Effect of precursors on structural, optical and surface properties of ZnO thin film prepared by spray pyrolysis method: efficient removal of Cu (II) from wastewater

In this study, ZnO thin films were prepared with different precursors using the spray pyrolysis technique, zinc acetate (ZAC-0.2), zinc chloride (ZCL-0.2), and dehydrated zinc nitrate (ZNH-0.2) precursors. The formation of ZnO thin films was confirmed using a variety of characterization techniques, including UV–vis spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction (XRD). The primary aim of this study is to explore how different precursor materials affect the properties of ZnO thin films and to demonstrate the efficacy of these films in removing copper ions from wastewater. The structure, microstructure, and optical properties of these materials were investigated, along with their adsorption activity. The results revealed that all ZnO films exhibited a hexagonal wurtzite crystal structure. The ZAC-0.2 sample demonstrated the highest transparency within the 400–800 nm wavelength range. The sample with the least band gap was ZNH-0.2, with a value of 1.96 eV, and exhibited the highest Urbach energy (Eurb) at 1.150 eV. Moreover, the ZnO thin films displayed high efficiency in removing 80% of copper ions from an aqueous solution.