Monodispersed colloidal spheres: Old materials with new applications

This article presents an overview of current research activities that cente r on monodispersed colloidal spheres whose diameter falls anywhere in the r ange of 10 nm to 1 mu m. It is organized into three parts: The first part b riefly discusses several useful methods that have been developed for produc ing monodispersed colloidal spheres with tightly controlled sizes and well- defined properties (both surface and bulk). The second part surveys some te chniques that have been demonstrated for organizing these colloidal spheres into two- and three-dimensionally ordered lattices. The third part highlig hts a number of unique applications of these crystalline assemblies, such a s their uses as photonic bandgap (PBG) crystals; as removable templates to fabricate macroporous materials with highly ordered and three-dimensionally interconnected porous structures; as physical masks in lithographic patter ning; and as diffractive elements to fabricate new types of optical sensors . Finally, we conclude viith some personal perspectives on the directions t owards which future research in this area might be directed.