| 1. |
- Björk, Jonas, et al.
(författare)
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Adsorption of Aromatic and Anti-Aromatic Systems on Graphene through π−π Stacking
- 2010
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 1, s. 3407-3412
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of neutral (poly)-aromatic, antiaromatic, and more generally π-conjugated systems on graphene is studied as a prototypical case of π-π stacking. To account for dispersive interactions, we compare the recent van der Waals density functional (vdw-DF) with three semiempirical corrections to density functional theory and two empirical force fields. The adsorption energies of the molecules binding to graphene predicted by the vdw-DFwere found to be in excellent agreement with temperature desorption experiments reported in litera- ture,whereas the results of theremaining functionals andforce fields only preserve the correct trends. The comparison of the dispersive versus electrostatic contribu- tions to the total binding energies in the aromatic and antiaromatic systems suggests that π-π interactions can be regarded as being prevalently dispersive in nature at large separations, whereas close to the equilibrium bonding distance, it is a complex interplay between dispersive and electrostatic Coulombic interactions. Moreover our results surprisingly indicate that the magnitude of π-π interactions normalized both per number of total atoms and carbon atoms increases signifi- cantly with the relative number of hydrogen atoms in the studied systems.
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| 2. |
- Liscio, Andrea, et al.
(författare)
-
Local Surface Potential of pi-Conjugated Nanostructures by Kelvin Probe Force Microscopy: Effect of the Sampling Depth
- 2011
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Ingår i: SMALL. - : John Wiley and Sons, Ltd. - 1613-6810. ; 7:5, s. 634-639
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Tidskriftsartikel (refereegranskat)abstract
- Kelvin probe force microscopy (KPFM) is usually applied to map the local surface potential of nanostructured materials at surfaces and interfaces. KPFM is commonly defined as a surface technique, even if this assumption is not fully justified. However, a quantification of the surface sensitivity of this technique is crucial to explore electrical properties at the nanoscale. Here a versatile 3D model is presented which provides a quantitative explanation of KPFM results, taking into account the vertical structure of the sample. The model is tested on nanostructured films obtained from two relevant semiconducting systems for field-effect transistor and solar cell applications showing different interfacial properties, i.e., poly(3-hexylthiophene) (P3HT) and perylene-bis-dicarboximide (PDI). These findings are especially important since they enable quantitative determination of the local surface potential of conjugated nanostructures, and thereby pave the way towards optimization of the electronic properties of nanoscale architectures for organic electronic applications.
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