Advanced sorting of single-walled carbon nanotubes by nonlinear density-gradient ultracentrifugation

Nat Nanotechnol. 2010 Jun;5(6):443-50. doi: 10.1038/nnano.2010.68. Epub 2010 May 9.


Existing methods for growing single-walled carbon nanotubes produce samples with a range of structures and electronic properties, but many potential applications require pure nanotube samples. Density-gradient ultracentrifugation has recently emerged as a technique for sorting as-grown mixtures of single-walled nanotubes into their distinct (n,m) structural forms, but to date this approach has been limited to samples containing only a small number of nanotube structures, and has often required repeated density-gradient ultracentrifugation processing. Here, we report that the use of tailored nonlinear density gradients can significantly improve density-gradient ultracentrifugation separations. We show that highly polydisperse samples of single-walled nanotubes grown by the HiPco method are readily sorted in a single step to give fractions enriched in any of ten different (n,m) species. Furthermore, minor variants of the method allow separation of the mirror-image isomers (enantiomers) of seven (n,m) species. Optimization of this approach was aided by the development of instrumentation that spectroscopically maps nanotube contents inside undisturbed centrifuge tubes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Centrifugation, Density Gradient / methods*
  • Circular Dichroism
  • Nanotubes, Carbon / chemistry*
  • Nanotubes, Carbon / classification
  • Nonlinear Dynamics
  • Spectrometry, Fluorescence
  • Spectrophotometry
  • Stereoisomerism
  • Ultracentrifugation / methods*


  • Nanotubes, Carbon