'Molecular Nanoparticles' of Magnetic Perovskite Manganites and Other Metal Oxides

在该项目中，由化学部化学结构、动力学和机理-B项目资助，佛罗里达大学化学系的George Christou教授正在使用合成化学方法制备尺寸和形状相同的重要金属氧化物纳米颗粒。这种“分子纳米颗粒”（尺寸小于十亿分之一米的分子）解决了纳米科学中当前的一个重要挑战，即如何避免尺寸和形状的混合，从而避免性能的混合。 目前大多数纳米颗粒的制备都会导致同一批次中产生不同的颗粒尺寸和形状。该项目最初的目标是制造二氧化铈和亚锰钙钛矿的分子纳米颗粒，这些材料在工业和医疗应用中具有广泛的重要性，以及潜在的新量子器件技术。克里斯图教授和他的团队开展了许多外展、教育和国际活动。他们参加在盖恩斯维尔购物中心举行的一年一度的化学日活动，活动对象为 K-12 学生、教师和家长以及当地社区和媒体。本科研究生参与实践研究，获得研究生工作或就业的重要技能。 Christou教授在佛罗里达州ACS地方分部年会上组织展示研讨会，并组织年度佛罗里达州无机和材料研讨会学生会议，该会议涉及佛罗里达州14所授予博士学位的大学、本科生和社区学院。 在国际上，他共同组织了两个两年一度的研讨会，即分子和纳米级磁性的当前趋势（2021年）和北美-希腊-塞浦路斯顺磁材料研讨会（2020年、2022年），其中包括来自学生和博士后的许多演讲。最后，该团队继续与国内和国际团体合作，为专门的物理研究提供样本，并协助合成化学家对其材料进行磁性表征。真正单分散（相同）纳米颗粒的合成及其在原子分辨率下的结构表征是纳米科学中极其重要的挑战。对于许多对下一代电子、磁性、催化和生物医学系统/设备的开发非常重要的纳米级材料来说，自上而下的方法具有局限性，因为随着尺寸的减小，单分散纳米颗粒的制造变得越来越困难。如果可以合成与本体材料具有相同结构的高核簇，则自下而上的分子方法提供了一种替代途径。这种“分子纳米颗粒”将分子化学的优势带入纳米科学，特别是真正的单分散性、溶解度和结晶度。这种合成方法尤其适用于纳米级金属氧化物，具有科学和技术重要性。 George Christou 教授的团队最近在簇化学方面取得了突破，可生产真正单分散的亚锰钙钛矿和二氧化铈纳米颗粒，开辟了有望在纳米尺度产生知识的新方向。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。

In this project, funded by the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Professor George Christou of the Department of Chemistry at the University of Florida is using synthetic chemistry methods to prepare nanoparticles of important metal oxides that are identical in size and shape. Such "molecular nanoparticles" (molecules less than one billionth of a meter in size) address an important current challenge in nanoscience, namely how to avoid mixtures of sizes and shapes, and thus of properties. Most current preparations of nanoparticles result result in various particle sizes and shapes in the same batch. The project is initially targeted at making molecular nanoparticles of cerium dioxide and manganite perovskites, materials of widespread importance in industrial and medical applications, as well as potentially new quantum device technologies. Professor Christou and his group carry out a number of outreach, education and international activities. They participate in the annual Chemistry Day at the Mall in Gainesville, targeted at K-12 students, teachers and parents, and the local community and media. Undergraduate research students participate in hands-on research gaining important skills for graduate work or employment. Professor Christou organizes the Showcase Symposium at the annual meeting of the Florida ACS Local Section, and also organizes the annual Florida Inorganic and Materials Symposium student meeting, which involves 14 Florida PhD-granting universities, and undergraduate and community colleges. Internationally, he co-organizes two biennial workshops, the Current Trends in Molecular and Nanoscale Magnetism (2021), and the North America-Greece-Cyprus Workshop on Paramagnetic Materials (2020, 2022), which include many talks from students and postdocs. Finally, the team continues to collaborate with national and international groups, providing samples for specialized physics studies, and assisting synthetic chemists in the magnetic characterization of their materials.Synthesis of truly monodisperse (identical) nanoparticles and their structural characterization at atomic resolution are extremely important challenges in nanoscience. For many nanoscale materials important to the development of next-generation electronic, magnetic, catalytic, and biomedical systems/devices, the top-down approach has limitations as the fabrication of monodisperse nanoparticles becomes more and more difficult with decreasing size. The bottom-up molecular approach provides an alternative route if high nuclearity clusters that have the same structure as the bulk material can be synthesized. Such "molecular nanoparticles" bring the advantages of molecular chemistry to nanoscience, particularly true monodispersity, solubility, and crystallinity. This synthetic approach is especially available nanoscale metal oxides, which are of scientific and technological importance. Breakthroughs in cluster chemistry to produce truly monodisperse nanoparticles of manganite perovskites and cerium dioxide have recently been achieved by the Professor George Christou's group, opening up new directions that promise knowledge generation at the nanoscale.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.