Impact of copper doping on optical, UV induced wettability and photo-catalytic properties of sol-gel synthesized ZnO thin films

Self-cleaning properties concerning with photo-catalytic activity of thin films are important to develop pollutant-free functional surfaces for various applications. In this work, enhanced self-cleaning properties (photo-catalytic properties) as well as UV induced wettability of ZnO thin films were achieved by the doping of copper through sol-gel spin coating method. X-ray diffraction pattern revealed c-axis and a-axis plane dominance for ZnO and Cu doped ZnO (CuZnO) films, respectively. Scanning electron microscopy images showed nano-grain surface for CuZnO films. Optical transmittance was found in the range 90–79%. Optical band gap values were estimated between 3.34 and 3.39 eV. CuZnO films were found to exhibit hydrophilic state having water contact angle (WCA) in the range of 35° to 57°. Irradiance with UV light produced super-hydrophilic state in all prepared films. Contact angle reduction rate was found best in case of 6% doped CuZnO thin film. The recovery time of contact angle was between 20 and 22 h for all the films. Photo-catalytic effect was evaluated with methylene blue (MB) and methyl orange (MO) dyes and better reduction rate of 38.4% and 40% respectively was attained with 6% Cu doped film. Moreover, MB & MO stain removal was observed.