Abstract: 1-naphthylamine is a probe with intra-molecular charge transfer in nature. Its characteristic band ( ) is sensitive to the polarity of environment. It was found that the semilogarithmic plot of versus surfactant concentration C appeared the two inflection points. The first inflection point corresponded to the critical micelle concentration (cmc), and the second inflection point (Ccm) addressed the critical point reaching dense structure in the micellar core. The results showed that gemini surfactant only form small aggregates at the cmc. Over the range of cmc to Ccm, the aggregation number of the micelle rapidly increases with increasing C.

Key words: Gemini surfactant, 1-naphthylamine probe, Micelle growth, The concentration close to the cmc.