Enhanced UV protection and photocatalytic activity in Samarium and Europium co-doped TiO2 thin films: A durable solution for protective coatings

This study explores Samarium (Sm³⁺)-doped and Europium-Samarium (Eu³⁺: Sm³⁺, 1:1) co-doped TiO₂ thin films for their potential as UV protective coatings. Thin films were fabricated via spin coating using sol–gel-derived powders dispersed in a PVA matrix, enabling uniform deposition on glass substrates. Powder X-ray diffraction (PXRD) analysis revealed that single-doped TiO₂ stabilized the anatase phase, while co-doping introduced some rutile content. With increasing doping concentration, the crystallite size decreased, remaining below 40 nm, which is advantageous for enhancing surface properties. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of characteristic Ti-O bond stretching vibrations at 430 cm⁻¹, consistent with the anatase phase of TiO₂ in all samples. UV–VIS spectroscopy showed strong light absorption below 400 nm and an indirect bandgap of about 3.74 eV, which means it can effectively absorb UV light. Excitation spectra showed a prominent absorption band in the 200–300 nm range, corresponding to intrinsic TiO₂ transitions (O²⁻→Ti⁴⁺). Emission spectra of Sm³⁺-doped TiO₂ exhibited peaks excited at 475 nm, attributed to ⁴G_5/2 → ⁶H_j (J = 5/2, 7/2, 9/2 and 11/2) transitions, while co-doped samples displayed maximum red emission at 612 nm, confirming the presence of both Sm³⁺ and Eu³⁺ ions. The films demonstrated superior UVB (280–320 nm) blocking efficiency (87 %) compared to UVB (320–400 nm) (34 %), as evidenced by transmission spectra. The photocatalytic performance evaluated via methylene blue (MB) dye degradation under UV irradiation indicated an inverse correlation between dye degradation and UV shielding. Durability tests measured under prolonged showed a slight increase (30–40 %) in transmittance within the 200–300 nm range but maintained stability at higher wavelengths. These findings support the efficiency of co-doped and doped TiO₂ thin layers to act as long-term, high-quality ultraviolet-blocking materials and are good applicants to be applied in protective coatings in various industries.