Detection of a Single Dendrimer Macromolecule with a Fluorescent Dihydropyrrolopyrroledione (DPP) Core Embedded in a Thin Polystyrene Polymer Film

Abstract

Three generations of dendrimers with a fluorescent core were synthesized by attaching dendrons of the Fréchet type to a dihydropyrrolopyrroledione (DPP) molecule. Samples were prepared by spin-coating a toluene solution containing 2 × 10-9 M of the dendrimers and 3 mg/mL polystyrene (MW 45 000) on a glass cover slip. By exciting near the absorption maximum of the chromophore in the dendrimer, single dendrimer molecules could be imaged via a confocal microscope. Using an electrooptical modulator (EOM) in the excitation beam path, linear polarized light with a slowly rotating polarization direction (1 Hz modulation frequency) was produced. Two APD's (avalanche photodiodes) and a polarizing beam splitter were placed in the detection path. In this way we were able to distinguish single molecules from small clusters. Furthermore, from variations of the two detected intensities and from the phase shift of the signal with respect to the modulation, it was shown that the orientation of the absorption transition dipole of single dendrimer molecules in the polymer film changes in a time window of seconds.

Revealing competitive Förster-type resonance energy-transfer pathways in single bichromophoric molecules

“…Atomic force microscopy measurements showed a film thickness between 200 and 300 nm. The confocal fluorescence microscope that works in the epiluminescence mode is described elsewhere in more detail (15). As excitation light we used the 488-nm line of a continuous-wave argon ion laser (Stabilite, Spectra-Physics) or the frequency-doubled output of a Ti-Sapphire laser (Tsunami, Spectra-Physics, 8.18 MHz and 1.2 ps full-width, halfmaximum).…”

Single-molecule orientations determined by direct emission pattern imaging

“…Examples are excited-state lifetimes, 3 emission intensity, and energy-transfer rates between molecules. Furthermore, the dipole orientation can be used as a probe for the molecule's photophysics, 4,5 for the properties of its environment, 6 and-most important for molecular biology-for the structure and dynamics of dye-labeled macromolecules. 7 In the past, different methods have been developed to determine either the two-dimensional projection or the full three-dimensional (3D) orientation of the absorptionemission transition dipole moment.…”

New photoluminescent conjugated polymers with 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) and 1,4-phenylene units in the main chain

“…While low molecular weight derivatives of DPP have been extensively studied on their optical and photophysical properties [3][4][5][6] , relatively little is known about DPP-containing polymers and their materials properties. As yet only few publications 7,8) and patents 9, 10) on DPP-polymers appeared. Recently photoluminescent aliphatic copolyesters and copolyurethanes with DPP units in the main chain were described 7) , and dendrimers with photoluminescent DPP core were reported 8) .…”

“…As yet only few publications 7,8) and patents 9, 10) on DPP-polymers appeared. Recently photoluminescent aliphatic copolyesters and copolyurethanes with DPP units in the main chain were described 7) , and dendrimers with photoluminescent DPP core were reported 8) . As these studies indicate, the presence of DPP induces highly fluorescent properties in the polymers.…”