity (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 639-652
Applications and Cost-Benefit Data (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 653-664
Student Zone: Overview, Training, Practices, and Exercises (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 665-766
Conclusions and Further Outlook (Boris Ildusovich Kharisov, Oxana Vasilievna Kharissova)....Pages 767-768
Back Matter ....Pages 769-790

Citation preview

Boris Ildusovich Kharisov · Oxana Vasilievna Kharissova

Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications

Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications

Boris Ildusovich Kharisov • Oxana Vasilievna Kharissova

Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications

Boris Ildusovich Kharisov Universidad Autónoma de Nuevo León Monterrey, Mexico

Oxana Vasilievna Kharissova Universidad Autónoma de Nuevo León Monterrey, Mexico

ISBN 978-3-030-03504-4 ISBN 978-3-030-03505-1 https://doi.org/10.1007/978-3-030-03505-1

(eBook)

Library of Congress Control Number: 2018960923 © Springer Nature Switzerland AG 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Carbon allotropes, especially their nanostructural forms (in particular, graphene and carbon nanotubes), are known to be of extreme importance in chemistry, technology, and nanotechnology. In the present book, we have tried to achieve the most possible complete and, at the same time, concise generalization of this enormous field of carbon allotropes and their metalcomplex chemistry. The material in this book is systematized in accordance with the appearance of carbon allotropes (classic, less-common, or theoretically predicted carbon forms) and size (macro-, micro-, and nano-level). We also respected classic current classifications of carbon forms and nanostructures according to their dimensionality and hybridization of carbon atoms. Currently, despite much reported data on carbon allotropes and their organic functionalization, a lack of generalization of metal-organic functionalizations of carbon allotropes is observed, and corresponding books are practically absent. We paid much attention to the so-called less-common carbon nanostructures, i.e., those described in the range of 1100 original articles. Available metal-complex composites are not known for all carbon allotropes, mainly for graphite, carbon nanotubes, fullerenes, and graphene. Also, because of insufficient generalized information on the solubilization of carbon allotropes, the chapter on the dispersion of several carbon forms (mainly nanocarbons) is added. The main destination of this book is for researchers/investigators in the carbon area and related fields. At the same time, we tried to present the material in the form suitable for a wider audience: students of all levels, professors, engineers, and technologists not only in chemical sciences (especially catalysis, coordination, and organometallic chemistry) but also in those areas where the nanotechnology, as an interdisciplinary science, has connections. In particular, we hope that the contents of this book will be useful for readers working in the bionanotechnology, nano-medicine, and materials chemistry, among many others. The book contains the sections with many practical examples of the preparation and characterization of carbons and their composites (useful for student practical works as a laboratory manual) and chapters on the cost-benefit data (availability and costs), metal complexes as precursors of carbon allotropes, and applications (both current and possible). Finally, the extremely important issue of carbon allotropes and their toxicity is discussed. The authors will be grateful to the readers for their comments and suggestions. Monterrey, Mexico

Boris Ildusovich Kharisov Oxana Vasilievna Kharissova

v

Contents

1

General Data on Carbon Allotropes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 8

2

Conventional Carbon Allotropes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Graphite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Diamond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Amorphous Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . .

9 9 19 23 30

3

Classic Carbon Nanostructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Structure and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Reactivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Fullerenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 C60 and Higher Fullerenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Small Fullerenes C20500
C; piezoelectric devices; high-power transistors; high-temperature integrated circuits), and as optical components (e.g., in protective coatings for infrared optics in harsh environments), among other high-perfomance applications. In whole, diamond area continues to be attractive for researchers (see detailed information in a recent special issue on the synthesis, properties, and applications of diamond crystals [82]).

2.3

Amorphous Carbon

Amorphous carbon, a big class of carbon allotropes, is a free, reactive carbon that does not have any crystalline structure. In a difference of well-defined carbon forms, diamond and graphite, which are crystalline in structure, the amorphous carbon forms – such as carbon black, charcoal, lampblack, coal, and coke – are sometimes called amorphous, but X-ray examination has revealed that these substances do possess a low degree of crystallinity [83]. Some features of amorphous carbon are as follows: – Amorphous carbon materials may be stabilized by terminating dangling π-bonds with hydrogen. – Amorphous carbon is also called diamond-like carbon. – Coal, soot, carbide-derived carbon (see section below), and other impure forms of carbon that are neither graphite nor diamond; use this name (amorphous carbon) in mineralogy. – True amorphous carbon has localized π electrons, on the contrary with the aromatic π bonds in graphite. – High concentration of dangling bonds. – The main method for characterization of amorphous carbon is based on the use of the ratio of sp2 to sp3 hybridized bonds. – The tetrahedral amorphous carbon has majority of sp3 bonds (diamond-like carbon) [84]. Structure and Properties Amorphous carbons (Fig. 2.16) contain a certain degree of disorder (non-crystallinity) in contrast to the crystalline structures of diamond and graphite [85]. The ternary phase diagram of the amorphous carbon–hydrogen system is shown in Fig. 2.17, with each side of the phase diagram representing the percentage of sp2 carbon (sp2 C), sp3 carbon (sp3 C), and hydrogen content, as depicted by the respective vertices [86]. Among recent studies, hydrogen-passivated amorphous carbon nanostructures were studied with semiempirical molecular orbital theory in order to provide an understanding of the factors that affect their electronic properties [87]. It was revealed that the elemental composition and the number of sp3-atoms only influence the electronic structure weakly (Fig. 2.18). Instead, the exact topology of the sp2-network in terms of effective conjugation defines the band gap. Thus, electronic structure of amorphous carbon depends most strongly on the geometry and less so on the atomic hybridization and heteroatom contents. In addition, the doping with heteroatoms can only work if the dopants are incorporated in a systematic manner. Structural information from liquid and amorphous carbon can be taken using other machine-learning models [88]. Also, the surface energy and surface atomic structure of tetrahedral amorphous carbon were calculated by an ab initio method [89]. The surface atoms were found to reconstruct into sp2 sites often bonded in graphitic rings. The even lower surface energy of hydrogenated amorphous carbon (a-C:H) is due to the hydrogenation of all broken surface bonds.

Fig. 2.16 Typical structure of amorphous carbon. Black atoms represent sp3-bonded carbon atoms, whereas grey atoms represent sp2-bonded carbon atoms in a disordered network (Reproduced with permission of the American Physical Society)

Fig. 2.17 Ternary-phase diagram of the amorphous carbon–hydrogen system (Reproduced with permission of the Elsevier Science)

Fig. 2.18 Left: Unit cell of a 2.5 g cm3 amorphous carbon structure. Atoms with sp (blue)- and sp2-hybridization (red) are highlighted as balls connected with sticks. Right: A different C128 unit cell with a planar hexagonal moiety highlighted as sticks (Reproduced with permission of the American Chemical Society)

2.3 Amorphous Carbon

25

Certain attention is paid to the films on the basis of amorphous carbon [90]. Thus, the structures of various types of amorphous carbon films and common characterization techniques were described in a review [91]. In whole, the carbon films can be amorphous and nanocrystalline and have special chemical and physical properties such as high chemical inertness, diamondlike properties, and favorable tribological proprieties. The materials usually consist of graphite and diamond microstructures and thus possess properties that lie between the two. There are several types of carbon films: (a) a-C films, softer carbon films without hydrogen usually formed at low energy or higher temperature; (b) a-C:H films, softer carbon films with hydrogen; (c) ta-C films, tetrahedral amorphous carbon films with high content of sp3 bonding and without hydrogen; (d) ta-C:H films, tetrahedral amorphous carbon hydrogen films with high content of sp3 bonding; (e) nanocrystalline diamond films, carbon films with nanodiamond crystalline structure; (e) nanocrystalline graphite films, carbon films with nano graphite crystal; (f) glassy carbon films, an interesting form of disordered carbon that microscopically consists of a mixture of graphite-like ribbons or micro fibrils; (g) polymeric a-C:H films, softer amorphous carbon films with a high hydrogen content; and (h) high hardness graphite-like carbon films, films possessing graphite-like structure and relatively high hardness, toughness, and wear resistance. Among this variety of films, Cu/Cr co-doped amorphous carbon films (a-C) were designed, demonstrating that compared with pure and Cu/Cr monodoped cases, the residual stress in Cu/Cr co-doped a-C films could be reduced by 93.6% remarkably [92]. It was revealed that the addition of Cu and Cr impurities in amorphous carbon structure resulted in the critical and significant relaxation of distorted CC bond lengths. Figure 2.19 shows the final atomic structures of Cu/Cr co-doped a-C films with different Cu/Cr concentrations using the precalculated cutoff distance to determine the nearest neighbor atoms.

Fig. 2.19 Atomic structures of (a) pure, (bd) Cu doped, (eg) Cr doped, and (hl) Cu/Cr co-doped a-C films, in which the numbers are the tetracoordinated C fractions in each film and red, yellow, and blue colors indicate the C, Cu, and Cr atoms, respectively (Reproduced with permission of the American Chemical Society)

26

2 Conventional Carbon Allotropes

Fig. 2.20 Illustration of the formation of ReS2/C dispersed layers prepared by thermal decomposition of metal-organic precursor (Reproduced with permission of the Elsevier Science)

In addition to metal-doped amorphous carbon films above, up to 6 at.% N-doped (nitrogen concentrations 0.2–1.5 at.%) thin amorphous carbon (α-C) films (20–150 nm) were obtained by plasma-enhanced chemical vapor deposition (PECVD) method from benzene as a precursor in Ar atmosphere [93]. The deposited layers consisted of a mixture of sp2 and sp3 hybridized amorphous carbon (containing predominantly C6H6; CH3-C6H5 and sp3 C aliphatic(-CH2-..-CH2-) species), whose mole fraction could be varied by the DC-plasma voltage in the range 90/10–60/40 at. %. More complex systems, for example, nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films, are also known [94]. Amorphous carbon can be also modified with other inorganic molecules. Thus, highly destacked ReS2 layers were embedded (Fig. 2.20) in amorphous carbon via the thermal decomposition of a tetraoctylammonium perrhenate precursor (Oct4N)ReO4)) at 400
C under sulfidizing atmosphere (15% v/v H2S mixture H2S/H2 gas) [95]. The synthesized compound (ReS2) was found as single layers with a minor proportion of few-layer arrangements, embedded in amorphous carbon. The special arrangement of these ReS2 layers has a potential use as a heterogeneous hydrodesulfurization catalyst due to the high proportion of edge sites. Another inorganic group, attached by amorphous carbon, is SO3H (Fig. 2.21); here the amorphous carbon with these groups behaves as an insoluble Brønsted acid available for various acid-catalyzed reactions [96]. This can be attributed to the specific carbon network of functional groups bonded to carbon sheets. Synthesis Methods Amorphous carbons are usually deposited as films on a substrate, containing a mixture of sp2 and sp3 bonding with little evidence of sp1 bonding being present [97]. As a part of classic high-temperature CVD technique, sputter deposition, and cathodic arc deposition, the preparation methods of amorphous carbon include the use of metal complexes as precursors. Thus, several types of metal–organic frameworks (Fig. 2.22) were exploited as templates/precursors to afford porous carbon materials with various nitrogen dopant forms and contents, degrees of graphitization, porosities, and surface areas [98]. One of them, PCN-224-templated porous carbon material optimized by pyrolysis at 700
C is composed of amorphous carbon coated with well-defined graphene layers, offering a high surface area, hierarchical pores, and high nitrogen content (mainly, pyrrolic nitrogen species). These carbons can be effectively used in catalysis, for instance, for conversion of 4-nitrophenol to 4-aminophenol. Nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms, can be also achieved from the bimetallic MOFs [99], for instance (CoxZn1  x(MeIm)2), prepared due to the crystal compatibility between ZIF-8 (Zn (MeIm)2) and ZIF-67 (Co(MeIm)2). The zinc and cobalt ions coexist in the bimetallic ZIFs and support different functionalities during the carbonization process. The physical and chemical properties of the bimetallic-ZIF-derived carbon can be designed via simply and precisely adjusting the ratio of Co2+/Zn2+ in the bimetallic ZIF precursor. The p-type films of nanostructured amorphous carbon with particle size in the range of 28–34 nm were prepared from natural palm oil precursor for heterojunction solar cell [100]. Solar simulator analysis results showed an open circuit voltage (VOC), current density (JSC), fill factor (FF), and conversion efficiency (η) of Au/a-C/n-Si/Au which were 264.62 mV, 1.50434 mA/cm2, 0.32632, and 0.130154%, respectively. In addition, amorphous helical carbon nanofibers were synthesized using copper nanocatalysts and an acetylene gas source at 468 K at atmospheric pressure [101]. The nanofibers were found to be a mixture of solid polymers and a small amount of carbon. The nanofibers growed mainly via acetylene coupling to solid

2.3 Amorphous Carbon

27

Fig. 2.21 Schematic structures of proposed SO3Hbearing CCSA (cellulosederived carbon solid acid) materials carbonized at different temperatures: (a) CCSA carbonized below 723 K and (b) CCSA carbonized above 823 K (Reproduced with permission of the American Chemical Society)

polymers on copper nanocrystal surfaces. Recently, a method was offered [102] in which the carbonization reaction can proceed (Fig. 2.23) at a lower annealing temperature (under 150
C) owing to the highly reactive nature of copper acetylide, thus avoiding crystallization processes and enabling the production of genuinely amorphous carbon materials with high surface area. Curiously, despite that copper acetylide is a well-known explosive compound, when the size of it crystals is reduced to the nanoscale, its explosive nature is lost, owing to a much lower thermal conductance that inhibits explosive chain reactions. Transformations of Amorphous Carbon to Other Allotropes Conversion of amorphous carbon can be done resulting diamond (in the form of nanodiamond (size range 100 nm)) by irradiating amorphous carbon films with nanosecond lasers at room temperature in air at atmospheric pressure, without any need for any catalysts and hydrogen to stabilize sp3 diamond bonding [103]. It was found that microdiamonds grow out of highly undercooled state of carbon, with nanodiamond acting as seed crystals. Amorphous state of carbon, laser parameters, and film substrate characteristics determines the temperature distribution and undercooling and plays a critical role in nucleation and growth of diamond. Also, crystallization of amorphous carbon to good-quality graphene by thermal annealing (Fig. 2.24) can be catalyzed by metals [104]. The thickness of the precipitated graphene is directly controlled by the thickness of the initial amorphous carbon layer, in contrast with CVD processes, where the carbon source is virtually unlimited, and controlling the number of graphene layers depends on the tight control over a number of deposition parameters. In addition, the amorphous carbon powders can be fully turned into crystalline graphite in 5 min my microwave heating (Fig. 2.25) [105]. Fullerenes also could be a final product starting from amorphous carbon clusters as precursors [106]. The fullerene formation occurs in two stages. First, fast transformation of the initial amorphous structure into a hollow sp2 shell with a few chains attached occurs with a considerable

28

2 Conventional Carbon Allotropes

Fig. 2.22 Schematic illustration for the synthesis of nitrogen-doped porous carbon materials by the pyrolysis of different MOFs (Reproduced with permission of Wiley)

decrease of the potential energy and the number of atoms belonging to chains and to the amorphous domain. Then insertion of the remaining carbon chains into the sp2 network takes place at the same time as the fullerene shell formation. All practical forms of hydrogenated carbon (e.g., smoke, chimney soot, mined coal such as bitumen and anthracite) contain large amounts of polycyclic aromatic hydrocarbon tars and are therefore almost certainly carcinogenic [107]. In addition to the applications above for amorphous carbons, the diamond-like carbon films have widespread applications as protective coatings in areas, such as magnetic storage disks, optical windows, and microelectromechanical devices (MEMs).

2.3 Amorphous Carbon

29

Fig. 2.23 Illustration of the method used to prepare amorphous carbon under 150∘C. Copper acetylide precursor was prepared via the reaction of CuCl and C2H2 under NH3 water. Then the precursor was separated by suction filtration and annealed at 150∘C. Finally, sulfuric acid treatment was carried out for eliminating copper (Reproduced with permission of Hindawi)

Fig. 2.24 The process schematics for the metalcatalyzed crystallization of a-C to graphene by thermal annealing (Reproduced with permission of the American Institute of Physics)

30

2 Conventional Carbon Allotropes

Fig. 2.25 Illustration of microwave graphitization. (a) Experimental procedure. Microwave was irradiated to the activated carbon powders after impregnating nickel chloride. (b) Detail description of microwave graphitization with metal catalyst. Nickel chloride was first decomposed to form nickel catalyst particles, and then amorphous carbon was transformed to graphite with the help of metal catalyst (Reproduced with permission of the Royal Society of Chemistry)

References 1. H. Lipson, A.R. Stokes, A new structure of carbon. Nature 149(3777), 328 (1942) 2. A.Q. Baig, M. Imran, W. Khalid, M. Naeem, Molecular description of carbon graphite and crystal cubic carbon structures. Can. J. Chem. 95(6), 674–686 (2017) 3. P. Delhaes, Graphite and Precursors. CRC Press. 312 pp. 2001

References

31

4. C. Barton. Did Graphite in the Chernobyl Reactor Burn? (2011), http://www.theenergycollective.com/charlesbarton/55702/did-graphitechernobyl-reactor-burn 5. https://www.texaspowerfulsmart.com/diamond-films/graphite-and-related-materials-rdk.html. Accessed 16 Jan 2018 6. T. Enoki, M. Suzuki, Graphite Intercalation Compounds and Applications (Oxford University Press, New York, 2003), p. 456 7. R.V. Lapshin, Automatic lateral calibration of tunneling microscope scanners. Rev. Sci. Instrum. 69(9), 3268–3276 (1998) 8. http://www.galleries.com/Graphite. Accessed 15 Jan 2018 9. https://sciencing.com/similarities-between-graphite-diamonds-8478868.html. Accessed 16 Jan 2018 10. http://www.newworldencyclopedia.org/entry/Graphite. Accessed 16 Jan 2018 11. P.P. Magampa, N. Manyala, W.W. Focke, Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder. J. Nucl. Mater. 436(1–3), 76–83 (2013) 12. G.-S. Wang, X.-J. Zhang, Y.-Z. Wei, et al., Polymer composites with enhanced wave absorption properties based on modified graphite and polyvinylidene fluoride. J. Mater. Chem. A 1, 7031–7036 (2013) 13. W. Wei, S. Hu, R. Zhang, C. Xu, F. Zhang, Q. Liu, Enhanced electrical properties of graphite/ABS composites prepared via supercritical CO2 processing. Polym. Bull. 74, 4279 (2017). https://doi.org/10.1007/s00289-017-1956-8 14. P.K.A. Ramanujam, Conducting polymer–graphite binary and hybrid composites: Structure, properties, and applications, in Hybrid Polymer Composite Materials: Applications, (Woodhead Publishing (Elsevier), Kidlington, Oxford, UK, 2017) 15. K. Kornaus, A. Gubernat, D. Zientara, P. Rutkowski, L. Stobierski, Mechanical and thermal properties of tungsten carbide – graphite nanoparticles nanocomposites. Pol. J. Chem. Technol. 18(2), 84–88 (2016) 16. I.M. Karzov, O.N. Shornikova, S.V. Filimonov, A.P. Malakho, V.V. Avdeev, Cu-expanded graphite composite material preparation and thermal properties. Eurasian Chem. Techn. J. 19(3), 273–277 (2017) 17. T. Hutsch, T. Schubert, T. Weissgaerber, B. Kieback, Graphite metal composites with tailored physical properties. Emerg. Mater. Res. 1(2), 107–114 (2012) 18. S.J. Turneaure, S.M. Sharma, T.J. Volz, J.M. Winey, Y.M. Gupta, Transformation of shock-compressed graphite to hexagonal diamond in nanoseconds. Sci. Adv. 3(10), eaao3561 (2017) 19. A. Alofi, G.P. Srivastava, Evolution of thermal properties from graphene to graphite. Appl. Phys. Lett. 104, 031903 (2014) 20. L. Dong, Z. Chen, S. Lin, K. Wang, C. Ma, H. Lu, Reactivity-controlled preparation of ultralarge graphene oxide by chemical expansion of graphite. Chem. Mater. 29(2), 564–572 (2017) 21. K.C. Knirsch, J.M. Englert, C. Dotzer, F. Hauke, A. Hirsch, Screening of the chemical reactivity of three different graphite sources using the formation of reductively alkylated graphene as a model reaction. Chem. Commun. 49, 10811–10813 (2013) 22. M. Mulet-Gas, L. Abella, M.R. Cerón, et al., Transformation of doped graphite into cluster-encapsulated fullerene cages. Nat. Commun. 8, 1222 (2017) 23. http://www.substech.com/dokuwiki/doku.php?id¼applications_of_graphite. Accessed 16 Jan 2018 24. K. Lee, Fundamental graphite techniques (Lydia Inglett Publishing, 2010), Hilton Head Island, SC, USA, p. 176 25. http://www.schunk-carbontechnology.com/. Accessed 15 Jan 2018 26. http://www.olmec.co.uk/graphite_and_carbon_use_in_industrial_applications.htm. Accessed 16 Jan 2018, 27. E.I. Zhmurikov, I.A. Bubnenkov, V.V. Dremov, S.I. Samarin, A.S. Pokrovsky, D.V. Harkov. Graphite in science and nuclear technique. 2013, arXiv:1307.1869 [cond-mat.mtrl-sci] 28. H.C. Schniepp, J.L. Li, M.J. McAllister, H. Sai, M. Herrera-Alonso, D.H. Adamson, R.K. Prud'Homme, R. Car, D.A. Saville, I.A. Aksay, Functionalized single graphene sheets derived from splitting graphite oxide. J. Phys. Chem. B 110(17), 8535–8539 (2006) 29. D.W. Lee, V.L. De Los Santos, J.W. Seo, L. Leon Felix, D.A. Bustamante, J.M. Cole, C.H.W. Barne, The structure of graphite oxide: investigation of its surface chemical groups. J. Phys. Chem. B 114(17), 5723–5728 (2010) 30. J.W. Suk, R.D. Piner, J. An, R.S. Ruoff, Mechanical properties of monolayer graphene oxide. ACS Nano 4, 6557–6564 (2010) 31. L. Sun, B. Fugetsu. Massive production of graphene oxide from expanded graphite. arXiv:1301.3253 [cond-mat.mtrl-sci], 2013 32. M. del Prado, Lavín López, J.L. Valverde Palomino, M.L. Sánchez Silva, A. Romero Izquierdo, Chapter 5. Optimization of the Synthesis Procedures of Graphene and Graphite Oxide, in Recent Advances in Graphene Research, ed. by P. Kumar Nayak (Ed), (INTECH, 2016), London, UK (2016) 33. (a) W.S. Hummers Jr., R.E. Offeman, Preparation of graphitic oxide. J. Am. Chem. Soc. 80, 1339–1339 (1958); (b) K.-H. Liao, A. Mittal, S. Bose, C. Leighton, K.A. Khoyan, C.W. Macosko, Aqueous only route toward graphene from graphite oxide. ACS Nano. 5, 1253–1258 (2011) 34. O. Jankovský, M. Nováček, J. Luxa, et al., Concentration of nitric acid strongly influences chemical composition of graphite oxide. Chem. Eur. J. 23(26), 6432–6440 (2017) 35. L. Tang, X. Li, R. Ji, K.S. Teng, G. Tai, J. Ye, C. Wei, S.P. Lau, Bottom-up synthesis of large-scale graphene oxide nanosheets. J. Mater. Chem. 22(12), 5676 (2012) 36. C. Paiva Pousa Soares, R. de Lacerda Baptista, D. Vargas Cesar, Solvothermal reduction of graphite oxide using alcohols. Mat. Res. 21 (1) (2018). https://doi.org/10.1590/1980-5373-mr-2017-0726 37. S. Pei, H.M. Cheng, The reduction of graphene oxide. Carbon 50, 3210–3228 (2012) 38. W. Gao, L.B. Alemany, L. Ci, P.M. Ajayan, New insights into the structure and reduction of graphite oxide. Nat. Chem. 1, 403–408 (2009) 39. S. Drewniak, R. Muzyka, A. Stolarczyk, T. Pustelny, M. Kotyczka-Morańska, M. Setkiewicz, Studies of reduced graphene oxide and graphite oxide in the aspect of their possible application in gas sensors. Sensors 16(1), 103 (2016) 40. A.G. Bannov, J. Prášek, O. Jašek, L. Zajíˇcková, Investigation of pristine graphite oxide as room-temperature chemiresistive ammonia gas sensing material. Sensors 17, 320 (2017) 41. R. Jamatia, A. Gupta, B. Dam, M. Saha, A. Kumar Pal, Graphite oxide: a metal free highly efficient carbocatalyst for the synthesis of 1,5-benzodiazepines under room temperature and solvent free heating conditions. Green Chem. 19, 1576–1585 (2017)

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42. V. Parra-Elizondo, B. Escobar-Morales, E. Morales, D. Pacheco-Catalán, Effect of carbonaceous support between graphite oxide and reduced graphene oxide with anchored Co3O4 microspheres as electrode-active materials in a solid-state electrochemical capacitor. J. Solid State Electrochem. 21(4), 975–985 (2017) 43. Z. Zeng, L. Yang, Q. Zeng, H. Lou, et al., Synthesis of quenchable amorphous diamond. Nat. Commun. 8, 322 (2017) 44. Y. Lin, L. Zhang, H.-k. Mao, et al., Amorphous diamond: a high-pressure superhard carbon allotrope. Phys. Rev. Lett. 107, 175504 (2011) 45. Y. Dilek, J. Yang, Ophiolites, diamonds, and ultrahigh-pressure minerals: new discoveries and concepts on upper mantle petrogenesis. Lithosphere 10(1), 3–13 (2018) 46. P. Cartigny, M. Palot, E. Thomassot, J.W. Harris, Diamond formation: a stable isotope perspective. Annu. Rev. Earth Planet. Sci. 42(1), 699–732 (2014) 47. F. Nabiei, J. Badro, T. Dennenwaldt, et al., A large planetary body inferred from diamond inclusions in a ureilite meteorite. Nat. Commun. 9, 1327 (2018) 48. P.V. Zinin, A.V. Nozhkina, R.I. Romanov, et al., Synthesis, characterization of elastic and electrical properties of diamond-like BCx nanophases synthesized under high and low pressures. MRS Adv. 3(1–2), 45–52 (2018). (Nanomaterials) 49. S. Fromentin. Resistivity of Carbon, Diamond. The Physics Factbook. Ed. Glenn Elert (2004). Accessed 7 June 2018 50. A. Shatskiy, D. Yamazaki, G. Morard, T. Cooray, T. Matsuzaki, Y. Higo, K. Funakoshi, H. Sumiya, E. Ito, T. Katsura, Boron-doped diamond heater and its application to large-volume, high-pressure, and high-temperature experiments. Rev. Sci. Instrum. 80(2), 023907 (2009) 51. W. Grochala, Diamond: electronic ground state of carbon at temperatures approaching 0 K. Angew. Chem. Int. Ed. 53(14), 3680–3683 (2014) 52. Y. Palyanov, I. Kupriyanov, Y. Borzdov, D. Nechaev, Y. Bataleva, HPHT diamond crystallization in the Mg-Si-C system: effect of Mg/Si composition. Crystals 7(5), 119 (2017) 53. B.I. Pepekin, Synthesis of diamond: a review. Russ. J. Phys. Chem. B 4(5), 769–772 (2010) 54. F.P. Bundy, R.C. DeVries, Diamond: high-pressure synthesis, in Reference Module in Materials Science and Materials Engineering, (Elsevier Science, In, 2016) 55. C. Chen, Q. Chen, Recent development in diamond synthesis. Int. J. Mod. Phys. B 22(4), 309–326 (2008) 56. J. Narayana, A. Bhaumik, Research update: direct conversion of amorphous carbón into diamond at ambient pressures and temperatures in air. APL Mater. 3, 100702 (2015) 57. S. Botti, M. Amsler, J.A. Flores-Livas, et al., Carbon structures and defect planes in diamond at high pressure. Phys. Rev. B 88, 014102 (2013) 58. Z. Lou, Q. Chen, Y. Zhang, W. Wang, Y. Qian, Diamond formation by reduction of carbon dioxide at low temperatures. J. Am. Chem. Soc. 125, 9302–9303 (2003) 59. P. Ji, J. Yu, T. Huang, et al., Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition. Plasma Sci. Technol. 20, 025505 (2018). (6pp) 60. M. Chen, J. Shu, X. Xie, D. Tan, H.-k. Mao, Natural diamond formation by self-redox of ferromagnesian carbonate. Proc. Natl. Acad. Sci. 115 (11), 2676–2680 (2018). 201720619 61. Y. Li, C. Wang, N. Chen, et al., Significant improvement of multi-seed method of diamond synthesis by adjusting the lateral cooling water temperature. Cryst. Eng. Comm. 19, 6681–6685 (2017) 62. M. Schwander, K. Partes, A review of diamond synthesis by CVD processes. Diam. Relat. Mater. 20(9), 1287–1301 (2011) 63. H. Kato, H. Yamada, S. Ohmagari, et al., Synthesis and characterization of diamond capsules for direct-drive inertial confinement fusion. Diam. Relat. Mater. 86, 15–19 (2018) 64. G.S. RistićI, M.S. TrticaI, Š.S. Miljanić, Diamond synthesis by lasers: recent progress. Quím. Nova 35(7), 1417–1422 (2012) 65. F.C.B. Maia, R.E. Samad, J. Bettini, R.O. Freitas, N.D. Vieira Junior, N.M. Souza-Neto, Synthesis of diamond-like phase from graphite by ultrafast laser driven dynamical compression. Sci. Rep 5, 11812 (2015) 66. Q. Liang, C.-s. Yan, J. Lai, Y.-f. Meng, et al., Large Area Single-Crystal Diamond Synthesis by 915 MHz Microwave Plasma-Assisted Chemical Vapor Deposition. Cryst. Growth Des. 14(7), 3234–3238 (2014) 67. C. Luo, X. Qi, C. Pan, W. Yang, Diamond synthesis from carbon nanofibers at low temperature and low pressure. Sci. Rep. 5, 13879 (2015) 68. L.F. Dobrzhinetskaya, H.W. Green, Diamond synthesis from graphite in the presence of water and SiO2: implications for diamond formation in quartzites from Kazakhstan. Int. Geol. Rev. 49(5), 389–400 (2007) 69. N. Chertkova, S. Yamashita, E. Ito, A. Shimojuku, High-pressure synthesis and application of a 13C diamond pressure sensor for experiments in a hydrothermal diamond anvil cell. Mineral. Mag. 78(7), 1677–1685 (2014) 70. D. Das, R.N. Singh, A review of nucleation, growth and low temperature synthesis of diamond thin films. Int. Mater. Rev. Published by Maney for the Institute and ASM International 52(1), 29–64 (2007) 71. D. Varshney, G. Morell, B.R. Weiner, V. Makarov. Low-energy, hydrogen-free method of diamond synthesis. U.S. Patent 8608850B1, 2009 72. N.A. Bulienkov, E.A. Zheligovskaya, O.P. Chernogorova, E.I. Drozdova, I.N. Ushakova, E.A. Ekimov, Nonequilibrium diamond growth during the high-temperature high-pressure synthesis of a composite material made of a mixture of cobalt and fullerene powders. Russ. Metall. (Metally) 2018(1), 35–41 (2018) 73. Y.N. Palyanov, I.N. Kupriyanov, Y.M. Borzdov, Y.V. Bataleva, High-pressure synthesis and characterization of diamond from an Mg–Si–C system. Cryst. Eng. Comm. 17, 7323–7331 (2015) 74. J.E. Shigley, Identifying Lab-Grown Diamonds (2016) https://www.gia.edu/identifying-lab-grown-diamonds. Accessed 7 June 2018 75. I.V. Klepikov, A.V. Koliadin, E.A. Vasilev, Analysis of type IIb synthetic diamond using FTIR spectrometry. IOP Conf. Ser. Mater. Sci. Eng. 286, 012035 (2017) 76. S. Eaton-Magaña, J.E. Post, P.J. Heaney, J. Freitas, et al., Using phosphorescence as a fingerprint for the Hope and other blue diamonds. Geology 36(1), 83–86 (2008) 77. R.B. Simon, J. Anaya, F. Faili, et al., Effect of grain size of polycrystalline diamond on its heat spreading properties. Appl. Phys. Express 9, 061302 (2016) 78. E. Bernardi, R. Nelz, S. Sonusen, E. Neu, Nanoscale sensing using point defects in single-crystal diamond: recent progress on nitrogen vacancy center-based sensors. Crystals 7(5), 124 (2017)

References

33

79. V. Nadolinny, A. Komarovskikh, Y. Palyanov, Incorporation of large impurity atoms into the diamond crystal lattice: EPR of split-vacancy defects in diamond. Crystals 7(8), 237 (2017) 80. V.L. Skvortsova, M.I. Samoylovich, A.F. Belyanin, Studies of phase composition of contact sites of diamond crystals and the surrounding rocks. Dokl. Earth Sci. 465(Part 1), 1187–1190 (2015) 81. Y.M. Belousov, Evolution in time of radiation defects induced by negative pions and muons in crystals with a diamond structure. Crystals 7(6), 174 (2017) 82. Special Issue “Diamond Crystals”. Y.N. Palyanov (guest editor). Crystals, 2018, 8(2). http://www.mdpi.com/journal/crystals/special_issues/ diamond_crystals 83. https://www.britannica.com/science/carbon-chemical-element#ref112004. Accessed 14 Jan 2018 84. J. Robertson, Diamond-like amorphous carbon. Mater Sci. Eng. R Rep. 37(4–6), 129–281 (2002) 85. D.G. McCulloch, D.R. McKenzie, C.M. Goringe, Ab initio simulations of the structure of amorphous carbon. Phys. Rev. B 61, 2349 (2000) 86. J. Robertson, Diamond-like amorphous carbon. Mater. Sci. Eng. R-Rep. 37, 129 (2002) 87. J.T. Margraf, V. Strauss, D.M. Guldi, T. Clark, The electronic structure of amorphous carbon nanodots. J. Phys. Chem. B 119(24), 7258–7265 (2015) 88. V.L. Deringer, G. Csanyi, D.M. Proserpio, Extracting crystal chemistry from amorphous carbon structures. Chem. Phys. Chem. 18, 873–877 (2017) 89. C.W. Chen, J. Robertson, Surface atomic properties of tetrahedral amorphous carbon. Diamond Relat. Mater. 15, 936–938 (2006) 90. Overview of Amorphous Carbon Films. In: R.J. Yeo, Ultrathin Carbon-Based Overcoats for Extremely High Density Magnetic Recording, Springer Nature Singapore Pte Ltd, Springer Theses, 2017 91. P.K. Chu, L. Li, Characterization of amorphous and nanocrystalline carbon films. Mater. Chem. Phys. 96, 253–277 (2006) 92. X. Li, P. Guo, L. Sun, A. Wang, P. Ke, Ab Initio investigation on Cu/Cr codoped amorphous carbon nanocomposite films with giant residual stress reduction. ACS Appl. Mater. Interfaces 7, 27878–27884 (2015) 93. I. Balchev, K. Tzvetkova, S. Kolev, et al., Synthesis and characterization of thin amorphous carbon films doped with nitrogen on (001) Si substrates. J Phy. Conf. Ser. 764, 012013 (2016) 94. H. Gima, A. Zkria, Y. Katamune, R. Ohtani, S. Koizumi, T. Yoshitake, Chemical bonding structural analysis of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition. Appl. Phys. Express 10(1), 015801 (2017) 95. J.A. Aliaga, G. Alonso-Núñez, T. Zepeda, et al., Synthesis of highly destacked ReS2 layers embedded in amorphous carbon from a metalorganic precursor. J. Non-Cryst. Solids 447, 29–34 (2016) 96. K. Nakajima, M. Hara, Amorphous carbon with SO3H groups as a solid brønsted acid catalyst. ACS Catal. 2(7), 1296–1304 (2012) 97. J. Robertson, Amorphous carbon. Adv. Phys. 35, 317 (1986) 98. G. Huang, L. Yang, X. Ma, J. Jiang, S.H. Yu, H.L. Jiang, Metal–organic framework-templated porous carbon for highly efficient catalysis: the critical role of pyrrolic nitrogen species. Chem. Eur. J. 22, 3470–3477 (2016) 99. J. Tang, R.R. Salunkhe, H. Zhang, et al., Bimetallic metal-organic frameworks for controlled catalytic graphitization of nanoporous carbons. Sci. Rep. 6, 30295, 8 pp (2016) 100. A. Ishak, M. Rusop, Complex and nano-structured amorphous carbon films from hydrocarbon palm oil as A P-type in photovoltaic heterojunction solar cell applications. Int. J. Sci. Technol. Res. 3(6), 109–113 (2014) 101. Y. Qin, X. Jiang, Low-temperature synthesis of amorphous carbon nanocoils via acetylene coupling on copper nanocrystal surfaces at 468 K: a reaction mechanism analysis. J. Phys. Chem. B 109(46), 21749–21754 (2005) 102. K. Judai, N. Iguchi, Y. Hatakeyama, Low-temperature production of genuinely amorphous carbon from highly reactive nanoacetylide precursors. J. Chem. 2016., Article ID 7840687, 1–6 (2016) 103. J. Narayana, A. Bhaumik, Research update: direct conversion of amorphous carbon into diamond at ambient pressures and temperatures in air. Appl. Mater. 3, 100702 (2015) 104. M. Zheng, K. Takei, B. Hsia, et al., Metal-catalyzed crystallization of amorphous carbon to graphene. Appl. Phys. Lett. 96, 063110 (2010) 105. T. Kim, J. Lee, K.-H. Lee, Full graphitization of amorphous carbon by microwave heating. RSC Adv. 6, 24667–24674 (2016) 106. A.S. Sinitsa, I.V. Lebedeva, A.M. Popov, A.A. Knizhnik, Transformation of amorphous carbon clusters to fullerenes. J. Phys. Chem. C 121, 13396–13404 (2017) 107. https://en.wikipedia.org/wiki/Amorphous_carbon. Accessed 14 Jan 2018

Chapter 3

Classic Carbon Nanostructures

The era of carbon-based nanotechnology, as it is well-known, started from 1985 when the fullerene C60 was discovered. The rediscovery of carbon nanotubes and unexpected discovery of graphene gave a powerful impulse to the further development of carbon nanostructures. At present, these nanocarbons, as well as nanodiamonds or nanofibers, can already be considered as “conventional” carbon nanostructures.

3.1

Graphene

Image reproduced with permission of the MDPI (Materials 2017, 10(9), 1066) © Springer Nature Switzerland AG 2019 B. I. Kharisov, O. V. Kharissova, Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications, https://doi.org/10.1007/978-3-030-03505-1_3

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Fig. 3.1 Ideal structure of graphene

Carbon allotropic form, 2D graphene (Fig. 3.1) {nano-graphenes are also known as polycyclic aromatic hydrocarbons (PAHs)}, discovered in 2004, had rapidly become rapidly rising star on the horizon of materials science and condensed matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Graphene represents a conceptually new class of materials that are only one atom thick (it is just one layer of carbon atoms [1], a similar structure to graphite, but is a single isolated sheet of carbon) and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications [2]. Strictly 2D crystals, such as planar graphene, have for a long time been considered as a thermodynamically unstable form with respect to the formation of curved structures such as fullerenes or nanotubes. Geim and Novoselov described that small size ( C28Br4 > C28Cl4 [302]. The small fullerene C28 was supposed to display reaction activity in the process of the dissociative addition of complexing agents. Also, construction of all 352,786 possible addition patterns C24H2m and optimization with the densityfunctional-based tight-binding model are used to deduce that the C24 fullerene has an effective valence of 12 [303]. The optimal structure of C24H12 has an equatorial ring of 12 sp3 sites and is reachable by a pathway involving cumulative addition

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Table 3.1 Parameters of unit cells simulating hybrid nanostructures (C20, C28)@(n,0)BN-NT Parameter Number of atoms in the cell Cell composition Nanotube diameter, nm Fullerene-nanotube wall distance, nm Fullerene-fullerene distance, nm

C20@(9,0)NT 92 C20B36N36 0.709 0.155 0.454

C20@(13,0)NT 124 C20B52N52 0.102 0.311 0.454

C28@(10,0)NT 108 C28B40N40 0.787 0.155 0.206

to low-energy isomers. Additionally, a quantum-chemical simulation of hybrid nanostructures consisting of regular chains of the small fullerenes C20 and C28 encapsulated into the bulk of achiral zigzag single-walled boron-nitrogen nanotubes [(C20, C28)@BN-NT] was carried out [304]. The electronic characteristics of hybrid nanostructures were compared with those of “isolated” fullerenes and nanotubes and (C20, C28) + BN-NT structures (Table 3.1) simulating fullerene adsorption on tube surface as the initial stage of (C20, C28)@BN-NT formation. A simple model of endohedral bonding in small fullerene clusters was proposed [305]. It was based on a meta-atom view of the cluster in which principal and angular momentum quantum numbers are assigned to the cluster eigenstates. The character of the valence electron states near the Fermi level of the cluster determines the nature of bonding to endohedral atoms. This model was found to be valid to explain the relative stability of Sn@C28 (hypothetical structure, not observed experimentally), Zr@C28 (experimentally produced structure), and U@C28 (complex with remarkable stability).

3.3

Carbon Nanotubes9

It is little known [306] that as far back as in 1952, Radushkevich and Lukianovich published clear images (Fig. 3.34) of 50-nmdiameter tubes made of carbon in the Russian Journal of Physical Chemistry [307]. Later results, obtained by Oberlin, Endo, and Koyama [308], clearly showed hollow carbon fibers with nanometer-scaled diameters using a vapor-growth technique. Additionally, the authors showed a TEM image of a nanotube consisting of a single wall of graphene. Later, Dresselhaus [309] referred to this image as a single-walled nanotube. Results of chemical and structural characterization of carbon

9

Image reproduced with permission of Elsevier Science (Modern Electronic Materials, 2016, 2(4), 95–105)

3.3 Carbon Nanotubes

63

Fig. 3.34 First carbon nanotubes, discovered in 1952

nanoparticles produced by a thermocatalytical disproportionation of carbon monoxide were reported in [310]. Since the formal rediscovery of CNTs in 1991 by Iijima [311], a number of device applications, such as full-color displays, field-effect transistors, and molecular computers, have been envisioned [312, 313]. These applications are highly dependent on the electronic properties of the CNTs, which can be tuned by their helicity, diameter, and defects presence. In recent years, novel strategies have been devoted to modify physical properties of the CNTs by surface modification with organic, inorganic, and biological species [314–319]. During the last 25 years, number of reports on carbon nanotubes, this one of the hottest topics in nanotechnology, corresponds to hundreds of thousands. Carbon nanotubes should not be confused with carbon nanofibers (see the section below). Some generalized features of carbon nanotubes are as follows: – Carbon nanotubes are members of the fullerene structural family. They can be single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). Sometimes, double-walled carbon nanotubes (DWCNTs) are described apart, as well as triple-walled carbon nanotubes (TWCNTs) [320]. – DWCNTs can be considered as a special class of nanotubes, since their properties and morphology are similar to those of SWCNTs; however, they are more resistant to chemical treatment. Only the outer wall in DWCNTs is modified by chemical treatment, meanwhile some C¼C double bonds in SWCNTs can be broken forming holes changing properties dramatically. – Increasing number of layers, the CNT form is deviated from an ideal cylindrical more and more. In some cases, the external layer seems as polyhedron. – Carbon nanotubes are unique “1D systems” which can be envisioned as rolled graphene or single sheets of graphite. – The chemical bonding of nanotubes involves entirely sp2-hybrid carbon atoms. This provides outstanding properties of this cylindrical form of carbon. – Two models describe the structures of MWCNTs: (1) Russian Doll model (graphene sheets are arranged in concentric cylinders, e.g., a (0,8) SWCNT within a larger (0,17) SWCNT) and (2) Parchment model (a single graphite sheet is rolled in around itself, resembling a scroll of parchment or a rolled newspaper). – The interlayer distance in MWCNTs is close to the distance between graphene layers in graphite, approximately 0.34 nm, and can slightly vary depending on defects and other several factors [321]. – SWCNT diameter is d ¼ (n2 + m2 + nm)1/2 (0.0783 nm). – On the external layer, such types of defects as pentagons and heptagons are sometimes formed, leading to curved and spiral-type nanotubes. – Individual nanotubes naturally align themselves into “ropes” held together by van der Waals forces, more specifically, π-stacking. – The longest carbon nanotubes grown so far are over 0.5 m (550 mm long) [322].

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Fig. 3.35 [9]-, [12]-, and [18]cycloparaphenylene and its precursors. (Reproduced with permission of the American Chemical Society)

– The shortest carbon nanotube is the cycloparaphenylene (Fig. 3.35, “carbon nanohoop structures”) [323]. – The thinnest carbon nanotube is the armchair (2,2) CNT with a diameter of 0.3 nm [324]. The thinnest freestanding SWCNT is about 0.43 nm in diameter [325]. – The highest density [326] of CNTs was observed 1.6 g cm3 (generally 1.3–1.4 g/cm3). – MWCNT has a tensile strength of 63 gigapascals (9,100,000 psi) [327], for stainless steel 0.38–1.55. – Standard SWCNTs can withstand a pressure up to 25 GPa without permanent deformation. – Young’s modulus for SWCNT is from 1 to 5 TPa, MWCNT (0.2–0.8–0.95), being compared with stainless steel 0.186–0.214. – Carbon nanotubes are either metallic or semiconducting along the tubular axis, in a difference with graphene, a 2D semimetal. The nanotubes (6,4), (9,1), etc. are semiconducting, and all armchair (n ¼ m) nanotubes are metallic (see details below). – Nanotubes with distinct magnitudes (n, m) are “polymers” with different structure, so they can possess distinct electric properties. Since nanotubes are conjugated aromatic systems, three from four valence electrons of each carbon atom form sp2-hybrid orbitals and localized σ-bonds; meanwhile the fourth electron takes part in the formation of delocalized π system like in graphite or benzene. These π electrons are weakly bound with their atoms, so precisely they take part in the charge transfer in the system. High (metallic) conductivity must appear, if the occupied π-states are not separated by an energetic hole from vacant π-states. If the hole is small, the CNT is a semiconductor; if the big one – dielectric. – Individual SWCNT has a r.t. thermal conductivity along its axis of about 3500 Wm1K1, which could be affected by crystallographic defects. – Graphitic substitution of carbon atoms in the CNT wall by nitrogen or boron dopants leads to n-type and p-type behavior, respectively. – Y- and T-junctions in CNTs are possible. – Carbon nanotubes are expected to be very good thermal conductors along the tube but good insulators lateral to the tube axis. Thermal properties are strongly affected by structural defects. – The temperature stability of carbon nanotubes is estimated to be up to 2800  C in vacuum and about 750  C in air. – The contact angles of CNT arrays are over 160 , exhibiting a superhydrophobic property (for graphite is around 90 ). – Nanotubes possess capillary properties, i.e., they can be filled with substances. – CNTs are slightly magnetic due to presence of nanoparticles of Fe, Ni, and other metals, whose compounds (e.g., ferrocene FeCp2 in the spray pyrolysis method of CNT synthesis at 800  C) are used as catalysts for CNT growth. – Decomposition of hydrocarbon molecule takes place on the metal catalyst surface; the formed CNT hangs down from the catalyst particle and captures it in the growth process. The CNT growth is accompanied by change of catalyst particle “spherical–elongated–spherical.” – Carbon nanotubes can be prepared also from EtOH as precursor using iron or cobalt acetates as catalyst precursors. – Horizontally or vertically ordered arrays of CNTs can be obtained on SiO2 from xylenes as carbon source and ferrocene as catalyst. – CNTs can be exposed to finish grinding (sharpening) subsequent evaporation of external layers close to a CNT terminal using electric current. – CNT terminals are usually closed by 5C- or 6C-atom cycles; the last ones are more stable against oxidation. – CNTs can encapsulate other metals inside, for instance, Gd@C60@SWCNT (Gd inside C60, which is inside SWCNT) or single CNT bundles encapsulating Gd@C82 and Er2@C82 [328]. A variety of combinations with inorganic nanomaterials is possible [329]. – In some CNTs with fullerene molecules inside, C60 can move and form vapor phase inside the CNT channel.

3.3 Carbon Nanotubes

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Fig. 3.36 Consecutive micrographs taken 15–30 s apart during in situ annealing of PLV material at 350  C. The sequence shows the mobility of exterior C60 molecules, which appear as circles 0.7 nm in diameter and occupy different positions in each image. A fixed position is indicated with an arrow. Scale bar, 5 nm. (Reproduced with permission of the Elsevier Science)

– Junctions between nanotubes can be frequently observed, when CNTs are synthesized by CVD or arc-discharge techniques. – Other carbon nanotube-containing morphologies include carbon nanobuds, nanotori (see sections below), carbon peapods [330] (fullerene inside a carbon nanotube, Fig. 3.36 [331]; see section below), and graphenated carbon nanotubes [332] (graphitic foliates grown along the sidewalls of MWCNTs or bamboo-like CNTs, Fig. 3.37 [333]).10 – Cup-stacked carbon nanotubes (CSCNTs, Fig. 3.38 [334]) are also known [335]. – CNTs have useful absorption, Raman spectroscopy, and photoluminescence (fluorescence) properties. – Carbon nanotubes can be easily functionalized by covalent and noncovalent modifications, as well as graphene. – Being hydrophobic, SWCNTs and MWCNTs tend to agglomerate hindering their dispersion in solvents. – Upon functionalization, the “solubility” (dispersibility) of CNTs in water and/or organic solvents can considerably vary [336]. The formed dispersions can be stable for several months. – SWCNTs (only) can explode by attempting to take a picture of their sample with flash in oxygen-containing media. Might be, this effect is related with heating oxygen both inside SWCNTs and between them, causing shock wave. When the local temperature inside SWCNT reaches 600–700  C, they instantly burn away. Another explanation is related with burning of the rests of catalyst (ultradisperse metal). – CNTs can be deformed (moved) under action of electric fields or radiation [337, 338]. – CNTs are subjected to capillary effects, for instance, absorbing (pulling in) liquid lead or gallium. Structural studies of carbon nanotubes continue being important due to a variety of applications for these materials. It is known that their geometry (Fig. 3.39) and a major part of their properties depend on diameter and chiral angle (θ) (Fig. 3.40), also known as helicity. These two parameters are completely determined by two Hamada indexes [339] (n, m). There are two types of nanotubes (Fig. 3.41), which can exist in the form of bundles (Fig. 3.42): single-walled nanotubes (SWCNTs) and multiwalled nanotubes (MWCNTs). A carbon nanotube may be viewed as a graphite sheet that is rolled up into a nanometerscaled tubular from (i.e., SWCNT) or with additional graphene tubes that form around the core of a SWCNT (i.e., MWCNT) [340]. Since the graphene sheet can be rolled up with varying degrees of twist along its length, carbon nanotubes can have a variety of chiral structures. Depending on their diameter and the helicity of the arrangement of graphitic rings in the walls, 10

The high surface area 3D framework of the CNTs coupled with the high edge density of graphene is the fundamental advantage of this integrated graphene-CNT structure.

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Fig. 3.37 Scanning electron microscopy (SEM) images of graphenated carbon nanotubes (g-CNTs). (a) Low-density graphene foliates on a CNT. (b) Medium-density graphene foliates on a CNT. (c) High-density graphene foliates on a CNT. Structures were reproducible and observed over several square centimeters after microwave plasma chemical vapor deposition growth. (d) Cross-sectional SEM image showing a typical aligned g-CNT film. (Reproduced with permission of the Materials Research Society)

Fig. 3.38 (a) TEM image of the as-synthesized CSCNTs with short lengths. (b) HRTEM image of the CSCNT wall. The inset in (b) is a schematic of a CSCNT. (Reproduced with permission of the Elsevier Science)

3.3 Carbon Nanotubes

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Fig. 3.39 Classification of carbon nanotubes from (top to bottom): chair, zigzag, and helicoidal or chiral

Fig. 3.40 Unrolled nanotube

Fig. 3.41 Conceptual diagram of single-walled carbon nanotube (SWCNT) (a) and multiwalled carbon nanotube (MWCNT) (b) delivery systems showing typical dimensions of length, width, and separation distance between graphene layers in MWCNTs. (Reproduced with permission of the Elsevier Science [342])

carbon nanotubes have been demonstrated to possess unusual electronic, photonic, magnetic, thermal, and mechanical properties [341]. Nanotubes form different types, which can be described by the chiral vector (n, m), where n and m are integers of the vector eq. R ¼ na1 + ma2 [344]. The chiral vector is determined by the diagram (Fig. 3.43). Connecting A and B with the chiral vector, R (red arrow), the wrapping angle φ is formed between R and the armchair line. If R lies along the armchair line (φ ¼ 0 ), then it is called an “armchair” nanotube. If φ ¼ 30 , then the tube is of the “zigzag” type. Otherwise, if 0 < φ 100  C, >1 atm) in aqueous solutions in closed system has a growing interest among the scientists in particular due to a possibility of synthesis of new phases or crystals growth [454]. This technique was also applied for ND synthesis [455]; thus, available hydrothermal techniques for ND synthesis were reviewed by Nickel et al. [456]. The hydrothermal synthesis of diamond was frequently carried out in the silicon carbide–organic compound system [457, 458]. Organic matter dissociated in a closed system to generate C–O–H supercritical fluids, known for their high dissolving power and influence on the type of elemental carbon formation. Formed carbon crystallites had typical spectra of sp3 hybridization, clearly demonstrating the formation of nanosized diamond crystallites under sub-natural conditions. Among other ND precursors in hydrothermal synthesis, chlorinated hydrocarbons such as dichloromethane and 1,1,1trichloroethane [459, 460] can be used. Hydrothermal processing was also used [461] to prepare ND composites, for example, zirconia-coated nanodiamond (ZrO2/ND) electrode material from ND itself and ZrOCl2.8H2O (Fig. 3.57).

Fig. 3.57 Field emission scanning electron microscope (FESEM) images of ZrO2/ND (a); Pt/ZrO2/ND (b); and the formation process of Pt/ZrO2/ ND (c). (Reproduced with permission of MDPI)

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79

Ion Bombardment A successful irradiation-induced transformation of MWCNTs to diamond nanocrystals was realized with double ions (40Ar+, C2H6+) bombardment [462]. This idea of multi-ion irradiation may also be used for fabricating other nanostructures. The growth of ND under prolonged DC glow discharge plasma bombardment of 1-μm-thick polycrystalline CVD diamond was studied by Gouzman et al. [463]. It was established that ND formation on diamond started directly. The amorphous carbon/ND composite structure was substantial to the ND nucleation under energetic plasma bombardment. The nucleation of diamond on graphitic edges as predicted by W. R. L. Lambrecht et al. in 1993 was experimentally confirmed by Yao et al. [464]. Thus, the precipitation of ND crystallites in the upper layers of a film deposited by a 1 keV mass-selected carbon ion beam onto silicon held at 800  C was observed by HRTEM, selected area electron diffraction, and electron energy loss spectroscopy. Molecular dynamic simulations showed that diamond nucleation in the absence of hydrogen can occur by precipitation of diamond clusters in a dense amorphous carbon matrix generated by subplantation. After cluster formation, they can grow by thermal annealing consuming carbon atoms from the amorphous matrix [465]. Laser Bombarding Pulsed laser ablation has become an attractive method for the preparation of ND in liquids [466] or solids using carbon powders. Thus, NDs were obtained [467] by suspending carbon powders (crystalline flake graphite, microcrystalline graphite, or carbon black with particle size less than 10 μm) in a circulating liquid medium (water, alcohols, ketones, ethers, and their solutions or mixtures), bombarding the carbon powders by laser, and further purifying the product to obtain the diamond nanopowders. It was shown that only microcrystalline graphite by laser transformed into diamond (cubic diamond about 5 nm) in the three carbon materials. It also demonstrated that microcrystalline graphite was more advantageous than carbon black and crystalline flake graphite when the laser power density was 106 W/cm2 [468]. A theoretical kinetic approach to elucidate the nucleation and growth of nanocrystals with respect to the capillary effect of the nanometer-sized curvature of crystalline nuclei was proposed by Wang et al. [469] on the example of the ND synthesis by pulsed laser ablating a graphite target in H2O. The authors predicted the nucleation time, the growth velocity, and the grown size of NDs from the proposed kinetic model. Pulsed laser irradiation of amorphous carbon films in a liquid phase (Fig. 3.58) at room temperature and ambient pressure led to a phase transformation from amorphous carbon to ND (4–7 nm) [470]. On the basis of the obtained results, it was concluded that laser irradiation in liquid actually opens a route toward self-assembly of surface microand nanostructures, i.e., functional nanostructure manufacturing. The diamond-like carbon films with the highest sp3 carbon bonding content were obtained at laser fluences of 850–1000 mJ/cm2 by irradiation of the polycarbyne polymer films, coated on silicon substrates, with a pulsed Nd:yttriumaluminum-garnet laser (λ ¼ 532 nm) in argon gas atmosphere [471]. Quartz substrates were used as supports in similar experiments (λ ¼ 1064 nm, τ ¼ 20 ns, q ¼ 4.9.108 W/cm2) under vacuum ( p ¼ 2.6.103 Pa) [472]. The effect of low-power

Fig. 3.58 Schematic illustration of the experimental setup of laser irradiation in liquid. (Reproduced with permission of the American Chemical Society)

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3 Classic Carbon Nanostructures

laser radiation on volume and surface microinclusions of graphite-like carbon during the CVD diamond film fabrication were studied [473]. The simulation calculations showed that laser irradiation accelerates the processes of graphite and non-diamond phase etching. Microwave Plasma Chemical Vapor Deposition (MWPCVD) Techniques An important research and industrial method, microwave and millimeter-wave processing of materials [474–476], in particular diamonds, was reviewed by Lewis et al. [477]. CVD techniques, in particular those based on microwave-assisted approach, have become one of the most classic methods in materials production, including various carbon nanoforms, and are well generalized in a series of books [478– 480]. The experimental findings providing a basic understanding of the plasma chemistry of hydrocarbon/Ar-rich plasma environment, used for growing ND films, were discussed by Gordillo-Vazquez et al. [481]. Both main ND types, NCD and UNCD, were obtained via this route. Among a series of related works [482], the NCD (40–400 nm) were grown without the help of initial nucleation sites on Ni substrates in a microwave plasma reactor (400–600  C) using hexane/nitrogen-based CVD [483]. In a related work, NCD thin films were prepared and characterized with MPCVD [484]. Ultra-smooth nanostructured diamond (USND) coatings were deposited by MPCVD technique using He/H2/CH4/N2 gas mixture as a precursor [485]. Various aspects of CVD applications for ND materials were studied in detail by Butler et al. [486], in particular the growth and characteristics of NCD thin films with thicknesses from 20 nm to 99.9% diamond crystallites. It was shown that the UNCD was usually grown in argon-rich, H-poor CVD environments and may contain up to 95–98% sp3bonded C. Effect of gas (mixed methane and hydrogen) flow rate on diamond deposition on mirror-polished silicon substrates in a microwave plasma reactor was studied by Chen et al. [487]. Microcrystalline diamond thin films were obtained at relatively low-gas flow rates (30–300 sccm), while NCD thin films with cauliflower-like morphology were obtained at higher gas flow rates (>300 sccm). This result may be attributed to the enhancement of diamond secondary nucleation arising from the increase in the flux rate of carbon-containing radicals reaching the diamond growth surface. A series of patents are dedicated to various presentations of microwave equipment for fabrication of distinct diamond forms. Thus, the equipment for MWCVD processing was patented by Nanba et al. [488]. The apparatus had a dielectric window for introducing microwave in a vacuum chamber and an antenna part with an edge electrode for introducing microwave in the chamber, wherein the window is sandwiched between the chamber inner surface and the electrode. The apparatus was suitable for forming a large-area high-quality semiconductor diamond film. Another microwave CVD apparatus precisely for the preparation of diamond, comprising a globe-shaped discharge chamber and a coaxial antenna for feeding microwave into the chamber, with the antenna tip equipped with a work holder, positioned in the center of the globe, was proposed by Ariyada et al. [489]. Detonation Methods for ND Fabrication Detonation techniques belong to the most conventional methods [490] for obtaining NDs, in particular at industrial scale. In this respect, we note a series of fundamental reviews of Dolmatov, dedicated to such various aspects of detonation-produced nanodiamonds (DND) as the structure [491], key properties and promising fields of application of detonation-synthesis NDs [492], modern industrial methods for their manufacture [493, 494], etc. DND purity is an important problem, which is being continuously studied. In particular, the mechanism of prolonged water washing to remove excessive acidity was described [495], which was offered to improve essentially the quality of NDs and the stability of their aqueous suspensions by treating them with ammonia water (to an alkalescent medium), followed by heating to 200–240  C under pressure (so-called thermolysis). Alternative methods to remove materials still unconverted to diamond (details see below) produced [496] with yields up to 60% by firing of high explosive mixtures in water confinement, avoiding the use of inert gas, and preventing the oxidation and graphitization of recovered diamonds and various selective oxidation treatments (with KNO3/KOH, H2O2/HNO3 mixtures) were carried out, leading to light gray ultradispersed diamond aggregates with a yield up to 60%. Mechanisms of various steps of DND formation have been established. Thus, problems associated with the final stages in the disintegration/purification of DND into monodisperse single-nanodiamond (DSND) particles were critically reviewed by Osawa et al. [497, 498]. Possible pitfalls that might encounter during the search of industrial application of DSND were identified: low diamond–graphite transition temperature and abnormally strong tendency of the dispersed primary particles to reaggregate. The formation kinetics of detonation NDs was proposed by Titov et al. [499]. As a conclusion of a series of detonation experiments with ultradisperse diamond in oxygen and oxygen-free media, the diamond cannot be produced immediately behind the wave front. The authors believed that there is a diamond-free zone and zones of diamond formation. Production of NDs with an increased colloidal stability by using an explosion synthesis was patented by Puzyr et al. [500]. A related method was proposed to synthesize extremely pure form with no sp2 carbon contaminations nanodiamond powder through the decomposition of graphitic C3N4 under high pressure and high temperature [501]. The C3N4 sample was compressed to a desired pressure at room temperature, heated to 800–2000  C for 5–30 min, and then quenched and

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81

decompressed to ambient condition. The product was formed as monodispersive crystals of a uniform size range, and the grain size can be controlled by adjusting heating temperature for the synthesis. Use of Ultrasound Ultrasonic action during the ND manufacture or its pretreatment has got a certain use in ND fabrication and compared with other treatments. Thus, carbon materials containing C  C were irradiated with X-rays, microwave, and/or ultrasonic waves to give varieties of carbon structures, in particular diamond thin film and fine-grain diamond [502]. Diamond microcrystals were prepared (size 6 or 9 μm, yield ~10% by mass) using ultrasonic cavitation of a suspension of hexagonal graphite in various organic solvents at ~120  C and at atmospheric pressure [503]. Thermal processing of ND powder in air at 440–600  C until powder weight loss reached 5–85% led to stable suspensions in water, EtOH, and other solvents upon ultrasonic treatment [504]. Effects of pretreatment on the nuclei formation of UNCD on Si substrates were studied [505], showing that either precoating a thin layer of titanium (~400 nm) or ultrasonication pretreatment using diamond and titanium mixed powder enhanced the nucleation process on Si substrates markedly. NCD coating using sol–gel technique as an easy coating technique for NCD films was reported by Hanada et al. [506], making a ND sol for coating by ultrasonic dispersion in water of diamond nanoparticles ( norfloxacin > bisphenol A > carbamazepine > atrazine. Bimetallic Zn/Co-based ZIFs coated on tellurium nanotubes were pyrolyzed, generating a structure with high surface area, hierarchical pore structure, abundant Co–Nx active sites, and a 1D tubular graphitic carbon framework [136]. Such hierarchically porous Co- and N-doped CNTs are highly efficient electrocatalysts for both oxygen and triiodide reduction reactions. We note (see above a Zn-based example of ZIF-8 on Te nanowires) that tellurium nanowires or nanotubes are frequently used as ZIF-8 supports for further formation of nanocarbons. Other Zn-/Co-containing nanocarbons, the C–ZnCo2O4–ZnO nanorod arrays (NRAs), were rational designed (Fig. 5.69) and synthesized via a facile template-based solution route on Ti foil substrate and used as high-performance anode for lithium–ion batteries (LIBs) [137]. The MOF-derived carbon layers (Fig. 5.70) on the ZnCo2O4–ZnO nanorods surface can serve as a conductive substrate as well as buffer layer to restrain volume expansion during charge–discharge process. When used as LIBs anode materials, the C–ZnCo2O4–ZnO NRAs showed excellent electrochemical performance with high capacity and superior cycling stability. Role of N-Doping N-doped nanocarbons are common and the presence of nitrogen frequently contributes to useful properties. In addition to examples throughout the text, the nitrogen-doped carbon sponges composed of hierarchical microporous carbon layers were prepared from MOFs via carbonization at high temperature under Ar and NH3 flow [138], and then Se was impregnated into 0.4–0.55 nm micropores by melting-diffusion and infiltration methods (Fig. 5.71). Nitrogen doping was found to improve the electrical conductivity of carbon matrix and to facilitate rapid charge transfer, making the carbon sponge a highway for charges involved in redox reactions. These large-surface rodlike N-doped carbon sponges with hierarchical porosity could be potential candidates in the related energy storage systems, having excellent electrochemical performance. Schematic discharge–charge mechanism of the composite cathode on their basis is shown in Fig. 5.72.

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Fig. 5.69 Schematic illustration for the formation of the C–ZnCo2O4–ZnO NRAs electrode. (Reproduced with permission of Springer)

Fig. 5.70 (a) TEM image, (b–d) HRTEM lattice images (the inset figures in c and d can be ascribed to crystal lattice of ZnCo2O4 and ZnO, respectively), and (e) elemental mapping images (Zn, Co, O, and C) of the C–ZnCo2O4–ZnO. (Reproduced with permission of Springer)

5.5 MOF-Derived Carbon

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Fig. 5.71 (a, b) FESEM images, (d–e) TEM and high-resolution TEM images, (c and f) Se elemental mapping results of the NCS/Se-50 composites. (g) N2 adsorption–desorption isotherms, (h) pore (>2 nm) size distribution, and (i) micropore size distribution of NCS and NCS/Se composites. (Reproduced with permission of the Royal Society of Chemistry)

Applications of MOF-derived nanoporous carbons are very promising and include [139] CO2 capture, catalysis (in that number, magnetically recoverable supported catalysts) and photocatalysis, fabrication of pseudo-capacitance electrodes, adsorbents for removal of heavy metals and toxic species from drinking water, drug delivery carriers, electrolyte/membrane materials for fuel cells, sulfur hosts for lithium–sulfur batteries, etc. As a specific case, on the basis of analysis [140] of applications of MOF-derived nanostructures in electrochemical energy storage, catalysis, sensing, and other industries, it can be concluded that ZIF-8-derived carbon materials generally have the highest surface area, which is desirable for electrochemical energy storage. As an example of sensing applications, a GO hybrid with Co-based MOFs (Co-MOFs@GO) was prepared by the hydrothermal process [141] and was found to have outstanding hydrogen sensing (stable, repeatable, and selective responses and recovery times below 12 s at 15
C), after improvement by sputtering platinum (Pt) as a catalyst (Figs. 5.73 and 5.74). This hybrid was offered a promising material for industrial application in hydrogen sensing.

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Fig. 5.72 Schematic discharge–charge mechanism of the NCS/Se-50 composite cathode. (Reproduced with permission of the Royal Society of Chemistry)

Several other application examples in different areas are as follows. Thus, a versatile strategy for the controllable synthesis of 3D MOF hybrid arrays by utilizing semiconducting nanostructures as self-sacrificing templates was developed [142]. These MOF-hybrid-array-derived carbon-based composites with well-aligned hierarchical morphology and self-supporting structure can be directly applied to both anodes and cathodes for water splitting. Nanoporous carbon particles of approximately 50-nm diameter, prepared [143] by direct carbonization of ZIF-8, exhibited very high biocompatibility and, hence, are promising as intracellular drug delivery carriers. Also, solvent exfoliation was applied to prepare exfoliated porous carbon (EPC) from an isoreticular MOF-8 (IRMOF-8, Zn4O(ndc)3, ndc ¼ naphthalene-2,6-dicarboxylate)-derived porous carbon [144]. The obtained product with high surface area (1854 m2 g1) and improved dispersibility was used as electrode modifier for glassy carbon electrode in square-wave voltammetry detection of chloramphenicol. In addition, a rational strategy (Fig. 5.75) to improve sodium storage performance of red phosphorus was offered by confining nanosized amorphous red P into

5.5 MOF-Derived Carbon

349

Fig. 5.73 SEM images of Pt-sputtered GO hybrid with Co-based MOFs (Co-MOFs@GO) in flowerlike structure (a–c), Pt elemental mapping (d). (Reproduced with permission of the IOP Publishing)

ZIF-8-derived nitrogen-doped microporous carbon matrix (P@N-MPC) [145]. The N-doped porous carbon with sub-1 nm micropore was found to facilitate the rapid diffusion of organic electrolyte ions and improves the conductivity of the encapsulated red phosphorus. Oxygen reduction reactions (ORR) are also a promising field of applications of MOF-derived carbons (see other examples above) [146].

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Fig. 5.74 Schematic illustration of H2 reaction with Pt-sputtered Co-MOFs@GO. (Reproduced with permission of the IOP Publishing)

Fig. 5.75 Schematic illustration of the preparation process for (a) P@N-MPC and (b) sodiation process of P@N-MPC. (Reproduced with permission of the Wiley)

5.6 Lonsdaleite

5.6

351

Lonsdaleite

Lonsdaleite (hexagonal diamond) is a carbon allotrope with a hexagonal lattice. It was observed in nature in places, where meteorites striked the Earth, and also it was artificially synthesized from graphite. Both processes involve high pressures and heating, transforming the graphite into diamond, but conserving hexagonal crystal lattice of graphite. Occurrences of lonsdaleite and nanometer-sized diamonds have been speculated to serve as a marker for meteorite impacts, having also been connected to the Tunguska explosion in Russia, the Ries crater in Germany, the Younger Dryas event in sites across North America, and more [147]. Main features of lonsdaleite are as follows: • • • • • • • • • • • •

Lonsdaleite was first described almost 50 years ago from the Canyon Diablo iron meteorite. The lonsdaleite (both natural and artificial) is usually observed in small amounts inside the diamond crystals. Lonsdaleite was obtained under 13 GPa of pressure at 1270 K in 1967. Lonsdaleite has never been produced or described as a separate, pure material. A 2H polytype of sp3-carbon. Can be synthesized in the laboratory by CVD or thermal decomposition of poly(hydridocarbyne). Is translucent, brownish-yellow. Refraction index 2.40. The theoretical density of lonsdaleite is 3.51 g.cm3, the same as for cubic diamond. Harder than cubic diamond (58% more). Can be considered as “stacking disordered diamond.” The stiffest quasi-2D films with lonsdaleite structure can potentially exist [148].

Lonsdaleite has a hexagonal unit cell (Fig. 5.76) [149]. Hexagonal diamond differs from the cubic one (3C) by the layers stacking. Crystal lattice of cubic diamond represents itself a sequence of atomic layers ABCABC..., whereas lonsdaleite lattice represents ABAB... stacking [150]. Some diffraction features attributed to lonsdaleite are shown in Fig. 5.77 [151]. The calculated strength and stiffness properties of lonsdaleite, based on a first-principles method, showed [152] that lonsdaleite exhibits excellent mechanical properties, as follows: a) the maximum stiffness coefficient of lonsdaleite is 1324.57 GPa, the maximum Young’s modulus is 1324.57 GPa, and the maximum compressive strength is 727.16 GPa, which are all above the corresponding values for diamond; b) the bulk modulus of lonsdaleite is 437.09 GPa, which is as good as the bulk modulus of diamond; and c) the maximum tensile strength of lonsdaleite is 130.23 GPa, which is close to that of diamond. The three key crystallographic axes of lonsdaleite are the [2 1 1 0], [0 1 ¯1 0], and [0 0 0 1] orientations (Fig. 5.78). Artificially, the lonsdaleite can be produced from graphite by shock compression. Thus, unprecedented in situ X-ray diffraction measurements of diamond formation on nanosecond timescales by shock compression of pyrolytic as well as polycrystalline graphite to pressures from 19 GPa up to 228 GPa (Fig. 5.79) were shown [153]. The direct formation of lonsdaleite was observed above 170 GPa for pyrolytic samples only. In a related report [154], applying high-temperature and high-pressure treatment of graphite, it was found that the synthesized material contains not only diamond nanoparticles but also some relatively large (up to several nanometers) fragments of lonsdaleite (Fig. 5.80). It was supposed that the formation of these polytypes and lonsdaleite layers is caused by the propagation and interaction of phonon waves in the crystal during

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Fig. 5.76 Hexagonal unit cell of lonsdaleite

the high-temperature treatment when the phonon wavelength has a value of approximately several interplanar distances in a diamond lattice. Apparently, deformational twinning was also responsible for the formation of polytypes and lonsdaleite. The transformation of graphite to lonsdaleite and diamond was also found to be initiated by sliding of hexagonal carbon planes of graphite along the [210] of the graphite structure [155], suggesting that lonsdaleite and diamond in ureilites formed directly from graphite through boat-type buckling and chair-type puckering of hexagonal carbon planes of graphite, respectively. In addition, in Raman spectra of carbonaceous rocks excavated from the Popigai crater (Siberia), the most intensive band at 1292–1303 cm1 was ascribed to A1g vibration mode of lonsdaleite, whereas the less intense band at 1219–1244 cm1 was attributed to E2g vibration mode [156]. This correlation permits a rough estimation of lonsdaleite/diamond phase ratio in sp3bonded carbon samples in the impact rocks. For the Fe-doped lonsdaleite, it was shown [157] that the Fe ions act as the luminescent center, while other K, Ca, Mg, Zn, and Tl dopants or C vacancy can induce widely distributed hole traps that can contribute to the remarkably prolonged decay time. Also, it was predicted that Cr and Mn ions in lonsdaleite may even give more favorable persistent luminescence property.

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Fig. 5.77 Stacking faults provide an explanation for the reflections and d-spacings of “lonsdaleite.” (a) STEM image from the Canyon Diablo sample; one of many {111} stacking faults is indicated by the dotted white line. (b) FFT calculated from a. White arrows indicate spacings (0.218, 0.193, and 0.151 nm) that have been attributed to “lonsdaleite.” (c) Amplitude image calculated from the {111} set of diamond reflections (white circles in b). Bright regions indicate domains two to four layers across separated by {111} stacking faults. (d) Structure model of the region marked with white corners in a. Stacking faults (black layers of atoms) result in d-spacings that are absent in single-crystal diamond and give rise to the broad X-ray and electron-diffraction features. Scale bars mark 1 nm for a, c. (Reproduced with permission of Nature)

Fig. 5.78 The supercell and coordinate system for lonsdaleite and diamond. (a) Rectangular solid supercell in the redefined orthorhombic coordinate system for the [2 1 1 0], [0 1 ¯1 0], [0 0 0 1] orientations of lonsdaleite. (b) Rectangular solid supercell in the redefined orthorhombic coordinate system for the [1 1 ¯2], [1 ¯1 0], and [1 1 1] orientations of diamond. (c) Cubic supercell in the redefined cubic coordinate system for diamond with [1 0 0], [0 1 0], and [0 0 1] orientations. (Reproduced with permission of the Elsevier Science)

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Fig. 5.79 Schematic of the experimental setup at the Matter at Extreme Conditions endstation of the Linac Coherent Light Source. Two high-energy laser beams drive shock waves into graphite samples generating pressures from 20 to 230 GPa. The shock transit times of few nanoseconds are recorded by a VISAR system, which detects the shock-induced reflectivity drop of a 100-nm thick aluminum coating when the shock exits on the target rear side. The microscopic state is probed by a single X-ray pulse with 6 keV photon energy and 50 fs pulse duration. X-ray diffraction is recorded by a large-area X-ray detector. (Reproduced with permission of Nature)

Fig. 5.80 A high-resolution image of a particle containing the diamond and lonsdaleite lattice inclusions, zone axis . Asterisks indicate the long incoherent boundaries of the twinned areas. Fragments of the diamond lattice are shown in parallelograms, and fragments of the lonsdaleite lattice are shown in rectangles. The left-upper corner inset shows the scheme of the whole structure. Three orientations of diamond lattice and two orientations of lonsdaleite are shown there. Twinning planes (111) and (111) of diamond correspond to (0001) and (3302) of lonsdaleite. Two fragments of lonsdaleite shown in the scheme are oriented as twins with respect to planes (010) and (101) of diamond. These two planes correspond to (¯3304) and (3¯308) of lonsdaleite. (Reproduced with permission of Wiley)

5.7 Chaoite

5.7

355

Chaoite

Chaoite (“white carbon,” colored from gray to white) was discovered in shock-fused graphite gneiss from the Ries crater in Bavaria in 1969. It is hexagonally stacked by cross-linking linear carbyne chains with sp-hybridized carbon atoms, so this phase belongs to the carbyne–diamond group. Chaoite is a less studied member among the known crystalline carbon phases and its existence is still under disputes. Chaoite is sometimes attributed as a part of “possible carbon forms.” Its main features are as follows: • Slightly harder than graphite (between talc and gypsum). • It is considered to have a carbyne structure. Indeed, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level [158]. • It can be prepared from graphite by sublimation at 2700–3000 K or by irradiating it with a laser in high vacuum. • It occurs in shock-metamorphosed graphite gneisses and in ureilite meteorites. • It crystallizes in hexagonal crystal system with cell dimensions a, 8.948; c, 14.078; Z, 168; V, 976.17; and space group, P6/mmm. • Chaoite can be converted to other carbon phases [159]. Synthesis methods are not well-developed for this carbon allotrope. Thus, a solid large-surface paramagnetic Si/C/O/N nanocomposite was obtained [160] by silica etching by laser-photolytic products of pyridine decomposition and found to be paramagnetic and composed of amorphous CN bonds containing poly(oxocarbosilane)-containing crystalline nanoregions of rare chaoite. Heating this product to 650
C, chaoite regions are depleted revealing regions of crystalline silica. The carbon– cobalt films were deposited by pulsed anodic electric arc system, using graphite rod electrode [161], exhibiting amorphous and crystallized zones corresponding to different phases of carbon (graphite, chaoite, and fullerene, Fig. 5.81).

Fig. 5.81 HRTEM image obtained for 0.3% cobaltdoped carbon thin film. Regions with curved fringes of fullerene-like graphitic layers and chaoite structure can be seen. (Reproduced with permission of Hindawi)

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Fig. 5.82 Chaoite-like carbon was prepared by quenching the pyrolysate of acetylene gas at 873 K and ambient pressure. (Reproduced with permission of the Elsevier Science)

Milder conditions for chaoite formation are of interest for researchers [162]. Thus, chaoite phase was synthesized by quenching the pyrolysate of acetylene gas at low temperature (873 K) and pressure (1 atm) [163, 164], having typical morphology of a tube with 20–60 μm in diameter and more than 8 mm in length (chaoite-like multicrystals, which are formed by cross-linking the kinked sp-bonded carbon chains, Fig. 5.82). These carbon macrotubes also possessed unexpected clear intrinsic ferromagnetism, indicating that the sp-hybridized structure may be an origin of ferromagnetism. A belt scrolling model was proposed for explaining the formation process of CMTs, including: (a) During heating, acetylene gas molecules are pyrolyzed into linear chains. (b) During cooling, the linear chains are parallel arranged to form hexagonal structure with the chain along the crystallographic c-axis. At the same time, cross-linking reaction between adjacent chains occurs to some extent to form belts with various cross-linking degree. (c) The belts are then scrolled tighter and tighter to form macrotubes due to thermal stress and/or anisotropic microstructure of tubes.

5.8

10

Graphane10 and Graphone

Graphane image is reproduced with permission of APS Physics (Phys. Rev. B, 2007, 75, 153,401).

5.8 Graphane and Graphone

357

In addition to graphene, graphyne, and graphdiyne, the 2D materials also include graphone and graphane (strictly, having hydrogen, they cannot be considered as carbon allotropes), which are hydrogenated forms of graphene [165, 166]. According to Novoselov [167], although graphite is known as one of the most chemically inert materials, the graphene can react with atomic hydrogen, which transforms this highly conductive zero-overlap semimetal into an insulator. Graphane is a hydrogenated sheet of graphene, where a primitive graphane cell contains two carbon atoms and two hydrogen atoms. The difference in this case is that the graphene sheet is 100% hydrogenated as opposed to 50% hydrogenated graphone. However, the structural parameters are similar. There is roughly a 5
difference in the C–C–C bond angle, while there is less than 0.1 Å difference in the C–C bond lengths. Unlike graphone, graphane has been successfully synthesized using a couple of different methods. Main features of graphane are as follows: • This (single layer) is a 2D polymer of carbon and hydrogen with the formula unit (CH)n where n is large (a form of hydrogenated graphene, a 2D form of carbon alone). • It is the fully saturated version of graphene. Ideally, every carbon atom of the graphene layer is covalently bonded to a hydrogen atom. • Carbon bonds in graphane are in sp3 configuration (graphene has sp2 bond configuration), thus graphane is a 2D analog of cubic diamond. • The length of the C–H bonds is about 1.10 Å which is typical for such bonds as found in organic chemistry. • The average length of the C–C bonds is close to the ideal single C–C bonds in diamond. • Graphane is a semiconducting material with a substantial direct electronic band gap about 3.5 eV [168]. • Room temperature ferromagnetism was observed in partially hydrogenated graphene. • The transition from graphene to graphane is that of an electrical conductor, to a semiconductor, and ultimately to an electrical insulator. • Hydrogenation of graphene on substrate affects only one side, preserving hexagonal symmetry. • Hydrogenation can be accomplished (1) via low-pressure H2 plasma, (2) in high-pressure H2 atmosphere, or (3) via wet chemistry (solution)-based approaches. Typical graphene hydrogenation process is shown in Fig. 5.83. • The hydrogenation occurs due to the hydrogen ions from the plasma and not due to the fragmentation of water adsorbates on the graphene surface by highly accelerated plasma electrons. • Partially hydrogenated graphene can be produced using thermal exfoliation of graphite oxide in H2 atmosphere under high pressure (60–150 bar) and temperature (200–500
C). • Hydrogenated graphene can be also further derivatized because of its extended reactivity in comparison with unmodified graphene.

Fig. 5.83 Graphene hydrogenation progress. (a) A graphene layer, where delocalized electrons are free to move between carbon atoms, is exposed to a beam of hydrogen atoms. (b) In nonconductive graphane, hydrogen atoms bond to their electrons with electrons of carbon atoms and pull the atoms out of the plane [170]. (Reproduced with permission of Springer)

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5 Other Existing Carbon Forms

• Hydrogenation opens a band gap of up to 3.7 eV, depending on the hydrogenation level and conformation, leading to the fluorescence of highly hydrogenated graphene. • The reaction of graphene with hydrogen is reversible, so that the original metallic state, the lattice spacing, and even the quantum Hall effect can be restored. The metallic character of graphene from graphane can be recovered by annealing graphane in Ar atmosphere at 450
C. • Dehydrogenation of graphane can be laser-induced [169]. • Applying an external electric field to a fully hydrogenated graphene can remove H atoms from one side of graphane, forming graphone. • It is also possible to completely hydrogenate multilayer graphene to form stacked sequences of, e.g., chair isomers, or, alternatively, only the top and bottom layer are hydrogenated from one side, resulting in a thin diamond films. • The wet chemical methods are based on the reduction of oxygen functionalities present on the graphene oxide surface, for instance, ketone and carboxylic acids can be reduced to hydroxyls together with carbon atom hydrogenation. Varieties of Graphane Structures The three best-known and most stable graphane isomers are, namely, the chair, stirrup, and boat configuration, together with two other isomers (Fig. 5.84) [171]. The stirrup configuration (also called washboard or zigzag configuration; this is an interesting isomer of graphane, proposed on the basis of DFT calculations [172], in which the C–H bonds of a hexagon alternate in three-up–three-down fashion on either side of the sheet) is more stable than the so-called boat configuration. Also, a 2D nanomaterial (good electrical insulator having a high specific heat capacity), which is a form of hydrogenated penta-graphene and called penta-graphane (Fig. 5.85), was obtained by adding hydrogen atoms to the sp2bonded carbon atoms of penta-graphene (penta-graphene has sp2- and sp3-bonded carbon atoms) [173]. Penta-graphane has diamond-like structure with sp3 hybridization. Also, graphanes can have various C/H ratios. A more promising case of singleside adsorption is C4H (Fig. 5.86). This structure is built from H pairs in the very stable para configuration in which atoms are adsorbed on opposite C atoms in the graphene hexagons [174]. Multilayer Structures A hydrocarbon called hydrographite (a black solid thermally stable under ambient conditions, consisting of graphane sheets in the chair conformation stacked along the hexagonal c axis in the ABAB sequence, with hexagonal crystal structure, Fig. 5.87), with the composition close to CH, was shown to be formed from graphite and gaseous hydrogen at pressures above 2 GPa and temperatures from 450 to 700
C [175]. Being heated in vacuum, it decomposes into graphite and molecular hydrogen at temperatures from 500 to 650
C. Heating above 720–750
C in an H2 gas compressed to 7.5 GPa transforms hydrographite to methane and/or other light hydrocarbons. Properties of Graphane Fully hydrogenated graphene contains only sp3-hybridized C atoms with four bonding partners (3 C and 1 H), so the ideal graphane isomers are not expected to show any interesting magnetic properties. Magnetism only occurs

chair

boat

strirrup

twist-boat

armchair

Fig. 5.84 Five isomers of graphane in which every C atom is equivalent. Blue and red colors indicate H adsorption, respectively, above and below the graphene layer. (Reproduced with permission of Wiley)

5.8 Graphane and Graphone

359

Fig. 5.85 Total energy of (a) C6H4 (not fully hydrogenated graphane) and (b) penta-graphane. Blue and red spheres represent carbon and hydrogen atoms, respectively. (Reproduced with permission of Taylor and Francis)

Fig. 5.86 Top and side view of the C4H crystal structure. (Reproduced with permission of Wiley)

at defect sites (missing H atoms) and in partially hydrogenated graphene. In respect of mechanical properties, the hydrogenation reduces the strength of graphene because the strong aromatic bond network is replaced with single σ bonds. Experimental values for Young’s modulus of graphane are not available at present, but they are expected to be lower than the theoretical value due to the presence of defects. The 2D nature of graphane has a significant impact on its optical properties and reduces the optical band gap significantly. In case of graphane nanoribbons, their optical properties were found to be independent of their edge shapes and widths. In addition, the vibrational properties of graphene fluoride and graphane were studied, showing that both sp3-bonded derivatives of graphene have different phonon dispersion relations and phonon densities of states [176]. Vacancies and Foreign Atoms/Groups The properties of graphane can be controlled by its interaction with various metallic ions [177]. Graphane can be further doped with Fe, Li, Ca, or Ge or functionalized with –OH, -F, or -NH2 groups. Potentially many derivatives of graphane can be fabricated by changing the substrate atoms (like C, Si, Ge, P) and the surface atoms (like H, –OH, -NH2, He, Li, Fe, Mn, and all the VIIA element). The impurities can be utilized for the modification of electronic and magnetic properties of graphane. In particular, fluorine-doped graphane is very sensitive to the doping configuration. In addition, the strong covalent bonds of graphene can be broken, and various vacancies are formed due to, e.g., continuous exposure to the high-energy electron beam or irradiation with low-energy Ar+. Electronic and magnetic properties of graphene can be modulated by various techniques such as synthesis of graphanes with different C/H ratios, formation of vacancies, application of strain, and dimensional reduction. Studies of the electronic structure of graphane with hydrogen vacancies, which are supposed to occur in the process of hydrogenation of graphene (it is always possible that a small amount of H vacancies remains after a hydrogenation process or occurs by means of physical or chemical desorption), revealed that a continuous chain-like distribution of hydrogen vacancies results in conduction of linear

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5 Other Existing Carbon Forms

Fig. 5.87 The P63mc structure of a graphane crystal. Large spheres represent C atoms; small spheres stand for D atoms. The atoms labeled C1 and D1 sit on the 2a positions; those labeled C2 and D2 are on the 2b positions. Numbers indicate the interatomic distances in Angstroms. (Reproduced with permission of the Elsevier Science)

dispersion, much like the transport on a superhighway cutting through the jungle of hydrogen [178]. H vacancies in graphane produce defect states that appear in the graphane bandgap. Magnetic moments can also be generated depending on whether there are unpaired electrons in the configuration. Studies of the role of H frustration (this is a configuration where the sequence of alternating up and down H atoms is broken (frustrated)) in graphane-like structures showed that a significant percentage of uncorrelated H frustrated domains are formed in the early stages of the hydrogenation process leading to membrane shrinkage and extensive membrane corrugations [179]. The net result is a decrease of the carbon–carbon distances in relation to the ideal graphane values. A certain attention is also paid to combined graphane/graphene composites, i.e., containing distinct grades of hydrogenation in different zones; for instance, electronic transport properties of zigzag graphane/graphene nanoribbons [180] and magnetic properties of graphene superlattices, modeled with a repeated structure of pure and hydrogenated graphenegraphane strips, were DFT-studied [181]. As graphene is charged, localized regions of graphene are transformed from sp2 bonded into sp3 bonded, giving rise to hydrogen-less graphane, which, if experimentally realized, may lead to a way of combining graphene and graphane in the same material [182]. It was suggested that the combination of graphene and graphane might be the basis of future electronic devices. Potential Applications Graphane may found applications in various fields such as hydrogen storage, piezoelectricity, spintronics, thermoelectrics, explosive detection, and sensing and biosensing devices. Thus, DFT was used to investigate the sensing property of graphane toward CO, H2O, and NO2 gas molecules [183]. Curiously, the pristine graphane sheet was found not to have sufficient affinity toward the mentioned gas molecules; the defected sheet (removing few surface H atoms) had a strong affinity toward the gas molecules. While CO and H2O are weakly physisorbed, the NO2 molecules are strongly chemisorbed to the defected graphane sheet. Various N-substituted/grafted graphanes can also adsorb CO2. It was found that the presence of co-adsorbed H2O on the surface promotes CO2 adsorption on both N and NH2 sites, with highly exothermic adsorption energies [184]. In case of other inorganic gases, neither a pristine graphane sheet nor the sheet defected by removing a few surface H atoms has sufficient affinity for either H2S or NH3 gas molecules [185]. However, a graphane sheet doped with Li adatoms shows a strong sensing affinity for both mentioned gas molecules.

5.8 Graphane and Graphone

361

Fig. 5.88 (a) The zero-energy state (substrate and molecule with no interaction), (b) formaldehyde attached to the surface (intermediate state), (c) transition state (hydrogen abstraction), and (d) final state, hydrogen attachment to the molecule. (Reproduced with permission of Elsevier Science)

Fig. 5.89 (a) The optimized structure of the fully hydrogenated CHCa with maximum number of hydrogen molecules adsorbed around each Ca atom. (b) The extended structure of relaxed CHCa with adsorbed hydrogen molecules. (Reproduced with permission of the AIP Publishing)

Organic molecules can also be sensed by graphane. Thus, the process of adsorption of a formaldehyde molecule on a hydrogenated graphene substrate was calculated to be a free radical-initiated reaction [186], beginning at a hydrogen vacancy on the graphane layer, in which the oxygen atom of the formaldehyde molecule attaches (Fig. 5.88). Then, the nearest hydrogen atom is abstracted by the carbon atom of the formaldehyde, forming a stable molecule and leaving behind a new dangling bond on the graphane substrate. The energy barrier for the entire process was found to be 0.56 eV. The advantage of using graphane as H2 storage material is its nano-size, large stability, and relatively stronger graphanemetal binding. It was predicted that with a doping concentration of 11.11% of Ca on graphane sheet (Fig. 5.89), a reasonably good H2 storage capacity of 6 wt. % could be attained [187]. Also, the detection of explosives is one of the main concerns for a secure and safe society. Toxic trinitrotoluene (TNT), main component in explosives, can be detected in seawater using partially hydrogenated graphene and graphene. Spintronics is another possible application area [188]. Graphone (first predicted in 2009) is the midpoint between graphene and graphane in which the graphene sheet is only partially hydrogenated. Unlike graphane (100% hydrogenation) and graphene (0% hydrogenation), graphone is a graphene sheet with 50% hydrogenation and stoichiometry C2H. Additionally, the hydrogen atoms are only on one side of the carbon sheet, resulting in a mixture of hybridized sp2 and sp3 carbon atoms. Many intermediate forms can also exist. Main features of graphone are as follows: • • • •

Graphone is a graphene sheet with 50% hydrogenation and stoichiometry C2H. The hydrogen atoms are only on one side of the carbon sheet, resulting in a mixture of hybridized sp2 and sp3 carbon atoms. Graphone is a ferromagnetic semiconductor with an indirect band gap of 0.43 eV. The stability of graphone is very weak, because the H atoms try to form pairs. However, graphone is considered as a stable structure at room temperature. • Graphone has a small in-plane stiffness (74%) as well as Poisson ratio (67%) compared to graphene, but similar to those of graphane. • The effect of hydrogenation on the mechanical properties is saturated when the graphene is only 50% hydrogenated. • Graphone still has yet to be synthesized easily.

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5 Other Existing Carbon Forms

Fig. 5.90 Configurations of graphone. (a) Graphone plane; (b) top view and directions; (c) side view. (Reproduced with permission of the Royal Society of Chemistry)

The synthesis of graphone can be achieved by desorption of hydrogen from graphane, but a reliable method for synthesizing graphone is yet to be found. The synthesis of graphone bound to a Ni(111) surface showed that the hydrogenation of graphene with atomic hydrogen indeed leads to graphone, that is, a hydrogen coverage of 4.2 wt.% [189]. The dehydrogenation of graphone reveals complex desorption processes that are attributed to coverage-dependent changes in the activation energies for the associative desorption of hydrogen as molecular H2. Structural Peculiarities [190] It was stated [165] that when half of the carbon atoms are hydrogenated, strong σ bonds are formed between the carbon and hydrogen atoms. These σ bonds not only disrupt the usual π bonding network of graphene that leads to the metallic and nonmagnetic two-dimensional sheet but also cause the electrons on the carbon atoms not bonded to hydrogen to become localized and unpaired. Graphone possesses a graphene-like honeycomb structure where there are two typical directions named “armchair” and “zigzag” (Fig. 5.90) [191]. The instability of a free-standing boatlike and armchairlike one-sided hydrogenated/fluorinated graphene nanoribbon (Fig. 5.91), i.e., graphone/fluorographene, was studied using ab initio, semiempirical, and large-scale molecular dynamics simulations [192]. The packed, spiral structures exhibit an unexpected localized highest occupied molecular orbital and lowest occupied molecular orbital at the edges with increasing energy gap during rolling. These rolled hydrocarbon structures are stable beyond room temperature up to at least T ¼ 1000 K within the simulation time of 1 ns. Other properties and possible applications. The temperature dependence of the characteristic time of disordering of graphone via hopping of hydrogen atoms to neighboring carbon atoms was established directly [193]. The activation energy of this process was determined at Ea ¼ (0.05  0.01) eV. This small value of Ea is indicative of the extremely low thermal stability of graphone, making this nanocarbon material unpromising for practical use in electronic devices. On the contrary, the DFT modellings performed showed that fluorinated graphone is rather more stable than the hydrogenated one [194], which makes it more suitable for further applications in electronic and spintronic devices. Graphone were examined as a possible material for FETs and organic ferroelectrics.

5.9 M-Carbon

363

Fig. 5.91 The rolled boatlike (left) and armchairlike (right) graphone nanoribbons after (a), (c) t ¼ 50 ps and (b), (d) t ¼ 80 ps. These systems are stable up to at least 1000 K. (Reproduced with permission of APS Physics)

5.9

M-Carbon11

Despite that the news about monoclinic C-centered carbon (M-carbon) appeared as far back as in 1963, passing a series of intermediate studies, the possibility of existence of this structure and formation from graphite by its overcompressing at room temperature were proven in 2012. Main features of the M-carbon are as follows [195]: • A monoclinic C2/m structure (8 atoms/cell). • It is stable over cold-compressed graphite above 13.4 GPa. • The hardness and bulk modulus of M-carbon are known to be 83.1 and 431.2 GPa, respectively, which are comparable to those of diamond. There are several distinct reports on M-carbon varieties. In particular, it was shown that the monoclinic phase carbon allotrope, C2/m-16 carbon, is a potential superhard material with a hardness of 59.5 GPa and a semiconductor with a wide and indirect band gap of 4.20 eV [196]. C2/m-20 carbon (containing sp3-hybridized covalent bonds) is mechanically stable and dynamically stable at 0 GPa and 100 GPa. C2/m-20 carbon has a larger bulk modulus of 412 GPa, a larger shear modulus of 463 GPa, a larger Young’s modulus of 1010 GPa, and a hardness of 70.6 GPa, which means that it is a superhard material with potential technological and industrial applications. In addition, C2/m-20 carbon is an indirect and wide semiconductor with a 11

Reproduced with permission of the Royal Society of Chemistry (RSC Adv., 2016, 6, 32,740–32,745).

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5 Other Existing Carbon Forms

Fig. 5.92 The crystal structure of C2/m-16 carbon (a), C2/m-20 carbon (b), M-carbon (c), C2/m-16 carbon along the [010] direction (d), C2/m-20 carbon along the [010] direction (e), and M-carbon along the [010] direction (f). At zero pressure, C2/m-20 carbon contains five inequivalent crystallographic sites, occupying the 4i (0.07488, 0.0, 0.51860), 4i (0.50848, 0.0, 0.33322), 4i (0.75150, 0.0, 0.04876), 4i (0.99004, 0.0, 0.90598), and 4i (0.36506, 0.0, 0.73151) positions, respectively. (Reproduced with permission of the Royal Society of Chemistry)

band gap of 5.10 eV. The most extraordinary thing is that the band gap increases with increasing pressure. The crystal structures of C2/m-20 carbon, C2/m-16 carbon, and M-carbon are illustrated in Fig. 5.92. C2/m-20 carbon, C2/m-16 carbon, and M-carbon all belong to the C2/m phase. In their crystal structures, six-membered carbon rings exist in C2/m-16 carbon and C2/m-20 carbon. In addition, C2/m-16 carbon and C2/m-20 carbon also have five-membered carbon rings and sevenmembered carbon rings, while M-carbon only has five-membered carbon rings and seven-membered carbon rings. In addition, an allotrope of carbon, a transparent, superhard material, called M10-carbon (Fig. 5.93), with P2/m symmetry was identified during an ab initio minima-hopping structural search [197]. This structure, consisting purely of sp3 bonds, was proposed to be more stable than graphite at pressures above 14.4 GPa. It has a high bulk modulus and is almost as hard as diamond.

5.10

Q-Carbon

365

Fig. 5.93 The structure of M10-carbon from two different angles. The left panel shows the five- and sevenmembered rings, while the right panel reveals the six-membered rings. (Reproduced with permission of Springer)

5.10

Q-Carbon12

Q-carbon (“quenched”) was discovered in 2015. The Q-carbon is formed as result of quenching amorphous carbon from super undercooled state by using high-power nanosecond laser pulses (nanosecond laser melting). Its main features are as follows [198]: • Q-carbon is ferromagnetic (estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g1) and electrically conductive. • Q-carbon possesses an amorphous structure, consisted of a mixture of sp2 and sp3 bonding (mostly sp3, 75–85%). • It can be obtained by carbon conversion using a high-powered laser pulses. The formation of Q-carbon is achieved, when amorphous carbon films are heated to about 4000 K and melted and quenched rapidly [199]. • Q-carbon was found to be 60% harder than diamond-like carbon. • It can be used in creating artificial body components, improving instruments like deep water drills, and producing much brighter, long-lasting screens for televisions and cellphones. • Nanodiamonds, microdiamonds, nanoneedles, microneedles, and thin films are readily formed from the Q-carbon depending upon the time allowed for growth during the quenching period. • Sometimes it glows when exposed to low levels of energy. • It is quite inexpensive to make, and maybe, it is a replacement of diamond. • Q-carbon can be made to take multiple forms, from nanoneedles to large-area diamond films. • It took researchers only 15 min to make 1 karat of Q-carbon. Q-carbon could have a series of applications: high-powered electronic and photonic devices, high-speed machining, deep sea drilling, efficient field emission displays, medicinal purposes (like nanoneedles, microneedles, nanodots, and films), and sensor applications (biomedical sensing, single-photon sensors, nanoscale electronic and magnetic sensing, single-spin magnetic resonance and fluorescent biomarkers), among others [200].

12

Reproduced from https://newatlas.com/q-carbon-new-phase-of-carbon/40668/ (Q-carbon film covered with microdiamonds).

366

5.11

5 Other Existing Carbon Forms

T-Carbon13

This carbon allotrope was first proposed in 2011. In the T-carbon, every carbon atom in diamond is replaced with a carbon tetrahedron (hence “T-carbon”). T-carbon possesses the same space group Fd3̄ m as diamond [201]. Main features of T-carbon are presented as follows: • Each unit cell of the T-carbon structure contains two tetrahedrons with eight carbon atoms. • T-carbon has a density 1.50 g/cm3. • Semiconductor with a direct band gap about 3.0 eV has a Vickers hardness 61.1 GPa lower than diamond but comparable with cubic boron nitride. • It would have wide applications in photocatalysis, adsorption, hydrogen and lithium storage (since it has large interspaces between atoms), and aerospace materials [202]. • T-carbon could have astronomical implications as a potential component of interstellar dust and carbon exoplanets. T-carbon with a nanowire-like morphology was synthesized by picosecond-pulsed laser irradiation of a MWCNT suspension in methanol [203]. The diameters of most T-carbon NWs were found to be in the range 10–20 nm, similar to the diameter distribution of the starting shortened MWCNTs. sp2 hybridization in MWCNTs was confirmed to be transformed to sp3 hybridization. The structure is diamond-like with each carbon atom replaced by a carbon tetrahedron (Fig. 5.94), consistent with the theoretically predicted T-carbon with a lattice constant of 7.52 Å. Among other varieties of T-carbon, a Fig. 5.94 Structural model of T-carbon (Fd3̄m, lattice constant ¼ 7.80 Å). (Reproduced with permission of Nature)

13

Reproduced from https://www.nextbigfuture.com/2011/04/t-carbon-novel-carbon-allotrope.html.

References

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Fig. 5.95 (a) The crystal structure of T-carbon. (b) T-carbon moving 1/2 lattice vector along a axis. (c) The crystal structure of T-II carbon. (d–f) Views from [100], [110], and [111] directions of T-II carbon, respectively. (Reproduced with permission of the Royal Society of Chemistry) Fig. 5.96 Schematic depiction of the structure of C20-T-carbon. C20-T-carbon has P213 symmetry with a lattice constant of 4.945 Å. The carbon atoms occupy the 12b(0.4274, 0.7301, 0.8103), 4a(0.2694, 0.2307, 0.7694), and 4a(0.0894, 0.4106, 0.5894) Wyckoff positions, which are denoted by C1(blue), C2(red), and C3(green), respectively. (Reproduced with permission of the IOP Science)

modulated T-carbon-like carbon allotrope (T-II carbon, structurally similar to T-carbon, having the smallest unit of T-carbon, Fig. 5.95) was predicted by means of first-principles calculations [204]. This structure has eight atoms in the unit cell, possesses the Pn3̄m space group, and can be derived by stacking up two T-carbons together. T-II carbon is a semiconductor with band gap 0.88 eV and has a higher hardness (27 GPa) than that of T-carbon (5.6 GPa). Also, a superhard carbon allotrope named C20-T was also predicted [205], which belongs to a cubic T symmetry with space group P213 and possesses all sp3-hybridized bonding network with 20 atoms in its primitive unit cell (Fig. 5.96). Interestingly, despite the fact that C20-T-carbon has a porous structure with large cavities, the calculations identified its superhard properties with the Vickers hardness of 72.76 Gpa. This carbon phase has great potential for application in mechanical devices, hydrogen storage, and related fields.

References 1. M.P. Manoharan, H. Lee, R. Rajagopalan, H.C. Foley, M.A. Haque, Elastic properties of 4–6 nm-thick glassy carbon thin films. Nanoscale Res. Lett. 5, 14 (2009)

368

5 Other Existing Carbon Forms

2. K. Jurkiewicz, S. Duber, H.E. Fischerd, A. Burian, Modelling of glass-like carbon structure and its experimental verification by neutron and X-ray diffraction. J. Appl. Crystallogr. 50, 36–48 (2017) 3. O.J.A. Schueller, S.T. Brittain, G.M. Whitesides, Fabrication of glassy carbon microstructures by pyrolysis of microfabricated polymeric precursors. Adv. Mater. 9(6), 477–480 (1997) 4. J. Bauer, A. Schroer, R. Schwaiger, O. Kraft, Approaching theoretical strength in glassy carbon nanolattices. Nat. Mater. 15, 438–443 (2016) 5. C.M. Lentz, B.A. Samuel, H.C. Foley, M.A. Haque, Synthesis and characterization of glassy carbon nanowires. J. Nanomater 2011, (2011). Article ID 129298, 8 pp 6. A.F. Goncharov, Graphite at high pressures: Pseudomelting at 44 GPa. Sov. Phys. JETP 71(5), 1025–1027 (1990) 7. M. Yao, X. Fan, W. Zhang, et al., Uniaxial-stress-driven transformation in cold compressed glassy carbon. Appl. Phys. Lett. 111, 101901 (2017) 8. M. Hu, J. He, Z. Zhao, et al., Compressed glassy carbon: An ultrastrong and elastic interpenetrating graphene network. Sci. Adv. 3, e1603213 (2017) 9. J. Csontos, Z. Toth, Z. Pápa, et al., Periodic structure formation and surface morphology evolution of glassy carbon surfaces applying 35-fs– 200-ps laser pulses. Appl. Phys. A Mater. Sci. Process. 122, 593 (2016) 10. M. Collaud Coen, Functionalization of graphite, glassy carbon, and polymer surfaces with highly oxidized sulfur species by plasma treatments. J. Appl. Phys. 92, 5077–5083 (2002) 11. I. Emahi, M.P. Mitchell, D.A. Baum, Electrochemistry of pyrroloquinoline quinone (PQQ) on multi-walled carbon nanotube-modified glassy carbon electrodes in biological buffers. J. Electrochem. Soc. 164(3), H3097–H3102 (2017) 12. F. Campanhã Vicentini, B.C. Janegitz, C.M.A. Brett, O. Fatibello-Filho, Tyrosinase biosensor based on a glassy carbon electrode modified with multiwalled carbon nanotubes and 1-butyl-3-methylimidazolium chloride within a dihexadecylphosphate film. Sens. Actuators B Chem. 188, 1101–1108 (2013) 13. F. Chekin, S. Bagheri, S. Bee Abd Hamid, Glassy carbon electrodes modified with gelatin functionalized reduced graphene oxide nanosheet for determination of gallic acid. Bull. Mater. Sci. 38(7), 1711–1716 (2015) 14. S. Robin Nxele, P. Mashazi, T. Nyokong, Surface functionalization of glassy carbon electrodes via adsorption, electrografting and click chemistry using quantum dots and alkynyl substituted phthalocyanines: a brief review. Fourth Conference on Sensors, MEMS, and ElectroOptic Systems, 2017, Proceedings Volume 10036, 100360D 15. M.L. Valenzuela, R. Cisternas, P. Jara-Ulloa, L. Rodriguez, Electroanalytical analysis of glassy carbon electrode modified with COOH- and NO2- functionalized polyspyrophosphazenes. J. Chil. Chem. Soc. 62(2), 3515–3518 (2017) 16. I. Kocak, Characterization of the reduction of oxygen at anthraquinone-modified glassy carbon and highly oriented pyrolytic graphite electrodes. Anal. Lett. 50(9), 1448–1462 (2017) 17. J. Lv, Y. Tang, L. Teng, D. Tang, J. Zhang, Aminobenzene sulfonic acid-functionalized carbon nanotubes on glassy carbon electrodes for probing traces of mercury(II). J. Serb. Chem. Soc. 82(1), 73–82 (2017) 18. P. Actis, G. Caulliez, G. Shul, et al., Functionalization of glassy carbon with diazonium salts in ionic liquids. Langmuir 24(12), 6327–6333 (2008) 19. J. Liu, S. Dong, Grafting of diaminoalkane on glassy carbon surface and its functionalization. Electrochem. Commun. 2(10), 707–712 (2000) 20. M. Balooei, J. Bakhsh Raoof, F. Chekin, R. Ojani, Novel sensor based on 3-mercaptopropyltrimethoxysilane functionalized carbon nanotubes modified glassy carbon electrode for electrochemical determination of Cefixime. Anal. Bioanal. Electrochem. 9(3), 266–276 (2017) 21. R. Sakthivel, S. Dhanalakshmi, S.-M. Chen, et al., A novel flakes-like structure of molybdenum disulphide modified glassy carbon electrode for the efficient electrochemical detection of dopamine. Int. J. Electrochem. Sci. 12, 9288–9300 (2017) 22. J. Marwan, T. Addou, D. Bélanger, Functionalization of glassy carbon electrodes with metal-based species. Chem. Mater. 17(9), 2395–2403 (2005) 23. https://www.2spi.com/catalog/documents/glassy-vitreous-carbon-info.pdf. Accessed on 26 Oct 2017 24. C. Canales, L. Gidi, G. Ramírez, Electrochemical activity of modified glassy carbon electrodes with covalent bonds towards molecular oxygen reduction. Int. J. Electrochem. Sci. 10, 1684–1695 (2015) 25. J. Miliki, N. Markicevi, A. Jovic, R. Hercigonja, B. Šljuki, Glass-like carbon, pyrolytic graphite or nanostructured carbon for electrochemical sensing of bismuth ion? Process. Appl. Ceramics 10(2), 87–95 (2016) 26. Y.E. Seidel, R.W. Lindström, Z. Jusys, et al., Stability of nanostructured Pt/glassy carbon electrodes prepared by colloidal lithography. J. Electrochem. Soc. 155(3), K50–K58 (2008) 27. Y. Jalit, M.C. Rodríguez, M.D. Rubianes, S. Bollo, G.A. Rivas, Glassy carbon electrodes modified with multiwall carbon nanotubes dispersed in polylysine. Electroanalysis 20(15), 1623–1631 (2008) 28. S.E. Subramani, T.V. Vineesh, T. Priya, V. Kathikeyan, N. Thinakaran, Electrochemical detection of Pb(II) ions using glassy carbon electrode surface modified by functionalized mesoporous carbon. Sens. Lett. 15(4), 320–327 (2017) 29. C. Sun, L. Rotundo, C. Garino, Electrochemical CO2 reduction at glassy carbon electrodes functionalized by MnI and ReI organometallic complexes. ChemPhysChem 18(22), 3219–3229 (2017) 30. A. Braun, J. Ilavsky, S. Seifert, Highly porous activated glassy carbon film sandwich structure for electrochemical energy storage in ultracapacitor applications: Study of the porous film structure and gradient. J. Mater. Res. 25(8), 1532–1540 (2010) 31. V.D. Chekanova, A.S. Fialkov, Vitreous carbon (preparation, properties, and applications). Russ. Chem. Rev. 1971(40), 413–428 (1971) 32. C. Garion, Mechanical properties for reliability analysis of structures in glassy carbon. World J. Mech. 4, 79–89 (2014) 33. N. Komarevskiy, V. Shklover, L. Braginsky, C. Hafner, J. Lawson, Potential of glassy carbon and silicon carbide photonic structures as electromagnetic radiation shields for atmospheric re-entry. Opt. Express 20(13), 14189–14200 (2012) 34. J. Myalski, B. Hekner, A. Posmyk, The influence of glassy carbon on tribological properties in metal – ceramic composites with skeleton reinforcement. Additional Conferences (Device Packaging, HiTEC, HiTEN, & CICMT), 2015, Vol. 2015, No. CICMT, (2015) pp. 000121–000124 35. Y. Koval, A. Geworski, K. Gieb, I. Lazareva, P. Müller, Fabrication and characterization of glassy carbon membranes. Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena 32, 042001 (2014)

References

369

36. M. Vomero, E. Castagnola, F. Ciarpella, E. Maggiolini, N. Goshi, E. Zucchini, S. Carli, L. Fadiga, S. Kassegne, D. Ricci, Highly stable glassy carbon interfaces for long-term neural stimulation and low-noise recording of brain activity. Sci. Rep. 7, 40332 (2017) 37. https://www.alfa.com/es/glassy-carbon/ Accessed on 27 Oct 2017 38. S. Dadkhah, E. Ziaei, A. Mehdinia, T. Baradaran Kayyal, A. Jabbari, A glassy carbon electrode modified with amino-functionalized graphene oxide and molecularly imprinted polymer for electrochemical sensing of bisphenol a. Microchim. Acta 183(6), 1933–1941 (2016) 39. J. Bakhsh Raoof, R. Ojani, M. Baghayeri, M. Amiri-Aref, Application of a glassy carbon electrode modified with functionalized multi-walled carbon nanotubes as a sensor device for simultaneous determination of acetaminophen and tyramine. Anal. Methods 4, 1579–1587 (2012) 40. www.orioncarbons.com. Accessed on 31 Oct 2017 41. C.M. Long, M.A. Nascarella, P.A. Valberg, Carbon black vs. black carbon and other airborne materials containing elemental carbon: Physical and chemical distinctions. Environ. Pollut. 181, 271–286 (2013) 42. https://en.wikipedia.org/wiki/Carbon_black. Accessed on 31 Oct 2017 43. http://www.climatecentral.org/news/black-carbon-second-only-to-co2-in-heating-the-planet-new-study-15465. Accessed on 31 Oct 2017 44. https://birlacarbon.com/learning-center/carbon-black/ Accessed on 31 Oct 2017 45. N. Probst, E. Grivei, Structure and electrical properties of carbon black. Carbon 40, 201–205 (2002) 46. M. Ozawa, E. Ōsawa, Carbon blacks as the source materials for carbon nanotechnology. In: “Carbon Nanotechnology”, 2006, L. Dai. (Ed.), Chapt. 6, p. 127-151. Elsevier: Dordrecht 47. http://www.carbonblack.jp/en/cb/tokusei.html. Accessed on 31 Oct 2017 48. S. Lim, X. Faïn, P. Gino, et al., Black carbon variability since preindustrial times in the Eastern part of Europe reconstructed from Mt. Elbrus, Caucasus, icecores. Atmos. Chem. Phys. 17, 3489–3505 (2017) 49. C. Garland, S. Delapena, R. Prasad, C. L’Orange, D. Alexander, M. Johnson, Black carbon cookstove emissions: A field assessment of 19 stove/fuel combinations. Atmos. Environ. 169, 140–149 (2017) 50. A. Guha, B. De Kumar, P. Dha, et al., Seasonal characteristics of aerosol black carbon in relation to long range transport over Tripura in Northeast India. Aerosol Air Qual. Res. 15, 786–798 (2015) 51. W. Min Hao, A. Petkov, B.L. Nordgre, et al., Daily black carbón emissions from fires in northern Eurasia for 2002–2015. Geosci. Model Dev. 9, 4461–4474 (2016) 52. Ö. Gustafssona, V. Ramanathan, Convergence on climate warming by black carbon aerosols. PNAS 113(16), 4243–4245 (2016) 53. V. Ramanathan, G. Carmichael, Global and regional climate changes due to black carbon. Nat. Geosci. 1, 221–227 (2008) 54. O.A. Al-Hartomy, F. Al-Solamy, A. Al-Ghamdi, et al., Volume 2011. Article ID 521985, 8 pp (2011) 55. http://www.asahicarbon.co.jp/global_site/product/cb/characteristic.html. Accessed on 31 Oct 2017 56. G. Datt, C. Kotabage, A.C. Abhyankar, Ferromagnetic resonance of NiCoFe2O4 nanoparticles and microwave absorption properties of flexible NiCoFe2O4–carbon black/poly(vinyl alcohol) composites. Phys. Chem. Chem. Phys. 19, 20699–20712 (2017) 57. Q. Zhang, B.-Y. Zhang, Z.-X. Guo, J. Yu, Tunable electrical conductivity of carbon-black-filled ternary polymer blends by constructing a hierarchical structure. Polymers 9, 404, 11 pp (2017) 58. S.K.H. Gulrez, S. Al-Assaf, G.O. Phillips. Hydrogels: methods of preparation, characterisation and applications. in Progress in Molecular and Environmental Bioengineering. From Analysis and Modeling to Technology Applications. ed. by A. Carpi, ISBN: 978-953-307-268-5 (InTech, London, UK, 2011) 59. L. Zuo, Y. Zhang, L. Zhang, Y.-E. Miao, W. Fan, T. Liu, Polymer/carbon-based hybrid aerogels: Preparation, properties and applications. Materials 8, 6806–6848 (2015) 60. J. Shen, D.Y. Guan, Preparation and application of carbon aerogels, in Aerogels Handbook. Advances in Sol-Gel Derived Materials and Technologies, ed. by M. Aegerter, N. Leventis, M. Koebel, (Springer, New York, 2011) 61. X. Yao, Y. Zhao, Three-dimensional porous graphene networks and hybrids for Lithium-ion batteries and supercapacitors. Chem 2, 171–200 (2017) 62. K.-S. Lin, Y.-J. Mai, S.-W. Chiu, J.-H. Yang, S.L I. Chan. Synthesis and rage. J. Nanomater. 2012, Article ID 201584, 9 pp (2012) 63. K. Kreek, K. Kriis, B. Maaten, et al., Organic and carbon aerogels containing rare-earth metals: Their properties and application as catalysts. J. Non-Cryst. Solids 404, 43–48 (2014) 64. C. Macias, G. Rasines, T.E. García, et al., Synthesis of porous and mechanically compliant carbon aerogels using conductive and structural additives. Gels 2, 4 (2016) 65. B. Xue, M. Qin, J. Wu, et al., Electroresponsive supramolecular graphene oxide hydrogels for active Bacteria adsorption and removal. ACS Appl. Mater. Interfaces 8(24), 15120–15127 (2016) 66. C. Shen, E. Barrios, M. McInnis, J. Zuyus, L. Zhai, Fabrication of graphene aerogels with heavily loaded metallic nanoparticles. Micromachines 8, 47 (2017) 67. Y. Liu, H. Wang, D. Lin, J. Zhao, C. Liu, J. Xie, Y. Cui, A Prussian blue route to nitrogen-doped graphene aerogels as efficient electrocatalysts for oxygen reduction with enhanced active site accessibility. Nano Res. 10(4), 1213–1222 (2017) 68. H. Guo, T. Jiao, Q. Zhang, W. Guo, Q. Peng, X. Ya, Preparation of graphene oxide-based hydrogels as efficient dye adsorbents for wastewater treatment. Nanoscale Res. Lett. 10, 272 (2015) 69. Y. Hu, X. Tong, H. Zhuo, et al., 3D hierarchical porous N-doped carbon aerogel from renewable cellulose: An attractive carbon for highperformance supercapacitor electrodes and CO2 adsorption. RSC Adv. 6, 15788–15795 (2016) 70. M. Yu, Y. Han, J. Li, L. Wang, One-step synthesis of sodium carboxymethyl cellulose-derived carbon aerogel/nickel oxide composites for energy storage. Chem. Eng. J. 324, 287–295 (2017) 71. J. Štefelová, M. Mucha, T. Zelenka, Cellulose acetate-based carbon xerogels and cryogels. WIT Transactions on Engineering Sciences 77., WIT Press, 65–75 (2013) 72. P. Hao, Z. Zhao, J. Tian, et al., Hierarchical porous carbon aerogel derived from bagasse for high performance supercapacitor electrode. Nanoscale 6, 12120–12129 (2014) 73. A. Feaver, S. Sepehri, P. Shamberger, A. Stowe, T. Autrey, G. Cao, Coherent carbon Cryogel-ammonia borane nanocomposites for H2 storage. J. Phys. Chem. B 111, 7469–7472 (2007)

370

5 Other Existing Carbon Forms

74. C. Alegre, D. Sebastián, E. Baquedano, et al., Tailoring Synthesis Conditions of Carbon Xerogels towards Their Utilization as Pt-Catalyst Supports for Oxygen Reduction Reaction (ORR). Catalysts 2, 466–489 (2012) 75. N. Mahata, A.R. Silva, M.F.R. Pereira, C. Freire, B. de Castro, J.L. Figueiredo, Anchoring of a [Mn(salen)Cl] complex onto mesoporous carbon xerogels. J. Colloid Interface Sci. 311, 152–158 (2007) 76. W. Kicinski, M. Szala, M. Nita, Structurally tailored carbon xerogels produced through a sol–gel process in a water–methanol–inorganic salt solution. J. Sol-Gel Sci. Technol. 58, 102–113 (2011) 77. W. Xia, B. Qiu, D. Xia, R. Zou, Facile preparation of hierarchically porous carbons from metal-organic gels and their application in energy storage. Sci. Rep. 3, 1935, 7 pp (2013) 78. E. Kowsari, High-performance supercapacitors based on ionic liquids and a graphene nanostructure, in Ionic Liquids – Current State of the Art, (Intech, London, UK, 2015), pp. 505–542 79. G. Yushin, A. Nikitin, Y. Gogotsi, Carbide-derived carbon, in Nanomaterials Handbook, (Taylor & Francis Group, Boca Raton, 2006) 80. V. Presser, M. Heon, Y. Gogotsi, Carbide-derived carbons – From porous networks to nanotubes and graphene. Adv. Funct. Mater. 21, 810–833 (2011) 81. P. Simon, Y. Gogotsi, Materials for electrochemical capacitors. Nat. Mater. 7(11), 845–854 (2008) 82. V. Presser, L. Zhang, J.J. Niu, J. McDonough, C. Perez, H. Fong, Y. Gogotsi, Flexible Nano-felts of carbide-derived carbon with ultra-high power handling capability. Adv. Energy Mater. 1(3), 423–430 (2011) 83. J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P. Simon, P.L. Taberna, Anomalous Increase in Carbon Capacitance at Pore Sizes of Less Than 1 Nanometer. Science 313(5794), 1760–1763 (2006) 84. S.H. Yeon, P. Reddington, Y. Gogotsi, J.E. Fischer, C. Vakifahmetoglu, P. Colombo, Carbide-derived-carbons with hierarchical porosity from a preceramic polymer. Carbon 48, 201–210 (2010) 85. Y. Gogotsi, Not just graphene – The wonderful world of carbon and related nanomaterials. MRS Bull. 40, 1110–1120 (2015) 86. M. Rose, Y. Korenblit, E. Kockrick, L. Borchard, M. Oschatz, S. Kaskel, G. Yushin, Hierarchical micro-and mesoporous carbide-derived carbon as a high-performance electrode material in supercapacitors. Small 7(8), 1108–1117 (2011) 87. R. Dash, J. Chmiola, G. Yushin, Y. Gogotsi, G. Laudisio, J. Singer, J.E. Fischer, S. Kucheyev, Titanium carbide derived Nanoporous carbon for energy-related applications. Carbon 44(12), 2489–2497 (2006) 88. M. Sevilla, R. Mokaya, Activation of carbide derived carbons: A route to materials with enhanced gas and energy storage properties. J. Mater. Chem. 21, 4727–4732 (2011) 89. E.N. Hoffman, G. Yushin, B.G. Wendler, M.W. Barsouma, Y. Gogotsi, Carbide-derived carbon membrane. Mater. Chem. Phys. 112(2), 587–591 (2008) 90. C. Portet, D. Kazachkin, S. Osswald, Y. Gogotsi, E. Borguet, Impact of synthesis conditions on surface chemistry and structure of carbidederived carbons. Thermochim. Acta 497, 137–142 (2010) 91. B. Krüner, C. Odenwald, A. Tolosa, A. Schreiber, M. Aslan, G. Kickelbick, V. Presser, Carbide-derived carbon beads with tunable nanopores from continuously produced polysilsesquioxanes for supercapacitor electrodes. Sustainable Energy Fuels 1, 1588–1600 (2017) 92. S. Ishikawa, T. Saito, K. Kuwahara, Carbon Materials with Nano-sized Pores Derived from Carbides. Sei Technical Review 82, 152–157 (2016) 93. M.R. Lukatskaya, J. Halim, B. Dyatkin, M. Naguib, Y.S. Buranova, M.W. Barsoum, Y. Gogotsi, Room-temperature carbide-derived carbon synthesis by electrochemical etching of MAX phases. Angew. Chem. 126, 4977–4980 (2014) 94. H.S. Cheng, M.R. Shen, C.L. Mak, P.K. Lim. Liquid phase electrochemical route to carbon nanotubes at room temperature. Proceedings of the 1st IEEE International Conference on Nano/Micro Engineered and Molecular Systems, January 18–21, 2006, Zhuhai, China. pp.484–487 (2006) 95. A. Shawky, S. Yasuda, K. Murakoshi, Room-temperature synthesis of single-wall carbon nanotubes by an electrochemical process. Carbon 50, 4184–4191 (2012) 96. S.K. Mandal, S. Hussain, A.K. Pal, Growth mechanism of carbon nanotubes deposited by electrochemical technique. Ind. J. Pure Appl. Phys. 43, 765–771 (2005) 97. K. Yamagiwa, J. Kuwano, Synthesis of highly aligned carbon nanotubes by one-step liquid-phase process: Effects of carbon sources on morphology of carbon nanotubes. Jap. J. Appl. Phys. 56, 06GE05 (2017) 98. L. Zhang, X. Qina, G. Shaoa, Z. Ma, S. Liu, C. He, A new route for preparation of titanium carbide derived carbon and its performance for supercapacitors. Mater. Lett. 122, 78–81 (2014) 99. A.H. Farmahini, D.S. Sholl, S.K. Bhatia, Fluorinated carbide-derived carbon: More hydrophilic, yet apparently more hydrophobic. J. Am. Chem. Soc. 137(18), 5969–5979 (2015) 100. B. Li, H.-M. Wen, W. Zhou, J.Q. Xu, B. Chen, Porous metal-organic frameworks: Promising materials for methane storage. Chem 1, 557–580 (2016) 101. S.K. Bhatia, T.X. Nguyen, Potential of silicon carbide-derived carbon for carbon capture. Ind. Eng. Chem. Res. 50, 10380–10383 (2011) 102. Z. Zondaka, R. Valner, A. Aabloo, T. Tamm, R. Kiefer, Embedded carbide-derived carbon particles in polypyrrole for linear actuator. Proc. SPIE 9798, 97981H-7 (2016) 103. W. Xing, C. Liu, Z. Zhou, J. Zhou, G. Wang, S. Zhuo, et al., Oxygen-containing functional group-facilitated CO2 capture by carbide-derived carbons. Nanoscale Res. Lett. 9, 189 (2014) 104. L. Borchardt, F. Hasche, M.R. Lohe, et al., Transition metal loaded silicon carbide-derived carbons with enhanced catalytic properties. Carbon 50, 1861–1870 (2012) 105. J. Gläsel, J. Diao, Z. Feng, M. Hilgart, T. Wolker, D. Sheng Su, B.J.M. Etzold, Mesoporous and graphitic carbide-derived carbons as selective and stable catalysts for the dehydrogenation reaction. Chem. Mater. 27, 5719–5725 (2015) 106. J. Tae Lee, H. Kim, M. Oschatz, D.-C. Lee, F. Wu, H.-T. Lin, et al., Micro- and mesoporous carbide-derived carbon–selenium cathodes for high-performance lithium selenium batteries. Adv. Energy Mater. 5, 1400981 (2014) 107. W. Nickel, M. Oschatz, M. von der Lehr, M. Leistner, et al., Direct synthesis of carbide-derived carbon monoliths with hierarchical pore design by hardtemplating. J. Mater. Chem. A 2, 12703 (2014)

References

371

108. P.-C. Gao, W.-Y. Tsai, B. Daffos, P.-L. Taberna, C.R. Pérez, Y. Gogotsi, P. Simon, F.G. Favier, Carbide derived carbon for high-power supercapacitors. Nano Energy 12, 197–206 (2015) 109. H. Wang, Q.-L. Zhu, R. Zou, Q. Xu, Metal-organic frameworks for energy applications. Chem 2, 52–80 (2017) 110. K. Shen, X. Chen, J. Chen, Y. Li, Development of MOF-derived carbon-based nanomaterials for efficient catalysis. ACS Catal. 6(9), 5887–5903 (2016) 111. Q. Ren, H. Wang, X.-F. Lu, Y.-X. Tong, G.-R. Li, Recent Progress on MOF-derived heteroatom-doped carbon-based Electrocatalysts for oxygen reduction reaction. Adv. Sci. 5(3), 1700515 (2018) 112. L. Lux, K. Williams, S. Ma, Heat-treatment of metal–organic frameworks for green energy applications. CrystEngComm 17, 10–22 (2015) 113. A. Dhakshinamoorthy, H. Garcia, Catalysis by metal nanoparticles embedded on metal–organic frameworks. Chem. Soc. Rev. 41, 5262–5284 (2012) 114. P. Silva, S.M.F. Vilela, J.P.C. Tome, F.A. Almeida Paz, Multifunctional metal–organic frameworks: From academia to industrial applications. Chem. Soc. Rev. 44, 6774–6803 (2015) 115. B. Liu, H. Shioyama, H. Jiang, X. Zhang, Q. Xu, Metal–organic framework (MOF) as a template for syntheses of nanoporous carbons as electrode materials for supercapacitor. Carbon 48, 456–463 (2010) 116. M. Yang, X. Hu, Z. Fang, et al., Bifunctional MOF-derived carbon photonic crystal architectures for advanced Zn–air and li–S batteries: Highly exposed graphitic nitrogen matters. Adv. Funct. Mater. 27(36), 1701971 (2017) 117. X. Li, J. Zhang, Y. Han, M. Zhu, S. Shang, W. Li, MOF-derived various morphologies of N-doped carbon composites for acetylene hydrochlorination. J. Mater. Sci. 7 (2018). https://doi.org/10.1007/s10853-017-1951-3 118. B. Chen, G. Ma, D. Kong, Y. Zhu, Y. Xia, Atomically homogeneous dispersed ZnO/N-doped nanoporous carbon composites with enhanced CO2 uptake capacities and high efficient organic pollutants removal from water. Carbon 95, 113–124 (2015) 119. W. Zhang, Z.-Y. Wu, H.-L. Jiang, S.-H. Yu, Nanowire-directed templating synthesis of metalorganic framework nanofibers and their derived porous doped carbon nanofibers for enhanced Electrocatalysis. J. Am. Chem. Soc. 136, 14385–14388 (2014) 120. H.-L. Jiang, B. Liu, Y.-Q. Lan, et al., From metal-organic framework to Nanoporous carbon: Toward a very high surface area and hydrogen uptake. J. Am. Chem. Soc. 133(31), 11854–11857 (2011) 121. B. Ding, J. Wang, Z. Chang, G. Xu, et al., Self-sacrificial template-directed synthesis of metal–organic framework-derived porous carbon for energy-storage devices. Chem. Electro. Chem. 3(4), 668–674 (2016) 122. R. Chen, T. Zhao, T. Tian, et al., Graphene-wrapped sulfur/metal organic framework-derived microporous carbon composite for lithium sulfur batteries. APL Materials 2, 124109 (2014) 123. H. Bin Wu, S. Wei, L. Zhang et al. Embedding Sulfur in MOF-Derived Microporous Carbon Polyhedrons for Lithium–Sulfur Batteries. Chemistry, a Eur. J., 2013, 9(33), 10804–10808 124. A. Banerjee, K.K. Upadhyay, et al., MOF-derived crumpled-sheet-assembled perforated carbon cuboids as highly effective cathode active materials for ultra-high energy density li-ion hybrid electrochemical capacitors (li-HECs). Nanoscale 6(8), 4387–4394 (2014) 125. T. Segakwenga, N.M. Musyoka, J. Ren, et al., Comparison of MOF-5 and MIL-101 derived carbons for hydrogen storage application. Res. Chem. Intermed. 42, 4951 (2015). https://doi.org/10.1007/s11164-015-2338-1 126. A. Li, Y. Tong, B. Cao, H. Song, et al. MOF-derived multifractal porous carbon with ultrahigh lithium-ion storage performance. Scientific Rep. 7, Article number: 40574 (2017) 127. H. Li, L. Chi, C. Yang, L. Zhang, et al., MOF derived porous Co@C hexagonal-shaped prisms with high catalytic performance. J. Mater. Res. 31(19), 3069–3077 (2016) 128. S. Hoon Ahn, A. Manthiram, Self-templated synthesis of co- and N-doped carbon microtubes composed of hollow Nanospheres and nanotubes for efficient oxygen reduction reaction. Small 13(11), 1603437 (2017) 129. Y.-X. Zhou, Y.-Z. Chen, L. Cao, et al., Conversion of a metal–organic framework to N-doped porous carbon incorporating co and CoO nanoparticles: Direct oxidation of alcohols to esters. Chem. Commun. 51, 8292–8295 (2015) 130. K.-Y.A. Lin, H.-A. Chang, B.-J. Chen, Multi-functional MOF-derived magnetic carbon sponge. J. Mater. Chem. A 4, 13611–13625 (2016) 131. N.L. Torad, M. Hu, S. Ishihara, et al., Direct synthesis of MOF-derived nanoporous carbon with magnetic co nanoparticles toward efficient water treatment. Small 10(10), 2096–2107 (2014) 132. X. Liu, X. Quan, Fe-MOF derived ferrous hierarchically porous carbon used as EF cathode for PFOA degradation. Journal of Geoscience and Environment Protection 5(6), 9–14 (2017) 133. E.C. Walter, T. Beetz, M.Y. Sfeir, L.E. Brus, M.L. Steigerwald, Crystalline graphite from an organometallic solution-phase reaction. J. Am. Chem. Soc. 128(49), 15590–15591 (2006) 134. W. Sisi, Z. Yinggang, H. Yifeng, et al., Bimetallic organic frameworks derived CuNi/carbon nanocomposites as efficient electrocatalysts for oxygen reduction reaction. Sci. China Mater. 60(7), 654–663 (2017) 135. D.Z. Chen, C.Q. Chen, W.S. Shen, et al., MOF-derived magnetic porous carbon-based sorbent: Synthesis, characterization, and adsorption behavior of organic micropollutants. Adv. Powder Technol. 28(7), 1769–1779 (2017) 136. S. Hoon Ahn, M.J. Klein, A. Manthiram, 1D co- and N-doped hierarchically porous carbon nanotubes derived from bimetallic metal organic framework for efficient oxygen and tri-iodide reduction reactions. Adv. Energy Mater. 7(7), 1601979 (2017) 137. Q. Gan, K. Zhao, S. Liu, Z. He, MOF-derived carbon coating on self-supported ZnCo2O4–ZnO nanorod arrays as high-performance anode for lithium-ion batteries. J. Mater. Sci. 52(13), 7768–7780 (2017) 138. Z. Li, L. Yin, MOF-derived, N-doped, hierarchically porous carbon sponges as immobilizers to confine selenium as cathodes for li–se batteries with superior storage capacity and perfect cycling stability. Nanoscale 7, 9597–9606 (2015) 139. W. Chaikittisilp, K. Ariga, Y. Yamauchi, A new family of carbon materials: Synthesis of MOF-derived nanoporous carbons and their promising applications. J. Mater. Chem. A 1, 14–19 (2013) 140. M. Hui Yap, K. Loon Fow, G. Zheng Chen, Synthesis and applications of MOF-derived porous nanostructures. Green Energy Environ. 2(3), 218–245 (2017) 141. S. Fardindoost, S. Hatamie, A. Iraji Zad, F. Razi Astaraei, Hydrogen sensing properties of nanocomposite graphene oxide/co-based metal organic frameworks (co-MOFs@GO). Nanotechnology 29, 015501 (2018). (7 pp)

372

5 Other Existing Carbon Forms

142. G. Cai, W. Zhang, L. Jiao, S.-H. Yu, H.-L. Jiang, Template-directed growth of well-aligned MOF arrays and derived self-supporting electrodes for water splitting. Chem 2(6), 791–802 (2017) 143. T. Nagy, L. Yunq, I. Shinsuke, et al., MOF-derived nanoporous carbon as intracellular drug delivery carriers. Chem. Lett. 43(5), 717–719 (2014) 144. L. Xiao, R. Xu, Q. Yuan, F. Wang, Highly sensitive electrochemical sensor for chloramphenicol based on MOF derived exfoliated porous carbon. Talanta 167, 39–43 (2017) 145. W. Li, S. Hu, X. Luo, et al., Confined amorphous red phosphorus in MOF-derived N-doped microporous carbon as a superior anode for sodium-ion battery. Adv. Mater. 29(16), 1605820 (2017) 146. S. Pandiaraj, H.B. Aiyappa, R. Banerjee, S. Kurungot, Post modification of MOF derived carbon via g-C3N4 entrapment for an efficient metalfree oxygen reduction reaction. Chem. Commun. 50, 3363–3366 (2014) 147. Shock compression research shows hexagonal diamond could serve as meteor impact marker. https://www.llnl.gov/news/shock-compressionresearch-shows-hexagonal-diamond-could-serve-meteor-impact-marker. Accessed on 2 Nov 2017 148. A.G. Kvashnin, P.B. Sorokin, Lonsdaleite films with nanometer thickness. J. Phys. Chem. Lett. 5, 541–548 (2014) 149. http://aflowlib.duke.edu/users/egossett/lattice/struk.picts/hexdia.s.png. Accessed on 2 Nov2017 150. Structure of the Diamond-lonsdaleite System. http://www.imaging-git.com/science/electron-and-ion-microscopy/structure-diamondlonsdaleite-system. Accessed on 2 Nov 2017 151. P. Nemeth, L.A.J. Garvie, T. Aoki, N. Dubrovinskaia, L. Dubrovinsky, P.R. Buseck, Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material. Nat. Commun. 5, 5447, 5 pp (2014) 152. L. Qingkun, S. Yi, L. Zhiyuan, Z. Yu, Lonsdaleite – A material stronger and stiffer than diamond. Scr. Mater. 65, 229–232 (2011) 153. D. Kraus, A. Ravasio, M. Gauthier, D.O. Gericke, et al., Nanosecond formation of diamond and lonsdaleite by shock compression of graphite. Nat. Commun. 7, 10970, 6 pp (2016) 154. B. Kulnitskiy, I. Perezhogin, G. Dubitskya, V. Blank, Polytypes and twins in the diamond–lonsdaleite system formed by high-pressure and high-temperature treatment of graphite. Acta Cryst B69, 474–479 (2013) 155. Y. Nakamuta, S. Toh, Transformation of graphite to lonsdaleite and diamond in the Goalpara ureilite directly observed by TEM. Am. Mineral. 98(4), 574–581 (2015) 156. S.V. Goryainov, A.Y. Likhacheva, S.V. Rashchenko, A.S. Shubin, V.P. Afanas’eva, N.P. Pokhilenko, Raman identification of lonsdaleite in Popigai impactites. J. Raman Spectrosc. 45, 305–313 (2014) 157. B. Qu, B. Zhang, L. Wang, R. Zhou, X. Cheng Zeng, L. Li, Persistent luminescence hole-type materials by design: Transition-metal-doped carbon allotrope and carbides. ACS Appl. Mater. Interfaces 8(8), 5439–5444 (2016) 158. A. Milani, M. Tommasini, V. Russo, et al., Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires. Beilstein J. Nanotechnol. 6, 480–491 (2015) 159. V.V. Sobolev, V.Y. Slobodskoy, S.N. Selyukov, A.A. Udoyev, Some conversions of chaoite to other carbon phases. Int. Geol. Rev. 28(6), 680–683 (1986) 160. J. Pola, A. Ouchi, S. Bakardjieva, et al., Laser photochemical etching of silica: Nanodomains of crystalline chaoite and silica in amorphous C/Si/O/N phase. J. Phys. Chem. C 112(34), 13281–13286 (2008) 161. A. Tembre, J. Henocque, M. Clin. Infrared and Raman spectroscopic study of carbon-cobalt composites. Int. J. Spectrosc. 2011, Article ID 186471, 6 pp (2011) 162. S.K. Simakov, A.E. Kalmykov, L.M. Sorokin, et al., Chaoite formation from carbon-bearing fluid at low PT parameters. Dokl. Earth Sci. 399A (9), 1289–1290 (2004) 163. S. Li, Z. Huang, et al., Ferromagnetic chaoite macrotubes prepared at low temperature and pressure. Appl. Phys. Lett. 90, 232507 (2007) 164. S. Li, G. Ji, Z. Huang, F. Zhang, Y. Du, Synthesis of chaoite-like macrotubes at low temperature and ambient pressure. Carbon 45, 2946–2950 (2007) 165. Q. Peng, A.K. Dearden, J. Crean, et al., New materials graphyne, graphdiyne, graphone, and graphane: Review of properties, synthesis, and application in nanotechnology. Nanotechnol. Sci. Appl. 7, 1–29 (2014) 166. J.O. Sofo, A.S. Chaudhari, G.D. Barber, Graphane: A two-dimensional hydrocarbon. Phys. Rev. B 75, 153401 (2007) 167. D.C. Elias, R.R. Nair, T.M.G. Mohiuddin, S.V. Morozov, P. Blake, M.P. Halsall, A.C. Ferrari, D.W. Boukhvalov, M.I. Katsnelson, A.K. Geim, K.S. Novoselov, Control of Graphene’s properties by reversible hydrogenation: Evidence for Graphane. Science 323(5914), 610–613 (2009) 168. H. Sahin, O. Leenaerts, S.K. Singh, F.M. Peeters. GraphAne: From synthesis to applications. arXiv:1502.05804 [cond-mat.mtrl-sci], (2015) 169. H. Zhang, Y. Miyamoto, A. Rubio. Laser-induced preferential dehydrogenation of graphane. Phys. Rev. B. 85, 201409(R) (2012) 170. C. Zhou, S. Chen, J. Lou, J. Wang, et al., Graphene’s cousin: The present and future of graphene. Nanoscale Res. Lett. 9, 26 (2014) 171. H. Sahin, O. Leenaerts, S.K. Singh, F.M. Peeters, Graphane. WIREs Comput. Mol. Sci. 5, 255–272 (2015) 172. A. Bhattacharya, S. Bhattacharya, C. Majumder, G.P. Das. Third conformer of graphane: A first-principles density functional theory study. Phys. Rev. B. 83, Article ID 033404 (2011) 173. H. Einollahzadeh, S. Mahdi Fazeli, R. Sabet Dariani, Studying the electronic and phononic structure of penta-graphane. Sci. Technol. Adv. Mater. 17(1), 610–617 (2016) 174. D. Haberer, C.E. Guusca, Y. Wang, et al., Evidence for a new two-dimensional C4H-type polymer based on hydrogenated graphene. Adv. Mater. 23, 4497–4503 (2011) 175. V.E. Antonov, I.O. Bashkin, A.V. Bazhenov, et al., Multilayer graphane synthesized under high hydrogen pressure. Carbon 100, 465–473 (2016) 176. H. Peelaers, A.D. Hernández-Nieves, O. Leenaerts, B. Partoens, F.M. Peeters, Vibrational properties of graphene fluoride and graphene. Appl. Phys. Lett. 98, 051914 (2011) 177. M. Pumera, Z. Sofer, Towards stoichiometric analogues of graphene: Graphane, fluorographene, graphol, graphene acid and others. Chem. Soc. Rev. 46, 4450–4463 (2017)

References

373

178. B.-R. Wu, C.-K. Yang, Electronic structures of graphane with vacancies and graphene adsorbed with fluorine atoms. AIP Adv. 2, 012173 (2012) 179. M.Z.S. Flores, P.A.S. Autreto, S.B. Legoas, D.S. Galvao, Graphene to graphane: A theoretical study. Nanotechnology 20, 465704, 6 pp (2009) 180. W. Liu, F.-H. Meng, J.-H. Zhao, X.-H. Jiang, A first-principles study on the electronic transport properties of zigzag graphane/graphene nanoribbons. J. Theor. Comput. Chem. 16(4), 1750032, 12 pp (2017) 181. J.-H. Lee, J.C. Grossman, Magnetic properties in graphene-graphane superlattices. Appl. Phys. Lett. 97, 133102 (2010) 182. A.S. Barnarda, I.K. Snook, Size- and shape-dependence of the graphene to graphane transformation in the absence of hydrogen. J. Mater. Chem. 20, 10459–10464 (2010) 183. T. Hussain, P. Panigrahi, R. Ahuja, Sensing propensity of a defected graphane sheet towards CO, H2O and NO2. Nanotechnology 25(32), 325501 (2014) 184. J. Xiao, S. Sitamraju, M.J. Janik, CO2 adsorption thermodynamics over N-substituted/grafted Graphanes: A DFT study. Langmuir 30(7), 1837–1844 (2014) 185. T. Hussain, P. Panigrahi, R. Ahuja, Enriching physisorption of H2S and NH3 gases on a graphane sheet by doping with li adatoms. Phys. Chem. Chem. Phys. 16(17), 8100–8105 (2014) 186. E. Ventura-Macias, J. Guerrero-Sánchez, N. Takeuchi, Formaldehyde adsorption on graphane. Computational and Theoretical Chemistry 1117, 119–123 (2017) 187. T. Hussain, B. Pathak, M. Ramzan, T.A. Maark, R. Ahuja, Calcium doped graphane as a hydrogen storage material. Appl. Phys. Lett. 100, 183902 (2012) 188. S.C. Ray, N. Soin, T. Makgato, et al., Graphene supported Graphone/Graphane bilayer nanostructure material for Spintronics. Sci. Reports 4, 3862 (2014) 189. W. Zhao, J. Gebhardt, F. Spath, et al., Reversible hydrogenation of graphene on Ni(111)—Synthesis of “Graphone”. Chem. Eur. J. 21, 3347–3358 (2015) 190. L. Feng, W.X. Zhang, The structure and magnetism of graphone. AIP Adv. 2, 042138 (2012) 191. Q. Peng, A.K. Dearden, X.-J. Chen, et al., Peculiar pressure effect on Poisson ratio of graphone as a strain damper. Nanoscale 7, 9975–9979 (2015) 192. M. Neek-Amal, J. Beheshtian, F. Shayeganfar, S.K. Singh, J.H. Los, F.M. Peeters, Spiral graphone and one-sided fluorographene nanoribbons. Phys. Rev. B 87, 075448 (2013) 193. A.I. Podlivaev, L.A. Openov, On the thermal stability of Graphone. Semiconductors 45(7), 958–961 (2011) 194. D.W. Boukhvalov, Stable antiferromagneticgraphone. Physica E43, 199–201 (2010) 195. Q. Li, Y. Ma, A.R. Oganov, et al., Superhard monoclinic polymorph of carbon. Phys. Rev. Lett. 102, 175506 (2009) 196. M.J. Xing, B.H. Li, Z.T. Yu, Q. Chen, Monoclinic C2/m-20 carbon: a novel superhard sp3 carbon allotrope. RSC Adv. 6, 32740–32745 (2016) 197. M. Amsler, J.A. Flores-Livas, M.A.L. Marques, S. Botti, S. Goedecker, Prediction of a novel monoclinic carbon allotrope. The European Physical Journal B 86, 383 (2013) 198. J. Narayan, A. Bhaumik, Novel phase of carbon, ferromagnetism, and conversion into diamond. J. Appl. Phys. 118, 215303 (2015) 199. J. Narayan, A. Bhaumik, Q-carbon discovery and formation of single-crystal diamond nano- and microneedles and thin films. Mater. Res. Lett. 4(2), 118–126 (2016) 200. J. Pandey, R. Khare, S. Khare, Q-carbon: A new, inexpensive and affordable diamond in Everyones hand. International Journal for Research in Applied Science & Engineering 5(V), 89–91 (2017) 201. https://www.nextbigfuture.com/2011/04/t-carbon-novel-carbon-allotrope.html. Accessed on 26 Nov 2017 202. X.-L. Sheng, Q.-B. Yan, F. Ye, Q.-R. Zheng, G.S. T-Carbon, A novel carbon allotrope. Phys. Rev. Lett. 106, 155703 (2011) 203. J. Zhang, R. Wang, X. Zhu, et al. Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol. Nat. Commun. 8, Article number 683 (2017) 204. D. Li, F. Tian, D. Duan, Z. Zhao, et al., Modulated T carbon-like carbon allotropes: An ab initio study. RSC Adv. 4, 17364–17369 (2014) 205. J.Q. Wang, C.X. Zhao, C.Y. Niu, Q. Sun, Y. Jia, C20-T carbon: A novel superhard sp3 carbon allotrope with large cavities. J. Phys. Condens. Matter 28(47), 475402 (2016) 206. Aegerter, Michel A., Leventis, Nicholas, Koebel, Matthias M. (Eds.), Aerogels Handbook. Advances in Sol-Gel Derived Materials and Technologies. (Springer, New York, 2011)

Chapter 6

Predicted Carbon Forms

As it has been shown above, a grand variety of carbon allotropes and forms is currently known. They can be very common (graphite, coal) or rare (nanoplates or nanocups) and can be well-developed industrially (carbon black) or intensively studied on nano-level (carbon nanotubes or graphene), doped with metals and functionalized with organic and organometallic moieties. At the same time, applying modern computational methods, a host of new carbon nanoforms (e.g., novamene [1] or protomene [2]) are possible, which have not yet been observed experimentally. An efficient and reliable methodology for crystal structure prediction was developed [3], merging ab initio total energy calculations and a specifically devised evolutionary algorithm. This method allows one to predict the most stable crystal structure and a number of low-energy metastable structures for a given compound at any P-T conditions without requiring any experimental input. While in many cases it is possible to solve crystal structure from experimental data, theoretical structure prediction is crucially important for several reasons. 1. 2. 3.

When experimental data are of poor quality for structure solution (defective or small samples, especially at high pressures and temperatures), theory provides the last resort. Theory is the only way of investigating matter at conditions that cannot be studied with today’s experimental techniques, e.g., at ultrahigh pressures. The ability to predict crystal structures will open up new ways of materials design.

Several carbon allotropes have been predicted, in particular M-carbon [4], F-carbon [5], orthorhombic W-carbon [6], Z-carbon [7], H-carbon and S-carbon [8], Imma-carbon [9], M585-carbon [10], T12-carbon [11], C2/m-16 carbon [12], P2221-carbon [13], Cco-carbon [14], and so on. But only Z-carbon-1, Z-carbon-2, Z-carbon-3, Z-carbon-7, and Z-carbon-10 are potential superhard materials (Fig. 6.1), unlike Z-carbon-5 and Z-carbon-6 which have a hardness of 34.1 GPa and 34.2 GPa, respectively. In this section, we present several representative predicted carbon allotropes.

© Springer Nature Switzerland AG 2019 B. I. Kharisov, O. V. Kharissova, Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications, https://doi.org/10.1007/978-3-030-03505-1_6

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Fig. 6.1 The newly predicted superhard structures of carbon: (a) P2221, (b) Imma, (c) C2/m-16, (d) Cm-32, (e) P21/m, (f) Cm-40, (g) C2/m-20, (h) C2/m-28, (i) Amm2, and (j) I-4, respectively. The circled atoms in (j) are the wrinkled 5 + 6 + 8 member rings, as shown in (k). The dished lines in (b) and (c) indicate the wrinkled six member rings [15]. (Reproduced with permission of the AIP Publishing Co.)

6.1

Graphyne

Graphyne [16] is a theorized allotrope of carbon, whose existence was conjectured before 1960 and confirmed by DFT calculations. It has not yet been synthesized in large quantities, although research is continuing, and will be needed to provide experimental data against which to test the computational predictions as well as to clarify some discrepancies regarding mechanical properties. Graphyne was first proposed in 1987 by Baughman et al. as part of a larger investigation into the properties of new forms of carbon that had been sporadically reported, but not systematically investigated. Graphyne is a variation of graphene that has acetylenic linkages connecting the hexagons of graphene. The proposed structures of graphyne are derived from insertion of acetylene bonds in place of C-C single bonds in a graphene lattice (simply replacing one-third of the C-C bonds in graphene by triple-bonded -C
C- linkages, Fig. 6.2).

6.1 Graphyne

377

Fig. 6.2 Examples of carbon allotrope materials, from graphene to graphyne and other carbon allotropes [17]. (Reproduced with permission of Nature)

Aromatic bonds C

C

180oC Triple bonds

Single bonds C

120oC

C

C

C

C

C

C

b a Fig. 6.3 Graphyne cells with (a) different interatomic bonds and (b) bond angles. (Reproduced with permission of Hindawi. Reproduced from: Journal of Nanomaterials, 2016, Volume 2016, Article ID 7487049, 15 pp.)

Main features of graphyne are as follows: – It can be considered as a lattice of benzene rings connected by triple bonds. Bonding in graphyne cell is shown in Fig. 6.3. – It is similar to graphene, since it is also a 2D structure of carbon. – There are many types of graphynes – as their 2D framework contains triple bonds and not just double bonds as in graphene. According to [18], seven basic structural modifications of graphyne can theorically exist: α-, β1-, β2-, β3-, γ1-, γ2-, and γ3graphyne.

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Fig. 6.4 Graphyne, graphdiyne, graphyne-3, graphyne-4, and graphyne-5

– γ-Graphynes should be the most stable structural modifications of graphyne. – Mixed hybridization spn (1 < n < 2), in a difference with graphene (sp2) or diamond (sp3). – The presence of sp- and sp2-hybridized carbon atoms in graphyne causes distinct properties, including large surface area, chemical stability, and electrical conductivity, in addition to the remarkable properties of graphene. – It can exist in several different geometries, including a hexagonal lattice structure and a rectangular lattice structure. – Graphyne-like BN sheets can also exist [19]. Graphyne, graphdiyne, graphyne-3, graphyne-4, and graphyne-5 (Fig. 6.4) are allotropes of carbon, all belonging to a family called graphyne-N. These structures are planar sheets of sp and sp2 bonds of carbon atoms arranged in a crystal lattice. The main difference between these types of graphyne is the number of acetylenic links existing between the hexagonal lattices of carbon atoms (Fig. 6.5). Graphyne-N has 33% of the C-C bonds of graphene replaced by one acetylenic unit. Although having a fixed amount of C-C bonds, there are several structures of graphyne. The most known are α-, β-, γ-, and R-graphyne and 6,6,12-graphyne (Fig. 6.6). Four other 2D p-metallic carbon allotropes, it is also known about possible existence of hexagonal ones (C65-, C63-, and C31-sheets) and one tetragonal one (C41-sheet) [20]. The C65-, C63-, and C41-sheets are more stable, and the C31-sheet is slightly less stable than graphyne. Graphdiyne (it is part of the graphyne family; however, due to its interesting properties, it is typically considered separately) is a variant of graphyne that contains two acetylenic linkages in each unit cell rather than the one linkage as in graphyne. As a result, graphdiyne does not share graphyne’s exceptional mechanical properties. Graphdiyne is a softer material than either graphyne or graphene, with an in plane stiffness of 120 N/m, which is equivalent to a Young’s modulus of 375 GPa, if a thickness of 0.320 nm is assumed. Graphdiyne was first predicted by Haley et al. in 1997. Main features of graphdiyne are as follows: – It was synthesized on Cu and Ag surfaces. – It exhibits a nanoweb-like structure characterized by triangular and regularly distributed pores, which form a nanoporous membrane. A 2D carbon allotrope, rectangular graphyne (R-graphyne, Figs. 6.6, 6.7, and 6.8) with tetra-rings and acetylenic linkages, was proposed [22] by first-principles calculations, showing that it is metallic as the valence band crosses the Fermi level. Among other results, the most intriguing feature is that bandgaps of R-graphyne nanoribbons oscillate between semiconductor

Fig. 6.5 Types of acetylenic links. (Reproduced with permission of Hindawi. Reproduced from: Journal of Nanomaterials, 2016, Volume 2016, Article ID 7487049, 15 pp.)

Fig. 6.6 α-, β-, γ-, and R-graphyne and 6,6,12-graphyne [21]. (Reproduced with permission of Springer)

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Fig. 6.7 The configurations of R-graphyne nanoribbons obtained by cutting through an infinite R-graphyne along two directions. (a) Armchair nanoribbons of R-graphyne with widths NA ¼ 1, 2 and 5, where NA denotes the number of chains of tetra carbon rings. (b) Zigzag edged R-graphyne nanoribbons with widths NZ ¼ 1, 1.5, and 3.5 expressed by NZ. The black and white balls represent carbon and hydrogen atoms, respectively. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 6.8 The electronic structures and charge-density distribution of R-graphyne nanoribbons. (a) Amplification of the band structure(I) and DOS (II) around the meeting point for NZ ¼ 2.5. The charge-density distribution near EF for armchair R-graphyne nanoribbons (NZ ¼ 3). (b) The maximum point at valence band (c)/(e) and the minimum point at conduction band (d)/(f) for NZ ¼ 2.5/NZ ¼ 3. The black balls represent carbon atoms. (Reproduced with permission of the Royal Society of Chemistry)

and metallic states as a function of width. Particularly, the zigzag edge nanoribbons with half-integer repeating unit cell exhibit unexpected Dirac-like fermions in the band structures. Certain attention is paid to graphyne scrolls and ribbons, since graphyne could exist not only in the plane form but also in scroll-like structure. Thus, the formation of graphyne and graphdiyne nanoscrolls, structures obtained by rolling up graphyne

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381

sheets into papyrus-like structures, was calculated [23] for a series of graphyne (α-, β-, and δ-types) structures, as well as their thermal stability for a temperature range of 200–1000 K. Their stability was found to be dependent on a critical value of the ratio between length and height of the graphyne sheets. Additionally, these structures are structurally less stable then graphene-based nanoscrolls, which were explained by the graphyne higher structural porosity which results in a decreased π-π-stacking interactions. The intrinsic electronic and transport properties of four distinct polymorphs of graphyne (α-, β-, γ-, and 6,6,12-graphynes) and their nanoribbons (GyNRs) were studied using DFT coupled with the non-equilibrium Green’s function (NEGF) method [24]. Their nanoribbons possess many electronic, magnetic, and transport properties that are notably different from those of known graphene and BN nanoribbons. Among the four graphyne sheets, 6,6,12graphyne displayed notable directional anisotropy in the transport properties. In a related report [25], it was shown that all graphyne and graphdiyne nanoribbons with armchair and zigzag edges are semiconductors (with bandgaps of 0.59–1.25 eV armchair, 0.75–1.32 eV zigzag for graphyne nanoribbons, and of 0.54–0.97 eV armchair, 0.73–1.65 eV zigzag for graphdiyne nanoribbons) with suitable bandgaps similar to silicon and their bandgaps decrease as widths of nanoribbons increase. Several other properties of graphynes have also been DFT-calculated. Thus, the mechanical properties of graphyne sheets were evaluated by full atomistic first-principles-based ReaxFF molecular dynamics [26]. It was established that, unlike graphene, (a) the fracture strain and stress of graphyne depends strongly on the direction of the applied strain and the alignment with carbon triple-bond linkages, ranging from 48.2 to 107.5 GPa with ultimate strains of 8.2–13.2%; (b) the sparser carbon arrangement in graphyne combined with the directional dependence on the acetylenic groups results in internal stiffening dependent on the direction of applied loading, leading to a nonlinear stress–strain behavior. In case of metaldecorated graphyne, the mechanical properties of Na- and Pt-decorated arrays of graphyne sheet were DFT-investigated [27]. The proposed structures were consisted of Na- and Pt-decorated graphyne sheet (CC), analogous system of boron nitride sheet (BN-yne), and graphyne-like BN sheet (CC-BN-yne). The largest value was presented by CC, which was higher than that of obtained from non-decorated systems. The elastic properties of graphyne (Young’s modulus, Poisson’s ratio, bulk modulus, and shear modulus) were established [28], and an analytical molecular mechanics model was proposed for relating the elastic properties of graphynes to their atomic structures directly [29]. Thermal conductance of β-graphyne is only approximately 26% of that of the graphene counterpart and also shows evident anisotropy [30]. Various forms of graphynes have been studied in respect of their interaction with metal and nonmetal surfaces, in particular possible formation of graphyne (α-, β-, and γ-phases) on transition-metal surfaces (Ru(0001), Rh(111), and Pd(111), Fig. 6.9) [31]. The interlayer binding between graphynes and the metal substrates was found to reduce the formation energies of graphynes by 0.16–0.34 eV, such that the growth of graphynes is competitive to that of graphene on the metal surfaces. The α-phase of graphyne is thermodynamically most favorable in the carbon-poor environment, while formation of graphene is dominant in the carbon-rich condition. Similar studies, related more with carbyne than graphyne, on the electronic and geometric structures of carbyne on transition-metal surfaces were also investigated by theoretical calculations [32]. It was found that carbyne on non-active metal surfaces (Cu) has a polyynic structure, while a polycumulenic structure is more stable on active catalyst surfaces (Ni, Rh, Ru) (Figs. 6.10 and 6.11). Carbyne with a size of N < 10–13 is predicted to be the ground state of carbon clusters on various transition-metal surfaces. Beyond the critical size of 10–12, the carbyne structure becomes

Fig. 6.9 Simulated STM images of α-graphyne on (a) Ru(0001), (b) Rh(111), and (c) Pd(111), respectively, using a bias voltage of 2 V. The top views of the atomic structures of α-GY on the three metal substrates are shown below each STM image. The C, Ru, Rh, and Pd atoms are indicated in silver, blue, green, and wine, respectively. The yellow balls indicate the C atoms, which are buckled up in the out-of-plane direction and hence show larger brightness in the STM images. (Reproduced with permission of the American Chemical Society)

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6 Predicted Carbon Forms

Fig. 6.10 The polyynic carbyne formation with alternative single and triple bonds (–C
C–)n (a) and the polycumulenic carbyne with double bonding (¼C¼C¼)n (b); the electron densities of polyynic carbyne (c) and polycumulenic carbyne (d); the formation of a carbon chain with 8 carbon atoms on the Cu(111) surface (e) and Ru(0001) (f) surfaces and their corresponding electron densities (g, h). (Reproduced with permission of the Royal Society of Chemistry)

less stable than the sp2 carbon network. The polyynic carbyne tends to be curved up on the less active metal surface, while polycumulenic carbyne prefers to be formed in a straight line on the active metal surface. The self-assembly of carbyne on a metal substrate could lead to the synthesis of graphyne (Fig. 6.12). In addition, atomic, electronic, and quantum transport properties of γ-graphyne absorbed on the silicon (111) surface were investigated from atomistic first principles [33]. The most interesting result is that the transmission spectra of the γ-graphyne/Si(111) hybrid device has a high broad peak at the Fermi level due to a combination of states on γ-graphyne/Si(111), and this peak persists even for the trenched γ-graphyne/Si(111) systems where the Si is removed underneath the γ-graphyne in the scattering region. Although graphyne has yet to be synthesized well, its properties are promising for several applications, such as nanofillers, transistors, sensors for inorganic and organic substances, semiconductor metal hybrids, anisotropic conductors, and desalinators, among others. Thus, a nanoscale capacitor composed of heterostructures derived from finite size graphyne flake and graphene (nitride) flake (graphyne/graphene, graphyne/h-BN, graphyne/AlN, graphyne/GaN) was proposed and DFT studied [34], taking into account a significant charge transfer between two flakes generates permanent dipole in this heterostructures. The formation process of these heterostructures was found to be exothermic and comparable with the binding energy of graphene bilayer. The charge stored by each flake, energy storage, and capacitance are switchable under external electric field. These structures can be considered as a suitable template for charge and energy storage. The adsorption of sulfur dioxide (SO2) on pristine and modified graphyne (with defects and adatoms) was investigated by DFT calculations [35], showing changes according to the dopant atom, site of doping, and vacancy. These changes were especially strong in case of boron doping at the sp-hybridized carbon site and introducing a single carbon atom vacancy, causing deformation of the graphyne structure and electron redistribution. It was established that these graphynes are a potential material for SO2 gas sensors. Similarly, the adsorption of formaldehyde on graphyne was investigated to search high sensitivity sensors for detection of formaldehyde [36]. It is found that formaldehyde is physisorbed on the graphyne (and also

6.1 Graphyne

383

Fig. 6.11 (a) Selected structures of carbon chains (C3, C7, C13) on Cu(111) and Ru(0001) surfaces. (b) The relative binding energy of a carbyne on the Cu(111) surface as a function of the tilt angle, θ. (c) Charge-density difference (CDD) for carbon chains with seven carbon atoms on Cu(111) and Ru(0001) surfaces. (d) Formation energies of carbyne/carbon chains (1C–15C) on Cu, Rh, Ru, and Ni surfaces, respectively. All the energies are fitted by the inserted linear equations. (e) Formation energies per carbon atom of carbon chains on Cu, Rh, Ru, and Ni surfaces. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 6.12 Illustration of graphyne formation on a transition-metal surface by the self-assembly of the carbyne chains. (Reproduced with permission of the Royal Society of Chemistry)

on graphene) with large binding distance, small binding energy, and small charge transfer, modifying the electronic properties of semimetallic graphene, α-graphyne, and β-graphyne and semiconducting γ-graphyne. HCOH prefers to orient perpendicularly with H atoms close to the sheets (Fig. 6.13). Also, adsorption of polycyclic aromatic hydrocarbons (PAHs) onto graphyne was calculated [37], showing that, due to the porous character of graphyne, the adsorption strength of PAHs onto graphyne surfaces is expected to be lower with respect to graphene (a perfect π-extended system).

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6 Predicted Carbon Forms

Fig. 6.13 Adsorption configurations of formaldehyde on graphene, α-graphyne, β-graphyne, and γ-graphyne. (Reproduced with permission of the Elsevier Science)

6.2

Metallic Carbon1,2

One of the unsolved issues in carbon science has been to find a 3D form of carbon that is metallic under ambient conditions. Carbon has abundant allotropes with superhardness, but few of them are metallic. Some rare carbon structures seem to be metallic (for instance, armchair carbon nanotube [38, 39] in 1D systems or 2D graphene sheet) or were proved to be nonmetallic (dense cold compressed graphite, T-, L-, Y-carbon, and cubane-based porous carbon). DFT studies are widely used for prediction of possible metallic carbon allotropes and evaluation of their stabilities and magnetic properties. Thus, for example, carbon nanostructures with unusually large paramagnetic moments were discovered [40] in a theoretical study of the electronic and magnetic properties of carbon nanotubes bent into toroids (see the section above on carbon nanotori). The large paramagnetic moment is due to the interplay between the toroidal geometry and the ballistic motion of the π electrons in the metallic nanotube. Metallic carbon has been extensively studied for its potential applications in superconductivity, catalysis, and electronic devices. Currently, the design of metallic carbon is mainly by educated intuition which could miss some more stable

1 2

This term does not deal with carbon nanotubes containing metals as impurities. Reproduced with permission of the PNAS (Proc. Natl. Acad. Sci. USA. 2013, 110(47), 18809–18813).

6.2 Metallic Carbon

385

allotropes. Metallic carbon structures can possess properties even more novel than the semiconducting carbon structures, possessing the following features: – – – – –

Exhibits phonon–plasmon coupling and displays negative differential resistance and superconductivity. Highly efficient catalytic property is possible due to its high electronic density of states (DOS) at the Fermi level. Metallic carbon can become magnetic when the stoner-like criterion is satisfied. Metallic carbon, due to its high density of states (DOS) at the Fermi level, can be effective as a catalyst. Metallic carbon showed a number of intriguing properties such as phonon-plasmon coupling, superconductivity, and negative differential resistance. – Metallic 3D carbon at this point does not exist: this is only theoretically predicted (see below). Some hypothetical metallic 3D carbon allotropes such as ThSi2-type tetragonal carbon, hexagonal H-6 carbon, and K4 carbon were found to be dynamically unstable. Some recent studies by first-principles calculations have revealed possibilities of existence of several metallic carbon allotropes at distinct conditions. Thus, a stable anisotropic metallic carbon allotrope (Hex-C24, Fig. 6.14) phase with superhardness was proposed by DFT calculations [41]. The Hex-C24 can be thought of as a superlattice of carbon nanotubes and graphene nanoribbons composed of sp2- and sp3-hybridized carbon atoms. An evaluated possible synthetic route (Fig. 6.15) toward Hex-C24 from graphyne multilayers indicated to a uniaxial pressure of around 25 GPa, with the energy

Fig. 6.14 Atomic structure of Hex-C24 composed of sp2- and sp3-hybridized carbon atoms. (a) Top view, (b) side view, and (c) schematic representation of the superlattice of (3, 0) CNTs and GNRs. (Reproduced with permission of the Royal Society of Chemistry)

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6 Predicted Carbon Forms

Fig. 6.15 A possible pathway of the structural transition of graphyne to Hex-C24. The energy of the product (Hex-C24) is set to zero, and the numbers in parentheses are the energy referenced to the product (eV per atom). I (reactant), II (critical state), III (TS), IV (intermediate), and V (product) columns show the key states in the reaction process. (a), (b), and (c) rows show the transition processes of α, β1, and β3 structures. (Reproduced with permission of the Royal Society of Chemistry)

barrier of this endothermic transition to be 0.04 eV per atom, while at a pressure of 34 GPa, the transition is barrierless for specific initial configurations. A 3D metallic carbon (Tri-C9, Fig. 6.16) was built by distorting the sp3 hybridization bond [42]. The Tri-C9 is a metastable metallic carbon with a considerable bulk modulus of 365 GPa and that the metallic behavior of Tri-C9 originates from the π bonds near Fermi level. A feasible synthesis route for Tri-C9 was proposed by compressing graphite. The theoretical existence of a 3D form of carbon, that is, metallic under ambient conditions and pressure, was predicted that it is formed from interlocking hexagons, dynamically, mechanically, and being thermally stable, and may be synthesized chemically by using benzene or polyacenes molecules, unlike high-pressure techniques that require 3 TPa to make metallic carbon [43]. It was demonstrated that 3D carbon structures formed of interlocking hexagons are metallic under ambient conditions; they are systems with hybridized sp3 and sp2 bonding. The sp3-bonded carbon atoms guarantee their stability, and the sp2-bonded carbon atoms ensure their metallicity. At 500 K, the metallic T6 phase (Fig. 6.17) changes to the T12 phase, whereas the metallic T14 phase changes to the metallic T28 phase. The predicted metallic carbon could have potential applications ranging from electronics and superconductivity to lightweight space materials. A 3D metallic carbon phase, termed Hex-C18 (Fig. 6.18), also composed of sp2- and sp3-hybridized carbon atoms, was found [44] to be energetically more favorable than most of the previously identified 3D metallic carbon allotropes. It was DFT-predicted that Hex-C18 not only possesses a high thermodynamic stability, large heat capacity, high Debye stiffness, anisotropic elasticity, and super hardness but also is a promising anode material for lithium-ion batteries. Another stable

6.2 Metallic Carbon

387

Fig. 6.16 (a–c) Building block (top) and corresponding crystal structure (bottom) for diamond, bct C4, and Tri-C9 (1  2  1 supercell), respectively. (d–f) Bonding charge density (top) and its 2D slices (bottom) for diamond, bct C4, and Tri-C9, respectively. The bonding charge density is the difference between the total charge density of the structure and the superposition of the charge density of the neutral constituent atoms. The isosurface of the bonding charge density is 0.2 e/Å3. The red and blue colors in the slices indicate the electron accumulation and depletion, respectively. (Reproduced with permission of the American Chemical Society)

metallic carbon allotrope is H18 carbon (Fig. 6.19) with a mixed sp2–sp3-hybridized bonding network [45]. It would be one of the unidentified carbon phases observed in detonation experiments, and it has a metallic feature mainly due to the C atoms with sp2 hybridization. This phase is composed of 18 atoms per hexagonal primitive cell (hereafter termed H18 carbon), having a larger atom density of 3.135 g/cm3 compared to 2.28 g/cm3 for graphite. This phase is anticipated to be useful for practical applications such as electronics and mechanics devices.

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6 Predicted Carbon Forms

Fig. 6.17 Crystal structure of T6-carbon: (a) perspective view and (b) polyhedral view from three axial directions. (c) Corresponding first Brillouin zone and the high-symmetry K point paths. (Reproduced with permission of the PNAS)

Fig. 6.18 (a) Top view and (b) side view of the optimized structure of Hex-C18. (c) A schematic illustration of a possible synthesis strategy for Hex-C18 by using C-H chains via dehydrogenation and assembly. (Reproduced with permission of the Elsevier Science)

6.3 bcc-Carbons and Other Related Polymorphs

389

Fig. 6.19 Top (a) and side (b) views of H18 carbon in P6/mmm (D16h) symmetry with single and double bonds. (Reproduced with permission of Nature)

6.3

bcc-Carbons3 and Other Related Polymorphs

It was predicted that the diamond can be transformed into the so-called C8 structure (such crystal structures are described in detail in [46]), a body-centered cubic structure (bcc-carbon) with eight atoms in the unit cell at ultrahigh pressures of above 1000 GPa. Some peculiarities of various bcc-carbons, found in available literature, are as follows: – – – – –

bcc-Carbon was first predicted in 1989 [47]. bcc-C6 has an indirect band gap of 2.5 eV. bcc-C6 is an excellent material for building few-layer structures. bcc-C6 possesses exceptionally low-surface energy. Cubic C8 was predicted to be aromatic (according to Hirsch’s rule), but very reactive, both with itself and triplet oxygen [48]. – bcc-Carbon phase might have importance in astrophysics.

3

Reproduced with permission of the American Chemical Society (J. Phys. Chem. C, 2012, 116(45), 24233–24238).

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6 Predicted Carbon Forms

Fig. 6.20 Crystal structures of (a) fcc-C32, (b) bcc-C20, (c) fcc-C12, and (d) fcc-C10, respectively. They consist of identical C32, C20, C12, and C10 cages, respectively. Notably, a central atom in the C10 cage bonds to the nearest four atoms

Among many existing and predicted elemental carbon architectures, a group of 3D allotropes with cubic modifications (fcc-C10, fcc-C12, bcc-C20, and fcc-C32, Fig. 6.20) and with quite low density were proposed by employing an ab initio particle-swarm optimization methodology for crystal structure prediction [49]. Some of them were experimentally synthesized and naturally exist. The lightest fcc-C10 has a comparable density to C60 fullerene, and the densest fcc-C32 has a slightly higher density than graphite. All they are semiconductors with excellent mechanical performance, high ductility, and specifically superhardness, having potential applications as molecular sieves, shape-selective catalysts, absorbents, cutting tools, and coatings, among others. Also, nanocrystals of the superdense carbon with a bcc structure (bcc-C8) were synthesized by a pulsed-laser induced liquid–solid interface reaction [50, 51]. The formed micro- and nanocubes are single crystals (Fig. 6.21) with a bcc structure with a lattice constant of 5.46 Å, having a slightly truncated shape bounded mainly by {200} facets. This carbon nanomaterial was found to be a semiconductor with blue luminescence. The known carbon allotrope, 2D bcc-C6 (Fig. 6.22, a metastable, body-centered carbon allotrope with six atoms per primitive unit), according to DFT calculations, should have exceptionally low-surface energy and little size dependence down to only a couple layer thickness [52], explained by the existence of the relatively-high-energy bcc-C6 during growth. bcc-C6 belongs to low-surface-energy allotropes but with much stronger layer–layer interaction than that in graphite. bcc-C6 is more similar to the experimental superdense carbon than the previously proposed supercubane C8.

6.3 bcc-Carbons and Other Related Polymorphs

391

Fig. 6.21 SEM images of the synthesized carbon micro- and nanocubes (a, b) and the insets are high-magnification SEM images of slightly truncated carbon nanocube. Two distribution histograms of the size ration of cubes are shown in (c). The corresponding XRD pattern is shown in (d). (Reproduced with permission of the American Chemical Society)

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6 Predicted Carbon Forms

Fig. 6.22 2D layered bcc-C6 with (a) (111), (b) (110), and (c) (100) surfaces. Atoms in the first, middle, and third layers are shown in green, orange, and purple, respectively. (Reproduced with permission of the Royal Society of Chemistry)

6.4

bct-Carbon4

Body-centered tetragonal carbon (bct-carbon) was first proposed in 2010. The bct-C4 phase (Fig. 6.23) is transparent and dynamically stable at zero pressure [53]. All carbon atoms are symmetrically equivalent, forming a structure closely related to those of graphite and hexagonal diamond. bct-C4 is an accessible form of sp3 carbon along the graphite-to-hexagonal diamond transformation path (Fig. 6.24) [54]. By rearranging half of carbon atoms, i.e., by changing the buckling pattern of these layers, bct-C4 can be transformed into hexagonal diamond. In addition, bct-C8 (Fig. 6.25) can be formed by sp3-bonded carbon atoms and can be regarded as a compressed bundle of carbon nanotubes (CNTs) [55]. bct C8 is a semiconductor with an indirect gap of 1.66 eV, can be transformed to semimetal being doping with boron and nitride atoms, and would have fruitful applications in carbon-based electronics and energy storage (Li storage), in case of its synthesis.

4

Reproduced with permission of the American Physical Society (Phys. Rev. B, 2010, 82, 134126).

6.4 bct-Carbon

393

Fig. 6.23 Crystal structure of bct-C4: (a) three-dimensional view, (b) view along the b axis, and (c) along the c axis. In (c), if pairs of carbon atoms in the gray boxes are flipped across the planes denoted by dashed lines, bct-C4 transforms to (d) hexagonal diamond. (Reproduced with permission of the American Physical Society)

Fig. 6.24 Transition paths of bct-carbon under pressure of 20 GPa (Reproduced with permission of the American Physical Society)

Selected features of bct-carbon are as follows: – – – – – – –

bct-Carbon is crystalline with sp3 configuration with body-centered tetragonal I4/mmm symmetry. bct-Carbon consists of sheets of squares of four carbon atoms each, joined by “short” bonds perpendicular to the sheets. It can be synthesized when graphite is exposed to high pressure at normal temperatures. Its shear strength is 17 percent greater than diamond’s. It is more stable than graphite at 18.6 GPa. bct-Carbon has a higher shear strength than diamond due to its perpendicular graphene-like structure. bct-C4 presents a super uniaxial compressive strength of 524.3 GPa, which is 6.9% more than the corresponding value of diamond [56]. The high compressive strength originates from the high compressive rate of chemical bond deviating from compressive direction.

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6 Predicted Carbon Forms

Fig. 6.25 Schematic drawing of the crystal structure of Bct C8; (a) and (b) are the perfective views; (c) and (d) are the side view and the top view, respectively. The dash line indicates the unit cell. (Reproduced with permission of Elsevier Science)

6.5

Prismane C85

Prismane C8 (Fig. 6.26; should not be confused with corresponding hydrocarbon with the same name) is a theoretically predicted metastable carbon allotrope. It consists of an atomic cluster of eight carbon atoms, with the shape of an elongated triangular bipyramid – a six-atom triangular prism with two more atoms above and below its bases [57, 58]. It possesses a rather high stability, the activation energy for prismane decay being about 0.8 eV. The prismane lifetime increases rapidly as the temperature decreases, indicating the possibility of experimental observation of this cluster.

5

Reproduced with permission of Springer (Journal of Experimental and Theoretical Physics Letters, 1998, 68(9), 726–731).

6.5 Prismane C8 Fig. 6.26 A (C8)5 ensemble consisting of 5 C8 prismanes [59]. (Reproduced with permission of Springer)

395

396

6.6

6 Predicted Carbon Forms

K4 Crystal

The K4 crystal is a theoretically predicted 3D crystalline metastable carbon structure, where each sp2-hybridized carbon atom is bonded to three others, at 120 angles (like graphite) but where the bond planes of adjacent layers lie at an angle of 70.5 , rather than coinciding. Various physical properties of the K4 carbon crystal, especially for the electronic properties, were evaluated by first-principles calculations [60]. A possible pressure-induced structural phase transition from graphite to K4 was suggested. Twisted π states across the Fermi level resulted in metallic properties in this carbon crystal. Structural differences of diamond, graphite, and K4 crystal are shown in Fig. 6.27. A significant difference is that the K4 crystal, with its threecoordinated and three-dimensional (3C-3D) structure, has chirality, while the diamond crystal [with tetracoordinated (4C)-3D structure] does not [61]. Fig. 6.27 Binding energy vs. volume curves of diamond (blue), graphite (grey and black), and K4 (red) crystal structures composed of carbon atoms based on (a) LDA and (b) GGA. (Reproduced with permission of the American Physical Society)

Intensity [arbitary unit]

0 2 4

Binding Energy [eV/atom]

6

a LDA (CA)

diamond

K4

graphite

30

50

70

90

30 2q [°]

50

70

90

8 10 0

b GGA (PW91) 2 4 graphite

diamond

K4

6 8 10

diamond graphite, c = 2.7a 4

5

6

7

graphite, c = const. K4 8

Volume [Å3/ atom]

9

10

11

6.7 Penta-Graphene

6.7

397

Penta-Graphene6

Whereas hexagons are the primary building blocks of many of carbon allotropes (except for C20 fullerene), carbon structures made exclusively of pentagons are not known. The penta-graphene, composed of only carbon pentagons and resembling Cairo pentagonal tiling, can be dynamically, thermally, and mechanically stable. Proposed in 2014, it is a carbon allotrope containing both sp2- and sp3-hybridized carbon atoms, composed entirely of carbon pentagons and resembling the Cairo pentagonal tiling. It is unstable in pure form but can be stabilized by hydrogenation resulting penta-graphane [62]. Several features of penta-graphene are as follows: – It is dynamically stable and can withstand temperatures up to 1000 K, although it is energetically metastable compared with graphene. – It exhibits negative Poisson’s ratio, a large band gap, and an ultrahigh mechanical strength. – Penta-graphene is an insulator with an indirect band gap of 4.1–4.3 eV. – Its room-temperature thermal conductivity is about 167 W/mK [63], which is much lower than that of graphene. – Penta-graphene can be rolled up to form a 1D pentagon-based nanotube and stacked to form 3D stable structures. – It can be functionalized with hydrogen and other different functional groups, changing the failure stress, strain, and other properties [64–66]. – Penta-graphene is a promising anode material as the Li/Na-ion battery [67]. The data on penta-graphene stability are contradictory [68]. For example, as it was suggested, a 2D carbon sheet, pentagraphene (Fig. 6.28), composed entirely of pentagons, could be obtained by chemically exfoliating a single layer from the T12-carbon phase [69]. However, it was suggested and calculated by Kroto et al. [70] that penta-graphene will not be an

Fig. 6.28 (a) Crystal structure of T12-carbon viewed from the [100] and [001] directions, respectively. (b) Top and side views of the atomic configuration of penta-graphene. The square marked by red dashed lines denotes a unit cell, and the highlighted balls represent the sp3 hybridized C atoms. (Reproduced with permission of PNAS)

6

Reproduced with permission of PNAS (PNAS, 2015, 112(8), 2372–2377).

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6 Predicted Carbon Forms

Fig. 6.29 A calculated structural transformation route from (a) penta-graphene to (d) graphene; each step is exothermic. Red arrows indicate direction of motion of atoms for 90 rotation of carbon–carbon bonds. Red (blue) lines indicate C–C bonds that are broken (formed). Note that structures A–C were constrained within orthogonal unit cells; this constraint was lifted for step C to D. The final structure, graphene, is 0.761 eV per atom more stable than A. Unit cells are marked with dotted lines; calculated cell dimensions are (a) 5.095  5.095 Å, (b) 4.769  5.510 Å, (c) 4.888  5.318 Å, and (d) 4.883  6.476 Å, α ¼ 100.88 . (Reproduced with permission of PNAS)

experimentally achievable allotrope of carbon. The problem is not only in its isolation among similar-energy isomers but also due to its rapid restructurization yielding graphene (Fig. 6.29) in presence of impurities as catalysts. At the same time, it was suggested that chiral penta-CNTs on penta-graphene basis are good candidates to be obtained experimentally. Thus, a computational study on the structure and electronic properties of penta-graphene nanotubes (penta-CNTs, Fig. 6.30), based on a periodic plane wave-pseudopotential approach, was carried out [71], considering chiral structures, among zigzag and armchair structures. In particular, it was revealed that the energetic stability (binding energy per atom or BEA) of chiral pentaCNTs is comparable with (n,n) penta-CNTs. In addition, penta-CNTs with reversed indexes (i.e., penta-CNTs with index (n, m) and (m,n)) are equal, because of their chiral angles which are comprised between 0 and 45 degrees. Mechanical properties of penta-graphene nanotubes [72] and its monolayer [73] were also studied. Finally, the mechanism of translation symmetry breakdown in penta-graphene with multiple sp2/sp3 sublattices was studied by GGA DFT, DFTB, and model potential approaches (Fig. 6.31) [74]. It was shown that 2D sp2/sp3 nanostructures are correlated transition states between two symmetrically equivalent bent structures. Strong mechanical stress prevents stabilization of the nanoclusters on any type of supports by either van der Waals or covalent bonding and should lead to formation of pentatubes, nanorings, or nanofoams rather than infinite nanoribbons or nanosheets. There are also other recent studies on approaches to penta-graphene models and its possible transformations [75, 76].

6.7 Penta-Graphene Fig. 6.30 Various pentaCNT structures. Red lines delimitate each unit cell, while the magnitude of its translational vector are shown under each nanotube. (Reproduced with permission of the Elsevier Science)

399

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6 Predicted Carbon Forms

Fig. 6.31 Top (a) and side (b) projections of 2D pentagraphene and 1D pentaribbon (c, d) calculated using PBC approach. Carbon atoms of sp3 sublattice are depicted in red, the sp2 carbon dimers of the top and bottom subblattices are depicted in blue, and the unit cells of penta-graphene and pentaribbon are marked by green rectangles. (Reproduced with permission of the American Chemical Society)

6.8

Haeckelites

Haeckelites, first proposed by Terrones in 2000, are layered sp2-like threefold coordinated networks of carbon atoms in 2D Bravais lattices, generated by a periodic arrangement of pentagons, hexagons, and heptagons. They can consist, in particular, of equal numbers of pentagons and heptagons, in addition to any number of hexagons. Similar atomic arrangements have been observed in 5–7 and 5–8 defect lines, among others. Some features of haeckelites are as follows: – Haeckelites can be rolled so as to generate nanotubes of different diameter and chirality. – Haeckelite structures were shown to be good candidates of conducting wires with great potential in nanoelectronics [77]. – Haeckelite sheets and tubes (Fig. 6.32) are metastable and more favorable than C60; their mechanical properties are similar to those of graphene [78]. All structures, according to calculations, possess an intrinsic metallic behavior, independent of orientation, tube diameter, and chirality. Starting from a planar Haeckelite array, tubular structures (Fig. 6.33) were obtained by applying the same wrapping procedure as for the usual nanotubes, which are rolled up sheets of graphene [79]. The haeckelite nanotubes may adopt various shapes, in particular coiled structures, double-screw molecules, corrugated cylinders, and pearl-necklace-like nanotubes. Studying lithium insertion to such haeckelite nanotubes, as well as to classic carbon nanotubes, it was revealed [80] that the metal interacts preferably with the pentagonal and heptagonal rings of the haeckelite rather than the hexagonal of the carbon nanotube. Haeckelites were found to be more promising materials for lithium storage applications (storing Li with a density of LiC1.6) than carbon nanotubes. Among several other recent investigations on haeckelites, DFT structural studies together with DFT-based non-equilibrium Green function calculations were applied to investigate how the presence of non-hexagonal rings affects electronic transport in graphitic structures [81], resulting that infinite monolayers, finite-width nanoribbons, and nanotubes formed of 5–8 haeckelite with only five- and eight-membered rings are generally more conductive than their graphene-based counterparts.

Fig. 6.32 Haeckelite sheets consisting of various units cells: (a) rectangular _R5,7, (b) hexagonal _H5,6,7_, and (c) oblique _O5,6,7_. Nonchiral haeckelite tubes of similar diameters (ca. 1.4 nm) have been created using the three types of layered crystals: (d) R5,7 _6, 0_, (e) H5,6,7 _6, 0_, and (f) O5,6,7 _0, 8_ [Note: Subindices _5, 6, 7_ of the above structures indicate the presence of pentagonal, hexagonal, and heptagonal rings, respectively]. (Reproduced with permission of the APS Physics)

Fig. 6.33 Ball-and-stick representations of (0,m) nanotubes generated from the haeckelite stripe. (Reproduced with permission of the IOP Publishing)

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6.9

6 Predicted Carbon Forms

Phagraphene

Among graphene allotropes, penta-graphene and phagraphene, the Haeckelite-like Phagraphene, proposed in 2015, is composed of 5-6-7 carbon rings (Fig. 6.34); it is only dynamically and thermally stable [82, 83]. Phagraphene, as well as graphene, is a material where Dirac cones appear, and electrons behave similar to particles without mass. In phagraphene, due to the different number of atoms in the rings, the Dirac cones are inclined. This 2D carbon structure with Pmg plane group is lower in energy than most of the predicted 2D carbon allotropes due to its sp2-binding features and density of atomic packing comparable to graphene. Some features of phagraphene are as follows:

Fig. 6.34 (a) Structure of phagraphene with notable space-inversion symmetry, C1–C6 are unequivalent carbon atoms in its unit cell. (b) Distorted Dirac cone formed by the valence and conduction bands in the vicinity of the Dirac point. (c) Comparison of band structures from DFT (blue line) and TB (red circle) model. The corresponding DOS is zero at the Fermi level. Inserted first BZ with high symmetric k points: Γ (0,0,0), X (0.5,0,0), Z (0.5,0.5,0), Y (0,0,5,0), and Dirac point: D (0, 0.377,0). (d) Charge-density distributions near the distorted Dirac cone, both Dirac bands (denoted as I and II) are from pz orbitals of sp2-carbon atoms. Fermi level has been set to zero. (Reproduced with permission of the American Chemical Society)

6.9 Phagraphene

403

Fig. 6.35 Schematics of the atomic structures for penta-graphene and phagraphene. Unit cells are shown in pink. Side views of penta-graphene are shown on the top of this figure with three planes of atom (P1, P2, and P3). The atoms in P2 plane are marked in green. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 6.36 A periodic supercell in the atomic structure of phagraphene. A 20-atom unit cell is also shown. In this study the properties are investigated along the armchair and zigzag directions. (Reproduced with permission of the Royal Society of Chemistry)

– – – –

Phagraphene is unstable or, at least, almost unstable with respect to transverse atomic displacements in the monolayer [84]. Phagraphene has a potential energy of 193.2 kcal/mol. The bond order is 1.33, the same as for graphene. Phagraphene is considered an advanced material for flexible electronic devices, transistors, solar batteries, display units, and many other things.

DFT calculations were applied to evaluate the mechanical properties of penta-graphene and phagraphene (Fig. 6.35) and compared with graphene, graphane, and pentaheptite [73], resulting that the ultimate tensile strength (UTS) and the strain corresponding to UTS in both penta-graphene and phagraphene are smaller than that of graphene. Also, the charge density in sp3 bonds is lower than that in the sp2 bonds. In phagraphene, all the broken bonds were found to belong to the largest carbon ring in the structure. The thermal conductivity was found [85] to be anisotropic, with room-temperature values of 218  20 W m1 K1 along the armchair direction and 285  29 W m1 K1 along the zigzag direction (Fig. 6.36). Both values are one order of magnitude smaller than for pristine graphene.

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6 Predicted Carbon Forms

Effects of Doping and Impurities A mixed-edge phagraphene ribbon was selected to study B-, N-, and BN-doping effects, respectively, on the geometric stability, electronic structure, carrier mobility, and device property [86]. These structures were found to be energetically stable. N or BN doping at different positions can modify the bandgap of ribbons, making ribbons become a wide, medium, or narrowed bandgap semiconductor. In case of silicon impurities, the structural, electronic, and magnetic properties were investigated systematically of pristine and Si-doped phagraphene nanoribbons (PHAGNRs) with different edges, including zigzag edge (ZPHAGNR) and mixed edge (MPHAGNR) [87]. It was revealed that the geometric structure is drastically changed when silicon atom replaces the different carbon atom on 5-6-7 rings of PHAGNRs. Among other effects, Si atom always prefers to substitute carbon atom at the edge position or on heptagon carbon ring both in 6-MPHAGNR and 4-ZPHAGNR. Also, DFT calculations on the lithium-ion storage capacity of two membranes, biphenylene (BP) membrane and phagraphene (PhG), showed a larger capacity than graphene, Li2C6, and Li1.5C6 compared to LiC6 [88]. Li was found to be very mobile on these materials and does not interact as strongly with the membranes. Li atoms transfer a significant amount of charge to each of the membranes and that the bonding character is ionic. Further Reading Stone–Wales defects in phagraphene [89]; simulation of the elastic properties of phagraphene [90]; modulation of the electronic and mechanical properties of phagraphene [91].

6.10

R3-Carbon7

Phase transformation in glassy carbon (GC), simulated by means of DFT calculations in a wide range of pressures (0–79 GPa), revealed change in bonding type from sp- and sp2-type to sp3-type bonding [92], leading to a crystalline carbon allotrope possessing R3 symmetry (R3-carbon, Fig. 6.37). Its mechanical properties significantly vary due to the change of bonding type. With increasing pressure, the bulk moduli, shear moduli, and Young’s moduli approach diamond values.

7

Reproduced with permission of Nature (Scientific Reports, 2013, 3, Article number: 1877).

6.10

R3-Carbon

405

Fig. 6.37 (a) The R3-structure, the (001)-plane and the (010)-plane. Three-membered rings are colored in purple. (b) The calculated diffraction pattern of the R3 phase, Cco-C8 Carbon, Bct-Carbon, M-Carbon, Z-Carbon, P-Carbon, R-Carbon, S-Carbon, T-Carbon, W-Carbon, and X-Carbon, respectively. (Reproduced with permission of Nature)

406

6.11

6 Predicted Carbon Forms

Imma-Carbon

The polymorph sp3 carbon allotrope, Imma-carbon (Fig. 6.38), is dynamically stable and a semiconductor with a direct band gap of 2.6 eV [93]. Calculations of bulk modulus and hardness indicate that this carbon is an ultra-incompressible and superhard material (bulk modulus of 444.7 GPa and a Vickers hardness of 83.5 GPa, which are larger than that of c-BN (66.3 GPa and 403.0 GPa)).

Fig. 6.38 (a, b) Polyhedral views of the crystal structure of Imma-carbon along two different directions, respectively. (c) Enthalpy differences of various carbon allotropes relative to graphite. (Reproduced with permission of the Elsevier Science)

6.13

6.12

Superdense Carbon Allotropes

407

I-Carbon8

I4-carbon was first proposed by Zhang et al. [15] This is a three-dimensional superhard carbon allotrope, which is confirmed to be thermodynamically, mechanically, and dynamically stable, having larger bulk modulus (393 GPa), shear modulus (421 GPa), Young’s modulus (931 GPa), and hardness (55.5 GPa), all of which are all slightly larger than those of c-BN. I4– carbon is an indirect bandgap semiconductor [94].

6.13

Superdense Carbon Allotropes

Searching for possible superdense carbon allotropes, three structures (hP3, tI12, and tP12, Fig. 6.39) were found [95] that have significantly greater density. The hP3 and tP12 phases have strong analogy with two polymorphs of silica (β-quartz and keatite), while the tI12 phase is related to the high-pressure SiS2 polymorph. At ambient conditions, the hP3 phase is a semiconductor with the GW band gap of 3.0 eV, tI12 is an insulator with the bandgap of 5.5 eV, while tP12 is an insulator, the band gap of which is remarkably high (7.3 eV), making it the widest-gap carbon allotrope. These allotropes are metastable and have comparable to diamond or slightly higher-bulk moduli. Superdense carbon allotropes are predicted to have remarkably high refractive indices and strong dispersion of light. Authors believe that it is possible to obtain them by rapid dynamical compression of low-density forms of carbon. Alternatively, these allotropes can be synthesized by CVD techniques on a suitable substrate. Their dynamical stability indicates that, once synthesized, these allotropes can exist long at ambient conditions.

8

Image reproduced with permission of the MDPI (Materials, 2016, 9, 484, 15 pp.).

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6 Predicted Carbon Forms

Fig. 6.39 Crystal structures and hybrid functional band structures of (a) hP3, (b) tI12, and (c) tP12 allotropes. For carbon allotropes, hybrid functional is believed to give the same level of accuracy as more rigorous GW quasiparticle calculations. The white (dark gray) spheres represent the different types of carbon atoms. (Reproduced with permission of APS Physics)

References 1. L.A. Burchfield, M. AlFahim, R.S. Wittman, F. Delodovicic, N. Manini, Novamene: a new class of carbon allotropes. Heliyon 3(2), e00242 (2017) 2. F. Delodovicic, N. Manini, R.S. Wittman, Protomene: a new carbon allotrope. Carbon 126, 574–579 (2018) 3. A.R. Oganov, C.W. Glass, Crystal structure prediction using ab initio evolutionary techniques: Principles and applications. J. Chem. Phys. 124, 244704 (2006) 4. Q. Li, Y.M. Ma, A.R. Oganov, H.B. Wang, H. Wang, Y. Xu, T. Cui, H.K. Mao, G.T. Zou, Superhard monoclinic polymorph of carbon. Phys. Rev. Lett. 102, 175506 (2009) 5. F. Tian, X. Dong, Z.S. Zhao, J.L. He, H.T. Wang, Superhard F-carbon predicted by ab initio particle-swarm optimization methodology. J. Phys. Condens. Matter 24, 165504 (2012) 6. J.T. Wang, C. Chen, Y. Kawazoe, Low-temperature phase transformation from graphite to sp3 orthorhombic carbon. Phys. Rev. Lett. 106, 075501 (2011)

References

409

7. Z.P. Li, F.M. Gao, Z.M. Xu, Strength, hardness, and lattice vibrations of Z-carbon and W-carbon: first-principles calculations. Phys. Rev. B 85, 144115 (2012) 8. C.Y. He, L.Z. Sun, C.X. Zhang, X.Y. Peng, K.W. Zhang, J.X. Zhong, New superhard carbon phases between graphite and diamond. Solid State Commun. 152, 1560–1563 (2012) 9. Q. Wei, M.G. Zhang, H.Y. Yan, Z.Z. Lin, X.M. Zhu, Structural, electronic and mechanical properties of Imma-carbon. EPL 107, 27007 (2014) 10. C.Y. He, J.X. Zhong, M585, a low energy superhard monoclinic carbon phase. Solid State Commun. 181, 24–27 (2014) 11. Z.S. Zhao, F. Tian, X. Dong, Q. Li, Q.Q. Wang, H. Wang, X. Zhong, B. Xu, D.L. Yu, J.L. He, et al., Tetragonal allotrope of group 14 elements. J. Am. Chem. Soc. 134, 12362–12365 (2012) 12. M.J. Xing, B.H. Li, Z.T. Yu, Q. Chen, C2/m-carbon: structural, mechanical, and electronic properties. J. Mater. Sci. 50, 7104–7114 (2015) 13. M.J. Xing, B.H. Li, Z.T. Yu, Q. Chen, Structural, elastic, and electronic properties of a new phase of carbon. Commun. Theor. Phys. 64, 237–243 (2015) 14. Z.S. Zhao, B. Xu, X.F. Zhou, L.M. Wang, B. Wen, J.L. He, Z.Y. Liu, H.T. Wang, Y.J. Tian, Novel superhard carbon: C-centered orthorhombic C8. Phys. Rev. Lett. 107, 215502 (2011) 15. X.X. Zhang, Y.C. Wang, J. Lv, C.Y. Zhu, Q. Li, M. Zhang, Q. Li, Y.M. Ma, First-principles structural design of superhard materials. J. Chem. Phys. 138, 114101 (2013) 16. J.-J. Zheng, X. Zhao, Y. Zhao, X. Gao, Two-dimensional carbon compounds derived from graphyne with chemical properties superior to those of graphene. Sci. Reports 3, 1271 (2013) 17. Z. Li, M. Smeu, A. Rives, et al., Towards graphyne molecular electronics. Nat. Commun. 6, 6321 (2014) 18. T. Belenkova, V. Chernov, V. Mavrinskii, Structures and electronic properties of graphyne layers. Mater. Sci. Forum 845, 239–242 (2016) 19. R. Majidi, Electronic properties of porous graphene, α-graphyne, graphene-like, and graphyne-like BN sheets. Can. J. Phys. 94(3), 305–309 (2016) 20. H. Lu, S.-D. Li, Two-dimensional carbon allotropes from graphene to graphyne. J. Mater. Chem. C 1, 3677–3680 (2013) 21. Z. Li, Z. Liu, Z. Liu, Movement of Dirac points and band gaps in graphyne under rotating strain. Nano Res. 10(6), 2005–2020 (2017) 22. W.-J. Yin, Y.-E. Xie, L.-M. Liu, et al., R-graphyne: a new two-dimensional carbon allotrope with versatile Dirac-like point in nanoribbons. J. Mater. Chem. A 1, 5341–5346 (2013) 23. D. Solis, C.F. Woellner, D.D. Borges, D.S. Galvao, Mechanical and thermal stability of graphyne and graphdiyne nanoscrolls. arXiv:1701.05790, 2017. 0.1557/adv.2017.130 24. W. Wu, W. Guo, X. Cheng Zeng, Intrinsic electronic and transport properties of graphyne sheets and nanoribbons. Nanoscale 5, 9264–9276 (2013) 25. L.D. Pan, L.Z. Zhang, B.Q. Song, S.X. Du, H.-J. Gao, Graphyne- and graphdiyne-based nanoribbons: density functional theory calculations of electronic structures. Appl. Phys. Lett. 98, 173102 (2011) 26. S.W. Cranford, M.J. Buehler, Mechanical properties of graphyne. Carbon 49, 4111–4121 (2011) 27. A. Ahmadi, M. Faghihnasiri, H. Ghorbani Shiraz, M. Sabeti, Mechanical properties of graphyne and its analogous decorated with Na and Pt. Superlattice. Microst. 101, 602–608 (2017) 28. R. Couto, N. Silvestre, Finite element modelling and mechanical characterization of graphyne. J. Nanomater. 2016., Article ID 7487049, 15 (2016) 29. J. Hou, Z. Yin, Y. Zhang, T. Chang, An analytical molecular mechanics model for elastic properties of graphyne-n. J. Appl. Mech. 82(9.), 5 pp), 094501 (2015) 30. T. Ouyang, M. Hu, Thermal transport and thermoelectric properties of beta-graphyne nanostructures. Nanotechnology 25(24), 245401 (2014) 31. N. Han, H. Liu, S. Zhou, J. Zhao, Possible formation of graphyne on transition metal surfaces: a competition with graphene from the chemical potential point of view. J. Phys. Chem. C 120, 14699–14705 (2016) 32. Q. Yuan, F. Ding, Formation of carbyne and graphyne on transition metal surfaces. Nanoscale 6, 12727–12731 (2014) 33. A. Saraiva-Souza, M. Smeu, L. Zhang, M.A. Ratner, H. Guo, Two-dimensional γ-Graphyne suspended on Si(111): a hybrid device. J. Phys. Chem. C 120(8), 4605–4611 (2016) 34. B. Bhattacharya, U. Sarkar, Graphyne–graphene (nitride) heterostructure as nanocapacitor. Chem. Phys. 478, 73–80 (2016) 35. S. Kim, J.Y. Lee, Doping and vacancy effects of graphyne on SO2 adsorption. J. Colloid Interface Sci. 493, 123–129 (2017) 36. R. Majidi, A.R. Karami, Adsorption of formaldehyde on graphene and graphyne. Phys. E. 59, 169–173 (2014) 37. D. Cortes-Arriagada, Adsorption of polycyclic aromatic hydrocarbons onto graphyne: comparisons with graphene. Int. J. Quantum Chem. 117, e25346 (2017) 38. D. Zhang, J. Yang, E.H. Hasdeo, et al., Multiple electronic Raman scatterings in a single metallic carbon nanotube. Phys. Rev. B 93, 245428 (2016) 39. T. Isoniemi, A. Johansson, J.J. Toppari, H. Kunttu, Collective optical resonances in networks of metallic carbon nanotubes. Carbon 63, 581–585 (2013) 40. L. Liu, G.Y. Guo, C.S. Jayanthi, S.Y. Wu, Colossal paramagnetic moments in metallic carbon nanotori. Phys. Rev. Lett. 88(21), 217206 (2002). 4 pp 41. H. Bu, M. Zhao, W. Dong, S. Lu, X. Wang, A metallic carbon allotrope with superhardness: a first-principles prediction. J. Mater. Chem. C 2, 2751–2757 (2014) 42. Y. Cheng, R. Melnik, Y. Kawazoe, B. Wen, Three dimensional metallic carbon from distorting sp3-bond. Cryst. Growth Des. 16(3), 1360–1365 (2016) 43. S. Zhang, Q. Wang, X. Chen, P. Jena, Stable three-dimensional metallic carbon with interlocking hexagons. Proc. Natl. Acad. Sci. U. S. A. 110 (47), 18809–18813 (2013) 44. J. Liu, T. Zhao, S. Zhang, Q. Wang, A new metallic carbon allotrope with high stability and potential for lithium ion battery anode material. Nano Energy 38, 263–270 (2017) 45. C.-X. Zhao, C.-Y. Niu, Z.-J. Qin, X.Y. Ren, et al., H18 carbon: a new metallic phase with sp2-sp3 hybridized bonding network. Sci. Rep. 6, 21879 (2016)

410

6 Predicted Carbon Forms

46. A. Pokropivny, S. Volz, ‘C8 phase’: supercubane, tetrahedral, BC-8 or carbon sodalite? Phys. Status Solidi B 249(9), 1704–1708 (2012) 47. R.L. Johnston, R. Hoffmann, Superdense carbon, C8: supercubane or analog of .gamma.-silicon? J. Am. Chem. Soc. 111(3), 810–819 (1989) 48. D. Sharapa, A. Hirsch, B. Meyer, T. Clark, Cubic C8: an observable allotrope of carbon? Chem. Phys. Chem. 16(10), 2165–2171 (2015) 49. M. Hu, F. Tian, Z. Zhao, et al., Exotic cubic carbon allotropes. J. Phys. Chem. C 116(45), 24233–24238 (2012) 50. P. Liu, H. Cui, G.W. Yang, Synthesis of body-centered cubic carbon nanocrystals. Cryst. Growth Des. 8(2), 581–586 (2008) 51. P. Liu, Y.L. Cao, C.X. Wang, X.Y. Chen, G.W. Yang, Micro- and nanocubes of carbon with C8-like and blue luminescence. Nano Lett. 8(8), 2570–2575 (2008) 52. W.J. Yin, Y.P. Chen, Y.E. Xie, L.M. Liu, S.B. Zhang, A low-surface energy carbon allotrope: the case for bcc-C6. Phys. Chem. Chem. Phys. 17 (21), 14083–14087 (2015) 53. K. Umemoto, R.M. Wentzcovitch, S. Saito, T. Miyake, Body-centered tetragonal C4: a viable sp3 carbon allotrope. Phys. Rev. Lett. 104, 125504 (2010) 54. X.-F. Zhou, G.-R. Qian, X. Dong, L. Zhang, Y. Tian, H.-T. Wang, Ab initio study of the formation of transparent carbon under pressure. Phys. Rev. B 82, 134126 (2010) 55. H.-J. Cui, Q.-B. Yan, X.-L. Sheng, et al., The geometric and electronic transitions in body-centered-tetragonal C8: a first principle study. Carbon 120, 89–94 (2017) 56. L. Qing-Kun, Y. Sun, Y. Zhou, F.L. Zeng, First principles study of the uniaxial compressive strength of bct-C4 carbon allotrope. Acta Phys. Sin. 61(9), 093104 (2012) 57. L.A. Openov, V.F. Elesin, Prismane C8: a new form of carbon? J. Exp. Theor. Phys. Lett. 68(9), 726–731 (1998) 58. V.F. Elesin, A.I. Podlivaev, L.A. Openov, Meta-stability of the three-dimensional carbon cluster Prismane. Phys. Low-Dim. Struct. 11/12, 91 (2000) 59. N.N. Degtyarenko, V.F. Elesin, N.E. L’vov, L.A. Openov, A.I. Podlivaev, Metastable quasi-one-dimensional ensembles of C8 clusters. Phys. Solid State 45(5), 1002–1003 (2003) 60. M. Itoh, M. Kotani, H. Naito, et al., New metallic carbon crystal. Phys. Rev. Lett. 102, 055703 (2009) 61. N.U. Zhanpeisov, Theoretical DFT study on structure and chemical activity of new carbon K4 clusters. Res. Chem. Intermed. 39, 2141–2148 (2013) 62. H. Einollahzadeh, S. Mahdi Fazeli, R. Sabet Dariani, Studying the electronic and phononic structure of penta-graphane. Sci. Technol. Adv. Mater. 17(1), 610–617 (2016) 63. W. Xu, G. Zhang, B. Li, Thermal conductivity of penta-graphene from molecular dynamics study. J. Chem. Phys. 143, 154703 (2015) 64. Y. Zhang, Q. Pei, Z. Sha, Y. Zhang, H. Gao, Remarkable enhancement in failure stress and strain of penta-graphene via chemical functionalization. Nano Res. 10(11), 3865–3874 (2017) 65. S. Ebrahimi, Effect of hydrogen coverage on the buckling of penta-graphene by molecular dynamics simulation. Mol. Simul. 42(17), 1485–1489 (2016) 66. X. Wu, V. Varshney, J. Lee, T. Zhang, et al., Hydrogenation of Penta-graphene leads to unexpected large improvement in thermal conductivity. Nano Lett. 16(6), 3925–3935 (2016) 67. B. Xiao, Y.-c. Li, X.-f. Yu, J.-b. Cheng, Penta-graphene: a promising anode material as the Li/Na-ion battery with both extremely high theoretical capacity and fast charge/discharge rate. ACS Appl. Mater. Interfaces 8(51), 35342–35352 (2016) 68. B. Rajbanshi, S. Sarkar, B. Mandal, P. Sarkar, Energetic and electronic structure of penta-graphene nanoribbons. Carbon 100, 118–125 (2016) 69. S. Zhang, J. Zhouc, Q. Wang, et al., Penta-graphene: a new carbon allotrope. PNAS 112(8), 2372–2377 (2015) 70. C.P. Ewels, X. Rocquefelte, H.W. Kroto, et al., Predicting experimentally stable allotropes: instability of penta-graphene. PNAS 112(51), 15609–15612 (2015) 71. J.J. Quijano-Briones, H.N. Fernández-Escamilla, A. Tlahuice-Flores, Chiral penta-graphene nanotubes: structure, bonding and electronic properties. Comput. Theor. Chem. 1108, 70–75 (2017) 72. M. Chen, H. Zhan, Y. Zhu, H. Wu, Y. Gu, Mechanical properties of Penta-graphene nanotubes. J. Phys. Chem. C 121(17), 9642–9647 (2017) 73. H. Sun, S. Mukherjee, C. Veer Singh, Mechanical properties of monolayer penta-graphene and phagraphene: a first-principles study. Phys. Chem. Chem. Phys. 18, 26736–26742 (2016) 74. P. Avramov, V. Demin, M. Luo, et al., Translation symmetry breakdown in low-dimensional lattices of pentagonal rings. J. Phys. Chem. Lett. 6 (22), 4525–4531 (2015) 75. T. Stauber, J.I. Beltrán, J. Schliemann, Tight-binding approach to pentagraphene. Sci. Rep. 6(22672), 8 (2016) 76. O. Rahaman, B. Mortazavi, A. Dianat, G. Cuniberti, T. Rabczuk, Metamorphosis in carbon network: from penta-graphene to biphenylene under uniaxial tension. FlatChem 1, 65–73 (2017) 77. X. Rocquefelte, G.-M. Rignanese, V. Meunier, et al., How to identify Haeckelite structures: a theoretical study of their electronic and vibrational properties. Nano Lett. 4(5), 805–810 (2004) 78. H. Terrones, M. Terrones, E. Hernández, N. Grobert, J.C. Charlier, P.M. Ajayan, New metallic allotropes of planar and tubular carbon. Phys. Rev. Lett. 84, 1716 (2000) 79. P. Lambin, L.P. Biró, Structural properties of Haeckelite nanotubes. New J. Phys. 5, 141 (2003) 80. G. Mpourmpakis, G.E. Froudakis, Haeckelites: a promising anode material for lithium batteries application. An ab initio and molecular dynamics theoretical study. Appl. Phys. Lett. 89, 233125 (2006) 81. Z. Zhu, Z.G. Fthenakis, D. Tomanek, Electronic structure and transport in graphene/haeckelite hybrids: an Ab Initio study. arXiv:1502.07050, 2015; 2D Mater. 2015, 2, 035001 82. Z. Wang, X.-F. Zhou, X. Zhang, et al., Phagraphene: a low-energy graphene allotrope composed of 5–6–7 carbon rings with distorted dirac cones. Nano Lett. 15(9), 6182–6186 (2015) 83. Z. Wang, X.-F. Zhou, X. Zhang, et al., Phagraphene: a low-energy graphene allotrope composed of 5-6-7 carbon rings with distorted dirac cones. arXiv:1506.04824, 2015 84. A.I. Podlivaev, L.A. Openov, Possible nonplanar structure of phagraphene and its thermal stability. Pis'ma v Zh. Èksper. Teoret. Fiz. 103(3), 204–208 (2016)

References

411

85. L.F.C. Pereira, B. Mortazavi, M. Makaremic, T. Rabczukde, Anisotropic thermal conductivity and mechanical properties of phagraphene: a molecular dynamics study. RSC Adv. 6, 57773–57779 (2016) 86. A.Y. Luo, R. Hu, Z.Q. Fan, H.L. Zhang, J.H. Yuan, C.H. Yang, Z.H. Zhang, Electronic structure, carrier mobility and device properties for mixed-edge phagraphene nanoribbon by hetero-atom doping. Org. Electron. 51, 277–286 (2017) 87. Y. Liu, Z. Chen, S. Hu, G. Yu, Y. Peng, The influence of silicon atom doping phagraphene nanoribbons on the electronic and magnetic properties. Mater. Sci. Eng. B 220, 30–36 (2017) 88. D. Ferguson, D.J. Searles, M. Hankel, Biphenylene and phagraphene as lithium ion battery anode materials. ACS Appl. Mater. Interfaces 9(24), 20577–20584 (2017) 89. L.A. Openov, A.I. Podlivaev, Various stone–wales defects in phagraphene. Phys. Solid State 58(8), 1705–1710 (2016) 90. L.A. Openov, A.I. Podlivaev, Negative poisson’s ratio in a nonplanar phagraphene. Phys. Solid State 59(6), 1267–1269 (2017) 91. D. Wu, S. Wang, J. Yuan, B. Yang, H. Chen, Modulation of the electronic and mechanical properties of phagraphene via hydrogenation and fluorination. Phys. Chem. Chem. Phys. 19, 11771–11777 (2017) 92. X. Jiang, C. Århammar, P. Liu, J. Zhao, R. Ahuja, The R3-carbon allotrope: a pathway towards glassy carbon under high pressure. Sci. Rep. 3, 1877 (2013) 93. Y. Liu, M. Lu, M. Zhang, First-principles study of a novel superhard sp3 carbon allotrope. Phys. Lett. A 378(45), 3326–3330 (2014) 94. M. Xing, B. Li, Z. Yu, Q. Chen, A reinvestigation of a superhard tetragonal sp3 carbon allotrope. Materials 9, 484 (2016). 15 pp 95. Q. Zhu, A.R. Oganov, M.A. Salvadó, P. Pertierra, A.O. Lyakhov, Denser than diamond: Ab initio search for superdense carbon allotropes. Phys. Rev. B 83, 193410 (2011)

Chapter 7

Coordination/Organometallic Compounds and Composites of Carbon Allotropes

7.1

7.1.1

Metal-Complex Chemistry of Nanocarbons1

Carbon Nanotubes

1 The image (functionalization possibilities for SWCNTs: (a) defect-group functionalization, (b) covalent sidewall functionalization, (c) noncovalent functionalization with surfactants, (d) noncovalent exohedral functionalization with polymers, and (e) endohedral functionalization) is reproduced with permission of Intech (I.-Y. Jeon, D.W. Chang, N. Ashok Kumar, and J.-B. Baek. Functionalization of Carbon Nanotubes. IntechOpen, 2010, DOI: https://doi.org/10.5772/18396. Available from: https://www.intechopen.com/books/carbon-nanotubes-polymernanocomposites/functionalization-of-carbon-nanotubes).

© Springer Nature Switzerland AG 2019 B. I. Kharisov, O. V. Kharissova, Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications, https://doi.org/10.1007/978-3-030-03505-1_7

413

414

7.1.1.1

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Introduction

Metal complexes have a lot of useful applications in organic and organometallic chemistry, catalysis [1], medicine as anticancer pharmaceutics and for drug delivery [2], various biological systems [3], polymers [4] and dyes, separation of isotopes [5], and heavy metals [6], among many other uses. Sometimes they are applied for increasing solubility [7, 8] of classic objects, carbon nanotubes (CNTs),2 which form bundle-like structures with very complex morphologies with a high number of Van der Waals interactions, causing extremely poor solubility in water or organic solvents. Metal complexes are also able to serve as precursors to fill CNTs with metals [9] or oxides [10], to decorate CNTs with metal nanoparticles [11], as well as to be encapsulated by CNTs [12]. Various techniques are nowadays applied in order to obtain functionalized CNTs [13–16]. The simplest functionalization by mineral acids, usually used as a first step in many reports, leads to formation of -OH and -COOH groups, which further can be replaced with more complex organic moieties. In particular, as it will be shown below, a series of coordination and organometallic compounds have been successfully anchored onto CNTs by covalent or noncovalent mode. In this section, we describe peculiarities of functionalization of CNTs with metal complexes, paying particular attention to the ligand type (N-, O-, N,O-, N,S-, N,P-containing moieties), bond type inside complexes {coordination bond M-O, M-N, M-S, M-P; σ- and π-metal–carbon bond in organometallics}, and interaction type between CNTs and complex. Representative examples for the synthesis of CNTs hybrids/composites with metal complexes are shown in Table 7.1 and their main applications – in Table 7.2 at the end of the section.

Table 7.1 Overview of representative examples on the synthesis of metal-complex-functionalized carbon nanotubes Composite of metal complex with CNTs Conditions/procedure Complexes of organic acids or crown ethers [Na(dibenzo-18-crown-6)]n[SWCNT] Reduction of CNTs by Na/Hg amalgam in the presence of dibenzo-18-crown-6 Solvothermal synthesis {MWCNTs@Cu3(btc)2} (btc ¼ 1,3,5-benzenetricarboxylate) Complexes of amines, polypyridyl ligands, Schiff bases, porphyrins, and phthalocyanines Cobalt chloride complexed aminoalkylalkoxysilane FCNTs Reaction of N-[3-(trimethoxysilyl)propyl]-ethylenediamine with FCNTs pro(fluorinated CNTs) duced the corresponding aminoalkylalkoxysilane FCNTs. Cobalt salt was then complexed to these FCNTs by the addition of cobalt chloride to form cobalt complexed nanocomposite Ruthenium tris(bipyridyl) complex linked through peptidic Radical addition of thiol-terminated SWCNT to a terminal C¼C double bond bonds to SWCNTs of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex SWCNT–Cu2+ complex with stearic acid (SA) or A metal coordination reaction in ultrasonic conditions (before ligand ethylenediaminetetraacetic acid (EDTA) coordination) SWCNTs modified with metal-free porphyrin units Electropolymerization of pyrrole or pyrrole-substituted porphyrin monomers or interaction between glycyl-substituted porphyrin and non-modified CNTs SWCNT-PVPZn(TPP) nanohybrid {PVP ¼ poly Dispersible SWCNTs grafted with poly(4-vinylpyridine), SWCNT-PVP, were (4-vinylpyridine); (TPP ¼ tetraphenyl porphyrin)} tested in coordination assays with zinc tetraphenylporphyrin {Zn(TPP)} CNTs/MPc nanohybrids A mixture of FePc, CoPc, FePh, or CoPh and MWCNTs in isopropanol was prepared and sonicated for 30 min followed by magnetic stirring for 1 h Complexes of sulfur-containing ligands [PPh4][Cu(DMED)2] (DMED ¼ 1,2-dicarbomethoxy-1,2The reaction between a copper polysulfide precursor with activated acetylene, dithiolate) formation of nanospheres, and their further aggregation with water-soluble (carboxylated) carbon nanotubes (wsCNTs) Cyclopentadienyls, carbonyls, and π-complexes with aromatic compounds Cp2ZrCl2/MWCNTs Direct adsorption of Cp2ZrCl2 onto MWCNTs Ferrocene derivatives, π-stacked or covalently grafted onto a The immobilization of the ferrocene moiety via π–π interactions was done with film of CNTs a ferrocene derivative bearing a pyrene group. The covalent grafting on the film of CNTs was achieved in two steps via the electroreduction of an aminoethylbenzenediazonium salt followed by post-functionalization with an activated ester derivative of ferrocene (continued)

2

The image above is reproduced with permission of Elsevier Science (Chemical Physics Letters, 541, 81–84 (2012)).

7.1 Metal-Complex Chemistry of Nanocarbons

415

Table 7.1 (continued) Composite of metal complex with CNTs (η6-SWCNT)Cr(CO)3, (η6-SWCNT)Cr(η6-C6H6), (η6SWCNT)2Cr A multifunctional block copolymer incorporated with pyrene and ruthenium terpyridyl thiocyanato complex moieties Cobalt bis(4-pyren-1-yl-N-[5-([2,20 ;60 ,200 ]terpyridin-40 -yloxy)pentyl]-butyramide)-functionalized SWCNTs

Conditions/procedure Reactions of SWCNT and SWCNT-CONH(CH2)17CH3 with chromium hexacarbonyl and (η6-benzene)chromium tricarbonyl Reversible addition-fragmentation chain-transfer polymerization Direct functionalization SWCNTs via noncovalent ππ stacking interactions

For references, see corresponding sections above

Table 7.2 Overview of representative examples on the applications of metal-complex-functionalized carbon nanotubes Composite of metal complex with CNTs Applications Organic acids, crown ethers Determination of trace levels of lead {MWCNTs@Cu3(btc)2} (btc ¼ 1,3,5-benzene-tricarboxylate) Li@CNT@[Cu3(btc)2] Uptakes of CO2 and CH4 Complexes of amines, polypyridyl ligands, Schiff bases, porphyrins, and phthalocyanines Ethylenediamine-functionalized CNTs Good capacity to retain Hg2+ from complex matrix including fish and real water samples Tris(2,20 -bipyridyl)ruthenium(II) {Ru(bpy)32+}/CNTs Electrogenerated chemiluminescence (ECL) sensor for tripropylamine Nickel salen and salophen complexes/CNTs Catalysis for oxidation of primary and secondary alcohols MWCNT-palladium(II)-Schiff base complex Efficient catalysis in the coupling reactions of acid chlorides with terminal alkynes under copper-, phosphorous-, and solvent-free conditions in air FeIII-DETPA complex/CNTs Sensor to hydrogen peroxide Hybrid Ag-containing CNT composites on the basis of ligands NIonophores and as ion-to-electron transducers to construct Ag+ carbon (2-vinylsulfanyl-ethylidene)-benzene-1,2-dimine, N-pyridin-2paste electrodes ylmethylene-benzene-1,2-dimine, and N-furan-2-ylmethylene-benzene1,2-dimine Mixed assembly of ferrocene/porphyrin onto carbon nanotube arrays Candidates for molecular memory devices SWCNT doped with porphyrin-like nitrogen defects (4ND-CNxNT) Hydrogen storage with ten different transition metals (TMs ¼ Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) Phthalocyanine- and porphyrin-functionalized MWCNTs Nonprecious electrocatalysts for the electroreduction of oxygen FePc coated on SWCNTs Methanol oxidation in the ORR (organic reduction reaction) GOD@TiO2/FePc-CNTs (GOD ¼ glucose oxidase) Glucose biosensor [100, 101] Hybrid material composed of SWCNTs and cobalt phthalocyanine Excellent sensitivity and selectivity to dimethyl methylphosphonate (CoPc) derivatives (DMMP) (stimulant of nerve agent sarin) Cyclopentadienyls, carbonyls, and π-complexes with aromatic compounds SWCNTs and MWNTs covalently functionalized with a titanium alkSurface initiated titanium-mediated coordination polymerizations of oxide catalyst containing cyclopentadienyl (Cp) L-lactide, ε-caprolactone and n-hexyl isocyanate Ferrocene-functionalized SWCNTs Electrode for L-glutamate detection MWCNTs functionalized with pyrene nickel complexes through π–π Robust, noble-metal-free electrocatalytic nanomaterials for H2 evolustacking tion and uptake CNTs nanohybrid materials containing iridium N-heterocyclic carbene Use in heterogeneous iridium-catalyzed hydrogen-transfer reduction of (NHC)-type organometallic complexes cyclohexanone to cyclohexanol with 2-propanol/KOH as hydrogen source

7.1.1.2

Composites of CNTs with Metal Complexes of O-Containing Ligands

A few crown ethers have been used for CNTs functionalization, showing higher dispersibility of formed hybrids. Thus, SWCNTs may be made soluble in a range of organic solvents without sidewall functionalization via their reduction by Na/Hg amalgam in the presence of dibenzo-18-crown-6 [17]. The [Na(dibenzo-18-crown-6)]n[SWCNT] complex was consistent with no additional sidewall functionalization as compared with raw SWCNTs; the presence of the [Na(dibenzo-18-crown-6)]+ ion was shown. Solubility was found to be greatest in CH2Cl2 and DMF being comparable to surfactant dispersed SWCNTs; measurable solubilities were also detected in hexane, toluene, and alcohols. We note that benzo-18-crown-6 covalently linked to multiwalled carbon nanotubes (MWCNTs) can be used as ion sensors, in particular for Pb2+ determination [18].

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Other ligands, containing donor oxygen atom only, are rare. Thus, functionalization of oxidized SWCNTs by a zwitterionic interaction (COO  NH3+) between protonated amine on crown ether and an oxyanion from a carboxylic acid group on SWCNT was described [19]. The functionalization was achieved by adding 4-aminobenzo-9-crown-3 to SWCNTs (reactions 7.1.1.1). The ionic interaction led to a considerable increase in the solubility of SWCNTs in both organic and aqueous solvents such as ethanol, dimethyl sulfoxide, dimethylformamide, and H2O, showing the highest solubility in DMF and DMSO. The ionic bonded 4-benzo-9-crown-3 ether allowed the hosting of Li+, and the ionic bond of crown ether to SWCNT was identified. We note the important major differences of ionic functionalization to covalent functionalization made by authors: (a) the acid–base reaction represents the simplest possible route to soluble SWCNTs and can be readily scaled up at low cost. (b) Unlike the covalent amide bond, it seems that the presence of zwitterions (ionic functionalization) can significantly improve the solubility of SWCNT-CE (crown ether) in aqueous solvents. (c) The cation in crown ether of the ionic bond of SWCNT-COONH3+ of SWCNTs can be readily exchanged by other organic and inorganic cations. (d) The authors found that the covalent functionalization approach generally gave a much higher yield (30.4%) of SWCNT–CE than the ionic functionalization approach (26%). O

O

NH2

+

O O

Functionalization of SWCNTs-COOH with 4-amino benzo-9-crown-3 ether. O

NH3

O

Li

10 min sonication DMF (7.1.1.1)

C

SWCNTs-CE

O

Incorporation of Li in SWCNT-CE

C

O

O

O

HO

+

LiCl/H2O-DMF

.))), 1h

NH3

O

+

O

O O

C

SWCNTs-CE-Li +

The solvothermally prepared MWCNT-metal–organic frameworks {MWCNTs@Cu3(btc)2} (btc ¼ 1,3,5benzenetricarboxylate 7.1.1.1) were studied for the determination of trace levels of lead [20]. The experimental procedure was carried out by accumulating lead on the electrode surface and subsequently measuring with differential pulse anodic stripping voltammetry in a lab-on-valve format. The main parameters affecting the analytical performance, including the amount of MWCNTs@Cu3(btc)2 suspension, supporting electrolyte and its pH, stripping mode, and flow rate, have been investigated in detail. Under the optimum conditions, the oxidation peak current displayed a calibration response for lead over a concentration range from 1.0  109 to 5.0  108 mol L1 with an excellent detection limit of 7.9  1010 mol L1. In a related research [21], Li@CNT@[Cu3(btc)2] composite was applied for the uptakes of CO2 and CH4.

7.1 Metal-Complex Chemistry of Nanocarbons

417

O

O

O

O

O

O

BTC anion 7.1.1.1 7.1.1.3

Composites of CNTs with Metal Complexes of N- and N,O-Containing Ligands

As an application of ligands (generally amines), containing only nitrogen donor atoms,3 participating in the coordination with metal, we note the reaction of N-[3-(trimethoxysilyl)propyl]ethylenediamine with fluorinated carbon nanotubes (FCNTs) produced the corresponding aminoalkylalkoxysilane FCNTs [22]. Cobalt salt was then complexed (reactions 7.1.1.2) to these FCNTs by the addition of cobalt chloride to form cobalt complexed nanocomposite in high yield. The amino-functionalization of MWCNTs with ethylenediamine (Fig. 7.1) led [23] to functionalized MWCNTs having a good capacity to retain Hg2+ from complex matrix including fish and real water samples, in a difference with the raw and purified MWCNTs, which were found not to adsorb Hg2+ ions. Effective parameters on Hg2+ retention such as pH, flow rate, nature of the eluent, the ionic strength, selectivity coefficient, and retention capacity were studied, revealing, in particular, that the enrichment factor and maximum capacity of the sorbent were 100 mL and 11.58 mg/g, respectively. Selectivity experiments showed that the adsorbents have a stronger specific retention for Hg2+ than Fe3+, Cu2+, Pb2+, Ni2+, Mn2+, Ca2+, and Mg2+. The Hg2+ ions adsorbed by aminofunctionalized MWCNTs were found to be mainly aggregated on the ends and at the defect sites on the amino-functionalized MWCNTs. The sorption mechanism appears mainly attributable to supramolecular interaction between the mercury ions and the surface functional groups of amino-functionalized MWCNTs which have a negative charge.

F

x + R

pyridine, 120oC

H N

H N

Si(OCH3)3

z

- HF F

y THF

R = N-[3-(trimethoxysilyl)propyl]-ethylene diamine x >> y

CoCl2.6H2O (7.1.1.2)

Cl

Cl

Co N

F

N

Si(OCH3)3

z

y

Ruthenium polypyridyl complexes are widely used as light harvesters in dye-sensitized solar cells. At the same time, one of potential applications of SWCNTs is their use as active components in organic and hybrid solar cells; so, the study of the

3

Porphyrin and phthalocyanine composites with carbon nanotubes will be discussed below in separated sections.

418

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

O

M

M

W

W

O

O

M

OH Aminofunctionalization

NH2

W

Oxidation

C

HNO3

C

1) SOCl2 2) C2H4(NH2)2

M

NH

SPE

C

HgCI2(aq)

Hg2+

NH

W

NH2

C

N

N

O

N

O

N

O

T

T

OH

T

NH

T

NH

NH2

Hg2+ NH2

(a) Chemical reaction (b) Chemical reaction (c) Supramolecular interaction Fig. 7.1 Schematic illustration of amino-functionalization of MWCNTs {(a) and (b)} and solid-phase extraction step (c). In the first step, MWCNTs are oxidized by HNO3 (a), and subsequently the oxidized MWCNTs are amino-functionalized by ethylenediamine (b). In the solidphase extraction step, mercury ions are adsorbed on the surface of amino-functionalized MWCNTs, and this is a kind of supramolecular interaction

(a)

(b) CO2H

O C NH

HNO3/H2SO4 HO C 2 70 °C, 4 h

1) EDC, NHS (pH 5.45), 1 h HO2C 2)Ru(bpy)2(5-NH2-1,10phen)2+ (pH 7.40), 24 h

CO2H

100 nm

MWNTs

FCNT

N N

N Ru N

N N

CO2H FCNT-Ru(bpy)2(5-NH21,10-phen)2+

Fig. 7.2 TEM image of FCNTs (a) and a schematic showing the steps involved in the process of combining [Ru(bpy)2(5-NH2-1,10-phen)]2+ with the FCNTs using the EDC and NHS linking reaction (b)

photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important and a variety of such complexes have been obtained and studied. Among other applications of Ru/CNT composites, we emphasize their uses as sensors. Thus, mesoporous films of platinized carbon nanotube–zirconia–Nafion composite were used for the immobilization of tris(2,20 -bipyridyl)ruthenium(II) {Ru(bpy)32+} on an electrode surface to yield a solid-state electrogenerated chemiluminescence (ECL) sensor [24]. The composite films of Pt–CNT–zirconia–Nafion exhibited much larger pore diameter (3.55 nm) than that of Nafion (2.82 nm) and thus leading to much larger ECL response for tripropylamine (TPA) because of the fast diffusion of the analyte within the films. The present ECL sensor based on the Pt–CNT–zirconia–Nafion gave a linear response (R2 ¼ 0.999) for TPA concentration from 3.0 nM to 1.0 mM with a remarkable detection limit (S/N ¼ 3) of 1.0 nM, which is much lower compared to those obtained with the ECL sensors based on other types of sol-gel ceramic–Nafion composite films such as silica–Nafion and titania–Nafion. In a closely related research [25], an effective ECL sensor was developed by combining bis(2,20 -bipyridine)-5-amino-1,10-phenanthroline ruthenium(II) [Ru(bpy)2(5-NH2–1,10-phen)2+] with functionalized carbon nanotubes (FCNTs) coated on a glassy carbon electrode (Fig. 7.2). The modified electrode exhibited good electrochemical activity and ECL response. The ECL detection limit (S/N) for TPA using this modified electrode was 8.8  107 mol L1 with a linear range from 1.0  106 to 2.0  103 mol L1 (R2 ¼ 0.9969). The dispersion of SWCNTs in the presence of water-soluble polypyridyl complexes of the general formula [Rux(bpy)yL]2+ (L ¼ dppz 7.1.1.2, dppn 7.1.1.3, tpphz 7.1.1.4) was achieved [26]. These ligands have extended planar π systems, which aid in the solubilization of SWCNTs via π–π interactions (composites 7.1.1.5–7.1.1.7). Another example is a water-soluble ruthenium tris(bipyridyl) complex 7.1.1.8 linked through peptidic bonds to SWCNTs (Ru-SWCNTs) that was prepared by radical addition of thiol-terminated SWCNT to a terminal C¼C double bond of a bipyridyl ligand of the ruthenium tris (bipyridyl) complex [27]. The resulting macromolecular Ru-SWCNT (500 nm, 15.6% ruthenium complex content) was found to be water-soluble. The emission of Ru-SWCNT was 1.6 times weaker than that of a mixture of [Ru(bpy)3]2+ and

7.1 Metal-Complex Chemistry of Nanocarbons

419

Fig. 7.3 Molecular graphs of (a) the CNT complex and their NCI-RDG (noncovalent interaction reduced-density-gradient) isosurfaces, and (b) the buckyball complex and (c, d) their NCI-RDG isosurfaces. The isosurface value is s ¼ 0.3. (Reproduces with permission of the Australian Journal of Chemistry)

SWCNT of similar concentration. Time-resolved absorption optical spectroscopy allowed the detection of the [Ru(bpy)3]2+excited triplet and [Ru(bpy)3]+. In a related report [28], dedicated to phenanthroline derivatives, the stacking of the anticancer metal complex [(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)-platinum(II)]2+ 7.1.1.9 onto the MWCNT surface and fullerenes (Fig. 7.3) was examined. The formation of a supramolecular complex with MWCNTs was confirmed (90% efficiency of binding, 95% with addition of the surfactant, pluronic F-127), but not with C60-buckyballs. The loading of 7.1.1.9 onto the MWCNTs takes place via π–π stacking from the metal complex’s phenanthroline ligand and C–H. . . ..π bonding from the diaminocyclohexane ligand. Analogously, MWCNTs (1–3 μM in length and 20–25 nm in diameter) were functionalized with a 2,20 :60 200 -terpyridine4-chelated ruthenium(II) complex 7.1.1.10 by covalent amidation (reactions 7.1.1.3) [29]. The resulting functionalized ruthenium MWCNTs (RuMWCNTs) were 1–2 μM in length and 10–20 nm in diameter. The functional group coverage of terpyridine–ruthenium–terpyridine (tpy–Ru–tpy) was found to be 0.7036 mmol/ 1.0 g carbon. The tpy–Ru–tpy moieties are interconnected or attached as aggregated structures (100–200-nm range) on the surfaces of the MWCNTs after functionalization. RuMWCNTs can be easily dispersed in DMF, DMSO, and MeCN to form a stable suspension after sonication. In addition, hexameric metallomacrocycles on the basis of terpyridine-metal(II)-terpyridine (M ¼ Ru, Fe) connectivity were attached to MWCNTs through cation exchange [30].

4

See also information below about other terpyridine complexes, noncovalently attached to CNTs through pyrene moiety.

420

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

N

N

N

N

N N

N

N

7.1.1.2, dppz = dipyrido[3,2-a:2',3'c]phenazine

7.1.1.3, dppn = 4,5,9,16-tetraazadibenzo[a,c]naphthacene, benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine

N N

N

N

N

N Ru

N N

N

N

N

N

N

N

7.1.1.4, tpphz = tetrapyridophenazine

N

N

N

N

N

N

N Ru

N

7.1.1.5, [Ru(bpy)2(dppz)]2+ composite with SWCNTs

N

N

N

N

N

Ru

N Ru

N N

N

N

N

N

N

N

7.1.1.6, [Ru(bpy)2dppn]2+

7.1.1.7, [(bpy)2Ru(tpphz)Ru(bpy)2]4+

7.1 Metal-Complex Chemistry of Nanocarbons

N

N

N

421

2PF6-

Ru2+

N

N N

HO N

S

O

HO

N

N

N

Ru2+

O

HO

N

N N

HO N

S

2PF67.1.1.8

2+

H2 N

N Pt

N H2

N

7.1.1.9

N

N H2N

N

Ru

N

(BF4)2 NH2

N

N

7.1.1.10

422

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes COCl COCl

COOH COOH COOH

HOOC

HNO3

SOCl2

85oC

80oC

HOOC

COOH

ClOC

COCl

ClOC

COCl COCl COCl

COOH COOH

H2N

N

Ru N

O

N

N N

NH2

N

N

(7.1.1.3)

O N

Ru

N

DMF

N

N

H N

(BF4)2

N H

N

2BF4

Other compounds are represented by a variety of N,O-donor ligands, classic compounds as EDTA, salen or salophen ligandsp. Thus, nickel salen {N,N0 -bis(4-hydroxysalicylidene)ethylene-1,2-diamine, 7.1.1.11} and salophen {N,N0 -bis (4-hydroxysalicylidene)phenylene-1,2-diamine, 7.1.1.12} complexes were covalently anchored on 20–40 nm MWCNTs (reactions 7.1.1.4) [31]. Their catalytic performance for the oxidation of ten distinct primary and secondary alcohols was evaluated using periodic acid H5IO6 as oxidant in acetonitrile at 80  C. The reusability of supported catalysts was investigated in the multiple sequential oxidation of benzyl alcohol, indicating excellent results. Reaction conditions were optimized for MWCNT-supported salen and salophen complexes by considering the effect of parameters such as solvent, reaction time, concentration of catalyst, amount of oxidant, etc. The catalytic activity was found to be higher for supported catalysts than similar homogeneous ones. These supported catalysts were highly stable and reused several times without the loss of catalytic activity. Similar results were also reported for salen complexes with cobalt(II) [32], nickel(II) [33], and oxo-vanadium(IV) [34]. In the last case, liquid-phase oxidation of cyclohexane with H2O2 to a mixture of cyclohexanone, cyclohexanol, and cyclohexane-1,2-diol in CH3CN was reported using oxo-vanadium(IV) Schiff base complex 7.1.1.13 covalently anchored on modified MWNTs as catalysts.

7.1 Metal-Complex Chemistry of Nanocarbons

423

N

N

N

N

HO

OH

HO

HO

OH

OH

7.1.1.11

7.1.1.12

HO

OH

HNO3 COOH

SOCl2

Reflux, 4 h

65oC, 24 h

COCl

(7.1.1.4)

N O

HO

Ni N O

OH

N

N Ni

O

O OH

COO

COCl

N O COO

Ni

N O OOC

Synthesis of MWCNT-supported nickel complexes.

424

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes N

N

O

O V O

O

O

7.1.1.13

Related Cu2bisalophen complex 7.1.1.14 can be assembled in a noncovalent manner (Fig. 7.4) on SWCNTs elaborated by HiPCO and hot filament-assisted chemical vapor deposition techniques [35]. The origin of the nanotubes seems to not affect the electronic interaction responsible for this assembly. Noncovalent grafting of metal transition complexes onto SWCNTs in a CNFET channel leads to electron transfer from the molecules to the nanotube and generates a tunable ambipolar effect in ambient air conditions. This opens the possibility to design new kinds of nanohybrid circuits. In addition, the MWCNT– palladium(II)–Schiff base complex (for the synthesis, see reaction scheme 7.1.1.5) was found to efficiently catalyze the coupling reactions of acid chlorides with terminal alkynes under copper-, phosphorous-, and solvent-free conditions in air (reaction 7.1.1.6) for the synthesis of α,β-acetylenic ketones under aerobic conditions. This moisture- and air-stable heterogeneous catalyst could be simply recovered and used in four successive runs [36].

N

N

O

Cu

Cu O

O

N

N

7.1.1.14

O

7.1 Metal-Complex Chemistry of Nanocarbons

425

Fig. 7.4 View of the optimized structure (perpendicular orientation for 7.1.1.14 grafted onto a (7,6) nanotube from theoretical calculations). Blue, red, light blue, and brown spheres correspond to copper, oxygen, nitrogen, and carbon atoms, respectively, and hydrogen atoms are indicated as brown sticks. (Reproduced with permission of the American Chemical Society)

O

O

SOCl2, DMF, N2 OH

Cl

65oC,

24 h

OH

N

CHCl3, N2, reflux

N Pd

(7.1.1.5)

O

O

O

O

N

N Pd

O

O

+ R2 R1

Cl

H

O

NEt3, neat, r.t. Pd-Schiff-base@MWCNTs Cat. R1 30-120 min.

O

R2 (7.1.1.6) 53-94%

426

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.5 Procedures for the metallization of SWCNTs with Cu2+ ions by the metal coordination reaction and for the subsequent surface modification of SWCNTs with carboxylic acid and methyl groups by coordination between the Cu2+ and EDTA or SA, respectively. X in the final products, SWCNT–Cu2+–EDTA or SA represents functional group terminated on SWCNT surfaces after coordination reaction between SWCNT–Cu2+ and EDTA or SA. (Reproduced with permission of the Elsevier Science)

An interesting functionalization method for SWCNTs was offered [37]. The Cu2+ ion was effectively coordinated with a SWCNT to produce a SWCNT–Cu2+ complex by a metal coordination reaction in ultrasonic conditions. Since the complex was very reactive toward the carboxylic acid group, the chemical functionalization of SWCNTs was easy to accomplish. This approach was used to functionalize the surface of the SWCNTs with stearic acid (SA) or ethylenediaminetetraacetic acid (EDTA) (Fig. 7.5) for tuning of the relative hydrophobicity and hydrophilicity of the surface, respectively. Functionalization of SWCNTs by metal coordination reaction effectively modified the SWCNT surface while conserving the excellent physical properties of the SWCNTs. The surface properties of the SWCNTs were easily tuned by introduction of the functional groups required for specific applications. Using the EDTA analogue, DETPA (diethylenetriaminepentaacetic acid 7.1.1.15), by combining the electrostatic interaction between the FeIII-DETPA complex and polyallylamine (PAH)-functionalized MWCNTs as well as the ionotropic cross-linking interaction between PAH and ethylenediamine-tetramethylene phosphonic acid (EDTMP 7.1.1.16), the electroactive FeIII–DETPA complex was incorporated within the MWCNT matrix and firmly immobilized on the Au substrate electrode [38]. The influences of solution pH and ionic strength on this electrochemical sensor were investigated, showing that the sensor had a fast response to hydrogen peroxide ( Fe > Co. In a related report [62], aminofunctionalized a-MWCNT-supported iron phthalocyanine (FePc) (a-MWCNT/FePc) was investigated as a catalyst for the ORR in an air–cathode single-chambered microbial fuel cell (MFC), providing a potential alternative to Pt in MFCs for sustainable energy generation. In addition, FePc coated on SWCNTs, synthesized as a non-noble electrocatalyst for the ORR, exhibited higher activity than the commercial Pt/C catalyst and excellent anti-crossover effect for methanol oxidation in the ORR [63]. The preparation of other phthalocyanine-CNT-based hybrid covalent-functionalized materials is shown in reaction Scheme 7.1.1.135 [64]. Pd(II)Pc-SWCNT and Ru(II)bis(pyridine)Pc-SWCNT were prepared by multistep procedures and attached to modified SWCNTs. It was noted that, for the second composite, although spectroscopic characterization supports the covalent binding of Pc molecules to the modified SWCNT sidewalls, direct evidence of the presence of Ru(II) in the hybrid material could not be obtained.

t-Bu

t-Bu

N N

N N

Pd

N

N

N N

O

t-Bu

O

O

HO

O N

O N

N-methylglycine 4-formbenzoic acid

O

7.1.1.27, EDC, HOBt, THF

O

7.1.1.28, EDC, HOBt, THF (7.1.1.13) HiPco SWCNTs

7.1.1.27, EDC, HOBt, THF i) SOCl2, DMF

i) methylaminobenzoate isoamylnitrite ii) NaOH

ii) 7.1.1.28, THF

u

t-B

O COOH

N N N

u

t-B

N

u

t-B

5

Reproduced with permission of the Royal Society of Chemistry

N

N Ru

N

N NN

O

440

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Several examples of noncovalent functionalization are also known for phthalocyanine-CNT composites. Thus, studies of a hybrid material composed of SWCNTs and cobalt phthalocyanine (CoPc) derivatives 7.1.1.29 revealed [65] that the CoPc derivatives were anchored on the surface of nanotubes through π–π stacking. Gas sensor tests were performed to check the potential of this hybrid material while the sensing devices were fabricated. The synergetic behavior between both of the candidates allowed an excellent sensitivity and selectivity to dimethyl methylphosphonate (DMMP) (stimulant of nerve agent sarin). Also, MWCNTs were noncovalently functionalized with different metal (M ¼ Zn, Cu, Ni) phthalocyanines by π–π stacking method [66] via dispersion by sonication into the phthalocyanines solution in chloroform or N, N-dimethyl formamide before refined purification by centrifugation. It could be observed that the metal phthalocyanine molecules adhered to the surface of MWCNTs in the TEM images. R

R N

N

N N

Co

N

N

N

N R

7.1.1.29 R O

R=

C

H N

CF3 OH CF3

A family of pyrene 7.1.1.30 (Pyr)-substituted phthalocyanines (Pcs) (see also the detailed pyrene section below), i.e., ZnPc-Pyr and H2Pc-Pyr, were designed, synthesized (reaction scheme 7.1.1.14), and probed in light of their spectroscopic properties as well as their interactions with SWCNTs [67]. Owing to the strong ability of pyrene to adhere to SWCNT sidewalls by means of π–π interactions, this polyaromatic anchor was exploited to immobilize metal-free (H2Pc) as well as zinc (ZnPc) phthalocyanines onto the surface of SWCNTs. The pyrene units provided the means for noncovalent functionalization of SWCNTs via ππ interactions, ensuring that the electronic properties of SWCNTs are not impacted by the chemical modification of the carbon skeleton. Transient absorption experiments reveal photoinduced electron transfer

7.1 Metal-Complex Chemistry of Nanocarbons

441

between the photoactive components. ZnPc-Pyr/SWCNT and H2Pc-Pyr/SWCNT have been integrated into photoactive electrodes, revealing stable and reproducible photocurrents with monochromatic internal photoconversion efficiency values for H2Pc-Pyr/SWCNT as large as 15 and 23% without and with an applied bias of +0.1 V. Related zinc monoamino phthalocyanine ZnMAPc–pyrene complex and its hybrid with SWCNTs was also described [68].

7.1.1.30 R

R

N R

M

N

HO

N

N

R

R

R O

N N

R

N

N

N M

N

N

N

(7.1.1.14)

N

O

R N

N

N

O

OH R

R

7.1.1.6

R

M = H2

H2Pc-OH

R = O(C6H4)-p-t-Bu

R

ZnCl2 o-DCB/DMF (1:1)

M = H2

H2Pc-Pyrene

M = Zn

ZnPc-Pyrene

Composites of CNTs with Complexes of Sulfur-Containing Ligands

The sulfur-containing ligands are practically absent in the form of their CNT composites. The only exception is the synthesis, and structural characterization of a stable discrete bis-dithiolene complex, [PPh4] [Cu(DMED)2] (DMED ¼ 1,2dicarbomethoxy-1,2-dithiolate), involving the reaction between a copper polysulfide precursor with activated acetylene, was reported [69]. This complex, possessing terminal –COOCH3 groups, forms nanospheres by hydrogen bonding in a mixture of solvents containing water as one of the components. These nanospheres further aggregate with water-soluble (carboxylated) carbon nanotubes (wsCNTs). These nanocomposites are assisted by hydrogen bonding between the carboxylic acid groups of the wsCNTs and the peripheral –COOCH3 groups of the coordinated dithiolenes of the nanospheres, which is promoted by water molecules.

7.1.1.7

Functionalization of CNTs with Organometallics

Metal Cyclopentadienyls A simple method for tuning catalytic property of a classic widely used metallocene-based catalyst, Cp2ZrCl2, for ethylene polymerization by the direct adsorption (Fig. 7.17) of Cp2ZrCl2 onto MWCNTs was reported as far back as in 2006 [70]. The direct interactions between MWCNTs and the Cp rings of Cp2ZrCl2 controlled the polymerization behaviors, and the polyethylene with an extremely high molecular weight (MW ¼ 1,000,000) can be thus generated. Also, SWCNTs and MWNTs were covalently functionalized with a titanium alkoxide catalyst through a Diels–Alder cycloaddition reaction (reaction scheme 7.1.1.15) [71] and used for the surface-initiated titanium-mediated coordination polymerizations of L-lactide, ε-caprolactone, and n-hexyl isocyanate employing the “grafting from” technique. The final polymer-grafted CNTs were readily dissolved in organic solvents as compared to the insoluble pristine and catalyst-functionalized CNTs. In addition, the interaction of organometallic chromium-centered free radicals generated by the homolytic dissociation of

442

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.17 Preparation of Cp2ZrCl2-MWCNT. (Reproduced with permission of Wiley)

(pentamethylcyclopentadienyl)-chromiumtricarbonyl dimer [Cp*Cr(CO)3]2 {forming *Cp•Cr(CO)3} in toluene with SWCNTs was investigated [72]. It was noted that chromium-centered free radicals were found to be added to the surface of nanotubes through rather oxygen atoms than to sidewall carbon atoms. It was concluded that chromium atom in the *Cp•Cr (CO)3 free radical attacks irreversibly oxygen atoms in the oxidized nanotube with substantial transfer of electron density from chromium to oxygen. It was also shown that chromium-centered free radicals interact preferentially with SWCNT of a smaller diameter; the addition of chromium-centered radicals to SWCNT resulted in partial changes in the electronic structure of nanotubes. The observed sidewall-functionalized carbon nanotubes involving the addition of chromium metal complex can be useful for the development of new supported catalysts with interesting catalytic properties.

Br

CH2CH2OH

MgBr O

Cl Ti

Cl

Mg

Cl

THF (7.1.1.15)

Cl CH2CH2O

Cl Ti Cl

CH2CH2O

Ti Cl

235oC, tetradecane 25-35 min. n

Grignard synthesis of (1-benzocyclobutene ethoxy)dichlorocyclopentadienyltitanium (BCBEOTiCpCl 2) and covalent functionalization of MWNTs using a [4+2] Diels-Alder cycloaddition reaction. A theoretical characterization of transition metal cyclopentadienyls (CpM, M ¼ Fe, Ni, Co, Cr, Cu) adsorbed on pristine and boron-doped carbon nanotubes (B-CNTs) and boron-doped graphenes was carried out using spin-polarized DFT calculations (Fig. 7.18) [73]. Significant increases of the binding energies between CpTM and boron-doped CNTs and graphenes (versus pristine carbon supports), surpassing even the adsorption strength of the isolated metals atoms (by about 2 eV), were revealed. Both the delocalization of the metal d-state by the presence of the Cp ring and the π-stacking interactions between the Cp ring and the carbon substrate are responsible for the enhancement of the binding energies. This stabilization may play an important role in immobilizing ferrocene-based catalysts. The following characteristics, with some exceptions, were observed for the CpM adsorption: (a) most CpM complexes occupy the hollow sites of the six-membered ring center and (b) some complexes adsorb near the center on the sidewall.

7.1 Metal-Complex Chemistry of Nanocarbons

443

Fig. 7.18 Optimized geometries of CpFe on CNT/B-CNT complexes. Selected distances are shown in units of angstroms, corresponding to the Fe to Cp ring center distance. (a) CpFe/B-CNT(6,6). (b) CpFe/CNT(6,6). (c) CpFe/B-CNT(8,0). (d) CpFe/CNT(8,0). (Reproduced with permission of the American Chemical Society)

Fig. 7.19 Functionalization process of FWCNT sample by ferrocene derivatives. (Reproduced with permission of Wiley)

Ferrocene-functionalized [74, 75] CNTs are the object of a series of recent reports; their interaction could be covalent, noncovalent, or of both types at the same time. Thus, a ferrocene-functionalized SWCNT noncovalent nanohybrid was investigated by using a ferrocene-/SWCN- interdigitated construction film as an electrode for L-glutamate detection {exhibiting a high catalytic efficiency, high sensitivity, and fast response during the detection of a low concentration of Lglutamate (1 μM)} [76]. Ferrocene could immobilize on the surface of SWCNT bundles, and the ferrocene/SWCNT hybrid had a high stability not only in water but also in an organic solvent such as ethanol and acetone (no sediment was observed for more than 3 months). Unlike the previous example, the covalent functionalization (Fig. 7.19) of few-walled CNTs (FWCNTs) by ferrocene derivatives showed to a) improve their dispersion efficiency in water and b) graft electroactive chemical groups on their side walls in order to promote electron transfer to biomolecules [77]. Thus functionalized CNTs (f-CNTs) were used to modify a glassy carbon electrode, and this modified electrode was applied for oxidizing the cofactor NADH (dihydronicotinamide adenine dinucleotide). Shortened and oxidized MWCNTs were also functionalized with adenine using the amidation strategy [78] and further complexed with a uracil substituted ferrocene (Fig. 7.20). The presence of corrugations on the nanotube surface was revealed; the complexation between CNT-bound adenine and uracil was confirmed, as well as the presence of iron from ferrocene on the nanotube surface. Finally, ferrocene derivatives were π-stacked or covalently grafted (Fig. 7.21) onto a film of CNTs in order to determine the most effective method to immobilize redox centers on those high surface area electrodes for sensors or catalytic applications [79].

444

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.20 Schematic illustration of the assembly of electroactive ferrocene onto functionalized MWCNTs by exploiting the supramolecular noncovalent interactions of adenine–uracil base pairs. (Reproduced with permission of Elsevier Science)

Fig. 7.21 The two methods used to functionalize MWCNTs with ferrocene. Up, via π–π stacking and down, via covalent grafting. (Reproduced with permission of Elsevier Science)

The immobilization of the ferrocene moiety via π–π interactions was done with a ferrocene derivative bearing a pyrene 25 group. The covalent grafting on the film of CNTs was achieved in two steps via the electroreduction of an aminoethylbenzenediazonium salt followed by post-functionalization with an activated ester derivative of ferrocene. The covalent grafting route gave more redox centers fixed on CNTs than the π-stacking one, and the probes were found to be located differently on the electrodes. Comparing both processes, the authors noted that they gave access to immobilized redox molecules on CNTs for a wide variety of applications. The facile π-stacking of pyrene affords the attachment of a single monolayer of molecules in a self-assembled manner homogenously divided on the MWCNTs. The covalent derivatization of CNTs with ferrocene moieties unlike the πstacking one gives a stable and reliable glucose sensor electrode material. Carbonyls and π-Complexes with Aromatic Compounds As a classic work (2002) in this area, we note the report [80], where the coordinatively unsaturated Vaska’s compound 7.1.1.31, trans-chlorocarbonyl-bis(triphenylphosphine) iridium(I), was complexed with raw SWCNTs as well as with oxidized, purified nanotubes. The coordination modes were revealed to be different in each case (reaction schemes 7.1.1.16 and 7.1.1.17). Later on, the functionalization of SWCNTs with Vaska’s complex containing bromine, trans-Ir(CO)Br(PPh3)2, was investigated by means of hybrid quantum mechanics/molecular mechanics (QM/MM) calculations [81]. It was not able to find a stable bound adduct between Vaska’s complex and the perfect

7.1 Metal-Complex Chemistry of Nanocarbons

445

Fig. 7.22 Model of nonbonding interactions that develop during complex adsorption onto the MWCNT sidewall. (Reproduced with permission of the American Chemical Society)

hexagonal network of a (9,0) CNT, thus suggesting that the sidewall is relatively inert to an attack from Vaska’s complex. However, nanotube end caps or defective sites on the sidewall show a higher propensity to coordination with the inorganic fragment, indicating such sites as more suitable coordination centers for an η2 bonding, similar to the case of C60. Hence, a stable adduct is more likely to be formed when at least one of the coordinating carbon atoms belongs to a pentagonal ring. For η4-(1E,3E)-dienyl-Fe(CO)3 iron complexes, it was demonstrated [82] that they can bind noncovalently and reversibly to MWCNT sidewalls via hydrophobic and/or ππ stacking interactions (Fig. 7.22). It was emphasized [83] that these ironcomplexed MWCNTs may be readily dissociated in CH3CN as a result of the weak noncovalent binding to the nanotubes.

OC

PPh3

OC

+

Ir

Ir Ph3P

PPh3

Ph3P

Cl

Cl

(7.1.1.16)

7.1.1.31 PPh3 Ir OC

Cl

PPh3

O

OH

O O

KMnO4 H2SO4/HCl

OH

Ir(CO)Cl(PPh3)2

O

OH HO PPh3

OC O

O Ph3P

O

Ir

OH

Cl

(7.1.1.17) O O

OH O

PPh3

OC H Ph3P

OH O

Ir Cl

O OH

O

H

O Ph3P

Ir

CO PPh3

Cl

446

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.23 Scanning electron micrographs of (a–b) pristine SWCNTs, (c–d) (η6-SWCNT)-Cr(CO)3, and (e–f) (η6-SWCNT)Cr(C6H6). (Reproduced with permission of Wiley)

Fig. 7.24 Schematic presentation of organometallic chromium sidewall complexes of SWCNT with different modes of bonding. (Reproduced with permission of Wiley)

In addition to related chromium complex [Cp*Cr(CO)3]2 described in one of previous sections, organometallic sidewall complexes of pristine and octadecylamine-functionalized SWCNTs (reactions 7.1.1.18–7.1.1.21) were prepared under conditions, which allowed the study of both mono- and bis-hexahapto SWCNT coordination compounds [(η6-SWCNT)Cr (CO)3, (η6-SWCNT)Cr(η6-C6H6), (η6-SWCNT)2Cr] (Fig. 7.23) [84]. Both endohedral and exohedral modes of chromium complexation to SWCNTs are possible (Fig. 7.24), as well as bridging mode (Figs. 7.24 and 7.25) [85]. In the first case, a stable and kinetically inert mode of CNT sidewall bonding with chromium reagents was established, which partially preserves

7.1 Metal-Complex Chemistry of Nanocarbons

447

Fig. 7.25 (Left) SEM image of a metalSWCNT film. (Right) Bis(hexahapto) bond formation at the inter-nanotube junction via a chromium atom. (Reproduced with permission of the American Chemical Society)

the band electronic structure of the CNTs. The bonding of the Cr(CO)3 moieties and Cr(η6-benzene) fragments to the SWCNTs is primarily covalent in nature, with slight charge-transfer character in the case of Cr(CO)3. The electrical conductivity of SWCNT thin films was significantly enhanced by sidewall bonding to Group 6 transition metals (M ¼ Cr, Mo, and W), which serve to reduce the inter-carbon nanotube junction electrical resistance by the formation of SWCNT interconnects [(η6-SWCNT)2M]. Similar results were discussed for other related extended periodic π electron systems: exfoliated graphene (XG), epitaxial graphene (EG), and highly oriented pyrolytic graphite (HOPG) [86]. In the case of HOPG, (η6-HOPG)Cr(CO)3 was isolated, while the exfoliated graphene samples were found to give both (η6-graphene)2Cr and (η6-graphene)Cr(CO)3 structures. CO OC

CO Cr

Cr(CO)6

(7.1.1.18)

Bu2O, 110 oC, 5 days

CO CO

OC Cr

O

NH(CH2)17CH3

O

NH(CH2)17CH3

Cr(CO)6

(7.1.1.19)

Bu2O, 110 oC, 5 days

Cr

(C6H6)Cr(CO)3

(7.1.1.20)

Bu2O, 110 oC, 5 days

Cr

O

NH(CH2)17CH3

(C6H6)Cr(CO)3 Bu2O, 110 oC, 9 days

O

NH(CH2)17CH3

(7.1.1.21)

Reactions of SWCNT and SWCNT-CONH(CH2)17CH3 with chromium hexacarbonyl and (η6-benzene)chromium tricarbonyl.

448

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Carbonyl organometallics can be entrapped in CNT channels. Thus, SWCNTs were found to be effective nanoscale containers (Fig. 7.26) for a redox-active organometallic half-sandwich complex CpMeMn(CO)3, acting simultaneously as nano-reactor and nano-electrode [87]. It was proposed for this complex that the characteristics of metallocenes (CpMe ligand) provide effective interactions with the nanotube π system; at the same time, three carbonyl ligands can serve as a spectroscopic marker and good leaving groups in electrochemical reactions. It was proved that the nanotube confinement prevents reaction 7.1.1.22 of this complex with the MeCN solvent (Fig. 7.27). In electrochemical experiments, the complex remained inside the SWCNTs, which indicates that the carbon nanotubes act as a physical bridge between the individual encapsulated molecules and the macroscopic GCE electrode.

Fig. 7.26 (a) HRTEM image of two CpMeMn(CO)3@SWCNT structures showing Mn metal as dark contrast (white arrows) located solely inside the SWCNT. (b) EDX spectra confirming the presence of Mn in the CpMeMn(CO)3@SWCNT sample (Cu peaks are due to the sample holder). (c) Infrared spectroscopy of free CpMeMn(CO)3 (blue) and CpMeMn(CO)3@SWCNT (green) shows a blue shift in ν(CO) upon nanotube confinement. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.27 Prevention of CO group substitution by MeCN inside the SWCNT. (Reproduced with permission of the Royal Society of Chemistry)

7.1 Metal-Complex Chemistry of Nanocarbons

449

As a theoretical justification for the composites above, the first-principles density-functional calculations were employed to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry [88]. It was revealed that functionalization with M-bis-arene (M ¼ Ti, V, Cr, Mn, Fe) molecules led to an opening in the bandgap of graphene (up to 0.81 eV for the Cr derivative) and, as a result, transformed it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring was attributed to modification of π-conjugation and depended on the concentration of functionalizing molecules. In a related report [89], the interaction of two organometallic π-aryl (ML2) complexes, cobaltocene [Co(η5-C5H5)2] and bis(benzene) chromium [Cr(η6-C6H6)2], with a series of semiconducting (n,0) (n ¼ 11–18) SWCNTs was investigated using density-functional theory calculations. Both cobaltocene and bis(benzene) chromium were found to act as electron donors to form composites [ML2]q+[SWCNT]q- in which the extent of the charge transfer, and hence the binding energy, is modulated by the diameter and band structure of the nanotube. A related theoretical study [90] was dedicated to spin transport in a class of molecular systems consisting of an organometallic benzenevanadium cluster placed in between graphene and SWCNT-model contacts (Fig. 7.28) and carried out by combining spin DFT and non-equilibrium Green’s function techniques and considering strong and weak cluster-contact bonds. The multidecker benzene-vanadium sandwich (VnBZm, where BZ ¼ C6H6 and /n–m/ ¼  1) was considered as organometallic cluster, synthesized from laser-vaporized vanadium atoms and C6H6. From 73% (strong bonds) up to 99% (weak bonds) spin polarization of the electron transmission was found depending on the bonding. The transmission spin polarization (TSP) depends on the nature of bonds between contacts and cluster. All other available “organometallic” literature data correspond to the complexes containing a pyrene moiety, capable to π–π stacking with CNT surface. In particular, ruthenium polypyridyl complexes, described above, can be modified with pyrene and this way functionalize the CNTs. Thus, the synthesis of a multifunctional block copolymer incorporated with pyrene and ruthenium terpyridyl thiocyanato complex moieties by reversible addition-fragmentation chain-transfer polymerization was carried out [91]. The pyrene block in the copolymer facilitates the dispersion of MWCNTs in DMF solution because of the strong π–π interaction between the pyrene moieties and nanotube surface (Fig. 7.29). On the other hand, the ruthenium complexes greatly enhance the photosensitivity of the functionalized nanotubes in the visible region.

Fig. 7.28 The geometry with a V4BZ3 contacting two graphene electrodes. The arrow shows the current direction from contact “1” ¼ {L1R1} to contact “2” ¼ {L2R2}. Periodic boundary conditions are employed in the x direction, while transport in the graphene contacts is along z. The xperiodic contacts can also be viewed as the GSM (graphene sheet model) of armchair nanotube contacts (inset). (Reproduced with permission of APS Physics)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.29 Target block copolymer Ru-b-Py and its functionalization of CNT surface. (Reproduced with permission of the American Chemical Society)

Fig. 7.30 Electrocatalytic nanomaterial on the basis of nickel–pyrene complex. (Reproduced with permission of Wiley)

A cobalt-terpyridine6 transition metal complex, cobalt bis(4-pyren-1-yl-N-[5-([2,20 ;60 ,200 ]terpyridin-40 -yloxy)-pentyl]butyramide) 7.1.1.32, with pendant pyrene moieties, was shown to functionalize SWCNTs via noncovalent ππ stacking interactions [92]. The noncovalent modification of MWCNTs with pyrene-functionalized nickel complexes 7.1.1.33 through π–π stacking produced robust, noble-metal-free electrocatalytic nanomaterials (Fig. 7.30) for H2 evolution and uptake [93]. The catalysts were found to be compatible with the conditions encountered in classical proton-exchange membrane devices and were tolerant of the common pollutant CO, thus offering significant advantages over traditional Pt-based catalysts. Also, a pyrene-tagged gold(I) complex 7.1.1.34 (reaction scheme 7.1.1.23) was synthesized and tested as a

6

Terpyridine-containing complexes can also be covalently attached to CNTs; see above.

7.1 Metal-Complex Chemistry of Nanocarbons

451

Fig. 7.31 Mechanisms for the boomerang effect (left) and supported homogeneous catalysis (right). R reagents, P products. (Reproduced with permission of Wiley)

homogeneous catalyst [94]. Being immobilized onto MWCNTs, this catalyst remained intact on the CNT surface after immobilization, and remarkably its activity and selectivity in cyclization were not affected in comparison with its homogeneous counterpart. This immobilization through pyrene allowed a “boomerang” effect (Fig. 7.31) to take place during catalysis, and this effect was found to be strongly dependent on the temperature.

HN O

N

O

N

Co2+

N

N

N

O

N

O

7.1.1.32

NH

452

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes Pyrene

2+

2BF4-

pyrene N

N R

R

P

P

N

Ni

N

pyrene P

pyrene

P R

R = Ph, Cy

R

7.1.1.33 Nickel complex containing pyrene moiety

O

Ph

O PPh2

P

N H

N H

Au

Cl

Ph

ClAuSMe2

(7.1.1.23)

7.1.1.34

Synthesis of the pyrene-tagged gold complex

AgNTf2

AgCl F O Ph

O N H

P Ph

S Au

N O

S

F O Ph

O N H

P Ph

F F MWCNTs

F F

S Au

N O

S

O O F

F F

O O F

F F

Incorporation of the pyrene-tagged gold complex onto MWCNTs

The functionalization of nanostructured graphene-based electrode with an original [bis(2,20 -bipyridine)(4,40 -bis(4-pyrenyl1-ylbutyloxy)-2,20 -bipyridine)]osmium(II) hexafluoro-phosphate complex bearing pyrene groups was carried out [95]. The flexible functionalization of graphene-based electrodes using either supramolecular binding of the Os(II) complex bearing pyrene groups or its electropolymerization via the irreversible oxidation of pyrene was finally achieved. Thanks to its divalent binding sites, the Os(II) complex constitutes a useful tool to probe the π-extended graphitic surface of RGO (reduced graphene oxide) and MWCNT films. The Os(II) complex interacts strongly via noncovalent π–π interactions, with π-extended graphene planes 7.1.1.35, thus acting as a marker to quantify the electroactive surface of both MWCNT and RGO electrodes and to

7.1 Metal-Complex Chemistry of Nanocarbons

453

illustrate their ease of functionalization. Pyrene groups were revealed to be a versatile way of functionalization of nanostructured graphitic carbon electrodes. Similar pyrene-Ru/SWCNT nanohybrid 7.1.1.36 was formed through noncovalent π–π stacking interactions too. After oxidative treatment, the pyrene-Ru/SWCNT-functionalized Pt electrode achieved a highly reversible redox process and exhibited excellent electrogenerated chemiluminescence behavior [96]. Due to the high conductivity and high surface area of SWCNTs, the electrogenerated poly-/oligopyrene derivative exhibited enhanced electrochemical behavior with fast electron transfer and highly reversible redox process for RuIII/ RuII.

N N N

Os

N

N N

O O

Reduced graphene oxide

7.1.1.35

454

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

N

N

N

Ru

N

N

N

O

O

Carbon nanotubes

7.1.1.36

Composites with Metal Carbene Complexes Oxidized MWCNTs were covalently modified [97] with appropriate hydroxylending imidazolium salts using their carboxylic acid groups and then used to prepare nanohybrid materials containing iridium N-heterocyclic carbene (NHC)-type organometallic complexes 7.1.1.37–7.1.1.38 with efficiencies as high as 95% (reactions 7.1.1.24). These nanotube-supported iridium–NHC materials were found to be active in the heterogeneous iridium-catalyzed hydrogen-transfer reduction of cyclohexanone to cyclohexanol with 2-propanol/KOH as hydrogen source, being more efficient than related homogeneous catalysts based on acetoxy-functionalized Ir–NHC complexes with initial TOFs up to 5550 h1. A good recyclability of the catalysts, without any loss of activity, and stability in air was observed. The heterogeneous catalysts remained stable through successive catalytic runs.

7.1 Metal-Complex Chemistry of Nanocarbons

455

Cl

O

N

O

Ir

O

Cl N

N

O

7.1.1.37

[{Ir(OMe)(cod)}2]

O

N

I N

(7.1.1.24)

Cl

O O

N

Ir

O N

N

7.1.1.38 Synthesis of NHC-iridium complexes anchored on the carbon nanotubes. 7.1.1.8

Coordination Polymers

Several metal-complex polymers were already mentioned above. In addition, an interesting and very efficient method to grow micro-size flowers (tiny flower bundles with ultrathin petals (7 nm)) of organometallic polymers along CNTs was developed [98], allowing the one-step combination of synthesis and threading flowers onto CNTs at the same time. Crystallization of polyethylene end-functionalized with cyanoferrate groups (PE-Fe 7.1.1.39, Fig. 7.32) along CNTs resulted in flowers threaded onto CNTs, and subsequent coordination polymerization of cyanoferrate groups with Fe3+ gave polyethylene/ Prussian blue/CNT (PE-PB/CNT) hybrid flower bundles (Figs. 7.33 and 7.34). These PE-PB/CNT flower bundles exhibited enhanced thermostability and were found to be electrochemically active, having possible applications in nanodevices and biosensors. In a related report [99], poly(4-vinylpyridine) (P4VP) and P4VP/pentacyanoferrate(II) (electroactive iron complex) metallopolymer were used to disperse (up to 1 mg mL1 of MWCNTs) in ethanol/water mixtures upon sonication. The polymer side chains and CNTs interact via π–π stacking, in a difference with charge-transfer interaction reported for many nitrogenated interacting molecules. The metal-to-ligand charge-transfer band was assigned as Fe(dπ) ! py(π*b1); [Fe (CN)5]3 units are still coordinated to pyridyl moieties of the P4VP chain after interaction with MWCNTs, as it was suggested by solvatochromic shift. The amount of dispersed MWCNTs was found not to be proportional to the amount of uncoordinated pyridyl groups. Due to the formation of this system MWCNT/P4VP/Fe(CN)53, it was predicted possible existence of a host of transition metal compounds, coordinated to the P4VP/MWCNT aggregate with unique optical, magnetic, and catalytic properties.

Fig. 7.32 Ballstick modeling of polyethylene terminated with [Fe(II)(CN)5(4-(dimethylamino)pyridine)] (PE-Fe). (Reproduced with permission of the American Chemical Society)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.33 Schematic illustration of synthesis of PE-PB/CNT flower bundles. (Reproduced with permission of the American Chemical Society)

Fig. 7.34 Typical scanning electron microscopy (SEM) images at low magnification (a) and at high magnification (b), transmission electron microscopy (TEM) image at low magnification (c) and at high magnification (d), and EDX spectrum (e) of PE-PB/CNT flower bundles. PE-PB/CNT flower bundles were synthesized at PE-Fe concentration of 0.1 mg/mL, PE-Fe/CNT weight ratio of 5:1, and crystallization temperature of 46  C. (Reproduced with permission of the American Chemical Society)

7.1 Metal-Complex Chemistry of Nanocarbons

457 N

N

Br O

25

+2 N

7.1.1.39

N

N

N

Fe

N

Conclusions to the CNT Section As it was discussed above, CNTs can form hybrids with metal complexes of O-containing ligands (crown ethers, carboxylates), N- and N,O-containing ligands (amines, Schiff bases, polypyridyl compounds, porphyrins, phthalocyanines), as well as σ- and π-organometallics: carbonyls, cyclopentadienyls, pyrene-containing moieties, and other aromatic structures. The interaction “metal complex-CNTs” could take place via either covalent or noncovalent (π–π-stacking) interaction; in some cases both routes at the same time are possible. A series of interesting effects have been discovered for distinct groups of metal complex-CNT composites/hybrids. For example, in case of polynuclear {Mn4} complexes, it was shown that the reaction can only be achieved for tubes which were oxidized to create carboxylic groups. The reaction “{Mn4} complex/CNTs” is based on ligand exchange between the ligands of the complex and the carboxylic groups created on the CNTs by oxidation in air. For ferrocene-functionalized CNTs, their mutual interaction could be covalent, noncovalent, or of both types at the same time. For a variety of pyrene-containing complexes, their units provide the means for noncovalent functionalization of SWCNTs via ππ interactions, ensuring that the electronic properties of SWCNTs are not impacted by the chemical modification of the carbon skeleton. DFT calculations also revealed intriguing aspects of “metal complex/CNTs” hybrids. For instance, both cobaltocene and bis(benzene) chromium were found to act as electron donors to form composites [ML2]q+[SWCNT]q- in which the extent of the charge transfer, and hence the binding energy, is modulated by the diameter and band structure of the nanotube. Another example is an iron porphyrin FeP on different surfaces of SWCNTs. Two mechanisms for the FeP attachment on metallic and semiconducting CNTs were considered: by physisorption through π–π-stacking interaction and by chemisorption through sp2 and sp3 bonding configurations. In addition to “real” “metal complex/CNTs” hybrids, investigations of porphyrin-like defects in CNTs surface have led to conclusions about their strong binding to hydrogen molecule (this can act as a media for storing hydrogen) or an excellent oxygen reduction catalytic activity. A very important aspect is related to the solubility (more exactly, dispersibility) of formed composites “metal complex/CNTs.” Thus, in the case of CNTs/crown ether complexes with alkaline metals, the ionic interaction leads to a considerable increase in the solubility of SWCNTs in both organic and aqueous solvents such as ethanol, dimethyl sulfoxide, dimethylformamide, and H2O. The dispersion of SWCNTs was also achieved in the presence of water-soluble ruthenium polypyridyl complexes, non-TPP-type porphyrins. It is interesting that the presence of catalytically active atoms of rhenium inserted into CNTs, the nanotube sidewall, can be engaged in chemical reactions from the inside, although it is generally supposed that the outer surface of SWCNTs can be involved in a wide range of chemical reactions and the interior surface of nanotubes is unreactive [102]. Talking about applications of the discussed CNTs/metal complex hybrids, we emphasize their rich variety. Catalytic applications (Table 7.2), for example, for the oxidation of primary and secondary alcohols, used as nonprecious electrocatalysts for the electroreduction of oxygen, among others, have a high value, as well as other uses (ion, gas and ECL sensors, Pb2+ determination, Hg2+ retaining, uptakes of CO2 and CH4, carbon paste electrodes, molecular memory devices, photosensitizers [103] (Fig. 7.35), or nanohybrid circuits).

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.35 Carbon nanotubes and photosensitizers. SWCNT and molecular structures of representative photosensitizers based on phthalocyanines (ZnPc) (green), π-extended TTFs (exTTF) (yellow), and rylenes (pink and purple)

7.1.2

Graphene

7.1.2.1

Introduction

Graphene7 (G) and graphene oxide (GO)8 have attracted much recent attention for applications such as catalysis, chemical and biological sensing, energy storage, and electronics as a result of their extraordinary physicochemical and structural properties derived in large measure from their electronic structure peculiarities. The electronic structure of graphene is characterized by a linear energy dispersion of bands 1 eV near the Fermi level [104, 105], and the bands intersect at the Dirac point defining a semimetal. Over the course of the last decade, several reports on graphene hybrids with a variety of metal complexes have appeared, where a series of coordination and organometallic compounds have been successfully anchored onto graphene by covalent or noncovalent modes. It is known that metal complexes have a plethora of useful applications in organic and organometallic chemistry, catalysis [106], medicine (for diagnostics, therapeutics, and delivery) [107], various biological systems [108], and polymers and dyes [4] and for engineering the separation of isotopes [5] and remediation of heavy metals [6]. Hybrid nanostructures comprising graphene and metal complexes thus have the potential to yield multifunctional materials with properties that are greater than a simple “sum of their parts.” 7 8

The image above is reproduced with permission of Nature (Nat. Chem. 9(1), 33–38 (2017)). See chapter above, dedicated to the graphene properties.

7.1 Metal-Complex Chemistry of Nanocarbons

459

It is instructive to consider two specific examples wherein hybrid composites yield properties not accessible for each of the individual components. Pristine graphene is a semimetal and does not have a bandgap, which represents a major impediment to applications of this material in field-effect transistors and other active logic devices. Devices constructed from pristine graphene can have very high mobility values but because they cannot be turned off are of limited utility, and indeed the range of on/off ratios that can be realized by electrostatic modulation of the gate voltage is limited. Interfacial hybridization represents an attractive approach for introducing and tuning the bandgap of graphene, and indeed there are indications that bandgaps spanning the range from 0.20 to 1.10 eV can be induced by complexation of low-valent metal–ligand clusters via η6 coordination from the π-conjugated basal planes of graphene. To consider an intriguing property wherein graphene in turn adds functionality to a molecular complex, the high electronic and ionic conductivity of graphene makes it an excellent catalyst support and diffusion limitations can be substantially mitigated by use of this material thereby potentially tremendously enhancing the catalytic activity (and even selectivity) of a coordination complex. Before embarking upon a detailed discussion of interfacing graphene with molecular complexes, it is instructive to consider graphene/metal interfaces. Bare metal ad-atoms show remarkable ability to modify the electronic structure of graphene, spanning the range from covalent hybridization observed for Ni and Co to distance-dependent electron- or holedoping noted for Cu and a rigid band shift observed for alkali metals [109, 110]. Hybridization with Ni is further predicted to transfer magnetization to carbon atoms of graphene enabling spintronics applications [111]. While the modulation of the electronic structure of graphene induced at the interfaces of graphene with ad-atoms or metal surfaces is intriguing and indeed instructive [112–114], the primary focus of this review will be hybrid materials wherein discrete molecular coordination complexes and not bare metal atoms are interfaced with graphene. Graphene oxide presents an altogether different set of opportunities. GO is commonly obtained by oxidative exfoliation of graphite, which extensively disrupts the π-conjugation of graphene basal planes yielding heavily functionalized domains characterized by epoxy and alcohol groups [115]. The edges of graphene oxide feature pendant carboxylate and keto moieties [116]. The modified Lerf–Klinowski model of graphene oxide has now gained widespread acceptance and features basal planes of graphene functionalized with epoxide and hydroxyl moieties, with the edges and rim sites around vacancies being decorated with pendant carboxylic acid, quinoidal, ketone, and lactone groups [117–119]. The abundance of functional groups on GO surfaces enables coordinative binding of metal cations wherein these functional groups essentially serve as ligands to coordination complexes. Similar constructs have also been explored for oxidized single- and multiwalled carbon nanotubes. Particular aspects of graphene functionalization with metal complexes have been briefly mentioned in some books and chapters [120–123], reviews [124–133], and patents [134]. In this section, we describe the state of the art in the area of functionalization of graphene and graphene oxide with metal complexes, emphasizing (1) functionalization of graphene’s π system (or defects within graphene) with coordination complexes and (2) reaction of the O-containing functional groups of GO with coordination complexes (metals or ligands). The purpose of this section is to place in perspective recent advances in the design of hybrid materials combining graphene and coordination complexes, to discuss the challenges and opportunities for this emerging area of research, and to establish some fundamental design principles for preparing such hybrid constructs.

7.1.2.2

Defective Graphene with Oxygen- and Nitrogen-Containing Functional Groups

Interactions of metal cations such as Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, and Zn2+ (in the form of nitrates) with ammonia-treated graphene sheets (G) and the thermal stability of coordination complexes resulting from interactions of these cations with oxygen- and nitrogen-containing functional groups on G were investigated by rinsing G coordinated with metal cations (G-M) in 2-propanol using sonication and by heating G-M complexes up to temperatures of 773 K [135]. The resulting interactions between these metal cations and G can be classified into three types (A, B, and C, as illustrated by Fig. 7.36). Metal cations of Type A (hard acids according to the HSAB theory) have either no interaction or weak interactions with G and are readily removed by rinsing. Type B metal cations were agglomerated into clusters by heat treatment and subsequently oxidized indicating that cohesive M–M interactions are greater than M–G interactions, whereas those of Type C remained dispersed across the defect and vacancy sites without severe agglomeration. Phenanthroline-like groups on edges of graphene have been predicted by DFT calculations to show the strongest interactions with Ni2+ among all of investigated N- and O-containing functional groups. The presence of pyrazole-type species that can coordinate metal cations has further been definitively confirmed upon hydrazine reduction of graphene oxide using near-edge X-ray absorption fine-structure spectroscopy. In contrast, the presence of O-containing functional groups is thought to result in oxidation and agglomeration of metal cations. Initial binding of metal cations likely serves to nucleate clusters that can grow by the

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Fig. 7.36 Proposed structures illustrating three putative types of interactions between metal cations and ammonia-treated graphene sheets. Type A: monovalent alkali metal cations such as Li+, Na+, and K+; divalent alkaline-earth metal cations such as Mg2+, Ca2+, and Sr2+; divalent transition metal cations such as Mn2+; and the other divalent metal cation such as Zn2+. Type B: trivalent transition metal cations such as Cr3+ and Fe3+. Type C: divalent transition metal cations such as Co2+, Ni2+, and Cu2+. (Reproduced with permission of the Elsevier Science)

Fig. 7.37 Model of the interactions of graphene oxide with metal ions

subsequent diffusion of monomeric species. In a related report of Laure et al. [136], interactions of graphene oxide with Ag+, Cu2+, Fe2+, Fe3+, and Bi3+ ions under ultrasonic treatment were studied. A possible model of coordination of the metal ions to oxygen-containing groups of GO was proposed and is illustrated in Fig. 7.37. On the basis of the obtained results, the authors have suggested the potential utility of GO as an efficient sorbent of metal ions from aqueous solutions.

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Fig. 7.38 Introduction of sp3-character in defective graphene (VCSymm) upon adsorption of chromium. (Reproduced with permission of the APS Physics)

Fig. 7.39 The staggered, eclipsed, and distorted–eclipsed geometries at equilibrium formed by the Bz/M/G complexes created using different graphene templates: (1) pristine graphene, (2) VCJT, (3) VCSymm., (4) NC, (5) 1NC-VC, and (6) 3NC-VC. (Reproduced with permission of the APS Physics)

A chemical route to creating defect-stabilized benzene(Bz)-transition metal(TM)-graphene(G) sandwich structures (Figs. 7.38 and 7.39) was theoretically offered (but hard to be created experimentally) [137], taking into account that they are prototypes of larger sandwich structures and supposing that (1) the TM-G binding energy is enhanced through adsorption at appropriate defects, (2) the capping the metal with a Bz ring stabilizes the structure, and (3) the stability of these composites can vary due to different defects (vacancies, N-doping atoms in graphene). Transition metals tend to cluster on pristine graphene due to their high mobilities on graphene and high elemental cohesivities.

7.1.2.3

Intermediate Werner-Like Complexes

A facile “greener” strategy to combine an organic amine with a palladium complex on GO as a cooperative catalyst (GO–NEt2–2 N–Pd) for Tsuji–Trost allylation was developed (Fig. 7.40) by Zhao et al. [138] A tertiary amine and

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.40 Synthetic methodology for the preparation of GO–NEt2–2 N–Pd and Tsuji–Trost allylation catalyzed by the cooperative catalyst. Nu nucleophile, LG leaving group. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.41 Tsuji–Trost allylation of allyl methyl carbonate with ethyl acetoacetate. (Reproduced with permission of the Royal Society of Chemistry)

palladium–diamine complex were simultaneously immobilized on a GO support; PdCl2 was employed as the palladium precursor, with no necessity for extra coordination ligands. The catalyzed reaction was performed in dioxane at 70  C using K2CO3 as an external base (Fig. 7.41). GO–NEt2–2 N–Pd can be readily recovered and recycled several times without reduction of its efficiency.

Low-Valent Complexes of Graphene: Coordination to π-Conjugated Domains A series of reports (in particular, the patent [139]) have examined the donation of electron density (and concomitant back donation) from π-conjugated domains on G basal planes to metal centers, thereby yielding G|M|(C6H6 or CO) complexes similar to the described in the above sections (an example is shown in Fig. 7.42). Specifically, η6-complexation reactions of chromium with graphene as well as graphite and carbon nanotubes and the formation of (η6-arene)Cr(CO)3 or (η6-arene)2Cr were confirmed by Haddon et al. [86], where arene ¼ single-walled carbon nanotubes (SWCNTs), exfoliated graphene (XG), epitaxial graphene (EG), and highly oriented pyrolytic graphite (HOPG) (Fig. 7.43). As an example, in the case of HOPG, (η6HOPG)Cr(CO)3 was isolated, whereas exfoliated graphene samples were found to yield both (η6-graphene)2Cr and (η6graphene)Cr(CO)3 structures (Fig. 7.44). Figure 7.45 illustrates three different functionalization routes adopted [140] to chemically modify the graphene flakes. Haddon and co-workers also suggested that such hexahapto coordination preserves the band structure of graphene although some rehybridization is locally induced upon metal coordination (“constructive hybridization”); the sandwich (η6graphene)2Cr complexes are particularly intriguing and suggest that single atoms can mediate interconnects between nanoscale components that the authors have labeled “atomtronics.” The ability of the CO groups to switch from terminal to bridging coordination modes further enables stabilization and growth of clusters of Cr(CO)3 on the G surfaces. Schematic of the formation of metal complexes with the surface of graphene nanoplatelets is shown in Fig. 7.46. DFT and Other Calculations Electronic properties of such complexes with covalent monohexahapto-M (M ¼ Cr, Fe, Ni) bonds were elucidated by Dai et al. [143] using DFT calculations. It was shown that Fe and Ni, in addition to Cr, can also bind strongly with the graphene. At the experimentally determined coverage ratios (M:C ¼ 1:18), the calculations, in particular, suggested that the computed bandgap of perfectly arranged networks of (η6-graphene)-Cr(CO)3, (η6-graphene)-Fe(CO)2, and

Fig. 7.42 (a) Unit cell topology of the graphene|Cr| ligand (G|Cr|L) systems, described in [141]. The surface distribution of the Cr|L elements determines the substrate symmetry and, consequently, its electronic properties. (b) Typical π-ligand molecular complexes of Cr. (c) Optimized structures of different G|Cr|L systems. (Reproduced with permission of the American Chemical Society)

Fig. 7.43 Representative reactions of graphite and graphene with (η6-benzene)Cr(CO)3 and Cr(CO)6 based on product structures. (Reproduced with permission of the Royal Society of Chemistry)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.44 Types of η6-coordinated graphene composites. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.45 Organometallic functionalization of single-layer graphene devices. (a) Schematics of functionalization approaches using three different reaction routes to obtain hexahapto-chromium complex, (η6-SLG)Cr(CO)3; (b) illustration of the graphene device and the functionalization process; and (c) 3D model of the (η6-SLG)Cr(CO)3 organometallic complex. (Reproduced with permission of the Wiley-VCH)

(η6-graphene)-NiCO can be enlarged to 1.08, 0.61, and 0.29 eV, respectively. (η6-Graphene)-Cr(CO)3 exhibits a bandgap in the visible-light range of the electromagnetic spectrum, whereas (η6-graphene)-Fe(CO)2 and (η6-graphene)-NiCO may be promising for application in infrared detectors. In a related report of Plachinda et al. [144], it was shown that functionalization with M-bis-arene (M ¼ Ti, V, Cr, Mn, Fe) molecules leads to an opening of the bandgap of graphene (up to 0.81 eV for the Cr derivative) and, as a result, transforms it from a semimetal to a semiconductor. The bandgap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. In addition, a recent theoretical study focuses on a chemical route for creating stable benzenetransition metal-graphene sandwich structures [137]. The binding energy of the transition metal to graphene is enhanced through adsorption at appropriate defects, immobilizing the metal onto the graphene web. Capping the metal with a benzene ring further stabilizes the structure. Functionalization with low-valent complexes thus represents a remarkably facile solutionphase strategy for inducing and modulating a bandgap in graphene.

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Fig. 7.46 Schematic of the formation of metal complexes with the surface of graphene nanoplatelets. Their different colors represent different nanoparticles [142]. (Reproduced with permission of the American Chemical Society)

7.1.2.4

Ferrocene and Other Cp Complexes

DFT studies for MCp-graphene composites have been performed by Zhang et al. [145] in order to determine the possibility of using these complexes as redox-active materials for electrochemical applications. CpFe/B-doped graphene complexes with a series of different side chains were found to have comparable redox potentials as ferrocene molecules and other ferrocenebased electrochemical sensors, which portens potential applications of these complexes in electrochemical systems. These results further suggest that the enhanced electrochemical stability is not derived from a fundamental lateration of the CpFe electronic structure but instead arises from the mitigation of electronic and ionic bottlenecks to charge transport. In case of GO, the use of ethylenediamine (ED)-functionalized GO as the building block in the preparation of ferrocene– graphene nanosheets (Fc–GNs) with remarkable electrocatalytic activity for the decomposition of H2O2 has been recently demonstrated by Fan et al. [146] (Fig. 7.47). It was indicated that Fc grafted onto graphene retains electrochemical activity over prolonged cycling and the Fc–GNs has excellent electron transfer (ET) properties. An excellent mediation of H2O2 based on Fc/Fc+ used as ET mediators for the oxidation of H2O2 to O2 was observed (Fig. 7.48), suggesting specific properties of Fc–GNs due to a combination of Fc and graphene. In contrast to the above, ferrocene analogues with M ¼ Ti and Zr have been utilized for an entirely different purpose. Two types of reduced graphene oxide (RGO) nanoplatelets, N-doped RGO (N-RGO) and thermally reduced graphene oxide (T-RGO), were attached to zirconocene or titanocene complexes, respectively [147], via simple π-stacking interactions between Cp rings of metallocenes and graphitic surfaces of graphene, and were used as catalysts for the generation of polyethylenes (Fig. 7.49). The materials prepared using these hybrid catalysts show a remarkable increase in molecular weight relative to those produced by free catalysts. Specifically, ultrahigh molecular weight

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.47 Schematic illustration of the preparation of ferrocene-functionalized graphene sheets. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.48 Reaction schemes of the oxidation of H2O2 to O2 mediated by graphene (a) and Fc–GNs (b). (Reproduced with permission of the Royal Society of Chemistry)

(up to 3.106) polyethylenes were produced from polymerization at low temperature using hybrid catalysts prepared from N-doped graphene nanoplatelets. The remarkable catalytic properties noted here are likely not just derived from improved diffusion rates facilitated by RGO but also by the steric footprint of these unusual ligands. Among other applications, ferrocene/graphene (and also hemin(7.1.2.1)/graphene) nanocomposites are also used in electrochemical sensing (Figs. 7.50 and 7.51) [148].

7.1 Metal-Complex Chemistry of Nanocarbons

Fig. 7.49 Use of M(Cp)2 (M ¼ Ti, Zr) for ethylene polymerization. (Reproduced with permission of the Wiley-VCH)

Fig. 7.50 The biosensing of cholesterol ester mediated by Fc-GO on SPE. (Reproduced with permission of Hindawi)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.51 (a) Magnetically driven fuel-free graphene carrier with loading of redox-active cargo-Fc working as an electron mediator for mediated bioelectrocatalysis of glucose to gluconic acid by GOx switched between “on” and “off” states under alternate positioning of the graphene carrier with loaded Fc (i) near and (ii) away from the conductive support. (b) The loading of Fc onto the graphene carrier by π–π interaction between Py– CHO and the unoccupied areas of the graphene nanosheet, followed by the formation of imine bond (–C¼N–) between –CHO group of the Py–CHO modified graphene carrier and the –NH2 group of the Fc–NH2. (Reproduced with permission of Wiley from [149])

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7.1.2.5

469

Pyrene: The Role of π-Stacking Interactions

In the case of pyrene–GO composites, this ligand is not used itself for coordination of metal complexes but only as a part of more complex structures containing chelating moieties. Instead, the molecules are tethered to graphene surfaces through the pyrene π-aromatic system. Pyrene–GO composites are currently known for noble metals only. A primary obstacle with the use of pyrene–graphene complexes is the operation of an adsorption–desorption equilibria and the resulting instability of the hybrid materials; this can be substantially mitigated by polyvalent binding with multiple tethered pyrene groups. As a salient example, an ultrasound-assisted co-immobilization of palladium and ruthenium complexes with pyrene-tagged N-heterocyclic carbene ligands onto RGO yielded a highly efficient multiply recyclable catalyst (Fig. 7.52) for the hydrodefluorination of fluoroarenes [150]. The activity of the catalyst was attributed to the synergistic action of the two metals. Related individual GO-supported complexes of Ru and Pd were applied by Le Goff et al. [151] for palladium-catalyzed hydrogenation of alkenes and for the ruthenium-catalyzed alcohol oxidation by Sabater et al. [152]. In addition, the functionalization of a nanostructured graphene-based electrode with a (bis(2,20 -bipyridine)(4,40 -bis(4-pyrenyl-1-ylbutyloxy)-2,20 -bipyridine]osmium(II) hexafluoro-phosphate complex 7.1.2.2 bearing pyrene groups has been performed. Due to its divalent binding sites, the Os(II) complex constitutes a useful tool to probe the π-extended graphitic surface of RGO films. It interacts strongly via noncovalent ππ interactions, with π-extended graphene planes, thus acting as a marker to quantify the electroactive surface of RGO electrodes.

Fig. 7.52 Preparation of a Pd–Ru complex nanocatalyst

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

N N N

II Os

N

N N

O O

Bis(2,20 -bipyridine)(4,40 -bis(4-pyrenyl-1-ylbutyloxy)-2,20 -bipyridine]-osmium(II) hexafluoro-phosphate complex bearing pyrene groups. 7.1.2.6

Heterocyclic N-Ligands: Bipyridine, Terpyridine, Polypyrrole, and Related Compounds

Heterocyclic ligands are ubiquitously used for energy harvesting and conversion owing to their ability to tune the redox potentials of transition metal centers, the presence of basic sites, and their high extinction coefficients for absorbing visible light. As a very distinctive approach with implications for clean energy, an intriguing strategy (Fig. 7.53) to synthesize hybrids of cobalt oxide and polypyrrole (PPy) coupled with graphene nanosheets (Co3O4-PPy/GN) has been developed by Ren et al. [153], in which the exfoliation of graphite and polymerization of pyrrole are engineered simultaneously during ball milling. The Co3O4 and Co-Nx oxygen reduction reaction active sites are generated from oxidation of the precursor Co complex during processing. The Co3O4-PPy/GN catalysts showed efficient electrocatalytic performances for ORR in alkaline medium, comparable to those of the Pt/C catalyst. As a prominent example of graphene composites designed for energy applications, the covalent anchoring of four transition metal water oxidation catalysts of the formula M-L(H2O)4x+ (M ¼ Fe3+, Co2+, Ni2+, or Cu2+, L ¼ 2,20 -bipy) to a graphenemodified electrode (ITO or glassy carbon) affords surface-bound catalysts with high activity in neutral water at ambient temperature (Fig. 7.54) [154]. In this scheme, the ligand was functionalized with an amino group and grafted to graphene oxide (GO) via a diazonium coupling reaction. Proposed metal-binding motifs for L-functionalized graphene are shown in Fig. 7.55. Among the four studied M-L complexes, Co-L bound to a graphene-modified ITO electrode was found to exhibit the best catalytic activity. A very distinctive adsorption mechanism was reported for the copper counterpart. Thus, copperintercalated graphite oxides (GO) were prepared by Szabó et al. [155] by adding complex solutions of cupric ions and 2,20 -bipy (L) ligands to a suspension of exfoliated GO at neutral pH. Electron spin resonance spectra reveal two principal adsorption mechanisms: the [CuL3]2+ complex undergoes ion-exchange adsorption, whereas [CuL]2+ and [CuL2]2+ bind to GO by coordination. In related work, 3D nanosheets of GO decorated with hybrid nanoparticles of a bimetallic silver– ruthenium bipyridine complex (Ag@[Ru(bipy)3]2+) as the core and chitosan as the shell were obtained through a sequential wet-chemical approach using in situ reduction, electrostatic, and coordination reaction and also got an electrochemical

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Fig. 7.53 Schematic depiction (PG ¼ graphite flakes) of the synthesis of the Co3O4-PPy/GN composite. The top right panel indicates a digital photograph of the Co3O4-PPy/GN suspension with a concentration of 0.05 g L1; the manifestation of the Tyndall effect is shown using a laser pointer. (Reproduced with permission of the Springer)

Fig. 7.54 Method for covalent attachment of first-row transition metals to graphene-modified ITO electrodes. (Reproduced with permission of the American Chemical Society)

Fig. 7.55 Proposed metal-binding motifs for L-functionalized graphene. (Reproduced with permission of the American Chemical Society)

application [156]. Electrodes modified with these hybrid nanosheets retained their biocompatibility and displayed an amplified redox property suitable for a broad range of sensing studies. A graphene-based porous material for CO2 sorption (with a projected CO2 capacity ranging up to 11.7 wt.% at 273 K) was designed by Zhou et al. [157] and fabricated through an azide–alkyne click reaction between alkynyl group-modified GO

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.56 Illustration of the synthesis of a terpyridine-based composite and a magnified view of the molecular structure of the cross-linker separating individual graphene sheets. (Reproduced with permission of the Elsevier Science)

(alkynyl-GO) and an azido-terpyridine (tpy) complex (Fig. 7.56). It was observed that the incorporation of the non-planar tpy complexes between graphene sheets increases the porosity of the graphene terpyridine complex hybrid porous materials (GTCF) materials. Meanwhile, three distinctive types of N-containing groups (amine, triazole, and tpy groups) were introduced or formed during the modification and cross-linking of this composite, which therefore yields a high density of basic sites for acidic gas sorption. This approach specifically uses the high surface area of graphene (every atom of singlelayered graphene is surficial) to trap CO2 molecules within the galleries of the composite. The graphene was also noncovalently functionalized [158] with the Ni(II) complex of 5,7,12,14-tetramethyldibenzo1,4,8,11-tetraazacyclotetradeca- 3,5,7,10,12,14-hexaene (Ni(II)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA 7.1.2.3), which is a simple model of porphyrins and phthalocyanines described below. Tetraazaannulene molecules cover graphene sheets with a dense layer (mainly monolayer). NiTMTAA forms a full double-sided adsorption layer on the graphene surface; in addition, flat orientation of the complex molecule with respect to graphene plane is energetically preferable (Fig. 7.57), with a little difference depending on whether benzo or methyl groups contact the sheet. Homogeneous graphene composites (Fig. 7.58) based on a 2D pillared-bilayer MOF (Cd-PBM), {[Cd4(azpy)2(pyrdc)4(H2O)2]9H2O}n (azpy ¼ 4,40 -azopyridine, pyrdc ¼ pyridine-2,3-dicarboxylate), were also prepared [159], using both graphene oxide (GO)and benzoic acid-functionalized graphene (BFG). For the composites GO@Cd-PBM and BFG@Cd-PBM, the growth of the 2D nanosheets of MOF on the graphene surface was confirmed, as well as CO2, H2O, and MeOH uptake.

Nickel(II) complex of 5,7,12,14-tetramethyldi-benzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12,14-hexaene (Ni(II)tetramethyldibenzotetraaza[14]annulene, NiTMTAA).

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Fig. 7.57 Two models of graphene sheets employed for DFT calculations of NiTMTAA interaction with nonoxidized and oxidized graphene (Gh and Go, respectively), along with the corresponding noncovalent complexes in which NiTMTAA adopts three possible orientations with respect to the graphene surface: NiTMTAA-b + Gi (where i ¼ h,o), flat with benzo rings contacting Gi; NiTMTAA-m + Gi, flat with CH3 substituents contacting Gi; and NiTMTAA-e + Gi, perpendicular orientation with only two CH3 substituents contacting Gi. The geometries were optimized by using PBE GGA functional with Grimme dispersion correction in conjunction with the DNP basis set. Atom colors: C, gray; H, white; O, red; N, deep blue; Ni, light blue. (Reproduced with permission of the Royal Society of Chemistry)

On the example of N-containing ligands, the differences of functionalization of distinct carbon allotropes with metal complexes were observed and explained by DFT calculations (Figs. 7.59 and 7.60), which were employed [160] to explain why the attempts of authors to coordinatively functionalize nanodiamond (ND) with tetraazamacrocyclic cations [Ni (cyclam)]2+ 7.1.2.4 and [Ni(tet b)]2+ 7.1.2.5, and to produce paramagnetic hybrid materials, failed, contrary to the successful functionalization of graphene oxide (GO) [161]. The formation of high-spin complex was shown to be highly unfavorable with ND contrary to GO model: ΔΔE3–1 values obtained are 13.22 and  4.64 kcal mol1, respectively. Mn(III) catalyst (Mn(III)-amidomacrocyclic complex) supported on graphene and further coated with polydopamine 7.1.2.6 was prepared (Fig. 7.61) [162], resulting in superior ORR (oxygen reduction reactions) activity compared to the uncoated PDA structures. During the formation of the PDA coating, the Mn(III) complex was reduced to a Mn(II) complex (Fig. 7.62). The material was shown to reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells.

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.58 Schematic representation of intercalation of 2D Cd-PBM between functionalized graphene sheets. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.59 Low-spin square planar tetraazamacrocyclic complexes of Ni(II) (top) and their conversion into respective high-spin octahedral carboxylates (bottom). (Reproduced with permission of the Royal Society of Chemistry)

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475

Fig. 7.60 Optimized geometries of coordination complexes: (a) singlet [Ni(cyclam)]2+GO; (b) triplet [Ni(cyclam)GO]+; (c) singlet [Ni(cyclam)]2 + ND; (d) triplet [Ni(cyclam)ND]+. The values specified are Ni–O distances (in Å). Atom colors: gray, carbon; white, hydrogen; red, oxygen; blue, nitrogen; violet blue, nickel. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.61 Preparation of polydopamine (PDA)-coated Mn-graphene (Gn/Mn) nanocomposite. (Reproduced with permission of Nature)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.62 (a) Possible reduction pathway of Mn(III) to Mn(II) with PDA-coated material and (b) proposed mechanism of Mn-graphene or PDAMn-graphene nanocomposite in acidic and alkaline conditions. (Reproduced with permission of Nature)

PDA structure (“never-ending story” [163]). Reproduced with permission of the American Chemical Society

7.1.2.7

Phthalocyanines

Interfacing metal phthalocyanines (MPcs) with graphene has attracted substantial attention owing to the possibility of stabilizing charge-transfer complexes with distinctive photophysics. The alignment of frontier orbitals and charge-transfer probabilities have been computationally explored by Cardenas-Jiron et al. [164] for 18 complexes of cobalt phthalocyanine (CoPc) and cobalt tetraaminephthalocyanine (CoTAPc) adsorbed on graphene functionalized with carboxylate anion CO2 or CO moieties using density-functional theory and a Green’s function approach. Three distinctive clusters are used to model the basal planes of graphene as depicted in Fig. 7.63, a pristine honeycomb-like network saturated with H atoms, a defective

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477

Fig. 7.63 Graphene structural models (G, Def, and Vac) and cobalt phthalocyanines (CoPc and CoTAPc). (Reproduced with permission of the American Chemical Society)

Fig. 7.64 G and CoPc (CoTAPc) complexes attached to Au atoms. (a) G-CO2-CoPc-Au2; (b) G-CO2-LAT-CoPc-Au2; (c) G-CO-CoTAPc-Au2; and (d) G-CO-LAT-CoTAPc-Au2. Color code: carbon (purple), hydrogen (cyan), nitrogen (blue), oxygen (red), cobalt (steel blue), and gold (yellow). (Reproduced with permission of the American Chemical Society)

model incorporating a 5–7 Stone–Wales defect, and a cluster with a distinctive vacancy, leading to 12 complexes with CO2functionalized graphene and 6 complexes with functionalized CO graphene. Figure 7.64 shows the four conformations of the complex structures of graphene and phthalocyanine: two cobalt-centered (a) parallel and (b) perpendicular and two ligandcentered (c) perpendicular and (d) coplanar. It was suggested that several of these complexes behave as charge-transfer compounds wherein phthalocyanine acts as an electron donor and graphene as an electron acceptor. The spectroscopic signatures of the charge-transfer bands reside within the UV–visible region of the electromagnetic spectrum and could serve as a probe for detecting polar species. However, for graphene hybridized with a Ni(111) substrate, the directionality of charge transfer is reversed. The energy level alignment of CuPc and FePc on single-layered graphene/Ni(111) (SLG/Ni) substrate

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.65 Geometries of uniform and nonuniform F16CuPc overlayers adsorbed on graphene[(3,4)  (8,6)]: (a) the αα pattern; (b–d) the α–β stripes with relative azimuthal angles of (b) 20 , (c) 30 , and (d) 40 . The unit cell (red parallelogram) contains two Pc molecules. (Reproduced with permission of the AIP Publishing)

was investigated by Wei-Guo et al. [165] by using UPS and XPS methods. In particular, the highest occupied molecular orbitals (HOMOs) in a thick layer of CuPc and FePc were found to lie at 1.04 eV and 0.90 eV, respectively, below the Fermi level of the SLG/Ni substrate. An interfacial electronic feature was also observed in the UPS taken from the first layer of FePc on graphene/Ni, which has been attributed to a charge transfer from graphene/Ni to an Fe-related unoccupied orbital of FePc. A sensitive electrochemical sensor for the determination of 4-nitrophenol (4-NP) has been devised based on graphene nanosheets (GN) decorated with iron phthalocyanine (FePc) [166]. The reduction of 4-NP occurring at the GNS-FePc film on a glassy carbon electrode is a diffusion-controlled process. The practical feasibility of such a sensor has been demonstrated for human urine samples. The self-assembly of CuPc molecules on surfaces of epitaxial graphene grown on SiC has been examined by scanning tunneling microscopy, and the observed electron-density contours have been interpreted with the help of DFT calculations. These results indicate that both CuPc and F16CuPc are assembled in a coplanar fashion on the surface of the epitaxial graphene with the central Cu atom situated on top of a C atom of the graphene substrate [167]. In particular, for F16CuPc adsorption on epitaxial graphene, the molecules form incommensurate crystalline islands comprising alternating α and β-stripes (Fig. 7.65). Other phthalocyanines have been explored to a considerably lesser extent. A suspension of GO has been functionalized by Zhu et al. [168] with zinc phthalocyanine (ZnPc) through an amidation reaction depicted in Fig. 7.66. For the same linear extinction coefficient, the GO-ZnPc hybrid exhibited much larger nonlinear optical extinction coefficients and broadband optical limiting performance as compared to GO at both 532 and 1064 nm, indicating a remarkable accumulation effect arising from the covalent linkage of GO and PcZn.

7.1.2.8

Porphyrins

Porphyrin-containing graphene composites are more represented and better studied being compared with phthalocyanines; several computational models have been offered [169]. Thus, the rectification properties of porphyrin–graphene nanoflake complexes (and also endohedral complexes of C28 fullerene) with metal atoms were studied [170] using the fully ab initio method. An interesting theoretical construct that has been explored computationally for CO2 and CO conversion to methane or methanol places a metal atom at the center of an approximately planar coordination environment defined by four nitrogen atoms that are substitutionally incorporated within graphene (Fig. 7.67). A wide range of transition metal ions have been placed at the center of such a porphyrin-like environment defined within the graphene lattice (M ¼ Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os (d ); B, Al, Ga ( p); Mg (s)) [171]. The Rh–porphyrin-like-functionalized graphene stands out as most active catalyst for producing methanol from CO (with a calculated overpotential of 0.22 V) and is expected to exhibit similar reactivity for the hydrogen evolution reaction. A synthetic strategy to incorporate four coplanar nitrogen atoms to define a porphyrin-like site remains to be experimentally realized.

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479

Fig. 7.66 Synthesis of GO-ZnPc. (Reproduced with permission of the Elsevier Science)

Next, turning our attention to experimental studies of discrete porphyrin molecules interfaced with graphene, a remarkable phenomenon is the ability of these planar molecules to intercalate between van der Waals’ bonded layers. As a case in point, graphene-dimesitylporphyrin hybrids were synthesized by Bernal et al. [172] by direct exfoliation of graphite in a solution of the porphyrins and are observed to be stable in suspension after several months without any sign of precipitation. Despite the presence of bulky mesityl groups, which are expected to hinder the efficient π–π stacking between the porphyrin core and graphene, the liquid-phase exfoliation of graphite is strongly promoted by intercalation of the porphyrins between the graphitic layers (Fig. 7.68). Remarkably, metallation of the porphyrin further enhanced this effect. The peculiarities of some transition metal ions yield intriguing behavior. The large ionic radius of Zr4+, 0.72 Å, results in an unusual 0.9 Å to 1 Å displacement from the mean plane of the macrocyclic nitrogen atoms (Figs. 7.69, 7.70, and 7.71). Such a chelating capability facilitates the efficient self-organization 5,10,15,20-tetraphenylporphyrinato-ZrIV, ZrIV(TPP) (or for that matter the phthalocyanine analogues of Zr) on GO [173].

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.67 Atomic structure of porphyrin-likefunctionalized graphene. The central metal atom is coordinated to four nitrogen atoms, forming the porphyrin ring that is embedded in a graphene matrix. (Reproduced with permission of the American Chemical Society)

Fig. 7.68 Cartoon representation of the exfoliation mechanism to produce few-layered graphene (FLG)/porphyrin hybrids: (a) addition of graphite to porphyrin solution and (b) porphyrin molecules intercalate between the graphitic layers and exfoliate graphite to graphene sheets yielding FLG/porphyrin hybrids. (Reproduced with permission of the MDPI)

Several applications of porphyrin-graphene composites have been developed; for instance, such hybrids have been used by Karimne et al. [174] as solid-phase adsorbents for the preconcentration and extraction of Cr(III) from water. The electrocatalysis is also of interest. As its representative example, graphene oxide nanoribbons have been electrochemically reduced and functionalized with water-soluble iron(III) meso-tetrakis(N-methylpyridinum-4-yl) porphyrin (FeTMPyP) that stack onto the sp2-hybridized domains via π–π noncovalent interactions on the electrode surface [175]. The resulting hybrid

7.1 Metal-Complex Chemistry of Nanocarbons

481

Fig. 7.69 Since the eight-coordinate ZrIV ion protrudes from one face of the 5,10,15,20-tetraphenylporphyrin (TPP) and phthalocyanine (Pc), the ZrIV axially coordinates GO by replacement of bidentate acetate groups with oxygen groups on the GO (bottom). The four-coordinate Zn analogue very weakly accepts axial ligands and does not bind GO (top). (Reproduced with permission of the American Chemical Society)

Fig. 7.70 Three potential binding modes of ZrIV(Pc) to the functional groups of graphene oxide are depicted. Three-dimensional renderings are approximated from MM2 calculations (top, left to right) for internal diol, side carboxylates, and side diols; gray, C; blue, N; red, O; dark gray, ZrIV; H is omitted for clarity. (Reproduced with permission of the American Chemical Society)

film showed excellent electrocatalysis for the reduction of dissolved oxygen at a peak potential of 0.28 V, enabling the design of a biosensor for the amperometric detection of glucose. Metal porphyrin–graphene composites can be also applied as sensors, in particular for selective electrochemical determination of salicylate ion having vast uses. The corresponding electrode was prepared by incorporating Cu(II)–5–4(aminophenyl)-10,15,20-triphenyl porphyrin-grafted graphene oxide (CuTPP-GO) into the plasticized poly(vinyl chloride) membrane [176]. This sensor showed a Nernstian response in the concentration range of 5.0  101–5.0  107 M with detection limit of 8.0  108 M and stability in the pH range of 5–7. The sensor was successfully used for determination of salicylate in an aspirin tablet.

7.1.2.9

Schiff Bases and β-Diketones

Given its rich surface chemistry and high surface area, GO was found to be a convenient and efficient supporting material for grafting of Schiff bases via covalent attachment. A series of transition metal complexes with Schiff bases, immobilized on

482

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.71 Representation of the possible intermolecular interactions between multilayers of dye-bound GO made by layer-by-layer methods. The higher density of oxygen groups at the edges of GO results in greater binding of the ZrIV dyes. Other variations of these interactions are also present, for example, H-bond and ππ interactions between GO flakes. (Reproduced with permission of the American Chemical Society)

GO, have been used to demonstrate catalytic applications; for instance, salen-related complexes have been utilized for the epoxidation of alkenes. Thus, cobalt(II), iron(III), or oxo-vanadium(II) Schiff base metal complexes were covalently grafted by Su et al. [177] onto GO previously functionalized with 3-amino-propyltriethoxysilane and evaluated for the epoxidation of styrene, using air as the oxidant (Fig. 7.72). Co-GO and Fe-GO exhibit high styrene conversion (90.8 versus 86.7%) and epoxide selectivity (63.7 versus 51.4%), whereas the VO-GO construct exhibits relatively poorer catalytic performance. To synthesize a copper(II)-salen complex onto GO support [178], GO was covalently modified with an aminosilane, followed by condensation with salicylaldehyde (Fig. 7.73). The immobilized copper-salen complex [Cu(salen)  f  GO] retained the 2D sheetlike character of GO and was found to be highly effective for the epoxidation of olefins (Fig. 7.74). A similar dioxomolybdenum(VI) MoO2–salen-GO hybrid showed high activity in the epoxidation of various alkenes using tertbutylhydroperoxide or H2O2 as the oxidant [179]. The catalytic potential of the related oxo-vanadium hybrid 7.1.2.7 was also studied for the oxidation of various alcohols to carbonyl compounds using tert-butylhydroperoxide as the oxidant [180]. This graphene-bound oxo-vanadium Schiff base was successfully reused for several runs without significant loss in its catalytic activity.

7.1 Metal-Complex Chemistry of Nanocarbons

Fig. 7.72 Schematic outline of synthesis of M-GO (M ¼ Co, Fe or VO). (Reproduced with permission of the John Wiley & Sons)

Fig. 7.73 Synthesis methodology of Cu(salen)  f  GO. (Reproduced with permission of the American Chemical Society)

483

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.74 Illustration for (a) the mass transfer phenomenon in the reaction mixture (“the reactive species can readily reach or leave the catalytic active sites with limited mass transfer resistance”) and (b) the robust immobilization strategy (“the plierlike chelate ligands not only keep the planar steric structure of the copper complex but also increase the electron cloud density around the copper center”). (Reproduced with permission of the American Chemical Society)

Fig. 7.75 Oxidation of secondary amines in the presence of the GrO-immobilized MTO catalyst

Other catalytic processes include, for example, amine oxidation. Thus, a rhenium-oxo complex methyltrioxorhenium was homogeneously immobilized on a Schiff base-modified GO support via covalent bonding and was found to be an efficient catalyst for the oxidation of various amines to the corresponding N-oxides (Fig. 7.75) using H2O2 as an oxidant in high to excellent yields [181]. The best results were obtained while the reaction was carried out in methanol under refluxing conditions.

7.1 Metal-Complex Chemistry of Nanocarbons

485

Fig. 7.76 The detailed synthetic procedure for the formation of Ni(Curc)2/GO nanocomposite. (Reproduced with permission of the International Journal of Electrochemical Science)

Fig. 7.77 FESEM images of (a) curcumin (b) Ni(Curc)2, (c) GO (d) Ni(Curc)2/GO nanocomposite. (Reproduced with permission of the International Journal of Electrochemical Science)

A glassy carbon electrode, modified by nickel-curcumin nanocomposite film (curcumin is (1E,6E)-1,7-bis(4-hydroxy-3methoxyphenyl)-1,6-heptadiene-3,5-dione 7.1.2.8) [Ni(Curc)2]/graphene oxide (GO) [182], was used as sensitive electrochemical sensor for ecologically harmful p-nitrophenol with low limit of detection and good sensitivity property (Figs. 7.76 and 7.77). In addition, the synthesized nanocomposite was found to be highly dispersible in several solvents such as ethanol, water, N-methyl-2-pyrrolidone, and DMF.

486

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes H O

O

O

HO

OH OCH3

Ketone form

OCH3

O

HO

OH OCH3

Enol form

OCH3

7.1.2.8 Keto and enol form of curcumin

7.1.2.10

Hybrid Structures with Metal–Organic Frameworks (MOFs)

Intriguing protein adsorption properties have been observed for GO-La(BTC)(H2O)6 (H3BTC ¼ 1,3,5-benzenetricarboxylic acid) metal–organic framework composites (LaMOF-GOn, n ¼ 1–6, corresponding to the percentage of GO at 1, 2, 3, 4, 5, and 10%), prepared through a facile method at room temperature, developed by Liu et al. [183]. The presence of GO significantly changes the morphologies of the composites from spindly rectangular rods to irregular thick blocks and increases their surface area from 14.8 cm2 g1 (LaMOFs) to 26.6 cm2 g1 (LaMOF-GO3) while still retaining the crystalline structure of La(BTC)(H2O)6. LaMOF-GO composites exhibit outstanding adsorption properties for proteins due to the strong hydrophobic interactions, especially ππ interaction between proteins and the composite, which serves as the primary driving force for protein adsorption. Several other coordination polymer-GO hybrids have been examined for applications related to the detection of glucose. Metal coordination polymer–graphene nanosheets (MCPGNs, Fig. 7.78) combine the unique properties of graphene (excellent conductivity and high specific surface area) and MCPs (tunable pore size, large internal surface areas, and versatility of functionality). One of these hybrids, a high-quality Pt-based metal coordination polymer supported on graphene nanosheets, can act as an efficient matrix to immobilize glucose oxidase (GOD) [184]. Furthermore, the MCPGNs exhibited substantially better conductivity and electrocatalytic activity for H2O2 reduction than graphene. Another construct used for the same purpose is a Ni(II)-based metal–organic coordination polymer nanoparticle/reduced graphene oxide (NiCPNP/rGO)

Fig. 7.78 Illustration of the procedure for preparing graphene–metal coordination polymer composites and glucose electrochemical biosensing strategy. (Reproduced with permission of the Royal Society of Chemistry)

7.1 Metal-Complex Chemistry of Nanocarbons

487

TA

GO

NiCl2, DMF Hydrothermal Treatment

NiCPNPs/rGO

Fig. 7.79 A schematic diagram illustrating the NiCPNP/rGO nanocomposite formation process. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.80 Schematic of the chemical structures of (a) GO, (b) Cu-MOF, and (c) the paddle-wheel secondary building units of pure Cu-MOF. (Reproduced with permission of the Wiley-VCH)

nanocomposite, which is created in a single step by hydrothermal treatment of a mixture of tannic acid, GO, and NiCl2 in N,Ndimethylformamide and water as illustrated by Lu et al. [185] in Fig. 7.79. The assembly of graphene oxide (GO) and a copper-centered MOF (Fig. 7.80) yields a versatile system that shows excellent performance for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). Jahan et al. [186] affirmed that the enhanced electrocatalytic properties and acid stability of the GO-MOF composite that arises from the unique porous scaffold structure improved charge transport and synergistic interactions between GO and the MOF. GO sheets decorated by -OH and epoxy groups on either side of the sheets are analogous to pillar connectors such as 1,4-benzene dicarboxylic acid used in classic MOF synthesis, which serve as bifunctional linkers for the paddle-wheel unit.

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.81 Schematic representation of (a) the preparation of MGMOF composites and size-selection mechanism and (b) selective enrichment and magnetic separation of peptides using MGMOF (a dispersive sandwich-like magnetic graphene/MOF composite material). (Reproduced with permission of the American Chemical Society)

MOFs have attracted much attention also as adsorbents for the separation of CO2 from flue gas or natural gas [187]. A copper-based MOF and GO composite (HKUST-1/GO) was found to improve the CO2 adsorption capacity and CO2/N2 selectivity. This composite exhibited about a 38% increase in CO2 storage capacity as compared to the parent MOF HKUST1 at 305 K and 5 atm. As an entirely different application, a nanocomposite material, assembled from azobenzenefunctionalized GO and stilbene-MOF, was found to be capable of luminescent quenching by explosive gases [188]. This unique system displayed selectivity to dinitrotoluene (71% quenching) over trinitrotoluene (20% quenching) with sub-ppm sensitivity and response times of less than a minute. Photophysical studies showed that the composites exhibit a typical π–π* transition which gives rise to strong fluorescence, which is quenched upon interactions with dinitrotoluene. Magnetic nanoparticle–graphene–MOF composites with high specific surface area (345.4 m2 g1) were constructed [189] (Fig. 7.81) via a strategy for self-assembly of well-distributed, dense, and highly porous MOFs on both sides of graphene nanosheets. The magnetic nanoparticles were embedded in the composite nanostructure, endowing them with an excellent magnetic response without damaging the unique structure of the MOF layer. This product was found to be a highly effective affinity material in selective extraction and magnetic separation of low-concentration biomolecules from biological samples, thus being an excellent platform for selective capture and extraction of peptides.

7.1.2.11

Intermediate Grignard Reagents

In addition to metal-complex composites of graphene, the use of organometallics as intermediate species for graphene functionalization is known. Thus, the covalent double-sided and high-degree (5.5–11.2%) functionalization of graphene was achieved [190] by exfoliation of the commercially available material graphite fluoride and its reaction with Grignard reagents (Fig. 7.82) in mild conditions. Concurrent reductive defluorination allowed the preparation of fluorine-free (with almost quantitative elimination of fluorine atoms) and well-defined graphene derivatives, highly dispersible in organic solvents. Conclusions to the Graphene Section As it was discussed above, graphene or graphene oxide can form hybrids with metal complexes of a variety of reported ligands, N- and N,O-containing ligands (Schiff bases, polypyridyl compounds, porphyrins, phthalocyanines), as well as σ- and π-organometallics: carbonyls, cyclopentadienyls, pyrene-containing moieties, and other aromatic structures. A recently discovered example of N,S,O-containing ligands is also known {copper(II) L-methionine

7.1 Metal-Complex Chemistry of Nanocarbons

489

Fig. 7.82 Overview of the reaction of fluorographene with Grignard reagents, yielding covalently functionalized graphenes. The partial charges on the nucleophilic carbons in the hydrocarbon anions are shown in bold. (Reproduced with permission of the American Chemical Society)

(Met) complex/silver nanoparticles/graphene-coupled nanoaggregates (Cu(Met)2/Ag/G) [191]}. The interaction “metal complex–graphene” in these composites could take place via either covalent or noncovalent (π–π-stacking) interaction; in some cases both routes at the same time are possible. Defects within graphene can obviously contribute to the possibility of composite formation. For a variety of pyrene-containing complexes, their units provide the means for noncovalent functionalization of graphene via ππ interactions, ensuring that the electronic properties of graphene are not impacted by the chemical modification of the carbon skeleton. We emphasize that graphene oxide composites with metal complexes are more widespread, in comparison with graphene hybrids, due to more possible varieties for reactions of the O-containing functional groups of GO with coordination complexes (metals or ligands). These nanocomposites can be synthesized by a variety of methods, from room temperature wet-chemistry techniques to hydrothermal reactions, using already prepared graphene or in situ formed from graphite as a result of its exfoliation. Ultrasonic treatment is sometimes applied in these processes. Resulting hybrids of G(GO) and metal complexes possess a host of useful applications, first of all in the catalysis (water oxidation catalysts, various electrocatalysts, substitution of expensive catalysts by nonprecious metal catalysts, generation of polyethylenes, aerobic epoxidation of styrene, epoxidation of olefins, reduction to methane or methanol, oxidation of various amines to the corresponding N-oxides), as well as as biosensors, detection of glucose, carbon dioxide or metal ion sorption, antitumor activity, and photosensitizers (Fig. 7.83) [103], among others. Frequently, such effects are reached by combination of the counterparts in these composites. Thus, for example, metal coordination polymer–graphene nanosheets (MCPGNs) combine the unique properties of graphene (excellent conductivity and high specific surface area) and MCPs (tunable pore size, large internal surface areas, and versatility of functionality). In whole, the research field of hybrids of graphene-supported coordination and organometallic compounds is a fastdeveloping area, which is a perfect niche for “hot-topic” investigations due to a series of useful applications of these nanocomposites. Obviously, this research area will be developed synchronically with the synthesis of related composites of carbon nanotubes due to high and permanently increasing importance of these two carbon allotropes.

490

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.83 Graphene and photosensitizers. Illustration of a graphene sheet and molecular structures of representative photosensitizers based on phthalocyanines (ZnPc) (green), π-extended TTFs (exTTF) (orange), and porphyrins (ZnP) (red). (Reproduced with permission of the Elsevier Science)

7.1.3

Fullerenes

7.1.3.1

Classification and Metal-Fullerene Coordination Modes

Metal(free or ion)-fullerene interactions are of a permanent interest [192–196]. The boom in the synthesis of fullerene9 derivatives, including their metal complexes, took place in the last decade of the twentieth century. The preparation, applications, and other achievements in metal-complex fullerene chemistry have been described in a series of reviews [197–199], books [200–204], and book chapters [205–207] (see numerous references therein). There is no sense to present all aspects of their structures and chemistry, so here we show only their most important examples and main current trends. In brief, the most important discovered kinds of metal(M)-fullerene(Ful) complexes, discovered up to date and described in an excellent comprehensive review [208], include (a) organometallic M-Ful complexes (in which the metal is attached directly to carbon atoms of the fullerene cage), (b) systems in which the metal center is coordinated to a metal-binding moiety attached to the fullerene cage using covalent or noncovalent interactions (Ful-containing metal coordination complexes, i.e., with N-donor and other ligand groups; M-Ful complexes based on noncovalent interactions), (c) complexes based on nondirectional intermolecular interactions (ionic fulleride [209] salts, solution associates [210], and cocrystallates [211]

9

The image above is reproduced with permission of the American Chemical Society (Inorg. Chem., 55(17), 8277–8280 (2016)).

7.1 Metal-Complex Chemistry of Nanocarbons

491

Fig. 7.84 (a) Shows short intermolecular contacts between the porphyrin and C60 along the one-dimensional chains in H2TPP(Ph)4C60. (b) Relative orientation of C60 (shown in purple color) to the porphyrin ring. Short contact atoms are labeled for simplicity. The phenyl groups are not shown for clarity. Porphyrin: C, gray; N, blue; H, green. C60, purple color. (Reproduced with permission of the American Chemical Society)

(an example is Cu(TPP)(Ph)4(CH3)4.C60, TPP ¼ 2,3,5,10,12,13,15,20-octaphenylporphyrin, Fig. 7.84) [212] with transition metal complexes (fullerenes in porous coordination capsules (see below), solution associates of fullerenes with porphyrin and phthalocyanine derivatives [213], and cocrystallates of fullerenes with various transition metal complexes)). There are several other similar classifications, describing, for instance, for exohedral fullerene complexes: dihapto coordination of fullerenes to transition metals (an example (Ph3P)2Pt(η2-C60)), multinuclear transition-metal complexes (an example (Me3P)4Re2H8(η2,η2-C60)), other types of coordination of metal atoms to the C60 molecule (an example (CpFe)(η5-C60Me5)), and dimeric transition-metal complexes with C60 (an example (Me3P)2Ir4(CO)3(μ4-CH)(μ-Me2P) (CNR)(μ-η2,η2-C60)(μ4-η1,η1,η2,η2-C60)) [214]. Most works describe C60 metal complexes, less C70 [215], and very small number of reports for heavier fullerenes C76, C78, and C84. Examples of complexes, which have now become classic, are (η2C60)Pd(PPh3)2, (η2-C60)Ti(C5H5)2, as well as endohedral metallofullerenes, such as La@C60, Y@C60, and M@C82 (M ¼ Y, Ce), generalized in a review [216]. In whole, transition-metal compounds with fullerenes can be formally divided into two large families: endohedral (the metal atom is inside the fullerene cage but is not involved in coordination) and exohedral in which the metal atom is coordinated to the fullerene sphere.

7.1.3.2

Classic Organometallic and Coordination Metal-Fullerene Complexes

Classic Organometallic Metal-Fullerene Complexes For the first group of compounds (organometallics), possible metal-binding modes of fullerene are shown in Fig. 7.85, revealing that C60 can form bonds with a variety of metal clusters via σ- or π-bonds of types η2-C60, μ-η2:η2-C60, and μ3η2:η2:η2-C60, acting as donor ligands of 2e-, 4e-, and 6e-. The main modes are η2 and η5 (the great majority of fullerene organometallic compounds belong to these two groups), but the others are also represented; this area is open giving several opportunities for theoretical and experimental works for studying these structures (several illustrative examples are shown in Fig. 7.86) [217]: – – – –

η1 hapticity with the metal atom directly above any carbon atom (an σ bond is expected) η2 hapticity; this may be (6,6) or (6,5) type, although the last of these is not common η3 hapticity; the metal atom linked to three carbon atoms, theoretically this could be on either a six- or five-membered ring η4 hapticity, the metal atom linked to four carbon atoms

492

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

M3

M M

M η 2:η 2

η2

η 2:η2:η 2

M

M

M η 3[6:5, 6:5]

η 3[6:6, 6:5]

η 4[6:6, 6:6]

M

M η

5

η6

Fig. 7.85 Possible metal-binding modes of fullerene

– η5 hapticity, metal atom linked directly above the center of a five-membered ring – η6 hapticity, metal atom linked directly above the center of a six-membered ring In particular, a certain attention was paid to bucky-ferrocenes, hybrids of a ferrocene, and a fullerene (Fig. 7.87) with a η5-metal coordination [218]. Classic Fullerene-Containing Metal Coordination Complexes Fullerene-containing ligands (Fig. 7.88) include relatively simple molecules, such as fullerene-phosphides, as well as some other structurally more complex ones including polypyridine groups, metallocenes, crown ethers, and porphyrins. The binding of more complex structures is usually achieved through cyclopropanes with diazomethane or through the addition of azomethine ylide. Fullerene-phosphides can be prepared by the direct addition of the phosphide to the C60 with subsequent protonation of the formed anion. Polydentate phosphorus binders can be obtained by series of reactions from C60(OH)x. For example, C60(OH)12 reacts with PClPh2 to form C60(OPPh2)12 which, in turn, makes it possible to obtain complexes with transition metals. Thus, C60(OPPh2)12{RhCl(CO)2}6{RhCl(CO)}3 was synthesized from C60(OPPh2)12 and {RhCl(CO)2}2. Chemically modified fullerenes with olefinic or acetylenic groups can act as binders through these extra units. Examples of such compounds are {2-H,1-(Me3SiC C)C60}Co2(CO)6 y {2-H,1-(Me3SiC C)C60}Ni2(η5-C5H5)2 [219]. Peptide bridges between metal complex and fullerene are also common, for instance, for the diade [Peptide ¼ Aib-Glu(OR)-Ala-Aib-Glu (OR)-Ala; Aib ¼ α-aminoisobutyric acid; R ¼ (CH2CH2O)3Me] (Fig. 7.89) [220].

7.1 Metal-Complex Chemistry of Nanocarbons OC

CO

OC Re

OC OC

493 R3P

CO

OC

CO

PR3 Ir

OC Fe

Cl

CO

CO

CO

Re L

OC

L

OC L L

η1

η2

Tl

CO

Cr Ph

Ph

Co

OC

η3

OC R

R Ph

Ph

η4

η5

η6

Fig. 7.86 Representative examples for η1 η6 metal coordination to fullerene C60 (σ, π, or mixed σ-π coordination can occur) Fig. 7.87 η5-Bonding in complexes “buckyferrocene”

Cr

η 5-C60

494

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

R1 Fe

P R

NMe

H

N OEt

O

O

N

O

O

O

N

O O

O

O

O O

NMe

NH N

N HN

Fig. 7.88 Some examples of fullerene-containing ligands

7.1 Metal-Complex Chemistry of Nanocarbons

495 2PF6-

N N N

O

Ru2+ N

Peptide

N

N N

Fig. 7.89 A diade united to a C60 through a peptide

Classic and Less-Common Synthesis Routes Classic Methods The conventional synthesis of metal complexes of fullerenes can be carried out through four general classes of reactions that are typical in classical organometallic chemistry: 1. Adding the metal to the olefinic C–C bond in 6:6 ring junctions to form type coordination complexes η2 (an example: treatment of C60 with OsO4 in presence of pyridine (py) yielding C60O2OsO2(py)2 and C60{O2OsO2(py)2}2) 2. Reduction of fullerene to form the corresponding fulleride salt (an example: the interaction of C60 with {(η5-C5H5)FeI(η6C6Me6)} yielding [(η5-C5H5)FeII(η6-C6Me6)+](C60), among other products) 3. Addition of ligand groups to the fullerene so that the metal center is attached to the fullerene through some type of bridge group (an example: C60 in toluene reacts with Fe2S2(CO)6 resulting C60S2Fe2(CO)6) 4. The formation of solids in which fullerene and a metal-complex co-crystallize (an example: solutions of C60 or C70 with ferrocene, crystallizing the adducts C60.2{(η5-C5H5)2Fe} and C70.2{(η5-C5H5)2Fe}, respectively) Additionally, M-Ful complexes can be produced electrochemically [221] or in vapor phase [222], among several other routes, for instance, using metal or organofullerene halides. Thus, a series of penta(organo)[60]fullerene halides, C60R5X (R ¼ Me and Ph; X ¼ F, Cl, and I) (Fig. 7.90), were prepared [223] by the reaction of a C60R5 anion with appropriate transition metal halides (route a), by metal-mediated CH bond activation of C60R5H (route b), by hydrometalation of [60]fullerene (route c), and by the reaction of a fullerene halide either with a metal anion or with a low-valent metal complex (routes d, e). The formed compounds were further used in the synthesis of transition metalpenta(organo)[60]fullerene complexes, Re(C60Me5)(CO)3 (Fig. 7.91), Fe(C60Me5)Br(CO)2, Ru(C60Me5)Br(CO)2, and Co(η5-C60Me5)(CO)2. DFT Simulations of Synthesis Routes For the C60[CpRu(CO)2]2, which is the only transition-metal fullerene complex with pure η1-coordinated bonds, DFT calculations were applied to study its formation through the reaction between dinuclear Ru complex [CpRu(CO)2]2 and C60 (Fig. 7.92) [224]. A DFT study discloses that the η1-coordinated bond is formed by a large overlap between the Ru dσ orbital and C pσ one involved in the lowest unoccupied molecular orbital (LUMO) (π*) of C60 unlike the well-known η2-coordinated metal-fullerene complex which has a π-type coordinate bond with metal dπ orbital. The formation reaction was found to occur via Ru–Ru bond cleavage on the C60 surface followed by a direction change of CpRu (CO)2 to afford C60[CpRu(CO)2]2 in a stepwise manner via two asymmetrical transition states to avoid a symmetry-forbidden character. The use of nonpolar solvent is another important factor for the synthesis of the η1-coordinated metal complex with Li+@C60, which use is theoretically predicted to accelerate the reaction.

7.1.3.3

Recent Trends on Metal-Fullerene Complexes

Pyrazine, Pyrazolate, and Bispyridine Ligands A novel M2L2 molecular tube capable of binding C60 was synthesized [225] from bispyridine ligands with embedded anthracene panels and Ag(I) hinges (Fig. 7.93). This open-ended tubular host can accommodate a single molecule of various

496

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.90 Synthesis of fullerene complexes starting from metal halides as precursors. (Reproduced with permission of the American Chemical Society)

Fig. 7.91 Molecular structure of the rhenium tricarbonyl complex Re(η5-C60Me5)(CO)3 with 30% probability level ellipsoids. A CS2 molecule in the unit cell is omitted for clarity. (a) ORTEP drawing. (b) CPK model, top view. (c) CPK model, side view. (Reproduced with permission of the American Chemical Society)

C60 derivatives with large substituents. The fullerene guest can then be released by using the ideal, noninvasive external stimulus, light (Fig. 7.94). These results could be a practical platform for the development of novel photo-responsive molecular hosts in chemical and biological systems. The synthesis and characterization of supramolecular assemblies {C60[M3]4}1 consisting of C60 and coinage metal pyrazolates [M3] (i.e., [(3,5-(CF3)2Pz)M]3, where Pz ¼ pyrazolate and M ¼ Au, Ag, and Cu) were reported [226]. It is known that homoleptic pyrazolate complexes of copper, silver, and gold are of significant interest because of their structural

7.1 Metal-Complex Chemistry of Nanocarbons

497

Fig. 7.92 Reaction between [CpRu(CO)2]2 and C60-Ih. (Reproduced with permission of the American Chemical Society)

Fig. 7.93 Chemical structures of curved bispyridine ligand 1, Ag(I)-linked molecular tube 2, and C60 derivatives 3a–c. (Reproduced with permission of the American Chemical Society)

Fig. 7.94 Catch and release of a large guest molecule (e.g., fullerene C60) by using a tubular host composed of two curved ligands and two metal ions. Guest catch and release are triggered by the addition of metal hinges and the removal of the hinges upon photoirradiation, respectively. (Reproduced with permission of the American Chemical Society)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.95 Trinuclear [M3] systems involving the metal ions (M) copper(I), silver(I), and gold(I) and fluorinated pyrazolate [3,5-(CF3)2Pz]. (Reproduced with permission of the American Chemical Society)

Fig. 7.96 X-ray structures of {C60[Au3]4}1 showing the basic stoichiometry and tetrahedrally encapsulated C60 by four [Au3]. {C60[Cu3]4}1 and {C60[Ag3]4}1 analogues are isomorphous. (Reproduced with permission of the American Chemical Society)

Fig. 7.97 View of the supramolecular structure of {C60[Au3]4}1 (carbon, fluorine, and hydrogen atoms of pyrazolyl moieties are removed for clarity). (Reproduced with permission of the American Chemical Society)

diversity, fascinating luminescent properties, and rich supramolecular chemistry; trinuclear units featuring nine-membered M3N6 metallacycles (M ¼ Cu, Ag, Au) are the most common structural motif found in these systems (e.g., [(3,5-(CF3)2Pz)M]3 (Fig. 7.95). Indeed, it is possible to use systems like [M3] directly (without any modifications) to effectively catch buckyballs. For these pyrazolate adducts with fullerene, it was shown that {C60[Cu3]4}1, {C60[Ag3]4}1, and {C60[Au3]4}1 (Figs. 7.96, 7.97, and 7.98) form isomorphous crystals. The [M3] moieties adopt a concave conformation to complement the convex C60 surface. They exist as dimers of trimers (i.e., hexanuclear [M3]2 units) that are held together by three close MM metallophilic interactions at 3.1580(17), 3.2046(7), and 3.2631(7) Å for copper, silver, and gold systems, respectively. The

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499

Fig. 7.98 View showing C60 sandwiched [Au3]2 with three intertrimer AuAu contacts. (Reproduced with permission of the American Chemical Society)

Fig. 7.99 Possible structure of adducts of 2,6-bis(porphyrin)-substituted pyrazine derivatives with fullerene. (Reproduced with permission of Taylor & Francis)

[M3]2 moieties surround each C60 in a tetrahedral fashion, while each [M3]2 is sandwiched by two C60 molecules to form a supramolecular 3D assembly. Hybrid products like {C60[M3]4}1 resulting from the combination of two important classes of compounds [fullerenes and metal pyrazolate (or analogous systems)] offer many options to develop new material that may show interesting photochemical, electronic, and redox properties. 2,6-Bis(porphyrin)-substituted 3,5-dimethylpyrazine and its zinc complex were found to bound C70 to yield 1:1 inclusion complexes [227]. The existence of a charge-transfer interaction between C70 and porphyrin was suggested on the basis of a decrease in absorbance of the Soret band of the pyrazine derivative by the effect of C70. Palladium complexation of the porphyrin–pyrazine ligand enhanced the association with fullerene (Fig. 7.99). It was also found that inclusion room for C70 in

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

the Pd(II) complex was maintained, juxtaposed between porphyrins attached to the opposite sides of the pyrazine ligands. This pyrazine derivative with porphyrin rings at the 2,6-positions was found to be a significantly better host for C70 than for C60.

Porphyrins and Phthalocyanines Porphyrin–fullerenes are widely represented, possess unique electrochemical and photophysical properties, and are the promising compounds for nanotechnology, as well as for the preparation of liquid crystals, extra-hard composites, bioactive compounds, conductive materials, and pharmaceuticals [228–237]. Among other applications, porphyrin- (Fig. 7.100) [238] and phthalocyanine- (Fig. 7.101) [239] linked fullerenes have got applications in solar cells [240–242]. Indeed, porphyrins and fullerenes are indeed excellent building blocks for the construction of molecular photovoltaic devices due to the small reorganization energies of porphyrins and fullerenes in electron transfer. On the basis of porphyrin-linked C60 dyads and triads, solar-energy conversion systems consisting of self-assembled monolayers on electrodes can be constructed [243]. Several applications require distinct substituents with different lengths and volume. Thus, the synthesis by Prato reaction (Fig. 7.102) of covalent-bound porphyrin–fullerene conjugates based on fullerene C60 and meso-aryl-substituted porphyrins with long-chain substituents was carried out [244]. Also, the first example of a cocrystallized organometallic porphyrin and C60 fullerene is represented by a compound FcInTFcP@4C60 (Fig. 7.103) [245]. It was suggested that in this assembly, porphyrin and C60 molecules could be described as essentially neutral, weakly interacting fragments.

O

I T O

Os NC

Si

O

Os

N

N Os

Zn

CH2NH

CN

N

O

N

ZnP-C60/ITO

Fig. 7.100 A porphyrin–fullerene-linked dyad that was attached to an ITO substrate using a 3-(triethoxysilyl)propyl isocyanide as a surfaceanchoring ligand

N N N Zn

N

N

N

N

N N

N N

N

Zinc - Phthalocyanine: Pyrrolidinofullerene Fig. 7.101 ZnPc–C60 dyad solar cell and its photovoltaic properties

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501

OR

NH

OR

N OR

N

N

i

RO

M salt

HN

N

ii

M

RO N

OR N

M = Cu, Ni

OR OR

OR

NMe

O H N

N

OR

O H

iii

N M

RO

OR

N

N M

RO N

N

OR N

R = n-C10H21, n-C14H29

OR

OR

Fig. 7.102 Reagents and conditions: (i) NiCl2, DMF, 6 h or Cu(OAc)2, CH2Cl2, MeOH, 4 h; (ii) DMF, POCl3, CH2Cl2, 6 h, Ar; (iii) C60, Nmethylglycine, toluene, Ar, 20 h

Porphyrin-Based Fullerenes in Porous Coordination Capsules The combination of a bent diamino(nickel(II)porphyrin) with 2-formylpyridine and FeII yielded [246] an FeII4L6 cage (Fig. 7.104), which, being treated with C60 or C70, was transformed into a new host–guest complex incorporating three FeII centers and four porphyrin ligands. Similar to pyrazolate adducts above (acting through the same metal atoms), these compounds belong to rare examples of heterometallic host–guest species that employ different metal centers arranged in similar ligand environments. Another example of related polymetallic compound is an outstanding molecular catalyst, a ruthenium complex–porphyrin–fullerene-linked molecular pentad (Fig. 7.105) on Zn-Ru-Zn basis [247]. Its highly important application is a visible-light-driven water oxidation by this integrated photosynthetic model compound, which is achieved in the presence of sacrificial oxidant and redox mediator. According to the authors, this is the first example of WOC (water oxidation catalyst)–sensitizer–acceptor-linked photosynthetic model system, in which light harvesting, charge separation, and water oxidation are integrated into a single molecule. Next compound (Fig. 7.106) is an example of C60 aggregates with different macrocyclic ligands (porphyrin and phthalocyanine). Their structures for three sandwich-type neutral unprotonated mixed (phthalocyaninato)(porphyrinato) dysprosium (III) double-decker complexes Dy(Pc)(Por) [Por ¼ TCPP, TPP, TBPP; Pc ¼ unsubstituted phthalocyaninate, TCPP ¼ 5,10,15,20-tetrakis(4-cyanophenyl)porphyrinate, TPP ¼ 5,10,15,20-tetrakis(phenyl)porphyrinate, TBPP ¼ 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]-porphyrinate] (synthesis with 16–22% yields) were determined (Figs. 7.107 and 7.108) [248]. The quite similar coordination geometry for the dysprosium ion sandwiched between the two tetrapyrrole ligands in these three double-decker compounds was observed by XRD; meanwhile slight difference in their electronic structure was found by electronic absorption spectroscopic and electrochemical studies due to different electron-donating or

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.103 Perspective view of the FcInTFcP@4C60 assembly along the crystallographic c-axis. C60 molecules are represented by spheres for clarity. (Reproduced with permission of the American Chemical Society)

electron-withdrawing nature of substituent at the meso-attached phenyl moieties of the porphyrin ligand. Also, a fullerene ammonium derivative (Fig. 7.109) [249] was combined with different metalloporphyrin–crown ether receptors generating very stable “cup-and-ball”-type supramolecules due to a strong chelate effect. The nice complementarity of π–π and ammonium–crown ether interactions in the self-assembly of the dyads was elucidated. It was clearly shown that, whereas π–π interactions are governed by dispersion forces in free base porphyrins, they arise both from electrostatic and dispersion interactions in metalloporphyrins. Regarding to subphthalocyanines, noncovalent π–π interactions between chloroboron subphthalocyanine, 2,3-subnaphthalocyanine, 1,4,8,11,15,18-(hexathiophenyl)-subphthalocyanine, or 4-tert-butylphenoxyboron subphthalocyanine (Fig. 7.110) with C60 and C70 fullerenes were studied by Nemykin et al. [251] On the basis of theoretical data for the 1,4,8,11,15,18-(hexathiophenyl)subphthalocyanine, authors suggested that the weak (3.5–10.5 kcal/mol) van der Waals-type interaction energies tend to increase with an increase of the electron density at the subphthalocyanine core being the best platform for noncovalent interactions with fullerenes (Fig. 7.111). DFT calculations also indicated that 1:2 (fullerene:subphthalocyanine) noncovalent complexes are more stable than the corresponding 1:1 assemblies.

P-Containing Ligands Three monodentate diphosphine (dppm (bis(diphenylphosphino)methane), dppf (bis(diphenylphosphino)ferrocene), and dppb (bis(diphenylphosphino)butane)) complexes of the ruthenium-pentamethyl[60]fullerene (thus bearing monodentate diphenylphosphino-methane, diphenylphosphino-ferrocene, and diphenylphosphino-butane ligands) were synthesized [252] from Ru(C60Me5)Cl(CO)2 (useful metal-fullerene complex, in which carbon monoxide and chloride ligands can be replaced with various other ligands to obtain phosphine, alkyl, alkynyl, isocyanide, π-allyl, and Cp complexes). The rutheniumpentamethyl[60]fullerene complex was found to prefer monodentate coordination to fullerene (Fig. 7.112).

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503

O

+ Fe(OTf) 2 + NH2

N

C60 or C70

C60 or C70

N Ni

N

N

NH2

CuOTf + C60 or C70

CuOTf + C60 or C70

1

Fig. 7.104 Subcomponent self-assembly of 2-formylpyridine, iron(II) triflate, and the Ni-porphyrin-containing dianiline 1 to yield FeII4L6 tetrahedral assembly 2 in the absence of a templating guest. On the addition of different fullerenes, FeII3L4 cone-like host–guest complex C60/70 3 is obtained. Simultaneous addition of fullerenes and CuI yielded heterometallic host–guest complex C60/70 4. L, gray; Fe, purple; Cu, red; Ni, light blue. (Reproduced with permission of Wiley)

Buckymetallocenes Abovementioned buckymetallocenes, a unique class of transition metal penta(organo)[60]fullerene complexes possessing electron-donating metallocene and electron-accepting fullerene moieties, nowadays continue to be of an interest. Thus, acylated buckyferrocene and ruthenocene, Fe(η5-C60Me5)(η5-C5H4COR) (R ¼ Me, Ph, and CH¼CHPh) and Ru(η5C60Me5)(η5-C5H4COR) (R ¼ Me and Ph), were obtained (Fig. 7.113) by Friedel–Crafts acylation of the parent buckymetallocenes with the corresponding acid chlorides and aluminum chloride in CS2 at r.t [253]. Their structures are shown in Figs. 7.114 and 7.115. It was revealed that the Cp moiety in the acetyl buckyruthenocene was less sterically congested than that of the acetyl buckyferrocene. Further functionalization of these acylated compounds through reduction and esterification reactions has been made (Fig. 7.113).

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.105 Chemical structures of C60-ZnP-Ru-ZnP-C60 and reference compounds (ZnP-Ru-ZnP and ZnP-C60). (Reproduced with permission of Wiley)

Fig. 7.106 Schematic molecular structure of a mixed (phthalocyaninato) (porphyrinato) dysprosium double-decker compound and fullerene C60 [250]. (Reproduced with permission of The Royal Society of Chemistry)

Endohedral Metal-Fullerenes Certain attention is paid to nitride clusterfullerenes and methods of their separation and purification. Thus, magnetic properties of three nitride clusterfullerenes with one (GdSc2N@C80), two (Gd2ScN@C80), and three (Gd3N@C80) Gd ions inside were studied [254], taking into account their prospective application as contrast agents in magnetic resonance imaging. The paramagnetic behavior for GdSc2N@C80 and a ferromagnetic intramolecular coupling of the Gd ions inside the fullerene cage Gd2ScN@C80 and Gd3N@C80 were revealed. To develop non-chromatographic separations of rare-earth metallofullerenes containing di-metallic (M2), di-metallic carbide (M2C2), and tri-metallic nitride (M3N) clusters trapped inside fullerene cages, a “green” non-HPLC method for purifying Er3N@Ih-C80, a rare-earth, metallic nitride clusterfullerene, was offered (Fig. 7.116) [255]. Higher fullerene cages (e.g., Gd2C90–Gd2C140 and Er2C76–Er2C122 for M2C2n species and M3N@C78–

7.1 Metal-Complex Chemistry of Nanocarbons

505

Fig. 7.107 Schematic molecular structure of the sandwich-type mixed (phthalocyaninato) (porphyrinato) double-decker complexes [R ¼ CN, H, C (CH3)3]. (Reproduced with permission of The Royal Society of Chemistry)

Fig. 7.108 Molecular structure of Dy(Pc)(TCPP) (1) in top and side views with the hydrogen atoms omitted for clarity [Dy(III) green, C gray, N blue]. (Reproduced with permission of The Royal Society of Chemistry)

Fig. 7.109 Formation of supramolecular complexes from their corresponding building blocks (M ¼ 2H, Co, Ni, Cu, Zn) and fullerene derivatives. (Reproduced with permission of Wiley)

Fig. 7.110 Structure of subphthalocyanines, used for testing as potential receptors for C60 and C70 fullerenes. (Reproduced with permission of the American Chemical Society)

Fig. 7.111 ORTEP and MERCURY diagrams for X-ray structure of 1,4,8,11,15,18-(hexathiophenyl)subphthalocyanine:C60. Hydrogen atoms are omitted for clarity. (a) Prospective view of the unit cell; (b) “concave” 1:2 motif; (c) one out of three “sitting atop” motifs; and (d) one out of three fullerene:2 thiophenol noncovalent interactions motifs. (Reproduced with permission of the American Chemical Society)

7.1 Metal-Complex Chemistry of Nanocarbons

507

Fig. 7.112 Synthesis of monodentate phosphine complexes of the ruthenium-pentamethyl[60]fullerene

M3N@C92 for M3N@C2n endohedrals) containing entrapped dimetal and metallic nitride clusters can also be treated by this fractionation process.

Metal-Fullerenes Inside Nanotubes: Studies of Reaction Pathways Behavior of fullerene molecules inside carbon nanotubes remains to be of an interest for researchers [256]. Nowadays, using “in molecule-by-molecule transmission electron microscopy (TEM),” it is possible to trace the motions and reactions of individual molecules supported by nano-carbon materials. Thus, the chemical reactions of fullerenes and metallofullerene derivatives, focusing on their deformation process, were recently described in an excellent and highly intriguing review [257]. Indeed, confinement of molecules in a narrow nanotube provides a unique environment by limiting the molecular arrangement in one dimension and enables to investigate multiple reaction pathways. The reactivity of molecules can be quantitatively compared (by measuring electron doses) due to the differences in numbers of carbon atoms (C60, C70, and C82), molecular shape (sphere, endohedral oval, or exohedral), and contained metal atoms (4f block and 3d-group 8 transition metals). Among other important results, multiple reaction pathways were observed, and a decrease of metal oxidation state from 2 to 0 during the transformation process, similar to the classical oxidative addition and reduction elimination pathway, was proposed. Such changes in electronic configurations may result in deformation of the structure into energetically more stable structures. Selected investigations in this area are as follows: dimerization reaction of C60 in nanotubes (Fig. 7.117), reaction of endohedral metallo-[82]fullerene (M@C82) in a nanotube (Fig. 7.118), and reaction of bucky metallocene in a nanotube (Fig. 7.119). In a related report [102], strong van der Waals interactions between the nanotube interior and the

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.113 Synthesis of buckymetallocenes. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.114 Molecular structure of acetyl buckyferrocene(CS2)0.5 with 30% probability level ellipsoids. The solvent molecule in the unit cell has been omitted for clarity. Right figures show the comparison of the bond lengths with acetyl ferrocene and acetyl pentamethylferrocene. (Reproduced with permission of the Royal Society of Chemistry)

7.1 Metal-Complex Chemistry of Nanocarbons

509

Fig. 7.115 Molecular structure of acetyl buckyruthenocene(CS2)0.5 with 30% probability level ellipsoids. Solvent molecule in the crystal packing has been omitted for clarity. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.116 Overview of the separation strategy for purifying Er3N@Ih-C80 with the SAFA process and for procuring enriched fractions of Er2@C2n and Er3N@C2n higher metallofullerenes using CS2 release chemistry. (Reproduced with permission of the Royal Society of Chemistry)

fullerene cage in Re(μ5-C60H5)(CO)3 (Fig. 7.120) can be used for metal transportation inside a nanotube. In the presence of catalytically active atoms of rhenium inserted into SWCNTs, the nanotube sidewall can be engaged in chemical reactions from the inside, despite that it is generally thought that the interior surface of nanotubes is unreactive. The authors also demonstrated that the nanoprotrusions can be formed in three stages: (i) metal-assisted deformation and rupture of the nanotube sidewall, (ii) the fast formation of a metastable asymmetric nanoprotrusion with an open edge, and (iii) a slow symmetrization process that leads to a stable closed nanoprotrusion.

Molecular Dynamics Simulations Several theoretical investigations have been made for possible creation of novel fullerene-based complexes in the future. Thus, molecular dynamics simulations were applied for prediction of interaction of a graphene flake with a nickel cluster,

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.117 Dimerization reaction of C60, observed by TEM. When a molecule is isolated, the fullerene maintains its original structure as no dimerization occurs. Images are recorded at E ¼ 120 kV and dose ¼ 5.3  106 electrons nm2 but at different temperatures: (a) T ¼ 293 K and (b) T ¼ 793 K. Contrast inside the fullerene cage indicates the orientation of molecules. (c–e) TEM image. (f–h) Extracted fullerene contrast. (i–k) TEM simulations based on model structures (m–o) are shown as a series of electron doses indicated on the right bottom side of panels (c–e). The bond formation of phase 1 is reversible (l, m), whereas phase 2 is observed as an irreversible fusion (m, n). A time-series movie revealed that the fused structures (d, e) are explained as 10-degree rotations of the same model structure (n, o). The simulation parameters are spherical aberration coefficient (Cs) ¼ 30 μm, defocus (Δf) ¼ 10 nm, and defocus spread (ds) ¼ 5 nm. Scale bar indicates 1 nm. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.118 Orientation of molecules in the reactions. (a, b) Reaction of Er@C82 selectively progresses in tube ii, observed at E ¼ 80 kV, T ¼ 293 K, and dose ¼ 2.1  106 electrons nm2 (a), 5.7  107 electrons nm2 (b). Er@C82 molecules are packed in tubes i and iii as in model (c) and in tube ii as in model (d). C82 cages are colored pink and the closest atoms on the pentagons are colored blue. (d–f) The existence of metal accelerates fusion with a small electron dose in both the La@C82 peapod (e–i: 5.2  106 electrons nm2, e–ii: 5.7  107 electrons nm2) and Er@C82 (f–i: 1.1  106 electrons nm2, f–ii: 9.3  106 electrons nm2) observed at T ¼ 293 K (Cs ¼ 30 μm). (g) The specimen stage at 4 K (g–i: 2.7  105 electrons nm2, g–ii: 5.4  106 electrons nm2) does not affect the motion of the Er atom in the fullerene cage. The 4 K stage reduces the rate of fusion. (h) The La catalysts observed at E ¼ 120 kV and T ¼ 293 K effectively cut the nanotube in half with the accumulated electron dose of 107 electrons nm2 (h–i: 2.5  106 electrons nm2, h–ii: 9.7  106 electrons nm2, h–iii: 1.1  107 electrons nm2). Scale bars represent 1 nm. (Reproduced with permission of the Royal Society of Chemistry)

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511

Fig. 7.119 Cryo-TEM images of molecule Fe(C60Me5)Cp inside a nanotube and reaction analysis of individual molecules. (a) Twenty-three molecules are aligned one-dimensionally along the tube axis recorded at 7.5  105 electrons nm2. Each molecule is numbered from left (¼1) to right (¼23). Scale bar represents 5 nm. (b–d) The courses of the chemical reactions: (b) intramolecular fusion, (c) decomposition followed by reaction with the tube wall, and (d) intermolecular fusion through decomposition, are shown, respectively, with their model structure on the leftmost figure. Five continuous images are averaged and shown with their recorded electron doses at the bottom. Scale bars represent 1 nm. (e) Some possible chemical reactions of Fe(C60Me5)Cp are illustrated. (Reproduced with permission of the Royal Society of Chemistry)

showing that M-C nanoobjects can be found to range from heterofullerenes with a metal patch to particles consisting of closed fullerene and metal clusters linked by chemical bonds [258]. Also, DFT methods were used in simulations to predict coordination modes in organometallic complexes of fullerene C80 and aryl ligands [259]. Of C80 seven possible isomers (see fullerene section of description of carbon allotropes), six simulations were carried out (Fig. 7.121). The family presents four cases of complexes which yield promising results with respect to thermodynamic stability; they are the complexes with fullerenes with symmetry C2v, D3, D2, and D5d, whereas the two remaining isomers coming from the more symmetrical fullerenes, i.e., Ih and D5h, seem to be unstable species. Strong π-bonding and influence of other factors ruling this interaction were discussed.

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.120 (a) Organometallic fullerene complex Re(μ5-C60H5)(CO)3 (1) used for the transportation of a single Re atom into the SWCNT with the Re atom grafted to the outside of the fullerene cage. (b) The Re–fullerene complexes were drawn into the nanotube because of strong van der Waals interactions between the nanotube interior and the fullerene cage. (c) 80 kV AC-HRTEM images of the Re(μ5-C60H5)(CO)3 @SWCNT structure show the presence of Re atoms (indicated by a black arrow) in the vicinity of the fullerene cages. (d) A time series (top to bottom) of AC-HRTEM images of 1@SWCNT that shows the organometallic fullerene molecules to be very sensitive to the e-beam, which results in rapid changes to their structure and leads to the polymerization and/or decomposition of the fullerene cages and the detachment of the Re atoms (an example of an individual Re atom per image is indicated by a black arrow). (e) EDX spectroscopy confirmed the presence of Re atoms within the nanotubes (peaks other than those of Re result from the carbon of the nanotube and the copper of the TEM specimen grid). (Reproduced with permission of Nature)

Fig. 7.121 C80 isomers under study (blue metal atom is chrome). (Reproduced with permission of MDPI)

7.1 Metal-Complex Chemistry of Nanocarbons

7.1.3.4

513

Main Applications of Metal-Complex Fullerenes

In addition to mentioned above several uses of the complexes, fulleropyrrolidines [260] and other C60 metal complexes get their applications in Grätzel solar cells and other photovoltaics [261], development of oligothiophene-based optoelectronic materials and artificial photosynthetic systems, as well as other C60 metal complexes, especially those on porphyrin basis used as photosensitizers (Fig. 7.122) [262]. Other applications include hybrid materials and photoconductors, for obtaining superhard and liquid crystal materials [263], hydrogen storage and catalysis [264], metallosupramolecular receptors for fullerene binding and release [265], drug delivery purposes [266], and other medical applications [267]. Thus, it is known that the “cisplatin” (cis-[Pt(II)(NH3)2Cl2], Cis) is currently one of the most effective therapeutic agents used against cancer deceases, in particular, ovarian cancer, bladder cancer, esophagus cancer, lung cancer, and cancer of head and neck. The selforganization of C60 fullerene and cisplatin in aqueous solution was investigated [268] using the computer simulation, dynamic light scattering, and AFM techniques, resulting in clear evidence of the complexation between the two compounds (Fig. 7.123). In particular, it was established that C60 fullerene in the C60 + Cis nanocomplex affects the cell death mode in treated resting lymphocytes from healthy persons and reduces the fraction of necrotic cells.

Fig. 7.122 Fullerenes and photosensitizers. Illustration of fullerenes C60, La@C80, La2@C80, and Sc3N@C80 and molecular structures of representative photosensitizers based on porphyrins (ZnP) (red), corroles (light red), phthalocyanines (ZnPc) (green), π-extended TTFs (exTTF) (orange), tetracyanoanthracenoquinone (TCAQ) (purple), and subphtalocyanine (SubPc) (blue)

Fig. 7.123 The calculated energy-optimized structure of the C60 + Cis nanocomplex in aqueous solution. (Reproduced with permission of Beilstein Journal of Nanotechnology)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

7.1.4

Nanodiamonds

7.1.4.1

Conventional ND-Complex Composites

Metal complexes with nanodiamonds10 (ND) are represented considerable lesser in comparison with ND functionalizations using organic compounds or biomolecules, as well as organometallics of graphene and CNTs. A theoretical approach was given for iron-containing NDs, simulating their structure and nature of the frontier molecular orbitals is [269]. It was predicted that the coordination compounds of ND joint to an iron atom by means of two carboxylic groups can have very different behavior than the pristine ND. Thus, normal semiconductor behavior corresponds to the composite with two ND units and carboxylic groups in the opposite ends (Fig. 7.124a); insulator, to the ND unit; and the composite without terminal carboxylic groups (Fig. 7.124b) – to conductor with strong paramagnetic behavior. Figure 7.125 shows a spin-density map for (C24O4Fe), where the blue region corresponds to density for an unpaired electron in the occupied upper level. The green region corresponds to an electron density of unpaired electrons from level HOMO-1. Experimentally, individual NDs were functionalized [270] with metal(Fe)-phenolic networks that enhance the photoluminescence from single nitrogen-vacancy centers. A one-step self-assembly between iron(III) ions and phenol compound (tannic acid, TA, 7.1.4.1) for this process is

Fig. 7.124 Iron coordination complexes of nanodiamond C22H28. (a) With terminal carboxyl radicals C26O8Fe. (b) Without terminal carboxyl radicals C24H27O4Fe. (Reproduced with permission of the Elsevier Science)

10

The image above is reproduced with permission of the Elsevier Science (International Journal of Pharmaceutics, 514(1), 41–51 (2016)).

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515

Fig. 7.125 Density spin map for C24H27O4Fe. (Reproduced with permission of the Elsevier Science)

Fig. 7.126 Complex preparation and photoluminescence spectrum. (a) Schematic illustration of the complex preparation and the coating process of the NDs. A one-step assembly of coordination complexes on a substrate through the mixing of TA, iron(III), and NDs with NV centers; (b) SEM and EDS elemental maps of coated ((i)–(iii)) and uncoated ((iv)–(vi)) NDs with metal–organic complexes. Red color ((ii) and (v)) corresponds to carbon content, while green color ((iii) and (vi)) corresponds to oxygen atoms. Scale bar is 2 μm. (c) Room temperature photoluminescence spectrum recorded from conjugated NDs hosting a single NV center. (Reproduced with permission of Royal Society of Chemistry [272])

shown in Fig. 7.126, consisting of mixing solutions of NDs, FeCl36H2O and TA, further vigorous agitation, and final addition of buffer solution (3-(N-morpholino)propanesulfonic acid). NDs can enhance fluorescence via coating using this complex without affecting the emission spectra of NDs. Due to the biocompatibility (NDs are nontoxic, as well as the metal-phenolic network), the formed complex can be safely used in biological applications.

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.127 Nanodiamond particles. (Reproduced with permission of Springer)

In addition to iron, several ND–metal-complex compounds have been experimentally reported also for other transition metals. Thus, the (5-nitrotetrazolato-N2) pentaammine-cobalt(III) perchlorate (NCP, 7.1.4.2), belonging to energy-saturated compounds and having a considerable practical interest, was modified [272] with NDs (Fig. 7.127) by mixing them in 2-propanol, further evaporation of solvent at r.t. and drying at 80  C. Also, carboxyl(RCOO)-functionalized NDs (CarNDs) were attached [273] with three osmium carbonyl clusters Os3(CO)10(MeCN)2 7.1.4.3, Os3(CO)10(μ-H)(μ-OH) 7.1.4.4, and Os3(CO)10(OOCC6H4NH4) 7.1.4.5. Their analogues for 1-adamantanecarboxylic acid (AA, 7.1.4.6), having a diamondoid structure and a carboxylic acid group, are different from CarNDs products as they form carboxylate structures.

2+ N

N NH3 H 3N

N

NO2 N

Co H 3N

NH3 NH3

7.1.4.2

-

(ClO4 )2

7.1 Metal-Complex Chemistry of Nanocarbons

517 NH2

O

H

Os

Os

O

OH

Os

O NCCH3

O

Os

Os

Os

Os

Os Os

NCCH3

7.1.4.3

7.1.4.4

7.1.4.5

7.1.4.6

Azide-functionalized ND was modified (Fig. 7.128) with a manganese tricarbonyl complex ([Mn(CO)3(tpm)]PF6) carrying an alkyne group at the peripheral position of the tris(pyrazolyl)methane (tpm) ligand using the copper-catalyzed 1,3-dipolar azide–alkyne cycloaddition reaction [274], resulting in functionalized ND particles with size about 10 nm. The process was carried out in in a DMF–water mixture using a tenfold excess of metal carbonyl complex over surface azide groups. This is an example of attachment of a biologically active CO delivery agent (photoactivatable CO-releasing molecule) to modified ND as a highly biocompatible carrier, which could open new ways for the targeted delivery of carbon monoxide to biological systems. Influence of spatial configurations of ligands (with N, O, and S as the donor atoms), attached to NDs, on separation efficiency of extractants on their basis was studied, using single(SA)- and double(DA)-armed ligands (Fig. 7.129) with O

+ N N

N N

N

N N

+

N +

N

O N

Mn

CO

N

CO Mn

N

N N

N

CuSO4.5H2O sodium ascorbate

N

N

N

CO CO

DMF/water (4:1)

CO

CO

PF6-

DND

DND

Fig. 7.128 Synthesis of [Mn(CO)3(tpm)]+-functionalized detonation nanodiamonds (DND) via “click” reaction on an azide-modified DND surface. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.129 Single- and double-armed ligands with identical coordination unit (amide–thiourea), attached to NDs, and their use for metal ion extraction. (Reproduced with permission of the Elsevier Science)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

identical coordination unit (amide–thiourea) and several d- and f-metal ions [275]. It was established that ND-SA and ND-DA possess excellent selectivities (up to 82% and 72%, respectively), large adsorption capacities, and very fast adsorption kinetics for uranium. In case of ND-DA, its tweezer-like double arms serve to catch metal ions providing a stronger chelate interaction. However, the ND-SA adsorbent exhibited better adsorption selectivity for uranium than ND-DA owing to its more flexible spatial configuration. These results are considered as valuable guideline for design of solid-phase extractants for uranium recovery on the basis of the strategy using amide–thiourea structures (functional groups) and NDs (solid matrix) and taking into account the spatial configuration of the ligand molecule.

7.1.4.2

Intermediate Metal Complex: ND Composites

Metal-complex composites with NDs can be formed as intermediate species in some processes, for example, for preparation of metal-ND particles. Thus, magnetic nanofluids (ND-Ni), based on a hybrid composite of NDs and nickel nanoparticles, were prepared [276] in situ involving the dispersion of carboxylated ND (c-ND) nanoparticles in ethylene glycol (EG) followed by mixing of NiCl2 and the use of sodium borohydrate as the reducing agent to form the ND-Ni nanoparticles (Fig. 7.130). These magnetic nanofluids combine the good magnetic properties of nickel and the high thermal conductivity of ND. It was

Fig. 7.130 Schematic representation of in situ growth of ND-Ni nanocomposite. (a) As-received detonated nanodiamond soot, (b) c-ND powder. (c) ND-Ni hybrid nanocomposite. (Reproduced with permission of Nature)

7.1 Metal-Complex Chemistry of Nanocarbons

519

Fig. 7.131 Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. (Adapted from Wikipedia)

established that the nanofluid for a 3.03% wt. of ND-Ni nanoparticles, dispersed in water and EG, exhibits a maximum thermal conductivity enhancement of 21% and 13%, respectively. Possible applications are heat-transfer equipment and magnetic resonance imaging. In addition, this method could be expanded to obtain other ND-based magnetic nanofluids, for instance, ND-Co, ND-Fe2O3, or ND-Fe3O4.

7.1.4.3

ND Composites with Biomolecules Containing Coordination Moieties

According to Wikipedia, the myoglobin (Fig. 7.131) (symbol Mb or MB) is an iron- and oxygen-binding protein with a crystallographic size of 2.5  3.5  4.5 nm found in the muscle tissue of vertebrates in general and in almost all mammals. This protein, among others, was used [277] for the static attachment onto the ND nanoparticles of two types (positively charged jND and negatively charged hND, resulting clear differences in results) with an average diameter of 4 nm as the adsorbents. It was shown that the protein surface coverage is predominantly determined by the competition between proteinprotein and proteinND interactions, showing a Langmuir-type adsorption behavior and forming 1:1 complex at saturation. The monocrystalline hND favors monolayer protein coverage, similar to a thin film on the particle surface; meanwhile, the detonated jND shows a significantly less proteinsurface interaction with the proteins. Both NDs have great potential to serve as biocompatible vehicles for drug delivery in biology and nanoscale medicine.

7.1.4.4

Applications

In addition to the applications mentioned above, similar to carbon nanotubes or carbon nanodots [278], the ND nanodiamonds exhibit high MR contrast because of a high payload of gadolinium ions and a slow tumbling motion of particles and can be used as T1 NP-based contrast agents. Discussing such applications of composites of metal coordination compounds with NDs, in particular, for a Gd(III) complex attached to NDs (Fig. 7.132), a tenfold relaxivity increase was observed compared with the monomeric Gd(III) complex [279, 280]. Other interesting application is related with use of NDs as vehicles for metal ion delivery via “Troyan horse” (Figs. 7.133 and 7.134) [281]. Thus, cell responses were studied after exposure of NDs, metal ions, or ND-ion mixtures. NDs were mixed for 2 h with Cu2+, Ni2+, Cd2+, and Cr3+ at 37  C, which are widely dispersed in the environment and interact with living systems showing toxic effects. Among other results, it was shown that addition of NDs improved the metal ion-induced toxicity to L929 cells with different extent and the IC50 values of Cu2+, Ni2+, and Cd2+ decreased by approximately 40%, 20%, and 10%, respectively. A broader description of applications for functionalized NDs is given in a series of reviews [282–285].

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

O

O

O

1) Sulfo-NHS, EDC, HEPES, NaCl pH=7 2)

ND

O O

NH

O N

Gd(III)-ND

Gd

N

O O

N

N

H2N

N N

O

Gd

HEPES, NaCl; pH=7

O

N N

O

O O

Fig. 7.132 Conjugation of the Gd(III) contrast agent to the ND surface. (Reproduced with permission of the American Chemical Society)

Fig. 7.133 Interactions of NDs with metal ions trigger cytotoxicity. (a) Scheme of adsorption of metal ions on NDs leads to cellular responses. (b) The adsorption amounts (blue) and adsorption energies (red) of metal ions on NDs obtained by ICP-MS measurements and theoretical computation, respectively. (c) The IC50 values of metal ions and ND-ion mixture and the differences between them. (d) Optical images of L929 cells after incubation with NDs, Cu2+, and ND-Cu2+ mixture for 24 h. (Reproduced with permission of Springer)

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521

Fig. 7.134 Release profile of Cu2+ from ND-Cu2+ complex at different pH values. (a) Desorption amount of Cu2+ from ND-Cu2+ complexes in different pH values: pH 7.4 and pH 5.5 within 24 h. (b) The most stable structures of the ND-Cu2+ complex at high and low pH (denoted by ND-Cu2 + and NDH-Cu2+, respectively) obtained by theoretical computation. (c) Molecular modeling illustrations for the adsorption of Cu2+ on ND aggregates at high pH and low pH. (Reproduced with permission of Springer)

7.1.5

Nanoonions

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.135 Noncovalent assembly of p-CNO. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.136 Synthetic procedure for the synthesis of pyrene–BODIPY dyad. (i) CuI, ascorbic acid, DMF, N2, 60  C. (Reproduced with permission of the Royal Society of Chemistry)

In a difference with CNTs or graphene, metal-complex-functionalized carbon nanoonions (CNOs [286] 11) are represented by a considerably lesser number of examples. On the contrary, a higher number of organic functionalizing agents have been reported to be attached the CNOs by a covalent or noncovalent manner [287]. Among metalloids, we note a coordination compound, boron-containing pyrene–BODIPY conjugates (Figs. 7.135 and 7.136) [288] on the CNO surface, formed by means of π–π-stacking mechanism and resulting fluorescent carbon nanoparticles. This functionalization led to an increase of CNOs’ dispersibility. The long-term perspective for these compounds is their applications for drug delivery, in combination with cellular imaging. Metal complexes are shown by a few examples only with ferrorene (Fc) and metal porphyrins. Thus, a first supramolecular CNO/Zn-porphyrin complex was reported by Echegoyen (Fig. 7.137) [289], and its surface structure was further analyzed by Spampinato [290]. This functionalization also led to an increase of solubility. In an intermediate step (formation of pyridine derivative), it was estimated the presence of approximately one pyridine functionality per 120 CNO surface carbon atoms. Similar complexes, according to authors, are possible using metals such as Pt and Pd and may have potential applications in the fields of hydrogen storage and catalysis. At last, ferrocene (Fc)-decorated CNOs were reported by Prato et al. [291], who functionalized CNOs in a 1,3-dipolar cycloaddition reaction and subsequent deprotection of the formed amino functionality, and reaction with Fc-carboxylic acid chloride leading to Fc-functionalized CNOs. In this case, the CNOs contained one functional group per 36 surface carbon atoms. Environmental applications Formation of metal complexes between surface-oxidized CNOs and metal ions can be used for development of innovative in situ remediation technologies. Thus, CNOs, synthesized [292, 293] using a laser-assisted combustion and further surface oxidized, possessed 10 times higher sorption capacity being comparing with C60 for metal ions

11

The image above is reproduced with permission of the Wiley (Chemistry – A European Journal, 12(2), 376–387 (2005)).

7.1 Metal-Complex Chemistry of Nanocarbons

523

Fig. 7.137 Preparation of pyridyl-CNOs and an illustration of their supramolecular interaction with Zn-tetraphenylporphyrin (ZnTPP). (Reproduced with permission of the American Chemical Society)

Fig. 7.138 TEM images of formed nanoonions. (Reproduced with permission of Elsevier Science)

Pb2+, Cu2+, Cd2+, Ni2+, and Zn2+. CNOs aqueous suspension was found to be highly stable in NaCl and CaCl2 solutions in certain ranges of ionic strength and pH ranged. The authors emphasized that a good control of CNO mobility in porous media can be achieved by controlling solution chemistry of injected CNO suspension. Metal complexes as precursors for CNOs In addition to classic CNO fabrication methods, metal–organic frameworks (MOFs) can be also used as their precursors, for example, Basolite F-300 (iron 1,3,5-benzenetricarboxylate) [294]. The formed CNOs (Fig. 7.138) consisted of multiple graphitic shells that form both a hierarchical micro- and mesoporous carbon

524

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

material, due to the highly dispersed iron in the precursor structure which catalyzes the formation of graphitic carbon. These carbon materials can be used in supercapacitors, anode materials in lithium-ion batteries, or electrochemical hydrogen storage. Other nanoonion precursors on the basis of metal complexes are trigonal-prismatic lanthanide tris(2,2,6,6-tetramethyl-3,5heptanedionate) (Ln(tmhd)3) complexes [295]. Nanoonion structure formation can be described as bilayer formation of adducts which are generated by an interaction between free coordination sites of the Me(tmhd)n complex and a coordinating surfactant (e.g., alkyl sulfate, carboxylate, or alkyl phosphate). Lamellar structures are generated with layer spacings dependent on the carbon-chain length of the surfactant.

7.1.6

Nanobuds

The data on metal-complex composites with nanobuds12 are practically absent. In case of modeling interaction between ReC2 with a SWCNT forming protrusions and further nanobud-like structures, it was suggested [102] that the Re(III)C2 species should show greater reactivity toward the SWCNT for a carbon end-on attack of the sidewall than either the C2 biradicial alone or a Re(I)C2 species (Fig. 7.139). Authors proposed that the nature of the ReC2–SWCNT interaction is not just covalent; a charge transfer takes place from the sidewall of the SWCNT to the metal. Under bond formation, the complex perturbed the SWCNT structure, creating a tetrahedrically distorted C atom. Naturally existing defects on the SWCNT sidewalls may also be involved in interactions with Re atoms and the process of nanoprotrusion formation. It was indicated that Re can catalyze reactions with the structurally perfect SWCNT inner surface. The incorporation of additional C2 units into the edge of a growing nanoprotrusion is a spontaneous process that does not require catalysis by Re. The metal atoms cannot be incorporated into the final structure of the nanoprotrusion. The calculations showed that the chemical nature of Re makes it capable of activating several transformations in SWCNTs.

12

The image above is reproduced with permission of Nature (Nat. Nanotech., 2, 156–161 (2007)).

7.1 Metal-Complex Chemistry of Nanocarbons

525

Fig. 7.139 Activation of the concave side of SWCNT for chemical reactions. (a) The HOMO of alpha (spin-up, left) and of beta (spin-down, right) spin electrons for species 2 and 3. The bonding of Re(III) to the biradical C2 (2), generated under the e-beam from decomposing fullerene molecules, made the beta spin HOMO localize mainly on the terminal carbon and thus increased its reactivity. (b) The extent to which the reaction was activated by Re is illustrated as a ratio of the binding energies for ReC2 and C2 to SWCNT (EReC2/EC2) plotted as a function of Re oxidation state. (c) The bonding of ReC2 to the interior of the SWCNT stretched the C–C bonds in the nanotube sidewall and thus created a weak point susceptible to e-beam damage (lengths of individual C–C bonds are shown in Å, blue atom 1/4 Re, red 1/4 C atoms of biradical, and gray 1/4 C atoms of SWCNT). (d) Dangling bonds of a vacancy defect created at the site of the ReC2 reacted readily with additional C2 species, which led to nanoprotrusion growth. (e) Closure and symmetrization of the nanoprotrusion were dictated by a thermodynamic requirement for the minimization of the number of dangling bonds in the SWCNT structure. (Reproduced with permission of Nature)

526

7.1.7

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Carbon Nanofoams

Metal complexes have a relation with carbon nanofoams13 as their precursors only; no reported metal-complex composites with nanofoams are available. Thus, laser ablation of selected coordination complexes (Nd:YAG laser ablation of thick layers of coordination and organic compounds in air atmosphere, Fig. 7.140) [296] led to formation of nanostructured carbon foams (NCF): P-containing, P-free, and metal-NCFs. The following complexes were used as precursors: (a) for metal-NCFs (dichlorobis (triphenylphosphine)-nickel(II) [NiCl2(PPh2)2], dichlorobis (triphenylphosphine)-cobalt(II) [CoCl2(PPh3)2], and [1,2-bis (diphenylphosphino)ethane]dichloroiron(II) [FeCl2(Dppe)]); (b) for P-free metal-NCFs (bis(benzonitrile)dichloropalladium(II) [PdCl2(PhCN)2], dichloro(1,10-phenanthroline)-palladium(II) [PdCl2(Phen)], and (2,2 ́-bipyridine) dichloropalladium(II) [PdCl2(Bipy)]); and (c) for metal-free, P-free NCFs (naphthalene, phenanthrene, and 1,10phenanthroline). It was revealed that final NCFs are low-density mesoporous materials with relatively low specific surface areas (Fig. 7.141) and thermally stable in air up to around 600  C and well-dispersible well in a variety of solvents (Fig. 7.142). In addition to metal complexes above, the organic compounds (naphthalene, phenanthrene (resulting NCF is shown in Fig. 7.141b), and 1,10-phenanthroline) can be also used as precursors yielding a NCF material (metal-free and P-free) which consisted of both amorphous carbon aggregates and graphitic nanodomains.

Fig. 7.140 Schematic diagram of the experimental setup used for the laser ablation production of NCFs. A galvanometer mirror box (A) distributes the laser radiation (B) through a flat-field focal lens and a silica window (C) onto layers of the employed organometallic compounds (D) deposited onto a ceramic tile substrate (E) placed inside a portable evaporation chamber (F). The synthesized soot is mainly collected on an entangled metal wire system (G). The produced vapors are evacuated through a nozzle (H). (Reproduced with permission of Springer)

13

The image above is reproduced with permission of the American Chemical Society (ACS Nano, 9(8), 8194–8205 (2015)).

7.1 Metal-Complex Chemistry of Nanocarbons

527

Fig. 7.141 SEM images showing the spongy microstructure of NCFs. SEM micrographs of NCFs produced by laser ablation of [FeCl2(Dppe)] (a) and phenanthrene (b). (Reproduced with permission of Springer)

Fig. 7.142 NCFs easily disperse in various solvents. Top image shows NCFs in different solvents 60 s after being dispersed by mild sonication. Bottom image shows the same dispersions after 48 h. Solvents: 1, water; 2, acetone; 3, ethanol; 4, diethyl ether; 5, toluene; 6, dichloromethane; 7, hexane. (Reproduced with permission of Springer)

Coordination polymers were also used as carbon nanofoam precursor [297]. Thus, three compounds with different substituents, [Zn(5-R-isophthalate)(4,40 -bipyridyl)]n (Fig. 7.143, CID-R, where R ¼ H, OCH3, NO2), were chosen, since these compounds undergo exothermic de- composition and gas evolution takes place upon heating beyond their decomposition temperaturas. Among several organic groups, the nitro group was found to be crucial for the preparation of a porous foam-like carbon microstructure owing to the fast kinetics of gas evolution during carbonization. Also, a catalytic chemical vapor deposition (CCVD) technique was applied [298] for obtaining an alumina substrate coated CNF at 1000  C, using ferrocene (FeCp2, a simultaneous source of iron and carbon), H2 as reducing gas, and Ar as dragging gas (Fig. 7.144). It was found that the novel compound exhibits a high specific surface area, due to the porous morphology, and a high thermal stability.

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.143 (From top) Coordination environment, packing structures, and scanning electron microscopy (SEM) images of the guest-free materials: (a) CID-H, (b) CID-OCH2, and (c) CID-NO2. (Reproduced with permission of Wiley)

Fig. 7.144 Scheme of the reactor CVD employed the synthesis of the CNF. (Reproduced with permission of Springer)

7.1 Metal-Complex Chemistry of Nanocarbons

7.1.8

529

Nanocapsules

Nano-encapsulated metal complexes are almost unknown. Thus, an ab initio (DFT) study of carbon fullerenes (C20, C36, C56, C60, and C68), substitutionally doped with transition metals coordinated to several nitrogen atoms (capsules with porphyrin-like metal sites), was carried out [299]. The design of nanocapsules14 corresponded to substitutionally doped fullerenes merged with nanocones (Figs. 7.145 and 7.146): smallest metallocapsule (C8N8Ni2), C24N8Ni2, C40N8Ni2, C48N8Ni2, and C50N8Ni2, among others (B2C22N8 Ni2, C8N8Th, etc.). These capsules can be extended by adding larger carbon atom cones or CNT segments that would elongate them and increase their diameter. In particular, it was established that nickel atom doping of fullerenes yields capsules with binding energies comparable to NiII-doped nanocones and NiII-porphyrin. The capsules can selectively encapsulate heavy metal ions. In addition, these capsules could be applied in molecular electronics, catalysis, light harvesting (H26B5C61N18S2RuReOs), and nanomechanics (H6C118N18Ni2Ru2). Another example is an ultra-short SWCNT (US-tube, chemically reduced by Na0/THF)-based drug delivery system for the treatment of cancer, containing encapsulated cisplatin (Figs. 7.147 and 7.148), a widely used anticancer drug, which was prepared, characterized, and in vitro tested [300]. Cisplatin release from the capsule can be controlled (retarded) by wrapping the composite with Pluronic-F108 surfactant. Preparation of carbon nanocapsules from metal salts and organometallics It is known [301] that carbon nanocapsules can be formed from C60 nanowhickers and metal salts, for instance, Fe(NO3)39H2O. In this case, Fe3C-encapsulated carbon nanocapsules were formed (Fig. 7.149). The present method is suitable for the production of carbon nanocapsules and CNTs encapsulating various foreign nanomaterials. The capsules containing an Fe–P composite material can be produced from [CpFe(arene)]PF6 [302].

7.1.9

14

Carbon Nanofibers

The image above is reproduced with permission of the Royal Society of Chemistry (J. Mater. Chem. A, 3, 24,428–24,436 (2015)).

530

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.145 Metal-doped carbon nanocapsules. (Reproduced with permission of AIP)

Carbon nanofibers15 (CNFs) have been investigated in both fundamental scientific research and practical applications [303]. They have a series of useful applications in many fields, such as electrical devices, electrode materials for batteries, and supercapacitors and as sensors [304]. Despite their similarity with carbon nanotubes (which have a lot of reports on functionalization with coordination compounds and organometallics, see section above), the metal-complex composites with nanofibers are rare and frequently represent quasi-coordination compounds with participation of metal atoms and N-doped surface of nanofibers, forming porphyrin-like structures (Figs. 7.150 and 7.151). Such composites can be used as catalysts, for instance, for decomposition of formic acid [305]. It was shown that the decomposition of HCOOH takes place more rapidly on 15

The image above is reproduced with permission of the Wiley (ChemPhysChem, 16(15), 3214–3232(2015)).

7.1 Metal-Complex Chemistry of Nanocarbons

531

N

N

N Ni N

fused 5-5 rings

N Ni

N

4-4 rings

N

fused 6-6 rings

N

5-5 rings

Fig. 7.146 Some metal- and nitrogen-doping patterns for carbon nanocapsules

Fig. 7.147 HRTEM images of (a) bundled cisplatin@US-tubes and (b) bundled empty US-tubes. (Reproduced with permission of the Elsevier Science)

Fig. 7.148 Preparation and purification of CDDP@US-tubes. (Reproduced with permission of the Elsevier Science)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.149 Bright-field image of Fe3C-encapsulated carbon nanocapsule. (Reproduced with permission of Hindawi)

Fig. 7.150 Platinum coordination with N atoms, doping carbon nanofibers, and its use for catalysis purposes. (Reproduced with permission of the American Chemical Society)

Fig. 7.151 TEM image of the Pt/N-CNFs catalyst after testing of the sample in decomposition of formic acid. (Reproduced with permission of the American Chemical Society)

7.1 Metal-Complex Chemistry of Nanocarbons

533

Fig. 7.152 Geometries of models with the formic acid molecule above Pt and Ru atoms located in different positions in nitrogen-containing graphene fragments optimized at PBE/LACVP* + level. Interaction of the formic acid molecule with (a) a Pt atom attached to the divacancy with two pyridinic N atoms, (b) a Pt atom attached near the graphitic type N atom, (c) a Pt atom attached to two pyridinic N atoms on the armchair edge, (d) a Pt atom attached to two pyridinic N atoms on the zigzag edge, (e) a Ru atom attached to two pyridinic N atoms on the armchair edge, and (f) a Ru atom attached near the graphitic type N atom. Blue color indicates N; red, O; and yellow, H. (Reproduced with permission of the American Chemical Society)

single metal atoms, which can be obtained by rather simple means through anchoring Pt-group metals onto mesoporous N-functionalized carbon nanofibers. The metal atom is coordinated by a pair of pyridinic nitrogen atoms, according to DFT modeling (Fig. 7.152); this chelate (which can be considered as a kind of efficient and stable macro-ligand) binding provides an ionic-/electron-deficient state of these atoms preventing their aggregation and thereby leading to an excellent stability under the reaction conditions. A remarkably high rate of formic acid decomposition, along with excellent selectivity, was observed; the advantages of heterogeneous and homogeneous catalysts can be successfully combined. The immobilization of the rhodium–anthranilic acid (AA, 7.1.9.1) complex onto fishbone carbon nanofibers (produced by catalytic decomposition of CH4 on a Ni/Al2O3 catalyst) was carried [306] out in several steps (Fig. 7.153): (a) surface oxidation of the fibers, (b) conversion of the carboxyl groups into acid chloride groups, (c) attachment of anthranilic acid, and d) complexation of rhodium by the attached AA. The complex is connected with fibers by an amide linkage of the CNF carboxyl groups and the amine functionality of AA. This immobilized complex is not active in the hydrogenation of cyclohexene, but upon reduction with NaBH4, a highly active catalyst consisting of extremely small rhodium metal particles was obtained. Another example having catalytic applications is an amine-modified CNFs (AN-CNFs), prepared (Figs. 7.154 and 7.155) through the Billups reaction from CNFs and further used as supports of cobalt tetracarboxylphthalocyanine (CoTCPc) for the efficient catalytic oxidation of Acid Orange 7 (AO7) in the CoTCPc-AN-CNFs/H2O2 system [307].

HO H2N

O

7.1.9.1

534

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

O

HNO3/H2SO4

SOCl2

O

O

HO

AA C

NH

C OH

O

Cl

Nanofibre RhCl3.2H2O/H2O

H2O

Cl Rh

O

O

N

C

C

O

Molecular modelling study of RhAA/CNF

Fig. 7.153 Experimental procedures used for the immobilization of Rh/AA on fishbone CNFs. (Reproduced with permission of Wiley)

NH2

Billups reaction

H2N

1. Na, liquid NH3 2. p-iodoaniline CNFs

NH2

AN-CNFs 1. CoTCPc 2. SaturatedNaHCO3

NHCoPcCOONa NaOOCPcCoHN

NHCoPcCOONa

CoTCPcNa-AN-CNFs

Fig. 7.154 Functionalization of CNFs to produce AN-CNFs and CoTCPcNa-AN-CNFs through the Billups reaction

Several reports are devoted to the preparation of CNFs from MOFs [308]. Thus, ultrathin tellurium nanowires (TeNWs) can act as templates for directed growth and assembly of ZIF-8 nanocrystals (a typical MOF), resulting in the formation of uniform 1D ZIF-8 nanofibers (Figs. 7.156 and 7.157) [309]. Under calcination, this product was converted into highly porous doped carbon nanofibers, exhibiting complex network structure, hierarchical pores, and high surface area. After further doping, these fibers were found to have an excellent electrocatalytic performance for OORs, better than Pt/C catalyst. In another related report [310], a highly efficient, nanofibrous nonprecious metal catalysts were prepared (Fig. 7.158) for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. This catalyst (for PEM fuel cell application) consists of a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites.

7.1 Metal-Complex Chemistry of Nanocarbons

535

Fig. 7.155 TEM image of the CNFs, AN-CNFs, and CoTCPcNa-AN-CNFs. (a) CNFs at 50 nm; (b) CNFs at 20 nm; (c) AN-CNFs at 100 nm; (d) AN-CNFs at 50 nm; (e) CoTCPcNa-AN-CNFs at 50 nm; (f) CoTCPcNa-AN-CNFs at 20 nm. (Reproduced with permission of MDPI)

Fig. 7.156 Illustration of the nanowire-directed templating synthesis of ZIF-8 nanofibers and derived porous doped carbon nanofibers. (Reproduced with permission of the American Chemical Society)

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7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.157 (ae) TEM images of as-prepared Te@ZIF-8 by regulating the amounts of precursors. (ae) corresponding to samples AE; the average diameter of AE corresponds to 27, 36, 45, 73, and 95 nm, respectively; scale bar: 100 nm. Inset in (d) shows the photo of the sample D. (f) PXRD patterns of as-prepared samples AE. (Reproduced with permission of the American Chemical Society)

PAN/PMMA/DMF FEN6C36H24O8Cl2 ZIF-8

Oxidation at 250C/Air, Carbonization at 1000C/Ar, NH3 treatment from 900C

Eletrospinning

Raw composite fibers

Carbonized fibers

Washed by 0.5 M H2SO4,

Heat treatment in NH3 at 700 C

Final catalysts

Fig. 7.158 The schematic diagram of Fe/N/CF synthesis by electrospinning. The spun composite fibers contain uniformly mixed polymer, TPI salt, and ZIF-8 nanoparticles. The fibrous nanonetwork retains its morphology after pyrolysis, acid wash, and posttreatment. (Reproduced with permission of the PNAS)

7.1 Metal-Complex Chemistry of Nanocarbons

537

7.1.10 Carbon Nano-/Quantum Dots

Certain information is available on metal-complex composites of carbon quantum dots (C-dots or Cdots, sometimes called as carbon nanodots), which, being discrete, quasispherical particles with sizes below 10 nm generally possess a sp2-conjugated core and contain suitable oxygen content in the forms of multiple oxygen-containing species represented by carboxyl, hydroxyl, and aldehyde groups [311]. As it was noted in the section above on Cdots, they are widely used in sensing, such as detection of ions, small molecules, and biomolecules, based on their photoluminescence (PL) quenching by metal ions. In case of Cu2+, the metal inhibits the fluorescence of carbon dots through static and diffusional quenching mechanisms [312]. The mechanism of the PL quenching of C-dots by Cu2+ was elucidated [313]: C-dots coordinate with Cu2+ through their carboxyl groups, and the quenching occurs by a photoinduced electron transfer (PET) process (Fig. 7.159) from the photoexcited C-dots to the empty d orbits of Cu2+ combining with C-dots.

Fig. 7.159 Normalized PL intensity of C-dots, C-dots-PS, and C-dots-PS-NaOH as the concentration of Cu2+ increased (a), PL titrations of C-dots and C-dots-PS-NaOH with Cu2+ (b), and the proposed quenching mechanism of C-dots by Cu2+ (c). (Reproduced with permission of the American Chemical Society)

538

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Metal coordination to Cdots through surface groups is the basis of sensing. Thus, the detection process of metal ions and anions using carbon dots through carboxylate groups is shown in Fig. 7.160 [314]. Due to strong interaction between Fe3+ and S2O32 ions, the associated Fe3+ ions react with S2O32 to forms free Cdots. These interactions lead to exhibition of off–on fluorescence behavior, applied for creation of off–on (Fe3 +-S2O32) and on–off (Zn2 +-PO43) sensors, exhibiting excellent selectivity and sensitivity toward the detection of biologically important Fe3+, Zn2+ metal ions and S2O32, PO43 anions. Carbon nanodot functional composites with MOFs16 are also known, retaining the intact structure of MOFs (for instance, UMCM-1)17 [315] with high luminescence and longer stability, which were synthesized by a stepwise synthetic approach (Figs. 7.161 and 7.162) [316] and found to have an enhanced H2 storage capacity and fluorescent sensing for nitroaromatic explosives.

Fig. 7.160 Schematic representation for the sensing process of metal ions and anions with C-dots. (Reproduced with permission of Nature)

Fig. 7.161 Schematic illustration of Cdots@MOF composites. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.162 Optical micrographs of Cdots@MOFs (inset: SEM image). (Reproduced with permission of the Royal Society of Chemistry)

16

See also the section on the MOF-derived nanocarbons. UMCM-1 (University of Michigan Cryst. Material-1), a mesoporous material with unprecedented levels of microporosity, arises from the coordination copolymn. of a dicarboxylate and a tricarboxylate linker mediated by Zn. See details in: A crystalline mesoporous coordination copolymer with high microporosity. Angewandte Chemie, International Edition, 2008, 47 (4), 677–680. 17

7.1 Metal-Complex Chemistry of Nanocarbons

539

Fig. 7.163 Illustration of the synthesis of a complex GQDs conjugate. (Reproduced with permission of Springer)

A few reports are dedicated to metal-complex composites of graphene quantum dots (GQDs) [317]. Thus, a polypyrrole (PPy) and GQDs (GQDs)@Prussian Blue (PB) nanocomposite, grafted on a graphite felt (GF) substrate (PPy/GQDs@PB/ GF), was found to be an efficient electrochemical sensor for the determination of L-cysteine (L-cys) [318]. Supramolecular hybrid conjugates of GQDs and metal-free and zinc phthalocyanines (Pcs) were prepared via an in situ one-step bottom-up route (Fig. 7.163) [319]. It was observed that the singlet oxygen quantum yields of the Pcs in the presence of GQDs were considerable higher, as compared to the Pcs alone. The elaborated hybrid materials have a potential for various photophysicochemical applications such as photodynamic therapy and photocatalysis. A multifunctional platform for synergistic chemo- and photothermal therapy, composed of zeolitic imidazolate framework8 (ZIF-8) as drug nanocarriers and the embedded graphene quantum dots (GQDs) as local photothermal seeds, was developed (Figs. 7.164 and 7.165) [320]. Using doxorubicin (DOX) as a model anticancer drug, it was shown that monodisperse ZIF-8/

540

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.164 Schematic illustration of the synthesis of ZIF-8/GQD nanoparticles with encapsulation of DOX molecules and synergistic DOX delivery and photothermal therapy. (Reproduced with permission of the American Chemical Society)

Fig. 7.165 SEM and TEM images of ZIF-8 (a, d), ZIF-8/GQD (b, e), and DOX-ZIF-8/GQD (c, f) nanoparticles

GQD nanoparticles with a particle size of 50–100 nm could encapsulate DOX during the synthesis procedure and trigger DOX release under acidic conditions, being promising as versatile nanocarriers for synergistic cancer therapy. In addition, using GQDs, which have smaller lateral size, better biocompatibility, and a conjugate state higher than that of GO, the mechanism of GQDs in enhancing nuclease activity of copper complexes was investigated [321]. It was found that, due to the efficient electron transfer between the electron-rich GQDs to the copper complexes though coordination of GQDs to the copper centers, GQDs promote the reduction of copper ions and accelerate their reaction with O2, forming superoxide anions and copper-centered radicals (Fig. 7.166) and then oxidizing DNA molecules. Most important conclusion was made that unique and rich 3D structures of metal complexes can serve to prepare highly active DNA cleavage reagents with a high selectivity for DNA sequences and structures.

7.2 Organometallics and Composites with Other Carbon Forms

541

Fig. 7.166 GQDs enhanced the reduction of copper ions, promoting the formation of oxidative species and consequently exhibiting DNA cleavage activity. (Reproduced with permission of the American Chemical Society)

7.2

7.2.1

Organometallics and Composites with Other Carbon Forms

Glassy Carbon

Glassy carbon composites with metal complexes are not widespread; metal complexes are normally used here for modification of surface of glassy carbon electrodes (GCE), or they can be intermediate products, if the goal is to modify GCE with inorganic compounds [322]. Electrochemical applications [323] of several types of coordination compounds in respect of glassy electrodes have been recently reviewed. In particular, metal–Salen complexes (the family of Schiff bases derived from ethylenediamine and ortho-phenolic aldehydes (N,N´-ethylenebis(salicylideneiminato)–Salen) of various transition metals, such as Al, Ce, Co, Cu, Cr, Fe, Ga, Hg, Mn, Mo, Ni, and V, have a wide range of applications such as catalysts for the oxidation of hydrocarbons, oxygenation of organic molecules, epoxidation of alkenes, electrocatalysts for sensors development, and mimicking the catalytic functions of enzymes, among many other catalytic uses [324]. Chemically modified electrodes can be used as electrochemical sensors for the detection of heavy metals such as lead, cadmium, mercury, and arsenic [325]. Recent developments of carbon-based electrocatalysts for hydrogen evolution reactions (HER) were also discussed [326]. For oxygen evolution reactions (OER), bimetal–organic frameworks on GCE are also known [327]. In major original reports, these composites “GCE–metal complex” do not have a real covalent bond between components. Selected examples of electrochemical study of metal complexes on GCE are shown in Table 7.3. In original reports, a certain attention is paid to porphyrins [328], in particular looking for efficient electrocatalytic system for the HER (hydrogen evolution reaction). Thus, metalloporphyrins M-OEP (M ¼ Co(II), Cu(II), Zn(II), Ru(II), Fe(III), and Ni(II), OEP ¼ 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine) were deposited on GCE followed by further modifications [329], yielding different supramolecular architectures. For HER purposes, Co(II) and Cu(II) porphyrins represented the most active systems, where the presence of the linking molecules and metalloporphyrins in the electrocatalytic metalloporphyrin films was revealed. GCE were covalently modified, providing good electronic communication between the electrode and

542

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Table 7.3 Selected examples of electrochemical study of metal complexes on glassy carbon electrodes Complex [ReL(CO)3Cl]0.5H2O NO2

Observations The rhenium fragment is acting as an electron acceptor by decreasing the electron density on the TTF unit

Reference [349]

In case of the cobalt(II)-salen complex, it was noted that hydrophobic interactions can play an important role for the immobilization of organometallics. It was indeed possible to incorporate the neutral cobalt(II)-salen complex due to these interactions Interaction between Ru-phen and the protein is very weak, and for this reason the apparent binding constant is low (Kb ¼ 2.9  103 4.4  103) The presence of Shewanella oneidensis MR-1 on GCE results an asymmetric redox peak, with almost disappearance of the cathodic peak and strengthen of the anodic peak, which is a typical catalysis feature of electrochemical oxidation The quasi-reversible one-electron transfer redox process

[350]

S N

S

S S

NH

NO2

N

[Ni(bpy)3(BF4)2], [Co(bpy)3(BF4)2], and Co(salen) (where bpy ¼ 2,20 -bipyridine, and salen ¼ N,N´- bis(salicylidene)ethylenediamine) Ru(phen)3]Cl2 (phen ¼ phenantroline) and bovine serum albumin Electrocatalysis toward electrochemical oxidation of K4[Fe (CN)6]

Schiff base chelate of Cu(II) derived from anthracene-9 (10H)one with (s)-2-amino-5-guanidinopentanoic acid H2N

O

O

N

HN

O

O

O

[352]

[353]

NH

NH

Cu

Cu HN

O

[351]

O

O

N

NH2

[Cr(CO)5{C(OEt)Th}] [W(CO)4(PPh3){C(OEt)Th}]

A seven-coordinate manganese(II) complex with the tripodal tetradentate ligand tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb), with composition [Mn(Mentb)(α-methacrylate)(DMF)](ClO4)(DMF) Modification of GCE with ligands complex-formers The 4-hydroxybenzylidene-carbamide-cetyltrimethylammoniumbromide modified GCE (ligand-CTAB/GCE) was prepared by drop-coating technique and used to study its complexation effect with Mn2+ with the ligand

The Cr carbenes are oxidized in two one-electron oxidation processes, namely, Cr(0) to Cr(I) and Cr(I) to Cr(II). On the contrary, Fischer carbene complexes of tungsten are directly oxidized from W(0) to W(II) A quasi-reversible Mn3+/Mn2+ couple

NH2

N

[355]

[356]

O

HO Mn F

[M(PtBu2NR2)(CH3CN)n](BF4)2 M ¼ Co(II) and Ni(II), n ¼ 2, 3 The complex of iron(II) tris(3-Br-phen) (3-Br-phen; 3-bromo1,10-phenanthroline)

[354]

F F

[Tris-fluoro-4-hydroxybenzylidene-carbamidomanganese (II)] complex 4-hydroxybenzylidene-carbamide-CTAB/GCE can be used for removal of excess of Mn2+ ions in real samples Electrocatalysts for H2 production

[357]

Precursor of electropolymerization

[358] (continued)

7.2 Organometallics and Composites with Other Carbon Forms

543

Table 7.3 (continued) Complex [(η6-p-cymene)-RuCl(L)] (L ¼ mono anionic 2-(naphthylazo)phenolato ligands)

Observations OH

R

[η6-p-cymene)RuCl(L)] R'

NMO/CH2Cl2, reflux

Reference [359]

O

+ H2O R

R'

R = R´= alkyl or aryl or H

A GCE modified with nickel complex (S)-[O-[(N-benzylpropyl)amino](phenyl)methyleneimino-acetate (2-)-N,N0 ,N00 -nickel (II) (Ni-(S)BPBGly), irreversibly adsorbed on the electrode surface Copper complexation with guanine

Useful for the oxidation of primary and secondary alcohols in CH2Cl2 in the presence of NMO (N-methylmorpholine-N-oxide) Glucose sensor. Glucose is oxidized on the electrode surface via an electrocatalytic mechanism

[360]

Copper and guanine form a 1:2 ratio complex

[361]

The method can be carried out directly without any separation or pretreatment due to the selective electrocatalytic oxidation of sulfite

[362]

N H N

H2N

N

O

N

Cu2+ N N

O

N H

NH2

N

Copper (II) and guanine complex (proposed structure) Oxidation of sulfite by acetylferrocene

Fig. 7.167 AFM and SEM images of (a) bare GCE (glassy carbon electrode) and modified GCEs: (b) oxidized GC (GCox), (c) GC + 4aminopyridine (GC + 4AP), (d) GC + Cu(II)OEP, (e) GCox + Cu(II)OEP, (f) GC + 4AP + Co(II)OEP. (Reproduced with permission of the Elsevier Science)

catalytic sites in the metalloporphyrins. The AFM images (Fig. 7.167) supported the idea that the covalent bond is important for generating molecular stacks on the carbon surface. In addition to the HER uses, porphyrins were also applied for the oxygen reduction reaction (ORR). Thus, the effects of different redox mediators on the ORR catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], were investigated by cyclic voltammetry

544

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.168 Use of bimetallic porphyrins for ORR purposes. (Reproduced with permission of the Royal Society of Chemistry)

N

N

N N

Ru Cl N

N

N

N Cl N Ru

N

Co

N

Ru

N

N N

N

N

Cl N N

N

N Cl N N N

N

Fig. 7.169 Structure of μ-{meso-5,10,15,20-tetra(pyridyl)porphyrin}tetrakis{bis-(bipyridine) (chloride) ruthenium(II)}(PF6)4 (CoTRP)

(CV) and spectroelectrochemistry in conjunction with DFT calculations [330]. It was shown that that only the 2,20 -azino-bis (3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR; strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator was suggested. This redox mediator caused lengthening of the dioxygen-iron bond, which thus made dioxygen reduction easier. For similar ORR purposes, bimetallic porphyrins (Fe, Co) were obtained from Suzuki polycondensation and used for template-free preparation of metal N-doped carbons (Fig. 7.168) [331]. This bimetallic catalyst combines the physical properties of the cobalt-based catalyst (discontinuous, ribbon-like structure) with the advantages of the electrochemical properties of iron-based catalysts (high-onset potential, low hydrogen peroxide evolution). The coordination of Fe within the N-doped carbon matrix was confirmed by 57Fe Mossbauer spectroscopy. Also, the modification of a GCE with tetraruthenated porphyrins (Fig. 7.169) electrostatically assembled onto a Nafion film, previously adsorbed on the electrode surface, was

7.2 Organometallics and Composites with Other Carbon Forms

545

reported [333], indicating that Ru(II) is the active site for the electrocatalysis. Thus, modified GCE catalyzes HSO3 oxidation in water–ethanol solutions, showing (1) an enhanced stability compared with the electrode modified with the dip-coating method and (2) that the charge propagation in the film is the main kinetic factor affecting the whole oxidation process. Porphyrin analogues, phthalocyanines, were also used for GCE modification in the form of tetrabutylammonium (TBA) salts TBA[LnPc2] (Ln ¼ Nd, Yb or Gd) to be used for oxygen reduction [333]. Schiff bases, as it was mentioned above, are also of an interest [334]. Thus, Hg+2 ion was determined by the nickel Schiff base complex 7.2.1.1 modified GCE, prepared by electrochemical polymerization of this metal complex on the GCE surface [335]. Thus modified GCE showed a good linear response within the ranges of 16.7–166.4 μM and the detection limits were 0.054 nM for Hg+2. GCE modified by two polymer films of nickel complexes 7.2.1.2 with Schiff base ligands containing methoxy substituents in their aromatic parts were electrochemically studied [336], revealing a noticeable splitting of cycling voltammetric curves into at least two ox/red transitions, among other effects. In whole, the introduction of methoxy groups into aromatic parts of the Schiff bases affects the electrochemical properties of electrodes modified by polymer Ni complexes with these ligands. In addition, a GCE, modified with a copper(II) Schiff base complex [Cu(Sal-β-Ala)(3,5-DMPz)2] (Sal ¼ salicylaldehyde, β-Ala ¼ β-alanine, 3,5-DMPz ¼ 3,5-dimethylpyrazole) and SWCNTs [337], was used to detect catechol and hydroquinone simultaneously, exhibiting good electrocatalytic activities toward their oxidation, sensitivity, stability, and reproducibility.

Y R4

Cl

N

R4

N M

N

O

R3

Ni N

Cl

7.2.1.1

O

R3

O

O R2

R1

R1

R2

7.2.1.2 Y is a “bridge” group, R1–R4, substitutes in the aromatic part of a ligand. Schiff = Salen at R1–R4 = H and Y = CH2-CH2.

The Schiff bases, synthesized by reaction of D-chloro-glucosamine with salicylaldehyde derivatives (2-hydroxy-5methoxybenzaldehyde (R ¼ OCH3), 5-hydroxy-5- nitrobenzaldehyde (R ¼ NO2), 5-hydroxy-5- methylbenzaldehyde (R ¼ CH3), 5-hydroxy-5-chlorobenzaldehyde (R ¼ Cl), 5-hydroxy-5-fluorobenzaldehyde (R ¼ F), and 5-hydroxy-5bromobenzaldehyde (R ¼ Br)), were introduced into interaction with FeCl2, CoCl2, and NiCl2 solutions, yielding metal glucosamines [338]. A GCE modified with these glucosamines was used for the electroanalytical determination of melatonin (a hormone produced mainly in the pineal gland and participates in neuro-endocrine and neuro-physiological processes). The most active complex was found to be CoGlu-Cl; all these complexes presented high selectivity for the oxidation of melatonin. The Ni complex with a related ligand salophen is N,N´-bis(salicylidene)-1,2-phenylenediamine) on GCE was used for or electrochemical sensing of glucose in an alkaline medium (Fig. 7.170) [339], being a promising nonenzymatic sensor for glucose determination in biological samples. Carboxylates were also used for heavy metal detection. For instance, a Zn4O(BDC)3 (MOF-5; BDC2 ¼ 1,4benzenedicarboxylate) modified carbon paste electrode (Fig. 7.171) was used for lead detection [340] in the real water samples with satisfied sensitivity and reproducibility via chemical accumulation of the adsorbed metal ions at the electrode surface, followed by electrochemical detection of the preconcentrated species using differential pulse stripping voltammetry. The electrochemical behavior of a highly water-dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) ¼ copper terephthalate metalorganic framework, GO ¼ graphene oxide), prepared through an ultrasonication method, was investigated through casting the composite on a GCE (Fig. 7.172) [341]. Using this modified GCE as a sensor model for the determination of acetaminophen and dopamine, a high sensitivity and low interference of the two drugs were reached. Derivatives of pyridine and other heterocycles as quinoline or phenantroline [342], among others, have been used as modificators of GCE surface for distinct purposes. Thus, a dimeric Cu(II)complex[Cu(μ2-hep)(hep-H)]2.2ClO4 7.2.1.3

546

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.170 Schematic representation for preparation of modified electrode and electrochemical glucose oxidation. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 7.171 SEM image of the prepared MOF-5 modified carbon paste electrode. (Reproduced with permission of the Elsevier Science)

containing bidentate (hep-H ¼ 2-(2-hydroxyethyl)pyridine) ligand, together with Ag nanoparticles (Fig. 7.173), was used as modifier in the construction of a biomimetic for determining certain catecholamines, epinephrine and norepinephrine [343]. This sensor has a potential for practical application in quantitative analysis of molecules possessing phenolic–OH group. Pyridine, quinoline, and phenanthroline molecules were covalently bonded to GCE surfaces (Fig. 7.174) using the diazonium modification method, and the complexation ability of the modified films with ruthenium metal cations (Ru(NH3)63+) was investigated [344]. It was revealed that the heteroaromatic films were indeed formed on GCE surfaces and that the surface coverage of the 5-phen layer was lower than those of the other studied films. The ruthenium complexes were formed on the ligand films attached to the GC electrodes. It was confirmed that functionalized electrodes with N-containing ligands (pyridine, quinoline, and especially phenanthroline) can be used as templates because of their wellknown complexation ability, yielding metal-functionalized surfaces.

7.2 Organometallics and Composites with Other Carbon Forms

547

Fig. 7.172 Illustration for the sonication-assisted preparation of Cu(tpa)-GO and its application for the simultaneous determination of acetaminophen and dopamine. (Reproduced with permission of the American Chemical Society)

Fig. 7.173 SEM images of (a) GCPE (glassy carbon paste electrode), (b) SNP (Ag nanoparticles)–GCPE, (c) 7.2.1.3–GCPE, and (d) 7.2.1.3–SNP– GCPE. (Reproduced with permission of the Elsevier Science)

548

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.174 Diazonium modification method of GCE surfaces. (Reproduced with permission of the Elsevier Science)

ORTEP view of copper complex. Reproduced with permission of the Elsevier Science

A family of Mo- and Co-polypyridyl molecular catalysts ([(PY4)Co(CH3CN)2]2+, [(PY5Me2)MoO]2+, among others, Fig. 7.175) for electrochemical and photochemical water reduction were developed [345], being suitable to catalysis under environmentally benign aqueous conditions. Finally, two Ni(II) complexes with the tetradentate ligand N2S2 (pdto ¼ 1,8-bis (2-pyridyl)-3,6-dithioctane 7.2.1.4) and the hexadentate ligand N6 7.2.1.5 (bdahp ¼ 2,9-bis-(20 ,50 -diazahexanyl)-1,10phenanthroline) were used as molecular catalysts for the hydrogen evolution reaction [346]. It was shown that the pdto ligand promotes reduction over Ni(II) at less negative reduction potential in comparison when the ligand bdahp is presented.

7.2 Organometallics and Composites with Other Carbon Forms

Fig. 7.175 Molecular metalpolypyridyl H2 evolution catalysts. (Reproduced with permission of the American Chemical Society)

549

550

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.176 Proposed catalytic cycle of proton reduction. (Reproduced with permission of the American Chemical Society)

Fig. 7.177 Covalent attachment of the cobaltocenium ion to a glassy carbon surface. (Reproduced with permission of the American Chemical Society)

Ligands N2S2 (pdto) ¼ 1,8-bis(2-pyridyl)-3,6-dithioctane, and N6 (bdahp) ¼ 2,9-bis-(20 ,50 -diazahexanyl)-1,10phenanthroline). In case of P-containing ligands, two organometallic Ni pincer P-containing complexes 7.2.1.6 and 7.2.1.7 were found to be active catalysts (Fig. 7.176) for electrochemical proton reduction (the quantity of produced H2 showed good Faradaic yields (90–95%)) [347]. These complexes showed similar electrochemical behavior (complex 7.2.1.6 is more easily reduced) and a single reduction wave, which was assigned to a NiII/NiI couple. In addition, an “organometallic electrode” is known [348], when an electrochemical reduction of a cobaltocenium diazonium complex [CoCp(C5H4N2)]2+ resulted in covalent attachment of the cobaltocenium ion to a GCE surface (Fig. 7.177). This modified GCE is stable in ambient air for several weeks and does not appear to undergo a significant loss of surface material, being washed with water or organic solvents. It retains most of its coverage even when subjected to extensive sonication in water and can be applied in the areas of metallocenyl-based sensors and also in catalysis.

7.2 Organometallics and Composites with Other Carbon Forms

7.2.2

551

Carbyne

Since the term “carbyne” has various senses, we note that in this section, the linear acetylenic carbon (C C)n, a carbon allotrope with chains of alternating single and triple bounds, is described. Other meanings as a carbyne R-C∴, a class of free radicals with three dangling bonds on a carbon atom, or the methylidyne radical ∴CH, the parent member and namesake of the carbyne family, are excluded from description here. Because of stability issues, the carbyne, a one-dimensional chain of carbon atoms, has been much less investigated than other recent carbon allotropes such as graphene [363]. Acetylenic carbon compounds are not particularly moisture or oxygen sensitive but are moderately light sensitive [364]. Carbon-chain length in carbynes and their complexes with transition metals can vary; in a series of recently synthesized conjugated polyynes as models for carbyne, the longest consisted of 44 contiguous acetylenic carbons, maintaining a framework clearly composed of alternating single and triple bonds [365]. The synthesis of triisopropylsilyl end-capped polyynes with up to 20 sp-hybridized carbon atoms was carried out; an estimated conjugation length for carbyne of 32 acetylene units was predicted on the basis of UV-vis analysis [366]. The effective conjugation length for this series of polyynes is estimated to be ca. n ¼ 32, providing insight into characteristics of carbyne. In a report [367], diplatinum adducts of polyynediyls consisting of as many as 28 carbon atoms were synthesized by generating the labile PtCxH complexes in the presence of a suitable oxidizing agent. The resulting air-stable, p-tolyl-substituted diplatinum complexes provided the closest models for 1D carbyne. Carbyne metal complexes were mentioned long ago in a book [368]. Currently, this area does not belong to priority research fields; main reports correspond to the first decade of this century. Some their examples of are shown in Fig. 7.178 [369–372]. They indeed represent carbon-rich organometallics with σ-bond between metal atom and C atom of an acetylene unit. Carbyne compounds in which unsaturated elemental carbon chains span two metals, LmMCxM’Lm´ (Fig. 7.179), constitute the most fundamental class of carbon-based molecular wires [373].

OMe

Re ON

OMe

Re n

n = 3-10

PPh3

PPh3

ON

N

MeO

N

Ru

4

N Ru

Ru n = 4-10

Ru

n

P(p-Tol)3

P(p-Tol)3 Fe OC

Pt

Fe 6

CO

OC

CO

Pd

n = 3-5

n

Pt n

P(p-Tol)3

PPh3

PPh3

Fig. 7.178 Representative examples of metal-carbyne complexes

P(p-Tol)3

n = 8-14

Ph2P

(CO)3 Co

PPh3 R

OMe 4

N

(OC)2Co

Ph2P

PPh2 Co(CO)2

(OC)2Co Co(CO)2 PPh2

n = 7-12

n

Co (CO)2

552

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes LmMCxM´L´m´ Some valence structures of carbyne X X

C

C

C

n

C

X X

X

X C

C

C

n

X

C X

X C

X

C

C

n

X

C X

Fig. 7.179 Carbon-chain compounds

Fig. 7.180 The scheme of the colloidal system (C:Au: Ag) irradiation. (Reproduced with permission of Springer)

Fig. 7.181 REM images of metal–carbon cluster structures (a, b) and complexes (c), obtained by the irradiation of colloidal system with mass ratio Au(1):Ag(1):C(10) by the laser radiation with average power – 40 W (a), 30 W (b), and 20 W (c). (Reproduced with permission of Springer)

Synthesis methods for metal-carbyne complexes normally belong to classic organometallic techniques. Sometimes, nanotechnology-assisted techniques are applied. Thus, the laser irradiation with YAG:Nd3+ nanosecond pulse of colloidal systems, consisting of carbon and noble-metal nanoparticles (Fig. 7.180), resulted metal-carbyne clusters (Fig. 7.181), in which metal nanoparticles are interrelated by carbon chains [374, 375]. The Raman spectra of those systems depend on the concentration of the particles in the solution and on the laser radiation conditions. As a background, the authors used the fact

7.2 Organometallics and Composites with Other Carbon Forms

I

553

R

n CH2Cl2, r.t., 5-10 min [Pd(PPh3)4]

R = NO2 or CN

Ph P I

Pd

n

R

P Ph

Fig. 7.182 Synthesis of palladium end-capped polyynes

Fig. 7.183 Structural plot of one of formed complexes, hydrogen atoms are omitted for clarity. (Reproduced with permission of the American Chemical Society)

that, when exposed to fluids, the stabilization of carbyne allotropic form can be achieved by laser ablation in the presence of gold nanoparticles, leading to the consolidation of the ends of linear chains on the surface of gold particles and preventing them from destruction. Several carbyne metal complexes were prepared from metal salts or other organometallics and polyynes. Thus, organometallic octatetraynes C8[Pd]I and decapentayne C10[Pd]I (Fig. 7.182) are palladium end-capped polyyne compounds with the longest carbon chains known up to date [376]. Using 1-iodopolyynes as precursors, their reactions with [Pd(PPh3)4] in CH2Cl2 led to the compounds above via oxidative addition. However, it was necessary to avoid reaction times longer than 5–10 min, since alkynyl palladium complexes are highly unstable in solution and longer reaction times initiate the formation of by-products. Also, a series of Ru2(Xap)4-capped polyyn-diyl compounds 7.2.2.1, where Xap is either 2-anilinopyridinate (ap) or its aniline-substituted derivatives, were reported [377]. Their formation was reached by Glaser coupling reactions. In addition, Cu-catalyzed oxidative coupling of the hexatriynyl complex Fp*-(CtC)3-H (Figs. 7.183 and 7.184) affords the dodecahexynediyl diiron complex Fp*-(CtC)6-Fp* with slightly twisted structure [378]. Complexes containing Co3 carbonyl clusters end-capping carbon chains of various lengths with dppm ligand are known (Fig. 7.185) [379].

554

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Me3Si

C

C

C

C

C

SiMe3

C

1) MeLi 2) Fp*-I Fp*

C

C

C

C

C

C

SiMe3

K2CO3 / MeOH-THF Fp*

C

C

C

C

C

H

C

CuCl.TMEDA / O2, acetone Fp*

C

C

C

C

C

Fp*

C

C

C

C

C

C

C

C

C

C

C

Fp*

C

Fp*

C

Fp*-Cl

Fig. 7.184 Synthesis of Fp*-(CtC)6-Fp*

(CO)3 Co

(CO)3 Co C

(OC)2Co Ph2P

C

C

C

C

C

C

C

(OC)2Co

X

C

PPh2

n

PPh2 I

C

C

n

I

Hg(OAc)2 NaOMe

Pd(0) / Cu(0) Ph2P

(CO)3 Co

(OC)2Co

PPh2

x

Co (CO)2

x = 7, 8, 9, 13

(OC)2Co

(OC)2Co

Co(CO)2 Co(CO)2

Ph2P

(CO)3 Co

PPh2

(OC)2Co Ph2P

SiMe3

C

Co(CO)2

Ph2P

Co(CO)2

C Co(CO)2

Ph2P

PPh2

C x

Hg

C

C x

x = 1, 2

Fig. 7.185 Co3 carbonyl clusters with carbynes

X

Y N

N

Ru

N

4

Ru

Ru

N Ru

n

X = Y = 3-isobutoxy X = 3-isobutoxy, Y = H X = Y = 3,5-dimethoxy

7.2.2.1 Complexes Ru2−Polyyn−Ru2

4

PPh2 Co(CO)2

Co (CO)2

7.2 Organometallics and Composites with Other Carbon Forms

7.2.3

555

Graphite

It is known long ago that graphite aromatic system is capable to form composites with transition metals [380] and their complexes. In addition to a host of intercalation compounds with metals (especially lithium), other atoms, and molecules, several compounds of metal complexes (both coordination compounds as organometallics) with graphite and graphite oxide (GrO) are known, which have many useful application. Last decade, after discovery of graphene, main attention of researchers has been redirected to graphene-organometallic composites, so last years no serious activity in graphite-metal coordination has been observed. In this section, we briefly describe main achievements in this field, where predominant activities lie in the area of carboxylates (in particular, of a “HKUST-1” type18) and related components of graphite/metal-complex composites, for absorption and sensor applications, among others. Thus, a solid-phase extraction sorbent, on the basis of MOFs and graphite oxide, a hybrid composite Cu3(BTC)2/GrO (H3BTC ¼ 1,3,5-benzenetricarboxylic acid) (Fig. 7.186), was prepared by a solvothermal technique [381]. Luteolin (one of the more common flavonoids, having antioxidant, anti-inflammatory, anti-allergic, anticancer, and immune-modulating properties) was chosen as a model analyte to evaluate its extraction performance. The hybrid composite was found to have good adsorption capacity for the target analyte. For the same composites (Cu3(BTC)2/GrO) (Fig. 7.187), GrO was demonstrated to be a promising stabilizer for producing the Pickering emulsion, providing a large interfacial area for the in situ growth of Cu3(BTC)2 nanoparticles [382]. The wellexfoliated and extended GrO sheets in the obtained Cu3(BTC)2/GrO composites showed a great affinity for H2O molecules and significantly reduced their occupation in Cu3(BTC)2 nanoparticles. These composites were used as adsorbents for CO2 capture from the simulated humid flue gas, reaching uptake 3.30 mmol/g. In a related work [383], this composite (HKUST-1/ GrO) was found to improve the CO2 adsorption capacity and CO2/N2 selectivity, exhibiting about a 38% increase in CO2 storage capacity than the parent MOF HKUST-1 at 305 K and 5 atm. We note that also the composites of a water-stable chromium-based MOF MIL-101 and mesoporous carbon CMK-3, in situ synthesized with different ratios of MIL-101 and CMK-3 using the hydrothermal method, were used for the same purpose [384]. The hybrid material possessed the same

Fig. 7.186 SEM pictures of (a) Cu3(BTC)2 and (b) Cu3(BTC)2/GrO. (Reproduced with permission of the Elsevier Science)

18

HKUST-1 (“Hong Kong University of Science and Technology”) is a metal organic framework (MOF) made up of copper nodes with 1,3,5benzenetricarboxylic acid struts between them (see http://www.chemtube3d.com/solidstate/MOF-HKUST-1.html). This MOF is frequently used for obtaining graphite hybrid materials (Langmuir, 2011, 27, 10234–10242).

556

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.187 Schematic illustration of the synthesis approach for Cu3(BTC)2/GrO. (Reproduced with permission of the American Chemical Society)

Fig. 7.188 Schematic fabrication process of MOF-199/GrO composites coated SPME fiber. (Reproduced with permission of the Elsevier Science)

crystal structure and morphology as its parent MIL-101 and exhibited an enhancement in CO2 adsorption uptakes because of the formation of additional micropores and the activation of unsaturated metal sites by CMK-3 incorporation. The hybrid material of a copper-H3BTC-based MOF (MOF-199) and graphite oxide (GrO) was explored as the solid-phase microextraction coating [385]. This fiber was fabricated by using 3-amino-propyltriethoxysilane (APTES) as the cross-linking agent (Fig. 7.188), which enhanced its durability and allowed more than 140 replicate extractions. The composite is expected to show high adsorption affinity and satisfactory recoveries toward aromatic compounds via the strong π–π stacking interaction, being already used for simultaneous determination of eight OCPs (organochlorine pesticides) from river water,

7.2 Organometallics and Composites with Other Carbon Forms

557

Fig. 7.189 Schematic of the adsorption process of NH3, H2S, and NO2 on the Cu-based materials with evidence of the color changes and the identification of the reaction products. (Reproduced with permission of the Royal Society of Chemistry)

soil, water convolvulus, and longan with satisfactory recoveries of 90.6–104.4%, 82.7–96.8%, 72.2–107.7%, and 82.8–94.3%, respectively. In addition to coatings, sensor applications for these composites are of a high interest. Thus, the composites of MOFs (MOF-5, HKUST-1, or MIL-100(Fe)) and a graphitic compound (graphite or graphite oxide, GrO) were synthesized and tested for the removal of NH3, H2S, and NO2 under ambient conditions [386]. It was revealed that strong chemical bonds appearing between the MOF and GO are a result of the coordination between the GO oxygen groups and the MOFs’ metallic centers; such interactions induce the formation of a new pore space in the interface between the carbon layers and the MOF units, which enhances the physical adsorption capacity of the toxic gases. The target gases are also adsorbed via coordination to these centers, leading to the formation of complexes (Fig. 7.189) and collapse of the MOF structure. Both physisorption mechanism and the reactive adsorption of NH3, H2S, and NO2 were proposed, including the formation of Cu(NH3)4+, CuS, and Cu(NO3)2, depending on the adsorbate. In a related work [387], dedicated to sensor applications, to improve electrical contacts, blends of MOFs with graphite were generated using a solvent-free ball-milling procedure (Fig. 7.190). Thus, compressed solid-state MOF/graphite blends were easily abraded onto the surface of paper substrates equipped with gold electrodes to generate functional sensors for NH3, H2S, and NO at parts-per-million concentrations. The main limitation of this approach is centered on the limits of detection of the analytes, which currently cannot compete with those of chemiresistors employing materials such as metal oxides and conductive polymers. Two types of MOF/graphite oxide hybrid materials were prepared, based on a zinc-containing, (Zn4O(H-BDC)3, BDC ¼ 1,4-benzenedicarboxylate) MOF-5, and the other on a copper-containing HKUST-1 (Figs. 7.191, 7.192, and 7.193) [388, 389]. Their porosity likely located between the two components of the hybrid materials was found to be responsible for the enhanced ammonia adsorption capacity of the compounds, causing, however, a collapse of the framework, observed as a result of ammonia adsorption due to the interactions of ammonia with the metallic centers of MOFs. It was also observed that the MOF-5-based compounds collapse in the presence of humidity; meanwhile, the copper-based materials are stable. These processes (collapse of the structure and ammonia interaction with MOF-5 carboxylic groups) can also occur simultaneously owing to the competition between water and ammonia for the most reactive centers. In addition to simple inorganic gaseous molecules, the carboxylate composites of a copper-based MOF (HKUST-1) in the presence of graphite oxide (GrO), synthesized via a solvothermal method, can be used to remove thiophene (TP) [390]. The desulfurization performance of TP from the model fuels by GO/HKUST-1 with different content of GrO was investigated, showing that the composite material 1.75%GrO/HKUST-1 exhibited excellent adsorption capacity of 60.67 mg/g, which was attributed to the highest surface area and porosity. Also, a highly porous MOF, MIL-101 (Cr-benzenedicarboxylate), was synthesized in the presence of graphite oxide (GrO) to produce GrO/MIL-101 composites [391]. The porosity of the

558

7 Coordination/Organometallic Compounds and Composites of Carbon Allotropes

Fig. 7.190 Synthesis of metal–organic frameworks (MOFs) and fabrication of sensors. (a) The synthetic scheme for the series of two-dimensional (2D) MOFs. (b) A schematic showing the stepwise process for integration of MOF-based materials into chemiresistive devices. Direct compression of the MOF and abrasion led to limited implementation in solid-state devices. Ball milling of M3HHTP2 MOF and graphite formed a blend that was subsequently compressed into a pellet. Loading of the pellet into a pencil-style holder, followed by mechanical abrasion directly onto paper- or ceramic-based devices equipped with gold electrodes, produced a series of chemiresistors with different architectures. (Reproduced with permission of the MDPI)

Fig. 7.191 Oxygen coordination sites available in (a) MOF-5 and (b) HKUST-1. (Reproduced with permission of Springer)

composites increased remarkably in the presence of a small amount of GrO (99.6%) and ethylene (C2H4, Air Liquide, 99.995%). Similar CVD reactors (tubular quartz hot wall, resistively heated furnaces, containing 65 and 72 mm inner diameter quartz tubes, respectively) were used for both carbon precursors. In the acetylene system (using 800 sccm Ar (Air Liquide, 99.999%) as carrier gas, 30 v% H2 (Air Liquide, 99.999%), and 7 v% C2H2), the substrates were positioned on a special quartz holder that allows inserting and removing the samples from the hot zone of the CVD furnace (at 700
C) under a controlled, inert atmosphere. Besides argon, either N2 or He can also be used as a carrier gas. The heat up and cool down was done in only 5 min by inserting and removing the samples in the already hot reactor. This procedure reduces drastically the total syntheses to only 15 min, what allowed approximately four forest synthesis runs per hour (reproduced with permission of the Elsevier Science). Further Reading Catalysts for the growth of carbon nanotube “forests” [93]. Superhydrophobic carbon nanotube forests [94]. SWCNTs forest [95]. Field emission from nanoforest CNTs [96].

11.1.2.37

Synthesis of Carbon Nanoflowers

Carbon nanoflowers with graphitic feature were synthesized with high yield using a reduction–pyrolysis–catalysis route. The reaction took place at 650
C with glycerin as carbon source and magnesium and ferrocene as reductants and catalysts [97]. All materials were commercially obtained and used as received. In a typical experiment, 0.45 g of magnesium powder (99%), 0.1 g of ferrocene (99%), and 5 mL of glycerin were mixed in a high-pressure stainless steel autoclave of 40 mL. The autoclave was sealed carefully and maintained at 650
C for 12 h and then cooled to room temperature naturally. Some of the obtained black products were treated with 50 mL of 5 M HCl aqueous solution at 65
C for 2 h and then left in the acidic solution

11.1

Synthesis and Characterization Methods

697

Fig. 11.32 Synthesis procedure for CNF@NG. (Reproduced with permission of Wiley)

for 2 days at room temperature. Then the products were washed with absolute methanol and distilled water. After that, the obtained samples were dried in a vacuum oven at 50
C for 10 h. The morphology and structure of the as-prepared products were examined by means of transmission electron microscopy (TEM, JEOL 2010) using an accelerating voltage of 200 kV, scanning electron microscopy (SEM, JEOL JSM-6700F), X-ray powder diffraction (XRD) on a Rigaku X-ray diffractometer (model2028, Cu Kα radiation, 20 kV), and Raman spectroscopy at ambient temperature on Spex 1403 Raman spectrometer with an argon–ion laser at an excitation wavelength of 514.5 nm (reproduced with permission of the Elsevier Science). Further Reading Reviews on nanoflowers [98, 99]. Growth of carbon nanoflowers on glass slides [100].

698

11.1.2.38

11

Student Zone: Overview, Training, Practices, and Exercises

Synthesis of Boron-Doped Diamond Nanograss Array

Polycrystalline boron-doped diamond (BDD) thin films were grown on Si(111) substrates using microwave plasma chemical vapor deposition (MPCVD) in an 8 kW MPCVD reactor (Seki Technotron Corp., Model AX6500). A mixture of acetone and methanol in the ratio of 9:1 (v/v) was used as the carbon source. B2O3 as the boron source was dissolved in the acetone– methanol solution at the preferred concentrations. The bubbling of the acetonemethanol-B2O3 solution was carried out by high-purity hydrogen gas. The amount of boron atoms in the diamond films was evaluated using a CAMECA IMS 6f instrument. When a boron to carbon (B/C) weight ratio in the solution was 10,000 ppm, the boron doping level in the diamond film estimated by IMS measurement was 2.1  1021 cm3. The nanograss arrays were obtained by etching experiments performed in a parallel-plate reactive ion-etching plasma system with radio-frequency (RF) powering at 13.56 MHz (SAMCO, RIE-10NR). For all experiments the RF power was 300 W, the pressure of the O2 plasma was 20 Pa, and the total O2 flow rate was 10 sccm. As a primary ion, O2+ accelerated at 5.5 kV was used. The samples were characterized by field emission scanning electron microscopy (LE01530VP, Zeiss, Germany). The as-grown BDD film was obtained with hydrogen termination. The BDD nanograss array was obtained with oxygen termination by oxygen plasma etching. To compare the difference between BDD film and BDD nanograss array and confirm the effect of nanostructure, the BDD film with oxygen termination was obtained by the following process: the as-grown BDD film was immersed in 0.1 M KOH, and a potential of +2.6 V vs SCE was applied for 75 min [101] (reproduced with permission of the Royal Society of Chemistry). Further Reading Boron-doped diamond nanograss array [102].

11.1.2.39

Synthesis of Graphene@PANI Nanoworm Composites

Graphene@PANI Nanoworm Composites In a typical synthesis procedure (Fig. 11.33), the purified aniline (20 mL, 0.22 mol) was dissolved in HCl aqueous solution (22.5 mL HCl added to 100 mL of H2O). The mixture was stirred for 30 min in an ice bath. Then (NH4)2S2O8 (APS, 26 g, 0.11 mol) dissolved in 50 mL of DI water was slowly (about 60 mL/h) added into the acid aniline solution. The mixture was allowed to stir at room temperature for 12 h, polymerization was completed, and the suspension was dark green. The precipitated polymer was collected by filtration and repeatedly washed with DI water until the filtrate became neutral. At this point, the acid-doped product of PANI was obtained. The remaining product of the above filtration was added into 100 mL of concentrated ammonia. After stirring for about 24 h, the precipitated polymer was collected by filtration and repetitively washed with DI water until the filtrate became neutral and finally dried under vacuum at 60
C to obtain the product as a deep blue powder. Graphene oxide (GO) was prepared using a modified Hummers method. To fabricate graphene-wrapped PANI nanoworms, a general strategy could be achieved by dispersing the PANI nanoworms sequentially into the following three solutions for varied durations at room temperature. Typically, some fresh PANI nanoworm powders (10 mg) were first added into 1 g/L poly(allylamine hydrochloride) (PAH) solution and then dispersed by ultrasonication for 1 h. Next, the above reaction solution was dispersed into 0.2 g/L GO solution with the aid of ultrasonication and vigorous stirring at 0
C for 5 h. Subsequently, 20 mL of hydrazine solution (N2H4, 80 wt.% in water) was added, and the mixture solution was heated at 98
C for 1 h. Finally, the sample was collected by filtration, washed with deionized water, and dried at 60
C to obtain the graphene@PANI nanoworm composites [103] (reproduced with permission of the Royal Society of Chemistry).

11.1.2.40

Synthesis of Carbon Nano-urchins

Preparation of the solid core/mesoporous shell silica template and the spherical carbon hollow capsule using the solid core/ mesoporous shell silica template is described in [104]. Then, monodisperse iron oxide nanoparticles were dispersed in hexane. The spherical carbon hollow capsules were then stirred in the slurry for 6 h in order to allow the iron nanoparticles to adsorb on the surface. The spherical carbon hollow capsules containing the iron oxide nanoparticles on the surface were heated at 650
C for 2 h under a 60 sccm H2 flow. The subsequent CVD of ethylene at 650
C for 1 h produced the carbon nanotubes on the hollow carbon spheres (Fig. 11.34) (reproduced with permission of the Royal Society of Chemistry). Further Reading Core–leaf onion-like carbon/MnO2 hybrid nano-urchins (Fig. 11.35) [105]. Sea urchin-like carbon nanotubes on nanodiamond powder [106]. Sea urchin-like carbon nanotubes/porous carbon superstructures derived from waste biomass [107]. Sea urchin-like particles of carbon nanotubes directly grown on stainless steel cores [108].

11.1

Synthesis and Characterization Methods

699

Fig. 11.33 Schematic representation for the formation processes of graphene@PANI nanoworms, (a) aniline, (b) PANI, (c) PANI nanoworms, (d) graphene@PANI nanoworms. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 11.34 Schematic diagram of the procedure for preparing carbon nano-urchins: (a) adsorption of iron oxide nanoparticles onto hollow carbon spheres, (b) growth of carbon nanotubes on hollow carbon spheres by CVD. (Reproduced with permission of the Royal Society of Chemistry)

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Student Zone: Overview, Training, Practices, and Exercises

Fig. 11.35 Schematic diagram of the synthesis procedure of the core–leaf OLC/MnO2 hybrid nano-urchins. (Reproduced with permission of the Elsevier Science)

Fig. 11.36 Schematically synthetic procedure of the Pd/CNB nanohybrids. (Reproduced with permission of the Elsevier Science)

11.1.2.41

Synthesis of Carbon Nanobowls

The high-quality carbon nanobowls (CNBs) with high surface area were synthesized by a simple sol–gel synthetic method and used as advanced supporting material to anchor Pd nanocrystals by a facile homogeneous precipitation–reduction method (Fig. 11.36) [109]. For the synthesis of the CNBs, 0.15 mL of NH3H2O solution, 0.3 g of CTAB, and 0.15 g of C6H6O2 were added in 21 mL of CH3CH2OH solution. Then, 0.75 mL of TEOS was added in the mixture. After stirring for 0.5 h, the 0.21 mL of HCHO solution was added. A brown mixture was obtained after stirring for 24 h at room temperature and then hydrothermal treatment at 100
C for 24 h. The solid product was recovered, dried, and carbonized at 850
C for 2 h with a heating rate of 1
C/min. Finally, the carbon nanobowls (CNBs) were obtained after etching the silica in the carbon–silica composites by 3 M NaOH solution under ultrasonic condition for 2 h. In the synthesis of the Pd/CNB nanohybrids, the Pd/CNB nanohybrids were synthesized as follows. 8.57 mg of PdCl2 and 12.37 mg of CNBs were added into 10 mL distilled water and sonicated for 2 h. After adjusting the solution pH to 6.3, the solution was heated at 40
C for 6 h. Then, 0.189 g NaBH4 was added into the solution and stirred for 60 min. After centrifugation, washing, and drying, the Pd/CNBs nanohybrids were obtained. For comparison, the XC-72 supported Pd nanocrystals (Pd/C-72), and nanohybrids were also synthesized under the same experimental conditions (reproduced with permission of the Elsevier Science). Further Reading MoS2@C nanobowls (Fig. 11.37) [110]. Nanobowls of carbon by oxidative chopping of carbon nanospheres [111].

11.1

Synthesis and Characterization Methods

701

Fig. 11.37 Schematic illustration of the formation mechanism of the MoS2@C nanobowls (OA oleic acid). (Reproduced with permission of the Royal Society of Chemistry)

11.1.2.42

Synthesis of Carbon Nanocups

Low-aspect ratio carbon nanostructures were synthesized by using a chemical vapor deposition process. The AAO template was first placed in a quartz tube, and after which the tube was purged with high-purity argon gas (99.9%) for 5 min. During heat up, high-purity argon gas (99.9%) was supplied, and the pressure was maintained at 760 Torr. When the temperature of the inside quartz tube reached 650
C, acetylene (a carbon source for the deposition of a graphitic carbon layer inside predesigned short AAO nanochannels) and argon mixture gas (5 acetylene: 30 argon) were supplied resulting in the connected arrays of carbon nanocup film structure [112] (reproduced with permission of the American Chemical Society). Further Reading Nitrogen-doped carbon nanomaterials [113]. Highly ordered low-aspect ratio carbon nanocup arrays [114].

11.1.2.43

Synthesis of Carbon Nanoplates

Dispersible mesoporous nitrogen-doped hollow carbon nanoplates have been synthesized using gibbsite nanoplates as templates (Fig. 11.38). After the synthesis of hollow silica nanoplates and their coating [115], the silica nanocasting process was realized as follows. 2 mL of HCl (0.1 M) was added to 20 mL of polydopamine-coated hollow silica nanoplate dispersion (40 g/L) under stirring. After 10 min of stirring followed with 10 min of ultrasonication, 15 mL of TEOS were added in portions under the liquid surface of the mixture while being vigorously stirred. The reaction was run at room temperature overnight under stirring. After removing ethanol by rotary evaporation, the mixture was freeze-dried. Carbonization was then carried out at 800
C for 2 h under argon (heating rate of 2
C/min). The pyrolyzed product was treated by the ammonium hydrogen difluoride (NH4HF2) aqueous solution to remove the silica. The desired products hollow carbon nanoplates were obtained after careful washing (reproduced with permission of the American Chemical Society). Further Reading Carbon nanoplates from regenerated silk proteins (Fig. 11.39) [116, 117]. Carbon nanoplate/amorphous ruthenium oxide hybrids [118].

11.1.2.44

Synthesis of Carbon Nanobrushes

NiOCoO nanoneedles are grown on carbon fibers by a solvothermal strategy to form nanobrushes [119]. Self-supported NiOCoO nanoneedles were prepared by a facile hydrothermal synthesis method. In a typical procedure, 0.291 g of Co (NO3)26H2O, 0.566 g of Ni(NO3)26H2O, and 0.96 g of urea were dissolved in 17 mL of deionized (DI) water and 3 mL of ethanol. Subsequently, the above mixed solution stirred for 20 min became transparent pink. Then the solution was transferred into a 50 mL Teflon-lined stainless steel autoclave. A 0.3 mg sample of carbon fibers was then immersed into the above

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Student Zone: Overview, Training, Practices, and Exercises

Fig. 11.38 Schematic synthesis route to prepare hollow carbon nanoplates (HCPs). (Reproduced with permission of the American Chemical Society)

Fig. 11.39 Fabrication process of the H-CMNs (carbon nanoplates). Silk fibroin fibers degummed from natural cocoons were dissolved in LiBr (9.3 M), and then as-casted regenerated silk fibroin film and regenerated silk fibroin KOH film were carbonized. (Reproduced with permission of Wiley)

solution followed by heating of the solution to 120
C in an oven for 12 h and cooling to room temperature. The as-synthesized carbon fibers were then taken off and rinsed with DI water and ethanol and dried at 80
C in air overnight. Finally, the obtained productions were annealed at 300
C in Ar for 2 h to gain NiOCoO nanoneedles on the carbon fibers. Samples using different solvents were also synthesized under the same experimental conditions except replacing 3 mL absolute ethanol with water and isopropanol (Fig. 11.40) (reproduced with permission of the American Chemical Society). Further Reading Carbon nanobrush, the fibrous aggregate of carbon nanohorns [120]. Multifunctional brushes made from carbon nanotubes [121].

11.1

Synthesis and Characterization Methods

703

Fig. 11.40 Schematic illustrations of (a) carbon fibers, (b) disordered NiOCoO/carbon fiber nanobrushes, (c) NiOCoO/carbon fiber nanobrushes, and (d) dense NiOCoO/carbon fiber nanobrushes. (Reproduced with permission of the American Chemical Society)

11.1.2.45

Synthesis of Graphene Carbon Nanotube Carpets

GCNTs (graphene–CNTs, Fig. 11.41) were grown from CVD-deposited graphene on copper foil (G–Cu foil), graphene nanoribbons (GNR), and carbon fiber (CF). The deposition of the Fe3O4/AlOx binary catalyst was performed by spin coating over G–Cu substrate. A volume of catalyst, typically 100 μL/cm2 of substrate or enough to cover all the surface, was deposited and spin coated at 1000 rotations per min (rpm). The dip coating method was used in the GNR paper (5 mg, prepared by filtration) and the CF paper. The substrate was immersed into the solution for 20 s and then removed. A hot plate at 70
C was used to dry the substrate with the catalyst solution at room pressure. The GCNT’s growth was based on a water-assisted hot-filament CVD process, and the protocol started with the catalyst activation, using 30 s of atomic hydrogen reduction by hot-filament (W wire, 30 W). The entire process was conducted at 750
C under the flow of C2H2 (2 sccm), H2 (400 sccm), and H2O vapor flow by H2 gas bubbling (2 sccm). During catalyst activation, the total pressure of the furnace was held at 25–26 Torr. At the end of the 30-s activation process, the pressure was reduced immediately to 8.5 Torr, and the growth process was extended for 15 min at that pressure. Control experiments were done with e-beam evaporation of 1 nm of Fe, followed by 3 nm of Al2O3 over G–Cu substrate [122].

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Student Zone: Overview, Training, Practices, and Exercises

Fig. 11.41 Scheme for the growth of GCNT hybrid materials. (Reproduced with permission of the American Chemical Society)

Ar

Dispersing syringe Fumace Exhaust

MWCNTs

SiO2 Si

Aerosol

Substrate

Fig. 11.42 Diagram of a spray pyrolysis setup for the growth of CNT arrays on oxidized Si wafer. (Reproduced with permission of the Elsevier Science)

Further Reading Nanotube carpets grown on Si-wafers (Fig. 11.42) [123]. Wafer scale integration of carbon-nanotubebased nanocarpets [124].

11.1.2.46

Synthesis of Carbon Nanospindles by Laser Ablation

Carbon nanospindles were synthesized by laser ablation of carbon black suspension [125]. Furnace carbon black particles with an average 200 nm diameter were used as the precursor. They were mixed with water, and then the carbon black suspension in the water was irradiated by a Nd:YAG pulsed laser with power density of 6106 W/cm2. The laser beams were focused on the suspension surface with a spot diameter of 0.3 mm. The wavelength length, frequency, pulse width, and irradiation time were 1064 nm, 5 Hz, 8 ms, and 2 h, respectively. Simultaneously, ultrasonics were employed to expedite the movement of carbon black particles during laser irradiation. The unreacted carbon blacks were removed by boiling in perchloric acid, and then the sample was obtained (reproduced with permission of the Royal Society of Chemistry).

11.1.2.47

Synthesis of 3D Branched Carbon Nanowebs

Three-dimensional open macroporous carbon nanowebs (3-DOM-CNWs) were prepared [126] using bacterial cellulose (BC) hydrogels, synthesized using Acetobacter xylinum BRC5 in the Hestrin and Schramm (HS) medium. The BC hydrogels were immersed in tert-butanol to exchange the solvents. After freezing at 30
C for 6 h, the BCs were freeze-dried at 45
C and 4.5 Pa for 72 h. The as-prepared BC cryogels were heated to 800
C for 2 h under a N2 atmosphere. A heating rate of 2
C/ min and a N2 flow rate of 200 mL/min were applied during the pyrolysis process. The resulting 3-DOM-CNWs were stored in a vacuum oven at 30
C. Further Reading Electrospinning of carbon nanowebs on metallic textiles (Fig. 11.43) [127]. Carbon nanoweb from cellulose nanowhisker [128]. O- and N-doped carbon nanowebs [129].

11.1

Synthesis and Characterization Methods

705

Fig. 11.43 Schematic illustration of the fabrication procedures of supercapacitor fabrics. The inset shows the details of the one-step electrospinning setup. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 11.44 Schematic of the fabrication process for CNT sponges. (Reproduced with permission of Wiley)

11.1.2.48

Synthesis of 3D Carbon Nanotube Sponges

Fabrication of SACNT (Superaligned CNT) Sponges by a Self-Assembly Method (Fig. 11.44). Typically, 50 mg SACNTs were added into 50 mL deionized water in a 100 mL beaker and dispersed for 45 min using an intensive ultrasonication probe (power, 350–450 W). The mixture was then poured into a desired mold and underwent freeze-drying for about 24 h. The product was a freestanding 3D sponge with density of 1 mg/cm3 and volume of about 50 cm3. By changing the concentrations of the suspensions, pure SACNT sponges with densities of 1–50 mg/cm3 can be achieved. The porosities of the SACNT sponges were calculated based on their apparent densities and the density of SACNT at 2 g/cm3.

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Fabrication of CNT Sponges with SDS CNTs were dispersed in water with SDS as surfactant using an intensive ultrasonication probe (power: 300 W) for 30 min. In this suspension, the weight fraction of CNT was controlled at 10 mg/ mL, and the weight ratio of CNT:SDS was 1:5. The suspension was standing for 24 h and then underwent freeze-drying for 24 h. CNT–SDS sponges with density of 10 mg/cm3 were obtained [130] (reproduced with permission of Wiley). Synthesis of CNT sponges by CVD process using ferrocene and 1,2-dichlorobenzene as the catalyst precursor and carbon source, respectively, is described in [131]. Ferrocene powders were dissolved in dichlorobenzene to make a solution at a concentration of 0.06 g/mL, which was then continuously injected into a 2 inch quartz tube housed in a resistive furnace by a syringe pump at a feeding rate of 0.13 mL/min. The reaction temperature was set as 860
C. Carrier gas, a mixture of Ar and H2, was flowing at a rate of 2000 mL/min and 300 mL/min, respectively. A 2 inch1 quartz sheet was placed in the reaction zone as the growth substrate. The sponge-like products were collected from the quartz substrate after CVD, which typically reach a thickness of 0.8–1 cm for a growth period of 4 h. Further Reading Carbon nanotube sponges for oil absorption [132, 133]. Carbon-nanotube sponges for cell inactivation [134].

11.1.2.49

Synthesis of Carbon Nanofoam

Low-density carbon nanofoam, different from the commonly observed micropearl morphology, was obtained by hydrothermal carbonization (HTC) of a sucrose solution [135]. A 2 M sucrose solution and 9 mg of naphthalene were filled into a 130 mL stainless steel autoclave with a headspace of 7 mm and heated at 130
C. After 72 h, the formed foam was removed from the autoclave, filtered with hot water, and dried at room temperature. The resulting mass density of the foam is 0.21 g/ cm3, calculated using a high-precision balance and a pre-defined volume container (reproduced with permission of the MDPI). Further Reading Fundamental properties of high-quality carbon nanofoam [136].

11.1.2.50

Synthesis of Carbon Nanosprings/Nanocoils/Nanospirals

Carbon nanocoils (CNCs) were synthesized by thermal chemical vapor deposition (CVD) using Fe–Sn–O catalyst prepared by a sol–gel process. Three kinds of catalyst precursors, Fe2(SO4)3/SnCl2, FeCl3/SnCl2, and Fe(NO3)3/SnCl2, were selected. The molar ratios of iron to tin in three combinations were maintained at 3:1. A sol–gel process was used to prepare the catalysts, where 0.01 mol Fe2(SO4)3 (0.02 mol for FeCl3 and Fe(NO3)3), 0.0067 mol SnCl2, and 0.03 mol C6H8O7H2O were mixed with 100 mL ethanol, and then the mixture was heated and stirred at 80
C for 3 h to transform the solution into a sol and then into a gel. The gel was heated in air at 700
C for 3 h for the generation of catalyst particles containing the oxides of iron and tin (Fe–Sn–O). The catalysts were labeled as P1, P2, and P3 corresponding to the particles prepared using precursor combinations of Fe2(SO4)3/SnCl2, FeCl3/SnCl2, and Fe(NO3)3/SnCl2, respectively. Catalyst particles of P1, P2, or P3 with a weight of 0.010 g were dispersed on SiO2 substrates (size, 1010 mm). CNCs were synthesized on these substrates in a thermal CVD system at 700
C for 2–30 min by introducing acetylene diluted by argon gas with a total flow rate of 260 sccm. Approximately 0.251 g deposits were collected after CVD. In order to study the effect of CVD conditions on the synthesis of CNCs, the growth temperature was changed from 650 to 800
C, and the flow rate of acetylene was changed from 15 to 60 sccm. The deposits were observed and analyzed by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a Raman spectrometer [137] (reproduced with permission of the Elsevier Science). Further Reading Stretchable carbon nanosprings [138]. Highly dispersible buckled nanospring carbon nanotubes [139]. Growth of carbon nanocoils using Fe catalyst films [140]. Toroidal and coiled carbon nanotubes [141]. Synthesis of carbon nanocoils on substrates made of plant fibers [142]. Coil-in-coil carbon nanocoils: 11 gram-scale synthesis [143]. Meter-long spiral carbon nanotube fibers [144]. CVD synthesis of Y-junction carbon nanocoils (Fig. 11.45) [145]. Self-organized micro-spiral of SWCNTs [146]. Review: the synthesis, properties and uses of carbon materials with helical morphology [147].

11.1.2.51

Fabrication of Carbon Nanothermometers

The nanothermometer is based on biocompatible fluorescent carbon nanodots (CDs). Unpassivated CD (UCD) was prepared from alanine via a one-step NaOH-assisted microwave treatment. In a typical procedure, 2 g alanine (2 g, 22 mmol) was

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707

Fig. 11.45 Schematic description of operational processes for Y-CNC synthesis. (Reproduced with permission of Nature)

dissolved in NaOH solution (8 mL, 0.5 M), and then the solution was heated in a domestic microwave oven (700 W) for 2.5 min. After cooling, the as-obtained brownish-black solid powder was dissolved with 10 mL ultrapure water. The supernatant was collected by centrifugation at 12000 rpm for 20 min and then dialyzed against ultrapure water through a dialysis membrane (molecular weight cutoff ¼ 8000–14,000, Shanghai Baoman Biological technology Co. Ltd) for 48 h to remove the excess precursors and small molecules. The resultant CDs were maintained at 4
C for further characterization and use. Passivated CDs (PCDs) were prepared through introducing 0.1 mmol polymer passivating agents into the initial alanine NaOH solution. In the preparing process of the MSCD, 0.05 mmol PEG–NH2 and 0.05 mmol PNIPAM–NH2 were added. 0.1 mmol PEG–NH2 and 0.1 mmol PNIPAM–NH2 were separately added to prepare the CD with only PEG or PNIPAM passivated (PEG–CD or PNI–CD) [148] (reproduced with permission of the Royal Society of Chemistry). Further Reading Nanothermometer takes the temperature of living cells [149]. Carbon nanothermometer containing gallium [150].

11.1.2.52

Synthesis of Carbon Nanotube Tweezers

See detailed experimental details in [151–153]. Further Reading Rippled carbon nanotube nanotweezers [154].

11.1.2.53

Synthesis of Carbon-Containing Nanocars/Nanotrucks3

The synthesis of a new nanovehicle, a porphyrin-based nanotruck 1,4 consisted of three steps: preparation of a wheel/axle component 7, chassis section 10, and final assembly of the nanotruck 1 (Fig. 11.46; see details in [155]). Further Reading Fullerene based nanocars [156–159]. See also a variety of original references, cited in a review dedicated to the synthesis of single-molecule nanocars (Fig. 11.47) [160].

3 4

These nanocars do not contain carbon only but also N, H, and B, among other elements. Original numeration in Fig. 11.46.

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Fig. 11.46 Synthesis of a porphyrin-based nanotruck 1. (Reproduced with permission of Elsevier Science)

11.1.2.54

Synthesis of Carbon Nanomesh

Carbon nanomesh constructed by small carbon nanocages (designated as CMCNCs) was prepared through the direct carbonization of the intermediate products obtained from Ni(NO3)2 and sucrose (Fig. 11.48) [161]. Ni(NO3)2 serves as the oxidizing agent and catalyst for graphitization. In a typical process, 7 g of nickel nitrate hexahydrate (Ni(NO3)26H2O) and 10 g of sucrose are dissolved in 15 mL of deionized water to form a homogeneous solution. Then, the solution was transferred into a specially designed quartz bowl and put into the preheat oven at 200
C. After 20 min, the earthy yellow product with a large volume expansion was obtained. Subsequently, this earthy yellow-colored intermediate product was crushed in an agate mortar and pyrolysis in a horizontal tubular furnace equipped with a corundum tube at 600
C for 2 h with a ramping rate of 2
C/min under an argon flow. After cooling down to room temperature naturally, the black products were treated with concentrated HCl (12 M) to remove the nickel residues and washed with abundant deionized water until pH value of the filtrate became neutral. Finally, the products were dried in an oven at 80
C for 12 h. For simplicity, the as-obtained samples

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Synthesis and Characterization Methods

709

Fig. 11.47 Overview of single-molecule nanocars. (Reproduced with permission of the American Chemical Society)

were described as CMCNC-X in subsequent discussions, where X is the mass of Ni(NO3)2 (g) used (X ¼ 3, 5, 7, and 9 is corresponding to the mass of Ni(NO3)2 which is 3, 5, 7, and 9 g, respectively). The morphologies and microstructures of the products were characterized by scanning electron microscope (SEM, Zeiss Supra 55) and transmission electron microscope (TEM, JEOL JEM-2100F). Powder X-ray diffraction (XRD) measurements were carried out on a Shimadzu X-ray 6000 diffractometer with Cu Kα radiation (wavelength ¼ 1.54 Å) between 5
and 80
at a step width of 0.02
. Room-temperature Raman spectra measurements were performed on an InVia Raman microscope with a laser wavelength of 532 nm. The surface elemental compositions and chemical states were analyzed by the X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, USA) with an Al Kα X-ray source. The binding energy was corrected by referring to the C 1 s peak at 284.8 eV. The specific surface area, pore volume, and pore size distribution of the samples were determined by N2 adsorption–desorption at 77 K (ASAP 2020, Micromeritics, USA) after being degassed at 150
C overnight. The specific surface area of the samples was obtained from Brunauer–Emmett–Teller (BET) theory, and the

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Fig. 11.48 Schematic illustration of the fabrication and ions–electrons transportation through CMCNCs. (Reproduced with permission of the Elsevier Science)

Fig. 11.49 Schematic illustration of the fabrication process for mesopore carbon nanomesh (MCNM) through explosion-assisted activation route. (Reproduced with permission of the Elsevier Science)

pore size distribution was estimated by adsorption branch from the Barrett–Joyner–Halenda (BJH) method (reproduced with permission of the Elsevier Science). Further Reading Carbon nanomesh prepared through explosion-assisted5 activation approach (Fig. 11.49) [162]; chemical vapor deposition (CVD) method to prepare carbon nanomesh (CNM) with MgAl-layered double oxides (LDO) as sacrificial template and ferrocene as carbon precursor (Fig. 11.50) [163].

5

Explosion-assisted activation process employs carboxymethylcellulose sodium (CMCS) as the carbon precursor, while potassium nitrate (KNO3) acts as both an explosive and activating reagent.

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Fig. 11.50 Schematic illustration of the fabrication steps for CNM. (Reproduced with permission of the Wiley)

11.1.2.55

Synthesis of Carbon Nanotetrahedra/Nanoribbons

Chains of carbon nanotetrahedra/nanoribbons are formed via sequential switching of the flattening direction of multiwall carbon nanotubes, in which neighboring two nanotetrahedra are connected by a short nanoribbon, namely, a flattened nanotube. In an experiment, a 20-nm-thick Fe layer was deposited on a SiO2 substrate. Then, this sample was sealed in an evacuated silica tube (inner diameter 6 mm, length 11.5 cm) with 0.5 mg of hexadecanoic acid [C15H31C(¼O)OH] as a carbon source. The sample was heated at 1000
C for 30 min and then cooled to room temperature after growth. The grown carbon nanostructures were mounted on a carbon microgrid for transmission electron microscopy (TEM) and scanning electron microscopy (SEM). A JEOL JEM-2010 TEM system (operated at 160 kV), an FEI Tecnai G2-20 TEM system (operated at 200 kV), and a JSM-7300F SEM system (operated at 5 kV) were used for the observations [164, 165] (reproduced with permission of AIP Publishing). Further Reading Splitting and joining in carbon nanotube/nanoribbon/nanotetrahedron growth [166]; formation of carbon nanotetrahedra using electron beam tomography [167].

11.1.2.56

Synthesis of Carbon Nanocubes

Mesoporous carbon nanocubes (MCCs) were synthesized [168] through a hard template method. MnCO3 cubes were synthesized in the first step. In a typical synthesis process, 3.5 mmol MnSO4H2O, 100 mmol (NH4)2SO4, and 35 mL ethanol were dissolved in 350 mL deionized water under strong stirring at 50
C. Then, 350 mL (NH4)2CO3 solution (0.15 M) was added into the above solution under vigorous stirring for 9 h. The precipitation was collected by filtration, washed with deionized water several times, and dried at 80
C under vacuum for 12 h. MnO cubes were obtained after annealing the precursor at 600
C for 5 h in air. Carbon-coated mesoporous MnO cubes were synthesized via a chemical vapor deposition (CVD) method: MnO nanocubes were placed in a quartz tube furnace and preheated to 650
C in Ar atmosphere. Then, acetylene (10 vol.% in Ar) was introduced with a flow rate of 100 sccm for 1 h. After cooling down to room temperature, the obtained composite was washed with 1 M HCl for 24 h to remove MnO templates. MCCs were obtained after being washed by distilled water and dried at 80
C in a vacuum oven overnight. Ruthenium functionalized MCCs were prepared by an impregnation method. MCCs (35 mg) were dispersed in RuCl3 (Ru, 15.0 mg)/ethanol (10 mL) solution with constant gentle stirring at r.t. for 24 h in a sealed bottle. Then the bottle was opened, and the mixture was dried under room temperature with continuous stirring. The dried sample was then heat-treated at 300
C for 3 h under 5% H2/Ar atmosphere to obtain the final product (reproduced with permission of Wiley).

11.1.2.57

Synthesis of Glassy Carbon Nanowires

Furfuryl alcohol was polymerized inside the pores of an anodized alumina template to form the nanowires, which were subsequently pyrolized at temperature ranging from 600 to 2000
C (Fig. 11.51). In a typical process, 1 M p-toluenesulfonic acid solution is added to 5 mL of Triton X-100. 5 mL furfuryl alcohol (FA) is added to the resultant solution using a syringe pump at a rate of 10 mL/min. The solution is allowed to polymerize (PFA) in an ice bath for 24 h and then filled inside Anodisc anodic alumina membrane (Whatman) with 200 nm pores by capillary effect. The PFA-lled template is then pyrolyzed for 8 h and then dissolved in 6 M KOH aqueous solution to produced dispersed nanowires. High-temperature treatment (HTT) was carried out in a Red Devil furnace (R.D. Webb Company, Natick, MA). The hot zone was evacuated to 103 mbar for 24 h prior to annealing and then backfilled to atmospheric pressure with argon. A 25
C/min heating rate was employed with a 1 h soak at temperatures between 1200 and 2000
C. The nanowires are then inspected with a JEOL 2010 LaB6 transmission electron microscope to obtain information about the crystallite structure within the samples. The average diameter was found to be 150 nm (10 nm), which is due to the volume shrinkage during pyrolysis (reproduced with permission of Hindawi [169]).

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Fig. 11.51 Anodized alumina template-based synthesis of poly-furfuryl alcohol nanowires. The glassy carbon nanowires are obtained by pyrolyzing the polymeric precursor nanowires and then heat treating them at desired temperatures. (Reproduced with permission of Hindawi)

11.1.2.58

Synthesis of Carbon Hydrogels, Cryogels, Xerogels, and Aerogels

Sponge-Like Carbonaceous Gels and Magnetite Carbon Aerogels (MCAs) [170]. The carbonaceous hydrogel was prepared by a simple one-pot hydrothermal reaction. Watermelon was first cut into the appropriate volume and then put into a Teflonlined stainless steel autoclave. After that, the autoclave was put into an oven and heated at 180
C for 12 h. Black carbonaceous hydrogel monolith was obtained after the hydrothermal reactions. The product was immersed in water and ethanol for several days to remove the soluble impurities. The corresponding carbonaceous aerogel was obtained by cutting the carbonaceous hydrogel monolith into small pieces followed by freeze-drying. To prepare the MCAs, a piece of carbonaceous aerogel with a dimension of about 2  3  3 cm3 was fully immersed in a 20 mL aqueous solution containing 1.30 g of FeCl3 (8 mmol) and FeSO47H2O (1.25 g, 4.5 mmol) for 15 min under N2 protection. The mixture was heated to 80
C, and a large amount of N2 was introduced into liquid to stir the liquid. After that, 10 mL of 30% ammonia solution was added to the mixture and kept at 80
C for 30 min. At last, 3.0 g of trisodium citrate was added to the solution, while the temperature increased to 95
C. The obtained Fe3O4/carbonaceous hydrogel composites were rinsed by Milli-Q water and dried in an oven at 70
C. To obtain the MCAs, the above Fe3O4/carbonaceous hydrogel composites were calcined in N2 atmosphere at 550
C for 4 h (reproduced with permission of the American Chemical Society). Hydrothermal Synthesis of Fluorescent Nanocrystallinecellulose/Carbon Dot Hydrogels (NCC/CDs, Fig. 11.52) [171]. NCC kraft softwood pulp was first milled and then passed through a 0.5 mm screen to ensure uniform particle size. An aqueous NCC suspension was prepared mainly by following the sulfuric acid hydrolysis method. The milled pulp was hydrolyzed in sulfuric acid (64 wt.%; 8.75 mL of sulfuric acid solution per gram of pulp) at 45
C for 30 min with vigorous stirring. The cellulose suspension was then diluted, centrifuged, washed, and dialyzed against distilled water until the exterior water reached neutrality before further use. Then, the NCC suspension (1.5 wt.%, 30 mL) was added to a stainless steel autoclave with a volume of 50 mL. The autoclave was heated in a furnace at 180, 200, 220, 240, or 260
C for 4 h and then allowed to cool to room temperature. The resulting brown hydrogel was collected and centrifuged at 10,000 rpm for 2  10 min to remove black solids. The obtained brown hydrogel was then subjected to dialysis (1000 molecular weight cutoff) for about 48 h to obtain the NCC/CD hydrogel (reproduced with permission of the Elsevier Science). Carbon Xerogel Particles [172]. Carbon structures were obtained by inverse emulsification of resorcinol–formaldehyde (RF) sol in cyclohexane containing a nonionic surfactant Span 80, followed by its pyrolysis at 1173 K in nitrogen. RF hydrogels were synthesized by the polycondensation of resorcinol (99% purity) with formaldehyde (37% w/v; stabilized by 11–14 wt.% methanol) in water (W), in the presence of a basic catalyst. Potassium carbonate (99.0% purity) was used as the basic catalyst. Resorcinol was added to formaldehyde, and the mixture was stirred for 15 min to get a clear solution. Potassium

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713

Fig. 11.52 Schematic model of the hydrothermal synthesis of NCC/CD fluorescent hydrogels. (Reproduced with permission of the Elsevier Science)

carbonate was dissolved in ultrapure Milli-Q water to form a separate solution. The two solutions were then mixed and stirred continuously for 30 min until the colorless RF sol changed to golden yellow. The resorcinol to formaldehyde molar ratio was 0.50, and resorcinol to water molar ratio was 0.037. It is important to note here that reported resorcinol to water molar ratio does not take into account the water present in the formaldehyde solution. Various resorcinol/catalyst (R/C) molar ratios of 0.2, 1.0, 10, 25, 50, 100, and 500 were chosen to study the effect of catalyst on the size and shape of particles. Spherical RF hydrogel particles were obtained by inverse emulsion polymerization route. A viscous RF sol (1 mL) was added slowly to 50 mL of cyclohexane (high-performance liquid chromatography grade) and agitated in the presence of a surfactant, nonionic sorbitan monooleate, Span 80. The same surfactant with a hydrophile–lipophile balance (HLB) of nearly 4.3 was obtained from three different sources (Sigma-Aldrich, USA; SD Fine Chemicals, India; and Loba Chemie, India) to establish the robustness of the results. The RF solution was dispersed as spherical droplets throughout the cyclohexane. The emulsion droplets assumed different shapes and sizes depending on the stirring time and the amount of surfactant. Surfactant concentration (v/v; vol. of surfactant/vol. of total solution) was varied from 1% to 50%. The suspension was stirred at room temperature. Stirring time of the suspension was varied from 1 to 24 h to investigate its effect on the particle size distribution of final product. Particle size could be measured by rapidly (5–30 min) desiccating the RF hydrogel particle suspension on quartz substrates to partially evaporate the solvent and arrest the movement of particles. Subsequently, samples were dried in subcritical conditions by heating in oven at 333 K for 12 h to obtain the RF xerogel particles. After drying, the quartz substrates with the RF xerogel particles were placed in a quartz boat and heated to 1173 K under inert nitrogen (N2) atmosphere in a tubular, high-temperature furnace for carbonization of the polymer. The rate of heating

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Fig. 11.53 Schematic showing the various steps of synthesis of RF xerogel nanoparticles using repetitive inverse emulsion polymerization [173]. (Reproduced with permission of the Royal Society of Chemistry)

was programmed at 7.5 K/min, while the N2 gas flow was kept constant at 0.3 L/min. Once the maximum temperature was reached, it was kept constant for 60 min. The furnace was then cooled to room temperature in about 10 h to obtain RF-derived carbon xerogel particles. The inert atmosphere was maintained by purging N2 gas until the furnace attained the room temperature (reproduced with permission of the Elsevier Science). A related procedure is shown in Fig. 11.53. Further Reading Sol-gel-derived carbon aerogels and xerogels [174]; synthesis of carbon aerogels with different catalysts [175]; carbon xerogels [176]; review on carbon aerogels [177].

11.1.2.59

Preparation of Atomic and Diatomic Carbon

Diatomic carbon was produced simultaneously with C1, C3, and C4, in the carbon vapor generated from a positive-hearth electron-gun furnace. A stainless steel bell jar was used as the reaction vessel. Two tungsten filaments were heated by a current of about 38 A. The potential difference between the filaments and the positive hearth was slowly increased to induce electrons to bombard a small piece of carbon rod placed on the hearth. This electron bombardment resulted in the heating of carbon, eventually forming carbon vapor. Carbon vapor was then cocondensed with a large excess of reactants on the liquid nitrogen cooled walls of the reaction vessel at a very low pressure (2105 Torr). Products were recovered by pumping into a secondary vacuum line and were identified by the interpretation of the spectral data. Gas chromatographic analyses were performed on one of the following instruments: a Hewlett-Packard 5790A FID equipped with a 95% dimethylpolysiloxane to 5% diphenyl polysiloxane (DB-5) quartz capillary column (30 m  0.25 mm) and a HP3390A integrator or a Gow-Mac 10–677 thermistor detector equipped with a 13 ft 20% SE-30 packed column and a Northrop Speed-0-Max G chart recorder. Yields were determined by gas chromatography [178] (reproduced with permission of the American Chemical Society). Further Reading Atomic and diatomic carbon spectra [179].

11.1.2.60

Carbyne and Carbon Atom Wires

Synthesis of Metalated Carbyne On-surface synthesis (Fig. 11.54) of metalated carbyne chains is carried out by dehydrogenative coupling of ethyne molecules and copper atoms on a Cu(110) surface under ultrahigh vacuum conditions [180]. All the STM experiments were carried out in situ in a UHV chamber (base pressure 1  1010 mbar) equipped with a variable-temperature “Aarhus-type” STM, a molecular evaporator, and standard facilities for sample preparation. All of the samples are prepared in UHV chambers with base pressure ~1  1010 mbar. After the Cu(110) substrate was carefully

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715

Fig. 11.54 Illustration of the bottom-up synthesis of metalated carbyne on Cu (110) through dehydrogenative coupling of ethyne precursors and copper adatoms on Cu(110) under UHV conditions. Gray carbon; white hydrogen; brown copper substrate atom; red copper adatom. (Reproduced with permission of the American Chemical Society)

cleaned with repeated Ar+ sputtering and annealing processes under UHV conditions, the ethyne molecules were dosed into the preparation chamber from a leak valve with a partial pressure of 1  108 mbar for 5–20 min (depending on the desired surface coverage) while, most importantly, keeping the substrate temperature at ~450 K. The STM measurements were carried out in a typical temperature range of 100 ~ 150 K in constant current mode. Typical scanning conditions are It ¼ 0.5 ~ 1.0 nA and Vt ¼ 1.0 ~ 2.0 V (reproduced with permission of the American Chemical Society). Carbon–Atom Wires Produced by Nanosecond Pulsed Laser Deposition (PLD) PLD of carbon films was performed [181] at room temperature by focusing a frequency-doubled lamp-pumped Q-switched Nd:YAG pulsed laser (λ ¼ 532 nm, pulse duration 7–9 ns, 10 Hz repetition rate) on a graphite target (purity 99.999%) in a vacuum chamber. The laser energy (250 mJ) and the spot size on the target were adjusted to have an energy density on the target (i.e., fluence) of about 2.7 J/cm2. Ablation was performed in the presence of argon with a background pressure (PAr) varying in the 10–500 Pa range and a target-tosubstrate distance (dts) in the 25–110 mm range. Deposition time was adjusted according to the pressure and dts, which strongly affect the deposition rate (typical values are between 1 and 30 min). The vacuum chamber is equipped with a scroll pump and a turbomolecular pump with a base pressure of about 103 Pa. Background gas pressure is tuned by means of flow mass controllers and capacitance pressure gauges. Time-integrated pictures of the plume shape were taken by a camera through a viewport. Surface-enhanced Raman scattering (SERS) spectra were acquired with a Renishaw InVia micro-Raman spectrometer using the 514.5 nm wavelength of an Ar+ laser and a Peltier-cooled CCD camera, with a spectral resolution of about 3 cm1. SERS was accomplished by directly depositing carbon on SERS-active substrates consisting of Ag nanoparticles grown on Si substrates by thermal evaporation. The equivalent Ag thickness, as monitored by a quartz microbalance, was adjusted at about 3 nm in order to have a good matching between the resonance plasmon peak and the excitation laser line used for Raman (i.e., 514.5 nm), as measured by UV–Vis absorption spectroscopy (not shown). As-prepared SERS-active substrates were accurately cleaned to avoid SERS signals coming from contaminations. In particular a cleaning procedure has been adopted, just before PLD, consisting in cleaning in isopropanol and ultrasonic bath for a few minutes followed by drying under gentle flux of pure nitrogen. Such procedure ensures that no features in the 1800–2200 cm1 spectral range (i.e., region of sp carbon) are present in the spectra of pristine SERS-active substrates due to ambient contaminations. A weak contribution, consisting of sharp peaks in the region of amorphous sp2 carbon (1200–1600 cm1), is always present possibly due to carbon-based molecular species present in ambient air. The cleaning procedure does not remove or modify Ag nanoparticles deposited on the substrate, as checked by SEM and SERS activity. Laser power on the PLD samples was carefully selected (1 mW) to prevent laser-induced damage and graphitization. Scanning electron microscopy (SEM) images were acquired with a Zeiss Supra 40 field emission SEM (reproduced with permission of the Elsevier Science). Further Reading Carbyne fiber synthesis within evaporating metallic liquid carbon [182]; metal-carbyne clusters [183]; carbon displacement-induced single carbon atomic chain formation [184]; carbon-atom wires (synthesis methods Fig. 11.55) [185].

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Fig. 11.55 Sketches representing several known physical methods adapted to synthesize linear sp carbon wires. (Reproduced with permission of the Royal Society of Chemistry)

11.1.2.61

Synthesis of Carbyne-Rich Carbon Thin Film

Further Reading Carbyne-rich nanostructured carbon thin film [186].

11.1.2.62

Synthesis of Chaoite-Like Macrotubes

A high-purified vitreous silica tube with inner diameter of 8 mm as the reaction chamber was placed into a tube-type furnace [187]. The high-purified acetylene gas (Fig. 11.56) was floated from one side of the tube. The chamber was heated at 873 K for 1 h under the acetylene flux of 30 cc/min. The chamber was then removed from the furnace and quenched by cool water (18
C) immediately or by flowing ambient air. Tightly scrolled and loosely scrolled CMTs (referred to TS- and LS-CMTs, respectively) were found in cases of quenching by cool water and air, respectively. CMTs with the maximum length equal to the inner diameter of the tube (i.e., 8 mm in this study) were obtained. The sample structures were characterized by optical microscope (OM), scanning electron microscope (SEM), micro-area X-ray diffractometer (MA-XRD), high-resolution transmission electron microscope (HRTEM), and a Raman spectroscope. The impurities of CMTs were detected by an induction-coupled plasma (ICP) mass spectrometry (reproduced with permission of the Elsevier Science).

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Fig. 11.56 The formation process of CMTs. (Reproduced with permission of the Elsevier Science)

Fig. 11.57 Preparation of GQDs from citric acid. (Reproduced with permission of Springer)

11.1.2.63

Synthesis of Carbon Nanodots and Graphene Quantum Dots

Carbon Nanodots from Waste Paper The synthesizing process of C-dots was done by mixing 5 g of waste paper in 40 mL of aquades, 30 mL H2SO4, and 50 mL NaOH 2 M. Preparation of the precursor was done by adding urea as surface passivation agent into 20 mL mixing solution. Synthesis of C-dots is done by heating the precursor hydrothermally using a furnace with three conditions, namely, with 1–4 g of urea, 20–50 min of synthesis time, and 150–300
C of temperature. In a variation of urea and time, the temperature is controlled at 300
C. In a variation of the time and temperature, urea is controlled at 3 g. In a variation of the urea and temperature, time is controlled for 30 min. Synthesis of C-dots was done by varying the amount of urea, temperature, and synthesis time to determine its effect on the optical properties and structure of the C-dots. Initial testing of the optical properties of the C-dots is carried out using a UV lamp 15 W to determine its luminescence. C-dot absorption was tested using VIS–NIR spectrophotometer (Ocean Optics USB type 4000) to determine the effect, the amount of urea, temperature, and synthesis time on absorbance spectra and energy gap [188] (reproduced with permission of AIP Publishing). Pyrolysis of Citric Acid to Prepare Graphene Quantum Dots (GQDs) Five grams of citric acid was heated and melted, which is then converted into dark orange color within 25–30 min. 1.5 M solution of NaOH was added dropwise in the melted dense solution of citric acid at room temperature, to prepare the solutions of different pH ranging from 8 to 12. The effect of different pH on the yield and size of the graphene quantum dots (GQDs) was studied in detail [189]. The mechanism of formation of GQDs from the citric acid is shown in Fig. 11.57.

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Fig. 11.58 (a) Illustration of the oxidation and cage-opening of fullerene C60 with treatment of strong acid and chemical oxidant. (b) Luminescence of graphene QDs excited with a blue laser pointer (405 nm). (Reproduced with permission of the American Chemical Society)

Fluorescent Graphene Quantum Dots by Cage-Opening Buckminsterfullerene (Fig. 11.58). The fullerene C60 was oxidized using Hummers method. Fullerene C60 (2.5 g) and sodium nitrate (1.3 g) were stirred with sulfuric acid (98%, 57 mL). The mixture was then cooled to 0
C. Potassium permanganate (7.5 g) was then added over a period of 2 h. During the next 4 h, the reaction mixture was allowed to reach room temperature before being heated to 35
C for 30 min. The reaction mixture was then poured into a flask containing deionized water (125 mL) and heated to 70
C for 15 min. The mixture was then poured into deionized water (0.3 L). The unreacted potassium permanganate and manganese dioxide were removed by the addition of 3% hydrogen peroxide. The reaction mixture was then neutralized using 1 M NaOH at pH 8. The obtained graphene QD solution was purified by dialysis [190] (reproduced with permission of the American Chemical Society). Further Reading Various methods (chemical and physical) for the synthesis of carbon nanodots [191]; photoluminescent carbon nanodots [192]; synthesis of graphene quantum dots using a continuous hydrothermal flow synthesis approach [193]; graphene quantum dots from corn power [194]; review on graphene quantum dots [195].

11.1.2.64

Synthesis of the Carbide-Derived Carbon

Synthesis of Nanoporous Carbide-Derived Carbon by Chlorination of Titanium Silicon Carbide The Ti3SiC2 powder was placed onto a quartz simple holder and loaded into the hot zone of a horizontal quartz tube furnace. The tube was Ar purged for 30 min before heating at a rate of ~30
C/min up to the desired temperature. Once the desired temperature was reached and stabilized, the Ar flow was stopped, and a 3 h chlorination began in Cl2 flowing at a rate of 10 sccm. After the completion of the chlorination process, the samples were cooled down under a flow of Ar to remove residual metal chlorides from the pores and taken out for further analyses. In order to avoid a back stream of air, the exhaust tube was connected to a bubbler filled with sulfuric acid [196] (reproduced with permission of the Elsevier Science). Further Reading Room-temperature carbide-derived carbon synthesis [197]; mesoporous and graphitic carbide-derived carbons [198]; titanium carbide derived carbon [199]; carbide-derived carbon membrane [200]; carbide-derived carbon beads (Fig. 11.59) [201]; fluorinated carbide-derived carbon [202].

11.1

Synthesis and Characterization Methods

719

Fig. 11.59 Schematic overview of the synthesis method: (1) the production of the polymer beads with the MicroJet reactor, (2) the pyrolysis, and (3) the chlorine treatment. VTMS vinyltrimethoxysilane; PTMS phenyltrimethoxysilane; MeOH methyl alcohol; RT room temperature; (A and B) solution A or solution B; HPLC high-performance liquid chromatography. (Reproduced with permission of the Royal Society of Chemistry)

Fig. 11.60 Schematic illustration of the synthesis of Co-CoO@N-doped porous carbon nanocomposites via the pyrolysis of ZIF-67. (Reproduced with permission of the Royal Society of Chemistry)

11.1.2.65

Synthesis of the MOF-Derived Carbon

Porous Carbon Incorporating Co and CoO Nanoparticles (Fig. 11.60) [203]. Synthesis of ZIF-67: In a typical synthesis, 0.45 g cobalt nitrate hexahydrate was dissolved in 3 mL of deionized (DI) water, and then 5.50 g 2-methylimidazole (Hmim) was dissolved in 20 mL of DI water. The two solutions were mixed (Co2+: Hmim: H2O ¼ 1: 58: 1100) and stirred for 6 h at room temperature, and then the resulting purple precipitates were collected by centrifuging, washing with water and methanol subsequently for three times, and finally being dried in vacuum at 50
C overnight. The activated ZIF-67 powder was obtained by heating at 150
C for 24 h. Introducing dicyandiamide as additional nitrogen source into ZIF-67, in a typical procedure, the activated ZIF-67 sample (500 mg) was immersed into 20 mL aqueous solution containing dicyandiamide (DCDA, 750 mg). Then, the suspension was put into a glass container at room temperature under reduced pressure for accelerating the introduction of DCDA molecules into the nanopores in ZIF-67. Once the solvent evaporation is completed, the procedure was terminated, and the excess of DCDA was removed by thorough washing with water. Finally, the sample was dried at 80
C overnight. Preparation of Co-CoO@N-Doped Porous Carbon via Pyrolysis of ZIF-67 The activated ZIF-67 (500 mg) was placed into a porcelain boat, which was put in the middle of a quartz tube in a furnace, and its one end was charged with nitrogen gas. After air in the quartz tube was drained, the furnace was gradually heated from room temperature to the target temperature (500 ~ 800
C) with a heating rate of 5
C/min under a continuous nitrogen flow of ~50 mL/min. After the calcination under the target temperature for desired time, followed by natural cooling down to room temperature, the resultant catalysts

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Fig. 11.61 Schematic illustration for the synthesis of CoM (M ¼ Fe, Cu, Ni)-NC composites. (Reproduced with permission of the Elsevier Science)

were obtained and denoted as NC-T-t (NC is denoted as nanocomposite, T refers to carbonization temperature, and t represents carbonization time). The NC-700-3h-250-3h means that the NC-700-3h sample was further oxidized in air at 250
C for 3 h. For further experimental details, see here6 (reproduced with permission of the Royal Society of Chemistry). Preparation of CoM (M ¼ Fe, Cu, Ni)-embedded nitrogen-enriched porous carbon framework (Fig. 11.61) [204]. Typically, Co(NO3)26H2O (0.5 mmol) and 2-methylimidazole (2 mmol) were dissolved in H2O (15 mL), respectively. The above two solutions are then mixed under continuous stirring for 30 s, and the final solution is kept for 24 h at room temperature. The purple precipitate is collected by centrifugation, washed in ethanol several times, and dried at 80
C. The as-produced samples were put into a tube furnace and carbonization at 800
C for 2 h in N2 to obtain Co–NC composite. Similarly, CoxM1–x-NC composites with different Co/M molar ratio (4:0, 3:1, 1:1, 1:3) were prepared. All synthesis procedures are unaltered except for the percentages of metal nitrates. For example, for Co0.75Fe0.25-NC, a mixed solution of Co(NO3)26H2O (0.375 mmol) and Fe(NO3)36H2O (0.125 mmol) in 15 mL of H2O was rapidly poured into a solution of 2-methylimidazole (2 mmol) in 15 mL of H2O stirred vigorously for 30 s, and final solution was incubated at room temperature for 24 h. The resulting precipitates were collected by centrifugation and washed with ethanol several times and finally vacuum-dried at 80
C. The as-produced samples were put into a tube furnace and carbonization at 800
C for 2 h in N2 to obtain Co0.75Fe0.25-NC composite (reproduced with permission of the Elsevier Science). Further Reading MOF-derived magnetic porous carbon-based sorbent [205]; MOF-derived porous nanostructures (review) [206].

11.1.2.66

Ultrafine Carbon Black by Pyrolysis of Polymers

DC thermal plasma process system was composed of a pyrolysis reactor [207] (inner graphite vessel for polymer degradation), DC plasma torch, decomposing chamber (outer graphite chamber for carbon black synthesis), and cooling system (Fig. 11.62). The pyrolysis reactor is used for degradation of polymer (PS and PE) into the gas or liquid hydrocarbons (mainly monomer styrene and light hydrocarbons). Its inner diameter was 5 cm, wall thickness 1 cm, and depth 15 cm. The vessel is round-bottom-shaped cylinder, which is made of graphite. The outer side of that pyrolysis reactor was heated by DC plasma jet, and the inside temperature of the chamber was controlled by adjusting the distance between the plasma torch and graphite vessel. The produced gas and liquid hydrocarbons from PS (or HDPE) have passed through DC plasma torch jet and decomposed directly into the carbon particles. The nitrogen was employed as a carrier gas for thermally degraded hydrocarbons form PS or HDPE. Finally the carbon particles deposited on the surface of outer graphite chamber were collected as a fine powder. Water cooling system was used to protect the overheating of the DC plasma torch and the outer graphite chamber. The used plasma generator was a non-transferred arc DC thermal type with a maximum power level of 20 kW. Arc voltage (V) and current (A) were measured between the cathode and anode using a digital multimeter. The torch efficiency was about 90%. The plasma working gas was nitrogen, and its flow rate was controlled as 25 slpm. The rotameters were used to monitor the flow rates. The thermocouples were inserted into the pyrolysis chamber to measure the temperature of PS (or HDPE) bed and that of the catalyst bed. Two types of products, such as degraded liquid hydrocarbons and solid carbon black, could be synthesized by present DC thermal plasma process. All experiments were conducted under a nitrogen atmospheric pressure environment with the reactor preheated for 5–30 min depending on the requiring temperature. Once the steady condition is established, a feedstock (polymer pellet) was radically put into the pyrolysis reactor. PS or HDPE pellet (30 g) was degraded into the oils and gases at the bottom of the inner graphite reactor. In the case of catalytic degradation of PS, the catalyst pellets (30 wt.% BaO/Silica, 3.0 g) were packed

6

http://www.rsc.org/suppdata/c5/cc/c5cc01588j/c5cc01588j1.pdf. Accessed 21 May 2018.

11.1

Synthesis and Characterization Methods

721 Valve

5

B

6

Water out

9 Condenser 4

A

2 1

Mass flow meter

Outer Graphite chamber

3

Water in

7 N2

Cooling jacket

N2 8

10

Power supply

Water tank

Fig. 11.62 Diagram of the DC thermal plasma system: 1, polymer; 2, thermocouple; 3, pyrolysis reactor; 4, catalyst bed; 5, temperature controller; 6, carrier gas; 7, plasma jet; 8, DC plasma torch; 9, cooling gas; 10, plasma working gas. (Reproduced with permission of Springer)

in a stainless steel gauge and located at the upper position of the reaction chamber near outlet. Accordingly, the vapor of thermally degraded products could pass through the catalyst bed. In comparison with the catalytic degradation, PS was also pyrolyzed thermally in the absence of a catalyst. To better investigate the temperature effect on the pyrolysis of polymers, the pyrolysis chamber was preheated to maintain the wide-range temperature from 300 to 900
C. In the case of HDPE, the polymer sample was pyrolyzed only thermally in the graphite vessel. Thermally and catalytically degraded products were collected by passing through a water-cooled condenser to analyze the compositions. Yield and selectivity of the pyrolysis products (hydrocarbons) were analyzed by gas chromatography (Agilent Technologies 6890N gas chromatography equipped with a HP-5 capillary column and a flame ionization detector (FID)). Generally, for the production of carbon particles, non-cooled stream of hydrocarbons was directly introduced into the flame of DC thermal plasma jet (reproduced with permission of Springer). Further Reading A numerical model of the synthesis of carbon black by benzene pyrolysis [208].

11.1.2.67

Synthesis of Graphyne

Synthesis of γ-Graphyne by Mechanochemistry (Fig. 11.63). First, 3.0 g PhBr6, 2.0 g CaC2, 375 g stainless steel balls of five different diameters (15, 12, 10, 8, and 5 mm), and 60 mL absolute ethanol (AR) were mixed in a stainless steel pot (250 mL). The pot was sealed and operated at 450 rpm for 16 h (a cooling interval of 15 min was implemented after every 30 min to avoid overheating) by a planetary ball mill (Tencan QXQM-2, China). Then, the pristine mixture was washed with dilute nitric acid (1 mol/L), benzene, and deionized water in succession to remove the residual CaC2 and PhBr6. Finally, the purified mixture was dried at 60
C, and γ-graphyne (GY) powders were obtained. If all PhBr6 were converted into γ-graphyne, 0.783 g sample should be obtained. The average product mass of final powder was 0.624 g; therefore, the conversion rate of PhBr6 was about 79.7% [209] (reproduced with permission of the Elsevier Science). Further Reading Possible formation of graphyne on transition metal surfaces [210]; synthesis of annulenic subunits of graphyne [211].

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Fig. 11.63 Proposed reaction pathway for the preparation of γ-graphyne by mechanochemical route. (Reproduced with permission of the Elsevier Science)

11.1.2.68

Synthesis of Graphane and Graphone

Synthesis of Graphane (C1H1.14)n by Hydrogenation of Carbon Nanofibers [212] Graphite nanofibers (250 mg) and 8.1 g of potassium (or 1.5 g of lithium) were placed into a flask with magnetic stirrer in argon atmosphere. The flask connected to equipment for refluxing of ammonia (cold finger with CO2/acetone bath) was flushed with argon to remove air, and ammonia (170 mL) was condensed into the flask using CO2/acetone cooling bath. Mixture of liquid ammonia with alkali metal and graphite nanofibers was refluxed and stirred for 2 h. Subsequently the reaction mixture was cooled in acetone/CO2 bath, and 1.8 mL of distilled water was slowly added (during 10 min). The mixture was then removed from cooling bath and stirred under reflux for 2 h. Then, an additional amount of 1.8 mL of distilled water was slowly added (over a period of 10 min), and the mixture was stirred under reflux for the next 30 min. At the end, 20 mL of distilled water was added slowly (over a period of 30 min) to decompose unreacted alkali metals, and ammonia was evaporated at room temperature. Finally, solid products were dispersed in distilled water, separated by filtration, redispersed in water acidified with HCl, and separated by suction filtration. The product was washed with distilled water/ethanol and dried in vacuum oven at 50
C for 48 h. Caution: fast addition of water can lead to violent reaction with alkali metals and explosive reaction (reproduced with permission of the Royal Society of Chemistry). Further Reading Graphyne, graphdiyne, graphone, and graphane: review [213]; graphane synthesized under high hydrogen pressure [214]; one side-graphene hydrogenation (graphone) [215]; graphene supported graphone/graphane bilayer nanostructure material [216].

11.1.3 Metal Complex Chemistry of Nanocarbons 11.1.3.1

Synthesis of Metal Complex Hybrids of Carbon Nanotubes

Substituted Copper Phthalocyanine/MWCNT Hybrid Material CuPcOC8 and MWCNTs were procured from Sigma-Aldrich. MWCNTs were functionalized with acidic groups according to the multistep procedures described in literature. CuPcOC8– MWCNT hybrid in DMF was synthesized through the π–π interaction between MWCNTs and CuPcOC8. In brief, 30 mg of MWCNTs were added into 15 mL of DMF, and 15 mg/mL solution of CuPcOC8 in DMF was added in it and sonicated for 24 h and filtered/dried subsequently to obtain CuPcOC8–MWCNT hybrid material. The surface morphology of drop-casted CuPcOC8–MWCNT hybrid films on glass substrate was investigated by atomic force microscopy (XE-70 Park Systems) and a field emission surface electron microscopy instrument (SEM, Carl Zeiss Supra55). FTIR spectra were obtained by using a C92035 PerkinElmer spectrometer. Ultraviolet–visible spectroscopy (UV–Vis spectra) was recorded by UV-2450 spectrophotometer. The electrical measurements are performed by using a programmable digital Keithley electrometer (6517 A) and Hioki LCR (HiTester 3532-50) (reproduced with permission of the AIP Publishing) [217]. Further Reading Organometallic chemistry of carbon nanomaterials [218, 219]; terpyridine chelate complex-functionalized SWCNTs [220]; pyridylimine cobalt(II) and nickel(II) complex functionalized MWCNTs [221].

11.1

Synthesis and Characterization Methods

11.1.3.2

723

Synthesis of Metal Complex Hybrids of Graphene

Chromium(0) hexacarbonyl (98%, Cr(CO)6 F.W. ¼ 220.06, m.p. ¼ 150
C, b.p. ¼ 210
C (decomposes)), tris(acetonitrile) tricarbonylchromium(0) (Cr(CO)3(CH3CN)3, F.W. ¼ 259.18, m.p. ¼ 67–72
C (decomposes)), naphthalene (F.W. ¼ 128.17, m.p. ¼ 80.26
C), n-dibutyl ether (b.p. ¼ 140–142
C), anhydrous tetrahydrofuran (b.p. ¼ 66
C), and anisole (b.p. ¼ 154
C) were all obtained from Sigma-Aldrich. All chromium reagents have high vapor pressures, and direct exposure to the reagents should therefore be avoided. Raman spectra were collected in a Nicolet Almega XR dispersive Raman microscope with a laser excitation of 532 nm and with spectral resolution of 6 cm1 and spatial resolution of 0.7 μm. X-ray photoelectron spectroscopy (XPS) characterization was carried out by using a Kratos AXIS Ultra DLD XPS system equipped with an Al Kα monochromatic X-ray source and a 165 mm electron energy hemispherical analyzer. Vacuum pressure was kept below 3  109 Torr during the acquisition. The survey spectra were recorded using 270 W of X-ray power, 80 pass energy, and 0.5 eV step size. A low-energy electron flood from a filament was used for charge neutralization. Scanning electron microscopy (SEM) images were acquired in a XL30-FEG SEM instrument. Electrospray ionization mass spectroscopy (ESI-MS) analysis was performed using the Agilent LC–TOF instrument. Device Fabrication Single-layer graphene flakes were isolated from bulk graphite by using standard micromechanical exfoliation technique and are placed on an oxidized silicon wafer (with 300 nm SiO2). The contacts were deposited by e-beam lithography (Cr/Au, 10 nm/150 nm). Organometallic Complexation Reactions (Fig. 11.64): The hexahapto–metal complexation reactions were performed at elevated temperatures under argon atmosphere using either chromium hexacarbonyls (in absence or presence of naphthalene as an additional ligand, method A and B, respectively) or tris(acetonitrile)tricarbonylchromium (method C). Method A SLG devices were immersed in a chromium hexacarbonyl [Cr(CO)6, 0.1 M] solution in dibutyl ether/tetrahydrofuran (THF) (5:1) and refluxed under argon atmosphere at 140
C for 48 h. After functionalization the graphene devices were washed carefully with THF. Method B SLG devices were immersed in a solution of Cr(CO)6 (as in method A), with the addition of 0.25 equivalents of naphthalene ligand, and heated to 80
C for 12 h.

Fig. 11.64 Organometallic functionalization of single-layer graphene (SLG, 1) devices: (a) schematics of functionalization approaches using three different reaction routes to obtain hexahapto–chromium complex, (η6-SLG)Cr(CO)3 (2); routes: (A) Cr(CO)6, n-Bu2O/THF, 140
C, 48 h, under argon; (B) Cr(CO)6, naphthalene, n-Bu2O/THF, 80
C, 12 h, under argon; and (C) Cr(CO)3(CH3CN)3, THF, room temperature to 40
C, 6 h, under argon. (b) Illustration of the graphene device and the functionalization process and (c) three-dimensional model of the (η6-SLG)Cr(CO)3 organometallic complex. (Reproduced with permission of the Wiley)

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Method C SLG device was immersed in a solution of tris(acetonitrile) tricarbonylchromium(0) [Cr(CO)3(CH3CN)3] in THF (0.1 M) inside a glove box, and the reaction vessel was closed with rubber septum to maintain the argon atmosphere. The reaction vessel containing the graphene device and the solution were removed from the glove box, connected to an argon line, and heated slowly from room temperature of 40
C for 6 h. This procedure required rigorous exclusion of the atmosphere in order to avoid doping the graphene as a result of the decomposition of the chromium reagent to chromium oxide. Decomplexation Reactions In a typical reaction, the organometallic (η6-SLG)Cr(CO)3 complex was refluxed (at 150
C) in the presence of excess anisole (10 mL) under an atmosphere of argon overnight. The resulting SLG flake was washed with chloroform, acetone, and hexane, dried with gentle flow of argon. The decomplexation product of (η6-SLG)Cr(CO)3 with anisole yielded a light yellow solution, which was analyzed (after concentration with a rotary evaporator) using electrospray ionization mass spectroscopy (ESI-MS), which confirmed the chemical composition as (η6-anisole)Cr(CO)3 (chemical formula: C10H8CrO4, F.W. ¼ 243.98) [222] (reproduced with permission of the Wiley).

11.1.3.3

Synthesis of Metal Complexes of Fullerenes

Porphyrin-Based MOFs with Fullerenes (Fig. 11.65). H2TPyP, C60, and C70 were purchased from Sigma-Aldrich, while CuAcO and the solvents (special grade) were purchased from Wako Chemicals (Japan). The single crystal required for XRD analysis was prepared using a diffusion technique at room temperature. To generate 1, a solution of C60 dissolved in m-DCB was carefully layered over the top of a solution of H2TPyP dissolved in CHCl3, and after which a solution of CuAcO dissolved in MeOH was also layered over the top. The resultant mixture was allowed to stand for 2–4 weeks, during which time reddishbrown crystals of the product CuAcO-CuTPyP  m-DCB (1) were formed without intercalation of C60 between the porphyrins. To produce 2, a solution of C70 dissolved in m-DCB was carefully layered onto a solution of H2TPyP dissolved

Fig. 11.65 Construction of P-MOFs incorporating cavities. (Reproduced with permission of Wiley)

11.1

Synthesis and Characterization Methods

725

Fig. 11.66 Trinuclear [M3] systems involving the metal ions (M) copper (I), silver (I), and gold (I) and fluorinated pyrazolate [3,5-(CF3)2Pz]. (Reproduced with permission of the American Chemical Society)

in CHCl3, and after which a solution of CuAcO dissolved in MeOH was layered over the top. The resultant mixture was allowed to stand for 2–4 weeks, during which time dark-brown crystals of the product CuAcO-CuTPyPC70  m-DCBCHCl3 (2) were formed with C70 intercalated between the porphyrins [223] (reproduced with permission of Wiley). Further Reading Thorium fullerene, Th@C84 [224]; fullerene-functionalized monolayer-protected silver clusters: [Ag29(BDT)12(C60)n]3 (n ¼ 1–9) [225]. Coinage Metal Pyrazolates [(3,5-(CF3)2Pz)M]3 (M ¼ Au, Ag, Cu) as Buckycatchers All manipulations were carried out under an atmosphere of purified nitrogen using standard Schlenk techniques or in a MBRAUN Labmaster glove box equipped with a 10
C refrigerator. Solvents were purchased from commercial sources and purified by conventional methods prior to use. Glassware was oven-dried at 150
C overnight. NMR spectra were recorded at 23
C (unless specified) on a JEOL Eclipse 500 spectrometer (1H, 500.16 MHz; 13C, 125.77 MHz, 19F, 470.62). Proton and carbon chemical shifts are reported in ppm and referenced using the residual proton or carbon signals of the deuterated solvent. 19F NMR values were referenced to external CFCl3. Melting points were obtained on a MEL-TEMP II apparatus. C60 was purchased from Sigma-Aldrich. [(3,5-(CF3)2Pz)Cu]3 [Cu3], [(3,5-(CF3)2Pz)Ag]3 [Ag3], and [(3,5-(CF3)2Pz)Au]3 [Au3] (Fig. 11.66) were prepared as reported previously. Thermogravimetric analysis was performed in a Shimadzu TGA-51 analyzer using a platinum crucible. Prior to the experiments, the thermogravimetric equipment was calibrated using the process described in the Shimadzu instruction manual. {C60[Cu3]4}1 [(3,5-(CF3)2Pz)Cu]3 ([Cu3], 200 mg, 0.25 mmol) was dissolved in 10 mL of carbon disulfide and transferred to a C60 solution (48 mg, 0.067 mmol dissolved in 35 mL of carbon disulfide) using a cannula. The resulting mixture was covered with aluminum foil to protect from light, stirred for 1 h, warmed slightly to redissolve minor precipitate, and kept at room temperature overnight to obtain dark purple (almost black to naked eye) X-ray quality crystals of {C60[Cu3]4}1. The supernatant was collected, and the solvent was reduced to half the original volume, and the mixture was kept at room temperature to get the second crop of crystals of the product. This process could be repeated once more to get a third crop. The combined product was dried under reduced pressure to get 225 mg of {C60[Cu3]4}1 (92% yield based on [Cu3]). Mp ¼ melting point decomposition started at ca. 280
C and completely decomposed at ca 315
C (metallic copper deposition observed) [226] (reproduced with permission of the American Chemical Society).

11.1.3.4

Synthesis of Hybrids of Metal Complexes and Nanodiamonds

Gd(III)–Nanodiamond Conjugates7 Sulfo-NHS (0.182 g, 0.84 mmol) and EDC (0.165 g, 0.84 mmol) were dissolved in 4 mL of 0.1 M HEPES and 0.1 M NaCl (pH ¼ 7.0). 0.500 mL of a 10 mg/mL nanodiamond solution was added, and the resultant mixture was sonicated for 15 min (Fig. 11.67). Compound 5 (0.051 g, 0.085 mmol), dissolved in 0.500 mL of the aforementioned buffer, was added, and the reaction mixture was shaken overnight. The Gd(III)–nanodiamond conjugates were pelleted at 2465  g for 20 min. Excess reagents were removed by resuspending the pellet in 5 mL of water and pelleting the conjugate by centrifugation (2465  g, 20 min). The process was repeated for a total of four washes, with Gd(III) concentration reaching a minimum by wash 3. The conjugates were resuspended and stored in 5 mL of water to give 1 mg ND/mL suspensions of Gd(III)–ND [227].

7 Original numeration of the compounds. See all experimental details for the precursors 1–4 in https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC2829273/.

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Fig. 11.67 Conjugation of the Gd(III) contrast agent (5) to the nanodiamond surface. (Reproduced with permission of American Chemical Society)

Fig. 11.68 Synthesis of pyridyl CNOs (Py-CNOs). (Reproduced with permission of the American Chemical Society)

Further Reading Functionalized nanodiamonds for biological and medical applications [228].

11.1.3.5

Synthesis of Metal Complex Functionalized Nanoonions

Pyridyl-Functionalized and Water-Soluble Carbon Nanoonions [229] Typically 100 mg of CNOs were oxidized using a 3:1 mixture of sulfuric acid and nitric acid for 10 min. Following this the acid was diluted with distilled water, and the CNOs were separated from the acid by centrifugation and washed with 0.1 M sodium hydroxide and finally with water until a neutral pH was reached. The CNOs were further dried in a vacuum oven at 100
C. The oxidized CNOs were then reacted with 4-aminopyridine in an evacuated ampoule for 24 h at 170
C (Fig. 11.68). The ampoule was opened carefully and the contents washed multiple times with dichloromethane to remove unreacted 4-aminopyridine. The material was then resuspended in water and sonicated for about 30 min and then filtered through 0.2 μm PTFE membrane. The resultant solution was dried, and 36 mg of a Py-CNOs were collected as black residue. Complexation of Py-CNOs with ZnTPP (Fig. 11.69). For the NMR measurements, about 5 mg of Py-CNOs were dissolved in 0.7 mL of deuterated DMF. A 1 mM solution of ZnTPP in deuterated DMF was separately prepared and added in 20 μL aliquots until the proton resonances stopped shifting. In the case of electrochemical measurements, the OSWV of ZnTPP was recorded in DMF. Following this, 1 weight equivalent of Py-CNOs was added to the solution, and after stirring for 15 min, the OSWV was repeated.

11.1

Synthesis and Characterization Methods

727

Fig. 11.69 Complexation of Py-CNO with Zn-TPP. (Reproduced with permission of the American Chemical Society)

Further Reading Carbon nano-onions (multi-layer fullerenes): chemistry and applications [22]. Research progress in nano onion-like fullerenes [230].

11.1.3.6

Synthesis of Metal Complex Hybrids with Carbon Nanofibers

Nanofiber Carbon-Supported Phthalocyanine Metal Complexes [231]. Iron phthalocyanines (FePc, 90% purity) were purchased from Sigma-Aldrich and used without further purification. Graphite nanofiber (GNF) materials were commercially purchased (Carbon Nanomaterial Technology, Co., Ltd. South Korea) and treated with 96.8 mL sulfuric acid and 42 mL nitric acid before being utilized for any further processes. GNF_FePc composites were prepared by a simple three-step process via π–π interactions. The π–π interaction is the molecule–carbon interaction that occurs between the aromatic structure of the carbon surface and the macrocyclic ligand of the complex. The first step was to prepare FePc and GNF solutions by adding two equivalent amounts (40 mg) of FePc and GNF, respectively, in 100 mL dimethylformamide (DMF) solvent. The FePc solution was then added dropwise into the GNF dispersion under continuous stirring. The suspension was stirred for 7 h at room temperature and then ultrasonicated for 40 min. Finally, the GNF_FePc composite was washed with DMF and vacuumdried at 80
C. To see the effect of ball milling, FePc was ball-milled (BM), and the GNF_BM FePc composite was synthesized with the BM FePc using the abovementioned three-step process. For ball milling, 1 g of FePc was taken with the sample to ball ratio of 1:50 in a ball miller reactor, and the mixture was ball-milled at 250 rpm for 1 h (reproduced with permission of Elsevier Science).

11.1.3.7

Synthesis of Hybrids of Carbon Nanodots and Metal Complexes

Carbon Nanodots: Functional MOF Composites (Fig. 11.70) [232]. Preparation of C-dots. Citric acid (3 g) and urea (3 g) were added to 10 mL distilled water to form a transparent solution. Then, the solution was heated in a 750 W microwave oven for 5 min until the colorless solution finally changed into a dark-brown clustered solid, exhibiting the formation of C-dots. The obtained product was heated at 60
C for 1 h in a vacuum oven in order to remove the residual small molecules. The C-dot solution was purified through centrifugation at 3000 rpm for 20 min in favor of removing large or agglomerated particles.

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Fig. 11.70 Schematic illustration of C-dots@MOF composites. (Reproduced with permission of the Royal Society of Chemistry)

11.1.3.8

Important Related Information for Students

Microwave (MW) irradiation as a “non-conventional reaction condition” [233] has been applied in various areas of chemistry and technology to produce or destroy diverse materials and chemical compounds, as well as to accelerate chemical processes. The advantages of its use are the following [234]: 1. 2. 3. 4. 5. 6. 7.

Rapid heating is frequently achieved. Energy is accumulated within a material without surface limits. Economy of energy due to the absence of a necessity to heat environment. Electromagnetic heating does not produce pollution. There is no direct contact between the energy source and the material. Suitability of heating and possibility to be automated. Enhanced yields, substantial elimination of reaction solvents, and facilitation of purification relative to conventional synthesis techniques. 8. This method is appropriate for green chemistry and energy-saving processes. A typical reactor used for organic and/or organometallic syntheses [235] is presented in Fig. 11.71, which can be easily implemented using a domestic microwave oven. Due to some problems occurring during microwave treatment, for example, related with the use of volatile liquids (they need an external cooling system via copper ports), original solutions to these problems are frequently found in the reported literature. More modern laboratory MW reactors [236] are shown in Fig. 11.72.

Preparation of Cdots@MOFs Cdots@MOFs were synthesized by a stepwise synthetic method. First, 5 mL of DEF solution consisting of bdc (0.016 g) or btb (0.02 g) or bdc (0.02 g) and btb (0.0438 g) and Zn(NO3)26H2O (0.09 g) was thoroughly dissolved by ultrasonication. Subsequently, the solution was heated to 90
C and maintained at this temperature until the MOF crystals were formed. The MOF mother solution was filtered and cooled down to room temperature. Then, 0.5 mL of C-dot solution was added into the filtered solution and incubated at room temperature for 12 h. The obtained MOF crystals were preserved in a DEF solution, which were denoted as Cdots@MOF-5, Cdots@MOF-177, and Cdots@UMCM-1a, respectively. In the control experiments, MOF-5, MOF-177, and UMCM-1 were prepared by a solvothermal approach according to the reported method [18]. 5 mL of DEF solution consisting of bdc (0.016 g) or btb (0.02 g) or bdc (0.02 g) and btb (0.0438 g) and Zn(NO3)26H2O (0.09 g) were thoroughly dissolved by ultrasonication. Then, the mixture was placed in a Teflon reactor and heated at 85
C for 3 days, and then it was gradually cooled to room temperature. For comparison, Cdots@UMCM-1b were prepared as follows: 0.5 mL of C-dots were added into 5 mL of DEF consisting of bdc (0.016 g) and btb (0.0438 g) and Zn(NO3)26H2O (0.09 g), as per the abovementioned procedure under identical conditions (reproduced with permission of the Royal Society of Chemistry).8 Further Reading Synthesis MOF – quantum dot (QD@MOF) composites [237]; graphene quantum dots–phthalocyanines supramolecular hybrid [238]. 8

Reproduced from: CrystEngComm, 2015, 17, 1080–1085.

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Fig. 11.71 Typical MW reactor for organic and/or organometallic synthesis. With permission. (Reproduced with permission of the Chemistry Society of Japan)

Fig. 11.72 Microwave reactors for chemical syntheses. (a) Emrys Liberator (Biotage, Sweden, www.biotage.com); (b) CEM Discover BenchMate (CEM, USA, www.cem.com), Copyright CEM Corporation; (c) Milestone Ethos TouchControl (Milestone, Italy, www.milestonesci.com); (d) Lambda MicroCure2100 BatchSystem (Lambda, USA, www.microcure.com). (Reproduced with permission of the John Wiley and Sons)

11.1.3.9

Preparation of Glassy Carbon Modified with Metal Complexes

Modification of Glassy Carbon Electrode (GCE) with Iron-40 (phenyl)-2, 20 :60 ,200 -terpyridine Complex (Fe-PTPY) (See more details in [239].) Prior to electrode modification, the electrode surface was polished successively in 1.0, 0.3, and 0.05 μm alumina slurries on micro cloth pads. After polishing, the electrode was thoroughly rinsed with water and sonicated in ethanol

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Fig. 11.73 Complexes which C16C28 polyynediyl chains span two platinum atoms. (Reproduced with permission of the American Chemical Society)

and distilled water, successively. The PTPY/OMC9/GCE was prepared according to the following methodology. In the first step, 2 μL of a mixture containing 5 mg OMC in 1 mL N,N0 -dimethyl formamide was transferred onto the GCE surface, and the solvent was evaporated under an infrared lamp. Then, PTPY was electrochemically grafted on the OMC/GCE using the existing methodology for the in situ generation of aryldiazonium salts and their electrografting on the GCE. According to this methodology, APTPY was dissolved in ice-cold 0.5 M HCl solution, and ice-cold sodium nitrite aqueous solution was added into this solution drop by drop. Final concentrations of APTPY and NaNO2 were 1 mM and 2 mM, respectively. After the mixture was stirred for 1 h at 0
C, the OMC/GCE was immersed into this solution derivatized by cyclic voltammetry (CV) scanning from 0 to 1.0 V at 100 mV/s scan rate for 2 scans. Finally, the resulting PTPY-modified OMC/GCE was thoroughly rinsed with water and transferred into a 0.5 mM iron(III) solution for 8 h to obtain the Fe-PTPY/OMC/GCE. For comparison Fe-PTPY/GCE was also prepared (reproduced with permission of the Elsevier Science). Further Reading A glassy carbon electrode modified with a nickel(II) norcorrole complex and carbon nanotubes [240]; functionalization of glassy carbon electrodes with metal-based species [241].

11.1.3.10

Metalated Carbynes

Isolable Complexes with C16C28 Polyynediyl Chains Span Two Platinum Atoms (Fig. 11.73) [242]. Reaction of PtC4H and H(C C)2SiEt3 (PtC8Si, PtC12Si, PtC16Si). A three-neck flask was charged with PtC4H (0.260 g, 0.275 mmol) 2, and acetone (40 mL) and fitted with a gas dispersion tube and a condenser. A Schlenk flask was charged with CuCl (0.200 g, 0.204 mmol) and acetone (20 mL), and TMEDA (0.400 mL, 2.67 mmol) was added with stirring. After 0.5 h, stirring was halted and a grayish solid separated from a blue supernatant. Then O2 was bubbled through the three-neck flask with stirring. After ca. 5 min, H(C C)2SiEt3 (0.905 g, 5.51 mmol) was added, followed by the blue supernatant in portions. After 1.5 h, the solvent was removed by rotary evaporation. The residue was extracted first with hexane (3  25 mL) and then with toluene (3  30 mL). The extracts were passed in sequence through an alumina column (2  7 cm). The solvent was removed from the toluene extracts by rotary evaporation. The residue was chromatographed on a silica gel column (3.5  40 cm, packed in hexane, eluted with 15:85 v/v CH2Cl2/hexane). The solvent was removed from the product-containing fractions by rotary evaporation and oil pump vacuum to give PtC16Si as a deep red solid (0.004 g, 0.003 mmol, 1%), PtC12Si as an orange solid (0.102 g, 0.0880 mmol, 30%), and PtC8Si as a yellow solid (0.088 g, 0.080 mmol, 29%) (reproduced with permission of the American Chemical Society). Further Reading Wirelike C6C20 polyynediyl chains [243].

11.1.3.11

Preparation of Metal Complex Composites with Graphite

Metal Coordination with Graphite Nanoplatelets (Fig. 11.74) [244]. Preparation of graphite nanoplatelets (GNP). The GNPs were prepared by acid intercalation (H2SO4/HNO3, 3:1; 15 h, room temperature), followed by thermal shock exfoliation; the resulting material consists of incompletely exfoliated graphene sheets, in which there is a broad distribution of particle sizes. The exfoliated material (1 g) was dispersed in dibutyl ether (400 mL Bu2O) by shear mixing for 30 min followed by bath sonication for 24 h to obtain the final GNP suspension (~2.5 mg/mL). UV–Vis spectra of the diluted suspensions were collected in order to confirm the concentration of the suspension (by reference to the graphitic molar extinction coefficient, ε550 nm ¼ 500 L/mol/cm).

9

OMC ¼ ordered mesoporous carbon.

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Fig. 11.74 Preparation of metal–GNP complexes: (1) reaction of GNP surfaces with metal carbonyls, (2) annealing and compaction to cross-link the GNPs. (Reproduced with permission of the Elsevier Science)

Synthesis of Metal Coordination Complexes In a typical experiment, a mixture of the GNP/Bu2O suspension (20 mL, 50 mg, 4.17 mmol carbon, 500 equivalents) and tetrahydrofuran (2 mL THF) was degassed with argon for 1 h, and the metal carbonyl (0.008 mmol, 1 equivalent) was added. The resulting mixture was refluxed at 140
C under argon for 24 h, allowed to cool to room temperature, and then filtered. Thin films of the M-GNP complexes of predetermined diameter and thickness were fabricated by vacuum filtration (Durapore 0.1 μm VVPP membrane filter) of a known volume of the GNP suspension in dibutyl ether (GNP/Bu2O). Preparation of Annealed and Compacted M-GNP Films In a typical experiment, the M-GNP films were pressed in a stainless steel cell, in which the pole faces of the die were covered with Teflon films. The cell was connected to a vacuum system, which included a liquid nitrogen trap, and evacuated to a pressure of 104 Torr and a pressure of 500 lb applied to the plunger. The temperature was slowly increased to 100
C by heating the plates of the hydraulic press and held at this temperature for 2 h. Then the pressure was increased to 1000 lb, and a temperature of 200
C was applied to the film for 4 h; after which the apparatus was allowed to cool to room temperature, the vacuum was released, and the M-GNP film (thickness, t ~ 200 μm) was removed from the die for characterization. Further Reading MOF/graphite hybrid materials [245]; coordination chemistry of MOF–graphite oxide composites [246].

11.1.4 Solubilization of Carbon Allotropes 11.1.4.1

Dispersion of Graphite

Graphene Layers Using Graphite Dispersion [247]. Graphene layers were synthesized using ultrasonic dispersion of graphite flakes followed by ultracentrifugation in sodium cholate and polyoxyethylene nonylphenyl ether aqueous solutions. Graphene samples were prepared by using horn-type ultrasonication of graphite flakes (NGS Naturgraphit GmbH) in a 50 mL aqueous solution of 4% w/v sodium cholate (SC, Sigma-Aldrich) or 4% w/v polyoxyethylene nonylphenyl ether (PNE, Sigma-Aldrich). For sample preparation conditions for the ultrasonicator and the ultracentrifuge, see original article. A horntype ultrasonicator (VCX 750, Sonics & Materials) was used at a 540 W power, and the solution was cooled during the ultrasonication in order to maintain the solution temperature around 26
C (reproduced with permission of the Journal of the Korean Physical Society).

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Fig. 11.75 Schematic device for electrochemical preparation of CNCs. (Reproduced with permission of the American Chemical Society)

Fig. 11.76 Left: graphite completely settles down after sonication at the bottom of a vial containing benzene, thus leaving the supernatant liquid colorless. Right: partial solubilization of graphite in pyridine by sonication affords a dark colloidal dispersion with concentration 0.3 mg/mL. (Reproduced with permission of the Wiley)

Water-Soluble Carbon Nanocrystals Released Electrochemically from Graphite [248]. The electrochemical preparation of CNCs was performed in an electrochemical cell, consisting of a graphite rod (GR) working electrode (WE) with a size of 5.0 cm  ∅1.0 cm, a Pt mesh counter electrode (CE), and a Ag/AgCl reference electrode (RE) and 20 mL pH 7.0 phosphate electrolyte solution (Fig. 11.75). The applied potential on GR electrode was cycled between 3.0 and 3.0 V at a scan rate of 0.1 V/s, and ECL and electrochemical signals were measured simultaneously by an ECL and EC multifunctional detection system (MPI-E, Remex Electronic Instrument Lt. Co., Xi’an, China). During the electrochemical preparation of CNCs, quite stable cyclic voltammogram (CV) was obtained, indicating that the area of GR surface was basically unchanged during the electrolysis. Meanwhile, large amounts of gases were found to evolute from the graphite rod at potential higher than +2.0 V or lower than 2.0 V. The gas evolution not only stirred the electrolyte efficiently but also might play an important role in transporting CNCs from inner of the porous GR electrode to the outside bulk solution. In increasing the scan cycle of potential, the color of the electrolyte solution changed from colorless to yellow and finally dark brown; however, on the other hand, no visible destruction of the GR electrode was found during the whole electrolytic process (1.5 h). Interestingly, the resulting dark brown solution was very clear, i.e., almost no deposit was found, and the solution could easily pass through a 0.2 μm filter membrane. As comparison, CNC solution was prepared by a constant oxidation potential (+3.0 V). In that case, the color of electrolyte solution turned to dark brown quickly, but strong destruction of the GR electrode was found accompanied with large amounts of visible particles with various shapes leaving the electrode surface and depositing to the bottom of the electrolytic cell (reproduced with permission of the American Chemical Society). Solubilization of Graphite in F-Containing Solvents and Pyridine The graphite powder was supplied by NUKEM GmbH (Germany). Hexafluorobenzene, octafluorotoluene, pentafluorobenzonitrile, pentafluoronitrobenzene, pentafluoropyridine, and pyridine (Fig. 11.76) were all purchased from Sigma-Aldrich and used as received. IR spectra were taken on a Fourier transform infrared (FTIR) spectrometer (Bruker Equinox 55/S) using KBr pellets. Raman spectra were obtained using an InVia Reflex micro-Raman spectrometer (Renishaw) with a 100 objective lens and a crystal laser excitation of 514.5 nm operating at 0.1 mW. The optical spectra were recorded on a Shimadzu UV2100 spectrophotometer using quartz cuvettes. TEM was carried out on a JEOL JEM 2010 microscope operated at 200 kV using a holey carbon-coated copper grid. A FEI Inspect apparatus operating at 15–30 kV under vacuum was used to record the SEM images of the sheets on Ag substrates. For both TEM and SEM studies, a drop of very dilute dispersion after settling was placed on a substrate and dried at ambient

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conditions. AFM images were obtained with an AFM (Explorer, ThermoMicroscopes) using a mica substrate in a noncontact mode with silicon tips of the 1650-00 type and resonance frequencies ranging from 180 to 240 kHz. For this purpose, a drop of very dilute dispersion after settling was placed on the mica support and allowed to dry by evaporation at ambient temperature. Generally, dilute dispersions prevented a complete reaggregation of the graphenes. For the liquid-phase extraction of single layers, graphite fine powder (5 mg) was suspended in a particular aromatic solvent (1 mL) (hexafluorobenzene, octafluorotoluene, pentafluoronitrobenzene, pentafluorobenzonitrile, pentafluoropyridine, or pyridine) by 1-h sonication in an ultrasound bath (135 W) using sealed glass vials. Each suspension was left for 5 days at ambient conditions in order to settle out any insoluble particles, and the supernatant clear colloids were carefully collected for further microscopy characterization. The concentration of a given dispersion was measured quantitatively by filtering a large volume of the colloid through a pre-weighed filter (Millipore HVLP 0.45 μm). After the solvent had been completely removed, the filter with the solid residue on it was dried and reweighed using a high precision balance. The solubilization yields, expressed as percentages, were calculated for each case from the soluble content in mg per 1 mL solvent divided by the initially added amount of graphite in 1 mL solvent (5 mg). To prepare the gold–graphene hybrid, a solution of HAuCl43H2O (0.5 mg) in DMF (1 mL) was added in the graphite colloidal dispersion in pyridine (10 mL, 0.1 mg/mL) followed by reduction with NaBH4 (2 mg) under vigorous stirring. The resulting precipitate was centrifuged, washed with ethanol, and air-dried (reproduced with permission of the Wiley) [249]. Further Reading Thermal reduction of graphite oxide dispersed in solvent (H2O and dimethylformamide (DMF) [250]; soluble graphene obtained by graphite oxidation [251]; solution properties of graphite [252].

11.1.4.2

Dispersion of Nanoonions (Functionalized by Fluorination)

Fluorination Procedure [253]. The fluorination of CNO was carried out in a custom-built fluorination apparatus described elsewhere. In a typical fluorination process, 200 mg of carbon nanoonions was loaded into a Monel-foil boat and then placed into a Monel reactor. Thereafter, the reactor was sealed and purged by continuous flow of helium for 2 h at room temperature and then under heating to reaction temperature. The reactor was heated to a selected temperature of 350, 410, or 480
C. The sample was kept at that temperature for 2–3 h to remove the residual air and moisture adsorbed on the samples and reactor walls before fluorine and hydrogen were introduced into the reactor. Fluorine and hydrogen gases were introduced separately at a controlled 3:1 flow rate ratio. The purpose of using hydrogen in the process is in situ generation of HF, which is known to catalyze the fluorination of the other sp2-bonded carbon materials, e.g., graphite and carbon nanotubes. The fluorination time was kept at 6 h. Thereafter, the reactor was cooled down to room temperature, and the flows of hydrogen and fluorine gases were stopped. The sample weight was observed to increase from 200 mg to 231, 369, and 450 mg after the fluorination at temperatures of 350, 410, and 480
C, respectively. Solubility of Fluorinated Nanoonions We found that the pristine CNO forms a black-colored colloidal suspension in ethanol after 2030-min sonication. The majority of the CNO material precipitated from the suspension within 10 days, leaving a gray-colored supernatant solution. In contrast, the similarly prepared colloidal suspensions of F–NO materials in ethanol were light green-colored and remained quite stable for a long time. For instance, even after 1 year, the suspension solutions of the most fluorinated F-NO-410 and F-NO-480 samples do not show any visible precipitation, and the F-NO-350 sample, containing fluorine predominantly on the onion’s outer layer, shows only a minor precipitation. These observations demonstrate the significantly improved solubility of CNO due to functionalization through direct fluorination, similar to nanodiamond and carbon nanotubes (reproduced with permission of the American Chemical Society). Further Reading Composites of CNOs and polyaniline [254]; solubilization of cyclodextrin modified carbon nanoonions [255].

11.1.4.3

Dispersion of Fullerenes

Solubility of Light Fullerenes in N-Nonane: Solubility Measurement Techniques at Atmospheric Pressure [256]. The temperature dependence of the light fullerene (C60 or C70) solubility in n-nonane in the temperature range 293.3–353.3 K was carried out by the method of isothermal saturation in ampoules. The saturation time was equal to 8 h. Temperature was measured with an uncertainty of 0.1 K (k ¼ 2). For the saturation of the fullerene solutions, a thermostatic shaker (LAUDA ET 20) was used at a shaking frequency ~80 Hz. The fullerene concentrations (after the dilution and cooling of saturated solutions) were determined using a double beam spectrophotometer (SPECORD M40, Karl Zeiss, Germany) at characteristic

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wavelengths of 335 and 472 nm corresponding to the maximum absorbance. The accuracy of wavelength was 0.5 nm, the photometric accuracy (ΔD) was 0.005, and the thick of the absorption layer was 1 cm. The experimental method was previously used to study the C60 (or C70) solubility in 1-hexanol. The relative expanded uncertainty of the solubility values was 10%. Relative air humidity was 40–50 %. For the determination of the solvent content in solid crystal solutes, the following experimental method was used. The solid phase deposited from n-nonane solution was filtered on a Schott filter (porosity factor 10), rinsed quickly with ethanol, and then dried for 10–15 min at 293 K. Then, the solid phase was weighted, repeatedly washed with ethanol in a Soxhlet apparatus at 351 K and 0.101 MPa, dried for 1 h under vacuum (13.3 Pa) at 473 K, and weighed again. The weight change corresponded to the n-nonane content in the initial crystal solutes. The estimated uncertainty with the solid solvate concentration in the mixture is 5% (k ¼ 2) (reproduced with permission of the Elsevier Science). Aqueous [C60] and [C70] Fullerene Aggregates [257]. Solutions of C60 (99.5%; Sigma-Aldrich) or C70 (98%; SES Research) in toluene (50 mL, 1 g/L) were added to 450 mL DI water, and the binary mixture was sonicated in closed bottles for 24 h. The bottle was opened, ultrasonication was further applied at 60
C to evaporate residual toluene, and the resulting solution was filtered through 0.45 μm nitrocellulose filters (Whatman). A similar preparation was used to produce nC70 in deuterium oxide (D2O) for control experiments. Fullerene stock solutions were stored in the dark at room temperature. The concentration of fullerene stocks was determined through a solvent exchange method, where acetic acid (100 mM) was used to destabilize the fullerene particles and allow transport into the toluene phase. UV–Vis spectroscopy (Varian Cary 50 Bio) was used to determine the concentration of fullerene in the toluene solution and to confirm that no fullerene remained in the aqueous phase after extraction (reproduced with permission of the American Chemical Society). Further Reading Solubilities of buckminsterfullerene in various solvents [258]; highly stable reproducible C60 fullerene aqueous colloid solution [259].

11.1.4.4

Dispersion of Graphene

Highly Reduced GO in a Wide Variety of Organic Solvents [260]. A colloidal suspension of individual graphene oxide sheets in purified water (4 mL, 3 mg/mL) was prepared in 2 L batches with 2 h of bath ultrasound (VWR B2500A-MT). The graphene oxide suspension in the H2O/DMF solvent mixture was obtained by addition of DMF (36 mL) into the aqueous graphene oxide suspensions (thus, volume ratio DMF:H2O ¼ 9), producing a homogeneous suspension of the graphene oxide sheets. Hydrazine monohydrate (1 μL for 3 mg of GO) (98%, Aldrich) was subsequently added to the suspension (pH ¼ ~6.5). Additional stirring with a Teflon-coated stirring bar at 80
C for 12 h yielded a black suspension (pH ¼ ~7) of HRG sheets. After cooling to room temperature, HRG paper was made by filtration of the colloidal suspension through an Anodisc® membrane filter (47 mm in diameter, 0.2 μm pore size, Whatman, Middlesex, UK), and after which the deposit was dried in air and peeled off. Some air-dried HRG paper samples were put in a tube furnace under Ar gas flow (pressure: ~1 atm, rate: 100 sccm); the temperature was increased at 1
C/min, held at 150
C for 12 h, and then the furnace was cooled naturally to room temperature. Square-shaped paper samples (~9 mm  9 mm) were prepared, and electrical conductivity was measured for three such samples of the HRG paper dried in air at room temperature and for three such samples of the heat-treated HRG paper. Graphene oxide paper samples were prepared by a similar filtering method and dried in air. Tests to disperse HRG in other organic solvents were done by addition of the organic solvents (9 mL each of DMF, N-methylpyrrolidone, ethanol, dimethyl sulfoxide, acetonitrile, acetone, tetrahydrofuran, diethyl ether, toluene, 1,2-dichlorobenzene, methanol, benzene, chloroform, pyridine, and propylene carbonate) to 1 mL of the HRG suspension in the 9:1 DMF/H2O mixture (reproduced with permission of the American Chemical Society). Further Reading Graphene dispersions [261]; graphene at extremely high concentration [262].

11.1.4.5

Dispersion of Nanodiamonds

Clear Colloidal Solutions of Detonation Nanodiamond in Organic Solvents [263]. The nanodiamond used in this study was produced by detonation synthesis and purchased from Link Korea Corporation (97%, Korea), having an average particle size of 4–5 nm. Thermal oxidation was carried out on this as-received detonation nanodiamond by treating the powder in a furnace (F-12-3.3, Tender Scientific Co., Ltd., Taiwan) and keeping it at 420
C under air conditions for different time periods of 1.0, 1.5, 3.0, 4.5, and 14.5 h. The as-received nanodiamond and the oxidized detonation nanodiamond are denoted as P-ND and T-ND in the following text, respectively. In experiments involving dispersion, 1 wt.% nanodiamond powder was dispersed

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into an organic solvent containing a previously added 30 wt.% surfactant (based upon the weight of the nanodiamond), and the mixture was then de-agglomerated by a high-energy ultrasonic horn (Sonifier S-450D, Branson Ultrasonics Co., Ltd., USA) for 5 min. Three surfactants were used in these experiments including oleylamine (OLA) (70%, Sigma-Aldrich, USA), octadecylamine (ODA) (90%, Acros, USA), and oleic acid (OA) (65%, Riedel-deHaën, Germany). Solvents of tetrahydrofuran (THF) (Mallinckrodt, 99.8%, USA), methyl ethyl ketone (MEK) (99.6%, Tedia, USA), and acetone (99.9%, Echo, Taiwan) were used as the dispersion media. In another experiment for preparing transparent colloidal solutions of nanodiamond, the as-prepared suspensions mentioned above were further de-agglomerated by a mechanical comminuting of bead milling on wet-grinding equipment (JBM-B035, Just Nanotech Co., Ltd., Taiwan) for 40 min, in which the peripheral speed of the rotor was fixed at 10.5 m/s and the size of the zirconia beads was 30 μm (reproduced with permission of the Elsevier Science). Further Reading Deaggregation of nanodiamond powders using salt- and sugar-assisted milling [264]; dispersion of nanodiamond in clean oil [265].

11.1.4.6

Dispersion of Carbon Nanodots

Synthesis of Water-Soluble 1-Methyl-2-pyrrolidinone (NMP)-Derived Polymer-Coated Nitrogen-Doped Carbon Nanodots (pN–CNDs) [266]. The pN–CNDs were synthesized by a facile direct solvothermal reaction. Typically, 50 mL of NMP was put in an 80 mL Teflon-lined autoclave and heated at 200
C for about 10 h. The pN–CNDs were recovered by removing the residual solvent NMP and the other impurities first through vacuum rotary evaporation and then dialysis against water for 3 days. The obtained pN–CNDs were dispersed in water or another physiological media for further usage. The post-thermal treatment of the pN–CNDs was carried out in a pipe furnace with an air atmosphere under 200
C for 2 h (reproduced with permission of Wiley). Further Reading Separated non-sedimental carbon dots [267]; water-soluble highly fluorescent nitrogen-doped carbon nanodots [268].

11.1.4.7

Dispersion of Carbon Nanotubes: General Methods

Ultrasonication SWCNTs synthesized by the HiPco process, both as-produced (batch CNI 002) and in purified form (batch CNI 26-0036B-2), were purchased from Carbon Nanotechnologies. In the experiments, the SWCNTs were dispersed in water by means of the surfactant sodium dodecylbenzene sulfonate (SDBS), which has recently been shown to allow the dispersion of the tubes as individuals in aqueous solution. Nanotube dispersions were prepared by a combined tip and bath ultrasonication approach as follows. A small piece of HiPco SWCNT mat was added to an aqueous solution (5 mg/mL) of the surfactant and subjected to ultrasonic treatment in a tip sonicator (Dr. Hielscher UP 200s). A small number of pulses (usually five), with 0.5-s-on/0.5-s-off pulse cycles at 40 W/cm2, were applied to a volume of 1.5 mL. Subsequently, the obtained suspension was centrifuged (Eppendorf 5417C Centrifuge) at 20 200 g for 30 min. The upper 80% of the resulting supernatant was then carefully decanted and subjected to ultrasonication in a bath sonicator (Branson 1510, 80 kHz) for time periods ranging from a few minutes to several hours [269] (reproduced with permission of the American Chemical Society).

11.1.4.8

Important Related Information for Students

Ultrasound (US), as it is well-known, is a part of the sound spectra having frequency of ~16 kHz, which is out of the normal range of human hearing. The effects produced by ultrasound are derived from the creation, expansion, and destruction of small bubbles, which appear under US irradiation of a liquid phase. After creation, these bubbles grow to 2–10 times the initial diameter of a few microns and undergo radial vibration. The circulating liquid cools these unstable cavities, so, after a few cycles of rarefaction and compression, they collapse violently in 105–107 s. This phenomenon, named cavitation, produces high temperatures and pressures in the liquid. The temperature of cavitation varies from 1000 to 10,000 K, more frequently in the range 4500–5500 K. It should be noted that acoustic irradiation is a mechanical energy (no quantum), which is transformed to thermal energy. Contrary to photochemical processes, this energy is not absorbed by molecules. Due to the extensive range of cavitation frequencies, many reactions are not well reproducible. Therefore, each publication related to the use of US generally contains a detailed description of equipment (dimensions, frequency used, intensity of US, etc.). Sonochemical

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Fig. 11.77 Schematic diagram of the plasma reactor. (Reproduced with permission of Hindawi)

reactions are usually marked )))), in accordance with internationally accepted usage. For successful application of US, the influence of various factors can be summarized as follows: 1. Frequency. Increase of frequency leads to the decrease of production and intensity of cavitation in liquids. This fact can be explained as follows: at high frequencies, the time necessary for a bubble to appear as a result of cavitation and to have sufficient size to affect the liquid phase is too low. 2. Solvent. Cavitation produces considerably minor effects in viscous liquids or those with higher surface pressures. 3. Temperature. Increase of temperature allows the cavitation to be performed at lower acoustic intensities. This is a consequence of increasing vapor pressure of the solvent with increasing temperature. 4. Application of gases. In the case of application of gases (poor or very soluble), the intensity of cavitation decreases due to the formation of a large number of additional nuclei in the system. 5. External pressure. Increase of external pressure leads to the increase of intensity of destruction of cavitation bubbles, that is, the effects of US in this case are more rapid and violent in comparison with normal pressure. 6. Intensity. In general, the increase in intensity of US intensifies the produced effects. Plasma Treatment A schematic setup of the plasma reactor and a flow chart of the functionalization process are shown in Fig. 11.77 to 100 mg of MWCNT powder (Sigma-Aldrich, outer diameter, 10–30 nm; inner diameter, 3–10 nm; length, 1–10 μm; purity, >90%) which is added to 10–20 mL of pure ethanol (Wako Pure Chemicals Co., purity >95%) and sonicated at room temperature using a supersonic homogenizer (Sonics Vibra cell, VC 130, Sonic & Materials Inc., f ¼ 20 kHz, 6.0 mmϕ probe) at an input power of 10–20 W for 15–120 min. The suspension is dried under reduced pressure and soaked in 0.0–0.30 mol (5 mL) of citric acid (Wako Pure Chemicals Co., assay >98%) solution for 0–120 h. The MWCNTs in the citric acid solution are then placed on the lower electrode (SUS, 50 mmϕ) of the reactor, which is evacuated to ca. 400 Pa using a rotary pump at a very slow rate. When the wet phase starts to disappear, oxygen gas is introduced into the reactor at a rate of 0–10 sccm, and the background chamber pressure is kept at about 400 Pa. Then the plasma reaction is carried out for 10–30 min by an RF input power of Prf ¼ 100–300 W and f ¼ 13.56 MHz. The reflected RF power is minimized ( 1). Nanotube surface is formed with correct hexagons with a side 0.142 nm. Hydrogen molecule can be considered as a sphere with diameter 0.3 nm. 6. Offer two other (non-related with carbon) methods of hydrogen storage, and note their main advantages and disadvantages. Solutions 1.

H2 þ 1=2 O2 ¼ H2 O ðж:Þ, Q ¼ ΔH ¼ 286 kJ=ðmol H2 Þ ¼ 143 kJ=ðg H2 Þ; C þ O2 ¼ CO2 , Q ¼ ΔH ¼ 393 kJ=ðmol CÞ ¼ 33 kJ=ðg CÞ; СH 4 þ 2O2 ¼ CO2 þ 2H2 O ðliq:Þ, Q ¼ ΔH ¼ 890 kJ=ðmol CH4 Þ ¼ 56 kJ=ðg CH4 Þ; C8 H18 þ 25=2 O2 ¼ 8CO2 þ 9H2 O ðliq:Þ, Q ¼ ΔH ¼ 5616 kJ=ðmol C8 H18 Þ ¼ 49 kJ=ðg C8 H18 Þ: Hydrogen has highest specific heat of combustion.

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2. For the reaction H2 + 1/2 O2 ¼ H2O (liq.), taking place in a hydrogen fuel cell, the change of free Gibbs energy at 298 K is equal to:
 ΔG ¼ DH  TΔS ¼ 286  298  163  103 ¼ 237 kJ=mol H2 ¼ 119 kJ=g H2 : The work, carried out upon combustion of 1 kg of H2 with energy conversion efficiency 50%, is equal to: 119  103  0, 5 ¼ 59  103 kJ: The distance equals to the work, divided on the friction force: l¼

W W 59  106 ¼ ¼ 60, 200 m ¼ 60 km: ¼ F Tp kTp mg 0, 1  1000  9, 8

3. The highest mass fraction of hydrogen is in methane CH4. It equals 25%. 4. Each carbon atom in graphite or nanotube can accept one hydrogen atom. In this case, mass fraction of hydrogen is maximal and equals: 1=ð1 þ 12Þ ¼ 0:077, or 7:7%: If 1 mol of С joined x mol of H, the mass fraction of hydrogen is: ωðΗÞ ¼

x ¼ 0:065, x þ 12

откуда x ¼ 0.83. The part of connected carbon atoms is 83%, i.e., approximately 5/6. 5. The nanotube has a shape of cylinder with length l and diameter d. Tube volume: V ¼ πd2l/4 Tube surface: S ¼ πdl The number of hexagons on the tube surface equals to the ratio of the tube surface to hexagon surface: N hexag: ¼

S πdl ¼ pffiffi ¼ 60dl: Shexag: 3 3  0, 1422 2

Each carbon atom belongs to three hexagons; therefore 6/3 ¼ 2 carbon atoms are per one hexagon. So a total number of carbon atoms in a nanotube is: N С ¼ 120 dl: Let’s find the number of hydrogen molecules. It is known that the spheres in a closest packing occupy 74% of space volume. The number of spheres in a tube channel is the ratio of 74% of tube volume V to the volume of hydrogen molecule V H2 : 0, 74  πd4 l 0, 74  V ¼ ¼1 ¼ 41 d2 l: 3 V H2 6  π  0, 3 2

N H2 Mass fraction of hydrogen is: ωð H 2 Þ ¼

2N H2 82 d2 l d , ¼ ¼ 2 2N H2 þ 12N C 82 d l þ 1440 dl d þ 17, 6

where d is expressed in nm. If the tube has a diameter of 3 nm, the mass fraction of hydrogen inside the tube could reach 15%. 6. The students should offer their replies, which could vary. There are many versions of replies to this question.

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Problems and Calculations

749

Problem Calculation of Number of Carbon Atoms in Nanodiamond Question How many carbon atoms are in a nanodiamond with diameter of 5 nm? What percent of a total volume of diamond carbon atoms do occupy? Covalent radius of carbon atom is 0.077 nm (one half of the C–C bond). Density of diamond is 3.52 g/cm3. Solution Volume of one nanodiamond is V(С) ¼ πd3/6 ¼ π5.03/6 ¼ 65 nm3 ¼ 6.51020 cm3, and its weight is m(С) ¼ ρV ¼ 3.526.541020 ¼ 2.31019 g. Number of atoms can be found through the quantity of carbon: N(С) ¼ υ(C)NA ¼ m/MNA ¼ 2.31019/ 126.021023  12,000. Knowing the number of atoms, let’s calculate their total volume: V(at.) ¼ N4/3 πr3 ¼ 12,0004/3π0.0773 ¼ 23 nm3. The percent of total volume of the nanodiamond is 23/65. 100 ¼ 35%. Reply: 12,000; 35%. Problem Evaluation of Nanotube Diameter Question Specific surface of opened SWCNTs is 1000 m2/g, and their density is 1.3 g/cm3. Considering that for all the material, the ratio volume/surface is the same as that for one SWCNT, evaluate the nanotube diameter. Solution Let’s take 1 g of the material. Its volume is 1/1.3 ¼ 0.77 cm3 ¼ 7.7107 m3, and its surface is 1000 m2. The ratio volume/ surface is: V/S ¼ 7.7107 m3/1000 m2 ¼ 7.71010 m. Opened SWCNTs can be represented as cylinders with diameter d and length l. For a cylinder, the ratio volume/surface is: 

πd2 4

 l

V d ¼ ¼ : S 4 πdl Therefore, d ¼ 47.71010 ¼ 3.1109 m  3 nm. Indeed, the ratio volume/surface (V/S) is higher than for one nanotube, and since the tubes cannot fill densely all volume, a free space between SWCNTs exists. Therefore, a real diameter of such nanotubes is less than 3 nm. Problem Calculation of the Distance Between Fullerene Molecules Question Find the distance between the centers of neighboring fullerene molecules in its low-temperature modification (density 1.7 g/cm3), which has a primitive cubic lattice, where the molecules are in the vertices of cubic elemental cell only. Solution In a primitive cubic lattice (Fig. 11.83), each molecule in a vertex of the cube belongs to eight neighboring elemental cells. 81/8 ¼ 1 C60 molecule is per one cell. The volume of 1 mol of fullerene is Vm ¼ M/ρ ¼ 720.6/1.7 ¼ 424 cm3/mol. The volume of one elemental cell is Vcell ¼ Vm/NA ¼ 424/6.021023 ¼ 7.041022 cm3 ¼ 0.704 nm3. The distance between the centers of neighboring molecules is equal to the edge of the elemental cell: 1=3

a ¼ V cell ¼ 0:89 nm:

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Fig. 11.83 Cubic cell

Fig. 11.84 Graphene structure

Problem Calculation of Weight of a Graphene Square Question Graphite monolayer (2D net of correct hexagons of carbon atoms) is graphene (Fig. 11.84). In 2004 Geim and Novoselov were able to isolate such layer from graphite monocrystal and collocate it as a film on the surface of silicon support. In 2010, this achievement was awarded with a Nobel Prize in physics. Calculate the weight of graphene square with size of 10  10 mm. Find the C–C bond in a guide. To saturate free valencies, the carbon in graphene can form bonds with gaseous substances. What is the maximal number of hydrogen atoms, which can be accepted by this graphene square? Solution Let’s find the number of carbon atom graphene square with size of 10  10 mm. First, we will calculate the number of hexagons. The C–C bond length in graphite is 0.142 nm. The surface of one hexagon is: Shexag:

pffiffiffi 2 3 3
 0:142  109 ¼ 5:24  1020 m2 ¼ 2

The number of hexagons equals to the graphene surface divided on the hexagon surface: N hexag:


2 10:103 m SKB ¼ ¼ ¼ 1:91  1015 : Shexag: 5:24  1020 m2

Each carbon atom belongs to three hexagons. Therefore, 6/3 ¼ 2 carbon atoms are per one hexagons. So total number of carbon atoms in a graphene square is: N C ¼ 2N hexag: ¼ 3:82  1015 : Graphene weight is: mc ¼

Nc 3:82  1015 MC ¼  12 ¼ 7:61  108 g ¼ 76:1 ng: NA 6:02  1023

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Problems and Calculations

751

Each carbon atom in graphene is bound with three neighboring carbon atoms and can accept one hydrogen atom more. So maximal number of hydrogen atoms, bound with graphene, is: N H ¼ N C ¼ 3:82  1015 : Problem Fluor-C60 Derivatives Questions (a) High electronegativity of fullerene C60 allows its use in fabrication of solar cells, in nanoelectronics and nanomedicine. Fluorfullerenes possess a higher electronegativity. The highest polyfluorfullerene is C60F48, obtained by direct fluorination of fullerene. The treatment of C60 with metal fluorides, where metals are in high oxidation numbers (MnF3, CeF4, K2PtF6), leads to fluorfullerenes with lesser fluor content. One of the carbon percentages is 67.82%. Calculate its formula. (b) After completion of the reaction of C60 with AsF5 in liquid SO2 and evaporation of volatile reaction products, a product A was isolated, which contained 65.61 wt.% of carbon. The best yield of A was reached at the ratio С60:AsF5 ¼ 1:3. The obtained compound is a very effective electron acceptor and easily reduced with NaI. In addition, the A revealed a weak electrical conductivity even at r.t. However, in a difference with common polyfluorfullerenes, the A is unstable in air; its reduction product does not contain fluor. Determine the formula of the compound A, offer its posible structure, and write the reaction of its formation and the reaction of A interaction with sodium iodide. Use exact atomic weights. Solutions (a) The compound has a formula С60Fn. The carbon content in this compound is 720.66/(720.66 + 18.998n) ¼ 0.6782. So, 231.908 ¼ 12.884n. Therefore, n ¼ 18. This is С60F18. (b) Let’s first calculate the molecular weight of the compound A. This is 720.66/0.6561 ¼ 1098.4. If the compound A contains carbon and fluor only, this magnitude is close to the molecular formula C60F20. This compound really exists; however, it behaves analogously to other polyfluorfullerenes. If we guess that the A contains also As, the following formulae are possible: С60AsF16 (М ¼ 1099.55), С60As2F12 (М ¼ 1098.48), and С60As3F8 (М ¼ 1097.41). The electrical conductivity of A testifies that this is an ionic compound. The optimal ratio С60:AsF5 for the synthesis of A (1:3) and calculated molecular weight prove in favor of С60As2F12; in what connection the compound has formula C602+(AsF6–)2? It is formed as a result of a redox reaction, where AsF5 is an oxidant, transforming to AsF3: С60 þ 3 AsF5 ¼ C60 2þ ðAsF6  Þ2 þ AsF3  C60 2þ ðAsF6  Þ2 C60 2þ ðAsF6  Þ2 þ 2 NaI ¼ C60 þ 2 NaAsF6 þ I2 Problems for Individual Solution 1. What is maximal possible weight of carbon nanotubes, which can be obtained from 1.00 g of graphite? Reply: 1.00 g. 2. Carbon nanotubes were obtained in 1991 by graphite evaporation in an electric arc followed by aqueous cooling. Another method to get carbon nanotubes is high-temperature decomposition of benzene. In what case is it physical or chemical process? 3. A common method to obtain nanoparticles of simple substances consists in the evaporation of an elemental substance and its further sharp cooling, when vapors enter into a vacuumed camera. When the elements X and Y, whose atomic weights differ in 4.65 times, the nanoclusters form, having sizes in the range 0.7–3.0 nm. The element X forms a wide series of clusters with different sizes. For Y, the main contribution is made by two particles, whose weights are 1.1667:1. The clusters of X burn instantly upon contact with oxygen of air; meanwhile the ingot of the element X is stable in air. On the contrary, the behavior of the element Y in relation with oxygen does not depend in whole on its particle sizes: they are stable at room temperature but are oxidized by heating. Determine the elements X and Y and the composition of nanoparticles of Y. Reply: Fe and C, C60 and C70. 4. Evaluate the thickness of the nanodiamond film, obtained by chemical precipitation from methane on the substrate surface with size 10  10 cm in a camera with volume of 3 L at 1000 K, if the initial pressure of methane was 18 mmHg. The density of diamond is 3.52 g/cm3. Reply: 295 nm. 5. 2D material graphane represents a completely hydrogenated graphite plane. Determine the brutto formula of graphane. Graphane was offered for hydrogen storage. The most important characteristics for storage method is the ratio of the weight

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of “conserved hydrogen” to the weight of the “container.” The higher is this ratio, the better. Where is the hydrogen storage more efficient, in graphane or in a steel tank of 10 kg weight, volume 20 L under 100 bar pressure at r.t.? Reply: CH; in graphane. Questions for Test of Learning of the Material 1. What are carbon allotropes? Examples. 2. What are differences between the structures of diamond, graphite, graphene, graphane, and carbon nanotube? 3. Why the fullerenes and nanotubes are called as “framework” structures? Do they exist in nature? How does this peculiarity influence their mechanical properties? 4. What type of conductivity (metal, dielectric, semiconductor, superconductor) is characteristic for carbon nanotubes? 5. What areas of application do you know for fullerenes and carbon nanotubes? 6. What chemical elements and compounds, additionally to carbon, can form nanotubes? 7. Describe synthesis methods for fullerenes and carbon nanotubes. 8. Discuss the idea of “space elevator” and its advantages and disadvantages. 9. What is the chirality of carbon nanotubes and how it appears? 10. Describe what are the fullerenes and history of their discovery. 11. Describe fullerene structures and physicochemical properties. 12. Describe the synthesis, isolation, and purification of fullerenes. 13. Describe chemical properties of fullerenes including addition reactions and electron transfer reactions. 14. Describe the synthesis, structures, and properties of nanoonions. 15. Describe endohedral fullerene complexes, their structures, synthesis, and applications. 16. Carbon nanotubes: synthesis, structural peculiarities, properties, functionalization, and applications. 17. Carbon nanotubes: solubilization methods (physical, chemical, biological). 18. Carbon nanofibers: synthesis, structural peculiarities, properties, and applications. 19. Graphene: synthesis, structural peculiarities, properties, functionalization, and applications. 20. Theoretically predicted carbon nanostructures. Example: Typical Exam for Beginners in the Nanotechnology Grade____________ Exam___________of __Nanotechnology_______________ Semester _________ Name: __________________________Group: __________Date _____________ I. Total: 50 points (5 points each one) 1. What carbon nanoparticles do you know? (a) Nanotubes, fullerenes (b) Nanotubes, fullerenes, graphene, nanodiamond, carbon black (c) Nanotubes, fullerenes, graphene, carbon black 2. What is the diameter of the C60 fullerene? (a) (b) (c) (d)

10.7 Å 7.10 Å 15.3 nm 7.10 nm

3. What are simple and double measurements in the fullerene structure? (a) (b) (c) (d)

1.40 Å, 1.46 Å 1.46 Å, 1.40 Å Å, 3.7 Å nm, 3.1 nm

4. Can the polymerization of fullerenes take place? (a) Yes (b) No

11.3

Problems and Calculations

753

5. How can the fullerene structure be modified? (a) (b) (c) (d)

By addition or elimination of atoms By new bond formation or breaking bonds By insertion of an atom inside fullerene structure By heating or cooling

6. What types of carbon nanotubes exist? (a) (b) (c) (d)

Metallic, organic Single-wall, multi-wall Single-wall, double-wall, triple-wall, multi-wall Covalent, ionic

7. What atomic arrangements are known for carbon nanotubes? (a) (b) (c) (d)

Chair, zigzag, helicoidal Chair, zigzag Helicoidal Single-wall, multi-wall.

8. What properties and atomic arrangements correspond to the following carbon nanotubes: (21,15), (13,13), (12,16), (22,0), and (19,12)? 9. What Hamada indexes the following fullerenes have?

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10. In 1985, a molecule was discovered and named as: (a) (b) (c) (d) (e) (f)

Giant molecule Rare molecule Fullerene Nanotube Graphene Nanodiamond

II. Total: 45 points (5 points each one) 1. Using tunnel microscopy images, calculate chiral or helicity angle for these nanotubes.

(a) (b) (c) (d) (e)

8 12 30 32 5

2. What techniques were applied to obtain this image?

(a) (b) (c) (d) (e) (f)

TEM SEM with retrodispersed electrons SEM with secondary electrons SEM with characteristic X-rays AFM Tunnel microscopy

11.3

Problems and Calculations

755

3. What techniques were applied to obtain this image?

(a) (b) (c) (d) (e) (f)

TEM SEM with retrodispersed electrons SEM with secondary electrons SEM with characteristic X-rays AFM Tunnel microscopy

4. What techniques were applied to obtain this image? cps/eV C Area.spx

8

C

7 6 5 4 3 2 1 Cu

Cu Cu

0 0

2

(a) (b) (c) (d) (e) (f)

4

keV

TEM SEM with retrodispersed electrons SEM with secondary electrons SEM with characteristic X-rays (elemental analysis) AFM Tunnel microscopy

6

8

10

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5. What techniques were applied to obtain this image?

(a) (b) (c) (d) (e) (f)

TEM SEM with retrodispersed electrons SEM with secondary electrons SEM with characteristic X-rays AFM Tunnel microscopy

6. What electrons do “work” to obtain the image in the range of 1–50 eV?

(a) (b) (c) (d)

Secondary Retrodispersed Characteristic X-rays Luminescence

7. What working modes does AFM have? (a) Contact mode, constant height mode, noncontact mode, dynamic mode (b) Contact mode, noncontact mode (c) Contact mode, noncontact mode, dynamic mode

11.3

Problems and Calculations

8. Calculate the nanoparticle size.

9. Calculate the nanoparticle size.

III. Total: 4 points (2 points each one) 1. In 1959, who is the researcher who talked in the conference about a possibility to construct things from atoms? (a) Richard Feynman (b) Richard Smalley (c) Eric Drexler 2. In what year the atomic force microscopy was discovered? (a) (b) (c) (d)

1985 1982 1986 1989

IV. Total: 1 point Change 14 angstroms to nanometers.

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References 1. Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, H. Yan, One-dimensional nanostructures: synthesis, characterization, and applications. Adv. Mater. 15(5), 353–389 (2003) 2. Y. Li, W. Cai, G. Duan, Ordered micro/nanostructured arrays based on the monolayer colloidal crystals. Chem. Mater. 20(3), 615–624 (2008) 3. M.T. Swihart, Vapor-phase synthesis of nanoparticles. Curr. Opin. Colloid Interface Sci. 8, 127–133 (2003) 4. S. Mourdikoudis, R.M. Pallares, N.T.K. Thanh, Characterization techniques for nanoparticles: comparison and complementarity upon studying nanoparticle properties. Nanoscale 10, 12871 (2018) 5. P.S. Karthik, A.L. Himaja, S. Prakash Singh, Carbon-allotropes: synthesis methods, applications and future perspectives. Carbon Lett. 15(4), 219–237 (2014) 6. J. Hodkiewicz., Raman spectroscopy can detect small changes in the structural morphology of carbon nanomaterials, making it an ideal solution for material sciences (2011), https://www.laboratoryequipment.com/article/2011/06/characterizing-carbon-nanomaterials. Accessed 5 June 2018 7. C.S. Casari, M. Tommasini, R.R. Tykwinskic, A. Milani, Carbon-atom wires: 1-D systems with tunable properties. Nanoscale 8, 4414–4435 (2016) 8. R. Eba Medjo, Characterization of carbon nanotubes, in Physical and Chemical Properties of Carbon Nanotubes, (Intech, Rijeka, 2013) 9. R.M. Jacobberger, R. Machhi, J. Wroblewski, et al., Simple graphene synthesis via chemical vapor deposition. J. Chem. Educ. 92, 1903–1907 (2015) 10. S. Gayathri, P. Jayabal, M. Kottaisamy, V. Ramakrishnan, Synthesis of few layer graphene by direct exfoliation of graphite and a Raman spectroscopic study. AIP Adv. 4, 027116 (2014) 11. Q. Lu, C. Wu, D. Liu, H. Wang, et al., A facile and simple method for synthesis of graphene oxide quantum dots from black carbon. Green Chem. 19, 900–904 (2017) 12. S. Nasimul Alam, N. Sharma, L. Kumar, Synthesis of graphene oxide (GO) by modified hummers method and its thermal reduction to obtain reduced graphene oxide (rGO). Graphene 6, 1–18 (2017). https://doi.org/10.4236/graphene.2017.61001 13. A. Kouloumpis, K. Spyrou, K. Dimos, et al., A bottom-up approach for the synthesis of highly ordered fullerene-intercalated graphene hybrids. Front. Mater. 2(10), 1–8 (2015). https://doi.org/10.3389/fmats.2015.00010 14. M.S.A. Bhuyan, M.N. Uddin, M.M. Islam, et al., Synthesis of graphene. Int. Nano Lett. 6(2), 65–83 (2016) 15. Q. Zheng, J.-K. Kim, Synthesis, structure, and properties of graphene and graphene oxide, in Graphene for Transparent Conductors. Synthesis, Properties and Applications, (Springer, New York, 2015), pp. 29–38 16. K. Hotta, K. Miyazawa, Synthesis and growth investigation of C60 fullerene nanowhiskers. J. Phys. Conf. Ser. 159, 012021 (2009) 17. K.H. Le Ho, S. Campidelli, Synthesis and self-assembly properties of fulleropyrrolidine prepared by Prato reaction. Adv. Nat. Sci. Nanosci. Nanotechnol. 5, 025008 (2014). (6 pp) 18. N. Jayaratna, M. Olmstead, B. Kharisov, H.V.R. Dias, Coinage metal pyrazolates [(3,5-(CF3)2Pz)M]3 (M ¼ Au, Ag, Cu) as buckycatchers. Inorg. Chem. 55(17), 8277–8280 (2016) 19. M. Mojica, J.A. Alonso, F. Méndez, Synthesis of fullerenes. J. Phys. Org. Chem. 26, 526–539 (2013) 20. L.T. Scott, Methods for the chemical synthesis of fullerenes. Angew. Chem. Int. Ed. 43, 4994–5007 (2004) 21. C. Zhang, J. Li, E. Liu, et al., Synthesis of hollow carbon nano-onions and their use for electrochemical hydrogen storage. Carbon 50(10), 3513–3521 (2012) 22. J. Bartelmess, S. Giordani, Carbon nano-onions (multi-layer fullerenes): chemistry and applications. Beilstein J. Nanotechnol. 5, 1980–1998 (2014) 23. O. Mykhailiv, H. Zubyk, M.E. Plonska-Brzezinska, Carbon nano-onions: unique carbon nanostructures with fascinating properties and their potential applications. Inorg. Chim. Acta 468, 49–66 (2017) 24. E.Y. Choi, C.K. Kim, Fabrication of nitrogen-doped nano-onions and their electrocatalytic activity toward the oxygen reduction reaction. Sci. Rep. 7, 4178 (2017) 25. A. Aguilar-Elguézabal, W. Antúnez, G. Alonso, et al., Study of carbon nanotubes synthesis by spray pyrolysis and model of growth. Diam. Relat. Mater. 15(9), 1329–1335 (2006) 26. S.Y. Chen, H.Y. Miao, J.T. Lue, M.S. Ouyang, Fabrication and field emission property studies of multiwall carbon nanotubes. J. Phys. D. Appl. Phys. 37, 273–279 (2004) 27. O. Jasek, P. Synek, L. Zajıckova, M. Elias, V. Kudrle, Synthesis of carbon nanostructures by plasma enhanced chemical vapour deposition at atmospheric pressure. J. Electr. Eng. 61(5), 311–313 (2010) 28. B. Hornbostel, M. Haluska, J. Cech, U. Dettlaff, S. Roth, Arc discharge and laser ablation synthesis of singlewalled carbon nanotubes, in Carbon Nanotubes, ed. by V. N. Popov, P. Lambin (Springer, Berlin, 2006), pp. 1–18 29. M. Keidar, A. Shashurin, O. Volotskova, Y. Raitses, I.I. Beilis, Mechanism of carbon nanostructure synthesis in arc plasma. Phys. Plasmas 17, 057101 (2010) 30. H.W. Zhu, X.S. Li, B. Jiang, et al., Formation of carbon nanotubes in water by the electric-arc technique. Chem. Phys. Lett. 366, 664–669 (2002) 31. J. Liu, M. Shao, X. Chen, et al., Large-scale synthesis of carbon nanotubes by an ethanol thermal reduction process. J. Am. Chem. Soc. 125, 8088–8089 (2003) 32. J. Prasek, J. Drbohlavova, J. Chomoucka, et al., Methods for carbon nanotubes synthesis—review. J. Mater. Chem. 21, 15872–15884 (2011) 33. V. Georgakilas, A.B. Bourlinos, E. Ntararas, et al., Graphene nanobuds: synthesis and selective organic derivatisation. Carbon 110, 51–55 (2016) 34. J. Raula, M. Makowska, J. Lahtinen, et al., Selective covalent functionalization of carbon nanobuds. Chem. Mater. 22(15), 4347–4349 (2010) 35. C.-H. Nee, S.-L. Yap, T.-Y. Tou, et al., Synthesis of nanodiamonds by femtosecond laser irradiation of etanol. Sci. Rep. 6, 33966 (2016) 36. M. Bilal Khan, Z.H. Khan, Nanodiamonds: synthesis and applications, in Nanomaterials and Their Applications, Advanced Structured Materials 84, ed. by Z. H. Khan (Springer Nature, Singapore, 2018). https://doi.org/10.1007/978-981-10-6214-8_1

References

759

37. J.C. Arnault, H.A. Girard, Hydrogenated nanodiamonds: synthesis and surface properties. Curr. Opinion Solid State Mater. Sci. 21, 10–16 (2017) 38. A.A. Fokin, T.S. Zhuk, A.E. Pashenko, et al., Oxygen-doped nanodiamonds: synthesis and functionalizations. Org. Lett. 11(14), 3068–3071 (2009) 39. J.E. Butler, A.V. Sumant, The CVD of nanodiamond materials. Chem. Vap. Dep. 14(7–8), 145–160 (2008) 40. A. Stacey, I. Aharonovich, S. Prawer, J.E. Butler, Controlled synthesis of high quality micro/nano-diamonds by microwave plasma chemical vapor deposition. Diam. Relat. Mater. 18(1), 51–55 (2009) 41. Q. Wang, R. Kitaura, Y. Yamamoto, S. Arai, H. Shinohara, Synthesis and TEM structural characterization of C60-flattened carbon nanotube nanopeapods. Nano Res. 7(12), 1843–1848 (2014) 42. T. Okazaki, Chapter 10 – Preparation and properties of carbon nanopeapods, in Carbon Nanotubes and Graphene, ed. by K. Tanaka, S. Iijima, 2nd edn. (Elsevier, Amsterdam, 2014), pp. 225–252 43. E. Hernández, V. Meunier, B.W. Smith, et al., Fullerene coalescence in nanopeapods: a path to novel tubular carbon. Nano Lett. 3(8), 1037–1042 (2003) 44. M. Velasquez, C. Batiot-Dupeyrat, J. Gallego, J.J. Fernández, A. Santamaria, Synthesis of carbon nano-chains from glycerol-ethanol decomposition over Ni-Fe alloy catalyst. Diam. Relat. Mater. 70, 105–113 (2016) 45. M. Zhang, C. He, E. Liu, et al., Activated carbon nanochains with tailored micro-meso pore structures and their application for supercapacitors. J. Phys. Chem. C 119, 21810–21817 (2015) 46. M. Zhang, N. Zhao, J. Sha, et al., Synthesis of novel carbon nano-chains and their application as supercapacitors. J. Mater. Chem. A 2, 16268–16275 (2014) 47. S. Kumar Sonkar, M. Saxena, M. Saha, S. Sarkar, Carbon nanocubes and nanobricks from pyrolysis of rice. J. Nanosci. Nanotechnol. 10, 4064–4067 (2010) 48. R. Ravindra, B. Badekai Ramachandra, High yield synthesis of carbon nanofibers in an environmental friendly route. Appl. Nanosci. 1(2), 103–108 (2011) 49. J. Ren, F.-F. Li, J. Lau, et al., One-pot synthesis of carbon nanofibers from CO2. Nano Lett. 15, 6142–6148 (2015) 50. N. Díaz Silva, B. Valdez Salas, N. Nedev, et al., Synthesis of carbon nanofibers with maghemite via a modified sol-gel technique. J. Nanomater. 2017, 5794312 (2017). (10 pp) 51. G. Zou, D. Zhang, C. Dong, et al., Carbon nanofibers: synthesis, characterization, and electrochemical properties. Carbon 44, 828–832 (2006) 52. Y. Shen, L. Yan, H. Song, J. Yang, et al., A general strategy for the synthesis of carbon nanofibers from solid carbon materials. Angew. Chem. 51(49), 12202–12205 (2012) 53. C.-T. Lin, T.-H. Chen, T.-S. Chin, C.-Y. Lee, H.-T. Chiu, Quasi two-dimensional carbon nanobelts synthesized using a template method. Carbon 46, 741–746 (2008) 54. J. Liu, M. Shao, Q. Tang, S. Zhang, Y. Qian, Synthesis of carbon nanotubes and nanobelts through a medial-reduction method. J. Phys. Chem. B 107, 6329–6332 (2003) 55. G. Povie, Y. Segawa, T. Nishihara, et al., Synthesis of a carbon nanobelt. Science 356(6334), 172–175 (2017) 56. X. Lu, J. Wu, After 60 years of efforts: the chemical synthesis of a carbon nanobelt. Chem 2(5), 619–620 (2017) 57. T. Ouyang, K. Cheng, F. Yang, et al., From biomass with irregular structures to 1D carbon nanobelts: a stripping and cutting strategy to fabricate high performance supercapacitor materials. J. Mater. Chem. A 5, 14551–14561 (2017) 58. C. Su, C. Pei, B. Wu, J. Qian, Y. Tan, Highly doped carbon nanobelts with ultrahigh nitrogen content as high-performance supercapacitor materials. Small 13, 1700834 (2017) 59. X. Wang, C. Zhao, T. Deng, et al., From amorphous carbon to carbon nanobelts and vertically oriented graphene nanosheets synthesized by plasma-enhanced chemical vapor deposition. Chem. Res. Chin. Univ. 29, 755–758 (2013) 60. J. Li, S. Qi Yap, S. Lee Yoong, et al., Carbon nanotube bottles for incorporation, release and enhanced cytotoxic effect of cisplatin. Carbon 50, 1625–1634 (2012) 61. J. Li, Y. Wang, Q. Wei, et al., Plasma-enhanced synthesis of carbon nanocone arrays by magnetic and electric fields coupling HFCVD. Surf. Coat. Technol. 324, 413–418 (2017) 62. J.A. Jaszczak, G.W. Robinson, S. Dimovski, Y. Gogotsi, Naturally occurring graphite cones. Carbon 41, 2085–2092 (2003) 63. M. Yudasaka, S. Iijima, V.H. Crespi, Single-wall carbon nanohorns and nanocones, in Carbon Nanotubes. Topics in Applied Physics, ed. by A. Jorio, G. Dresselhaus, M. S. Dresselhaus, vol. 111 (Springer, Berlin, Heidelberg, 2007), pp. 605–629 64. Y. Gogotsi, S. Dimovski, J.A. Libera, Conical crystals of graphite. Carbon 40(12)., 2002), 2263–2267 (2002) 65. A.G. Zestos, C. Yang, C.B. Jacobs, D. Hensley, B. Jill Venton, Carbon nanospikes grown on metal wires as microelectrode sensors for dopamine. Analyst 140(21), 7283–7292 (2015) 66. L.B. Sheridan, D.K. Hensley, N.V. Lavrik, et al., Growth and electrochemical characterization of carbon nanospike thin film electrodes. J. Electrochem. Soc. 161(9), H558–H563 (2014) 67. H. Wang, J. Wang, S. Xie, W. Liu, C. Niu, Template synthesis of graphitic hollow carbon nanoballs as supports for SnOx nanoparticles towards enhanced lithium storage performance. Nanoscale 10, 6159–6167 (2018) 68. W. Chen, Q. Li, Y. Chen, P. Dai, Z. Jiang, Preparation of carbon nanoball from starch by arc discharge. Adv. Mater. Res. 476–478, 1533–1536 (2012) 69. K. Pan, H. Ming, Y. Liu, Z. Kang, Large scale synthesis of carbon nanospheres and their application as electrode materials for heavy metal ions detection. New J. Chem. 36, 113–118 (2012) 70. P. Karna, M. Ghimire, S. Mishra, S. Karna, Synthesis and characterization of carbon nanospheres. Open Access Library J. 4, e3619 (2017) 71. R. Vié, E. Drahi, O. Baudino, S. Blayac, S. Berthon-Fabry, Synthesis of carbon nanospheres for the development of inkjet-printed resistive layers and sensors. Flexible Printed Electron. 1, 015003 (2016) 72. A. Pramanik, S. Biswas, A.K. Kole, et al., Template-free hydrothermal synthesis of amphibious fluorescent carbon nanorice towards anticounterfeiting applications and unleashing its nonlinear optical properties. RSC Adv. 6, 99060–99071 (2016)

760

11

Student Zone: Overview, Training, Practices, and Exercises

73. P. Sekar Parasuraman, H.-C. Tsai, T. Imae, et al., In-situ hydrothermal synthesis of carbon nanorice using Nafion as a template. Carbon 77, 660–666 (2014) 74. K. Sai Krishna, M. Eswaramoorthy, Novel synthesis of carbon nanorings and their characterization. Chem. Phys. Lett. 433, 327–330 (2007) 75. I.-L. Chang, J.-W. Chou, A molecular analysis of carbon nanotori formation. J. Appl. Phys. 112, 063523 (2012) 76. G. Li, H. Yu, L. Xu, et al., General synthesis of carbon nanocages and their adsorption of toxic compounds from cigarette smoke. Nanoscale 3, 3251–3257 (2011) 77. S. Xiang, Y. Shi, K. Zhang, et al., Design and synthesis of dodecahedral carbon nanocages incorporated with Fe3O4. RSC Adv. 7, 13257–13262 (2017) 78. D.A. Ziolkowska, J.S.D. Jangam, G. Rudakov, T.M. Paronyan, M. Akhtar, G.U. Sumanasekera, J.B. Jasinski, Simple synthesis of highly uniform bilayer-carbon nanocages. Carbon 115, 617–624 (2017) 79. Y. Tan, C. Xu, G. Chen, et al., Synthesis of ultrathin nitrogen-doped graphitic carbon nanocages as advanced electrode materials for supercapacitor. ACS Appl. Mater. Interfaces 5, 2241–2248 (2013) 80. J. Xiang, T. Song, One-pot synthesis of multicomponent (Mo, Co) metal sulfide/carbon nanoboxes as anode materials for improving Na-ion storage. Chem. Commun. 53, 10820–10823 (2017) 81. H. Hu, J. Zhang, B. Guan, X. Wen (David) Lou, Unusual formation of CoSe@carbon nanoboxes, which have an inhomogeneous shell, for efficient lithium storage. Angew. Chem. Int. Ed. 55, 9514–9518 (2016) 82. Y. Hayashi, N. Takada, Wahyudiono, H. Kanda, M. Goto, One-step synthesis of water–dispersible carbon nanocapsules by pulsed arc discharge over aqueous solution under pressurized argon. Res. Chem. Intermed. 43, 4201–4211 (2017) 83. B. Quan, G.-E. Nam, H. Jae Choi, Y. Piao, Synthesis of monodisperse hollow carbon nanocapsules by using protective silica shells. Chem. Asian J. 8(4), 765–770 (2013) 84. P. Wu, N. Du, H. Zhang, J. Yu, D. Yang, Carbon nanocapsules as nanoreactors for controllable synthesis of encapsulated Iron and iron oxides: magnetic properties and reversible lithium storage. J. Phys. Chem. C 115, 3612–3620 (2011) 85. T.-C. Liu, Y.-Y. Li, Synthesis of carbon nanocapsules and carbon nanotubes by an acetylene flame method. Carbon 44, 2045–2050 (2006) 86. D. Jain, A. Winkel, R. Wilhelm, Solid-state synthesis of well-defined carbon nanocapsules from organometallic precursors. Small 2(6), 752–755 (2006) 87. B. Xu, J. Guo, X. Wang, et al., Synthesis of carbon nanocapsules containing Fe, Ni or Co by arc discharge in aqueous solution. Carbon 44, 2631–2634 (2006) 88. T. Kizuka, K. Miyazawa, D. Matsuura, Synthesis of carbon nanocapsules and nanotubes using Fe-doped fullerene nanowhiskers. J. Nanotechnol. 2012, 613746 (2012). (6 pp) 89. Z. Yao, X. Zhu, X. Li, Y. Xie, Synthesis of novel Y-junction hollow carbon nanotrees. Carbon 45, 1566–1570 (2007) 90. Z. He, J.-L. Maurice, C. Seok Lee, C. Sorin Cojocarub, D. Pribat, Growth mechanisms of carbon nanostructures with branched carbon nanofibers synthesized by plasma-enhanced chemical vapour deposition. CrystEngComm 16, 2990–2995 (2014) 91. T.-N. Ye, L.-B. Lv, X.-H. Li, M. Xu, J.-S. Chen, Strongly veined carbon nanoleaves as a highly efficient metal-free electrocatalyst. Angew. Chem. Int. Ed. 53, 6905–6909 (2014) 92. X. Lepro, M.D. Lima, R.H. Baughman, Spinnable carbon nanotube forests grown on thin, flexible metallic substrates. Carbon 48, 3621–3627 (2010) 93. G. Chen, D.N. Futaba, K. Hata, Catalysts for the growth of carbon nanotube “forests” and superaligned arrays. MRS Bull. 42, 802–808 (2017) 94. K.K.S. Lau, J. Bico, K.B.K. Teo, et al., Superhydrophobic carbon nanotube forests. Nano Lett. 3(12), 1701–1705 (2003) 95. N. Yang, M. Li, J. Patscheider, S. Ki Youn, H. Gyu Park, A forest of sub-1.5-nm-wide single-walled carbon nanotubes over an engineered alumina support. Sci. Rep. 7, 46725 (2017) 96. Y.B. Zhang, S.P. Lau, Field emission from nanoforest carbon nanotubes grown on cobalt-containing amorphous carbon omposite films. J. Appl. Phys. 101, 033524 (2007) 97. J. Du, Z. Liu, Z. Li, B. Han, Z. Sun, Y. Huang, Carbon nanoflowers synthesized by a reduction–pyrolysis–catalysis route. Mater. Lett. 59, 456–458 (2005) 98. B.I. Kharisov, A review for synthesis of nanoflowers. Recent Pat. Nanotechnol. 2(3), 190–200 (2008) 99. H. Heli, A. Rahi, Synthesis and applications of nanoflowers. Recent Pat. Nanotechnol. 10(2), 86–115 (2016) 100. S. Thongtem, P. Singjai, T. Thongtem, S. Preyachoti, Growth of carbon nanoflowers on glass slides using sparked iron as a catalyst. Mater. Sci. Eng. A 423, 209–213 (2006) 101. M. Wei, C. Terashima, M. Lv, A. Fujishima, Z.-Z. Gu, Boron-doped diamond nanograss array for electrochemical sensors. Chem. Commun., 3624–3626 (2009) 102. M. Wei, G. Ying Zeng, Y. Liu, Q. Lu, Detection of heavy metals based on boron-doped diamond nanograss array, boron-doped diamond film and glassy carbon electrodes. Asian J. Chem. 25(2), 861–863 (2013) 103. Y. Luo, D. Kong, Y. Jia, et al., Self-assembled graphene@PANI nanoworm composites with enhanced supercapacitor performance. RSC Adv. 3, 5851–5859 (2013) 104. Y. Piao, K. An, J. Kim, T. Yu, T. Hyeon, Sea urchin shaped carbon nanostructured materials: carbon nanotubes immobilized on hollow carbon spheres. J. Mater. Chem. 16, 2984–2989 (2006) 105. Y. Wang, Z. Jun Han, S. Fung Yu, et al., Core-leaf onion-like carbon/MnO2 hybrid nano-urchins for rechargeable lithium-ion batteries. Carbon 64, 230–236 (2013) 106. E.J. Hwang, S.K. Lee, M.G. Jeong, Y.B. Lee, D.S. Lim, Synthesis of sea urchin-like carbon nanotubes on nano-diamond powder. J. Nanosci. Nanotechnol. 12(7), 5875–5879 (2012) 107. Y. Yao, C. Lian, G. Wu, et al., Synthesis of “sea urchin”-like carbon nanotubes/porous carbon superstructures derived from waste biomass for treatment of various contaminants. Appl. Catal. B Environ. 219, 563–571 (2017) 108. X. Hoa Nguen, Y. Bok Lee, C. Hyun Lee, D.-S. Lim, Synthesis of sea urchin-like particles of carbon nanotubes directly grown on stainless steel cores and their effect on the mechanical properties of polymer composites. Carbon 48(10), 2910–2916 (2010)

References

761

109. N. Jia, Y. Shi, S. Zhang, X. Chen, P. Chen, Z. An, Carbon nanobowls supported ultrafine palladium nanocrystals: a highly active electrocatalyst for the formic acid oxidation. Int. J. Hydrog. Energy 42, 8255–8263 (2017) 110. C. Cui, X. Li, Z. Hu, J. Xu, H. Liu, J. Ma, Growth of MoS2@C nanobowls as a lithium-ion battery anode material. RSC Adv. 5, 92506–92514 (2015) 111. A.S.H. Razi, K.Y. Jin, P. Yong-Ki, L. Chul Wee, Nano bowls of carbon by oxidative chopping of carbon nano sphere. Chem. Lett. 36(10), 1202–1203 (2007) 112. M. Gwan Hahm, A. Leela Mohana Reddy, D.P. Cole, et al., Carbon nanotubes-nanocups hybrid structures for high power supercapacitor applications. Nano Lett. 12(11), 5616–5621 (2012) 113. S. Majeed, J. Zhao, L. Zhang, S. Anjum, Z. Liu, G. Xu, Synthesis and electrochemical applications of nitrogen-doped carbon nanomaterials. Nanotechnol. Rev. 2(6), 615–635 (2013) 114. B. Kumar Gupta, G. Kedawat, P. Kumar, et al., Field emission properties of highly ordered low-aspect ratio carbon nanocup arrays. RSC Adv. 6, 9932–9939 (2016) 115. J. Cao, C.J. Jafta, J. Gong, et al., Synthesis of dispersible mesoporous nitrogen-doped hollow carbon nanoplates with uniform hexagonal morphologies for supercapacitors. ACS Appl. Mater. Interfaces 8, 29628–29636 (2016) 116. Y. Soo Yun, S. Youn Cho, J. Shim, et al., Microporous carbon nanoplates from regenerated silk proteins for supercapacitors. Adv. Mater. 25, 1993–1998 (2013) 117. Y. Soo Yun, K.-Y. Park, B. Lee, et al., Sodium-ion storage in pyroprotein-based carbon nanoplates. Adv. Mater. 27, 6914–6921 (2015) 118. M.E. Lee, N.R. Kim, M.Y. Song, H.-J. Jin, Microporous carbon nanoplate/amorphous ruthenium oxide hybrids as supercapacitor electrodes. J. Nanosci. Nanotechnol. 16(10), 10431–10436 (2016) 119. Y. Wei, F. Yan, X. Tang, et al., Solvent-controlled synthesis of NiOCoO/carbon fiber nanobrushes with different densities and their excellent properties for lithium ion storage. ACS Appl. Mater. Interfaces 7, 21703–21711 (2015) 120. NEC, NEC discovers “carbon nanobrush,” the world’s first fibrous aggregate of carbon nanohorns (30 June 2016), https://www.nec.com/en/ press/201606/global_20160630_01.html. Accessed 26 Apr 2018 121. A. Cao, V.P. Veedu, X. Li, et al., Multifunctional brushes made from carbon nanotubes. Nat. Mater. 4, 540–545 (2005) 122. R. Villegas Salvatierra, D. Zakhidov, J. Sha, et al., Graphene carbon nanotube carpets grown using binary catalysts for high-performance lithium-ion capacitors. ACS Nano 11, 2724–2733 (2017) 123. P. Szroeder, N.G. Tsierkezos, P. Scharff, U. Ritter, Electrocatalytic properties of carbon nanotube carpets grown on Si-wafers. Carbon 48, 4489–4496 (2010) 124. F. Seichepine, S. Salomon, M. Collet, et al., A combination of capillary and dielectrophoresis-driven assembly methods for wafer scale integration of carbon-nanotube-based nanocarpets. Nanotechnology 23, 095303 (2012). (7 pp) 125. S. Hu, Y. Dong, J. Yang, J. Liu, S. Cao, Formation and nonlinear optical properties of carbon nanospindles from laser ablation. CrystEngComm 14, 4243–4246 (2012) 126. H.-D. Lim, Y. Soo Yun, Y. Ko, et al., Three-dimensionally branched carbon nanowebs as air-cathode for redox-mediated Li-O2 batteries. Carbon 118, 114–119 (2017) 127. Q. Huang, L. Liu, D. Wang, J. Liu, Z. Huang, Z. Zheng, One-step electrospinning of carbon nanowebs on metallic textiles for high-capacitance supercapacitor fabrics. J. Mater. Chem. A 4, 6802–6808 (2016) 128. H. Eun Cho, S. Jung Seo, M.-S. Khil, H. Kim, Preparation of carbon nanoweb from cellulose nanowhisker. Fibers Polym. 16(2), 271–275 (2015) 129. L. Li, A. Manthiram, O- and N-doped carbon nanowebs as metal-free catalysts for hybrid li-air batteries. Adv. Energy Mater. 4(10), 1301795 (2014) 130. S. Luo, Y. Luo, H. Wu, et al., Self-assembly of 3D carbon nanotube sponges: a simple and controllable way to build macroscopic and ultralight porous architectures. Adv. Mater. 29, 1603549 (2017) 131. X. Gui, J. Wei, K. Wang, et al., Carbon nanotube sponges. Adv. Mater. 22, 617–621 (2010) 132. X. Gui, H. Li, K. Wang, et al., Recyclable carbon nanotube sponges for oil absorption. Acta Mater. 59, 4798–4804 (2011) 133. K. Zhu, Y.-Y. Shang, P.-Z. Sun, et al., Oil spill cleanup from sea water by carbon nanotube sponges. Front. Mater. Sci. 7(2), 170–176 (2013) 134. Z.-Y. Huo, Y. Luo, X. Xie, et al., Carbon-nanotube sponges enabling highly efficient and reliable cell inactivation by low-voltage electroporation. Environ. Sci. Nano 4, 2010–2017 (2017) 135. N. Frese, S. Taylor Mitchell, A. Bowers, A. Gölzhäuser, K. Sattler, Diamond-like carbon nanofoam from low-temperature hydrothermal carbonization of a sucrose/naphthalene precursor solution. J. Carbon Res. 3, 23 (2017) 136. N. Frese, S. Taylor Mitchell, C. Neumann, A. Bowers, A. Gölzhäuser, K. Sattler, Fundamental properties of high-quality carbon nanofoam: from low to high density. Beilstein J. Nanotechnol. 7, 2065–2073 (2016) 137. D. Li, L. Pan, J. Qian, D. Liu, Highly efficient synthesis of carbon nanocoils by catalyst particles prepared by a sol–gel method. Carbon 48, 170–175 (2010) 138. S. Vaudreuil, M. Bousmina, Stretchable carbon nanosprings production by a catalytic growth process. J. Nanosci. Nanotechnol. 9(8), 4880–4885 (2009) 139. Y.J. Lee, S.R. Ham, J.H. Kim, et al., Highly dispersible buckled nanospring carbon nanotubes for polymer nano composites. Sci. Rep. 8, 4851 (2018) 140. D. Li, L. Pan, K. Liu, W. Peng, Growth of multiwall carbon nanocoils using Fe catalyst films prepared by ion sputtering. J. Mater. Res. 28(10), 1316–1325 (2013) 141. L. Liu, J. Zhao, Toroidal and coiled carbon nanotubes, in Syntheses and Applications of Carbon Nanotubes and Their Composites, (Intech, Rijeka, 2013), pp. 257–281 142. R. Cui, L. Pan, C. Deng, Synthesis of carbon nanocoils on substrates made of plant fibers. Carbon 89, 47–52 (2015) 143. N. Tang, W. Kuo, C. Jeng, et al., Coil-in-coil carbon nanocoils: 11 gram-scale synthesis, single nanocoil electrical properties, and electrical contact improvement. ACS Nano 4(2), 781–788 (2010)

762

11

Student Zone: Overview, Training, Practices, and Exercises

144. Y. Shang, C. Hua, W. Xu, et al., Meter-long spiral carbon nanotube fibers show ultrauniformity and flexibility. Nano Lett. 16, 1768–1775 (2016) 145. E.-X. Ding, J. Wang, H.-Z. Geng, et al., Y-junction carbon nanocoils: synthesis by chemical vapor deposition and formation mechanism. Sci. Rep. 5, 11281 (2015) 146. K. Mae, H. Toyama, E. Nawa-Okita, et al., Self-organized micro-spiral of single-walled carbon nanotubes. Sci. Rep. 7, 5267 (2017) 147. A. Shaikjee, N.J. Coville, The synthesis, properties and uses of carbon materials with helical morphology. J. Adv. Res. 3, 195–223 (2012) 148. X. Liu, X. Tang, Y. Hou, Q. Wu, G. Zhang, Fluorescent nanothermometers based on mixed shell carbon nanodots. RSC Adv. 5, 81713–81722 (2015) 149. D. Castelvecchi, Nanothermometer takes the temperature of living cells (31 July 2013). https://www.nature.com/news/nanothermometer-takesthe-temperature-of-living-cells-1.13473. Accessed 28 Apr 2018 150. Y. Gao, Y. Bando, Nanotechnology: carbon nanothermometer containing gallium. Nature 415, 599 (2002) 151. S. Akita, Y. Nakayama, et al., Nanotweezers consisting of carbon nanotubes operating in an atomic force microscope. Appl. Phys. Lett. 79(11), 1691–1693 (2001) 152. C.-H. Ke, N. Pugno, B. Peng, H.D. Espinosa, Experiments and modeling of carbon nanotube-based NEMS devices. J. Mech. Phys. Solids 53, 1314–1333 (2005) 153. J. Chang, B.-K. Min, J. Kim, S.-J. Lee, L. Lin, Electrostatically actuated carbon nanowire nanotweezers. Smart Mater. Struct. 18, 065017 (2009). (7 pp) 154. J. Zare, A. Shateri, Instability threshold of rippled carbon nanotube nanotweezers in the low vacuum gas flow incorporating Dirichlet and Neumann modes of Casimir energy. Physica E 90, 67–75 (2017) 155. T. Sasaki, J.-F. Morin, M. Lu, J.M. Tour, Synthesis of a single-molecule nanotruck. Tetrahedron Lett. 48, 5817–5820 (2007) 156. S.S. Konyukhov, N.N. Artemov, I.A. Kaliman, I.V. Kupchenko, A.V. Nemukhin, A.A. Moskovskii, Electrostatically actuated carbon nanowire nanotweezers. Mosc. Univ. Chem. Bull. 65(4), 219–220 (2010) 157. A. Nemati, H. Nejat Pishkenari, A. Meghdari, S. Sohrabpour, Directing the diffusive motion of fullerene-based nanocars using nonplanar gold surfaces. Phys. Chem. Chem. Phys. 20, 332–344 (2018) 158. M. Ghorbanzadeh Ahangari, M. Darvish Ganji, A. Jalali, Interaction between fullerene-wheeled nanocar and gold substrate: a DFT study. Physica E 83, 174–179 (2016) 159. AZoNano, Nanocars and nanoguitars leading to better understanding of construction and properties of materials at the nanoscale (24 Jan 2007.), https://www.azonano.com/article.aspx?ArticleID¼1831. Accessed 29 Apr 2018 160. G. Vives, J.M. Tour, Synthesis of single-molecule nanocars. Acc. Chem. Res. 2(3), 473–487 (2009) 161. D. Wang, Y. Wang, H. Liu, W. Xu, L. Xu, Unusual carbon nanomesh constructed by interconnected carbon nanocages for ionic liquid-based supercapacitor with superior rate capability. Chem. Eng. J. 342, 474–483 (2018) 162. D. Wang, S. Liu, L. Jiao, G. Fang, G. Geng, J. Ma, Unconventional mesopore carbon nanomesh prepared through explosioneassisted activation approach: a robust electrode material for ultrafast organic electrolyte supercapacitors. Carbon 119, 30–39 (2017) 163. H. Wang, L. Zhi, K. Liu, et al., Thin-sheet carbon nanomesh with an excellent electrocapacitive performance. Adv. Funct. Mater. 25, 5420–5427 (2015) 164. H. Kohno, T. Hasegawa, Chains of carbon nanotetrahedra/nanoribbons. Sci. Rep. 5, 8430 (2015) 165. H. Kohno, Y. Masuda, In situ transmission electron microscopy of individual carbon nanotetrahedron/ribbon structures in bending. Appl. Phys. Lett. 106, 193103 (2015) 166. T. Hasegawaa, H. Kohno, Splitting and joining in carbon nanotube/nanoribbon/nanotetrahedron growth. Phys. Chem. Chem. Phys. 17, 3009–3013 (2015) 167. A. Yamauchi, H. Kohno, Verification of mechanism for the formation of carbon nanotetrahedra using Electron beam tomography. J. Nanosci. Nanotechnol. 17(1), 842–845 (2017) 168. B. Sun, S. Chen, H. Liu, G. Wang, Mesoporous carbon nanocube architecture for high-performance lithium–oxygen batteries. Adv. Funct. Mater. 25, 4436–4444 (2015) 169. C.M. Lentz, B.A. Samuel, H.C. Foley, M.A. Haque, Synthesis and characterization of glassy carbon nanowires. J. Nanomater. 2011, 129298 (2011). (8 pp) 170. X.-L. Wu, T. Wen, H.-L. Guo, S. Yang, X. Wang, A.-W. Xu, Biomass-derived sponge-like carbonaceous hydrogels and aerogels for supercapacitors. ACS Nano 7(4), 3589–3597 (2013) 171. W. Li, S. Wang, Y. Li, et al., One-step hydrothermal synthesis of fluorescent nanocrystallinecellulose/carbon dot hydrogels. Carbohydr. Polym. 175, 7–17 (2017) 172. C.S. Sharma, M.M. Kulkarni, A. Sharma, M. Madou, Synthesis of carbón xerogel particles and fractal-like structures. Chem. Eng. Sci. 64, 1536–1543 (2009) 173. M. Kakunuri, S. Vennamalla, C.S. Sharma, Synthesis of carbon xerogel nanoparticles by inverse emulsion polymerization of resorcinol– formaldehyde and their use as anode materials for lithium-ion battery. RSC Adv. 5, 4747–4753 (2015) 174. E.J. Zanto, S.A. Al-Muhtaseb, J.A. Ritter, Sol-gel-derived carbon aerogels and xerogels: design of experiments approach to materials synthesis. Ind. Eng. Chem. Res. 41, 3151–3162 (2002) 175. M.-F. Yan, L.-H. Zhang, R. He, Z.-F. Liu, Synthesis and characterization of carbon aerogels with different catalysts. J. Porous. Mater. 22, 699–703 (2015) 176. E.G. Calvo, C.O. Ania, L. Zubizarreta, J.A. Menendez, A. Arenillas, Exploring new routes in the synthesis of carbon xerogels for their application in electric double-layer capacitors. Energy Fuel 24, 3334–3339 (2010) 177. J. Shen, D.Y. Guan, Preparation and application of carbon aerogels, in Aerogels Handbook, Advances in Sol-Gel Derived Materials and Technologies, ed. by M. A. Aegerter et al. (Springer Science+Business Media, LLC, Dordrecht, 2011). https://doi.org/10.1007/978-1-44197589-8_36 178. P.S. Skell, L.M. Jackman, S. Ahmed, M.L. McKee, P.B. Shedin, Some reactions and properties of molecular Cz. An experimental and theoretical treatment. J. Am. Chem. Soc. 111, 4422–4429 (1989)

References

763

179. C.G. Parigger, J.O. Hornkohl, A.M. Keszler, L. Nemes, Measurement and analysis of atomic and diatomic carbon spectra from laser ablation of graphite. Appl. Opt. 42(30), 6192–6198 (2003) 180. Q. Sun, L. Cai, S. Wang, et al., Bottom-up synthesis of metalated carbyne. J. Am. Chem. Soc. 138, 1106–1109 (2016) 181. C.S. Casari, C.S. Giannuzzi, V. Russo, Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas. Carbon 104, 190–195 (2016) 182. C.B. Cannella, N. Goldman, Carbyne fiber synthesis within evaporating metallic liquid carbon. J. Phys. Chem. C 119, 21605–21611 (2015) 183. A. Kucherik, A. Antipov, S. Kutrovskaya, A. Osipov, A. Povolotckaia, S. Arakelian, Metal-carbyne clusters for SERS realization. J. Phys. Conf. Ser. 951, 012020 (2018) 184. J.B. Wallace, D. Chen, L. Shao, Carbon displacement-induced single carbon atomic chain formation and its effects on sliding of SiC fibers in SiC/graphene/SiC composite. Mater. Res. Lett. 4(1), 55–61 (2016) 185. C.S. Casari, M. Tommasini, R.R. Tykwinski, A. Milani, Carbon-atom wires: 1-D systems with tunable properties. Nanoscale 8, 4414–4435 (2016) 186. L. Giacomo Bettini, F. Della Foglia, P. Piseri, P. Milani, Interfacial properties of a carbyne-rich nanostructured carbon thin film in ionic liquid. Nanotechnology 27, 115403 (2016). (6 pp) 187. S. Li, G. Ji, Z. Huang, F. Zhang, Y. Du, Synthesis of chaoite-like macrotubes at low temperature and ambient pressure. Carbon 45, 2946–2950 (2007) 188. A. Fadllan, P. Marwoto, M.P. Aji, Susanto, R.S. Iswari, Synthesis of carbon nanodots from waste paper with hydrothermal method. AIP Conf. Proc. 1788, 030069 (2017) 189. J. Prakash Naik, P. Sutradhar, M. Saha, Molecular scale rapid synthesis of graphene quantum dots (GQDs). J. Nanostruct. Chem. 7, 85–89 (2017) 190. C. Kiang Chua, Z. Sofer, P. Simek, et al., Synthesis of strongly fluorescent graphene quantum dots by cage-opening buckminsterfullerene. ACS Nano 9(3), 2548–2555 (2015) 191. H. Li, Z. Kang, Y. Liu, S.-T. Lee, Carbon nanodots: synthesis, properties and applications. J. Mater. Chem. 22, 24230–24253 (2012) 192. P. Roy, P.-C. Chen, A. Prakash Periasamy, Y.-N. Chen, H.-T. Chang, Photoluminescent carbon nanodots: synthesis, physicochemical properties and analytical applications. Mater. Today 18(8), 447–458 (2015) 193. S. Kellici, J. Acord, N.P. Power, et al., Rapid synthesis of graphene quantum dots using a continuous hydrothermal flow synthesis approach. RSC Adv. 7, 14716–14720 (2017) 194. H. Teymourinia, M. Salavati-Niasari, O. Amiri, H. Safardoust-Hojaghan, Synthesis of graphene quantum dots from corn powder and their application in reduce charge recombination and increase free charge carriers. J. Mol. Liq. 242, 447–455 (2017) 195. M. Ozhukil Valappil, V.K. Pillai, S. Alwarappan, Spotlighting graphene quantum dots and beyond: synthesis, properties and sensing applications. Appl. Mater. Today 9, 350–371 (2017) 196. G.N. Yushin, E.N. Hoffman, A. Nikitin, et al., Synthesis of nanoporous carbide-derived carbon by chlorination of titanium silicon carbide. Carbon 43, 2075–2082 (2005) 197. M.R. Lukatskaya, J. Halim, B. Dyatkin, et al., Room-temperature carbide-derived carbon synthesis by electrochemical etching of MAX phases. Angew. Chem. 126, 4977–4980 (2014) 198. J. Gläsel, J. Diao, Z. Feng, et al., Mesoporous and graphitic carbide-derived carbons as selective and stable catalysts for the dehydrogenation reaction. Chem. Mater. 27, 5719–5725 (2015) 199. L. Zhang, X. Qin, G. Shao, et al., A new route for preparation of titanium carbide derived carbon and its performance for supercapacitors. Mater. Lett. 122, 78–81 (2014) 200. E.N. Hoffman, G. Yushin, B.G. Wendler, et al., Carbide-derived carbon membrane. Mater. Chem. Phys. 112, 587–591 (2008) 201. B. Kruner, C. Odenwald, A. Tolosa, et al., Carbide-derived carbon beads with tunable nanopores from continuously produced polysilsesquioxanes for supercapacitor electrodes. Sustain. Energy Fuels 1, 1588–1600 (2017) 202. A.H. Farmahini, D.S. Sholl, S.K. Bhatia, Fluorinated carbide-derived carbon: more hydrophilic, yet apparently more hydrophobic. J. Am. Chem. Soc. 137, 5969–5979 (2015) 203. Y.-X. Zhou, Y.-Z. Chen, L. Cao, et al., Conversion of metalorganic framework to N-doped porous carbon incorporating Co and CoO nanoparticles: direct oxidation of alcohols to esters. Chem. Commun. 51, 8292–8295 (2015) 204. X. Feng, X. Bo, L. Guo, CoM (M ¼ Fe, Cu, Ni)-embedded nitrogen-enriched porous carbon framework for efficient oxygen and hydrogen evolution reactions. J. Power Sources 389, 249–259 (2018) 205. D. Chen, C. Chen, W. Shen, et al., MOF-derived magnetic porous carbon-based sorbent: synthesis, characterization, and adsorption behavior of organic micropollutants. Adv. Powder Technol. 28(7), 1769–1779 (2017) 206. M. Hui Yap, K. Loon Fow, G. Zheng Chen, Synthesis and applications of MOF-derived porous nanostructures. Green Energy Environ. 2, 218–245 (2017) 207. X.-F. Guo, G.-J. Kim, Synthesis of ultrafine carbon black by pyrolysis of polymers using a direct current thermal plasma process. Plasma Chem. Plasma Process. 30, 75–90 (2010) 208. J.J. Ivie, L.J. Forney, A numerical model of the synthesis of carbon black by benzene pyrolysis. AlChE J. 34(11), 1813–1820 (1988) 209. Q. Li, Y. Li, Y. Chen, L. Wu, C. Yang, X. Cui, Synthesis of γ-graphyne by mechanochemistry and its electronic structure. Carbon 136, 248–254 (2018) 210. N. Han, H. Liu, S. Zhou, J. Zhao, Possible formation of graphyne on transition metal surfaces: a competition with graphene from the chemical potential point of view. J. Phys. Chem. C 120, 14699–14705 (2016) 211. M.M. Haley, Synthesis and properties of annulenic subunits of graphyne and graphdiyne nanoarchitectures. Pure Appl. Chem. 80(3), 519–532 (2008) 212. D. Bousa, J. Luxa, D. Sedmidubsky, et al., Nanosized graphane (C1H1.14)n by hydrogenation of carbon nanofibers by Birch reduction method. RSC Adv. 6, 6475–6485 (2016) 213. Q. Peng, A.K. Dearden, J. Crean, et al., New materials graphyne, graphdiyne, graphone, and graphane: review of properties, synthesis, and application in nanotechnology. Nanotechnol. Sci. Appl. 7, 1–29 (2014)

764

11

Student Zone: Overview, Training, Practices, and Exercises

214. V.E. Antonov, I.O. Bashkin, A.V. Bazhenov, et al., Multilayer graphane synthesized under high hydrogen pressure. Carbon 100, 465–473 (2016) 215. C.F. Woellner, P.A. da Silva Autreto, D.S. Galvao, One side-graphene hydrogenation (graphone): substrate effects. MRS Adv. 1(20). (Nanomaterials and Synthesis)), 1429–1434 (2016) 216. S.C. Ray, N. Soin, T. Makgato, et al., Graphene supported graphone/graphane bilayer nanostructure material for spintronics. Sci. Rep. 4, 3862 (2014) 217. A. Kumar Sharma, R. Saini, R. Singh, A. Mahajan, R.K. Bedi, D.K. Aswal, Substituted copper phthalocyanine/multiwalled carbon nanotubes hybrid material for Cl2 sensing application. AIP Conf. Proc. 1591, 671–673 (2014) 218. L.J. Brennan, Y.K. Gun’ko, Advances in the organometallic chemistry of carbon nanomaterials. Organometallics 34(11), 2086–2097 (2015) 219. A.N. Khlobystov, A. Hirsch, Organometallic and coordination chemistry of carbon nanomaterials. (Editorial). Dalton Trans. 43, 7345–7345 (2014) 220. Z.-Y. Wu, W. Wang, Terpyridine chelate complex-functionalized single-walled carbon nanotubes: synthesis and redox properties. Fullerenes, Nanotubes, Carbon Nanostruct. 23(2), 131–141 (2015) 221. S.M. Alshehri, T. Ahamad, A. Aldalbahi, N. Alhokbany, Pyridylimine cobalt(II) and nickel(II) complex functionalized multiwalled carbon nanotubes and their catalytic activities for ethylene oligomerization. Adv. Polym. Technol. 35(1) (2016). https://doi.org/10.1002/adv.21528 222. S. Sarkar, H. Zhang, J.-W. Huang, et al., Organometallic hexahapto functionalization of single layer graphene as a route to high mobility graphene devices. Adv. Mater. 25(8), 1131–1136 (2013) 223. T. Ohmura, A. Usuki, Y. Mukae, et al., Supramolecular porphyrin-based metal–organic frameworks with fullerenes: crystal structures and preferential intercalation of C70. Chem. Asian J. 11, 700–704 (2016) 224. J. Kaminsky, J. Vícha, P. Bour, M. Straka, Properties of the only thorium fullerene, Th@C84, uncovered. J. Phys. Chem. A 121, 3128–3135 (2017) 225. P. Chakraborty, A. Nag, G. Paramasivam, et al., Fullerene-functionalized monolayer-protected silver clusters: [Ag29(BDT)12(C60)n]3 (n ¼ 19). ACS Nano 12(3), 2415–2425 (2018) 226. N.B. Jayaratna, M.M. Olmstead, B.I. Kharisov, H.V. Rasika Dias, Coinage metal pyrazolates [(3,5-(CF3)2Pz)M]3 (M ¼ Au, Ag, Cu) as buckycatchers. Inorg. Chem. 55(17), 8277–8280 (2016) 227. L.M. Manus, D.J. Mastarone, E.A. Waters, et al., Gd(III)-nanodiamond conjugates for MRI contrast enhancement. Nano Lett. 10(2), 484–489 (2010) 228. L. Lai, A.S. Barnard, Functionalized nanodiamonds for biological and medical applications. J. Nanosci. Nanotechnol. 15(2), 989–999 (2015) 229. A. Palkar, A. Kumbhar, A.J. Athans, L. Echegoyen, Pyridyl-functionalized and water-soluble carbon nano onions: first supramolecular complexes of carbon nano onions. Chem. Mater. 20(5), 1685–1687 (2008) 230. B.-S. Xu, Prospects and research progress in nano onion-like fullerenes. New Carbon Mater. 23(4), 289–301 (2008) 231. A. Arul, M. Christy, M. Young Oh, Y. Sung Lee, K. Suk Nahm, Nanofiber carbon-supported phthalocyanine metal complexes as solid electrocatalysts for lithium-air batteries. Electrochim. Acta 218, 335–344 (2016) 232. J.-S. Li, Y.-J. Tang, S.-L. Li, et al., Carbon nanodots functional MOFs composites by a stepwise synthetic approach: enhanced H2 storage and fluorescent sensing. CrystEngComm 17, 1080–1085 (2015) 233. R.A. Giguere, in Organic Synthesis: Theory and Application, ed. by T. Hudlicky (Ed), vol. 1, (JAI Press Inc., Bingley, UK, 1989), pp. 103–172 234. G. Roussy, J.A. Pearce, Foundations and Industrial Applications of Microwave and Radio Frecuency Fields (Wiley, Chichester/New York/ Brisbane/Toronto/Singapore, 1995) 235. T. Matsumura-Inoue, M. Tanabe, T. Minami, T. Ohashi, A remarkably rapid synthesis of ruthenium(II) polypyridine complexes by microwave irradiation. Chem. Lett., 2443–2446 (1994) 236. F. Wiesbrock, R. Hoogenboom, U.S. Schubert, Microwave-assisted polymer synthesis: state-of-the-art and future perspectives. Macromol. Rapid Commun. 25, 1739–1764 (2004) 237. J. Aguilera-Sigalat, D. Bradshaw, Synthesis and applications of metal-organic framework – quantum dot (QD@MOF) composites. Coord. Chem. Rev. 307(2), 267–291 (2016) 238. G. Fomo, O.J. Achadu, T. Nyokong, One-pot synthesis of graphene quantum dots–phthalocyanines supramolecular hybrid and the nvestigation of their photophysical properties. J. Mater. Sci. 53, 538–548 (2018) 239. E. Ghasemi, E. Alimardani, E. Shams, G.A. Koohmareh, Modification of glassy carbon electrode with iron-terpyridine complex and ironterpyridine complex covalently bonded to ordered mesoporous carbon substrate: preparation, electrochemistry and application to H2O2 determination. J. Electroanal. Chem. 789, 92–99 (2017) 240. K. Deng, X. Li, H. Huang, A glassy carbon electrode modified with a nickel(II) norcorrole complex and carbon nanotubes for simultaneous or individual determination of ascorbic acid, dopamine, and uric acid. Microchim. Acta 183(7), 2139–2145 (2016) 241. J. Marwan, T. Addou, D. Bélanger, Functionalization of glassy carbon electrodes with metal-based species. Chem. Mater. 17(9), 2395–2403 (2005) 242. Q. Zheng, J.A. Gladysz, A synthetic breakthrough into an unanticipated stability regime: readily isolable complexes in which C16-C28 polyynediyl chains span two platinum atoms. J. Am. Chem. Soc. 127, 10508–10509 (2005) 243. R. Dembinski, T. Bartik, B. Bartik, M. Jaeger, J.A. Gladysz, Toward metal-capped one-dimensional carbon allotropes: wirelike C6C20 polyynediyl chains that span two redox-active (η5-C5Me5)Re(NO)(PPh3) endgroups. J. Am. Chem. Soc. 122(5), 810–822 (2000) 244. X. Tian, S. Sarkar, M.L. Moser, et al., Effect of group 6 transition metal coordination on the conductivity of graphite nanoplatelets. Mater. Lett. 80, 171–174 (2012) 245. C. Petit, B. Mendoza, D. O’Donnell, T.J. Bandosz, Effect of graphite features on the properties of metal–organic framework/graphite hybrid materials prepared using an in situ process. Langmuir 27(16), 10234–10242 (2011) 246. C. Petit, T.J. Bandosz, Exploring the coordination chemistry of MOF–graphite oxide composites and their applications as adsorbents. Dalton Trans. 41, 4027–4035 (2012) 247. Y. Sim, J. Park, Y.J. Kim, M.J. Seong, S. Hong, Synthesis of graphene layers using graphite dispersion in aqueous surfactant solutions. J. Korean Phys. Soc. 58(4), 938–942 (2011)

References

765

248. L. Zheng, Y. Chi, Y. Dong, J. Lin, B. Wang, Electrochemiluminescence of water-soluble carbon nanocrystals released electrochemically from graphite. J. Am. Chem. Soc. 131(13), 4564–4565 (2009) 249. A.B. Bourlinos, V. Georgakilas, R. Zboril, T.A. Sterioti, A.K. Stubos, Liquid-phase exfoliation of graphite towards solubilized graphenes. Small 5(16), 1841–1845 (2009) 250. Z. Lin, Y. Yao, Z. Li, Y. Liu, Z. Li, C.P. Wong, Solvent-assisted thermal reduction of graphite oxide. J. Phys. Chem. C 114(35), 14819–14825 (2010) 251. J. Liu, H. Jeong, J. Liu, K. Lee, J.Y. Park, Y. Ahn, S. Lee, Reduction of functionalized graphite oxides by trioctylphosphine in non-polar organic solvents. Carbon 48(8), 2282–2289 (2010) 252. S. Niyogi, E. Bekyarova, M.E. Itkis, J.L. McWilliams, M.A. Hamon, R.C. Haddon, Solution properties of graphite and graphene. J. Am. Chem. Soc. 128(24), 7720–7721 (2006) 253. Y. Liu, R.L. Vander Wal, V.N. Khabashesku, Functionalization of carbon nano-onions by direct fluorination. Chem. Mater. 19(4), 778–786 (2007) 254. M.E. Plonska-Brzezinska, J. Mazurczyk, B. Palys, J. Breczko, A. Lapinski, A.T. Dubis, L. Echegoyen, Preparation and characterization of composites that contain small carbon nano-onions and conducting polyaniline. Chemistry 18(9), 2600–2608 (2012) 255. E. Wajs, A. Molina-Ontoria, T.T. Nielsen, L. Echegoyen, A. Fragoso, Supramolecular solubilization of cyclodextrinmodified carbon nanoonions by host-guest interactions. Langmuir 31(1), 535–541 (2015) 256. K.N. Semenova, N.A. Charykov, E.R. López, et al., Pressure dependence of the solubility of light fullerenes in n-nonane. J. Chem. Thermodyn. 112, 259–266 (2017) 257. K.J. Moor, S.D. Snow, J.-H. Kim, Differential photoactivity of aqueous [C60] and [C70] fullerene aggregates. Environ. Sci. Technol. 49(10), 5990–5998 (2015) 258. Y.J. Marcus, Solubilities of buckminsterfullerene and sulfur hexafluoride in various solvents. Phys. Chem. B 101(42), 8617–8623 (1997) 259. U. Ritter, Y.I. Prylutskyy, M.P. Evstigneev, N.A. Davidenko, V.V. Cherepanov, A.I. Senenko, O.A. Marchenko, A.G. Naumovets, Structural features of highly stable reproducible C60 fullerene aqueous colloid solution probed by various techniques. Fullerenes, Nanotubes, Carbon Nanostruct. 23(6), 530–534 (2015) 260. S. Park, J. An, I. Jung, et al., Colloidal suspensions of highly reduced graphene oxide in a wide variety of organic solvents. Nano Lett. 9, 1593–1597 (2009) 261. J. Texter, Graphene dispersions. Curr. Opin. Colloid Interface Sci. 19(2), 163–174 (2014) 262. U. Khan, H. Porwal, A. O’Neill, K. Nawaz, P. May, J.N. Coleman, Solvent-exfoliated graphene at extremely high concentration. Langmuir 27, 9077–9082 (2011) 263. C.C. Li, C.L. Huang, Preparation of clear colloidal solutions of detonation nanodiamond in organic solvents. Colloids Surf. A Physicochem. Eng. Asp. 353(1), 52–56 (2010) 264. A. Pentecost, S. Gour, V. Mochalin, I. Knoke, Y. Gogotsi, Deaggregation of nanodiamond powders using salt- and sugar-assisted milling. ACS Appl. Mater. Interfaces 2(11), 3289–3294 (2010) 265. Y. Zhu, X. Xu, B. Wang, Z. Feng, Surface modification and dispersion of nanodiamond in clean oil. China Particuol. 2(3), 132–134 (2004) 266. Y. Wang, Y. Meng, S. Wang, C. Li, W. Shi, J. Chen, J. Wang, R. Huang, Direct solvent-derived polymer-coated nitrogen-doped carbon nanodots with high water solubility for targeted fluorescence imaging of glioma. Small 2015(29), 11, 3575–3581 267. L. Deng, X. Wang, Y. Kuang, C. Wang, L. Luo, F. Wang, X. Sun, Development of hydrophilicity gradient ultracentrifugation method for photoluminescence investigation of separated non-sedimental carbon dots. Nano Res. 8(9), 2810–2821 (2015) 268. F. Arcudi, L. Dordevic, M. Prato, Synthesis, separation, and characterization of small and highly fluorescent nitrogen-doped carbon nanodots. Angew. Chem. Int. Ed. Engl. 55(6), 2107–2112 (2016) 269. J.I. Paredes, M. Burghard, Dispersions of individual single-walled carbon nanotubes of high length. Langmuir 20, 5149–5152 (2004) 270. M. Jellur Rahman, T. Mieno, Water-dispersible multiwalled carbon nanotubes obtained from citric-acid-assisted oxygen plasma functionalization. J. Nanomater. 2014, 508192 (2014). (9 pp) 271. A. Graf, Y. Zakharko, S.P. Schießl, C. Backes, M. Pfohl, B.S. Flavel, J. Zaumseil, Large scale, selective dispersion of long single-walled carbon nanotubes with high photoluminescence quantum yield by shear force mixing. Carbon 105, 593–599 (2016) 272. K. Jagadish, S. Srikantaswamy, K. Byrappa, L. Shruthi, M.R. Abhilash, Dispersion of multiwall carbon nanotubes in organic solvents through hydrothermal supercritical condition. J. Nanomater. 2015, 381275 (2015). (6 pp) 273. O. Byl, J. Jie Liu, J.T. Yates Jr., Etching of carbon nanotubes by ozones. A surface area study. Langmuir 21, 4200–4204 (2005) 274. L.P. Lukhele, B.B. Mamba, N. Musee, V. Wepener, Acute toxicity of double-walled carbon nanotubes to three aquatic organisms. J. Nanomater. 2015, 219074 (2015). (19 pp) 275. Y. Liu, I. Zhitomirsky, Aqueous electrostatic dispersion and heterocoagulation of multiwalled carbon nanotubes and manganese dioxide for the fabrication of supercapacitor electrodes and devices. RSC Adv. 4, 45481–45489 (2014) 276. M. Park, S. Kim, H. Kwon, et al., Selective dispersion of highly pure large-diameter semiconducting carbon nanotubes by a flavin for thin-film transistors. ACS Appl. Mater. Interfaces 8, 23270–23280 (2016) 277. K. Huang, A. Saha, K. Dirian, C. Jiang, P.-L. Chu, J.M. Tour, D.M. Guldi, A.A. Martí, Carbon nanotubes dispersed in aqueous solution by ruthenium(II) polypyridyl complexes. Nanoscale 8, 13488–13497 (2016) 278. S.H. Min, H.-I. Kim, K.-s. Kim, et al., Selective dispersion of single-walled carbon nanotubes by binaphthyl based conjugated polymers: integrated experimental and simulation approach. Polymer 96, 63–69 (2016) 279. C. Hu, Y. Zhang, G. Bao, et al., DNA functionalized single-walled carbon nanotubes for electrochemical detection. J. Phys. Chem. B 109, 20072–20076 (2005) 280. S.S. Karajanagi, H. Yang, P. Asuri, et al., Protein-assisted solubilization of single-walled carbon nanotubes. Langmuir 22(4), 1392–1395 (2006) 281. C. Jiang, A. Saha, C. Xiang, et al., Increased solubility, liquid-crystalline phase, and selective functionalization of single-walled carbon nanotube polyelectrolyte dispersions. ACS Nano (7, 5), 4503–4510 (2013)

766

11

Student Zone: Overview, Training, Practices, and Exercises

282. R.E. Anderson, A.R. Barron, Solubilization of single-wall carbon nanotubes in organic solvents without sidewall functionalization. J. Nanosci. Nanotechnol. 7(10), 3646–3640 (2007) 283. L. Henao-Holguín, V. Meza-Laguna, T.Y. Gromovoy, E. Basiuk, M. Rivera, V.A. Basiuk, Solvent-free covalent functionalization of fullerene C60 and pristine multi-walled carbon nanotubes with crown ethers. J. Nanosci. Nanotechnol. 16(6), 6173–6184 (2016) 284. J. Chen, P.C. Collier, Noncovalent functionalization of single-walled carbon nanotubes with water-soluble porphyrins. J. Phys. Chem. B 109 (16), 7605–7609 (2005) 285. H. Wu, Z. Chen, J. Zhang, et al., Stably dispersed carbon nanotubes covalently bonded to phthalocyanine cobalt(II) for ppb-level H2S sensing at room temperature. J. Mater. Chem. A 4, 1096–1104 (2016) 286. D.M. Guldi, G.M. Aminur Rahman, S. Qin, M. Tchoul, W.T. Ford, M. Marcaccio, D. Paolucci, F. Paolucci, S. Campidelli, M. Prato, Versatile coordination chemistry towards multifunctional carbon nanotube nanohybrids. Chem. Eur. J. 12, 2152–2161 (2006) 287. D. Priftis, N. Petzetakis, G. Sakellariou, M. Pitsikalis, D. Baskaran, J.W. Mays, N. Hadjichristidis, Surface-initiated titanium-mediated coordination polymerization from catalyst-functionalized single and multiwalled carbon nanotubes. Macromolecules 42, 3340–3346 (2009) 288. N. Tagmatarchis, M. Prato, D.M. Guldi, Soluble carbon nanotube ensembles for light-induced electron transfer interactions. Physica E 29(3), 546–550 (2005) 289. G.E. Jay Poinern, A Laboratory Course in Nanoscience and Nanotechnology (CRC Press, Boca Raton, 2015)., 230 pp 290. http://www.chemengr.ucsb.edu/~ceweb/faculty/scott/Chemical%20SOPs/CarbonPowder.pdf. Accessed 6 July 2018 291. http://www.carbonfiber.gr.jp/english/material/safety.html. Accessed 6 July 2018 292. https://www.safeworkaustralia.gov.au/system/files/documents/1702/safe_handling_and_use_of_carbon_nanotubes.pdf. Accessed 6 July 2018 293. A. Groso, A. Petri-Fink, A. Magrez, M. Riediker, T. Meyer, Management of nanomaterials safety in research environment. Part. Fibre Toxicol. 7, 40 (2010). (8 pp) 294. Y. Liu, Y. Zhao, B. Sun, C. Chen, Understanding the toxicity of carbon nanotubes. Acc. Chem. Res. 46(3), 702–713 (2013) 295. https://www.shponline.co.uk/shrinking-certainty/. Accessed 6 July 2018 296. S. Bellucci, Carbon nanotubes toxicity, in Nanoparticles and Nanodevices in Biological Applications. Lecture Notes in Nanoscale Science and Technology, vol. XII, (Springer-Verlag, Berlin, Heidelberg, 2009), pp. 47–67 297. W. Qi, L. Tian, W. An, et al., Curing the toxicity of multi-walled carbon nanotubes through native small-molecule drugs. Sci. Rep. 7, 2815 (2017) 298. N. Kobayashi, H. Izumi, Y. Morimoto, Review of toxicity studies of carbon nanotubes. J. Occup. Health 59(5), 394–407 (2017) 299. A. Jafar, Y. Alshatti, A. Ahmad, Carbon nanotube toxicity: the smallest biggest debate in medical care. Cogent Med. 3, 1217970 (2016) 300. https://www.cdc.gov/niosh/docs/2013-145/pdfs/2013-145.pdf. Accessed 6 July 2018 301. E. Oberdorster, Manufactured nanomaterials (fullerenes, C60) induce oxidative stress in brain of juvenile largemouth bass. Environ. Health Perspect. 112(10), 1058–1062 (2004) 302. G.V. Andrievsky, V.K. Klochkov, L.I. Derevyanchenko, Is C60 fullerene molecule toxic?! Fullerenes, Nanotubes, Carbon Nanostruct. 13(4), 363–376 (2005) 303. N. Gharbi, M. Pressac, M. Hadchouel, H. Szwarc, S.R. Wilson, F. Moussa, [60]Fullerene is an in vivo powerful antioxidant with no acute or sub-acute toxicity. Nano Lett. 5(12), 2578–2585 (2005) 304. N. Shinohara, M. Gamo, J. Nakanishi, Fullerene C60: inhalation hazard assessment and derivation of a period-limited acceptable exposure level. Toxicol. Sci. 123(2), 576–589 (2011) 305. https://www.nanowerk.com/news/newsid¼2373.php. Accessed 6 July 2018 306. H. Aschberger, J. Johnston, V. Stone, et al., Review of fullerene toxicity and exposure – Appraisal of a human health risk assessment, based on open literature. Regul. Toxicol. Pharmacol. 58(3), 455–473 (2010) 307. J. Kolosnjaj, H. Szwarc, F. Moussa, Toxicity studies of fullerenes and derivatives, in Bio-Applications of Nanoparticles. Advances in Experimental Medicine and Biology, ed. by W. C. W. Chan, vol. 620 (Springer, New York, 2007) 308. http://www.ipacom.com/index.php/en/full-and-water/about-the-non-toxicity-of-fullerenes. Accessed 6 July 2018 309. G. Lalwani, B. Sitharaman, Multifunctional fullerene and metallofullerene based nanobiomaterials. Nano LIFE 3, 1342003 (2013) 310. D. Bradley, Is graphene safe? Mater. Today 15(6), 230 (2012) 311. L. Ou, B. Song, H. Liang, et al., Toxicity of graphene-family nanoparticles: a general review of the origins and mechanisms. Part. Fibre Toxicol. 13, 57 (2016) 312. M. Ema, M. Gamo, K. Honda, A review of toxicity studies on graphene-based nanomaterials in laboratory animals. Regul. Toxicol. Pharmacol. 85, 7–24 (2017) 313. X. Guo, N. Mei, Assessment of the toxic potential of graphene family nanomaterials. J. Food Drug Anal. 22(1), 105–115 (2014) 314. A.B. Seabr, A.J. Paula, R. de Lima, O.L. Alves, N. Durán, Nanotoxicity of graphene and graphene oxide. Chem. Res. Toxicol. 27(2), 159–168 (2014) 315. G. Lalwani, M. D’Agati, A. Mahmud Khan, B. Sitharaman, Toxicology of graphene-based nanomaterials. Adv. Drug Deliv. Rev. 105(Pt B), 109–144 (2016) 316. CDC – NIOSH Pocket Guide to Chemical Hazards – Graphite (natural). www.cdc.gov. Accessed 3 Nov 2015 317. https://www.nwmissouri.edu/naturalsciences/sds/g/Graphite.pdf. Accessed 8 Aug 2018 318. http://www.sciencelab.com/msds.php?msdsId¼9924202. Accessed 8 Aug 2018 319. E.D. Kuempel, T. Sorahan, Identification of research needs to resolve the carcinogenicity of high-priority IARC carcinogens. Views and Expert Opinions of an IARC/NORA Expert Group Meeting, Lyon, France, 30 June – 2 July 2009. IARC Technical Publication No. 42. Lyon, France. Int. Agency Res. Cancer 42, 61–72 (2010) 320. T. Sorahan, J.M. Harrington, A “lugged” analysis of lung cancer risks in UK carbon black production workers, 1951–2004. Am. J. Ind. Med. 50 (8), 555–564 (2007) 321. ICBA, Health and hygiene – what is carbon black? (2016), http://www.carbon-black.org/index.php/what-is-carbon-black/health-and-hygiene. Accessed 8 Aug 2018 322. Flexicon, Carbon black (2018), https://www.flexicon.com/Materials-Handled/Carbon-Black.html. Accessed 8 Aug 2018

Chapter 12

Conclusions and Further Outlook

As it has been shown above, a grand variety of carbon allotropes and forms is currently known. They can be very common (graphite, coal) or rare (nanobuds, nanoplates, or nanocups) and can be well-developed industrially (carbon black) or intensively studied on nano-level (carbon nanotubes or graphene), doped with metals and functionalized with organic and organometallic moieties. The hexagonal network of nanotube cylinders, graphene sheets, or fullerene molecules consisting of hexagons and pentagons of carbon atoms are highly aesthetically pleasing, providing inspiration both to artists and scientists [1]. The shape of carbon nanotubes also influences their outstanding physical properties, such as electrical and heat conductance, which are already exceeding many traditional materials, as well as mechanical strength. Fully carbon electronic devices are now a main dream and great expectative of modern technologies, where a lot of researchers are working. Despite low number of reports, carbon “less-common nanostructures” tend to have much more applications in future. For example, the combination of relatively chemically inert carbon nanotubes and more active fullerenes (carbon nanobuds, CNBs) can be compatible with a variety of other materials, in particular polymers forming composites with enhanced flexibility and sensor characteristics. Among other possible applications, the uncontaminated magnetic nanobuds hold good promise in the field of spintronics. Greater opened space between SWCNTs allows CNBs to be more effective for gas storage. Coordination and organometallic chemistry of carbon allotropes, in particular graphene and carbon nanotubes, is very important for the following reasons. Metal nanoparticles, atoms, clusters, or cations, being bound with carbon nanostructures directly through M-C σ- or π-bonds or via a ligand group, electrostatic or van der Waals interactions, or charge transfer, are responsible for new properties of formed metal–carbon composites, which are absent in primary carbons. Metals can provide optical, redox, and magnetic activities to the carbon nanostructures. These new properties lead to novel applications, for example, magnetic and photoluminescent properties of endohedral metal fullerenes, novel electrochemical properties of metal-modified glassy carbon, catalytic properties of metal surface-decorated CNT composites, nanoreactor properties of metal clusters embedded within nanotube channel, etc. The chemistry of carbon nanostructures is still limited by many practical peculiarities, such as lack of purity, polydispersity, or structural complexity. New horizons for these fascinating carbon materials can be open upon more profound understanding of bonding and interactions M-C in these composites. Any application of metal complexes could be extrapolated to their carbon-containing composites, since these materials have and could have a host of applications in many fields, such as drug delivery [2], devices, sensors, catalysis on supporting materials (due to the presence of metallic ions and carbon support), and water treatment (using porous carbon structures), among others. Applying modern computational methods, a host of new carbon nanoforms (e.g., novamene [3] or protomene [4]) are possible, which have not yet been observed experimentally. In this respect, an efficient and reliable methodology for crystal structure prediction was developed [5], merging ab initio total-energy calculations and a specifically devised evolutionary algorithm. This method allows one to predict the most stable crystal structure and a number of low-energy metastable structures for a given compound at any P-T conditions without requiring any experimental input. While in many cases it is possible to solve crystal structure from experimental data, theoretical structure prediction is crucially important for several reasons. The area of carbon allotropes is currently one of most dynamically developing fields of science and technology, leading to new horizons of the progress. It could be proposed that such trends will remain in the next 10–20 years.

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References 1. A. N. Khlobystov, A. Hirsch, Organometallic and coordination chemistry of carbon nanomaterials. Dalton Trans. 43, 7345 (2014) 2. H. Sadegh, R. Shahryari-ghoshekandi, Functionalization of carbon nanotubes and its application in nanomedicine: a review. Nanomed. J. 2(4), 231–248 (2015) 3. L.A. Burchfield, M. AlFahim, R.S. Wittman, F. Delodovicic, N. Manini, Novamene: a new class of carbon allotropes. Heliyon 3(2), e00242 (2017) 4. F. Delodovicic, N. Manini, R.S. Wittman, Protomene: a new carbon allotrope. Carbon 126, 574–579 (2018) 5. A.R. Oganov, C.W. Glass, Crystal structure prediction using ab initio evolutionary techniques: principles and applications. J. Chem. Phys. 124, 244704 (2006)

Index

A ab initio method, 56, 59 Acetone, 584 Acetylene black process, 313 Acidic functional groups, 596 Acidic/alkaline functional groups, 310 Al-based metal-organic gels, 323 Amine oxidation, 484 Amine-modified CNFs (AN-CNFs), 76, 533 Amino-functionalized a-MWCNTs-supported iron phthalocyanine (FePc) (a-MWCNT/FePc), 439 3-Amino-propyltriethoxysilane (APTES), 556 Amorphous carbon atomic structures, 25 carbon allotropes, 23 carbon films, 25, 26 carbonization reaction, 29 features, 23 and hydrogen system, 23, 24 ReS2 layers, 26 SO3H, 27 sp3-atoms, 24 structure and properties, 23, 24 synthesis methods carbonization reaction, 27 nitrogen-doped porous carbon, 26, 28 p-type films, 26 sp2 and sp3, 26 transformations diamond, 27 fullerenes, 27 microwave graphitization, 30 thermal annealing, 27, 29 Analytical method, 39 Anthropogenic carbon nanotubes, 642 Anthropogenic climate change, 641 Antiferromagnetic (AFM) phase, 42 Applications carbon nanofibers, 656 CB, 654 CNTs, 656–659 diamond, 655 glassy carbon, 655 graphene, 655 graphite, 653 nanodiamonds, 655 natural coals, 654 Arc discharge CNTs, 680 fabrication, 175, 177 water–dispersible carbon nanocapsules, 695 Armchair-edged graphene nanoribbons (AGNRs), 42

Armchair-like hydrogenated/fluorinated graphene (AC-GH/AC-GF), 249 Aryl groups, 46 Atomic carbon, 113, 714 Atomic-scaled electronic devices, 43

B Bamboo-like CNTs, 65 Bamboo-shaped carbon nanotubes (B-CNTs), 336 Barrett-Joyner-Halenda (BJH), 710 Basicity scale, 582 Batteries, 54 Beads-assisted sonication (BASD) process, 85 Belt scrolling model, 356 Berry phase, 41 Bilayer graphene, 42 Bimetallic MOF-DC, 345, 346 Black carbon (BC), 309, 310, 314, 315, 674 in environment ambient air, 641 anthropogenic sources, 641 biofilms, 642 features, 641 graphitized soot, 642 PM, 642 Blue-luminescent graphene quantum dots (bGQDs), 118 Boat configuration, 358 Boatlike hydrogenated/ fluorinated graphene (B-GH/B-GF), 249, 250 Body-centered cubic (BCC) carbon C8 structure, 389 crystal structures, 390 features, 389 liquid–solid interface reaction, 390 SEM images, 391 2D bcc-C6, 390, 392 Body-centered tetragonal (BCT) carbon, 392 bct C4, 393 bct C8, 392, 394 features, 393 graphite-to-hexagonal diamond transformation path, 392, 393 “Boomerang” effect, 451 Boron-doped diamond (BDD), 698 Boron-doped MWCNTs (CBXMWNTs), 242 Bovine serum albumin (BSA) protein, 657 Broccoli-like nano- and microparticles, 219, 221, 222 Broncho-alveolar lavage fluid (BALF), 645 Brunauer-Emmett-Teller (BET), 678, 709 Buckminsterfullerene (C60) amorphous structure, 52 applications, 54–55 bandgap, 51

© Springer Nature Switzerland AG 2019 B. I. Kharisov, O. V. Kharissova, Carbon Allotropes: Metal-Complex Chemistry, Properties and Applications, https://doi.org/10.1007/978-3-030-03505-1

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770 Buckminsterfullerene (C60) (cont.) chemical processes, 52 definition, 48 electric arc arrester, 51 electronegativity, 51 ferromagnetic materials, 52 fullerene arc, 50 fullerites, 51 graphite in, 48 metal-fullerene films, 51 molecular surgical method, 52 molecule, 48 photoconductivity, 51 photodetectors and optoelectronic devices, 52 PIR, 50 polyfullerene films, 51 polymer-fullerene materials, 51 property, 52 room temperature, 52 string of pearls, 52 structure, 49 superaromaticity, 49 synthesis, 50, 51 synthetic pathway of H2, 52 thermal stability, 52 Bucky-diamond, 82 Buckymetallocenes, 503, 508

C Cage-opening buckminsterfullerene, 718 Calf-thymus dsDNA, 273 Capacitance–voltage (C-V) characteristics graphene, 42 Carbide-derived carbon (CDCs), 718, 719 applications, 328–334 CDC-Pt catalyst, 330, 332 chlorine-based synthesis, 324 CNT development, 327 CO2 adsorption, 328 configuration, equipment, 327, 330 dehydrogenation of ethylbenzene, 333 electrochemical etching, Ti3AlC2, 327, 329 electrochemical method, 327 energy-related applications, 324 fluorinated sheet, graphene, 327, 330 gas filtration, 333 hydrogen bonding interaction and FT-IR spectra, 330, 331 hydrothermal reactions, 327, 329, 330 MAX phases, 327, 329 MD simulations, 327, 328, 330, 331 mechanism, MC and Cl2, 324 metal atom, 327 microemulsion approach, 332 MicroJet reactor technique, 327 microstructure, 324 monoliths, 333 nanocasting method, 324, 325 nomenclature purposes, 324 O atoms, 330 OM-SiC-CDC, 324 physical/chemical processes, 324 polymer-derived ceramics, 324 preparation, metal containing polymeric PCS, 330, 332 structures, 324, 325

Index supercapacitor electrode materials, 334 synthesis, 324, 327 synthetic mechanism, 334 thin film formation, 324, 326 Ti3SiC2, 324 TiC coating, 324, 326 TiC-CDCs, 327, 333 virgin and fluorinated models, SiC-DC, 327, 331 Vi-SiOC-CDC, 327, 328 volatile organic compounds, 334 Carbon aerogels (CAs) activation process, 318 C–AB nanocomposites, 321 definition, 316 doping with transition metals/lanthanides, 316 fabrication process, 3D Fe/Fe3C@N-rGO, 317, 318 fabrication, porous bagasse-derived, 320 graphene oxide, 317 high-performance supercapacitors, 318 lanthanide-doped, 317 monolithic, 317 natural products, 318 and NiO composites, 318, 320 PB, 317 Pd nanoparticles, 317 porous N-doped, 318, 319 RF method, 316 rGO, 317 supercapacitor device, 321 temperatures, 321 Carbon allotropes amorphous carbon (see Amorphous carbon) BC, 641, 642 carbon nanotropes, 3 catenation, 1 characterization carbon nanotubes, 671 electron microscopy, 672 microscopy-based methods, 670 parameters, 670 Raman spectroscopy, 670, 671 XANES, 672 X-ray diffraction, 672 classifications, 2, 3 combustion soot, 641 composites/materials, 8 descriptions, 7 diamond (see Diamond) dimensionality, 3, 4 electronic and mechanical properties, 2 fullerenes, 733 GFNs, 645 in environment BC, 641, 642 (see also Black carbon (BC)) CB, 640, 642 (see also Carbon black (CB)) CNTs, 642, 643 elemental form, 639 fullerenes, 647–649 GFMs, 645, 646 PM (see Particulate matter (PM)) graphene, 734 graphite (see Graphite) graphite dispersion, 731–733 graphyne, 377, 378 hybridization, 2

Index Mendeleev’s Periodic Table, 1 MOF-DC, 7 nanodiamonds, 734, 735 nanoonions fluorination procedure, 733 solubility, 733 nanosized, 3 nanostructures, 2, 3 NMP, 735 novamene, 3 pN–CNDs, 735 production methods, 7 sp-hybridized carbon, 2 superhard structures, 376 SWCNTs, 650 synthesis, 7 fullerenes, 667 nanofibers, 669 nanoonions, 669 nanospheres, 669 nanotubes, 669 quantum dots, 669 synthetic, 2 tiling, protomene structure, 3, 7 toxicity, 649 types, 375 Carbon atom wires (CAWs), 715, 716 electrical conductivity, 129 peculiarities, 126, 127 polyynes, 128 sp2 graphitic fragment, 127, 128 sp-sp2 moiety, 129 synthesis in situ, 130 nanosecond pulsed laser deposition, 129 physical methods, 129 Carbon black (CB), 654 acetylene black process, 313 aerosol composition, 315 applications, 314, 654 climate, 314 crystallization, 313, 314 Degussa gas black process, 310, 311 dry-pelletized, 310, 311 emissions, 314 in environment DNA damage, 642 EC, 640 rheumatoid arthritis, 642 soils, 642 structure, 640 vegetable black, 641 furnace black process, 310, 311 graphitic carbon, 309 hazards, 743 high surface area, 313 Lamp black particles, 311, 312 Lamp black production process, 311, 312 multi-shell fullerenes, 313 noncontinuous/cyclic process, 311 particles, 311, 312 powder, 310, 311 production methods, 310 properties, 309, 310, 313, 314 raw materials, 310 surface, 310

771 thermal black production process, 311, 313 wet-pelletized, 310, 311 Carbon cages, 60 Carbon–cobalt films, 355 Carbon cryogels cellulose-derived, 318 definition, 316 hydrogen storage capacity, 322 impregnation, 321 surface area, 321 unmodified, 321 Carbon fibers, 62 Carbon hydrogel classification, 316 definition, 316 dye-adsorbed, 318 GO/PEI, 318, 319 graphene oxide, 317 PB@GO, 318 resorcinol–formaldehyde, 321 structure, 316 Carbon microcoils, 248 Carbon nano/quantum dots (Cdots) GQDs, metal-complex composites, 539–541 metal coordination, 538 with MOFs, 538 PL quenching, 537 in sensing, 537 sensing process, metal ions and anions, 538 Carbon nanobelts (CNBs), 151, 152 acid leaching, 146 formation, 148, 149 HRTEM images, 147 MoO3/C, 149 polyporous structure, 149 pyrolysis, 146, 150 SEM images, 148 stripping and cutting strategy, 146 synthesis, 687–689 synthetic approaches, 147 TEM images, 147, 148 thermal treatment, 146 VO2(B)/C, 150 Carbon nanobowls (CNBs), 700 Carbon nanobrushes, 8, 701, 702 Carbon nanobuds, 65 Carbon nanocages (CNCs), see Nanocages Carbon nanocapsules (CNC), see Nanocapsules Carbon nanochains, 684, 685 Carbon nanocoils (CNCs), 706 Carbon nanocone (CNC), 153, 154, 689 Carbon nanocrystals (CNCs), 594, 595 Carbon nanocubes applications, 280 CNCs, 281, 284 FeCox-NPC-T, 282 GCNCs, 281 glucose biosensor, 280 MCC, 280 PEDOT, 282, 283 PtNPs/CNCs, 280 Carbon nanocups (CNCs), 701 EDLCs, 228 fabrication process, 229 hybrid 3-D CNT–CNC structure, 228

772 Carbon nanodiamonds (CNDs) solubilization carboxyl groups, 607 carboxylation, 606 deaggregation, 607 dispersions, 608, 612 distribution, 611 fluorination, 608–611 magnetic, 607 mechanical methods, 607 microwave-assisted chemical functionalization, 606 milling, 607, 608 ODA, 607–609 oil
water interfaces, 611 organic, polymer and biomolecule treatments, 611, 612 oxidation, 607 polymerization, glycidol, 611 polystyrene, 611 PtBMA, 611 surfactants YS-1 and SB-18, 611 synthesis, polymer-grafted ND particles, 612 T-CND, 607 water and organic solvents, 606 water-soluble FM-CNDs, 607 Carbon nanodots (CDs) applications, 119 features, 115 functionalization, 119 grafting and doping, 119 MOFs composites, 727 solubilization (see Solubilization) synthesis, 717 aqueous dispersion, 118 bottom-up methods, 115 electrochemical fabrication, 117 graphene intercalation compounds, 116 hydrothermal methods, 115 large-scale, 119 laser ablation, 115 macroscale, 119 top-down methods, 115 ZIF-8 NPs, 118 Carbon nanofibers (CNFs), 21, 63, 616 AN-CNFs, 76, 533 applications, 76, 530 catalytic and electrochemical applications, 74 and CCFs, 71 chemical functionalization/thermal treatment methods, 71 CO2, 685, 686 and CoNi2S4 nanoparticles, 75, 76 CoP nanoparticles, 74 CoTCPc, 76 CoTCPcNa-AN-CNFs and AN-CNFs, functionalization, 534 CVD growth method, 72 decoration, 74 diameters, 71 electrode materials, 76 electron microscopy, 71 electrospinning, 72, 74 fabrication and structure, 74, 75 Fe/N/CF synthesis, by electrospinning, 534, 536 formic acid molecule, in nitrogen-containing graphene fragments, 533 functionalization, 76 maghemite CNF/γ-Fe2O3, 687

Index melt mixing method, 72 MOF-derived, 72, 74 NACNFs, 72, 73 nanonetwork architecture, 73 nanowire-directed templating synthesis, ZIF-8, 534, 535 N-CNFs, 74 NCPFs, 74 nonprecious, 76 PCNF, 74 PI-based carbon nanofibers, 74 polyacrylonitrile-based heteroatomic, 76 porous doped, 73 porphyrin-like structures, 530 preparation, 72, 73 processing, 71 Pt-CNFs, 74 Rh/AA immobilization, fishbone CNFs, 533, 534 rhodium–anthranilic acid, immobilization of, 533 safety risks, 76 solubility, 76 solution process method, 72 structures, 72 surface characterization, 72 surface modification, 75 surface of carbon microfibers, 72 synthesis, 71, 685 Te nanowire, 72, 73 TEM images, 535 ultrathin tellurium nanowires (TeNWs), 534 units, 74 van der Waals forces, 71 ZIF-8 nanofibers, 72, 73 Carbon nanofoams (CNFs), 244, 245, 706 coordination polymers, 527, 528 metal complexes, 526 NCFs, 526, 527 Carbon nanoforests, 696 Carbon nanoforms, 767 Carbon nanoleaves, 696, 697 Carbon nanomesh (CNM) BET, 709 fabrication, 262, 711 field-effect transistors, 262 graphene, 261, 262 LDO, 262 PCACM, 262, 263 SEM, 709 TEM images, 262 UV exposure process, 263 XPS, 709 XRD, 709 Carbon nanoonions (CNOs), 522, 523 applications, 186 arc discharge, 175, 177 carboxy-functionalized ox-CNO, 187 chemical activation, 179, 180 CuCl2.2H2O, 173 CVD, 173 decoration, 180, 181 dopation, 181 electron field emitter, 188 fabrication, 172 features, 179 Fe-Ni alloy nanosheet, 173 FESEM image, 175

Index FFT analysis, 176 fluo-CNO, 187 fluorination procedure, 733 functionalization, 182, 183 graphene shells, 172 HRTEM images, 178 Hydra, 186 limitation, 187 molecular dynamics simulations, 184, 185 MWCNTs, 177 NNOs, 181 NO, 181 ONO, 181 platinum cluster, 181 pristine, 181 properties diamagnetism, 184 fluorescent, 184 pyrolysis of propane, 173 solubility, 733 solubilization carboxylation, 589 colloidal suspensions, 587 DMF, 587 Drosophila melanogaster, 589 ethanol, 587 fluorination, 587, 588 functionalization, 587, 589 materials, 587, 588 organic functionalization, 589–592 oxidation, 589 PANI composites, 589, 590 pristine, 587 samples, 587, 588 TEM images, 589, 591 water dispersions, 588, 589 water solubilization, 587 water-soluble, 589, 590 with fluorine groups, 589 supercapacitors, 184 synthesis, 184, 678 arc-discharge evaporation, 172 CVD, 172 high-energy laser, 172 HRTEM images, 173, 174 TEM image, 176 toxicological effects, 185 TP, 177–179 water-soluble low-cytotoxic, 187 XRD patterns, 176 Carbon nanoplates, 701, 702 Carbon nanorice (CNR), 690, 691 hydrothermal treatment, 189, 190 NCNR, 190 Carbon nanorings, 150, 691, 692 Carbon nanospheres (CNSs), 690, 691 Carbon nanospike (CNS), 155, 689 Carbon nanospindles, 704 Carbon nanospirals, 706 Carbon nanostructures, 2, 3 graphene (see Graphene) nanofibers (see Nanofibers) NDs (see Nanodiamonds (NDs)) Carbon nanotetrahedra/nanoribbons, 711 Carbon nanothermometers, 706

773 Carbon nanotori, 691 Carbon nanotrees, 696 Carbon nanotropes, 3 Carbon nanotube forests (CNTFs) applications, 215 BDDNF, 216 buckling-driven delamination, 215 CVD method, 211 diamond-based, 215, 216 electrical conductance, 215 growth process, 212, 213 HNS, 214 liquid flow slippage, 215 mechanical compression effect, 215 morphologies, 211 MWCNTs, 213 PfHRP-2, 215 SiO2, 212 SWCNT, 213 synthesis, 211 thermal diffusivity, 215 waviness, 213 ZnO/C core–shell structure, 213, 214 Carbon nanotubes (CNTs) applications, 63, 65, 70 arc discharge, 68, 679 catalyst/carbon deposition, 68, 69 characterization, 671 chemical and structural characterization, 62 classification, 65, 67 composites, 68 coordination polymers organometallic polymers, 455 P4VP and P4VP/pentacyanoferrate(II) metallopolymer, 455 PE-PB/CNT flower bundles, 455 polyethylene terminated with PEFe, ball
stick modeling, 455 cup-stacked, 65, 66 CVD, 679 description, 62, 63 dispersibility, 65 dispersion (see Dispersion) double-wall (see Double-wall CNTs (DWCNTs)) electric-arc technique, 681 electronic properties, 63 in environment BALF, 645 MWCNT, 643 Parisian children, 643 PM, 644 toxicity, 642, 643 features, 63–65 Fe-filled, 69 graphenated, 65, 66 graphene, 47 growth, 68 hazards, 742 hybrids with metal complexes BCB-EO, 740 BCB-EOTiCpCl2, 740, 741 N-containing ligands, 740 O-containing ligands, 739 hybrids/composites with metal complexes applications, 414, 415 synthesis of, 414 lamp, 68, 70

774 Carbon nanotubes (CNTs) (cont.) large-scale, 681, 682 laser ablation, 68 mechanism, 68, 70 with metal complexes (see CNTs with metal complexes) microwave heating, 68, 69 morphologies, 65 multiwall (see Multi-wall CNTs (MWCNTs)) nanoscience and nanotechnology, 70 ND precursors, 78 physical properties, 63, 767 properties, 65, 67 rediscovery, 63 safety risks, 76 semiconducting, 68 single-wall (see Single-wall CNTs (SWCNTs)) solubilization method, 658, 659 spray pyrolysis, 64, 678, 679 structures, 64 synthesis, 71, 722 synthetic methods, 68 TEM image, 62 thermodynamical and quantum-mechanical systems, 70 transition state, 68 trends, 70 triple-wall (see Triple-wall CNTs (TWCNTs)) types, 67, 657 ultrasonication, 735 unrolled nanotube, 65, 67 Carbon nanourchins, 698, 699 Carbon nanoworms, 8 Carbon peapods, 65 Carbon radicals, 134 Carbon xerogel particles, 712, 714 Carbon xerogels Al-based metal–organic gels, 323 capacity, 322 catalysts, 322 cellulose, 318 definition, 316 Li–S batteries, 323 MOF structure, 322 MOG template, 322 and organic, 322 precursors, 322 size and shape, 322 solvent composition, 322 surface oxygen functional groups, 322 water–methanol–inorganic salt solution, 322 Carbyne applications, 123, 124 atomic and chemical structures, 128 bottom-up synthesis, 715 carbon chain length, 551 colloidal system (C:Au:Ag) irradiation, 552 crystal structure, 124 dehydrogenative coupling, 714 DFT-optimized structure model, 127 diplatinum adducts, polyynediyls, 551 features, 120 vs. graphite and diamond, 126 group velocity, 128 LAL, 125 linear acetylenic carbon, 551 metal complexes, 551, 552

Index metal–carbon cluster structures, 552 morphology and structural characterization, 123 organometallic octatetraynes C8[Pd]I and decapentayne C10[Pd]I, 553 phonon dispersion, 128 phonon DOS, 128 STM image, 127 synthesis bottom-up, 126 dehydrogenative coupling, 122, 126 gold and alcohol, 122 HTHV, 121 LLCCs@DWCNTs, 122 TiC surface, 122 Carbyne–diamond group, 355 Car emissions diesel exhaust gas, 650 filtration, DPF, 650 PM, 650 Catalytic chemical vapor deposition (CCVD), 527 Catenation, 1 Cavitation, 735 Cdots@MOFs, 728 C60 fullerene nanowhiskers, 675 Chaoite belt scrolling model, 356 carbon–cobalt films, 355 carbon macrotubes, 356 features, 355 formation, 356 heating, 355 multicrystals, 356 prepared, 356 shock-fused graphite gneiss, 355 sp-bonded carbon chains, 356 Chaoite-like macrotubes, 716, 717 Characterization carbon allotropes carbon nanotubes, 671 electron microscopy, 672 microscopy-based methods, 670 parameters, 670 Raman spectroscopy, 670, 671 XANES, 672 X-ray diffraction, 672 parameters, 669 techniques and information, 668 Chemical solubilization graphite flakes, 596, 597 Hummers process, oxidation, 596 ODA, 596 solvents, 595, 596 stability, 596 thermal reduction, 595 Chemical vapor deposition (CVD) applications, 80 and arc-discharge techniques, 65 classroom testing, 672, 674 CNFs synthesis, 72 CNTs, 679 and conventional thermal, 47 diamond film fabrication, 80 from hydrocarbons, 68 graphene synthesis, 673

Index growth method, 72 hot-filament, 88 microwave apparatus, 80 microwave plasma, 66, 78, 80 MP (see MPCVD) MWP (see Microwave plasma (MWPCVD)) N2/IPA, 672 Ni foil, 672 and PECVD deposition, 75 plasma enhanced (see Plasma enhanced CVD (PECVD)) pyrolisis techniques, 43 Chemisorption behavior, 59 Chiral quasiparticles, 41 Chiral vector, 67, 68 Chitosan-based biopolymers, 89 Chlorination technique, 324 Cisplatin, 529 CNOs-βCD/Fc-Dex particles, 589, 592 CNTs hybrids with metal-complexes N-containing ligands, 621, 623–630 O-containing ligands, 619 organometallics and Grignard reagents, 631 S-containing ligands, 629, 630 solubility, 618 CNTs with metal complexes functionalization with organometallics (see Organometallics, CNTs functionalization) of N- and N,O-containing ligands amide linked MWCNT interconnection, 429 amino-functionalization, MWCNTs, 417, 418 anticancer metal complex, 419 CNT–pDAPy–Co hybrid and DAPy–Co complex, 429, 430 Cu2bisalophen complex, in noncovalent manner, 424 DAPyH+ assembly process and [Co(dmgH)(dmgH2)Cl2], 429 Hg2+ retention, parameters, 417 metal chelate affinity, 427 metallization, SWCNTs with Cu2+ ions, 426 MWCNTs-palladium(II)-Schiff base complex, 415, 424 MWCNT-supported nickel complexes, 422 nickel salen and salophen complexes, 422 polynuclear {Mn4} coordination complexes, 427 Pt–CNT–zirconia–Nafion, 418 ruthenium MWCNTs (RuMWCNTs), 419 ruthenium polypyridyl complexes, 417 SWCNT–Cu2+ complex with SA/EDTA, 414 synthetic procedure, for MWCNT hybrids, 427 water-soluble ruthenium tris(bipyridyl) complex, 418 of O-containing ligands [Na(dibenzo-18-crown-6)]n[SWCNT] complex, 415 ionic functionalization, to covalent functionalization, 416 MWCNTs-metal–organic frameworks {MWCNTs@Cu3(btc) 2}, 416 phthalocyanine-functionalized (see Phthalocyanine-functionalized CNTs) porphyrin-functionalized CNTs (see Porphyrin functionalization, CNTs) sulfur-containing ligands, 441 Cobalt oxide and polypyrrole (PPy) coupled with graphene nanosheets (Co3O4-PPy/GN), 470, 471 Cobalt phosphide (CoP) nanoparticles, 74 Cobalt tetracarboxylphthalocyanine (CoTCPc), 76 Cobalt–nickel sulfide (CoNi2S4) nanoparticles, 75, 76 Combustion soot, 641 Confined growth, 667

775 Conventional carbon fibers (CCFs), 71 Coronene bisimide (CBI), 602, 603 Costs carbon nanofibers, 656 CB, 654 CNTs, 656 diamond, 655 glassy carbon, 655 graphene, 655 graphite, 653 natural coals, 654 Covalently bonded graphenes (CBGs), 48 Cryogel-ammonia borane (C-AB) nanocomposites, 321 CuNi-DABCO-n, 345 Cup-stacked carbon nanotubes (CSCNTs), 65, 66 C–ZnCo2O4–ZnO nanorod arrays (NRAs), 345, 346

D DC Krätschmer reactor, 680 DC-thermal plasma process system, 720, 721 Deformational twinning, 352 Degussa gas black process, 311 Density-functional-based tight-binding model, 61 Density-functional theory (DFT), 39, 42 Detonation nanodiamonds (DNDs), 81 Detonation-produced nanodiamonds (DNDs), 80, 81 DFT-based Dmol3 method, 61 Diamond carbon allotrope, 19 conversion of carbon, 21 CVD, 21, 22 features, 19, 20 HPHT, 21 Mg–Si–C system, 22 as quenchable amorphous diamond, 19 thermal conductivity, 21 types, classification system, 20 uses, 23 Diamond anvil cell (DAC), 306 Diamond-like carbon (DLC), 23, 248 Diatomic carbon, 113, 714 Diazonium salts, 610 Diesel particulate filters (DPFs), 650 Dimensionality, 4 Dimers (C28)2, 56, 58 3,4-Dimethyl-3,4-dihydroperylene, 45 Dipole
dipole interaction, 595 Direct-current glow-discharge (DC-GD) deposition, 88 Dispersibility, 65, 84, 85 Dispersion CNTs applications, 578 biological/biochemical methods, 581 characterization methods, 578 coordination and organometallic compounds, 581 inorganic compounds, 580 liquid media, 578 lysine, 581 organic compounds, 580 physical methods, 579 poly-L-lysine, 581 polymers, 578 reactivity, 578

776 Dispersion (cont.) rubbers, 579 solubilization, 578 SWCNT sample, 580 thermodynamic basis, 578 interactions, 582 water and organic solvents, 578 DND into monodisperse single-nanodiamond (DSND), 80 Double-wall CNTs (DWCNTs), 63 Droplet-to-particle conversion, 667 Drosophila melanogaster, 589 Dry-pelletized CB, 310, 311 DWCNT suspensions, 738 Dye-adsorbed hydrogels, 318 Dynamic light scattering (DLS), 672

E Ecotoxicology, 643 Electric arc arrester, 51 Electric-arc technique, 681 Electric double-layer capacitors (EDLCs), 228 Electrochemical exfoliation, 598 Electrochemical method, 327 Electro-Fenton degradation mechanism, 343 Electrolytic heating, 50 Electron energy loss spectra (EELS), 692 Electron microscopy, 672 Electronic p-n junctions, 59 Electropolymerization, 623 Electrospinning, 71–74, 76, 89 Electrostatic attraction, 45 Elemental carbon (EC), 639 Elongated nanocarbons CNBs, 151 (see Carbon nanobelts (CNBs)) CNC, 153, 154 CNS, 155 nanobars, 146 nanobricks, 146 nanochains, 143–145 nanopeapods, 142, 143 nanopencils, 131 NBs (see Nanobuds (NBs)) EMS software package, 60 Endohedral bonding model, 62 Endohedral fullerenes formation, 54 forming, 52 high-performance anticancer drugs, 54 ion implantation method, 54 in macroquantities, 54 Zn@C28, 61 Endoprostheses, 54 Energy-related applications, 324 E-nose, 270, 271 Environment, carbon allotropes, see Carbon allotropes Epoxy-polyurethane (EPU), 235 Equivalent black carbon (EBC), 641 Ethanol, 684 Ethanol–glycerol vapor, 684 E-tongues, 270, 271 Euler theorem, 55 Exercises, 751–757 Exfoliated porous carbon (EPC), 348

Index F Fe-filled CNTs, 69 Ferrocene-functionalized CNTs, 443, 457 Field emission scanning electron microscope (FESEM) images, 78 Field-effect transistors (FETs), 63, 262 Flame ionization detector (FID), 721 Flattened carbon nanotube (C60@FNTs), 683 Flower-like hierarchical carbon nanospheres (FCNS), 167, 169, 170 Fluorescent MNDs (FMNDs), 89 Fluorescent nanocrystallinecellulose/carbon dot hydrogels, 712 Fluorinated CNTs (FCNTs), 414, 417, 418 Fluorinated nanoonions (F-CNOs), 182 Fluorographene with Grignard reagents, 488, 489 fMWCNT-MGCE, 308, 309 Focused ion-beam CVD (FIB-CVD), 248, 254 Fourier transform infrared (FTIR), 732 Full-color displays, 63 Fullerene arc, 50 Fullerenes (Ful) applications, metal complex fullerenes, 513 arc discharge, 48 batteries, 54 C60 (see Buckminsterfullerene (C60)) C76 film, 55 chemical reactions, 507 classic methods, 495 classification and metal-fullerene coordination modes, 491–493 complexes, 491 coinage metal pyrazolates, 725 [CpRu(CO)2]2 and C60, 495, 497 deuteration, 53, 54 endohedral, 54 endohedral metal-fullerene, 504 endoprostheses, 54 in environment Bacillus subtilis, 649 nC60 aggregates, 647, 649 oxygen, 648 soils, 647, 649 transformation, soils, 649 trichloroethylene, 649 water, 647, 648 evaporator temperatures, 51 extraction, 50, 51 features, 49 fullerene-containing ligands, 492, 494 fullerene-phosphides, 492 hazards, 743 higher (see Higher fullerenes) hydrogenation, 53, 54 in macroscopic quantities, 48 in medicine and pharmacology, 54 MeOH, 725 metal-fullerene complexes buckymetallocenes, 503, 508 nitride clusterfullerenes, 504 P-containing ligands, 502, 507 porphyrins and phthalocyanines, 500–505 pyrazine, pyrazolate and bispyridine ligands, 495–499 subphthalocyanines, 502, 506 M-Ful complexes, 490, 495 molecular dynamics simulations, 509, 511 n-nonane, 734 nonpolar solvents, 50, 54

Index nontoxic, 54 insoluble in polar solvents, 52 in vitro studies, 54 optical closures–limiters, laser radiation intensity, 54 optical information processing devices, 55 P-MOFs, 724 polymerization, 55 porphyrin and C60, 491 purification, 51 reaction pathways, 507, 510, 511 reaction products, 48, 49 Re–fullerene complexes, 512 rhenium tricarbonyl complex, 496 separation, 51 size measurements, 48 small (see Small fullerenes) solar cells, 55 solubility, 50, 733 solubilization (see Solubilization) soluble in organic solvents, 52 synthesis routes, DFT simulations, 495 trinuclear systems, 725 XRD analysis, 724 water-soluble, 54 Fullerides, 49 Fullerites, 49, 51, 55 Fulleropyrrolidines, 53, 677, 678 Functionalization biochemical, 75 biomolecules, 85 capacity, 92 chemical, 71, 75 CNFs, 76 CNOs' dispersibility, 522 CNTs, 71 amino-functionalization, MWCNTs, 417, 418 CNT-COOH, 427 covalent functionalization, metallic CNTs, 438 non-covalent, 440 non-metal porphyrin, SWCNTs, 431 O-containing ligands, metal complexes of, 415, 416 with organometallics (see Organometallics, CNTs functionalization) porphyrin (see Porphyrin functionalization, CNTs) SWCNTs, 426, 427 fullerenes, 503 graphene (G), 459 with low-valent complexes, 464 organometallic, 464 reaction with Grignard reagents, 488 graphene oxide, 85 inorganic, 86 nanodiamond, 85 ND, 84–87, 514 nucleic acid molecules, 77 of CNFs, 534 solubility, 65 and solubilization CNTs, 70 surface, 46, 85, 86, 91 Furnace black process, 310, 311

G Gas filtration, 333 Gas-phase chemical preparation, 666

777 Gas-phase growth pathways, 226 Gas-phase physical preparation, 666 General data, on carbon allotropes, 1 See also Carbon allotropes Generalized gradient approximation (GGA), 39, 47 Glassy carbon (GC), 404 AFM images, 543 applications, 306, 308 bimetallic porphyrins, 544 carboxylates, 545 commercial suppliers, 304 electrochemical applications, 541 electrochemical oxidation of Ac and Tyr, 308, 309 electrodes as sensors, 308 fabrication procedure, GO/APTES–MIP sensor, 308 fMWCNT-MGCE, 308, 309 functionalization, 306 high pressures, 304 laser pulse treatment, 306, 307 microstructure, 304 Mo- and Co-polypyridyl molecular catalysts, 548, 549 modification, 306 non-graphitizing, 303 optical images, 304, 306 oxidation, 306 phthalocyanines, 545 porphyrins, 543–545 poyridine, quinoline and phenanthroline, 546 properties, 303, 304 proton reduction, proposed catalytic cycle, 550 pyrolysis temperature, 304 Schiff bases, 545 sp2-hybridized, 304 sp2-sp3 carbons, 304 structure, 304, 305 synthesized, 304 template-based methods, 304, 305 uniaxial stress field, 304, 306 Glassy carbon electrodes (GCE), 729, 730 AFM and SEM images, 543 carboxylates, 545 covalent attachment, cobaltocenium ion, 550 diazonium modification method, 548 electrochemical applications, 541 electrochemical study, metal complexes, 541, 542 with FCNTs, 418, 443 GNS-FePc film, 478 graphene (G), 485 pyridine, quinoline and phenantroline, 545, 546 with tetraruthenated porphyrins, 544 Glassy carbon nanowires, 711, 712 Glassy carbon paste electrode (GCPE), 547 GO/polyethylenimine (PEI) hydrogels, 318, 319 Gold–graphene hybrids, 593 Gold-template technique, 192, 193 GouyChapman–Stern theory, 215 Graphane adsorption, formaldehyde molecule, 361 advantages, 361 applications, 360, 361 boat configuration, 358 C4H crystal structure, 358, 359 dehydrogenation, 358 DFT, 360 features, 357, 358

778 Graphane (cont.) hexagonal crystal structure, 358, 360 hydrogenated sheet, 357 hydrogenation progress, 357 isomers, 358 multilayer structures, 358, 360 P63mc structure, 358, 360 penta-graphane, 358, 359 pristine graphane sheet, 360 properties, 358, 359 single-side adsorption, 358 spintronics, 361 stirrup configuration, 358 structures, 358, 359 TNT, 361 2D materials, 357 vacancies and foreign atoms/groups, 359, 360 Graphdiyne definition, 378 features, 378 Graphenated carbon nanotubes (g-CNTs), 65, 66 Graphene (G) adatom C63H20, 38 adatom pair C64H20, 38 amine oxidation, 484 applications, 47–48, 458 carbon nanotubes, 47 chemical sensor properties, 48 covalent and non-covalent functionalization anionic coronene derivative, 600 CBI, 602, 603 chloroform dispersions, 603 dealkylation, 600 graphene–coronene composites, 600, 602 graphite fluoride, 601 halogenated solvents, 599 SDBS, 600 TTF derivatives, 602, 603 composite materials, 47 Cu(salen)
f
GO, synthesis methodology, 483 C–V characteristics, 42 CVD/pyrolisis techniques, 43 decomplexation reactions, 724 derivatives, 38 device fabrication, 723 DFT calculations, 462 dispersion, 734 electronic properties, 41, 42 electronic structure, 458 electrostatic attraction, 45 features, 36 ferrocene and other Cp complexes, 465, 466 ferrocene–graphene nanosheets (Fc–GNs), preparation of, 465, 466 films, 43 fullerenes/nanotubes, 36 functionalization, 459 GCE, 485 GO (see Graphene oxide (GO)) GQDs, 37, 38 graphene|Cr|ligand (G|Cr|L) systems, 463 graphite microcrystals, 43 graphite platelets, 43 hazards, 743 HBC oligomers, 38, 41 heptagonal cells, 37

Index heteroatoms, 43 heterocyclic N-ligands bimetallic silver–ruthenium bipyridine complex (Ag@[Ru(bipy) 3]2+), 470 CO2 sorption, 471 Co3O4-PPy/GN catalysts, 470 coordination complexes, 475 homogeneous graphene composites, 472 L-functionalized graphene, 470, 471 Mn(III) catalyst (Mn(III)-amidomacrocyclic complex), 473 nanodiamond (ND) with tetraazamacrocyclic cations [Ni (cyclam)]2+, 473 noncovalently functionalized with NiTMTAA, 472 polydopamine (PDA)-coated Mn-graphene (Gn/Mn) nanocomposite, 475 hexagonal cells, 37 hexa-peri-hexabenzocoronene, 38, 40 hydrogen abstraction reactions, 45 iGrOs, 45 intermediate Grignard reagents, 488, 489 intermediate Werner-like complexes, 461 larger, 38, 41 laser ablation, 45, 46 layers (sheets), 39–41 low-valent complexes, 464 M(Cp)2 (M ¼ Ti, Zr), for ethylene polymerization, 467 magnetic nanoparticles–graphene–MOF composites, 488 magnetic properties, 42 materials, 36 mechanisms, 45 metal cations and ammonia-treated graphene sheets, 460 metal-graphene interactions, 46 MWCNTs, 47 nanodevices, 47 nano-graphene growth, 45, 46 nanoscaled graphene plate material, 43 non-compensated charge, 43 optical properties, 42 with oxygen- and nitrogen-containing functional groups, 459, 461 palladium–graphene complex, 43, 44 Pd–Ru complex nanocatalyst, 469 pentagonal cells, 37 and photosensitizers, 490 and phthalocyanines basal planes, 476 cobalt phthalocyanines (CoPc and CoTAPc), 477 cobalt-centered, 477 diffusion-controlled process, 478 G and CoPc (CoTAPc) complexes, 477 MPcs, 476 and porphyrins (see Porphyrin-containing graphene composites) principal method, 43 pristine graphene, 459 pyrene–GO composites, 469 Raman spectroscopy, 42 reactivity, 45–46 refractive index, 39 ruthenium–graphene complex, 43, 44 Schiff bases and β-diketones, 481 SEM, 723 series of forms, 37 single-layer graphene devices, 464 solubilization (see Solubilization) synthesis BC, 674

Index chemical vapor deposition, 672, 674 direct exfoliation, 674 flow chart, 676 fullerene-intercalated graphene hybrids, 676 solution properties, 42 stoichiometric analogues, 38 stoichiometric derivatives, 38, 41 structure, 36, 37 surface migration, 45 surface oxygen groups, 43, 44 symmetric and asymmetric derivatives, 38, 40 T-graphene, 37, 38 thickness, 43 3D warping, 36 2D, 36 tube-in-tube nanostructures, 43 ultrasonic treatment, 489 wet-chemical methods, 43 XPS, 723 Graphene carbon nanotube carpets (GCNTs), 268, 269, 703, 704 Graphene dispersion, 674 Graphene family materials (GFMs), 646 cytotoxicity, 647 toxicity, 645, 646 Graphene-family nanomaterials (GFNs), 743 Graphene film, 674 Graphene nanoflakes (GNFs), 42 Graphene nanoribbons (GNRs), 42, 47 Graphene-nanotube-nanobud, 137 Graphene oxide (GO) alkynyl group modified GO (alkynyl-GO), 471 and copper-centered MOF, 487 copper-intercalated, 470 description, 459 formation, 45 GO-ZnPc, synthesis of, 479 growth, 45 insulator, 37 La(BTC)(H2O)6. LaMOF-GO composites, 486 with metal ions, 460 modified Lerf–Klinowski model, 459 NiCPNP/rGO) nanocomposite, 486 optical photographs, 40 oxygen-containing groups, 37, 39 preparation and characterization, 47 rGO, 38, 40 structure, 38, 39 thermal annealing, 38 with zinc phthalocyanine (ZnPc), 478 Graphene oxide quantum dots, 674 Graphene oxide sheets (GOs)-PB nanocomposites, 280 Graphene quantum dots (GQDs), 37, 38, 539–541, 717 applications, 119 bGQDs, 118 features, 115 vs. GO, 115 3D GQDs/rGO composites, 117 Graphene@PANI nanoworm, 698, 699 Graphenopaper, 12 Graphic method, 39 Graphite applications, 12, 13, 653 aromatic system, 555 clusterfullerenes, 12, 14 cointercalation and organometallic composites, 562 copper-based MOF (HKUST-1), 557

779 copper-intercalated GO, 470 copper-intercalated GrO, 559 Cu3(BTC)2/GrO composites, 555, 556 description, 9 and diamond differences, 10 similarities, 10 dispersion F-containing solvents, 732, 733 gold–graphene hybrid, 733 graphene layers, 731 liquid-phase extraction, 733 pyridine, 732, 733 water-soluble carbon nanocrystals, 732 evolution, 11 features, 10 GNPs, 730 GO, 459 and graphene with (η6-benzene)Cr(CO)3 and Cr(CO)6, 463 and graphite oxide (GrO), 13, 555 HOPG, 462 intercalation, 11 iridium(III) fac-tris(2-phenylpyridine) fac-[Ir(ppy)3] complexes, 560 laser ablation and electrochemical, 594, 595 metal coordination complexes, 731 M-GNP films, 731 MOF/graphite oxide hybrid materials, 557 MOF-199/GrO composites coated SPME fiber, 556 MOFs composites, 557 natural, 9 nitrogen-containing metal complexes, 559 Os(II) complex, 452 properties, 10 reductive exfoliation, 12, 13 SEM pictures, 555 sensor applications, 557, 558 solubilization (see Solubilization) starting materials, 13 structure, 11 surface oxygen groups, 43, 44 UGLO, 12 ZnPc/dipy-pra coordination, 560 Graphite nanofibers (GNF), 727 Graphite nanoplatelets (GNP), 730 Graphite oxide (GrO/GtO) amorphous and crystalline phases, 14, 15 exfoliation, 45 formation, 45 functionalized, 45 graphene, 15 HNO3 concentrations, 14, 18 Hummer’s method, 17 hydrophilic, 14 improved and optimized improved Hummers methods, 17 oxidation, 43 RGO, 14 structural model, 44 structure, 16, 39 synthesis methods, 14 thermal exfoliation, 45 thermal expansion mechanism, 43 Graphitization processes, 87 Graphone applications, 362 armchair, 362

780 Graphone (cont.) configurations, 362 features, 361 graphene-like honeycomb structure, 362 hydrogen atoms, 361 nanoribbons, 362, 363 properties, 362 synthesis, 362 zigzag, 362 Graphyne acetylenic linkages, 376, 379 adsorption configurations, 384 applications, 382 bonds, 377 C-C bonds, 376, 378 DFT calculations, 376 features, 377 formations carbyne/carbon chains, 383 polyynic carbyne, 382 STM images, 381 transition-metal surface, 381, 383 (see also Graphdiyne) properties, 381 R-graphyne nanoribbons, 378, 380 structures, 378, 379 Grignard reagents, 631

H Haeckelites ball-and-stick representations, 401 features, 400 green function calculations, 400 lithium storage applications, 400 sp2-like threefold coordinated networks, 400 structures, 401 Halogen intercalation, 11 Hamada indexes, 65 Hansen and Hildebrand parameters, 598 Hazards CB, 743 fullerenes, 743 graphene, 743 HBC oligomers, 38, 41 HeLa cells, 607 Helical carbon nanotubes (HCNTs), 223 Hexagonal diamond (HD), 11 Hexagonal-shaped prisms, 341 Hexa-peri-hexabenzocoronene, 38, 40 2HG-SL, 46 Hierarchical carbon nanocages (hCNC), 195 Higher fullerenes chloro-derivatives of C98, 50 composition, 51 mass fraction, 51 non-abutting pentagons, 50 Highly-oriented pyrolytic graphite (HOPG), 10, 462 High-pressure high-temperature (HPHT), 21 High-voltage electrophoretic deposition (HVEPD), 213 Hollow carbon nanoballs (HCNBs), 690 Hollow carbon nanoplates (HCPs), 231, 702 Home-like nanostructures CNCs fabrication process, 229 hybrid 3-D CNT–CNC structure, 228

Index CNFs, 244, 245 nanobowl, 227 nanobrooms, 231, 232 nanobrushes CNT arrays, 233 GaN, 233 glucose biosensing, 234, 235 SEM image, 233, 234 nanocarpets, 236, 237 nanoladders, 246, 247 nanoplates, 230, 231 nanospindles, 237, 238 nanosponges CBXMWNTs, 242, 243 CVD, 241 metal cluster doping, 242 oil absorption, 241 PECVD, 241 SWCNT bundles, 242, 243 nanotepees, 231, 232 nanowebs, 239–241 Hot-filament chemical vapor deposition (HFCVD), 689 Hot-filament CVD (HFCVD), 88 Hueckel model calculations, 56 Hummers method, 675, 718 Hybrid pulsed laser deposition (HPLD), 83 Hybridization carbon, 2 carbon nanostructures, 2, 3 chemical bond, 2 sp, 2 sp2, 2 sp3, 2 type, 2 Hydrocarbons, 358 Hydrogen abstraction reactions, 45 Hydrogen bond donation ability, 582 Hydrographite, 358 Hydrophile–lipophile balance (HLB), 713 Hydrothermal carbonization (HTC), 706 Hydrothermal method, 115, 737 Hydrothermal reactions, 327, 329, 330 Hydrothermal synthesis NDs, 78 Hydrothermal synthesis and the reduction of carbide (HSRC), 81

I I-carbon, 407 Imma-carbon, 406 Ion bombardment, NDs, 79 Ion implantation method, 54 Ionic liquids (ILs), 585 Iron MOFs, 343 Isocyanate-treated GrOs (iGrOs), 45 Isopropyl alcohol (IPA), 672

J Jahn–Teller effect, 55

K K4 crystal, 396 Kekulé valence structures, 56

Index L Lamp Black particles, 311, 312 Lamp Black production process, 311, 312 Langmuir–Hinshelwood H + H recombination mechanism, 45 Langmuir–Schaefer deposition, 676 Larger graphenes, 38, 41 Laser ablation, 244, 245 Laser ablation and electrochemical solubilization graphite CNCs, 594, 595 hexane solution, 594 particles, 594 polymerization and hydrogenation, 594 polyynes, 594, 595 Laser ablation method, 45, 46 Laser bombarding, 79, 80 Laser pulse treatment, 306, 307 Laser vaporation source, 59 Leyssale’s data, 88 Liquid media, 578 Liquid-phase preparation, 667 Local-density approximation (LDA), 47 Lonsdaleite, 19 crystallographic axes, 351 deformational twinning, 352 and diamond, 351, 354 features, 351 Fe-doped lonsdaleite, 352 formation, 351 hexagonal unit cell, 351, 352 in situ X-ray diffraction measurements, 351 Linac Coherent Light Source, 351, 354 mechanical properties, 351 and nanometer-sized diamonds, 351 Raman spectra, 352 stacking faults, 353 supercell and coordinate system, 351, 353 Low molecular weight heparin (LMWH), 606 Low-cost process, 658 Luteolin, 555

M Magnetic carbon sponge (MCS), 344 Magnetic porous carbon-based sorbent (MPCS), 345 Magnetism, 42 Magnetite carbon aerogels (MCAs), 712 Magnetron sputtering technique, 324 MAX phases, 327, 329 M-carbon band gap, 364 crystal structures, 364 features, 363 formation, 363 indirect and wide semiconductor, 363 P2/m symmetry, 364 structure, 363 varieties, 363 M10-carbon, 364, 365 MCNFs, 75 MD simulations, 327, 328, 330, 331 Mechanochemical milling, 598 Medical grade nanodiamonds (MNDs), 89, 90 Melt mixing method, 72 Mendeleev’s Periodic Table, 1

781 Mesopore carbon nanomesh (MCNM), 710 Mesoporous carbon nanocubes (MCCs), 280, 711 Metal-complex chemistry carbon nanodots, 727 carbon nanofibers, 727 fullerenes, 724, 725 graphene, 723 and nanodiamonds, 725, 726 nanoonions, 726 Metal complexes as anticancer pharmaceutics, 414 applications, metal-complex-functionalized CNTs, 414, 415 with carbon nanofoams, 526 carbyne, 551, 552 Cdots, 537 with CNTs (see CNTs with metal complexes) with CNTs hybrids (see CNTs hybrids with metal-complex) ferrorene (Fc) and metal porphyrins, 522 Ful (see Fullerenes (Ful)) on GCE, 541, 542 glassy carbon composites, 541 graphene functionalization, 459 graphene nanoplatelets, 462, 465 nano-encapsulated, 529 with nanobuds, 524, 525 with nanoonions as precursors for CNOs, 523 surface-oxidized CNOs and metal ions, 522 with ND, 514 (5-nitrotetrazolato-N2) pentaammin-cobalt(III) perchlorate (NCP), 516 1-adamantanecarboxylic acid (AA), 516 ND-Ni nanoparticles, 518 single- and double-armed ligands, 517 nitrogen-containing, 559 with Schiff bases, 481 Metal coordination polymer–graphene nanosheets (MCPGNs), 486, 489 Metal cyclopentadienyls, 441, 442 Metal-doped MOFs, 341 Metal-fullerene films C60, 51 Metal-graphene interactions, 46 Metal organic frameworks (MOFs) copper-based MOF and GO composite (HKUST-1/GO), 488 Cu-MOF, chemical structures, 487 GO-MOF composite, 487 La(BTC)(H2O)6. LaMOF-GO composites, 486 Metal phthalocyanines (MPcs), 476 Metallated carbynes, 730 Metallic carbon features, 385 H18 carbon, 387, 389 Hex-C18, 386, 388 Hex-C24, 385, 386 sp3 hybridization bond, 386 superhardness, 384, 385 Tri-C9, 387 Metal-organic frameworks (MOFs) applications, 335 components, 334, 335 composites, 334 description, 334 functionality, 334 in situ texturing, 336 iron, 343

782 Metal-organic frameworks (MOFs) (cont.) nanoporous structures, 335, 336 organic linkers, 334 pore structure and surface area, 341 pyrolysis, 335 structure, 334, 335 Metal–organic gel (MOG) template, 322 Metals, 767 Meteorites, 77 Methyl ethyl ketone (MEK), 607 Methylene blue, 337, 342 Microelectromechanical devices (MEMs), 28 Microemulsion approach, 332 MicroJet reactor technique, 327 Microporous carbon polyhedrons (MPCPs), 338, 339 Microwave assisted plasma enhanced CVD (PECVD), 241 Microwave irradiation (MW) advantages, 728 chemical syntheses, 729 organic and/or organometallic synthesis, 728, 729 Microwave plasma chemical vapor deposition (MWPCVD) techniques, 80 Microwave-assisted hydrothermal method, 37, 38 Mixed shell carbon nanodots (MSCDs), 253 Mller–Plesset perturbation method, 48 MOF derived carbon (MOF-DC) advantages, 334 applications, 347–350 bimetallic, 345, 346 calcination temperature, 341 capacitor behaviors, 335 Co and CoO nanoparticles, 719 Co/NPC-600, 344 Co/NPC-800, 344 Co–CoO@N-doped porous carbon nanocomposites, 342, 719, 720 CoM, 720 Co–N–C microtubular structure, 341, 342 CoxM1-x-NC composites, 720 cuboid carbon, 338, 340 CuNi-DABCO-n, 345 C–ZnCo2O4–ZnO nanorod arrays (NRAs), 345, 346 dimensionality, 338 direct oxidation, alcohols to esters, 342, 343 discharge–charge mechanism, 345, 348 DOL/DME and EC/DEC electrolytes, 338 electro-Fenton degradation mechanism, 343 EPC, 348 Fe nanoparticles/Fe3O4, 343 FE-SEM images, 340 geometrical forms, 338 H2 reaction with Pt-sputtered Co-MOFs@GO, 347, 350 heteroatom-doped carbon-based electrocatalysts, 334 hexagonal-shaped prisms, 341 HR-TEM images, 340 Li-HECs, 340 magnetic metals, 341 MCS, 344 melting-diffusion and infiltration methods, 345, 347 metal-doped, 341 methylene blue, 337, 342 microstructure observation, nanocarbons, 342, 343 MPCPs, 338, 339 MPCS, 345 nanomaterials, 334, 335 nanoporous carbon, 338

Index N-doping, 345–348 NPCs, 336, 337 ORR, 349 P@N-MPC, 349, 350 porous carbon (FPC and VFPC), 341 porous Co@C, 341 porous doped carbon nanofibers, 338 preparation scheme, 342, 344 Pt sputtered GO hybrid, 347, 349 surface modification, 344 3D hierarchically structured GS–S/CZIF8-D composite, 338, 339 3D MOF hybrid arrays, 348 type of pyrolysis, 341 water steam, 337 ZIF-8/SAC composite, 336, 337 ZIF-67 crystals, 344, 719 Zn–air battery, 336 ZnO nanoparticles, 337 MOF-derived CNFs, 72, 74 Molecular computers, 63 Molecular surgical method, 52 Monocarboxylic acids, 587 Monolayer colloidal crystal template, 667 MPCVD, 80, 88, 89 MPWCVD, 83 Multiparameter linear model, 582 Multiwall carbon nanotubes-hard carbon spherule (MWNTs/HCS), 225 Multi-wall CNTs (MWCNTs), 657 arc-discharge grown, 68 conceptual diagram, 67 diameters, 47 graphene layers, 67 hydrogen microwave discharge, 78 structures, 63 tensile strength, 64 transformation, 79 Multiwalled carbon nanotubes (MWCNTs) fully telescoped, 248 processing and mechanical manipulations, 248 MWCVD bias-enhanced nucleation, 88 CH4/H2 gas, 82, 84 equipment, 80 femtosecond upconversion technique, 82 hydrogen-deficient conditions, 89 NCD deposition, 85 ND grains, 83 Myoglobin (Mb/MB), 519

N Nanoanimal HCNTs, 223 nanourchins, 225–227 nanoworms catalyst nanoparticles, 225 graphite intercalated compounds, 224 Pd crystals, 224 TEM image, 224 worm-like CNTs, 223 Nanobalance, 259 Nanoballs, 165, 166 Nanobars, 146 Nanobatteries, 268, 269 Nanobouquets, 219, 220

Index Nanobowls, 227 Nanoboxes applications, 197 CoSe@carbon, 198 CoSe@CNBs, 197 Fe–N-CNBs electrocatalysts, 198 MoS2/Co9S8/C, 198 ZIF-67, 198 Nanobricks, 146 Nanobrooms, 231, 232 Nanobrushes CNT arrays, 233 GaN, 233 glucose biosensing, 234, 235 SEM image, 233, 234 Nanobuds (NBs) aerosol-assisted CVD, 133 AgNB, 137 applications, 137, 140 C20 fullerene-chained, 136, 141 CNTs and Fs, properties, 132 CO disproportionation, 132 DFT calculations adatoms, 135 attachment of CNT, 136 attachment of fullerene, 135 C60-cap4 configuration, 137 CNT caps, 134 magnetism and optical properties, 134 Young's modulus, 134 F-SWCNTs, 132 geometric structures, 139 gold, 137 graphene nanobuds, 136 graphene–C60, 140 MD simulations C60 bombardment, 138 heat welded nanobuds chains, 134 mechanical properties, 134 SWCNT, 134 Pt, 137 SWCNTs, 132, 133 TEM images, 133 varieties, 132 Nanobushes, 216 Nanocages adsorption experiment, 197 Co-NGC, 194 Cu–ZnO@C yolk–shell, 192 Fe3O4, 693, 694 Fe3O4/C NCs, 193 Fe3O4/ZIF-8, 193 functionalization, 194 gold-template technique, 192, 193 graphite rods, 191 graphitic structure, 196 green one-step carbonization process, 194 hCNC, 195 Mag@CNCs, 194, 195 mesoporous, 195 NC, 194 NC@Co-NGC DSNCs, 195 ORR, 194 oxygen reduction and evolution, 194 preparation, 197

783 structural characters, 196 synthetic procedures, 191 ZIF-8, 193 ZIF-8@ZIF-67, 195 Nanocages Fe3O4, 693 Nanocapsules applications, 202 arc-discharge, 199, 201 carbon-encapsulated cobalt, 202 CDDP@US-tubes, preparation and purification, 531 Co3O4 catalyst, 203 Co–N–C tetragonal microstructures, 201, 202 drug-loading and drug-release, 201 Fe-filled core–shell, 201 FeNiMo/C, 201 HR-TEM images, 531 metal- and nitrogen- doping patterns, 531 metal complexes, 529 metal-doped carbon nanocapsules, 530 from metal salts and organometallics, preparation, 529 MgO-filled, 201 nonferrous metals, 201 pyrolysis, 199 ultra-short SWCNT-based drug delivery system, 529 water-dispersible, 202–204 Zn(Ac)2, ethanol-assisted thermolysis, 200 Nanocarpets, 236, 237 Nanocars, 709 gold surface, 257 motion, 259 p-carborane, 257 propulsion scheme, 258 synthesis, 258 top-down and bottom-up approach, 257 Nanocasting method, 324, 325 Nanochains, 143–145 Nanocrystalline diamond (NCD) films, 78 synthesis, 78 Nanodevices graphene, 47 Nanodiamonds (NDs), 682, 684, 725, 726, 734, 735 acrylate-modified silane and arylation, 85, 86 amine derivatives, 85 applications, 89–91, 519, 520 azide-functionalized ND, 517 bandgap and optical transparency, 77 basis and polymers, 88 binary combinations, 89 biocompatibility, 515 biomedical applications, 577 biomolecules, 85 (see also Carbon nanodiamonds (CNDs)) coating glass with fluoro-ND, 87, 88 complex preparation and photoluminescence spectrum, 515, 516 crystallites, 83 CVD, 77 depositation, 88 dispersed filler particles, 89 dispersibility, 84 dispersion, 86 DNDs, 80, 81 electronic/magnetic properties, 85 electroplating and lubrication, 85 electrospinning, chitosan-based biopolymers, 89 eminent material, 77

784 Nanodiamonds (NDs) (cont.) features, 77 films, 88 for C24H27O4Fe, density spin map, 514, 515 and fluorination, 87 functionalization, 84, 85, 87 graphitization processes, 87 growth, 84 hydrophobic blue fluorescent, 85 hydrothermal synthesis, 78 impurity, 84 inorganic-based diamond, 89 inorganic functionalization, 86 ion bombardment, 79 iron-containing NDs, 514 laser bombarding, 79, 80 Leyssale’s data, 88 magnetic nanofluids (ND-Ni), 518 meteorites, 77 microcapillary reactor, 86, 87 MNDs, 89–91 models, 81, 82 morphology, 89 MWPCVD, 80 myoglobin (Mb/MB), 519 nanocomposite films, 84 nanosized tetrahedral networks, 77 NCD (see Nanocrystalline diamond (NCD)) ND-ODA, 85, 86 nucleation, 84 organic solvents, 85 oxidation, 83 phase purity, 84 physical and chemical properties, 86 precursors, 78 properties, 77 purification, 82, 86 solubility, 84, 85 stability, 83 structural and electronic properties, 82, 83 structure, 85 Sun's formation, 77 surface, 86 ultrasound, 81 UNCD (see Ultrananocrystalline diamond (UNCD)) Nanodots See also Carbon nanodots (CNDots) Nanoelectromechanical systems (NEMs), 272 Nanofibers CNFs (see Carbon nanofibers (CNFs)) Nanoflowers, 217, 218, 696 Nanoforests, see Carbon nanotube forests (CNTFs) Nanographenes, 36 Nanograss, 222, 223 Nanojunctions, 264 Nanoladders, 246, 247 Nanoleaves, 208–210 Nanomechanical systems (NEMS), 162 Nanomotor, 272 Nanomushrooms, 217 Nanoonions boron-containing pyrene–BODIPY conjugates, 522 (see also Carbon nanoonions (CNOs)) CNO/Zn-porphyrin complex, 522, 523 complexation of Py-CNOs with ZnTPP, 726, 727

Index environmental applications, 522 MOFs, 523 non-covalent assembly, p-CNO, 522 pyridyl-functionalized and water-soluble, 726 TEM images, 523 Nanopalm, 207 Nanopapers, 265, 267 Nanopeapods, 142, 143 synthesis, 683, 684 Nanopencils, 131 Nanopillars, 156 Nanoplates, 230, 231 Nanoporous carbon fibers (NCPFs), 74 Nanoprism, 282, 285 Nanoprotrusion, 524, 525 Nanorelay, 272 Nanorings Brenner–Tersoff, 156 carbonization process, 156 CNR–graphene hybrid structure, 159 electronic structures, 156 FESEM image, 157 formation, 157 MD simulations, 156 NCN and MCN structures, 158 NCN:CNT system, 156 [N]-cycloparaphenylenes, 160 predicted types, 158 quasi-1D ballistic, 157 terahertz radiation, 157 Nanosized tetrahedral networks, 77 Nanosphere carbon-TiO2 composite, 167 catalysts, TEM images, 169 Co@MC, 168 FCNS, 167, 169, 170 MC, 167 N-doping, 166 Ni/NiO, 166 polydopamine, 166 pyrolysis, 166 QCNSs, 171 synthesis, 171 Nanospindles, 237, 238 Nanosponges, 112 CBXMWNTs, 242, 243 CVD, 241 metal cluster doping, 242 oil absorption, 241 PECVD, 241 SWCNT bundles, 242, 243 Nanosprings DLC nanowires, 248 FIB-CVD, 248 Nanostructured carbon foams (NCF), 526, 527 Nanotechnical structures and devices CNM fabrication, 262 field-effect transistors, 262 graphene, 261, 262 LDO, 262 PCACM, 262, 263 TEM images, 262 UV exposure process, 263 E-nose, 270, 271

Index E-tongues, 270, 271 nanobalance, 259, 260 nanobatteries, 268, 269 nanocars gold surface, 257 motion, 259 p-carborane, 257 propulsion scheme, 258 synthesis, 258 top-down and bottom-up approach, 257 nanocoils, 248 nanojunctions, 264 nanopapers, 265, 267 nanospirals, 248 nanosprings, 248 nanothermometers biological systems, 252 carbon nanodots, 252 double walled carbon nanotubes, 251 Ga-filled carbon nanotube, 251 indium-filled carbon nanotube, 252 liquid metals, 250 MSCDs, 253, 254 nanotubes of oxides, 250 PNIPAM, 252 red-emitting CNDs, 253 shuttle configuration, 251 telescope configuration, 251 TEM images, 252 nanotweezers applications, 254 FIB-CVD, 254, 256 polyhedron, 272 Nanotepees, 231, 232 Nanotetrahedron, 277–279 Nanothermometers biological systems, 252 carbon nanodots, 252 double walled carbon nanotubes, 251 Ga-filled carbon nanotube, 251 indium-filled carbon nanotube, 252 liquid metals, 250 MSCDs, 253, 254 nanotubes of oxides, 250 PNIPAM, 252 red-emitting CNDs, 253 shuttle configuration, 250 telescope configuration, 251 TEM images, 252 Nanotori, 65 C170, 164 C240 molecule, 164 electric conductance, 162 electronic structure, 162 Gaussian curvature G, 161–163 length, height and rotational symmetry, 161 local curvature energy Ec/A, 161–163 magnetism, 162, 163 NEMS, 162 polygonal, 161 structural models, 161–163 structural stability, 164 thermal stability, 164 Zeeman effect, 162 Nanotrees, 205, 207

785 Nanotriangles, 273, 276 Nanotruck, 708 Nanotubes, 36 Nano-turbine, 272 Nanotweezers FIB-CVD, 254, 256 Nanourchins, 225–227 Nanowebs, 239–241 Nanowick, 155 Nanoworms catalyst nanoparticles, 225 graphite intercalated compounds, 224 Pd crystals, 224 TEM image, 224 Natural coals applications, 654 N-containing ligands, 740 bipyridyl moieties, 621 cPcCo–B–aCNT, 629, 630 metal porphyrins, 624, 625 phthalocyanine-CNT composites, 629 polymer–nanotube complex, 626 porphyrin- and metal-porphyrin-functionalized CNTs, 623, 624 Sn(IV) porphyrin- functionalized SWCNTs, 628 transient absorption spectrum, 628 Zn-porphyrin complex, 626 Zn-porphyrin polymer, 626 ZnTNP–PAES, 627 ND-ODA, 85, 86 N-doped amorphous carbon nanofibers (NACNFs), 72, 73 N-doped carbon nanotube cups (NCNCs), 228 N-doping, 345–348 Nezara viridula, 271 N-functionalized carbon nanofibers (N-CNFs), 74 Ni(II)-based metal–organic coordination polymer nanoparticle/reduced graphene oxide (NiCPNP/rGO) nanocomposite, 487 Ni(II) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11tetraazacyclotetradeca- 3,5,7,10,12,14-hexaene (Ni (II)-tetramethyldibenzotetraaza[14]annulene (NiTMTAA), 472, 473 Nitride clusterfullerenes, 504 Nitrogen-doped carbon nanotube cups (NCNCs), 229 Nitrogen-doped nanoonions (NNO), 181 Nitrogen-rich porous carbons (NPCs), 336, 337 N-methylfulleropyrrolidine, 53 N-methylpyrrolidone (NMP), 584 Non-polymerized cages, 60 Nonprecious CNFs, 76 Nontoxic fullerene, 54 Novamene, 3 NP toxicity, 643

O O-containing ligands, 619, 739 OM-SiC-CDC, 324 Onion-like carbon (OLC), 87 Open circuit voltage (VOC), 26 Optical information processing devices, 55 Organometallic electrode, 550 Organometallics, 631 Organometallics, CNTs functionalization carbonyls and π-complexes “boomerang” effect, 451 carbonyl organometallics, 448

786 Organometallics (cont.) functionalized graphene, by metal-bis-arene, 449 Mn metal, 448 mono- and bis-hexahapto SWCNT coordination compounds, 446 multidecker benzene-vanadium sandwich, 449 nanostructured graphene-based electrode with Os(II) complex, 452 pyrene moieties and nanotube surface, 449, 450 pyrene-functionalized nickel complexes, 450 SWCNT with modes of bonding, 446 trans-chlorocarbonyl-bis(triphenylphosphine) iridium(I), 444 V4BZ3 with graphene electrodes, 449 composites with metal carbene complexes, 454 metal cyclopentadienyls, 441–443 Oxygen reduction reactions (ORR), 72, 281, 349 Ozonation, 737, 738

P Parchment model, 63 Particulate matter (PM), 639 car emissions, 650 diesel exhaust gas, 650 filtration, DPF, 650 Passivated CDs (PCDs), 707 Pentagon Isolation Rule (PIR), 50 Penta-graphene, 358, 359 cairo pentagonal tiling, 397 chiral structures, 397, 398 CNT structures, 399 features, 397 structural transformation, 398 T12-carbon phase, 397 2D structure, 400 Permanent/chemical gel, 316 Phagraphene atomic structures, 403 DFT calculations, 402, 403 doping effects, 404 edges, 404 features, 402, 403 haeckelite-like structure, 402 periodic supercell, 403 Stone–Wales defects, 404 UTS, 403 Photoabsorption spectrum, 55 Photoconductivity, 51 Photoluminescence (PL), 537 Photosensitizers and carbon nanotubes, 458 and fullerenes, 513 and graphene, 490 Phthalocyanine-functionalized CNTs a-MWCNT/FePc, 439 CNT–MPc catalytic activity, 438 metal phthalocyanine and porphyrin functionalized MWCNTs, 438 non-covalent functionalization, 440 O2 molecule, on CNT–MPc complex, 438 Pd(II)Pc-SWCNT and Ru(II)bis(pyridine)Pc-SWCNT, 439 peripheral phthalocyanine substituents, fragmentation of, 437 (Pyr)-substituted phthalocyanines (Pcs), 440 PI-based CNFs, 74 Planar graphene, 36 Plasma-enhanced CVD (PECVD), 26, 89

Index Plasma treatment, 736 Plasmodium falciparum histidine rich-protein-2 (PfHRP-2), 215 Poly(3,4-ethylenedioxythio-phene) (PEDOT), 282, 283 Poly(4-styrene sulfonate) (PSS), 602 Poly(N-isopropylacrylamide) (PNIPAM), 252 Polyacrylonitrile-based heteroatomic CNFs, 76 Polycyclic aromatic hydrocarbons (PAHs), 36, 383 Polyethylene/Prussian blue/CNT (PE-PB/CNT), 455, 456 Poly-furfuryl alcohol nanowires, 305 Polyhedron-like nanostructures, 272 Polymer-coated nitrogen-doped carbon nanodots (pN–CNDs), 735 Polymer-grafted graphene exfoliation yield, 605 graphene/poly(2-vinylpyridine) nanohybrids, 605 N3-PCL, 604 PCL-g-GF, 604 preparation methods, 604 PSS, 602 waterborne dispersions, 605 water-soluble, 602 Polyvinyl alcohol (PVA), 658 Porous carbon nanofiber (PCNF), 74 Porous doped CNFs, 73 Porous N-doped CAs, 318, 319 Porphyrin functionalization, CNTs dihydroxotin(IV) porphyrin functionalized SWCNTs nanohybrid, 434, 436 equilibrium geometries, FeP and FeP*, 433, 434 Fe-porphyrin-like CNTs, 434, 436 ferrocene/porphyrin onto carbon nanotube arrays, 434, 435 iron porphyrin FeP, covalent and noncovalent attachment, 433 non-TPP type chiral porphyrins, 431 porphyrin-like defects, 434 ruthenium porphyrin functionalized SWCNTs arrays, 434, 435 structural design, tin porphyrin, 434 SWCNT doped with porphyrin-like nitrogen defects (4ND-CNxNT), 415, 434 SWCNT-PVPZn(TPP) nanohybrid, 431 TM/4ND-CNXNT, 434 and zinc complexes, 431 Porphyrin-containing graphene composites applications, 480 atomic structure, 480 bulky mesityl groups, 479 few-layered graphene (FLG)/porphyrin hybrids, 480 graphene-dimesitylporphyrin hybrids, 479 rectification properties, 478 transition metal ions, 478 ZrIV(Pc), potential binding modes, 481 Powder CB, 310, 311 PPyrr/SWCNT-COOH film, 624 Predicted allotropes, 2, 3, 8 Pre-lithiation process, 226 Prismane C8, 394, 395 Pristine fullerene, 585 Pristine graphene (pG), 459, 461, 681–683 Problems and calculations buckminsterfullerene С60, 745 carbon atoms, 749 CNTs diameter, 749 enthalpy of formation, 746, 747 hydrogen energetics, 747, 748 distance between fullerene molecules, 749 Fluor-C60 derivatives, 751

Index graphene square, 750 nanocatalysts, 744 Prussian blue (PB), 317 p-SWCNTs–porphyrin solution, 623 Pt-CNFs, 74 Pulsed laser deposition (PLD), 715 Pyrolysis technique, 60 Pyrolytic graphite, 10

Q Q-carbon, 365 Quantum-chemical simulation, 62 Quaternized carbon nanospheres (QCNSs), 171 Quenchable amorphous diamond, 19

R R3-Carbon, 404, 405 Radial breathing mode (RBM), 671 Radio-frequency hot-filament CVD (RFHFCVD), 236 Raman scattering, 39 Raman spectroscopy, 670, 671 graphene, 42 Rare nanocarbons atomic carbon, 113 carbyne (see Carbyne) CAWs (see Carbon-atom wires (CAWs)) CDs (see Carbon nanodots (CDs)) diatomic carbon, 113 elongated carbon nanostructures (see Elongated nanocarbons) GQDs (see Graphene quantum dots (GQDs)) Rayleigh imaging, 39 Reduced graphene oxide (RGO), 14, 38, 40, 42 aerogels, 317 Refractive index graphene, 39 Refractory black carbon (rBC), 647 Resorcinol-formaldehyde (RF) method, 316 Reversible/physical gel, 316 Russian Doll model, 63

S Safety carbon fibers, 742 carbon powder and activated carbon, 741, 742 Schiff bases, 481, 482, 541, 545 S-containing ligands, 629, 630 Shear force mixing, 737 Sigma-Aldrich, 49 Single graphene sheet, 39 Single-wall CNTs (SWCNTs) applications, 657 BSA, 657 casting, 659 chiral vector, 67, 68 in concentrated sulfuric acid, 46 conceptual diagram, 67 diameter, 63 dispersion in solvents, 65 freestanding, 64 graphene nanoribbons, 47 interaction of GNRs, 47 mechanism, 70

787 nanometer-scaled tubular, 65 oxygen-containing media, 65 printing process, 658–660 properties, 63 PVA, 658 standard, 64 TEM image, 68 Young’s modulus, 64 Single-walled carbon nanotubes (SWCNTs), 132, 133 Small endohedral metallofullerenes M@Cn, 55–62 Small fullerenes ab initio method, 59 beam studies, 55 carbon cages, 60 chemisorption, 59 comparative analysis, 61 compounds, 61 density-functional-based tight-binding model, 61 DFT-based Dmol3 method, 61 dissociative addition of complexing agents, 61 EI mass spectrometry, 59 electronic characteristics of hybrid nanostructures, 62 electronic properties, 61 electronic transport properties, 56, 57, 59 EMS software package, 60 encapsulation, 59 endohedral bonding, 62 Euler theorem, 55 excluding evaporation, carbon via benzene pyrolysis, 60 ground-state structures, 55 Hf@C28 structure, 61 Hueckel model calculations, 56 image simulations, 60 instability, 55 Jahn–Teller effect, 55 Kekulé valence structures, 56 lower kinetic stability, 55 mechanism, 59 molecular crystals, 61 non-polymerized cages, 60 pyrolysis technique, 60 quantum-chemical simulation, 62 quasi-dynamic local-density simulations, 61 spectral properties, 56 stability, 55, 56 structures and electronic properties, 56 C28, 56, 58 cubic phase of (C28)8, 58 cubic-phase of (C28)8, 56 dimers (C28)2, 56, 58 molecules, 56, 58 synthesis, 59 tetravalent M@C28, 61 Ti@C28, 61 valence electron states, 62 variations, 55 Sodium dodecylbenzene sulfonate (SDBS), 600 Soil, 642 Solar cells, 48, 55 Sol-gel processing, 667 Solubilization carbon allotropes, 577 CB nanoparticles, 616 chemical functionalization, 618

788 Solubilization (cont.) CNDots carbonization, 613 fluorescence mechanism, 614 fluorescence of, 613 hydrothermal dehydration, 613 nitrogen, 613, 615 pN-CNDots, 613–615 sedimentation, 613 sedimentation process, 613 solubility, 613 synthesis, 614 tunable fluorescent emission, 615 water-soluble photoluminescent, 613, 615 CNFs, 616 CNOs (see Carbon nanoonions (CNOs)) CNTs (see Carbon nanotubes (CNTs) (see also Dispersion) dispersions, 616, 618 fullerenes aqueous solubility, 584 C60 molecule, 582 C70, 584, 586, 587 chemical functionalization, 584 C60-tris-malonic derivative, 583 fullerene–glycine, 583, 584 investigations, 582 malonate groups, 583 NMP, 584 organic solvents, 583 oxidation mechanisms, 584, 585 oxidation-induced water solubilization, 584 selected solvents, 584, 586 solubility, 582 solvent polarizability and polarity, 582 space-filling model, 583 graphene biomolecules, 606 characterization, 598 covalent and non-covalent functionalization, 599–603 dispersion, 598 electrocatalytic, 602 electrochemical exfoliation, 598 hydrophobic material, 597 mechanochemical milling, 598 nanotechnology, 597 polymer-grafted, 602, 604, 605 solvents, 598, 599 stabilization, 597 surfactants, 599–601 graphite chemical (see Chemical solubilization) GrO, 592 ultrasound, 595 ultrasound-assisted solubilization, 592–594 hollow carbon nanoplates, 617 metal-complexes (see Metal-complexes) nanofoams, 616 nanoplates, 616 NDs (see Carbon nanodiamonds (CNDs)) stability, carbon dispersions, 618 ultrasound treatment, 618 Solution process method, 72 Solvent exchange method, 584 Soot carbon, 641 Space-filling model, 583

Index Spherical activated carbon (SAC), 336 Spherical–elongated–spherical, 64 Spintronics, 361 Sponge-like carbonaceous gels, 712 Spray pyrolysis, 64, 678, 679 Stirrup configuration, 358 String of pearls, 52 Students information 1,10-binaphthyl-incorporated conjugated polymers, 739 characterization methods, 668, 669 coordination compound, 738 DNA, 739 DWCNT, 738 hydrothermal method, 737 MnO2, 738 MW, 728, 729 nanoparticles, 666 Ni corrosion experiment, 673 ozonation, 737, 738 plasma treatment, 736 proteins, 739 shear force mixing, 737 surfactant dodecyl Flavin FC12, 738 US, 735 Sulfur-containing ligands, 441 Sun's formation, 77 Superdense carbon allotropes, 407, 408 Superparamagnetism, 42 Surface-enhance Raman scattering (SERS), 715 Surfactant dodecyl Flavin FC12, 738 Surfactant sodium dodecylbenzene sulfonate (SDBS), 735 Suzuki coupling, 610 Suzuki coupling reactions, 85, 87 SWCNT–porphyrin composites, 623 Synthesis BDD, 698 C60NWs, 675 cage-opening buckminsterfullerene, 718 carbide-derived carbon, 718, 719 carbon allotropes fullerenes, 667 nanofibers, 669 nanoonions, 669 nanospheres, 669 nanotubes, 669 quantum dots, 669 carbon nanobrushes, 701, 702 carbon nanochains, 684, 685 carbon nanocone, 689 carbon nanocups, 701 carbon nanodots, 717 carbon nanoflowers, 696 carbon nanofoam, 706 carbon nanoforests, 696 carbon nanoleaves, 696, 697 carbon nanomesh, 709 carbon nanoplates, 701, 702 carbon nanorings, 691, 692 carbon nanospikes, 689 carbon nanospindles, 704 carbon nanotetrahedra/nanoribbons, 711 carbon nanotori, 691 carbon nanotrees, 696 carbon nanourchins, 698, 699 carbon xerogel particles, 712, 714

Index carbyne, 714, 715 chaoite-like macrotubes, 716, 717 CNBs, 687–689, 700 CNCs, 706 Fe3O4, 693, 694 CNFs CO2, 685, 686 CVD reactor, 685, 686 maghemite CNF/γ-Fe2O3, 687 CNM, 708, 710 CNO, 678 CNR, 690, 691 CNSs, 690, 691 CNTs arc discharge, 679 CVD, 679 electric-arc technique, 681 large-scale, 681, 682 MWCNTs, 722 spray pyrolysis, 678, 679 confined growth, 667 droplet-to-particle conversion, 667 fluorescent graphene quantum dots, 718 fluorescent nanocrystallinecellulose/carbon dot hydrogels, 712 fulleropyrrolidine, 677, 678 gas-phase chemical, 666 gas-phase physical, 666 GCNTs, 703, 704 glassy carbon nanowires, 711, 712 GQDs, 717 graphene BC, 674 chemical vapor deposition, 672, 674 direct exfoliation, 674 flow chart, 676 fullerene-intercalated graphene hybrids, 676 graphene nanobuds, 681, 682 graphene@PANI nanoworm, 698, 699 graphone, 722 graphyne, 722 HCNBs, 690 liquid-phase preparation, 667 MCAs, 712 MCCs, 711 metal-complex hybrids carbon nanodots, 727 carbon nanofibers, 727 fullerenes, 724, 725 graphene, 723 and nanodiamonds, 725, 726 nanoonions, 726 MOF-derived carbon, 719, 720 monolayer colloidal crystal template, 667 MoS2/Co9S8/C, 693, 694 nanodiamonds, 682, 684 nanopeapods, 683, 684 nanovehicle, 707–709 physical process, 667 physicochemical process, 667 sol-gel processing, 667 3D-branched carbon nanowebs, 704, 705 3D carbon nanotube sponges, 705, 706 vapor-phase synthesis, 667 water–dispersible carbon nanocapsules, 694, 695 “wet chemical” methods, 667

789 Y-CNC, 707 ZIF-67, 693 Synthetic diamonds, 20, 21 Synthetic graphite, 10

T T-carbon C20-T, 367 crystal structure, 367 features, 366 MWCNTs, 366 nanowire-like morphology, 366 NWs, 366 Pnm space group, 367 principles, 367 properties, 367 structural model, 366 Tetrahedral amorphous carbon, 23 Tetrathiafulvalene (TTF) derivatives, 602 Theraphthal (TP), 177–179 Thermal black production process, 311, 313 Thermal conductivity, 20, 21 graphene, 36 Thermal spraying, 51 Thermally oxidized nanodiamond (T-CND), 607 Thermaloxidative processes, 310 Thermo-gravimetric analysis (TGA), 678 Thermoplastic polyurethane (TPU), 314 3D-branched carbon nanowebs, 704, 705 3D carbon nanotube sponges, 705, 706 3D warping, 36 Ti:S laser-treated samples, 307 Tiling, protomene structure, 3, 7 TM/4ND-CNXNT, 434 Toxic trinitrotoluene (TNT), 361 Training, 742 Transistor production, 47 Trichloroethylene, 649 Triple-wall CNTs (TWCNTs), 63 Tsuji–Trost allylation, 461, 462 Tunable nanoporous carbon, 324 2D electron gas (2DEG) behavior, 47

U Ultimate tensile strength (UTS), 403 Ultradispersed diamond (UDD), 80, 82 Ultrafine carbon black, 720, 721 Ultrahigh concentration graphene, 599 Ultralarge graphene oxide (UGLO), 12 Ultrananocrystalline diamond (UNCD), 77, 80, 81, 84, 89 Ultra-smooth nanostructured diamond (USND), 80 Ultrasonic treatment in benzene, 43 Ultrasonication, 735 Ultrasound (US), 735 Ultrasound-assisted solubilization graphite dispersions, 592 exfoliation, graphene, 593 formation mechanism, 593 graphene flakes deposited, 593, 594 graphene layers, 592 liquid-phase exfoliation, 592, 593 treatment, 592

790 Unfractionated heparin (UFH), 606 Uniaxial stress field, 304, 306

V Valence electron states, 62 van der Waals force, 71, 248 Vapor-growth technique, 62 Vapor–solid (VS), 21 Vegetable black, 641 Vi-SiOC-CDC, 327, 328 Volatile organic compounds, 334

W Washboard/zigzag configuration, 358 Water–dispersible carbon nanocapsules, 695, 696 Water soluble carbon nanoonion (wsCNO), 273

Index Water steam, 337 Wet-chemical methods, 43 Wet-pelletized CB, 310, 311

X X-ray absorption near-edge structure (XANES), 672 X-ray diffraction (XRD), 672, 678, 709 X-ray photoelectron spectroscopy (XPS), 709

Y Young’s modulus, 36, 64

Z Zeeman effect, 162 Zeolitic imidazolate framework-8 (ZIF-8), 72, 73, 193, 336