In this paper we present a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution via solution method. Zinc acetate dihydrate and sodium hydroxide were used as a precursor, which was refluxed at 90 degrees C for an hour. The pH of the precursor solution (zinc acetate di hydrate) was increased from 6 to 12 by the controlled addition of sodium hydroxide (NaOH). Morphology of ZnO nanorods markedly varies from sheet-like (at pH 6) to rod-like structure of zinc oxide (pH 10-12). Diffraction patterns match well with standard ZnO at all pH values. Crystallinity and nanostructures were confirmed by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern, which indicates structure grew along [0001] direction with an ideal lattice fringes distance 0.52 nm. FTIR spectroscopic measurement showed a standard peak of zinc oxide at 464 cm(-1). Amount of H+ and OH- ions are found key to the structure control of studied material, as discussed in the growth mechanism. (C) 2008 Elsevier B. V. All rights reserved.