Enhanced Sensitivity and Accuracy of Tb3+-Functionalized Zirconium-Based Bimetallic MOF for Visual Detection of Malachite Green in Fish

The ratiometric fluorescent probe UiO-OH@Tb, a zirconium-based MOF functionalized with Tb³⁺, was synthesized using a hydrothermal method. This probe employs the fluorescence resonance energy transfer (FRET) mechanism between Tb³⁺ and malachite green (MG) for the double-inverse signal ratiometric fluorescence detection of MG. The probe's color shifts from lime green to blue with an increasing concentration of MG. In contrast, the monometallic MOFs' (UiO-OH) probe shows only blue fluorescence quenching due to the inner filter effect (IFE) after interacting with MG. Additionally, the composite fluorescent probe (UiO-OH@Tb) exhibits superior sensitivity, with a detection limit (LOD) of 0.19 μM, which is significantly lower than that of the monometallic MOFs (25 μM). Moreover, the content of MG can be detected on-site (LOD = 0.94 μM) using the RGB function of smartphones. Hence, the UiO-OH@Tb probe is proven to be an ideal material for MG detection, demonstrating significant practical value in real-world applications.