Ni-doped ZnO nanocrystals were prepared by a simple aqueous solution method at a low temperature. The microstructures of the samples were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive spectroscopy, inductively coupled plasma-atomic emission spectroscopy, and X-ray photoelectron spectroscopy. The Ni ions were successfully incorporated into the ZnO lattice and located at the substitutional sites of Zn atoms. The chemical bonding state of the doped Ni ions is 2+. The particle morphology of the samples changed from spindle- into rock-like after Ni-doping. The length and mean diameter of the doped ZnO particles both increased compared with undoped ZnO. Room temperature photoluminescence spectra showed a strong ultraviolet emission at 383 nm and a weak green emission band (500-600 nm), whose intensity was greatly reduced with increased dopant level. Magnetization (M)-magnetic field and M-temperature curves confirmed that the 3 mol%-doped sample had an obvious ferromagnetic property, and the 5 mol%-doped sample had a greater paramagnetism. (C) 2012 Elsevier B.V. All rights reserved.