Effect of pressure on the critical micelle concentration of neutral surfactant using fluorescence probe method

We have investigated the pressure effect on the critical micelle concentration (cmc) of neutral surfactant micelle, Triton-X-100 (TX100), in aqueous solution by means of the fluorescence probe method. 2-p-Toluidinylnaphthalene-6-sulfonate (TNS) was used as a probe molecule, whose fluorescence yield remarkably increases in the micellar state. With increasing pressure, turnover behavior of cmc was observed at ca. 100 MPa. The fluorescence yield of TNS is sensitive to the local polarity and the local viscosity of the medium, which is associated with the formation of twisted intramolecular charge-transfer (TICT) state of TNS in the excited state. (C) 1999 Elsevier Science S.A. All rights reserved.