Exploring the impact of Ag doping on improving the photocatalytic performance of SnO₂ nanoparticles for dye degradation

Silver-modified tin oxide (SnO₂) nanomaterials with different amounts of additive (1, 3, and 5%) were prepared through a simple co-precipitation method to enhance their efficiency in photocatalytic degradation of methylene blue under UV–visible light irradiation. Structural characterization by X-ray diffraction confirmed the formation of a tetragonal rutile phase of SnO₂ and in addition distinct reflections corresponding to face-centered cubic (FCC) phase of silver were observed upon doping, indicating the development of a dual-phase system comprising SnO₂ and metallic Ag with crystallite sizes ranging from 12 to 24 nm. Fourier-transform infrared spectroscopy confirmed the functional group of the synthesized samples by revealing metal–oxygen bonding and surface hydroxyl groups. UV–Vis spectroscopy revealed a blue shift in the absorption edge and an increase in band gap energy with Ag incorporation, suggesting quantum confinement and reduced defect states. Scanning electron microscopy revealed agglomerated flake-like morphologies, and EDX verified the even distribution of Sn, O, and Ag, supporting compositional purity. Thermal analysis (TGA/DTA/DSC) showed melting point reduction upon increased dopant concentration, supporting the increased thermal stability. Photocatalytic activity under visible light irradiation indicated that the highest degradation efficiency (81.53%) against methylene blue was achieved by 1% Ag-doped SnO₂ due to enhanced charge carrier separation and localized surface plasmon resonance effects at low Ag concentration. These findings illustrate that fine-tuning Ag content is essential in achieving maximum photocatalytic efficiency in environmental remediation technologies.