Abstract
Using two-dimensional (2D) nickel-based metal organic framework (Ni-MOF) nanosheets as a matrix, Eu3+ and Ag+ were incorporated to synthesize Ag/Eu@Ni-MOF with double luminescence centers of Eu3+ ion (615 nm) and organic ligand (524 nm). And a ratiometric luminescence sensor is constructed based on Ag/Eu@Ni-MOF for sensitive detection of biothiols in aqueous solutions. The dual-emissive fluorescence properties can be tuned by changing the amounts of Ag+ ions doping. The results of temperature and pH effects on the fluorescence of Ag/Eu@Ni-MOF indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range. Due to the binding of -SH in cysteine (Cys) and glutathione(GSH) with Ag+, the ligand luminescence was significantly inhibited by weakening the Ag + influence on the energy transfer process in the MOFs. Therefore, ratiometric fluorescent sensing of biomolecular thiols was realized based on the dual-emission Ag/Eu@Ni-MOF. More importantly, the fluorescence color change can be observed with naked eyes to realize visual detection. The ratiometric fluorescent sensor exhibits high performance for Cys and GSH detection with a wide linear range of 5-250 µM and a relatively low detection limit of 0.20 µM and 0.17 µM, respectively. Furthermore, the biothiols content in human serum was determined with satisfactory results. It proves the Ni-MOF nanosheets can be used as a stable matrix for construction luminescent MOFs for the first time, and validate the great potential of Ag/Eu@Ni-MOF as a ratiometric fluorescent probe for point-of-care testing (POCT) in disease diagnosis.
Highlights
Biological thiols such as glutathione (GSH) and cysteine (Cys) are the essential components for efficient operation of life maintenance.[1]
The results of temperature and pH effects on the fluorescence of Ag/Eu@nickel-based metal organic framework (Ni-Metal-organic frameworks (MOFs)) indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range
By FT-IR characterization (Figure S5), for Ag/Eu@Ni-MOF with addition of Cys and GSH, the absorption peak of ~ 2550 cm− 1 attributing to the sulfhydryl group in the thiol species and disappeared, which indicates that the fluorescence discoloration is due to the binding of the ratiometric fluorescent probe to the sulfhydryl group in the biothiols, resulting in the quenching of the emission for organic ligand (I524)
Summary
Biological thiols such as glutathione (GSH) and cysteine (Cys) are the essential components for efficient operation of life maintenance.[1]. Ag/Eu@Ni-MOF solution, due to the strong binding of Ag+ with -SH, the emission of organic ligand (524 nm) was significantly inhibited by weakening the Ag+ influence on the energy transfer process in the MOFs. A highly sensitive and selective ratiometric luminescence sensor was established for detection of biothiols. NiMOF (50 mg) was added to a solution (10 mL) containing Eu(NO3)3·6H2O (5 mM, 50 mM, 100 mM), transferred to a single-necked flask equipped with a reflux condenser, and reacted at 60 °C for 24 h.[33] The white powder product was separated by centrifugation at 8500 rpm, washed with deionized water several times, and vacuum dried at 30°C for 6 h. Different concentrations of GSH (20, 40, 60 μM) were added, and the fluorescence spectra were measured with an excitation wavelength of 315 nm
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