Preparation, microstructure and photochromism of a new nanocrystalline WO3 film

Nanocrystalline WO3 thin films were prepared using a colloid chemistry method. The particle size and crystallinity of the films were tailored by controlling the concentration of oxalic acid in the colloid solution. The growth process and microstructure of the films were observed with a transmission electron microscope (TEM). Using ultraviolet-visible absorption spectrum (UVAS), the dependence of photochromic behavior on crystallite size was investigated. Exposure of the films to ultraviolet light makes the films blue in color.