Influence of transition metal ion Ni2+ on optical, electrical, magnetic and antibacterial properties of phyto-synthesized CuO nanostructure

In the present work, nanostructured copper oxide (CuO) doped with various concentrations of Ni (0.003/0.006/0.009M) ions were prepared using the Azadirachta indica (A. indica) leaf extract. X-ray diffraction patterns confirmed that synthesized nanoparticles have monoclinic structure. The nanoflower like morphology and chemical composition were identified using FESEM and EDX spectra. The characteristic Cu-O stretching band is observed in the FTIR spectra. UV-Vis spectra show band gap variation from 2.72 to 2.9eV for pure CuO and Ni ion doped CuO NPs. Intensity of photoluminescence is found to increase with doping due to the substitution of Ni2+ ions into CuO lattice sites. Physical properties such as dielectric constant, dielectric loss and ac conductivity have been studied with regard to temperature, frequency and extent of doping. It is found that dielectric constant decreases with increase in frequency. The AC conductivity increases as temperature and frequency increase in all samples based on Koop's phenomenological theory. Enhancement in saturation magnetization and ferromagnetic properties of Ni doped CuO has been observed in VSM studies taken at room temperature. The antibacterial studies performed against Gram positive (Staphylococcus aureus and Streptococcus pneumoniae) and Gram negative (Escherichia coli and Klebsiella pneumonia) bacterial strains show enhanced antibacterial activity on doping.