Studies On The Application Of CdSe/CdS Quantum Dots On Environmental Analysis

Compared with conventional organic fluorescent dyes, quantum dots (QDs) have a lot of unique optical properties, which make them appealing as a new class of fluorescent probes. In this dissertation, new methods for the determination of microcystin-leucine- arginine (MC-LR) and cadmium ions in the environment sample are developed based on the aqueous soluble CdSe/CdS core-shell type QDs.The dissertation is divided into three sections.In the first section, studies on quantum dots are reviewed with the emphasis on its properties, synthesis and applications. The methods for the determination of harmful MC-LR and cadmium ions in the environment were introduced.In the second section, a novel way to detect the MC-LR by using the identifing technology based on quantum dots of CdSe/CdS. Under a condition of EDC ( 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride ) solution, the MC-LR was activated to form QDs-MC-LR antibody through MC-LR's covalent linking to quantum dots of CdSe. The fluorescence intensity of the QDs-MC-LR antibody was quenched in the presence of analytical MC-LR. The overall quenching percentage as a function of MC-LR concentration matched very well with linearity equation. The method is preponderant for its easy operation and quick detection. And a detection limit of 6.9×10-11mol/L MC-LR was obtained. The relative standard deviation is 1.1% for the determination of 1.0 nmol/L MC-LR (n=11).In the third section, dBSA was obtained by chemically treating BSA with NaBH4. Then, the dBSA was coupled to CdSe/CdS core-shell QDs, forming the dBSA-coated QDs bioconjugates. The dBSA-coated QDs bioconjugates were sensitive to Cd2+ over other metal ions, such as Ag+, Cu2+, Al3+, Ca2+, Mg2+. The dBSA-coated QDs bioconjugates were used to detect Cd2+ with a detection limit of 8.3μg/kg and a relative standard deviation of 2.7%. It was found that the enhanced luminescence intensity of the dBSA-coated QDs bioconjugates in a concentration of Cd2+ dependence is best described by a Langmuir binding isotherm equation. The method, which was simple rapid and low-cost, could be used to detect real samples.