Counterion-Dependent Morphology of Porphyrin Aggregates Formed at the Liquid/Liquid Interface Studied by Total Internal Reflection Resonant Rayleigh and Raman Scattering Microscopy

Specific domain formation due to the aggregation of the protonated tetraphenylporphyrin (H 2 TPP 2+ ) at the dodecane/acid aqueous solution interfaces was examined by using total internal reflection (TIR) resonant light scattering microscopy (RLSM). The domain morphology was remarkably dependent on the counterions in the acids: hydrochloric acid, perchloric acid, or sulfuric acid. The counterion effect on the morphology was further examined by the microscopic absorption spectra, the polarization RLSM, and the microscopic TIR-resonant Raman spectra. It was suggested that the counterion-dependent morphology, characterized by the angle between the direction of the transition moment of the H 2 TPP 2+ aggregates and the axis of the domain, could be related to the character of the J-band of the aggregates and hydrophobicity of the counterions.