ELECTRICAL DOUBLE-LAYER FORCES MEASURED WITH AN ATOMIC-FORCE MICROSCOPE WHILE ELECTROCHEMICALLY CONTROLLING SURFACE-POTENTIAL OF THE CANTILEVER

The atomic force microscope was used to detect electrostatic forces an d estimate surface potentials of samples in aqueous solution by applyi ng voltage to a conducting tip. We controlled surface potential of a A u-coated cantilever electrochemically, and measured force vs distance curves on monolayers with different kinds of functional groups. As a r esult, we detected force variation with applied voltage to the tip, an d the direction of force variation was found to agree with the polarit y of surface charges due to the dissociation of the functional groups.