Structural, morphological, and magneto-optical investigations of pure and (Sn, Zn) co-doped CuO nanoparticles: A novel corrosion inhibitor in acidic media

Abstract

The present study reports work to synthesize metal oxide semiconductors of pure and (Sn, Zn) co-doped copper oxide (CuO) nanoparticles, with the chemical formula of Cu1–2xSnxZnxO (x = 0.000, 0.005, 0.010, and 0.020), via the co-precipitation method. The structural, morphological, optical, and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV–vis), photoluminescence spectroscopy (PL), and vibrating-sample magnetometer (VSM), respectively. XRD results revealed the successful preparation of the monoclinic CuO phase, with small traces of secondary phase SnO appearing at samples of x = 0.010 and x = 0.020. The size of the prepared nanoparticles, obtained from XRD and TEM, showed an overall decrease when increasing the (Sn, Zn) co-doping concentrations, leading to an increase in the surface area appropriate for magnetic applications. At samples of x = 0.005 and x = 0.010, the co-dopants changed morphology from large spheres into nanorods and nanokernels. The diameters of the nanorods increased from 8.5 nm to 24.15 nm, while their lengths decreased from 51 nm to 48 nm. However, a flower-shaped nanostructure was observed in the x = 0.020 sample. FTIR confirmed the fingerprint vibration modes represented by antisymmetric vibration νas(Cu─O) in the crystal lattice. The first decrease in size was accompanied by a decrease in the energy gap caused by the lattice shrinkage, which in turn is caused by the vacancies and energy states in the bandgap stimulated by Sn and Zn ions. Following this decrease, there was an increase in the energy gap because of the shift in Fermi level to a higher energy state that is suitable for solar cell applications. PL results confirmed the excitation dependence nature of these nanoparticles. Correspondingly, the prepared nanoparticles can be utilized as potential applicants for blue chip and near-UV white light-emitting devices. VSM data revealed that paramagnetic and weak ferromagnetic behavior coexist in the co-doped nanoparticle samples. Through the electrochemical impedance spectroscopy and polarization measurements, the anticorrosion performance of these nanoparticles on mild steel has been studied in 0.5 M HCl solutions at 30 °C. The impedance results revealed that the corrosion process takes place under activation control. The polarization measurements showed that the prepared nanoparticles behave as a mixed-type inhibitor with 83 % efficiency in the x = 0.020 sample.