Infrared extinction properties of gold nanoshells

Gold nanoshells, nanoparticles consisting of a silica core coated with a thin gold shell, exhibit a strong optical resonance that depends sensitively on their core radius and shell thickness. Gold nanoshells have been fabricated with a peak optical extinction that can be varied across the near-infrared region of the spectrum (800 nm-2.2 mu m). Multipolar plasmon resonances are clearly resolvable in the extinction spectra and agree well with electromagnetic theory. Additional resonances due to particle aggregation are also 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].