Sensing, Imaging, Tuning and Creating Nanomaterial Chirality using Liquid Crystal Phases

手性是一个核心的科学概念，最好的描述是不能通过平移和旋转将物体叠加到其镜像上。最常见的例子是我们的左手和右手。另一个证明手性概念的例子是葛缕子和绿薄荷中的有效成分。虽然它们具有相同的分子结构，但这两种物质的味道却不同，因为它们的手性是相反的。在纳米尺度（比人类头发的厚度还小一千多倍）上创造和理解手性，对于光学器件中材料的使用，对于设计自然界中不存在的材料（超材料），对于表征大型复杂生物分子和制造新型传感器至关重要。为了理解这种纳米级的手性材料，我们需要检测、测量、可视化和转移纳米级的手性。在该项目中，由材料研究部固态与材料化学项目支持，研究团队使用液晶（通常用于lcd）来实现这些目标并寻找其应用。学生将体验一个跨学科的研究型环境，利用最先进的设备，并熟练地向同龄人展示他们的研究。学生还可以通过海外旅行和与欧洲同事一起工作来体验合作研究。该项目包括几项外展活动，包括科学研讨会和低收入家庭高中生的培训，为高中生和本科生提供动手讲座和实验室研究。虚拟现实也将用于探索和可视化手性纳米材料。技术摘要：金属纳米粒子或其原子表面在金属基电子跃迁中具有光学活性，从而表现出手性。这种手性既可以通过吸附手性有机分子来实现，也可以通过在手性环境中组装非手性或外消旋纳米颗粒来实现。手性从被吸附分子转移到金属纳米颗粒表面取决于吸附物的结构及其与周围环境的相互作用。这通常是难以阐明的，因此是这个项目的关键焦点。这项研究的动机是推进最近的发现，即纳米级的手性在软凝聚态系统（如液晶）中比它们的有机分子手性对应物能产生更强烈的响应。研究小组利用几种液晶相和材料作为理想的成分来检测、可视化和调节纳米级颗粒的手性。为了测量、调整和可视化纳米级手性，并充分发挥手性纳米材料的潜力，研究团队专注于不同尺寸和形状的手性基序功能化金属纳米颗粒的合成、表征和测试，以及用自组装的强手性分子单层功能化的纳米级金属图案。该研究还为纳米级手性诱导以及从各种液晶超结构到非手性和外消旋纳米颗粒的手性转移提供了新的前景。相反，在新发现的扭弯向列相中，稳定性和诱导光学活性也将被研究。结合起来，这些手性纳米材料可以作为可行的测试平台，应用范围从手性纳米传感器和可调手性超材料到手性纳米诱导剂、鉴别剂和催化剂。

Non-technical AbstractChirality is a central scientific concept, and best described by the inability to superimpose an object onto its mirror image by translation and rotation. The most common example is our left and right hands. Another example to demonstrate the concept of chirality is the active ingredients in caraway seeds and spearmint. While they have identical molecular structures, the two substances taste differently because they are chiral opposites. Creating and understanding chirality at the nanoscale (more than thousand times smaller than the thickness of a human hair), is critical for the use of materials in optical devices, to engineer materials not found in nature (metamaterials), for the characterization of large, complex biomolecules and to make novel sensors. To understand such chiral nanoscale materials one needs to detect, measure, visualize, and transfer nanoscale chirality. In this project, supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, the research team uses liquid crystals (commonly used in LCDs) to achieve these goals and to find their applications. Students will experience an interdisciplinary research-oriented environment, utilize state-of-the-art equipment, and become proficient in presenting their research to peers. Students also experience collaborative research by travelling oversees and working with colleagues in Europe. The project features several outreach activities including a scientific symposium and training of high school students from low-income households, hands-on lectures and lab research for high school and undergraduate students. Virtual reality will be also used to explore and visualize chiral nanomaterials. Technical AbstractMetal nanoparticles, or their atomic surfaces, can exhibit chirality by virtue of optical activity in metal-based electronic transitions. This chirality can be realized either by adsorption of chiral organic molecules, or by assembly of otherwise achiral or racemic nanoparticles in chiral environments. Transfer of chirality from an adsorbed molecule to a metal nanoparticle surface depends on the structure of the adsorbate and its interactions with the surrounding. This is often difficult to elucidate, and thus is the key focus of this project. The motivation for this research is to advance recent findings that chirality at the nanoscale is uniquely able to generate more intense responses in soft condensed matter systems such as liquid crystals than their organic molecular chiral counterparts. The research team utilizes several liquid crystal phases and materials as ideal constituents to detect, visualize, and tune chirality of nanoscale particles. To measure, tune, and visualize nanoscale chirality and apply the full potential of chiral nanomaterials, the research team focuses on the synthesis, characterization, and testing of chiral motif-functionalized metal nanoparticles differing in size and shape, and on nanoscale metal patterns functionalized with self-assembled monolayers of potent chiral molecules. The research also offers new prospects in nanoscale chiral induction and chirality transfer from various liquid crystal superstructures to achiral and racemic nanoparticles. Conversely, stabilization and induced optical activity will also be examined in the newly discovered twist-bend nematic phase. Combined, these chiral nanoscale materials serve as viable test platforms for applications ranging from chiral nanoscale sensors and tunable chiral metamaterials to chiral nanoscale inducers, discriminators, and catalysts.