Silica-coated metals and semiconductors.: Stabilization and nanostructuring

We present in this paper the use of silica-coating for nanostructuring metal and semiconductor nanoparticles. The basic concept is the strict tailoring of the interparticle spacing through the thickness of the silica shell. Three different experiments are presented that exemplify this concept. The first example consists of the preparation of thin films using the layer-by-layer self-assembly of gold nanoparticles, either uncoated or coated with thin silica shells. The observed optical effects are interpreted using effective medium theory. The second and third experiments are related to the preparation of three-dimensional nanostructures, either as concentrated dispersions of thickly coated Au or CdS nanoparticles, or as opals prepared from such core-shell nanoparticles. Within these crystalline solids, intercore distance is again dictated by the thickness of the silica shells.