Li Xiwen, Xie Yuxiang, Chen Zhangping, Zou Guolin
College of Life Sciences, Wuhan University, Wuhan 430072, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2005 Sep;61(11-12):2468-73. doi: 10.1016/j.saa.2004.09.011.
J-aggregates of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin (HQTHPP) induced by N-lauroyl sarcosine (SKL) in aqueous neutral solutions have been studied by optical absorption, fluorescence, and resonance light-scattering spectroscopies. As SKL concentration increases, the spectra evolve to reveal the presence of four independent species with relative concentration. The most important species is J-aggregates. The J-aggregates have two strong exciton bands corresponding to the B-band and Q-bands of HQTHPP monomers, and are found to be stable when the surfactant concentration is below 8.0 mmol/L. But above 8.0 mmol/L, the J-aggregates dissolve gradually into another species: porphyrin monomers. The total fluorescence of HQTHPP is quenched due to the aggregate formation. A strong and sharply peaked resonance light-scattering signal (>1800 counts/s, centered at 490 nm) is observed just slightly to the red of the J-aggregate absorption maximum. In the case of cetyltrimethyl-ammonium bromide, increasing surfactant concentrations have only shown to favor solubilization of porphyrin monomers. Evidently, the nature of polar headgroups of surfactants influences the tendency of THPP to aggregate.
通过光学吸收、荧光和共振光散射光谱法研究了在中性水溶液中，N-月桂酰肌氨酸（SKL）诱导2-对苯二酚-5,10,15,20-四（对羟基苯基）卟啉（HQTHPP）形成J聚集体的情况。随着SKL浓度增加，光谱变化显示存在四种相对浓度独立的物种。其中最重要的物种是J聚集体。J聚集体有两个对应于HQTHPP单体B带和Q带的强激子带，并且发现当表面活性剂浓度低于8.0 mmol/L时它们是稳定的。但高于8.0 mmol/L时，J聚集体逐渐溶解为另一种物种：卟啉单体。由于聚集体形成，HQTHPP的总荧光被猝灭。在J聚集体吸收最大值稍偏红处观察到一个强且尖锐的共振光散射信号（>1800计数/秒，中心在490 nm）。在十六烷基三甲基溴化铵的情况下，表面活性剂浓度增加仅显示有利于卟啉单体的增溶作用。显然，表面活性剂极性头基的性质影响THPP聚集的倾向。
