Photodegradation of methylene blue of niobium-doped zinc oxide thin films produced by electrostatic spray deposition

Nanocrystalline transparent ZnO thin films, with different concentrations of niobium (Nb~0, 5, 10, 15 atoms per formula unit, at%), were successfully deposited by the electrostatic spray deposition method. The crystalline phase, surface morphology, surface roughness and photocatalytic properties of these Nb:ZnO thin films were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and UV–visible spectroscopy, respectively. The Nb-doped films were tested for their photocatalytic abilities in aqueous solutions of methylene blue (MB) under UV illumination, where it showed that increasing Nb up to 10 at%, with respect to ZnO, enhanced the photocatalytic activity. ZnO films doped with 10 at% Nb demonstrated excellent photocatalytic activity, with degradation of MB achieved in fewer than 2 h of UV irradiation.