Infrared extinction properties of gold nanoshells

Gold nanoshells, nanoparticles consisting of a silica core coated with a th in gold shell, exhibit a strong optical resonance that depends sensitively on their core radius and shell thickness. Gold nanoshells have been fabrica ted with a peak optical extinction that can be varied across the near-infra red region of the spectrum (800 nm-2.2 mu m). Multipolar plasmon resonances are clearly resolvable in the extinction spectra and agree well with elect romagnetic theory. Additional resonances due to particle aggregation are al so observed. The frequency agile infrared properties of these nanoparticles make them particularly attractive for a range of technologically important applications. (C) 1999 American Institute of Physics. [S0003-6951(99)01945 -2].