Preparation and visible-light photochromism of phosphomolybdic acid/polyvinylpyrrolidone hybrid film

The visible-light photochromic hybrid film was constructed by entrapping phosphomolybdic acid(PMoA) into polyvinylpyrrolidone(PVPd) networks. The microstructure, photochromic properties and mechanism were investigated with transmission electron microscopy(TEM), atomic force microscopy(AFM), Fourier transform infrared spectroscopy(FTIR), ultraviolet-visible spectra(UV-Vis) and X-ray photoelectron spectroscopy(XPS). The results indicate that the Keggin geometry of PMoA and the basic structure of PVPd are not destroyed during the composite process. Irradiated with visible light, the transparent PMoA/PVPd film changes color from colorless to blue and exhibits reversible photochromism in the presence of oxygen. According to the XPS analysis, the charge-transfer bridge of N-H-O has been built between PMoA and PVPd matrix via non-covalent bonding, and the appearance of Mo5+ species indicates that the photo-reduction process is in accordance with the proton transfer mechanism.