Eco-Friendly Synthesis of Nickel Oxide Nanoparticles Using Microtrichia perotitii DC Plant Extract: Structural Characterization and Antibacterial Activity

The growing demand for sustainable nanomaterials has intensified interest in green synthesis routes that utilize plant-derived biomolecules as reducing and stabilizing agents. In this study, nickel oxide nanoparticles (NiO NPs) were synthesized for the first time using Microtrichia perotitii DC leaf extract, a medicinal plant known for its rich phytochemical profile and traditional therapeutic applications. Nickel (II) chloride hexahydrate (NiCl₂·6H₂O) served as the precursor, while the phytochemicals present in the extract flavonoids, alkaloids, tannins, phenolics, and saponins facilitated nanoparticle formation and stabilization. The NiO NPs were characterized using UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), and Thermogravimetry/Differential Thermal Analysis (TG/DTA). XRD confirmed crystalline nanoparticles with an average crystallite size of 24 nm, while FTIR revealed a strong Ni–O stretching vibration at 651 cm⁻¹. SEM analysis showed irregular, agglomerated structures, and TG/DTA confirmed good thermal stability with major decomposition attributed to phytochemical residues. Antibacterial assays demonstrated that the biosynthesized NiO NPs exhibited strong inhibitory effects, particularly against Bacillus subtilis and S. aureus (18.8±0.6 and 19.6±0.40 mm zone of inhibition) Although this activity was slightly lower than that of ciprofloxacin (5 µg/disc, 22.4 ± 0.50 mm and 23.1 ± 0.43 respectively), it indicates strong antibacterial potential for the biosynthesized NiO NPs. Gram-negative strains exhibited lower sensitivity, likely due to their outer membrane barrier. This first report of M. perotitii-mediated NiO NP synthesis highlights the plant’s untapped potential for eco-friendly nanomaterial production and underscores the applicability of these nanoparticles in biomedical and environmental fields.