Visible-light-activated Cu and Fe-doped TiO2 thin films on glass: photocatalytic, antibacterial and self-cleaning performance

In this study, TiO 2 thin films doped with varying loadings of Cu and Fe (0.8, 1.5, 2.2, and 3.0 wt.%) were synthesized via sol–gel dip-coating onto glass substrates at room temperature. The structural and optical properties of the photocatalysts were characterized using X-ray diffraction and specific surface area analyses, field emission scanning electron microscopy (FE-SEM), photoluminiscence and UV–Vis spectrophotometry. Photocatalytic performance was evaluated through methylene blue (MB) degradation, water contact angle (WCA), and Escherichia coli inactivation under visible light. Doping TiO 2 with Cu²⁺ and Fe³⁺ affected nanoparticle size and modified optical absorption, reducing the band gap. XRD confirmed anatase as the dominant crystalline phase for both pure and doped TiO 2 calcined at 500 °C, with crystallite sizes of 11–30 nm. Tauc plot analysis showed band gap narrowing from ∼3.20 eV for pure TiO 2 to ∼2.65 eV for Fe–TiO 2 and ∼2.40 eV for Cu–TiO 2 . Cu-doped TiO 2 exhibited enhanced MB degradation at low dopant levels, but activity declined beyond 0.8% Cu, likely due to agglomeration. Fe-doped TiO 2 showed progressive activity increases with higher dopant concentrations. Additionally, 0.8% Cu- and 3% Fe-doped TiO 2 displayed greater hydrophilicity (WCA 9.8° and 18°, respectively) than pure TiO 2 under visible light. Comparing both dopants, 0.8% Cu-TiO 2 achieved higher MB degradation than 3% Fe–TiO 2 . Antibacterial assays revealed that Cu–TiO 2 had superior activity against Escherichia coli compared to pure and Fe-doped TiO 2 . The best levels for enhanced hydrophilicity and photocatalytic performance were identified as 0.8% Cu and 3.0% Fe, respectively.