Understanding Nanomaterials

Malkiat S. Johal, Lewis E. Johnson

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9781482253238
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

Praise for the first edition
"clear and informative" ? Chemistry World

The authors provide the perfect training tool for the workforce in nanotech development by presenting the fundamental principles that govern the fabrication, characterization, and application of nanomaterials. This edition represents a complete overhaul, giving a much more complete, self-contained introduction. As before, the text avoids excessive mathematical detail and is written in an easy to follow, appealing style suitable for anyone, regardless of background in physics, chemistry, engineering, or biology. The organization has been revised to include fundamental physical chemistry and physics pertaining to relevant electrical, mechanical, and optical material properties.

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• Incorporates new and expanded content on hard materials, semiconductors for nanoelectronics, and nonlinear optical materials.

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• Adds many more worked examples and end-of-chapter problems.

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• Provides more complete coverage of fundamentals including relevant aspects of thermodynamics, kinetics, quantum mechanics, and solid-state physics, and also significantly expands treatment of solid-phase systems.

Malkiat S. Johal is a professor of physical chemistry at Pomona College, and earned his doctorate in physical chemistry at the University of Cambridge, UK.

Lewis E. Johnson is a research scientist at the University of Washington, where he also earned his doctorate in chemistry and nanotechnology.

1A Brief Introduction to Nanoscience

1.1The Scope of Nanoscience

Nanoscience—the study of systems with components on the scale of a billionth of a meter—is full of possibilities and presents us with the potential for significant technological breakthroughs in the near future. Nobel laureate Richard P. Feynman realized the importance of this field almost six decades ago. In his legendary speech, “There’s Plenty of Room at the Bottom,” he stated:

This field is not quite the same as others in that it will not tell us much of fundamental physics in the sense of, ‘What are the strange particles?’ But it is more like solid state physics in the sense that it might tell us much of great interest about strange phenomena that occur in complex situations. Furthermore, a point that is most important is that it would have an enormous number of technical applications.

(Full text available at http://www.zyvex.com/nanotech/feynman.html)

Nanotechnology, the application of nanoscience toward developing new technologies, is defined as the engineering or manipulation of functional systems at the molecular scale. A functional system is used to describe a material, or interface between materials, that has a well-defined responsibility and performs that responsibility efficiently and while minimizing undesired consequences. Although the term nanotechnology was popularized in the 1980s, scientists have been studying nanostructures for well over a century. As early as the mid-1800s, Michael Faraday investigated the properties that a ruby-colored solution forms when an aqueous solution of NaAuCl4 is treated with a reducing agent. Faraday concluded that fluid contained very finely divided metallic gold dispersed in the aqueous solution. A century later, electron microscopy showed that these solutions were indeed composed of colloidal gold particles (gold nanoparticles) with average diameters of around 6 nm.

Over the last few decades, nanotechnology has focused largely on the use of colloidal systems, polymers, and nanometer-sized particles (nanoparticles) in coatings and materials. For example, silver nanoparticles have found use in hundreds of products because of their antimicrobial properties. More recently, nanotechnology has been used to explore biologically active materials as novel biosensors and targeted drug delivery vehicles for the treatment of diseases. The field is also impacting electronics, including development of new transistors, amplifiers, and adaptive structures. The smallest features in the integrated circuits in computer central processing units, which were over a micron in 1985, are now on the order of 14 nm, with devices on scales of 10 nm or smaller at the prototype stage. The next few decades will inevitably move nanotechnology to the point where we will be able to fabricate complex nanosystems and molecular devices by design on an industrial scale. Feynman’s speech continued to discuss the transformative potential of nanotechnology:

I want to build a billion tiny factories, models of each other, which are manufacturing simultaneously. … The principles of physics, as far as I can see, do not speak against the ­possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big.

One example of how nanotechnology is impacting our lives involves silver nanoparticles. Each of these spherical particles is made up of hundreds or thousands of Ag atoms. The precise method of how these particles are prepared will be discussed later. These particles range in size from 1 nm to 100 nm, and their outer surface is usually comprised of silver oxide. Figure 1.1 shows some electron microscope images of silver nanoparticle samples of various sizes.

Figure 1.1Transmission electron microscopy (TEM) images of silver nanoparticles with diameters of (a) 20 nm, (b) 60 nm, and (c) 100 nm, respectively. Scale bars are 50 nm. (Image from Sigma-Aldrich.)

Among many applications, silver nanoparticles show a remarkable ability to kill bacteria. Thus, they are currently being used as antibacterial and antifungal agents in a host of industries including biotechnology, textile engineering, and water treatment. Some companies are even developing coatings containing silver nanoparticles for household products and medical equipment. While use of silver nanoparticles in consumer products has clear benefits, there are also associated health concerns. These particles can accumulate in the liver if ingested, and exposure has shown them to be toxic to several organs, including the brain.

While nanomaterials offer tremendous benefit, their small scale and high activity due to large surface area provide some challenges, especially concerning human health and the environment. Figure 1.2 shows a number of nanostructures that will be discussed extensively in this book, along with applications currently in use or being developed.

Figure 1.2Examples of nanostructures and their applications. Many of these structures will be discussed in later chapters.

1.2The Need for Nanoscience Education

Over the last decade, nanotechnology has been one of the fastest growing areas of research globally. Estimates had concluded that by 2015, over 10 million jobs worldwide would be affected by nanotechnology. In light of this, it is important to recognize that significant growth in areas of scientific research inevitably impacts education, first at the graduate level, and then at the undergraduate level. In the last decade, a healthy flow of publications has addressed the needs of graduate students and trained professionals in the field of nanoscience. Rapid research advances in areas such as soft matter, supramolecular science, and biophysical chemistry have fueled the recent surge in the number of professional journals in nanotechnology. Over 50 journals are currently publishing research in nanotechnology, and over 30 are devoted solely to nanomaterials. The impact in education is being felt as evidenced by the steady stream of articles on nanoscience education published in the Journal of Chemical Education, a monthly journal published by the American Chemical Society (ACS). These articles are usually aimed at the undergraduate level and cover new concepts in nanoscience, classroom demonstrations, and advanced laboratory exercises.

Examples of well-established nanoscience publications include the Royal Society of Chemistry’s Soft Matter and Nanoscale, which cover the interdisciplinary science underpinning the properties and applications of soft matter at the nanoscale, as well as the ACS journals ACS Nano and Nano Letters and other high-profile journals such as Nature Nanotechnology (Nature Publishing Group) and Advanced Functional Materials (Wiley-VCH). Open access platforms, which do not require a subscription fee for readers to access full-text articles, have also seen a recent surge in journals devoted to nanoscience. Examples include Applied Nanoscience (Springer), The Open Nanoscience Journal (Bentham Open), and the International Journal of Smart and Nano Materials (Taylor & Francis Group). In addition, there has been steady growth in funding for nanoscience from both private sources and government agencies such as the National Science Foundation (NSF), Department of Energy (DOE), and National Institute of Standards and Technology (NIST). The National Nanotechnology Initiative (NNI) was first implemented in 2001 by the U.S. federal government. The aim of the initiative was to advance nanotechnology research and development, promote transfer of this technology to the consumer, support the safe and responsible development of the technology, and to develop and sustain nanoscience education. The 2014 federal budget provided more than $1.7 billion for the NNI, reflecting steady growth in the NNI investment. Since its inception in 2001, the cumulative NNI investment now totals almost $20 billion. The 2014 NNI budget supports nanoscience research at 15 agencies, with the largest investments from the DOE, NSF, National Institutes of Health (NIH), Department of Defense (DOD), and NIST.

Together with the growth in research activity and sharp increase in professional publications, this rise in funding commitment provides a compelling reason to begin serious training of our future workforce in this area. Thus, the present textbook has been developed to be accessible to undergraduate students in chemistry, physics, materials science, and engineering, as well as professionals in related fields.

1.3The Nanoscale Dimension

The word “nano” is derived from the Latin word na...