This report presents a brief discussion on the importance of ZnO nanomaterial in gas sensing applications. Recent developments on ZnO-based gas sensors have been reviewed. The primary work in this report involves the study of the Raman spectrum of a ZnO wurtzite sample. Using the group theoretical background, the various vibrational modes of the ZnO wurtzite have been studied at length. Finally, the defect properties of ZnO wurtzite, mainly the oxygen vacancy defect which plays an important role in a gas sensing application, have been investigated