Equilibrium thermodynamics of semiconductor nanocrystal ligand and ion exchange via calorimetry

半导体纳米晶配体的平衡热力学和量热法离子交换

• 批准号: 1613388
• 负责人: Andrew Greytak
• 金额: $ 40.92万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-15 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1613388&HistoricalAwards=false
• 关键词: Equilibrium; thermodynamics; semiconductor; nanocrystal; ligand

Equilibrium thermodynamics of semiconductor nanocrystal ligand and ion exchange via calorimetryThis grant supports Dr. Andrew Greytak of the University of South Carolina in the effort to develop an improved understanding of colloidal quantum dot chemistry through the use of isothermal titration calorimetry (ITC). Nanocrystal quantum dots (QDs) are soluble, nanometer-scale particles composed of semiconductor materials. QDs can have bright and size-tunable fluorescence, and have current applications in flat-panel displays and in bio-imaging. QDs are also of interest for solution-processable solar cells that can be scaled sustainably to meet worldwide energy needs. However, the performance of QD solar cells remains far below the theoretical limit. There is considerable variability in fluorescence performance among QD samples of similar size and composition, due to structural differences at the QD surface. It is important to connect emerging analytical methods and theoretical models to the design of stable QDs with desirable surface properties. This project takes a new approach to developing a fundamental understanding of QD structure and chemistry by measuring the heat that is emitted or absorbed when chemical transformations of QDs take place. The ITC approach is expected to be broadly applicable to semiconductor nanocrystal science. The technique is being used here to advance knowledge that could lead to improved QD solar cell performance. Dr. Greytak's research program at the University of South Carolina engages students at the high school, undergraduate, and graduate levels. He has demonstrated nationally-recognized leadership in chemistry education. He also serves as the head judge for chemistry at the South Carolina Midlands Regional Science Fair for high school students.Colloidal nanocrystals (NCs) are complex assemblies of a crystalline core and an interfacial layer that, given time, may exchange matter with the solution and other NCs. It is highly advantageous to have a set of metrics that allows different NC samples to be profiled, both so that they can be characterized with sufficient precision to predict synthetic and physical behaviors. It is also adventitious to have a sufficiently rich experimental description of the system to constrain models that begin to capture the complexity of NC-ligand and ligand-ligand interactions. In this program, Dr. Greytak is being supported to measure equilibrium constants, enthalpies, equivalencies, and interaction terms associated with representative ligand exchange and ion exchange reactions at NC quantum dot (QD) surfaces in anhydrous solvents. Purification techniques such as gel permeation chromatography are used to provide QDs in a well-defined initial state. The knowledge acquired from these types of measurements represents a fundamental advance in QD chemistry that hastens the discovery of higher-performing and more sophisticated QD assemblies and solution structures. In particular, the performance and material scope of QD-based photovoltaics can be expanded through improved understanding of ligand exchange and ion exchange reactions. This project also provides research training opportunities to graduate and undergraduate students, who are building expertise in nanocrystal preparative chemistry, calorimetry, and other analytical techniques that are necessary to advance the field of nanoscience into practical technologies. Dr. Greytak has been active in broadening research participation through the Scientific Advocate Network and the American Chemical Society's Project SEED program. He has also initiated an annual USC Sustainability Research and Practice Showcase that creates a focal point for research groups, graduate and undergraduate students, and staff to educate each other about opportunities for research participation, entrepreneurship, integrative learning, and outreach that advances regional and national competitiveness.

通过量热法研究半导体量子点配体和离子交换的平衡热力学该基金支持南卡罗来纳州大学的Andrew Greytak博士通过使用等温滴定量热法（ITC）来提高对胶体量子点化学的理解。纳米晶体量子点（QD）是由半导体材料组成的可溶性纳米级颗粒。量子点可以具有明亮且尺寸可调的荧光，并且在平板显示器和生物成像中具有当前的应用。量子点也对可溶液加工的太阳能电池感兴趣，这些太阳能电池可以可持续地扩展以满足全球能源需求。然而，量子点太阳能电池的性能仍远低于理论极限。 由于量子点表面的结构差异，具有相似尺寸和组成的量子点样品之间的荧光性能存在相当大的变化。将新兴的分析方法和理论模型与具有理想表面性质的稳定量子点的设计联系起来是很重要的。该项目采取了一种新的方法，通过测量量子点发生化学转化时释放或吸收的热量，来发展对量子点结构和化学的基本理解。ITC方法有望广泛应用于半导体封装科学。 该技术被用于推进可能导致量子点太阳能电池性能改善的知识。Greytak博士在南卡罗来纳州大学的研究项目吸引了高中、本科和研究生层次的学生。他在化学教育方面表现出了全国公认的领导地位。 他还担任南卡罗来纳州米德兰兹地区高中生科学博览会的化学首席评委。胶体纳米晶体（NC）是一个晶体核心和一个界面层的复杂组合体，在一定时间内，可以与溶液和其他NC交换物质。具有一组允许对不同NC样品进行分析的度量是非常有利的，这两种度量都使得它们可以以足够的精度表征以预测合成和物理行为。 这也是偶然的，有一个足够丰富的实验描述的系统，以约束模型，开始捕捉NC-配体和配体-配体相互作用的复杂性。在该计划中，Greytak博士被支持测量与无水溶剂中NC量子点（QD）表面的代表性配体交换和离子交换反应相关的平衡常数，平衡常数，当量和相互作用项。纯化技术如凝胶渗透色谱法用于提供处于明确定义的初始状态的QD。从这些类型的测量中获得的知识代表了QD化学的根本性进步，加速了更高性能和更复杂的QD组件和溶液结构的发现。特别是，量子点为基础的photoprophics的性能和材料范围可以通过改进的配体交换和离子交换反应的理解扩展。该项目还为研究生和本科生提供研究培训机会，他们正在建立纳米制备化学，量热法和其他分析技术方面的专业知识，这些技术是将纳米科学领域推进到实用技术中所必需的。Greytak博士通过科学倡导者网络和美国化学学会的SEED项目积极扩大研究参与。他还发起了一年一度的南加州大学可持续发展研究和实践展示，为研究小组，研究生和本科生以及工作人员创造了一个焦点，以相互教育有关研究参与，创业，综合学习和推广的机会，从而提高区域和国家竞争力。