Quantifying and manipulating chirality and amplification of nanomaterials in liquid crystals

非技术性总结手征，最简单的描述是不存在镜像对称，可以在自然界的任何地方找到，可能在宇宙中。由开尔文勋爵于1894年建立，并由巴斯德和其他人显着推进，手性在化学，生物学，物理学，宇宙学和材料科学等方面具有重要意义。生命同手性的起源被瓦格纳称为“普遍的不对称性”，是最核心的科学问题之一。手性的放大是大多数描述自然界同手性的理论的基础，即只使用糖和氨基酸的一种对映体（单手性）来构建从简单到复杂的所有生命形式。该项目由固态和材料化学计划以及NSF的凝聚态物理计划支持，推进了最近的研究结果，即由单层手性分子覆盖的纳米级颗粒发出的手性独特地能够在液晶中产生比有机分子手性对应物更强烈的响应。液晶态，在自然界中无处不在，就像手性一样，在这里作为一个强大的测试平台，以建立大小-属性和形状-属性的关系，通过空间来控制手性的放大。肯特州立大学的这项研究产生的数据促进了对纳米级手性的理解，并为纳米级材料作为手性传感器，可调手性超材料和手性催化剂的新应用铺平了道路。学生体验多学科的培训环境，利用国家的最先进的设备，并成为在展示他们的研究同行精通。该项目作为一个平台，包括培训高中生，动手讲座和实验室研究的社区大学生，和一个科学symposium.TECHNICAL SUMMARYSignificant进步的理解和应用的独特功能的纳米材料手性只有可能的，如果一个可以检测，测量，可视化，调谐和转移纳米材料手性通过空间和跨越长度尺度。为了研究这一点，无处不在的液晶态提供了无与伦比的机会，纳米材料手性的基础理论和应用实验研究，通过允许可视化以及量化的手性放大在不同的长度尺度。一系列的成像技术，如偏光显微镜，荧光共聚焦显微镜，透射电子显微镜被用来研究这些系统。由赝标量手性指数的第一原理理论计算的指导下，这项实验工作还建立了如何在纳米尺度上的手性放大取决于纳米材料的类型，大小，形状和纵横比。该团队合成，表征和研究了手性配体覆盖的金属纳米棒，纳米盘，纳米星，纳米三角形和纳米笼，并将螺旋扭曲力的实验数据与计算的手性指数的理论值进行了比较。为了测试如何可以应用手性放大，创建类似于节肢动物或复眼的手性微透镜阵列，并使用磁场与非等轴手性分子覆盖的磁性纳米粒子分散在液晶相的研究。后者旨在了解液晶主体和分散的磁性纳米颗粒的相互竞争的弹性力和磁力如何分别转化为运动。该奖项反映了NSF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。

NON-TECHNICAL SUMMARYChirality, most simply described by the absence of mirror symmetry, can be found everywhere in nature and probably in the universe. Established as a term by Lord Kelvin in 1894, and significantly advanced by Pasteur and others, chirality has significant implications in Chemistry, Biology, Physics, Cosmology, and Materials Science alike. Described as "universal asymmetry" by Wagniere, the origin of homochirality of life is one of the most central scientific questions. Amplification of chirality underpins most theories proposed to describe nature's homochirality, i.e. the use of exclusively one enantiomer (one handedness) of sugars and amino acids to build all life forms, from simple to complex. This project, supported by the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program at NSF, advances recent findings that chirality emanating from nanoscale particles capped with a monolayer of chiral molecules is uniquely able to generate more intense responses in liquid crystals than their organic molecular chiral counterparts. The liquid crystalline state, pervasive in nature just like chirality, here serves as a powerful test platform to establish size-property and shape-property relationships governing the amplification of chirality through space. This research at Kent State University generates data that advance the understanding of nanoscale chirality and paves the way for new applications of nanoscale materials as chirality sensors, tunable chiral metamaterials, and chiral catalysts. Students experience a multidisciplinary training environment, utilize state-of-the-art equipment, and become proficient in presenting their research to peers. The project serves as a platform for several outreach activities including training of high school students, hands-on lectures and lab research for community college students, and a scientific symposium.TECHNICAL SUMMARYSignificant advances in the understanding and application of the unique features of nanomaterial chirality are only possible if one can detect, measure, visualize, tune, and transfer nanomaterial chirality through space and across length scales. To study this, the ubiquitous liquid crystalline state offers unrivaled opportunities for both fundamental theoretical and applied experimental research on nanomaterial chirality, by permitting the visualization as well as quantification of chirality amplification at different length scales. A range of imaging techniques such as polarized optical microscopy, fluorescence confocal microscopy, and transmission electron microcopy are used to study these systems. Guided by first principle theoretical calculations of a pseudoscalar chirality index, this experimental work also establishes how chirality amplification at the nanoscale depends on the nanomaterial type, size, shape, and aspect ratio. The team synthesizes, characterizes, and studies chiral ligand-capped metal nanorods, nanodiscs, nanostars, nanotriangles, and nanocages decorated with chiral ligand shells in nematic liquid crystals, and compares experimental data of the helical twisting power to theoretical values of the calculated chirality index. To test how chirality amplification can be applied, chiral nematic microlens arrays similar to arthropod or compound eyes are created, and the use of magnetic fields in combination with anisometric chiral molecule-capped magnetic nanoparticles dispersed in nematic liquid crystal phases examined. The latter seeks to understand how competing elastic and magnetic forces of liquid crystal host and dispersed magnetic nanoparticles, respectively, can be translated into motion.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.