Ag^＋-assisted heterogeneous growth of concave Pd@Au nanocubes for surface enhanced Raman scattering （SERS）

AgNO3 is often used in the preparation of Au nanostructures since Ag-based substances （AgBS） can selectively be adsorbed on Au（100） and significantly modulate the growth of Au nanocrystals. High-index-faceted Au nanostructures have demonstrated excellent performance in catalysis and surface enhanced Raman scattering （SERS）, thus attracting the interest of many researchers in the past several decades. Herein, high-index-faceted Pd@Au concave nanocubes （CNCs） were prepared using AgBS as growth-directing agents in the heterogeneous growth of Au on Pd nanocubes （NCs）. During the growth of Pd@Au CNCs, Au atoms are initially deposited on the Pd{100} facets leading to the formation of thin Au shells, and then AgBS are quickly adsorbed on the formed Au（100）, favoring the growth along 〈111〉 and the formation of Pd@Au CNCs. Transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, energy dispersive spectroscopy （EDS）, high angle annular dark field （HAADF）, and scanning transmission electron microscopy EDS （STEM- EDS） were used to systematically investigate the growth of Pd@Au CNCs. We also demonstrated that the high-index-faceted Pd@Au CNCs exhibited excellent SERS performances.