An eco-friendly, plant-mediated synthesis of antibacterial magnesium oxide nanoparticles using <i>Vernonia amygdalina</i> (bitter leaf)

Abstract

Green synthesis of metal oxide nanoparticles offers a promising, eco-friendly, and cost-effective solution. This study reports the first-time utilization of an aqueous leaf extract of Vernonia amygdalina as a bio-reducing and stabilizing agent for the synthesis of magnesium oxide nanoparticles (MgO-NPs). The influence of precursor concentration (0.1 M, 0.2 M, and 0.4 M magnesium nitrate hexahydrate) on the nanoparticle characteristics was investigated. The synthesized MgO-NPs were systematically characterized using Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectrophotometry, and X-ray diffraction (XRD). FTIR confirmed the role of plant-derived functional groups in the capping process, while UV–Vis spectrophotometry revealed that a higher precursor concentration resulted in a smaller optical band gap. XRD analysis verified the face-centered cubic crystalline structure of the nanoparticles, with a calculated average crystallite size of 11.94 nm, and showed that purity improved with increasing precursor concentration. The antibacterial efficacy, assessed by the disk diffusion method, demonstrated that the MgO-NPs exhibited significant, dose-dependent growth inhibition against both gram-negative Escherichia coli and gram-positive Staphylococcus aureus. This work confirms that V. amygdalina extract is an effective green agent for synthesizing crystalline MgO-NPs with potent antibacterial activity, positioning them as promising alternatives to conventional antibiotics.