Phototransformation-induced aggregation of functionalized single-walled carbon nanotubes: the importance of amorphous carbon

Hou, Wen-Che, He, Chen-Jing, Wang, Yi-Sheng, Wang, David K. and Zepp, Richard G. (2016) Phototransformation-induced aggregation of functionalized single-walled carbon nanotubes: the importance of amorphous carbon. Environmental Science & Technology, 50 7: 3494-3502. doi:10.1021/acs.est.5b04727


Author Hou, Wen-Che
He, Chen-Jing
Wang, Yi-Sheng
Wang, David K.
Zepp, Richard G.
Title Phototransformation-induced aggregation of functionalized single-walled carbon nanotubes: the importance of amorphous carbon
Journal name Environmental Science & Technology   Check publisher's open access policy
ISSN 0013-936X
1520-5851
Publication date 2016-04-05
Year available 2016
Sub-type Article (original research)
DOI 10.1021/acs.est.5b04727
Open Access Status Not Open Access
Volume 50
Issue 7
Start page 3494
End page 3502
Total pages 9
Place of publication Washington, DC, United States
Publisher American Chemical Society
Collection year 2017
Language eng
Formatted abstract
Single-walled carbon nanotubes (SWCNTs) with proper functionalization are desirable for applications that require dispersion in aqueous and biological environments, and functionalized SWCNTs also serve as building blocks for conjugation with specific molecules in these applications. In this study, we examined the phototransformation of carboxylated SWCNTs and associated amorphous carbon impurities in the presence or absence of H2O2 under simulated sunlight conditions. We found that while carboxylated SWCNTs were rather unreactive with respect to direct solar photolysis, they photoreacted in the presence of H2O2, forming CO2 and strongly aggregated SWCNT products that precipitated. Photoreaction caused SWCNTs to lose oxygen-containing functionalities, and interestingly, the resulting photoproducts had spectral characteristics similar to those of parent carboxylated SWCNTs whose amorphous carbon was removed by base washing. These results indicated that photoreaction of the amorphous carbon was likely involved. The removal of amorphous carbon after indirect photoreaction was confirmed with thermogravimetric analysis (TGA). Further studies using carboxylated SWCNTs with and without base washing indicate that amorphous carbon reduced the extent of aggregation caused by photoreaction. The second-order rate constant for carboxylated SWCNTs reacting with OH was estimated to be in the range of 1.7-3.8 × 109 MC -1 s-1. The modeled phototransformation half-lives fall in the range of 2.8-280 days in typical sunlit freshwaters. Our study indicates that photosensitized reactions involving OH may be a transformation and removal pathway of functionalized SWCNTs in the aquatic environment, and that the residual amorphous carbon associated with SWCNTs plays a role in SWCNT stabilization
Keyword Phototransformation
Single-Walled Carbon Nanotubes
SWCNTs
Amorphous Carbon
H2O2
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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