Ultrathin CuO nanowires grown by thermal oxidation of copper powders in air

•Ultrathin CuO nanowires were grown by thermal oxidation of Cu powders in air.•The growth temperature and time are 300 °C and 1 h respectively.•The diameters are distributed in the range of 5–10 nm.•The photoluminescent properties are studied.

Copper powders were thermally treated in the air at a wide temperature range of 200–700 °C. It was found that thin CuO nanowires were grown at 300 °C and thick CuO nanowires were grown at 500 °C. The diameters of the thin CuO nanowires were distributed in the range of 5–10 nm, and the growth directions along [1̄11] and [110] were observed. In addition, the thermally treated copper powders with ultrathin CuO nanowires showed a broad violet emission band peaking at 402 nm.