Behavior of surfactants in aqueous dispersions of single-walled carbon nanotubes

Abstract

Three aqueous dispersions of single-walled carbon nanotubes (SWCNTs) were prepared with different industrial surfactants: Tween 80, Triton X-100, and Pluronic F127. The pulsed field gradient (PFG)-NMR method showed that the mole fraction ratios of secondary particles composed of SWCNTs and surfactant were approximately 10 : 1 for SWCNT/Tween 80 and SWCNT/Triton X-100, and 5 : 1 for SWCNT/Pluronic F127. When the SWCNTs were dispersed in the aqueous surfactant solutions, the transverse relaxation times of the surfactants were dramatically reduced, indicating that all the surfactant molecules were bound to or interacted with the SWCNTs. After the SWCNT dispersions were mixed with aqueous solutions of artificial lung surfactant (ALS), the industrial surfactants remained strongly adsorbed to the surface of SWCNTs and were not exchanged with ALS. The zeta potentials for the mixtures of the SWCNT dispersions with the ALS solution were similar to the initial values for the SWCNT dispersions, which was consistent with the PFG-NMR results. Our results are significant for determining the inherent toxicity of SWCNTs in vivo.