SHEAR PLANE AND HYDRODYNAMIC DIAMETER OF MICROSPHERES IN SUSPENSION

Brownian motion of spherical particulate systems of different material s and surface conditions in dilute aqueous suspensions of various ioni c concentrations was studied using photon correlation spectroscopy, ze ta potential measurement, and static light scattering measurement. A r elation between the ionic concentration and the hydrodynamic diameters of spheres is found. This relation exists as an enlarged particle dia meter proportional to the electric double layer. Such size variation i s independent of sphere size but dependent on solution conductivity. A model directly relating the shear plane to the measured hydrodynamic diameters and a guide to the proper use of photon correlation spectros copy in sizing submicron particles are proposed.