Tuning the Photochromic Properties of WO₃-Based Materials toward High-Performance Light-Responsive Textiles

Abstract

The development of photoresponsive textiles with high color contrast, sunlight response, fast coloration/bleaching, and reversible properties has been a major quest for anticounterfeiting, camouflage, UV protection, and fashion. WO 3 materials are promising building blocks for textile applications, but their application has been limited by their slow color bleaching under ambient conditions and limited sunlight response. Herein, innovative tungsten oxide-based materials with tunable photochromism were produced by a low-cost, single-step, and scalable solvothermal process in the presence of different structuredirecting agents, and the most promising ones were screen-printed on fabrics to produce light-responsive smart textiles. The influence of the structure-directing agent type (polyethylene glycol, hexadecyltrimethylammonium bromide, polyoxyethylene(10) cetyl ether, Pluronic F127, and polyvinylpyrrolidone (PVP)) on the morphology, structure, composition and photochromism of the WO 3 -based materials was assessed, toward enhancing their color contrast and coloration/bleaching rates and endowing a sunlight response. All WO 3 -based materials exhibited UV/sunlight-responsive properties, with the materials prepared with PVP presenting the best performance, featuring 13× faster coloration than that of other WO 3 -based materials reported in the literature (7 min vs 60−90 min) and up to 2× higher total color difference (21.4−50.6 vs 25.2−25.8). These improvements were assigned to their Lindqvist-type hexatungstic acid structure hybridized with PVP, while the remaining materials were composed of WO 3 •H 2 O and WO 3 . The WO 3 _PVP-based materials led to high-performance photoswitchable textiles under sunlight and UV irradiation, changing color from white to blue in 3−7 min and bleaching in 3−7 h. The smart textiles presented fast hydrobleaching, especially the fabric based on WO 3 prepared using PVP with higher molecular weight, which hydrobleached in up to 20 s, surpassing reported works on WO 3modified fibers. This work opens horizons for the design of engineered UV/sunlight-responsive WO 3 -based materials and textiles with hydrobleaching properties through straightforward scalable processes, offering potential prospects for smart clothing and optical sensors.

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO3/MoO3 Composite Products

“…The exact process responsible for the photochromic behavior in WO 3 -based materials and composites remains a topic of ongoing discussion and research. However, there is acknowledgment of the significance of defects within the material structure, the presence of an amorphous structure, particle size, and the influence of adsorbed water in this context . The photochromic mechanism has been elucidated in the preceding equations (eqs –).…”

“…When subjected to simulated solar illumination, electrons within the valence bands of WO 3 and MoO 3 absorb energy, leading to the creation of electron–hole pairs. These electrons are subsequently captured by WO 3 and MoO 3 , forming W 5+ and Mo 5+ , while H + ions from the surrounding air or the sample’s surface are incorporated into WO 3 and MoO 3 , , resulting in the generation of H x WO 3 and H x MoO 3 , accompanied by the reduction of W 5+ and Mo 5+ . The blue coloration of the sample stems from the electron’s transition within the valence band. , WO 3 false( MoO 3 false) + hv → WO 3 * false( MoO 3 * false) + normalh + + normale − .25ex2ex normalW 6 + false( Mo 6 + false) + normale − → normalW 5 + false( Mo 5 + false) .25ex2ex normalH 2 O + normalh + → normalH + + normalO 2 .25ex2ex WO 3 false( MoO 3 false) + x e − + x h + → normalH x…”

“…When subjected to simulated solar illumination, electrons within the valence bands of WO 3 and MoO 3 absorb energy, leading to the creation of electron–hole pairs. These electrons are subsequently captured by WO 3 and MoO 3 , forming W 5+ and Mo 5+ , while H + ions from the surrounding air or the sample’s surface are incorporated into WO 3 and MoO 3 , , resulting in the generation of H x WO 3 and H x MoO 3 , accompanied by the reduction of W 5+ and Mo 5+ . The blue coloration of the sample stems from the electron’s transition within the valence band. , …”

“…It is extensively studied and falls into two major material categories: organic materials (e.g., spiro-pyrans, azobenzenes, and diarylenes) and inorganic materials (e.g., transition-metal oxides (TMOs), metal halides, and rare earth complexes). Transition-metal oxides, like tungsten oxide (WO 3 ) and molybdenum oxide (MoO 3 ) have garnered significant attention due to their stability and cost-effectiveness compared to organic counterparts. When exposed to irradiation within their band gaps, WO 3 and MoO 3 generate electron–hole pairs.…”

Cyclodextrin-Assisted Surface-Enhanced Photochromic Phenomena of Tungsten(VI) Oxide Nanoparticles for Label-Free Colorimetric Detection of Phenylalanine

“…Some transition metal oxides show an interesting photochromic effect and can be deeply colored by exposing the material to irradiation with appropriate energy. , Such photochromic phenomena of transition metal oxides have attracted considerable attention because they can be applied to display devices, erasable optical memory media, chemical sensors, smart-windows, and other cutting-edge applications. , Among them, tungsten­(VI) oxide (WO 3 ), a wide-bandgap n -type semiconductor, is mainly the most studied among inorganic photochromic materials because it has characteristics such as chemical stability, coloring efficiency, and fast coloring response time . Many researchers have reported that the hybridization between WO 3 nanomaterials and organic constituents enhances photochromic performance and consider that the monolayer of organic molecules surrounding WO 3 nanomaterials can behave as an active form of organized organic matter. − This unique enhanced photochromic phenomenon by organic molecules adsorbed on the metal oxide surface is called “surface-enhanced photochromic phenomenon” . Recently, we have focused on the surface-enhanced photochromic phenomena of colloidal WO 3 in aqueous media in the presence of amino acid compounds and experimentally demonstrated the usefulness of WO 3 nanoparticles as a colorimetric probe for high-sensitive “label-free” detection of amino acid compounds …”