【作者】 汤儆；

【导师】 毛秉伟； 田中群；

【作者基本信息】 厦门大学 ， 物理化学， 2002， 博士

【摘要】 当物质的尺寸进入纳米级的尺度时，将出现量子效应、小尺寸效应和表面及界面效应而呈现出既不同于宏观物体、也不同于单个原子的奇异现象。纳米科学与技术是研究和利用这一尺度上物质特性的多学科交叉的前沿和热点领域。纳米材料是纳米科学技术的基本组成部分，它是由三维空间中至少有一维处于纳米尺度范围的基本单元构成的材料，这一基本单元称为纳米结构。纳米微粒、纳米管、纳米棒和纳米薄层等都是纳米结构。若将它们按规律有序排列，则可以组装出常规体系不具备的物性。它们不仅具有单个纳米粒子的各种效应，而且还将出现许多如量子耦合效应与协同效应等新现象。 运用化学和物理等多种手段实现纳米至原子尺度范围的有序表面纳米结构的人工和自然构筑，是从结构到性能表征、研究和利用其物理化学基本性质的必要前提。遵循能量最低原理的自然构筑法可大面积制备表面纳米结构，而利用各种局域作用的人工构筑法则可“由下而上”按意愿构筑各种表面纳米结构并进行有关原理性探索。 电化学沉积方法具有简便、控制灵活等特点，是大范围制备表面金属或半导体纳米结构的一种有效的自然构筑法。依据沉积金属与基底表面的相互作用，金属的电化学沉积可以发生在其热力学平衡电位以负的过电位或以正的欠电位区间。当沉积金属与基底表面不具有强的结合能时，该金属的电沉积将在过电位区发生。控制条件使其按瞬时成核的机理进行，可制备较为均匀的表面金属纳米颗粒。若沉积金属与基底表面存在强的结合能，则可在欠电位区生成金属的(亚)单层。由于金属欠电位沉积本质上是一种特殊的电吸附过程，所形成的金属(亚)单层吸附层的结构强烈地依赖于电极表面的结构以及溶液中其它物种吸附的影响，可视为金属的电化学外延生长过程。 SPM(STM或AFM)作为一强有力的表面分析工具不仅是观察、认识原子分子世界的工具，也是实现表面修饰，甚至进行原子、分子操纵的重要手段。SPM针尖与表面存在各种相互作用，是对被研究表面的一种局域微扰，这种微扰在温和的电化学和隧道偏压条件下便可诱导电极表面发生特定的局域电化学反应。据此，可逐点构筑表面纳米结构，是一种先进的人工构筑法。 多孔氧化铝模板法借助自然构筑法和人工构筑法的概念，先自然地形成具有纳米尺度 摘要的有序孔洞(道)，再人为地用物理或化学的方法向其内注入所需的材料，可大面积制备大小或长径比可调的纳米点、纳米线或纳米管，被认为是一种低投入高产出的制备大面积纳米线阵列体系的有效方法，尤其适合用于制备直径为15一100lun的纳米线阵列。 虽然目前对纳米材料研究已是如火如茶，但是固体表面纳米结构的制备和物理化学研究则仍然较为少见，因此，需要实验和理论方法的创新和发展。本论文运用电化学，电化学扫描隧道显微镜(ECSTM)针尖诱导和模板法自然地和人工地构筑表面纳米结构，从简单的金属纳米粒子体系，拓宽到按意愿构筑表面有序纳米粒子阵列，从一维的纳米粒子体系拓宽到有序二维纳米结构体系;同时运用R滋man光谱和扫描电化学显微镜(SECM)等多种表面分析工具对有关纳米结构和性能进行初步的表征。主要研究内容和结果摘要如下:一、电化学瞬时成核法构筑HOPG表面Au纳米粒子 高序热解石墨(HOPG)电极表面具有原子平整度，可认为是理想的单晶碳电极。HOPG具有非常低的表面自由能，因此与沉积金属原子之间的结合能很小。这时金属的电化学沉积将发生在过电位区，并将遵循三维岛状生长的模式(volmer.w七bor模式)。控制条件可使金属电沉积按瞬时成核的机理进行。据此可制备尺寸较为均一、排列较为有序的表面Au纳米粒子阵列。我们从在HAuC肠溶液中Au向HOPG表面过电位沉积的成核和生长机理着手，借助轻敲模式原子力显微镜，探讨阶跃电位、基底处理等方面对An纳米粒子的形成及其尺寸和形貌的影响，并用电化学方法和表面增强拉曼光谱(SERS)技术初步研究了Au纳米粒子体系的电催化性能和光学效应，主要结果归纳如下:l)右况农寮件对A“动苯狡子尺寸掀形脱啪居时轻敲力模式AFM研究表明，Au在 HOPG表面电沉积605后的尺寸和形貌按沉积电位分为四种情况:0当电极电位控 制在0.3V(vs.SCE，下同)以正的电位范围，An粒子以各向同性方式生长，形成亚 微米尺寸的半球形Au粒子，粒子密度很小并且在电极表面比较分散;(ll)电位在0.3 V附近，由于该电位处于该体系的零电荷电位附近，Cl一从电极表面脱附，Au的沉积 表现为各向异性生长，形成棱角分明的多面体An纳米粒子;(m)恒定电位在0.3v- 一3v时沉积得到尺寸减小至几十纳米的半球形An粒子，但分布密度增大;(W)在众3II摘要V附近，沉积受到氢气在表面轻微溢出的影响，从而避免相邻粒子的扩散区间内的相互交盛，沉积得到的Au纳米粒子的尺寸分布狭窄，是构筑Au纳米粒子体系的理想条件。幻演面.Au动装对子村右艘钻疗汤及君.关尺寸拉彭时以乙二醉电氧化为探针反应，比 较了不同尺寸Au纳米粒子的电催化效应。研究表明，控?更多还原

【Abstract】 When the size of a substance is reduced to nanometer scale, several phenomena such as quantum confinement effect, small size effect, surface and interface effect may appear, which make the substance significantly different from its bulk or single atoms in physical and chemical properties. Being a disciplinary of many subjects, nanoscale science and technology (Nano-ST) includes fundamental research of properties in nanometer scale and application of the functional nano-materials, and has boomed up as the hottest field and frontier of science. Nano-material is composed of basic building block termed as nanostructure with at least one dimension in the nanometer range, nanoparticle, nanowire(rod), nanorod and thin film being such nanostructures. Assembly of the nanostructures into a system in a certain order would lead to some novel properties due to coupling between the nanostructures in addition to the above-mentioned four types of effects.Synthesis of nanostructures is the prerequisite of applying, investigating and utilizing the physical and chemical properties of these nanostructures. The present available physical and chemical methods in nanostructuring can be categorized into nature-driven and man-driven ones. The nature-driven nanostructuring process could produce surface nanostructure in large area following the minimum energy principle; while the man-driven nanostructuring process makes use of localized effect to fabricate surface nanostructures following the "bottom up" procedure, which is particularly useful in exploring novel property of the nanostrucutes.The convenient and flexible electrochemical deposition method is one of the efficient ways to fabricate metal and semiconductor nanostructures. Depending on the interaction between the depositing metal and the substrate, the metal deposition could take place at potentials negative of the equilibrium potential of the metal (over potential deposition, OPD) or positive of that equilibrium potential (under potential deposition, UPD) .In the absence of strong metal-substrate interaction the metal deposition will take place in the OPD region. If the deposition process can be controlled following the instantaneous nucleation mechanism, uniformly distributed metal nanoparticles is expected to form on the surface. In the presence of strong metal-substrate interaction, however, a (sub) monolayer of the metal will be formed in the UPD region before further its OPD. UPD is a special adsorption process of metal; the morphology of the metal monolayer is strongly influenced by the surface structure of the electrodes, the ionic adsorptionand electrode/solution double layer structure, which can be regarded as electrochemical epitaxy process.As an important surface analyzing tool, well-developed STM technique has been employed not only as an important tool to characterize the arrangement of atoms and/or molecules on the surface but also as a lithographic means to direct the individual atoms and molecules to the predetermined position on the substrate with the tip. Tip-substrate interaction of various kinds is regarded as a local perturbation that may induce local electrochemical reaction under mild conditions of tunneling current and voltage. Thus, the surface nanostructure could be fabricated point by point and serves as an advanced man-driven nanostructuring process.Template synthesis method for example anodic aluminum oxide (AAO) is based on the combination of two kinds of methods. The nano-channel arrays are formed spontaneously during anodization, and materials are filled into the nano-channels arrays purposely by chemical or physical methods to synthesize nanowire (rod) or nanotube arrays with different diameter and aspect ratio in a large scale. It is regarded as one of the low-input and high-output methods to fabricate metal nanowire arrays especially with the diameter ranging from 15 nm to 100 nm.1. Electrochemical instantaneous nucleation and preparation of Au nanoparticles on HOPGThe atomically flat HOPG (highly oriented p更多还原