Mixed-Ligand Eu(III) Coordination Polymer for Ratiometric Detection of Sodium Salicylate and Anticounterfeiting Application.

This study successfully constructed a Eu(III) coordination polymer (CP), [Eu(2,6-NDS)0.5(3,4-pydc)(H2O)4]n (1), based on mixed ligands of 2,6-naphthalenedisulfonate (2,6-NDS2-) and 3,4-pyridinedicarboxylate (3,4-pydc2-). Its performance for fluorescence sensing of sodium salicylate (SS) and anticounterfeiting application was systematically investigated. 1 shows a 3D supramolecular structure with a tfz-d topology and exhibits excellent fluorescence. After adding SS, the enhancement of SS emission at 420 nm was accompanied by quenching of the characteristic Eu(III) emission; thus, the on-off ratiometric sensor was established. The I420/I622 demonstrates a linear dependence on the SS concentration, and the detection limit was calculated to be 0.41 nM. Furthermore, a portable detection approach combined with mobile phone identification was established and successfully applied to detect SS in an actual food sample. The recovery rates are within 98.5-103.9%. Mechanistic studies revealed that the excellent selectivity and sensitivity of this sensor primarily originate from the combined influence of the inner filter effect (IFE) and weak interaction. This research supplies an effective design strategy for the development of a ratiometric sensor toward SS.