The conventional synthesis of nanoparticles often relies on toxic synthetic chemicals, raising concerns regarding environmental sustainability and ecological impact. In response, green synthesis utilizing phytochemicals has emerged as a promising alternative, offering a renewable, biodegradable, and environmentally benign platform for nanomaterial fabrication.

This study reports a green synthesis of magnesium oxide nanoparticles (MgO NPs) using an aqueous extract from the fruit shells of Strychnos pungens as an underutilized agro-waste product. The water-soluble phytochemicals present in the shell extract served as effective chelating and stabilizing agents during the chemical precipitation of magnesium ions, facilitating the formation of MgO NPs.

The structural and morphological properties of the biosynthesized nanoparticles were thoroughly characterized. X-ray diffraction (XRD) analysis confirmed the crystalline nature of the NPs, revealing a face-centered cubic structure with characteristic peaks at 2θ = 37.94°, 42.99°, 62.33°, 74.83°, and 78.76°. The average crystallite size was determined to be 9.8 nm and 18.59 nm via the Debye–Scherer and Williamson–Hall methods, respectively. Scanning electron microscopy (SEM) revealed an irregular morphology with microparticle aggregates ranging from 0.5 to 1.0 µm. Elemental composition analysis by energy dispersive X-ray spectroscopy (EDX) confirmed the predominant presence of magnesium and oxygen, unequivocally verifying the successful formation of MgO.

This work not only demonstrates the successful green synthesis and characterization of MgO NPs but also highlights the potential of Strychnos pungens fruit shells as a valuable, sustainable resource for advanced nanomaterial production, aligning with the principles of circular economy and green chemistry.