Au@Cu Core–Shell Nanocubes with Controllable Sizes in the Range of 20–30 nm for Applications in Catalysis and Plasmonics

Predominantly covered by a single type of {100} facets, Cu nanocubes are attractive catalytic material toward reactions such as electrochemical reduction of CO<sub>2</sub>. Here we report a seed-mediated approach to the facile synthesis of Au@Cu core–shell nanocubes with hexadecylamine and Cl<sup>–</sup> serving as capping agents toward the {100} facets of Cu and glucose as a reducing agent. The large (12%) lattice mismatch between Cu and Au led to the localized epitaxial growth of Cu shells on the Au seeds and the formation of nanocubes with randomly distributed Au cores. Compared to the same synthesis in the absence of Au seeds, the reduction of Cu­(II) ions was greatly accelerated in the presence of Au seeds because of the autocatalytic surface reduction. It was also found that the structure and morphology of the products were highly dependent on the concentration of Cu­(II) precursor in the reaction solution. Nanoplates rather than nanocubes were obtained when the concentration of Cu­(II) precursor was reduced down to a certain level. By variation of the reaction time and/or the amount of Au seeds, the size of the Au@Cu nanocubes could be tuned in a range of 20–30 nm. The as-synthesized core–shell nanocubes exhibited a strong localized surface plasmon resonance peak at 581 nm, and the resonance was dominated by absorption rather than scattering. It is expected that the Au@Cu nanocubes with uniform and controllable sizes will find use in a variety of applications such as plasmonics and catalysis.