Antioxidant, Antimicrobial, and Molecular Binding Affinity Applications of Green‐Synthesized Nickel Oxide Nanoparticles

ABSTRACT The preparation of metal or metal oxide nanoparticles (NPs) using the green method is rapid, low‐cost, and eco‐friendly. In this study, nickel oxide NPs (NiO NPs) were synthesized using Foeniculum vulgare seed extract. The green‐synthesized NiO NPs were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images revealed spherical and sheet‐like morphologies. The NiO NPs exhibited notable antioxidant, antimicrobial, and molecular interaction properties. Antioxidant activity was evaluated using DPPH + and ABTS + assays, showing IC 50 values of 12.68 ± 0.56 and 11.82 ± 0.84 µg/mL, respectively, compared to standard antioxidants ascorbic acid (8.94 ± 2.2 µg/mL) and gallic acid (1.2 ± 0.67 µg/mL). Antibacterial assays against Staphylococcus aureus , Bacillus sp., Pseudomonas aeruginosa , and Escherichia coli revealed concentration‐dependent inhibition, with maximum zones of inhibition at 80 µg/mL, measuring 7.86 mm for E. coli and 7.21 mm for S. aureus . Antifungal activity showed dose‐dependent inhibition of Aspergillus niger (6.00–7.96 mm) but minimal effect on Fusarium sp. (6.00–6.03 mm), compared to ketoconazole controls (9.36 and 9.21 mm, respectively). Molecular docking revealed strong binding affinities of NiO NPs with P. aeruginosa (−9.9 kcal/mol) and A. niger endoglucanase (−8.5 kcal/mol), comparable to streptomycin (−11.1 kcal/mol) and ketoconazole (−10.0 kcal/mol). These findings highlight the promising antioxidant and antimicrobial potential of NiO NPs for biomedical applications.