A WO_3/ZnO Nanoparticle Composite System with High Photochromic Performance

The colloids of ZnO and WO 3 were synthesized and ZnO colloid with different mass fractions was added into the WO 3 colloid to get WO 3/ZnO composite colloids. The experimental results indicate that the UV-light coloration of WO 3 nanoparticles could be improved greatly after the addition of ZnO. When the molar ratio of ZnO to WO 3 is about 1∶100, the magnitude of the difference of absorbance(ΔOD) at 900 nm after and before the coloration for WO 3/ZnO colloids is as about 135 times as that of WO 3 colloids. The surface photovoltaic spectra show that the state density of the surface state of WO 3 increases greatly after the addition of ZnO, thus, under the UV-light irradiation more electrons from ZnO nanoparticles can be captured in the surface state and those electrons can be excited to a higher energy level, resulting in the improved coloration.