Using molecular dynamics simulations, we investigated the dynamics of water within single-walled carbon- and boron-nitride nanotubes to understand the effect of nanoconfinement on the structure and on the diffusion coefficient.
Our simulations indicate that the structure of water near the walls of the nanotubes is ice-like even at room temperature. As a consequence the diffusion coefficient for water transport through small 9 Å wide nanotubes is three orders of magnitude smaller than the self-diffusion coefficient in unconfined water. However, the diffusivity rapidly increases with the nanotube radius where only the outer water molecules are caught in an ice-like phase. For nanotube diameters of 24 Å, the diffusivity of the water molecules in the center of the nanotubes even slightly exceeds the value of unconfined water.
T. Nanok, N. Artrith, P. Pantu, P. A. Bopp, and J. Limtrakul*,
J. Phys. Chem. A, 113, 2103–2108 (2009)