Molecular dynamics simulation of ion separation and water transport through boron nitride nanotubes

Molecular dynamics simulations were performed to investigate ionic selectivity of boron nitride nanotubes. The simulated systems were composed of a boron nitride nanotube inserted in a silicon nitride membrane immersed in an aqueous ionic solution. The considered nanotubes were fixed in a silicon nitride membrane and an external electrical field was applied on the systems along the axis of nanotubes. We found that the (7, 7) and (8, 8) boron nitride nanotubes were exclusively selective to ions. A (7, 7) boron nitride nanotube could selectively conduct Na+ ions. In contrast, a (8, 8) boron nitride nanotube could selectively conduct Cl- ions. Some simulated properties, including the ionic current, the water structure inside nanotubes, the retention time of the ions, ion-water radial distribution functions, and normalized transport rate of water with respect to the number of transported ions, were calculated. The current was found to increase linearly with voltage.