Hierarchical WS₂–WO₃ Nanohybrids\nwith P–N Heterojunctions for NO₂ Detection

Abstract

Two-dimensional (2D) transition metal\ndichalcogenide (TMD)-based\ngas sensors have received much attention due to their high sensitivity\nat room temperature. However, the long-term stability is limited by\ntheir poor stability against oxidation and hydration. This work develops\na facile and practical strategy for the construction of reliable WS₂-sensing devices under air conditions. A surface functionalization\nstrategy for WS₂ nanoflakes has been demonstrated, where\nWO₃ nanosheets are aligned on the surface of WS₂ nanoflakes <i>via</i> a facile sonochemical method. The\nsynthesis method and structure–response relationship of the\nWS₂–WO₃ nanohybrid are carefully studied.\nThe optimal device displays brilliant long-term stability and relatively\nstable sensing characteristics under the humidity conditions. Moreover,\nthe WS₂–WO₃ sensor exhibits a remarkably\nenhanced response, a quick response time, and an excellent recoverability\ncompared with the WS₂ sensor. The impressive NO₂-sensing performance of the WS₂–WO₃ nanohybrid\nis ascribed to the special hierarchical structure, the strong interlayer\nelectronic coupling, and the formed p–n heterojunctions. This\nstudy offers a perspective for the structural design of TMD-based\ngas sensors, which exhibit not only an enhanced NO₂-sensing\nperformance but also an environmental stability.