Early stages in the growth of small silver clusters in aqueous solution

Complete text of publication follows. One of the challenging contributions of radiation chemistry and the method of pulse radiolysis is the ability of producing and characterizing metal and semiconductor colloids on the nanometer scale, experiments which started as early as in the 1970', i.e., in the early days of nanotechnology. Since then, metal clusters and nanomaterials have attracted an immense attention due to their unique properties. Here, as a review of the work carried out at the Hahn-Meitner-Institut Berlin / Helmholtz Zentrum Berlin, the results of the reduction of silver ions in aqueous solution by products of the water radiolysis is presented. Attention focuses in general on silver clusters as a model because the monopositive cation Ag+ is the only noble cation that forms mononuclear species with appreciable stability in aqueous solution. While hydrated electrons simply reduce silver ions, the reduction by hydrogen atoms occurs via the intermediate complex of silver hydride ions. The reduced silver ion, i.e., a free silver atom, reacts further with bulk silver ions thus starting the growth of small silver clusters. Even the early stages of that growth result in interesting structures which gives insight into the valence states of the silver species being involved. Also, the influence of aliphatic alcohol radicals on these processes is discussed for medium and low bulk silver concentrations. Aliphatic alcohols are present in solution in basically all these experiments in order to simplify the redox system by scavenging oxidizing radicals. Aliphatic alcohol radicals obviously form some kind of complex with small silver clusters thus participating in the growth of silver clusters and determining their properties to some extend.