Synthesis and Nanoscale Characterization of Novel Magnetic Chalcogenide Nanocrystals

新型磁性硫属化物纳米材料的合成和纳米尺度表征新型磁性材料需要用于新兴的电子器件，这些电子器件除了利用电子的电荷外还利用电子的自旋，通常称为自旋电子学。特别地，显示半导体或绝缘特性的磁性材料是高度期望的，但是它们的选择目前是有限的。亚拉巴马大学的古普塔博士正在研究一类复杂的硫和硒基无机材料--被称为硫尖晶石--它们显示出新颖的磁性。他特别感兴趣的是使用湿化学方法以非常小的“纳米晶体”的形式合成新的半导体和绝缘硫尖晶石。与通常需要高温和延长的反应时间的本体合成不同，纳米级材料的基于溶液的合成可以在低得多的温度和缩短的时间尺度下进行。然而，由于缺乏合适的技术，直接探测单个纳米晶体的物理性质是具有挑战性的。除了合成，Gupta博士还积极与美国和国际合作者合作，开发新的基于显微镜的表征方法，用于探测纳米晶体的内在磁性和电学性质。该项目需要多学科的努力，为科学知识、教育、外联和基础设施做出重大贡献。Gupta博士还在与拟议研究相关的几项正在进行的教育和推广活动中发挥作用。其中包括与当地学校合作，以促进高中生参与研究，以及公众图尔斯和演示。在这项研究计划中，亚拉巴马大学的Arunava Gupta博士得到了大分子，超分子和纳米化学（MSN）计划，研究新的溶液化学路线，用于合成一类有前途的磁性Cr-纳米晶体形式的基于硫尖晶石的材料。这些材料的动机来自理论研究，表明在某些复杂的硫尖晶石中实现独特的磁性和电学性质的可能性。 这些材料还可以作为重要的模型系统，用于电荷载流子和磁性离子之间相互作用的基础研究。在能带结构计算的指导下，平行进行，取代的硫尖晶石家族的cathalspinels的合成正在探索中。与块体相比，纳米晶体的潜在限制是缺乏用于直接测量纳米级性质的适当方法。因此，该项目还利用新的电子光谱成像技术来探测纳米晶体的内在物理性质。Gupta博士是亚拉巴马大学多学科信息技术材料中心（MINT）的积极参与者，并利用MINT提供的大量资源，最大限度地发挥与这项工作相关的成果的推广和传播的影响。 Gupta博士还在与拟议研究相关的几项正在进行的教育和推广活动中发挥了关键作用。这些措施包括与当地学校合作，促进高中学生参与研究、公众图尔斯参观和示范。

Synthesis and Nanoscale Characterization of Novel Magnetic Chalcogenide NanocrystalsNew magnetic materials are required for use in emerging electronic devices that exploit the spin of the electron in addition to its charge, commonly referred to as spintronics. In particular, magnetic materials that display semiconducting or insulating characteristics are highly desirable, but their choice is presently limited. Dr. Gupta of the University of Alabama is investigating a class of complex sulfur and selenium-based inorganic materials - referred to as chalcospinels - that display novel magnetic properties. He is particularly interested in the synthesis of new semiconducting and insulating chalcospinels in the form of very small "nanocrystals" using wet chemistry approaches. Unlike bulk synthesis, which usually requires high temperatures and extended reaction time, solution-based synthesis of nanoscale materials can be carried out at much lower temperatures and at a reduced time scale. However, directly probing the physical properties of individual nanocrystals is challenging because of a lack of suitable techniques. In addition to synthesis, Dr. Gupta actively works with United States and international collaborators to develop new microscopy-based characterization methods for probing the intrinsic magnetic and electrical properties of the nanocrystals. The project requires a multidisciplinary effort that makes significant contributions to scientific knowledge, education, outreach and infrastructure. Dr. Gupta also plays a role in several ongoing education and outreach activities related to the proposed research. These include collaboration with local schools to facilitate participation by high school students in research, as well as public tours and demonstrations.In this research program, Dr. Arunava Gupta of the University of Alabama is supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program to investigate novel solution chemistry routes for the synthesis of a promising class of magnetic Cr-based chalcospinel materials in the form of nanocrystals. Motivation for these materials is derived from theoretical studies suggesting the possibility of realizing unique magnetic and electrical properties in some complex chalcospinels. These materials may additionally serve as important model systems for fundamental studies of the interaction between charge carriers and magnetic ions. Guided by band structure calculations that are conducted in parallel, nanocrystal synthesis of a family of substituted chalcospinels are being explored. A potential limitation of nanocrystals as compared to bulk is the lack of appropriate methods for directly measuring the nanoscale properties. Therefore, the project also utilizes novel electron spectroscopic imaging techniques to probe the intrinsic physical properties of the nanocrystals. Dr. Gupta is an active participant in the multi-disciplinary Center for Materials for Information Technology (MINT) at the University of Alabama and leverages the considerable resources available through MINT for the maximum impact of outreach and dissemination of results specifically related to this work. Dr. Gupta also plays a key role in several on-going education and outreach activities related to the proposed research. These include collaboration with local schools to facilitate participation by high school students in research, public tours, and demonstrations.