Enhanced visible-active photochromism of a polyoxometalates/TiO2 composite film by combining Bi2O3 nanoparticles

Abstract

A novel photochromic hybrid film was successfully synthesized by introducing Bi₂O₃ into a phosphomolybdic acid (PMoA)/TiO₂ system as a visible light sensitizer. The influence of Bi₂O₃ addition on microstructure and photochromic properties was studied via transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The results revealed that the Keggin geometry of PMoA and basic structure of Bi₂O₃ were preserved in the obtained film, and the interaction between PMoA and TiO₂ was strengthened after combining Bi₂O₃. Upon visible light irradiation, the composite films changed from colorless to blue and showed reversible photochromism in the presence of oxygen. Moreover, the photochromic performance of the Bi₂O₃/PMoA/TiO₂ film was better than that of PMoA/TiO₂ film. The amount of PMoA participating in the photo-reductive reaction increased after adding Bi₂O₃ into the PMoA/TiO₂ composite, which resulted in photochromic efficiencies enhancing.