Metal/semiconductor core/shell nanodisks and nanotubes

The low melting point of Zn and the high melting point of ZnO, as well as their hexagonal crystal structures, present great advantages for designing and fabricating various metal/semiconductor core/shell nanostructures. By controlling the kinetics in the Zn and ZnO system, the lower-energy facets, and the oxidation rates of different surfaces, we can control the fabrication of Zn/ZnO core/shell single-crystal, polycrystalline, and mesoporous nanodisks, as well as a variety of ZnO nanotubes. The oxidation of a Zn nano-object leads to the formation of Zn/ZnO core/shell nanodisks. A lower oxidation temperature results in the formation of a single-crystal-like Zn/ZnO core/shell structure, while a higher oxidation temperature leads to the formation of textured and even polycrystalline nanostructures. A re-sublimation process of Zn in the core leaves a ZnO shell structure. This is an approach for synthesizing metal/semiconductor core/shell or composite nanostructures. This article offers a detailed description of the kinetics controlling the procedures, the nanostructures obtained, their morphological and crystal structures, and their formation mechanisms.