Synthesis and Optical Properties of Complex Metal Nanostructures

复杂金属纳米结构的合成和光学性质

• 批准号: 9625151
• 负责人: Colby Foss
• 金额: $ 30.23万
• 依托单位: Georgetown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-06-01 至 2001-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9625151&HistoricalAwards=false
• 关键词: Synthesis; Optical; Properties; Complex; Metal

Abstract 9625151 Foss The general research goal of this Career proposal is to synthesize metal particles of sufficient uniformity and complexity such that they engender optical behaviors heretofore unseen in metal particle composite materials. This project deliberately targets particles whose dimensions lie between ca. 5 nanometers (nm) and 50 nm. Metal particles within these limits contain a sufficient number of atoms so as to possess bulk optical properties, but are small enough that they do not scatter appreciably light at visible and longer wavelengths. The synthetic work will focus specifically on three basic structural types: 1) cylindrical particles composed of two or more different elemental subunits; 2) branched metal nanostructures; and 3) chiral nanostructures. Type 1 particles will be prepared via template synthesis, which involves the electrodeposition of metals into the pores of anodic aluminum oxide films. The template synthesis method will allow for electrochemical control of both cylinder radius and length, as well as the sequence of the different metal layers of which the cylinder is composed. Type 2 particles will be prepared in similar fashion to type 1, except that the anodic alumina films will be grown using a voltage reduction regime that produces branched pore structures. The preparation of chiral structures (Type 3) will involve the vacuum deposition (at grazing incidence) of gold and other metals onto nanoscopic silver post substrates prepared via template synthesis. Oxidation of the silver foundation will facilitate release of the chiral particles into solution. Structural characterization of all particles will involve transmission electron microscopy (TEM) and/or atomic force microscopy (AFM). UV/Visible and near-infrared (NIR) spectroscopic studies of particles in all three types will be done to assess the relationship between particle structure and plasmon resonance absorption. Composite materials containing oriented particles of types 1 and 2 which have been prepared so as to lack inversion symmetry will also be evaluated for bulk second harmonic generation (SHG). Solutions containing type 3 particles are expected to exhibit optical activity, and will thus be examined using circular dichroism (CD) spectroscopy. %%% This project is concerned with the application of template synthesis methods to prepare nanoscopic metal particles of unprecedented geometric and compositional complexity. By virtue of their complexity, these particles are expected to exhibit optical behaviors that are normally considered the sole province of molecular entities. The project will lead to a more detailed understanding of the relationship between metal particle structure and composite optical properties. Furthermore, as some of the anticipated properties have not been observed previously to arise from gross particle asymmetry, this project may also lead to new applications of nanoscopic metal particles. Relatedly, since the proposed synthetic strategies are based primarily on chemical and electrochemical methods (as opposed to photo- and electron beam lithographies), they will be easily available to many research groups.

摘要：本文的总体研究目标是合成具有足够均匀性和复杂性的金属颗粒，从而产生金属颗粒复合材料中迄今未见的光学行为。该项目专门针对尺寸在5纳米到50纳米之间的粒子。在这个限度内的金属粒子包含足够数量的原子，从而具有大块的光学特性，但它们足够小，因此在可见光和较长波长的光线中不会散射明显的光。合成工作将特别关注三种基本结构类型：1)由两个或两个以上不同元素亚基组成的圆柱形颗粒；2)支链金属纳米结构；3)手性纳米结构。1型粒子将通过模板合成来制备，这涉及到将金属电沉积到阳极氧化铝膜的孔隙中。模板合成方法将允许对圆柱体半径和长度进行电化学控制，以及组成圆柱体的不同金属层的顺序。2型颗粒将以类似于1型的方式制备，除了阳极氧化铝薄膜将使用产生分支孔结构的电压降低制度生长。手性结构（类型3）的制备将涉及金和其他金属在通过模板合成制备的纳米级银柱衬底上的真空沉积（掠入射）。银基的氧化将促进手性颗粒释放到溶液中。所有粒子的结构表征将涉及透射电子显微镜（TEM）和/或原子力显微镜（AFM）。将对所有三种类型的粒子进行紫外/可见光和近红外光谱研究，以评估粒子结构与等离子体共振吸收之间的关系。制备的含有1型和2型取向粒子的复合材料也将用于体次谐波产生（SHG）的评价。含有3型粒子的溶液预计会表现出光学活性，因此将使用圆二色性（CD）光谱学进行检查。该项目涉及应用模板合成方法制备具有前所未有的几何和成分复杂性的纳米金属颗粒。由于它们的复杂性，这些粒子有望表现出通常被认为是分子实体的唯一领域的光学行为。该项目将导致更详细地了解金属颗粒结构和复合光学性能之间的关系。此外，由于以前未观察到的一些预期性质是由总体颗粒不对称引起的，因此该项目也可能导致纳米级金属颗粒的新应用。相关地，由于提出的合成策略主要基于化学和电化学方法（与光刻和电子束光刻相反），它们将很容易为许多研究小组所用。