Rapid evaluation of oxygen vacancies-enhanced photogeneration of the superoxide radical in nano-TiO2 suspensions

Abstract

Reactive oxygen species (ROS) play an important role in the photocatalytic degradation of pollutants and are closely related to the surface defects of a semiconductor. However, the characterization of surface defects is very complex and a deeper understanding of them remains a great challenge. In this work, a series of nano-TiO₂ was synthesized and their optical properties due to surface defects were studied. The results showed that the surface oxygen vacancies on nano-TiO₂ can induce chemiluminescence (CL) by luminol. The greater the number of surface oxygen vacancies, the stronger the luminescence signal, and the greater the production of reactive oxygen species. Further studies revealed that the CL intensity was positively correlated with the oxygen vacancy content on the surface of nano-TiO₂. Moreover, there was also a clear correlation between the oxygen vacancies and photogenerated superoxide radicals (O₂˙⁻) on nano-TiO₂ suspensions. Therefore, a simple and rapid CL method was developed for evaluating the oxygen vacancy content and their implied ability to photogenerate O₂˙⁻ on nano-TiO₂ and has great potential in distinguishing surface oxygen vacancies and judging photocatalytic performance in oxides.