Method for Growing Colloidal Crystals in Three-Dimensional Photonic　Crystal (3DPC） Space-Experiments

Abstract

This paper describes methodology for growing charged colloidal crystals that had been adopted in the three-dimensional photonic crystal (3DPC) space-experiments. The crystallization of charged colloids is driven by electrostatic interaction between the particles, whose magnitude is governed by experimental parameters such as the particle charge number Z, and ion concentration C. The interaction is stronger at larger Z, while it is reduced with increasing C due to the electrostatic screening effect by the ions. Z value of silica particle increases with pH. Thus, under appropriate conditions, silica colloids exhibit charge-induced crystallization by changing pH. The crystallization method used in the 3DPC space-experiments is based on the unidirectional crystal growth under gradients of Z or C. The former is enabled by diffusion of base for silica colloids. The resulting crystals consist of columnar- or cubic- crystal grains with a maximum height of a few centimeters and a maximum width of one centimeter.