Intensity Fluctuations in Single Molecule Surface-Enhanced Raman Scattering

单分子表面增强拉曼散射中的强度波动

• 批准号: RGPIN-2020-04236
• 负责人: Brolo, Alexandre
• 金额: $ 5.76万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=747799
• 关键词: Intensity; Fluctuations; Single; Molecule; Surface

Surface-enhanced Raman scattering (SERS) is a highly sensitive vibrational spectroscopy technique capable of providing unique molecular fingerprinting information. SERS is observed for molecules adsorbed on certain areas of nanostructured metallic surfaces known as SERS hotspots. The tightly focussed light at the hotspots allows even the detection of single individual molecules by Raman scattering. Experimentally, the single molecule signature consists of strong time- (or space-) dependent SERS intensity fluctuations (SIFs). Although the phenomenon of single-molecule SERS (SM-SERS) has been demonstrated more than 20 years ago, there were very few examples of actual uses of SM-SERS to either acquire fundamental information about the hotspot environment or for chemical applications, such as in analytical chemistry. The long term goal of our Discovery program is to lead the SERS field to a new direction that takes into consideration the statistics of single particle, single molecule and even single photon events. This new approach will lead to several interesting new insights and potential new applications. In order to achieve this long term goal, we propose the application of a new technology for the study of SIFs with high spatial and time resolution. In the short term, this new method will be used to follow dynamic processes at the hotspot that have remained hidden due to the notorious low acquisition rate (~ 1 Hz) typically used in a regular SERS measurements. Experiments will be realized at different temperatures, allowing, for instance, the quantification of the energetics of fundamental processes, such as metallic cluster reconstruction at the hotspot area. A systematic investigation of the role of several factors, such as the nature of the metal, the geometric characteristics of the nanometric environment at the hotspot region, and the molecular affinity to the metallic surface, will be investigated. The overall goal in the short term will be to extract fundamental information about the metal-molecule interaction at the hotspot that was not accessible before. The analysis of the frequencies of the fast fluctuations will be used to generate an alternative approach in SERS quantification. Although SERS is a very sensitive method, its application in analytical chemistry has been hampered by intrinsic intensity fluctuations that translate into large errors in analytical calibration curves. We suggest that, for very low concentrations, SIF frequencies might correlate well (less variations) with the concentration of a given analyte in solution. Finally, we will be able to combine SM-SERS measurements with high-speed acquisition to investigate single photons emitted by single molecules.

表面增强的拉曼散射（SERS）是一种高度敏感的振动光谱技术，能够提供独特的分子指纹信息。观察到在被称为SERS热点的纳米结构金属表面的某些区域吸附的分子。热点处的紧密聚焦光甚至可以通过拉曼散射检测单个分子。在实验上，单分子的特征由强时（或空间）依赖的SER强度波动（SIF）组成。尽管已在20年前证明了单分子SER（SM-SERS）的现象，但很少有SM-SER的实际用途的例子来获取有关热点环境或化学应用的基本信息，例如在分析化学中。 我们发现程序的长期目标是将SERS字段带到一个新的方向，该方向考虑了单个粒子，单分子甚至单个光子事件的统计数据。这种新方法将导致一些有趣的新见解和潜在的新应用程序。为了实现这一长期目标，我们建议将新技术应用于具有高空间和时间分辨率的SIF研究。在短期内，这种新方法将用于遵循热点处的动态过程，由于臭名昭著的低采集率（〜1 Hz），该过程一直隐藏，通常在常规SERS测量中使用。实验将在不同的温度下实现，例如，允许对基本过程的能量学定量，例如热点区域的金属簇重建。将研究多种因素的作用的系统研究，例如金属的性质，热点区域的纳米环境的几何特征以及对金属表面的分子亲和力。短期内的总体目标是提取有关以前无法访问的热点的金属分子相互作用的基本信息。 对快速波动的频率的分析将用于在SERS定量中生成另一种方法。尽管SERS是一种非常敏感的方法，但其在分析化学中的应用受到内在强度波动的阻碍，这些波动转化为分析校准曲线中的较大误差。我们建议，对于非常低的浓度，SIF频率可能与溶液中给定分析物的浓度良好（较少的变化）相关。最后，我们将能够将SM-SERS测量结果与高速获取相结合，以研究单分子发出的单个光子。