Transition metal element doping to optimize the photochromic properties of WO3.

This research prepared a photochromic material of WO₃ doped with Mo or Cu through a solvothermal method. The material exhibits selective absorption of UV light in the 200-350-nm range. The crystal structure of WO₃ remained unchanged after doping, but the bandgap was reduced, thereby increasing its coloration rate. The doping of Mo or Cu brought different new features to WO₃: Mo-doping imparted a purple hue upon UV irradiation, whereas Cu-doping accelerated the bleaching of WO₃ due to its multi-valent state. WO₃-0.1Mo and WO₃-0.1Cu were preferentially selected through a practical photochromic process and bandgap calculations, and further used to prepare photochromic ink. This ink is suitable for the preparation of writing and photochromic rewriting paper and retains good photochromic properties even after 50 uses. [ABSTRACT FROM AUTHOR]