Silica-coated metals and semiconductors. Stabilization and nanostructuring

We present in this paper the use of silica-coating for nanostructuring meta l and semiconductor nanoparticles. The basic concept is the strict tailorin g of the interparticle spacing through the thickness of the silica shell. T hree different experiments are presented that exemplify this concept. The f irst example consists of the preparation of thin films using the layer-by-l ayer self-assembly of gold nanoparticles, either uncoated or coated with th in silica shells. The observed optical effects are interpreted using effect ive medium theory. The second and third experiments are related to the prep aration of three-dimensional nanostructures, either as concentrated dispers ions of thickly coated Au or CdS nanoparticles, or as opals prepared from s uch core-shell nanoparticles. Within these crystalline solids, intercore di stance is again dictated by the thickness of the silica shells.