Synthesis of Au and Au-CuO cubic microcages via an in situ sacrificial template approach

The controllable synthesis of hollow polyhedral hetero-structures composed of metallic and metallic-semiconductor nanograins has aroused great attention not only for the synthetic challenge, but also for the novel functions offered by their unique micro-/nanostructures. Herein, both Au and Au-CuO hierarchical heterostructured cubic microcages have been prepared using Cu2O cubes as sacrificial templates in aqueous solution. The micro-sized Au cubic cages are composed of Au nanograins about 20 nm in size with abundant pores inside the cage walls. Each individual Au-CuO hetero-structured cubic cage is assembled with both gold nanoparticles and CuO nanoneedles. A growth mechanism for the formation process of these delicate hierarchical cubic architectures is presented. Furthermore, the reflection loss (dB) spectra measured in the frequency range 2-18 GHz showed that the Au-CuO hollow hetero-structured cubic cages have an improved electromagnetic interference (EMI) shielding effectiveness (SE) compared to that of both Au hollow cubic microcages and conventional Au hollow microspheres. Moreover, these Au cages and Au-CuO cubic cages might find novel applications in sensing and catalysis due to their hierarchically assembled structures.