NiO nanotubes assembled in pores of porous anodic alumina and their optical absorption properties

Nickel oxide (NiO) nanotubes, embedded in a porous anodic aluminum oxide (AAO) template, have been produced by a wet chemistry templating method using a nickel–ammine complex as a precursor. The dimensions of the nanotubes are about 60 μm in length, with an outer diameter of about 200 nm and a wall thickness of 60 nm. They possess a polycrystalline structure and the NiO nanotube arrays exhibit an optical absorption band gap of 3.90 eV, similar to that of bulk NiO.