Non-covalent functionalization, solubilization of graphene and single-walled carbon nanotubes (SWNTs) has been explored in non-polar organic solvents with various electron-donor and -acceptor molecules. Large aromatic surfaces of electron-donor and -acceptor molecules direct them onto the surface of the graphene/SWNTs through π-π stacking interactions whereas the alkyl chains as well as the glycol chains on the aromatic molecules promote the solubility, thereby giving stable dispersions of SWNT/graphene composites in non-polar solvents. Composites of graphene and SWNTs with electron-donor and -acceptor showed significant changes in the electronic and Raman spectra which were found to be characteristic of molecular charge-transfer interactions. © 2010 Elsevier B.V. All rights reserved.