Silver iodide sols, adsorption

The surface charge on a solid surface can be obtained by determining the adsorption of potential-determining ions at various potentials of the interface [1]. For example, in the case of a silver iodide sol the adsorption of Ag+ and I ions is determined at various concentrations of Ag" " and I" ions in bulk solution. Similarly, for an oxide the adsorption of H" " and OH" ions Fand respectively) is determined as... 

Fleer, G. J., and Lyklema, J. 1976. Polymer adsorption and its effect on the stability of hydrophobic colloids. El. Kinetics of the flocculation of silver iodide sols. t.Coll.lnt Sd. 55 228-238. 

A more accurate determination has been carried out by Verwey and Kruyt Using a concentrated, well dialyzed silver iodide sol, they determined the change in adsorption of I-ions v/ith the activity of the I-ions in the solution and found the following simple relation,... 

Polymer adsorption is important in the flocculation and stabilization of colloidal sols and has been reviewed by Vincent et al. (1) and Tadros (2). Polyvinyl alcohol (PVA) has been used in these studies because of its practical application in textiles, adhesives, and coatings. The adsorption of PVA has been studied on silver iodide by Fleer (3) and Koopal (4), and on polystyrene (PS) latex particles by Garvey (5). The adsorption isotherms reported by these workers extend up to 600 ppm PVA. The adsorption at... 

Van Laar used the sol concentration effect in order to determine the zero point of charge of Agl. He determined the pAg for which there was no difference in E.M.F. between a salt bridge in a silver iodide suspension and a salt bridge in the equilibrium solution. At this pAg there is no diffuse double layer and when specific adsorption is absent the zero point of charge is reached Sec also 6a, p 161 ... 

This author points out that Sols prepared with different stabilizers often have quite different absorption spectra even though the particle size distributions appear similar. This statement could readily be applied to our sols. The adsorption of iodide or sulfide ions [20] or of stabilizers such as gelatin or poly(vinyl pyrrolidone (PVP) [21-23] onto silver colloids led to a marked red shift, with damping of the plasmon band. The same phenomena were observed in this study experimentally as blue and red shifts of the plasmon maximum peak. The observed red shift, associated with the addition of surfactant stabilizers, is due to the displacement of nucleophiles (i.e., anions adsorbed on the particle surface) by the surfactants from the surface. 

---