Hierarchical WS2-WO3 Nanohybrids with P-N Heterojunctions for NO2 Detection

Two-dimensional (2D) transition metal dichalcogenide (TMD)-based gas sensors have received much attention due to their high sensitivity at room temperature. However, the long-term stability is limited by their poor stability against oxidation and hydration. This work develops a facile and practical strategy for the construction of reliable WS2-sensing devices under air conditions. A surface functionalization strategy for WS2 nanoflakes has been demonstrated, where WO3 nanosheets are aligned on the surface of WS2 nanoflakes via a facile sonochemical method. The synthesis method and structure-response relationship of the WS2-WO3 nanohybrid are carefully studied. The optimal device displays brilliant long-term stability and relatively stable sensing characteristics under the humidity conditions. Moreover, the WS2-WO3 sensor exhibits a remarkably enhanced response, a quick response time, and an excellent recoverability compared with the WS2 sensor. The impressive NO2-sensing performance of the WS2-WO3 nanohybrid is ascribed to the special hierarchical structure, the strong interlayer electronic coupling, and the formed p-n heterojunctions. This study offers a perspective for the structural design of TMD-based gas sensors, which exhibit not only an enhanced NO2-sensing performance but also an environmental stability.