Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Molecular Electronics and Photonics
CPP 18.3: Vortrag
Dienstag, 8. März 2016, 10:00–10:15, H42
Controlling position and orientation of molecules in a thin plastic film — •Felix Hofmann1, Dominik Würsch1, Vikas Aggarwal2, Stefan-S. Jester2, Jan Vogelsang1, Sigurd Höger2, and John Lupton1 — 1University of Regensburg, Regensburg, Germany — 2University of Bonn, Bonn, Germany
For many single-molecule applications it is mandatory to embed the molecules under investigation in non-fluorescent host matrices. Single molecule spectroscopy was used to determine the position and orientation of molecules utilizing a monodisperse ring-shaped model system with a high triplet yield. The triplet state can be easily depopulated under ambient conditions for molecules close to the surface, but remains partly unquenched inside the film. Therefore, the fluorescence intensity serves as an observable for the spatial distribution of the molecules inside the film. The ring-shaped structure of the molecule together with excitation polarization spectroscopy reveals the orientation of the molecule with respect to the sample plane. A low modulation in intensity upon rotation of the polarisation of the laser indicates a molecule oriented flat with respect to the sample plane whereas a high modulation means that it is oriented perpendicularly to the sample plane. As an additional step in sample preparation, solvent vapor annealing enables diffusion of the molecules within the host matrix. This is achieved by applying a constant flow of solvent-saturated nitrogen to the sample, which lowers the glass transition temperature of the film. We found that after this additional treatment, all molecules lie flat with respect to the surface close to the plastic/air interface.