Flower-shaped zinc oxide (ZnO) structures have been synthesized in the reaction of aqueous solution of zinc nitrate and NaOH at 90 degrees C. To examine the morphology of ZnO nanostructures, time-dependent experiments Were Carried out. Detailed structural observation showed that the flower-like structures consist of triangular-shaped leaves, having sharpened tips with wider bases. Photoluminescene spectrum measured at room temperature show a sharp UV emission at 381 nm and a strong, and broad green emission at 480-750 nm attributed to structural defects. A possible growth mechanism for the formation of flower-shaped ZnO structures is discussed in detail. (C) 2008 Elsevier Ltd. All rights reserved.