Biosynthesis of Cu-doped Zinc Oxide nanoparticles Using Leaf Extract of Azadirachta indica: Antibacterial Properties and Application in Photocatalytic Degradation

Abstract

The green synthesised Zinc Oxide and Copper-doped Zinc Oxides are oxide-based photocatalysts possessing nanostructures and show efficient photocatalytic degradation of organic pollutant i.e. Methylene Blue (MB) dye and effective antimicrobial activities against Staphylococcus aureus and Bacillus subtilis gram positive bacteria. The photocatalytic degradation has been studied under a constant source of visible light and the antimicrobial activity has been studied using agar dilution or the disk diffusion method. The doped oxides of general formula Zn1-xCuxO(x= 0.005, 0.01 and 0.02) were synthesised by calcination process in a muffle furnace and were obtained in powder form. The sample powder was characterised by Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDAX), X-ray Diffraction (XRD), Dynamic Light Scattering (DLS) and Atomic Absorption Spectroscopy (AAS). The formation of phase-pure materials with a wurzite structure was indicated by XRD. FESEM images reveal that prepared sample exhibit nanoscale structure. The elemental composition of the sample was confirmed by the EDAX spectroscopy which verified the correct stoichiometry of the oxides. The photocatalytic activity of the sample was evaluated by studying its performance in degrading methylene blue, an organic water pollutant under specific pH conditions and a constant dose of irradiation over duration of several hours. The results demonstrated significant visible light photocatalytic activity that was dependant on the duration of irradiation. With the goal of determining the optimal doping level for enhanced degradation performance, Zn0.99Cu0.01O with the ideal doping amount, demonstrated the highest degrading efficiency of 72% after approximately 90 minutes. The Cu-doped ZnO nanoparticles synthesized via a green method also exhibited enhanced antimicrobial activity against Gram-positive bacteria which can be attributed to the synergistic effect of Cu and ZnO. These findings suggest potential applications in medical and environmental fields.