Flavonol-based fluorescent probe for bisulfite detection in plant cells and environmental water samples.

A ratiometric fluorescent probe for HSO3− and its application in environmental and food analysis

Bisulfite (HSO3−) is widely used as a preservative and antioxidant in the food industry and chemical manufacturing, yet its excessive residues pose risks to food quality, environmental safety, and human health. To achieve rapid, selective, and quantitative detection of HSO3−, a ratiometric fluorescent probe based on a benzothiazole–carbazole unit and a benzoindole ion was developed. Upon reaction with HSO3−, the probe exhibits a distinct dual-emission response, fluorescence intensity decreases at 612 nm and increases at 467 nm, enabling robust ratiometric sensing (F467/F612). Owing to its pronounced fluorescence modulation (emission signal change > 145 nm) and high sensitivity (limit of detection = 0.62 μM), the probe demonstrates reliable performance in aqueous samples and has been successfully integrated into portable test strips and swabs. Furthermore, when coupled with a smartphone-based colorimetric application software, the probe allows convenient and real-time quantification of both gaseous SO2 and aqueous HSO3− across environmental and food-related matrices. This work thus delivers a practical, instrument-free platform for sulfite monitoring in complex real-world settings.

A Fluorescent Probe Based on Carbazole and Benzoindole for On‐Site Detection of Sulfite

Sulfites are widely used as preservatives and antioxidants in food, but excessive intake poses health risks. Therefore, rapid, sensitive, and on‑site detection of sulfites is essential for food safety. In this work, a cationic small‑molecule fluorescent probe was synthesized via the condensation of N ‑ethylcarbazole (electron donor) and a benzoindolium ion (electron acceptor). It exhibits a D–π–A architecture with an intramolecular charge transfer (ICT) effect, showing red fluorescence at 617 nm. Upon reaction with HSO 3 − through Michael addition at the conjugated C═C bond, the ICT pathway is blocked, leading to fluorescence quenching. The probe displays excellent selectivity for HSO 3 − (limit of detection = 0.1 µM). Significantly, it can be simply deposited onto filter paper to fabricate easy‐to‐use test strips. Under a 365 nm UV lamp, the test strips exhibit a visible color change from red to blue with increasing HSO 3 − concentration, allowing naked‑eye detection. Coupled with a smartphone color‑reading application, a linear relationship between the blue‐to‐red intensity ratio (B/R) and HSO 3 − concentration enables rapid on‑site quantitative analysis. The test strips were successfully applied to detect residual HSO 3 − in various dried fruit samples. This work provides a simple, low‑cost, and practical method for detecting sulfite levels in food and environmental samples.

A new ratiometric fluorescence probe based on cinnamic acid for hydrazine detection and its applications in environmental and biological systems.

Experimental data indicate that probe CDP can effectively detect N2H4 across a broad pH range (5-12) and demonstrates significant potential for imaging N2H4 in living cells and mice models.

A nopinone-based ratiometric fluorescent probe for rapid detection of GSH and its applications in the environment and biological imaging.

Herein, we have developed a novel ratiometric fluorescent probe through rational design and synthesis, named 2-((5-(4-(3,3-dimethyl-1,2,3,4-tetrahydro-2,4-methoxyacridin-9-yl) phenyl) thiophen-2-yl) methylene)-1H-indene-1,3 (2H)-dione, abbreviated as TA-PT-ID. TA-PT-ID is based on the nopinone skeleton and utilizes a Michael addition reaction as the GSH recognition mechanism. TA-PT-ID exhibits excellent photophysical properties, including a rapid response to GSH (within 1 min), a good linear correlation (R2 = 0.9919), and a low detection limit of 50 nM. TA-PT-ID was successfully applied to the detection of GSH in soil and water samples. Furthermore, ratiometric imaging of endogenous GSH was achieved using TA-PT-ID in HeLa cells, RAW264.7 cells, and zebrafish. In summary, TA-PT-ID provides a powerful new tool for the real-time detection of GSH in complex environments, and its rapid response and broad pH adaptability make it highly promising for applications in biological imaging and environmental monitoring.

A novel two-channel ratiometric fluorescent probe for monitoring hypochlorous acid fluctuations in inflammation.

A ratiometric fluorescent probe based on benzothiazole with a large Stokes shift for fluoride ion sensing in living cells, animals and plants.

The sensitive and selective detection of fluoride ions (F-) is of great significance in both environmental and biological systems. A novel near-infrared ratiometric fluorescent probe, PC-SZ-TBS, was designed and synthesized by rationally linking dicyanoisophorone with 2-(2-hydroxyphenyl)benzothiazole. The probe operates via F--triggered cleavage of the silicon-oxygen bond, resulting in a distinct fluorescence color change from yellow to bright red, along with significant fluorescence enhancement at 700 nm. Spectroscopic studies revealed that PC-SZ-TBS exhibits a low detection limit of 2.22 × 10-6 mol L-1 toward F-, maintains excellent stability over a pH range of 4-10, and displays high selectivity with minimal interference from competing species. Biocompatibility assays demonstrated that PC-SZ-TBS possesses low cytotoxicity and robust cell permeability in 4T1 cells, as well as favorable imaging capabilities in living organisms including zebrafish and Arabidopsis thaliana, enabling effective visualization of F- in biological tissues. Furthermore, PC-SZ-TBS was successfully applied to determine F- in real samples such as tap water, lake water, Chinese baijiu, and various fruits. Integrated with a smartphone-based RGB analysis platform, a strong linear correlation between the R/G ratio and F- concentration (R2 = 0.9978) was established, allowing for real-time, portable semi-quantitative detection of F-. This work provides a reliable and versatile tool for the visual monitoring of fluoride ions in both environmental and biological contexts.