Bayreuth 1998 – scientific programme
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CP: Chemische Physik
CP 19: Sondersymposium: Einzelmolekülspektroskopie
CP 19.3: Talk
Thursday, March 12, 1998, 14:40–15:00, H18
Single Molecule Detection of Dendrimers with a DPP (dihydropyrrolopyrrololedione) core — •J. Hofkeps1, R. Shukla1, W. Dehaen1, F. C. DeSchryver1, D. Hu2, Ji Yu2, and P. F. Barbara2 — 1Katholic University Leuven, Department of Chemistry, Celestijnenlaan 200 F, 3001 Heverlee Belgium — 2University of Minnesota, Department of Chemistry, Minneapolis, MN 55455, USA
Three generations of dendrimers with a fluorescent core were synthesized by attaching dendrons of the Fretchet type to a dihydropyrrolopyrroledione (DPP) molecule. By spincoating a toluene solution containing 2 × 10−9 M of the dendrimers and 3 mg/ml polystyrene (MW 45000) on a glass cover slip, samples consisting of a 30 nm thick polymer film containing a few dendrimers per square micrometer were obtained. By exciting near the absorption maximum of the dendrimeres (488 nm line of an argon laser) it was possible to image single dendrimers via a confocal microscope. By placing an electro-optical modulator in the excitation beam path, it was possible to modify the linear polarized excitation light into circular polarized light with a 1 Hz modulation frequency. Two APD‘s (avalanche photodiodes) and a polarizing beam splitter were placed into the detection path. In this way, by parking the laser beam on a single fluorescent spot of the previous acquired image and by following the fluorescence as a function of time, we were able to distinguish single molecules from small clusters. Furthermore, it was shown that the single molecules in the polymer films rotate.