Molecule-substrate interaction in functionalized graphene

The study of carbon-based hybrid nanostructures is an emerging field of current research. In particular, photo-active molecules have been shown to considerably influence optical properties of carbon nanotubes suggesting realization of molecular switches. Here, we focus on the qualitative nature of molecule-substrate coupling within carbon-based hybrid nanostructures including nanoribbons and graphene. Our theoretical approach is based on density-matrix formalism and predicts a molecule-induced splitting of the pristine spectral resonances combined with a considerable spectral shift. Both effects strongly depend on the electronic bandstructure of the substrate. Furthermore, we investigate the impact of the substrate dimension on the coupling by increasing the width of nanoribbons from the very narrow up to graphene. Our calculations reveal a clear increase of the optical absorption of graphene in the vicinity of the Dirac point and a peak broadening at the saddle point due to the appearance of a high-energy shoulder. Our results give new insights into the molecule-substrate coupling and can guide future experiments towards the realization of tailored hybrid materials with desired optical properties. (C) 2013 Elsevier Ltd. All rights reserved.