Incorporation of perovskite nanocrystals into lanthanide metal-organic frameworks with enhanced stability for ratiometric and visual sensing of mercury in aqueous solution.

In-situ growth of CsPbBr nanocrystal into Eu-BTC was realized for synthesis of dual-emission CsPbBr@Eu-BTC by a facile solvothermal method, and a novel ratiometric fluorescence sensor based on the CsPbBr@Eu-BTC was prepared for rapid, sensitive and visual detection of Hg in aqueous solution. The transmission electron microscopy (TEM), X-ray diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis were used to verify the successful incorporation of CsPbBr into the Eu-BTC. Meanwhile, the CsPbBr@Eu-BTC nanocomposite maintained high fluorescence performance and stability in aqueous solution. After adding Hg, the green fluorescence of CsPbBr was quenched and the red fluorescence of Eu remained unchanged, while the color changed from green to red obviously. The occurrence of dynamic quenching and electron transfer were verified by fluorescence lifetime, Stern-Volmer quenching constant and XPS analysis. The ratiometric fluorescence sensor shows high analytical performance for Hg detection with a wide linear range of 0-1 μM and a low detection limit of 0.116 nM. In addition, it also shows high selectivity for the detection of Hg and can be successfully applied to detect Hg in environmental water samples. More importantly, a novel paper-based sensor based on the CsPbBr@Eu-BTC ratiometric probe was successfully manufactured for the visual detection of Hg by naked eyes. This new type of ratiometric fluorescent sensor shows great potential for applications in point-of-care diagnostics.