A facile route to model catalysts: the synthesis of Au@Pd core–shell nanoparticles on γ-Fe2O3 (0001)

A straightforward method of synthesising Au@Pd core-shell particles on a well characterised γ-Fe₂O₃ (0001) substrate has been developed which will enable fundamental studies into the surface chemistry of these catalytically interesting systems. Au and Pd were sequentially deposited onto a γ-Fe₂O₃ (0001) substrate in ultra high vacuum by metal vapour deposition and probed by LEIS and STM. Deposition of Au followed by heating at 573 K formed nanoparticles of 5 to 10 nm in diameter whereas subsequent deposition of Pd produced smaller nanoparticles of 2 to 4 nm diameter. At this stage, LEIS shows both metals to be present but heating the combined system to 573 K resulted in the loss of the Au signal in the LEIS and disappearance of the smaller particles from the STM images indicating the formation of Au@Pd core-shell structures.