Porphyrin nanotubes composed of highly ordered molecular arrays prepared by anodic aluminum template method

Nanotubes of metal-free 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (H2TClPP) are fabricated by using nanoporous anodized aluminum oxide (AAO) membrane as the template. The morphology and structure of the nanotubes are investigated by using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM). It is found that the outer diameter of the nanotubes matches well with the pore diameter of the AAO membranes, and interestingly, the porphyrin molecules packed orderly within the nanotube walls. The properties of the nanotubes of H2TClPP have been investigated by using UV-vis absorption spectroscopy and steady-state fluorescence spectroscopy. Absorption spectra reveal the formation of J aggregates of the porphyrin molecules within the nanotubes. While fluorescence spectra show a significant fluorescence quenching for the nanotubes dispersed in a water solution in comparison to the solution of H2TClPP in chloroform, due to strong supramolecular π–π and van der Waals interactions.