Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 89: Inorganic/Organic Interfaces: Molecular Switches

O 89.4: Talk

Thursday, March 19, 2015, 15:45–16:00, MA 043

Probing the Photostationary State of Photochromic SAMs by Two-Photon Photoemission Spectroscopy — •Wibke Bronsch, Daniel Przyrembel, Cornelius Gahl, and Martin Weinelt — Freie Universität, Berlin, Deutschland

In densely packed monolayers of azobenzene derivatives, trans-cis photoisomerization is strongly suppressed due to electronic and steric interaction among the chromophores [1]. Mixing and thus diluting an azobenzene derivative with an alkanethiol of appropriate chain length allows tuning the free volume around the chromophores in the SAM and thereby controlling their interactions. We investigate optical switching in SAMs of azobenzene-decorated undecane thiol diluted with dodecanethiol on Au(111) by means of two-photon photoemission (2PPE) spectroscopy. Along with changes in the electronic structure, we observe a pronounced isomerization-induced shift of the work function up to 250 meV. In order to tune the photostationary state between predominantly trans and cis we vary the intensity ratio of femtosecond UV pulses and a 450 nm continuous-wave laser.

[1] C. Gahl, R. Schmidt, D. Brete, E. R. McNellis, W. Freyer, R. Carley, K. Reuter, and M. Weinelt, J. Am. Chem. Soc. 132, 1831 (2010).