Easy and portable fluorescent probe for ClO^- detection in pure water: A versatile platform for environmental samples, bioimaging, and smartphone-assisted technologies

Hypochlorite (ClO^-) is widely used as a major component of disinfectants, but its indiscriminate use causes significant environmental and human health risks, which make its detection crucial. A coumarin-based turn-on fluorescent probe, HCMP-Cl ((E)-1-(2-(2-((7-hydroxy-2-oxo-2H-chromen-8-yl)methylene)hydrazineyl)-2-oxoethyl)pyridin-1-ium chloride), was synthesized for detection of ClO^-. HCMP-Cl showed a selective ClO^- detection with blue fluorescence turn-on in 100 % water. HCMP-Cl exhibited a detection limit of 1.98 μM, far lower than the standard of the World Health Organization for free chlorine (5 mg/L; 0.14 mM) in drinking water. HCMP-Cl operated effectively in a pH range of 5-9 and revealed sufficient recovery rates in various water samples and commercial disinfectant. Additionally, test strips and smartphone-based detection methods provided advantages for easy and convenient detection. Notably, HCMP-Cl offered efficient bioimaging of ClO^- in plant, fungus, and zebrafish, highlighting its potential for diverse biological and environmental applications. The detection mechanism of ClO^- by HCMP-Cl was suggested to be the cleavage process of HCMP-Cl through ESI-MS, NMR titration, and density functional theory (DFT) calculations.