Determination of Co-Surfactant Coverage Density and Location for Density Gradient Ultracentrifugation Based Metallic-Semiconducting Separation of Carbon Nanotubes Using Analytical Ultracentrifugation

We present an analytical ultracentrifugation (AUC) study to determine the density and location of an introduced co-surfactant, sodium-dodecylsulfate (SDS), mimicking the applied perturbation used in density gradient ultracentrifugation (DGU) based separation of metallic and semiconducting nanotubes.  Previously isolated empty and water-filled carbon nanotubes¹ via a rate-zonal centrifugation were utilized to allow resolution of the co-surfactant effects.  Analytical ultracentrifugation allows live spectroscopic observation of the sedimentation properties of nanotube and surfactant dispersions under the influence of high centrifugal field. Sedimentation velocity experiments were performed on the fractionated empty and water-filled nanotubes in sodium deoxycholate (Na-DOC) – SDS surfactant solutions in both H₂O and D₂O.  The predictive ability of the AUC experiments were then tested with DGU experiments.

1. Fagan, J.A. et al. Separation of Empty and Water-Filled Single-Wall Carbon Nanotubes. ACS Nano (2011). doi:10.1021/nn200458t