<i>In situ</i> fabrication of alumina nanotube array and photoluminescence

Aluminum foil was anodized in aged electrolyte under high voltage. The morphology observation shows that the alumina film has a three-layer structure from bottom to top and the middle layer shows large quantities of individual alumina nanotubes. Their formation mechanism is discussed in detail. Under ultraviolet excitation, the alumina film exhibits an emission centered at ∼400nm. Based on annealing behavior of the emission band and electron paramagnetic resonance result, the origin of the emission is considered to be due to optical transition in single ionized oxygen vacancy (F+ center) in the alumina. The experimental results can be expected to have favorable applications in optoelectronics and biotechnology.