Effect of Gold Nanoclusters on the Production of Ti3+ Defect Sites in Titanium Dioxide Nanoparticles under Ultraviolet and Soft X-ray Radiation

The production rate and saturation point of Ti³⁺ defect sites on titanium dioxide P-25 and anatase nanoparticles doped with Au₁₀₁(PPh₃)₂₁Cl₅ (Au₁₀₁) metal nanoclusters were investigated under synchrotron X-ray irradiation alone, as well as combined X-ray and UV radiation. The saturation point in the growth of the normalized relative populations of Ti³⁺ centers on anatase and P-25 titania nanoparticles with and without Au₁₀₁ nanoclusters present at the surface was found to vary with the type of support. It was influenced by the presence of gold nanoclusters: a higher concentration of Ti³⁺ centers was generated where gold nanoclusters were deposited onto anatase nanoparticles and irradiated by both X-ray and UV photons, compared with X-ray irradiation alone. Conversely, all samples based on the TiO₂ P-25 support displayed reduced levels of Ti³⁺ center populations at the saturation points under combined X-ray and UV combined radiation, compared to the samples exposed exclusively to X-ray radiation. The initial rate of production of Ti³⁺ defect sites was found to decrease for combined UV and X-ray irradiation in the case when Au₁₀₁ was deposited onto anatase. However, the opposite trend in the initial production rate of Ti³⁺ centers was observed in the case of Au₁₀₁ deposited onto the TiO₂ P-25 surface.