The binding energy of a fused pyrrolidine ring at different binding sites of a carbon nanohorn (CNH) has been determined by density functional theory (DFT) calculations employing a 217 C-atom model of CNH. In agreement with previous work, significant binding is found at sites closer to the conical tip. Secondly, DFT and time dependent density functional theory (TDDFT) calculations have been carried out on CNH nanohybrids with photo- or electro-active substituents, porphyrin, pyrene and tetrathiafulvalene, of interest for photo-induced charge transfer. It is found that the relevant excitations in the individual substituents retain their characteristics in the nanohybrid systems. (c) 2007 Elsevier B.V. All rights reserved.