Microwave-irradiated WS2/WO3–graphene composites for high-performance NO2 detection

Abstract

The chemical and structural transformations of transition-metal dichalcogenides (TMDs) have garnered significant research attention for gas-sensing applications owing to their unique composition-dependent physicochemical properties. However, achieving precise and reproducible control of TMD oxidation and heterostructure formation remains a critical challenge. Herein, we report the NO2 sensing properties of microwave-irradiated tungsten disulfide/graphene (WS2 /Gp) composites, in which the partial oxidation of WS2 generates a WS2 /WO3–Gp heterostructure. By optimizing the WS2 oxidation level and Gp content, we achieved a record-high and stable response of 56% for 10 ppb of NO2 and an extremely low detection limit of 0.76 ppb, with a power consumption of only approximately 12.5 μW. The composite-based sensors retained their sensing performance in the presence of humidity and a mixture of NO and NH3 , and exhibited strong signal enhancement towards NO2 over other highly toxic reactive gases. Moreover, the composite sensors showed excellent cyclic stability and durability, maintaining consistent performance under extreme humidity (80%). The enhanced sensing performance can be attributed to multiple heterojunctions, oxygen vacancies, and abundant active sites, which improve the charge transport and response time. The proposed novel sensing mechanism highlights the charge transfer between the gas molecules and the sensing surface. This work provides insights into the microwave-irradiated structural modulation of TMDs and represents a significant advancement towards the fabrication of low-cost, intelligent gas sensors with robust environmental stability for practical applications.