Determination of the Critical Micelle Concentration of Surfactant in Aqueous Solution by Twisted Intramolecular Charge Transfer Probe DMABN

With p-N,N-dimethylaminobenzonitrile (DMABN) as a probe, the variations of the intensity of its second fluorescence emission (Ia) and the corresponding characteristic wavelength (λa) with the surfactant concentration (c), here the examined surfactants (C12TABr, SDS, C12E23, and C12-3-C12·2Br), were measured by Hitachi F4500 fluorescence spectrophotometer. The results showed that both the break points on the Ia-c curve and the minimum of the derivative variation corresponding to the λa-c curve agreed very well with the critical micelle concentration (cmc) of the surfactant in aqueous solution as measured by surface tension technique. Due to strong aggregation of C12-3-C12·2Br in aqueous solution, the information about loose micellar structure could be obtained by its λa-c curve.