Synthesis of CuO nanotubes with controlled diameters by chemical transformation of Cu nanowires

The simple, low-cost, and scalable transformation of Cu nanowires into CuO nanotubes was demonstrated by employing a thermal oxidation processes. The diameter of the Cu nanowires was controlled by utilizing anodic alumina templates with controlled pore sizes and this resulted in CuO nanotubes with various outer and inner diameters after thermal oxidation at 350°C for 2 h. The morphology, phase, and microstructure of the transformed nanostructures were systematically investigated and it was confirmed that the transformation to the tubular nanostructures resulted from the Kirkendall effect caused by the different diffusion rates of Cu and O in Cu_xO generated during thermal oxidation. The transformed CuO nanotubes with the controlled diameters have a wide range of applications in photovolatics, catalysis, gas sensors, and field effect transistor because of their dimensionalities and large specific surface areas.