AOT Concentration Research Articles

Effect of AOT/Heptane Reverse Micelles on Oxidation of Ferroin by Metaperiodate: Kinetic and Mechanistic Aspects

A kinetic study of the oxidation of Ferroin, [Fe(phen)3]2+ by metaperiodate (IO4-) has been carried out in AOT/heptane reverse micelles by changing W = ([H2O]/[AOT]) and AOT concentration. The reaction order is first order with respect to Ferroin, while zero order with respect to IO4-. The reaction rate is faster in aqueous medium compared to AOT reverse micelles by eight times. The oxidation rate increases with an increase in the value of W (at fixed surfactant concentration, [AOT]) and decreases with AOT concentration. The effect of W on rate is elucidated based on the low dielectric constant of the water pool. Berezin's pseudo-phase model has been applied to explain the effect of AOT on rate.

X-ray study of structural changes in “di-(2-ethylhexyl) sulfosuccinic acid (AOT) /n-heptane-water” liquid crystalline system depending on the concentration of components

Structural changes in the “sodium salt of di-(2-ethylhexyl)sulfosuccinic acid (AOT) - n-heptane-water” liquid-crystalline system depending on the AOT concentration in the n-heptane-water mixed solvent were studied using the X-ray diffraction method. The studies were carried out in a wide range of the AOT concentrations from 27 to 92% in a mixed solvent n-heptane/water=5.8 ratio.The mesomorphism of a liquid-crystalline system is on the concentration of the system. It is confirmed that at concentrations the AOT above 50%, a liquid crystal structure with an intradomain "flat" liquid crystal layered phase takes place. A “flat” lamellar lyotropic-liquid-crystalline phase with an intradomain lamellar structure is formed in the system. The structural parameters, the compactness of the liquid crystal system, the thickness of the formed layers, the surface area per molecular head on the surface of the layers depending on the concentration and thickness of the bound water layer are revealed. The liquid crystal system under study can serve as a model for studying various problems of biological membranes.

Influence of sodium carboxymethylcellulose on sodium dodecyl benzene sulfonate and sodium dioctyl sulfosuccinate micelles in the presence of phenol red dye

Strong dye-surfactant interactions and innovative formulations are required for dyeing, which is one of the most important operations in the pharmaceutical, food, cosmetic, and textile industries for colouring goods and other uses. The interactions of sodium dioctyl sulfosuccinate (AOT) and sodium dodecyl benzene sulfonate (SDBS) with the dye phenol red (sodium salt of PR) in the presence and absence of the polyelectrolyte sodium carboxymethylcellulose (NaCMC) were investigated using conductometric analysis. The critical micelle concentration (CMC) of SDBS and AOT was found to decrease as PR concentration increased in the water and NaCMC medium. However, in the presence of PR, the counterion binding (βc) of SDBS and AOT increased and negative (∆Gmic°) values indicated that micelle formation was energetically favourable. The results of the UV absorbance experiments indicated that the majority of the binding in the DBS¯ and DS¯ micelles was caused by the ketone proton groups (H+PR¯) of the PR. In NaCMC media, PR (H+PR¯) binding to DBS¯ and DS¯ micelles has been regulated by electrostatic interactions, which have been demonstrated by absorption data and binding constant values. According to dynamic light scattering (DLS) examinations, increasing the amount of PR increased SDBS and AOT micellar size in aqueous and NaCMC media.

X–Ray study of structural changes in the liquid crystal systemAOT / N–Heptane–Water depending on the concentration of components

The work investigated the structural changes of the multicomponent liquid crystal system sodium salt of di– (2–ethylhexyl) ester of sulfosuccinic acid (AOT) –n–heptane – water depending on the concentration of AOT in a mixed solution by X–ray diffraction. The studies were carried out in a wide concentration range from 27 to 92% AOT in a mixed solvent with an initial n–heptane / water ratio of 5.8. The studies were carried out with a gradual decrease in the n–heptane / water ratio to the content of bound water in the system and an increase in the concentration of AOT in the solution to 92%. The mesomorphism of the liquid crystal system is established depending on the content of the concentration of the components and the region of the compact liquid crystal lamellar “smooth” phase for modeling biological membranes is established

Investigation of structural changes in the liquid crystal system AOT / n–heptane–water under the influence of vitamin E by the method of X–ray analysis

Structural rearrangements of the lyotropic liquid–crystal system sodium salt of di–(2–ethylhexyl) ester of sulfosuccinic acid (AOT) –n–heptane – water under the influence of vitamin E were studied by X–ray diffraction. The studies were carried out in the concentration range from 50 to 80% AOT+E in a mixed solvent n–heptane/water. The studies were carried out with a gradual increase in the concentration of vitamin E in the system and with an increase in the concentration of AOT + E in a solution of n–heptane/water. It has been established that, in the model liquid crystal system under study, vitamin E penetrating into the structure of the liquid crystal phase AOT–n–heptane–water leads to structural rearrangements and compactization of the molecular packing of the “smooth” phase.

Intramolecular charge transfer of coumarin dyes confined in methanol-in-oil reverse micelles

The reverse micelles (RMs) of bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) are considered as a model system for the molecular dynamics investigation of small chromophores, where the micelle-size-dependent dynamics are interpreted as the unique solvent properties in the core of RMs. The sizes of RMs are practically proportional to the molar ratio between polar solvent and surfactant. However, the formation of RMs with nonaqueous polar solvents methanol or acetonitrile is not clearly understood yet. In this work, we have shown that the formation of RMs with methanol core depends strongly on the concentration of surfactant AOT by the experimental evidence of the absorption, emission, and Raman spectroscopic measurements. In addition, the intramolecular charge transfer dynamics of coumarin 481 (C481) and coumarin 153 in methanol RMs were investigated by steady-state and time-resolved electronic spectroscopy, where the differences of the excited-state dynamics in the RMs are understood as the effect of the molecular rotation of diethylamino group of C481.

Solvent Extraction of Copper Ions from Wastewater using Reverse Micelles: Experimental and Optimization

In this study, the optimum conditions for different process parameters were determined for solvent extraction of copper ions from wastewater using reverse micelles. The process parameters viz. copper ion concentration, sodium bis-2-ethyl hexyl sulphosuccinate (AOT) concentration, solution pH, organic to aqueous phase volume ratio, and NaCl concentration were taken into consideration in response surface methodology, ranging from 30-150 mg/l, 0.04-0.2 [M], 3-11, 0.2-1.0, 0-4 g/100 ml respectively and their effect on percentage removal of copper ions were studied. A regression model was developed by conducting response surface methodology for the analysis of percentage removal of copper ions from wastewater. As many as fifty four experiments were procured from the design of experiments for the percentage removal of copper ions. The developed model was employed to optimize the process parameters being considered to maximize the response. The optimum conditions were found to be 30 mg/l copper ion concentration, 0.20 [M] AOT concentration, 3.12 pH, 0.57 organic to aqueous phase volume ratio, and 0.134 g/100 ml NaCl concentration. The obtained model was validated with experimental data and found to be best fitted within the tolerance limit. The effect of cross-interaction among the process parameters on the percentage removal of copper ions were also investigated. In this study, the copper ion concentration was analyzed by Atomic absorption spectroscopy (AAS).

Electrophoretic mobility and stability of SiO2 nanoparticles in the solutions of AOT in n-hexadecane-chloroform mixtures.

Electrophoretic mobility of SiO2 nanoparticles in a n-hexadecane-chloroform mixture depending on AOT concentration and chloroform content was determined. It was shown that an increase in chloroform content and a decrease in AOT concentration cause a growth in electrophoretic mobility. The use of the values of Debye lengths (characteristic thickness) of the diffuse part of the electric double layer (EDL) that were determined previously allowed us to calculate the electrokinetic potential and to evaluate the stability of organosols. The obtained data were in good correlation with the dynamics of temporal changes of hydrodynamic radius and the intensity of light scattering. Organosols may be used for heteroaggregation (sorption) of Au and Ag nanoparticles on SiO2 .

Binding behaviour of hydrophobic drug tetracaine hydrochloride used as organic counterion on ionic surfactants

Many excipients have been used in the formulation of medications to improve drug properties during the drug delivery process. Current research may show that hydrophobic drugs can be used as organic counterions that improve the excipients properties of the medicine formulation. We have used the anesthetic cationic drug tetracaine hydrochloride (TC) as an organic counterion and anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium dodecyl sulfate (SDS) for this system. In aqueous media, TC significantly reduced the critical micelle concentration (CMC) of AOT and SDS. The counterion binding (B) and binding constant (Kb) values revealed that AOT micelles had a stronger interaction with TC than SDS micelles. Therefore, TC as an organic counterion could improve the micellization of surfactants. The UV spectroscopy experiment has also been used to estimate the TC mean ion occupancy (i0) per AOT/SDS micelles. We found that i0 values were 113.6 and 23.27 for AOT and SDS, respectively. These results indicated the i0 values were controlled by electrostatic interaction between drug and surfactants. Dynamic light scattering (DLS) and Transmission electron microscopy (TEM) measurement provided that the catanionic vesicle was formed with increased TC concentration. Finally, we concluded that the above formulation could be used to enhance interaction properties between the medicine and excipients in the pharmaceutical application.

Multivalent counterion induced multilayer adsorption at the air-water interface in dilute Aerosol-OT solutions

The formation of surface multilayer structures, induced by the addition of multivalent counterions in dilute surfactant solutions, has been widely observed in a range of anionic surfactants. The phenomenon is associated with the ability to manipulate surface properties, especially in the promotion of enhanced surface wetting, and in the presence of an extensive near surface reservoir for rapid surface delivery of surfactant and other active components.Hypothesis.In the single alkyl chain anionic surfactants, such as sodium dodecysulfate, SDS, sodium alkylethoxylsulfate, SAES, and alkylestersulfonate, AES, surface multilayer formation is promoted by trivalent counterions such as Al3+, and is generally not observed with divalent counterions, such as Ca2+ or with monovalent counterions. In the di-alkyl chain anionic surfactant, dodecylbenzenesulfonate, LAS, surface multilayer formation now occurs in the presence of divalent counterions. It is attributed to the closer proximity of a bulk lamellar phase, resulting in a greater tendency for surface multilayer formation, and hence should occur in other di-alkyl chain anionic surfactants.Experiments.Aerosol-OT, AOT, is one of the most commonly used di-alkyl chain anionic surfactants, and is extensively used as an emulsifying, wetting and dispersing agent. This paper reports on predominantly neutron reflectivity, NR, measurements which explore the nature of surface multilayer formation of the sodium salt of AOT at the air-solution interface with the separate addition of Ca2+ and Al3+ counterions.Findings.In the AOT concentration range 0.5 to 2.0 mM surface multilayer formation occurs at the air-solution interface with the addition of Ca2+ or Al3+ counterions. Although the evolution in the surface structure with surfactant and counterion concentration is broadly similar to those reported for SDS, SAES and AES, some notable differences occur. In particular the surfactant and counterion concentration thresholds for surface multilayer formation are higher for Ca2+ than for Al3+. The differences encountered reflect the greater affinity of the di-alkyl chain structure for lamellar formation, and how the surface packing is controlled in part by the headgroup structure and the associated counterion binding affinity.

Silver Nanoparticles Formation by Nanosecond Pulsed Laser Irradiation in an Aqueous Solution of Silver Nitrate; Effect of Sodium bis (2-ethyl hexyl) Sulfosuccinate

A photochemical reduction of a silver salt precursor using near-ultra-violet (UV) pulsed laser (355 nm) irradiation into aqueous surfactant sodium-bis (2–ethylhexyl) sulfosuccinate (AOT) solution has succeeded in synthesizing homogenous speculative silver nanoparticles (Ag NPs). Without using any additive, the irradiation from ns laser pulses to aqueous silver nitrate solution was observed to create nanocubes (NCs). The photoproduct was transformed into a nanosphere when irradiated with a particular AOT concentration. The photoproduct concentration of NCs to NSs was approximately ten times lower than the critical concentration of micellar (CMC) in AOT, which means that the growth of NSs was aided in a single layer of AOT adsorbed on silver surfaces. A UV / Visible Spectrophotometer and Transmission/Scanning electron microscopy (TEM/SEM) were used to characterize the photochemically synthesized sample thoroughly. The mean size of AgNSs, analyzed by TEM, was 8 nm. These parameters have shown the growth of AgNSs and discussed in the paper. These nanoparticles are potential candidates for catalyst, semiconductor, photovoltaic equipment, medical diagnostics applications than bulk materials.

UV–Vis studies of methyl red in the presence of sodium dioctylsulfosuccinate/acetone and sodium dioctylsulfosuccinate/acetone/water

This paper reports the spectra of methyl red (MR) in the presence of sodium dioctylsulfosuccinate (AOT) by UV–Vis spectrophotometer at 298.15 ± 0.1 K. The experiment shows the effect of acetone, AOT and water concentration on methyl red. The spectral study was based on R parameter, which is defined as [H2O]/[AOT]. The spectral study was possible in the range of R = 0–20 only because the solution appeared to be cloudy above this amount of water. When the concentration of AOT increased, the absorption of MR decreased, indicating a hypochromic shift, which is due to the interaction between AOT and MR. The absorbance increases with the increasing value of R, which indicates that the H2O molecule hinders the interactional forces between AOT and MR. The distribution constant was calculated by using nonlinear regression analysis and its variation with different R values indicate the effect of water content in the distribution behavior of MR in between the solvent and micellar region whereas the variation of the binding constant with different R values indicates the affinity of micelles to bind MR molecule. The study of this binding affinity will be very helpful in textile dyeing, decolorization of industrial effluents and development of azo-based molecules in novel photonic and optoelectronic devices.

UV-VIS studies on interaction between sodium dioctylsulfosuccinate (AOT) and methyl red

"This paper deals with the interaction of sodium dioctylsulfosuccinate (AOT) and methyl red (MR) by UV-Vis spectrophotometry at 298.15 K. The concentration of AOT varies from 0 to 0.12530 mol/kg and the concentration of methyl red is 3.71×10-5 M. Here, water concentration is defined by the R parameter. The R parameter in this study varied from 0 to 20. Two intense absorption bands were observed within the 380 to 540 nm wavelength of methyl red in methanol. Band 1(380 to 450 nm) of methyl red contains a higher absorbance peak than band 2(450 to 540 nm). When the concentration of AOT increased, band 1(380 - 450 nm) of methyl red decreased the absorbance peak, whereas band 2 (450 to 540 nm) of methyl red increased the absorbance peak with increasing AOT concentration. Band 1 shows a hypochromic shift of methyl red with an increase in AOT concentration, whereas band 2 shows a hyperchromic shift of methyl red with an increase in AOT concentration. On comparing the absorbance versus concentration graph for different R parameters, we observed that absorbance increases with the increase in the R parameter. The binding constant and distribution constant were calculated using a non-linear regression procedure (NLREG). The experiment shows the effect of methanol, AOT and water concentration on methyl red."

Nanocarrier-loaded block copolymer dual domain organogels

Loaded polymer gels are prevalent materials in the controlled release community and, fairly recently, have been formulated to include nanocarrier domains such as micelles and vesicles. One mechanism used to establish the solid-like characteristic of gels is block copolymer self-assembly, which can result in a system-spanning, physically-crosslinked network. The combination of nanocarrier and crosslink domain presence offers gels with a rich nanoscale phase space capable of intricate macroscopic property tuning. The current manuscript provides an overview of nanocarrier-loaded block copolymer organogels wherein nanocarriers are reverse micelles formed by sodium dioctyl sulfosuccinate (AOT), the block copolymer is a styrenic ABA triblock copolymer, and the gel solvent is aliphatic mineral oil. This introductory overview starts by identifying the envelope in ternary phase space wherein nanocarrier-loaded block copolymer organogels form (2–49 wt% triblock copolymer and 8x10−3-1 wt% AOT). Next, a detailed nanostructural description of gels varying in AOT and triblock copolymer concentration is presented. The manuscript concludes with demonstration of AOT reverse micelle release and gel uniaxial tensile response for gels containing 0–1 wt% AOT and 5–40 wt% styrenic triblock copolymer.

Foam Destabilization Effect of Sodium Bis(2-ethylhexyl)sulfosuccinate on Sodium Alkylsulfate Aqueous Solutions Based on Its Fast Surface Tension Gradient Relaxation

Abstract This study investigated the relationship between the air–water interfacial dilational viscoelasticity and foam properties in mixed anionic surfactant aqueous solutions of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), sodium n-dodecylsulfate (C12AS), sodium n-tetradecylsulfate (C14AS), and sodium n-hexadecylsulfate (C16AS). The surfactants used here differ only in hydrophobic chains. The air–water interfacial viscoelasticity of AOT aqueous solutions mixed with C12AS or C14AS was similar to that of AOT single aqueous solutions at the same constituent concentration of AOT. On the other hand, the air–water interfacial viscoelasticity of mixed aqueous solutions of AOT and C16AS was intermediate between the respective single aqueous solutions. The foam properties of these mixed aqueous solutions were evaluated by a modified Ross–Miles method and it was shown that foam stability is correlated with the maximum value of viscoelastic modulus in mixed aqueous solutions of AOT and AS.

Analysis of ionic and nonionic surfactants blends used for the reverse micellar extraction of Lactoperoxidase from whey

AbstractBovine Lactoperoxidase (LP), a minor whey protein, is used as an antimicrobial in cosmetic, food, and pharmaceutical preparations. Industries are in pursuit of reliable, cheap, and scalable purification methods as the conventional techniques for LP purification like chromatography and membrane separation suffer from several drawbacks. The present work investigates the selective reverse micellar extraction of LP using the reverse micellar system formed by mixing food grade nonionic (Tween, Span, and Triton series) and ionic (AOT) surfactant blends. The analysis of LP extraction efficiency was performed by varying the concentration of nonionic surfactants with a constant AOT concentration of 100 mM and the initial pH of the system. Complete LP solubilization was achieved with reverse micelles formed by 100 mM AOT and 20 mM Tween 80 at pH 8. It was found that the extraction efficiency was dependent on the chain length or the number of ethylene oxide units in the Triton surfactant tail and the carbon–carbon double bond in Tween 80 tail, that is, on oleic acid. Span series however showed poor extraction in the organic phase substantiating the lesser water content. The forward extracted LP was successfully back‐extracted into a fresh aqueous phase containing 1 M KCl at pH 10.5. The aqueous phase (whey) from the forward transfer can be further used to fractionate other whey proteins.

Electrostatic interactions of poly (methyl methacrylate) colloids: deposition patterns of evaporating non-aqueous colloidal droplets

We generate controllable micrometer-range electrostatic interactions in a suspension by using a charge control additive: an anionic surfactant, dioctyl sodium sulfosuccinate (AOT), and an organic salt, tetradodecylammonium tetrakis (3,5-bis (trifluoromethyl)phenyl)borate (TDAT) in non-aqueous solvents. Both systems function via different mechanisms of altering the electrostatic interaction between poly (methyl methacrylate) (PMMA) colloids. For the AOT system, the particle surface charge is modified by the adsorption of charged and neutral AOT micelles on the surface, hence affecting the interactions between particles. The measured scaled surface potential is independent on the AOT concentration, so that the AOT-PMMA system approximates the constant surface potential (CSP) limit. For the electrolytic TDAT non-aqueous system, the screening length of the solution was altered due to the presence of free ions in the solution. This is confirmed by the conductivity and theoretical Debye length λD values. However, from the force measurement using the blinking optical tweezers (BOTs), it was revealed that the measured screening length κ−1, and the particle effective charge Zeff shows a non-monotonic dependence on the TDAT concentration. The deviation between these values revealed that at high TDAT concentrations, the classical DLVO theory-Debye-Huckel limit is no longer valid for the system. We relate the formation of clusters and aggregates formed in the bulk system with the deposition patterns of a colloidal droplet on a hydrophobically coated glass substrate. The drying of droplets containing monodisperse PMMA particles was studied by confocal microscopy.

The Study of the Dispersity of Gold Aerosols with the Use of Au–AOT Composite Films

Approaches have been proposed for determining the dispersity of a gold organosol with an AOT concentration of 0.25 M by examining the surface of an Au–AOT composite film by scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. The film has been obtained from a concentrated sol by the Doctor Blade method and subjected to thermolysis at 523 K for 2 h. The composite consists of individual Au nanoparticles coated with a surfactant adsorption layer. The average sizes of the particles are 11 ± 2 and 12 ± 3 nm, as determined by SEM and AFM, respectivelt, and correlate with the data of classical methods used for determining dispersity of sols, namely, photon-correlation spectrometry (13 ± 1 nm), transmission electron microscopy (7 ± 2 nm), and plasmon resonance spectrophotometry (15 nm).

Structure and conductivity of AOT solutions in n-hexadecane-chloroform mixtures.

The structure and conductivity of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) solutions (2.5 × 10-4 -2.5 × 10-1 M) in n-hexadecane-chloroform mixture at the chloroform concentration from 50 to 100 vol% were studied. The diffusion ordered spectroscopy NMR study revealed that in the indicated range, the observed hydrodynamic diameter of micelles depends only on the AOT concentration and does not depend on the chloroform content. Molar fractions of free AOT molecules and those aggregated into micelles were calculated using the Lindman's law: at concentrations above 2.5 × 10-1 М, the solutions contain mostly the micelles, whereas at concentrations below 2.5 × 10-4 M, the solutions contain AOT molecules. The transition region contains both the AOT molecules and the micelles. Conductivity measurements were used to determine free charge carriers in the bulk of solutions and their contributions to conductivity.

Unraveling the binding and micellization behavior of dioctylsulfosuccinate Sodium Salt with vitamin B1 and B6: A physiochemical and computational study

The outcomes of drug delivery rely on the route of administration which further depends on the understanding of interactional or partitioning mechanism of drugs within the self assembled structures. Thus, identification of various interactions in such systems is of utmost importance. Herein, the partitioning of vitamins: B1 (thiamine hydrochloride; THC) and B6 (Pyridoxine hydrochloride; PyH) in dioctyl sulfosuccinate sodium salt (AOT) have been addressed by employing experimental and computational techniques. The values of partial molar volumes (ΔtrV2,фo) and partial molar isentropic compressions ΔtrKS,2,фo of transfer for PyH have been calculated from density and sound velocity measurements which suggest the presence of hydrophilic interactions between AOT and PyH. The obtained results were further supported by Density Functional Theory Calculations which suggest that hydrogen bonding plays important role in PyH/AOT binding. The binding constants along with thermodynamic parameters at different temperatures have been calculated using calorimetric measurements. In case of THC/AOT the negative values of ΔrS are overcome by more negative values of ΔrH, making the overall process favorable. In case of PyH, two set of binding sites with stronger affinity for second site have been observed along with favorable entropy. Calorimetric and surface tension measurements were used to study the impact of PyH/THC on the Critical micelle concentration of AOT. Spectroscopic and Dynamic light scattering studied have been used as complementary techniques that also confirmed the partitioning of vitamins in AOT micelles.