All Fiber-Optic Multigas (NH₃, NO₂, and CO) Sensor Based on MoWS₂ Coated Fiber

In this paper, we fabricate and demonstrate Molybdenum Tungsten Disulfide (MoWS 2 ) composite based all-optical gas sensor for environmental monitoring applications. This proposed sensor is fabricated by coating the synthesized MoWS 2 nanosheets on a side polished fiber (SPF) and analyzed the sensing performance of three important hazardous gases such as ammonia (NH 3 ), Nitrogen dioxide (NO 2 ) and Carbon monoxide (CO). The MoWS 2 nanosheets are synthesized using the hydrothermal exfoliation technique. This novel nanocomposite offers broadband absorption and desorption of gas molecules due to more edge sites, which in turn enhances the sensing properties for various gases. Thus, the MoWS 2 coated SPF sensor utilized for sensing three hazardous gases such as NH 3 , NO 2 and CO. Besides, the gas sensor is operated at normal humidity (60-75%) and room temperature for varying gas concentration from 0 to 500 ppm. The sensor shows high sensitivity of 86, 72, and 48% for various gases such as NH 3 , NO 2 and CO respectively. Furthermore, the results exhibit rapid response and fast recovery time, which are measured as 21 s and 60 s for NH 3 gas, whereas 42 s and 71 s for NO 2 gas and 93 s and 56 s for CO gas. The selectivity test for the sensor is conducted with methane and formaldehyde along with NH 3 , CO, and NO 2 gases in the same experimental condition. Further, the results confirm that the sensor possesses a high degree of selectivity for NH 3 gas among the other gases. Hence, the proposed sensor is eminently suitable to detect hazardous gases in high traffic and industrial fields.