Structure Control Mechanism of Polymer-Protected Composite Metal Clusters

1)两种贵金属离子的乙醇/水（1/1,V/V）溶液在聚乙烯吡罗烷酮存在下回流得到双金属团簇的胶体分散。通过EXAFS技术分析，双金属簇具有“核壳”结构，其中一个元素形成核，另一个元素覆盖在核上形成壳。2)利用多通道光电二极管阵列跟踪电子能谱，分析了双金属团簇的形成过程。发现还原顺序是由氧化还原电位决定的。3)“微团簇”是一种细小的金属颗粒，对双金属团簇的形成起着重要的作用，特别是那些具有“团簇中团簇”结构的双金属团簇。4)聚合物在受聚合物保护的金属团簇中作为配体，对确定双金属团簇中的“核-壳”结构起着重要作用。5)开发了一种制备轻质过渡金属/贵金属双金属簇的新方法，该方法一直被认为是非常困难的。该方法涉及在初始阶段制备金属氢氧化物颗粒，并用多元醇方法还原离子。用这种方法制备了铜/钯和铜/铂双金属团簇。

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.