苯胺与其衍生物共聚的原位紫外—可见光谱电化学研究

【作者】 张春花；

【导师】 张雷；

【作者基本信息】 上海师范大学 ， 分析化学， 2009， 硕士

【摘要】 聚苯胺因其具有高导电性、良好的氧化还原可逆性和稳定性好等特点,引起了人们广泛的研究热情。与聚苯胺相比,苯胺的衍生物以能提供更多的修饰基团也倍受关注。近年来,有关苯胺及其衍生物电化学聚合的研究已经有很多,因此对于其聚合机理的研究也有了相应的发展。但是常规的电化学研究方法是以电信号为检测手段,得到的是电化学体系的各种微观信息的总合,难以直观、准确的反映出电极/溶液界面的性质变化,这对于正确地解释电化学反应机理带来很大的问题。紫外-可见光谱电化学技术把紫外-可见光谱技术和电化学方法结合起来,可以同时获得多种信息,在鉴别反应产物,特别是反应的瞬间态和中间体方面具有独到的优越性,是检测苯胺及其衍生物聚合过程中生成的中间体,研究聚合机理、电极上聚合物膜的电化学性质的强有力手段。本文主要研究了以下几个方面的工作:1.采用原位紫外-可见吸收光谱法研究了苯胺(AN)和邻-氨基酚(OAP)在0.5 mol/L H2SO4溶液中的电化学共聚过程。结果表明,在AN和OAP的共聚过程中,OAP首先被氧化生成其阳离子自由基,对应于λ=460 nm处的吸收峰,然后OAP阳离子自由基与继而生成的AN阳离子自由基和溶液中的AN和OAP单体发生交互反应,生成混合二聚物中间体,对应于λ=490 nm处的吸收峰,此混合二聚物中间体再继续反应生成中性低聚物,对应于λ<460 nm处的吸收峰。在研究不同浓度比的AN和OAP进行电化学共聚时发现,当溶液中OAP浓度增大时,对AN的聚合会产生抑制作用。2.采用原位紫外-可见吸收光谱法研究了邻苯二胺(OPD)和苯胺(AN)在恒电位下的共聚过程。实验以氧化铟锡(ITO)导电玻璃作为工作电极,AN和OPD的单独聚合以及共聚均在0.1 mol/L H2SO4+0.1 mol/L Na2SO4溶液中进行。光谱研究发现,在OPD单独聚合以及与AN的共聚过程中,都产生中间体。在共聚过程中,中间体是由AN和OPD的阳离子自由基发生交互反应产生的,在紫外-可见吸收光谱中对应于λ=480 nm处的吸收峰。实验还采用电子顺磁共振波谱证实了共聚过程中确实产生自由基中间体。结果说明AN和OPD共聚过程中,OPD分子掺杂进入AN聚合物骨架。3.通过电化学氧化法在对氨基苯磺酸功能化的玻碳电极表面制备了纳米网状结构的聚苯胺(PAN),得到复合膜修饰的玻碳电极(PAN-ABSA/GCE),并将其用于对抗坏血酸(AA)和尿酸(UA)的催化氧化及同时测定。实验通过X-射线光电子能谱(XPS)和电化学技术对玻碳电极表面修饰的ABSA单分子层进行了表征。并分别采用原子力学显微镜(AFM)、电化学交流阻抗(EIS)、紫外-可见吸收光谱(UV-Vis)和循环伏安法研究了PAN-ABSA复合膜,结果表明该复合膜确实修饰在电极表面,而且该修饰电极在中性甚至碱性溶液中仍然能够保持电化学活性。由循环伏安图和示差脉冲伏安图可知,该修饰电极可以将UA和AA重叠的氧化峰分离成两个完全独立的氧化峰,因此,可以用于在混合溶液中对二者进行同时或选择性测定。UA和AA的催化峰电流与其浓度分别在50-250μmol/L和35-175μmol/L范围内成良好的线性关系,相关系数分别是0.997和0.998,检测限分别为12μmol/L和7.5μmol/L。该电极具有良好的稳定性,重现性和选择性。更多还原

【Abstract】 Polyaniline (PAN) has been attracting significant interest due to its high conductivity, good redox reversibility and environmental stability. Aniline derivatives also receive greater attention because they can provide more functional groups.In recent years, several studies have been reported on the electropolymerization of aniline and its derivatives. So research on the copolymerization mechanism and electrochemical properties of the electrode developed accordingly. However, the traditional analysis of electrochemistry depends on the electricity signals, and only the total microcosmic information can be acquired, which can not reflect the changes of electrode/solution interface clearly and accurately. So it is difficult for people to interpret the electrochemical reaction mechanism correctly. In situ UV-Vis spectroelectrochemistry technique combine the UV-Vis spectra and electrochemical method together, as a result, two kinds of information can be reported simultaneously. It becomes an effective method to detect the intermediates during the polymerization of aniline and its derivatives.The paper includes the following three sections:1. The electrochemical copolymerization of o-aminophenol (OAP) with aniline (AN) in 0.5 mol/L H2SO4 has been investigated using in situ UV-Vis spectroelectrochemistry. The results reveal that OAP can be firstly oxidized to its cation radical,which shows a peak atλ=460 nm in the UV-Vis spectra. Then a mixed dimer intermediate is formed through the cross-reaction of OAP and AN cation radicals with their monomers in solution. The absorption peak atλ=490 nm in the UV-Vis spectra is assigned to this intermediate. The intermediates then react each other to form the oligomer which shows an absorption peak atλ<460 nm. On the other hand, the spectroelectrochemical results reveal that OAP can inhibit the polymerization of AN with the increase of the amount of OAP in the mixed solutions.2. In situ UV-Vis spectroelectrochemical study of the electrochemical copolymerization of o-phenylenediamine (OPD) with aniline (AN) at a constant potential using the indium tin oxide (ITO)-coated glass electrodes as the working electrode has been carried out. The electrochemical copolymerization is performed in 0.1 mol/L H2SO4 aqueous solution containing 0.1 mol/L Na2SO4. The homopolymerizations of OPD and AN are also done independently in the same medium. The intermediate species for the homopolymerization of OPD and the copolymerization of OPD with AN have been identified by spectroelectrochemical studies. The spectroelectrochemical results reveal the formation of an intermediate in the initial stage of copolymerization through the cross-reaction of OPD cation radicals and AN cation radicals. An absorption peak atλ=480 nm in the UV-Vis spectra is assigned to this intermediate. Electron paramagnetic resonance (EPR) has been used to verify the existence of intermediates such as radicals in the initial stage of copolymerization.3. A composite film of polyaniline (PAN) nano-networks/p-aminobenzene sulfonic acid (ABSA) modified glassy carbon electrode (GCE) has been fabricated via an electrochemical oxidation procedure and applied to the electrocatalytic oxidation of uric acid (UA) and ascorbic acid (AA). The ABSA monolayer at GCE surface has been characterized by X-ray photo-electron spectroscopy (XPS) and electrochemical techniques. Atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), UV-Visible absorption spectra (UV-Vis) and cyclic voltammetry (CV) have been used to investigate the PAN-ABSA composite film, which demonstrates the formation of the composite film and the maintenance of the electro-activity of PAN in neutral and even in alkaline media. Due to its different catalytic effects towards the electro-oxidation of UA and AA, the modified GCE can resolve the overlapped voltammetric response of UA and AA into two well-defined voltammetric peaks with both CV and differential pulse voltammetry (DPV), which can be used for the simultaneous and selective determination of these species in a mixture. The catalytic peak currents are linearly dependent on the concentrations of UA and AA in the range of 50-250 and 35-175μmol/L with correlation coefficients of 0.997 and 0.998, respectively. The detection limits for UA and AA are 12 and 7.5μmol/L, respectively. The modified electrode exhibits good stability, reproducibility, sensitivity and selectivity.更多还原