Abstract
This study presents the green synthesis of silver nanoparticles (AgNPs) using an aqueous extract of murici (Byrsonima crassifolia) leaves as a reducing and stabilizing agent alongside a 1 mM AgNO₃ precursor. We systematically evaluated the effect of extract volume fraction (20% and 30% v/v) and pH (~6, 8.0, and 10.0) on reduction kinetics and particle dimensions. Reactions were monitored via UV-Vis spectroscopy. Results indicate that an alkaline environment (pH 10) drives reaction efficiency. The optimal condition (30% extract, pH 10) presented a well-defined surface plasmon resonance absorbance band at 419 nm, estimating particle sizes to be below 50 nm, and maintained spectral stability over 60 minutes. Unlike pH ~6, which caused heterogeneous growth, pH 10 resulted in narrow bandwidths (FWHM < 100 nm), indicating lower polydispersity. Zeta potential analysis (< -24 mV) confirmed the negative surface charge of the nanoparticles, evidencing electrostatic repulsion and subsequent colloidal stability. This scalable route avoids hazardous chemicals, providing a reliable methodology for producing AgNPs for potential catalytic, sensing, and biomedical applications.

Acknowledgments: Financed by CAPES (Finance Code 001) and FAPEPI (Doctoral fellowship to P.S.C., Edital Nº 003/2025; Project "Ciência, Inovação e Sustentabilidade" at UFPI).