Heterostructure membrane Fabry−Pérot cavity based on LiCl@MIL-53-(OH)2/TiO2 for high performance of ammonia monitoring

Optical sensor research has drawn great attention for significant market potential and a wide range of applications. Ammonia (NH 3 ) is a gas widely used in industry, but it is also a significant safety hazard for its toxicity, corrosiveness and explosiveness. However, it is challenging to create reliable NH 3 optical sensors with high sensitivity, excellent selectivity and fast response simultaneously. In this work, heterostructure membrane Fabry ‐ P e ´ rot (F–P) cavities constructed by LiCl@MIL-53-(OH) 2 (LiCl was anchored in MIL-53-(OH) 2 ) and TiO 2 (LiCl@MIL-53-(OH) 2 /TiO 2 ) were fabricated for NH 3 detection. Compared to the MIL-53-(OH) 2 /TiO 2 heterostructure membrane F–P cavity, the LiCl@MIL-53-(OH) 2 /TiO 2 heterostructure membrane F–P cavity exhibited superior sensing performance toward NH 3 . Experimental results indicated that the LiCl@MIL-53-(OH) 2 -2.0/TiO 2 heterostructure membrane F–P cavity exhibited excellent selectivity and sensitivity (3.075 nm/ppm), and the lower detection limit achieved to 98 ppb. The results were attributed to the multiple actions of hydrogen bonding of NH 3 with Cl − and NH 3 coordination to Li + . Additionally, the sensor showed fast optical response time 500 ms, outstanding repeatability and stability. The sensitivity of LiCl@MIL-53-(OH) 2 -2.0/TiO 2 heterostructure membrane F–P cavity toward NH 3 at 2.5 ppm and 25 ppm is outstanding, showing the F–P cavity offers a promising solution for real-time NH 3 monitoring. Therefore, LiCl was introduced into MIL-53-(OH) 2 /TiO 2 F–P cavity NH 3 sensor, which provides a new idea for future optical gas sensors with high performance for gas sensing.