It has been reported that some experts fabricated nanocrystalline tungsten oxide based NO2 sensor by thin film microfabrication technique. And the sensitivity of this NO2 sensor was at parts per billion (ppb) level.
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In the study, the experts prepared the porous nanocrystalline tungsten oxide film from WCl6 by a sol-gel technique, and investigated the surface morphology and sensitivity to NO2 of the tungsten oxide films calcined at various temperatures. Also, they carried out the NO2 adsorption behavior on the tungsten oxide surface by XPS measurement. The results indicated that the tungsten oxide film calcined at 550 °C for 1 h showed the best performance as a sensing material to NO2, and the optimal operational temperature of the sensor was 300 °C. The sensor showed high sensitivity to low NO2 concentration in the range from 50 to 550 ppb with relatively fast response time (～3 min) and recovery time (～1 min), respectively.
