Two Birds with One Stone: Manipulating Colloids Assembled into Amorphous and Ordered Photonic Crystals and Their Combinations for Coding–Decoding

Abstract

Photonic crystals, including amorphous and ordered photonic crystals (APCs and OPCs), show wide applications in color displays, sensors, and pigments. The fabrication of APCs and OPCs by one method is highly desired; however, it remains a big challenge due to the lack of fine control of the assembly behavior of the colloids. Herein, an efficient surface-charge-assisted colloidal assembly (SCACA) has been developed to fabricate APCs with noniridescent structural colors and OPCs with iridescent colors by the coassembly of aminated silica particles and nanosized carbon black (CB) in solution with different pH values. The surface charge of the particle is demonstrated to be the key factor manipulating the assembly behavior of the particles; thus, the structure, defect, reflection intensity, and angle-in/dependent structural color of the photonic crystals can be precisely controlled. Compared with previous strategies, SCACA is considerably simple and efficient in preparing APCs and OPCs, which makes the fabrication more controllable, convenient, and scalable. Moreover, by combining the noniridescent and iridescent structural colors of APCs and OPCs, a single color- and multicolor-based coding–decoding system has been developed, in which the structural colors, numbers, positions, and angle in/dependency of codes can be hidden and recognized by naked eyes at varied viewing angles. This work provides a new insight for precisely manipulating the assembly of the colloids into APCs and OPCs and extends their combined applications in anticounterfeiting and information storage.