| Quantum dots as new type of fluorescent nanomaterials with unique fluorescence properties were widespread concerned in the field of analytical chemistry. In recent years, fluorescent sensors based on quantum dots had become one of the most active research in the field of analytical chemistry. Cadmium-based quantum dots was the most widely applied in the field of analytical chemistry, but the toxicity of cadmium ions in sensing analysis based on quantum dots brought secondary pollution of the environment. So it was significant that look for environmentally friendly quantum dots as novel fluorescent sensor to replace cadmium-based quantum dots in the field of analytical chemistry.In this paper, lysozyme was effectively detected by a fluorescence resonance energy transfer based on CdTe quantum dots as an energy donor and rhodamine B as an acceptor. A novel fluorescent sensor for detecting hydroquinone and Cu2+, Pb2+, and Hg2+in water based on the quenching of fluorescence of ZnSe which were modified with glutathione was developed. Studies had shown that ZnSe quantum dots as fluorescent probes could achieve high sensitivity and was expected to become a new type of environmentally friendly fluorescent probes. The thesis was divided into the following several parts:(1) Fluorescent sensor of lysozyme based on fluorescence resonance energy transfer between CdTe quantum dots and rhodamine B. The water-soluble CdTe was synthesized using thioglycolic acid as stabilizer. The fluorescence resonance energy transfer between the CdTe quantum dots and rhodamine B in the presence of cetyltrimethylammonium bromide using the CdTe quantum dots with an emission wavelength of530nm as an energy donor and rhodamine B as an acceptor was investigated. Lysozyme of lysozyme buccal tablets was determined by fluorescence resonance energy transfer. The results show that the extent of fluorescence energy transfer quenching was linearly proportional to the concentration of lysozyme from2.0×10-7mol-L"1to8.0×10-6mol·L-1with a correlation coefficient of0.9910. The limit of detection was2.0×10-8mol·L-1. Under the optimal conditions, it was found that there was highly sensitive and selectivity of detection of lysozyme.(2) Fluorescent sensor of hydroquinone based on ZnSe quantum dots. In this part, a novel fluorescent sensor for detecting hydroquinone in water based on the quenching of fluorescence of ZnSe which were modified with glutathione was developed. Under the optimal conditions, it was found that the fluorescence of the ZnSe quantum dots was significantly quenched in the presence of Cu2+, Pb2+, and Hg2+. The experimental results showed that the quenching effect of the above cations can be effectively decreased by adding EDTA as a masking reagent. In the concentration in the range of hydroquinone, the interference of resorcinol and catechol was negligible. There was a linear relationship between the relative fluorescence intensity (△F=F0/F1) and the concentration in the range of4.0×10-9～4.0×10-7mol·L-1for hydroquinone. The limit of detection was6.0x10-10mol·L-1. Finally, under the optimum conditions, the concentration of hydroquinone for tap water was detected and the standard adding recovery ratios of hydroquinone were98.9%-103%. Compared with other reported methods, there was highly sensitive and selectivity of detection of hydroquinone. At the same time, the quenching mechanism was discussed by the Stern-Volmer equation and ultraviolet spectrum. The result showed that the fluorescence quenching of ZnSe quantum dots could be caused by the chemical reaction between the surface parcel agent of ZnSe quantum dots and hydroquinone.(3) Fluorescent sensor of Cu2+, Pb2+, and Hg2+based on ZnSe quantum dots. A novel fluorescent sensor for detecting Cu2+, Pb2+, and Hg2+in water based on the quenching of fluorescence of ZnSe was developed. There was a linear relationship between the relative fluorescence intensity(△F=F0/F1) and the concentration in the range of4.8×10’8-6.4×10-7mol·L-1for Cu2+, and the limit of detection was8.0×10-9mol·L-1. The concentration in the range and the limit of detection for Pb2+were6.0×10-8～6.0×10-6mol·L-1and6.0×10-99mol·L-1. The concentration in the range of2.0x10-7-2.0×10-5mol-L-1for Hg2+, and the limit of detection was8.0×10-8mol·L-1. Compared with other reported methods, there was highly sensitive of detection for Cu2+and it was simple and convenient, and safe to detect Pb2+. It was simple and convenient, and low toxicity to detect Hg2+. The mechanisms of interaction of the metal ions and ZnSe quantum dots were explored. Addition of Cu2+to ZnSe quantum dots leads to the binding of copper ions onto the surface of the semiconductor accompanied by reduction of Cu2+to Cu+. It is suggested that formation of isolated Cu+ions takes place. Then the fluorescence quenching of ZnSe quantum dots in the presence of lead ions was likely that the glutathione was broke away from ZnSe quantum dots due to the strong affinity of Pb-S. It was found that Hg2+could not only bind to the surface of ZnSe quantum dots, but also coordinate with the glutathione on the surface of ZnSe quantum dots, due to its strong affinity towards R-SH and RSe-compounds. |
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