Fluctuation induced effects in confined electrolyte solutions

Abstract

We examine electrolyte systems confined between two parallel, grounded metal plates using a field-theoretic approach truncated at one-loop order. For symmetric electrolytes, the density distribution of the ions is non-uniform, with a maximum value at the center of the system. For asymmetric electrolytes, the system is no longer locally neutral, and there is a non-zero static electric potential. In addition, the surface of the metal plates becomes charged. When the plate separation becomes greater than the screening length, the charge distribution possesses two peaks with a local minimum at the center of the system. When the plates are immersed in a bulk electrolyte solution, an attractive fluctation induced force develops between them that is analogous to the Casimir force. Unlike the Casimir force, however, this attractive interaction has a finite limit in the zero separation limit and decays inversely with the separation at large separations.