  Within a dipolar Poisson-Boltzmann theory including electrostatic
correlations, we consider the effect of explicit solvent structure on solvent
and ion partition confined to charged nanopores. We develop a relaxation scheme
for the solution of this highly non-linear integro-differential equation for
the electrostatic potential. The scheme is an extension of the approach
previously introduced for simple planes (S. Buyukdagli and Ralf Blossey, J.
Chem. Phys. 140, 234903 (2014)) to nanoslit geometry. We show that the reduced
dielectric response of solvent molecules at the membrane walls gives rise to an
electric field significantly stronger than the field of the classical
Poisson-Boltzmann equation. This peculiarity associated with non-local
electrostatic interactions results in turn in an interfacial counterion
adsorption layer absent in continuum theories. The observation of this enhanced
counterion affinity in the very close vicinity of the interface may have
important impacts on nanofludic transport through charged nanopores. Our
results indicate the quantitative inaccuracy of solvent implicit nanofiltration
theories in predicting the ionic selectivity of membrane nanopores.
