Fabrications of Three- and Two-dimensional Colloidal Crystals

Submicron-sized colloidal particles having a narrow size distribution self-assemble into ordered “crystal” structures in their liquid dispersion, under appropriate conditions. Hard sphere colloids crystallize at the particle concentration of approximately 50 vol%. For charged particles, the crystallization occurs at much lower particle concentrations because of long-ranged electrostatic interparticle repulsion. In the coexistence of linear polymers, depletion attraction acting between the particles results in opal type crystals. Here we briefly review formation of 3D colloidal crystals due to electrostatic repulsion and depletion attraction. We also report our recent studies on fabrications of two-dimensional (2D) colloidal crystals by using electrostatic adsorption of three-dimensional (3D) charged colloidal crystals.