Seeded Growth of Noble-Metal Nanocrystals

贵金属纳米晶体的种子生长

• 批准号: 1104614
• 负责人: Younan Xia
• 金额: $ 54.5万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-15 至 2012-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1104614&HistoricalAwards=false
• 关键词: Seeded; Growth; Noble; Metal; Nanocrystals

TECHNICAL SUMMARY:This project, supported by the Solid State and Materials Chemistry (SSMC) program at NSF, will build a scientific basis for the synthesis of noble-metal nanocrystals with controlled properties for a variety of applications. The key approach is to separate and then independently control the nucleation and growth steps using a seed-mediated method. The research will be organized into four thrusts: i) Synthesis and characterization of single-crystal, cubooctahedral seeds made of Ag, Au, Pd, or Pt, and with sizes below 10 nm. The effects of capping agent, precursor, and oxidative etching on the crystallinity, yield, and size distribution of the seeds will all be examined. ii) Growth of metals same as the seeds. This work will seek to correlate the reduction kinetics with the growth modes, including site-selected overgrowth, conformal coating, and dendritic growth. It will also develop a screening method for rapid identification of capping agents capable of promoting the formation of specific facets. iii) Growth of metals different from the seeds. This work will address issues such as galvanic replacement that will occur spontaneously when the metal for seeds is more reactive than the metal to be grown by introducing a strong reducing agent to setback the replacement reaction. It will also fully explore the core-shell nanocrystals in terms of control over composition, shape, and shell thickness. iv) Properties and applications of the novel nanocrystals. In addition to a systematic study of the optical properties for nanocrystals with different sizes, shapes, and compositions, this work will investigate how the shells with various thicknesses shield the plasmonic excitation of the cores. It will also systematically investigate the effect of a substrate in forming hot spots with nanocrystals having different shapes. Furthermore, it will examine the catalytic and electrocatalytic properties of core-shell nanocrystals with both well-defined facets on the surface and tightly controlled thicknesses for the shellsNON-TECHNICAL SUMMARY:Interest in noble-metal nanocrystals with controlled sizes and shapes has grown steadily because of strong correlations between the size/shape of nanocrystals and chemical, physical, electronic, optical, magnetic, and catalytic properties. The interest has also been enhanced by the technological applications of these nanocrystals in areas ranging from catalysis (e.g., in fuel cells and catalytic converters) to biomedical research (e.g., as contrast and therapeutic agents). However, attempts to systematically and predictably control these properties have been met with limited success. One barrier is the lack of a mechanistic understanding and experimental control of the evolution pathway from atoms to nuclei, seeds, and finally nanocrystals. This work will bring significant advances to the field by unraveling the essential knowledge and design rules for synthesizing noble-metal nanocrystals with controlled sizes, shapes, morphologies, compositions, and structures crucial to various applications. This research will have profound impacts on the society in the following aspects: i) developing novel materials for sensing, biomedical applications, and catalysis that will address issues related to national security, health, environment, and energy; ii) forging links between different scientific fields that include solid state chemistry, condensed matter physics, surface science, materials science, colloid science, catalysis, and photonics; iii) enhancing both graduate and undergraduate education through multidisciplinary research and collaboration; iv) generating and disseminating new scientific knowledge resulting from the proposed work through peer-reviewed publications, reports, seminars, conference presentations, undergraduate and graduate teaching, summer school lectures, and websites; and v) promoting diversity in higher education by engaging women, minorities, and other underrepresented groups into the research program.

技术摘要：该项目得到了 NSF 固态与材料化学 (SSMC) 项目的支持，将为合成具有受控特性的贵金属纳米晶体奠定科学基础，适用于各种应用。关键方法是使用种子介导的方法分离并独立控制成核和生长步骤。该研究将分为四个重点：i）由 Ag、Au、Pd 或 Pt 制成且尺寸低于 10 nm 的单晶立方八面体晶种的合成和表征。封端剂、前体和氧化蚀刻对晶种的结晶度、产量和尺寸分布的影响都将被检查。 ii) 金属的生长与种子相同。这项工作将寻求将还原动力学与生长模式联系起来，包括选点过度生长、保形涂层和枝晶生长。它还将开发一种快速鉴定能够促进特定面形成的封端剂的筛选方法。 iii) 与种子不同的金属的生长。这项工作将解决诸如电偶置换等问题，当种子金属比要生长的金属更具反应性时，通过引入强还原剂来阻止置换反应，电偶置换会自发发生。它还将在成分、形状和壳厚度的控制方面全面探索核壳纳米晶。 iv）新型纳米晶体的特性和应用。除了对不同尺寸、形状和成分的纳米晶体的光学特性进行系统研究之外，这项工作还将研究不同厚度的壳如何屏蔽核的等离子体激发。它还将系统地研究基底对不同形状的纳米晶体形成热点的影响。此外，它将检查表面具有明确刻面和严格控制壳厚度的核-壳纳米晶体的催化和电催化性能非技术摘要：对具有受控尺寸和形状的贵金属纳米晶体的兴趣稳步增长，因为纳米晶体的尺寸/形状与化学、物理、电子、光学、磁性和催化特性之间存在很强的相关性。这些纳米晶体在催化（例如燃料电池和催化转换器）到生物医学研究（例如作为造影剂和治疗剂）等领域的技术应用也增强了人们的兴趣。然而，系统地、可预测地控制这些特性的尝试取得了有限的成功。其中一个障碍是缺乏对从原子到原子核、种子和最终纳米晶体的演化途径的机械理解和实验控制。这项工作将通过阐明合成贵金属纳米晶体的基本知识和设计规则，为该领域带来重大进展，这些贵金属纳米晶体具有受控的尺寸、形状、形态、成分和对各种应用至关重要的结构。这项研究将在以下方面对社会产生深远影响：i）开发用于传感、生物医学应用和催化的新型材料，以解决与国家安全、健康、环境和能源相关的问题； ii) 在不同科学领域之间建立联系，包括固态化学、凝聚态物理学、表面科学、材料科学、胶体科学、催化和光子学； iii) 通过多学科研究和合作加强研究生和本科生教育； iv) 通过同行评审的出版物、报告、研讨会、会议演讲、本科生和研究生教学、暑期学校讲座和网站，产生和传播拟议工作产生的新科学知识； v) 通过让妇女、少数民族和其他代表性不足的群体参与研究计划，促进高等教育的多样性。