Nanoconfined Electrolyte Solutions in Porous Hydrophilic Silica Membranes

Manipulating of electrolyte solutions is ubiquitous in numerous fields ranging from condensed to soft matter. The fundamental understanding of the molecular mechanism ruling the macroscopic properties is inescapable to well rationalize the engineering processes. In confined situations such as nanofluidic or nanofiltration, interactions between the fluids and the surface drastically modify the usual macroscopic properties. In this work we addressed a structural and dielectric analysis of confined NaCl, NaI, MgCl2, and Na2SO4 in nanoporous hydrophilic silica membranes. We highlight a dielectric anisotropy of confined water and an unusual increase in the radial component of permittivity (epsilon(perpendicular to)) of confined solutions with respect to the decrease in e in the bulk solution phase. Structurally, we investigate the size, the polarizability, and the salt effect on water confinement and ions translocation through a cylindrical silica nanopore.