Collaborative Research: Thermochemistry and Chemical Kinetics of Halide-driven Crystal Structure Control of Manganese and Lanthanide Chalcogenide Nanocrystals

在化学系大分子、超分子和纳米化学项目的支持下，特拉华州大学的Emil Hernánal-Pagán博士、亚利桑那州立大学的Kristina Lilova博士和圣路易斯华盛顿大学的Robert Wexler博士将研究卤化物的存在是如何影响纳米材料的性质的。（氯化物、溴化物和碘化物）影响某些类别的纳米颗粒合成中原子的最终排列（晶体结构）。该团队将采用实验技术，包括在反应发生时提供信息的技术，以及计算方法来深入了解这一过程。特定的晶体多晶型物通常决定了纳米晶体材料的关键性质，因此决定了这些材料可以用于的应用，例如，在光致发光、催化和能量储存中。因此，掌握控制晶体结构的知识和能力非常重要。这项工作的更广泛的影响是围绕（a）提供实验和计算培训的学生在这个项目上工作和（B）夏季研究经验的本科生从波多黎各，旨在补充他们在他们的家乡机构接受的培训，以更好地为他们准备的劳动力和/或追求研究生学位。 合理合成纳米颗粒的给定多晶型物或相的能力是期望的，因为这些决定了它们的机械、光学和电子性质。所提出的工作协同结合实验和计算方法，提供一个整体框架的模型系统，其中卤化物驱动控制的晶体结构/相在锰硫属化物纳米晶体的合成。该框架将包括识别预成核分子种类，进行反应和表面配体相互作用的热化学测量，并监测成核和生长的动力学。一套原位技术将被用来使这种测量的反应条件下。基于量子力学的计算将用于确定原子尺度的相互作用和导致观察到的晶体结构/相的机制。这些计算将提供输入的动力学和热力学模型的成核和生长，因此，将产生多尺度为基础的计算指导金属硫族化物纳米晶体的控制合成。这些研究将扩展到镧系硫属元素纳米晶体，尽管具有独特的光学和磁性，但在很大程度上尚未开发。这项工作预计将进一步提高锰和镧硫属元素纳米晶体合成的化学理解水平，这种见解有可能为科学界合成其他类别的材料提供指导。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Drs. Emil Hernández-Pagán of the University of Delaware, Kristina Lilova of Arizona State University, and Robert Wexler of Washington University in St. Louis will investigate how the presence of halides (chloride, bromide, and iodide) influences the final arrangements of atoms (crystal structure) in the synthesis of certain classes of nanoparticles. The team will employ experimental techniques, including ones that provide information as the reaction occurs, and computational methods to gain in depth insight into this process. The particular crystal polymorph often dictates key properties of nanocrystalline materials and, consequently, the applications for which these can be used, for example, in photovoltaics, catalysis, and energy storage. Therefore, having the knowledge and ability to control the crystal structure is important. The broader impacts of this work are centered around (a) providing experimental and computational training to the students working on this project and (b) summer research experiences for undergraduate students from Puerto Rico that aim to complement the training they receive at their home institutions to better prepare them for the workforce and/or pursuing a graduate degree. The ability to rationally synthesize a given polymorph or phase of a nanoparticles is desirable as these dictate their mechanical, optical, and electronic properties. The proposed work synergistically combines experimental and computational methods to provide a holistic framework for a model system where halides drive the control of crystal structure/phase in the synthesis of manganese chalcogenide nanocrystals. This framework will encompass identifying pre-nucleation molecular species, performing thermochemical measurement of reaction and surface-ligand interactions, and monitoring the kinetics of nucleation and growth. A suite of in situ techniques will be employed to enable such measurements under the reaction conditions. Quantum-mechanics-based calculations will be used to identify atomic-scale interactions and the mechanisms that lead to the observed crystal structures/phases. These calculations will provide input for kinetic and thermodynamic models of nanocrystal nucleation and growth and, therefore, will produce multi-scale-based computational guidance for the controlled synthesis of metal chalcogenide nanocrystals. The studies will be extended to lanthanide chalcogenide nanocrystals, which have remained largely unexplored despite unique optical and magnetic properties. This work is anticipated to further increase the level of chemical understanding of the synthesis of Mn and Ln chalcogenide nanocrystals, and such insights have the potential to provide guidance to the scientific community for the synthesis of other classes of materials.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.