多糖凝胶的孔径和化学结构对单壁碳纳米管流动性和选择性分离的影响

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

基于凝胶柱色谱分离技术研究了单分散的单壁碳纳米管(SWCNTs)在不同化学结构多孔多糖凝胶中的流动特性以及对金属型(m-)/半导体型(s-)SWCNTs分离的影响.通过比较SWCNTs在一系列不同孔径的葡聚糖Sephacryl凝胶中的流动行为,发现减小孔径尺寸能够增强s-SWCNTs与凝胶之间的吸附作用力,使大直径的m-SWCNTs快速地流过凝胶颗粒,而选择性地保留了小直径的s-SWCNTs.进一步发现多糖凝胶化学结构比孔径尺寸在SWCNTs的m/s分离中起着更重要的作用.当基于葡聚糖结构的Sephacryl凝胶中的氨基结构被琼脂糖结构所取代时,如Superdex 200和Sepharose 2B凝胶会增强它们与SWCNTs之间的作用力,使SWCNTs的保留时间延长,降低了s-SWCNTs的选择性和纯度.此外,即使拥有与Sephacryl S100类似的孔径范围,当Sephacryl凝胶中的氨基被疏水环氧丙烷基团取代时,葡聚糖凝胶Sephadex G100与SWCNTs的作用力很弱,导致所有SWCNTs快速流动,无法实现SWCNTs的m/s分离.因而,我们认为凝胶孔径和化学结构共同影响并调控了SWCNTs的m/s分离的选择性、纯度以及分离效率.

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.