Ammonia sensors based on metal oxide nanostructures

Ammonia sensing characteristics of nanoparticles as well as nanorods of ZnO, In2O3 and SnO2 have been investigated over a wide range of concentrations (1–800 ppm) and temperatures (100–300 °C). The best values of sensitivity are found with ZnO nanoparticles and SnO2 nanostructures. Considering all the characteristics, the SnO2 nanostructures appear to be good candidates for sensing ammonia, with sensitivities of 222 and 19 at 300 °C and 100 °C respectively for 800 ppm of NH3. The recovery and response times are respectively in the ranges 12–68 s and 22–120 s. The effect of humidity on the performance of the sensors is not marked up to 60% at 300 °C. With the oxide sensors reported here no interference for NH3 is found from H2, CO, nitrogen oxides, H2S and SO2.