Electrolytic Transport in Modified Carbon Nanotubes

Molecular dynamics simulations were used to study ionic flow in carbon nanotubes with the goal of using carbon nanotubes as artificial protein channels found in cell membranes. Previous simulations show that water and molten ions enter carbon nanotubes spontaneously. Our simulations show that ion occupancy in a carbon nanotube solvated in an electrolyte is very low for a (16,16) uncapped tube. When partial charges were placed on the rim atoms of the tube and an external electric field was applied, it was found that the ion occupancy increased significantly. To mimic an ion channel in a membrane, functional groups were attached at the ends and the tube was placed in a slab. The functionalized tube was found to conduct ions in the presence of an electric field. It is also shown that cationic or anionic selectivity could be obtained by symmetrical placement of the functional groups.