Fabrication of a room-temperature NO2 gas sensor based on WO3 films and WO3/MWCNT nanocomposite films by combining polyol process with metal organic decomposition method

Polyol process was combined with metal organic decomposition (MOD) method to fabricate a room-temperature NO2 gas sensor based on a tungsten oxide (WO3) film and another a nanocomposite film of WO3/multi-walled carbon nanotubes (WO3/MWCNTs). X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the structure and morphology of the fabricated films. Comparative gas sensing results indicated that the sensor that was based on the WO3/MWCNT nanocomposite film exhibited a much higher sensitivity than that based on a WO3 film in detecting NO2 gas at room temperature. Microstructural observations revealed that MWCNTs were embedded in the WO3 matrix. Therefore, a model of potential barriers to electronic conduction in the composite material was used to suggest that the high sensitivity is associated with the stretching of the two depletion layers at the surface of the WO3 film and at the interface of the WO3 film and the MWCNTs when detected gases are adsorbed at room temperature. The sensor that is based on a nanocomposite film of WO3/MWCNT exhibited a strong response in detecting very low concentrations of NO2 gas at room temperature and is practical because of the ease of its fabrication.