Cross-sensitivity and selectivity studies on ZnO surface acoustic wave ammonia sensor

ZnO coated one-port surface acoustic wave (SAW) resonators are used as ammonia sensor in the present study. The cross-sensitivity of the sensor with commonly available volatile organic compounds (VOCs)/gases has been analyzed. An interesting feature through which the presence of ammonia can be differentiated from rest of the vapors/gases has been observed. The differential frequency shift (Δf) of the sensor is positive for liquor ammonia and negative for the rest. Further Δf for ammonia in the presence of water vapors is found to be positive. The sensor has good sensitivity, selectivity, reversibility and repeatability. The results are analyzed by considering possible sensing mechanisms such as electrical loading, elastic loading and mass loading. The results suggest the possibility of utilizing the ZnO coated sensor for the efficient selective detection of ammonia.