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O: Fachverband Oberflächenphysik
O 56: Metal substrates: Adsorption of organic / bio molecules VI
O 56.5: Talk
Wednesday, March 24, 2010, 16:00–16:15, H36
Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy — •Felix Leyssner1, Steffen Wagner1, Christian Kördel1, Sebastian Zarwell2, Karola Rück-Braun2, Martin Wolf1, and Petra Tegeder1 — 1Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195 Berlin — 2Technische Universität Berlin, Institut für Chemie, Strasse des 17. Juni 135, D-10623 Berlin
We studied the reversible photoinduced trans/cis-isomerization of an azobenzene-functionalized self-assembled monolayer on a gold substrate using sum-frequency generation (SFG) vibrational spectroscopy. A cyano-group in para-position at the outer phenyl-ring is utilized as a marker to directly investigate the molecular orientation and therefore the switching state. The azobenzene unit is connected to a tripodal linker system with an adamantane core. This linker system provides: i) an adequate free volume to prevent steric hindrance and ii) sufficient decoupling from the metallic substrate to enable the isomerization process. Light exposure at a wavelength of 405 nm induces the trans → cis isomerization whereas illumination at 470 nm leads to the back reaction. The effective cross section for the photoinduced trans → cis reaction at 405 nm is σeff(cis) = 4± 1× 10−18cm2, while for the back reaction (cis → trans) at 470 nm we obtain σeff(trans) = 2.5± 0.9× 10−19cm2. Our study demonstrates that SFG vibrational spectroscopy is a highly suitable technique to analyze the molecular structure of functional surfaces.