Ligand Exchange Equilibrium at Quantum Dot Surfaces in Polar and Aqueous Solvent Environments

在化学系大分子，超分子和纳米化学项目的支持下，南卡罗来纳州大学的Andrew Greytak博士将研究量子点（QD）在极性溶剂（如水）中的表面化学，以提高其在生物应用中的实用性。量子点是由半导体化合物组成的纳米级颗粒，通常通过附着在其表面的有机分子层在溶液中稳定。量子点通常表现出明亮的和尺寸可调的荧光，这导致它们在成像应用中的使用，但它们的实用性受到未知的控制原理的限制。Greytak博士和他的团队正在将新兴的分析方法和物理模型与产生水溶性量子点的化学反应联系起来，以更好地理解这些限制。更广泛的影响涉及研究生和本科生的指导;引入新的实验模块到物理化学实验室课程;与南卡罗来纳州可持续发展办公室的研究和实践展示的协调，提供了一个机会，讨论量子点和其他先进材料在照明，显示和太阳能应用中的作用;该研究采用等温滴定量热法（ITC）结合核磁共振技术来研究表面配位和相互作用的相对重要性。配体相互作用在极性溶剂环境中控制量子点上配体的结合强度和交换速率。在过去的几年中，Greytak小组已经证明，等温滴定量热法（ITC）可以是表征QD-配体相互作用的重要技术，在测量配体缔合，配体交换和硫属化物QD表面的顺序交换和结合过程中取得了成功。该提案将通过将ITC应用于极性溶剂中的新类别的氢化反应来扩展和超越这些成就，特别是那些探测适合于生物成像应用的水溶性量子点的形成和行为的反应。由于ITC可以区分顺序结合到不同的网站的基础上，他们的结合焓的差异，这种方法有望导致胶体量子点表面化学的理解。在水性缓冲液中的代表性小分子阴离子配体之间进行比较。额外的调查试图澄清的性质结合在新兴的嵌段共聚物配体的基础上咪唑和类似heterocyclic.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Dr. Andrew Greytak of the University of South Carolina will investigate the chemistry at the surface of quantum dots (QDs) in polar solvents such as water to increase their utility in biological applications. QDs are nanometer-scale particles composed of semiconducting compounds, that are typically stabilized in solution by layers of organic molecules attached to their surfaces. QDs often exhibit bright and size-tunable fluorescence that has led to their use in imaging applications, but their utility is limited by unknown governing principles. Dr. Greytak and his group are connecting emerging analytical methods and physical models to chemical reactions that yield water-soluble QDs to better understand these limitations. Broader impacts involve mentorship of graduate and undergraduate students; introduction of new experimental modules into a physical chemistry lab course; coordination of a research and practice showcase with the University of South Carolina Office of Sustainability that provides an opportunity to discuss the role of QDs and other advanced materials in lighting, display, and solar energy applications; and outreach through a local science and engineering fair for junior and senior high school students.The research employs isothermal titration calorimetry (ITC) in combination with NMR techniques to investigate the relative importance of surface coordination and inter-ligand interactions in governing the binding strength and exchange rate of ligands on quantum dots (QDs) in polar solvent environments. In the last few years, the Greytak group has demonstrated that isothermal titration calorimetry (ITC) can be an important technique for characterizing QD-ligand interactions, with success in measuring ligand association, ligand exchange, and sequential exchange and binding processes at chalcogenide QD surfaces. This proposal will extend and go beyond these achievements by applying ITC to new classes of nanocrystal reactions in polar solvents, especially those that probe the formation and behavior of water-soluble QDs suitable for bio-imaging applications. Because ITC can distinguish sequential binding to various sites based on differences in their enthalpy of binding, this approach is expected to lead to improved understanding of colloidal QD surface chemistry. Comparisons are to be made among representative small molecule anionic ligands in aqueous buffers. Additional investigations seek to clarify the nature of binding in emerging block copolymer ligands based on imidazoles and analogous heterocyclic.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.