| Abstract
| - Au-core/Pt-shell bimetallic clusters have been loaded on the surface of TiO2 (Au(x wt %)−Pt(y wt %)−TiO2(Pt/Au atomic ratio, z)) in a highly dispersed state by a two-step method consisting of the Au depositionand the subsequent Pt photodeposition. The mean diameter of the metal particles increases as a result of thePt deposition from 3.6 (x = 0.39, y = 0, z = 0) to 4.3 nm (x = 0.37, y = 0.74, z = 2.0), while their numberdensity hardly changes. High-resolution transmission electron spectroscopy directly confirms an Au-core/Pt-shell structure for a sample (z = 0.82). Adsorption experiments of bis(2-dipyridyl) disulfide, selected as asulfur-containing compound, clarify that it adsorbs preferentially on the metal surfaces and the saturatedadsorption amount on Au−Pt/TiO2 significantly decreases as compared to those on Au/TiO2 and Pt/TiO2.From X-ray photoelectron spectroscopic measurements, the Pt4f7/2 binding energy for the Au−Pt/TiO2 samplehas been found to shift to a lower energy relative to that for bulk Pt by 1.4 eV. Also, the Pt photodepositioncauses a red shift in the absorption maximum of the Au plasmon band. These spectroscopic results arerationalized in terms of the partial electron transfer from Au to Pt, which is also suggested by the calculationsof a model cluster (Au2−Pt2/TiO2) using the density functional theory (DFT). Further, the DFT calculationsindicate that the bonding and antibonding metal−sulfur orbitals are formed and the latter contribution ismore significant to the bond for the Pt-containing clusters.
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