Electrochemical Study on Spectral Sensitization of Silver Chloride

The spectral sensitization of silver chloride using dyes has been studied electrochemically by measuring the dye-sensitized photocurrent. The following electrochemical cell was constructed: Pt ( I ) /electrolyte ( I ), dye/AgCl/electrolyte ( II ) /Pt ( II ), where the dimension of the silver chloride crystal was 8 x 8 x 0.5 mm. Dyes used as senitizesrs were 1, 1'-diethyl-2, 2'-quinocyanine chloride, 3, 3'-diethylthiacarbocyanine iodide, fluorescein, etc. Since the dark current was greater by a factor of more than 103 than the photocurrent, a light chopper and a lock-in amplifier were used to determine the photocurrent selectively. It was found that the sensitized photocurrent incr eased with increasing concention of the dye up to about 10-4 mol/l, then attained a saturated value. This behavior was interpreted in terms of the Langmuir adsorption of the dye to the silver chloride crystal. It was observed that the sensitized photocurrent increased remarkably with increasing concentration of silver ions in the electrolyte solution ( I). The results obtained in the present study were in good agreement with those obtained in the photographical investigation.