Enabling Ultrasensitive Optical Measurements with Plasmonics

金属纳米结构在各种应用中取得了重大进展，从执行逻辑功能的光子设备、医学研究到更好地针对肿瘤进行进一步局部光热治疗、太阳能电池技术到高灵敏度光学传感器。电磁场，如限制在单个银或金纳米颗粒或一组相互作用的颗粒附近的激光，显示出依赖于纳米结构的光学几何性质的共振。在合适的实验条件下，这种局域共振的激发可以产生几个数量级的电磁场增强，这可用于超高灵敏度光学光谱。它在材料科学和生物材料中的应用是巨大的，提供了更高的空间分辨率和灵敏度，甚至可以检测到单个分子。这项研究计划旨在提供解决方案，以实现光学光谱学中的超高灵敏度测量，并围绕四个主要目标阐述：*(I)将使用尖端增强拉曼光谱对生物材料进行高空间分辨率振动光谱分析。我们将把重点放在DNA链上，并制定一种策略来更好地评估DNA链中的损伤。我们的设置提供了10纳米范围的分辨率，允许人们探测和操作组成DNA的几个碱基的序列。(2)将利用表面增强效应开发等离子体介导的神经细胞之间生物分子交换的检测。我们将通过等离子体传感器结合表面图案来指导细胞生长，从而能够探测细胞膜附近发生的化学和生化交换。荧光和拉曼增强将用于探测化学交换。(3)我们将制定战略，设计和优化中红外等离子体平台。为了在中红外光谱的宽光谱范围内产生较大的增强，我们将发展分形等离子体结构。由于等离子体平台的体积很小(通常为100x100微米)，使用加拿大光源处的明亮红外光源将对这些平台的研究具有重要价值。(4)最后，将研究等离子体结构中产生的非线性光学效应。非中心对称几何结构将导致较大的光学非线性，将由二次谐波产生显微镜来探测。最终，等离子体结构的手性也将是利用非线性效应进行手性传感的一个参数，在光学生物传感中打开了各种应用。该项目旨在提供纳米级成像的尖端方法，以探索最基本的细胞过程中涉及的化学和生化过程的亲密性质。**

Metallic nanostructures have enabled critical advances in a variety of applications ranging from photonic devices that perform a logical function, medical research to better target tumors for further localized photothermal treatment, solar cells technology to high sensitivity optical sensors. An electromagnetic field such as a laser light confined in the vicinity of a single silver or gold nanoparticle or an ensemble of interacting particles, displays resonances that are dependent on the opto-geometric properties of the nanostructure. Under the right experimental conditions, the excitation of such local resonance can yield enhancement of the electromagnetic field by several orders of magnitude which can be exploited for ultrahigh sensitivity optical spectroscopy. Its application in materials science and biomaterial is tremendous offering improved spatial resolution and sensitivity at a level down to the detection of a single molecule. This research program aims at providing solutions to enable ultrahigh sensitivity measurements in optical spectroscopy and is articulated along four principal objectives:****(i) High spatial resolution vibrational spectroscopy of biomaterials using tip-enhanced Raman spectroscopy will be conducted. We will focus on DNA strands and develop a strategy to better evaluate lesions in DNA strands. Our setup offers a resolution in the 10 nm range allowing one to probe and manipulate a sequence of a few bases that compose the DNA. (ii) Plasmon mediated detection of biomolecular exchanges between neuronal cells will be developed using surface-enhanced effects. We will combine surface patterning to direct cell growth over plasmonic sensor enabling to probe chemical and biochemical exchanges occurring in the vicinity of the cell membrane. Fluorescence and Raman enhancements will be used to probe chemical exchanges. (iii) We will develop strategies to design and optimize mid-infrared plasmonics platforms. To yield a large enhancement over a wide spectral domain in the mid-IR we will develop fractal plasmonic structures. Because of the small size (typically 100x100 micron square) of the plasmonic platform, the use of a bright infrared source such as the one accessible at the Canadian Light Source will be of great value for the study of these platforms. (iv) Finally, nonlinear optical effects generated in plasmonic structures will be conducted. Non-centrosymmetric geometries should lead to large optical nonlinearities will be probed by second-harmonic generation microscopy. Ultimately the chirality of the plasmonic structure will also be a parameter that will be valued for chiral sensing using nonlinear effects opening a variety of applications in optical biosensing.This program aims at providing cutting-edge approaches in nanoscale imaging to probe the intimate nature of chemical and biochemical processes involved in the most basic cellular processes. **