(188g) Dynamics of Surfactant-Suspended Single Walled Carbon Nanotubes In a Centrifugal Field

Nair, N., Massachusetts Institute of Technology
Kim, W., Massachusetts Institute of Technology
Strano, M. S., Massachusetts Institute of Technology

A hydrodynamic model is used to describe the motion of surfactant-suspended single walled carbon nanotubes in a density gradient, while being subjected to a centrifugal field. The number of surfactant molecules adsorbed on each nanotube determines its effective density, and hence, its position in the gradient after centrifugation has been completed. Analysis of the spatial concentration distributions of CoMoCAT nanotubes suspended with 2 w/v% sodium cholate yielded 2.21, 2.36 and 2.74 surfactant molecules adsorbed per nanometer along the length of the (6,5), (7,5) and (8,7) nanotubes, respectively. The estimates are commensurate with experimental values reported in the literature. Based on these results, a linear relation is proposed between SWNT diameter and the adsorbate population, which can be used to predict the fate of a species in the separation process. Since the density of the surfactant-nanotube assembly is highly sensitive to the number of adsorbed molecules, a perturbation would cause it to be enriched at a different location in the gradient. The level of sensitivity is also reflected in the 95% confidence levels that are reported in this work.