Eco-Friendly Synthesis of Iron Oxide Nanoparticles Using Plants: Structural Insights and Biological Significance

Iron oxide nanoparticles (FeONPs) have emerged as an important class of nanomaterials owing to their remarkable magnetic, physicochemical, catalytic, and biocompatible properties. Various forms of iron oxides, including hematite, magnetite, maghemite, ferrihydrite, and wüstite, exhibit distinct crystal structures, space groups, lattice parameters, morphologies, and functional characteristics that significantly influence their properties and applications. Although several physicochemical methods have been developed for the synthesis of FeONPs, these approaches often involve toxic chemicals, high energy consumption, and harsh reaction conditions. Consequently, plant-mediated green synthesis has attracted considerable attention as a sustainable and eco-friendly alternative, where phytochemicals serve as natural reducing and stabilizing agents during nanoparticle formation. Compared with conventional methods, green synthesis offers several advantages, including low toxicity, cost-effectiveness, environmental compatibility, and suitability for large-scale production. Owing to their multifunctional nature, green synthesized FeONPs have shown promising potential in antimicrobial, anticancer, and many other biological applications. This review highlights the different forms of iron oxide nanoparticles, their structural and physicochemical characteristics, plant-mediated green synthesis strategies, and emerging biological applications