Evaluation of Interaction Forces between Surfaces in Electrolyte Solutions by Atomic Force Microscope

Abstract

Interaction forces between a cleaved mica and the SiO₂ surface of an apex of an AFM probe in electrolyte solutions were measured using an Atomic Force Microscope (AFM). It is found that (1) the AFM is a powerful apparatus to measure in-situ the interaction forces between surfaces in solutions on the molecular level, (2) the long-range interaction force between surfaces is estimated well by the classical DLVO theory, (3) the magnitude of the short-range interaction force corresponds to the order of the hydration enthalpy of the ions in the solution. A possible model for the structure of water molecules and ions adsorbed on the surface was discussed.