Quantifying and manipulating chirality and amplification of nanomaterials in liquid crystals

量化和操纵液晶中纳米材料的手性和放大

• 批准号: 1904091
• 负责人: Torsten Hegmann
• 金额: $ 31.98万
• 依托单位: Kent State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904091&HistoricalAwards=false
• 关键词: Quantifying; manipulating; chirality; amplification; nanomaterials

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.

非技术性摘要手性，最简单地描述为不存在镜像对称性，在自然界中甚至在宇宙中都可以找到。手性这一术语由开尔文勋爵于 1894 年创立，并由巴斯德等人大力推进，它对化学、生物学、物理学、宇宙学和材料科学等领域具有重要意义。生命同手性的起源被瓦尼埃描述为“普遍不对称性”，是最核心的科学问题之一。手性的放大是大多数描述自然同手性的理论的基础，即仅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。该项目得到了美国国家科学基金会固态和材料化学项目以及凝聚态物理项目的支持，推进了最新的发现，即由单层手性分子覆盖的纳米级粒子发出的手性能够在液晶中产生比有机分子手性对应物更强烈的响应。液晶态在自然界中普遍存在，就像手性一样，这里作为一个强大的测试平台来建立控制手性在空间中放大的尺寸特性和形状特性关系。肯特州立大学的这项研究产生的数据可以促进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道路。学生体验多学科的培训环境，利用最先进的设备，并熟练地向同行展示他们的研究成果。该项目是多项外展活动的平台，包括高中生培训、社区学院学生的实践讲座和实验室研究以及科学研讨会。技术摘要只有能够通过空间和跨长度尺度检测、测量、可视化、调整和转移纳米材料手性，才能在理解和应用纳米材料手性独特特征方面取得重大进展。为了研究这一点，普遍存在的液晶态通过允许不同长度尺度的手性放大的可视化和量化，为纳米材料手性的基础理论和应用实验研究提供了无与伦比的机会。使用偏光光学显微镜、荧光共焦显微镜和透射电子显微镜等一系列成像技术来研究这些系统。在赝标量手性指数的第一原理理论计算的指导下，这项实验工作还确定了纳米尺度的手性放大如何取决于纳米材料的类型、尺寸、形状和纵横比。该团队合成、表征和研究了向列液晶中手性配体封端的金属纳米棒、纳米圆盘、纳米星、纳米三角形和装饰有手性配体壳的纳米笼，并将螺旋扭转力的实验数据与计算出的手性指数的理论值进行了比较。为了测试如何应用手性放大，创建了类似于节肢动物或复眼的手性向列微透镜阵列，并检查了磁场与分散在向列液晶相中的不等轴手性分子覆盖的磁性纳米粒子的结合。后者旨在了解液晶主体和分散的磁性纳米粒子的竞争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。

项目成果

Molecular Conformation of Bent-Core Molecules Affected by Chiral Side Chains Dictates Polymorphism and Chirality in Organic Nano- and Microfilaments

• DOI: 10.1021/acsnano.1c00527
• 发表时间: 2021-03-18
• 期刊: ACS NANO
• 影响因子: 17.1
• 作者: Liu, Jiao;Shadpour, Sasan;Hegmann, Torsten
• 通讯作者: Hegmann, Torsten

Optical properties of nematic microlenses doped with chiral nanoparticles

• DOI: 10.1117/12.2568570
• 发表时间: 2020-08
• 作者: Kelum Perera;Alham Nemati;E. Mann;T. Hegmann;A. Jákli

Recent progress at the interface between nanomaterial chirality and liquid crystals

• DOI: 10.1080/21680396.2021.1930596
• 发表时间: 2021-01
• 期刊: Liquid Crystals Reviews
• 影响因子: 5.1
• 作者: Diana P. N. Gonçalves;M. Prévôt;Şenay Üstünel;Timothy Ogolla;Ahlam Nemati;Sasan Shadpour;T. Hegmann

Binary mixtures of bent-core molecules forming distinct types of B4 phase nano- and microfilament morphologies

• DOI: 10.1080/02678292.2020.1847333
• 发表时间: 2020-11
• 期刊: Liquid Crystals
• 影响因子: 2.2
• 作者: Jiao Liu;Sasan Shadpour;Ahlam Nemati;M. Prévôt;E. Hegmann;Chenhui Zhu;T. Hegmann

Polymer Stabilized Paraboloid Liquid Crystal Microlenses with Integrated Pancharatnam–Berry Phase

• DOI: 10.1002/adom.202101510
• 发表时间: 2021-11
• 期刊: Advanced Optical Materials
• 影响因子: 9
• 作者: Kelum Perera;H. N. Padmini;E. Mann;A. Jákli