Aggregation behavior of naphthalimide fluorescent surfactants in aqueous solution

Research paper by Yingyuan Zhao, Xiyou Li

Indexed on: 22 Nov '13Published on: 22 Nov '13Published in: Colloid and polymer science


A group of novel fluorescent surfactants, N-n-alkyl-4-(1-methylpiperazine)-1,8-naphthalimide iodine [Cnndi]I (n = 8, 10, and 12), have been synthesized and their aggregation behavior in aqueous solution have been explored by surface tension, electric conductivity, hydrogen-1 NMR spectra, absorption, and fluorescence spectra. Compared with traditional cationic surfactants, the [Cnndi]I have a rather lower critical micelle concentration and higher surface activity. Absorption and fluorescence spectra were proved to be facile method to monitor directly the aggregation states of fluorescent surfactant molecules in solution and revealed clearly the formation of face-to-face stacked structure of the [Cnndi]I molecules driven by the π–π interactions. The micelle formation process for [Cnndi]I was demonstrated to be enthalpy-driven in the temperature range investigated. Possible aggregation process was given based on the experimental results. The combination of dye and surfactant provides a way for monitoring the formation process of micelle directly by fluorescence spectra.