Bowling Green State University, Department of Chemistry, Center for Photochemical Sciences, Bowling Green, OH 43403; *hplu@bgsu.edu Single-molecule redox reaction dynamics1 of Hemin (Chloride) adsorbed on Ag nanoparticle surfaces has been probed by single-molecule surface-enhanced Raman spectroscopy (SMSERS) combined with spectroelectrochemistry.2 Redox reaction at the molecule/Ag interface is identified and probed by the prominent fluctuations of the Raman frequency of a specific vibrational mode ν4, which is a typical marker of the redox state of the Iron center in a Hemin molecule. The spontaneous fluctuation dynamics of the single-molecule redox reaction is measured under no external potential across the molecule-metal interfaces, which provides a novel and unique approach to characterize the interfacial electron transfer at the molecule-metal interfaces. We have also probed single surface states and the involved interfacial charge transfer coupling on the TiO2 surface using a tip-enhanced near-field topographic-spectroscopic imaging analysis on a Niobium-doped rutile TiO2 (110) surface.3,4 The nanoscale optical images of single surface states are visualized by the strong exciton plasmon-polariton coupling localized at the sub-domain boundaries with a spatial resolution of ~ 15 nm (far beyond the optical diffraction limit). We suggest that the abundant surface states in the doped TiO2 generate excitons under laser excitation which are strongly coupled to the surface plasmon-polaritons of the Au tip. Our demonstrated approaches are powerful for obtaining molecular electronic coupling and dynamics involving in interfacial electron transfer processes. Reference: Vishal Govind Rao, Bharat Dhital, Yufan He, H. Peter Lu, " Single-Molecule Interfacial Electron Transfer Dynamics of Porphyrin on TiO2 Nanoparticles: Dissecting the Complex Electronic Coupling Dependent Dynamics," J. Phys. Chem. C., 118, 20209-20221 (2014). Yuanmin Wang, Papatya C. Sevinc, Yufan He, H. Peter Lu, "Probing Ground-State Single-Electron Self-Exchange Across a Molecule-Metal Interface," J. Am. Chem. Soc., 133, 6989-6996 (2011). Sevinc, Papatya; Wang, Xiao; Wang, Yuanmin; Zhang, Dai; Meixner, Alfred; Lu, H. Peter, "Simultaneous Spectroscopic and Topographic Near-Field Imaging of TiO2 Single Surface States and Interfacial Electronic Coupling," Nano Letters, 1490-1494 (2011).

Probing ground-state single-electron self-exchange across a molecule-metal interface and molecule-substrate electronic coupling by simultaneous spectroscopic and topographic Near-field SERS Imaging

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.