Nominally undoped ZnO nanorods, grown by a chemical method, have been post-treated to intentionally incorporate high concentrations of zinc vacancies and zinc interstitials and were studied with electron microscopy and low temperature photoluminescence spectroscopy. The Zn-i are related to the 3.405 eV peak at 4.2 K, verifying that Zn-i is a shallow donor lying 30 meV below the conduction band minimum, while the acceptors V-zn are related to the 3.308 eV peak at 4.2 K and have an activation energy of 123 meV. (C) 2011 Elsevier B.V. All rights reserved.