INTRODUCTION
Over the last decade there has been increased interest in “nanochemistry.” A variety
of supermolecular ensembles , multifunctional supermolecules , carbon
nanotubes , and metal and semiconductor nanoparticles have been synthesized
and proposed as potential building blocks of optical and electronic devices
. This has arisen for a variety of reasons, not the least of which is technological
advance, and the promise of control over material and device structure at length
scales far below conventional lithographic patterning technology
Metal particles are particularly interesting nanoscale systems because of
the ease with which they can be synthesized and modified chemically. From the
standpoint of
also offer an advantage over other systems because their optical., Perhaps the most intriguing observation is that metal particles often exhibit strong plasmon resonance extinction bands in the visible spectrum, and therefore deep colors reminiscent of molecular dyes. Yet, while the spectra of molecules (and semiconductor particles) can be understood only in terms of quantum mechanics, the plasmon resonance bands of nanoscopic metal particles can often be rationalized in terms of classical free-electron theory and simple electrostatic limit models for particle polarizability . Furthermore, while the composition of a metal particle may be held constant, its plasmon resonance extinction maximum can be shifted hundreds of nanometers by changing its shape and/or orientation in the incident field , or the number density of particles in a composite material . Thus, in contrast to molecular systems, the linear optical properties of nanoscopic metal particle composites can be changed significantly without a change in essential chemical composition. The electrical properties of metal particles are also similar in form to .those of their corresponding bulk metals
constants resemble those of the bulk metal to exceedingly small dimensions
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