Concentrated crystallization of closely packed colloidal crystal films from aqueous suspension immersed in silicone oil

Abstract

AbstractColloidal crystals have been attracting much attention due to their novel use as 3D-photonic crystals and to their structural color. We have been developing a method for the colloidal crystal growth of opal films immersed in silicone oil. This method is one of the evaporative self-assembly techniques for opal films from colloidal particle suspensions. Understanding the mechanism of the process is important to assure the coating of high-quality opal thin films. The colloidal crystallization from suspension was observed with a long working distance optical microscope and Bragg's diffraction peaks were measured with a miniature fiber optic spectrometer. The transition from a non-crystalline to a crystalline phase is observed within a region between the disordered colloidal suspension and the colloidal crystal film. Within this region, that spans a distance of about 400μm, the lattice of the colloidal crystal reduces until it transitions to the close-packed structure.