Nano-crystalline tungsten oxide NO2 sensor

Sensitive porous tungsten oxide nano-crystalline based NO2 sensor was fabricated by thin film microfabrication technique. The sensitivity of this NO2 sensor was at parts per billion (ppb) level. The nano-crystalline porous tungsten oxide film was prepared from WCl6 by a sol–gel technique. The surface morphology and sensitivity to NO2 of the tungsten oxide films calcined at various temperatures were investigated. The NO2 adsorption behavior on the tungsten oxide surface was carried out by XPS measurement. Experimental 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.