Dispersion of single-walled carbon nanotubes by using surfactants: Are the type and concentration important?

A facile method to disperse a high concentration of SWNTs in aqueous solution by determining the minimum concentration needed to suspend a particular fraction of nanotubes under specific experimental conditions was investigated. Three different surfactants namely Igepal CO-990 [polyoxyethylene(100) nonylphenyl ether] (IGP), cetyltrimethylammonium bromide (CTAB), and sodium dodecylsulfate (SDS) was used for dispersing a high concentration of individual single-walled carbon nanotubes (SWNT) in an aqueous solution by a supramolecular approach. It was found that IGP could disperse SWNTs at very low concentrations with a high yield of mass percent conversion. A few studies on the surfactant adsorption on graphite indicate that surfactants adsorb forming hemimicelles that sheath the surface. The surfactant-suspended nanotubes were found to be stable for more than four months, except for the case of the CTAB-suspended SWNTs, which showed a slight aggregation after three months.