Balancing Reduction and Stabilization: A Kinetic Route to Uniform Spherical Silver Nanoparticles

Silver nanoparticles (AgNPs) are widely investigated due to their unique optical, electronic, and antimicrobial properties, yet challenges remain in achieving rapid, reproducible, and environmentally friendly synthesis. Here, we report a detailed three-component wet-chemical synthesis as an answer to current drawbacks, employing silver nitrate, trisodium citrate, and ascorbic acid as reactants. Systematic investigations revealed the critical role of ascorbic acid concentration in modulating nucleation and growth. The produced AgNPs are spherical and highly uniform, with an average diameter of 43.6 ± 3.3 nm, characterized by a narrow-localized surface plasmon resonance (LSPR) band at 400 nm with a full width at half-maximum (FWHM) of 55 nm, and excellent colloidal stability, confirmed by zeta potential measurements. Deviations from this protocol led to increased polydispersity and anisotropic growth. Complementary studies on citrate concentration highlighted its dual role as a weak reductant but a good stabilizer. Time-resolved kinetic analyses further demonstrated two distinct reaction pathways: a rapid, ascorbic acid-driven reduction where citrate primarily stabilizes the final NPs, as proven by time-dependent SEM images, and a slower reaction route, where citrate contributes simultaneously to reduction and stabilization. This work establishes a clear kinetic framework for controlling AgNP dispersity, highlighting the decisive role of reductant–stabilizer balance and providing a blueprint for scalable, reproducible production of high-quality AgNPs.