【作者】 高伟；

【导师】 宋俊峰；

【作者基本信息】 西北大学 ， 分析化学， 2009， 博士

【摘要】 界面现象研究一直是科学研究的核心领域,它为电化学、胶体科学、材料科学、界面科学以及生物物理学等学科的发展奠定了理论基础。界面电位检测是实现界面现象研究的重要途径,开发高效的界面电位检测技术具有重要意义。本论文基于界面电位检测,设计了一种新型的电化学检测系统。通过对其检测原理的理论研究和实验验证,提出了零流电位法和安培法两种检测模式,并重点探讨了它们在材料pH响应性质研究中的应用。本研究已取得以下几项成果。(1)将某种固体电极串联在伏安仪的工作电极和辅助电极之间,与参比电极一起浸入溶液中,构建了一种新型电化学检测系统。通过对其检测原理的理论研究与实验验证,发现电流仅在电极内部流通,遵守欧姆定律,电流值取决于电极的电子学性质、外加电位和“固/液”界面的界面电位。当采用不同的控制电位检测技术,如线性扫描电位法、方波伏安法、脉冲伏安法、安培法时,可以得到不同的电流-电位曲线。在这些曲线上,外加电位和电流分别是物理输入信号和输出信号;界面电位是与电极表面和溶液化学性质有关的化学参数,是一个待测的隐藏变量。可以根据电流-电位曲线随溶液组分的变化关系,实现对界面电位的检测和对“固/液”界面界面现象的研究。基于检测相同电流时外加电位的变化,和检测相同电位时电流变化,提出了零流电位法和安培法两种典型的检测模式。(2)在新型电化学检测系统中,采用线性扫描电位,记录I-E(电流-电位)曲线。将I-E曲线上电流为零时的扫描电位定义为零流电位,将检测零流电位的技术称之为零流电位法。通过检测多种非特征吸附界面的界面电位对方法进行了实验验证和性能分析。结果表明:与开路电位法相比,本方法具有精确度高,稳定性好,检测灵敏快速等优点。使用零流电位法考察聚苯胺膜pH响应性质和羧基化多壁碳纳米管表面酸碱性质,结果满意。零流电位法为开发新型电位型pH传感器提供了新思路。(3)在新型电化学检测系统中,固定施加电位,记录I-t曲线,考察电流随溶液组分的变化,提出了安培检测模式。采用安培检测模式,考察聚苯胺膜的pH响应性质,开发了一种聚苯胺膜安培型pH传感器,设计了一种聚苯胺膜pH可控电流方向分子开关。与传统安培检测相比,该安培检测模式实际上是采用安培检测技术来实现对界面电位的检测,具有较高的稳定性、选择性、准确度、灵敏度以及较短的响应时间。该研究模式为安培传感器和电化学pH分子开关的开发提供了新的研究思路。更多还原

【Abstract】 The solid/solution interface widely occurs in nature,and deals with our vital processes. daily livings,industry,and interdisciplinary research and engineering.Understanding of interface phenomena at the solid/solution interface is of paramount importance for interpreting some problems in electrochemistry,colloid science,surface science,and biophysics,and has been a topic of intensive research.Measurement of interface potential at the interface region is a significant avenue to study the interface phenomena.It is of imporatance to develop some highly effective techniques for measuring interface potential at the solid/solution interface.In this dissertation,a new electrochemical measurement system is proposed for measuring the interface potential at the solid/solution interface.Based on the distinct measurement principle of the system,two topic measurement modes containing zero current potentiometry and amperometric techniques are developed.By using these two modes,the pH sensitive property of the polyaniline film and the surface acid-base property of carboxylic MWNTs are investigated,respectively.The chief contributions of the author are as follows:1) A solid electrode is connected in series between the terminal points of the working electrode and the counter electrode of a potentiostat.The electrode and a reference electrode are immersed in the electrolyte solution,thereby establishing a new electrochemical system. The theoretical and experimental studies show that the distinct connection excludes the possibility of the current passing through the interface of the electrode and solution and the electrolyte solution.The circuit current only flows inside the electrode,and its value rests with the electronic property of the electrode,the applied potential controlled by the potentiostat and the interface potential at the interface of the electrode/solution.When different controlled-potential techniques such as linear sweep voltammetry,square wave voltammetry,different pulse voltammetry and amperometry,are used in the new electrochemical measurement system,various current-potential curves and current-time curves are recorded.In these profiles,the potential and current are the input and output parameters,respectively.They are two detectable physical data in nature.Meanwhile.the interface potential depends strongly on the properties of the sensing surface and the solution composition.It is a latent chemical variable whose information can be drawn from the profiles by measuring the shift of the potential or current with the change of the solution composition. Based on measuring the potential shift at the same current level and the variation of the current at the same potential level,two new measurement modes,zero current potentiometry and amperometric measurement are proposed for the study of the interface phenomena at the solid/solution.2) With the new electrochemical system,a linear sweep potential is applied:the resulting curve I-E of current versus potential is recorded.In the curve I-E,the applied potential when the current is zero is defined as zero current potential E_zcp,which can be used as a key parameter for indicating interface potential at the sensor/solution interface.The corresponding technique to measure zero current potential is named as zero current potentiometry.The measurement principle and the performance of the proposed approach are discussed on the examples of measuring the interface potential at several interfaces without specific adsorption.Zero current potentiometry offers rapidity,high stability,and high accuracy compared to open circuit potentiometry.Zero current potentiometry has been used for investigating the pH sensitivity of the polyaniline film and surface acid-base property of the carboxylic groups terminated MWNTs.The results are consitent with the literatuers.These studies may provide a promising way for the development of the new potentiometric pH sensors.3) A new amperometric mode is proposed based on the use of the amperometric technique in the new electrochemical system.When the applied potential is fixed,the curve of current versus time is recorded.The relationship of the current and the solution compostion provides the therotical basis for the amperometric mode in investigating interface phenemena. The pH sensitive property of the polyaniline film has been investigated using the new amperometric mode,and the result is in agreement with the previous reports.Based on this work,a polyaniline film based amperometric pH sensor has been developed,and a polyaniline film pH switch of current direction has been designed.Different from the classic amperometric measurements based on the study of the redox reactions at the electrode,the new mode actually employ the amperometric technique to measure the interface potential variation.The new mode exhiblits high stability,accuracy,selectivity,sensitivity and a short time.This study may offer an effective means of the development of amperometric sensors and the design of the electrochemical molecular switches.更多还原