A xanthene-aldehyde based ratiometric fluorescent probe for hypochlorite detection in environmental waters and bioimaging.

Hypochlorite (ClO-) is a highly reactive oxidant involved in biological processes and residential settings, motivating the development of rapid and quantitative sensing tools. Here we report a ratiometric fluorescent probe DEXC for specific detection of ClO- by incorporating an aldehyde recognition unit onto a xanthene scaffold. Upon reaction with ClO-, DEXC undergoes an intramolecular charge transfer (ICT) disruption, leading to a distinct ratiometric fluorescence change from yellow (560 nm) to blue (462 nm) within 60 s. Under optimized conditions, DEXC exhibits a limit of detection of 1.48 µM and maintains reliable performance over a broad pH range (pH 2-12). The proposed aldehyde to carboxylic-acid conversion is supported by high-resolution mass spectrometry and density functional theory calculations. Practical utility is demonstrated by portable paper-based test strips and quantitative analysis of real water samples with recoveries of 91.2-110.6%. In addition, DEXC enables ratiometric imaging of exogenous ClO- fluctuations in living cells and zebrafish embryos, indicating its applicability for both environmental analysis and biological imaging.