Growth process and structures of opaline-type colloidal crystals fabricated in a fluidic cell

Abstract

Opaline-type colloidal crystals composed of monodispersed microspheres have recently attracted great attention because of their application in photonic crystals. Polystyrene (PS) and silica spherical particles as are often used as materials for colloidal crystals. In this paper, the growth process and structure of the colloidal crystal composed of PS microspheres fabricated in a fluidic cell were investigated in comparison with those of the colloidal crystal composed of silica microspheres. During the growth process of both colloidal crystals, three distinct states were observed, in each of which the crystals exhibited different optical properties. Angle-resolved reflection spectroscopy revealed that PS microspheres undergo a shrinkage of ca. 3% in diameter at the drying process. The origin of the cracks observed on the PS colloidal crystal surface was discussed on the basis of the shrinkage.