AVS 62nd International Symposium & Exhibition
    In-Situ Spectroscopy and Microscopy Focus Topic Wednesday Sessions
       Session IS+AS+SA+SS-WeM

Paper IS+AS+SA+SS-WeM3
Isomerization of One Molecule Observed through Tip-Enhanced Raman Spectroscopy: Azobenzene Thiol on Au(111)

Wednesday, October 21, 2015, 8:40 am, Room 211C

Session: In-situ Studies Using X-ray Absorption Spectroscopy and Vibrational Spectroscopy for Catalytic and Energy Materials
Presenter: Joonhee Lee, University of California, Irvine
Authors: J. Lee, University of California, Irvine
N. Tallarida, University of California, Irvine
L. Rios, University of California, Irvine
V.A. Apkarian, University of California, Irvine
Correspondent: Click to Email
The reversible cis-trans isomerization of a single azobenzene thiol (ABT) molecule is captured in tip-enhanced Raman trajectories in which the anti-correlated flip-flop between discrete, on and off-states of the two structural isomers is seen. The strongly blue-shifted spectra are recorded from a molecule that appears at the junction plasmon of a scanning tunneling microscope (STM), consisting of an atomically flat Au(111) surface and a silver tip. The variation in frequencies of switching events identifies heterogeneously photocatalyzed chemistry. The chemisorbed ensemble of ABT molecules lie flat on Au(111) surface with azobenzene headgroup strongly coupled to the surface. Nevertheless, we establish through STM imaging that the ABT molecules undergo both current driven and photoinduced cis-trans isomerization. Rather than decoupling from the surface, we suggest that strong coupling of the reaction coordinate to a vibrational energy sink is required for cis-trans isomerization of azobenzenes on metal surfaces.