Fluorescent Ionic Liquid Membranes Based on Coumarin for the Real-Time and Visual Detection of Gaseous SO2

Presented here is a novel design strategy that utilizes anion-functionalized ionic liquids (ILs) to achieve visual and real-time detection of gaseous SO2. A coumarin fluorophore was innovatively covalently linked onto an IL and exhibited fluorescent signal response for SO2 due to strong chemical interactions. The sensor consisting of this IL displayed high sensitivity and selectivity, even toward trace amounts of SO2 (<0.2 ppm). Furthermore, this sensor overcame weak anti-interference ability and water-sensitivity issues. Benefiting from its excellent solubility, the sensor could be assembled into a simple and portable membrane device and exhibited excellent reusability (>12 times). The reported membrane sensor may be used as a next-generation gas sensor with superior SO2-response performance, enabling a wide application for monitoring harmful gases.