[Aggregation number determination of gemini anionic surfactant micelle by intrinsic fluorescence quenching]

The p-phendioxyl base in the spacer of gemini surfactant C11pPHCNa emits fluorescence under exciting. When the gemini concentration is over 0.45 mmol x L(-1), the topological structure of the excitation spectra yields various changes resulting in them being significantly different from the corresponding absorption spectra. As the aromatic base in the spacer of C11pPHCNa obviously quenches the fluorescence of pyrene that is as additional probe, it is hardly to determine the average micelle aggregation number by the usual method of quenching pyrene. In the present paper, using the property of methylviologen (MV2+) effectively quenching the fluorescence of C11pPHCNa, the authors established the method to determine the average aggregation number N of C11pPHCNa micelle. For individual C11pPHCNa micelle, N was determined to be 20.6 at c=2 mmol L(-1), while the average aggregation number of C11pPHCNa/C12-2-E1-C12 x 2Br mixed micelle in the aqueous solution with a total concentration of 2 mmol x L(-1) and C11pPHCNa of mole fraction 0.3 in the bulk was obtained to be 11.8.