Optical properties of ordered macroporous materials made by colloidal assembly

Summary form only given. There is currently a major interest in the design and fabrication of periodic dielectric structures exhibiting photonic bandgaps (PBG) at optical and near-infrared frequencies. Apart from their applications in catalysis and separation processes, PBG materials also have several unique optical properties, such as inhibition of spontaneous emission or photon localization. We have used this idea to make periodic macroporous materials using a simple and effective method. Our technique employs monodisperse polystyrene as templates and ultrafine (<100 nm) metal oxide particles as the surrounding high dielectric material. The process involves slowly drying a monodisperse polystyrene dispersion with a colloidal dispersion of the desired oxide. As the mixture is drying, the polystyrene spheres organize themselves in an ordered lattice and the oxide particles pack into the voids between the spheres. Subsequent removal of the polystyrene by heat treatment leads to an ordered macroporous material with the oxide particles forming the walls of the pores.