Highly sensitive synchronous fluorescence determination of mercury (II) based on the denatured ovalbumin coated CdTe QDs

Chemically denatured ovalbumin (dOB) was used to modify the surface of 3-mercaptopropionic acid (MPA) stabilized CdTe quantum dots (QDs), which resulted in a great enhancement of the synchronous fluorescence intensity. Moreover, dOB shell layer can effectively prevent the binding of other cations onto the QDs core and enhance the selective binding ability of Hg2+ to dOB coated CdTe QDs (CdTe-dOB QDs). A simple method with high sensitivity and selectivity was developed for the determination of Hg2+ with the CdTe-dOB QDs as fluorescence probe based on the merits of synchronous fluorescence spectroscopy (SFS). When scanning with excitation and emission wavelengths of 250 nm and 470 nm (Δλ=λem−λex=220 nm), respectively, the maximum synchronous fluorescence peak of the CdTe-dOB QDs was located at 328 nm. Under optimal conditions, the change of the synchronous fluorescence intensity was in good linear relationship with the Hg2+ concentration in the range of 0.08×10−7 to 30.0×10−7 mol L−1 and the detection limit was 4.2×10−9 mol L−1 (S/N=3). The relative standard deviation of seven replicate measurements for the concentration of 2.0×10−7 mol L−1 and 20.0×10−7 mol L−1 were 2.8% and 2.3%, respectively. Compared with general fluorescence methods, the proposed method, which combined the advantages of high sensitivity of synchronous fluorescence and specific response of Hg2+ to CdTe-dOB, had a wider linear range and higher sensitivity. Furthermore, the proposed method was applied to the determination of trace Hg2+ in water samples with satisfactory results.