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History of Nanotechnology
Scrivener Publishing 100 Cummings Center, Suite 541J Beverly, MA 01915-6106 Advances in Nanotechnology & Applications Series Editor: Madhuri Sharon The unique properties of nanomaterials encourage the belief that they can be applied in a wide range of fields, from medical applications to electronics, environmental sciences, information and communication, heavy industries like aerospace, refineries, automobile, consumer and sports good, etc. This book series will focus on the properties and related applications of nanomaterials so as to have a clear fundamental picture as to why nanoparticles are being tried instead of traditional methods. Since nanotechnology is encompassing various fields of science, each book will focus on one topic and will detail the basics to advanced science for the benefit of all levels of researchers. Series Editor: Madhuri Sharon, Director, Walchand Centre for Research in Nanotechnology & Bionanotechnology W.H. Marg, Ashok Chowk, Solapur 413 006 Maharashtra, India E-mail:[email protected] Publishers at Scrivener Martin Scrivener ([email protected]) Phillip Carmical ([email protected])
History of Nanotechnology From Pre-Historic to Modern Times
This edition first published 2019 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA © 2019 Scrivener Publishing LLC For more information about Scrivener publications please visit www.scrivenerpublishing. com. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. Wiley Global Headquarters 111 River Street, Hoboken, NJ 07030, USA For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Limit of Liability/Disclaimer of Warranty While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials, or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Library of Congress Cataloging-in-Publication Data ISBN 978-1-119-46008-4 Cover image: Pixabay.Com Cover design by Russell Richardson Set in size of 13pt and Minion Pro by Exeter Premedia Services Private Ltd., Chennai, India Printed in the USA 10 9 8 7 6 5 4 3 2 1
Contents Preface Foreword 1 How Old is Nanotechnology? Mrinal Chakre and Madhuri Sharon Preamble 1.1 Introduction 1.2 Nano-Geosystem for Abiotic Nanoparticles Formation 1.2.1 Nanoparticles Occuring in Mineral Composites 184.108.40.206 Allophane and Smectites 220.127.116.11 Opal 1.2.2 Nanoparticles From Volcanic Activities 1.2.3 Nanoparticles From Dust of Cosmic Sources 1.2.4 Nanoparticles From Desert Surfaces 1.3 Nano-Biosystem Consisting of Biotic Nanoparticles 1.3.1 Nanobe 1.3.2 Virus 1.3.3 Bacteria 1.4 Concluding Remarks References 2 Prehistoric Evidence of Nanotechnology Aparna A Bhairappa and Madhuri Sharon 2.1 Introduction 2.2 Evolutionary Study and Theories 2.2.1 Aristotelian Theory 2.2.2 Einstein’s General Theory of Relativity 2.2.3 Hubble’s Hypothesis 2.3 Prehistoric Era 2.4 What Is Nanotechnology?
xi xiii 1 1 3 5 7 7 8 9 9 10 11 12 13 14 16 17 21 21 22 25 25 26 28 29
Contents 2.5 Was Nature the First to Fabricate Nanomaterials? 2.6 Concluding Remarks References
30 34 35
3 Nanotechnology in Ancient India Vaishali A Gargade 3.1 Introduction 3.2 Glimpses of Remnants of Nanotechnology-Based Materials Made in Ancient India 3.3 Advancement of Nanoscale Metallurgy in Ancient India 3.3.1 Damascus Sword 3.3.2 Iron Pillars 3.4 Applications of Nanometals in Ancient India 3.4.1 Ornaments 3.4.2 Paints and Coatings 3.5 Nanomedicine Evolved in Ancient India that Still Prevails Today 3.6 Carbon Nanoforms Used in Cosmetics in Ancient India that still Prevail Today 3.6.1 Herbal Kajal 3.7 Concluding Remarks References
Are Bhasma Nanomedicine of Ancient Times Archana S Injal 4.1 Introduction 4.1.1 Ayurveda: An Age-Old Science That Originated in India with Dhanvantari 4.1.2 History of Ayurveda 4.2 Bhasma: An Ancient Indian Medicine Concept Also Followed by the Chinese and Egyptians 4.2.1 Types of Nano-Size Bhasma 18.104.22.168 Metal Bhasma: Element Form (Toxic), Compound Form (Safe) 22.214.171.124 Metal Mixture/Alloy Bhasma 126.96.36.199 Herbo-Mineral Bhasma 188.8.131.52 Other Bhasma 4.2.2 Properties of Bhasma 184.108.40.206 Physical Properties 220.127.116.11 Chemical Properties 4.3 The Similarity of Bhasma Preparation to Contemporary Nanoparticle Synthesis Method
37 39 40 41 43 45 45 46 47 51 51 52 53
57 58 60 62 63 63 64 72 74 75 75 77 78
Contents vii 4.4 Various Medicinal Uses of Bhasma 4.5 Concluding Remarks References 5 The Maya’s Knowledge of Nanotechnology Vinod P Sinoorkar 5.1 Introduction 5.2 The Maya 5.2.1 Yucatec Maya 5.2.2 Chiapas 5.2.3 Belize 5.2.4 Guatemala 5.3 The Maya Civilization 5.3.1 The Maya During the Preclassic Period 18.104.22.168 The Maya of the Early Preclassic Period 22.214.171.124 The Maya During the Middle Preclassic Period 126.96.36.199 The Maya During the Late Preclassic Period 5.3.2 The Maya During the Classic Period 5.4 Some Characteristic Features of the Maya 5.4.1 Beauty Expressions 5.4.2 Jade: The Green Gold of the Maya 5.4.3 Maya Hieroglyphics 5.4.4 The Maya’s Eyes on the Heavens 5.4.5 The Maya Calendar 5.4.6 Maya Art 5.4.7 Maya Paintings 5.5 Maya Blue and Maya Yellow – Ancient Nanostructured Materials 5.5.1 Resistance to Weathering 5.5.2 Preparation of Maya Blue 5.5.3 Chemical Composition of Maya Blue 5.5.4 Are Maya Paintings Nano Based? 5.6 Concluding Remarks References 6
81 81 84 91 91 92 92 92 93 93 94 95 95 96 97 97 99 99 100 100 101 102 103 104 105 107 107 108 109 110 110
Did Nanotechnology Flourish During the Roman Empire and Medieval Periods? 113 N B Patkar and Manisha Sharan 6.1 Introduction 113 6.1.1 Transition Elements of the d-Block Elements 114
Contents 188.8.131.52 Melting and Boiling Point 184.108.40.206 Formation of Colored Ions 6.2 Nanotechnology During Roman Civilization 6.2.1 Historical Records of Use of Luster Ceramics 6.2.2 Technology of Luster Decorations of Ceramics 6.2.3 Soluble Gold Concept and Use of Soluble Gold 220.127.116.11 Development of the Lycurgus Cup 6.3 Nanotechnology During the Medieval Period of European Civilization 6.3.1 Medieval Metals and Glass 6.3.2 Use of Gold, Silver and Other Metal Nanoparticles in the Middle Ages 6.3.3 Purple of Cassius 6.3.4 Contribution of Johann Kunckel 6.4 Conclusion References
7 European Nano Knowledge That Led to Faraday’s Understanding of Gold Nanoparticles Anil Kumar S Katti and Madhuri Sharon 7.1 Introduction 7.1.1 Reflection of Light 7.2 Michael Faraday’s Painstaking Efforts 7.3 The Role of Gustav Mie and Richard Gans in Understanding Metal Nanoparticles 7.4 Zsigmondy’s Seed-Mediated Method 7.5 Research that Led to the Understanding of Metal Nanoparticles Optical Properties 7.5.1 Surface Plasmon Resonance and Plasmonics 7.5.2 Quantum Confinement Effect 7.6 Approaches to Fabricate Nanomaterials 7.7 Advancements in Various Fabrication Methods of Nanoparticles 7.7.1 Physical Methods 18.104.22.168 Mechanical 22.214.171.124 Melt Mixing 126.96.36.199 Hydrothermal and Solvothermal Synthesis 188.8.131.52 Templating 184.108.40.206 Electron Beam Lithography 220.127.116.11 Vapor Phase Synthesis
115 115 116 116 118 119 122 125 125 126 134 136 136 137 141 141 142 146 148 149 150 150 155 159 161 161 161 165 166 166 168 169
Contents ix 18.104.22.168 22.214.171.124 126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168
Gas Phase Methods Thermal Decomposition and Combustion Sputtering Arc Discharge Laser Ablation and Pulsed Laser Ablation Ion Implantation Synthesis of Nanoporous Polymers Using Membranes 7.7.2 Chemical Methods 22.214.171.124 Colloidal Methods 126.96.36.199 Conventional Sol-Gel Method 188.8.131.52 LB Technique 184.108.40.206 Microemulsion-Based Methods 7.7.3 Biosynthesis or Biological Methods of Synthesizing Nanoparticles 220.127.116.11 Nanometal Synthesis Using Microorganisms 18.104.22.168 Nanometal Synthesis Using Fungi and Actinomycetes 22.214.171.124 Nanometals Synthesis Using Plants 126.96.36.199 Nanometals Biosynthesis Using Algae 188.8.131.52 Nanometals Biosynthesis Using DNA 184.108.40.206 Nanometals Biosynthesis Using Enzymes 7.7.4 Hybrid Methods 7.8 Concluding Observations References 8 Contemporary History of Nanotechnology CH Godale and Madhuri Sharon 8.1 Introduction to the Concept of Nano after 1959 8.2 Feynman’s Idea: Entry of Nanotechnology in Modern Science 8.3 Drexler’s Engines of Creation 8.4 Impetus Given by SEM, TEM and AFM 8.5 The Entry of Nano Forms of Carbon 8.5.1 Fullerene: The First Fabricated Carbon Nanomaterial 8.5.2 Carbon Nanotubes 8.5.3 Graphene 8.6 Advancements in Various Fabrication Methods
171 173 174 177 180 181 182 184 184 184 185 186 187 187 192 193 194 195 196 197 197 198 213 214 215 217 218 219 221 225 230 232
Contents 8.7 Immeasurable Applications of Nanotechnology in All Fields of Science 8.7.1 Electronics 8.7.2 Energy 8.7.3 The Environment 8.7.4 Automobiles 8.7.5 Agriculture and Food 8.7.6 Industries 8.7.7 Textiles 8.7.8 Cosmetics 8.7.9 Domestic Appliances 8.7.10 Space and Defense 8.7.11 Therapeutics and Diagnostics 220.127.116.11 Early Detection of Cancer 18.104.22.168 Bioimaging and Biological Labeling 22.214.171.124 Targeted Drug Delivery 126.96.36.199 Photothermal Therapy 188.8.131.52 Tissue Engineering and Better Body Implants 184.108.40.206 Nanotechnology-Based Biochips and Microarrays 220.127.116.11 Nanotechnology-Based Cytogenetics 18.104.22.168 Nanotechnology for Protein Detection 22.214.171.124 Nanoparticles for Tracking Stem Cells 126.96.36.199 Nanonephrology: A New Attempt at Tackling Renal Disease 188.8.131.52 Nano Intervention for Neurodegenerative Diseases 184.108.40.206 Possibility of Medical Application of Molecular Nanotechnology 220.127.116.11 Nanorobots and Theranostics 18.104.22.168 Nanomachines for Cell Repairs 8.8 Important Milestones of Nanotechnology 8.9 Summary References
233 233 236 237 239 240 241 242 242 244 246 249 249 251 251 252 252 253 254 254 255 255 256 257 258 258 259 259 264 271
Preface Nanotechnology is a very rich field of science due to informational input by physicists, chemists, engineers, geologists and biologists. However, this book was written from a layman’s perspective and questions whether it is a new science, or, like other sciences, was already discovered and utilized by nature. Did nature, which created an entire universe made up of galaxies, the solar system, the Earth and even living beings from the smallest known entities, also create nanoparticles? It is a difficult subject to write about since compiling knowledge about nature that has not been recorded in an easily decipherable form, coupled with the possibility of some natural records having been lost during the long periods of history either by nature or us, makes most information unavailable to us. We realized that apart from nature, human beings have also knowingly or unknowingly fabricated and utilized nanoparticles for various reasons. Looking back through history and searching for the existence of nanoparticles, not visible to the eye, and nanotechnology, not yet known to us but seen in nature, has been an interesting journey for us. I hope we have made it interesting enough for the readers also. Madhuri Sharon September 2018
Foreword It is a novel idea to write about nanotechnology in ancient periods. Since I have been a student of ancient Indian history and culture, it is difficult for me to review science, especially nanotechnology and its effect in ancient times. Dr. Madhuri Sharon and her teammates have very effectively described this Dr. Neelam Koomar rich field of science applied in the past. They have very lucidly described its application in prehistoric times. In ancient India, unknowingly, people have used it in the field of medicine, cosmetics, metallurgy, etc. Nanotechnology flourished in the Maya civilization of South America and also in Roman culture. If you sincerely analyze the Vedic period and Ramayana era, nanoparticles and nanotechnology were utilized. Thanks to Dr. Madhuri Sharon who introduced me to nanotechnology a decade ago. I wish Dr. Sharon and her team great success. Dr. Neelam Koomar Retd. Head of the Department of History and Culture T.M. Bhagalpur University, India
1 How Old is Nanotechnology? Mrinal Chakre and Madhuri Sharon Walchand College of Arts and Science, Solapur University, Solapur, Maharashtra, India
I want to know why the universe exists, why there is something greater than nothing. Stephen Hawking
Preamble When we sat down to write this chapter, the first thing that came to mind was whether there are nanoparticles existing in nature which are not man-made or fabricated. Both biotic and abiotic natural nanoparticles came to mind. The next question was, “Since when?” Nanoparticles by definition are particles of any shape with an equivalent diameter of 1–100 nm, i.e., specifically those particles that are intermediate in size between bulk materials and atomic/molecular structures or quantum dots. These nano-size particles exhibit unique physical and chemical properties due to their distinctive novel properties related to a high surface area to volume ratio and/or quantum effects.
Madhuri Sharon (ed.) History of Nanotechnology, (1–20) © 2019 Scrivener Publishing LLC
History of Nanotechnology
Table 1.1 Scales of Measurement. Factor
A quick glance at various scales of measurement (Table 1.1) gives an idea of how small a nanometer is. A nanometer (nm) is one thousand-millionth of a meter. For comparison, a red blood cell is approximately 7,000 nm wide and a water molecule is almost 0.3 nm across. People are interested in the nanoscale (which is defined to be from 100 nm down to the size of atoms (approximately 0.2 nm) because it is at this scale that the properties of materials can be very different from those at a larger scale. Nanoscience is defined as the study of phenomena and manipulation of materials at atomic, molecular and macromolecular scales, where properties differ significantly from those at a larger scale; and nanotechnologies as the design, characterization, production and application of structures, devices and systems by controlling shape and size at the nm scale. Let us look at some of the known naturally occurring nanoparticles. Depending on the origin, a distinction is made between three types of nano-size particles: (i) natural, (ii) incidental and (iii) engineered. Natural nanoparticles from volcanic dust, lunar dust, mineral composites, etc., have existed since the beginning of the Earth. Some such nanoparticles still
How Old is Nanotechnology?
occur in the environment and are termed incidental nanoparticles, also defined as waste or anthropogenic particles, which take place as the result of man-made industrial processes such as diesel exhaust, coal combustion, welding fumes, etc.
Our present awareness of nanotechnology (materials of a size between 1–100 nm, having novel properties that are not found in their bulk counterpart) started in the 1980s, caused by the convergence of experimental advances such as the invention of the scanning tunneling microscope in 1981 and the discovery of fullerenes in 1985, with the elucidation of a conceptual framework for the goals of nanotechnology. Nanotechnology became popularized as a result of the Nobel Prize being awarded for many nanoparticle discoveries; i.e., Nobel Prizes were awarded to Heinrich Rohrer in 1986 for the invention of the scanning tunneling microscope, to Kroto et al., in 1985 for the discovery of fullerene, and to Geim and Novoselov in 2010 for graphene. The ideas and concepts behind nanoscience and nanotechnology started with a talk entitled “There’s Plenty of Room at the Bottom” by physicist Richard Feynman at an American Physical Society meeting at the California Institute of Technology (Caltech) on December 29, 1959, long before the term nanotechnology was coined in 1974 by Taniguchi. Our concern in this chapter is to address the questions of “How old is nanotechnology?” and “Are there naturally occurring nanoparticles; if so, since when?” To know the existence of nanoparticles on Earth, which is part of this universe, we realize that their origin plays a great role in the existence of any matter. There was a time when scientists thought Earth was at the center of the universe. As late as the 1920s, we did not realize that our galaxy was just one of many in a vast universe. Only later did we recognize that the other galaxies were running
History of Nanotechnology
away from us—in every direction—at ever greater speeds. Our universe is both ancient and vast, and expanding out farther and faster every day. This accelerating universe, the dark energy that seems to be behind it and other puzzles, like the exact nature of the Big Bang and the early evolution of the universe, are among the great puzzles of cosmology. About 11 to 15 billion years ago all of the matter and energy in the universe was concentrated into an area the size of an atom. At that moment, matter, energy, space and time did not exist. Then suddenly, the universe began to expand at an incredible rate and matter, energy, space and time came into being (the Big Bang). As the universe expanded, matter began to coalesce into gas clouds, and then stars and planets. Our solar system formed about 5 billion years ago when the universe was about 65% of its present size. Today, the universe continues to expand along with the existence of nanoparticles. Though the chemical properties of a bulk material depend on its molecular structure, when they assemble at the nano level they exhibit other unique and novel physicochemical properties. That may be why nature decided to naturally synthesize particles at the nano level to contribute to the evolution of our Earth or perhaps other planets also. Prehistoric events date back to the time before the invention of writing—roughly 5,000 years ago. Without access to written records, scientists investigating the lives of prehistoric people face special challenges. A lot of knowledge has been lost due to man-made activities like wars, as well as natural calamities such as earthquakes, tsunamis, floods, volcanic eruptions and meteor showers, which have caused tremendous adverse effects. What are natural nanomaterials? As the name suggests, natural nanoparticles are synthesized by nature without the interference of man. At a very vast level of understanding of naturally occurring nanoparticles, Sharma et al.,  have considered five
How Old is Nanotechnology?
major points, namely, (i) the presence of naturally occurring nanoparticles in the atmosphere, hydrosphere, lithosphere and biosphere, (ii) the presence of naturally occurring organic matter and its role in the formation of metal nanoparticles like silver and gold, (iii) another important matter that they have considered is how the reaction between reactive oxygen species and natural organic matter at elevated temperature and/or exposure to light supports the formation of metal nanoparticles, (iv) how the properties and role of water especially related to the pH, redox conditions, ions/ionic strength and concentrations of natural organic matter determine the growth and stability of NPs in the aquatic environment, and finally (v) the impact of natural conjugation of organic matter with natural metal nanoparticles on toxicity, which may be less than that of the engineered nanoparticles that are surface-coated by polymers and/or surfactants. These considerations are based on the fact that there are naturally occurring nanoparticles that came into existence even before the formation of Earth. In nature, nanoparticles are naturally formed in all spheres of the Earth (atmosphere, hydrosphere, lithosphere and biosphere), either by chemical, photochemical, mechanical, thermal, and biological processes separately or in combination; and/or also by extraterrestrial inputs. Typical naturally occurring nanoparticles include (a) metals such as Ag, Au and Fe, (b) metal oxides, e.g., Al2O3, Fe2O3, MnO2 and SiO2, (c) metal sulfides like FeS2 and ZnS, etc.
Nano-Geosystem for Abiotic Nanoparticles Formation
In the first stage of chemical evolution on earth, molecules formed in the primitive environment were simple organic substances such as amino acids. This concept was first proposed in 1936 by Oparin . He considered hydrogen, ammonia,
History of Nanotechnology
water vapor and methane to be components present in the early reducing atmosphere. Oxygen was lacking in this chemically reducing environment. He stated that UV radiation from the Sun provided the energy for the transformation of these substances into organic molecules. In the second stage of chemical evolution, the simple organic molecules, e.g., amino acids, formed, which eventually joined together, forming structures such as peptides, proteins, etc. Linking of smaller units (in the absence of enzymes provided by living systems) occurred by the process of dehydration to form polymers. These polymers or organic monomers by some process must have moved onto the fresh lava or hot rocks, which would have allowed polymers to form abiotically. To support this hypothesis, Fox and Harada  abiotically synthesized polypeptides. The third step in chemical evolution suggests that polymers interacted with each other and organized into aggregates, known as protobionts. Protobionts are not capable of reproducing but have other properties of living things. In the final step of chemical evolution, the protobionts developed the ability to reproduce and pass genetic information from one generation to the next. Some scientists theorize that RNA was the original hereditary molecule. Gradually DNA replaced RNA as the genetic material. “Do nanoparticles exist in nature?” and “If so, since when?” are million-dollar questions!!! The answer to the first question is YES, almost every chemical formed (except liquids and gases) has some sort of structure on the nanometer scale. Moreover, many such examples provided by nanogeoscience studies prove it. Another example worth mentioning regarding the existence of nanoparticles in Earth’s atmosphere is mentioned by Eather  and Savage . They suggested that the northern sky bright lights near the polar region (known as aurora borealis, a term coined by Galileo Galilei), which appear in September, October, March and April, are optical
How Old is Nanotechnology?
phenomena caused by the interactions between the ionosphere nanoparticles and solar wind particles under the influence of Earth’s magnetic field. In nature, the formation of nanoparticles occurs via processes like weathering, i.e., mechanical processes combined with dissolution/precipitation; colloid formation in rivers, and by volcanic activity that involves fast cooling of fumes and explosions expelling tephra. In a nutshell, it is evident that nanoparticles are formed at phase boundaries, e.g., solid–gas wind erosion, liquid–gas evaporation of sea spray, solid–liquid weathering of rocks/minerals, etc. Such nanoparticles are produced in the form of colloids, aerosols, and dust (present as cosmic dust, constituents of soils and sediments, hydrothermal/chemical deposits, mineral nuclei). Chemical composition of these nanoparticles can be categorized as: Metal oxides/hydroxides, metals or alloys, non-metals such as carbon allotropes and others, silicates, sulfides of Cu and Zn containing pyrites FeS2 and ZnS, and nanoframboids in high temperature black smoker hydrothermal vents, sulfates, halides, and carbonates. Moreover, natural Au particles have been observed in both low- and high-temperature locations during ore mining activities .
1.2.1 Nanoparticles Occurring in Mineral Composites 22.214.171.124 Allophane and Smectites Allophane is an amorphous to poorly crystalline hydrous aluminium silicate clay mineral. Its chemical formula is Al2O. According to Theng and Yuan , soil has complex ecosystems with diverse compositions which also include nanoparticles. Hochella et al.,  and Parfitt  supported this belief and suggested that due to either biotic or abiotic processes, all the minerals go through a nanophase stage during formation. Allophane is one of the typical examples of natural nanoparticles that only
History of Nanotechnology
exist in the nano-size range of red > yellow >white .
Impotency, nocturnal emission, diabetes, frequent urination, recurrent miscarriages, leucorrhea, and infertility. It mainly affects nerves, testes, uterus, ovaries, and urinary bladder
Yashad Bhasma for zinc deficiency, throat, eyes, respiratory system, heart, blood, digestive system, and diabetes mellitus
Uses (As drug or in equipment)
68 History of Nanotechnology
Are Bhasma Nanomedicine of Ancient Times
Table 4.2 Different Types of Suvarna (Gold) Bhasma and Their Uses. Utilization in therapeutics: Internal administration Sr. no.
Brahma Rasayana – II
Apara Indrokta Rasayana
Raktapitta hara (bleeding disorders)
Visha hara (antipoison)
Utilization in Therapeutics: External Application Metal Sheet
Pitta Jwara (fever of Chikitsa 3/262 pitta origin)
Preparation of Equipment / Instruments, etc. Probable translation
Jihva Nirlekhana Dravya
Nabhi Kartana Dravya
Scissors for cutting umbilical cord
Vasti Netra Karnika Dravya
Nozzle of enema pot Siddhi 3/7
History of Nanotechnology
Table 4.2 Cont. Utilization in therapeutics: Internal administration Sr. no.
Vessels and containers
Chikitsa 1–2/4* Chikitsa 24/15** Chikitsa 24/154**
Purusha Anupramanam under Pumsavana Karm
A very small sized idol of male gender
Teekshna Soochi Shastra
Sharp instruments (used in labor room)
Other Purposes 1
Wearing gold / gold ornaments
Vimana 8/9 Vimana 8/11
General reference regarding Shodhana
Parthiva Dravya Ganana
Subclassification of the metal-based source
Kanaka is one of the synonyms for gold referred to even in Brahma Rasayana - I  and in Madhwasava , which has been clarified as Nagakesara by the commentator Chakrapani. All Chikita are mentioned in the Charaka. The dose of Swarna Churna (powder of gold) mentioned here is 1 Shana (3 g). Pharmaceutical procedure is to be carried out in a gold vessel. Water stored in a gold vessel is to be consumed 
Are Bhasma Nanomedicine of Ancient Times
Table 4.3 Different Types of Rajata (Silver) Bhasma and Their Uses . Utilization in therapeutics: Internal administration Sr. no.
Brahma Rasayana – II
Apara Indrokta Rasayana
Pandu Roga (hematinic)
Reference Chikitsa 1–1/58
Chikitsa 16/78 Chikitsa 16/82
Hicca (hiccup), Swasa Chikitsa 17/126 (respiratory distress)
Preparation of Equipment/Instruments, etc. Sr. no.
Probable Translation Reference
Jihva Nirlekhana Dravya
Vasti Netra Karnika Dravya
Pushpa Netra Dravya
Purusha Anupramanam under Pumsavana Karma
Nozzle of enema pot Siddhi 3/7 Siddhi 9/51 Silver containers
Idol of male gender
Sharira 8/9 Chikitsa 1-2/4
History of Nanotechnology
Table 4.3 Cont. Utilization in therapeutics: Internal administration Sr. no.
Teekshna Soochi Shastra
Nabhi Kartana Dravya
Sharp instruments Sharira 8/34 placed in labor room Scissors for cutting umbilical cord
Other Purposes 1
Parthiva Dravya Ganana
Wearing gold / gold ornaments
Vimana 8/9 Vimana 8/11
Classification of metal Sutra 1/70 based on the source
Pharmaceutical procedure is to be carried out in a silver vessel. Water stored in a silver vessel is to be consumed .
In Ayurvedic Rasa-Chikitsa, copper (Tamra) is an important metal used in the form of Bhasma in various preparations which are indicated for treating diseases like Pandu (anemia), Kustha (skin diseases), Arsha (piles), etc .
126.96.36.199 Herbo-Mineral Bhasma Anand Chaudhary and Neetu Singh of the department of Rasa Shashtra, Faculty of Ayurveda, Banaras Hindu University, have claimed that the Bhasma of herbo-mineral formulations are equivalent and in tune with nanotechnology that is being witnessed today in the production of nanoparticles . The studies by Yadav et al., , Kulkarni  and Khedekar et al.,  have confirmed that Bhasma are metallic/mineral nanoparticles (NPs). Although herbo-mineral formulations in the form of Bhasma of metals, herbs and minerals have been used since the 7th century, it was only assumed that these medicines had a superior level of efficacy in comparison to other Ayurvedic
Are Bhasma Nanomedicine of Ancient Times
Table 4.4 Different Types of Tamra (Copper) Bhasma and Their Uses. [Galib et. al., 2011] ] Utilization in therapeutics: Internal administration Sr. no.
Brahma Rasayana Rasayana – II (rejuvenators)
Apara Indrokta Rasayana
Hicca (hiccup), Chikitsa 17/126 Swasa (respiratory distress)
Visha hara (Antipoison)
Utilization in Therapeutics: External Application 1
Kusta (skin disorders)
Collyrium for Akshi Roga (eye disorders)
Preparation of Equipment/Instruments, etc. Sr. no.
Probable translation Reference
Jihva Nirlekhana Dravya
Chikitsa 7/117 Chikitsa 26/255
Vasti Netra Nozzle of enema pot Siddhi 3/7 Karnika Dravya Other Purposes (Continued)
History of Nanotechnology
Table 4.4 Cont. Utilization in therapeutics: Internal administration Sr. no.
Parthiva Dravya Ganana
Classification of Sutra 1/70 metal based on the source
Visha Kwathita Tamra
Simile for disrespect of a quack
Pharmaceutical procedure is to be carried out in a copper vessel.
dosage forms. It has also been established that manufacturing methods of Bhasma are in tune with nanotechnology of the modern era and are nearer to nanocrystalline materials, which have similar physicochemical properties. Lauha Bhasma has been found to contain traces of iron nanoparticles along with some herbal content.
188.8.131.52 Other Bhasma Shanka Bhasma: Prepared from calcinated conch shell of marine origin, it is used to treat peptic ulcer, cough, piles and some types of gastrointestinal disorders . Also, it is used in the treatment of hyperchlorhydria, sprue, colic and hepatosplenomegaly . Praval Pishti: A purified powder of corals, this Bhasma is used to treat calcium deficiency, blood pressure disorders, insomnia and agitation . Praval Panchamrit: Prepared from powder of corals, pearls and conch shells, this Bhasma is the richest source of natural calcium and is used to treat agitation, acidity and burning sensation . Jaharmohra Pishti: Prepared from the powder of serpentine orephite, this Bhasma is a natural source of calcium, useful in treating burning sensation, acidity and heartburn .
Are Bhasma Nanomedicine of Ancient Times
Mukta Pishti: Prepared from the powder of pearls, it is a good source of calcium. This Bhasma is also used for cooling and soothing, and to treat blood pressure disorders, acne, headaches, acidity, ulcers and heat disorders . Varatika Bhasma: Varatika is identified as the external shell of the sea animal Cypraea moneta Linn . , which is found in coastal areas of the sea. The common name for Cypraea moneta is money cowry. The herbo-mineral Bhasma prepared from Varatika is a rich source of calcium . Similarly, other materials of animal origin, such as bird feathers, eggshells, animal horns, bones, fish scales, etc., are also used for Bhasma preparations . Recent studies have confirmed that these Bhasma are composed of nanoparticles (Figure 4.2).
Properties of Bhasma
Some of the physical and chemical properties designated to Bhasma in ancient literature which correspond to the properties of nanoparticles are mentioned below. Most of the properties mentioned suggest that Bhasma are of nano size.
184.108.40.206 Physical Properties Varitara or floating property is applied to study the lightness and fineness of Bhasma, which floats on the surface of stagnant water. The Varitara test depends on the law of surface tension. Bhasma which is properly incinerated can float on the water surface [12, 59], which means they are hydrophobic and have a density lower than 1. Unama is a confirmatory test of Varitara in which a small grain of rice that is carefully kept on the layer of Bhasma floating on stagnant water does not sink . Rekhapoorna or furrow filling property testing depends on the fineness of Bhasma, so that Bhasma particle internalization or absorption is easily assimilated by the body . To
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Figure 4.2 SEM images of different Bhasma: (a) Mandura Bhasma (contains Fe2O3 and SiO2) showing uniformly arranged nanometal agglomerates of size 200–300 nm (Photo reproduced from ); (b) Rajata Bhasma showing spherical morphology with an average particle size of 350 nm (Photo reproduced from ). (c) Tamra Bhasma showing particle size of 45.4 nm (Photo reproduced from ). (d1) SEM and (d2) TEM images of Vanga Bhasma prepared by traditional method of 50% nanoparticles of 150–300 nm (Photos reproduced from ).
test this property, a pinch of Bhasma was rubbed in between the index finger and thumb. After a few seconds of rubbing it was observed that the Bhasma was completely filled in between the small lines of the fingers and thumb, which was not easily washed out . A Bhasma has to be Susukshama or very fine (perhaps of nano size) to have this physical property.
Are Bhasma Nanomedicine of Ancient Times
Slakshnatwa is complementary to fineness and relates to the smoothness of Bhasma, which produces a tactile sensation to the fingertips. Slakshna Bhasma can be absorbed and assimilated in the body without producing any irritation to the mucous membrane of the gastrointestinal tract. Moreover, such particles have the property of Anjana Sannibha, i.e., softness (collyrium) that gives the Bhasma a smooth character and does not create any irritation whenever applied . Rasibhava or readily absorbable, adaptable, assimilable properties and Sjhighravyapti, i.e., quickly spreading property of Bhasma, depends on its smoothness and small size. Shighravyapti property indicates that after Marana, Bhasma becomes easily absorbable and assimilable in the body and spreads quickly throughout the body. Dantagre Kachkachaabhava or particle size is an important property. When Bhasma does not feel rough when chewing, i.e., Kachkachaabhava, and have consistency like pollen grains of the Ketaki flower (Pandanus odoratissimus), then it is said to be suitable for use [62, 63]. Varna or color refers to the specific color characteristic of each Bhasma. Alteration or change in each color is suggested to be due to some discrepancy in preparing the Bhasma. The color depends on the preparation and the parent material . The nanoparticles, especially colloidal nanoparticles, exhibit size- and shape-dependent color. Nishchandra (luster) of Bhasma is another important criterion since Bhasma must be lusterless (as observed under bright sunlight) before its therapeutic application. If luster is still present, it indicates the need for further incineration [12, 61].
220.127.116.11 Chemical Properties Rasayanaich is a property that corresponds to the immunomodulation and anti-aging quality of Bhasma, which are checked after preparation because Bhasma is prepared from metals, minerals, herbs and their various combinations. A
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review of the current literature available on Rasayanas indicates that antioxidant and immunomodulation are the most studied activities of the Rasayan drugs. In view of this correlation, Bhasma was subjected to in-vitro screening to assess its immunomodulatory effect on various immunological cells and processes, like number and activation of leucocytes with respect to phagocytic-like activities . Yogavahi is another property that is suitable for targeted drug delivery. The present-day use of targeted drug delivery uses attachment of navigational molecules to the nanoparticles carrying drug. Yogavahi is a physicochemical property of nanoparticle that depends on the chemical stability, surface chemistry and optical properties of nanoparticle . Agnideepana shows the catalytic property of Bhasma, as it increases metabolism at the cellular level. It is a well-known fact that many nanosized metals exhibit catalytic or photocatalytic property, e.g., TiO2, carbon nanotubes, etc. Nirdhuma is a property that eliminates the generation of fumes/smoke when burnt or heated . Mishra et al.,  tested it by sprinkling different Bhasma over burning coal and no smoke was emitted. Apunarbhhava or irreversibility of Bhasma to original metallic form, is tested by mixing Bhasma with an equal quantity of seeds of Abrus precatorius, honey, ghee and borax, which is then sealed in earthen pots and heated . Hence, Bhasma is called Nirutha or irretrievable.
The Similarity of Bhasma Preparation to Contemporary Nanoparticle Synthesis Method
Bhasma is prepared by a process known as Bhasmikaran, in which even an otherwise non-biocompatible substance is made biocompatible. The objectives of the process are to (a) eliminate
Are Bhasma Nanomedicine of Ancient Times
harmful matter from the precursors, (b) modify their undesirable physical properties, (c) convert some of the characteristics, and (d) enhance the therapeutic action . The Bhasmikaran procedure involves the following activities, depending on the type of Bhasma to be prepared. 1. Shodhana or purification eliminates harmful matter. However, prior to purification, some intermediate steps are taken depending on the Bhasma to be prepared, which are: (a) Chalan or stirring, (b) Dhavan or washing, (c) Galan or filtering through a sieve to separate adulterants and heterogeneous particles, (d) Patana or distillation of raw material, (e) Putapaka or heating the herbs along with metal in closed, freshly made containers. Herbometallic Bhasma are called Mulikamarita Bhasma . Puta are selected on the basis of the heat tolerance capacity of a particular metal or mineral, and (f) Mardana or triturating of raw material with some vegetable juices, decoctions, cow’s milk, etc., is done for detoxification and disintegration of raw material. 2. Bhavana is the trituration of mineral and metals with different herbs to obtain the organometallic compound and make it in the palette form. It involves wet grinding along with herbs for coating with the herbal extract or decoctions and/or chemicals such as metallic mercury or mercury perchloride, amalgam of sulfur and mercury, to minimize the poisonous character and increase the therapeutic potency. After Bhavana, the drugs are dried and after closing them in an earthen pot (Sarava Samputa) or in a crucible (Musha) they are subjected to heat treatment (Putapaka).
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3. Marana is incineration or calcination . After grinding the purified metals, depending on the nature of the substance to be calcinated, they are burnt in open air, or especially metals are burnt/ heated in closed containers in the absence of oxygen in a furnace. Today many nanoparticles are also synthesized at high temperature by pyrolyzing them. The end product is a Bhasma of substance taken for marana, e.g., in the case of silver (rajata) it is called Rajata Bhasma. Marana of inorganic substances is called puta and the process of marana of herbs in closed freshly made containers is known as puta-paka. Bhasma obtained by marana from primary metals together with herbs (mulika) are called Mulikamarita Bhasma . Different types of puta are developed for the heat treatment of different metal and mineral drugs. For most of the puta cow dung is used as fuel. According to the study of Anand Chaudhary , it has been confirmed that the unique Ayurvedic metallic/mineral preparations, i.e., Bhasma, are biologically produced nanoparticles (NPs) and are the backbone of several other Ayurvedic medicines. Furthermore, he also stated that the metal and mineral Bhasma (herbo-mineral formulations) have been used since the 7th century but it was not specified whether these Bhasma medicines had a superior level of efficacy in comparison to other Ayurvedic dosage formulations. But the science of nanotechnology has proven that the physicochemical properties of Bhasma are very close to nanocrystalline materials. The common properties of Bhasma, such as its immunomodulation and anti-aging quality (Rasayana), its ability to act as drug carrier for targeted drug delivery (Yogavahi), and the fact that it is readily absorbable, adaptable and incorporated in the body without any toxic effect, are comparable with nanoparticles in the contemporary era.
Are Bhasma Nanomedicine of Ancient Times
Various Medicinal Uses of Bhasma
Apart from herbs, Bhasma (metallic oxides) are also used as therapeutic agents in the Ayurvedic system of medicine even today (see Table 4.5); for example, to dissolve stones in the kidneys, bladder and gallbladder within a short period of time. Tamra Bhasma (copper bhasma) is one of the significant Bhasma that is used to cure anemia (Pandu disease), skin disease (Kushtha), piles (Arsha), etc . There are also some liquid formulations of Bhasma that are mixed with plant juices and given to cure disorders of the liver, respiratory system (asthma, cough, etc.) and digestive system. Some Bhasma are used for external application to cure skin problems. Bhasma prepared by using various alum, salt, quartz, etc., are applied internally as well as externally. Bhasma called Lohavedha and Dehvedha which are prepared using Dhatu (metal) and Upadhatu (mineral) are used for preventing aging and for good health. These metals are mostly gold, silver, zinc, copper, lead, iron, and tin. These metals are present in the body in trace amounts and take part in body metabolism. A balance of these Dhatus are necessary for good health. Some antimicrobial properties of Bhasma have been assessed by Tambekar and Dihikar . Bhasma of copper (Tamra Bhasma), iron (Mandura Bhasma) and silver (Rajata Bhasma) have shown the presence of nanometals in the SEM images by Jagtap et al., , Mulik and Jha  and Mukkavalli et al.,  respectively (Figure 4.2).
One of the major aspects of the synthesis of nanoparticles is the concept of size reduction. The above-mentioned preparation details suggest that this concept was practiced from the time of Charaka—as explained in Charaka Samhita (1500 BC)—using biological methods, where nano-size metals, such as iron, zinc, calcium, silver, gold, etc., were used in different Bhasma. Now
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Table 4.5 Marketed Bhasma and Their Uses. (Adapted From ) Bhasma and its sources
Navratan Kalpamrit Ras Cancers of all types; anemia; (Gems/minerals like ruby, sapphire, complications from diabetes emerald, cat’s eye stone, pearl, coral, silver, gold, iron, zinc) Heerak Bhasma (Diamond)
Cancers; immunity disorders; crippling rheumatoid arthritis; bone marrow depression
Trailokya Chintamani Ras (Diamond, gold, silver, iron)
Severe respiratory tract infection; marrow depression; ovarian cysts; uterine fibroids
Swarna Basant Malti Ras (Gold, Piper nigrum, white pear powder)
Tonsillitis; fevers; cough; bronchitis; decreased immunity; cancers; autoimmune disorders
Kamdudha Ras (Ochre, Tinospora cordifolia, mica [calcined])
Hyperacidity; headache; fever; blood pressure
Vasant Kusumakar Ras (Gold, silver, coral)
Complications of diabetes; neuropathy; general weakness
General debility in children; fever; Kumar Kalyan Ras respiratory tract infections (Gold, iron, mica, copper pyrite, red sulfide of mercury) Tamra Bhasma (Copper, mercury, sulfur)
Anemia; jaundice; digestive disturbance; abdominal disorders
Loha Bhasma (Iron)
Cinnabar enlargement of liver; anemia; jaundice
Loknath Ras (Mercury, sulfur, conch shell)
Diarrhea; respiratory disorders; immunity disorders; cancers; ovarian cysts (Continued)
Are Bhasma Nanomedicine of Ancient Times
Table 4.5 Cont. Bhasma and its sources
Abhrak Bhasma (Calcined purified mica ash)
Respiratory disorders; diabetes; anemia; general weakness
Swarna Bhasma Gold Ash (Calcined gold)
Improving immunity; general weakness; anemia
Rajat Bhasma Silver Ash (Calcined silver)
Irritable bowel syndrome; acidity; pitta disorders
Ras Raj Ras Red sulfide of mercury, mica, gold, iron, silver, Withania somnifera, Syzygium aromaticum
Paralysis; hemiplegia; rheumatism; insomnia; stroke
Shwas Kuthar Ras Black sulfide of mercury, Aconitum ferox, sodium bicarbonate, Piper nigrum, Trikatu
Cough; pneumonia; bronchitis
Swarnmakshik Bhasma Copper pyrite (calcined), mercury, sulfur
Anemia; jaundice; stomatitis; chronic fever
Kaharva Pishti Bleeding Amber of succinite (trinkant mani), Rosa centifolia (rose) Yogendra Rasa Red sulfide of mercury, gold (calcined), magnetic iron, mica, Myristica fragrans
Polio; paralysis; muscular weakness; insomnia; headache
Bolbadh Ras Black sulfide of mercury, Tinospora cordifolia, Commiphora mukul
Praval Pishti Purified powder of corals
Calcium deficiency; blood pressure; insomnia; agitation
Praval Panchamrit Powder of corals, pearls, conch shells
Richest source of natural calcium for agitation, acidity, burning sensation (Continued)
History of Nanotechnology
Table 4.5 Cont. Bhasma and its sources
Jaharmohra Pishti Powder of serpentine orephite
Calcium source for acidity and burning sensation; heartburn
Sarvatobhadra Vati Mercury, sulfur (purified and calcined) with gold
Renal failure (dialysis, high urea and creatinine); nephrotic syndrome
Mukta Pishti Blood pressure; acne; headaches; Pearl powder (moti pishti), calcium acidity; ulcers; heat-related cooling and soothing disorders
nanoparticles are being industrially produced in large amounts, but the ancient technology provided an economical way of synthesizing nanoparticles used for therapeutic purposes. As seen in this chapter, the processes involved in the preparation of Bhasma are conceptually similar to those used in the contemporary processes of ball-milling, pyrolysis, thermolysis, reduction of metal ions, etc. Moreover, as some of the assessments using electron microscopy have shown, Bhasma are composed of nano-size material.
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40. Singh J. Yashad (Jasad) Bhasma, Indications, Uses, Benefits, Dosage & Side Effects. Ayur Times, Nov 9, 2017. 41. Suresh P., Dhannapuneni V.K. Rasendra Sara Sangrah of Sri Gopal Krishna Bhatt. Chap. 1. Varanasi: Chaukhambha Sanskrit Sansthan. p. 32, 2007. 42. Cakrapani on Caraka’s ‘Caraka Samhitaa’. Chikitsa 1–1/49, Choukhambha Sanskrit Sansthaan. Varanasi India, 2000. 43. Cakrapani on Caraka’s ‘Caraka Samhitaa’. Chikitsa 7/74, Choukhambha Sanskrit Sansthaan. Varanasi India, 2000. 44. Galib B.M., Barve M., Mashru M., Jagtap C.Y., Patgiri B.J., Prajapati P.K. Therapeutic potentials of metals in ancient India: A review through Charaka Samhita. J. Ayurveda Integr. Med., 2(2), 55–63, 2011. 45. Goodman L. S., Gilman A. G.. eds Goodman and Gilman’s: The Pharmacological Basis of Therapeutics. 6th ed. New York, Macmillan Publishing Co. p. 714, 1980. 46. Chaudhary A., Singh N. Herbo mineral formulations (rasaoushadhies) of ayurveda an amazing inheritance of ayurvedic pharmaceutics. Anc. Sci. Life, 30(1), 18–26, 2010. 47. Yadav V., Makawana M., Kamnble S., Qureshi F., Sarmalkar B., Salve D. Different Au-content in Swarna Bhasma preparations: Evidence of lot-to-lot variations from different manufacturers. Adv. Appl. Sci. Res, 3, 3581–3586, 2012. 48. Kulkarni S.S. Bhasma and nano medicine. Int. Res. J. Pharm., 4(4), 10–16, 2013. 49. Khedekar S., Anupriya G.R., Patgiri B., Prajapati P.K. Chemical characterization of incinerated gold (Swarna Bhasma). Adv. Appl. Sci. Res, 6(12), 89–95, 2015. 50. Rasheed S.P., Shivashankar M. Synthesis and characterization of Shanku bhasma-an anti-ulcer herbomineral formulation. IOP Conf. Ser. Mater. Sci. Eng., 263: 022026, 2017. 51. Gopal R., Vijayakumaran M., Venkatesan R., Kathiroli S. Marine organisms in Indian medicine and their future prospects. NPR, 7, 139–145, 2008. 52. Pal D., Sahu C., Haldar A. Bhasma : The ancient Indian nanomedicine. J. Adv. Pharm. Technol. Res., 5(1), 4–12, 2014. 53. Sachau E.C. Alberuni’s India (transl. Ludgate Hill), vol. 1, Trübner & Co. London, 1888.
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5 The Maya’s Knowledge of Nanotechnology Vinod P Sinoorkar Walchand College of Arts and Science, Solapur University, Solapur, Maharashtra, India
History never really says goodbye. History says, “See you later.” Eduardo Galeano
While looking at the Maya possibly having knowledge of nanotechnology, I came across the very fascinating history of the Maya people of early civilizations that flourished as one of the most advanced civilizations from 300–900 AD. To understand the scientific knowledge that they had acquired in the past it is important to know about them. Moreover, it is interesting to know that their descendants still keep some of their old-world inheritance and language. I begin this chapter with an introduction to the Maya.
Madhuri Sharon (ed.) History of Nanotechnology, (91–112) © 2019 Scrivener Publishing LLC
History of Nanotechnology
The Maya are a group of indigenous peoples of Mesoamerica. They inhabit southern Mexico, Guatemala, Belize, El Salvador and Honduras. The pre-Columbian Maya population was approximately eight million . But by the start of the 21st century it decreased to seven million [2, 3], who reside in Guatemala, southern Mexico and the Yucatán Peninsula, Belize, El Salvador, and western Honduras. They have managed to maintain numerous remnants of their ancient cultural heritage. Some are quite integrated into the majority hispanicized mestizo cultures of the nations in which they reside, while others continue a more traditional, culturally distinct life, often speaking one of the Mayan languages as a primary language. A large population of contemporary Maya that still follow age-old Maya culture inhabit the Mexican states of Yucatán, Campeche, Quintana Roo, Tabasco and Chiapas and are accordingly identified.
5.2.1 Yucatec Maya One of the largest groups of modern Maya can be found in Mexico’s Yucatán state and the neighboring states of Campeche, Quintana Roo and Belize. They speak “Yucatec Mayan” language, and Spanish is their second or first language.
5.2.2 Chiapas Maya groups in Chiapas include the Tzotzil and Tzeltal in the highlands of the state, the Tojolabal concentrated in the lowlands around Las Margaritas, and the Ch'ol in the jungle. The most traditional of Maya groups are the Lacandon, a small population who avoided contact with outsiders until the late 20th century by living in small groups in the Lacandon Jungle. These Lacandon Maya came from the Campeche/Petén area (northeast of Chiapas) and moved into the Lacandon rainforest at the end of the 18th century.
The Maya’s Knowledge of Nanotechnology
5.2.3 Belize The Maya population in Belize is concentrated in the Corozal, Cayo, Toledo and Orange Walk districts, but they are scattered throughout the country. The Maya have been in Belize and the Yucatán region since the second millennium BC. Much of Belize’s original Maya population died as a result of new infectious diseases and conflicts between tribes and with the Europeans. They are divided into the Yucatec, Kekchi, and Mopan. These three Maya groups now inhabit the country.
In Guatemala, indigenous people of Maya descent comprise around 40% of the population. The largest and most traditional Maya populations are in the western highlands in the departments of Baja Verapaz, Quiché, Totonicapán, Huehuetenango, Quetzaltenango, and San Marcos; their inhabitants are mostly Maya. The Maya people of the Guatemala highlands include the Achi, Akatek, Chuj, Ixil, Jakaltek, Kaqchikel, K'iche', Mam, Poqomam, Poqomchi', Q'anjob'al, Q'eqchi', Tz'utujil and Uspantek. In Guatemala, the Spanish colonial pattern of keeping the native population legally separate and subservient continued well into the 20th century. This resulted in many traditional customs being retained, as the only other option than traditional Maya life open to most Maya was entering the Hispanic culture at the very bottom rung. Because of this, many Guatemalan Maya, especially women, continue to wear traditional clothing that varies according to their specific local identity. The southeastern region of Guatemala (bordering Honduras) includes groups such as the Ch'orti'. The northern lowland Petén region includes the Itza, whose language is near extinction but whose agro-forestry practices, including the use of dietary and medicinal plants, may still tell us much about the pre-colonial management of the Maya lowlands.
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Figure 5.1 Map of the Maya area. This is a retouched image, which means that it has been digitally altered from its original version (Modifications made by Simon Burchell: Text labels added. The original can be viewed at ).
The Maya Civilization
Maya civilization is one of the most mysterious ancient civilizations of all time. Until now, no one is certain about who the Maya were, how they lived, and the reason behind the sudden collapse of their civilization. The Maya are believed to have developed their country and their civilization in a giant thumb north of the Gulf of Mexico, which is in between North and South America (Figure 5.1), called the Yucatán Peninsula . With respect to modern day geography, the region that was occupied by the ancient Maya is comprised of the states of Yucatan; Campeche; Tabasco; the eastern half of Chiapas; the territory of Quintana Roo; the Republic of Mexico; the department of Petén in Guatemala; and the adjacent highlands to the south (that is to say, most of Guatemala except the Pacific Coastal Plain); the contiguous western section of the Republic of Honduras; and all of British Honduras.
The Maya’s Knowledge of Nanotechnology
It covers 125,000 square miles . The whole area of the Maya region lies south of the tropic of cancer and north of the equator. The region is mostly covered by rainforest and has a tropical climate except for the Guatemalan Highlands, which has lower temperatures. However, the lack of knowledge about the Maya civilization may have underestimated the size of the region covered by the Maya. More and more Maya sites are being discovered today.
5.3.1 The Maya During the Preclassic Period The Archaic Period was followed by the Preclassic Period, extending from 2000 BC to 300 AD. The Preclassic is further divided into the Early Preclassic Period (from 2000 to 1000 BC), the Middle Preclassic Period (1000 to 400 BC), and the Late Preclassic Period (400 BC to 300 AD). Some scholars call this the Formative Period because it includes the centuries during which the Maya first began to exhibit cultural characteristics distinct from the other groups. This included the rise of city states, individual cities ruled by a king or queen, whose power extended to the countryside and villages immediately surrounding the city. Unlike Aztecs of central Mexico and the Incas of South America, the Maya never unified into a single empire. Instead they evolved into a less centralized feudal society. During the Preclassic Period the Maya also developed large-scale ceremonial architecture and the beginnings of hieroglyphics.
The Maya of the Early Preclassic Period
Many distinct characteristics were exhibited by the Maya of the Early Preclassic Period. Larger multifamily villages led by a chief were established. Agriculture was expanded to include more crops and improved farming techniques. More sophisticated art was evident in the manufacture and use of ceramics and in the development of iconographic artistic expression—the
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painting and carving of images of people and symbols representing ideas or events. The Maya of this period also exhibited the beginnings of a more complex, hierarchical society. During this era, cultures across Mesoamerica first developed the rudiments of writing systems and an interest in measuring time and in studying astronomy. Evidence uncovered at Cuello, an Early Preclassic site in northern Belize, indicates that these early Maya all lived in more permanent homes of pole-and-thatch huts constructed on low earthen platforms. Archaeologists have discovered clusters of these platforms, along with artefacts left behind by their inhabitants. Evidence also shows the expanded cultivation of crops such as maize, beans, squash, and manioc. The manufacture of ceramics is further evidence that the early Maya were settling into more permanent home bases. Particular examples of this art form have been found at Cuello as well as along Guatemala’s Pacific Coastal Lowlands at Monte Alto, Tilapa, La Blanca, Ocós, El Mesak, and Ujuxte. At some Early Preclassic sites along the Pacific coast of the Mexican state of Chiapas—at sites such as Izapa and Ojo de Agua—ceramics and stone carvings have a marked resemblance to art from the Olmec culture that developed about the same time on the southern Gulf Coast of Mexico. These similarities indicate that the two cultures must have made contact .
The Maya During the Middle Preclassic Period
During the Middle Preclassic Period, from 1000 to 400 BC, a more hierarchical class structure continued to develop. The old tribal society became more similar to the feudal society of medieval Europe or the city-states of ancient Greece, with leadership in the hands of a single king or queen and an elite upper class to support that ruler. Members of the developing Maya upper class were either religious, military, or political leaders. Such leaders usually demanded the construction of public structures. Many of these structures were used for governmental or religious ceremonies, but others were monuments
The Maya’s Knowledge of Nanotechnology
and ornate tombs to honor the leaders themselves. Examples of such public architecture can be seen in the Pacific coastal lowlands of Guatemala, at Abaj Takalik and Cocola, as well as at Kaminaljuyú . During the final centuries of the Middle Preclassic Period, the Maya spread farther inland from the Pacific coastal areas and they established ceremonial centers and more extensive public architecture at Piedras Negras, Seibal, Cival, Dos Pilas, and El Perú. Archaeologists have discovered two of the largest ceremonial centers ever built by the Maya at Nakbe and El Mirador in the northern Petén region of Guatemala and the two largest pyramids, La Danta and El Tigre, which compare in size with the Great Pyramid in Egypt. Archaeologists believe these structures were used as raised platforms for religious ceremonies. No tombs have been discovered beneath them.
The Maya During the Late Preclassic Period
In the Late Preclassic Period, from 400 BC to about AD 300, the Maya developed their writing system, calendar, interest in astronomy and level of artistic expression. These intellectual developments are demonstrated in temples with stuccoed and painted facades, such as those found at El Mirador and in dramatic murals such as those discovered at San Bartolo in extreme northeastern Guatemala. The Late Preclassic is the period of Maya history that has undergone the most rethinking due to recent discoveries in the jungles of northern Guatemala and the coastal regions of Guatemala and El Salvador.
5.3.2 The Maya During the Classic Period Over the next six centuries, from AD 300 to 900, the Maya enjoyed their golden age during the Classic Period, when they reached the pinnacle of intellectual achievement. Maya citystates evolved from purely ceremonial centers into full cities
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surrounding the ceremonial centers, some with populations in the tens of thousands. Each was ruled by a succession of single kings or queens, with a much more organized nobility to support the ruler and oversee the day-to-day operations of the citystate; yet it was never unified into a centralized empire. Each Maya city-state featured a huge, ornately decorated ceremonial center with steep-sided pyramids topped with temples and palaces. Many of these pyramids were built atop the richly decorated tombs of their rulers and were continually being rebuilt, layer upon layer. Beyond the ceremonial center were outlying structures that housed artisans, craftsmen, and bureaucrats. Farther out, and in the surrounding countryside, were farmers and laborers who supported the elite. Most of these city-states were located in the Petén region of northern Guatemala and in the southern Yucatán lowlands . Their interest in astronomy, recording of the passage of time in a calendar, artistic expression, a system of writing, and the construction of public monuments continued. All of these came together in the stone stela, an architectural feature that set apart the Maya cities that were built during this period. A stela is a stone column erected in a public location to commemorate a particular event or person, usually the birth, marriage, accession to the throne, military victory, or death of a king or queen. Maya stelae are the only remaining written record of Classic Maya history. Each stela featured the face of a mythological figure or an actual ruler on one side, with hieroglyphic carvings of dates, names, and events on the other. They were erected in central areas in front of temples and palaces. The earliest dated stela sits in the central plaza of Tikal, with the equivalent of the date AD 292 carved onto its side. The latest stela stands at Tonina, in southern Mexico, and is dated AD 909. One particular stela, Tikal’s Stela 31, has now been decoded and provides written evidence that an invasion by an outside force significantly altered the development of Classic Maya civilization.
The Maya’s Knowledge of Nanotechnology
Some Characteristic Features of the Maya Beauty Expressions
For the Maya nobility, public displays of wealth and physical ornamentation demonstrated their status. Hairstyles, clothing, jewelry, tattoos, and intentional scars were part of their public image. Mayan noblemen wore their hair long, either braided around the head with a pigtail hanging down the back, carefully braided in ornate designs across the scalp, or arranged into an intricate design atop the head. If they had a pigtail, it almost always had an obsidian disc hanging from its tip. Men often cut their hair on top of his head short, or singed it off, as part of the overall design. Facial hair was discouraged, and many pulled it out with copper tweezers. The practices of tattooing, intentional scarring and body painting were quite common among both men and women and the colors and designs employed by individuals were indications of social position. Tattoo designs were pricked into the skin with a sharp bone, and pigment was then rubbed into the wounds. This was an extremely painful experience, so tattoos represented valor and courage . For intentional scarring, the goal was a raised scar in a particular pattern. To accomplish this, the skin was cut or pierced in the desired pattern. Then, to make sure substantial scars would form, the individual encouraged the growth of the scars by keeping the wounds open for a time. Any adult without tattoos and scarring patterns was looked down upon. Moreover, both sexes had their frontal teeth filed in various patterns, and we have many ancient Maya skulls in which the incisors have been inlaid with small plaques of jade. Until marriage, young men painted themselves black and so did warriors at all times . The colors used for body and face painting were very important to Maya men. Blue was the color of priests and the color that victims of sacrificial rites were painted. Women usually painted their faces red. A feature unique to the Maya
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Figure 5.2 Maya jade necklace obtained from excavation. (Source: http://www. latinamericanstudies.org/maya-jade-ornaments.htm).
was a dramatically sloping forehead, but this was not a natural characteristic. It had to be shaped very early in life in order to form the head into what the Maya felt was a noble appearance.
5.4.2 Jade: The Green Gold of the Maya Jade was the most prized green stone in Mesoamerica. To the Maya it symbolized the color of sprouting maize. Maya artisans carved it into jewelry (Figure 5.2) for both nobility and commoners. The Motagua River Valley in southern Guatemala was the source of jade.
5.4.3 Maya Hieroglyphics The Maya were the only ones in the Western Hemisphere to develop a complete, complex system of writing. Like the ancient Egyptians, the Maya incorporated pictograms into their system of writing; for example, to convey the word snake, the Maya drew a small snake, usually stylized within a roughly square image. Using pictograms and number symbols, they recorded rudimentary stories about events that occurred around them. To enrich their written language, the Maya developed symbols called ideograms to represent nonphysical concepts. They
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had symbols for concepts such as love, hate, anger, and pride. To express the phonetic sounds of their spoken language they had developed symbols called syllabograms. Each syllabogram contained one consonant and one vowel; like English, a vowel could be pronounced more than one way. Because of its use of pictograms and syllabograms, Maya writing is referred to as a logosyllabic language. About eight hundred writing signs have been identified so far, and most can now be read, allowing scholars to understand minute details about the Maya—names, places, and concepts .
5.4.4 The Maya’s Eyes on the Heavens In cities throughout the Yucatán, alongside pyramids, ball courts, and temples, the Maya built observatories to watch the skies. For the Maya, their gods resided in the heavens, so worship included watching the sky. Centuries of watching the sun, moon, and stars rise above the horizon eventually led the Maya to develop a sophisticated astronomy. Maya scholars noticed that the location from which the heavenly bodies emerged on the horizon varied depending on the season. They studied the phenomenon by driving two stakes in the ground or by placing two vertical stones to align them with the location on the horizon of those celestial events. Over time they noticed recurring patterns that made it possible for them to predict when certain events would occur. They eventually built stone observatories with windows aligned with those points; this allowed them greater accuracy in their predictions. During the Late Preclassic and Classic periods, they built pyramids and plazas along astronomical lines. They aligned these structures with the path of the sun on certain days of the year or with the cardinal directions. At many of these pyramids, a person standing at the entrance of the temple could look out over the surrounding smaller pyramids and perhaps see the sun rise directly over one pyramid on the summer solstice, over another on both the
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fall and spring equinoxes, and over yet another on the winter solstice. Without the use of telescopes or computers, Maya astronomers achieved a remarkable degree of accuracy. They were able to chart the movement of stars and planets, calculating, for example, that the revolution of the planet Venus, which the Maya called Chak ek', took 584 days. Modern astronomers know that its revolution is precisely 583.92 days, a margin of error just over one-hundredth of 1 percent. Using only fixed lines of sight, crossed sticks, and fixed observation points, Maya astronomers and mathematicians also calculated the length of a year on Earth to be 365.2420 days, incredibly close to the actual figure of 365.2422. They were also able to predict the changing of seasons, the arrival of comets, and the occurrences of solar and lunar eclipses .
5.4.5 The Maya Calendar Knowledge of astronomy and mathematics were tools for the creation of the most important technological advance for the Maya—their calendar. Almost twelve hundred years before the adoption of the Gregorian calendar used by most of the world today, the more accurate Maya calendar was used. Maya scribes listed dates on almost every painting, stela, and ceramic vase they created, but they never seem to have carved or otherwise depicted their entire complex calendar. Some sources suggest that the circular stone calendar of the Aztecs—sometimes referred to as the Aztec Sun Stone—also represented the Maya calendar, but the two are totally different. The Maya calendar was actually three separate calendars that ran at the same time, and no graphical depiction of all three has been discovered. The secular Haab calendar, based on the solar year, contained eighteen sections, each having twenty days, which constituted one Tun. At the end of each Tun was a separate period of 5 days to finish the 365 day year. This 5 day period, called u wayeb u haab, “sleepers of the year,” or ma k'aba k'in, “the nameless
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Figure 5.3 Maya solar calendar. (Source: http://hesed.info/blog/mayancalendar-vs-aztec-calendar.abp).
days,” was considered unlucky. Each Tun in the Haab calendar begins with the Maya month Pop and ends with Kumk'u, which is then followed by the Wayeb, the empty, unlucky days. The days of Haab began with 1 Pop, 2 Pop, 3 Pop, and so forth, and they ended with 3 Wayeb, 4 Wayeb, and 5 Wayeb. Longer time periods in the Haab had different terms. A K'atun, for example, was a period containing 7,200 days, or twenty Tuns. Their largest measurement of time was a Bak'tun. This was a period of 144,000 days, or 20 K'atuns—approximately 394 years. Bak'tuns were used to describe dates in the far distant past or future. The Maya felt the end of a Bak'tun was a particularly significant date because of their belief in the importance of observing cycles. The custom of observing the changing of one century to another, as happened at the beginning of the twenty-first century, is a modern example of humankind’s ongoing fascination with repeating cycles of time (Figure 5.3).
Ancient Maya art refers to the material arts of the Maya civilization that took shape in the course of the later Preclassic Period (500 BCE to 200 CE). Its greatest artistic flowering occurred
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during the seven centuries of the Classic Period (c. 200 to 900 CE). The Maya’s fantastic stepped pyramids from the Terminal Preclassic Period and beyond were based on the general Mesoamerican architectural traditions. These pyramids relied on intricate carved stone in order to create a stair-step design. Each pyramid was dedicated to a deity whose shrine sat at its peak. During this “height” of Maya culture, the centers of their religious, commercial and bureaucratic power grew into incredible cities, including Chichen Itza, Tikal, and Uxmal. Maya artists attached their name to their work. The rich art of the Maya has a great complexity of patterns and variety of media expressions. Limestone structures faced with lime stucco were the hallmark of ancient Maya architecture. Maya buildings were adorned with carved friezes and roof combs in stone and stucco. Maya architects used the corbel vault principle, which is arch-like structures with sides that extend inward until they meet at the top. Other matchless features of the Maya include (i) use of colorful murals, (ii) ceramics with a variety of forms and complex scenes, (iii) flint, bone and shell made into various designs, (iv) decorated cotton textiles, and (v) metal used for ceremonial purposes. Items made with metal include necklaces, bracelets and headdresses.
5.4.7 Maya Paintings Due to the humid climate of Central America, only a few Maya paintings have survived to the present day. The paintings at Bonampak were preserved when a layer of calcium carbonate covered the paintings, preventing moisture from destroying them. The murals, which date from 790 CE, show scenes of nobility, battle, and sacrifice as well as a group of ritual impersonators in the midst of a row of musicians (Figure 5.4). Some murals were painted in stark colors, depicting savage battle scene extending over 20 meters in length, two figures of Maya lords standing on serpents, and an irrigated maize and cacao
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Figure 5.4 A Bonampak wall mural featuring musicians. (Source: photo © 2004 Jacob Rus; http://www.wikiwand.com/en/Bonampak).
field visited by the Maya merchant deity. Wall painting on vault capstones in tombs were usually executed in black on a whitened surface with the additional use of red paint.
Maya Blue and Maya Yellow – Ancient Nanostructured Materials
A subject of interest is the bright turquoise blue color known as “Maya blue,” which has survived through the centuries due to its unique chemical characteristics. The use of Maya blue was prevalent until the 16th century, after which the technique was lost. The Maya considered blue to be the color of gods. Maya blue, a pigment without equal with regard to boldness, beauty, and durability, was used for ritual purposes, art objects, and murals. Maya blue (Figure 5.5) is made of indigo embedded in a special clay mineral called palygorskite. It first appeared around 800 AD, and was still used in the 16th century in several convents of colonial Mexico, notably in the paintings of the Indian Juan Gerson in Tecamachalco. These paintings are a clear example of the combination of Indian and European techniques sometimes
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Figure 5.5 Painting of a warrior with Maya blue (Spanish: azul Maya) in the background. (Source: http://www.wikiwand.com/en/Maya_blue).
known as Arte Indocristiano (Indochristian art). After that, the techniques for its production were lost in Mexico, but in Cuba there are examples from as late as 1830. Maya yellow: A team led by Antonio Doménech of the University of Valencia in Spain has now discovered that some “Maya yellow” pigments are based on similar components as Maya blue. The Maya appear to have developed a preparative technique that was not limited to Maya blue and anticipated modern syntheses of organic-inorganic hybrid materials. The yellow hue of a series of samples (Figure 5.6) from wall paintings in several Maya archaeological sites have been found to be attributed to the presence of indigoid compounds, including isatin and dehydroindigo, attached to palygorskite, a local phyllosilicate clay. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy, and voltammetry of microparticles show that the ancient Maya could prepare indigo, Maya blue, and Maya yellow during successive stages.
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Figure 5.6 A Maya wall painting showing a yellow hue. (Source: https:// en.wikipedia.org/wiki/File:Mic_bonampak.gif).
Resistance to Weathering
Despite time and the harsh weathering conditions, paintings colored by Maya blue have not faded over time. More remarkably, the color has resisted chemical solvents and acids such as nitric acid. Recently, its resistance against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation was tested, and it was shown that Maya blue is an extremely resistant pigment. However, it can be destroyed using very intense acid treatment under reflux.
5.5.2 Preparation of Maya Blue The Maya blue pigment is a composite of organic and inorganic constituents, primarily indigo dyes derived from the leaves of Indigofera suffruticosa plants combined with palygorskite, a natural clay which, mysteriously, is not known to exist in abundant
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deposits in Mesoamerica . Smaller trace amounts of other mineral additives have also been identified.
5.5.3 Chemical Composition of Maya Blue The chemical composition of Maya blue as determined by powder diffraction in the 1950s was found to be a composite of palygorskite and indigo, most likely derived from the leaves of the indigo plant. An actual recipe to reproduce Maya blue pigment was published in 1993 by the Mexican historian and chemist, Constantino Reyes-Valerio . The combination of different clays (palygorskite and montmorillonite), together with the use of the indigo leaves and the actual process is described in his paper. Reyes-Valerio’s contributions were possible due to his combined background in history and chemistry, through a thorough revision of primary texts, microscopic analysis of the mural paintings and Fourier transform infrared spectroscopy. After the formula for the production was published in the book De Bonampak al Templo Mayor: Historia del Azul Maya en Mesoamerica, many developments in the chemical analysis of the pigment occurred in collaborations between Reyes-Valerio and European scientists. A comprehensive study of the pigment which describes history, the experimental study techniques (diffraction studies, infrared spectroscopies, Raman amplification, optical spectroscopies, voltammetry, nuclear magnetic resonance, and computer modeling), the syntheses, properties and nature of Maya blue and the research in relation to archaeological and historical contexts has been published by del Rio . Maya blue is so fascinating because it has a special brightness and a singular color that can range from a bright turquoise to a dark greenish blue. Does the color stem from a unique organic component, a unique linking of the molecules, or a unique production process? Doménech et al., [13, 14] have tested these hypotheses. They surmise that the hue is determined by the ratio of indigo to dehydro-indigo, the oxidized form. This
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ratio depends on how long the Maya heated their formulation. This would allow for the formation of different variations of the addition compound formed by the indigo compounds and the mineral. The researchers further conjecture that the Maya were also able to produce yellow and green pigments from indigo-based pigments.
5.5.4 Are Maya Paintings Nano Based? According to the studies made by Doménech et al., [13, 14], Maya blue is a nanostructured organic-inorganic hybrid material that is prepared by attaching a natural indigo dye to a phyllosilicate clay, palygorskite. Their results suggest that the Maya blue pigment is a complex system in which different topological isomers of various indigoid molecules attached to the palygorskite matrix coexist. By means of various spectroscopic and microscopic methods, as well as voltammetry—a special electrochemical process that allows for the identification of pigments in micro- and nanoscale samples from works of art—the scientists examined a series of yellow samples from Maya murals from different archaeological sites in the Yucatán Peninsula in Mexico. The results confirm that a whole series of yellow pigments from Maya mural paintings are made of indigoids bound to palygorskite. The researchers also found ochre. Doménech and his coworkers think it very likely that the preparation of such “Maya yellow” pigments was an intermediate step in the preparation of indigo and Maya blue. Leaves and branches from indigo plants were probably soaked in a suspension of slaked lime in water and the coarse material filtered out. A portion of the yellow suspension could then be removed and added to palygorskite to make Maya yellow. The remaining suspension would then be stirred intensely and ventilated until it took on a blue color. It was then filtered and dried to obtain indigo for use as a dye. It could also be ground together with palygorskite and heated to produce Maya blue.
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Though we have no information whether these colors were made by a process currently known, these days it is known that the same ingredients if used in different sizes, produce different colors. Perhaps differently treated indigo-based pigments might have produced different nano sizes giving different colors.
The ancient Maya combined skills in organic chemistry and mineralogy to create an important technology—the first permanent organic pigment. The unique color and stability of Maya blue can be explained by a new model where indigo dye fills the grooves present at the surface of palygorskite clay, forming hydrogen bonded organic/inorganic complex. The existing theory assumes that the dye is dispersed inside the channels of an opaque mineral. Based on data from thermal analysis, synchrotron and neutron diffraction, ESEM and chemical modeling calculations, the new concept of Maya blue structure resolves this contradiction and suggests some novel possibilities for more durable, environmentally benign pigments and that the use of nanotechnology may have existed.
References 1. Norman B. Footsteps: Nine Archaeological Journeys of Romance and Discovery. Topsfield, MA: Salem House. pp. 170–171, and 173, 178, 1988. 2. Von Hagen V.W. Maya Explorer: John Lloyd Stephens and the Lost Cities of Central America and Yucatan. Norman: University of Oklahoma Press. p. 75, 1948. 3. Grube N. ed. Maya: Divine Kings of the Rain Forest. Germany: H.F. Ullmann:Nordrhein-Westfalen. p. 11, 2006 . 4. Maya civilization location map-blank.svg. Modifications made by Simon Burchell., CC BY-SA 4.0. 2015. Available from: https:// commons.wikimedia.org/w/index.php?curid=40476910.
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5. Lemonick M.D. Secrets of the Maya, Time, Aug 9, 1993. 6. Morley S.G. The Ancient Maya. Stanford University Press, 2004. 7. George C., George L. Maya Civilization. Lucent Books, 2010. 8. Coe M.D. Breaking the Maya Code. New York, USA: Thames & Hudson, 1992. 9. McKillop H. The Ancient Maya. New York: Norton Publishers, 2006. 10. Del Río M.S., Picquart M., Haro‐Poniatowski E., Van Elslande E. Victor Hugo UC. J. Raman Spectrosc., 37(10), 1046–1053, 2006. 11. Reyes-Valerio C. De Bonampak al Templo Mayor, El Azul Maya en Mesoamerica [in Spanish]. United States: Published by Siglo XXI Ediciones, 1993. 12. Del Rio M.S., Doménech A., Doménech-Carbó M.T., Vázquez de Agredos Pascual ML., Suárez M., García-Romero E, et al. Developments in Clay Science. 3. pp. 453–481, 2011. 13. Doménech A., Doménech-Carbó M.T., del Río M.S., Vázquez de Agredos Pascual M.L.V. Comparative study of different indigoclay Maya Blue-like systems using the voltammetry of microparticles approach. J. Solid State Electrochem., 13(6), 869–878, 2009. 14. Doménech A., Doménech-Carbó M.T., Sánchez del Río M., Vázquez de Agredos Pascual M.L., Lima E., del Río M.S. Maya Blue as a nanostructured polyfunctional hybrid organic–inorganic material: the need to change paradigms. New J. Chem., 33(12), 2371–2379, 2009.
6 Did Nanotechnology Flourish During the Roman Empire and Medieval Periods? N B Patkar1 and Manisha Sharan2 1
Walchand College of Arts and Science, Solapur University, Solapur, India 2 Bakers College, Clinton Township Michigan, USA
Civilization is the limitless multiplication of unnecessary necessities. Mark Twain
Although the scientific community began to focus on the optical properties of metallic colloids in the early 20th century after the work of Gustav Mie in 1908, the use of their outstanding properties is reported to be much older, i.e., several millennia ago . One of the objects of nanotechnologists of the contemporary era, who focused their attention on the possibility of nanoparticles being used in older civilizations, were the many intriguing properties of transition metals like gold, silver, and copper. The concept of soluble gold existed in China and Egypt in the 4th
Madhuri Sharon (ed.) History of Nanotechnology, (113–140) © 2019 Scrivener Publishing LLC
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Century BC and its use as pigment for coating glasses, enamel and chinaware came into existence in the mid-17th century in many countries and civilizations. Today it is confirmed that these were nanoparticles of gold, silver and copper. Nanometer-sized metallic particles suspended in molten glasses have been used for centuries to produce colored glassware . Let us take a brief look at the transition metals that have been used during Roman and Medieval European civilizations.
6.1.1 Transition Elements of the d-Block Elements The d-block elements are located between the s-block and p-block elements in the modern periodic table. They are also known as “transition elements” because they bridge the two blocks of elements and show a transition in their properties from metals to non-metals. Most of the transition elements naturally occur as carbonates, oxides and sulfides and only a few elements like Au and Pt occur in a free state. The d-block elements represent a change (or transition) from the most electropositive s-block elements to the least electropositive p-block elements and are, therefore, also named transition elements. Elements present in d subshell are partially filled either in atomic state or in ionic state. According to the Aufbau principle, the valence electrons fill up the penultimate d-orbital energy level, giving rise to four series of d-block elements—3d, 4d, 5d and 6d series. The general outer electronic configuration of d-block elements follows (n-1) d1-10 n s1-2 but in some cases they show deviations in general electronic configuration because of: 1. The energy difference among the (n-1) d- and ns-orbitals. 2. The relative stability of half-filled and completely filled d-orbitals over other configurations. Elements like palladium (Pd), silver (Ag), gold (Au) and many more elements of the 4d series show exceptional electronic configuration. These
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elements usually show typical metallic behavior and exhibit properties like more tensile strength, malleability, ductility, thermal and electrical conductivity as well as metallic luster. Because of the larger amount of metallic bonding by assets of d-electrons, these elements are rigid and have elevated melting and boiling points. It may be noted that although elemental copper, silver and gold as well as Ag1+, Cul+ and Au1+ have a d10 configuration, Cu2+ has a 3d9, Ag2+ a 4d9 and Au3+ have a 5d8 configuration and hence these elements are classified as transition elements.
18.104.22.168 Melting and Boiling Point The combination of d-orbital electrons with s-orbital electrons in metallic bonding causes the elevation of melting and boiling points of transition elements.
Formation of Colored Ions
The transition element ions are identified by the variety of colors exhibited by their ions (Figure 6.1). Most of the compounds of d-block elements are colored or they give colored solution when dissolved in water; incomplete (n-1) d subshell of the transition metal is responsible for the color development. Excitation and de-excitation of valence electrons produces colored ions. From the incident light, those frequencies are Cr2+
Ti 3+ V2+ V3+
Figure 6.1 The colors of aqueous transition metal ions.
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absorbed by the electrons whose energies equal the energy for excitation of the electron from the lower energy state of the d-orbital to the higher energy state of d-orbital. When this frequency of light is absorbed, the light transmitted through the salt solution exhibits the color which is complementary to the frequency absorbed. The color of the ions varies with its oxidation state. This chapter encompasses two great civilizations that existed in Europe and beyond—the Roman Empire and Medieval Europe—in which the existence of metal nanoparticles in many of their crafts and decorative objects has been shown.
Nanotechnology During Roman Civilization
The civilization of the Roman Empires flourished from 753 BC to 27 BC (the Imperial Period) and again from 64 AD to 1453 AD (the Republican Era). The Roman Empire ruled the area from the Rhine River to Egypt and from Britain to Asia Minor.
Historical Records of Use of Luster Ceramics
Before going into detail about various aspects of luster technology and its relation to present-day nanotechnology, a brief history of lusters is given in order to establish a few chronological and geographic references. The earliest lustered potteries were found in Mesopotamia and most of them originated from the site of the Abbasid Caliph’s palace of Samarra in present-day Iraq 1991] . This monumental palace complex, whose building was begun by Caliph Mu'tasim in 836 CE, was abandoned in 883 CE. Early luster manufacturing is therefore rather well dated, though it is currently assumed that the first experiments may have occurred earlier, possibly in the time of Harun al-Rashid (766–809 CE). Abbasid lusters were also found
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in some quantity in other Mesopotamian cities such as Baghdad, Basra, Kufa or Susa in present-day Iran. These cities are often presented as potential production centers, but it is yet an open question. Mesopotamian lusters were discovered outside this geographic area. Tiles with luster decorations from Iraq were used in the partial reconstruction of the Great Mosque of Kairouan, Tunisia, in the 9th century. Fragments have been found at Fustat, which was the main citadel of Lower Egypt in the 9th century. Shards have also been excavated from the site of the palace of Qal'a in Algeria, which up until 1052 CE was the capital of the Hammamid princes. In fact, luster decorations were certainly created in the early 9th century for courts and courtiers and seldom appeared in any other settings. For several centuries, lusterware kept its status as luxury tableware for princely courts. The annexation of Egypt by the Fatimids (969 CE) led to profound modifications, not only on a governmental level, but also in the general population. The Fatimid capital was transferred from Tunisia to al-Qahira, modern Cairo, and the old city of Fustat provided quarters for craftsmen who worked for the new capital a few kilometers to the north. The demand for luster by the new court led to the development of local production. It is now attested that lusters were made in Fustat before the Fatimid period. However, this production, often called preFatimid, seems to have been very limited and of poor quality. The Egyptian production actually began with the arrival of the Fatimids, and during two centuries, a great deal of good quality luster was being made that reflected the interests and cultural traditions of the new dynasty and its courtiers. During the 12th century, the luster technique began to extend from Egypt to Syria and to Persia (present-day Iran). Craftsmen from Fustat allegedly brought the technique there during the decline of the Fatimid dynasty, which occurred in the middle 12th century. It seems that the technique appeared in the Occident (southern Spain) during the same period, as
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soon as the taifa emerged after the dissolution of the Spanish Umayyad caliphate. However, it is only under the Nasrid dynasty (1237–1492 CE) that the luster technique really flourished in Spain. Its apogee, between the 14th to 15th centuries, gave rise to the Hispano-Moresque ceramics, which were elaborated in the Valencia region up to the 18th century. Early luster manufacturing is therefore rather well dated, though it is currently assumed that the first experiments may have occurred earlier, possibly in the time of Harun al-Rashid (766–809 CE). Abbasid lusters were also found in some quantity in other Mesopotamian cities such as Baghdad, Basra, Kufa or Susa in present-day Iran. These cities are often presented as potential production centers, but it is yet an open question. Mesopotamian lusters were discovered outside this geographic area.
Technology of Luster Decorations of Ceramics
Luster is a variety of glaze decorations on ceramics which appeared in medieval times, as previously mentioned in the introduction to this chapter. Like ruby glass, the color of the luster decorations has a physical basis coming from metallic nanoparticles [4, 5]. Bobin et al.,  have reported that the optical properties of metallic luster of glazed ceramics are characterized by a change of color according to the observation conditions. In diffuse light, these decorations are often green, brown, or ochre‐yellow. In specular reflection, they show an associated colored metallic reflection (blue, golden‐yellow, orange, etc.). Metallic copper and/or silver colloids almost always compose the metallic luster decorations. The coloration of these two metals was observed in diffuse light as well as in specular reflection. A relationship was found to exist between the proportions of copper and silver, and the diffuse color. The green decorations contain more silver than copper, and the ochre‐yellow and brown decorations contain more copper than silver. This means that the
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composition of the glaze has an important influence in the coloration process. But there is no relationship between the specular color and the overall concentration of copper and silver. However, luster possesses the peculiarity of having a color which can change depending on the angle through which it is observed. The color change under specular reflection is often spectacular and produces a very intense colored metallic shine, which can be golden-yellow, blue, green, pink, etc. The density of nanoparticles in the top layers of glaze is higher than that for ruby glass and shows a structuration in depth, which can be more or less complex. This multilayer structuration on the scale of wavelengths of visible light gives rise to interference phenomena and scattering through rough interfaces, which adds to the surface plasmon effect and strongly contributes to the observed color. As pointed out by Lafait et al.,  in their paper concerning the physical colors in cultural heritage, the colors with structural origin are particularly striking and very brilliant. The understanding of these structural effects on optical properties (photonic crystals) is very recent and it is fascinating to see that Islamic potters were able to create such complex structure through empirical chemical means in order to exploit their outstanding optical properties. While working on the gold ruby glass and luster ceramics of cultural heritage, Lafait et al.,  explained that the main physical effect at the origin of their color is the excitation of surface plasmon modes in metal nanoparticles. They suggested that in luster, interference effects due to a multilayer structure add a bright iridescence. The luster ceramics attracted their attention because of the complexity of the effects involved: plasmon, scattering, interference between specular reflected light beams and also between scattered beams.
Soluble Gold Concept and Use of Soluble Gold
While the use of gold was prevalent in the Roman Empire, it was also simultaneously used by China and Egypt as pigment
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for coating glasses in the 4th century BC, as well as for enamel and chinaware in the mid-17th century. The use of nanoparticles prepared from copper, gold and silver has a long history. Without understanding how nanoparticles are actually produced, ancient potters and glassmakers as well as glass-stainers luxuriantly used nanoparticles in the glass melt for more than 3000 years. They developed techniques to reduce metal compounds in the presence of a suitable reducing agent to fine particles, presently known as nanoparticles. In Egypt and Mesopotamia, by adding copper or cuprite nanoparticles into molten glass mixtures the first colored glasses were successfully manufactured. Gold has infrequently been used in glassmaking . The presence of gold in metallic form during the preparation of Roman dichroic glasses imparts color to them . Since the 17th century, gold has been predominantly used to impart a ruby red color to glasses after addition of colloidal metal particles to the matrix during their preparation [8, 9]. During the 13th to 14th centuries gold or a gold alloy was used as red coloring agent in the enamel of Islamic glass vessels . Artificial gold pigment is also called arium musicum, mosaic gold or ormolu. It is also termed stannic sulfide and manufactured to look like mineral gold. The yielded scaly yellow crystalline powder was deliberately used as a pigment in bronzing and gilding of wood and metal materials . Ancient Egyptian goldsmiths were greatly skilled  and had a special symbol for gold (Figure 6.2). An exceptional example is the death mask of Tutankhamun that was prepared by beating thick gold plate and inlaid with colored glass paste and various stones. Goldsmiths utilized silver soldering for gold items and plated silver onto gold by immersing it into molten electrum (an alloy of gold and silver) . For the production of Egyptian blue glass, copper (Cu) was used. During the 12th century, cobalt (Co) was used for the synthesis of cobalt blue color, which was the coloring constituent
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Figure 6.2 Ancient Egyptian’s decoded symbol for Gold based on Peter Loyson’s suggestion .
of stained glass as well as Chinese porcelain glazes in the Tang and Ming dynasties. Although we are currently discussing nanotechnological activity during the Roman Empire, China cannot be left out, as during the 17th century (i.e., 1696), with the help of French Jesuits they established a large-scale production unit imperial glass workshop. Later they produced a variety of decorative glasses in association with the German Johann Kilian Stumpf. In 1699 two European glassworkers joined the imperial workshop in Beijing for the same reason . Beijing’s glassware workshop was heavily engaged in producing high-quality glassware, including decorative snuff bottles in different colors and shapes . High-quality enameled glassware produced in this workshop were gifted to the high officials of different regions of the world by the Kangxi Emperor; he also sent two large cases of enamelware and 136 pieces of Beijing glass to the pope [16, 17]. Another emperor who allowed the Jesuits to supervise glass production was Yongzheng. Under his regime production reached its peak. In the 1750s, along with constructing European-style palaces and gardens for the Lofty Pavilion, the Jesuits also started preparing European-style glassware to decorate the elaborate buildings . Hence, the Chinese decorative themes adorning the glassware were influenced by European illustrative skills regarding shading and viewpoint
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. Later on, the Chinese begin sending enamel colors to the imperial pottery kilns located in Jingdezhen, where a new variety of enamel-decorated porcelains were manufactured for the first time. The famous overglaze blue enamel color which was prepared during the Kangxi Period had been added to the production in Jingdezhen in 1700, while under the Yongzheng supremacy, colloidal gold was used to prepare translucent pink enamel, which was handsomely used in the porcelain. The newly developed enamel of the imperial workshop used for coloring glasses was likely opaque pink glaze with tiny spots of metallic gold, while they used a ruby colored glass from an ancient Venetian formula, which was later rediscovered and developed again in Germany . Chinese artisans of the imperial workshop of Jingdezhen developed famille rose (meaning “the pink family”) ware having various shades of pink color, by creating a solution of stannous chloride as well as gold chloride for the synthesis of new enamel . Due to the guidance of Nian Xiyao, the director of the Jingdezhen factory, the purple of Cassius as well as famille rose wares became prominent at Jingdezhen, as did blue-and-white glass ware and eggshell porcelain at that time in China . The Romans used gold salts in their sand and soda ash mixtures and found that by careful annealing they could produce a red transparent glass, now known to be attributable to gold nanoparticles. The achievements of ancient craftsmen and scientists are concisely presented in Table 6.1.
Development of the Lycurgus Cup
The famous Lycurgus Cup was made from dichroic glass during the Roman era (around 290–325 AD). The most captivating property of this special type of dichroic glass is that due to the properties of “soluble” gold, it is ruby red in transmitted light and green in reflected light. However, this technology of Roman glassworkers was short lived. The method of fabrication
Did Nanotechnology Flourish 123 Table 6.1 History of Gold and Soluble Gold.
Historical events related to gold and soluble gold
Use of gold to fashion decorative objects first began in Eastern Europe.
Earliest records of use of gold for medicinal purposes in Alexandria, Egypt
Gold jewelry found in the tomb of King Djer of the First Dynasty of Egypt.
The Egyptians started beating gold into leaf and alloying it with other metals for hardness and color variations.
The Chinese started using small squares of gold as money.
Gold was used in prosthetic dentistry in the Etruscan culture .
The Greeks and Jews of ancient Alexandria start to practice alchemy in the quest for turning base metals into gold.
The Romans started gold mining in Spain.
The Romans began using a gold coin called the aureus.
Venice introduced the gold ducat, which later became a popular coin in the world. (Continued)
124 History of Nanotechnology Table 6.1 Cont. Year
Historical events related to gold and soluble gold
Islamic alchemist Jabir ibn Hayyan published his Summa Perfectionis Magisterii describing the preparation of aqua regia, a mixture of hydrochloric and nitric acid, which is able to dissolve gold. Soluble gold was used in medicine.
Gold was added to the official drug compendia (there was a big controversy about its value).
Johann Rudolf Glauber prepared colloidal gold as purple by reduction of gold salts by tin chloride (Purple of Cassius), which turned out to be gold nanoparticle.
Johann Kunckel used the purple for his glassworks in Potsdam .
Purple of Cassius reached China, where it was used in Famille Rose porcelain.
involved exceptional workmanship. Because the glass of the Lycurgus Cup is dichroic it displays unusual optical effects. It is known as a “cage cup” or diatretum. The components of the Lycurgus Cup and modern glass are Silicon dioxide 73% 70 %, Sodium oxide 14% 15% and Calcium oxide 7% 10%. Minute microscopic crystals/colloidal systems of Au and Ag give rise to light-scattering phenomena that result in dichroic effects. The gold is mainly responsible for the reddish transmission and silver for greenish reflection. The colors produced depend on the precise colloidal concentration, particle diameter, proportions and oxidation states of certain elements, time and temperature of heating and probably the atmosphere during heating.
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Nanotechnology During the Medieval Period of European Civilization
After the fall of the Roman Empire in 27 BC, the Medieval Period (Middle Period) started in the 5th century and lasted till the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance and the Age of Discovery.
Medieval Metals and Glass
Very few additional metals were discovered until the Industrial Age. Platinum, bismuth, and zinc are among these intermediate discoveries. Most of the later developments in metallurgy began with the involvement of hotter furnaces, purer smelting, and greater control of alloys. A curious precursor to modern chemistry is the medieval activity known as alchemy. Alchemy has many philosophical aspects, but as a physical study it involves characterizing and manipulating the properties of substances. The seven known metals were elemental substances; interestingly, each metal was paired with one of the seven known planets. Alchemy began in the medieval Arab world (alchemy is an Arabic word) and was picked up by Western Europe. During the Middle Ages, glass manufacturing expanded considerably in Europe, especially to address the demand for stained glass . This development was accompanied by an increase in the type of colloidal metal used for coloring glass [25, 26]. Medieval skilled workers (400 to 1300 AD) lavishly used gold salts in addition to molten glass for manufacturing tiny gold colloids with a prosperous ruby color, and its color variations were successfully used for coloration of glassware, ceramics, chinaware and pottery .
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Use of Gold, Silver and other Metal Nanoparticles in the Middle Ages
As mentioned above, the enigmatic behavior of gold colloids led to the curious endeavor of using it as a pigment for coating glasses, enamel and chinaware in the Medieval Period. Andreas Cassius, a painter and sculptor, developed a colored solution of gold sol which was purple in color and hence named “Purple of Cassius,” which was painted on the glass of many houses and churches. Johann Kunckel then developed a ruby red colored paint to be coated on glasses. Two examples of the uses of “soluble” gold were making ruby red glass and coloring ceramics. The Romans added gold salts to their sand and soda ash mixtures and found that by careful annealing they could produce a red transparent glass, which was attributable to gold nanoparticles. In the Middle Ages, the use of gold and silver nanoparticles to produce the bright red and yellow stained glass windows in churches was very popular. One of the most documented examples of nanotechnology known in history is medieval stained glass windows composed of metal impregnated glass. The craftsmen who made stained glass were the first nanotechnologists, as they, although unaware, trapped gold nanoparticles in the “glass matrix” in order to generate the ruby red color in the windows. They also trapped silver nanoparticles in glass, which gave it a deep yellow color. Silver was introduced into medieval glass by an ancient painting process using different clay minerals (ochre, illite, montmorillonite, and kaolinite clays). Today’s findings indicate that the size of the metal nanoparticles (whether it be gold or silver) define the variations in the bright red and yellow colors of medieval stained glass church windows. The variation in color is an indication of the dramatic change in material properties at the nanoscale. Pérez-Villar et al.,  studied the colorimetric properties of color and structural changes in silver painted medieval glasses by UV-Vis spectroscopy. Since clay minerals were used in the
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process of introducing silver into glass, it was found that the color was dependent on the clay minerals as a result of different concentrations of Ag ions diffused into the glass surface. They further characterized it by using transmission electron microscopy (TEM) analysis, and the images showed the presence of silver nanoclusters, which gave a yellow color to the glass. Moreover, they evidenced that the specific surface area, pore volume and iron concentration (Fe2O3) of the clay, were important factors that affected the yellow coloration. It was found that Fe2O3 acts as an oxidizing agent for silver atoms providing the Ag2O formation. This oxide cannot diffuse into the glass and avoid the ion-exchange process. Raman spectroscopic analysis showed that after Ag ion diffusion some structural changes occur in the glass. And the diffusion process leads to depolymerization of the glass network, as determined by analyzing the Qn components of the Raman spectra. Two Raman bands at 148 and 244 cm−1 assigned to Ag–O bonds can be associated with the presence of Ag2O on the glass painted surface. Colomban  had characterized red‐flashed and red‐coated medieval potash lime and 19th century soda lime stained glass pieces from windows, using different instruments and laser wavelengths, both lower and higher than the surface plasmon resonance (SPR) of copper. After comparing the Raman signatures of the transparent glass matrix and the red glass layers with model glasses containing a dispersion of Cu0 nanoparticles, they found that the conformation of the silica network in the vicinity of the metal nanoparticles differs from that of the glass matrix. Moreover, they recorded traces of hematite and carbon in the Cu0‐rich layers, which is due to the use of a combination of a reducing atmosphere and redox couples to control the growth of metallic copper particles. Rubio et al.,  studied the diffusion of silver ions in medieval glasses by a heat treatment process and found that silver ions, after redox reactions with reducing glass ions, got
128 History of Nanotechnology 20 = 28 nm σ = 30 nm
Nanocluster 0.1 μm
100 Particle size (nm)
Figure 6.3 TEM images of OG, SG and Ag nanoparticle-nanocluster distribution (OG = Original glass sample; SG = Silver glass. (Reproduced from )
converted to silver nanoparticles as well as silver nanoclusters. A visible spectroscopic analysis showed that due to these silver nanoparticles the glass color changed (Figure 6.3). The glass structure was analyzed by Raman scattering, using confocal Raman spectroscopy and by means of gradient Raman spectroscopy where the silver ion and silver nanoparticle diffusion were analyzed on a fractured glass surface. Silver nanoparticle was found to produce a depolymerization of the glass structure and that such depolymerization increases with the amount of silver nanoparticles.By using microprobe analysis their results proved that when the concentration of silver nanoparticle is higher on the glass surface, it decreases with the distance to the surface according to a diffusion process. Moreover, by using nano-indentation measurements on original (glass surface with high silver nanoparticle concentration) and gradient glass surfaces (glass without silver) they showed an increase in the Young’s modulus from 60 to 85 GPa, This result supports and is in accordance with the Raman and microprobe analysis. Chemical characterization was performed on the stained glass from the rose window of the Siena Cathedral (Duomo di Siena) in Italy (1288–1289), which has several colored glasses (deep green, olive green, yellow, purple, pink, deep blue, light blue, red plaqué and also uncolored), was done by Gimeno
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et al., . These glasses were found to be composed of sodiumcalcium glass (chemical compositions in the range 13–14 wt% Na2O, 56–64 wt% SiO2, 4 wt% MgO, 9–10 wt% CaO, 2,5–4 wt% K2O). Inductively coupled plasma mass spectrometry also showed the presence of trace elements. So far as the color contents are concerned: The deep blue, light blue and deep purple were obtained after the artisan dosed addition of a cobalt salt. Olive green and deep green glasses were produced with addition of copper along with manganese and iron, previously prepared as a pigment that has as excipient a potassium glass. Pink and yellow glass was produced following the traditional recipe compiled by Theophilus. This implies that separate processes of raw material purification and a careful control of the redox kiln conditions were involved for each color. To modern eyes, the end goals of the alchemists of turning lead into gold or creating the philosopher’s stone and the perfect elixir of life, seem misplaced. Nevertheless, alchemists developed techniques that are still used today. Alchemists, particularly the early Islamic practitioners, created specialized laboratory equipment (and laboratories), repeated experiments and had a toolbox of procedures. Each metal was considered to have a small number of fundamental attributes. For example, lead is “cold” and gold is “hot.” To transform one into another, alchemists developed procedures such as distillation, filtration, and crystallization. The right combination of techniques would presumably turn “cold” lead into “hot” gold. Logically, turning gold into lead would be just as difficult as the reverse. Somehow, no efforts toward that end are attested to.
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The mystical aspects of alchemy fell somewhat out of fashion during the Renaissance and early industrial period. Nevertheless, famous figures such as Isaac Newton (1643– 1727) spent a great deal of time on alchemical investigation. Not until the 18th century did alchemy substantially evolve into modern chemistry. The scientific community began to focus on the optical properties of metallic colloids in the early 20th century, beginning with Gustav Mie’s works . The excitation of surface plasmons in metallic nanoparticles (NPs) induces optical properties yielding a wide range of applications. However, the use of their outstanding properties is much older, dating back several millennia ago . Investigations using various techniques showed that red glasses of the late Bronze Age (1200–1000 BCE) from Frattesina di Rovigo (Italy) were colored thanks to the excitation of plasmon surface modes of copper nanoparticles [31, 32]. The protohistoric community of this region developed advanced glass-manufacturing technology and was able to induce the exsolution of metallic copper crystals in the top layer of glass by exposing the material to reducing conditions. The presence of copper nanoparticles and cuprous oxide (cuprite Cu2O) had already been reported in Celtic red enamels dating from 400 to 100 BCE . The use of metallic particles for coloring glass spread during the Roman period. Most of the red tesserae used in Roman mosaics were made of glass containing a dispersion of copper nanocrystals . In addition to the copper crystals, gold nanoparticles were identified in some red tesserae, showing that other metallic nanocrystals were used during Roman times (Colomban et al., 2003) . It is precisely the case of the well-known Roman Lycurgus Cup in glass dating from the 4th century CE and currently exhibited at the British Museum . The glass of this cup is dichroic and resembles jade with an opaque greenish-yellow tone, but when light shines through the glass
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(transmitted light) it turns into a translucent ruby color. It has been demonstrated that the spectacular color change is caused by colloidal metal and more precisely by nanocrystals of a silver-gold alloy dispersed throughout the glassy matrix . A handful of other Roman glasses showing a dichroic effect were also reported and although the color change is not so spectacular, the Lycurgus Cup is obviously the result of the good technical mastery of Roman glassworkers . The Roman craftsmen knew that glass could be red colored and that the unusual color change effect generated by the addition of noble metal-bearing material when the glass was molten could be engineered. Nevertheless, the difficulties in controlling the coloration process meant that relatively few glasses of this type were produced, and even fewer have survived. During the Middle Ages, glass manufacturing expanded considerably, especially to address the demand for stained glass . This development was accompanied by an increase in the type of colloidal metal used for coloring glass [25, 26, 28]. This age also saw the emergence of lusterware, a special type of glazed ceramic, with striking optical effects again obtained from metallic nanoparticles [36, 37]. Luster is a decorative metallic film that was applied on the surface of medieval glazed pottery. It is suggested by PérezArantegui et al.,  that luster is obtained by low-temperature (650 °C) reduction of copper and silver compounds. They analyzed Spanish luster pottery from the 13th to 16th century. Their analysis showed that luster is a thin layered film (200– 500 nm thick) of metallic spherical nanocrystals dispersed in a silicon-rich matrix and is covered by a metal-free outermost glassy layer that is 10–20 nm thick. Silver nanocrystals and copper nanoparticles are separated, forming aggregates 5–100 mm in diameter. Their optical properties depend on the particle size and the matrix. It is believed that luster is the first man-made reproducible, nanostructured, thin metallic film.
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100 nm (b)
Figure 6.4 TEM images of (a) red-brown copper-like luster and (b) olive-green yellowish luster samples. Insert corresponds to CBED pattern of a metallic copper particle A and the SAD pattern showing the rings corresponding to the metallic silver particle B. (Reproduced from ; Copyright © 2003 Elsevier Science B.V.).
The analytical approach by Pérez-Arantegui et al.,  using transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDS) and electron diffraction (ED) facilities, confirmed the presence of nanoparticles in the luster (Figure 6.4). Then the progress in glass chemistry during the Renaissance period  and especially in modern times allowed for better tuning of coloration effects based on the surface plasmons of metallic nanoparticles [40, 41]. The manufacturing process of red glass was used worldwide. The famous Satsuma glass produced in Japan in the mid-19th century was obtained using
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a similar technique and its ruby color also comes from the absorption properties of copper nanocrystals. Nakai et al.,  examined Satsuma glasses by electron microprobe analysis (EPMA), X-ray absorption fine structure (XAFS) and optical absorption spectroscopy analyses. The analyses revealed that the red color in Satsuma copper-ruby glass is derived from colloidal particles of metallic copper. Their extensive work made them conclude that the trace amount of copper in the ruby glass, which is below the detection limit of the EPMA and XAFS techniques, exists as metallic copper particles of nanometer size and is responsible for the ruby-red appearance of the Satsuma glass. Ahmed and Ashour  have reported the production and characterization of Cu2O aventurine glass. The precipitated Cu2O in the aventurine glasses exhibited different colors ranging from yellow to red, depending on the synthetic conditions and on the heat-treatment temperature in particular. Their electron microscopic study revealed that the modification from yellow to red is due to an increase in crystal size. Cu2O crystals of 150 mm in diameter are red, whereas crystals with diameters falling between these values are orange. This is also the case of the famed red flambé and mixed bluered Jun glazed porcelains from the Song and Ming to the Qing dynasties of China . Using high dynamic range (HDR) imagery (i.e., photographic data collection) luminances (or per-pixel brightness), the relative transmissivity (a measure of the ability of a material or medium to transmit electromagnetic energy as light) of adjacent panels of glasses from medieval churches of Western Europe were estimated by Simmons and Mysak ; and it was found that the red glass has a fixed average transmissivity. This red standard was then applied over a large database of images collected from different churches. The results indicated that the use of brighter colors during the 12th century admitted more
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light compared to 13th century glass; and the more translucent glasses of the 15th and 16th centuries had further increased light transmission into the interior. The data indicated that red glass has the lowest transmissivity, whereas white (or grisaille) glass is the most transmissive color. Moreover, transmissivity of red glass was the most stable across the ages.
Purple of Cassius
Synthesis of colored glass was prominent among the ancient Egyptians and Romans, but this art was lost for many centuries and again reinvented in the 17th century. Another popular color that was painted on the glasses of many houses and churches during the medieval period was “Purple of Cassius,” which was named after the German chemist Andreas Cassius (1605–1673). In the 1650s he discovered the first synthetic purple colored pigment, which was used in coloring glass and porcelain, giving a remarkably beautiful purple color. It was prepared by adding tin chloride to dilute gold solution. History states that there was a father and son both named Andreas Cassius at that time. The father was the inventor of Purple of Cassius; however, it was his son, Andreas Cassius (1645–c. 1700), that brought it to light by publishing the details in De Auro, which reads: “Thoughts concerning that last and most perfect work of nature and chief of metals, gold, its wonderful properties, generation, affections, effects and fitness for the operations of art; illustrated by experiments.” . It must be mentioned here that Purple of Cassius was known to be used for various colors (Figure 6.5) for over two centuries as stable colorant for ceramics and glasses, but its exact nature and composition was elucidated at the end of the 19th century when the Viennese chemist Richard Zsigmondy (1865–1929) gave its exact synthesis process. He suggested that after reduction of AuCl3 solution with formaldehyde in a weakly alkaline solution, a red colloidal gold solution is formed which was like red wine, and after
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Figure 6.5 Museum pieces of glass colored with Purple of Cassius. (Reproduced from )
further reduction with hydrazine or hydroxylamine the dilute gold chloride solution gives Blue colloidal gold . Richard Zsigmondy also invented the ultramicroscope for the examination of various colloids. After joining the Schott Glassworks in Jena in 1897, he spent some years studying gold colors. He concluded that Purple of Cassius contained very finely divided gold particles with stannic oxide. For this research, he was awarded the Nobel Prize in Chemistry in 1925. Recently, Kirk et al., (2014)  described the preparation of Purple of Cassius, during which the nanoparticles are precipitated by the addition of stannous chloride to AuCl3 and are stabilized by the colloidal hydrated SnO2 (stannic acid) produced during the redox reaction, which is still widely used today in the production of ruby glass and as enamel color on ceramics. Gold-based glass and enamel painted with Purple of Cassius was produced in the Meissen porcelain factory. In 1720, Purple of Cassius reached China, where it was used in Famille Rose porcelain. The chemical nature of Purple of Cassius was a challenge for the scientists. Around 1897, almost 250 years after its discovery, Richard Zsigmondy, a chemist working on gold colloids at the Schott Glassworks in Jena, showed that Purple of Cassius consisted of colloidal gold and stannic acid.
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6.3.4 Contribution of Johann Kunckel In the 17th century, another big contribution was made by the renowned chemist Johann Kunckel (1679–1689), who rediscovered coloring of glasses and preparation of colored ceramics by meticulously using different metals. He belonged to a glassmaking family and the results drawn from his experiments were published in a famous book, Ars Vetraria Experimentalis, in 1679. In his book Coloured Glasses, Weyl  writes: “The beauty alone of gold-ruby glass justified neither the tremendous efforts made in its development nor the high prices which these glasses brought. It was no doubt the mystic power attributed to gold and the ruby colour produced by it which was responsible for the extraordinary demand.” He did not realize he was dealing with gold nanoparticles. He developed a ruby red colored paint to be coated on glasses in 1670. Two examples of uses of “soluble” gold were making ruby red glass and coloring ceramics. His experiments proved the importance of the cooling rate of gold ruby colored glasses in imparting different shades of red. According to him, if the glass is allowed to cool slowly it causes spoilage of the ruby tint, so it must be cooled rapidly. During the fabrication of red ruby glass, the “thermal history” is significant. “Appropriate treatment of a gold-containing glass could lead to practically all colours of the rainbow” . Rose reds and carmines of many shades derived from gold (Purple of Cassius), began to predominate, and the porcelain of this class is called famille rose.
A survey of the work done by contemporary scientists about decoding various unique decorative products and the results of analysis data showed that a high level of technological knowledge of materials science was required to obtain metal nanoparticles in order to reproduce luster layers; this knowledge
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existed during the Roman and medieval civilizations in Europe and other parts of the world. Ancient Egyptians and Romans were very aware that transition metals, like Au, Hg and Cu, have the ability to scatter light when they are present in the colloidal form; and this property can be harnessed for coloring glasses, preparing colored ceramics, and synthesizing enamel, which was used later on in the preparation of colored porcelain in the Chinese dynasties. Many successful achievements in the preparation of colored decorative materials were later recorded by medieval scientists. Between the 4th century to the middle of the 17th century (till the discovery of Purple of Cassius), glass staining practices lagged behind. Cassius successfully discovered the process of purple pigment formation from gold and its use in the staining of glasses without knowledge of nanoparticles. Later on, Zsigmondy explained the scientific theory of the preparation of Purple of Cassius, which imparts color to the glasses due to finer particles of gold in the solution.
References 1. Colomban P., Ricciardi P., Tournié A., Colomban P. J. Raman Spectrosc. 12. 40. pp. 1949–1955, 2009. 2. Bamford C.R. Colour Generation and Control in Glass. The Netherlands: Elsevier: Amsterdam, 1977. 3. Caiger-Smith A. Lustre Pottery: Technique, Tradition and Innovation in Islam and the Western World. New York, USA: New Amsterdam Books, 1991. 4. Bobin O., Schvoerer M., Ney C., Rammah M., Pannequin B., Platamone E.C, et al. The role of copper and silver in the colouration of metallic luster decorations (Tunisia, 9th century; Mesopotamia, 10th century; Sicily, 16th century): A first approach. Color Res. Appl., 28(5), 352–359, 2003. 5. Lafait J., Berthier S., Andraud C., Reillon V., Boulenguez J. Physical colors in cultural heritage: Surface plasmons in glass. Comptes Rendus Physique, 10(7), 649–659, 2009.
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6. Towle A.C, A scientific and archaeological investigation of prehistoric glasses from Italy University of Nottingham, 2002. 7. Bimson M., Freestone I.C. Annales du 9e Congrès de l’Association Internationale pour l’Histoire du Verre. France: Nancy. pp. 22–28, 1983. 8. Barber D.J. Freestone IC. Archaeometry, 32(1), 33–45, 1990. 9. Henderson J. The Science and Archaeology of Materials, An Investigation of Inorganic Materials. Routledge, 2000. 10. Henderson J., Allen J. Archaeomaterials, 4, 167–183, 1990. 11. Baker C., Pradhan A., Pakstis L., Pochan D.J., Shah S.I. Synthesis and antibacterial properties of silver nanoparticles. J. Nanosci. Nanotechnol., 5(2), 244–249, 2005. 12. Habashi F. Metall, 88(990), 60: Bull. Can. Inst. Min–69, 1995. 13. Loyson P. J. Chem. Educ., 88(2), 146–150, 2011. 14. Ogden J., Metals, Nicholson P. T, Shaw I, eds. Ancient Egyptian Materials and Technologies. Cambridge: Cambridge University Press. pp. 148–173, 2000. 15. Curtis E. Arts Asiatiques, 56, 81: Paris–90, 2001. 16. Lam, P. The glasswork of the Qing Imperial Household Department. The Chinese University of Hong Kong: Art Museum;. 46–47, 2000. 17. Boda Y. Palace Museum Journal, v. 4, 1983 (in Chinese); idem, An account of Qing Dynasty glassmaking, in: Scientific Research in Early Chinese Glass, Brill RH, Martin JH (Eds. Corning: The Corning Museum of Glass, 1991. 18. Lam P. Elegant Vessels for the LoftyPavilion: The Zande Lou Gift of Porcelain with Studio Marks. Chinese University of Hong Kong: Hong Kong. pp. 33–36, 1993. 19. Scott R. Eighteenth century overglaze enamels: The influence of technological development on painting style In: Rosemary Scott R, Hutt G, eds. Colloquies on Art & Archaeology in Asia. London: Percival David Foundation of Chinese Art. pp. 156– 158, 1987. 20. Beurdeley M., Raindre G. Qing Porcelain. New York: Rizzoli. pp. 8–10, 1986. 21. Corsi E. Sinological Studies in Memory of Giuliano Bertuccioli In: Forte A, Masini F, eds. A Life Journey to the East. Kyoto: Scuola Italiana di Studi sull’Asia Orientale. pp. 201–233, 2002.
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22. Donaldson J.A. The use of gold in dentistry: an historical overview. Gold Bull., 13(3), 117–124, 1980. 23. Hunt L.B. Gold Bull., 9(4), 134–139, 1976. 24. Kurmann-Schwarz B., Lautier C. Perspective-La Revue De L INHA. 1. Europe: The Medieval stained-glass window. pp. 99– 130, 2009. 25. Rubio F., Pérez-Villar S., Garrido M.A., Rubio J., Oteo J.L. Application of Gradient and Confocal Raman Spectroscopy to Analyze Silver Nanoparticle Diffusion in Medieval Glasses. J. Nano Res., 8, 89–97, 2009. 26. Gimeno D., Aulinas M., Bazzocchi F., Fernandez-Turiel J.L., Garcia-Valles M., Novembre D. Bol. Soc. Esp. Ceram., 49(3), 2050366–2133175, 2010. 27. Sajanlal P.R., Pradeep T. Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons. pp. 1–22, 1998. 28. Pérez-Villar S., Rubio J., Jose O.J.L, . Study of color and structural changes in silver painted medieval glasses. J. Non. Cryst. Solids, 354(17), 1833–1844, 2008. 29. Mie G. Ann. Phys., 25(3), 377–445, 1908. 30. Garcia M.A. J. Phys. D, 44(28). 31. Angelini I., Artioli G., Bellintani P., Diella V., Gemmi M., Polla A, et al. Chemical analyses of Bronze Age glasses from Frattesina di Rovigo, Northern Italy. J. Archaeol. Sci., 31(8), 1175–1184, 2004. 32. Artioli G., Angelini I., Polla A. Crystals and phase transitions in protohistoric glass materials. Phase Transitions, 81(2&3), 233– 252, 2008. 33. Brun N., Mazerolles L., Pernot M. Microstructure of opaque red glass containing copper. J. Mater. Sci. Lett., 10(23), 1418–1420, 1991. 34. Colomban P., Mazerolles L., Karmous T., Ayed N., Ennabli A, et al., Raman identification of materials used for jewellery and mosaics in Ifriqiya. J Raman Spectrosc., 34(3), 205–213, 2003. 35. Freestone I., Meeks N., Sax M., Higgitt C. The Lycurgus Cup — A Roman nanotechnology. Gold Bull., 40(4), 270–277, 2007. 36. Caiger-Smith ALustre Pottery:Technique, Tradition and Innovation in Islam and the Western World. FL,Oviedo: GentleBreeze Publishing. p. 246 pages, 1991.
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37. Pérez-Arantegui J., Molera J., Larrea A., Pradell T., Vendrell-Saz M., Borgia I, et al. Luster Pottery from the Thirteenth Century to the Sixteenth Century: A Nanostructured Thin Metallic Film. J. Am. Ceram. Soc., 84(2), 442–446, 2001. 38. Pérez-Arantegui J., Larrea A., The secret of early nanomaterials is revealed, thanks to transmission electron microscopy. Trends Anal. Chem., 22(5), 327–329, 2003. 39. Simmons C.T., Mysak L.A. Transmissive properties of Medieval and Renaissance stained glass in European churches. Archit. Sci. Rev., 53(2), 251–274, 2010. 40. Gil C., Villegas M.A., Navarro J.M.F. TEM monitoring of silver nanoparticles formation on the surface of lead crystal glass. Appl. Surf. Sci., 253(4), 1882–1888, 2006. 41. Hartland G.V. Optical Studies of Dynamics in Noble Metal Nanostructures. Chem. Rev., 111(6), 3858–3887, 2011. 42. Nakai I., Numako C., Hosono H., Yamasaki K. Origin of the Red Color of Satsuma Copper-Ruby Glass as Determined by EXAFS and Optical Absorption Spectroscopy. J. Am. Ceram. Soc., 82(3), 689–695, 1999. 43. Ahmed A.A., Ashour G.M. Glass Technol, 22(1), 24–33, 1981. 44. Wood N. Chinese Glazes: Their Origins, Chemistry and Recreation. Philadelphia, USA: University of Pennsylvania Press, 1999. 45. Habashi F. Purple of Cassius: Nano gold or colloidal gold? Section B-Review. Eur. Chem. Bull, 5(10), 416–419, 2016. 46. Zsigmondy R. Dingler’s Polytechnisches J., 306, 91, 1987. 47. Kirk K.L., Jacobson K.A., Zumbulyadis N. History of Chemistry in the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).. Bull. Hist. Chem., 39(1), 150–165, 2014. 48. Weyl W.A. Coloured glasses. Sheffield: Society of Glass Technology, 1951.
7 European Nano Knowledge That Led to Faraday’s Understanding of Gold Nanoparticles Anil Kumar S Katti and Madhuri Sharon Walchand College of Arts and Science, Solapur University, Solapur, India
Aum Asato mā sad gamaya From ignorance, lead me to truth; Tamaso mā jyotir gamaya From darkness, lead me to light; M tyormā am tam gamaya From death, lead me to immortality; Aum śānti śānti śānti Aum peace, peace, peace; B hadāra yaka Upani ad 1.3.28
Nanotechnology is a new emerging and fascinating field of science. Its concepts have been developing over the course of more than sixty years. Interestingly, people have been employing nanotechnology for over a thousand years; from painting to making steel. However, what has changed recently is the ability to manipulate and engineer material at the nanometer scale and see it under very advanced microscopes.
Madhuri Sharon (ed.) History of Nanotechnology, (141–212) © 2019 Scrivener Publishing LLC
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Prior to c. 1000, this technology was employed mostly for coloring glasses. The glass used at that time was of a soda-lime silica composition. In Northern Europe, soda glass was eventually almost totally superseded by potash-lime-silica glass (forest glass). Forest glass continued to be used in stained glass for the duration of the medieval period until soda glass again began to be used in the 16th century. The potash (K2O) found in forest glass was derived from wood ash. In his treatise De Diversis Artibus, the German monk Theophilus describes the use of beech wood as the preferred source of ash. Other plant matter, such as bracken, was also used. As well as containing potash, beech ash comprises an assortment of compounds including iron and manganese oxides, which are particularly important for generating color in glass. Medieval stained glass panels could be created either by the cylinder blown sheet or crown glass (window) method. Inherent color refers to the colors that may be formed in the molten glass by manipulating the furnace environment. Theophilus describes molten glass changing to a “saffron yellow color,” which will eventually transform to a reddish yellow on further heating. He also refers to a “tawny color, like flesh” which, upon further heating will become “a light purple” and later “a reddish purple, and exquisite.” These color changes are the result of the behavior, under redox conditions, of the iron and manganese oxides which are naturally present in beech wood ash. Scientists of the medieval period had a good understanding of the phenomena of absorption, reflection and scattering of light when they used metal colloids. Let’s take a look at the fascinating basic properties of colloidal metal in context of the optical properties of light.
Reflection of Light
Reflection is when light bounces off an object. Most of the things we see are because light from a source has reflected off them. The angle at which light hits a reflecting surface is called
European Nano Knowledge that Led 143 Mirror reflection Incident ray
Angel of Angel of incident reflection
Figure 7.1 Types of reflection of light from flat surfaces.
the angle of incidence, and the angle at which light bounces off a reflecting surface is called the angle of reflection. If you want to measure these angles, imagine a perfectly straight line at a right angle to the reflective surface (this imaginary line is called “normal”). If you measure the angle of incidence and the angle of reflection against the normal, the angle of incidence is exactly the same as the angle of reflection.
Types of Reflection: 1. If the surface is smooth and shiny, like glass, water or polished metal, the light will reflect at the same angle (i.e., reflected light rays travel in the same direction) as it hits the surface. This is called specular reflection (Figure 7.1). 2. For a rough surface, reflected light rays scatter in all directions. This is called diffuse reflection. With a flat mirror, it is easy to show that the angle of reflection is the same as the angle of incidence. It is possible to make mirrors that behave like humps or troughs, i.e., “concave” or “convex,” and because of the different way they reflect light, they can be very useful. A rough surface has concave and convex surfaces. Concave mirrors: When parallel light rays hit a concave mirror, they reflect inwards towards a focal point (F). Each individual ray is still reflecting at the same angle as it hits that small part of the surface (Figure 7.2). Concave mirrors are used in certain
144 History of Nanotechnology Reflection of light on cancave mirror
Principal axis C
Figure 7.2 Reflection of light from concave mirror.
types of astronomical telescopes called reflecting telescopes. The mirrors condense lots of light from faint sources in space onto a much smaller viewing area and allow the viewer to see far away objects and events in space that would otherwise be invisible to the naked eye. Light rays travel towards the mirror in a straight line and are reflected inwards to meet at a point called the focal point. Concave mirrors are useful for make-up mirrors because they can make things seem larger. This concave shape is also useful for car headlights and satellite dishes. Convex mirrors: Convex mirrors curve outwards. When parallel light rays hit a convex mirror they reflect outwards and travel directly away from an imaginary focal point (F). Each individual ray is still reflecting at the same angle as it hits that small part of the surface (Figure 7.3). If imaginary lines are traced back, they appear to come from a focal point behind the mirror. Convex mirrors are useful for shop security and rear-view mirrors on vehicles because they give a wider field of vision. Scattering of Light: Some light is scattered in all directions when it hits either very small particles, such as gas molecules, or much larger particles such as dust or droplets of water. The amount of scattering depends on how big the particle is compared to the
European Nano Knowledge that Led 145 Reflection of light on convex mirror
Principal axis F
Figure 7.3 Reflection of light on convex mirror.
wavelength of light that is hitting it. Smaller wavelengths are scattered more. This scattering answers questions such as: “Why is the sky blue?” Light from the sun is made up of all the colors of the rainbow. As this light hits the particles of nitrogen and oxygen in our atmosphere, it is scattered in all directions. Blue light has a smaller wavelength than red light, so it is scattered much more than red light. When we look at the sky, we see all the places that the blue light has been scattered from. This is similar to the question, “Why are sunsets red?” When the Sun appears lower in the sky, the light that reaches us has already travelled through a lot more of the atmosphere. This means that a lot of the blue light has been scattered in all directions well before the light reaches us, so the sky appears redder. “Why do clouds appear white?” It is because the water droplets are much larger than the wavelengths
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of light. In this situation, all wavelengths of light are equally scattered in all directions.
Michael Faraday’s Painstaking Efforts
Michael Faraday’s gold colloids: Modern scientific evaluation of colloidal gold did not begin until the work of Michael Faraday in the 1850s [1, 2]. In 1856, in a basement laboratory of the Royal Institution in London, Faraday accidentally created a ruby red solution while mounting pieces of gold leaf onto microscope slides (www.rigb.org). Since he was already interested in the properties of light and matter, Faraday further investigated the optical properties of the colloidal gold. He prepared the first pure sample of colloidal gold in 1857, which he called “activated gold.” He used phosphorus to reduce a solution of gold chloride. These liquids are some of the first examples of metallic gold colloids made by Michael Faraday over 150 years ago. The colloidal gold Faraday made 150 years ago is still optically active. For a long time, the composition of the “ruby” gold was unclear. Due to its preparation, several chemists suspected it to be a gold tin compound [3, 4]. Faraday recognized that the color was actually due to the miniature size of the gold particles. He noted the lightscattering properties of suspended gold microparticles, which is now called the Faraday-Tyndall effect , because Faraday is seen as one of the first researchers of nanoscience and nanotechnology. Faraday spent a significant amount of time in the mid-1850s investigating the properties of light and matter. He made several hundred gold slides and examined them by shining light through them. To make the gold leaf thin enough to be transparent, Faraday had to use chemical means rather than mechanical ones (commercial gold leaf was made by hammering the metal into very thin sheets but these were too thick for his purposes). Part of this process involved washing the films of gold, which Faraday noticed produced a faint ruby-colored
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fluid. He kept samples of the fluid in bottles and used them for similar experiments by shining a beam of light through the liquid. In his notebook, Faraday observes: “The cone was well defined in the fluid by the illuminated particles.” Interestingly, these colloids are still optically active. We can do exactly the same experiment as Faraday by shining a modern laser pointer through the bottle and producing a cone of light. Nobody knows why this is, as we can’t unseal the bottles without damaging them, but it’s very unusual. While most colloids last for a few months or even a year, Faraday’s are now over 150 years old. So, we can say that the foundations of metal colloid science were laid by Michael Faraday in the 19th century with his ground-breaking experiments on gold sols.
Michel Faraday (1791–1867). (Source: Wikimedia Commons, the free media repository)
Further important progress in the description of NP behavior was achieved by Nobel laureate Wilhelm Ostwald, the father of physical chemistry, in particular by his theory of particle growth via Ostwald ripening. The painstaking efforts of colloidal giant Michael Faraday comprehended that the ruby red color of colloidal gold stems from the agglomerations of gold atoms; he also proved the stability of such solutions by synthesizing the colloidal solution and, moreover, he gave mathematical expressions proving the stability of the solution.
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The Role of Gustav Mie and Richard Gans in Understanding Metal Nanoparticles
After the publication of Michael Faraday’s paper in Philosophical Transactions of the Royal Society of London in 1857, which attempted to explain how metal particles affect the color of church windows, Gustav Mie  was the first to provide a theoretical explanation and evidence of the dependence of the color of the glasses on metal size and type. He explained the origin of the red color of gold colloidal nanoparticles by providing analytical solutions of Maxwell’s equations, giving Faraday’s experiment a theoretical footing. Through a series of demonstrations by scientists like Gans and Mie, experimental and theoretical principles were applied to several properties of colloidal gold nanoparticles. Nano-scale gold possesses few atoms and hence mainly exhibits statistical mechanical principles in which the energy is quantized as well as discrete. This consequently leads to the dominion of surface energies due to the excited electrons of the surface atoms of nanomaterials, and thus gold nanoparticles exhibit specific surface energy . The magical confrontation between gold nanoparticles and light led to the Mie theory and surface plasmon resonance. Moreover, colloidal stability of gold nanoparticles (due to the electrical double layer theory) plays a pivotal role in their clinical and paraclinical applications, viz., drug delivery, hyperthermia or antimicrobial therapy. In a solution of colloidal dispersion, stability is governed by a plethora of factors. According to Mie, the color of gold colloidal nanoparticle is due to the collective oscillations of the conduction band electrons called localized surface plasmon resonance (LSPR), which can be tuned anywhere in the spectral region depending upon its size, shape, surrounding medium, metal composition and so on. Moreover, Mie was able to provide the exact solution for a single spherical nanoparticle of arbitrary size in non-absorbing medium, but for other complex geometries, it is not possible to solve the Maxwell’s equations exactly.
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In 1912, Richard Gans extended the Mie theory for approximating the optical properties of spheroidal shape such as oblate and prolate nanoparticles . Later on, Aden and Kerker  were the first to extend this theory for the coated spherical nanoparticles and since then many algorithms have been developed, but the code given by Bohren and Huffman  is mostly used.
Zsigmondy’s Seed-Mediated Method
Faraday could not staunchly interpret his observations with any analytical armamentarium like a transmission electron microscope. However, his brilliant work was forgotten for about 40 years before it was revived by another great Nobel laureate, Richard Adolf Zsigmondy, who combined his synthesis method with Faraday’s work and called it the seed-mediated method . He even went to the extent of analyzing the size and mobility of such nanometer-sized colloidal gold by designing an ultramicroscope. His work won him the Nobel Prize in Chemistry in 1925.
Nobel laureate Richard Adolf Zsigmondy. (Source: Wikimedia Commons, the free media repository)
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Another Nobel laureate, Theodor Svedberg, not only synthesized colloidal solutions but also paved the way for size and shape separation of gold nanoparticles.
Research that Led to the Understanding of Metal Nanoparticles Optical Properties
The tremendous growth in the field of surface plasmon resonance (SPR) benefited from the theoretical work of the German physicist Gustav Mie, who first explained with rigorous analysis the origin of the red color of colloidal Au particles. Modifications of the classical Mie theory and the development of new models and theories have been continuously carried out since then to better understand the optical properties of metal nanoparticles with different parameters such as composition, size, shape, structure, embedding matrix, etc. These understandings, in turn, helped to develop advanced approaches for synthesizing colloidal nanoparticles with more precisely tailored properties.
Surface Plasmon Resonance and Plasmonics
Although a plasmon is made up of electrons, it is not an electron: it is a gang, or collection, of electrons that get together under the urging of the long-range Coulomb force and decide to act in concert. Hence, for the purpose of discussing their behavior, they may, like an orchestra or choir, be considered as a single entity following the same (Coulombic) conductor. Bohren and Huffman
Surface plasmon is coherent electron oscillations that exist at the interface between any two materials where the dielectric function alters the sign across the interface. Surface plasmons possess lower energy than bulk (or volume) plasmon which quantize the longitudinal electron oscillations about positive
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ion cores within the bulk of an electron gas (or plasma). When surface plasmons couple with a photon, the resultant hybridized excitation is called a surface plasmon polariton (SPP). This SPP can propagate along the surface of a metal until energy is lost either via absorption in the metal or radiation into free space. The existence of surface plasmon was first predicted in 1957 by R. H. Ritchie. Surface plasmon is coherent electron oscillations that exist at the interface between any two materials where the dielectric function alters the sign across the interface. Surface plasmons possess lower energy than bulk (or volume) plasmon which quantize the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma). When surface plasmons couple with a photon, the resultant hybridized excitation is called a surface plasmon polariton (SPP). This SPP can propagate along the surface of a metal until energy is lost either via absorption in the metal or radiation into free space. The existence of surface plasmon was first predicted in 1957 by R. H. Ritchie. Surface plasmon resonance (SPR) or localized surface plasmon polariton resonance (LSPPR) is the coherent excitation of all the freely oscillating electrons within the conduction band, E-field Scattering + + + Absorption
Figure 7.4 Surface plasmon resonance oscillation of electrons of a noble metal nanoparticle, resulting in the strong enhancement of the electric field, and the light scattering and absorption cross sections. (Reproduced from )
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leading to in-phase oscillation (Figure 7.4). Factors that collectively lead to these oscillations are: Acceleration of the conduction electrons by the electric field of incident radiation. Presence of restoring forces that result from the induced polarization in both the particle and surrounding medium. Confinement of the electrons to dimensions smaller than the wavelength of light. The imaginary part of the metal dielectric function must be small at the SPPR frequency to provide efficient electron oscillations. Several processes can damp the oscillations such as 1) Electron scattering by lattice phonon modes, 2) Inelastic electron–electron interactions, 3) Scattering of the electrons at the particle surface, and 4) Excitation of bound electrons into the conduction band. Absorption and scattering are present in large nanoparticles with the latter becoming more dominant as particle size increases. Absorption can cause a drastic temperature change in the particles when high-energy, pulsed laser excitation is used such that breathing modes of the particle lattice are excited, which can be seen as very small Stokes-shifted peaks (8–15 cm-1) in the Raman spectra. The relative contributions from radiative damping through resonant scattering and absorption strongly depend on the particle size. Absorption and resonant scattering contribute to extinction with respect to particle size. Whereas particles smaller than 30 nm exhibit only absorption, light extinction of particles larger than about 50 nm is dominated by resonant scattering. At 50 nm, both the absorption and scattering become equal, but their spectral maxima are shifted relative to each other. The tremendous growth in the field of SPR benefited from Gustav Mie’s theoretical work, whose rigorous analysis first
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explained the origin of the red color of colloidal Au particles. Modifications of the classical Mie theory and the development of new models and theories have been continuously carried out since then to better understand the optical properties of metal nanoparticles with different parameters, such as composition, size, shape, structure, embedding matrix, etc. These understandings, in turn, helped to develop advanced approaches for synthesizing colloidal nanoparticles with more precisely tailored properties. Plasmonics is one of the fastest growing fields in nanoscience, which deals with the resonant interaction of light with metal nanostructures. The resonance occurs when conduction band electrons on the surface of metal nanoparticles (NPs) oscillate collectively with the same frequency as that of the incident electromagnetic (EM) waves, a phenomenon called localized surface plasmon resonance (LSPR) . The main goal of plasmonics is to control, tune, and manipulate incident light on the nanometer length scale. Conventionally, the confinement of light to a size smaller than its wavelength is not allowed due to the diffraction limit; however, the plasmon resonance presents an opportunity to confine the EM field to a nano-size volume . Therefore, the optical absorption/scattering properties of plasmonic NPs are strongly enhanced at LSPR in comparison to their geometrical cross sections. Absorption and scattering together constitute the light extinction of the nanoparticle. The main requirement for the LSPR is a large negative real component and a small positive imaginary component of the dielectric function of the material. Thus, a number of metals such as Li, Na, Pb, Hg, Sn, In, Ga, Al and Cd satisfy this criteria but their nanoparticles support surface plasmon resonances in the UV (ultraviolet) region of the EM spectrum and are also readily oxidized, making surface plasmon experiments difficult, which limits their applications in plasmonics [14–16]. However, the noble metals, such as Ag,
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Au, and Cu (coinage metals), are quite exceptional, as they form air stable colloids and exhibit fascinating optical properties due to excitation of the surface plasmon resonances in the visible regime of the EM spectrum at about 550–600 nm, 360–400 nm, and 520 nm, corresponding to Cu, Ag, and Au nanospheres, respectively. Hence, surface plasmon experiments are most commonly carried out with Cu, Ag, and Au nanoparticles . The surface plasmon resonance wavelength (SPR), scattering/absorption intensity, and full width at half maxima (FWHM) of the resonance spectra of such noble metal NPs are highly sensitive to their size, shape, material, and embedding medium of the nanoparticle and can be tuned from the ultraviolet-visible (UV-Vis) to infrared (IR) region of the spectrum [18–23]. When Gustav Mie wrote his classic paper on light scattering by dielectric absorbing spherical particles in 1908 he was interested in explaining the colorful effects connected with colloidal gold solutions. He gave a first outline of how to compute light scattering by small spherical particles using Maxwell’s electromagnetic theory. With his first computations he managed to explain the color of gold colloids changing with the diameter of the gold spheres, which was later interpreted in terms of surface plasmon resonances. The first computations of scattering diagrams for larger spheres of diameters up to 3.2λ were presented by Ricard Gans (1880– 1954)  and Hans Blumer (1925) . Later on, in 1965 a study of scattering by a sphere was traced by Logan , who commented that Hans Blumer’s results missed the regular undulations in the scattering diagram because of numerical mistakes. This paper is interesting reading for all those interested in the history of light scattering. Nowadays, the interest in Mie’s theory is much broader. Interests range from areas in physics problems involving interstellar dust, near-field optics and plasmonics to engineering subjects like optical particle characterization. Mie’s
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theory is still being applied in many areas because scattering particles or objects are often homogeneous isotropic spheres or can be approximated in such a way as to make his theory applicable. Electromagnetic scattering by a homogeneous, isotropic sphere is commonly referred to as the Mie theory, though he was not the first to formulate this electromagnetic scattering problem. Before him, Ludvig Lorenz  contributed to solving the elastic point source scattering problem of a perfectly rigid sphere using potential functions. In 1909, Peter Debye considered the related problem of utilizing two scalar potential functions like Mie. Therefore, plane wave scattering by a homogeneous isotropic sphere is also referred to as the Lorenz-Mie theory , or even Lorenz-Mie-Debye theory . The incorrect name Lorentz-Mie theory is also quite commonly used, e.g., in Burlak’s book . In 1890, the Danish physicist Ludvig Lorenz published essentially the same calculation on the scattering of radiation by spheres .
Quantum Confinement Effect
The most popular term in the nano world is quantum confinement effect (QCE) which is essentially due to changes in the atomic structure as a result of direct influence of ultra-small length scale on the energy band structure [30, 31]. As the exciton radius of semiconductors is 2–8 nm, it is expected that particles of nanometer dimensions undergo transition from the bulk to the quantum-confined state. Metal nanoparticles are well known for their quantum size effect. Quantization effects become most important when the particle dimension of a semiconductor is near to and below the bulk semiconductor Bohr exciton radius, which makes material properties size dependent. When the particle size approaches Bohr exciton radius, the quantum confinement effect causes an increase in the excitonic transition energy and blue shift in the absorption and luminescence band gap energy . Science is
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Figure 7.5 Schematic of the discrete energy level of a semiconductor.
awaiting new discoveries in nanomaterials research, particularly in quantum physics, such as quantum confinement effect (QCE) at nanoscale. It is expected that control of the nanostructure’s dimension will facilitate the study of QCE since the diameter of nanostructures will be beyond the exciton Bohr diameter. Several parameters affect the QCE in nanostructures, such as barrier layers and band offsets. Until today, however, there have been few nanostructures that have been synthesized down to this subatomic level. Self-assembled nanostructures basically do not show any blue shift, but the core/shell nanostructures exhibit a significant blue shift, leading to the QCEs. For example, 4.8 nm diameter lead selenide nanocrystals (PbSe NCs) show an effective band gap of approximately 0.82 eV, exhibiting a strong confinement-induced blue shift of >500 meV compared to the bulk PbSe band gap of 0.28 eV (the Bohr exciton radius in PbSe is 46 nm). In addition, quantum confinement leads to a collapse of the continuous energy bands of a bulk material into discrete, atomic-like energy levels. The discrete structure of energy states leads to a discrete absorption spectrum, which is in contrast to the continuous absorption spectrum of a bulk semiconductor, as shown in Figure 7.5. A quantum confined structure is one in which the motion of the carriers (electron and hole) are confined in one or more
European Nano Knowledge that Led 157 Table 7.1 Classification of Quantum Confined Structures.
Number of free dimension
Quantum well/ superlattices
Quantum dot/ nanocrystals
directions by potential barriers. Based on the confinement direction, a quantum confined structure will be classified into three categories as quantum well, quantum wire and quantum dots or nanocrystals. The basic types of quantum confined structures are shown in Table 7.1. So, the quantum confinement effect is a phenomenon in which the diameter of the particle is reduced so much that it is of the order of the wavelength of the electron wave function. The optical and electronic properties of bulk and nano materials vary from each other. The optical properties of matter are due to the spatial freedom executed in the motion of its electrons. The electronic motion depends on the type of material and space allotted (i.e., degree of confinement). Electrons in a bulk metal spread as waves of various wavelengths called “de Broglie wavelength.” The electrons are delocalized in the conduction band of a metal. In quantum dots (QDs), the charge carriers are confined in all three dimensions in which the electrons exhibit a discrete atomic-like energy spectrum. Quantum wires are formed when two dimensions of the system are confined. In a quantum well, charge carriers (electrons and holes) are confined to move in a plane and are free to move in two dimensions.
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Also, the energy level of one of the quantum numbers that changes from continuous dimension of the metal particle is a multiple of de Broglie wavelength λ. If the band structure size range, i.e., in the case of metals, begins to ebb away and discrete energy levels become dominant, then quantum mechanical principles are followed rather than classical theory. The individual spacing of successive quantum levels, δ, also known as the kubo gap, is given by δ = 4 Ef / 3 n
Where Ef is the fermi energy of the bulk metal and n is the number of the valence electrons in the nanoparticle (generally called its nuclearity). Compared with bulk semiconductors, the quantum well has a higher density of electronic states near the edges of the conduction and valence bands, and therefore a higher concentration of carriers can contribute to the band edge emission . As more numbers of the dimension are confined, more discrete energy levels can be found; in other words, carrier movement is strongly confined in a given dimension. Quantum confinement effect (QCE) can be observed once the diameter of the particle is of the magnitude of the wavelength of electron wave function. When the materials are so small, their electronic and optical properties deviate substantially from those of bulk materials. A particle behaves as if it were free when the confining dimension is large compared to the wavelength of the particle. During this state, the band gap remains at its original energy due to the continuous energy state. However, as the confining dimension decreases and reaches a certain limit, typically on the nanoscale, the energy spectrum turns discrete. As a result, the band gap of the nanostructures becomes size- and shape-dependent. This ultimately results in a blue shift in optical illumination as the size and shape of the particles decrease. Specifically, QCE describes the phenomenon that results from electrons
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and holes (excitons) being squeezed into a dimension that approaches a critical quantum measurement, called the exciton Bohr radius.
Approaches to Fabricate Nanomaterials
An understanding of nanoscience has led to efforts being made to synthesize various nanoparticles. Material scientists started conducting research to develop novel materials with better properties, more functionality and lower cost than the existing ones. Several physical-chemical methods have been developed to enhance the performance of nanomaterials displaying improved properties with the aim of having better control over the particle size and distribution . In general, the two main approaches envisaged for nanomaterials synthesis are: 1) Top-down method, which involves size reduction from bulk materials (Figure 7.6). The Top-down routes are included in the typical solid-state processing of the materials. This route is based on the bulk material and makes it smaller, thus breaking up larger particles by the use of physical processes like crushing, milling or grinding. Usually this route is not suitable for preparing uniformly shaped materials, and it is very difficult to realize very small particles even with high energy consumption. The biggest problem with the top-down approach is the imperfection of the surface structure. Such imperfection would have a significant impact on the physical properties and surface chemistry of nanostructures and nanomaterials. It is well known that the conventional top-down technique can cause significant crystallographic damage to the processed patterns. 2) Bottom-up nanomaterial synthesis from atomic level. This method refers to building up a material from the bottom: atomby-atom, molecule-by-molecule or cluster-by-cluster. This route is more often used for preparing most of the nanoscale materials with the ability to generate a uniform size, shape and distribution. It effectively covers chemical synthesis and precisely
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Atoms Bottom up Figure 7.6 Schematic view of top-down and bottom-up approaches for nanomaterial synthesis.
controls the reaction to inhibit further particle growth. Although the bottom-up approach is nothing new, it plays an important role in the fabrication and processing of nanostructures and nanomaterials. Synthesis of nanoparticles to have better control over particle size distribution, morphology, purity, quantity and quality, by employing environment-friendly economical processes has always been a challenge for researchers . The choice of synthesis technique can be a key factor in determining the effectiveness of the particles. There are many methods of synthesizing nanoparticles such as hydrothermal [36, 37] and combustion synthesis , gas-phase methods , microwave synthesis and sol-gel processing , etc.
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Advancements in Various Fabrication Methods of Nanoparticles
It is interesting to note that most of the nanoparticle fabricating technologies are based on time-tested techniques that have been used for other syntheses or fabrication purposes. Methods for fabricating nanoparticles can be categorized as physical, chemical and biological.
Physical Methods Mechanical
Mechanical milling (MM) of a suitable powder in a high-energy mill, along with a suitable milling medium to reduce the particle size and blending of particles in new phases is the basic concept of MM. Different types of ball milling are used for synthesis of nanomaterials in which fine surface balls impact the powder charge . The balls either roll down the surface of the chamber in a series of parallel layers or they are allowed to fall freely and impact the powder and balls beneath them. For large-scale production of nano-size grain, mechanical milling is a more economical process . The kinetics of mechanical milling or alloying depends on the energy transferred to the powder from the balls during milling . The energy transfer is governed by many parameters such as the type of mill, the powder supplied to drive the milling chamber, milling speed, size and size distribution of the balls, dry or wet milling, temperature of milling and the duration of milling . Mechanical attrition produces its nanostructures by the structural decomposition of coarser grained structures as a result of plastic deformation. By this process elemental powders of Al and β-SiC ceramic/ceramic nanocomposites are fabricated. The ball-milling and rod-milling techniques belong to the mechanical alloying process, which has received much attention as a powerful tool for the fabrication of several
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Figure 7.7 Planetary ball mill (RETSCH PM 400: department of Physics, BHU).
advanced materials. Mechanical alloying is a unique process, which can be carried out at room temperature. The process can be performed on high-energy mills, centrifugal-type mill and vibratory-type mill, and low-energy tumbling mill [45–47]. However, the principles of these operations are the same for all the techniques. High-energy mills include: Attrition Ball Milling: The milling procedure takes place by the stirring action of an agitator, which has a vertical rotator central shaft with horizontal arms (impellers). The rotation speed is later increased to 500 rpm. Also, the milling temperature has greater control. Planetary Ball Milling: Centrifugal forces are caused by rotation of the supporting disc and autonomous turning of the vial (Figure 7.7). The milling media and charge powder alternatively roll on the inner wall of the vial and are thrown off across the bowl at high speed (360 rpm). Vibrating Ball Milling: It is used mainly for production of amorphous alloys. The changes of powder and milling tools are agitated in the perpendicular direction at very high speed (1200 rpm). Low-Energy Tumbling Milling: The tumbler ball mill, shown in Figure 7.8, is a cylindrical container rotated about its axis in
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Figure 7.8 A rock tumbler/ball mill.
which balls impact upon the powder charge. The balls may roll down the surface of the chamber in a series of parallel layers or they may fall freely and impact the powder and balls beneath them. A tumbler ball mill is operated close to the critical speed beyond which the balls are pinned to the inner walls of the mill because of the centrifugal force dominating over centripetal force. For large-scale production, tumbler mills are more economical when compared to the other high-energy ball mills . While a number of ingenious milling devices were developed early in the century, the one high-energy ball mill that has been adopted by industry was invented by Andrew Szegvari in 1922 in order to quickly attain fine sulfur dispersion for use in vulcanization of rubber. This mill is called an attritor or attrition mill and is illustrated in Figure 7.9b. Low-energy tumbling mills have been used for successful preparation of mechanically alloyed powder. They are simple to operate with low operation costs. A laboratory-scale rod mill was used to prepare homogeneous amorphous Al30Ta70 powder by using stainless steel cylinder rods. Single-phase amorphous powder of AlxTm100-x with low iron concentration can be formed by this technique.
164 History of Nanotechnology Horizontal section
Water-cooled stationary tank
Movement of the supporting disc
Steel ball bearings
Rotation of the milling bowl
Figure 7.9 Schematic view of (a) motion of the ball and powder mixture and (b) arrangement of rotating arms on a shaft in the attrition ball mill.
High-Energy Ball Milling: In the ball milling process, a powder mixture placed in the ball mill is subjected to highenergy collision from the balls. The synthesis of materials by high-energy ball milling of powders was first developed by John Benjamin  and his coworkers at the International Nickel Company in the late 1960s. The goal of this work was the production of complex oxide dispersion-strengthened (ODS) alloys for high temperature structural applications. It was found that this method, termed mechanical alloying, could successfully produce fine, uniform dispersions of oxide particles (Al2O3, Y2O3, ThO2) in nickel-base superalloys, which could not be made by more conventional powder metallurgy methods. Benjamin and his coworkers at Paul D. Merica Research Laboratory in partnership with INCA (Inventors Network of the Capital Area) also explored the synthesis of other kinds of materials, e.g., solid solution alloys and immiscible systems, and pointed out  that mechanical alloying (MA), in addition to synthesis of dispersion-strengthened alloys, could make metal composites, compounds, and/or new materials with unique properties . However, one of the major applications of MA so far
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has been the production of oxide-dispersion-strengthened (ODS) materials . Their innovation has changed the traditional method in which production of materials is carried out by high temperature synthesis. Besides synthesis of materials, high-energy ball milling is a way of modifying the conditions in which chemical reactions usually take place either by changing the reactivity of asmilled solids (mechanical activation increasing reaction rates, lowering reaction temperature of the ground powders) or by inducing chemical reactions during milling (mechanochemistry). It is, furthermore, a way of inducing phase transformations in starting powders whose particles have all the same chemical composition: amorphization or polymorphic transformations of compounds, disordering of ordered alloys, etc. High-energy ball milling is an already established technology but has been considered dirty because of contamination problems with iron. However, the use of tungsten carbide component and inert atmosphere and/or high vacuum processes has reduced impurity levels to within acceptable limits. Common drawbacks include low surface, highly polydisperse size distribution, and partially amorphous state of the powder. These powders are highly reactive with oxygen, hydrogen and nitrogen. Mechanical alloying leads to the fabrication of alloys, which cannot be produced by conventional techniques. It would not be possible to produce an alloy of Al-Ta because of the difference in melting points of Al (933 K) and Ta (3293 K) by any conventional process. However, it can be fabricated by mechanical alloying using the ball milling process.
Polymer melting and mixing involves various types of mixing elements or components used for the homogeneous mixing of the polymer melt inside the extruder. The most common dry mixing methods are volumetric mixing and gravimetric mixing. It is possible to form or arrest nanoparticles in glass, which
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is structurally an amorphous solid, lacking the symmetric arrangement of atoms/molecules. Metals, when cooled at very high cooling rates (105–106 K/s), can form amorphous solidsmetallic glasses. Mixing molten streams of metals at high velocity with turbulence forms nanoparticles, e.g., a molten stream of Cu-B and molten stream of Ti form nanoparticles of TiB2.
22.214.171.124 Hydrothermal and Solvothermal Synthesis In hydrothermal synthesis the reaction is typically carried out in a pressurized vessel called an autoclave in aqueous solution. The temperature in the autoclave can be raised above the boiling point of water, reaching the pressure of vapor saturation. Hydrothermal synthesis is widely used for the preparation of TiO2 nanoparticles, which can easily be obtained through hydrothermal treatment of peptized precipitates of a titanium precursor with water . The hydrothermal method can be useful to control grain size, particle morphology, crystalline phase and surface chemistry through regulation of the solution composition, reaction temperature, pressure, solvent properties, additives and aging time . The solvothermal method is identical to the hydrothermal method except that a variety of solvents other than water can be used for this process. This method has been found to be a versatile route for the synthesis of a wide variety of nanoparticles with narrow size distributions, particularly when organic solvents with high boiling points are chosen. The solvothermal method normally has better control of the size and shape distributions and the crystallinity than the hydrothermal method, and has been employed to synthesize TiO2 nanoparticles and nanorods with/without the aid of surfactants.
126.96.36.199 Templating The synthesis of nanostructure materials using the template method has become extremely popular during the last decade. In order to construct materials with a similar morphology of
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known characterized materials (templates), this method utilizes the morphological properties with reactive deposition or dissolution. Therefore, it is possible to prepare numerous new materials with a regular and controlled morphology on the nano- and microscale by simply adjusting the morphology of the template material. A variety of templates have been studied for synthesizing titania nanomaterials [54, 55]. This method has some disadvantages, including the complicated synthetic procedures and, in most cases, templates need to be removed, normally by calcinations, leading to an increase in the cost of the materials and the possibility of contamination . 188.8.131.52.1 Inverse Micelles as Nanotemplate Reverse micelles as nano-sized aqueous droplets existing at certain compositions of water-in-oil microemulsions (the term microemulsion was coined by Schulman et al., in 1959 ) are widely used today in the synthesis of many types of nanoparticles. Reverse micelles as nanoscale hydrophilic cavities of microemulsions have been known since the 1960s, but these diverse multimolecular structures were used for the first time as nanotemplates for materials synthesis (of monodispersed Pt, Pd, Rh and Ir particles) in 1982 . After these pioneering studies, many different materials comprising de-agglomerated and monodispersed particles have been prepared [59–62] by using reverse micelles. Microemulsions are transparent, thermodynamically stable dispersions of two immiscible liquids containing appropriate amounts of surfactant. The success of the reverse micellar procedure for materials synthesis is closely related to the fact that particle nucleation can be initiated simultaneously at a large number of locations within reverse micelles, with the nucleation sites well isolated from each other due to the presence of surfactant films that may act as stabilizers of the formed particles. Normally, monodisperse particles are formed only when the nucleation and growth stages are strictly separated, which is a property of reverse micelle material synthesis
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Figure 7.10 Schematic diagram of (a) a reverse micelle (Reproduced from ) and (b) a more realistic model of a reverse micelle (Reproduced from ). Blue spheres represent the surfactant’s head groups, whereas smaller yellow spheres denote counterions. Note that the surfactant head groups do not completely shield the aqueous interior of the modeled reverse micelle.
due to the uniform nanodroplet structure and specific intermicellar interactions. Reverse micelle phases are tiny droplets of water encapsulated by surfactant molecules and thus physically separated from the oil phase (Figure 7.10). Simplified representation of the reverse micellar preparation of particles takes that aqueous “pools” of the reverse micelles act as nanoreactors for performing simple reactions of synthesis, and that the sizes of the microcrystals of the product are directly determined by the sizes of these pools [65–67]. It is possible to control the sizes of reverse micelles by controlling the parameter w, defined as molar ratio of water-to-surfactant. The higher the w, the larger the water pools of the micelles and the nanoparticles formed within, and vice versa.
Electron Beam Lithography
Lithography is an old technique used for ink imprinting that dates back to 17th century. Nowadays, the techniques and applications of lithography have been diversified, but lithography is the process of transferring a pattern from one media to another. Base on the same concept, electron beam lithography was developed in the late 60s and consists of electron irradiation
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of a surface covered with a resist sensitive to electrons by means of a focused electron beam. The energetic absorption in specific places causes the intramolecular phenomena that define the features in the polymeric layer. This lithographic process, capable of creating submicronic structures, consists of three steps: exposure of the sensitive material, development of the resist and pattern transfer. It is important to consider that these should not be realized independently, and that the final resolution is conditioned for the accumulative effect of each individual step of the process. A great number of parameters, conditions and factors within the different subsystems are involved in the process and contribute to the electron beam lithography (EBL) operation and result. In a direct write EBL system, the designs are directly defined by scanning the energetic electron beam, and then the sensitive material is physically or chemically modified due to the energy deposited from the electron beam. This material is called the resist, since, later on, it resists the process of transference to the substrate. The energy deposited during the exposure creates a latent image that is materialized during chemical development. For positive resists, the development eliminates the patterned area, whereas for negative resists, the inverse occurs. As a consequence, the shape and characteristics of the electron beam, the energy and intensity of electrons, the molecular structure and thickness of the resist, the electron– solid interactions, the chemistry of the developer in the resist, the conditions for development and the irradiation process, from the structure design to the beam deflection and control, are determinant for the results, in terms of dimensions, resist profile, edge roughness, feature definition, etc.
184.108.40.206 Vapor Phase Synthesis Physical vapor deposition (PVD) is a collective set of processes used to deposit thin layers of material (Figure 7.11), typically in the range of a few nanometers to several micrometers .
170 History of Nanotechnology U– Sputtering target Ar Sputtered target atom
Figure 7.11 Schematic of physical vapor deposition (PVD).
PVD involves vacuum deposition techniques consisting of three fundamental steps: Vaporization of the material from a solid source assisted by high temperature vacuum or gaseous plasma. Transportation of the vapor in vacuum or partial vacuum to the substrate surface. Condensation onto the substrate to generate thin films. Different PVD technologies utilize the same three fundamental steps but differ in the methods used to generate and deposit material. The two most common PVD processes are thermal evaporation and sputtering. Thermal evaporation is a deposition technique that relies on vaporization of source material by heating the material using appropriate methods in a vacuum. Sputtering is a plasma-assisted technique that creates a vapor from the source target through bombardment with accelerated gaseous ions (typically argon). In both evaporation and sputtering, the resulting vapor phase is subsequently
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deposited onto the desired substrate through a condensation mechanism . Deposited films can span a range of chemical compositions based on the source material(s). Further compositions are accessible through reactive deposition processes. Relevant examples include co-deposition from multiple sources, reaction during the transportation stage by introducing a reactive gas (nitrogen, oxygen or simple hydrocarbon containing the desired reactant), and post-deposition modification through thermal or mechanical processing . PVD is used in a variety of applications, including fabrication of microelectronic devices, interconnects, battery and fuel cell electrodes, diffusion barriers, optical and conductive coatings, and surface modifications [71–73].
220.127.116.11 Gas Phase Methods Gas phase methods are ideal for the production of thin films. Gas phase can be carried out chemically or physically. Chemical vapor deposition (CVD) is a widely used industrial technique that can coat large areas in a short space of time. During the procedure, titanium dioxide is formed from a chemical reaction or decomposition of a precursor in the gas phase [39, 74]. Physical vapor deposition (PVD) is another thin film deposition technique. Films are formed from the gas phase but without a chemical transition from precursor to product. For TiO2 thin films, a focused beam of electrons heats the titanium dioxide material. The electrons are produced from a tungsten wire heated by a current. This is known as electron beam (E-beam) evaporation. Titanium dioxide films deposited with E-beam evaporation have superior characteristics over CVD grown films such as smoothness, conductivity, presence of contaminations and crystallinity. Reduced TiO2 powder (heated at 900 °C in a hydrogen atmosphere) is necessary for the required conductance needed to focus an electron beam on the TiO2 .
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Quartz tube Gas inlet
Quartz boat Oven 720ºC
Figure 7.12 Schematic diagram of the chemical vapor deposition apparatus.
In 1993, the CVD technique was first reported to produce multi-walled carbon nanotubes (MWNTs) by Endo et al., . Three years later, Dai in Smalley’s group successfully adapted CO-based CVD to produce single-walled carbon nanotubes (SWNTs) . CVD technique can be achieved by taking a carbon source in the gas phase and using an energy source, such as plasma or a resistively heated coil, to transfer energy to a gaseous carbon molecule. The CVD process uses hydrocarbons as the carbon sources, including methane, carbon monoxide and acetylene. The hydrocarbons flow through the quartz tube in an oven at a high temperature (~720 °C) (Figure 7.12). At high temperature, the hydrocarbons are broken down into the hydrogen–carbon bond, producing pure carbon molecules. Then, the carbon will diffuse toward the substrate, which is heated and coated with a catalyst (usually a first row transition metal such as Ni, Fe or Co) where it will bind. Carbon nanotubes will be formed if the proper parameters are maintained. The advantages of the CVD process are low power input, lower temperature range, relatively high purity and, most importantly, the possibility of scaling up the process. This method can produce both MWNTs and SWNTs depending on the temperature, in which production of SWNTs will occur at a higher temperature than MWNTs.
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This process is often used in the semiconductor industry to produce high-purity, high-performance thin films. In a typical CVD process, the substrate is exposed to volatile precursors, which react and/or decompose on the substrate surface to produce the desired film. Frequently, volatile by-products that are produced are removed by gas flow through the reaction chamber. The quality of the deposited materials strongly depends on the reaction temperature, the reaction rate, and the concentration of the precursors . Cao et al., prepared Sn4+-doped TiO2 nanoparticle films by the CVD method and found that more surface defects were present on the surface due to doping with Sn . Gracia et al., synthesized M (Cr, V, Fe, Co)-doped TiO2 by CVD and found that TiO2 crystallized into the anatase or rutile structures depending on the type and amount of cation present in the synthesis process. Moreover, upon annealing, partial segregation of the cations in the form of M2On was observed . The advantages of this method include uniform coating of the nanoparticles or nanofilm. However, this process has limitations, including the higher temperatures required, and it is difficult to scale up.
Thermal Decomposition and Combustion
Pure and doped metal nanomaterials can be synthesized via thermally decomposing metal alkoxides and salts by applying high energy using heat or electricity. However, the properties of the produced nanomaterials strongly depend on the precursor concentrations, the flow rate of the precursors and the environment. Kim et al., synthesized TiO2 nanoparticles with a diameter less than 30 nm via the thermal decomposition of titanium alkoxide or TiCl4 at 1200 °C . Liang et al., produced TiO2 nanoparticles with a diameter ranging from 3 to 8 nm by pulsed laser ablation of a titanium target immersed in an aqueous solution of surfactant or deionized water . Nagaveni et al., prepared W, V, Ce, Zr, Fe, and Cu ion-doped anatase TiO2 nanoparticles by a solution combustion method and found that
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the solid solution formation was limited to a narrow range of concentrations of the dopant ions . However, the drawbacks of these methods are high cost and low yield, and difficulty in controlling the morphology of the synthesized nanomaterials. Combustion synthesis leads to highly crystalline particles with large surface areas . The process involves a rapid heating of a solution containing redox groups. During combustion, the temperature reaches approximately 650 °C for one or two minutes, making the material crystalline. Since the time is so short, the transition from anatase to rutile is inhibited.
The ejection of atoms from the surface of a material (the target) by bombardment with energetic particles is called sputtering . Sputtering is a momentum transfer process in which atoms from a cathode/target are driven off by bombarding ions. Sputtered atoms travel until they strike a substrate, where they deposit to form the desired layer (Figure 7.13). Sputter deposition is a widely used technique to deposit thin films on substrates. The technique is based on ion bombardment of a source Target
Figure 7.13 Schematic of sputtering.
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material, the target. Ion bombardment results in a vapor due to a purely physical process, i.e., the sputtering of the target material. Hence, this technique is part of the class of physical vapor deposition techniques, which includes, for example, thermal evaporation and pulsed laser deposition. The most common approach for growing thin films by sputter deposition is the use of a magnetron source in which positive ions present in the plasma of a magnetically enhanced glow discharge bombard the target. The sputtering process is classified as DC (direct current) or RF (radio frequency) depending on the type of power supply used. DC sputtering is mainly used to deposit metals. In the case of insulators after the ions strike the surface, their charge will remain localized and with passage of time positive charge will build up on the target, making it unfeasible to further bombard the surface. This can be prevented by bombarding the insulator by both positive ions and electrons simultaneously . That is done by applying a RF potential to the target. The RF potential provides sufficient energy to the electrons oscillating in the alternating field to cause ionizing collisions, and a self-sustained discharge is maintained. As electrons have higher mobility compared to ions, more electrons will reach the insulating target surface during the positive half cycle than the positive ions during the negative half cycle. Hence, the target will be self-biased negatively. This repels the electrons from the vicinity of the target and forms a sheath enriched in positive ions in front of the target surface. These ions bombard the target and sputtering is achieved. The simplest source of ions for sputtering is provided by the well-known phenomenon of glow discharge due to an applied electric field between two electrodes in a gas at low pressure. The gas breaks down to conduct electricity when a certain minimum voltage is reached. Such an ionized gas is called plasma. Ions of the plasma are accelerated at the target by a large electric field. When the ions impact the target, atoms (or molecules)
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Glow discharge Substrates Anode
Figure 7.14 Basic elements of a DC sputtering system.
are ejected from the surface of the target into the plasma, where they are carried away and then deposited on the substrate. This type of sputtering is called “DC sputtering” (Figure 7.14). In order to avoid any chemical reaction between the sputtered atoms and the sputtering gas, the sputtering gas is usually an inert gas such as argon. However, in some applications, such as the deposition of oxides and nitrides, a reactive gas is purposely added to argon so that the deposited film is a chemical compound. This type of sputtering is called “reactive sputtering.” When the plasma ions strike the target, their electrical charge is neutralized and they return to the process as atoms. If the target is an insulator, the neutralization process results in a positive charge on the target surface. This charge may reach a level where bombarding ions are repelled and the sputtering process stops. To continue the process, the polarity must be reversed to attract enough electrons from the plasma to eliminate surface charge. This periodic reversal of polarity is done automatically by applying a radio-frequency (RF) voltage on the target assembly. Thus, this type of sputtering is known as “RF sputtering,” (Figure 7.15).
European Nano Knowledge that Led 177 Matching network 13.56 MHz Insulation
Glow discharge Substrates Anode
Figure 7.15 Basic elements of an RF sputtering system.
In order to increase the efficiency of the sputtering process, it is common for the sputtering source to have some magnetic confinement through a magnetron source. The effect of the magnetic field is to spiral the electrons so that they have a better chance of undergoing an ionizing collision, thus enabling the plasma to be operated at a higher density. This type of sputtering is called “magnetron sputtering” and it can be used with DC or RF sputtering. Materials that can be sputtered include elements (such as pure metals and elemental semiconductors), alloys, and compounds (such as oxides, nitrides, sulfides, and carbides). Sputtering allows for the deposition of films having the same composition as the target source. This is the primary reason for the widespread use of sputtering as a thin-film deposition technique. Compared to other deposition techniques, sputtering gives more uniform and reproducible results.
18.104.22.168 Arc Discharge Arc discharge was the first recognized technique for producing MWNTs and SWNTs. The arc discharge technique generally
178 History of Nanotechnology ANODE DOPED WITH Ni, Co
PURE GRAPHITE ELECTRODE Helium atmosphere, 400 mbar
Graphite anode Plasma Deposit Graphite cathode
To pumps DC Current source
Single wall nanotubes
Figure 7.16 Schematic of the arc discharge apparatus.
involves the use of two high-purity graphite electrodes as the anode and the cathode. The electrodes are vaporized by the passage of a DC current (~100 A) through two high-purity graphite electrodes separated (~1–2 mm) in 400 mbar of helium atmosphere. The experimental set up of the arc discharge apparatus is shown in Figure 7.16. After arc discharging for a period of time, a carbon rod is built up at the cathode. This method can mostly produce MWNTs but can also produce SWNTs with the addition of metal catalyst such as Fe, Co, Ni, Y or Mo, on either the anode or the cathode. The quantity and quality, such as lengths, diameters, purity, etc., of the nanotubes obtained depend on various parameters such as the metal concentration, inert gas pressure, type of gas, plasma arc, temperature, the current and system geometry. Electric arc deposition: Cathodic arc deposition or arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode target. The vaporized material then condenses on a substrate, forming a thin film (Figure 7.17). The technique can be used to deposit metallic, ceramic, and composite films. Industrial use of
European Nano Knowledge that Led 179 Are confinement ring Anode Cathode
Are lgniter N Power supply
Figure 7.17 Cathodic arc source design (Sablev type). (Source: www.wikipedia. com).
modern cathodic arc deposition technology originated in the Soviet Union around 1960–1970. By the late 70 s the Soviet government released the use of this technology to the West. Among the many designs in the USSR at that time, the design by L. P. Sablev et al., was allowed to be used outside the USSR. The arc evaporation process begins with the striking of a high current, low voltage arc on the surface of a cathode (known as the target) that gives rise to a small (usually a few micrometers wide), highly energetic emitting area known as a cathode spot. The localized temperature at the cathode spot is extremely high (around 15000 °C), which results in a high velocity (10 km/s) jet of vaporized cathode material, leaving a crater behind on the cathode surface. The cathode spot is only active for a short period of time, then it self-extinguishes and reignites in a new area close to the previous crater. This behavior causes the apparent motion of the arc.
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Fumace at 1200 C Cooled collector Argon gas
Nenotube felt Nd-Yag laser Graphene target
Figure 7.18 Schematic diagram of laser ablation apparatus.
Laser Ablation and Pulsed Laser Ablation
In 1995, Smalley and coworkers produced carbon nanotubes using laser ablation technique . In the laser ablation technique, a high-power laser was used to vaporize carbon from a graphite target at high temperature. Both MWNTs and SWNTs can be produced with this technique. In order to generate SWNTs, metal particles must be added as catalysts to the graphite targets similar to the arc discharge technique. The quantity and quality of the carbon nanotubes produced depend on several factors such as the amount and type of catalysts, laser power and wavelength, temperature, pressure, type of inert gas, and the fluid dynamics near the carbon target (Figure 7.18). The laser is focused on carbon targets containing 1.2% of cobalt/ nickel with 98.8% of graphite composite that is placed in a 1200 °C quartz tube furnace under argon atmosphere (~500 Torr). These conditions were achieved for production of SWNTs in 1996 by Smalley’s group . In such a technique, argon gas carries the vapors from the high temperature chamber into a cooled collector positioned downstream. The nanotubes will self-assemble from carbon vapors and condense on the walls of the flow tube. The diameter distribution of SWNTs from this method varies about 1.0–1.6 nm. Carbon nanotubes produced by laser ablation were purer (up to 90% purity) than
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those produced in the arc discharge process and have a very narrow distribution of diameters.
22.214.171.124 Ion Implantation Ion implantation is an alternative to deposition diffusion and is used to produce a shallow surface region of dopant atoms deposited into a silicon wafer. This technology has made significant inroads into diffusion technology in several areas. In this process a beam of impurity ions is accelerated to kinetic energies in the range of several tens of kV and is directed to the surface of the silicon. As the impurity atoms enter the crystal, they give up their energy to the lattice in collisions and finally come to rest at some average penetration depth, called the projected range, expressed in micrometers. Depending on the impurity and its implantation energy, the range in a given semiconductor may vary from a few hundred angstroms to about one micrometer. Typical distribution of impurity along the projected range is approximately Gaussian. By performing several implantations at different energies, it is possible to synthesize a desired impurity distribution, e.g., a uniformly doped region. A gas containing the desired impurity is ionized within the ion source. The ions are generated and repelled from their source in a diverging beam that is focused before it passes through a mass separator that directs only the ions of the desired species through a narrow aperture. A second lens focuses this resolved beam, which then passes through an accelerator that brings the ions to their required energy before they strike the target and become implanted in the exposed areas of the silicon wafers. The accelerating voltages may be from 20 kV to as much as 250 kV. In some ion implanters, the mass separation occurs after the ions are accelerated to high energy. Because the ion beam is small, means are provided for scanning it uniformly across the wafers. For this purpose, the focused ion beam is scanned electrostatically over the surface of the wafer in the target chamber (Figure 7.19). Repetitive scanning in a raster
182 History of Nanotechnology Single-charged ion n+ -charged ion
E = e(HV) E = ne(HV)
E-range: 5–500 keV Current: 1–100 mA
Ion source HV+ ION LENSES T a r g e t
eElectrostalic deflection (RASTERING)
Thru ion separation
Here ion deflection due to magnetic field
Figure 7.19 Schematic of ion implantation system.
pattern provides exceptionally uniform doping of the wafer surface. The target chamber commonly includes automatic wafer handling facilities to speed up the process of implanting many wafers per hour.
126.96.36.199 Synthesis of Nanoporous Polymers Using Membranes Most of the work in template synthesis has entailed the use of two types of nanoporous membranes: track-etch polymeric membranes and porous alumina membranes. 188.8.131.52.1 Track-Etch Membranes A number of companies (i.e., Millipore, Nuclepore and Poretics) sell microporous and nanoporous polymeric filtration membranes that have been prepared by the track-etch method . This method entails bombarding a nonporous sheet of the desired material with nuclear fission fragments to create damage tracks in the material, and then chemically etching these tracks into pores. The resulting membranes contain cylindrical
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pores of uniform diameter which are randomly distributed in the volume of the membrane. Membranes with a wide range of pore diameters (down to 10 nm) and pore densities approaching 109 pores/cm2 are commercially available . The most commonly used materials are polycarbonate or polyester. Other materials, such as mica, are amenable to the track-etch process . 184.108.40.206.2 Anodic Alumina Membranes (AAMs) Porous alumina membranes are electrochemically prepared from an aluminum sheet in an appropriate aqueous solution . The pore structure of a porous alumina membrane is a self-ordered hexagonal array of cells with cylindrical pores of almost uniform diameter and length, which can be controlled by changing the experimental conditions. Pore densities as high as 1011 pores/cm2 can be achieved . Such membranes are commercially available (i.e., Whatman) in a limited number of pore diameters (20, 100, 200 nm). Membranes of this type have also been prepared at the lab scale with pore size as small as 5 nm . 220.127.116.11.3 Other Nanoporous Membranes A variety of other membrane templates have been used. Ionomer membranes have been used as templates for the preparation of various nanoparticles . The ionomer membrane was obtained by wet casting from a solution of the sulfonimide ionomer in dimethylformide, followed by careful annealing at high temperature. Nafion ionomer membranes are provided by DuPont. Biomembranes have been used for template synthesis of nanomaterials, i.e., living biomembrane bi-templates of the mungbean sprout to prepare semiconductor lead selenide nanorods and nanotubes , and lamellar DNA-cationic membrane complexes to form CdS nanorods . Mesoporous zeolite membranes have been used for the template synthesis of nanomaterials: polyaniline nanowires have been prepared in
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the 3-nanometer-wide hexagonal channel system of the aluminosilicate MCM-41 .
Colloidal methods are simple wet chemistry precipitation processes in which solutions of the different ions are mixed under controlled temperature and pressure to form insoluble precipitates. For metal nanoparticles the basic principles of colloidal preparation have been known since antiquity; e.g., gold colloids used for high quality red and purple stained glass from medieval times to date. However, proper scientific investigations of colloidal preparation methods started only in 1857, when Faraday published the results of his experiments with gold. He prepared gold colloids by reduction of HAuCl4 with phosphorus. Today, colloidal processes are widely used to produce such nanomaterials like metals, metal oxides, organics, and pharmaceuticals.
18.104.22.168 Conventional Sol-Gel Method The sol-gel method is a versatile process used for synthesizing various oxide materials . This synthetic method generally allows control of the textural, chemical, and morphological properties of the solid. This method also has several advantages over other methods, such as allowing impregnation or co-precipitation, which can be used to introduce dopants. The major advantages of the sol-gel technique include molecular scale mixing, high purity of the precursors, and homogeneity of the sol-gel products with a high purity of physical, morphological, and chemical properties . In a typical sol-gel process, a colloidal suspension, or a sol, is formed from the hydrolysis and polymerization reactions of the precursors, which are usually inorganic metal salts or metal organic compounds such as metal alkoxides . A general flowchart for a complete sol-gel process is shown in Figure 7.20. Any factor that affects either or
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Add supernatant Xero-Gel
Caking DENSE CERAMIC
Figure 7.20 Schematic diagram of sol-gel method.
both of these reactions is likely to impact the properties of the gel. These factors, generally referred to as sol-gel parameters, include type of precursor, type of solvent, water content, acid or base content, precursor concentration, and temperature. These parameters affect the structure of the initial gel and, in turn, the properties of the material at all subsequent processing steps. After gelation, the wet gel can be optionally aged in its mother liquor, or in another solvent, and washed. The time between the formation of a gel and its drying, known as aging, is also an important parameter.
The Langmuir-Blodgett (LB) technique is a room temperature deposition process that may be used to deposit monolayer and multilayer films of organic materials. Furthermore, this method permits the manipulation of organic molecules on the nanometer scale, thereby allowing intriguing superlattice architectures to be assembled . Advances to the discovery of LangmuirBlodgett films began with Benjamin Franklin in 1773, when he dropped about a teaspoon of oil onto a pond. Franklin noticed that the waves were calmed almost instantly and that the calming of the waves spread for about half an acre. What Franklin did not realize was that the oil had formed a monolayer on top
186 History of Nanotechnology Microemulsion I
Microemulsion II Aqueous phase reducing agent (NH4OH, N2H2), NaBH4, etc....
Aqueous phase metal salt (FeCl3, FeCl2, CuCl2, etc...)
Mix microemulsions I and II
Collisions and coalescence of droplets
Precipitate (Metal or metal oxide)
Chemical reaction occurs
Figure 7.21 (a) Mechanism for the synthesis of metal nanoparticles by the microemulsion approach, and (b) the percolation mechanism in detail. (Reproduced from )
of the pond surface. Over a century later, Lord Rayleigh quantified what Benjamin Franklin had seen. Knowing that the oil, oleic acid, had spread evenly over the water, Rayleigh calculated that the thickness of the film was 1.6 nm by knowing the volume of oil dropped and the area of coverage.
Ultrafine metal nanoparticles of diameter between 5 nm and 50 nm can be prepared by water-in-oil microemulsions. The nanodroplets of water are dispersed in the oil phase (Figure 7.21). The size of the droplets can be varied in the range of 5–50 nm by changing the water/surfactant ratio. The surfactant molecules provide the sites for particle nucleation and stabilize the growing particles. Therefore, the microemulsion acts as a microreactor.
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Biosynthesis or Biological Methods of Synthesizing Nanoparticles
The tremendous potential offered by living organisms in biosynthesis of nanometals has spurred encouraging interest. Included in the biological methods is the study of the role of living cells (be it microbes, fungi, actinomycetes, algae or plants) in biosynthesizing nanometals, both intra- as well as extracellularly. The capability of living cells to sequester metal ions and meticulously define the dimensions via fetter-like capping proteins, such as glutathione, phytochelatins and metallothioneins, is intriguing, giving it a monodispersed size. The role of extracellular electron shuttlers in the formation of nanoparticles is also the subject of interest in biogenic synthesis. The evolutionary challenges and selection pressures over millions of years faced by living organisms have led to the emergence of proficient biological systems and molecules that are adept nanomachines. It took a fraction of a period for scientist to realize the cost-effectiveness and high maintenance of the biosynthetic route for the synthesis of nanometals. Biosynthesis of nanometals is accepted as a “green chemistry” approach. Nature has conferred living systems with proficient processes, endowing them with competency that cannot be aped at lab scale. Many microbes and higher plants are known to possess metal tolerance potential. Due to environmental concerns, ease of synthesis and the need for deft methods for nanometal synthesis, living systems have entered the limelight and are being considered as dexterous candidates for “nanofactories.” There is a plethora of literature available addressing biologically synthesized nanoparticles, which is being added to each day. Some of the literature is listed in Table 7.2.
Nanometal Synthesis Using Microorganisms
By now it is an open secret that microbes take up metal in ionic form and accumulate it within the cell without affecting
Ti/Ni Alloy Ceramic Si-Germanium oxide Gold
Sargassum wightii Fucus vesiculosus
Emblica officinalis Azadirachta indica Jatropha curcas
40–50 20–40 20–30 10–20 65–80 5–30 20–150
Azadirachta indica Geranium Lemongrass Emblica officinalis Cinnamomum camphora Barbated Skullcup Volvariella volvacea
Biosynthesized nanometal Size (nm)
Table 7.2 Various Organisms That Have Shown the Capacity to Biosynthesize Nanometals.
  
      
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Silver sulfide Silver
Bacillus subtilis Thiobacillus ferroxidans Lactobacillus spps. Pseudomonas stutzeri ATCC 90271 Rhodopseudomonas capsulate Escherichia coli DH5α
Thiobacillus ferroxidans Thiobacillus thioxidans
Pseudomonas stutzeri AG259 Plectonema boryanum Klebsiella pneumonia
Klebsiella aerogenes Rhodopseudomonas palustris
20–200 8.01 ± 0.25
200 200 1–6 nm
50–100 20–50 100–250 10–20 10–20 10–20
Biosynthesized nanometal Size (nm)
  
     
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Palladium Zinc sulfide Zinc Platinum
Mycobacterium paratuberculosis Shewanella putrefaciens. Leptothrix ochracea
Desulfovibrio desulfuricans D. desulfuricans
Cyanobacterium spps. and Pseudomonas putida
Shewanella algae Mixed consortium of sulphate-reducing bacteria
Biosynthesized nanometal Size (nm)
  
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20–50 2–5 10 10–60 5–25 23–105
Cadmium sulfide Lead sulfide
Verticillium spps. Fusarium oxysporum Aspergillus flavus Fusarium semitectum Penicillium fellutanum Penicillium brevicompactum WA 2315
Candida glabrata Schizosaccharomyces pombe
20–40 5–10 7–12 10–20 5–10
Yarrowia lipolytica (pH 7 and 9) Verticillium spps Thermomonospora spps. Trichothecium Fusarium oxysporum
Fungi and Actinomycetes
Biosynthesized nanometal Size (nm)
     
    
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its regular metabolic activities. This phenomenon is termed “resistance for metal” by microorganisms. But at some stage of the life cycle, if the metal accumulation is uncontrollable by the microorganisms, then the cell produces toxicity, finally leading to the death of the microbe and to the advantage of those who are interested in nanometal synthesis. These microbes die or burst open, releasing nanometals. Microorganisms have been shown to be important nanofactories that hold immense potential as eco-friendly and cost-effective tools, avoiding toxic, harsh chemicals and the high energy demand required for physiochemical synthesis. Microorganisms have the ability to accumulate and detoxify heavy metals due to various reductase enzymes, which are able to reduce metal salts to metal nanoparticles with a narrow size distribution and, therefore, less polydispersity.
22.214.171.124 Nanometal Synthesis Using Fungi and Actinomycetes Fungi and actinomycetes have also been stated to be advantageous in the synthesis of nanoparticles , which can be scaled up easily, is economically viable, and has the possibility of easily covering large surface areas by suitable growth of the mycelia. This transition from bacteria to fungi as a means of developing natural nanofactories has the added advantage that downstream processing and handling of the biomass would be simpler. To get filtrates from colloidal bacterial broth, sophisticated equipment is a must, whereas filtrates from fungal broths can be obtained by using simple equipment. Fungi have been found to be efficient secretors of soluble proteins and their mutant strains can secrete up to 30 g/l of extracellular protein. It is this character of high level protein secretion that has made fungi a favorite host of heterologous expression of high-value mammalian protein for manufacturing by fermentation. The ability of fungi and actinomycetes as nanofactories was explored later than bacteria. However, they were found to be
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more efficient than bacteria. Almost all the nanometals that could be synthesized by bacteria have been successfully biosynthesized also using fungi. The first attempt at biosynthesizing nanometal using fungi was made by Torres-Martínez .
Nanometals Synthesis Using Plants
Plants respond to heavy metal toxicity in a variety of different ways. Such responses include immobilization, exclusion, chelation and compartmentalization of the metal ions; and the expression of more general stress response mechanisms such as ethylene and stress proteins. These mechanisms have been reviewed comprehensively  for plants exposed to cadmium (Cd), the heavy metal for which there has arguably been the greatest number and most wide-ranging studies over many decades. Understanding the molecular and genetic basis for these mechanisms will be an important aspect of developing plants as agents for the phytoremediation of contaminated sites . One recurrent general mechanism for heavy metal detoxification in plants and other organisms is the chelation of the metal by a ligand and, in some cases, the subsequent compartmentalization of the ligand-metal complex. A number of metal binding ligands have now been recognized in plants. The roles of several ligands have been reviewed . Extracellular chelation by organic acids, such as citrate and malate, is important in mechanisms of aluminum tolerance. For example, malate efflux from root apices is stimulated by exposure to aluminum and is correlated with aluminum tolerance in wheat . Some aluminum-resistant mutants of Arabidopsis have also increased organic acid efflux from roots . Organic acids and some amino acids, particularly histidine, also have roles in the chelation of metal ions both within cells and in xylem sap . Peptide ligands include the metallothioneins (MTs), small gene-encoded, cysteine-rich polypeptides. Our current understanding of the functions and expression of MTs in plants, particularly Arabidopsis, have been reviewed elsewhere
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[148, 152]. In contrast, the phytochelatins (PCs) are enzymatically synthesized cysteine-rich peptides. The PC structure, biosynthesis, and function have been extensively reviewed [148, 153]. Recent advances in our understanding of aspects of PC biosynthesis and function are derived predominantly from molecular genetic approaches using model organisms for the gold and silver nanoparticles synthesis.
126.96.36.199 Nanometals Biosynthesis Using Algae The capacity of unicellular algae, called diatoms, to take up silica from the surrounding medium and convert it into very fascinating intricate patterns and symmetries on the cell wall has become a field of interest to many materials scientists and has drawn nanotechnologists towards it. Diatoms contain an enzyme called silaffin that can catalyze the polymerization of silica spheres—tiny structures reminiscent of the nanoparticles known to constitute diatom biosilica . Kröger et al., have now further defined the structure of the silaffins and discussed their pivotal role in the nanofabrication of diatom biosilica. A peptide, derived from the silaffin-1A protein of the diatom Cylindrotheca fusiformis, has been found to convert magnesium oxide microfilaments into nanocrystalline magnesium oxide . Fluid (gas or liquid)/silica displacement reactions leading to a variety of other oxides have also been identified. This hybrid (biogenic/synthetic) approach has opened the door to biosculpt ceramic microcomponents with multifarious tailored shapes and compositions for a wide range of environmental, aerospace, biomedical, chemical, telecommunications, automotive, manufacturing, and defense applications. A marine diatom, Nitzschia frustulum, has already been harnessed to fabricate Si-Ge oxide nanocomposite materials . Moreover, apart from diatoms other fresh water as well as marine algae has been successfully used for biosynthesis of nanometals. Singaravelu et al.,  exploited Sargassum wightii for extracellular synthesis of gold nanoparticles. Oza
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EHT = 10.00 kV WD = 5.6 mm
Single A = InLens Date :10 Dec 2010 Mag = 503.19 K X TIFR Mumbai Photo No. = 2627
Figure 7.22 (a) SEM image of gold nanoparticle synthesized from Sargassum wightii. (b) Schematic representation of nitrate reductase activity in the reduction of gold salt and formation of gold nanoparticles. (Reproduced from ; photo courtesy of Madhuri Sharon)
et al., [155, 156] have also extracellularly synthesized gold nanoparticles using the fresh water algae Chlorella pyrenoidosa and the marine algae Sargassum wightii. Nitrate reductase has been proved to be the most influential reducing enzyme involved in the synthesis of gold nanoparticle by these two algae (Figure 7.22).
188.8.131.52 Nanometals Biosynthesis Using DNA The search for unique biogenic nanoparticle synthesis methods led scientists to take advantage of a self-replicating biogenic polymer having high specific interactions between complementary bases in DNA, which evolved into a new branch of technology now known as DNA origami [157, 158]. At present, DNA nanostructures in many cases are formed with DNA origami technology. An alternative method employs nonspecific interactions in DNA solution for the construction of nanosystems. The manipulations with solvent quality via the change in temperature or in solvent composition, pH and ionic strength variation, utilization of ligand binding, and organization of supramolecular structures in a solution can be extended to
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the manufacturing of DNA nanostructures. DNA is a unique polymer with extremely high charge density and huge bending stiffness. The relatively stable and tough double helix structure, however, can easily be transformed into a flexible single-stranded conformation. This allows us to use the conformational transitions for the formation of multicomponent systems and nanostructures. The specific binding of different ligands with a macromolecule provides the targeted modification of the polymer chain. One of the amazing challenges is to create nanowires and waveguides by the metallization of DNA molecules [159–161]. Two alternative approaches can be used for DNA metallization in a solution and on a substrate: the DNA linking with metallic nanoparticles and the reduction of silver ions after their binding to DNA. Among biological molecules, DNA has been used extensively as a biotemplate to grow inorganic quantum confined structure and to organize non-biological building blocks into extended hybrid materials because of its physicochemical stability, well-defined sequence of DNA base and a variety of superhelix structures . DNA template has also been described as smart glue for assembling nanoparticles. In general, synthesis of nanoparticles based on DNA template has been done by incubating metal ion-coated DNA in a reduction agent solution. The ion DNA complexes controlled the release of metal ions, slowed down their reduction and effectively inhibited metal ions from growing into big clusters. Nanostructures of metals, such as silver, gold, palladium, platinum, copper, and nickel, have been successfully synthesized by using DNA network templates [162, 163].
184.108.40.206 Nanometals Biosynthesis Using Enzymes Employment of microbial enzymes for synthesis of gold nanoparticles is a new field with growing importance due to the fact that the enzymatically produced nanoparticles have the potential for use in homogenized catalysts and are suitable for
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nonlinear optics. The biological agents, including fungi, bacteria and plants, secrete a large amount of enzymes, which are capable of hydrolyzing metals and thus bring about enzymatic reduction of metals ions . There are only a few examples of successful synthesis of nanoparticles using purified microbial enzymes [164–166]. Likewise, the majority of such studies have not examined antimicrobial activity and cytotoxicity of synthesized nanoparticles for biological systems.
There are some methods of fabricating various nanoparticles that utilize a combination of physical, chemical and biological methods. They can be classified under hybrid methods, such as electrochemical, CVD, particle arresting in glass or zeolites, polymers, microemulsion for specific nanomaterials, and microwave radiation-assisted synthesis, especially to eliminate the use of thermal energy utilized for nanoparticle synthesis. Using microwave radiations, carbon quantum dots , silver nanoparticles  and various TiO2 materials  have been synthesized; for example, high-quality rutile rods were developed combining hydrothermal and microwave synthesis, while TiO2 hollow, open-ended nanotubes were synthesized through reacting anatase and rutile crystals in NaOH solution [170, 171].
From the beginning of time to the present, smaller-sized materials have been used for the advancement of nanotechnology. A historical survey of the existence of nanotechnology leads us to believe that, knowingly or unknowingly, this science has existed since prehistoric times. Both nature and human beings have realized the importance of “small,” which has led to an avalanche in the application of nanomaterials by many
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civilizations that have existed. Nano-size structures have been used in the development of living beings, be it DNA or mitochondria in nature. Man has used nanotechnology for making long-lasting paints, lustrous ceramics, strong metallurgical materials, weather-resistant metals, herbal cosmetics (kaajal), medicines (Bhasmas) and even for deciphering the hidden knowledge of science. With this knowledge we stand at the verge of using this technology for scientific advancements in all scientific domains. If we take a cursory glance at the perspectives and the future of nanocarbon, it is clear that over the last 20 years, the field of nanoscale carbon has developed exponentially. Since the discovery of fullerenes in 1985, with the bulk synthesis of nanocarbons, the structural identification of nanotubes, the isolation of graphene, and the development of graphene-based applications, we are witnessing an accelerated development of both carbon nanoscience and technology. The number of publications per year in the three nanocarbon fields (fullerenes, nanotubes, and graphene), especially in nanotubes, continues to increase, and it is expected that real applications and devices will soon become an important part of international markets. However, both adoption of reliable standards and addressing biosafety issues need to be put in place, without overregulating, so that fundamental research continues to accelerate while applications keep developing productively.
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8 Contemporary History of Nanotechnology CH Godale and Madhuri Sharon Walchand College of Arts and Science, Solapur University, Solapur, India
Everything we see around us is made of atoms, the tiny elemental building blocks of matter. From stone, to copper, to bronze, iron, steel, and now silicon, the major technological ages of humankind have been defined by what these atoms can do in huge aggregates, trillions upon trillions of atoms at a time, molded, shaped, and refined as macroscopic objects. Even in our vaunted microelectronics of 1999, in our highest-tech silicon computer chip the smallest feature is a mountain compared to the size of a single atom. The resultant technology of our 20th century is fantastic, but it pales when compared to what will be possible when we learn to build things at the ultimate level of control one atom at a time. Richard E. Smalley
Madhuri Sharon (ed.) History of Nanotechnology, (213–270) © 2019 Scrivener Publishing LLC
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Introduction to the Concept of Nano After 1959
The term “nanometer scale” is due to Richard P. Feynman’s great contribution to the field of nanotechnology. One can define the essence of nanotechnology as the ability to work at the molecular level, atom by atom, to create large structures with fundamentally new molecular organization. The aim is to exploit these properties by gaining control of structures and devices at atomic, molecular, and supramolecular levels and to learn to efficiently manufacture and use these devices. Nano is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, and manipulating matter at this length scale. Nanotechnology is the ability to create and manipulate atoms and molecules on the smallest of scales. Nanotechnology can be defined as being concerned with materials and systems whose structures and components exhibit novel and significantly improved physical, chemical and biological properties, phenomena and processes due to their nanoscale size. Nanoscience is the study of phenomena and manipulation of material at atomic, molecular and macromolecular scales, where properties of the material differ significantly from the properties of material at larger scale. The term “nano” evolves from the Greek word “nanos,” meaning “dwarf.” It is used as a prefix to denote one billionth in a measuring system. So, the particle which has a size of 1 nm is nothing but 1 billionth of a meter by considering the size of the particle. It is generally considered that the modern-day history of nanotechnology started from a speech by Richard Feynman entitled “There’s Plenty of Room at the Bottom,”
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which was given at an American Physical Society meeting at the California Institute of Technology in 1959 in which he identified the potential of nanotechnology. He did not use the word nanotechnology. He only stated the possibility of manufacturing small machines and objects with atomic precision. Norio Taniguchi first used the term “nanotechnology” in 1974. He used the term in regard to an ion sputtering machine when referring to “production technology to get the extra-high accuracy and ultrafine dimensions, i.e., preciseness and fineness on the order of one nanometer.”
Feynman’s Idea: Entry of Nanotechnology in Modern Science
Richard Feynman was the American physicist who gave the lecture “There’s Plenty of Room at the Bottom” at a meeting of the American Physical Society on December 29, 1959. Manipulation of individual atoms is a more powerful form of synthetic chemistry than the forms which were used at that time. Initially his talk was unnoticed. In 1990 it was rediscovered and published. Feynman considered a number of interesting things to manipulate matter at the atomic scale. His interest was in microscopes which could see much smaller things than the scanning electron microscope, which was realized after the invention of the scanning tunneling microscope, atomic force microscope and scanning probe microscope, and in the formation of denser computer circuitry. He also suggested that it is possible for us to arrange atoms as we want and then carry out the chemical synthesis by mechanical manipulation. He also discussed the possibility of “swallowing the doctor,” a concept which involves building a tiny, swallow-able surgical robot. Moreover, he proposed an experiment to build a set of one-quarter-scale manipulator hands slaved to the operators’ hands to build
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a one-quarter-scale machine tool found in any machine shop. The small hands can use these small set of tools to build and operate ten sets of one-sixteenth-scale hands and tools so that billions of tiny factories can be used for specific operations. As size gets smaller and smaller, a person can redesign some of the tools due to the relative changes in various forces, namely gravity, becoming unimportant; i.e., it has no importance at that small scale or size. Van der Waals attraction and surface tension becomes more important at smaller scale or size. Feynman stated this point in his talk, yet no one has attempted it in experiments; however, it has been found that some enzymes and their complexes, usually ribosome, function chemically according to his vision.
Nobel laureate Dr. Richard Phillips Feynman. (Courtesy of bubbewisdom.com)
In his talk, Feynman also mentioned that due to their greater uniformity the use of glass and plastic may avoid problems at very small scale. Feynman concluded his talk with two challenges. The first challenge was constructing a tiny motor and the second one was scaling down letters small enough so as to fit the entire Encyclopedia Britannica on the head of a pin.
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The first challenge was achieved in November 1960 by the engineer William Howard McLellan by using conventional tools . In 1985, Tom Newman, then a graduate student at Stanford University, successfully reduced a paragraph of the book A Tale of Two Cities to 1/25,000 of its original size. Nowadays, many scientists are interested in nanotechnology. The development of various techniques/methods in all the fields of science, i.e., physical, chemical, biological and engineering, are aware of the quote of Nobel laureate Richard Smalley, “Just wait—the next century is going to be incredible. We are about to be able to build things that work on the smallest possible length scales, atom by atom. These little nanothings will revolutionize our industries and our lives.”
Drexler’s Engines of Creation
In 1979, Eric Drexler, after encountering Feynman’s talk on atomic manipulation and “nanofactories,” authored the most important book about nanotechnology, Engines of Creation: The Coming Era of Nanotechnology, which was published in 1986 . In this book he introduced the concept of molecular manufacturing to the public. The history of contemporary nanotechnology traces the development of the concepts and experimental work falling under the broad category of nanotechnology. Although nanotechnology is a relatively recent development in the scientific field, the development of its central concepts, including the discovery of fullerenes in 1985, happened over a longer period of time with the elucidation and popularization of a conceptual framework for the goals of nanotechnology, beginning with the 1986 publication of Drexler’s book. Due to growing public awareness, the field of molecular nanotechnology was the subject of controversy in the early 2000s, with prominent debates about both its potential implications as well as the feasibility of the applications envisioned by its advocates,
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which coincided with governments moving to promote and fund research into nanotechnology.
In 1981, Drexler’s article, “Molecular Engineering: An Approach to the Development of General Capabilities for Molecular Manipulation,” was published in Proceedings of the National Academy of Sciences of the United States of America . Again, in 1992, Drexler published “Nanosystems,” a technical work outlining a way to manufacture extremely high-performance machines out of molecular carbon lattice.
Impetus Given by SEM, TEM and AFM
The emergence of nanotechnology in the 1980s was caused by the convergence of experimental advances such as the invention of the scanning tunneling microscope in 1981. The scanning tunneling microscope, an instrument for imaging surfaces at the atomic level, was developed in 1981 by Gerd Binnig and Heinrich Rohrer at the IBM Zurich Research Laboratory, for which they received the Nobel Prize in Physics in 1986.
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Some of the limitations in microscopy were eliminated through the 1986 invention of the atomic force microscope (AFM). Using contact to create an image, this microscope could get an image from non-conducting materials such as organic molecule. Though a scanning electron microscope (SEM) can achieve resolution better than one nanometer, usually, in practice, SEM gives good resolution for particles larger than about 5 nm. For particles smaller than 5 nm, a transmission electron microscope (TEM) gives better resolution.
The Entry of Nano Forms of Carbon
Carbon fascinates us with its flexibility to be transformed into different materials via its different degrees of hybridization (sp, sp2, and sp3). After its structural identification at the beginning of the 20th century by John D. Bernal, graphite became a material of intense study. In the 1950s and 1960 s, the physics and chemistry of graphite started to be developed from both theoretical and experimental perspectives. It would not be wrong to say that the graphitic form of carbon morphology was the predecessor to nano forms of carbon. Prior to 1985 we knew about only two carbon allotropes: 1) Graphite (softest material) and 2) Diamond (hardest material). But after the discovery of fullerene by Kroto et al., in 1985, it is well known that carbon has three allotropic forms, namely, diamond, graphite and fullerene, that led to the discovery of nanoforms of carbon . Sharon had earlier  argued whether or not the number of allotropes of carbon keep on increasing as we develop new forms of carbon, or should we classify carbon such that no matter how many types of carbon are developed the number of allotropes remains constant, as is the case with most other inorganic materials. He then suggested that since graphite has100% sp2 carbon and diamond has 100sp3 carbon and since carbon nanomaterials including fullerene possess both sp2 and sp3 carbon, the third allotrope of carbon should
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be intermediate carbon possessing a mixture of sp2 and sp3 carbon. They concluded that no matter how many different carbon forms are discovered they all will fall into the three types of allotropes: graphite-like, diamond-like and intermediate. Fullerene became the first fabricated nano form of carbon. Emergence of an additional carbon crystal structure alongside graphite and diamond led to the development of CNTs by Iijima’s group . From their discovery in the early 1990s, CNTs have attracted significant attention in multiple disciplines, including physics , chemistry  and materials science , an interest that has yet to wane. The structural identification of nanotubes and the isolation of graphene became material available for in-depth investigations, spurred on by the development of reliable production methods. Today, these three novel nanocarbons are being intensively studied. The progress in terms of understanding the properties and chemistry of carbon nanomaterials has opened a whole new world of applications for nanomaterials in general. To our knowledge, the earliest nanocarbon research dates back to the work of the Russian researchers Radushkevich and Lukyanovich in the 1950s . Mildred S. Dresselhaus started the study of carbon-related materials in 1960 when she became a staff member at the Massachusetts Institute of Technology (MIT) Lincoln Laboratory . Monolayer graphene, an sp2 hybridized hexagonal carbon network, was in fact discovered by Hanns-Peter Boehm and his coworkers in 1962 , but this research direction was not seriously pursued at that time. Instead, emphasis was given to the study of 3D graphite, consisting of nature’s assembly of many weakly coupled graphene layers to form the mineral graphite, which is normally found in nature as small flakes. In 1960, a synthetic form of graphite, highly oriented pyrolytic graphite (HOPG), was produced by Ubbelohde et al.,  using a hightemperature, high-pressure process. The material thus formed provided larger (millimeter) sized samples with long carrier
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mean free paths, thereby enabling many experiments that previously had been difficult, like magneto-optics .
8.5.1 Fullerene: The First Fabricated Carbon Nanomaterial Advances in surface science have led to studies of clusters, first in considering chains of carbon atoms, then rings of carbon atoms as large as 15-carbon-atom rings. A team at the Exxon Research Laboratory in New Jersey (U.S.A.) succeeded in making large clusters of carbon atoms and published their interesting result in 1984. Figure 8.1a shows that clusters up to about 20 atoms could be formed for all integer values, but that clusters with larger numbers of carbon atoms showed only even numbers of carbon atoms up to about 100 carbons, with especially large probabilities of forming C60 and C70 clusters. It was in 1985 when Kroto, Smalley and Curl, independently, explained the occurrence of these two characteristic phenomena by proposing the formation of large highly symmetrical molecules which they called fullerenes, with 60 carbons at the vertices of regular truncated icosahedrons similar to the structure of a soccer ball (Figure 8.1b inset). One side of the fullerene story began in the 1970s, when Harold W. Kroto and David R. M. Walton of the University of Sussex in the U.K. were working with cyanopolyynes H-(CC) nCN (chains in which carbon atoms are linked by alternating single and triple bonds, and end-capped by hydrogen and nitrogen). These molecules show microwave spectra commensurate with their linear dipole structure. At that time, Kroto and Walton together with A. J. Alexander (a BSc thesis student) synthesized HC5N and, with C. Kirby (a PhD student), produced HC7N. Takeshi Oka, one of Kroto’s collaborators doing radio astronomy in Canada, found that these linear molecules [HCnN(n ¼ 5)] were located in the center of our galaxy . With this in mind, Kroto believed that it could be possible to perform
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60 23 50
80 40 60 Cluster size (carbon atoms)
TRANSIAC 2001 TOF DATA
1000 of 1000 shots
7000 6000 5000 4000 3000 2000 1000 0 15 9-14-1985
Figure 8.1 Mass spectrometry profiles from experiments carried out by (a) the Exxon team and (b) the Sussex/Rice team, exhibiting C60 and C70 as the most intense peaks: additionally, they observed two groups of clusters: 1) those with lower mass (G 30 C atoms) consisting of both odd and even numbers of C atoms; and 2) high mass clusters (>36 atoms) exhibiting only even numbers of C atoms The inset shows a soccer ball which resembles the structure of C60. (Courtesy of H. W. Kroto).
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a lab experiment simulating the explosion of a red giant star in which linear clusters, such as the cyanopolyynes, could be obtained. In 1984, when Kroto traveled to the United States, he visited Robert Curl at Rice University in Houston, Texas, and was introduced to Richard Smalley, who was carrying out cluster experiments using a laser to vaporize solid targets. Smalley was mainly interested in silicon clusters. Based on the linear carbon chains explained above, Kroto thought of vaporizing graphite so that their extreme vaporization/expansion conditions would be similar to those occurring in red giant stars.
Nobel laureate Professor Sir Harold W. Kroto.
A year later, in late August of 1985, Kroto participated in the laser vaporization experiment with graphite in Houston, Texas . The Smalley apparatus involved the laser vaporization of a rotating graphite disc in the presence of a helium flow (using a Nd:YAG 532 nm laser). The carbon clusters coming from the laser ablation were expanded in a supersonic molecular beam, photoionized with an excimer laser and detected by a timeof-flight mass spectrometer (Figure 8.1b). Kroto and the Rice University researchers obtained a mass spectrum exhibiting two main groups of carbon clusters: 1) those with low mass (G 30 carbon atoms) with both odd and even numbers of carbon atoms; and 2) high mass clusters (>36 atoms) showing only even numbers of carbon atoms. The Exxon group proposed
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that the carbon masses below nine were due to linear carbon chains, and the odd masses between 11 and 23 (i.e., 11, 15, 19, 23) were due to carbon rings (Figure 8.1a). However, the experiments carried out at Rice University showed a clear preference for the 60-atom cluster, and Kroto, Smalley, Curl, and coworkers believed that this special 60 atom cluster corresponded to a truncated carbon icosahedral cage, containing 20 hexagons and 12 pentagons, so that all carbon sp2 hybridized without any dangling bonds (Figure 8.1b, inset). The Sussex-Rice team named this molecule Buckminsterfullerene in honor of the American architect R. Buckminster Fuller, who built geodesic domes with similar topologies. At that time, only picogram quantities were available from the laser vaporization experiment and bulk amounts of C60 were needed to perform a full characterization.It was not until 1990, when Krätschmer et al.,  were able to prepare mg quantities of C60, that more detailed spectroscopy experiments could be carried out. Such samples were prepared by extracting the molecule from the soot produced after arcing two graphite electrodes in a helium atmosphere. Simultaneously, C60 was successfully isolated using chromatography techniques by the Sussex team. In the solid state, C60 displays a cubic structure with a lattice constant of 14.17 Å, with a nearest neighbor C60–C60 distance of 10.02 Å and density of 1.72 g/cm3. Interestingly, at room temperature, the C60 molecules rotate rapidly in a face centered cubic (fcc) structure about their lattice positions. An unusual transition to a simple cubic phase (a ¼ 14.17 Å consisting of four C60 molecules per unit cell) occurs below 261 K. In order to demonstrate the icosahedral symmetry of C60, Krätschmer et al.,  recorded the infrared spectra of C60. Because of the high icosahedral symmetry of the C60 molecule, the selection rules included 200 infrared-active and 200 Raman-active overtones and combination modes, which were predicted on the basis of group theoretical considerations and were observed experimentally. The availability of high quality fullerene samples led
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to a large amount of activity in the chemistry and physics of fullerenes and carbon nanoscience. In 1994, Sharon et al.,  were the first to synthesize fullerene by chemical vapor deposition (CVD) process using camphor, a plant-derived precursor.
8.5.2 Carbon Nanotubes Carbon nanotubes (CNTs) are one of the most extensively studied carbon nanomaterials (CNMs). Carbon filaments less than 10 nm in diameter were prepared in the 1970s and 1980s through the synthesis of vapor-grown carbon fibers by the decomposition of hydrocarbons at high temperatures in the presence of transition metal catalyst particles of