ZnO@Ti₃C₂T_<i>x</i> MXene Hybrid Composite-Based Schottky-Barrier-Coated SAW Sensor for Effective Detection of Sub-ppb-Level NH₃ at Room Temperature under UV Illumination

Abstract

Smart sensors capable of detecting NH3 at sub-ppb levels are important for human health in our daily life. Here, we demonstrate a surface acoustic wave (SAW) sensor based on ZnO@MXene hybrid heterostructure for ultrahigh NH3 gas detection under UV illumination at room temperature (RT). Under UV illumination, the ZnO@MXene SAW sensor not only significantly enhances the frequency response (Δf ≈ 32.24 kHz/20 ppm) but also effectively improves the selectivity with a low detection limit (89.41 ppb), short response/recovery times (92/104 s), long-term stability, and robust sensitivity under various relative humidity conditions (dark) to NH3 at RT. These unique NH3 sensing properties might be attributed to the enriched functional groups, oxygen vacancies, and excellent charge transfer at the Schottky barrier via band bending, which is explained using an energy band theory sensing mechanism. Overall, the current study offers strategic insights for designing light-activated high-performance SAW-based RT NH3 sensors in safety assurance and environmental monitoring.