A Study On The Quantitative Characterization Of Dispersionand Separation For Single-wall Carbon Nanotubes

Owing to their unique and excellent physical and chemical properties, single-wall carbonnanotubes (SWCNTs) are very promising for a wide range of applications. Their propertiesdiffers in accordance with the different structures. Howerer, according to the current productionmethod, they are mixtures of different diameter and chirality. And there is no appropriatemethod for separation, an unified criterion to evaluate the effects. This situation not onlyincreases the difficulty to control the quality of SWCNTs, but also greatly affects its application.This work is based on the purpose to disperse and separate SWCNTs, and try to establish aquantitative evaluation criteria. In addition, in order to develop suitable gel fillers to separateSWCNTs, preparation of chitosan microspheres were explored.（1）Sodium dodecyl sulfate, sodium deoxycholate, sodium cholate, sodium dodecyl benzenesulfonate (SDBS), Tritron X-405and hexadecyltrimethyl ammonium bromide have been used todisperse SWCNTs. The dispersancy are evaluated quantitatively using the indictors of theabsorbance and the resonance ratio, which were calculated through the selected wavelengthrange of UV-Vis-NIR absorption spectrum. The results show that the total dispersancy ofsurfactants were SDS> DOC> X405> SC> CTMAB> SDBS while the individualdispersancy were DOC> SC> CTMAB> X405> SDBS> SDS.（2）A new method was established to evaluate the influence of the properties of SDS,DOC, SC, SDBS and Tritron X405as eluent on the separating efficiency of SWCNTs by singleGel chromatography. It was established by calculating the area percentage Si,jand the sum of itsrange∑Rsiaccording to the results of the absorption spectrum as the indicator of quantitativecharacterization. We found that SDS solution is the preferred mobile phase for the separation ofSWCNTs. （3）We used the single Gel Chromatography method to separate the SWCNTs, andinvestigated the the kind of fillers on the separating efficiency of SWCNTs. It is found thatdifferent gels have various selectivity on the chiral SWCNTs. On the basis of this conclusion,for the first time using a variety of gel filler and four columns step method (gel column orderis: Bio Gel, Sephacry, Toyopearl, Sepharose) to separate SWCNTs further. We got the SWCNTssamples with relative single chiral index type.（4）A new technique that centrifugal flow field-flow fractionation with a uv detector andmulti-angle light scatterer was used to separate six surfactants dispersed SWCNTs and theprocesses were tested online. The results show that no matter what the dispersion of SWCNTsin the samples, could got the size distribution Therefore, This new method is suitable for theseparation of SWCNTs.（5）Chitosan microspheres were prepared with Inverse Suspension-ChemicalCrosslinking Method by controlling the stirring speed, concentration of chitosan, acetic acidconcentration and emulsifier content. Separation of SWCNTs, with the chromatographiccolumn was filled with uniform size and stable properties of microspheres. The results showedthat the separating efficiency of SWCNTs is poor, because of the space mesh structure ofchitosan microspheres, and there is no effective mobile phase to separate SWCNTs from themicrospheres. However, through the characterization of chitosan microspheres-SWCNTs,proved that chitosan microspheres can absorb a large amount of SWCNTs, and the stability,electrical conductivity was enhanced, and maintain their excellent properties.