Copper Oxide Nanocubes Wrapping Metals by Microwave Synthesis
Miquel Torras, Anna Roig
Abstract
Copper and copper oxide nanoparticles (NPs) are industrially important. In particular, Cu-based nanocatalysts find applicability in electrocatalysis and photocatalysis, profiting from the accessible oxidation states of copper and a band gap in the visible region of the Cu2O phase. However, in this case, the fast recombination of the charge carriers compromises the final photocatalytic efficiency. The combination of Cu2O with metals often results in higher and more stable photocatalytic efficiency. Here, the fabrication of noble metal NPs [Au, Ag, Pd, and Pt] and Cu2O heterostructures (HSs) by a microwave (MW)-assisted synthesis is presented. The selectivity of the MW technique with a fast two-step protocol enabled us to easily prepare these multicomponent nanoparticles in a short time (∼40 min). First, metal NPs (Au, Ag, or Pd) are synthesized through a MW-assisted polyol approach, and these NPs serve as nucleation seeds for cubic Cu2O wrapping. Other types of heterostructures were found when using smaller Pt NPs instead. Focusing on Au NPs as the core, we analyzed the effect of the gold to copper molar ratio on the shape yield of the nanocubes, reported their optic and plasmonic properties, and demonstrated the reproducibility and scalability of the synthetic routes. Here, we are providing a pioneering example of MW heating as a non-conventional energy source for a general chemical approach to attain a family of complex metal/metal oxide heterostructures.