Bright, Angle-Independent, Solvent-Responsive, and Structurally Colored Coatings and Rewritable Photonic Paper Based on High-Refractive-Index Colloidal Quasi-Amorphous Arrays

Bright structural colors with an angular-independent character are in increasing demand in many fields such as pigments, buildings, sensors, color displays, and anti-counterfeiting labels. However, the structural colors produced by amorphous colloidal assemblies with low refractive index contrast or without black additives often exhibit low color visibility and low liquid-bleaching resistibility. Herein, large-scale and angle-independent structural colors were constructed from Fe3O4@SiO2 colloidal quasi-amorphous arrays (QAAs) prepared through a rapid “spraying” process. Due to the high-refractive-index and intrinsic black nature of Fe3O4, the coatings exhibit high brightness of structural colors even on white substrates under ambient lighting conditions. Moreover, as-obtained structural colors possess the ability of antiliquid bleaching and solvent-responsiveness. More importantly, flexible Fe3O4@SiO2/PDMS photonic paper can be fabricated by permeation of PDMS into the voids of Fe3O4@SiO2 colloidal QAAs. This QAAs-based photonic paper shows the ability to infuse silicone oils into its structure, locally swelling it and changing the reflected color. In turn, the resulting colored patterns can be easily erased by applying ethanol or low molecular weight silicone oils. The as-prepared photonic paper exhibits excellent durability and is rewritable at least 50 times without any significant changes in performance. Compared with the traditional long-range ordered photonic crystals, the rapidly prepared QAAs-based photonic coatings have unique advantages in the applications of permanents, color coatings, color printing, liquid colorimetric sensors, rewritable photonic paper, etc. because of the good structural color performance and are suitable for rapid and large-area preparation.