Controlled synthesis and characterization of Ru-core-Pt-shell bimetallic nanoparticles

A combined polyol and redox-transmetalation strategy has been proposed to synthesize Rucore-Ptshell bimetallic nanoparticles. By following the in situ X-ray absorption spectroscopy (XAS) at the Pt LIII and Ru K edges, the reduction mechanism of Ru nanoparticles (NPs) in tetraethylene glycol (TEG) solutions and the corresponding reaction of Ru NPs with the added Pt\ub2\u207a ions in ethylene glycol (EG) solutions to form Rucore-Ptshell bimetallic nanoparticles was examined. The Pt LIII-edge XAS indicates that when the pH of H\u2082PtCl\u2086 in EG solution is adjusted to 12 and heated at 80 \ub0C for 5 min, the platinum compound is found to be reduced to a Pt(II) form corresponding to [PtCl\u2084]\ub2\u207b anionic species. At further reaction time of 10 min, the ligand environment around Pt(II) is changed from Cl\u207b to OH\u207b forming the [Pt(OH)\u2084]\ub2\u207b species. Analysis of the Ru K-edge XAS results confirms that Ru\u2083(CO)\u2081\u2082 in TEG undergoes a partial decarbonylation when it is heated at 300 \ub0C for 30 min and forms Ru\u2083(CO)\u2089 species. At further reaction time of 60 min, Ru\u2083(CO)\u2089 species are subjected to a complete decarbonylation to form Ru clusters in TEG solutions. When the EG solution containing [Pt(OH)\u2084]\ub2\u207b ionic species is mixed with preformed Ru clusters, Pt\ub2\u207a ions are reduced to Pt\ub0 on preformed Ru clusters at the expense of Ru via a redox-transmetalation process. The XAS structural parameters suggested that the resulting nanoparticles were of Rucore-Ptshell type structure with a higher extent of atomic distribution of Pt in the cluster when compared with Ru. The unique application of XAS as a fundamental characterization tool to realize the core-shell structure demonstrated here on the Ru-Pt bimetallic system can easily be extended to construct many other types of bimetallic systems for interesting applications.Peer reviewed: YesNRC publication: Ye