The extensive use of synthetic dyes in industrial sectors such as textile, leather, and paper manufacturing generates large volumes of colored wastewater, posing serious risks to human health and the environment. Semiconductor photocatalysis has emerged as an efficient and environmentally friendly strategy for the degradation of organic pollutants in water. Among semiconductor materials, TiO₂ nanoparticles have attracted considerable attention due to their chemical stability, low cost, and non-toxicity; however, their photocatalytic efficiency is often limited by rapid electron–hole recombination and limited light absorption. Rare-earth ion doping has been proposed to overcome these limitations.
In this study, pure TiO₂ and Sm³⁺-doped TiO₂ nanoparticles were successfully synthesized via a sol–gel method. The structural, morphological, textural, optical, and photoluminescent properties of the nanoparticles were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, UV–Vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. Photocatalytic activity was evaluated by the degradation of methylene blue (MB) in aqueous solution under UV irradiation. Experiments were conducted using 50 mL of MB solution with an initial concentration of 20 mg·L⁻¹, while photolysis tests confirmed that no degradation occurred in the absence of a photocatalyst.
The results indicate that Sm³⁺ doping significantly enhances the photocatalytic activity of TiO₂ nanoparticles. After 90 min of irradiation, pure TiO₂ achieved a degradation efficiency of approximately 20%, corresponding to an apparent quantum yield (AQY) of 0.7%, whereas Sm³⁺-doped TiO₂ nanoparticles reached about 80% degradation, with an AQY of 2.8% under identical conditions. The enhanced photocatalytic performance is attributed to improved light absorption and reduced electron–hole recombination induced by Sm³⁺ incorporation. These findings demonstrate that Sm³⁺-doped TiO₂ nanoparticles are promising photocatalysts for efficient wastewater treatment applications.
