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

Abstract

Predominantly covered by a single type of {100} facets, Cu nanocubes are attractive catalytic material toward reactions such as electrochemical reduction of CO2. Here we report a seed-mediated approach to the facile synthesis of Au@Cu core–shell nanocubes with hexadecylamine and Cl– 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.

Controlling the Surface Oxidation of Cu Nanowires Improves Their Catalytic Selectivity and Stability toward C2+ Products in CO2 Reduction

“…In the X‐ray photoelectron spectroscopy (XPS) spectrum recorded from A‐CuNWs (Figure 1 e), two peaks were resolved at 932.1 and 951.9 eV, which could be assigned to Cu 0 or Cu I 2p peaks. Additionally, we observed two peaks at 933.9 and 953.7 eV, together with satellite peaks around 941, 943, and 962 eV, and all of them could be assigned to Cu II 2p peaks [17] . These results indicate that the oxide sheath was made of a mix of Cu 2 O and CuO.…”

“…In the X-ray photoelectron spectroscopy (XPS) spectrum recorded from A-CuNWs ( Figure 1e), two peaks were resolved at 932.1 and 951.9 eV,which could be assigned to Cu 0 or Cu I 2p peaks.Additionally,weobserved two peaks at 933.9 and 953.7 eV,t ogether with satellite peaks around 941, 943, and 962 eV,a nd all of them could be assigned to Cu II 2p peaks. [17] These results indicate that the oxide sheath was made of am ix of Cu 2 Oa nd CuO.I nt he X-ray diffraction (XRD) pattern, however,n op eaks of copper oxides were observed ( Figure 1d). We only resolved three peaks at 43.48 8, 50.58 8,a nd 74.28 8,c orresponding to the diffraction from Cu-(111), (200), and (220) planes.T he absence of Cu x Opeaks in the XRD pattern confirmed the dominance of amorphous phase,i na greement with our conclusion drawn from STEM imaging.…”

Kinetically Controlled Synthesis of Pd–Cu Janus Nanocrystals with Enriched Surface Structures and Enhanced Catalytic Activities toward CO2 Reduction

“…After another 30 min, the majority of the nanocrystals grew into the pentagonal-bipyramidal shape, and further extension of the reaction time to 120 min did not cause additional changes to the shape and size of the nanocrystals (Figure , c and d). We also observed some Cu nanocrystals containing no Pd seeds in the products, which could be attributed to homogeneous rather than heterogeneous nucleation . Since the nanocrystals made of pure Cu and the Pd–Cu nanocrystals were more or less similar in terms of size, both of them could prevail in the products owing to the suppression of Ostwald ripening .…”

“…We also observed some Cu nanocrystals containing no Pd seeds in the products, which could be attributed to homogeneous rather than heterogeneous nucleation. 37 Since the nanocrystals made of pure Cu and the Pd−Cu nanocrystals were more or less similar in terms of size, both of them could prevail in the products owing to the suppression of Ostwald ripening. 38 From the penta-twinned structure of the bipyramid, it can be concluded that the Cu atoms initially nucleated from one of the vertices of an icosahedral seed, followed by gradual growth into an elongated, pentagonal bipyramid.…”

Controlling the Surface Oxidation of Cu Nanowires Improves Their Catalytic Selectivity and Stability toward C2+ Products in CO2 Reduction

“…Forschungsartikel resolved at 932.1 and 951.9 eV,which could be assigned to Cu 0 or Cu I 2p peaks.Additionally,weobserved two peaks at 933.9 and 953.7 eV,t ogether with satellite peaks around 941, 943, and 962 eV,a nd all of them could be assigned to Cu II 2p peaks. [17] These results indicate that the oxide sheath was made of am ix of Cu 2 Oa nd CuO.I nt he X-ray diffraction (XRD) pattern, however,n op eaks of copper oxides were observed ( Figure 1d). We only resolved three peaks at 43.48 8, 50.58 8,a nd 74.28 8,c orresponding to the diffraction from Cu-(111), (200), and (220) planes.T he absence of Cu x Opeaks in the XRD pattern confirmed the dominance of amorphous phase,i na greement with our conclusion drawn from STEM imaging.…”