Adsorption of cyanine dyes at silver halide surfaces. Part 2.—Spectral properties and coverage

Abstract

Adsorption isotherms and spectral reflectance measurements of four cyanine dyes adsorbed at silver-halide surfaces of known specific area showed that more dye was adsorbed from water than from alcohol and that each dye was adsorbed initially in an “unperturbed” form. Further adsorption of the dye from water, at points approaching the plateau of the isotherm, suggested that a second layer of dye was adsorbed on top of the first layer with a different orientation. The results were consistent with a first layer adsorbing flat-on and showing “unperturbed” spectral properties and a second layer was adsorbing side-on and showing “perturbed” properties. Some of these data are inconsistent with aggregation of the “perturbed” dye in the sense of cluster formation on the surface.