Aucore-Ptshell (Au@Pt) nanoparticles were syn-thesized at room temperature by reducing K2PtCl6 with hy-drogen in the solution containing Au colloids and polyvi-nylpyrrolidone (PVP). The particles obtained were charac-terized with UV-Vis, TEM and XPS techniques. UV-Vis spectra show that the surface plasmon absorption feature of Au colloids is significantly reduced with increasing the amount of reduced Pt. TEM images that the metals are found always appear as spherical nanoparticles and their sizes grow apparently due to the reduction of PtCl62? ions, indicating that Pt is deposited from solution onto Au particle surface and forms a Pt-layer with uniform thickness. In the XPS spectra, the signals of Au metal decrease due to the re-ductive deposition of Pt on the surface of the Au colloids. UV-Vis and XPS data are consistent in showing that when the amount of Pt in the AuPt colloids is increased to reach an overall atomic ratio of Pt/Au = 2, the Pt deposits form a shell covering completely the surface of Au particles, demonstrat-ing the core-shell structure of the synthesized AuPt particles.
