Enhancement of J Aggregation of Zinc Tetraphenylporphyrin in Water/Ethanol Binary Solution in the Presence of Cyclodextrin

Abstract

An aggregation behavior of zinc tetraphenylporphyrin (ZnTPP) in water/ethanol binary mixture in the presence of cyclodextrins was investigated by means of steady-state absorption, fluorescence, and resonance light scattering (RLS) spectra. In absorption spectra, only broad Soret band at 422 nm was observed in the absence of γ-cyclodextrin (γ-CD), which indicates that ZnTPP exists as weakly bound random-structure aggregates. As the γ-CD concentration increased, a satellite peak, that is characteristic to J aggregate, appeared at around 450 nm. In RLS spectra, the intensity of the J band was enhanced with increasing γ-CD concentrations. In the atomic force microscopy (AFM) image, rod-shape feature was observed, and its height and width were 1.5 nm and 30 nm, respectively.

Keywords:

• AFM
• cyclodextrin
• fluorescence
• tetraphenylporphyrin

Acknowledgments

This work was supported by Grant-in-Aid for Scientific Research (C) (No. 20550001) from MEXT Japan to S.-i.S, and by Grant-in-Aid for JSPS Fellows (No. 20·2850) from JSPS to T.K.