Highly sensitive ammonia sensor based on carboxylated MXene-functionalized microfiber

To meet the demand for high-sensitivity ammonia (NH₃) detection at room temperature, this study develops an ultra-sensitive gas sensor by integrating the exceptional sensing properties of 2D MXene with the evanescent field advantages of optical microfibers. A carboxylated MXene-functionalized microfiber sensor was designed and fabricated. Density functional theory (DFT) calculations confirmed that carboxylation significantly enhances the adsorption energy between the MXene surface and NH₃ molecules compared to pristine MXene, theoretically validating its superior sensitivity. Experimentally, a uniform and robust carboxylated MXene thin film was coated onto the microfiber, demonstrating excellent mechanical stability for practical sensing. Gas sensing tests show a strong linear response within the 10-250 ppm range. Notably, the sensitivity is an order of magnitude higher than previously reported microfiber sensors, with a practical detection limit of 10 ppm and a theoretical limit as low as 6.90 ppm. Furthermore, the sensor exhibits excellent long-term stability over a 10-day measurement and gas selectivity. This research provides a new strategy for developing high-performance room-temperature gas sensors with significant potential for environmental atmospheric monitoring.