CuO Nanotubes Synthesized by the Thermal Oxidation of Cu Nanowires

Abstract

Copper oxide (CuO) is a narrow band-gap semiconducting oxide that has been widely used as a cathode in dye-sensitized solar cells, gas sensors and heterogeneous catalysts. Much effort has been devoted to synthesizing unique CuO nanostructures, such as, rods, wires, ribbons, cubes, spheres and dandelions. Unlike nanorods and nanowires, only a few groups have synthesized CuO nanotubes due to fabrication difficulties within hollow nanorods and nanowires. CuO nanotubes were synthesized by pyrolyzing copper acetylacetonate within the pores of the anodic alumina membranes. CuO nanotubes of average length 100 nm were also synthesized by a hydrothermal process involving microemulsified Cu(OH)42−.12 The simplest method of making CuO is from the direct thermal oxidation of copper metal, and many research groups have prepared CuO nanowires and nanorods by oxidizing copper foils. However, due to self aggregation, it is difficult to obtain long copper nanowire or nanorod precursors for the preparation of CuO nanotubes by direct thermal oxidation. Here, we describe the preparation of CuO nanotubes from long copper nanowires by simple thermal oxidation. The morphologies of the CuO nanotubes produced were determined by scanning electron microscopy and transmission electron microscopy.