4-羟基苯硫酚论文：非水溶液中硫醇在金表面的自组装及电化学实时原位表征.doc

4-羟基苯硫酚论文：非水溶液中硫醇在金表面的自组装及电化学实时原位表征【中文摘要】自组装单分子膜(Self-assembled monolayers, SAMs)是近30年来发展起来的一种新型有机超薄膜,具有均匀一致、高密度堆积和低缺陷等优良性能,在电分析化学、化学与生物传感器、表面吸附、防腐、润滑、电子器件、光学元件等诸多领域具有广阔的应用前景。SAMs的实时原位表征是完美SAMs制备与调控的关键技术之一,但至今仍缺少一种有效的实时原位表征方法。本文首次利用电化学交流阻抗技术(EIS)对4-羟基苯硫酚(4-HTP)在金表面的自组装过程进行跟踪,建立了一种金表面上4-HTP SAMs实时原位表征的新方法,考察了溶剂种类及溶液浓度对成膜速率的影响。本论文工作主要包括以下三个方面：1、乙腈-水介质中4-HTP在金表面自组装过程的实时原位表征通过乙腈体系和乙腈-水体系的对比研究,发现采用乙腈-水体系更有利于SAMs的EIS表征。在乙腈与水的摩尔比例为1：0.6、极化电位-0.5V、支持电解质高氯酸钠(NaClO4)浓度为600 mmolL-1、探针离子二茂铁(Fc)浓度为15 mmolL-1的优化条件下,当4-HTP的浓度 1 mmolL-1时,可用EIS进行实时原位表征。2、碳酸丙烯酯溶液中4-HTP在金表面自组装过程的实时原位表征碳酸丙烯酯(PC)溶液不易挥发,是一种常用的非水电解质溶液,4-HTP在PC中易溶。本章选择PC为溶剂,在开路电位下,选择NaC104浓度为500mmolL-1, Fc浓度为15mmolL-1,对4-HTP在金电极表面的自组装过程进行EIS原位实时表征。结果表明,随着4-HTP浓度的增大,形成有序致密的4-HTP SAMs所需的时间逐渐缩短,平衡后的电子传递电阻(Rct)随之增大。当4-HTP的浓度大于3mmolL1时,平衡后的Rct几乎不再变化。3、乙醇溶液中4-HTP在金表面自组装过程的实时原位表征乙醇是制备硫醇SAMs的常用试剂。本章首先对EIS表征乙醇溶液中4-HTP在金电极表面的自组装过程的测试条件进行了优化,在开路电位下,当NaC104浓度为200mmolL-1, Fc浓度为15mmolL-1时,所得到Rct随时间的延长呈现很有规律的变化。由Rct计算4-HTP SAMs在Au表面的覆盖度。实验结果表明,4-HTP浓度的增大,形成有序致密的4-HTP SAMs所需的时间变短,平衡后的Rct增大,表面覆盖度也逐渐变大。当4-HTP的浓度大于3 mmolL-1时,4-HTP SAMs的Rct几乎不再变化。通过上述比较研究发现,对于实时原位表征4-HTP SAMs而言,乙腈-水混合溶液不是理想溶剂,当4-HTP的浓度较小时,可能受相平衡的影响,造成Rct值很不稳定。乙醇是一种既能溶解许多无机物,又能溶解许多有机物的两性溶剂,但由于其易挥发,要求反应器必须密闭,进行实时原位表征的时间较长,难以保证硫醇浓度不变,所以乙醇体系也不是一个理想的选择。碳酸丙烯酯一种性能优良的高沸点溶剂,它具有较高的介电常数,性质稳定,是进行实时原位表征的较好的非水溶液。【英文摘要】Over the past three decades, self-assembled monolayers (SAMs) has been a new type of organic ultra-thin film with high-density accumulation, the rules of an orderly, uniform, excellent performance, which has been used for many different areas, such as electroanalytical chemistry, chemical and biological sensors, adhesion, lubrication, corrosion on surfaces and interfaces, electronic devices, optical element etc.,showing a broad application prospect. Real-time in-situ characterization of SAMs which can be used to prepare and regulate SAMs is one of the key technology.However, there is lacking an effective method of real-time in-situ characterization.In nonaqueous solvent, electrochemical impedance spectroscopy(EIS) was used to track the film-forming process of the 4-hydroxy thiophenol on gold electrodes.A new mothod of real-time in-situ characterization was built, then the fixed assembly time and the rules of film-forming of 4-hydroxy thiophenol self-assembled monolayers (4-HTP SAMs) was inverstigated. The major contents in this thesis are described as follows:1、Real-time in-situ characterization of the modified electrodes by 4-HTP SAMs in mixed solution of aetonitrile and waterFirstly, the test experimental conditions of EIS in mixed solution of aetonitrile and water have been optimized. The molar ratio of acetonitrile and water is 1:0.6.The polarization potential is-0.5 V.The concentration of NaClO4 and ferrocene is respectively 600mmolL-1 and 15 mmolL-1. In the best condition of experiment, the modified electrodes by 4-HTP SAMs are real-time in-situ characterized in mixed solution of aetonitrile and water by EIS. The results shows that the film-forming process is related to the concentration of mercaptan. Real-time in-situ characterization of EIS can be carried out, when the concentration of 4-HTP is more than lmmol-L-1.However, when the concentration of 4-HTP is less than 1 mmolL-1, experimental method of EIS can be not feasible.2、Real-time in-situ characterization of the modified electrodes by 4-HTP SAMs in propylene carbonate solutionPropylene carbonate(PC) is a common nonaqueous electrolyte solution which do not volatilize easily.4-HTP can dissolve in PC more easily.In this paper, PC solution has been chosen as solvent.At an open circuit potential, the modified electrodes by 4-HTP SAMs are real-time in-situ characterized in PC solution. The concentration of NaClO4 and ferrocene was respectively 500 mmolL-1 and 15 mmol-L”1.The results show that the film-forming process is related to the concentration of mercaptan. The compact fixed assembly time is shorter and the Ret gradually is increased when the concentration of 4-hydroxy thiophenol is increased. When the concentration of 4-HTP is more than 3mmolL-1, the film-forming process on longer changes.3、Real-time in-situ characterization of the modified electrodes by 4-HTP SAMs in ethanol solutionEthanol is a common reagent that prepares for mercaptan SAMs .The tested experimental conditions of EIS in ethanol solution has been optimized. At an open circuit potential, the modified electrodes by 4-HTP SAMs were real-time in-situ characterized in ethanol solution.The concentration of NaC104 and ferrocene was respectively 200mmolL-and 15mmolL-1. The surface coverage of 4-HTP SAMs/Au has got from Rct, which changes with assembled time regularly. The results show that the film-forming process is related to the concentration of mercaptan. The compact fixed assembly time is shorter and the Rct gradually is increased when the concentration of 4-HTP is increased. When the concentration of 4-HTP is more than 3mmolL-1, the film-forming process no longer changes.The result shows that the mixed solution of aetonitrile and water is not the best choice for establishing a method of real-time in-situ characterization, because this method depends on the concentration of 4-HTP.Ethanol is a good kind of solvent,and can not only dissolve many inorganic compound,but also dissolve organic compound.Due to the volatility of ethanol, the reactor must have good leakproofness.If test time is to be longer,ethanol is not a good choice. Propylene carbonate is a kind of solvent,which has excellent properties,hgher dielectric constant,so PC is a good kind of solvent for real-time in-situ characterization.【关键词】4-羟基苯硫酚 电化学交流阻抗法 实时原位表征 乙腈 碳酸丙烯酯 乙醇【英文关键词】Self-assembled monolayers Electrochemical impedance spectroscopy Real-time in-situ characterization Nonaqueous solution【目录】非水溶液中硫醇在金表面的自组装及电化学实时原位表征摘要4-6Abstract6-71 绪论10-211.1 自组装单分子膜技术10-141.1.1 自组装单分子膜的研究进展10-111.1.2 自组装单分子膜的结构及特点11-121.1.3 自组装单分子膜的制备121.1.4 自组装单分子膜的应用12-141.2 自组装单分子膜的表征方法14-161.2.1 电化学表征方法14-151.2.2 其他表征方法15-161.2.3 研究中存在的问题161.3 常见的非水溶剂16-181.3.1 非水溶剂的种类16-171.3.2 非水溶剂的应用17-181.4 芳香硫醇自组装单分子膜研究进展18-191.5 本论文工作的内容及意义19-212 乙腈-水介质中对羟基苯硫酚修饰电极的实时原位表征21-332.1 实验部分22-232.1.1 仪器与试剂222.1.2 实