Ligand-Stabilized Bimetallic Colloids Identified by HRTEM and EDX

Gold colloids are covered by platinum and palladium shells when an aqueous solution of the colloids is added to a solution of H2PtC16 or H2PdCl4 and H3NOHCl, stabilizing the particles thus formed with p‐H2NC6H4SO3Na. A heterogenous agglomerate is formed for the Au/Pt system, a homogeneous system with well‐ordered shells of palladium atoms for Au/Pd, as is shown by the electron microscope image (illustration on the right) and the optical diffractogram (insert). Such studies are relevant to the clarification of the mechanism for alloy formation and for heterogeneous catalysis.