The research we are performing at Clemson University is grounded in the fundamental aspects of crystalline colloidal array derived photonic bandgap (PBG) materials and the extension of photonic crystal research into functional polymeric composites. Since the original proposal that three-dimensional periodic dielectric structures could exhibit a photonic bandgap, considerable attention has been focused on developing these materials into a form that is suitable for use in photonic applications. Unfortunately, the general exploitation of visible photonic crystals as devices has been hindered by the challenges in creating 3D periodic dielectric structures with a feature size comparable to the wavelength of visible light, as well as achieving significant dielectric contrasts that result in a strongly scattering system. To surmount these challenges, current effort is being directed at systems which undergo self-assembly at a nanometer length scale, such as colloidal crystals.

Our group has focused on electrostatically-stabilized crystalline colloidal arrays. A crystalline colloidal array is a three dimensionally ordered lattice of self-assembled monodisperse colloidal particles, most commonly amorphous silica or a polymer latex, dispersed in aqueous or non-aqueous media. At high particle concentrations, long-range electrostatic interactions between particles result in a significant inter-particle repulsion which yields the adoption of a minimum energy colloidal crystal structure with either bcc or fcc symmetry. The ordering of the particles in the media results in spatial periodicities that range from ca. 100-1000 nm, often resulting in optical bandgap effects. The three main research thrusts within my group on these systems include (1) particle synthesis; (2) self-assembly & collective properties; and (3) device development. These three thrusts will be the major themes of my talk and will be presented in detail.