High-pH-induced reduction sensitization was used to form silver clusters on the surfaces of octahedral silver bromide grains. This method had the advantage of not leaving unreacted reducing agent in the emulsion, which could cause further silver cluster formation over time. Diffuse reflection spectroscopy measurements showed these silver clusters to be similar to those formed by dimethylamine borane and SnCl2, except that the absorption peaks were noticeably less intense. Large emulsion grains sensitized in this manner benefited most from the hole-removal ability of the silver clusters. The result was a linear relationship between speed and grain volume for edge lengths 0.28 to 1.22 µm, with a slope of 0.93 +/- 0.08, which is close to the theoretical slope of 1.0. Core–shell emulsions in which the cores were oversensitized with sulfur also benefited from the high-pH-induced reduction sensitization on the surface. Instead of desensitization of the core when oversensitized, these emulsions showed dramatically increased internal sensitivity, consistent with the proposed hole-removal property of the surface silver clusters. No evidence of electron trapping by these chemically produced silver clusters could be found.

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This article may be accessed on the publisher's website (additional fees may apply) at: http://www.imaging.org/store/epub.cfm?abstrid=282 ISSN:1062-3701 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)


RIT – Main Campus