UV-promoted NH₃ sensor based on Ti₃C₂T_x/TiO₂/ graphene sandwich structure with ultrasensitive RT sensing performances for human health detection

Gases produced by human respiration can effectively forewarn physiological health, and developing high-performance gas sensors for breath detection can help in the early diagnosis of many diseases. In this paper, Ti₃C₂T_x/TiO₂/graphene composite with a unique sandwich structure was fabricated by hydrothermal method for resistive NH₃ sensor, which is composed of the staggered interlayer of graphene, Ti₃C₂T_x, and in situ grown TiO₂ nanosheets. The results indicate that the Ti₃C₂T_x/TiO₂/graphene composite sensor has a response value of 35.8 at 50 ppm NH₃ at room temperature and in a dark environment, which is 12.8 times higher than that of the single Ti₃C₂T_x and can detect dilute NH₃ at ppb level with a calculated limit of 26 ppb. The sensor also possesses a fast response/recovery time of 19/29 s and excellent humidity resistance. Furthermore, with the assistance of UV illumination, the sensor response value for 50 ppm NH₃ is increased to 45.18, the response/recovery time is accelerated to 18/25 s, and the calculated limit of detection is 22.23 ppb. Additionally, simulated breath detection demonstrates the potential application of the sensor for early respiratory warning in patients with renal failure. Finally, the NH₃ gas sensing mechanism is discussed in terms of heterogeneous structure, morphology promotion, and energy band theory. It is believed that the sensing material with this structure has great potential for human health applications.