伏安法的谐波和相角研究及其分析应用

Voltammetry is an important and widely used electrochemical characterization and analysis method. Traditionally, the selectivity of voltammetric analysis depends on the difference of redox potentials. However, for the substances with very close electrochemical properties, it hard to achieve selective detection with voltammetry. In order to enhancing the selectivety, previous researches placed much emphasis on modifying electrodes. However,the preparation of the modifyed electrodes is tedious, and during the testing process the working electrode are often instabile. Specifically, we attempt to perturbe the electrochemical system with large-amplitude sinusoidal and the responsive current is subsequently analysis in the fraquency domain by Fourier transform. The selective detection can be realized by quantifying the amplitude of certain harmonic element at the characteristic "fingerprint" phase angle. that is, for a given electrochemical system, Fourier transform large amplitude step sinusoidal voltammetry were first introduced in for realizing optimum resolution target substance from the interference by harmonic and the phase difference, and then the electrochemical system was perturbed with a large-amplitude sinusoidal potential signal and the responsive current signal was subsequently analyzed in the frequency domain by Fourier transformation . The selective detection can be realized by quantifying the amplitude of a certain harmonic element at the characteristic "fingerprint" phase angle of each redox couple; and their phase angle difference can be regulated to be close to 90 to eliminate interferences and optimize the selective detection.This project intends to build a harmonic and phase detection technique theory and application method, which will be applied to biological material electrochemical sensor and ionic liquid|liquid interface migration sensor research

伏安法是一种非常重要而且应用广泛的电化学表征、分析方法。传统的伏安法主要依据氧化还原电位分辨不同物质，然而对于电化学性质十分接近的物质，一直存在选择性差、分辨率低的问题；近来大量研究集中在修饰电极以解决这一问题，但是修饰电极存在制备过程繁琐，测试过程中不稳定的问题。本项目的研究拟利用大振幅正弦伏安法激发电化学体系，对响应电流进行傅里叶变换，采集基次及高次谐波的信号，利用"指纹相角"信号分辨电化学性质相近的物质。即，对于给定的电化学体系，首先采用傅里叶变换大振幅阶梯正弦伏安法寻找可以实现目标物质与干扰物质的最佳分辨的谐波与相位差，然后在给定的直流电位上叠加大振幅正弦波施加于电化学体系，通过傅里叶变换在最佳的谐波和相位下实验目标物质的高灵敏度检测。本项目拟通过研究构建一套谐波与相位的分析检测技术理论和应用方法，并将其应用于生物物质电化学传感器及液|液界面离子迁移转感器的研究。

以谐波的相角作为研究对象,结果表明正弦伏安中谐波的相角与电化学过程热力学和动力学都有非常密切的关系: (1) 二次谐波的相角在氧化还原电位附近会发生急剧的翻转，且其他高次谐波也有类似规律(N次谐波有N-1个翻转点)，因此谐波相角在氧化还原电位附近有很高的分辨率；(2) 各次谐波具体的相角值与电化学过程动力学有很直接的相关性，随着电化学过程逐渐从可逆转向不可逆，谐波的相角也从45度或者135度逐渐负移； (3) 借助谐波的这两个性质，对于化学结构非常相近的物质，即使其氧化还原电位非常接近甚至完全相同，通过谐波相角依然可以将其区分开来予以选择性检测，这对提高伏安法的分辨率有重要意义。.通过将正弦伏安与超微电极上纳米粒子的碰撞相结合构建具有单纳米粒子级别分辨率的电分析方法，结果表明如果在超微电极上施加一个大振幅的正弦波，当一个纳米粒子碰撞到超微电极后谐波的相位会出现一个突变。这个突变可作为纳米粒子碰撞到电极的指示。在此碰撞点附近，单个纳米粒子所产生的信号可同时在时域和频域予以提取和分析，通过该手段可实现对单个纳米粒子的性质进行分析。该方法实现了单纳米粒子多维度的电化学分析，具有重要的应用意义。此外该方法的实验和数据分析策略可应用于其他离散信号体系，具有很强的通用性。