We report a simple electrochemical etching and a subsequent heat treatment to synthesize nanowire-like Cuo thin films with pure phase at room temperature. The reaction media has great effect on microstructure of products to significantly improve optical and photocatalytic activities of materials. Detailed characterizations of the synthesized nanomaterials are performed utilizing X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to study their crystalline phase and morphology. The photoluminescene (PL) spectrum shows a main emission peak and a blue emission band whose centers are located at 352 nm and 463 nm, respectively. Photocatalytic study demonstrated the degradation of methylene blue (MB) can reach 95.6% after 210 min irradiation, showing its potential application in waste water treatment. A plausible growth mechanism for the transformation is also proposed. (C) 2015 Elsevier B.V. All rights reserved.