Analytical TEM observation of Au–Pd nanoparticles prepared by sonochemical method

The Au–Pd nanoparticles prepared by sonochemical technique were investigated by the analytical transmission electron microscopy. The core (Au)–shell (Pd) structure without apparent mixing layers and with similar thickness of Pd shells was clearly confirmed by the image and intensity profile of annular dark field scanning transmission electron microscopy (ADF-STEM) and also by the line-scan analysis of energy dispersive X-ray spectroscopy (EDS) in STEM mode. Detailed analyses of the ADF-STEM imaging, the electron diffraction pattern and the FFT pattern of HRTEM images complementarily show that the Pd shell epitaxially grows on the Au core expanded with the same lattice constant as Au and with the coherent Pd/Au interface structure.