The effect of nanocrystalline tungsten oxide concentration on surface properties of dip-coated hydrophilic WO₃-SiO₂ thin films

WO₃-SiO₂ compound thin films were deposited on glass substrates using the sol-gel method, and then all the samples were dried at 100 °C and annealed at 400 °C in air. The effect of WO₃ concentration on the hydrophilicity of WO₃-SiO₂ compound films was studied for the first time and it was shown that the films containing 85 mol% of the concentration possessed a superhydrophilic surface without UV or visible irradiation. Optical properties of the films such as transmittance, reflectance and bandgap energy were investigated using a UV-visible spectrophotometer. According to atomic force microscopy, the surface ratio was maximized in 85 mol% concentration of WO₃ similar to hydrophilicity. Surface chemical states of the films were studied by x-ray photoelectron spectroscopy, which determined the stoichiometry of the deposited thin films. X-ray diffraction patterns showed that the compound thin films constituted of nanocrystalline tungsten oxide grains with 60-10 nm grain size depending on the WO₃ concentration.