Silver nanoshells: Variations in morphologies and optical properties

The production of silica core-silver shell nanoparticles (silver nanoshells) by three different chemical methods is described. Each method produces a silver outer layer with a unique morphology, ranging from smooth and uniform, to rough on the 2-5 nm length scale, to spiky with extremely sharp, needlelike protrusions extending outward from the surface of the nanoparticle. The nanoshells produced by each growth method were studied using transmission electron microscopy and W-vis spectroscopy. In particular, one reduction method produced silver nanoshells with smooth and highly uniform morphologies whose optical extinction corresponded quantitatively to Mie scattering theory for a silica core-silver shell nanostructure.