Preparation of a colloidal photonic crystal containing CuO nanoparticles with tunable structural colors

Polystyrene (PS) colloidal photonic crystal (CPhC) structures containing copper oxide nanoparticles (CuO NPs) present tunable structural colors, which are highly useful properties. We prepared PS CPhC color films containing CuO NPs using self-assembly of a gravitational sedimentation method by electrostatic interactions. Incorporating CuO NPs into PS CPhC color films dramatically changed the structural color without affecting the structure quality of CPhCs. The iridescent structural color of CuO-PS CPhC films was based on Bragg diffraction and backward scattering absorption using CuO NPs. The structural color of CuO-PS CPhC films was measured using color measurements under the Commission International d'Eclairage standard colorimetric system. The random adsorption of CuO NPs on PS nanospheres affected the photonic stop band, resulting in structural color changes. This paper presents a simple and inexpensive method to produce tunable structural color for numerous applications, such as in decorative, security, textile fabrics, bionic colors, and optical devices.