Large Populations of Individual Nanotubes in Surfactant-Based Dispersions without the Need for Ultracentrifugation

Abstract

Stable dispersions of single-walled carbon nanotubes have been produced using the surfactant sodium dodecylbenzene sulfonate (SDBS). Atomic force microscopy analysis shows that, on dilution of these dispersions, the nanotubes exfoliate from bundles, resulting in a concentration-dependent bundle diameter distribution which saturates at Drms ≈ 2 nm for concentrations, CNT < 0.05 mg/mL. The total bundle number density increases with concentration, saturating at ∼6 bundles per μm3 for CNT > 0.05 mg/mL. As the concentration is reduced the number fraction of individual nanotubes grows, approaching 50% at low concentration. In addition, partial concentrations of individual SWNTs approaching 0.01 mg/mL can be realized. These values are far superior to those for solvent dispersions due to repulsion stabilization of the surfactant-coated nanotubes. These methods facilitate the preparation of high-quality nanotube dispersions without the need for ultracentrifugation, thus significantly increasing the yield of dispersed nanotubes.