EFFECT OF AMINO ACIDS ON AGGREGATION BEHAVIOR OF NONIONIC SURFACTANT HEXADECYL(POLYOXYETHYLENE (20)) ALCOHOL IN AQUEOUS SOLUTIONS (original) (raw)
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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.
Investigation of Micelle Formation by Fluorescence Correlation Spectroscopy
The Journal of Physical Chemistry B, 2005
We show that noncovalently bound dye molecules can be used as labels in single-molecule fluorescence experiments for the determination of aggregate formation in standard surfactant systems. Aqueous solutions of sulfosuccinic acid bis(2-ethylhexyl) ester sodium salt, hexadecyltrimethylammonium chloride, and pentaethylene glycol monododecyl ether have been studied by fluorescence correlation spectroscopy using commercially available dyes. The translational diffusion coefficient and the critical micelle concentrations have been determined and compare well to values reported in the literature. The respective charges of the surfactant and of the dye molecule are crucial for the effectiveness of the presented method.
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.
Characterization of fluorescent surfactant aggregates by fluorimetric and viscosimetric techniques
Monatshefte f�r Chemie Chemical Monthly, 1997
A combination of fluorimetric and viscosimetric methods was used to characterize N,Ndimethyl-N-2-(4-(t-butylphenoxy)ethoxy)ethyl-N-hexadecylammonium chloride (BDHC), a doubletailed surfactant with dissimilar tail groups. BDHC was observed to fluoresce at 315 nm when excited at 274 nm, a feature which could be utilized to determine its critical micelle concentration (CMC). A value of 3.98 × 10 5 M was obtained and was observed to be slightly temperature dependent with a Tmin of 25.35°C. Fluorescence quenching experiments using 4-nitroaniline as a quencher were performed in order to determine the aggregation number which was found to be 42.0. The hydrodynamic radius of 21.91 A was obtained using data from viscosimetric experiments. These data, together with the Tanford and Einstein-Stokes relationships, were used to determine the micellar structure (spherical) and the diffusion coefficient (D = 0.97 x 10-6 cm2/s), respectively. The AG of micellization for BDHC was determined to be-34.9 kJ/mol.
Journal of Photochemistry and Photobiology A: Chemistry, 2011
The micellar aggregation behavior and micropolarity characteristics of a series of N,N-bisalkyl-N,N-bis[(3-d-aldonylamido)propyl]ethylenediamines referred to as gemini bis(C n X) surfactants (where C n = n-butyl, n-octyl, n-decyl and n-dodecyl; X = gluconyl and lactobionyl, denoted as GA and LA, respectively) has been investigated by steady-state fluorescence, SSF (by emission spectra of pyrene) and time-resolved fluorescence quenching, TRFQ (using pyrene as the fluorescence probe and cetylpyridinium ion as the fluorescence quencher). Remarkably low magnitude cmc values were found for the studied aldonamide-type gemini surfactants, in a range from 4.5 × 10 −6 M (bis(C 12 GA)) to 2.3 × 10 −3 M (bis(C 4 LA)). The variation of cmc for bis(C n LA) (n = 4, 8, 10 and 12) follows a linear semi-logarithmic pattern. The obtained I 1 /I 3,c > cmc ratios from 1.41 to 1.5 indicate a considerable high polarity sensed by pyrene in micelles of bis(C n X), dependent upon both the kind of aldonyl entity, and the length of hydrophobic tail. According to TRFQ, all studied systems display micellar growth (demonstrated by values of an average aggregation number of surfactant chains per micelle) with increasing surfactant concentration typically from 100 up to 1000 times more than the cmc. The aggregation numbers, N agg (N tail) and the "polydispersity index", /N ω (less than ∼0.3), show that micelles of bis(C n LA)'s of up to ca. 500cmc, are nearly spherical and almost monodisperse. Their spheroidal micelle growth and enhanced micellar polydispersity is observed as the surfactant concentration increases. Such a behavior was found to be strictly related to geometric aspects of a given surfactant dimeric structure.
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.
Journal of Colloid and Interface Science, 2002
Apparent molar relative enthalpies were measured for the nonionic ethoxylated surfactant CH 3 -(CH 2 ) 5 -(OCH 2 -CH 2 ) 5 OH (C 6 E 5 ) in aqueous solution at constant molality of the ionic surfactant CH 3 -(CH 2 ) 5 -SO − 3 Na + (C 6 SNa) at 25 • C. The experimental data obtained by a stepwise dilution process allowed evaluation of the C 6 E 5 first interaction parameter at several constant molalities of C 6 SNa. The C 6 E 5 critical micelle composition as a function of the C 6 SNa molality was also estimated. The experimental calorimetric data, together with the mixed micelles composition computed in the past by some of us [Ciccarelli et al., Langmuir 14, 7130 (1998)], allowed computation of the h Mic of micellization. The experimental data are compared to those predicted by the ideal solution model and regular solution model of mixed micellization. From a calorimetric study performed on the water-hexanol-C 6 SNa and water-penthaethylene glycol-C 6 SNa model systems, it can be argued that the interactions among the hydrophilic heads in the C 6 E 5 -C 6 SNa mixed micelles prevail on the contribution of the hydrophobic tails in ruling the enthalpic properties of the system. C 2002 Elsevier Science (USA)
Fluctuating micelles: a theory of surfactant aggregation part 1. Nonionic surfactants
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1995
Micelle formation was described by means of small system thermodynamics and interpreted in terms of the fluctuations of a single micelle. A simple interaction model was used to estimate the standard free energy change of nonionic micelle formation. The model gives good predictions of the critical micelle formation concentrations for the alkyl-polyoxyethylene homologous series.
Journal of Physical Chemistry B, 2008
Steady-state and time-resolved fluorometric techniques have been exploited to study the photophysical and distribution behavior of an efficient cancer cell photosensitizer, norharmane (NHM), in well-characterized, biomimicking nanocavities formed by cationic micelles with varying surfactant chain length. Amphiphiles like dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB), and cetyl trimethyl ammonium bromide (CTAB) have been used for the purpose. Emission behavior of NHM is very much dependent on the surfactant concentration as well as their hydrophobic chain length. The binding constant (K) and free-energy change (∆G) for the interaction of NHM with the cationic micelles have been determined from the fluorescence data. Polarity of the microenvironment around the probe has been determined in the cationic micellar environments from a comparison of the variation of fluorescence properties of the two-prototropic species of the probe in water/dioxane mixture with varying composition. Experimental results demonstrate that the variation in the cationic surfactant chain length plays an important role in promoting a specific prototropic form of the probe molecule. Fluorescence decays are biexponential in all the micelles indicating that the probe molecules are distributed between the two distinct regions of the micelles. The population of the component with a longer lifetime corresponds to the probe in the head group site, while the short-lived component comes from the probe bound to the core region of the micelles. On the basis of the lifetime measurements, the partitioning behavior of the chromophore in the head group and in the core regions in the micelles has been determined. 3685 P ) [NHM] Stern /[NHM] core ) a 1 /a 2 (8)