WS2-Amorphous Carbon Heterointerfaces for Humidity-Tolerant Sub-ppb NO2 Sensing

Controlled structural and electronic modulation of transition-metal dichalcogenides (TMDs) is central to realizing high-performance gas sensors, yet reproducible strategies that simultaneously combine sensitivity, stability, and environmental robustness remain limited. Here, we report a high-performance room-temperature NO2 sensor based on tungsten disulfide nanosheets decorated in situ with defect-rich amorphous carbon (WS2-aC), fabricated via a simple and scalable flame chemical vapor deposition process. Precise regulation of the aC coverage enables strong interfacial coupling and defect modulation without disrupting the WS2 lattice. The optimized WS2-aC heterostructure delivers a high response of 240% to 10 ppm NO2, an ultralow detection limit of 5 ppb (LOD ∼0.15 ppb), and a power consumption of only ∼1.6 μW. Remarkably, the sensor maintains high sensitivity, selectivity, and signal stability under extreme humidity conditions, significantly mitigating a long-standing limitation of TMD-based gas sensors. Spectroscopic and electrical analyses reveal that the enhanced performance originates from interfacial charge transfer, vacancy-dominated defect states, and an increased density of active adsorption sites introduced by aC decoration. Thus, the direct aC integration is an effective route to environmentally robust TMD heterostructures and highlights its potential for practical, low-power gas-sensing technologies.