Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 19: Poster: New Methods, Thin Polymer Films, Monolayers
CPP 19.15: Poster
Donnerstag, 5. April 2001, 12:30–15:00, AT1
Fluorescence Correlation Spectroscopy as a Tool to investigate Single Molecule Probe Dynamics in Thin Polymer Films — •Alain Casoli and Monika Schönhoff — Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam/Golm
Fluorescence correlation experiments are performed on rhodamine 6G in PDMS spin coated films on glass surfaces. From the statistics of single molecule intensity fluctuations taken at different positions in the film, correlation functions are calculated. Two modes of motions with exponentially decaying shapes and correlation times of τc = 0.15 s and τc = 0.7 s are detected. Potential origins of intensity fluctuations are lateral diffusion, rotational diffusion or intramolecular fluctuations of dyes involving spectral diffusion or photo- induced processes. From the experimental results, lateral diffusion is ruled out as a motional mode. Single molecule fluctuations are assigned to changes of the molecular configuration of the dyes, which are rigidly bound to the glass. To assess the environmental influence on such molecular motions, the bulk viscosity of the PDMS is varied over two orders of magnitude leading to changes of tc of the slow mode by a factor of four. This proves the sensitivity of the single molecule fluctuations to the molecular scale dynamics of the surrounding polymer matrix and makes the correlation time a measure of the local environment of dye probes.