| As one of the amazing allotropes of carbon,carbon nanotubes(SWNTs)have attracted much attention since early 1990s,and the high-purity semiconducting SWNTs(s-SWNTs)are desired for high-performance electronic devices.Therefore,to prepare individually dispersed high-purity s-SWNTs in a low cost is of great significance.The raw SWNTs were prepared using improved arc-discharged method and purified by air oxidation and concentrated hydrochloride acid acidification.The purified SWNTs sample was verified to consist of pure nanotubes by vis-NIR optical absorption spectra,thermogravimetric analysis and scanning electronic microscope and Raman spectra.Floating catalyst chemical vapor deposition(FCCVD)method was also applied to the SWNTs preparation,in which Gd was used as growth promotor to improve the yield and quality of SWNTs.Based on the characterization results of electron microscope,thermogravimetric analysis and Raman spectroscopy,the application of Gd leads to a great increase in the production of large-diameter SWNTs with a narrow diameter distribution and an enhanced thermal stability.Sodium N-dodecanoyl amino acid was synthesized by different kinds of amino acids and dodecanoyl chloride via Shorten-Baumann reaction under alkaline condition and applied to the individual dispersion of SWNTs in aqueous media.Optical absorption spectra demonstrate that among the obtained seven derivates,sodium Ndodecanoyl proline exhibits the most effective dispersing ability towards arcdischarged SWNTs and FCCVD-SWNTs.Atomic force microscope and transmission electronic microscope characterization further confirm the SWNTs were individually dispersed in the aqueous solution.In addition,it is found that N-dodecanoyl proline also displays selectivity towards s-SWNTs and recognizes SWNTs with large chiral angles.According to the conversion relationship between sodium N-dodecanoyl proline and N-dodecanoyl proline,an experimental scheme for cyclable selectively dispersing s-SWNTs was designed,which provides a new experimental idea for large-scale preparation of s-S WNTs in aqueous media.Density gradient ultracentrifugation separation was applied to isolate m-SWNTs and s-SWNTs,in which sucrose was used as a density gradient medium and sodium dodecyl sulfate was selected as co-surfactant.s-SWNTs with ultrahigh purity and mS WNTs with high purity were successfully isolated. |
