【作者】 姚冬娜；

【导师】 卢小泉； 康敬万；

【作者基本信息】 西北师范大学 ， 分析化学， 2010， 硕士

【摘要】 由于液/液界面可以看作是模拟生物膜或人造膜的简单模型,研究其上电子转移过程对理解生物体复杂的生理变化过程具有重要的意义。薄层循环伏安法是Anson等于1998年提出来的一种研究液/液界面上电荷转移过程的新方法。该法因其具有简单、易操作等优点成为研究液/液界面电子转移过程的有力手段,因此用该方法测定液/液界面电子转移速率的研究显得尤为重要。本文共分为四部分,主要包括以下内容:1.简要地回顾了薄层循环伏安法测量液/液界面电子转移的发展历程,详细综述了近年来薄层循环伏安法测定液/液界面电子转移速率在理论以及实验方面的研究进展,并对其可能的影响因素进行了总结与分析。本章主要包括:（1）薄层循环伏安法的发展背景;（2）薄层循环伏安法的实验原理;（3）薄层循环伏安法测量液/液界面电子转移速率的影响因素;（4）薄层循环伏安法在液/液界面电化学中的应用。2. Anson等提出了薄层循环伏安法测量液/液界面电子转移速率的理论,但是该理论由于缺乏边界条件而未引起研究者的重视。本章提出了新的理论指导,完善了Anson所提出的理论中的不足。新的理论指导不仅是有机相中反应物浓度的选择标准,同时也是选取适当水相反应物浓度的先决条件。我们也通过实验证明了该理论的有效性。此外,我们还深入分析了薄层厚度对液/液界面电子转移速率的影响,结果表明可通过增加薄层厚度来测定反应速率较快的体系,从而克服通过增加水相反应物浓度的手段测量快速反应体系中所存在的困难。3.本章描述了一个简单测量液/液界面多步电子转移速率的方法。基于所提出的理论,多步电子转移过程的速率常数可通过薄层循环伏安法很便利地测得。通过该方法我们测定了包含在水相中的K₄Fe（CN）₆与硝基苯薄层中的ZnTPP间的两步一电子转移过程,其速率常数分别为k₁=0.12 cm s^–1 M^–1,k₂=0.15 cm s^–1 M^–1。此外,依照该理论,我们利用数值模拟进一步考察了界面多步电子转移反应的一些相关影响因素,并且通过实验对其进行了验证。所得结果不仅给出了两相反应物浓度比以及薄层厚度对多步电子转移的影响,而且理论与实验的吻合也证明了该理论的有效性。4.薄层循环伏安法作为最简单的测定液/液界面上电子转移速率的新方法,以其独有的优势成为探测界面电子转移速率的有利手段。本文通过数值模拟对薄层循环伏安法对界面多步电子转移和单步电子转移速率的测定进行了对比研究。分别探讨分析了两相反应物浓度比、薄层厚度以及扩散系数对界面多步电子转移速率和单步电子转移速率的影响。结果显示对于多步电子转移中的第一步电子转移反应所得到的结果与单步电子转移过程几乎是一致的,这也暗示了对于多步电子转移中的第一步电子转移可以近似为单步电子转移过程来处理。此外,结果也显示了对于多步电子转移中第二步电子转移反应其变化规律与其第一步的电子转移不尽相同甚至是相反。这就表明了对于多步电子转移中第二步以后的电子转移过程更加复杂,其影响因素更加繁多,变化规律也更加多变。更多还原

【Abstract】 The study of electron transfer across liquid/liquid interface has important significance for understanding complex physiological change process of organisms, because liquid/liquid interface could be treated as simple models of biologic or artificial membrane. The thin-layer cyclic voltammetry proposed by Anson et al. in 1998 is a new method of studying electron transfer at liquid/liquid interface. The method becomes a powerful measure of studying cross-phase electron transfer, due to its simplicity and convenience. Thus, study of thin-layer cyclic voltammetry for measuring electron transfer rate at liquid/liquid interface is very important.There are four parts in this paper, main contents are as follows:1. This paper 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 application of thin-layer cyclic voltammetry in the liquid/liquid interface electroanalytical chemistry.2. Anson et al. has proposed the theory of thin-layer cyclic voltammetry for measuring the rates of electron transfer at liquid/liquid interface. However, 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. We also demonstrated the utility of the theory by experimental tests. In addition, the effect of thin layer thickness on the electron transfer rate was analyzed in detail. The result showed that rate constants of electron transfer of rapid kinetics systems would be expediently determined by increasing the thickness of the thin layer. This can avoid the existing difficulties that larger electron transfer rate constants were determined by meaning of adding concentrations of reactants contained in the aqueous phase.3. A simple method of measuring the rates of multi-step electron transfer across liquid/liquid interfaces is described. Based on a theory, the rate constants of multi-step electron transfer reaction can be obtained expediently by the thin-layer cyclic voltammetry. The bimolecular rate constants for the two-step electron transfer reactions between ZnTPP in the organic phase and K₄Fe（CN）₆ located in the adjacent aqueous phase were obtained simultaneously by the method as the rate constant of the 1st step is 0.12 cm s^–1 M^–1, and the rate constant of the 2nd step is 0.15 cm s^–1 M^–1. In addition, numerical simulation according to the treatment was used to model the voltammetric responses of electrodes to study facters. Meanwhile, we also have done a further validation by experiments. Results obtained not only gave information regarding the effect of the concentration ratio of the reactants in two phases and the thin layer thickness on multi-step electron transfer, but also the agreement between simulations and experiments proved the validity of the theory.4. 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.更多还原