A novel ratiometric fluorescent probe for the detection of co-existing Fe³⁺ and Ag⁺ ions: characterization and mechanism exploration

A novel white-light-emitting Ln-MOF composite, g-C₃N₄@TbEu(cpioa), was developed as a ratiometric fluorescent probe for the qualitative and quantitative analysis of metal ions. Among the tested ions, only Fe³⁺ and Ag⁺ exhibited distinct quenching behaviors. Mechanistic studies revealed that Fe³⁺ and Ag⁺ quench luminescence <i>via</i> dynamic and static processes, respectively, involving energy competitive absorption (ECA), photoinduced electron transfer (PET), Förster resonance energy transfer (FRET), and intramolecular weak interactions. The probe demonstrated high sensitivity with limits of detection (LODs) of 0.117 μM for Fe³⁺ and 0.383 μM for Ag⁺. Notably, the observable chromaticity variations enabled differentiation of co-existing Fe³⁺ and Ag⁺ in solutions-a pioneering achievement. Empirical equations derived from orthogonal experiments and multiple regression analysis validated the probe's capability for dual-ion detection. This work pioneers the application of Ln-MOF-based probes in analyzing mixed analytes, offering significant potential for environmental monitoring, clinical diagnostics, and industrial applications.