Green and Sustainable Synthesis of Silver and Gold Nanoparticles: A Stevia Leaf Extract Approach

Silver and gold nanoparticles were synthesized by reducing silver and gold ions using previously unexplored stevia extracts prepared with water, methanol, and ethanol as solvents. These extracts served as both reducing and stabilizing agents. The nanoparticles were characterized using ultraviolet-visible (UV-Vis) spectroscopy, which confirmed surface plasmon resonance (SPR) at 400-450 nm for AgNPs and 500-550 nm for AuNPs, with an additional peak at 650-700 nm. Zeta potential analysis revealed polydispersity index (PdI) values of 0.269, 0.328, and 0.184 for AgNPs, and 0.428, 0.366, and 0.408 for AuNPs in water, ethanol, and methanol extracts, respectively. The Z-average particle sizes were 68.66, 163.9, and 146.4 nm for AgNPs, and 207.2, 96.27, and 160.6 nm for AuNPs. TEM images confirmed that the nanoparticles were spherical and well-dispersed. FTIR analysis indicated that functional groups such as hydroxyl and carbonyl from the stevia extracts were involved in the reduction and stabilization of nanoparticles. This study highlights the potential of Stevia rebaudiana extracts as efficient, eco-friendly agents for the synthesis of metallic nanoparticles, offering a sustainable alternative to conventional chemical and physical methods with potential applications in antimicrobial and biomedical fields.