Synthesis and Characterization of SCDs/TiO2 Composite

Synthesis of sulphur-doped carbon nanodots immobilized on the TiO₂ surface (SCDs/TiO₂) composite was carried out using the sol-gel method with SCDs and titanium tetraisopropoxide (TTIP) as precursors. SCDs were prepared from citric acid monohydrate, urea, and sodium disulphite using the microwave technique. SCDs/TiO₂ was then visually observed under UV 365 nm and characterized by UV-Vis diffuse reflectance spectrophotometry (UV-Vis/DRS), Photoluminescence (PL) spectroscopy, Fourier transform infrared (FT-IR), and X-ray diffraction (XRD). The SCDs/TiO₂ composite product had a brown solid with a green luminescent under UV light. Furthermore, UV-Vis/DRS for variations in SCDs concentrations of 0.5%; 1.25%, and 2.5% showed Eg values of 2.33 eV, 2.14 eV, and 1.61 eV, respectively. The results showed that SCDs caused the maximum emission peak (λ_Em) to redshift and also affected the intensity of PL TiO₂. There was also a shift in the absorption peak towards the visible light region. Based on the results, the 0.5% SCDs/TiO₂ was the optimum concentration with the lowest intensity as an indication of separation of the (e^-) and (h⁺) charge pairs, which greatly enhanced the photocatalytic efficiency.