Achieving saturated non-iridescent structural colors via island-like polypyrrole coating on SiO2 microspheres and enhancing their stability through a melt-curing strategy†

Abstract

High saturation and high stability are two issues that must be addressed in the practical application of structural color based on the self-assembly of colloidal microspheres. Herein, we coated SiO₂ microspheres with island-like polypyrrole (PPy), a black substance that can absorb incoherent scattered light, thereby enhancing the saturation of structural colors on both black and white substrates. Besides, the irregular island-like structure prompts the SiO₂@PPy microspheres to form a short-range ordered amorphous structure, exhibiting non-iridescent structural colors. Importantly, we propose a melt-curing strategy that can enhance the interaction forces between the two microspheres and between the microspheres and the substrate, thus enabling the structural colors to exhibit good stability. Even after rubbing, folding, and ultrasonic cleaning tests, the color of the cured sample remains virtually unchanged. The SiO₂@PPy microspheres prepared and the melt curing strategy in this work can lay foundations for the practical application of structural colors.