Enhanced Gas Sensing Properties of Liquid-Processed Semiconducting Tungsten Chalcogenide (WXi, X = O and S) Based Hybrid Nanomaterials

A high temperature chemiresistive ammonia sensor based on nanohybrids of semiconducting tungsten chalcogenides i.e. tungsten oxides (WO
₃
) and tungsten sulfides (WS
₂
) is reported in this paper. The sensitivity of the devices was investigated over a wide range of concentration i.e. (250-2000 ppm) and temperature (25 °C-400 °C). The sensor with composition of WO
₃
/WS
₂
(70:30 wt.%) showed optimized performance when operated at 250 °C. The response of the sensor was found to be 1.5-12.6 times in the 250-2000 ppm range. The response and recovery times for 1000 ppm ammonia were found to be 160 s and 310 s, respectively. The sensor showed high selectivity towards ammonia over other volatile organic compounds, like ethanol, methanol, and acetone. The response from the sensor was found to be highly stable and reproducible over time. The plausible mechanism behind the excellent performance of the hybrid nanomaterial over the metal oxide based sensor suggests that the incorporation of transition metal dichalcogenides like WS
₂
could be beneficial for metal oxide based sensors in terms of lowering the operating temperature of sensing device, response enhancement, and improvement in the performance.