  We study electrostatic correlations in structured solvents confined to
nanoscale systems. We derive variational equations of Netz-Orland type for a
model liquid composed of finite size dipoles. These equations are solved for
both dilute solvents and solvents at physiological concentrations in a slit
nanopore geometry. Correlation effects are of major importance for the
dielectric reduction and anisotropy of the solvent resulting from dipole image
interactions and also lead to a reduction of van der Waals attractions between
low dielectric bodies. Finally, by comparison with other recently developed
self-consistent theories and experiments, we scrutinize the effect of
solvent-membrane interactions on the differential capacitance of the charged
liquid in contact with low dielectric substrates. The interfacial solvent
depletion driven by solvent-image interactions plays the major role in the
observed low values of the experimental capacitance data, while non-locality
associated with the extended charge structure of solvent molecules only brings
a minor contribution.

Soft Condensed Matter