【作者】 刘才；

【导师】 杨士成； 李永军；

【作者基本信息】 湖南大学 ， 分析化学， 2012， 博士

【摘要】 纳米粒子薄膜是指以纳米粒子为基本单元所构成的二维纳米结构材料，在催化、能源、传感以及医疗诊断等领域有广泛的应用。此外，二维纳米结构薄膜也可以进一步作为构筑单元来制备三维纳米结构。由于纳米粒子薄膜中纳米粒子间的相互作用，纳米粒子薄膜经常呈现出单个纳米粒子和本体材料不具备的宏观特性，因此，控制纳米粒子薄膜的结构就成为调控其特性的有效手段。为此，科研工作者发展了各式各样的纳米粒子薄膜制备方法。然而，在众多的纳米粒子薄膜的制备方法中，纳米粒子的液体/液体界面自组装以其简单、便捷和无需仪器的优势，备受科学家们的关注。因此，发展可控液/液界面自组装方法和研究纳米结构与其性能的关系，将是一项非常有意义且负有挑战性的工作。基于此，本论文主要开展了以下的研究：(1)液/液界面自组装机理研究：以乙醇诱导界面自组装方法为实验基础，以球体、立方体、圆柱体三种理论模型为研究对象，讨论粒子被吸附至界面过程中体系的能量变化。在球体、立方体和圆柱体粒子进行相应的理论和实验研究表明在热力学最稳定状态下球体、立方体和圆柱体三种构型的纳米粒子均能在油/水界面吸附，并组装成薄膜。同时，也讨论了表面活性剂和油的类型对纳米粒子组装的影响。(2)界面组装纳米粒子薄膜的机械稳定性研究：以铂纳米粒子为对象，采用循环伏安法和旋转圆盘电极计时电流法研究了界面组装的铂纳米粒子对氧分子的电还原。结果表明：界面组装制备的单层铂纳米粒子薄膜不仅具有良好的电催化能力，并且高强度地粘滞在玻碳电极表面，在电极旋转的这种恶劣的条件下也不脱落。(3)界面组装的金纳米粒子薄膜结构对CO电催化研究：将乙醇和甲苯混合溶液注入到金溶胶内部，诱导金纳米粒子在甲苯/水界面上吸附，并组装成纳米粒子薄膜，通过逐渐增加乙醇在混合物中的浓度来控制薄膜中金纳米粒子的聚集度。相对粒子状的金纳米粒子薄膜而言，链状聚集的金纳米粒子薄膜能够有效地电催化氧化CO。(4)金/铂复合纳米结构薄膜对甲醇的电催化研究：通过组装金纳米棒单层薄膜和金纳米粒子单层薄膜，并采用湿法化学方法在薄膜上修饰超薄纳米铂，考察铂修饰在金纳米材料薄膜上对碱性条件下甲醇的催化活性。结果表明，各种材料的催化能力如下：铂修饰的金纳米棒电极>铂修饰的金纳米粒子电极>铂修饰的电极，揭示了Au和Pt的协同效应是复合催化剂高活性的起源，同时也表明金纳米粒子的形状对电催化影响。(5)银纳米线和碳纳米管复合薄膜对H2O2的电催化研究：采用多次转移界面纳米粒子薄膜的方法制备了银纳米线和碳纳米管复合薄膜，由于层与层之间没有加入任何交联剂，这种复合材料显示出良好的电子传导能力，对H2O2的响应迅速，实现了对H2O2的快速检测。(6)“三明治”式的银纳米线薄膜的拉曼增强效应：采用层层组装技术将染料分子夹在两层银纳米线单层膜之间，上下两层纳米线的耦合能够进一步增强了表面等离子体共振强度，从而实现拉曼信号的增强。(7)界面上的银纳米立方体定向刻蚀：理论计算显示银纳米立方体在界面上是最稳定的状态：一面浸在油相，相同体积的一面浸没在水相。根据此原理，利用水溶性刻蚀试剂原位定向刻蚀处于油/水界面上的银纳米立方体，在立方体的一个面上定向刻蚀空洞。更多还原

【Abstract】 Nanoparticle thin-films are two-dimensional (2D) nanostructures involvingnanoparticles as building blocks, which have wide applications in the fields ofcatalysis, energy source, sensing, medical diagnosis and so on. Further,2Dnanostructured films can be employed as novel building blocks to designthree-dimensional nanostructures. Due to interactions between nanoparticles innanoparticle films, nanoparticle films usually exhibit unique collective propertiesdifferent from the single nanoparticle or bulk counterparts. It means that theproperties of as-prepared nanoparticle films can easily be tuned by controllingstructures of nanoparticle films. Thus, varied methods for fabricating nanoparticlefilms have been proposed so now, but among which, the oil/water interfacialassembly is paid a lot of attention because it is simple, convenient andinstrument-free. Therefore, it is a very meaningful, challenging task to developcontrollable interfacial assembly and exploit the relations between nanostructuresand their properties. Based on the above consideration, this thesis involves thefollowing contents:(1) Mechanism of oil/water interfacial assembly: Base on ethanol-mediatedinterfacial assembly, the energy change of single nanoparticle was caculated when itmigrated from the bulk solution onto oil/water interfaces. The theoretical andexperimental data indicate that thermodynamical states of sphere, cube and cylindernanoparticle are the stablest when they are located at oil/water interfaces, formingnanoprticle films, respectively. Additionally, the effects of the type of surfactant andoil on interfacial assembly were discussed roughly, respectively.(2) Machanical stability of nanoparticle monolayer films obtained by theinterfacial assembly: Take Pt nanoparticles as an example, oxygen reduction wascarried out on Pt nanoparticle monolayer films by cyclic voltammetrical and rotatingdisk electrode techniques. The results showed the Pt nanoparticle monolayer filmexhibited satisfactory electrocatalytic activity, and was still fixed firmly on theelectrode surface under a relative harsh condition ofelectrode rotation.(3) Gold nanoparticle films for CO electrooxidation: Gold nanoparticles canadsorp onto toluene/water interfaces by injecting a mixture of ethanol and tolueneinto Au aqueous colloid, and then gradually formed a Au nanoparticle monolayer film. The fine nanostructure of as-prepared Au nanoparticle monolayer film wascontrolled well simply by changing the ethanol:toluent volume ratio in the mixture.Carbon monoxide was used as a probe for testing the electrocatalytic performancesof the above Au nanoparticle film. The results indicate that, compared with isolatedAu nanoparticle monolayer film, the chain-like Au nanoparticle film showed anexcellent catalytical activity.(4) Au/Pt composit nanofilms for methanol electrooxidation: Two types ofAu nanosturctures, Au nanorods and gold nanospheres, were fabricated, respectively,by the above interfacial assembly, and then each Au nanoparticle film was modifiedby a platinum ultra-thin films using wet chemistry method. Pt thin films on goldnanomaterials show satisfactory electrocatalytic activities for methanolelectrooxidation. By comparison, the performance of catalyst is in this order: Pt-goldnanorod film>Pt-gold nanoparticle film>Pt-bare electrode. The results disclosed thecontribution of the synergitical effect of Au and Pt and the effect of the shape of Aunanoparticle on methanol electrooxidation.(5) Ag nanowire/carbon nanotube composite films for H2O2electrooxidation: Ag nanowire monolayer film and carbon nanotube film fabricatedat oil/water interfaces, respectively, were transferred alternatively onto galssycarbon surface without any linkers, forming a composite film. As-preparedcomposite film showed good electronic conductivity and catalytic activity. Due tothe linker-free merit, it responded quickly to H2O2, and may be used in rapiddetection of H2O2.(6) Ag nanowire “sandwich” structures for surface-enhanced Ramanscattering: Ag nanowire “sandwich” structures were fabricated by repeatedlytransfering Ag nanowire monolayer film locating at a oil/water interface onto thesame slide glass. Before repeating the transfer of Ag nanowire monolayer film, theslide galss covered with one layer of Au nanowire monolayer film was inmmersedinto a dye aqueous solution to absorb dye molecules. Due to the location of dyemolecules between two layers of Ag nanowire monolayer films, the “sandwith”structure showed better SERS activity than Ag nanowire monolayer film with dyemolecuels, which may result from enhancement of electromagnetic field betweentwo layers of Ag nanowire monolayer film.(7) Oriented etcting of Ag nanocube at oil/water interface: The theoreticalcalculations above show that the stablest state of each silver nanocube at theinterface is one of its sides in the oil phase and the opposite side was in the aqueous phase. According to this principle, in-situ etching of silver nanoparticles at oil/liquidinterfaces was done to prepare a concavity on the side of Ag nanocube.更多还原