We report the effect of surfactant treatment on the structural and magnetic properties of Co-doped ZnO (Zn0.95Co0.05O) and Co-doped Li-co-cloped ZnO nanoparticles (Zn(0.85)Co(0.05)Lio(0.10)O), prepared by a low-temperature solid-state pyrolitic reaction. The X-ray diffraction and transmission electron microscopy analyses (TEM, HRTEM and SAED) of these samples showed the formation of phase pure nanocrystals with wurtzite ZnO structure. DC magnetization measurements, at room temperature, of AOT-treated samples showed enhanced ferromagnetism compared with the untreated samples. (C) 2008 Elsevier B.V. All rights reserved.