Influence of temperature on evolution of coaxial ZnO/Al2O3 one-dimensional heterostructures:: From core-shell nanowires to spinel nanotubes and porous nanowires

In this paper, we present the influence of temperature on the Kirkendall effect-related evolution of coaxial ZnO/Al2O3 one-dimensional heterostructures based on a solid-state reaction. Controllable fabrication of spinel ZnAl2O4-based nanotubes and porous nanowires can step-by-step be achieved from ZnO/Al2O3 core-shell nanowires with a change in the reaction temperature. In particular, we demonstrate that the formation of completely hollow nanotubes in this system is not strictly limited to a fixed stoichiometry of ZnO/Al2O3 required for the spinel-forming reaction when an annealing temperature of 800 degrees C is employed. Combined with atomic layer deposition, the wall thickness of the formed nanotubes can be further precisely tailored and defined. Our finding provides an effective route to fabricate spinel nanotubes as well as nanotube arrays on a large scale.