COLLOIDAL PARTICLES AT WATER-GLASS INTERFACE - DEPOSITION KINETICS AND SURFACE HETEROGENEITY

Videomicroscopy in combination with evanescent field illumination is a pplied to study the sorption of colloidal particles from flow in a par allel plate channel on a glass surface. The experiments, carried out i n the presence of a repulsive electrostatic barrier, reveal surprising ly complex results: The glass surface, though optically hat and well c leaned, is not homogeneous, but rather the sorption occurs at a limite d number of preferred sites. Moreover, these sites are not static: new sites keep appearing at random positions on the observed surface and disappearing at a rate of k(d) = 1.3 x 10(-5) s(-1). These findings ca n be understood within a simple model that takes into account slow but inevitable dissolution of the glass surface. The bulk glass contains potential adsorbers, which are continuously being exposed by the disso lution process and act as transient adsorption sites, before being was hed off by the flowing buffer solution, (C) 1998 Academic Press.