Introduction to Nanoparticles
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Abstract
Nanotechnology is the science that deals with matter at the scale of 1 billionth of a meter (i.e., 10 − 9 m = 1 nm), and is also the study of manipulating matter at the atomic and molecular scale. A nanoparticle is the most fundamental component in the fabrication of a nanostructure, and is far smaller than the world of everyday objects that are described by Newton ’ s laws of motion, but bigger than an atom or a simple molecule that are governed by quantum mechanics. The United States instituted the National Nanotechnology Initiative ( NNI ) back in 2000, which was soon followed (2001) by a plethora of projects in nanotechnology in nearly most of the U.S. Departments and Agencies [1] . About 20 Research Centers were subsequently funded by the Nationa1 Science Foundation ( NSF ), an agency responsible solely to the President of the United States and whose mandate is to fund the best of fundamental science and technology projects. NSF was the lead U.S. agency to carry forward the NNI. The word “nanotechnology” soon caught the attention of various media (TV networks, the internet, etc.) and the imagination and fascination of the community at large. In general, the size of a nanoparticle spans the range between 1 and 100 nm. Metallic nanoparticles have different physical and chemical properties from bulk metals (e.g., lower melting points, higher specifi c surface areas, specifi c optical properties, mechanical strengths, and specifi c magnetizations), properties that might prove attractive in various industrial applications. However, how a nanoparticle is viewed and is defi ned depends very much on the specifi c application. In this regard, Table 1.1 summarizes the defi nition of nanoparticles and nanomaterials by various organizations. Of particular importance, the optical property is one of the fundamental attractions and a characteristic of a nanoparticle. For example, a 20-nm gold nanoparticle has a characteristic wine red color. A silver nanoparticle is yellowish gray. Platinum and palladium nanoparticles are black. Not surprisingly, the optical characteristics of nanoparticles have been used from time immemorial in sculptures and 1