Visible-light photochromism of phosphomolybdic acid and polyvinyl alcohol by inorganic-organic nanocomposite multilayer films

A novel visible-light photochromic inorganic-organic multilayer was constructed based on phosphomolybdic acid (PMoA) and polyvinyl alcohol (PVA) which was prepared using the layer-by-layer (LbL) assembly technique to form the multilayer film. The structures of the multilayer films were characterized via Fourier transform infrared spectra (FT-IR) and atomic force microscopy (AFM). The grown process, internal interaction, the surface topography and photochromic properties could be obviously studied through ultraviolet–visible (UV–vis) spectra and X-ray photoelectron spectra (XPS). The advantage of the structure and performance of the multilayer films prepared by layer-by-layer method could be found. It was suggested that the nearly linear growth process in peak-top absorbance in multilayer assembly. The PVA polymer substrate could disperse PMoA particles and changed the surface morphology. The polymer skeleton and PMoA particles were with strong interfacial interactions. The PMoA/PVA LbL film had wonderful visible light response. The oxygen acted a significant part during the bleaching process. According to XPS resoults, 51% of Mo⁶⁺ in the PMoA turned into Mo⁵⁺, obvious photoinduce oxidation and reduction reactions happened from PVA and PMoA through the proton transfer mechanism.