Abstract: The colloids of ZnO and WO₃were synthesized and ZnO colloid with different mass fractions was added into the WO₃colloid to get WO₃/ZnO composite colloids.The experimental resultSIndicate that the UV-light coloration of WO₃nanoparticles could be improved greatly after the addition of ZnO.When the molar ratio of ZnO to WO₃is about 1∶100, the magnitude of the difference of absorbance(ΔOD) at 900 nMAfter and before the coloration for WO₃/ZnO colloidSIs as about₁₃₅times as that of WO₃colloids.The surface photovoltaic spectra show that the state density of the surface state of WO₃increases 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.

Key words: Photochromism, Nanoparticle, Surface photovoltage spectrum