Highly selective MXene/V₂O₅/CuWO₄-based ultra-sensitive room temperature ammonia sensor

A Schottky junction based on Ti₃C₂T_x MXene sheet integrated with marigold flower-like V₂O₅/CuWO₄ heterojunction was designed and fabricated for robust ammonia sensing by monitoring the electrical resistance changes in air and ammonia. The electron transport behavior of the sensor was investigated by electrochemical analysis, ultraviolet photoelectron spectroscopy and reflection electron energy loss spectroscopy. Besides, negative zeta potential obtained for sensor components was in consistent with surface functional groups (e.g. OH and F) observed by XPS analysis helping better understanding of the ammonia sensing mechanism. The results desirably confirmed high sensitivity, selectivity, linear range (1-160 ppm), the limit of quantification, repeatability, long-term stability, very short response time (few seconds) and low working temperature (25 °C) of the sensor. The measurements on the resistance changes of the MXene/V₂O₅/CuWO₄-based sensor under the exposure to various types of analytes (Ammonia, Acetone, Benzene, Chloroform, DMF, Ethanol, humidity (80%), Methanol and Toluene as well as NO, NO₂, H₂S, SO₂, CO and CH₄) at different concentrations revealed that the fabricated sensor is excellently selective to ammonia with ultra-high sensitivity. Intra-day stability (7 runs a day) and long-term stability (every 10 days over 70 days) as important sensor characteristics were investigated at 51 ppm and ambient temperature, which showed very good repeatability and recoverability in both short and long periods for sensing the ammonia. Overall, MXene/V₂O₅/CuWO₄ was shown to be cost-effective, easy to handle and suitably applicable for simple, ultrafast and extremely efficient trace ammonia detection, which could be of high interest for future exhaled breath analysis and the development of a novel noninvasive diagnostic strategy to monitor chronic kidney disease to stop a large measure of unnecessary invasive testing.