A Coumarin-Based AIE Probe for Eco-Friendly Hg²⁺ Sensing

As a toxic, non-degradable, and bioaccumulative heavy metal pollutant, Hg²⁺ poses serious risks to human organs and ecosystems, creating an urgent need for sensitive and selective detection technologies. Dongfeng Li, Ruibin Hou (Changchun University of Technology, China), and colleagues have synthesized the coumarin-derived probe TXDS, addressing this challenge while advancing applications of aggregation-induced emission (AIE) materials.

Traditional coumarin fluorescent probes are limited in practical use due to aggregation-caused quenching (ACQ). AIE materials, which emit stronger fluorescence upon aggregation, overcome ACQ but often suffer from random, uncontrollable disordered stacking—caused by conformations such as propeller-like structures—which undermines stable luminescence. Regulating AIE molecular conformation and optimizing aggregated-state luminescence is therefore key to overcoming this bottleneck.

TXDS, with coumarin as the core and a triphenylamine group forming a donor–acceptor (D–A) structure,uses an “intramolecular conformation locking” strategy: intramolecular interactions fix the molecule’s conformation, increase rigidity, optimize planar conjugation, and reduce disordered stacking. When encountering Hg²⁺, its thiocarbonyl group binds strongly to the ion, precisely locking the conformation and triggering AIE.

With a 100 nm Stokes shift, TXDS enables sensitive and selective Hg²⁺ detection (0.1–10 μM). Its innovative colorimetric-fluorescent dual-mode detection combines high-sensitivity fluorescence for low concentrations with intuitive, equipment-free colorimetric detection for 10–100 μM, achieving a 10× broader dynamic range.

In practice, TXDS shows strong utility: mechanochemical integration allows visual Hg²⁺ analysis in soil samples within 20 seconds via simple grinding—no complex pretreatment or expensive equipment—making it low-cost, efficient, eco-friendly, and ideal for rapid mercury screening in resource-limited regions. Additionally, TXDO (a TXDS analog) has adjustable, reversible piezochromic properties, providing new opportunities for forensic identification and information encryption.

In summary, TXDS serves as both an efficient Hg²⁺ detection tool and a model for the functional design and practical application of AIE materials.