Attractive potential between confined colloids at low ionic strength

Abstract

Digital video microscopy is used to locate the positions of 1.27 μm diameter polystyrene spheres suspended in low ionic strength water and confined between two glass plates. A method is developed to obtain the pair potential of the colloidal particles from measurements of the pair-correlation function of both dilute and moderately concentrated dispersions. We find that the measured pair potential has an attractive component much greater than predicted by the Derjaguin-Landau-Verwey-Overbeek theory of nonconfined colloids and suggest that the confining plates are responsible for the observed deviations from theory.