Green Synthesis and Physicochemical Characterization of NiO-ZnO Nanocomposites Derived from Aloe barbadensis Miller Leaf Extract

Abstract

Green nanotechnology has emerged as an environmentally sustainable approach for synthesizing nanomaterials using plant-based extracts. Aloe vera-mediated synthesis offers an eco-friendly alternative for producing ZnO-based nanocomposites with enhanced structural, dielectric, and antimicrobial properties suitable for advanced biomedical and electronic applications. This study investigates the structural, optical, and biological properties of NiO-ZnO nanocomposites synthesized via a sustainable green sol-gel method using Aloe vera (Aloe barbadensis Miller) leaf extract. X-ray diffraction (XRD) analysis confirmed the formation of crystallite size ranging from 19 to 20 nm. The nanocomposites exhibited a hexagonal wurtzite structure for ZnO and a fcc structure for NiO. Fourier transform infrared (FTIR) spectroscopy confirmed the presence of metal-oxide stretching vibrations in the 400–600 cm⁻¹ range. Scanning electron microscopy (SEM) identified hexagonal and spherical morphologies with particle clusters measuring 250–350 nm. Dielectric studies indicated that the dielectric constant and loss tangent can be tuned by varying the NiO doping concentration, with the 5% NiO-ZnO composite exhibiting the highest dielectric constant. Furthermore, the 10% NiO-ZnO composite demonstrated superior antimicrobial activity against Bacillus cereus and Klebsiella pneumoniae compared to the standard antibiotic Tetracycline. These results suggest that green-synthesized NiO-ZnO nanocomposites are promising candidates for advanced dielectric and biomedical applications.