Single molecule and single particle spectroelectrochemistry

点击翻译按钮获取中文摘要

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.