Green synthesis of ZnO-NiO nanocomposite using <i>citrus sinensis</i> peel extract and their significant antibacterial properties against series of pathogenic strains

This paper discusses the green synthesis of a ZnO-NiO nanocomposite using an extract of <i>citrus sinensis</i> peel as a capping and reducing agent. The green synthesized nanocomposite was characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Ultraviolet-Visible Spectroscopy (UV-Vis) techniques. XRD is explored for crystallinity, and the crystalline size is found to be 36 nm for the nanocomposite. EDX is utilized for purity, and FTIR is used to establish the composition of the nanocomposites. SEM revealed that ZnO-NiO nanocomposites have a spherical-like surface morphology. The bandgap of the green synthesized nanocomposite is found to be 3.08 eV from reflectance data. By calculating the Zone of inhibition (ZOI) using the agar well diffusion method, the antibacterial activity (ABA) was investigated against three Gram-positive strains and five Gram-negative bacterial strains. The ZOI values for different bacterial strains ranges from 3 ± 0.5 mm to 16 ± 0.5 mm for a 75 µL nanocomposite concentration. The findings in the present work demonstrate that with an increase of the concentration of ZnO-NiO nanocomposite, their antibacterial activity (ABA) also increases, suggesting its merit in showing broad applicability for various uses in medicine.