Humidity enhanced ammonia sensing of porous polyaniline/tungsten disulfide nanocomposite film

Abstract A significant threat of poisonous and colorless ammonia (NH3) emission at low level to environmental protection and human health urgently necessitates sensitive NH3 detection. Meanwhile, low-powered gas sensing is quite favorable in the fields of wearable and portable devices with the ultimate target of battery-free operation. To achieve these goals, in this work we prepared a porous polyaniline/tungsten disulfide (PANI/WS2) nanocomposite film to detect ppm-level NH3 gas at room temperature (25 °C) under humid background atmosphere. The as-prepared PANI/WS2 sensor with 1.5 mg of WS2 loading exhibited a stronger response (1.25 vs. 1.02), better operation stability and accelerated response/recovery speeds toward 10 ppm NH3 at a relative humidity of 68 % (the optimal RH level) in comparison with PANI counterpart. Moreover, decent repeatability and NH3 selectivity were demonstrated. Noteworthy was that excess WS2 loading adversely weakened the sensor response. More WS2 incorporation induced wider aggregations of PANI nanorods acting as the supporting pillars within the porous composite film, which obviously strengthened film structure and then the operation robustness under humid atmosphere compared with pure PANI sensor. The presented design strategy by subtle optimization of operation RH and WS2 loading paves the avenue for further sub-ppm NH3 detection of PANI-related gas sensors in the aspects of high sensitivity and strong stability.