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

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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.