Density-controlled ZnO nanorods were grown on seeded transparent conducting oxide substrates from 20 mM aqueous solutions of zinc nitrate and hexamethylenetetramine at different volume ratios and at 90 degrees C for 4 degrees h. The average diameters of the hexagonal ZnO nanorods were higher when equal volume ratios of the precursor solutions were used. The reduced zinc chemical potential inside the precursor solution split the single nanorod into many smaller nanorods with reduced density and average diameters. The high resolution transmission electron microscopy confirms that the prepared single ZnO nanorods are single crystalline and the lattice spacing of approximately 0.22 nm correspond to the distance between two (0001) crystal planes. (C) 2010 Elsevier B.V. All rights reserved.