Photochromic Textiles Based upon Aqueous Blends of Oxygen-Deficient WO_3-x and TiO₂ Nanocrystals

With the main objective being to develop photochromic smart textiles, in this paper, we studied the photochromic behavior of WO_3-x nanocrystals (NCs) cooperatively interacting with variable amounts of TiO₂ NCs. We tested several blends of WO_3-x:TiO₂ NCs, admixed in different compositions (relative molar ratio of 4:0, 3:1, 2:2, 1:3, 0:4) and electrostatically interfacing because of opposite values of Z-potential, for photo-induced chromogenic textiles. We further monitored the photochromic sensitivity of NC-impregnated textiles after exposure to a few solvents (i.e., methanol, ethanol, and isopropanol) or when over-coated with different polymeric matrices such as natural cellulose or ionic conductive Nafion. The optimization of the compositions of the WO_3-x:TiO₂ blends embedded in polymeric matrices, allowed the nanostructured photochromic textiles to show rapid and tunable coloration (<5 min) and bleaching kinetics (~5 in at 75 °C or 6 h at room temperature) along with good recovery and cycling stability. This study features a simple strategy for the widespread application of WO_3-x:TiO₂-based photochromic smart textiles.