Water redissoluble chiral porphyrin–carbon nanotube composites

The redissoluble functional compound/carbon nanotube (CNT) composites are important for post processing because CNT dispersions usually easy aggregate and therefore make additional processing very difficult. Due to the outstanding electronic, photophysical and photochemical properties of porphyrin and CNT composites, the chiral nanocomposites of chiral porphyrins and single-walled carbon nanotubes (SWNTs) are quite promising for applications in chiral catalysis and bio-sensing. The porphyrins used for the solubilization of CNTs are usually tetra-phenyl porphyrin (TPP) analogues. However, TPP analogues do not favor the formation of π–π interactions because the aryl groups prevent the porphyrin moiety from approaching the CNT surface due to the perpendicular conformation of the porphyrin moiety and its aryl group substituents. In this paper, non-TPP type porphyrins with chiral and hydrophilic substituents, that make the porphyrins soluble in water, were synthesized. SWNTs were effectively dissolved into water by the non-TPP type chiral porphyrins, and the dissolved chiral porphyrin/SWNTs composites could be easily redissolved. Both the dissolved and redissolved SWNT solutions are very stable and did not form apparent aggregates even after being kept for six months. Spectroscopic studies show that the binding properties of the chiral porphyrins to SWNTs are different in basic and neutral solution, which should contribute to the development and understanding in the study of sensors, biosensors, and catalysts made from chiral molecule/CNT composites.