Some New Developments in the Synthesis,Functionalization, and Utilization of Monodisperse Colloidal Spheres

This article provides an overview of some recent developments related to the synthesis and functionalization of monodisperse colloidal spheres, a class of colloidal materials that has found widespread use in applications such as the fabrication of photonic crystals, optical sensing, and drug delivery. Traditionally, the choice of materials has been limited to polystyrene and silica. We and other groups have recently expanded the scope of materials by developing a number of methods for producing monodisperse colloidal spheres from various semiconductors and metals. This article is confined to our own work; it covers three different synthetic strategies: the bottom–up approach, the top–down approach, and template‐directed synthesis. The colloidal spheres may have a solid, hollow, or core–shell structure, and the chemical compositions can include Se, Bi, Pb, In, Sn, Cd, Pt, Ag₂Se, CdSe, PbS, or TiO₂. As an example to illustrate the attractive features of these colloidal spheres, we demonstrate the fabrication of Ag₂Se‐based photonic crystals whose stop bands can be thermally switched between two spectral positions.