An efficient Eu-based anion-selective chemosensor: Synthesis, sensing properties, and its use for the fabrication of fluorescent hydrogel probe

A novel Eu-complex Eu(TTA)2vinyl-phen has been designed and synthesized via simple reaction as an efficient fluorescent sensor for F−, CH3COO−, and H2PO4−. The anion-sensitivity of Eu-complex was evaluated using a series of anion in DMSO solution. On binding with F−, CH3COO−, or H2PO4−, fluorescence quenching of Eu-complex was easily observed, while no obvious fluorescence change could be observed in the presence of other anions. More importantly, the Eu-complex exhibited excellent selectivity and sensitivity for F− and H2PO4− in water/DMSO (5/5) solution. The titration results of UV–vis, fluorescence, and 1H NMR spectra indicated that the fluorescence quenching can be attributed to the strong hydrogen bonding interaction between anions and imidazole group of Eu-complex. To meet application requirements for biological and environmental detection in water, we successfully prepared a Eu-based fluorescent hydrogel probe using Eu(TTA)2vinyl-phen and N-isopropyl acrylamide (NIPAAm) as monomers through free radical copolymerization in DMF. Emission spectra titration experiments indicated that this hydrogel probe can effectively recognize H2PO4− (detection limit 10−5 M), but cannot recognize F− and CH3COO− in pure water. To the best of our knowledge, this is first report that Eu-based fluorescent hydrogel probe for H2PO4− detection in pure water. In addition, the emission of Eu-complex is also found to be sensitive to molecular oxygen through energy back-transfer mechanism.