Molecular dynamics simulations on aqueous solution confined in charged nanochannels: asymmetric effect of surface charge

This work aims at investigating the effect of surface charge sign on static and dynamic properties of aqueous solutions confined in the charged nanochannel. Molecular dynamics simulations of two confinement systems have been performed, in which the nanochannel walls were modelled as the structureless walls with the uniform continuous distribution of surface charge. It is found that the sign of surface charge has a noticeable impact on the aqueous solution in a region close to the wall. The aqueous solution is more strongly layered and less translational and rotational diffusive in the positively charged nanochannel. But, the water molecules are more preferably oriented in the negatively charged nanochannel. The results have been consistently explained by microscopically analysing the forces acting atoms of water molecules and counter-ions, and the contributions into the torque acting on the water molecule.