Blue/red light-triggered reversible color switching based on CeO2-x nanodots for constructing rewritable smart fabrics

Photoreversible color switching systems (PCSSs) have attracted increasing attention in various applications, but in most PCSSs the discoloration process usually relies on harmful UV light as stimulus and the recoloration requires high temperature. To solve these problems, we have designed and prepared CeO2-x nanodots as novel photocatalytic components in PCSS that responds two kinds of visible light. CeO2-x nanodots are prepared by solvothermal reaction with L-ascorbic acid as the reducing agent. CeO2-x nanodots with size of ~2 nm have high concentration of oxygen vacancies, which confers a broadened photoabsorption with an edge at 500 nm, as well as, a weak photoabsorption tail in the visible region (500-800 nm). To realize the color switching, both CeO2-x/Dye/H2O solution and CeO2-x/Dye/HEC-coated fabric have been prepared. Under blue (450 nm) light irradiation, both solution and fabric show a rapid discoloration in 30 s and 150 s, respectively, due to the efficient photocatalytic reduction of the redox dye by CeO2-x. Conversely, red (630 nm) light irradiation with air confers the rapid recoloration in 35 s for solution and 200 s for fabric, resulting from CeO2-x-mediated self-catalyzed oxidation. In particular, the required images and letters can be remotely printed on CeO2-x/Dye/HEC-coated T-shirts by 450 nm laser pen, and then erased by 630 nm light, with high reversibility and stability. Therefore, the present CeO2-x/Dye/HEC PCSS have great potential to construct rewritable smart fabrics for various applications.