Facile green synthesis of Cu₂O nanoparticles using Azadirachta indica extract and evaluation of their activity against Staphylococcus aureus

Copper(I) oxide (Cu₂O) nanoparticles were synthesized using Azadirachta indica (neem) leaf extract as a reducing and stabilizing agent. Previous reports on neem-mediated synthesis have mainly dealt with CuO or metallic Cu nanostructures; but the present study targets the Cu₂O phase and evaluates its activity against Gram-positive bacterium, Staphylococcus aureus . The synthesis was carried out in water at 60 °C without using any toxic chemicals. The nanoparticles were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. XRD indicated crystalline cubic Cu₂O, UV-Vis spectroscopy showed a broad absorption maximum at 601 nm (about 2.06 eV), and SEM showed agglomerated particles made up of nanoscale primary particles. Activity against S. aureus was evaluated by the disc diffusion method. The nanoparticles resulted in increased zones of inhibition with concentration (2.5 ± 0.2, 2.7 ± 0.05 and 2.9 ± 0.15 mm at 0.5, 1 and 2 mg/mL, respectively), when compared with 2.5 ± 0.1 mm for tetracycline (10 µg) and no inhibition for the negative control (0.5% DMSO). The comparison with tetracycline was qualitative. Overall, the study presents a simple green route to synthesis of Cu₂O nanoparticles that inhibit S. aureus in vitro; and findings of antibacterial activity and its possible scope for related use.