Flower-Like CNTs@MoS ₂ Core–Shell Nanostructure for NH ₃ 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.