Time-resolved determination of Fe(II) ions using cysteine-bridged Mn-doped ZnS quantum dots as a phosphorimetric probe
A time-resolved phosphorescence (TRP) is applied to the highly sensitive determination of Fe(II) ions. The method is based on the use of a phosphorescent probe consisting of cysteine-bridged Mn-doped ZnS quantum dots (Mn/ZnS QDs). The presence of cysteine enhances the phosphorescence of the QDs and also increases the efficiency of quenching caused by Fe(II) ions. This results in strongly improved selectivity for Fe(II). The linear response is obtained in the concentration range of 50–1000 nM with a 19 nM detection limit. Phosphorescence is recorded at excitation/emission peaks of 301/602 nm. The interference of short-lived fluorescent and scattering background from the biological fluids is eliminated by using the TRP mode with a delay time of 200 μs. The determination of Fe(II) in human serum samples spiked at a 150 nM level gave a 92.4% recovery when using the TRP mode, but only 52.4% when using steady-state phosphorescence. This demonstrates that this probe along with TRP detection enables highly sensitive and accurate determination of Fe(II) in serum.
KeywordsQuantum dots Delay time Cysteine Phosphorescence probe Ferrous ions Biological fluids Phosphorescence assay
The authors gratefully acknowledge the National Natural Science Foundation of China (Grant No. 21105066, No. 21775087), Beijing Natural Science Foundation (Grant No. 2162010), Scientific Research Project of Beijing Educational Committee (Grant No. KM201610028008), and Cross-Disciplinary Research Project of Capital Normal University.
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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