Zinc oxide nanostructures have been prepared by the sol-gel method on SiO2/Si substrates using acid (pH = 6) and neutral (pH = 7) solutions. Neutral solutions produce rod-like ZnO nanostructures that grow laterally during subsequent thermal annealing. Acid solutions result in a combination of regions consisting of either rods or platelets. Using spatially resolved cathodoluminescence spectroscopy, it is observed that thermal treatment of ZnO grown in neutral sol affects the deep-level luminescence, reducing the yellow emission but retaining the green luminescence. In material grown from acid solutions, stronger luminescence has been observed from rods compared to platelets. Luminescence from nanorods shows donor-bound exciton and donor-acceptor-pair emissions at low temperatures (<40 K) and a broad near-band-edge peak for higher temperatures. The role of pH on the growth mechanisms leading to rod and platelet formation is discussed. (C) 2007 Elsevier B.V. All rights reserved.