Facet‐Dependent Optical Properties Revealed through Investigation of Polyhedral Au–Cu2O and Bimetallic Core–Shell Nanocrystals

Abstract

The ability to prepare Au–Cu₂O core–shell nanocrystals with precise control over particle size and shape has led to the discovery of facet-dependent optical properties in cuprous oxide crystals. The use of Au cores not only allows the successful formation of Au–Cu₂O core–shell nanocrystals with tunable sizes, but also enables the observation of facet-dependent optical properties in these crystals through the Au localized surface plasmon resonance (LSPR) absorption band. By tuning the Cu₂O shell morphology from rhombic dodecahedral to octahedral and cubic structures, and thus the exposed facets, the Au LSPR band position can be widely tuned. Such facet-dependent optical effects are not observed in bimetallic Au–Ag and Au–Pd core–shell nanocrystals with the same precisely tuned particle sizes and shapes. It is believed that similar facet-dependent optical properties could be observed in other ionic solids and other metal–metal oxide systems. The unusually large degree of plasmonic band tuning covering from the visible to the near-infrared region in this type of nanostructure should be quite useful for a range of plasmonic applications.