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The Kinetics of Single-Walled Carbon Nanotube Aggregation in Aqueous Media Is Sensitive to Surface Charge

Department of Pharmaceutical Sciences, University of Michigan, 428 Church Street, Ann Arbor, MI 48109, USA
Current Address: Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, CA 94305, USA
Author to whom correspondence should be addressed.
Academic Editor: Vijay Kumar Thakur
Received: 10 November 2015 / Revised: 13 January 2016 / Accepted: 1 February 2016 / Published: 19 February 2016
(This article belongs to the Special Issue Surface Modification of Carbon Nanotubes)
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Single-walled carbon nanotubes (SWCNTs) dispersed in aqueous media have many potential applications in chemistry, biology and medicine. To disperse SWCNTs into aqueous media, it is often necessary to modify the surface of SWCNTs by either covalent or noncovalent methods. As a result of this modification, the properties of SWCNTs may be profoundly influenced by the nature of the surface modification. Here, by using SWCNTs dispersed with single-stranded DNA of different lengths, we show that the kinetics of SWCNTs’ aggregation in aqueous media is strongly dependent on the status of the overall surface charge. SWCNTs with a greater number of surface charges showed faster aggregation. The difference in the rate of aggregation can differ by more than ten-fold among different conditions tested. AFM imaging of the discrete time points along the aggregation process suggests that aggregation starts with the formation of microfilaments, which can further grow to form bigger aggregates. The formation of bigger aggregates also renders it more difficult to redisperse them back into the aqueous media. The concentration of counterions required to trigger SWCNT aggregation also shows a dependence on the concentration of KCl in the aqueous solution, which supports that electrostatic interactions instead of van der Waals interactions dominate the interactions among these individually-dispersed SWCNTs in aqueous media. View Full-Text
Keywords: single-walled carbon nanotubes; aggregation; kinetics; DNA condensation; bundle size single-walled carbon nanotubes; aggregation; kinetics; DNA condensation; bundle size

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Koh, B.; Cheng, W. The Kinetics of Single-Walled Carbon Nanotube Aggregation in Aqueous Media Is Sensitive to Surface Charge. C 2016, 2, 6.

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