Synthesis of SWNT rings by noncovalent hybridization of porphyrins and single-walled carbon nanotubes

Single-walled carbon nanotube (SWNT) rings have been synthesized via the noncovalent hybridization of carbon nanotubes and porphyrins. Optical absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) results showed that the formation of the SWNT rings is strongly affected by the molecular architecture of the porphyrins, the hybrid concentration, the SWNT-to-porphyrin mass ratio, and the substrate on which the hybrid films were coated. We found that the SWNT hybrid rings result from the formation of porphyrin J-aggregates on the outer surfaces of the SWNTs and the tendency of porphyrins to aggregate in wheel structures. We also demonstrated that electron donation by the substituent groups in the para-positions of the phenyl rings in 5,10,15,20-tetraphenyl-21H,23H-phorphine (TPP) and the structural regularity of the substituent groups facilitate the formation of J-aggregates of the TPP derivatives. This novel method presents new theoretical challenges and potentially provides a simple approach based on the noncovalent hybridization of porphyrins and SWNTs to the synthesis of SWNT superstructures.