MgO Nanoparticles Based on Plant Extract-Assisted Green Synthesis: Structural Modulation and Antibacterial Mechanism Studies

MgO nanoparticles have garnered significant interest owing to their stability, environmental safety, and biocompatibility. However, the low antimicrobial activity of these nanoparticles limits their widespread utilization. Moreover, conventional methods to synthesize MgO nanoparticles are inefficient, costly, and harmful to the environment. To address these limitations, this study introduces a green synthesis approach using plant extracts as fuels. We systematically investigated the effect of three plant extracts, namely, Moringa oleifera Lam. leaves, [Formula: see text] (Aiton) Willd. leaves (London plane tree) and Camellia sinensis (L.) Kuntze leaves, on the microstructure and antimicrobial properties of MgO nanoparticles. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed spherical particles with small sizes ([Formula: see text]25[Formula: see text]nm). X-ray diffraction analysis outcomes confirmed that the synthesized MgO nanoparticles had high purity. Fourier-transform infrared spectroscopy confirmed the presence of Mg–O bonds (400–770[Formula: see text]cm[Formula: see text]. The plate-coating count test confirmed that MgO nanoparticles derived from Moringa oleifera, [Formula: see text] and Camellia sinensis displayed excellent antibacterial performance, achieving bactericidal rates of 99.99%, 99.92% and 99.99% against Escherichia coli, respectively, and 99.87%, 99.31% and 99.91% against Staphylococcus aureus, respectively. X-ray photoelectron spectroscopy (XPS) revealed higher oxygen vacancy concentrations in the sample synthesized using C. sinensis extract (61.75%) compared with those synthesized using M. oleifera (52.53%) and [Formula: see text] (46.28%). Electron paramagnetic resonance (EPR) further confirmed the generation of reactive oxygen species (ROS) associated with these vacancies. The zeta potentials of the samples synthesized with C. sinensis, M. oleifera and [Formula: see text] were 6.7[Formula: see text]mV, 9.8[Formula: see text]mV and 9.9[Formula: see text]mV, respectively, which facilitated strong electrostatic interaction with bacterial membranes. Together, these results demonstrate the dual antimicrobial mechanism of ROS-induced cytotoxicity and mechanical damage.