Photochemical Transformation of Carboxylated Multiwalled Carbon Nanotubes: Role of Reactive Oxygen Species

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• 作者：Xiaolei Qu ; Pedro J. J. Alvarez ; Qilin Li
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：December 17, 2013
• 年：2013
• 卷：47
• 期：24
• 页码：14080-14088
• 全文大小：400K
• 年卷期：v.47,no.24(December 17, 2013)
• ISSN：1520-5851

文摘

The study investigated the photochemical transformation of carboxylated multiwalled carbon nanotubes (COOH-MWCNTs), an important environmental process affecting their physicochemical characteristics and hence fate and transport. UVA irradiation removed carboxyl groups from COOH-MWCNT surface while creating other oxygen-containing functional groups with an overall decrease in total surface oxygen content. This was attributed to reactions with photogenerated reactive oxygen species (ROS). COOH-MWCNTs generated singlet oxygen (¹O₂) and hydroxyl radical (^{鈥?/sup>OH) under UVA light, which exhibited different reactivity toward the COOH-MWCNT surface. Inhibition experiments that isolate the effects of 鈥?/sup>OH and 1O₂ as well as experiments using externally generated 鈥?/sup>OH and 1O₂ separately revealed that 鈥?/sup>OH played an important role in the photochemical transformation of COOH-MWCNTs under UVA irradiation. The Raman spectroscopy and surface functional group analysis results suggested that 鈥?/sup>OH initially reacted with the surface carboxylated carbonaceous fragments, resulting in their degradation or exfoliation. Further reaction between 鈥?/sup>OH and the graphitic sidewall led to formation of defects including functional groups and vacancies. These reactions reduced the surface potential and colloidal stability of COOH-MWCNTs, and are expected to reduce their mobility in aquatic systems.}