Towards a Quantitative Knob for Controlling the Shape of Noble-Metal Nanocrystals

用于控制贵金属纳米晶体形状的定量旋钮

• 批准号: 1505400
• 负责人: Younan Xia
• 金额: $ 67万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505400&HistoricalAwards=false
• 关键词: Towards; Quantitative; Knob; Controlling; Shape

Non-Technical AbstractControlling the shape of nanocrystals has implications that go far beyond aesthetic appeal. For nanocrystals made of precious metals such as silver, gold, palladium and platinum, the shape determines not only their physicochemical properties but also their relevance for applications in catalysis, electronics, photonics, display, sensing, medicine, environmental protection, and energy production and storage. Taking silver nanorods as an example, they can be designed with superior electrical and thermal conductivity, while having no optical absorption in the visible region, to meet the requirements for touchscreen displays, energy-efficient transparent solar films, and smart windows. The shape of a nanocrystal is determined by the twin structure and growth pattern of the seed, which are, in turn, correlated with the reduction kinetics involved in a synthesis. With the support of the Solid State and Materials Chemistry program in the Division of Materials Research, the ultimate goal of this research is to establish the role of reduction rate as a quantitative knob for manipulating the shape of nanocrystals. This research has profound impacts on the advancement of a number of disciplines by forging links between different fields, including chemistry, physics, materials science, catalysis, photonics, electronics, and energy technology. The immediate outputs of this research are advanced nanomaterials with substantially improved performance for a broad range of applications, including those related to energy production (e.g., fuel cells), protection of the environment (e.g., catalytic converters), national security, and public healthcare. The ability to produce nanocrystals of precious metals with well-controlled shapes also offers a practical strategy for achieving sustainable and prolific use of these scarce elements that only exist in the Earth's crust at a level of parts per billion. The multidisciplinary and collaborative activity greatly enhances graduate and undergraduate education and also provides a natural vehicle to promote the diversity in higher education and enrich the K-12 education.Technical AbstractThe principal investigator will study the nucleation and growth of nanocrystals by achieving a quantitative understanding of the correlations between the reduction rate of a precursor and the number of twin defects in a seed, as well as its growth pattern. Using palladium as a model system, the research team will develop spectroscopy methods to determine the kinetic parameters (including rate constant and activation energy) of various reduction reactions used for nanocrystal synthesis and then determine the range of reduction rates responsible for the formation of a specific type of seeds characterized by a single-crystal, singly-twinned, multiply-twinned, or stacking-fault-lined structure. The kinetic parameters will also be applied to analyze the growth patterns of cubic and decahedral seeds (with single-crystal and five-fold twinned structures, respectively) in an effort to achieve a deep understanding of new phenomena such as symmetry breaking or reduction. As a powerful demonstration, the quantitative knowledge about the effects of reduction rate on the nucleation and growth of seeds will be further applied to design synthetic protocols for the production of silver nanorods with no optical absorption in the entire visible region by working with palladium decahedral seeds smaller than 20 nm. Taken together, this research will bring major advances to the field of nanotechnology by unraveling the essential knowledge and design rule for the deterministic syntheses of nanocrystals with well-controlled shapes and related properties central to a broad range of fundamental studies and industrially important applications.

非技术摘要控制纳米晶体的形状所带来的影响远远超出了审美吸引力。对于由银、金、钯和铂等贵金属制成的纳米晶体，其形状不仅决定其物理化学性质，还决定其在催化、电子、光子、显示、传感、医学、环境保护和能源生产等领域的应用。贮存。以银纳米棒为例，它们可以被设计为具有优异的导电性和导热性，同时在可见光区域没有光学吸收，以满足触摸屏显示器、节能透明太阳能薄膜和智能窗户的要求。纳米晶体的形状由种子的孪生结构和生长模式决定，而这又与合成中涉及的还原动力学相关。在材料研究部固态与材料化学项目的支持下，本研究的最终目标是确立还原率作为操纵纳米晶体形状的定量旋钮的作用。这项研究通过在化学、物理、材料科学、催化、光子学、电子学和能源技术等不同领域之间建立联系，对许多学科的进步产生了深远的影响。这项研究的直接成果是先进的纳米材料，其性能显着提高，适用于广泛的应用，包括与能源生产（例如燃料电池）、环境保护（例如催化转换器）、国家安全和公共医疗保健相关的应用。生产形状可控的贵金属纳米晶体的能力也为实现这些稀有元素的可持续和大量利用提供了一种实用的策略，这些稀有元素仅以十亿分之一的水平存在于地壳中。多学科和协作活动极大地增强了研究生和本科生教育，也为促进高等教育的多样性和丰富 K-12 教育提供了天然的工具。技术摘要首席研究员将通过定量理解纳米晶体的成核和生长来研究纳米晶体的成核和生长。前体的还原率与种子中孪生缺陷的数量及其生长模式之间的相关性。使用钯作为模型系统，研究小组将开发光谱方法来确定用于纳米晶体合成的各种还原反应的动力学参数（包括速率常数和活化能），然后确定负责形成特定物质的还原速率范围。以单晶、单孪晶、多孪晶或叠错排列结构为特征的种子类型。动力学参数还将用于分析立方晶种和十面体晶种（分别具有单晶和五重孪晶结构）的生长模式，以深入了解对称性破缺或对称性还原等新现象。作为一个强有力的论证，有关还原率对种子成核和生长影响的定量知识将进一步应用于设计合成方案，通过使用钯十面体种子来生产在整个可见光区域没有光学吸收的银纳米棒小于20纳米。总而言之，这项研究将揭示纳米晶体的确定性合成的基本知识和设计规则，为纳米技术领域带来重大进展，这些纳米晶体具有良好控制的形状和相关特性，这对于广泛的基础研究和工业重要应用至关重要。