An in-situ surface modification route for realizing the synergetic effect in P3HT-SnO2 composite sensor and strikingly improving its sensing performance

•P3HT-SnO2 composite gas sensors were fabricated via a new in-situ surface modification route.•P3HT-SnO2 composite gas sensors exhibited higher sensor response and excellent selectivity for detecting NO2 of few ppm.•The synergetic effect between P3HT and SnO2 greatly improved the performance of composite gas sensors. By developing a new in-situ surface modification route, P3HT-SnO2 composite gas sensor with strikingly improved performance was fabricated via modifying the surface of SnO2 porous nanosolid (SnO2 PNS). The experimental results indicate that the sensor fabricated from pristine SnO2 PNS exhibited quite poor sensing performance to NO2 gas. In contrast, when the adsorbed impurity molecules were removed from the surface of SnO2 PNS, followed by introducing P3HT into the pores in-situ way, P3HT-SnO2 composite gas sensors with greatly improved performance were fabricated, namely, lower working temperature, higher sensor response, much faster response-recovery speed and excellent selectivity. This phenomenon was explained by the appearance and disappearance of “synergetic effect” between P3HT and SnO2, which was resulted from the forward electron transfer process from P3HT to SnO2 and the backward process.