The Cathodic ECL Behavior Of The CdTe QDs-S₂O₈^2- System And Its Application For Environmental Analysis In Water Samples

Electrogenerated chemiluminescence or electrochemiluminescence（ECL） is a new analytical method based on the combination of electrochemistry（EC） with chemiluminescence（CL）. This method takes many advantages of electrochemistry and chemiluminescence, such as high sensitivity, high selectivity, low background signal, wide linear response range, and easy control, et al. It has been widely used in the field of Anal. Chem. Now, it is crucial for ECL analysis to look for new ECL reagents and then stablish new ECL systems. Quantum dots（QDs）, as one kind of functional nanocrystals, have received more attention to develop luminescence materials and build photosensitive sensors due to their advantages in optical and electronic characteristics. Recently, with various QDs as ECL nanoemitters, QDs-based ECL have been developed for designing novel analytical methodologies. However, the application of these methods for environmental analytysis is scarce.In this paper, the cathodic ECL behavior and mechanism of the thioglycerol stabilized Cd Te QDs coreacted with potassium persulfate on glassy carbon electrode（GCE） was discussed in detail.Given this Co2+ and phenol in water samples were determined with high sensitity. The present work aims to develop QDs-based ECL methods in the field of environmental analysis.The contents of this dissertation includes the following four parts:（1） Firstly, the overview of the nature and application of quantum dots, especially the research progress and application of Cd Te quantum dots were summarized; Secondly, the ECL detection were summarized; The principle and application of quantum dots as luminescents of ECL, especially QDs-based ECL with corectants were reviewed. Finally, the vista of ECL methods with QDs as luminescents were prospected. Totally 151 references were cited.（2） The adsorption behavior of thioglycerol stabilized Cd Te quantum dots with potassium persulfate as a coreactant in the cathodic ECL on GCE in phosphate buffer solution were studied. Cyclic voltammetry was applied to conduct the ECL process. When scanning under the potential window from 0 to-1.7V, the ECL intensity gradually increased and kept stable after 1800 s, which was considered as an equilibrium adsorption process. Then the ECL mechanism of the Cd Te quantum dots-potassium persulfate system were dicussed by CCD, fluorometry and electrochemistry. On the other hand, the effects of several factors such as scan rate, potential, Cd Te QDs concentration, potassium persulfate concentration, p H and buffer concentration on ECL intensity after equilibrium adsorption were investigated. Finally, hydroquinone was selected as a target and determined successfully, indicating that the present ECL system could be used for environmental analysis.（3） A novel electrochemiluminescence（ECL） method has been established for the determination of Co2+ ion in water samples, based on the ration quenching on the cathodic ECL of the Cd Te QDs-S₂O₈^2- system in HAc-Na Ac buffer solution. The effects of several factors such as scan rate, potential, Cd Te QDs concentration, potassium persulfate concentration, p H and buffer concentration were investigated. Under the optimized conditions, the ECL intensity decrement was in proportion to the log value of the Co2+ concentration in the range from 0.2 to 10.0 μg/m L with a detection limit of 0.017 μg/m L（S/N=3）. The relative standard deviation（RSD） of the ECL intensity decrement for 5.0 μg/m L theophylline standard solution was 2.32 %（n=10）. The proposed method has been successfully applied to determine Co2+ in simulated water samples with the recoveries between 96.1%- 105.5%.（4） A novel electrochemiluminescence（ECL） method has been developed for the determination of phenol based on the ration quenching on the cathodic ECL of the Cd Te QDs-S₂O₈^2- system in HAc-Na Ac buffer solution. The effects of several factors such as scan rate, potential, Cd Te QDs concentration, potassium persulfate concentration, p H and buffer concentration were investigated. Under the optimized conditions, the log value of the ECL intensity decrement was in proportion to the log value of the phenol concentration in the range from 0.01 to 0.5 μg/m L with a detection limit of 1.2×10-3 μg/m L（S/N=3）. The relative standard deviation（RSD） of the ECL intensity decrement for 0.2 μg/m L phenol standard solution was 2.45 %（n=10）. The proposed method has been successfully applied to determine phenol in simulated water samples with the recoveries between 96.0%- 103.5%.