title: The photochemistry of carbon nanotubes and its impact on the photo-degradation of dye pollutants in aqueous solutions.
abstract: It is reported that carbon nanotubes (CNTs) could either generate reactive oxygen species (ROS) under light irradiation or serve as high-efficient scavenger for ROS. However, it is unclear which role predominates as CNTs enter into aquatic environment. To answer this question, a systematic study of the photochemistry of a pristine and a surface-functionalized CNTs in aqueous suspensions was investigated with both time-resolved and steady state analytical approaches. The transient absorption spectra demonstrate that CNTs could be photo-ionized and trap hydrated electrons upon high energy irradiation. In steady state UV irradiation, CNTs could promote the generation of ROS, such as (1)O2 and OH. However, in the presence of H2O2, the OH scavenging effect predominated in the aqueous suspensions of CNTs. The presence of CNTs suppressed the photo-degradation of dye pollutants, as an integrated result of inner filter effect, adsorption effect, and ROS generation and scavenging effect. The results provide useful information for the understanding of the environmental implications of CNTs.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Bingdang
authors.initials: B
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Dunxue
authors.initials: D
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China. Electronic address: sjzhang@nju.edu.cn.
authors.forename: Shujuan
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Weizhen
authors.initials: W
authors.lastname: Lin
authors.affiliation: Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201203, China.
authors.forename: Guozhong
authors.initials: G
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Bingcai
authors.initials: B
authors.lastname: Pan
keywords: Electron paramagnetic resonance; Laser flash photolysis; Pulse radiolysis; Reactive oxygen species