Study On The Structure Separation Of Single-Walled Carbon Nanotubes By The Novel Gel-Based Technique

Single-walled carbon nanotubes(SWCNTs) have shown broad application prospects in various fields and become a research hotspot of researchers by virtue of its excellent and unique properties since they were discovered. However, at present, the synthesized products with current methods are always a mixture of various structural carbon nanotubes, in which the nanotubes with different properties seriously restrict the application of carbon nanotubes. For example, the electrical properties of the carbon nanotubes can be divided into semiconducting and metallic type, and the band width of semi conducting carbon nanotubes varies with the change of the structure. Therefore, the selective separation of different carbon nanotubes by post-processing methods is a difficult problem urgent to be solved in the scientific community.In this work, we regards the gel-based carbon nanotubes separation method as the research object, through optimizing the parameters of technology, and learning from other separation techniques, trying to find and to design a better separation technology. The main research contents and results as follows:(1) For the traditional separation method based on a kind of surfactant SDS, since the identification of the structure of carbon tubes is relatively low in this separation system, the separation process need to be repeated several times, and thus the method is very tedious. In this paper, a stepwise elution method of SDS solution is introduced. During the separation, the whole process just operates in a single gel column, which greatly improves the separation efficiency. In addition, we also found that ethanol has a great influence on the separation process, and invent a novel "ethanol-assisted gel chromatography". This method not only has the same high separation efficiency, but also reduces the work concentration of SDS, which greatly saves the experimental cost.(2) In order to further improve the separation quality of carbon nanotubes, we try to introduce several other surfactants to the gel-based separation method. We detailed explore the way of combination between SDS, SC and DOC and found their respective role. On the basis of these results, we finally obtain 11 species of single structure of semiconducting carbon nanotubes, and the purity of certain species is even more than 90%. The separation quality of the chiral structure of carbon nanotubes has been reached the currently best level, and the separation of optical isomer is even several times higher than the currently best result.(3) In addition, according to these experimental results, we have summed up the mechanism model of the gel-based separation method, which has great reference value for the structure separation of carbon nanotubes in the future. We found that the interaction between different structures of carbon nanotubes and gel is the key for their separation and the difference is due to the thickness and coverage of the surfactant micelle layer around the nanotube surface.