Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 89: Inorganic/Organic Interfaces: Molecular Switches
O 89.3: Talk
Thursday, March 19, 2015, 15:30–15:45, MA 043
Azobenzene based self-assembled monolayers as a means to control the work function — •Swen Schuster1, Musammir Khan1, Piotr Cyganik2, Andreas Terfort3, and Michael Zharnikov1 — 1Applied Physical Chemistry, Heidelberg University, 69120 Heidelberg, Germany — 2Smoluchowski Institute of Physics, Jagiellonian University, 30-059 Krakow, Poland — 3Institute for Inorganic and Analytical Chemistry, Frankfurt University, 60438 Frankfurt, Germany
Controlled adjustment of the work function of surfaces and interfaces by external stimuli is a challenging task. In this context we designed novel photoresponsive, azobenzene-based self-assembled monolayers (SAMs) bearing dipolar functional groups, even though the first experiments were performed on the non-substituted films. To monitor and partly relax the steric constraints upon the photoisomerization we introduced an aliphatic linker of variable parity between the azobenzene unit and the head group, relying on the odd-even effect in the monomolecular assembly. The variation of the packing density was found to be ca. 10% only, which appeared to be insufficient to avoid the steric constraints to the necessary extent. Consequently, photoinduced variation of the work function did not exceed 50 meV, independent of the parity of the aliphatic linker. To improve the photoresponsive properties, the azobenzene-based moieties were diluted with other, short molecules to create sufficient space for isomerization. A clear improvement of the photoisomerization behavior was found, correlated with both the extent of the dilution and the identity of the short molecules.