Effects of electrophoretic deposition conditions on the formation of colloidal crystal-line/amorphous arrays of SiO2 particles.

The ordering of monodispersed nano- and micro-scale particles has unique properties, such as selective light scattering, which are controlled by the degree of ordering. In structurally colored materials, particle arrays that have long-range-order (colloidal crystalline arrays) can exhibit vivid and illumination-angle-dependent color. In contrast, short-range-ordered arrays (colloidal amorphous arrays) exhibit matte and illumination-angle-independent color. We prepared SiO2 particle arrays with controlled ordering via electrophoretic deposition. Dispersant organic solvents determined the formation of uniform arrays, the applied voltage had minor effects on the ordering, and an additive salt solution significantly changed the structures from colloidal crystalline arrays to colloidal amorphous arrays. Controlling these structures will be important for applications of structurally colored materials as novel colorants, such as color-controllable pigments.This work was partially supported by JSPS KAKENHI Grant numbers JP18K19132, JP20H02439 and JP20K15368, MEXT Leading Initiative for Excellent Young Researchers, JSPS Core-to-Core Program, the Cooperative Research Program of Institute for Catalysis, Hokkaido University (Grant numbers 20B1016 and 21A1007), the facilities of the Institute of Materials and Systems for Sustainability, Nagoya University, Iketani Science and Technology Foundation, and the Takahashi Industrial and Economic Research Foundation