Plenarvorträge - DPG-Tagungen

Chemische Physik und Polymerphysik Dienstag
CPP 16.6 Di 17:00 B
Photogeneration of charge carriers in blends of conjugated
polymers and semiconducing nanoparticles — •Johannes
Sieger 1 , Michael Pientka 1 , Jürgen Parisi 1 , Vladimir
Dyakonov 1 , Andrey Rogach 2 , Dimitri Talapin 3 , and Horst
Weller 3 — 1 Institute of Physics, Energy and Semiconductor Research,
University of Oldenburg, 26111 Oldenburg, Germany — 2 LMU Munich,
Photonics and Optoelectronics, 80799 Munich — 3 Physical Chemistry,
University of Hamburg, 20146 Hamburg
We investigated photoinduced charge transfer reactions in blends of
CdSe, InP nanoparticles with conjugated polymer OC1C10-PPV. The
particle size was in the range 3.1nm-4.1nm. They were capped with a
HDA-TOPO TOP shell and pyridine washed. Photoinduced absorption
spectroscopy (PIA) reveals structured features which are attributed to
photoexcited polaronic states on the polymer chain. Additionally the
photoluminescence in the blends is strongly quenched. We find a broad
distribution of lifetimes and a nearly square root behaviour in the laser
intensity dependence which altogether is characteristic for dispersive recombination.
The temperature dependence of the PIA signal shows an
unusual increase from low temperature up to 300K. By applying light
induced electron spin resonance the charge transfer process between the
polymer and the nanoparticles is confirmed by determining the g- factor
of the polaronic anion of the polymer.
CPP 16.7 Di 17:00 B
Oberflächenstruktur- und Verstärkungseigenschaften von Carbon
Black — •Gerald Schneider, Antje Bergmann, Tobias
Pöpperl, Ulrich Schwenk, Andreas Weigert und Dietmar
Göritz — Institut für Physik, Universität Regensburg, 93040 Regensburg
Die Oberfläche von Carbon Black besteht aus Nanokristallen, die
aus drei bis vier graphitähnlichen Schichten mit den Abmessungen von
2 nm × 2 nm aufgebaut sind. Beim Prozess der Graphitierung, dem
Tempern bei 2700 ◦ C, wachsen die Nanokristalle zu ausgedehnten Graphitebenen
zusammen und die verstärkende Wirkung des Carbon Black
nimmt ab. Mit den Methoden der Rastertunnelmikroskopie und der
Röntgenkleinwinkelstreuung werden die Größe und die Anordnung der
Nanokristalle auf der Oberfäche verfolgt. Die Ergebnisse werden im Vergleich
zu Daten, gewonnen an Carbon Blacks unterschiedlicher Aktivität,
im Bezug auf ihren Verstärkungsmechanismus diskutiert.
CPP 16.8 Di 17:00 B
Nanoparticle superstructures in carbonaceous matrix upon ion
irradiation of polymer-metal nanocomposites — •Oral Cenk
Aktas 1 , Abhijit Biswas 1 , Devesh Kumar Avasthi 2 , Dietmar
Fink 3 , Jörn Kanzow 1 , Ulrich Schürmann 1 , Usman Saeed 1 ,
Vladimir Zaporojtchenko 1 , and Franz Faupel 1 — 1 Lehrstuhl
für Materialverbunde, Technische Fakultät der CAU, Kaiserstr. 2, D -
24143, Kiel, Germany — 2 Nuclear Science Centre, New Delhi - 110067,
India — 3 Hahn-Meitner-Institut, Glienicker Str. 100, D - 14109, Berlin,
Germany
Nanoparticle re-arrangement is observed upon 120 MeV Au ion beam
irradiation of nanocomposites (ca. 100 nm) of Teflon AF containing different
metallic clusters at ion fluences ranging from 1 x 10 11 ions/cm 2 to
3 x 10 12 ions/cm 2 . Two dimensionally distributed Au clusters are found
to be transformed into long cluster chains of seemingly helical pattern in
the organic matrix like pearls on a string. Comparatively diluted three
dimensionally arranged Ag nanoparticles are observed to be concentrated
in the formed mesh of carbon-enriched nanoregions upon irradiation. Diffusionally
moving clusters are assumed to be trapped in the ion beam
induced additional free volume leading to different nanostructures.
CPP 16.9 Di 17:00 B
Size-dependent Assembly and Segregation of Nanoparticles at
Liquid-liquid Interfaces — •Heiko Zettl 1 , Yao Lin 2 , Alexander
Böker 2 , Habib Skaff 2 , David Cookson 3 , A.D. Dinsmore 4 ,
Todd Emrick 2 , Georg Krausch 1 , and Thomas P. Russell 2 —
1 Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth, Germany
— 2 Department of Polymer Science and Engineering, University of
Massachusetts, Amherst, MA 01003, USA — 3 Advanced Photon Source,
Argonne National Laboratory, Argonne, IL 60439, USA and Australian
Nuclear Science and Technology Organization, PMB 1, Menai 2234, Australia
— 4 Department of Physics, University of Massachusetts, Amherst,
MA 01003, USA
The self-assembly of nanoparticles at fluid-fluid interfaces driven by
the reduction in interfacial energy was investigated. With nanoparticles
(2–6nm), thermal fluctuations compete with the interfacial segregation
giving rise to a size-dependent self-assembly of the nanoparticles and a
two-dimensional phase separation at the fluid interface. Studies on the
dynamics of the nanoparticles and the self-assembled structures formed
at the interface, using a pendant drop tensiometer, fluorescence photobleaching
methods and in-situ grazing incidence small angle x-ray scattering
(GISAXS), suggest a liquid-like behavior and ordering at the interfaces.
CPP 16.10 Di 17:00 B
Single Molecule Spectroscopy of Supramolecular Dye Assemblies
— •Erwin Lang 1 , Rainer Dobrawa 2 , Armin Sautter 2 ,
Frank Würthner 2 , and Jürgen Köhler 1 — 1 Experimental Physics
IV, University of Bayreuth — 2 Institute for Organic Chemistry, University
of Würzburg
Self-assembly processes of atoms and small molecules lead to
supramolecular structures with unbelievable variety and complex
functionality. One of the most intriguing examples in nature is the
light-harvesting system of purple bacteria, where bacteriochlorophyll
dyes are arranged in concentric rings by non-covalent interactions within
a self-assembled protein scaffold. As a model system for self-assembly
processes we study four pyridine-substituted perylene bisimide dyes and
four cis-Pt(II) metal centres, which form supramolecular squares by
metal-ion-directed coordination of the dye molecules.
In order to suppress inhomogenous line-broadening effects and to characterize
the mutual interactions between the subunits we apply singlemolecule
spectroscopic techniques. We present fluorescence-excitation
spectra of individual perylene bisimide dyes and preliminary studies of
individual multichromophoric perylene bisimide assemblies at low temperatures.
CPP 16.11 Di 17:00 B
Optical absorption of dendrimers — •Christoph Supritz, Andreas
Engelmann, and Peter Reineker — Department of Theoretical
Physics, University of Ulm, 89069 Ulm
Dendrimers are highly branched molecules, which are expected to be
useful for example as efficient artificial light harvesting systems in nanotechnological
applications. There exist two different classes of dendrimers:
compact dendrimers in which the distance between neighbouring branching
points is constant throughout the macromolecule and extended dendrimers,
where this distance increases from the system periphery to the
center. We investigate the linear absorption spectra of these dendrimer
types using the Frenkel exciton concept. To investigate the influence of
static disorder, we have chosen the localized exciton energies to be randomly
distributed. In our calculations we have taken the electron-phonon
interaction into account by introducing a heath bath, that interacts with
the exciton in a stochastic manner.
CPP 16.12 Di 17:00 B
Hydrogen Bonds and Molecule Trapping in Calix[4]hydroquinone
Nanotubes Investigated by Solid-State MAS NMR — •Anke
Hoffmann, Daniel Sebastiani, Erli Sugiono, Hans Wolfgang
Spiess, and Ingo Schnell — Max Planck Institut fuer
Polymerforschung, Postfach 3148, 55021 Mainz, Germany
Recent progress in solid-state NMR has opened up new possibilities for
investigations of supramolecular order phenomena. We use these methods
to study nanotubes built from calix[4]hydroquinones in the course of
a self-assembly process. In presence of water the bowl-shaped molecules
form the tubular structure via chains of hydrogen bonds, in which bridging
water molecules are inserted between hydroxyl groups of the hydroquinone
moieties. In the crystallites, these tubes form bundles with intertubular
aromatic-aromatic interactions (displaced π-π stacking pairs)
in chessboard like arrays of rectangular structure. The structure of the
hydrogen bonds and the localisation of aromatic π-electron systems as
well as the dynamics of solvent molecules trapped in the tubes are characterised
by 1H and 2H solid-state NMR experiments. The assignment
and interpretation of the 1H resonance frequencies is aided by 1H shift
calculations under periodic boundary conditions performed in the framework
of DFT. Future work will focus on the inclusion of metal ions as
well as on the formation of metal ”nanowires” inside the hydroquinone
tubes.