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.