MECHANISTIC CONSIDERATION OF FORMATION OF POLYMER-PROTECTED NANOSCOPIC BIMETALLIC CLUSTERS

Three types of polymer-protected bimetallic clusters of noble-metals, prepared by simultaneous alcohol reduction, have been totally shown to have special 'core-shell' structures, on the basis of X-ray diffraction and quantitative X-ray photoelectron spectroscopic measurements. In situ UV-VIS spectral changes during the formation of clusters indicated that the redox potentials of metal ions can control the order of the reduction and that redox reactions between two kinds of metal elements occur during the reduction. Thus, specific effects of the second element were observed. The special structures of these bimetallic clusters are concluded to be controlled by the orders of the reduction of the metal ions and the aggregation property of metal atoms which is attributed to the formation of a 'polymer-metal' complex with the protective polymer.