A new quinolinium-based colorimetric and NIR fluorescence dual response probe for bisulfite recognition and its application in real-world samples and cell imaging.

Sulfur dioxide (SO₂) has long been recognized as an environmental pollutant, and excessive intake of SO₂ and its derivatives can cause adverse effects on human health. In this work, three near-infrared (NIR) fluorescence turn-on probes (QT-BT, QT-BI and QT-PT) for HSO₃- detection were designed and synthesized. Among the probes, QT-PT exhibited superior overall HSO₃- recognition performance. In PBS:DMF (7:3, v/v, pH = 7.4) buffer solution, QT-PT enabled dual-channel recognition of HSO₃- through a distinct color change (from Light yellow to pink) and a remarkable fluorescence turn-on response (670 nm). The recognition product not only demonstrated excellent photostability, but also exhibited a range of advantages including high sensitivity (detection limit = 0.61 μM), a broad pH working range (pH 4-13), and a large Stokes shift (130 nm). Probe QT-PT was successfully applied to the rapid and quantitative determination of HSO₃- content in sugar samples. Furthermore, a smartphone-assisted portable sensing platform was constructed using QT-PT as the core element, enabling portable and on-site monitoring of HSO₃-. QT-PT was also utilized for visual monitoring and fluorescence imaging of bisulfite in live cells and zebrafish models, demonstrating its excellent biocompatibility. Therefore, QT-PT holds great potential for applications in food safety inspection, environmental monitoring, and bioimaging.