Brilliant thermochromic photonic liquid dominated by electrostatic repulsion

It is challenging for traditional methods to generate liquid photonic crystals (LPCs) with brilliant colors and clear self-assembly mechanisms, owing to the major limitations in solvent choice and undesired components. Here, novel LPCs with widely tunable solvents and desired components have been successfully fabricated by non-close-assembling silica particles from silica/ethanol solution into target solvents through alternative centrifugation and sonication. The as-fabricated LPCs exhibit 1) brilliant structural colors from high reflectance (maximal: 91%) by using solvents with low refractive indexes, much higher than those (20-40%) of traditional LPCs; 2) tunable color saturation with high precision, difficult for conventional LPCs; and 3) a clearer working mechanism: electrostatic repulsion rather than other interactions majorly dominating the non-close-packing of silica particles in solvents. Additionally, a new type of sensitive thermochromic display unit with thermo-switchable on-off structural colors has been prepared by constructing silica/bi-solvents LPCs. This work not only paves a new way for achieving thermal-responsive LPCs but also offers a new perspective for understanding colloidal assembly.