Langmuir, Vol.12, No.2, 293-300, 1996
Photophysical Characterization of Sulfonated Aluminum Phthalocyanines in a Cationic Reversed Micellar System
The photophysics of sulfonated aluminum phthalocyanines, AIPcS(n) (n = 0, 1, 2, 3, or 4), in cationic reversed micelles of benzyldimethyl-n-hexadecylammonium chloride (BHDC) have been investigated. Absorption and steady-state fluorescence emission spectroscopy indicate that only the di- and trisulfonated derivatives are essentially monomeric. Consequently, the triplet-state properties of only these nonaggregated phthalocyanines were investigated. Both derivatives exhibited enhanced intersystem crossing in this medium compared to homogeneous environments, yet the singlet oxygen quantum yields were found to be comparable to those obtained in homogeneous solutions. Time-resolved fluorescence emission studies yielded decays which were best fitted by a decay time distribution analysis rather than the more commonly used sum of exponentials model. The distributions were seen to broaden with increasing water concentration. The distribution of AIPcS(n) in the reversed micelles, which appears to be strongly influenced by the extent of sulfonation and the environment within the reversed micelle, is discussed.
Keywords:BIOLOGICAL-ACTIVITIES;MOLECULAR-OXYGEN;QUANTUM YIELDS;WATER;PHOTOSENSITIZERS;STATE;MICROEMULSIONS;DIMERIZATION;SENSITIZERS;AGGREGATION