Room-Temperature\nNO₂ Sensing of CVD-Modified\nWS₂–WSe₂ Heterojunctions

Abstract

Two-dimensional (2D) semiconducting heterojunction chemical\nsensors\nare in high demand because of their enhanced response, stability,\nand selectivity. However, fine-tuning heterojunctions using vapor\ndeposition growth still needs further research. Our present study\nfocuses on the ambient pressure chemical vapor deposition (CVD) synthesis\nof hexagonal tungsten sulfide-tungsten selenide (WS₂–WSe₂) p–p heterojunctions (as a 2D–2D arrangement).\nWe use the liquid-phase exfoliation method to disperse bulk WS₂ and WSe₂ and decorate large flakes of WS₂ with smaller WSe₂ nanosheets in CVD. Electron microscopy\nand related surface investigations reveal their homogeneity on drop-casting.\nTwo drops from the exfoliated heterojunction dispersion were drop-cast\non a transducer to study the NO₂ response and related sensing\nproperties. The sensor showed long-term stability (>2 months),\neven\nat high humidity levels (40–90%). The gas-sensing properties\nof this layered p–p heterojunction-based nanocomposite strongly suggest an affinity\ntoward NO₂ gas, leading to improved response, high stability,\nindependent of humidity effects, and high selectivity.