Electric Potential and Charge Density Profiles in Inhomogeneous Interfacial Regions

Abstract

This paper is concerned with certain fundamental questions raised by our studies (Vaidhyanathan, 1985, 1986), regarding the relations between concentration distributions of charged species and the electric potential profile in inhomogeneous interfacial regions. The existance of a dielectric profile and the finite nature of the extent of the inhomogeneous region are examined. One of the unsolved problem of major interest, in interfacial surface phenomena, is the relation existing between surface charge density and the value of the electric potential at the surface, when a surface containing fixed charges is in contact with an electrolyte of known composition. An expression, known as Gouy equation, is available in literature (Grahame,1947) for this relation, when the electrolyte contains only univalent ions. The validity of this equation is also restricted to the situation when the positional dependence of dielectric coefficient can be ignored. A general equation, valid for the case of multivalent many ion system, such as one encounters in biology, is not available. A critical examination of the classical theory of double layers, (Verwey and Overbeek, 1945), suggests that the assumption of constant dielectric coefficient should be justified. In biophysical systems of interest, the concentrations of ions are of the order of unimolar. Therefore, the results of strong electrolyte theory, whose validity is limited to extremely dilute solutions, are not evidently applicable to these systems, without corrections.KeywordsInterfacial RegionElectrolyte SystemInhomogeneous RegionBiophysical SystemDielectric CoefficientThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.