INSPIRED BY NATURE: ROBUST EXCITONS IN SOFT SUPRA-MOLECULAR NANOTUBES.
Dörthe M. Eisele, Chemistry Department, City College of New York (CCNY) of City University of New York (CUNY)
The most remarkable materials that demonstrate the ability to capture solar energy are natural photosynthetic systems such as found in rather primitive marine algae and bacteria. Their light-harvesting (LH) antennae are crucial components, as they absorb the light and direct the resulting excitation energy efficiently to a reaction center, which then converts these excitations (excitons) into charge-separated states. Nature's highly efficient light-harvesting antennae, like those found in Green Sulfur Bacteria , consist of supra-molecular building blocks that self-assemble into a hierarchy of close-packed structures.
In an effort to mimic the fundamental processes that govern nature’s efficient systems, it is important to elucidate the role of each level of hierarchy: from molecule, to supra-molecular building block, to close-packed building blocks. Here, I will discuss the impact of hierarchical structure. I will present a model system [1, 2, 3] that mirrors nature’s complexity: cylinders self-assembled from cyanine-dye molecules (as illustrated in the figure). I will show that even though close-packing may alter the cylinders’ soft mesoscopic structure, robust delocalized excitons are retained: internal order and strong excitation-transfer interactions—prerequisites for efficient energy transport—are both maintained. These results suggest that the cylindrical geometry strongly favors robust excitons; it presents a rational design that is potentially key to Nature’s high efficiency, allowing construction of efficient light-harvesting devices even from soft supra-molecular materials.
Dr. Dörthe M. Eisele was born and educated in Germany and grew up in Berlin. She studied physics at the Technical University of Berlin, Germany, and finished an external Diploma Thesis (comparable with a US Master Thesis) from the Physikalisch Technische Bundesanstalt (German Institute of Standards), Germany, at the Berlin Electron Storage Ring Society for Synchrotron Radiation II (known as BESSY II), in collaboration with the Lawrence Livermore National Laboratory (LLNL), USA. In Dec. 2009 she received her doctoral degree, Dr. rer. nat. (PhD equivalent), in experimental physics from the Physics Department (group of Prof. Juergen P. Rabe) of the Humboldt University Berlin, Germany, in close collaboration with Prof. David A. Vanden Bout from the Chemistry Department of University of Texas at Austin, USA. From March 2011 till August 2014, she was a Postdoctoral Associate at the Center for Excitonics of the Massachusetts Institute of Technology (MIT), where she conducted her research projects in the groups of Prof. Moungi G. Bawendi and Prof. Keith A. Nelson. Throughout her career she initiated fruitful and long-term collaborations such as with research groups of Klaus Muellen (Max Planck Institute for Polymer Research, Germany), Jasper Knoester (Physics Department, University of Groningen, The Netherlands), Daniela Nicastro (Biology Department, University of Brandeis, USA), Robert Silbey† (Chemistry Department, MIT, USA), Andrei Tokmakoff (Chemistry Department, University of Chicago, USA). In 2011, Dr. Eisele received the prestigious Feodor-Lynen-Fellowship award and became a member of the Alexander-von-Humboldt-Foundation. In September 2014, she joined The City College of New York (CCNY) of The City University of New York (CUNY) as an Assistant Professor of Physical Chemistry.
 Orf, G. S. & Blankenship, R. E. “Chlorosome antenna complexes from green photosynthetic bacteria.” Photosynth. Res.in press (2014).
 Eisele, D.M., Knoester, J., Kirstein, S., Rabe, J.P., and Vanden Bout, D.A.: “Uniform exciton fluorescence from individual molecular nanotubes immobilized on solid Substrates.”
Nature Nanotech. 4, (2009) 658-663. (Cover Article)
 Eisele, D.M., Cone, C.W., Bloemsma, E.A., Vlaming, C.G.F. van der Kwaak, S.M., Silbey, R.J., Bawendi, M.G., Knoester, J., Rabe, J.P., and Vanden Bout, D.A.: “Utilizing Redox-Chemistry to Elucidate the Nature of Exciton Transitions in Supramolecular Dye Nanotubes.”
Nature Chem. 4, (2012) 655–662.
 Eisele, D.M., Arias, D.H., Fu, X., Bloemsma, Steiner, C.P., E., Jensen, R., Rebentrost, P., Eisele, H., Llyod, S., Tokmakoff, A., Knoester, J., Nicastro, D., Nelson, K.A., and Bawendi, M.G.:
“Robust Excitons in Soft Supramolecular Nanotubes.”
PNAS, 111 (2014) E3367-E3375.
Keywords: Supra-molecular Assembly, Self-assembled, Excitonic Nanoscale Systems, Exciton Theory,
Light-Harvesting Antennae Systems, Photosynthesis
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