Synthesis and Nanoscale Characterization of Novel Magnetic Chalcogenide Nanocrystals

新型磁性硫族化合物纳米晶体的合成和纳米级表征新型磁性材料需要用于新兴的电子器件，这些器件除了利用电子的电荷外，还利用电子的自旋，通常被称为自旋电子学。特别是，显示半导体或绝缘特性的磁性材料是非常可取的，但它们的选择目前有限。阿拉巴马大学的古普塔博士正在研究一类以硫和硒为基础的复杂无机材料，这种材料被称为硫尖晶石，它显示出新的磁性。他对利用湿化学方法合成非常小的“纳米晶体”形式的新型半导体和绝缘琥珀尖晶石特别感兴趣。与通常需要高温和延长反应时间的体合成不同，基于溶液的纳米材料合成可以在更低的温度和更短的时间内进行。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。除了合成之外，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，以探测纳米晶体的固有磁性和电学特性。该项目需要多学科的努力，为科学知识、教育、推广和基础设施作出重大贡献。Gupta博士还在与拟议研究相关的几个正在进行的教育和外展活动中发挥作用。其中包括与当地学校合作，促进高中生参与研究，以及公众参观和示范。在这个研究项目中，阿拉巴马大学的Arunava Gupta博士在大分子、超分子和纳米化学（MSN）项目的支持下，研究了一种新的溶液化学途径，以合成一种有前途的纳米晶体形式的磁性cr基铜尖晶石材料。这些材料的动机来源于理论研究，表明在一些复杂的铜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载流子与磁性离子相互作用基础研究的重要模型系统。在平行进行的能带结构计算的指导下，正在探索取代硫尖晶石家族的纳米晶体合成。纳米晶体的一个潜在限制是缺乏直接测量纳米尺度性质的合适方法。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博士是阿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，最大限度地扩大和传播与这项工作具体相关的结果。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关键作用。这些措施包括与当地学校合作，促进高中生参与研究、公共参观和示范。

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.