【作者】 邱翠翠；

【导师】 马厚义；

【作者基本信息】 山东大学 ， 物理化学， 2012， 博士

【摘要】 纳米金属材料自研制成功以来,已被广泛应用于很多学科和领域。纳米材料具有许多传统材料无法比拟的特性和功能,应用前景十分广阔,在研究及应用领域占据了越来越重要的地位。因此,不断改进和发展新的纳米材料的制备方法,一直是研究者的兴趣所在。相较而言,电化学法在制备纳米金属材料方面有许多优点,如反应条件温和可控、环境友好、适用范围广,产物纯度高,能更好地控制纳米粒子的尺寸和形貌等,是一种非常有前景的制备方法。纳米金属材料具有非常优越的催化性能,如纳米结构的金、钯等均在催化剂领域占有非常重要的地位,已成为相关领域的研究热点。本论文旨在通过一些简单、新颖的电化学方法来制备出纳米金薄膜及钯-铁双金属薄膜材料,以此为基础构建新型的功能化界面,研究了其电催化性能,探索所制备的钯-铁双金属薄膜在电化学处理含有机氯代物废水中的应用。并以纳米金薄膜为基底构建了以辣根过氧化物酶、葡萄糖氧化酶等为敏感元件的生物电化学传感器,以4-氯酚和葡萄糖为底物,检测其传感性能,探讨了其在环境监测及生命科学中潜在的应用价值。本论文的主要研究内容如下：(1)4-氯酚在纳米金薄膜上的电化学行为及安培检测近年来随着水污染问题的日益严峻,废水中有机化合物的数量和种类与日俱增。尤其是有机氯代物的“致畸”“致癌”“致突变”效应及其高毒、持久、生物富集等特性,其中多种已被美国环境保护组织EPA列为优先控制污染物。因此,有机氯代物的检测和降解一直是环境工程领域重要的课题。氯酚由于苯环上氯原子的存在增强了其化学稳定性及毒性；一旦进入环境,对生态环境危害周期很长。水环境中氯酚的检测得到了越来越多研究者的关注。因此,结合电化学检测的优点,我们建立了一个能够快速检测氯酚的电化学传感器。首先利用两步电位阶跃电沉积技术以玻碳电极为基底制备了纳米金薄膜,其微观结构特征可以通过调节电沉积的时间来进行控制。基于所制备的纳米金薄膜,我们重点研究了其对4-氯酚的电催化性能及传感性能。相较于体相金电极及玻碳电极,所制备的纳米金薄膜对4-氯酚表现出更高的电催化活性。4-氯酚对电极的毒化效应首先通过循环伏安法进行研究。研究表明,在含有4-氯酚的酸性溶液中进行连续电位扫描时,第一圈阳极扫描过程中在约0.9V处出现的氯酚的氧化峰会在随后的扫描中消失,而且金氧化物还原峰的电流随扫描次数的增加而逐渐降低,这些现象均表明氯酚的氧化产物会使金薄膜发生钝化。以此为基础,提出了4-氯酚在金薄膜上电化学氧化的反应机理。为了验证纳米金薄膜安培检测4-氯酚方法的可行性,我们用线性伏安法、差分脉冲伏安法及电化学交流阻抗法研究了4-氯酚浓度对金薄膜电化学行为的影响。研究表明在很低的氯酚浓度下,电极不会产生明显钝化。这证明了,所制备的金薄膜电极可用作4-氯酚电化学传感器。安培检测4-氯酚是在+0.85V下进行,线性检测范围为0.2-4.8mM,检测限为0.11mM(S/N=3)。通过这种简单的电沉积方法可以方便的控制金薄膜的微观结构特征,从而保证了电化学检测的可重复性。(2)辣根过氧化物酶修饰的纳米结构金薄膜电极对4-氯酚的电化学检测由于纳米金薄膜在氯酚电氧化过程中易受污染,降低了其检测灵敏度和稳定性,这限制了纳米金在氯酚的电化学检测中的应用。鉴于辣根过氧化物酶对酚类化合物具有优越的催化性能,为了提高电极的抗污染性能及检测灵敏度,我们构建了辣根过氧化物酶／纳米金薄膜生物功能化界面,研究了其对4-氯酚的电催化及传感性能。同样首先利用两步电位阶跃电沉积技术制备了纳米金薄膜电极,并以此为基底构建了辣根过氧化物酶／纳米金薄膜生物功能化界面。通过在含有4-氯酚的溶液中进行连续的循环伏安扫描,对比辣根过氧化物酶修饰前后金薄膜的电化学行为可以发现,在辣根过氧化物酶固定后金氧化物还原峰电流减小的趋势明显变缓。这证明了辣根过氧化物酶的固定明显提高了电极的抗污染性能。同时,SEM结果也验证了此项结论：在含氯酚溶液中进行连续电位扫描后金薄膜表面出现了严重粘连现象,而在辣根过氧化物酶固定后此现象得到明显改善。实验发现,在过氧化氢作为共同底物存在时,辣根过氧化物酶修饰的金薄膜对4-氯酚表现出良好的催化活性,并讨论了在过氧化氢为共同底物时4-氯酚在辣根过氧化物酶修饰金薄膜电极上电化学氧化的机理。电化学检测4-氯苯酚是在-0.55V下进行,其在2.5-40μM和62.5-117.5μM两个浓度范围表现出良好的线性关系,检测限为0.39μM(S/N=3)。此电极对4-氯苯酚可以产生快速响应,并且表现出很好的稳定性和可重复性。所制备的金薄膜具有良好的生物相容性,为辣根过氧化物酶的固定提供了良好的微环境,有利于酶活性的保持；而所固定的辣根过氧化物酶在4-氯酚电化学检测中发挥了重要作用。(3)固定于纳米金薄膜上的葡萄糖氧化酶的直接电化学行为及其在葡萄糖生物电化学传感器中的应用生物电化学传感器具有高灵敏度、高选择性、快速响应、可以在复杂的体系中实现连续在线检测等优点,已在食品、医药、环境监测等方面得到广泛应用。而纳米材料的迅速发展促进了生物电化学传感器的微型化。纳米材料独特的吸附性能和良好的生物相容性,被广泛应用于构建纳米-生物功能界面。而其中纳米金由于具有良好的催化性能,可直接作为有机小分子电化学氧化/还原的催化剂外,并且由于其优越的生物相容性、高表面能、光学性质、并且可以快速直接电子传递等独特优点,不仅可以为酶的固定提供大的比表面积,而且能够保持酶的活性,以构建新颖的性能优越的生物-电化学传感器。我们利用循环伏安法制备了纳米结构的钴薄膜,然后通过与氯金酸溶液进行自发氧化还原置换制备了分等级的纳米金薄膜电极。通过物理吸附可以使葡萄糖氧化酶吸附在金薄膜的表面,从而构建了葡萄糖氧化酶/纳米金生物功能化界面。基于这种酶修饰电极,我们重点研究了其对葡萄糖的电催化及传感性能。首先利用循环伏安法研究了固定化的葡萄糖氧化酶的直接电化学行为。研究表明,固定化的葡萄糖氧化酶在磷酸缓冲溶液中呈现出一对清晰的、可逆的、表面控制的氧化还原峰。此外,我们利用循环伏安和差分脉冲伏安研究了酶修饰电极对葡萄糖的电催化活性,结果发现葡萄糖的浓度对葡萄糖氧化酶的直接电化学行为会产生明显影响。基于此现象,电化学检测葡萄糖是在-0.55V下进行。其在2.5-32.5μM和60～130μM两个浓度范围表现出良好的线性关系,检测限为0.32μM(S/N=3)。同时所制备的葡萄糖生物电化学传感器表现出优越的稳定性,灵敏度和抗干扰性能。因此我们所制备的葡萄糖氧化酶修饰的金薄膜电极有助于构建高性能的葡萄糖传感器。这种方法为制备形貌可控的金薄膜提供了一种便利途径,并且有利于酶电极的制备和应用。所制备的酶电极一个明显的特点就是金薄膜为葡萄糖氧化酶的固定提供了一个良好的微环境,促进了酶活性中心与电极之间的直接电子传递。(4)纳米钯-铁双金属薄膜的制备及其对四氯化碳电还原脱氯活性研究有机氯代物是环境水体中常见的有机污染物。此类污染物毒性大,化学性质稳定,一旦进入环境水体将对人类及其生态环境造成长期威胁。有机氯代物的降解处理技术已引起了国内外的广泛关注。零价铁由于本身所具有非常优秀的物理化学性质,一直是有机物降解领域常用的催化剂。而纳米钯具有良好的储氢性能,在催化反应尤其是催化氢解反应中发挥着极其重要的作用。本论文利用电化学沉积与自发氧化还原置换结合,制备了纳米结构的钯-铁双金属薄膜材料,并以四氯化碳为靶向有机氯化物,研究了其电化学脱氯活性。首先在不断改变电解质溶液中Fe2+离子浓度的情况下,通过两步电位阶跃法在玻碳电极表面制备了一系列的纳米铁薄膜。并且利用部分的Fe0与Pd(Ⅱ)之间发生氧化还原置换反应制备了纳米钯-铁双金属薄膜。通过SEM及EDS表征验证了电解质溶液中Fe2+的改变会明显影响Fe薄膜的微观形貌,进而对钯-铁双金属薄膜的形貌及组成起到调控作用。根据钯-铁双金属薄膜在氢区的特征伏安响应,选取了不同的电位进行电化学还原脱氯,讨论了不同类型氢的脱氯活性及反应活化能。研究发现,钯-铁双金属薄膜的组成会明显影响其脱氯活性：当Pd/Fe质量比为5.9时,双金属薄膜表现出最高的脱氯活性。同时还研究了降解时间和温度对四氯化碳去除效率的影响。结果表明,随温度的升高和降解时间的延长,四氯化碳的去除效率增大,且此反应为准一级反应。这种电化学沉积法与氧化还原置换反应相结合是一种制备纳米贵金属薄膜材料的重要方法,在制备过程中贵金属(金、钯等)的消耗量极低。所制备的钯-铁双金属薄膜具有优异的电催化脱氯性能和低成本的优点,使其成为环境催化和污水治理等方面很有前景的催化剂。更多还原

【Abstract】 Since prepared successfully, nano-metallic materials have been widely used in various fields of research and application. Because of their unique properties compared with traditional materials, nano-materials play a more and more important role in the fields of research with bright prospects of application. Therefore, continuously improving and developing the new preparation method of nano-materials are of considerable current research interest. Compared with the traditional chemical synthesis of metal nanostructures, the electrochemical technique has many intrinsic advantages, such as mild reaction conditions, environment friendly, wide application, good controllability, high purity of products, and so on. Due to the superior catalytic property, nano-metallic materials (like nano-structured Au, Pd, etc) hold an important place in catalysis fields and have become a research focus.The aim of this paper is to fabricate the nanostructured Au and bimetallic Pd-Fe thin film materials by some simple and novel electrochemical methods, and to construct the new functional interface based on the as-prepared materials. Moreover, the catalytic performance of the as-prepared thin films was investigated. And the potential application of the bimetallic Pd-Fe thin film in electrochemical treatment of wastewater containing chlorinated organic compounds was discussed. Furthermore, as sensing elements, horseradish peroxidase and glucose oxidase were immobilized on the nanostructured Au thin film to construct bioelectrochemical sensors. In order to explore their potential application in the environmental monitoring and the life sciences, the sensing properties of the bioelectrochemical sensors were investigated when4-chlorophenol and glucose were used as the substrate, respectively.The main contents of this paper include:(1) Electrochemical behavior and amperometric detection of4-chlorophenol on nano-Au thin films modified glassy carbon electrodeIn recent years, with the water pollution becoming more and more serious, the types and amounts of organic pollutants in wastewater are increasing. Especially, due to the effect of "teratogenesis","carcinogenesis","mutagenesis" and the features of high toxicity, persistence and biological concentration, and many of chlorinated organic compounds have been list as the priority pollutants by EPA (United States Environmental Protection Agency). Therefore, the detection and degradation of chlorinated organic compounds have been always the important subjects in the environmental engineering field.The nanostructured Au thin film was prepared on glassy carbon electrodes by a template-free, double-potential step technique. And its structural feature can be controlled well by adjusting the deposition time. The nano-Au thin film shows a higher catalytic activity toward the electrooxidation of4-chlorophenol (4-CP) than the bulk Au and glassy carbon electrode. For the electrooxidation of4-CP, fouling of the Au thin film was observed as a dramatic current decrease of oxidation peak in the first anodic sweep and the diminishing reduction peak of Au oxides during the consecutive cyclic voltammetric scan. In order to discuss the feasibility to the amperometric detection, the effect of4-CP concentrations on the electrochemical behavior of nano-Au thin films in H2SO4solutions was investigated by linear sweep voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The results demonstrated that the electrode was hardly suffered from fouling at the low4-CP concentration. With the increase of4-CP concentrations, more serious fouling was observed on the electrode. The nano-Au thin film has a good sensing capability and an electrochemical sensor for4-CP at the mM concentration range with a fast amperometric response was achieved. The amperometric detection of4-CP was performed at+0.85V with a linear detection range from0.2to4.8mM and a detection limit of0.11mM (S/N=3).Through this simple electrodeposition method, the structural feature of nano-Au films can be controlled conveniently, which ensures the repeatability of the electrochemical detection.(2) Amperometric detection of4-chlorophenol based on horseradish peroxidase modified nanostructured Au thin filmsWith the rapid development of nanotechnology, a great number of nanomaterials, especially the noble metal, have been introduced into the bioelectrochemical sensor. However, severe fouling will be caused by oligomers and polymers as a result of chemical coupling of the corresponding phenoxy radicals during the electrooxidation of phenolic compounds on nano-Au thin film electrodes. So in order to enhance the resistance to fouling and improve the detection sensitivity, HRP was immobilized on the nanostructured Au thin film to construct the HRP/nano-Au biological function interface, considering its excellent catalytic activity toward chlorophenols.A nano-structured Au film was directly formed on the GCE substrate by double-potential step electrodeposition. The as-prepared nanostructured-Au thin films provide an excellent microenvironment for the immobilized of HRP and retention of its activity. And the immobilized HRP plays an important role in the electrochemical detection of4-CP. From the SEM and CV results, it was demonstrated that the immobilized HRP had a significant positive effect on the anti-fouling performance of the electrode material. In the presence of H2O2as co-substrate, the HRP modified electrode displayed a high catalytic activity toward4-CP. Furthermore, the enzyme modified electrode was used as a4-CP bioelectrochemical sensor, exhibiting a linear relationship in the concentration ranges of2.5to40μM and62.5to117.5μM with a detection limit of0.39μM (S/N=3) at an applied potential of-0.55V. The HRP modified electrode displays an excellent sensing performance with high sensitivity and good stability. A bio-electrochemical sensor of4-CP with a fast amperometric response was achieved.(3) Direct electrochemistry of glucose oxidase immobilized on nanostructured gold thin films and its application to bioelectrochemical glucose sensorWith its intrinsic advantage in high sensitivity and selectivity, fast response, easy operation, and continuous on-line detection, bioelectrochemical sensors have received increasing attention in clinical medicine, biochemistry and environmental monitoring. And the rapid development of nano-materials greatly accelerates the miniaturization of bio-electrochemical sensor. Due to its unique adsorptive properties and good biocompatibility, the nano-material is widely used in constructing the biological function interface. Considering its good catalytic activity, excellent biocompatibility, high surface energy, optical properties and quickly direct electron transfer, nano-Au can not only be directly used as electro-catalyst of a small organic molecules, but also provide a large specific surface for the immobilization of enzymes to construct novel and superior bio-electrochemical sensors.Nano/submicron structured Au films with were directly fabricated onto the glassy carbon electrode (GCE) by the combination of electrodeposition and galvanic replacement technology, which can provide a facile method to prepare morphology-controllable Au films and a more convenient boundary for enzyme immobilization than Au nanoparticles. Glucose oxidase (GOx) was stably immobilized via a simple physical adsorption method onto the nanostructured Au thin films. An obvious advantage of the as-prepared enzyme electrode is that the nano-Au films provide a favorable microenvironment for GOx and facilitate the electron transfer between the active center of GOx and electrodes. Cyclic voltammetry results indicate that the immobilized GOx displayed a direct, reversible and surface-confined redox reaction in the phosphate buffer solution. Furthermore, the enzyme modified electrode was used as a glucose bio-electrochemical sensor, exhibiting a linear relationship in the concentration ranges of2.5to32.5μM and60to130μM with a detection limit of0.32μM (S/N=3) at an applied potential of-0.55V. Due to the excellent stability, sensitivity and anti-interference ability, the Au thin films are hopeful in the construction of glucose biosensors.(4) Facile fabrication of nanostructured Pd-Fe bimetallic thin films and their electrodechlorination activityNanostructured Pd-Fe bimetallic thin films were directly fabricated on glassy carbon substrates by means of galvanic replacement of partial Fe0nanoparticles by Pd(II) ions. The composition and morphology of such Pd-Fe thin films are strongly dependent on the sacrificial Fe film templates. The nano/submicron structured Fe thin films were fabricated by a template-free, double-potential step electrodeposition technique. The size and morphology of the Fe nanoparticles that constitute the Fe thin films can be controlled well by adjusting the concentration of Fe2+ions in electrolyte solutions. Taking electrochemical reductive dechlorination of carbon tetrachloride (CT) as the research object, we investigated the removal efficiency of the as-prepared bimetallic Pd-Fe nano-catalysts under different conditions. Due to the good synergistic effect between Pd and Fe, the as-prepared Pd-Fe thin films with the novel microstructure display a high activity toward the electrochemical reductive dechlorination of CT. The Pd/Fe weight ratio in the bimetallic films is an important parameter that affects the dechlorination activity of the bimetallic catalysts and can be adjusted by selecting nanostructured Fe film templates with different thickness and surface morphology. When the weight ratio of Pd/Fe is5.9, the bimetallic thin film catalyst exhibits the highest dechlorination activity. The activation energy (Ea) for dechlorination by different types of hydrogen is in accord with the removal efficiency of CT, and a minimum Ea and the highest removal efficiency were obtained at-0.2V. Besides, the removal efficiency of CT increased considerably with increasing temperature. The dechlorination reaction of CT complied with pseudo-first-order kinetics.The present study will provide a new path to fabricate low-temperature high-efficiency nano-catalysts for the electrochemical reductive dechlorination of chlorinated organic compounds. The obtained results are of fundamental importance to give an in-depth understanding of electrochemical reductive dechlorination mechanism of chlorinated organic compounds.更多还原