לוח שנה משולב

Lecture will take place in the Perlman Building, room 402

Research on dye molecules has been continuing to be at the forefront of new developments in chemistry owing to their versatile functional properties associated with -conjugation. On a supramolecular level, appropriately controlled spatial arrangement of dyes enables pivotal functions in nature, the most intriguing examples being provided by the light-harvesting systems of purple and green bacteria which contain a large number of chlorophyll and carotene chromophores organized in cyclic arrays or tubular architectures by non-covalent interactions.

During the last few years, we have intensively investigated the organization of merocyanine, chlorin, and perylene bisimide dyes by non-covalent forces into desirable nanoscale architectures as well as liquid-crystalline and crystalline solid state materials. In this lecture, I will provide an overview on our achievements in the preparation of defined dye assemblies and their functional properties that originate from proper -stacking [1]. In particular, charge and exciton transport in dye aggregates [2,3] FRET processes in dye vesicles [4], and photovoltaic performance of dye-based bulk heterojunction solar cells [5] will be discussed.


[1] Z. Chen, A. Lohr, C. R. Saha-Möller, F. Würthner, Chem. Soc. Rev. 2009, 38, 564–584.
[2] Z. Chen, V. Stepanenko, V. Dehm, P. Prins, L. D. A. Siebbeles, J. Seibt, P. Marquetand, V. Engel, F. Würthner, Chem. Eur. J. 2007, 13, 436–449
[3] H. Lin, R. Camacho, Y. Tian, T. E. Kaiser, F. Würthner, I. G. Scheblykin, Nano Lett. 2010, 10, 620–626.
[4] X. Zhang, S. Rehm, M. M. Safont-Sempere, F. Würthner, Nature Chem. 2009, 1, 623–629.
[5] U. Mayerhöffer, K. Deing, K. Gruß, H. Braunschweig, K. Meerholz, F. Würthner, Angew. Chem. Int. Ed. 2009, 48, 8776–8779.

We propose a description of crystal growth from an undercooled melt where capillary waves of the solidification front interact with a
bulk-diffusion field which can be energy density, or the concentration field of the solute component in a binary alloy. Our approach does not
rely on the sharp-interface approximation, and even applies to the rapid-growth regime. It allows a surprisingly simple analysis of the effects
of solute trapping and solute drag, and for a sizable set of model systems permits a complete stability analysis of the interface morphology.
In addition to the Mullins-Sekerka instability, leading to dendritic growth, we find a, sometimes overlooked, instability of the type, discovered
by Cahn in grain-boundary motion. Assuming a sufficient amount of surface segregation of the diffusion field, the cooperation of both instabilities
can lead to the formation of a periodic array of layers with a homogeneous and a dendritic micro-structure which sometimes is called the banded-structure phenomenon.