Engineered Ce2Sn2O7/TiO2 Heterojunctions for High-Performance MEMS Ammonia Gas Sensor

Pyrochlore-based metal oxide nanocomposites offer an attractive pathway for developing next-generation gas sensors by exploiting interfacial charge transfer and band engineering. Here, we report for the first time the use of Ce 2 Sn 2 O 7 /TiO 2 nanocomposites for ultra-trace NH 3 detection at room temperature. The materials are synthesized via a facile hydrothermal route and systematically evaluated against common volatile organic compounds, including ethanol, acetone, methanol, n-butanol, isopropanol, and triethanolamine. The Ce 2 Sn 2 O 7 /TiO 2 heterojunction demonstrated outstanding selectivity toward NH 3 , with the optimized CeTi2 sensor delivering an ultrahigh response of 83.8% to 100 ppm, a rapid response time of 12 and 5 s, and an exceptionally low detection limit of 2 ppb under ambient conditions (25°C). At 100°C, the prepared CeTi2 sensor displays a gas sensing response of 82.1% towards 100 ppm of NH 3 . Beyond sensitivity, the device exhibited excellent repeatability and long-term stability, and ensured reliable operation under realistic environments. Mechanistic analysis revealed that the Ce 2 Sn 2 O 7 /TiO 2 interface induces strong surface band bending and remarkably accelerates charge transport and reversible adsorption–desorption dynamics. This work establishes Ce 2 Sn 2 O 7 /TiO 2 as a pioneering platform for ppt-level NH 3 detection, offering a powerful combination of selectivity, stability, and energy-efficient operation for environmental monitoring and industrial safety.