Full-Spectrum Low-Angle-Dependent Structural Color Coatings Based on Silica Nanospheres for Fabrics

Structural colors have attracted significant attention due to their unique advantages, including high color saturation, resistance to fading and environmental friendliness. However, most current fabrication strategies rely on tuning nanoscale features, typically by preparing nanospheres of varying sizes to achieve different structural colors, resulting in complex and laborious processes. To address this challenge, this study employs the principle of additive color mixing to simply and effectively fabricate structural-color textiles with a low angular dependency across the entire visible spectrum. Specifically, this goal was achieved by pairwise mixing three distinct sizes of silica (SiO2) nanospheres─each size corresponding to a structural-color output of red, green, or blue─in predetermined ratios, followed by their deposition onto textile substrates via gravitational sedimentation. Precise control over the nanosphere size directly determines the final primary-color output. However, excessive differences in the particle size between nanospheres can lead to poor color saturation. To optimize the low saturation resulting from mixed nanospheres, the process for producing high-saturation structural-color textiles based on multicomponent nanosphere synergy was refined by incorporating carbon black (CB) and introducing a fourth SiO2 nanosphere size that exhibits yellow color. Furthermore, to enhance the practicality of the nanostructured-color layer, a waterborne polyurethane (WPU) solution was introduced to strengthen the adhesion of the SiO2 nanospheres to the textile surface. This significantly improved the color fastness and color stability of the fabrics while preserving the integrity of the nanoscale structural arrangement of the SiO2 nanospheres. The developed nanoscale structural-color coatings exhibit promising application potential in eco-friendly nanocomposite materials and optical anticounterfeiting based on nanophotonic effects.