Dynamic properties of the AgI-solution interface: Implications for colloid stability

Abstract

This paper discusses the dynamics (i.e. the rates of the various charge displacement processes) of electrical double layers after disequilibration, taking the AgI-electrolyte solution interface as the model system. Relaxation studies performed with Ag/AgI electrodes lead to the conclusion that there is a relatively slow step, connected with the transfer of charge through the solid-solution interface. Evidence is given that this step occurs also with colloidal particles under interaction. It is inferred that in AgI sols interaction takes place at constant total particle charge, but at variable charge density distribution. The effect of particle radius a is also considered, an important parameter being the ratio τ l/τ int between the characteristic time scales of lateral charge flow and interaction. This ratio is dominated by the hydrodynamic drag. It appears that these dynamic factors level off the effect of the particle radius on the rate of coagulation. Other implications for colloid stability are discussed.