Confinement and surface effects of aqueous solutions within charged carbon nanotubes.

We have examined the structure of water and aqueous solutions in carbon nanotubes using molecular dynamics simulations. We find confinement changes the structure of water as well as the interactions between ions and their solvation shells. The density and orientation of water at the nanotube walls are strongly dependent on the surface charge and cations/anions present at the interfaces. Decreasing the nanotube diameter alters the ion hydration properties as well as hydrogen bonding structure and formation dynamics. The results indicate that fluid structure and hydrogen bond characteristics in nano-channels can be tuned through modification of tube charge and with ion selection.