Observation and Characterization of Sulfur Sensitization Centers Formed on Silver Halide Grains

摘要

In the previous study, we succeeded in observing sulfur sensitization centers, which were formed with sodium thiosulfate as a sensitizer on octahedral silver bromide grains in emulsions and decorated with silver clusters by use of a special physical developer. The concentration of the centers increased with increasing the amount of the sensitizer and reached the plateau with as many as 3200/μ m~2, when the sensitivity reached the maximum. The concentration didn't increase with further increasing the amount of the sensitizer. The comparison of the concentration of the observed centers with the amount of silver sulfide formed by sulfur sensitization revealed that each sulfur sensitization center contained two sulfide ions in the emulsion with the maximum sensitivity. In this study, we observed sulfur sensitization centers formed with triethylthiourea as a sulfur sensitizer on cubic silver iodobromide grains. In this emulsion, the sensitivity increased by prolonging the digestion time after the silver sulfide formation was completed. This result was ascribed to the progress of the aggregation of silver sulfide to form sensitization centers. We could observe that the increase in the sensitivity and the increase in the observed centers took place in a parallel fashion with increasing the digestion time after the silver sulfide formation was completed, and that the saturated concentration of the observed centers was 2100/μ m~2 on the cubic grains. Although sensitization centers were formed uniformly on the octahedral grains, they were formed preferentially at corner and edge sites on the cubic ones.