Styryl cyanine dyes: Aggregate behaviour, electrochemical properties and photographic performance

The aggregate behaviour of styryl cyanine dyes on silver halide emulsions w as investigated by measuring ultraviolet (UV)-visible (Vis) absorption spec tra and reflectance spectra. The lowest vacant and the highest occupied ele ctronic energy levels of these dyes were estimated using their redox potent ials. The effects of styryl cyanine dyes upon the ionic conductivity of cub ic silver halide grains with an average size of 0.18 mu m in photographic e mulsions have been studied with the aid of dielectric loss measurements. Th e ionic conductivity of the grains was increased by the adsorbed dye 2-(4'- diethylaminostyryl)-3-sulphopropyl-5-methoxybenzothiazole. The photographic performance in silver halide emulsion was examined and the correlation of photographic performance with electrochemical properties was studied. The e xperimental results indicate that the electrochemical properties of the dye s depend on their structure and the photographic performance of the dyes is determined by their electrochemical properties.