Mapping the mesoscale structural landscape using "sculpted" chiral plasmonic fields

光谱学可以通过探测量子化状态来探测和表征单个分子的特性。它是一种无处不在的工具，在过去100年的许多新发现中发挥了重要作用。光谱学的应用非常广泛：它使天文学家能够探测到数光年外行星大气中的水；并使艺术史学家能够确定古代大师在画作中使用的颜料。鉴于光谱学方法的巨大成功，中尺度的表征仍然是一个尚未征服的领域。中尺度是介于分子（量子）和宏观（经典）世界之间的中间长度尺度（10-1000 nm）。长度尺度很重要，因为它占据了集体性质开始支配单个分子的范围。例如，它标志着从化学到生物学的过渡，当单个分子构建块自组装成复杂的生物结构时。由于中尺度分子集合是有效的经典体，因此没有可以用光谱探测的代表物体整体结构的量子化状态。光谱学范式的这种限制确实具有实际意义。例如，虽然利用光谱学可以很容易地检测（甚至实时监测）水和大气中的原子和分子污染物，但检测和描述未知病毒等中尺度分子组合可能需要大量的时间和资源；从而延长诊断和有效治疗的时间。在本提案中，我们希望通过使用手性倏逝电磁场而不是光来快速检测和表征中尺度分子结构，从而解开已建立的光谱学范式的束缚。当光从手性等离子体纳米结构散射时，在近场产生具有手性不对称（即手性）的倏逝电磁场。从本质上讲，近场是由纳米结构的几何形状雕刻出来的，并且充满了手性感。格拉斯哥小组首先证明了这些手性场的存在，并且它们可以具有增强的手性不对称性（称为超手性）（Nature Nano 2010）。本提案的目的是通过使用野生型和合成病毒作为模型系统，表明这些超手性场可以独特地表征中尺度分子结构。为了说明光谱学的潜力，将演示刺入生物流体的病毒的无标签检测。

Spectroscopy can detect and characterise the properties of individual molecules through probing quantised states. It is a ubiquitous tool which has been instrumental in many new discoveries over the last 100 years. The applications of spectroscopy are numerous and wide ranging: it allows astronomers to detect water in the atmospheres of planets light years away; and enables art historians to determine the pigments used by old masters in their paintings. Given the unmitigated successes of the spectroscopic method, characterisation of the mesoscale is still one area which remains unconquered. The mesoscale is the intermediate length scale (10-1000 nm) between the molecular (quantum) and the macroscopic (classical) worlds. The length scale is important because it occupies the range over which collective properties begin to dominate those of individual molecules. For instance, it marks the transition from chemistry to biology, when individual molecular building blocks self-assemble into complex biological architectures. Since mesoscale molecular assemblies are effectively classical bodies, there is no quantised state which is representative of the overall structure of the object that can be probed spectroscopically. This limitation of the optical spectroscopic paradigm does have practical implications. For instance, while atomic and molecular pollutants in water and the atmosphere can be readily detected (even monitored in real time) with spectroscopy, detecting and characterising a mesoscale molecular assembly such as an unknown virus can take a significant amounts of time and resource; thus extending time to diagnosis and effective treatment. In this proposal we wish to unlock the shackles of the established optical spectroscopic paradigm by using chiral evanescent electromagnetic fields, rather than light, to rapidly detect and characterise mesoscale molecular structure. When light scatters from chiral plasmonic nanostructures, evanescent EM fields are created in the near field which have a chiral asymmetry (i.e. handedness). In essence the near fields are sculpted by the geometry of the nanostructure, and are imbued with a sense of chirality. The Glasgow Group were the first to demonstrate the existence of these chiral fields, and that they could possess enhanced chiral asymmetry (referred to as superchirality) (Nature Nano 2010). The purpose of this proposal is to show that these superchiral fields can uniquely characterise mesoscale molecular structure, through the use of wild type and synthetic viruses as model systems. To illustrate the potential of the spectroscopy, label free detection of viruses spiked into a biofluid will be demonstrated.