Aqueous synthesis of stable silver nanoparticles for efficient photocatalytic degradation of Rhodamine B

The development of simple and reproducible methods for preparing functional nanomaterials is important for catalytic and environmental applications. In this study, stable silver nanoparticles (AgNPs) were prepared through an aqueous-phase chemical reduction method using silver nitrate (AgNO₃) as the silver precursor, sodium borohydride (NaBH 4 ) as the primary reducing agent, and trisodium citrate as a stabilizing/capping agent. The synthesis was conducted under ambient conditions using water as the reaction medium and without organic solvents. The formation and physicochemical properties of the AgNPs were investigated using UV–Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), XPS, FTIR, and dynamic light scattering (DLS). The nanoparticles exhibited a characteristic surface plasmon resonance band at approximately 424 nm and crystalline reflections consistent with the face-centered cubic structure of metallic silver. SEM revealed predominantly spherical nanoparticles (20 nm), while DLS provided information on their hydrodynamic size distribution. The photocatalytic performance of the synthesized AgNPs was evaluated using Rhodamine B (RhB) as a model dye pollutant under 254 nm UV irradiation. The AgNPs achieved approximately 82% reduction in RhB absorbance within 60 min under the investigated conditions. Kinetic analysis showed that the experimental data were best described by a pseudo-first-order model, with a rate constant of 0.0123 min⁻¹. The observed decrease in RhB absorbance indicates substantial decolorization/apparent removal, while TOC and COD analyses indicate partial mineralization of the organic matter. Overall, this study demonstrates a straightforward aqueous chemical reduction route for preparing stable AgNPs with measurable photocatalytic activity toward RhB removal.