Well-aligned single-crystalline zinc oxide (ZnO) nanowires with high density were successfully synthesized on nickel monoxide (NiO) catalyzed alumina substrate through a simple metal-vapor deposition method at an extremely low temperature (450degreesC). The single-crystalline ZnO nanowires had a hexagonal wurzite structure and diameters of about 55 mn, and lengths up to 2.6 mum. The photoluminescence spectra under excitation 325 urn showed a ultra-violet (UV) emission at 3.26 eV and a green emission at 2.44 eV. The UV emission and green emission bands were attributed to near band-edge transition and radial combination of a singly ionized oxygen vacancy with a photo-induced hole, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.