Zeta-potential measurements of surfactant-wrapped individual single-walled carbon nanotubes

A systematic study of the zeta (zeta)-potential distribution of surfactant-wrapped individual single-walled carbon nanotubes (SWNTs) dissolved in water is presented here. The surface charge on the SWNT micelles, as measured by the zeta-potential, has implications for the stability of the dispersions and for the electrophoretic and diclectrophoretic assembly and alignment of SWNTs. Very highly charged SWNTs are obtained by dispersing the nanotubes in high concentrations of anionic and cationic surfactants, whereas almost neutral SWNTs are obtained by using non-ionic surfactants. The -potential of the dissolved SWNTs is tuned by adjusting the surfactant concentration, the alkyl chain length of the surfactant molecule, and the solution pH in different surfactant-SWNT systems.