Photonic crystals fabricated from gold-silica core-shell nanoparticles

An approach to metallic photonic crystals is demonstrated by using gold-silica core-shell colloids as the building blocks. The formation of gold-silica core-shell nanoparticles involved a base-catalyzed hydrolysis of precursor TEOS and subsequent condensation of silica onto the surfaces of gold cores. The obtained core-shell colloids were monodispersed in size and their shell thickness could be controlled in the range of a few nanometers to about 500 nm. The core diameter could also be varied from ~5 nm to ~100 nm. The core-shell colloids were then employed as building blocks to self-assemble highly ordered three-dimensional photonic crystals using a non-lithographic method. The photonic band-gap properties were characterized by taking the transmittance and reflectance spectra.