High-resolution length fractionation of surfactant-dispersed carbon nanotubes.

Length fractionation of colloidal single-wall carbon nanotube (SWCNT) dispersions is required for many studies. Size-exclusion chromatography (SEC) has been developed as a reliable method for high-resolution length fractionation of DNA-dispersed SWCNTs but has not been applied to surfactant-dispersed SWCNTs due to their lower dispersion stability and tendency to adsorb onto SEC stationary phases. Here, we report that SEC length fractionation can be achieved for bile salt dispersed SWCNTs by using porous silica-based beads as the stationary phase and bile salt solution as the mobile phase. We demonstrate that the SEC length sorting method can be combined with existing ultracentrifugation SWCNT sorting methods to produce "orthogonally sorted" samples, including length sorted semiconducting SWCNTs, which are important for electronics applications as well as length sorted empty-core SWCNTs. Importantly, we show that unlike simple length fractionation by SEC or any other method, orthogonal sorting produces samples of consistent quality for different length fractions, with similar UV-vis-nearIR absorption and Raman spectral features.