On the Adsorption of Photosensitive Dyes by Various Photoconductorst

Abstract

Adsorption state of typical sensitizing dyes (9-methylthiacarbocyanine, methylene blue, 2, 2'- quinocyanine, and erythrosin) on various photoconductors (AgBr, ZnO, Ti02, S, CdS, and Se) have been studied in order to clear the mechanism of spectral sensitization in photoconductors. The dependence of the amounts of adsorbed dye upon both the electric charge of dye molecules and the kind of photoconductors play an important role in determining whether or not the dye molecules are adsorbed by the photoconductors. However, the independence of the amounts of adsorbed dyes upon neutral salts added suggests that interactions other than the Coulombic interaction also take part in the dye adsorption. Compared with the absorption spectra of methanolic dye solutions, the absorption bands in the reflection spectra of the adsorbed dyes were assigned to unaggregated and aggregated dye molecules. Shifts of the band peaks which were explained as due to the van der Waals' and Coulombic interactions between dye molecules and photoconductors were observed. t Studies on Mechanisms of Photographic Sensitivity, LXIII.