Size- and Composition-Dependent Electronic and Vibrational Properties of Bimetallic Nanoclusters

双金属纳米团簇的尺寸和成分依赖性电子和振动特性

• 批准号: 0906562
• 负责人: Beatriz Roldan Cuenya
• 金额: $ 40.5万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906562&HistoricalAwards=false
• 关键词: Size; Composition; Dependent; Electronic; Vibrational

TECHNICAL SUMMARY:This Award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Metal nanoclusters exhibit intriguing electronic and atomic vibrational phenomena that deviate dramatically from the corresponding bulk properties. The goal of this study is to combine recently developed micelle-based nanocluster synthesis methods with advanced nanoscale physical analysis of both electronic and vibrational properties. Self-assembled size- and shape-selected bimetallic nanoclusters [57FePt, 57FePd, 57FeCu and 57FeAu] will be synthesized. A synergetic combination of experimental tools including X-ray photoelectron spectroscopy, scanning tunneling and transmission electron microscopy, 57Fe Mössbauer spectroscopy, and 57Fe nuclear resonant inelastic X-ray scattering will be used to find correlations between the nanostructure morphology and electronic structure and its size- and composition-dependent vibrational properties. In addition, modeling of the vibrational dynamics of supported clusters will be conducted by molecular dynamics simulations through an international collaboration (Canada). The intellectual merit of this work is based on the improvement of the current understanding on: (i) the formation, the structural and thermal stability of bimetallic alloys in isolated nanoclusters, (ii) their intrinsic electronic and vibrational properties, (iii) how these characteristics change due to cluster size-effects, cluster-support interactions, the presence of ligands on the cluster surface, and the composition of the nanoalloys, and (iv) whether phonon-induced structural phase transitions (known in ferromagnetic bulk Invar alloys) persist and can be tuned in nanoclusters. Since the electron and phonon density of states are key elements in understanding and predicting important materials properties, this project will advance the present knowledge of basic physical phenomena underlying electrical and thermal conductivity, heat capacity, vibrational entropy, electron-phonon coupling, and 1/f noise in electronic devices. In addition, insight will be obtained on whether phonon-assisted surface chemical reactions could play an important role in the comprehension of the catalytic properties of metal nanoclusters. NON-TECHNICAL SUMMARY:Metal nanoclusters exhibit intriguing electronic and atomic vibrational phenomena that deviate dramatically from the corresponding bulk properties. Metal nanoclusters are used in optics (nanophotonics), magnetism (recording media), medicine (targeted drug delivery), and in chemistry (catalytic materials). Many questions remain on the detailed nature of their electronic and vibrational properties, and a more thorough physical understanding is needed to advance the science and technology of these materials. This project will improve the present knowledge on the formation, the structural and thermal stability of bimetallic alloys in nanoclusters, and the parameters that can be used to tune their intrinsic physical properties such as cluster size, support and composition. A deeper insight into important material properties including electrical and thermal conductivity will be obtained. Graduate and undergraduate students will be trained and given the opportunity to conduct state-of-the-art research, not just at the University of Central Florida, but also at national and international user facilities, including the Advanced Photon Source (Chicago) and Spring8 (Japan). K-12 students teamed up with undergraduates will be in charge of the sample preparation. A website entitled ?Why?s of Science? will be setup to disseminate science-related educational activities among primary and middle school students. In order to stimulate the access of minority (Hispanic) parents to science, the website will be available in English and Spanish.

技术摘要：该奖项是根据 2009 年美国复苏和再投资法案（公法 111-5）资助的。金属纳米团簇表现出有趣的电子和原子振动现象，这些现象与相应的本体特性显着偏离。这项研究的目标是将最近开发的基于胶束的纳米团簇合成方法与电子和振动特性的先进纳米级物理分析相结合。将合成自组装尺寸和形状选择的双金属纳米团簇[57FePt、57FePd、57FeCu和57FeAu]。 X射线光电子能谱、扫描隧道和透射电子显微镜、57Fe穆斯堡尔能谱和57Fe核共振非弹性X射线散射等实验工具的协同组合将用于寻找纳米结构形态和电子结构及其尺寸和成分依赖性振动特性之间的相关性。此外，支持团簇的振动动力学建模将通过国际合作（加拿大）通过分子动力学模拟进行。这项工作的智力价值基于对当前理解的改进：（i）孤立纳米团簇中双金属合金的形成、结构和热稳定性，（ii）其固有的电子和振动特性，（iii）这些特性如何因团簇尺寸效应、团簇-支撑相互作用、团簇表面配体的存在以及团簇的组成而变化。 纳米合金，以及（iv）声子诱导的结构相变（在铁磁体因瓦合金中已知）是否持续存在并且可以在纳米团簇中进行调整。由于电子和声子态密度是理解和预测重要材料特性的关键要素，因此该项目将增进对电子器件中导电率和导热率、热容、振动熵、电子声子耦合和 1/f 噪声的基本物理现象的现有了解。此外，还将深入了解声子辅助的表面化学反应是否可以在理解金属纳米团簇的催化性能方面发挥重要作用。非技术摘要：金属纳米团簇表现出有趣的电子和原子振动现象，这些现象与相应的本体特性显着偏离。金属纳米簇用于光学（纳米光子学）、磁性（记录介质）、医学（靶向药物输送）和化学（催化材料）。关于其电子和振动特性的详细性质仍然存在许多问题，并且需要更彻底的物理理解来推进这些材料的科学和技术。该项目将提高目前关于纳米团簇中双金属合金的形成、结构和热稳定性的知识，以及可用于调整其内在物理性​​质（例如团簇尺寸、支撑和成分）的参数。将获得对包括导电性和导热性在内的重要材料特性的更深入的了解。研究生和本科生将接受培训，并有机会进行最先进的研究，不仅在中佛罗里达大学，而且在国家和国际用户设施，包括高级光子源（芝加哥）和 Spring8（日本）。 K-12 学生与本科生合作将负责样品制备。一个名为“科学为何？”的网站将设立在中小学生中传播与科学相​​关的教育活动。为了促进少数族裔（西班牙裔）家长接触科学，该网站将提供英语和西班牙语版本。