Molecular Transport through Finite-Length Carbon Nanotubes

The transport of helium molecules in open and finite-length single-walled carbon nanotubes was studied using non-equilibrium molecular dynamics simulations. We observed that helium molecules were transported through nanotubes with the high mobility characterized by superdiffusion. A transition from superdiffusion to near-ballistic motion occurs when the diameter is larger than a threshold value, and then the transport is again dominated by the superdiffusion. This change is closely related to nanotube ends. Simulations show that molecules are transported rapidly in the nanotubes via ballistic motion, which, however, is dispersed by the potential barrier at the ends of the nanotubes. This blocking effect is jointly determined by the potential barrier and the nanotube diameter.