Gel-Immobilized Colloidal Photonic Crystals with Tunable Properties

Abstract

Colloidal crystals, three-dimensional periodic arrays of monodisperse colloidal particles, have attracted considerable attention owing to their novel optical applications as photonic crystals. In particular, the possibility to tune the optical properties of colloidal crystals immobilized in polymer gels by adjusting the gel size through an external stimulus is a very attractive feature. Therefore, these crystals are expected to have applications such as tunable photonic crystals, and biological and chemical sensors for monitoring changes through the optical stop-band wavelength or reflection color. This chapter provides an overview of our recent work on the preparation and tunable properties of gel-immobilized colloidal crystals with high optical quality. We developed an air-pulse-drive system for preparing a large single-crystal-like colloidal crystal film. Polycrystalline charge-stabilized colloidal crystals could be converted into single-crystal-like ones through a flow-induced shear effect by running the suspension in a flat capillary cell. These crystals could be subsequently immobilized in a hydrogel network by a photopolymerization technique that preserves the high crystalline quality. Tuning of their properties by an external stimulus, such as solvent exchange, temperature change, and mechanical stress, is described. The optical stop-band wavelength of the crystals can be tuned over a wide wavelength region while preserving high spectral quality.