Detection of pesticide paraquat (PQ) is of considerable significance to ensure food safety, and its rapid and on-site detection is still a challenge. Aimed at the ion characteristics of PQ, an “enrichment and detection” strategy was proposed to improve the sensitivity through electrostatic attractions, and the ion characteristic of probes was adopted to increase the portability through avoiding aggregation-caused quenching effects in the paper strips. Herein, a novel anion-functionalized ionic liquid (IL) probe with a large conjugated plane and rich π-electrons ([Fluo][P66614]2) was designed as a fluorescent and colorimetric dual-channel probe to sensitively and rapidly detect trace amounts of PQ in vegetables and the environment. The proposed probe exhibited good linearity with a detection limit of 64.0 nM in the PQ concentration range of 0.3–7.0 μM (fluorometry) and 0.1 μM in that of 0.1–8.0 μM (colorimetry), respectively. In addition, it displayed a rapid fluorescence quenching response from green to dark (<5 s) and excellent anti-interference (among 23 other pesticides) due to dual effects of electrostatic attraction and π–π stacking. Most importantly, the lipophilic IL probe could be applied in real vegetables and environmental samples with a satisfying recovery rate of 98–103% and assembled into a handy paper strip that achieved the visual semiquantitative detection of PQ. This ionic probe provides a feasible approach for rapidly and conveniently detecting PQ for ensuring agricultural and food safety and opens a new avenue to detect ion-responsive analytes in real complex samples by an “enrichment and detection” strategy.

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.