Exploration of the antibacterial and photocatalytic properties of copper oxide (CuO) nanoparticles synthesized from Azadirachta indica leaf extract and electronic waste cable

Abstract

This study examined the antibacterial properties of CuO nanoparticles derived from Azadirachta indica leaf extract and waste Cu wire as a source of CuNO₃. This environmentally friendly material efficiently facilitated the breakdown of industrial pollutants (dye and ciprofloxacin). The X-ray diffraction (XRD) analysis confirmed that the produced sample was CuO, with a crystallite size ranging from 5 to 92 nm, determined using the Sahadat–Scherrer, Monshi–Scherrer, Halder–Wagner, size-strain plot, and Williamson–Hall methods and the linear straight-line method of Scherrer's equation. A thermogravimetric analyzer confirmed three stages of weight loss (totaling 30.22%), while scanning electron microscopy revealed spherical-shaped NPs. The elemental composition (76.55% Cu and 23.45% O) was confirmed through energy-dispersive X-ray spectroscopy. Fourier transform infrared spectroscopic analysis, along with XRD, confirmed the presence of Cu–O bonding, indicating the generation of CuO NPs. The degradation percentages of CR dye (95%) and ciprofloxacin (80%) were estimated at a 20 ppm concentration (pH 7) using 0.1 g of catalyst, with degradation occurring over 120 min and 210 min, respectively. The computed rate constants, based on the Langmuir–Hinshelwood model equation, were 0.0198 min⁻¹ for CR dye and 0.0047 min⁻¹ for ciprofloxacin. The zones of inhibition for two Gram-positive bacteria were 27 mm (Staphylococcus aureus) and 14 mm (Bacillus megaterium), while for Gram-negative bacteria, the zones were 20 mm (Escherichia coli) and 13 mm (Salmonella typhi).