Earlier attempts of various investigators to increase the sensitivity of photographic emulsions by addition of colloidal silver, silver sulfide, or gold are reviewed. Koslowsky’s discovery of the effect of certain gold complex salts as powerful sensitizers is described and a possible mechanism of the effect discussed. The importance of this effect for the manufacture of modern high speed and fine grain film as well as special x-ray emulsions is indicated.
F. W. H. MUELLER, "Some Remarks on Gold Treatment of Photographic Silver Halide Emulsions," J. Opt. Soc. Am. 39, 494-496 (1949)