Direct Force Measurements between TiO2 Surfaces

Abstract

An atomic force microscope (AFM) has been used to measure the force of interaction between a rutile titanium dioxide colloid and a single macroscopic rutile crystal in aqueous solution. The effect of pH and electrolyte concentration on the force has been investigated, ζ potentials were derived from electrophoretic mobility measurements on the rutile colloid as a function of pH and electrolyte concentration. Experimental decay lengths for the repulsive electrical double layer interaction are in good agreement with the theoretical Debye lengths at <10−2 M electrolyte. Measurements at the isoelectric point, i.e. pH = 5.6 of the TiO2, could be fitted with a nonretarded Hamaker constant of 6 ± 2 ..