Wall-drag effect on diffusion of colloidal particles near surfaces: A photon correlation study

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Abstract
The reduction of the diffusion coefficient of latex spheres near glass surfaces was measured by photon correlation spectroscopy. Theory and experiment are not in agreement; possible causes for the discrepancy are discussed. In addition, the diffusion coefficient of sedimented latex spheres on a glass surface decreases with decreasing Debye length of the solution. This shows that the mean particle-surface separation distance decreases as the strength of the double-layer repulsion between the latex spheres and the glass surface is weakened. The utility of photon correlation spectroscopy for studies of interactions between colloidal particles and surfaces is discussed.