On–Off Ratiometric Fluorescence Europium(III) Metal–Organic Framework for Quantitative Detection of the Inflammatory Marker Neopterin

Abstract

Benefiting from the unique photoluminescence behavior of the lanthanide(III) ions and organic ligands, a lanthanide(III) metal−organic framework (Ln-MOF) material can simultaneously demonstrate photoluminescence of lanthanide-(III) cations and organic molecules and endow its superior applications of fluorescence sensing behaviors. Herein, we present a europium(III) MOF material {[Eu 2 (BPTA)•(CH 3 COO) 2 •3DMA]•0.5DMA•3H 2 O} n (1) (where H 4 BPTA is 3,3′,5,5′-biphenyltetracarboxylic acid) for photoluminescence performance of quantitatively sensing the inflammatory marker neopterin (Neo). The obtained 1 comprises Eu 2 (COO) 4 paddlewheel secondary building units, which could be bridged by BPTA 4− ligands to extend a 2D framework. The fluorescence titration indicates 1 can achieve simultaneous fluorescence behavior of Eu 3+ ions and Neo via on−off ratiometric effects and thus could be exploited as the ratiometric fluorescence sensor matrix. Such a fluorescence phenomenon of 1 as a ratiometric sensor for quantitative detection of Neo via an on−off ratiometric effect is never observed in MOF chemistry. Moreover, naked-eye visible color variations of the fluorescence for 1 could be observed from red to blue with increasing concentrations of Neo, confirmed by fluorescent test strips as well as portable fluorescent hydrogels. And 1 also shows a low detection limit of 15.11 nM. A synergetic contribution of the competitive absorption, fluorescence resonance energy-transfer, and photoinduced electron-transfer mechanisms between Neo and the framework of 1 realizes the on−off ratiometric fluorescence behavior for Neo detection, supported by the UV−vis spectral overlap experiment and DFT calculations.

Multiresponsive luminescent sensing behaviour of a tetraimidazole ligand and its 3D Cd(ii) metal–organic frameworks

“…The detection of metal cations and anions in various environments is significantly important not only in agriculture, 1 industry 2 and biological processes, 3 but also in the ecosystem and public health. 4 To date, many methods for the detection of these ions have been applied in laboratories and industry, such as electrochemical detection, 5 atomic absorption spectroscopy, 6 inductively coupled plasma mass spectrometry, 7 high performance liquid chromatography, 8 neutron activation analysis, 9 X-ray fluorescence spectrometry, 10 surface plasmon resonance, 11 surface enhanced Raman scattering method, 12 absorption and fluorescence spectroscopy. 13 Among these methods, fluorescence sensing based on the changes in fluorescence intensities or emission wavelengths of sensor materials has been developed because of its good selectivity, high sensitivity, low cost, convenience and non-destructive nature towards substrates.…”