SPECTRAL SENSITIZATION, INTERFACIAL ELECTRONIC-STRUCTURE, AND ADSORPTION GEOMETRY AT MEROCYANINE DYE SILVER-HALIDE INTERFACES

Interfaces between merocyanine dyes and silver halides were investigated by a combination of various techniques for discussing the mechanism of spectral sensitization. The electronic structures were directly determined for dye/AgBr interfaces by UV photoemission spectroscopy and diffuse reflectance spectroscopy. The observed electronic structures showed excellent correlation with observed sensitizing behavior of dyes. The adsorption geometries of dyes were estimated by studying Langmuir isotherms and x-ray absorption near-edge structure spectra at the K edge of sulfur for dye/AgCl systems, directly demonstrating that dyes with thioketone group are adsorbed at this site. Orientation of molecular dipoles of dyes is deduced to contribute, at least partly, to the formation of electric dipole layers observed in UV photoemission spectroscopy experiments.