Flower-Like CNTs@MoS₂ Core-Shell Nanostructure for NH₃ Gas Sensor at Room Temperature

Ammonia (NH₃) is a hazardous gas requiring rapid detection at room temperature for practical environmental and agricultural monitoring. Herein, we report a flower-like CNTs@MoS₂ core-shell heterostructure synthesized via a facile hydrothermal process for room-temperature NH₃ sensing. Structural analyses confirm uniform MoS₂ nanosheets anchored on the CNT networks, forming well-defined p-n heterojunction interfaces that facilitate efficient charge transport. This architecture effectively combines the high surface activity and gas adsorption capability of MoS₂ with the superior electrical conductivity of CNTs, promoting rapid charge transfer and enhanced sensing performance. The optimized sensor achieves a high response of 94% toward 500 ppm of NH₃ with rapid response and recovery times of 36 and 68 s, respectively. Additionally, humidity-assisted interfacial charge transfer further improves the sensor response under high relative humidity. Long-term stability tests demonstrate ∼80% response retention after 150 days. This study elucidates the dominant role of MoS₂ and the synergistic charge modulation enabled by CNTs@MoS₂ heterostructures, providing a clear design strategy for high-performance NH₃ gas sensor at room temperature.