Aggregation and disaggregation of anionic aluminum phthalocyanines in cationic pre-micelle and micelle media: A fluorescence study

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• 作者：Raquel F. Correia ; ^{raquel.correia@ist.utl.pt} ; Suzana M. Andrade ; M. Isabel Viseu
• 关键词：AlPcS4 ; tetrasulfonated aluminum phthalocyanine ; AlPcS1 ; monosulfonated aluminum phthalocyanine ; AlPcSn ; (n)-sulfonated aluminum phthalocyanine ; CMC ; critical micelle concentration ; CTAC ; cetyltrimethylammonium chloride ; DTAC ; n-dodecyltrimethylammonium c
• 刊名：Journal of Photochemistry and Photobiology A ; Chemistry
• 出版年：2012
• 期刊代码：66_10106030
• 类别：ch
• 出版时间：1 May, 2012
• 卷：235
• 期：Complete
• 页码：21-28
• 文件大小：1141 K

摘要

The interactions of two anionic aluminum phthalocyanines (Pcs), the tetrasulfonated (AlPcS₄) and the monosulfonated (AlPcS₁) species, with the cationic detergent n-dodecyltrimethylammonium chloride (DTAC) were investigated. These studies were performed by UV-visible absorption, steady-state and transient-state fluorescence, fluorescence lifetime imaging microscopy (FLIM), and fluorescence correlation spectroscopy (FCS). For both AlPcS₄ and AlPcS₁, large complexes of Pc-DTAC were formed at low surfactant concentrations, in the pre-micelle range. These complexes were visualized by the FLIM technique, directly in a drop of the sample. As the DTAC concentration increased, the size of the complexes decreased significantly. Above the detergent critical micelle concentration (CMC 鈮?#xA0;22 mM), highly fluorescent monomers of both AlPcS₄ and AlPcS₁ were found to be strongly bound to the DTAC micelles surface: large equilibrium binding constants, K_b = 3.5 脳 10⁵ and 6.2 脳 10⁴, were obtained for AlPcS₄ and AlPcS₁, respectively. The aggregation/disaggregation behavior of phthalocyanines likely results from a delicate balance in the system, between hydrophobic attractions (Pc-Pc) and electrostatic attractions (anionic Pc macrocycles - cationic DTAC headgroups) and repulsions (between anionic sulfonated groups of Pc macrocycles).