Hamburg 2009 – scientific programme
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SYSM: Single Molecule Spectroscopy of Nanoobjects
SYSM 3: Single Molecule Spectroscopy of Nanoobjects III
SYSM 3.1: Invited Talk
Thursday, March 5, 2009, 16:30–17:10, VMP 8 HS
Fluorophores as optical sensors for local forces — •Stefan Marawske1, Denis Dörr1, Daniel Schmitz2, Axel Koslowski3, You Lu3, Helmut Ritter2, Walter Thiel3, Claus A.M. Seidel1, and Ralf Kühnemuth1 — 1Department of Molecular Physical Chemistry, Heinrich-Heine-University Düsseldorf — 2Department of Organic and Macromolecular Chemistry, Heinrich-Heine-University Düsseldorf — 3Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr
In this work we designed a custom-tailored oligopara*phenylenevinylene (OPV) derivative, which according to previous theoretical studies was expected to show a significant change in geometry if an external force is exerted. Thin foils made of PVC stained with OPV have been prepared. By applying uniaxial force the foils were stretched. Three major optical effects were observed simultaneously. At first, the fluorescence anisotropy increased, which indicates a reorientation of the fluorophores within the matrix. Second, the fluorescence lifetime decreased by approximately 2.5 %. Finally we observed a blue shift in the emission spectrum by about 1.2 nm. To relate the observed spectroscopic changes to the underlying changes in molecular properties, quantum-chemical calculations have been performed. Both the observed blue-shift of fluorescence and the reduced lifetime of OPV under tensile stress are consistent with the results of the semiempirical calculations. Our study proves the feasibility of fluorescence-based local force probes for polymers under tension.