Development Of Fluorescent Sensors For The Detection Of Hg²⁺ And H₂O₂ By Functionalized CdSe/CdS Quantum Dots

Quantum dots(QDs) have unique optical and electronic properties owing to the quantum confinement. Application of QDs in analytical chemistry and biomedical field has become a hot topic. In the dissertation, the functionalized QDs have been synthesized as fluorescent sensors for the detection of mercury ion and hydrogen peroxide.The dissertation is divided into three chapters.In chapter one, a brief review was given on the basic principle, luminescence properties, synthesis methods, surface modification of quantum dots. The application of luminescence QDs in analytical chemistry and biomedicine was also described. The conception of the research was thereby proposed.In chapter two, the hydrophobic core-shell CdSe/CdS QDs were firstly synthesized in organic phase and then capped by thioglycolic acid(TGA) in order to make it water-soluble. The TGA capped QDs were then functionalized with thiourea(TU) by bonding TU to the TGA on the surface of CdSe/CdS QDs. Thus, a sensitive and selective sensor for the determination of Hg2+ is established based on the quenching of the fluorescence of TU-modified QDs in the presence of mercury ions. A linear relationship was obtained from 1 to 300 μg L-1 between the extent of quenching and the concentration of mercury ion, with a detection limit of 0.56 μg L-1(3σ). The developed fluorescent sensor was successfully applied to several environmental samples and the results were satisfying.In chapter three, the glutathione was employed to modify the CdSe/CdS QDs. Due to the oxidation of hydrogen peroxide can oxidize GSH to GSSG, the fluorescence of QDs was recovered because of the glutathione removed from the surface of QDs. A new fluorescent sensor for hydrogen peroxide is reported based on the recovery of the fluorescence intensity of QDs in the presence of hydrogen peroxide. Under the optimal conditions, a linear relationship was obtained from 0.2 to 80 μmol L-1 between the extent of recovery and the concentration of hydrogen peroxide. However, the results were not satisfactory probably due to the presence of more interfering components in the detection of real samples.