Abstract
The adsorption process of fluorescein dyes, good sensitizers for electrophotographic zinc oxide layers, was studied by visible and infrared spectroscopic means. Thus crystalline, dissolved and adsorbed forms of the dyes were successively investigated by the above means in order to obtain informations on the structural changes of the dyes through the adsorption process from the solution to the surface of zinc oxide grains.
Exprimental results indicated that when the fluorescein dyes of free acid form, whether they were non-ionic lactoid or quinoid, were adsorbed on zinc oxide grains, structural changes of the dyes to the ionic quinoid form were accompanied, while disodium salt of them (ionic quinoid form) were invariant in the structure through the adsorption process. In other words, whether or not fluorescein dyes are ionic in the solution, they are ionized on the surface of zinc oxide, and the spectral sensitization occurs in almost the same manner.
Desorption experiments, in addition, suggested that the counter ion of the ionized dye on zinc oxide, as in the case of the former, was a zinc ion, while that was a sodium ion in the case of the latter.
