Stable Pd@Cu Core–Shell Nanocubes with Finely Tuned Sizes for the Reduction of Nitroaromatics

This paper reports a seed-mediated growth of Pd@Cu core–shell nanocubes with controllable edge lengths from 49 to 103 nm in an aqueous system using cetyltrimethylammonium bromide (CTAB) capped Pd nanocubes with sizes of 21 nm as seeds. During the growth, ascorbic acid (AA) was served as the reductant and hexadecylamine (HDA) as the capping agent and ligand to form a coordination complex with Cu2+. The edge lengths of Pd@Cu nanocubes could be finely tuned by changing the volume of Pd seeds while maintaining the amount of CuCl2 precursor. Cu atoms initially nucleated on one or two faces of a Pd seed via localized epitaxial growth. Due to the lattice mismatch between Pd and Cu (7.1%), Pd cores were not located in the center of Cu shells during the initial deposition of Cu. Interestingly, most of Pd cores could transfer to the center of Cu nanocubes by dissolving and regrowing of the boundary to decrease the interfacial strain when a sufficient amount of CuCl2 precursor and reaction time were provided. The Pd@Cu nanocubes exhibited strong LSPR signals and long-term stability which could be a low-cost potential substitute for Au and Ag for applications in sensing, surface-enhanced spectroscopy, optoelectronics, and photocatalysis. By comparison of the rate constant of p-nitrophenol reduction reaction over Pd@Cu nanocubes with different sizes as catalyst, 83 nm Pd@Cu nanocubes showed the highest catalytic activity.