▎ 摘　　要

Advanced semiconductor heterostructures based on 2D materials present fascinating chemical, electronic, and geometric effects on chemical sensing and hold a great promise for developing high-performance gas sensors. However, the conventional tandem heterostructures may suffer from severe defect scattering as well as inferior heterointerface, thus limiting their sensing performance as the result of hindered interfacial charge transfer. Herein, we present a hierarchical assembly of SnO2-rGO/SnS2 heterostructure with 2D reduced graphene oxide (rGO) acting as a transfer highway to bridge n-type SnO2 nanowires and n-type SnS2 nanoflakes, resulting in novel ternary n-g-n junctions for the improvement of charge transport efficiency and thus enabling ultra-sensitive NO2 gas detection. Compared to pure SnO2/SnS2 and SnS2 sensors, the sensing response of n-g-n junctioned SnO2-rGO/SnS2 sensor reaches 1064 toward 10 ppm NO2, exceeding the corresponding sensors by a factor of 18 and 35, respectively. The SnO2-rGO/SnS2 sensor also exhibits an extremely low detection limit down to 10 ppb, short response and recovery times (42 and 111 s, respectively), excellent selectivity, long-term stability, and humidity resistance. We believe such a ternary architectural design with the novel n-g-n heterojunction engineering would provide a new approach towards future ultrahigh-performance gas sensing.