Structure Control Mechanism of Polymer-Protected Composite Metal Clusters

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1)Refluxing an ethanol/water (1/1, V/V) solution of two kinds of noble metal ions in the presence of polyvinylpyrrolidone gave the colloidal dispersion of bimetallic clusters. The bimetallic clusters were analyzed by an EXAFS technique to have a "coreshell"structure, in which one element forms a core and the other element covers the core to from a shell.2)The formation process of the bimetallic clusters were analyzed by tracing the electronic spectra with a multi-channel photodiode array. The reduction order is found to be determined by the oxidation-reduction potential.3)"Microcluster , "a fine metal particle, plays an important role for the formation of bimetallic clusters, especially those with a "cluster-in-cluster"structure.4)The polymer works as a ligand in the polymer-protected metal clusters and plays an important role for the determination of the "core-shell"structure in bimetallic clusters.5)A novel method has been developed for the preparation of light transition metal/noble metal bimetallic clusters, which has been thought to be very difficult. The method involves the preparation of particles of metal hydroxide at an initial stage and the reduction of the ions with a polyol method.Copper/palladium and copper/platinum bimetallic clusters have been prepared by this method.