The colloidal stability of spectrally sensitized 3-D AgClI emulsions

The colloidal stability of silver halide emulsions precipitated in aqueous gelatin media is predominantly electro-steric in nature and is provided by gelatin adsorbed on the silver halide grains. It is believed that gelatin p rovides adequate colloidal stability for spectrally sensitized silver halid e emulsions, where the sensitizing dyes compete with gelatin for the silver halide surface. We have examined the details of the interaction of gelatin with unsensitized and sensitized 3-D AgCII emulsions by evaluating the int erfacial potential of the emulsions and their colloidal stability as a func tion of pH and ionic strength. The interfacial potential of the emulsions h as been determined using electrokinetic sonic amplitude (ESA) measurements and the colloidal stability of the emulsions was studied using filterabilit y measurements. The unsensitized and sensitized emulsions do not show any a ppreciable differences in their electrokinetic properties, while they do ex hibit differences in their filterability properties upon pH cycling. It is surmised that gelatin is more easily desorbed from the surface of sensitize d emulsions than unsensitized emulsions upon pH cycling, leading to aggrega tion. Hence, we conclude that the weaker adsorption of gelatin on silver ha lide emulsions is the root cause of the diminished colloidal stability of s pectrally sensitized silver halide emulsions. The results suggest that sens itized silver halide emulsions are more prone to destabilization due to pro cess variations than unsensitized silver halide emulsions.