Phase Control in Rare Earth Chalcogenide Nanomaterials

乔治城大学的Sarah Stoll教授进行研究，以开发合成含有稀土元素的纳米颗粒的新方法。这是一种相对未被开发的纳米结构，具有潜在的有用的电子和磁性。从这项研究中获得的基础知识可以为未来设计应用于电子学、磁学和量子计算的纳米粒子系统提供信息。该项目为本科生和研究生提供化学合成和磁性纳米颗粒表征的最新技术方面的培训。除了在华盛顿特区的公立学校开展外展活动外，斯托尔教授还为乔治城大学的“公共利益科学”项目开发了新的系列研讨会，并让乔治城的学生加入了“国家科学政策网络”组织。这些活动将对科学政策制定感兴趣的本科生和研究生群体联系起来，并为他们提供与从事科学政策的基金会、政府和学者代表会面的机会。在大分子，超分子和纳米化学计划的支持下，Stoll教授的研究小组开发了新的液相合成方法来制备镧系元素和硫系铀纳米颗粒。本研究旨在1)提供前驱体反应性在决定这些f块元素纳米晶体的组成、尺寸和结构中的作用机制；2)增加我们对从分子轨道到态密度图的能级演化的基本理解。铁磁铀硫族化合物之所以引起人们的兴趣，是因为预测表面各向异性高，这应该对作为粒度函数的磁滞曲线有显著影响。此外，镧系元素和铀硫系元素表现出较强的磁光性质。采用一系列技术（包括高分辨率透射电子显微镜、原子力显微镜、磁圆二色、x射线吸收光谱、SQUID磁强计、固态热裂解和动态光散射）来表征纳米颗粒并研究其磁性和电子特性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Prof. Sarah Stoll of Georgetown University conducts research to develop new methodologies for synthesizing nanoparticles containing rare earth elements. This is a relatively unexplored class of nanostructures with potentially useful electronic and magnetic properties. The fundamental knowledge to be gained from this research could inform future design of nanoparticle systems for applications in electronics, magnetics, and quantum computing. This project provides to undergraduate and graduate students training in chemical synthesis and the state-of-the-art techniques in characterization of magnetic nanoparticles. In addition to conducting outreach activities at D.C. public schools, Prof. Stoll develops new seminar series for the Georgetown University program called 'Science in the Public Interest' and engages Georgetown students in the organization called the 'National Science Policy Network'. These activities link groups of undergraduate and graduate students interested in science policy making and provide them opportunities to meet representatives from foundations, government and academics who are engaged in science policy.With the support from the Macromolecular, Supramolecular and Nanochemistry Program, the research group of Prof. Stoll develops new solution-phase synthetic methodologies for preparing lanthanide and uranium chalcogenide nanoparticles. This research aims to 1) provide mechanistic insights into the role of precursor reactivity in determining the composition, size, and structure of nanocrystals of these f-block elements; and 2) increase our fundamental understanding of the evolution of energy levels from molecular orbitals to the density of states diagram. Ferromagnetic uranium chalcogenides are of interest because of predicted high surface anisotropy, which should have a significant effect on the hysteresis curves as a function of particle size. In addition, the lanthanide and uranium chalcogenides exhibit strong magneto-optical properties. A suite of techniques (including high resolution transmission electron microscopy, atomic force microscopy, magnetic circular dichroism, X-ray absorption spectroscopy, SQUID magnetometry, solid-state thermolysis, and dynamic light scattering) is employed to characterize the nanoparticles and study their magnetic and electronic properties.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.