ELECTROSTATIC INTERACTION OF AN ION-PENETRABLE SPHERE WITH A HARD PLATE - CONTRIBUTION OF IMAGE INTERACTION

The exact expression for the potential energy of electrostatic interaction between a charged ion-penetrable sphere and a charged ion-impenetrable plate is obtained on the basis of the linearized Poisson-Boltzmann equation. Either the surface potential or the surface charge density of the plate is assumed to remain constant during interaction. The interaction energy is found to consist of two terms. The first term is a screened Coulomb interaction due to a simple linear superposition of the unperturbed potentials of the sphere and the plate, which is proportional to the product of their unperturbed surface potentials. The second term represents the interaction of the sphere and its image with respect to the plate. This image interaction is proportional to the square of the unperturbed surface potential of the sphere and does not depend on the unperturbed surface potential of the plate. The image interaction is attractive if the surface potential of the plate is constant and repulsive if the surface charge density of the plate is constant. © 1993 Academic Press. All rights reserved.