Enhanced ammonia sensing properties of rGO/WS2 heterojunction based chemiresistive sensor by marginal sulfonate decoration

Two-dimensional reduced graphene oxide (rGO) nanosheets were pre-sulfonated and further incorporated by WS 2 nanoflakes to form S-rGO/WS 2 heterojunctions by hydrothermal synthesis. The sulfonation and WS 2 incorporation in S-rGO/WS 2 heterojunction have been confirmed by EDS, XPS and FTIR. The sensing performance of rGO-based chemiresistive-type sensor to ammonia at room temperature has been significantly improved by the sulfonation and incorporation of WS 2 nanoflakes. The chemiresistive sensor based on S-rGO/WS 2 exhibits enhanced response signals to 10∼50 ppm ammonia, while the response/recovery time is significantly shortened compared to rGO/WS 2 reported previously at room temperature. It benefits from both the extra introduced active acid centers sensitive to ammonia molecules and the better desorption-ability facilitated significantly by sulfonate groups (S O 3 H). The adsorption energy calculation of ammonia molecule on the sulfonated graphene sheet based on density functional theory (DFT) has been performed to illustrate the adsorption capacity of S O 3 H group. The selectivity and stability of gas sensor based on S-rGO/WS 2 have also been studied.