论文部分内容阅读
Many of the environmental and biological effects of nanomaterials are attributed to their ability to facilitate the generation of reactive oxygen species(ROS)and/or electron/hole pairs.Identification of the dominantly active species and their reactive behavior in semiconductor photocatalysis is important for a clear understanding of the photocatalytic mechanism.Electron spin resonance(ESR)spectroscopy is a direct and reliable method to identify and quantify free radicals in both chemical and biological environments.We will discuss an effective method based on electron spin resonance spectroscopy(ESR)with spin trapping(ST)and spin labeling(SL)techniques for studying the reactive oxygen species(ROS)and charge carriers generated by irradiating nanomaterials(metal sulfide,metal oxide,and metal oxide/metal hybrid nanostructures),which have various applications in biological,chemical,and environmental science.Using ESR-ST-SL,we can not only distinguish the each kind of ROS and charge carriers and their contribution to photo-oxidation and photo-reduction elicited by photocatalytic nanomaterials,it is also possible to predict the generation of ROS and reactivity of electrons of semiconductors.In addition,ESR was used to investigate the enhancing effect of metal on the ability of ZnO in light-induced generation of hydroxyl radical,superoxide and singlet oxygen,and production of holes and electrons.