Comparative evaluation of Cu- and Fe-doped TiO₂ photocatalyst under visible light

The purpose of this study was to prepare Cu- and Fe-doped TiO₂ thin films using the sol-gel dipping method, thus determining how the addition of different dopants influenced its optical and antibacterial effectiveness. The structural and optical properties of the resulting photocatalysts were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV–Vis spectroscopy. The photocatalytic performance was evaluated through the degradation of methylene blue (MB) and the inactivation of Escherichia coli (E.Coli) under visible light irradiation. XRD analysis confirmed that the dominant crystalline phase for both pure and doped TiO₂ calcined at 500 °C was anatase, with crystallite sizes ranging from 11 to 40 nm. The optical properties were studied by UV-vis spectroscopy to measure the band gaps in the wavelength range of 300 to 800 nm. The absorbance spectrum of doped TiO₂ films shows that the absorption edge shifted towards longer wavelengths (redshifted) from 380 nm to 440 nm by increasing the amount of dopants. Tauc plot analysis revealed a band gap narrowing from 3.20 eV for pure TiO₂ to 2.65 eV and 2.40 eV for Fe–TiO₂ and Cu–TiO₂, respectively. In terms of photocatalytic activity, both dopants demonstrated greater MB degradation efficiency than pure TiO₂. Furthermore, antibacterial assays under visible light showed that 0.8Cu–TiO₂ possessed superior antimicrobial activity against E.Coli compared to both pure and Fe-doped TiO₂. The optimal doping levels for enhanced photocatalytic and antibacterial performance were identified as 0.8% Cu and 3.0% Fe, respectively.