Engineering nonspherical hollow structures with complex interiors by template-engaged redox etching

Despite the significant advancement in making hollow structures, one unsolved challenge in the field is how to engineer hollow structures with specific shapes, tunable compositions, and desirable interior structures. In particular, top-down engineering the interiors inside preformed hollow structures is still a daunting task. In this work, we demonstrate a facile approach for the preparation of a variety of uniform hollow structures, including Cu2O@Fe(OH)x nanorattles and Fe(OH)x cages with various shapes and dimensions by template-engaged redox etching of shape-controlled Cu2O crystals. The composition can be readily modulated at different structural levels to generate other interesting structures such as Cu2O@Fe2O3 and Cu@Fe3O4 rattles, as well as Fe2O3 and Fe3O4 cages. More remarkably, this strategy enables top-down engineering the interiors of hollow structures as demonstrated by the fabrication of double-walled nanorattles and nanoboxes, and even box-in-box structures. In addition, this approach is also applied to form Au and MnOx based hollow structures