Morphology and photoluminescence of nanostructured oxides grown by copper passivation in aqueous potassium hydroxide solution

Copper foil was anodized in 1 M KOH at potentials ranging from −400 to −100 mV vs. Ag|AgCl electrode. Cyclic voltammetry showed a distinct peak with a maximum at around −150 mV. For anodizing at −100 and −200 mV, nanowires with diameters of ca. 19 and 24 nm respectively were found to be grown. Moreover, photoluminescence and X-ray diffraction show that the dominant phase is the CuO phase. At lower potentials, cuboidal micron sized crystals were formed and Cu₂O was found to be the major phase.