Integrating plant-based green chemistry into sustainable nanomaterial production: eco-friendly synthesis of functional metal oxide nanoparticles

The increasing demand for sustainable nanomaterial production has driven the development of environmentally friendly synthesis routes that minimize the use of hazardous chemicals. Green synthesis using plant-derived extracts represents a promising alternative by exploiting naturally occurring phytochemicals as reducing and stabilizing agents. This study aimed to develop a sustainable process for the green synthesis of Fe₃O₄, ZnO, MgO, and NiO nanoparticles using local medicinal plant extracts and to evaluate the physicochemical properties of the resulting nanomaterials. Plant decoctions and hydrodistillates were prepared under controlled extraction conditions and employed as reducing and capping agents during the alkaline precipitation of metal salts. The synthesis process was optimized by controlling pH, temperature, agitation, and NaOH addition. The obtained nanoparticles were purified, dried, and characterized by X-ray diffraction (XRD), laser granulometry, scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). XRD analysis confirmed the successful formation of crystalline Fe₃O₄, ZnO, MgO, and NiO nanoparticles, with crystallite sizes ranging from 5 to 20 nm. Laser granulometry revealed particle sizes ranging from approximately 129 to 2700 nm, depending on the plant extract and metal precursor, reflecting varying degrees of aggregation. SEM images showed predominantly spherical nanoparticles with extract-dependent morphology. Fe₃O₄ nanoparticles exhibited soft magnetic behavior with a saturation magnetization of 45.36 emu g⁻¹, low coercivity (25.75 Oe), and negligible remanence, demonstrating their suitability for magnetic applications. The proposed green synthesis process provides a simple, cost-effective, and environmentally benign alternative to conventional chemical methods. Plant extracts efficiently served as both reducing and stabilizing agents, enabling the production of metal oxide nanoparticles with desirable structural, morphological, and magnetic properties while reducing the consumption of hazardous reagents. This sustainable approach offers significant potential for the scalable production of functional nanomaterials for biomedical, pharmaceutical, catalytic, and environmental applications.