金/席夫碱自组装单层膜电化学行为研究

【作者】 田娜；

【导师】 童汝亭；

【作者基本信息】 河北师范大学 ， 物理化学， 2002， 硕士

【摘要】 由于自组装单分子膜不仅具有传统LB膜的有序性，同时还具有较高的稳定性，易于应用近代物理和化学的表征技术进行研究，因而这种新型超薄有机膜得到了重视，迅速成为界面化学、材料化学等许多领域的研究热点。席夫碱是指含有亚胺或甲亚胺特性基团(-RC=N-)的一类有机化合物。席夫碱类化合物有着广泛的用途，但目前国内外对席夫碱自组装膜的研究却是空白。本论文首次成功地将席夫碱自组装到金基底上，并用交流阻抗和循环伏安法对这一自组装单层膜进行了表征，这为研究自组装膜和席夫碱开辟了新的思路和途径。 我们首先通过循环伏安和交流阻抗技术对席夫碱自组装膜的电化学行为进行了研究，实验内容和结果如下： 1．成功地在金基底上形成了席夫碱自组装膜，采用循环伏安和交流阻抗法对其成膜过程进行了研究。结果表明，席夭碱能在金基底上自组装成膜，但膜比较疏松。 2．考察了金／席夫碱膜电极在不同pH值的KCl溶液中的电化学行为。结果表明，在近中性直至强碱性溶液中，席夫碱单分子膜的膜电容基本不变；在酸性直至强酸性溶液中，席夫碱单分子膜的膜电容随酸性的增强而增大，这说明在酸性条件下，席夫碱单分子膜的结构随溶液酸性的增强而发生较大变化。 3．研究了填充十八硫醇的席夫碱自组装膜，得到的结果是：电化学反应电阻大大增大，表明席夫碱分子膜已趋于致密，同时也说明十八硫醇分子的填充对席夫碱单层膜的电化学行为有一定的改善作用，这为研究此席夫碱自组装膜中的电子传输等问题奠定了基础。 4．研究了极化电势对此席夫碱自组装膜的影响，结果表明：极化 河北帅他人学帧卜学位论A 电势使席夫碱膜的表观电化学反应电阻增大。这可能是山于席夫碱分 于间存在的某种“聚集作用”，在外加极化电势作用下受到了一定程度 的破坏，并使“分于聚集团”周围倒伏的分子趋于直立、趋向有序化。 这说明该席夫碱膜的结构是受电场影晌的，从而为研究席夫碱在不同 I 电场中的行为提供了新的思路。 在上述实验的基础上，我们进而对席夫碱与CU入的作用进行了检 测，实验结果如下： 1．其阻抗谱图表明了席夫碱膜电极与 C［l升有相互作用，这种作 用使席夫碱分子膜电极表观电化学反应电阻减小，并总结出作用过程 可分为快慢两个阶段。 2．在席夫碱膜填充十八硫醇的情况下，我们得出了Cll》与席夫 碱分子作用时，可能是每个 CU升与它周围的几个席夫碱分子同时作用， 并且这种作用需要一定的空问。 3．通过席夫碱分子膜电极与不同浓度的 Cllh的作用，我们得到一 条线性关系很好的直线，因此金／席夫碱单层膜电极有望实现对 Clly的 定量检测。 席夫碱分子中含C＝N，可被还原，因此我们又用交流阻抗和循环 伏安技术对席夫碱的还原性质进行了研究，实验结果如下： 1．用循环伏安和交流阻抗法测定发现席夫碱中的C＝N可以被还 原，且此反应为近似不可逆；随着膜中C—N含量的减少，循环伏安图 中还原峰电流减小，而在阻抗谱图中，膜的电荷传递电阻发生了变化。 ZW 观察了施加极化电势对膜的组成的影响，对膜施加其峰电位处 的极化电势，也可使席夫碱膜被还原，使C＝N含量减少。更多还原

【Abstract】 Self-assembled monolayer (SAM) is more regular and more stable than LB membrane and it has a high stability, we can investigate it easily by means of physical and chemical techniques. Thus, this new kind of super-thin organic film studied widely and quickly became a hot-topic in many fields, such as chemistry of interface, chemistry of material, et al. Schiff bases belong to a class of compounds that contain an imine or azomethine group (-RC=N-). Schiff bases are useful in many fields. However, there has no research being taken on schiff base SAM in and outside of the country-. In this report, a certain schiff base SAM was successfully prepared for the first time and its electrochemical behavior was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), which may develop a new w ay for the study of SAM and schiff base as well.Firstly, the schiff base SAM was investigated by means of EIS and CV7. The conclusions are as follows:1. The schiff base SAM was successfully prepared and the self-assembly process w as investigated by means of EIS. Results from CV7 and EIS experiments show that the membrane is somewhat loose when compared to the alkanethiol SAM.2. The electrochemical behavior of the schiff base monolayer in solutions with different pH value was also investigated. We concludedthat the membrane capacitance varied little when it was in neutral or basic solutions, while it become larger when the acidity of the solutions was enforced, implying that the structure of the schiff base SAM changed with the acidity of the solutions.3. Inserting ODT molecule in the schiff base SAM can improve the packness of the schiff base SAM’s structure and increase its blocking property.4. Electrochemical reaction resistance is greatly enhanced when over-potential was applied. We proposed that this phenomenon probably is due to the existence of some molecular force among schiff bases.The combination between schiff base and Cu2+ was also observed. The results are as follows:1. The reaction between schiff base and Cu + was investigated by means of EIS, which lead to the decrease of the electrochemical reaction resistance of the SAM and its combining process could be divided into two: a rapid step followed by a slow one.2. We concluded that certain space is necessary for the combination of Cu2+ with schiff base SAM during the reaction, while in the case of schiff base membrane fabricated by ODT, no variation was found.3. A good linear relationship between the concentration of Cu2+and the electrochemical charge resistance was obtained when the schiff base act with different concentration of Cu +.As the C=N was introduced into the schiff base, so it is necessaryfor us to probe the reduction behavior of schiff base SAM, the results are shown below:1. The CV and EIS experiments convinced us that the C=N can be reduced, and we knew from experiments that this reaction is almost irreversible. With the decrease of the number of C=N in the membrane, the current of reduction peak decreased.2. The influence of over-potential on the the membrane which may lead to the reduction of C=N group in schiff base SAM was also investigated by exerting an over-potential on the monolayer in the EIS experiments, which is consistent with the results from CV experiments.更多还原