Ultrafast Fluorescent Detection of Mercury(II) Ions in Aqueous and Biological Systems Using a Sulfur-Free Boronic Acid-Based Reaction Probe

Abstract

A new reaction-based fluorescent chemodosimeter for Hg²⁺ ions was developed based on the 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 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 sulfurfree 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.