The thermodynamically forbidden reaction between ZnCl2 and O-2 was able to take place by using oxygen plasma, yielding cone-shaped ZnO nanostructure. In situ optical emission spectroscopy was used to identify the excited species during the plasma enhanced reaction. The determination of excited temperature suggested that the addition of O-2 had great contribution to the enhanced dissociation of ZnCl2. The successful synthesis of ZnO indicates that the chlorides may replace the organometallics as a new precursor in thin film preparation industry. (C) 2011 Elsevier ay. All rights reserved.