Theoretical Study Of Thin-Layer Cyclic Voltammetry For Electron Transfer At Liquid/Liquid Interfaces

The study of electron transfer through liquid/liquid interface has attracted great attention because of the importance of the liquid/liquid interface, which are widely used by many fields, such as ion-selective sensor, phase transfer catalysis, pharmacology, colloidal chemistry, and solar energy transformation, as well as imitation biomembrane. Thin layer cycle voltammetry is one of the efficient methods to study liquid-liquid. The advantages of this approach lies on its simplicity and uncomplicated .The paper represents the progresses have been made in decade years to research electron transfer across liquid-liquid interface both experiments and theories. Analyze how to get steady-state current and the factors that affect rate constants. In addition,the theories about liquid-liquid that are discoveried by Anson apply to additional and deduction.According to the analysis and simulation By MATLAB,the optimizational conditions canbe found out to change the value in the experiments and to improve accuration and precition.There are three parts in this thesis, main contents are as follows:1. This thesis reviewed summarily the historical background of the thin-layer cyclic voltammetry for measuring electron transfer rate at liquid/liquid interface. Moreover, the research progress on theory and experiment of the thin-layer cyclic voltammetry for measuring the rates of cross-phase electron transfer were summarized in detail. Besides, all kinds of possible influencing factors were outlined briefly and analyzed. All contents are: (1) The historical background of thin-layer cyclic voltammetry; (2) The experimental principle of thin-layer cyclic voltammetry; (3) The influence factors for measuring rate of electron transfer across liquid/liquid interface; (4).The deduction procedure of the rate constant and effects factors.2. Anson et al. has proposed the theory of thin-layer cyclic voltammetry for measuring the rates of electron transfer at liquid/liquid interface .There are three equations to be deducted .in the paper ,including the cathodic plateau currents iobs ; steady‐ state diffusion‐ limited current iD and cross‐phase reaction kinetic current iET;morever,how to acquire rate constant is also given to explain the theory has not caused enough attention because of the absence of boundary conditions. This paper gave some new theoretical conditions to remedy the defects. That is, we gave the selection criteria to concentrations of coreactants, which not only provided the selective ranges of reactants concentration contained in the organic phase, but also was precondition for properly selecting concentrations of reactants contained in the aqueous phase. Two inequalities was derived which provides guides for the selection of suitable concentrations of coreactants.We also demonstrated the utility of the theory by simulation tests. In the thesis mult-step election transfer is stated in detail. The statements are principle, procedure, basical theories about two-step electical transfer. Studying and analysis the effect factors come from the measurement in the experiments. Finally, discussed the range of the value in the simulation programmer.3. Thin-layer cyclic voltammetry with its unique advantages has become a powerful means of measuring the rate of electron transfer at liquid/liquid interface. In this paper, numerical simulation was employed to comparative study the thin-layer cyclic voltammetry for determination of multi-step electron transfer and single-step electron transfer at liquid/liquid interface. The effects of the concentration ratio of two-phase coreactants, the thin layer thickness and the diffusion coefficient of reactants on the multi-step electron transfer and single-step electron transfer were investigated and analyzed respectively. The results showed that the results obtained for first step electron transfer reaction of multi-step electron transfer was consistent with single-step electron transfer process, which suggested that the first step electron transfer of multi-step electron transfer can be approximated to deal with as the single-step electron transfer process. In addition, the results also showed that the change for the second step electron transfer of multi-step electron transfer was different and even opposite from the first step electron transfer. This implied the electron transfer process of that starting from the second step electron transfer of multi-step electron transfer had more complex mechanism, more various factors and more diverse changes laws.