Metallophilic-interaction-triggered self-validated electrochemical-fluorescent Hg²⁺ detection with a single-probe...

Conventional single-signal readout strategies for mercury ions (Hg²⁺) detection are often susceptible to matrix interference, instrumental fluctuations, and probe instability, which may compromise analytical reliability. Dual-mode sensing provides an effective self-validation route; however, traditional dual-probe architectures often suffer from cumbersome fabrication, inconsistent recognition mechanisms, and potential signal crosstalk. Therefore, developing a simplified dual-mode platform with a unified recognition mechanism and independent signal outputs is crucial for achieving reliable Hg²⁺ detection.

Herein, we present an Ag(I)-functionalized metal-covalent organic framework (MCOF) (Ag-CIST) as a single-probe electrochemical-fluorescent dual-mode sensor for Hg²⁺ detection. In this architecture, Ag(I) is integrated into the metal-covalent organic framework MCOF scaffold and simultaneously serves as the specific Hg²⁺ recognition site, electrochemical signal source, and fluorescence emission center. Upon binding of Hg²⁺ to Ag(I), fluorescence quenching is induced, while the electrochemical response decreases owing to the inhibition of Ag(I) electroreduction to Ag(0). These two signal outputs operate independently without obvious mutual interference. Benefiting from the ordered porous structure and high specific surface area of Ag-CIST, the system facilitates efficient mass transport and local Hg²⁺ enrichment, yielding detection limits of 2.06 nM and 1.64 nM for the electrochemical and fluorescence modes, respectively. This work establishes a concise single-probe dual-mode sensing paradigm for reliable Hg²⁺ detection.