Double layer forces over large potential ranges as measured in an electrochemical surface forces apparatus

Electrodes specifically designed for use in the surface forces apparatus (S FA) were employed to study forces between mica and polycrystalline gold und er potential control. This control was achieved by soldering a wire to the gold surface and modifying the chamber of the SFA into a three-electrode ce ll configuration. The interactions measured were a strong function of the a pplied electrode potential, being more repulsive as the gold potential was moved toward more negative potentials. Independent force measurements betwe en mica surfaces were done to determine the mica surface potential. The exp erimental results were compared to Derjaguin-Landau-Verwey-Overbeek (DLVO) predictions of the forces between dissimilar charged surfaces. The long ran ge forces correspond well to DLVO predictions, including evidence of satura tion in forces at high applied potentials; forces deviate from theory at sh ort range.