Abstract Submitted to the ; NANOTUBE'05 Conference:

The ?-stacking interaction between various planar organic molecules (such as benzene, azulene, pyrene and DDQ), and carbon nanotubes is investigated within the framework of ab initio calculations [1]. The adsorption of these molecules on the sidewall of the cylindrical carbon structure induces a small binding energy compared to conventional covalent functionalization. Such a weak interaction is found to be only physisorption and leads to minor and predictable modifications of the electronic structure. These changes in the electronic behavior of the host carbon nanotube are ruled by the relative positions of the molecular levels of the isolated molecule and both the valence and conduction bands of the perfect tube.
The adsorption of the benzene molecule on carbon nanotubes with various diameters and chiral angles is investigated more specifically [2]. Our ab initio calculations suggest that for small diameter tubes, the most favorable adsorption site is one type of C-C bond. The disparities between the inequivalent bonds of a CNT are discussed in terms of the ??orbital axis vector misalignment. Moreover, the curvature and the chirality effect on benzene adsorption are analyzed, showing that large diameter nanotubes are the most reactive ones.
Although the ?-stacking interaction is weak, molecular physisorption could have an impact on the electronic transport properties of the carbon nanotubes. A tight-binding scheme, parametrized with first-principles calculations, is able to tackle with the complex electronic transport properties of chemically grafted conducting nanotubes with a random coverage of physisorbed molecules. Our calculations suggest that the effect will be strongly dependent on the nature of the attached molecules [3]. Such result could have important consequences on the understanding of the (bio)sensing capability of molecular objects such as nanotubes.

References:
[1]. F. Tournus, S. Latil, M. Heggie, and J.-C. Charlier, submitted for publication (2004).
[2]. F. Tournus and J.-C. Charlier, submitted for publication (2004).
[3]. S. Latil, S. Roche, and J.-C. Charlier, submitted for publication (2004).