The Selective Separation Of Single-walled Carbon Nanotubes Based On Different Separate Method

Single-walled carbon nanotubes (SWCNTs) have excellent electrical, mechanical and optical properties, offering the wide potential of applications in various fields of nanodevices, sensors, transparent conducting films, composite material and so on. However, the established synthesis methods of SWCNTs are still hard to harvest them with a single electronic types and chirality. Therefore, that how to separate SWCNTs by a simple, fast and effective, to harvest the high purity of semiconducting SWCNTs and all kinds of chirality becomes a critical challenge for researchers. The selective separation of conjugated polymer is a significant separation method, which separate SWCNTs by interacting with SWCNTs, the polymer that separate SWCNTs is divided three type of fluorene-based polymers, thiophene-based polymers, carbazole-based polymers respectively. This way can harvest the high purity of semiconducting SWCNTs, which is extremely important of applications in various high technology fields of sensors, devices, field effect transistor (FETs). Aqueous two-phase extraction (ATPE) was recently demonstrated to enable the isolation of single-walled carbon nanotubes populations. This method provides us an opportunity to separate SWCNTs with inherent structure, by a simple separation equipment and process, easy, short time and expected to realize macro separation way, which has the very good development prospect.The main contents are as follows:(l)Firstly, we chose four different kinds of pristine SWCNTs for qualitative analyses by thermogravimetric(TG), field emission electron microscope(SEM), UV-vis-IR absorption spectrum, Raman and atomic force microscope (AFM) to understand the basic features of each type of SWCNTs. We selected HiPCO and arc-SWCNTs as raw materials for the following separation.(2)We designed three kinds of carbazole-bascd polymers based on the non covalent banding selective separation of conjugated polymers. Firstly, we studied the influence of different solvents for the polymer dispersed arc-SWCNTs, finding that there was the highest concentration but no selectivity of SWCNTs in tetrahydrofuran, which owned the maximum polarity; high purity of s-SWCNTs could be isolated in the medium polarity of O-xylene and in the relatively small polarity of toluene, SWCNTs showed the minimum solubility, while s-SWCNTs had certain selectivity. The main reason is that different polarity of solvents change the self configuration of high molecular weight polymer in solution. Then we studied the influence of conjugated polymers with the different structures to disperse arc-SWCNTs, finding that PCO showed the best selectivity for semiconductor carbon nanotubes; PCP also exhibted good selectivity for semiconductor carbon nanotubes and was more likely to choose s-SWCNTs with minor diameter, while PCBP had the worst selectivity for s-SWCNTs. The reason is that the addition of pyridine has impacts on the geometries structure of polymer and energy matching between polymer and SWCNTs.(3)The several different kinds of surfactants were used to successfully separate the different conductive properties of arc-SWCNTs and different conductive properties, diameter, narrow chiral of HiPCO-SWCNTs using aqueous two-phase method. At first, sodium cholate (SC), sodium dodecyl sulfate (SDS) and sodium thiocyanate (NaSCN) separated s/m-SWCNTs at 20 ℃, discribing the method of secondary seperation to purify SWCNTs and two ways of enriching SWCNTs, as well as the practicality of expanding concentration and volume. Based on the different selectivities of SC and sodium deoxycholate (DOC) for HiPCO-SWCNTs in ATP system, SC, SDS and NaSCN were used to modulate the surface hydrophilicity of s/m-SWCNTs, achieving the m/s seperation of HiPCO-SWCNTs. For a further step, the concentrations of SDS and DOC were precisely controlled, combing a continuous multi-step separation strategy to achieve a high purity of different diameters and narrow chiral s-SWCNTs seperation.