Synthesis and visible-light photochromism of a new composite based on polymolybdate enclosed in magadiite

A new composite based on polymolybdate incorporated in layered magadiite has been synthesized via a exfoliation/self-assembly process. Various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), Raman spectroscopy, thermogravimetric (TG) analysis, UV-vis spectroscopy, and transmission electron microscopy (TEM), have been employed to characterize the composite. Results indicated that the polymolybdate particles were incorporated into the layered magadiite. Upon the irradiation of visible light (420-630 nm), the composite changed color from yellow to dark blue; moreover, the color can be bleached upon exposure to a 15% H2O2 solution. The visible-light illumination and H2O2 treatment can be repeated in excess of 10 times. The mechanism of photochromism has been investigated, and the reversibility is attributed to the hydration property of host magadiite and oxidative ability of H2O2 solution.