The influence of Fe2+ doping on the microstructure and photochromic behavior of polyoxometalates acid/polyacrylamide hybrid films

New hybrid films were synthesized by Fe2+ doping into polyoxometalates acid (POMs)/polyacrylamide (PAM) system, and the effect of Fe2+ doping 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 shape of molybdenumphosphoric acid (PMoA) particles changed from well dispersed sphere to irregular conglomeration. The vibrational spectra of FT-IR verified that the hydrogen bonding between PMoA and PAM was weakened after Fe2+ doping. The hybrid films exhibited a good photochromic property, which changed from colorless to blue under UV irradiation. The color change intensity of PMoA/PAM film was 2.56 times stronger than that of Fe2+/PMoA/PAM under the same condition. XPS results indicated that the amount of PMoA in photo-reductive reaction was decreased after Fe2+ doping, which resulted in the photochromic efficiencies weakened.

► Fe2+ doping had a great effect on the microstructure and photochromic properties.
► The absolute absorbency of irradiated PMoA/PAM films was stronger than Fe2+/PMoA/PMA films.
► The competition with Fe2+ resulted in decrease of PMoA in photoreductive reaction.