Influence of Raw-Material Processing on Gold and Silver Nanoparticles Stability Using Ultrasound-Extracted...

The ultrasound-assisted green synthesis of gold (AuNPs) and silver nanoparticles (AgNPs) from Schinus terebinthifolius extracts delivered stable colloids whose physicochemical properties depend on raw-material preprocessing. Ground sonicated extracts (GSE) produced narrower size distributions and more negative zeta potentials (-19.6 mV for AuNPs, -23.5 mV for AgNPs) than unprocessed sonicated extracts (USE), which favored aggregation, especially at 100°C. Surface-plasmon resonance (SPR) red-shifted for AuNPs-USE, indicating larger particles. High-resolution transmission electron microscopy (TEM) corroborated these trends: GSE-derived AgNPs formed 15-40 nm quasi-spheres, whereas USE yielded fused dendritic assemblies of 20-80 nm subunits; AuNPs ranged from densely coalesced 8-25 nm chains (100°C) to isolated spheres (25°C). Coherent lattice fringes with d = 0.23 nm {1 1 1} and 0.20 nm {2 0 0} confirmed phase-pure fcc structures, and fringe continuity across AgNP necks evidenced oriented attachment. Collectively, the data show that extract grinding enhances nucleation control, crystallinity, and colloidal stability, providing a scalable route to biogenic AuNPs and AgNPs for biomedical, catalytic, and food-preservation applications.