A new pyrene-based fluorescent probe for the determination of critical micelle concentrations (CMC) is described. The title compound 1 is obtained in five steps, starting from pyrene. Fluorescence spectroscopic properties of 1 are studied in homogeneous organic solvents and aqueous micellar solutions. In a wide range of organic solvents, probe 1 exhibits a characteristic monomer emission of the pyrene fluorophore, with three distinct peak maxima at 382, 404, and 425 nm. The spectra change dramatically in aqueous solution, where no monomer emission of the pyrene fluorophore is detected. Instead, only strong excimer fluorescence with a broad, red-shifted emission band at lambda(max) = 465 nm is observed. In micellar aqueous solution, a superposition of the monomer and excimer emission is found. The appearance of the monomer emission in micellar solution can be explained on the basis of solubilization of 1 by the surfactant micelles. The ratio of the monomer to excimer fluorescence intensities of 1 is highly sensitive to changes in surfactant concentration. This renders 1 a versatile and sensitive probe molecule for studying the micellization of ionic and nonionic surfactants. For a representative selection of common surfactants, the critical micelle concentrations in aqueous solution are determined, showing excellent agreement with established literature data.
"Pyrene has been used since more than 50 years as fluorescent probe par excellence for microheterogeneous systems such as micelles             , polymers   , proteins   , peptides  and biological membranes [18,21- 23]. The sensitivity of the pyrene fluorescence intensity to the solvent polarity is widely used for the determination of the cmc of micellar systems          . "
[Show abstract][Hide abstract] ABSTRACT: (Review Article) The systematic description of the complex photophysical behaviour of pyrene in surfactant solutions in combination with a quantitative model for the surfactant concentrations reproduces with high accuracy the steady-state and the time resolved fluorescence intensity of pyrene in surfactant solutions near the cmc, both in the monomer and in the excimer emission bands. We present concise model equations that can be used for the analysis of the pyrene fluorescence intensity in order to estimate fundamental parameters of the pyrene–surfactant system, such as the binding equilibrium constant K of pyrene to a given surfactant micelle, the rate constant of excimer formation in micelles, and the equilibrium constant of pyrene–surfactant quenching. The values of the binding equilibrium constant KTX100 = 3300·103 M− 1 and KSDS = 190·103 M− 1 for Triton X-100 (TX100) and SDS micelles, respectively, show that the partition of pyrene between bulk water and micelles cannot be ignored, even at relatively high surfactant concentrations above the cmc. We apply the model to the determination of the cmc from the pyrene fluorescence intensity, especially from the intensity ratio at two vibronic bands in the monomer emission or from the ratio of excimer to monomer emission intensity. We relate the finite width of the transition region below and above the cmc with the observed changes in the pyrene fluorescence in this region.
Advances in Colloid and Interface Science 11/2014; DOI:10.1016/j.cis.2014.10.010 · 7.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV–Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl-trimethyl-ammonium bromide as cationic, tert-octylphenol ethoxylates TOPEON (with N = 9.5, 7.5 and 35) and lauryl alcohol ethoxylate (23EO) as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of the CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in membrane technology.
Journal of Surfactants and Detergents 05/2012; 16(3). DOI:10.1007/s11743-012-1403-7 · 1.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel surfactant-like non-ionic fluorophore, 3-(bis(2-hydroxyethyl)amino)-N-(4-(pyrene-1-sulfonamido)butyl) propanamide (PSDA-DEA), was designed and prepared. Fluorescence and surface tension studies revealed that the fluorophore aggregates in aqueous medium, and its critical aggregation concentration (CAC) is ∼3.3 × 10−5 M. Cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements demonstrated that the diameter of the aggregates as formed is of a few hundred nano-meters. It was also shown that the profile of the emission spectrum of the compound is well dependent upon the polarity of its medium, as indicated by a change up to 53% of its intensity ratio at 399 nm and 380 nm (I399/I380) when the solvent changed from water to ethanol. It is of the polarity sensitive property that the fluorophore can be used for monitoring micelle formation of several anionic, cationic and non-ionic surfactants. Furthermore, PSDA-DEA is also a valuable probe for sensing transition of different aggregates such as micelles to vesicles. Comparative studies demonstrated that the present probe is more versatile than pyrene when it is used as a fluorescence probe.
Journal of Photochemistry and Photobiology A Chemistry 10/2012; 245:58–65. DOI:10.1016/j.jphotochem.2012.07.001 · 2.50 Impact Factor
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