ZnO nanowires (NWs) were deposited on a glass substrate by the successive ionic layer adsorption and reactionmethod (SILAR). Sensing response of ZnO NWs towards reducing vapours was tested at ambient temperature ($\sim$32$^{\circ}$C)by the chemiresistor method. The vapour response was found to be 80.2, 1.6, 1.1 and 1.1 for NH$_3$,H$_2$O, (CH$_3$)$_2$CO and C$_2$H$_5$OH, respectively. Also, density functional theory (DFT) calculations were performed to understand the charge transfer and electronic property change during adsorption of molecules over ZnO NW. The band of the Zn 3d state was altered after adsorption and no significant changes were observed in the O2p state.Higher binding energy (14.6 eV) with significant chargetransfer (0.04$|e|$) was observed in the ammonia-adsorbed ZnO NW. On comparing response obtained through experimentaland computational studies, almost a similar trend of response was observed except for the H$_2$O–ZnO system. This was dueto lack of dispersion interaction and steric effect influence in the DFT calculation with the chosen computational methods.

A portable continuous ammonia detecting device using nanostructured zinc oxide (ZnO) as a chemiresistive element is demonstrated in this work. Nanostructured ZnO was deposited on a commercially available ceramic tube with 5 mm length and outer diameter of 1 mm by spray pyrolysis technique at 350°C. The X-ray diffraction studies of ZnO showed the polycrystalline nature with multiple peaks. The morphological studies confirmed the uniform distribution of nanostructure over the entire surface of the tube. The ZnO crystal planes observed in the selected area electron diffraction pattern matched with the X-ray diffraction pattern. Since ZnO offers very high resistance, it was interfaced with operational amplifier TLC272CP with a gain of 13. The sensing module’s response to various concentrations of ammonia at elevated temperatures was studied. The selectivity of the sensing module towards major farm field and poultry gases were also investigated. Further, the sensing module was integrated with Arduino Uno R3 and thin film transistor display to show the continuous variation of ammonia concentration in poultry and farm fields. The estimated range of detection of the continuous ammonia detecting device was found to be 5–100 ppm.