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 CsPbBr3 nanocrystal into Eu-BTC was realized for synthesis of dual-emission CsPbBr3@Eu-BTC by a facile solvothermal method, and a novel ratiometric fluorescence sensor based on the CsPbBr3@Eu-BTC was prepared for rapid, sensitive and visual detection of Hg2+ 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 CsPbBr3 into the Eu-BTC. Meanwhile, the CsPbBr3@Eu-BTC nanocomposite maintained high fluorescence performance and stability in aqueous solution. After adding Hg2+, the green fluorescence of CsPbBr3 was quenched and the red fluorescence of Eu3+ 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 Hg2+ 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 Hg2+ and can be successfully applied to detect Hg2+ in environmental water samples. More importantly, a novel paper-based sensor based on the CsPbBr3@Eu-BTC ratiometric probe was successfully manufactured for the visual detection of Hg2+ by naked eyes. This new type of ratiometric fluorescent sensor shows great potential for applications in point-of-care diagnostics.