Effects of Pore-Size Range and Composition of Polysaccharide Gels on Flow Behaviors and Selective Sorting of Single-Walled Carbon Nanotubes

Abstract

We used gel-column chromatography to show the effects of the pore-size range and chemical composition of porous polysaccharide gels on the flow characteristics and metal/semiconductor (m/s) separation of dispersed single-walled carbon nanotubes (SWCNTs). Comparative studies of the flow behaviors of dispersed SWCNTs in a series of Sephacryl gels with different pore sizes showed that a small pore-size range increased the interaction strength of SWCNTs with gels, leading to rapid flow of thicker metallic (m-)SWCNTs through gel beads, and the selective entrapment of thinner semiconducting (s-)SWCNTs. We also found that the effect of the gel composition was more important than that of the gel porosity on the sorting of SWCNTs. When the amine group in the dextran-based Sephacryl gel was replaced by agarose, e.g., Superdex 200 or Sepharose 2B gel, the interaction with the dispersed SWCNTs was enhanced, resulting in slowing down of both the m- and s- SWCNTs throughout the gel, and obvious deterioration in the selectivity for, and purity of, the s-SWCNTs. In contrast, Sephadex G100 gel, which has one dextran group functionalized by hydrophobic epoxypropane, yielded very weak interactions with SWCNTs, leading to direct drainage of both types of SWCNT, despite its fine pore size, similar to that of Sephacryl S100. We therefore propose that the gel pore size and composition exerted a synergistic effect in governing the m/s sorting of SWCNTs with high selectivity, purity, and efficiency.