Cu nanoparticles doped with small amounts of noble metals were Synthesized by ultrasonication. The noble metals selected were Pd, Pt, Ru, Rh and Ir. Mean particle size was most reduced for Cu nanoparticles doped with Pd, with Cu-Pd nanoparticles of approximately 50nm in diameter being obtained. X-ray absorption, near-edge spectroscopy and extended X-ray absorption were used to conduct fine structure analysis, and these techniques confirmed that Cu-Pd nanoparticles possessed Cu-Pd bonds. High-angle annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectrometer mapping were used to show that Cu-Pd nanoparticles were dispersed as Pd clusters inside Cu nanoparticles. It was supposed that the surfaces of Cu-Pd nanoparticles were Cu-rich, and Pd clusters were dispersed inside these particles. It is proposed that heterogeneous nucleation of Cu onto Pd nuclei resulted when nucleation of Pd occurred.
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