Nanocrystalline ZnO thin film was deposited using spray pyrolysis technique on a glass substrate. The morphological, structural, chemical state, sensing response, as well as the bond formation of ammonia exposed ZnO were studied. The ammonia adsorption mechanism was examined for the ZnO thin films at ambient temperature (32 degrees C) through experimental and DFT studies. It revealed that ammonia was adsorbed over ZnO via N-Zn and O-H and transferred charge to ZnO. The electronic structure parameters such as charge transfer, HOMO/LUMO gap, and DOS for (ZnO)(12) cluster were analysed and reported. Nitrogen formation during the desorption of ammonia over ZnO was verified through GC-MS. (C) 2018 Elsevier B.V. All rights reserved.