Ultrafast fluorescent detection of mercury(II) ions in aqueous and biological systems using a boronic acid-based reaction probe.

A new reaction-based fluorescent chemodosimeter for Hg2+ ions was developed based on an irreversible substitution reaction between Hg2+ and a phenylboronic acid moiety. The probe exhibits a rapid and highly selective fluorescence turn-on response toward Hg2+ with dual green and red emissions under visible-light excitation. Notably, the sensing reaction is completed within 2-3 min in aqueous solution at pH 7.4 containing only 1% organic solvent, demonstrating excellent reactivity under near-physiological conditions. The probe (1) forms a well-defined 1 : 1 covalent adduct with Hg2+, avoiding complicated multi-adduct formation and enabling reliable quantitative detection. In addition, the boronic acid-based design effectively suppresses interference from competing metal ions. The probe shows efficient cellular uptake and allows real-time imaging of intracellular Hg2+ through simultaneous enhancement of green and red fluorescence signals. These results demonstrate that the present probe provides a robust sulfur-free platform for rapid, selective, and sensitive detection of mercury ions in aqueous environments and living cells, offering significant potential for environmental monitoring and biological mercury imaging.