【作者】 陈婧；

【导师】 高春光； 赵永祥；

【作者基本信息】 山西大学 ， 物理化学， 2010， 硕士

【摘要】 二茂铁桥联聚倍半硅氧烷(Ferrcene-bridged polysilsesquioxanes)是新型的二茂铁衍生物。利用此聚合物制备的化学修饰电极稳定性高、重现性好,更重要的是能实现电极表面的结构设计,获得结构可控的高性能化学修饰电极。本论文在大量文献调研及课题组前期工作的基础上,以课题组合成的1,1’-双[(2三乙氧基硅基)乙基]二茂铁单体(1,1’-bis[(2-triethoxylsilyl)ethyl]ferrocene, BTEF)为前驱物,与正硅酸乙酯(TEOS)、聚乙烯醇(PVA)经共溶胶-凝胶过程制备了两种二茂铁桥联聚倍半硅氧烷修饰电极：BTEF/TEOS/GCE和BTEF/PVA/GCE;优化了修饰电极的制备条件；采用循环伏安(CV)法,研究了修饰电极的电化学特性；并将修饰电极成功应用于抗坏血酸(H2A)的测定,特别是优化了水体系中测定H2A的条件(如电位扫描速度v、体系pH等)并探讨了催化反应机理。具体研究结果如下：1.用温和型催化剂催化溶胶-凝胶过程制备的BTEF/TEOS/GCE膜修饰电极的电化学性能要优于强酸、强碱催化下制备的修饰电极。其中,尤以NH4F为催化剂制备的修饰电极性能最好,峰电流大,电位差小,电极反应的可逆性及稳定性好。2.PVA的加入对溶胶又起到稳定及分散的作用,在溶胶-凝胶中加入少量的PVA,可以使胶体粒子大小均匀,孔径分布集中,胶体稳定性提高。优化结果：PVA的用量为300μL(V总=10 mL)时BTEF/PVA/GCE修饰电极性能最好,峰电流大,电位差小。3.支持电解质的离子尺寸和离子价态对电极性能有很大影响,不论是BTEF/TEOS/GCE还是BTEF/PVA/GCE膜修饰电极,NaC104为支持电解质时,修饰电极在水中具有较宽电位视窗,具有较好的可逆性及稳定性。4.扫描速度v对两种修饰电极的电化学反应过程有着显著影响。其中BTEF/TEOS/GCE膜修饰电极在低扫描速率下(0.01-0.1 V·s-1),CV峰形尖锐,峰形比较对称,峰电位Ep随扫描速度的变化较小,可逆性较好,相对时间充裕,传荷过程受物理扩散和表面过程两种因素共同作用；在高扫描速率下(0.1-1.0V·s-1),CV峰发生明显的宽化,可逆性下降,电极反应为扩散和电子转移速率同时控制的过程。而BTEF/PVA/GCE在整个考察范围内C0.01～1.0V·s-1),CV峰均发生明显的宽化,可逆性下降,电极反应为扩散和电子转移速率同时控制的过程。5.两种修饰电极均具有很好的电极稳定性,其中BTEF/TEOS/GCE的稳定性略优于BTEF/PVA/GCE,在不除氧的情况下连续扫描50次,电极电位不发生变化,峰电流分别下降4.95%、5.58%。6.pH是影响H2A测定的重要因素。其原因首先是不同pH下,H2A的存在形式不同；再者,pH对所制备的修饰电极本身性能有影响。从化学修饰电极的电催化用于分析目的必须具备的条件[①降低底物的过电位,尽可能的减小干扰及背景电流；②增大电流响应,降低检出限]出发,两种修饰电极均在pH=8.0时的0.1mol·L-1 NaClO4磷酸缓冲溶液中对H2A有较好的电催化氧化效果。更多还原

【Abstract】 Ferrocene bridged polysilsesquioxanes is a novel ferrocene detivatives. Chemical modified electrode which prepared by this polymer has high stability, good reproducibility. Morever, to a certain extent, we can get high-performance chemically modified electrode easily by introduction of other species or control the reaction conditions in the sol-gel process.In this thesis, We used a novel bridged monomer,(EtO)3Si-C2H4-Fc-C2H4-Si(OEt)3 (1,1’-bis[(2-triethoxylsilyl)ethyl]ferrocene, BTEF), to fabricate a series of GCE via sol-gel process. The sols were obtained respectively by co-hydrolysis of BTEF with TEOS and co-hydrolysis of BTEF with poly(vinylalcohol) (PVA). We optimized the preparation conditions and studied the electrochemical characteristics of the two modified electrodes by cyclic voltammetry (CV) method. In particular, we optimized the determination conditions of ascorbic acid(H2A), such as the scan rates v, system pH, etc.,and explored the mechanism of electrocatalytic reaction. The two ferrocene modified electrodes were shown excellent electrocatalytic response. The related exploration will laid an important foundation for the further application in practice.The research results were as follows:1.The type of catalyst has an influnce on the performance of BTEF/TEOS/GCE. The mild catalyst is benefit of getting a better reversible and stable modified electrode than the acid or alkali catalyst. The results shown that optimized catalyst for the preparation of BTEF/TEOS/GCE is NH4F.2.PVA has played a role of stabilizer and dispersion in the sol process. Adding a right amount of PVA, we can get uniform size of colloidal particles and pore size. The results shown that optimized dosage for BTEF/PVA/GCE is 300μL(Vtotal=10 mL).3.The ion size and valence of the supportting electrolyte have an influnce on the reversible and stable properties of BTEF/TEOS/GCE and BTEF/PVA/GCE. The results indecating that the optimized supporting electrolyte in aqueous solution is NaC104.4.The scan rates has a significant influnce on the two modified electrodes.The result shown that for BTEF/PVA/GCE,at the scan rate between 10 and 1000 mVs-1,a diffusion-controlled process plays the leading role in the charge transfer process. However, for BTEF/TEOS/GCE, at lower scan rates (between 10 and 100 mVs-1),a surface process plays the dominant role, while, at higher scan rates (between 100 and 1000 mVs-1) the charge transport process occurs mainly by a diffusion-controlled process.5.After successive 50 time’s cyclic voltammetric, there is no peak potential shift, and the peak current of BTEF/PVA/GCE and BTEF/TEOS/GCE only decreased 5.58%,4.95% respectively, and the electrochemical reversibility of the ferrocene modified electrodes are not affected. Noteworthily, all the experiments were conducted under aerobic conditions. The results indicate that the ferrocene bridged polysilsesquioxanes films have good stability in aqueous.6. pH is an important factor in the oxidation of H2A. Firstly, pH can influnce the existence forms of H2A. Secondly, pH also has an influnce on the electrochemical performance of the two modified electrodes.It is well-known that chemically modified electrodes for analytical purpose must meet two conditions,①can reduce the overpotential of the substrate, the interference and background current;②can increase the current response, reducing the detection limit. The results suggest that the two modified electrodes all have a better electrocatalytic oxidation effect on H2A in 0.1 mol·L-1 NaClO4 phosphate buffer solution at pH=8.0.更多还原