Ionic flow through partially blocked nanopores.

Employing atomistic molecular dynamics simulations, we investigate the ionic conductivity mechanisms in a partially blocked nanopore containing a centrally positioned spherical constriction, exploring the effects of pore diameter, surface charge, and blockage size. Our results show that ionic mobilities are significantly influenced by the polarity of the surface charge and the size of the pore gap. Particularly, we observe ion-specific effects for K and Cl ions based on their size and charge, especially in sub-nanometer pore gaps. Furthermore, we find that the current flow in partially blocked nanopores sensitively depends on the surface charges, consistent with the calculated free energy profiles. The percentage of the current drop is found to be correlated to the volume of the spherical constriction with the effects more pronounced when the sizes of the spherical blockage and nanopore are comparable.