Single molecule and single particle spectroelectrochemistry

光学方法的最新进展使得单分子检测的光谱技术得以发展。这些技术已被广泛用于揭示重要的机械方面，主要来自生物系统。例如，它们可以提供有关结合过程中蛋白质构象变化的信息，或有关单个物种跨细胞膜运输的信息。电化学过程是几种技术的核心，包括能源产生和储存（燃料电池和电池）。然后，可以探索提供电化学条件下表面过程分子图像的分析方法，以改进这些技术。然而，单分子技术很少应用于电化学过程的研究。在过去的几年里，我们的研究小组一直致力于开发金属纳米结构作为研究单分子表面过程的方便平台。通过系统的电化学和光谱响应（光谱电化学），可以控制这些纳米结构中的电位，并同时研究表面化学反应。金属体系的纳米尺度允许对单个分子的限制进行研究。这项发现基金的目标是利用这些进展来开发新的混合化学方法，重点是它们在单分子研究中的应用。该计划的一个方面将涉及来自带电界面的单分子表面增强拉曼散射（SM-SERS），这是我们小组首创的一项技术。将结合表面浓度的电化学测定，对SERS热点的性质和定量进行基础研究。这类信息将为确定SM水平上的动力学和热力学吸附特性提供基础。近场技术，如近场扫描光学显微镜（NSOM）和尖端增强拉曼散射（TERS），也将被用于研究固定在碳载体上的单纳米颗粒燃料电池催化剂（Au， Au- pt和Au- pd纳米颗粒）的电化学性能。从不同的簇的个别性质将导致更好地理解它们对催化剂的平均性质的影响。SM光谱电化学的第二种方法将涉及在金薄膜上应用纳米孔周期性阵列（PANH）作为纳米电极。只有孔内的体积是电化学上可以接触到的，所以，每个单独的孔都可以作为纳米电化学实验的小瓶。PANH电极将用于研究单个蛋白质的电化学动力学，并将成为单分子电化学研究的新平台。这里提出的研究将为电催化领域，特别是燃料电池领域的技术意义提供分子方面的基本见解。这些项目还将在单分子讯问设备上达到高潮，这些设备将被转化为生物医学应用，用于分析单个活细胞和神经化学。

Recent advances in optical methods have allowed the development of spectroscopic techniques for single molecule detection. These techniques have been widely used to unveil important mechanistic aspects, mainly from biological systems. For instance, they can provide information about the changes in protein conformation during binding or regarding the transport of individual species across cell membranes. Electrochemical processes are central to several technologies, including energy generation and storage (fuel cell and batteries). Analytical methods that provide a molecular picture of surface processes in electrochemical conditions could then be explored to improve those technologies. However, single molecules techniques have seldom been applied to study electrochemical processes. In the last few years, our research group has been engaged in the development of metallic nanostructures as convenient platforms to investigate single molecular surface processes. The electric potential in those nanostructures can be controlled and surface chemical reactions can be investigated simultaneously by the electrochemical and spectroscopic response of the system (spectroelectrochemistry). The nanometric dimensions of the metallic system allow the confinement of individual molecules for investigation. The goal of this discovery grant will be to use these advances to develop new hybrid chemical methods, with emphasis on their application in single molecule studies. One aspect of the program will be related to single molecule surface-enhanced Raman scattering (SM-SERS) from electrified interfaces, a technique pioneered by our group. Fundamental investigation of the nature and on the quantification of SERS hotspots will be carried out in combination with electrochemical determination of surface concentrations. This type of information will provide the basis for the determination of kinetics and thermodynamic adsorption properties at the SM level. Near field techniques, such as near-field scanning optical microscopy (NSOM) and tip-enhanced Raman scattering (TERS), will also be implemented to investigate electrochemical properties from single nanoparticle fuel cell catalyst (Au, Au-Pt and Au-Pd nanoparticles) immobilized in carbon supports. Individual properties from a variety of clusters will lead to a better understanding of their effect on the average property of the catalyst. A second approach to SM spectroelectrochemistry will involve the application of periodic array of nanoholes (PANH) in gold thin films as nanoelectrodes. Only the volume inside the holes will be electrochemically accessible, so, each individual hole will work as attoliter vials for nanoelectrochemistry experiments. The PANH electrodes will be used to study the electrochemistry dynamics of of single proteins and will became a new platform for single molecule electrochemistry studies.The research proposed here will then provide fundamental insights into molecular aspects of technological significance to the field of electrocatalysis, particularly for fuel cells. These projects will also culminate in devices for single molecule interrogation that will be translated to biomedical applications for the analysis of a single living cell and in neurochemistry.