Green synthesis of nickel oxide nanoparticles using Allium cepa stalks and investigation of their antibacterial activity

The most prominent inorganic antibiotic alternatives are metallic or metal oxide nanoparticles. Green-synthesized nickel oxide nanoparticles (NiONPs), known for their anti-inflammatory, antibacterial, and potential anticancer properties, and hold significant promise for novel biomedical applications. In this work, the extract of Allium cepa stalks was used as a precursor to synthesize NiONPs from nickel nitrate using the co-precipitation method. The antibacterial activity of NiONPs was examined after confirming the formation of NiONPs by investigating different physicochemical properties using UV–Vis spectroscopy, SEM, XRD, EDX, and FTIR. An absorption peak at 318.467 nm in the UV–Vis spectrum confirmed the formation of NiONPs. A highly crystalline face-centered cubic lattice, having an average size of 18.96 ± 1.6072 nm, was determined by XRD. SEM analysis revealed the surface morphology of the synthesized NiONPs, which was spherical in shape. A prominent peak at 509.21 cm −1 in the FTIR spectrum confirmed NiO formation, while the same analysis also identified functional groups responsible for stabilizing and capping the NiONPs. The antibacterial activity of NiONPs was quantitatively assessed against a gram-positive ( Streptococcus aureus ) bacterial strain and observed mortality rates of bacteria were 53.18 % after 20 h, whereas it reached 85.43 % after 24 h. This green synthesis approach using Allium cepa stalks successfully produced NiONPs exhibiting strong antibacterial activity against Gram-positive bacteria.