摘要
When exposed to light, TiO <sub>2</sub> nanoparticles (NPs) become photoactivated and create electron/hole pairs as well as reactive oxygen species (ROS). We examined the ROS production and degradation of a widely used azo dye, FD&C Yellow No. 5 (tartrazine), triggered by photoactivated TiO <sub>2</sub> NPs. Degradation was found to follow pseudo-first order reaction kinetics where the rate constant increased with TiO <sub>2</sub> NP concentration. Depositing Au on the surface of TiO <sub>2</sub> largely enhanced electron transfer and ROS generation, which consequently accelerated dye degradation. Alkaline conditions promoted ROS generation and dye degradation. Results from electron spin resonance spin-trap spectroscopy suggested that at pH 7.4, both hydroxyl radical (•OH) and singlet oxygen ( <sup>1</sup> O <sub>2</sub> ) were responsible for dye discoloration, whereas at pH 5, the consumption of <sup>1</sup> O <sub>2</sub> became dominant. Implications for dye degradation in foods and other consumer products that contain both TiO <sub>2</sub> and FD&C Yellow No. 5 as ingredients are discussed.