Colorful Photonic Pigments Prepared by Using Safe Black and White Materials

Abstract

The methods used to prepare vivid color materials that have supported our rich lifestyle are due for review, with the goal of using chemical substances that minimize the significant adverse effects on human health and the environment. In this research, we found that pigments of various colors can be obtained by utilizing submicron-sized amorphous silica fine particles and a complex of iron and tannic acid (Fe–TA complex), which are used for foods, cosmetics, etc. Silica fine particles with uniform submicron particle size appear as a white powder. When silica fine particles form spherical colloidal crystals with short-range order, long-distance order, and periodicity or form colloidal amorphous arrays with only short-range order, the fine particle arrays strongly scatter light with a specific wavelength in all directions. If the wavelength is in the visible light region, these arrays can be used as color materials displaying colors with low angle dependence. However, such arrays formed only from silica fin...