The Applications Of L-cysteine Capped Cdte Quantum Dots As Fluorescent Probes

Quantum dots have attracted much attention due to their unique optical performance. Compared with traditional organic fluorescent dyes, they have broad excitation spectra, narrow emission bandwidths and tunable size-dependent emission. About the stability, quantum dots express 1-2 orders of magnitude as that of common fluorescent dyes. Furthermore, they have good biocompatibility, so they are hopeful to become the first candidate as fluorescent probes. In this thesis, with L-cysteine capped CdTe quantum dots as the fluorescent probes, the conjugation between proteins and the water-soluble quantum dots, the selective response of quantum dots with heavy metal ions, and their applications in biological and chemical analysis were studied. The main contents are as follows:A new method for the determination of human serum albumin (HSA) using L-cysteine capped CdTe quantum dots as the fluorescent probes was developed. The carboxyl groups on the surface of quantum dots can be coupled with the amido groups of the proteins by covalent bond after being actived, which can effectively enhance the fluorescence intensity of the quantum dots. Under optimal conditions, the fluorescence intensity is proportional to the concentration of HSA in the range of 4.0×10-4-8.5 mg/L with a correlation coefficient of 0.9994, and a detection limit of 0.13μg/L HSA was obtained with a RSD of 0.5% (4.0 mg/L, n=11). The method has been applied for the determination of protein in human serum, and the results were in good consistent with those obtained in the Coomassie Brilliant Blue G-250 assay. The F test and t test results indicated that there was no remarkable difference between the two methods.The L-cysteine capped CdTe quantum dots were also used as ion probes to develop a new method for the determination of trace Hg2+ based on the selective response between QDs and Hg2+. Under optimal experimental conditions, a good linear relationship between fluorescence intensity and the concentration of Hg2+ was obtained in the range of 0.24-15.0μg/L and a detection limit of 0.07μg/L HSA was obtained with a RSD of 0.84% (7.38μg/L, n=11). Furthermore, the reaction mechanism of the fluorescent quenching was considered due to the formation of Hg(OH)2 with smaller band gap capping on the surface of CdTe QDs when Hg2+ was added. The method was successfully applied to the determination of Hg2+ in water samples.