Analyzing Surfactant Structures on Length and Chirality Resolved (6,5) Single-Wall Carbon Nanotubes by Analytical Ultracentrifugation

Published

March 26, 2013

Author(s)

Jeffrey A. Fagan, Ming Zheng, Jeffrey R. Simpson, Vinayak Rastogi, Constantine Y. Khripin, Carlos A. Silvera Batista, Angela R. Hight Walker

Abstract

The structure and density of the bound interfacial surfactant layer and associated hydration shell were investigated using analytical ultracentrifugation for length and chirality purified (6,5) single-wall carbon nanotubes (SWCNTs) in three different bile salt surfactant solutions. The minor differences in the chemical structures of the surfactants were found to affect significant changes to the size and density of the bound surfactant layers. As probed by exchange of a common parent nanotube population into sodium deoxycholate, sodium cholate, or sodium taurodeoxycholate solutions, the anhydrous densities of the nanotubes were found to be less for the deoxycholate surfactants, implying a larger, deoxycholate, and more densely packed, taurodeoxycholate, interfacial layer than observed using sodium cholate. This effect was correlated with a 25 % increase in fluorescence intensity relative to the cholate surfactant for the deoxycholate dispersed SWCNTs despite all samples displaying equivalent absorbance spectra. Separate sedimentation velocity experiments in solutions containing each surfactant along with the density modifying agent iodixanol were used to establish the buoyant density of the (6,5) SWCNT in each of the bile salt surfactants; from the difference in the buoyant and anhydrous densities, the largest hydrated diameter is observed for sodium deoxycholate. Understanding the effects of dispersant choice and the methodology for measurement of the interfacial density and hydrated diameter is critical for rationally advancing separation strategies and applications of nanotubes.

Citation

ACS Nano

Volume

7

Issue

4

Pub Type

Journals

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DOI Link

Keywords

nanotube, nanoparticle, single-wall carbon nanotube, SWCNT, analytical ultracentrifugation

Citation

Fagan, J. , Zheng, M. , Simpson, J. , Rastogi, V. , Khripin, C. , Silvera, C. and Hight, A. (2013), Analyzing Surfactant Structures on Length and Chirality Resolved (6,5) Single-Wall Carbon Nanotubes by Analytical Ultracentrifugation, ACS Nano, [online], https://doi.org/10.1021/nn4002165 (Accessed December 22, 2024)