Enhanced photocatalysis and photohydrophilicity in TiO2–W5O14 nanocomposite thin films grown by in-lay sputtering

Abstract

Investigation on the photocatalytic and photoinduced hydrophilic properties of pure and nitrogen doped TiO2–W5O14 nanocomposite thin films grown by in-lay sputtering process is reported. For comparison, similar properties of reactively sputtered nanocrystalline titanium dioxide (TiO2) and nanowire tungsten oxide (W18O49) thin films are studied as well. Structurally, TiO2–W5O14 thin films are highly crystalline and strongly multiphased while TiO2 and W18O49 thin films are anatase, monoclinic, respectively. The band gap of nitrogen doped TiO2–W5O14 thin film is ∼2.82 eV while that of TiO2 and W18O49 thin films are ∼3.27 eV. Surface morphology of TiO2–W5O14 and TiO2 films show nanocrystalline particulates of sizes 15–70 nm, 20–50 nm, respectively while W18O49 films show randomly dispersed nanowires with average diameter of ∼50 nm and maximum length of ∼30 μm. Owing to bandgap shift in visible range, porous surface structures and crystallinity, the nitrogen doped TiO2–W5O14 nanocomposite thin films are found to exhibit better (i) photohydrophilicity with water contact angle of ∼7° in 2 h under UV-A irradiation and (ii) photocatalytic efficiency with methylene blue degradation rate of −1.12μmol/(l.d), −0.78 μmol/(l.d) under ultraviolet and visible light sources, respectively.