Changing the shape of a metal at the nanoscale allows engineers and scientists to modify the properties of these plasmon waves, controlling the way that the metal nanostructure responds to light. Because of this, metal nanostructures can have beautiful, vivid colors that depend on their shape. Some nanoscale structures -- like nanorice and nanoshells -- act as superlenses that can amplify light waves and focus them to spot sizes far smaller than a wavelength of light.
In January 2005, for example, Halas and colleagues showed that nanoshells were about 10,000 times more effective at Surface-enhanced Raman Scattering (SERS) than traditional methods. Raman scattering is a type of spectrographic technique used by medical researchers, drug designers, chemists and others to determine the precise chemical makeup of materials.
"Plasmon resonance 'hot spots' formed at the junction between a pair of nanoparticles- called dimers- provide higher SERS intensity than single nanoshells," said co-author Peter Nordlander, professor of physics and astronomy and of electrical and computer engineering. "Our computer models and experimental results show that the plasmon resonances of single grains of nanorice are on the same order of magnitude intensities as those obtained in junctions of nanoparticle dimers."
"The distinct advantage of the nanorice particle over nanoparticle dimers is that the electric field enhancements occur on open-ended surfaces of the particle that are much more accessible," said Halas, The Stanley C. Moore Professor of Electrical and Computer Engineering and professor of ch