A multifunctional Eu-organic framework for fluorescence sensing properties and the detection of pyrimethanil in real samples

Abstract

Europium metal–organic frameworks (Eu-MOFs) have unique application prospects in the field of fluorescence sensing, due to the fluorescence characteristics of Eu3+ ion and organic ligands, and the advantages of obvious red luminescence, long emission lifetime, large Stokes shift, and high quantum yield. In this study, a novel Eu-MOF was synthesized hydrothermally using europium acetate hexahydrate (Eu(Ac)3·6H2O), 5-(4′-carboxybenzyloxy) isophthalic acid (5-H3CIA), and 4,4′-bipyridine (4,4′-bipy). Structural analysis revealed that the Eu-MOF exhibited a three-dimensional framework with 4,4′-bipyridine as the guest molecule. Fluorescence sensing experiments revealed that 2,4,6-trinitrophenol, ornidazole, pyrimethanil, and Cr2O72− effectively quenched the fluorescence of the Eu-MOF in aqueous solution, with corresponding limits of detection as low as 0.886, 0.732, 0.569, and 2.800 μM, respectively. Exploiting the ability of Cr2O72− to quench the fluorescence of the Eu-MOF, we devised a Cr2O72−@Eu-MOF fluorescence silencing system that, in the presence of ascorbic acid, gradually recovered its fluorescence to form a unique fluorescence “on–off-on” sensor. In addition, the fluorescence sensing mechanism of Eu-MOF was studied, the fluorescence test was prepared to detect Cr2O72− with an open eye, and the content of pyrimethanil was detected in real samples, including cucumber skin, tomato skin, grape skin, apple and kiwi.