Influence of endohedral water on diameter sorting of single-walled carbon nanotubes by density gradient centrifugation.

ABSTRACT

Separation of single-walled carbon nanotubes (SWNT) by diameter is an important prerequisite for controlled experimental studies and efficient application of these systems. By comparing experimental data with molecular dynamics (MD) simulations, we demonstrate that water filling has a significant, tube-diameter dependent effect on the effective mass density of individual single-walled carbon nanotubes suspended in aqueous surfactant suspensions. We present a model for the effective density of the nanotube-surfactant complex in aqueous solution that permits a comprehensive description of its density across the entire, experimentally relevant range of SWNT diameters. Parameters for this model can be obtained from molecular dynamics simulations and/or experiment and help explain the subtle interplay of surfactant coverage and endohedral water in the separation of a particular diameter species of SWNT by gradient centrifugation.