Photocatalytic Activity of Boron-Modified SnO₂ Nanoparticles for Crystal Violet Removal

Boron (B)-modified SnO₂ samples with various B concentrations (1, 2, and 5 at%) were successfully synthesized using the sol-gel method. The effect of the B/SnO₂ molar ratio on the crystal structure, microstructure, optical, and photocatalytic properties was investigated. The samples were characterized by X-ray diffraction (XRD), N₂ adsorption-desorption experiments, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Diffuse reflectance UV-Vis (DR UV-Vis) and photoluminescence (PL) spectroscopy. A decrease in particle size was observed with increasing B concentration. The B-doped samples exhibited a higher fraction of microporosity and a larger specific surface area than those of undoped SnO₂. FTIR spectra display characteristic absorption of B species. The band gap values were lower than that of bulk SnO₂, and the PL results indicated a reduced electron-hole recombination rate upon boron doping. The presence of defects, such as oxygen vacancies, is highlighted. The nanoparticles exhibited excellent photocatalytic activity toward the degradation of crystal violet (CV) dye, achieving a removal efficiency under UV irradiation of over 90% for the 5 at% B-doped SnO₂ sample after 90 min.