Silver halide photography, surface

Photoinduced electron injection is by no means a new development. This process has already been applied in areas such as silver halide photography. In this discussion, only sensitized TiC>2 surfaces will be considered. Many experiments have shown that the charge injection into the semiconductor surface is very fast. In order to study these processes, fast spectroscopic techniques are preferred. Whether or not charge injection takes place can be studied conveniently on the nanosecond time-scale by using transient absorption spectroscopy. However, to address the injection process directly, experiments are carried out on the femtosecond time-scale, while recombination and charge separation require the nanosecond to microsecond range. 

Silver photography is based on the formation, during the exposure, of the latent image made of silver clusters distributed at the surface of each silver halide crystal embedded in the gelatine and containing from 0 to 10 atoms. 

Although the environment ofthe clusters is different in solutions and at the surface of silver halide crystals, we proposed to extend the same growth mechanism, which was demonstrated by pulse radiolysisfor Ag J clusters free in solution, to a theoretical explanation ofthe development process in photography [7] (Fig. 10). The development occurs in both cases at the interface between an aqueous solution of an electron donor and a silver cluster acting as an autocatalytic growing site alternately accepting electrons and silver ions. 

Other uses in photography involve silica-hardened gelatin surfaces on X-ray film (726), colloidal silica-modified silver halide emulsions for higher sensitivity (727), and silica-polyvinyl alcohol as a replacement for gelatin in image-receiving layers (728). 

---