MSE Colloquium - Dr. Karl-Heinz Ernst, Laboratory for Nanoscale Materials Science
Date: October 21, 2011 from 2:00 pm to 3:00 pm EDT
Location: Room 214, S.W. Mudd
Contact: For further information regarding this event, please contact Wesley Hattan by sending email to wjh2121@columbia.edu or by calling 2128547860.
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Karl-Heinz Ernst
Laboratory for Nanoscale Materials Science

"Modification of surfaces with buckybowls"

Modification of surfaces with aromatic organic molecules is the key approach to new materials for organic photovoltaics (OPV), organic light-emitting devices (OLEDs), and molecular electronics such as organic field effect transistors (OFETs). The interfaces between active layers and electrodes influence the electronic and optical properties as well as the device performance. Furthermore, because the spatial extent of the molecular wavefunctions is rarely isotropic, the relative orientation of the molecules in the film, and thereby the degree of overlap of the frontier orbitals, will play an important role in determining film properties. Bowl-shaped polynuclear hydrocarbons offer a special opportunity in this arena owing to their substantial dipole moment, large conjugated network and shape complementarity.

I will present different aspects of the consequences of adsorption of bowl-shaped fullerene-fragment derivatives, based on corannulene (Fig. 1), on different surfaces. This includes spontaneous mirror-symmetry breaking,1 reversible phase transitions,2,3 tiling with pentagons and pentagonal stars,4 giant interface dipoles,5 and bowl-in-bowl stacking.6

[1] M. Parschau et al. Angew. Chem. Int. Ed. 46 (2007) 8258

[2] L. Merz, M. Parschau, L. Zoppi, K. K. Baldridge, J. S. Siegel, K.-H. Ernst  Angew. Chem. Int. Ed. 48 (2009) 1966

[3] L. Merz, T. Bauert, M. Parschau, G. Koller, J. S. Siegel, K.-H. Ernst Chem. Comm. (2009) 5871

[4] T. Bauert, L. Merz, D. Bandera, M. Parschau, J. S. Siegel, K.-H. Ernst,  J. Am. Chem. Soc. 131 (2009) 3460

[5] T. Bauert, L. Zoppi, G. Koller, A. Garcia, J. S. Siegel, K. K. Baldridge, K.-H. Ernst, J. Phys. Chem. Lett. (2011) (submitted)

[6] T. Bauert, K. K. Baldridge, Jay S. Siegel, K.-H. Ernst Chem. Comm. (2011) 47, 7995