Advances in nitrogen oxides sensors

Ihngsten trioxide has been repeatedly demonstrated to be the most sensitive material to a variety of nitrogen oxides - NO2 and NO, in particular. The vast bulk of the hterature focuses on investigating W03-based materials using a variety of fabrication techniques. 

Cross-sensitivity experiments conducted by Cantalini et aL (1996) indicated that, whilst poor gas responses were observed in the presence of CO or methane, ethanol and water did cause a gas response. It was found that different material-annealing temperatures affected the susceptibility of the films to cross-contaminates. 

11 The variation in resistance according to WO3 crystallite size. Reprinted with permission from J. Electrochem. Soc., 141, 2207 (1994). Copyright 1994,The Electrochemical Society (Tamaki etal., 1994). 

12 Demonstrating the effect of firing temperature on the responsivity of the material. Reproduced with permission (Chung etal., 1999). 

Heat treatment in 40-50% oxygen atmospheres gave the highest sensitivity control of oxygen content in the film was shown to be important in optimising the response behaviour of WO3 and reducing the required operating temperature. 

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