A UV-visible study of partitioning of pyrene in an anionic surfactant sodium dodecyl sulfate (original) (raw)
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The fluorescence intensities for various vibronic fine structures in the pyrene monomer fluorescence show strong solvent dependence. In the presence of polar solvents, there is a significant enhancement in the intensity of the 0-0 vibronic band at the expense of other bands. This strong perturbation in the vibronic band intensities is more dependent on the solvent dipole moment than on the bulk solvent dielectric constant. This suggests the operation of some specific solute-solvent dipole-dipole interaction mechanism. The strong perturbation of the vibronic band intensities has been used as a probe to accurately determine critical micelle concentrations and also to investigate the extent of water penetration in micellar systems.
INTERACTION OF 3-HYDROXY PYRIDINE AND SURFACTANT MICELLES: A FLUORESCENCE STUDIES
Asian Journal of Pharmaceutical and Clinical Research Journal, 2021
Objective: Micellar solubilization is a powerful alternative for dissolving hydrophobic compound in aqueous environment. 3-hydroxy pyridine (3-HP) derivatives are the potential endogenous photosensitizers. 3-HP derivatives show protective effect in clinical extreme condition such as hypoxia, hyperthermia, hypokinesia. Micellization of 3-HP followed by solubilization would catalyze its pharmaceutical activities which may serve better results in medicinal and analytical fields. Methods: Fluorescence and absorption spectroscopy techniques are used to monitor the micellar solubilization studies of 3-HP. Solubilization studies of 3-HP with various anionic, cationic and nonionic surfactants have been performed in aqueous medium around 23-25°C temperature. The solubilization action of the surfactant has also been determined by theoretical calculated spectral parameters such as empirical fluorescence coefficient, quantum yield, stokes, shift and molar absorption coefficient. Results: 3-HP shows fluorescence excitation peak at 315 nm and emission peak at 390 nm respectively while the absorbance of 3-HP has been found to be maximum at 305 nm. The fluorescence as well as the theoretically calculated spectral data has been used to characterize the hetero environment of the micelles in terms of their polarity, probe solubilization site and critical micelle concentration. Conclusion: This article briefly discusses the importance of surfactants in biological system model as well as the use of micelles in pharmacy as an important tool that finds numerous applications.
Fluorescence emission of pyrene in surfactant solutions
Advances in Colloid and Interface Science, 2015
The systematic description of the complex photophysical behavior 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 K TX100 = 3300 10 3 M -1 and K SDS = 190 10 3 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.
The Journal of Physical Chemistry, 1995
The aggregation numbers of sodium dodecyl sulfate (SDS) micelles and the fluorescence quenching constants, kq, of pyrene by Cu2+ have been measured as a function of SDS concentration from 25 to 200 mM. The results confirm an empirical observation made by small angle neutron scattering (Bezzobotnov, et al. J. Phys. Chem, 1988, 92, 5738) that SDS micelles grow linearly as the one-fourth power of the total detergent concentration. The aggregation numbers, computed under the assumption that the Cu2+ ions are distributed randomly among the micelles show a positive slope with increasing Cu2+ concentration, contrary to theoretical expectations; however, invoking, a small electrostatic repulsion between Cu2+ ions residing upon the same micelle brings the experimental observations into agreement with theory. This electrostatic repulsion decreases from €2 = 0.11 to 0.04kT (T = absolute temperature, k = Boltzmann constant) as the micelle size increases from 50 to 85 molecules. These electrostatic repulsion energies are comparable to those necessary to bring electron paramagnetic resonance results into agreement with theory as presented in the following paper. The quenching constant decreases with the size of the micelle according to kq = yD/R2 with a coefficient of correlation r = 0.994, consistent with a model of diffusion encounters between reactants moving on or near a sphere of radius R. D is the relative diffusion coefficient of the reactants and y is a constant. Taking R to be the radius of the micelle and reasonable estimates of y shows that the diffusion coefficient of Cu2+ is of the same order of magnitude as it is in water. This leads to the conclusion that the quenching rate constant is nearly diffusion controlled and that pyrene is readily available at the micelle surface to participate in molecular collisions with Cu2+. Further, the residence time of the Cu2+ upon any given head group must be rather short. Even though the data are better fit under a hypothesis of electrostatic repulsion, the conclusions that the micelles grow as the one-fourth power of the detergent concentration and that the quenching is consistent with a surface diffusion mechanism are unaffected if a random distribution is utilized. Under this latter interpretation, the micelles grow from 57 to 89 molecules as the SDS concentration increases from 25 to 200 mM. The observed micelle growth together with an absence of substantial polydispersity is inconsistent with thermodynamic predictions. 0 different compartments. Nevertheless, even in this case, the measurement of the bimolecular collision rate is complicated by the fact that a sample contains a statistical distribution of tion of signals due to compartments containing zero, one, two, OCHa additives among compartments. Thus, the signal is a superposi-
Characterization of non-ionic surfactant aggregates by fluorometric techniques
Journal of Photochemistry and Photobiology A: Chemistry, 2002
Steady-state and nanosecond time-resolved studies have been carried out on the fluorescence quenching of excited pyrene by N,Ndibutylaniline in an aqueous solution of non-ionic micelles of the six Tritons, (oxyethylene) m -p-(1,1,3,3-tetramethylbutyl)phenyl ethers with m ranging from 8 to 70. The aggregation numbers and the rate constants of intramicellar quenching have been determined. The critical micelle concentrations of investigated Tritons were determined using the dependence of the fluorescence spectrum of pyrene on the microenvironment. The local polarity was obtained from the intensity ratio of the first to the third peak (I 1 /I 3 ) in the fluorescence spectrum of pyrene. The microviscosity of the micellar core was estimated to be about 200 cP at ambient temperature on the basis of fluorescence spectra of 1,3-bis(1-pyrene)propane, from the excimer to the monomer emission intensity ratio using the calibration curve determined for a number of solvents of known viscosities.
Journal of Colloid and Interface Science, 2006
The critical micellar concentration (cmc) of both ionic and non-ionic surfactants can be conveniently determined from the measurements of UV absorption of pyrene in surfactant solution. The results on a number of surfactants have agreed with that realized from pyrene fluorescence measurements as well as that obtained following conductometric, tensiometric and calorimetric methods. The absorbance vs [surfactant] profiles for all the major UV spectral peaks of pyrene have been found to be sigmoidal in nature which were analyzed according to Sigmoidal–Boltzmann equation (SBE) to evaluate the cmcs of the studied surfactants. The difference between the initial and the final asymptotes (aiai and afaf, respectively) of the sigmoidal profile, Δa=(af−ai)Δa=(af−ai) and the slope of the sigmoid, SsigSsig have been observed to depend on the type of the surfactant. The Δa has shown a linear correlation with the ratio of the fluorescence intensities of the first and the third vibronic peaks, I1/I3I1/I3 of pyrene which is considered as a measure of the environmental polarity (herein micellar interior) of the probe (pyrene). Thus, Δa values have the prospect for use as another index for the estimation of polarity of micellar interior.
Langmuir, 1998
The effect of dissolved gas (air, argon, butane) on the properties of aqueous surfactant micelles (aggregation number, microviscosity and micropolarity) has been investigated by means of time-resolved fluorescence quenching and spectrofluorometry on a large number of surfactant systems differing by the nature of the surfactant (anionic, cationic, zwitterionic, and nonionic) and the temperature. The investigated properties were found to be independent of the state of the system: air-saturated, argon-saturated, or degassed. In the particular case of micellar solutions of cetyltrimethylammonium chloride, where the measurements involved 10 identical solutions, the average aggregation numbers measured for air-saturated, argonsaturated, and degassed solutions differed by less than 1%. The results indicate that if the hydrophobic interaction, which is the driving force for micelle formation, is affected by the dissolved gas, this would be to a very small extent, well below the sensitivity level of the methods of investigation of micellar solutions used in this study.
A fluorescent probe for alkanes, surfactants, lipids and self-organized molecular aggregates
2014
Low-toxic coralyne, a cationic benzo[c]phenanthridine type alkaloid (Fig. 1), has received extensive attention because of its DNA-and RNA-targeting properties, and antimicrobial, anticancer activity, more pronounced compared to other protoberberine alkaloids [1-3]. In a previous work we showed that the fluorescence intensity alteration of coralyne-impregnated silica gel plates allows the sensitive quantitative detection of a wide number of analytes by high-performance thin layer chromatographic techniques [4]. It has been shown that coralyne cation undergoes self-aggregation in aqueous solutions by stacking interactions, even at low dye concentration, being the dimer less fluorescent than the monomer [5, 6]. In this work we have studied the influence of temperature in dimer formation. Due to its large flat aromatic structure, coralyne also has a high tendency to penetration into organized assemblies in solution with hydrophobic core such as micelles or liposomes, and we present here a fluorescence study of coralyne in different microheterogeneous media. Fluorescence emission increases when coralyne probe is situated in apolar microenvironments which prevent non-radiative desexcitation pahtways (Fig. 2).
Russian Journal of Physical Chemistry, 2004
The influence of the internal (1-bromopyrene, as an example) and external (pyrene in the presence of thallium cations) heavy atoms on the phosphorescence of pyrene in micelle solutions at room temperature was studied. and. It was shown that phosphorescence of pyrene is determined by the types of heavy atom and micelleforming surfactant, their concentrations, and the concentration of sodium sulfite used to bind dissolved oxygen.