Transparent and flexible phosphomolybdate–agarose composite thin films with visible-light photochromism

Polyoxometalates (POMs) are promising photochromic materials, but flexible POM-based thin films sensitive to visible-light have not been reported so far. In this study, highly transparent flexible self-supporting phosphomolybdate(PMo12)–agarose thin films were successfully fabricated by the combination of hydrogel chemistry and a facile casting technique. It was identified that strong interaction between polyhydroxyl site of agarose and PMo12 by hydrogen bonds together with densely-packed 3D network structure in the gel state avoided the phase separation efficiently and resulted in the homogenous distribution of PMo12 as well as the good mechanical properties of the nanocomposite films. More importantly, the obtained thin films exhibited excellent visible-light photochromic performance. When exposed to blue light irradiation through a TEM copper grid as photomask, the image recorded on the film displayed good resolution at 2 μm scale. Therefore, the developed PMo12–agarose photochromic thin films are promising for applications in portable high-resolution displays and high-density memory devices.