Ultra high performance single-walled carbon nanotubes with density differentiation

Abstract

The aim of this project is to extract or enrich SWNTs of a certain required property (diameter, chirality or semi-conducting/metallic) through density gradient ultracentrifugation (DGU) via different surfactants and surfactant mixtures. This is done as purchased SWNTs are unsuitable for applications without pre-sorting. Experiments were carried out on three sources of SWNTs, namely produced from the CoMoCAT, HiPco and arc discharge method. Surfactants involved were sodium cholate (SC) and sodium dodecyl sulphate (SDS) in two weight percent solutions. Experiments showed that SC used as a surfactant alone and as a co-surfactant with SDS at four to one weight ratio yielded promising results, especially with CoMoCAT and HiPco SWNTs. Although a co-surfactant system of SC/SDS at two to three ratio was reported to yield satisfactory results according to literature, experiments performed in this project failed to show this and more studies would need to be conducted. Experiments involving arc discharge SWNTs showed a more dispersed and more concentrated levels of semi-conducting SWNTs. Several improvements were made to the prescribed procedures as the experiments were being conducted, with the narrowing of density gradient showing most promising returns with the appearance of colored bands that could not be obtained previously. More improvements have been suggested and referenced from literature for subsequent follow-ups to this project.