Enhanced photochromic response of ormosil–phosphotungstate nanocomposite coatings doped with TiO 2 nanoparticles

Photochromic ormosil–phosphotungstate hybrid materials were prepared by immobilizing phosphotungstic acid, H 3 PW 12 O 40 , (HPW) in hybrid organic–inorganic ormosil matrices via sol–gel route, and the effect of addition of TiO 2 nanoparticles (NPs) on the photochromic response of HPW was studied. For measurement of the photochromic response and the bleaching kinetics, the resulting sol–gel-derived ormosil–phosphotungstate hybrid materials with and without TiO 2 NPs were coated as thin films on glass substrate by dip coating. The hybrid films were characterized by scanning electron microscopy, Fourier transform infrared absorption spectroscopy, Raman spectroscopy and X-ray fluorescence spectroscopy. The addition of small amounts of TiO 2 was found to increase the photochromic response of the hybrid materials by as much as 277 % which is attributed to a possible interfacial electron transfer from the photoexcited TiO 2 to HPW. These highly UV-sensitive coatings can find useful applications in UV dosimeters and smart windows. Graphical Abstract