Flexible and highly sensitive H2S gas sensor based on in-situ polymerized SnO2/rGO/PANI ternary nanocomposite with application in halitosis diagnosis

A room temperature sub-ppb hydrogen sulfide (H2S) gas sensors based on tin oxide/reduced graphene oxide/polyaniline (SnO2/rGO/PANI) was synthesized by in-situ polymerization technique. The SnO2/rGO/PANI nanocomposite film was fabricated on a flexible polyethylene terephthalate (PET) substrate with interdigital electrodes (IDEs). The SnO2/rGO/PANI sensor possesses excellent sensing characteristics such as high response, fast response/recovery time, stable repeatability, outstanding selectivity and long-term stability. The response of SnO2/rGO/PANI film sensor prepared by in-situ polymerization is 23.9 toward 200 ppb H2S, which is two times higher than that of physical doping method, and the limit of detection is 50 ppb. The experimental result reveals that the SnO2/rGO/PANI sensor is an excellent candidate to detect H2S gas in exhaled human breath for early diagnosis of halitosis. The underlying sensing mechanism of the SnO2/rGO/PANI sensing device towards H2S gas is due to the high surface area of SnO2/rGO/PANI film, chemisorption of oxygen on surface of SnO2 hollow spheres and the special role of heterojunction.