Associate Professor of Materials Science and Engineering, Alexander von Humboldt Fellow, Visiting Fellow, Fitzwilliam College, University of Cambridge. Over 15 years of academic experience in Raman spectroscopy and over decade of experience in nanotechnology and fullerene behaviour.

Raman Spectroscopy, Fullerenes and Nanotechnology

By Maher S. Amer

The Royal Society of Chemistry

Copyright © 2010 Maher S. Amer
All rights reserved.
ISBN: 978-1-84755-240-2

Contents

Chapter 1 Nanotechnology, the Technology of Small Thermodynamic Systems, 1,
Chapter 2 Raman Spectroscopy; the Diagnostic Tool, 43,
Chapter 3 Fullerenes, the Building Blocks, 109,
Chapter 4 The Nano-frontier; Properties, Achievements, and Challenges, 182,
Appendix 1 Character Tables for Various Point Groups, 259,
Appendix 2 General Formula for Calculating the Number of Normal Vibrations in Each Symmetry Species, 267,
Appendix 3 Polarizability Tensors for the 32 Point Groups including the Icosahedral Group, 272,
Subject Index, 276,

CHAPTER 1

Nanotechnology, the Technology of Small Thermodynamic Systems

1.1 Introduction

This chapter introduces nanotechnology, emphasizing the fact that it is more related to the thermodynamic behaviour of small systems than to the physical dimensions of the system. The importance of entropic forces in such systems will be considered and examples of how such forces can alter the behaviour of materials systems and enable them to exhibit unusual chemical, physical, electrical, optical, and mechanical properties will be given. The building blocks of nanotechnology will be identified and discussed. Examples of biological and natural utilization of nanostructured system as well as recent engineering applications of such systems will be given.

1.2 Origins of Nanotechnology

Almost 50 years ago, on December 29, 1959, Richard P. Feynman, a great physicist and, later, a Nobel Laureate, gave a lecture at the annual meeting of the American Physical Society at California Institute of Technology, Pasadena, entitled ‘There’s Plenty of Room at the Bottom, an Invitation to enter a new field of Physics.’ The lecture was published later and was republished again in 1992 as the topic it first introduced overwhelmingly caught the attention of many of the scientists, politicians, and the public across the globe.

The term “nanotechnology” was never used in Feynman’s lecture; instead, Feynman spoke about miniaturization, emphasizing the important scientific and economic aspects of our ability to make things small. Small machines that are capable of making even smaller ones. In his own words ‘although it is a very wild idea, it would be interesting in surgery if you could swallow the surgeon’. Not to be misunderstood, Feynman emphasized that such a vision necessitates an ability to manipulate materials systems on a small scale. Feynman would not have missed the obvious and logical fact that atoms and molecules behave differently when arranged in a small system compared to their behavior in large or bulk systems. In his famous lecture Feynman said:

‘I can hardly doubt that when we have some control of the arrangement of things on a small scale we will get an enormously greater range of possible properties that substances can have.’

The obvious reason for that was:

“… Atoms on a small scale behave like nothing on a large scale, for they satisfy the laws of quantum mechanics. So, as we go down and fiddle around with the atoms down there, we are working with different laws, and we can expect to do different things.’

Hence, while Feynman did not explicitly speak about what is referred to nowadays as “nanotechnology,” he pointed out a new and important domain of physics where matter is investigated on a new scale at which quantum effects are dominant.

The term nanotechnology was actually coined in 1974 by Norio Taniguchi (1912–1988), a professor at Tokyo Science University, Japan. The term nano is Greek for “dwarf”. Professor’s Taniguchi’s main interest was in high precision machining of hard and brittle materials. He pioneered the application of energy beam techniques, including electron beam, lasers, and ion beams, to ultra-precision processing of materials. In his famous paper entitled ‘On the Basic Concept of ‘Nano-Technology”, Professor Taniguchi defined the field as:

‘Nano-technology mainly consists of the processing of, separation, consolidation, and deformation of materials by one atom or by one molecule.’

Professor Taniguchi was mainly using the term to describe possibilities in precision machining for the electronic industry to enable smaller and smaller devices down to the nanometer length scale. The prefix nano is known in the metric scale system to represent a billionth or 10~ of a unit. In 1974, Professor Taniguchi was interested in precision machining down to the nanometer level, which requires an ability to manipulate materials on the atomic or molecular level.

In 1986, K. Eric Drexler reused and popularized the term “nanotechnology” in a much broader prespective describing a whole new manufacturing technology based on molecular machinery. The premise was that such molecular machinery does exist, by countless examples, in biological systems, and, hence, sophisticated, efficient, and optimized molecular machines can be produced. In a series of books, Drexler described a number of possible molecular machinery suitable for a very wide range of applications. He also described ‘profiles of the possible’ as well as ‘dangers and hopes’ associated with the nanotechnology. Drexler was awarded a PhD in 1991. His work, indeed, triggered and inspired what is currently referred to as the nano-revo-lution. He adapted the viewpoint that although nanotechnology can be initially implemented by resembling biological systems, ultimately it could be based on pure mechanical engineering principles, rendering nanotechnology as a manufacturing technology based on the mechanical functionality of molecular size components. Such mechanical components, i.e., gears, bearings, motors, and structural members, would enable programmable assembly with atomic precission. Figure 1.1 shows the three scholars Richard Feynman, who first envisioned nanotechnology, Norio Taniguchi, who coined the term nanotechnology, and Eric Drexler, who popularized the term in a new perspective.

The pure mechanical viewpoint shaping Drexler’s proposed vision led, however, to a long and heated debate between him and Richard Smalley. Richard Smalley – a professor of chemistry at Rice University who shared the 1996 Nobel Prize in Chemistry with Robert Curl, Jr. and Sir Harry Kroto for discovering the C0 molecule (fullerene [60]) – had very well founded reservations on applying pure mechanical engineering principles to nano-machinery, and on the premise of mechanical functionality of molecules. The debate was indeed a significant controversy about nanotechnology’s meaning and possibilities. Drexler, later, backed off of his position on the basis that his original ideas have been misunderstood. Several analyses of the debate were published. Unfortunately, the debate left a negative impression on public view of the technology and, to a large extent, deepened the wrong concept that nanotechnology is the technology by which to make tiny (bug-like) machines capable of replicating themselves, working miracles, but that could run amok. Given the effective role media usually play on public viewpoint and understanding of science, it was concluded recently that the media has contributed to bounding nanotechnology by representing the term as a technology that trades on ideas of wonder as well as risk.

A good example that demonstrates the general misunderstanding of nanotechnology is the Winner illustration of the 2002 ‘Visions of Science Award’ by Coneyl Jay (Figure 1.2). The illustration shows how the public, in general, imagined what nanotechnology is all about; a bug-like tiny machine injecting stuff in a red blood cell! Unfortunately, that was the general impression of nano-medicine.

Such a simplistic understanding of nanotechnology bred enormous public concerns and suspicion. Well founded and justified concerns regarding the impact of nanotechnology on scientific, economic, ethical, and societal aspects of humankind future were raised and are still being debated. We will discuss these important issues in later sections of this chapter. At this point, however, it is beyond doubt that what we decided to call a dwarf (nano) turned out to be a giant.

1.3 What Nanotechnology Is

Nanotechnology has been described as the next industrial revolution in human history. As with each of the previous industrial revolutions, it is expected to have a huge and long-term impact on all aspects of human life. In addition, and not surprisingly, the new technology has not been very well understood in some cases and has been misunderstood in many other cases. According to the USA National Science Foundation 2007 released statistics, most Americans (54%) have heard ‘nothing at all’ about nanotechnology. In this section, we will address the nature of nanotechnology in very simple, even layperson, terms. As Albert Einstein pointed out, one can claim knowledge of a subject only when one is capable of explaining the subject to one’s grandmother. Time has changed since the Einstein era and many of nowadays grandmothers have advanced degrees. While this makes it easier for new generations to claim knowledge, it might be the time to change the rule of knowledge claiming to state that one may claim knowledge of a subject only if one is capable of correctly explaining the subject to the public.

1.3.1 What Can Nanotechnology Do For Us?

Everything we deal with is either man-made (made by humans) or natural (made by nature). For example, a car is a man-made transportation means, while a horse is a natural one. Currently, cars are faster and much stronger than horses. However, cars are still not capable of sensing the danger down the road as horses do. Also, cars cannot take their passenger home while the passenger is asleep as horses do. In addition, horses are much safer to travel by since none of us has ever heard about an accident between two horses resulting in a rider’s life loss! To this end, we can describe nanotechnology as a new level of knowledge that could enable us to bridge the gap between the capabilities of man-made and natural things. This would result in a new generation of regular size, and not tiny, cars capable of sensing the danger, driving home, and reducing or eliminating accidents due to operator errors. In addition, a more important and a major difference between man-made and natural things is their efficiency. Over billions of years, nature mastered the art of efficient design and operation. Humans, however, are still at the beginning of a learning curve in those regards. For example, the best gasoline car engine we currently make has an efficiency of 25–30%. Mechanical efficiency of athletes during running was measured to range between 47% and 62%. Other species and natural processes can even reach higher efficiencies. This clearly demonstrates how crucial nanotechnology can be considering the energy crises our civilization is currently facing.

1.3.2 Where did the Name “Nano” Came From?

The word nano is Greek for dwarf. This word was actually used to indicate the length unit equal to one billionth of a meter (10-9 meter). To have a good idea of what this length actually is, let us consider a typical single human hair. This is about 50–100 micron, which is 50 to 100 millionth of a meter. Hence, a single human hair would be 50 to 100 thousand times larger than a nanometer. Atoms and molecules are typically measured by a unit called the ångström (Å), which is one tenth of a nanometer (nm), or one ten billionth of a meter. Fifty years ago, Feynman predicted, and more recently, many scientists observed that the behavior of material clusters on the 1–100 nm scale is essentially different from that of larger clusters that we currently use. It can be scientifically sound to say that on the nanometer level the laws of nature controlling materials behavior are different, hence new phenomena can be observed. This is where the name “nanotechnology” came from.

1.3.3 Does Every Nanosystem Have To Be So Small?

The answer to this question is absolutely not. In fact, most biological systems, including ourselves, are nanosystems. This is in the sense that these systems on a certain level operate according to nanophysics and nano-chemistry laws. In fact, humans in their daily life activities obey two different sets of laws; the traditional laws of physics that we already know and nanoscale laws that we are still exploring. For example, if one jumps up, one’s body will follow the gravitational law that was first identified by Isaac Newton in the fifteenth century, and one will, according to this law, fall back down. However, as one breathes one’s blood exchanges carbon dioxide for oxygen at the lungs and does the opposite at the cells according to a different set of laws that we refer to here as nano-laws. The blood component in charge of the exchange (known as hemoglobin) is much larger than a nanometer, and so are our body cells, and definitely we and all other breathing creatures are. A nanosystem, or more appropriately, a nanostructured system is a system that is made of components that operate according to nano-laws regardless of the system size. Good examples to illustrate this point are butterfly wings and opal stones (Figure 1.3). The beautiful colors of butterfly wings and opals are due to light reflection by nanostructures and are not due to pigmentation. Different colors are due to different nanostructures. The opal example tells us that nanostructures are not limited to biological systems. In fact, over billions of years, nature has mastered nano-manufacturing techniques as the best and most efficient techniques to build sophisticated and efficient products.

1.3.4 How and Why do the Properties of Matter Change by Entering the Nano-domain?

A good example to illustrate how the properties of matter change as it enters the nano-domain is water. In its bulk form, water is a liquid that every one of us is familiar with. It is a colorless odorless liquid that is heavier than air. Hence, gravitational laws are in control of the system and it fills our lakes, seas, and oceans. As water evaporates, due to heat effects, in the form of single and tiny clusters of molecules, gravitational laws are no longer in charge. The bulk laws are actually overruled by the new nano-domain laws. Water in the form of tiny clusters becomes airborne. These tiny clusters of water can accumulate and form huge clouds containing enormous amounts of water but still can be transported by wind over very long distances. Controlled by weather conditions, the tiny clusters of water in the clouds can grow into bigger and bigger clusters until they depart the nano-domain and enter the bulk domain again in the form of water droplets. Once in the bulk domain, gravitational laws will take control again, and water droplets will fall as rain. To this end, it is very clear that nature has utilized nanotechnology, for billions of years, in transporting enormous amounts of water over great distances very efficiently. Interestingly, even with our current advanced technologies, as we like to call it, we are not capable of carrying out such a transportation operation as efficient, if at all. It might be wisely and timely to learn from nature.

1.3.5 Has Nanotechnology Been Used Before?

While nature has been utilizing nanotechnology in building biological systems, as we mentioned before, for almost 3.7 billion years, humans have also used nanotechnology before. The mysterious optical behavior of the famous Lycurgus Cup (AD 400, Figure 1.4) is a good example of nanotechnology effects on optical properties of matter. This Roman cup is made of ruby glass. When viewed in reflected light, for example in daylight, it appears green. However, when a light is shone into the cup and transmitted through the glass it appears red! Recently, this mysterious behavior was investigated and it was found that while the chemical composition of the glass of Lycurgus Cup is almost the same as that of modern glass, the fascinating optical behavior is totally due to gold nanoparticles within the cup glass.

In addition, it was revealed recently that the famous Damascus saber (14th – 16th century era), with its traditional wavy patternsii on the surface (Figure 1.5), owes its superior strength and performance to the presence of nanostructures in the form of tubes and wires within its alloy.

Nanotechnology, namely nano-medicine, was used even much earlier in human civilization, most probably unintentionally. Finely ground gold particles in the size range 10–500 nm can be suspended in water. Such suspensions were used for medical purposes in ancient Egypt over 5000 years ago. In Alexandria, Egyptian alchemists used fine gold particles to produce a colloidal elixir known as ‘liquid gold’ that was intended to restore youth! It is an interesting coincidence to realize that the 2007 Medal of Science, the U.S.A.’s highest honor in the field, was awarded to the Egyptian-American chemist Professor Mostafa El-Sayed, of Georgia Institute of Technology, for his many outstanding contributions, among which using gold nanorods in cancer tumor treatment was the most recent.

More recently, in 1856, Michael Faraday (1791–1867) independently prepared colloidal gold, which he called ‘divided state of gold’. Faraday’s samples are still preserved in the Royal Institution. In addition, in 1890, the work of the German bacteriologist Robert Koch (1843–1910) showed that gold compounds inhibit the growth of bacteria. He was awarded the Nobel Prize for Medicine in 1905. Figure 1.6 shows these scholars who pioneered the preparation and medical applications of gold nanoparticles.

(Continues…)Excerpted from Raman Spectroscopy, Fullerenes and Nanotechnology by Maher S. Amer. Copyright © 2010 Maher S. Amer. Excerpted by permission of The Royal Society of Chemistry.
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