Engineering a Stable Ti3C2Tx MXene/ZnPc Heterojunction for Selective Room-Temperature Ammonia Sensing

The reliable detection of ammonia (NH₃) at room temperature (RT) remains a critical challenge for applications in industrial safety and agricultural Internet of Things (IoT), where sensors must combine high sensitivity with robust stability against environmental interference. To address this, we engineered a stable chemiresistive heterojunction by integrating zinc phthalocyanine (ZnPc) nanoparticles with highly conductive two-dimensional (2D) Ti₃C₂T_x MXene nanosheets. Comprehensive characterization, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), confirms the successful formation of an intimate interface, which facilitates effective charge transfer. The optimized sensor demonstrates a response of ~25% to 100 parts per million (ppm) NH₃ at 25°C, a fivefold enhancement over pristine MXene, along with excellent selectivity against common volatile organic compounds (VOCs). Crucially, the device exhibits outstanding repeatability and maintains stable performance across a wide relative humidity (RH) range (20-80% RH), directly addressing key practical deployment hurdles. The enhanced performance is attributed to the synergistic combination of specific NH₃ adsorption at ZnPc molecular sites and efficient charge modulation through the conductive MXene network. This work provides a viable and manufacturable strategy for fabricating selective, stable, and room-temperature-operating gas sensors ready for integration into real-world monitoring systems.