Dynamics of the interaction forces at the silver/solution interface during amine adsorption

The forces of interaction between a silver-coated particle and a flat silver surface in an aqueous medium were measured in the presence of a series of organic amines of varying concentrations. Atomic force microscopy (AFM) was used to quantify the replacement rate of adsorbed citrate molecules on the silver surfaces by a variety of amines, under conditions where the time scale of the amine adsorption was significantly slower than the time scale of the AFM measurements. The decay length of the electrostatic double-layer interaction between the silver surfaces was found to be time independent; thus, the change in surface change density (determined from the interaction forces) was used to quantify the replacement rate of adsorbed citrate by amine. In the absence of amine, the interaction force between the silver surfaces exhibited evidence of a multilayer structure of adsorbed citrate molecules on each silver surface. Upon addition of the amine, a decrease in the interaction force was always observed, where the dynamics of the force were dependent on both concentration and the molecular structure of the amine. These results are discussed with respect to formation of colloidal particles in synthesis routes where particle aggregation has a significant impact on the control of particle morphology and size.