Tunable Colors in Opals and Inverse Opal Photonic Crystals

TLDR

Colloidal photonic crystals generate structural colors from incomplete photonic band gaps, and their hues can be reversibly tuned by external stimuli that modify lattice spacing, filling fraction, or refractive index. This review surveys the systems and mechanisms that enable tunable color in opaline and inverse opal photonic crystals. It examines inorganic and polymeric platforms—including hydrogels, metallopolymers, and elastomers—that realize such tunability.

Abstract

Abstract Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close‐packed or non‐close‐packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed.