Swelling the hydrophobic core of surfactant-suspended single-walled carbon nanotubes: a SANS study.

Localized solvent environments form around single-wall carbon nanotubes (SWCNTs) because of the ability of surfactant molecules to solubilize immiscible organic solvents. Although these microenvironments around SWCNTs have already been used for fundamental and applied studies, small-angle neutron scattering (SANS) was used here to assess the size and shape of the solvent domains, their uniformity and distribution on the sidewalls, and the effect of solvent swelling on the aggregation state of the suspension. SANS measurements confirm both the formation of local solvent environments and that no irreversible aggregation of the nanotube suspension occurs after the SDS molecules are swollen in solvent. The results also corroborate prior conclusions based on photoluminescence that the structure formed is dependent of the nature of the solvent-surfactant combination; SWCNTs suspended with SDS and swelled with benzene have a more uniform coating on the sidewall than those swelled with o-dichlorobenzene. These differences can be important to understanding the effect of the local environment on the photoluminescence properties and the interaction of SWCNTs with interfaces.