Determination of the Hydrated Surfactant Shell Density On Empty and Water-Filled Single Walled Carbon Nanotubes Using Analytical Ultracentrifugation

We present an analytical ultracentrifugation (AUC) study determining the adsorbed surfactant and hydration shell density of previously isolated empty and water-filled carbon nanotubes.¹  These results are intended to address an ongoing controversy over whether water-filled nanotubes ingest solvated ions or have an altered surfactant packing structures compared to capped, empty, nanotubes. Analytical ultracentrifugation allows live spectroscopic observation of the sedimentation rates under the influence of high centrifugal field. The experiments were performed on both empty and water-filled nanotubes in both H₂O and D₂O for two different sets of average diameter populations. A dilution series of each nanotube fraction in surfactant solution was tested to eliminate concentration and aggregation effects.  

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