CONTRIBUTIONS OF SURFACE-FEATURES TO THE ELECTROSTATIC PROPERTIES OF ROUGH COLLOIDAL PARTICLES

Although theoretical descriptions of colloidal particles deal almost e xclusively with idealized shapes and surface properties, real particle s are often characterized by irregular shapes and surface properties. In this paper a perturbation method is used to evaluate the effect of shape irregularities on the potential distribution in and around a rip pled sphere with a point charge at the center; of particular interest is the distribution around the bump or dimple in the polar region, sin ce real rough particles may be considered composites of such bumps and dimples. Computational results show that surface roughness has a much larger effect on the external potential distribution than on that ins ide the particle. As expected, the effect is larger for thin than for thick double layers. Results are presented from which the average surf ace potential of bumps and dimples may be calculated. The perturbation approach may be useful in calculating potential distributions for mor e complex surface shapes and internal charge distributions, e.g. for p roteins.