Au@Pd core-shell nanoparticles through digestive ripening

Colloids of gold and palladium nanoparticles have been prepared by the Solvated Metal Atom Dispersion (SMAD) method. Digestive ripening, a process involving mixing of the as-prepared gold and palladium colloids consisting of polydisperse nanoparticles and refluxing the mixture in the presence of a surfactant resulted in highly monodisperse Au@Pd core-shell nanoparticles with an average diameter of 6.6 +/- 0.5 nm. The synthesis has been successfully carried out reproducibly on gram scale. The core-shell structure was established by using UV-visible spectroscopy, high-resolution electron microscopy, energy filtered electron microscopy, energy dispersive X-ray analysis, high angle annular dark field imaging, and powder X-ray diffraction methods.