Excitation transfer in a luminescent porphyrin-SW carbon nanotube complex

Tailoring the properties of carbon nanotubes by functionalizing their side-wall is an important point towards the realization of carbon nanotube-based optoelectronic or electronic devices. Interactions between nanotubes and porphyrin molecules have attracted much attention for about five years [1-8]. We report here on "p-stacking" functionalization of CoMoCaT nanotubes with hydrosoluble porphyrins (TPPS). The mutual influence on electronic properties of both porphyrins molecules and nanotubes is studied by optical absorption, photoluminescence and excitation of photoluminescence spectroscopy in both species optical transitions energy range. The optical absorption spectrum of porphyrins adsorbed on nanotubes exhibits a 120 meV red shift of the Soret band. The porphyrin-nanotube complex shows a 99% quenching of the TPPS emission. In contrast with previous studies photoluminescence intensity of the nanotubes is enhanced in presence of porphyrins. Moreover this enhancement is much better when the excitation energy is in resonance with the “p-stacked" porphyrin absorption band. This reveals the existence of an excitation transfer from the porphyrin molecules to the nanotube.