Single-step total fractionation of single-wall carbon nanotubes by countercurrent chromatography

Development of simple processes to fractionate synthetic mixtures of single-wall carbon nanotubes (SWCNTs) into individual species is crucial to many applications. Existing methods for single-chirality SWCNT purification are cumbersome, often requiring multiple steps and different conditions for different species. Here, we report a method to achieve total fractionation of a synthetic SWCNT mixture by countercurrent chromatography, resulting in purification of many single-chirality SWCNT species in a single run. This method is based on a tunable partition of sodium deoxycholate dispersed SWCNTs in a polyethylene glycol/dextran aqueous two-phase system. By running the mobile phase with 0.02% of sodium deoxycholate and a gradient of sodium dodecyl sulfate from 0.1% to 0.7% (w/w), we observe clear diameter-dependent elution, with ∼ 90% total recovery. Among all the fractions collected, a number of them are enriched in single-chirality (9,4), (7,5), (7,6), (8,3), (6,5) species, while most of the remaining ones contain no more than 2-3 major species. We also observe strong (n,m)-dependent elution peak width due to the enantiomer-resolved partition. These results demonstrate countercurrent chromatography (CCC) as an effective way to obtain high purity (n, m) species, and suggest the potential of CCC as an analytical tool for chirality distribution mapping of synthetic SWCNT mixtures.