Superchiral Light Generation on Achiral Substrates for High Sensitive Detection of Chiral Molecules

手性是一种无处不在的生命属性，存在于从左旋氨基酸到右旋葡萄糖的许多生物系统中。它给DNA、蛋白质等带来了固有的手性，但由于无法获得精确的表征技术，至今仍未被探索。这些手性生物分子可以存在于两手对称结构中，具有难以区分的物理性质，如密度、分子质量或电子和振动跃迁频率，使得它们几乎不可能用常见的光谱技术来区分。这里提出了一种独特的非手征等离子体表面，其性能优于以往的方法。在初步工作中，手性分子的检测灵敏度比传统技术高出四个数量级，但不需要广泛而繁琐的样品制备，而且样品体积小得多。手性分子的药理学和毒理学表征在制药行业和FDA的批准过程中起着至关重要的作用。拟议的项目还将用于培训研究生纳米光刻和器件制造。基于这些属性，提出的新型分子手性检测方案具有很高的商业潜力，并可能在不久的将来成为现实世界的传感技术。技术：所提出的独特的腔耦合非手性等离子体表面在以下方面优于以往的方法：它没有几何手性，因此没有来自衬底的手性信号；它在暴露于目标分析物的上表面产生强烈的近场；近场是100%的单手手性和反手，仅依赖于同一衬底上的激发手性。由于简并等离子体和光子腔模之间的相干相互作用，这种独特的超手征近场产生机制是可能的。与以前的任何尝试相比，这些属性是独一无二的，在这些尝试中，不均匀的手性近场和结构CD减弱了来自分子的手性信号。在初步研究中，通过表面增强的振动圆二色谱证明了手性光与物质的相互作用，与传统的体积CD(VCD)技术相比，检测灵敏度提高了大约四个数量级。所提出的系统将允许有效的手性-光物质相互作用，用于检测与药物筛选相关的MIR域中的振动分子手性。与以前需要两个手性相反的独立手性底物的演示不同，这项工作承诺在单个非手性等离子体底物上进行手性近场相互作用，为表面增强手性光谱铺平道路。该项目的主要重点将是利用我们的非手性等离子体底物开发一种灵敏的手性化合物识别技术。该系统将以具有重要药理意义的手性药物化合物为基准，如布洛芬、沙利度胺、心得安、沙丁胺醇和异氟醚。这些手性化合物将使我们能够开始对该系统进行表征，并将进一步扩展。对映体的药理学和毒理学表征在制药行业和FDA的批准过程中起着至关重要的作用。因此，仍然迫切需要高效、准确和廉价的对映体检测。我们坚信，拟议的研究将使我们能够克服之前的一些挑战，使我们能够开发出低成本、高通量、高灵敏度的手性分子检测技术。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Chirality is a ubiquitous property of life, found at many levels of biological systems from left-handed amino acids to right-handed glucose. It gives rise to the inherent chirality to DNAs, proteins and more, which remained hitherto unexplored due to the unavailability of precise characterization techniques. These chiral biomolecules can be present in both handed symmetries with undistinguishable physical properties, such as density, molecular weight or electronic and vibrational transitions frequencies making them almost impossible to differentiate with common spectroscopic techniques. Here a unique achiral plasmonic surface is proposed, which outperforms previous approaches. In the preliminary work chiral molecule detection sensitivity that is four orders of magnitude higher compared to the conventional technique, but without the extensive and tedious sample preparation and at much lower sample volume, is demonstrated. Pharmacological and toxicological characterization of chiral molecules plays a crucial role in the pharmaceutical drug industry and FDA approval process. The proposed project will also serve to train graduate students in nanolithography and device fabrication. Based on these attributes the proposed novel molecular chirality detection scheme has high potential to generate commercial interests and can become real world sensing technique in near future.Technical: The proposed unique cavity-coupled achiral plasmonic surface outperforms previous approaches in the following aspects: It does not have geometrical chirality, hence no chiral signal from the substrate; It creates strong near-fields on the upper surface exposed to the target analyte; The near-field is 100% single-handed chiral and flip handedness depending only on the excitation handedness on the same substrate. Such a unique mechanism of superchiral near-field generation is possible due to the coherent interaction between degenerate plasmonic and photonic cavity modes. These attributes are exclusive compared to any previous attempts where inhomogeneous chiral near-field and structural CD diminishes chiral signal from molecules. In the preliminary studies, chiral light-matter interaction through surface enhanced vibrational circular dichroism with about four orders of magnitude enhancement in detection sensitivity compared to conventional volumetric CD (VCD) technique is demonstrated. The proposed system will permit efficient chiral-light matter interactions for the detection of vibrational molecular chirality in the MIR domain relevant for drug screening. Unlike previous demonstrations where two independent chiral substrates with opposite handedness were needed, the proposed work promises chiral near-field interaction on a single achiral plasmonic substrate paving the path towards surface enhanced chiroptical spectroscopy.The main focus of the project will be to develop a sensitive chiral compound identification technique using our achiral plasmonic substrates. The system will be benchmarked with pharmacologically significant chiral drug compounds like Ibuprofen, Thalidomide, propranolol, Albuterol, and Isoflurane. These chiral compounds will allow us to start the characterization of the system and will further expand. The pharmacological and toxicological characterization of enantiomers plays a crucial role in the pharmaceutical drug industry and FDA approval process. Therefore, there is still an active need for efficient enantiomer detection, precisely and cheaply. We strongly believe that the proposed research will allow us to overcome some of the previous challenges and enable us to develop a low cost, high throughput, high sensitive chiral molecule detection technique.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.