The Interactions Between CdTe Quantum Dots And Nitroxyl Free Radical, Surfactant And Their Applications In Fluorescence Analysis

Quantum dots (QDs) or semiconductor nanocrystal, special nanoparticles with diameters ranging from 1 nm to 100 nm, have great effect on photoelectricity transition, sensor, bioimaging and so on, due to their unique optical properties and special electronic and luminescent properties. They have been extensively used in life sciences, analytical sciences, material sciences, immune medicine. In this thesis, CdTe QDs were synthesized and characterized by HRTEM, and their optical properties have been investigated. Then the interactions of CdTe QDs with nitroxyl free radical and surfactant have been studied. The novel fluorescence methods for the determination of Vitamin C and surfactant have been developed, respectively, which further expand the analytical application of QDs. The thesis consists of four chapters.In chapter 1, the basic conception and analytical applications of QDs were first introduced. Then, research reports and status of the interactions between CdTe QDs and nitroxyl free radicals, surfactants were investigated and summarized. Finally, the research proposal for this thesis was presented.In chapter 2, CdTe QDs were synthesized and characterized by HRTEM and other optical techniques. The QDs capped with different sizes and stabilizers QDs were synthesized according to the literature. And the optical behaviors of CdTe QDs in different pH were studied.In chapter 3, the special optical behaviors of CdTe QDs were studied in the presence of nitroxyl free radical. The resulting fluorescence quenching of CdTe QDs and blue shift of the emission spectrum were observed. Mechanism investigation revealed that the quenching effect observed is of dynamic and static quenching, induced by NO and-NH₂, respectively. Furthermore, the addition of Vitamin C (Vc) into the above system could cause fluorescence recovery. And the logarithm of the fluorescence enhancement extent is linearly proportional to the concentration of V_C. Based on this fact, a new fluorescence method for the quantitative analysis of Vc has been proposed, by means of a ternary luminiscence system of quantum dots (QDs), nitroxyl free radical and Vc.In chapter 4, the interactions of CdTe QDs with surfactants were studied using spectral technique. The fluorescence quenching of CdTe QDs in the presence of surfactants was investigated, and the quenching mechanism was also discussed in detail. A novel fluorescence quenching method for the determination of surfactants has been developed, in which the possible interference from heavy and transition metal (HTM) has been efficiently eliminated through simple sample treatment with mercapto cotton made by ourselves. The proposed method, with high sensitivity and selectivity, avoided toxic organic solvent and tedious solvent extraction procedure, compared with traditional method. It has been applied to the determination of trace surfactants in natural river water and commodity samples with satisfactory results.