Hypochlorite detection via the irreversible imine-bond cleavage by a practical fluorescent sensor: applications to smartphone-assisted environmental water and food bioimaging.

Abnormally high levels of hypochlorite (ClO-) can cause serious damage to environmental and biological systems, thereby highlighting the necessity for detectors capable of sensitive monitoring and quantification of ClO- in these systems. In this study, we synthesized and evaluated a practical and portable fluorescent turn-off sensor, BHMT-Cl ((E)-2-(2-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride), for the detection of ClO-. BHMT-Cl exhibited selective and sensitive detection of ClO- in pure water via a green fluorescence turn-off, with a critically low detection limit of 2.78 μM. The sensing mechanism was elucidated to involve the cleavage of the imine bond in BHMT-Cl, supported by 1H NMR titration, ESI-mass analysis, FT-IR and DFT calculations. BHMT-Cl was readily applied for the sensitive detection and quantification of ClO- in diverse environmental water samples and demonstrated portability through smartphone-based analysis and test kits. In biological applications, BHMT-Cl enabled bioimaging of ClO- in zebrafish as well as in fungal and plant systems, confirming its broad applicability. Overall, BHMT-Cl showed strong potential as a versatile tool for monitoring ClO- in biological and environmental matrix.