【作者】 黄新建；

【导师】 廖世军； 王立世；

【作者基本信息】 华南理工大学 ， 应用化学， 2011， 博士

【摘要】 电化学系统在本质上是非线性的,非线性系统在大振幅交流信号的激发下会出现非常明显的谐波响应成分。电化学系统中的谐波响应具有非常特殊的性质,如背景电流抑制能力强,动力学分辨率高等,因此利用电化学谐波的这些优良性质来构建电分析方法具有非常重要的理论意义和实用价值。本论文研究工作旨在通过对电化学谐波性质和行为规律的系统性研究,建立一系列基于谐波分析的电分析方法,并尝试将这些分析方法用于各种实际电化学问题的研究之中。本研究工作首先研制了一个USB2.0-FPGA-24bit DA/AD-恒电位仪结构的通用性任意波形伏安仪,并编写了一系列仪器控制,电化学系统仿真和数据处理软件。这些工作为后续仿真和实验工作的开展提供了一个完备的软硬件平台。基于以上平台,本研究以傅里叶变换大振幅交流伏安法（FT-ACV）为切入点,对谐波分析中具有共性的数据处理方法,谐波的共性行为规律等进行了研究。完善了傅里叶变换-傅里叶逆变换模式的谐波数据处理方法;提出了高次谐波和高次微分在外在形式和内在性质上均具有相似性的规律;解释了傅里叶变换大振幅正弦伏安法之所以可以通过谐波的“指纹相角”来实现电分析的高选择性,是因为高次谐波波瓣交界处的相位会急剧变化从而放大了各个共存电化学过程细微的形式电位差异;提出了基于高次谐波波瓣对称性的电子转移系数的高灵敏测量方法。为克服FT-ACV中激发信号频带窄,谐波数量少的缺点,提出了傅里叶变换大振幅方波伏安法（FT-SWV）。研究发现通过FT-SWV可得到极为丰富的偶次谐波,且偶次谐波幅度谱为一个钟形,对应有一个与动力学相关的最大值（准可逆最大,QRM）。依此原理提出了一个基于FT-SWV偶次谐波QRM的表面体系电子转移动力学数据快速测定方法,即假设QRM所对应的频率为临界频率(f^max),则电子转移速率常数可表示为k0=k^maxf^max。其中,k^max是一个由实验参数决定的常数。分别通过仿真和细胞色素c体系以及偶氮苯体系实验对该方法进行了验证和系统研究。在当今电化学的研究相当大程度上已经从过去的纯溶液体系转移到表面、界面、微观等领域的背景下,该方法具有非常宽的应用范围。本研究将上述动力学数据快速测定方法推广到扩散受限电化学体系,提出了液/液界面离子转移动力学参数同样可以通过FT-SWV的偶次谐波予以快速测定的理论推断,并通过仿真和薄层电极实验对此予以证实。提出了基于FT-SWV的液/液界面离子转移动力学参数和热力学参数同步测定的快速方法,即利用FT-SWV偶次谐波频谱实现动力学测定,利用其各次谐波伏安图实现热力学测定。该方法通过各种阴离子在三相电极油/水界面的转移实验得到证实。在利用大振幅激发下进行电化学谐波研究的同时,本研究工作同时开展了电化学体系在小幅度交流信号激发下表现线性时的阻抗谱研究。本研究结合阻抗免疫传感器的仪器需求,对基于电位阶跃函数和傅里叶变换的阻抗谱测量方法进行改进,设计了一个实用性的仪器,并对仪器性能,使用限制等进行了讨论。更多还原

【Abstract】 Electrochemical system is inherently nonlinear, and a great number of harmonic responses will be induced if the system is perturbed with a large-amplitude AC signal. The harmonics of an electrochemical system own many unique properties, such as excellent background current suppression ability and superb performance with respect to kinetic discrimination. Therefore, it is of great theoretical importance and application value to develop analytical methods based on electrochemical harmonics. The intention of this study is to carry out a systematic investigation on the properties and patterns of behavior of electrochemical harmonics, and then to develop a series of harmonic analysis based electroanalytical techniques and finally to try to find the applications of the as-developed methods.We started the study by development of a versatile hardware/software platform to facilitate further investigations. The platform mainly consists of a USB2.0-FPGA-24bit DAC/ADC-Potentiostat structured arbitrary waveform voltammeter and a number of instrument controlling, digital simulation and data processing programs.Based on the platform mentioned above, data processing algorithms shared by all harmonic analysis based techniques and the patterns of behavior of electrochemical harmonics were investigated with Fourier transformed large-amplitude Alternating Current Voltammetry （FT-ACV） as an example. As a result of this study, the Fourier transform-invert Fourier transform based data processing method was improved; close similarities was found between higher harmonics and higher derivatives with respect to their intuitive curve shape and intrinsic properties; the underlying reason why high selectivity can be realized by―fingerprint phase‖in Fourier transformed Sinusoidal Voltammetry（FT-SV） was revealed as follows: the instant phase of harmonics changes dramatically in the crossover region between two neighboring lobes, and therefore marginal formal potential difference between species to be discriminated can be converted and amplified to be significant phase difference; a charge transfer coefficient measurement technique was proposed based on the symmetry of the lobes of each harmonics.In order to overcome the drawbacks of FT-ACV, such as very limited excitation bandwidth and very a few harmonics, Fourier transformed large-amplitude Square Wave Voltammetry （FT-SWV） was proposed. We found that the profile of even harmonics power spectra in FT-SWV was bell shaped, and there is an electron transfer kinetics dependent ^maximum (quasireversible ^maximum, QRM). A fast and simple electron transfer kinetics measurement method was proposed. Specifically, the frequency corresponding to the QRM was termed as critical frequency (f^max), and the charge transfer constant can be expressed as k0=k^maxf^max, where k^max is an experiment parameters dependent constant. This method was verified by cytochrome c and azobenzene system, and the influence factors were investigated by the above systems as well.The FT-SWV based fast and simple electron transfer kinetics evaluation method mentioned above was employed to evaluate the kinetics of anion transfer across liquid/liquid interfaces, which has been proven to be a diffusion limited process. FT-SWV was further utilized to simultaneously evaluate the thermodynamics and kinetics of interfacial anion transfer. The proposed methods were verified by a model system with thin film electrode as well as a three-phase electrode.We also investigated Electrochemical Impedance Spectroscopy （EIS） measurement methods involving perturbation the system under research with a potential step followed by appropriate data processing. We made the standard method more simple and easy of implementation by several technical modifications, and we further designed a portable and low-cost instrument based on the modified method for practical impedimetric biosensing. The performance and limitations of the instrument were discussed in detail.更多还原