A study of adsorption of a cyanine dye to cubic AgBr microcrystals suspended in a dried gelatin layer

Abstract

The amount of a cyanine dye [3,3′-bis(4-sulfobutyl)-9-methylthiacarbocyanine] adsorbed to cubic AgBr microcrystals m suspended in dried gelatin (i.e., dried emulsion) was measured by preparing dried emulsion layers, which were smooth and thick enough for treatment by the Kubelka–Munk equation and gave useful information on the adsorption of the dye and materials of photographic interests to the microcrystals. The saturated amount of the adsorbed dye M in a dried emulsion layer was smaller than that in a liquid emulsion, since functional groups of gelatin and a stabilizer (4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene) in the solution phase of the liquid emulsion were forced to be adsorbed to the microcrystals on drying. The dye adsorption increased the concentration of interstitial silver ions in the microcrystals by repelling silver ions at kink sites on the surface of the microcrystals into interstitial positions, especially when m approached M. The number of silver ions repelled into interstitial positions was less than 0.001 of that of the dye molecules adsorbed to the microcrystals.