Down to ppb level ethanol detection based on heterostructured SnO/rGO composites

•The hetero-structured SnO/rGO composites were successfully fabricated for the first time.•The fabricated SnO/rGO gas sensor has an excellent gas sensing character to ethanol at 170 °C.•The SnO/rGO gas sensor can detect ppb level C2H5OH. In this work, hetero-structured SnO/rGO nanocomposites were synthesized by hydrothermal method using GO raw materials prepared by Hummers’ method. The crystal structures, morphologies and microstructures of SnO/rGO nanocomposites were detailedly characterized. Moreover, the gas sensors based on SnO/rGO nanocomposites displayed a high response of 4.76 toward 5 ppm ethanol at 170 °C with a fast response time of ~20 s, even a relatively high response ~2.26 to 400 ppb ethanol. Series of analysis indicated that these excellent performances could be originated from three aspects: 1) the formed p-p hetero-junctions between SnOand rGO that separated the carriers, 2) the high conductivity of rGO components that facilitated the transport of electrons, and 3) the functional groups (such as CO and COOH) on rGO that enhanced for the absorption sensing of ethanol.