Purification of semiconducting single-walled carbon nanotubes by spiral counter-current chromatography

•Separation of single-walled carbon nanotubes using spiral CCC with the polymer phase solvent system.•Extraction methods for separation of chiral types of carbon nanotubes can be adapted to counter-current chromatography.•Separation of large molecules using the ATPS is accomplished in the specialized mixer-settler spiral disk rotor.•Semiconductor measurements of separated chiral types of carbon nanotubes discovery.

Over the last decade man-made carbon nanostructures have shown great promise in electronic applications, but they are produced as very heterogeneous mixtures with different properties so the achievement of a significant commercial application has been elusive. The dimensions of single-wall carbon nanotubes are generally a nanometer wide, up to hundreds of microns long and the carbon nanotubes have anisotropic structures. They are processed to have shorter lengths but they need to be sorted by diameter and chirality. Thus counter-current chromatography methods developed for large molecules are applied to separate these compounds. A modified mixer-settler spiral CCC rotor made with 3 D printed disks was used with a polyethylene glycol-dextran 2-phase solvent system and a surfactant gradient to purify the major species in a commercial preparation. We isolated the semi-conducting single walled carbon nanotube chiral species identified by UV spectral analysis. The further development of spiral counter-current chromatography instrumentation and methods will enable the scalable purification of carbon nanotubes useful for the next generation electronics.