High-Performance Ammonia QCM Sensor Based on SnO Quantum Dots/TiCT MXene Composites at Room Temperature

Ammonia (NH) gas is prevalent in industrial production as a health hazardous gas. Consequently, it is essential to develop a straightforward, reliable, and stable NH sensor capable of operating at room temperature. This paper presents an innovative approach to modifying SnO colloidal quantum dots (CQDs) on the surface of TiCT MXene to form a heterojunction, which introduces a significant number of adsorption sites and enhances the response of the sensor. Zero-dimensional (0D) SnO quantum dots and two-dimensional (2D) TiCT MXene were prepared by solvothermal and in situ etching methods, respectively. The impact of the mass ratio between two materials on the performance was assessed. The sensor based on 12 wt% TiCT MXene/SnO composites demonstrates excellent performance in terms of sensitivity and response/recovery speed. Upon exposure to 50 ppm NH, the frequency shift in the sensor is −1140 Hz, which is 5.6 times larger than that of pure TiCT MXene and 2.8 times higher than that of SnO CQDs. The response/recovery time of the sensor for 10 ppm NH was 36/54 s, respectively. The sensor exhibited a theoretical detection limit of 73 ppb and good repeatability. Furthermore, a stable sensing performance can be maintained after 30 days. The enhanced sensor performance can be attributed to the abundant active sites provided by the accumulation/depletion layer in the TiCT/SnO heterojunction, which facilitates the adsorption of oxygen molecules. This work promotes the gas sensing application of MXenes and provides a way to improve gas sensing performance.