Photochromism of WO3 Colloids Combined with TiO2 Nanoparticles

WO3 and TiO2 colloids were synthesized by the forced hydrolysis technique, and different amounts of the TiO2 colloids were added to WO3 colloids under sonication to get stable combined TiO2 and WO3 colloids (WO3/TiO2). The experimental results indicate that the UV-light coloration of WO3 colloids can be improved greatly after the TiO2 combination. When the molar ratio of TiO2 and WO3 is about 1:40, ΔOD at 900 nm for WO3/TiO2 colloids is about 12.7 times that of WO3 colloids. The improvement effect increases with the increased concentration of TiO2 in the composite colloids, and the maximum enhancement can increase more than 50-fold. It is shown that after the combination, the recombination of photogenerated carriers is suppressed efficiently, and more electrons can be trapped within the band gap of WO3 to contribute to the coloration process.