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A self-assembled layered superlattice composite film was fabricated by casting the chloroform solutions of ionic complex between dioctadecyldimethylammonium (DODA) and 18-molybdophosphate anion (P2Mo186−) onto CaF2, borosilicate glass, and quartz substrates. Infrared and UV spectra revealed that the Dawson structure characteristic of P2Mo186− was preserved in the composite film. A well-ordered superlattice structure was identified by X-ray diffraction (XRD). From XRD results and the cross-sectional area of DODA cation and P2Mo18 polyanion, a possible structural model was proposed. The P2Mo18/DODA film showed good photochromic properties. Irradiated with UV light, the transparent film changed from light yellow to blue. Then, bleaching occurred when the film was in contact with ambient air or O2 in the dark. A possible photochromic mechanism was proposed according to electron spin resonance (ESR), Fourier transform infrared (FTIR) spectra, and UV–Vis spectra. [Copyright &y& Elsevier]

A series of photochromic hybrid films were prepared through entrapping tungsten heteropolyoxometallate (PW12O403−) and molybdenum heteropolyoxometallate (PMo12O403−) in polyacrylamide (PAM) matrix, the corresponding structure and photochromic behaviors of the films were investigated with Fourier transform infrared (FT-IR), UV–Vis–near-infrared (NIR) absorption spectra (UV–Vis–NIR) and electron spin resonance (ESR). FT-IR results showed that the Keggin geometry of heteropolyoxometallate was still preserved inside the composites and strong Coulombic interaction was built between heteropolyoxometallate and PAM via hydrogen bonding. Irradiated with ultraviolet light, the transparent films changed from colorless to blue and showed reversible photochromism. The bleaching process occurred when the films were in contact with air or O2 in the dark. The molybdenum heteropolyoxometallate hybrid film had higher photochromic efficiency and slower bleaching reaction than tungsten heteropolyoxometallate hybrid film. The characteristic signals of radical and W(V) or Mo(V) in ESR spectra indicated that PAM is a hydrogen donor and the photoreduced process is in accordance with the radical mechanism. [Copyright &y& Elsevier]