Evidence of selective cation transport through sub-2 nm single-walled carbon nanotubes

ABSTRACTThe electrophoretic transport of ions through single walled carbon nanotubes (SWCNTs) of diameters between 1.2 and 1.8 nm was studied for different monovalent chloride salts using microfluidic devices incorporating either a single or few SWCNTs in parallel. The ionic conductance was found to be about one order of magnitude higher than would be expected from simple bulk electrophoresis without any surface effect. Importantly, the ionic conductance measured for different cations did not scale with their bulk electrophoretic mobility thus indicating a selective cation transport through these sub-2 nm SWCNTs. The transport of Na+ was notably found to be favored in comparison to that of Li+, K+ and Cs+. These results highlight the influence of steric and surface effects induced by the nano-confinement on the transport of ions through sub-2 nm SWCNTs.