Exploring the room-temperature ammonia sensing potential of exfoliated hexagonal boron nitride

Detection of ammonia (NH₃) is critical for ensuring environmental safety and protecting human health in industrial workplaces. However, its corrosive nature causes the sensing material to degrade over time, as well as room temperature sensors suffer humidity issues. Hexagonal boron nitride (hBN) is a layered, chemically stable material, making it a promising sensing material upon functionalization to address these challenges. In this study, hBN was synthesized and exfoliated to fabricate sensors that exhibited selective NH₃ detection at room temperature, with a detection limit of 90 parts per million (ppm) and a response of 93 % at 180 ppm. To enhance sensing performance further, hBN was treated with nitric acid, introducing functional groups that increased surface reactivity and adsorption sites for NH₃. Functionalized hBN based sensor exhibited a 225 % response towards 180 ppm NH₃, which is ∼ 2.5 times higher than that of pristine hBN based sensor, and lowered the detection limit down to 9 ppm, demonstrating superior sensitivity. Moreover, it demonstrated excellent resistance to Relative Humidity (RH: 20 %–80 %) and long‑term stability for 220 days. The enhanced performance is explained on the basis of strong polar-polar interactions between polar NH₃ molecules and the polar hBN sites induced due to functionalization which has been confirmed using the in-situ Fourier Transform Infrared Spectroscopy (FTIR) studies. The sensor may find application in stable, humidity resistant monitoring of NH₃ in industrial and environmental settings.