THE CATALYTIC ROLE OF SMALL COINAGE-METAL CLUSTERS IN PHOTOGRAPHY

We model the generation of the photographic latent image in silver-hal ide systems by the deposition of size-selected silver and gold cluster s onto silver-halide microcrystals. Coinage-metal cluster cations were produced in a sputtering arrangement, mass-selected by a quadrupole m ass filter, and deposited with a well-controlled kinetic energy onto b inderfree silver-bromide crystals. After exposure to the cluster beam, the samples were developed at a defined redox potential. The photogra phic action of the clusters was investigated as a function of their si ze, the coverage of the sample with clusters, the kinetic energy of th e clusters during the deposition, and the redox potential of the devel oper. Development was observed after the deposition of Ag-4(+) or larg er silver-cluster cations, and under some development conditions, afte r deposition of Ag-3(+). No development was observed after the deposit ion of smaller silver clusters, and after the deposition of gold clust er cations Au-n(+)(n less than or equal to 9).