Uniform CuO nanostructures have been synthesized on copper foil substrates by oxidation of Cu in alkaline condition by a simple wet chemical route at room temperature By controlling the alkaline condition (pH value) different CuO nanostructures like nanoneedles, self-assembled nanoflowers and staking of flake-like structures were achieved The phase formation and the composition of the films were characterized by X-ray diffraction and energy dispersive analysts of X-ray studies X-ray photoelectron spectroscopic studies indicated that the samples were composed of CuO The morphologies of the films were investigated by scanning electron microscopy. A possible growth mechanism is also proposed hew Band gap energies of the nanostructures were determined from the optical reflectance spectra The different CuO nanostructures showed good electron field emission properties with turn-on fields in the range 6-11 3 V mu m(-1). The field emission current was significantly affected by the morphologies of the CuO films. (C) 2010 Elsevier Ltd. All rights reserved