Tri-emissive red-green dye-encapsulated UiO-66-Ph as a white-light emission fluorescence sensor for Fe3+ and Cr2O72− detection in environmental water samples

Abstract

Excessive inorganic ions in water sources can accumulate abnormally or be deficient in the human body, leading to serious health risks, such as liver and kidney damage or even cancer. Therefore, efficient and accurate detection of excessive inorganic ions in water is urgently needed. Using an in situ encapsulation method under solvothermal conditions, we develop a series of triple-emission fluorescent sensors, C6&RhB@UiO-66-Ph (C&R@U), by encapsulating green-emitting Coumarin 6 (C6) and red-emitting Rhodamine B (RhB) into a blue-emitting UiO-66-Ph MOF with 1,4-H₂NDC as the ligand. Among them, C&R@U3 exhibits white-light emission with a CIE coordinate of (0.32, 0.32) and is used for the detection of Fe³⁺ ions and Cr₂O₇²⁻ ions in water. When the C&R@U3 fluorescent probe interacts with target ions, the three emission peaks of the probe are quenched due to the resonance energy transfer effect, resulting in significant shifts in its CIE coordinates compared to other ions. The fluorescence intensity of the C&R@U3 probe demonstrates excellent linearity with Fe³⁺ ion concentrations (0–0.6 mM) and Cr₂O₇²⁻ ion concentrations (0–0.1 mM), with detection limits of 0.71 μM and 16.9 nM, respectively. Experiments with real-world water samples and portable fluorescence test papers validate the practical applicability of C&R@U3, revealing its great potential in on-site inorganic ion detection. This work provides experimental basis and theoretical foundation for the development of new multifunctional fluorescent sensors, promoting the application of MOFs in environmental monitoring.