Sample records for aot microemulsion system

  1. Synthesis and characterization of silver nanoparticles in AOT microemulsion system

    NASA Astrophysics Data System (ADS)

    Zhang, Wanzhong; Qiao, Xueliang; Chen, Jianguo


    Colloidal silver nanoparticles have been synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of one microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another microemulsion as reducing agent, dodecane as the oil phase, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The UV-vis absorption spectra and transmission electron microscopy (TEM) have been used to trace the growth process and elucidate the structure of the silver nanoparticles. UV-vis spectra show that the Ag4+ intermediates formed at early stages of the reaction and then the clusters grow or aggregate to larger nanoparticles. TEM micrographs confirm that the silver nanoparticles are all spherical. The resulting particles have a very narrow size distribution. Meanwhile, the diameter size of the particles is so small that the smallest mean diameter is only 1.6 nm. IR results show that the surfactant molecules are strongly adsorbed on the surface of silver particles through a coordination bond between the silver atom and the sulfonic group of AOT molecules, which endows the particles with a good stability in oil solvents. As dodecane is used as oil solvent to prepare silver nanoparticles, the formed nano-silver sol is almost nontoxic. As a result, the silver nanoparticles need not be separated from the reaction solution and the silver sol may be directly used in antibacterial fields.

  2. Spinodal decomposition of the three-component microemulsion system: AOT/water/decane

    SciTech Connect

    Mallamace, F.; Micali, N.; Trusso, S.; Chen, S.H.


    The authors have performed a series of spinodal decomposition measurements of a three-component microemulsion system made of a surfactant AOT, water, and decane. The measurements were made by a temperature jump from a one-phase droplet microemulsion to a two-phase droplet microemulsion along the critical iso-volume fraction line (10%) using the time resolved light scattering intensity technique. All three stages of the evolution were studied. The typical scattering intensity distribution is in good agreement with recent dynamic scaling theories.

  3. Studies on the catalytic behaviour of a cholinesterase-like abzyme in an AOT microemulsion system.


    Franqueville, Eric; Stamatis, Haralambos; Loutrari, Heleni; Friboulet, Alain; Kolisis, Fragiskos


    The hydrolytic activity of a monoclonal catalytic antibody (9A8) (abzyme) with acetylcholinesterase-like activity was investigated in water-in-oil (w/o) microemulsions (reverse micelles) based on sodium bis-2-(ethylhexyl)sulfosuccinate (AOT) in isooctane, using p- and o-nitrophenylacetate (p-and o-NPA) as substrates. The dependence of the abzyme hydrolytic activity on the molar ratio of water to surfactant (w(o)) showed a bell-shaped curve, presenting a maximum at w(o)=11.1. An increase of the AOT concentration at constant w(o), resulted in a decrease of the catalytic activity suggesting a possible inhibition effect of the surfactant. The incorporation of the abzyme into the reverse micelle system caused a blue shift of the fluorescence emission maximum by a magnitude of 7-10 nm depending on the w(o) value. This result indicates that the antibody molecule, or a large part of it, is located in the aqueous microphase of the system. Kinetic studies showed that the hydrolysis of p-and o-NPA in microemulsion system as well as in aqueous solution follows Michaelis-Menten kinetics. The catalytic efficiency (k(cat)/K(m)) in w/o microemulsion was significant lower than in aqueous solution. PMID:12067523

  4. Phase behavior, transport properties, and thermodynamics of water/AOT/alkanol microemulsion systems

    SciTech Connect

    Ray, S.; Moulik, S.P.


    The phase diagrams of ternary systems of water/Aerosol-OT/alkanol (having carbon numbers 5, 6, 7, 8 and 10) are presented. Appreciable single-phase zones with viscous regions at higher proportions of Aerosol-OT (AOT) have been witnessed for all the alkanols. The ternary systems have also shown water-induced percolation of conductance with multistep phenomena in some cases. The viscous preparations have behaved like Bingham liquids (the viscosity has increased with the rate of shear). The enthalpy of the solubilization of water in alkanol/AOT medium has been calorimetrically determined to be positive; the free energy has been evaluated from the knowledge of maximum water intake until phase separation. The free energy and entropy of water solubilization (derived from Gibbs` equation) have been found to be positive and negative, respectively, and they follow a regular trend with the [alkanol]/[AOT] mole ratio (R) as well as with the alkanol carbon number. On the other hand, the enthalpy values, although they increased with R, increase with alkanol chainlength to a maximum for heptanol and then decrease for both octanol and decanol. It is considered that the heptanol acts as an efficient cosurfactant with AOT and helps to produce microdroplets with increased endothermicity.

  5. Phase behavior of AOT microemulsions in compressible liquids. [AOT = bis(2-ethylhexyl) sodium sulfosuccinate

    SciTech Connect

    McFann, G.J.; Johnston, K.P. )


    The phase behavior of bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-alkane-brine systems is described over a wide range of pressure, temperature, and salinity for alkanes from ethane to dodecane. The partitioning of AOT between the oil, middle, and brine phases is reported for propane in order to determine the natural curvature. This is important for understanding separation processes with water-in-oil microemulsions. For the lighter, more compressible alkanes, the pressure effect on the hydrophilicity of the surfactant is much larger and in the opposite direction as for the heavier, less compressible ones. In propane at constant temperature and salinity, water-in-oil (w/o) microemulsions have been converted to middle phase microemulsions and then to oil-in-water (o/w) microemulsions by decreasing the pressure. These phase inversions are described in terms of the immiscibilities in the binary systems, and the molecular interactions at the surfactant interface. Although temperature and salinity are used commonly to manipulate interactions primarily on the water side of the interface, these results show it is possible to control interactions on the oil side by adjusting the pressure. The well-established trends in the phase behavior and size of microemulsion drops for dodecane through hexane are not observed for the lighter alkanes. For butane through ethane, a new unusual behavior is identified and attributed to a significant decrease in the strength of the attractive interactions between the surfactant tails and the alkane.

  6. The influence of the structure and the composition of water/AOT-Tween 85/IPM microemulsion system on transdermal delivery of 5-fluorouracil.


    Yanyu, Xiao; Fang, Liu; Qineng, Ping; Hao, Cai


    The purpose of this study was to investigate the influence of the structure and the composition of water/Aerosol-OT (AOT)-Tween 85/isopropylmyristate (IPM) microemulsion system (WATI) on transdermal delivery of 5-fluorouracil (5-FU). The structure of WATI was characterized by measuring surface tension, density, viscosity, electric conductivity, and differential scanning calorimetry. The effect of the drug loading, water content, component compositions and the amount of mixed surfactant on permeation of 5-FU through mice skin was evaluated by using Franz-type diffusion cells. The results in vitro implied that WATI was W/O microemulsion when the water content was below 20 wt% at fixed 20 wt% of mixed surfactant at 25°C, then might be transformed to a bicontinuous structure, finally, formed O/W microemulsion with water content over 30 wt%. Increase of the drug loading can directly facilitate the penetration of the drug across the skin. Drug diffusion after 12 h from the bicontinuous microemulsion (795.1 ± 22.3 µg·cm(-2)) would be fastest compared to that from the W/O microemulsion (650.2 ± 11.7 µg·cm(-2)) and the O/W microemulsion (676.6 ± 14.8 µg·cm(-2)). The combination of AOT and IPM could bring about synergistic effect on the skin enhancement, however, Tween 85 in WATI decreased the cumulative permeation amount of 5-FU. The content of mixed surfactant had no effect on the permeation of 5-FU at fixed surfactant/cosurfactant ratio (K(m) = 2). Thus, the increased transdermal delivery the hydrophilic drug of 5-FU was found to be concerned with both of the structure and the composition of WATI. PMID:22324326

  7. Spectrometric study of AOT-hydrolysis reaction in water/AOT/isooctane microemulsions using phenolphthalein as a chemical probe.


    Mao, Shiyan; Chen, Zhiyun; Fan, Dashuang; An, Xueqin; Shen, Weiguo


    The kinetics of the alkaline hydrolysis of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in water/AOT/isooctane microemulsions has been studied by monitoring the absorbance change of the phenolphthalein in the system with time. The apparent first-order rate constant k(obs) has been obtained and found to be dependent on both the molar ratio of water to AOT ω and the temperature. The dependences of k(obs) on ω have been analyzed by a pseudophase model which gives the true rate constants k(i) of the AOT-hydrolysis reaction on the interface and the partition coefficients K(wi) for the distribution of OH(-) between aqueous and interface pseudophases at various temperatures; the latter is almost independent of the temperature and ω. The temperature dependences of the reaction rate constants k(obs) and k(i) have been analyzed to obtain enthalpy ΔH(≠), entropy ΔS(≠), and energy E(a) of activation, which indicate that the distribution of OH(-) between aqueous and interface pseudophases increases ΔS(≠) but makes no contribution to E(a) and ΔH(≠). The influence of the overall concentration of AOT in the system on the rate constant has been examined and found to be negligible. It contradicts with what was reported by García-Río et al. (1) but confirms that the first-order reaction of the AOT-hydrolysis takes place on the surfactant interface. The study of the influence of AOT-hydrolysis on the kinetics of the alkaline fading of crystal violet or phenolphthalein in the water/AOT/isooctane microemulsions suggests that corrections for the AOT-hydrolysis in these reactions are required. PMID:22168828

  8. Nanoparticles synthesis of tungsten disulfide via AOT-based microemulsions

    SciTech Connect

    Ghoreishi, S.M.; Meshkat, S.S.; Ghiaci, M.; Dadkhah, A.A.


    Graphical abstract: A controlled synthesis of WS2 nanoparticles (most probably inorganic fullerene (IF)) via microemulsion was applied for the first time to prepare WS2 (7–12 nm) by acidification of the water cores of the AOT reverse microemulsion. Highlights: ► An innovative reverse microemulsion technique was developed for WS{sub 2} synthesis. ► WS{sub 2} nanoparticles were obtained with narrow size distribution in range of 7–12 nm. ► Operating cost of microemulsion was lower in contrast to quartz reactor method. ► WS{sub 2} morphology could be controlled to obtain highly active and selective catalysts. ► Lower size of WS{sub 2} in this study overcomes the shortcoming of quartz reactor method. -- Abstract: The tungsten disulfide (WS{sub 2}) nanoparticles (most probably inorganic fullerene (IF)) with a narrow size distribution were synthesized by a reverse micelle technique for the first time. The particle size was controlled by varying water-to-surfactant molar ratio (W{sub 0}), aging time and reagent concentration. The synthesized WS{sub 2} nanoparticles were characterized by zetasizer, UV–visible spectrophotometers and transmission electron microscopy (TEM). The WS{sub 2} nanoparticles with particle diameter size of 7–12 nm were obtained via 24 h aging time. The particle size was controlled by changing the aging time and molar ratio of water/surfactant. Doubling W{sub 0} increased the amount and particle size of WS{sub 2} by 22 and 26%, respectively. The effect of aging time in the range of 6–24 h was investigated and the complete disappearance of yellowish color at 24 h resulted in an optically clear solution, which was the indication of WS{sub 2} formation with 100% conversion of reactant ((NH{sub 4}){sub 2}WS{sub 4}) in the batch reactor.

  9. Micelle and microemulsion properties of cesium di-dodecyl-dimethylsulfosuccinate, Cs-AOT

    SciTech Connect

    Sheu, E.Y.; Nostro, P.L.; Capuzzi, G.; Baglioni, P.


    Cesium di-2-ethylsulfosuccinate (Cs-AOT) micelles in aqueous solutions and Cs-AOT/water/n-decane microemulsions were investigated, at 22 {plus{underscore}minus} 0.1 C, by small angle neutron scattering (SANS). The critical micelle concentration of Cs-AOT is {approximately}2mM, comparable to that of Na-AOT. However, their solution properties and micellar structures were found to be very different. The solubility of Na-AOT in water is approximately 1 wt %, and the micelles grow from spherical (at a concentration of about 0.1 wt %) to oblate objects with eccentricity equal to about 0.8 (at a concentration of 1 wt %), whereas Cs-AOT is largely soluble in water, over 30 wt %, and its micelles are disklike at 1 wt %. As the surfactant concentration increases, micelles may go through an L{sub 3} region, and enter the lamellar phase. Cs-AOT/water/n-decane microemulsions, with a [water]/[Cs-AOT] = 29.1, form isotropic L{sub 2} phases only at very low Cs-AOT + ater volume fractions (below 0.0165), whereas Na-AOT has a large L{sub 2} region. These differences are probably due to the degree of charge condensation near the AOT polar headgroups. A theoretical description is needed to better understand this behavior.

  10. Electrical conductivity and permittivity of water-AOT-n-heptane microemulsions

    SciTech Connect

    Arcoleo, V.; Goffredi, M.; Liveri, V.T.


    Measurements of the electrical conductivity and of the complex permittivity of water-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-n-heptane microemulsions are reported. The experimental results are rationalized in terms of a hopping mechanism of AOT anions within clusters of reversed micelles. The dependence of the hopping rate and of the cluster dimensions upon the ratio [water]/[AOT] and temperature is discussed.

  11. Interdroplet attractive forces in AOT water-in-oil microemulsions formed in subcritical and supercritical solvents

    SciTech Connect

    Tingey, J.M.; Fulton, J.L.; Smith, R.D. )


    The van der Waals attractive interactions between aqueous droplets in water-in-oil type microemulsions have been investigated for a range of continuous-phase solvents including the alkanes from methane to isooctane and the noble gases, krypton and xenon. Hamaker constants for water droplets with surfactant shells of the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in subcritical and supercritical solvents were calculated by using Lifshitz theory and the resulting interaction potential calculations qualitatively account for many features of the phase behavior of these systems.

  12. Complex permittivity of FeCl3/AOT/CCl4 microemulsions probed by AC impedance spectroscopy.


    Calandra, Pietro; Ruggirello, Angela; Turco Liveri, Vincenzo


    The complex permittivity of FeCl(3)/AOT/CCl(4) microemulsions in the 1-10(5) Hz frequency range has been measured by the conventional AC complex impedance technique. Measurements as a function of the volume fraction of the dispersed phase (FeCl(3)+AOT) and temperature at fixed salt-to-AOT molar ratio (R, R = 0.5) show that the entrapment of FeCl(3) clusters significantly enhances the local permittivity of the AOT reverse micelles and the number density of charge carriers resulting from the peculiar state of the confined inorganic salt. An estimate of the apparent static permittivity of the FeCl(3) ionic clusters entrapped in the core of AOT reverse micelles gives the very high and quite surprisingly value of about 237. Moreover, a thorough analysis of conductivity data and of their temperature dependence strongly supports the hypothesis that the charge transport in these systems is mainly sustained by a mechanism of hopping consisting in the continuous jumping of charged species within supra-micellar aggregates of AOT reverse micelles whose aggregation is driven by fluctuating opposite charges on contacting micelles. PMID:19481764

  13. Water-AOT-alkylbenzene microemulsions: influence of alkyl chain length on structure and percolation behavior.


    Appel, Markus; Spehr, Tinka Luise; Wipf, Robert; Stühn, Bernd


    We study the percolation behavior of the water-in-oil (w/o) droplet phase of AOT (sodium bis[2-ethylhexyl] sulfosuccinate)-based microemulsions with different alkylbenzenes (toluene, ethylbenzene, butylbenzene or octylbenzene) as oil phase. We use microemulsions of varying composition with molar water to surfactant ratios 0≤W≤ 50 and droplet (water plus surfactant) volume fractions 10%≤φ≤50%. Using dielectric spectroscopy, a percolation transition is observed in w/o microemulsions with butylbenzene or octylbenzene. With increasing molecular weight of the alkylbenzene, the percolation temperature T(P) decreases. The structure of the microemulsions is determined by small angle X-ray scattering (SAXS). With increasing molar weight of the alkylbenzene, the stability range of the L(2) droplet phase extends to higher W. The larger amount of solubilizable water can be related to variable oil penetration of the AOT monolayer, which affects the spontaneous curvature of the surfactant shell. PMID:22446149

  14. Electrochemistry and electrocatalysis with vitamin B sub 12 in an AOT water-in-oil microemulsion

    SciTech Connect

    Owlia, Azita; Wang, Zhenghao; Rusling, J.F. )


    Vitamin B{sub 12a} solubilized in water pools of highly resistive water-in-oil (w/o) microemulsions of 0.2 M Aerosol OT (AOT, bis(2-ethylhexyl) sulfosuccinate)/4 M water/isooctane gave separate reductions of base-on cob(III)alamine to base-on cob(II)alamine (E{sub 1/2} = {minus}0.03 V vs SCE) and base-on cob(II)alamine to base-off cob(I)alamine (E{sub 1/2} = {minus} 0.87 V). Diffusion coefficients suggested that vitamin B{sub 12} induces the formation of surfactant aggregates in w/o microemulsions that are larger than in solute-free systems. Relative reactivities toward reductions of three oil-soluble alkyl vicinal dihalides by electrochemically generated cob(I) alamine were modified in the microemulsion compared to isotropic water-acetonitrile. Changes in relative reactivity are not explained by simple partition of vicinal dibromides between isooctane and water and suggest specific interactions with surfactant aggregates or significant reaction in the bulk isooctane phase.

  15. Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Arleth, Lise; Pedersen, Jan Skov


    Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10 °C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D2O/decane microemulsion is 10 °C and the temperature of the AOT/D2O/iso-octane microemulsion is 20 °C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D2O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index (σ/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D2O/decane microemulsion. In the AOT/D2O/iso-octane system

  16. Effect of proteins on dynamics of water-in-oil AOT microemulsions

    NASA Astrophysics Data System (ADS)

    Hirai, M.; Kawai-Hirai, R.; Iwase, H.; Hayakawa, T.; Kawabata, Y.; Takeda, T.

    By using neutron spin echo and small angle X-ray scattering methods, we studied the effect of the occlusion of proteins on the structure and dynamics of a water-in-oil sodium bis(2-ethylhexyl)sulfosuccinate (AOT) microemulsion with varying protein concentration. We observed a change of the peak height of the effective diffusion coefficient, indicating that the occlusion of proteins enhances a shape fluctuation of the microemulsion. Such an enhancement would be essentially important for an appearance of super-activity of enzymes occluded in microemulsions.

  17. Anomalous change in interfacial tension induced by collapses of AOT microemulsions at heptane/water interface

    NASA Astrophysics Data System (ADS)

    Takahashi, Masahiko; Yui, Hiroharu; Ikezoe, Yasuhiro; Sawada, Tsuguo


    Dynamic behavior of water-in-oil microemulsions at the oil/water interface was investigated using the quasi-elastic laser scattering method. We observed an anomalous rebound behavior of interfacial tension γ induced by collapses of microemulsions and adsorptions of AOT molecules at the interface. γ rapidly decreased and reached a minimum value (5.5 mN/m) at about 500 s after the preparation of the interface, and then increased gradually for about 2000 s to the equilibrium value (8.0 mN/m). We considered the mechanism of the rebound behavior in terms of transient change in interfacial thickness induced by the collapses of AOT microemulsions.

  18. [Controllable synthesis and UV-Vis spectral analysis of silver nanoparticles in AOT microemulsion].


    Zhang, Wan-Zhong; Qiao, Xue-Liang; Luo, Lang-Li; Chen, Jian-Guo


    Colloidal silver nanoparticles were synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of a microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another one as reducing agent, cyclohexane as the continuous phase, and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The main factors affecting the formation of silver nanoparticles were systematically studied. Ultraviolet-visible (UV-Vis) spectra were used for analyzing the effects of reaction parameters, including the type of reducing agents, the molar ratio of water to surfactant and the concentration of AgNO3 and AOT and so on, on the formation of silver nanoparticles. Original results for the controllable synthesis of silver nanoparticles were obtained when the synthesis proceeded in AOT-cyclohexane-AgNO3 microemulsion. The UV-Vis spectra of silver sols formed in the microemulsion with various parameters were studied systematically. The results show that the amount and average size of the obtained nanoparticles obviously depend on the above parameters. When the concentration of AgNO3 is lower, smaller silver nanoparticles are easy to form by increasing the concentration of AgNO3 appropriately. The higher W value was found to form larger numbers of silver nanoparticles with larger particle size. Compared to the solubility of NaBH4 in AOT reverse micelles, hydrazine hydrate is well soluble in these micelles, and thus it is favorable to reduce the silver ions solubilized in the water core of AOT-cyclohexane-AgNO3 microemulsion. The increase in the concentration of AOT induces an increase in the number of AOT micelles and a decrease in the molar ratio of water to surfactant. As a result, the solubilization capacity of reactants in the micelles increases and the radii of the micelles decrease. That is to say, with the increase in AOT concentration, the amount of the formed nanoparticles increases and the average size of the

  19. Formation of nanosized titania particles in AOT microemulsions

    SciTech Connect

    Moran, P.D.; Bowmaker, G.A.; Cooney, R.P.


    Titania nanoparticles have been produced by the controlled hydrolysis of tetraisopropyltitanate (TPT) in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. Particle formation and aggregation were investigated by static and dynamic light scattering and the chemical species by FT-IR and FT-Raman spectroscopy. The kinetics of particle formation and aggregation were controlled by varying [H{sub 2}O]/[AOT] (w{sub o}), [H{sub 2}O]/[Ti(IV)] and [AOT]/[Ti(IV)]. Nanoparticles, with diameters < 10 nm, could be produced at relatively high Ti(IV) concentrations (up to 0.05 M). These nanoparticles aggregated into sols, with colloid sizes of 20 to 200 nm, eventually forming gelatinous precipitates. Different titania phases were produced, depending on the size of the micellar water pool; small pools (w{sub 0} < 6) yielded amorphous particles, while large pools (w{sub 0} > 10) produced anatase.

  20. Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions

    NASA Astrophysics Data System (ADS)

    Dandapat, Manika; Basu, Saswati; Ghosh, Deborin; Mandal, Debabrata


    Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents.

  1. Changes in the bending modulus of AOT based microemulsions induced by the incorporation of polymers in the water core.


    Kuttich, Björn; Grefe, Ann-Kathrin; Stühn, Bernd


    The bending modulus κ is known to be a crucial parameter for the stability of the droplet phase in microemulsion systems. For AOT based water in oil microemulsions the bending modulus of the surfactant has values close to kBT but can be influenced by the presence of polymers. In this work we focus on the water soluble polymer polyethylene glycol and how it influences the bending modulus. An increase by a factor of three is found. For the correct evaluation of the bending modulus via percolation temperatures and droplet radii, thus by dielectric spectroscopy and small angle X-ray scattering, the determination of the radii right at the percolation temperature is crucial as we will show, although it is often neglected. In order to precisely determine the droplet radii we will present a global fitting model which provides reliable results with a minimum number of free fitting parameters. PMID:27416768

  2. Effect of AOT on enzymatic activity of the organic solvent resistant tyrosinase from Streptomyces sp. REN-21 in aqueous solutions and water-in-oil microemulsions.


    Rodakiewicz-Nowak, Janina; Ito, Masaaki


    The effect of AOT (sodium-bis(2-ethylhexyl sulfosuccinate)) on enzymatic activity of the organic solvent resistant tyrosinase (OSRT) in aqueous phosphate buffer solutions and in water-in-oil microemulsions of the water/AOT/isooctane system has been investigated. In contrast to mushroom tyrosinase, AOT does not activate OSRT in aqueous solutions, altering its activity very little at concentrations lower than 2 mM. Increasing contents of AOT in isooctane reduce the observed initial reaction rates of oxidation of t-butylcatechol (tBC) and 4-methylcatechol (4-MC). Similarly to mushroom tyrosinase, the effect has been described using an equation based on preferential binding of the substrates by surfactant interface layers. The apparent Michaelis-Menten substrate binding constants increase linearly with AOT concentration (with slopes of 0.12+/-0.02 and 0.051+/-0.006 for tBC and 4-MC, respectively), and the effective enzyme turnover number in the microemulsions remains practically constant. PMID:15780309

  3. Study of AOT-stabilized microemulsions of urea dispersed in carbon tetrachloride

    NASA Astrophysics Data System (ADS)

    Ruggirello, A.; Turco Liveri, V.


    Measurements of some physico-chemical properties (density, viscosity, permittivity) of the urea/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/CCl 4 system as a function of the volume fraction of the dispersed phase (0< Φ<0.7) at various urea to AOT molar ratio ( Rurea) have been carried out at 25 °C. The experimental data analysis are consistent with the hypothesis that urea is entrapped as small-size molecular clusters within the hydrophilic core of the AOT reversed micelles and that this structure is preserved well above a threshold Φ value where a percolative transition occurs. Besides, X-ray diffraction spectra of samples at Φ=1, obtained by complete evaporation under vacuum of the apolar solvent of urea/AOT/CCl 4 solutions, indicates that, even in the typical two-dimensional hexagonal structure of AOT liquid crystals, urea is encapsulated as uni-dimensional molecular clusters.

  4. Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering

    SciTech Connect

    Arleth, Lise; Pedersen, Jan Skov


    Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10{degree}C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D{sub 2}O/decane microemulsion is 10{degree}C and the temperature of the AOT/D{sub 2}O/iso-octane microemulsion is 20{degree}C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D{sub 2}O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index ({sigma}/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D{sub 2}O

  5. Degradation of carbofuran derivatives in restricted water environments: basic hydrolysis in AOT-based microemulsions.


    Morales, Jorge; Manso, José A; Cid, Antonio; Lodeiro, Carlos; Mejuto, Juan Carlos


    The effect of sodium bis(2-ethylhexyl)sulfosuccinate/isooctane/water microemulsions on the stability of 2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl methylcarbamate (carbofuran, CF), 3-hydroxy-2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate (3-hydroxycarbofuran, HCF) and 3-keto-2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate (3-ketocarbofuran, KCF) in basic media has been studied. The presence of these microheterogeneous media implies a large basic hydrolysis of CF and HCF on increasing surfactant concentration and, also, on increasing water content in the microemulsion. The hydrolysis rate constants are approximately 2- and 10-fold higher than those in pure water for HCF and CF, respectively. In contrast, a steep descent in the rate of decomposition for KCF was observed. These behaviours can be ascribed to the presence of CF derivatives both in the hydrophilic phase and in the lipophilic phase, while the hydroxyl ions are only restricted to the water pool of the microemulsion (hydrophilic phase). The kinetic rate constants for the basic hydrolysis in AOT-based microemulsions have been obtained on the basis of a pseudophase model. Taking into account that an important part of soils are colloids, the possibility of the presence of restricted water environments implies that soil composition and its structure will play an important role in the stability of these carbamates. In fact, we observed that the presence of these restricted aqueous media in the environment, in particular in watersheds and in wastewaters, could reduce significantly the half-life of these pesticides (33% and 91% for HCF and CF, respectively). PMID:22325067

  6. AOT water-in-oil microemulsions as a penetration enhancer in transdermal drug delivery of 5-fluorouracil.


    Gupta, Reeta R; Jain, Swantrant K; Varshney, Manoj


    In vitro transdermal permeation of 5-fluorouracil (antineoplastic), a hydrophilic drug encapsulated in AOT/water/isopropylmyristate water-in-oil microemulsions (MEs), were studied using a modified Keshary and Chien diffusion cell. AOT (aerosol-OT or sodium bis(2-ethylhexyl) sulfosuccinate) is an anionic surfactant, which forms 'water-in-oil' ME in non-aqueous medium. The effect of water and AOT concentrations in MEs to the transdermal permeation of 5-fluorouracil through hairless mouse skin was investigated. MEs with 5:95 weight ratio of AOT:isopropylmyristate, containing 0.9, 1.8, 2.7 and 3.6% w/w of water have showed 1.68-, 2.36-, 3.58- and 3.77-fold increases in the skin flux of 5-fluorouracil (5-FU) respectively, compared to the aqueous solution of drug. The MEs with 5:95, 9:91 and 13:87 weight ratio of AOT:isopropyl myristate at fixed water content W0=15 (W0=[H2O]/AOT]) gave 3.58-, 5.04- and 6.3-fold enhancement of drug. In addition, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to examine the effect of ME on lipid alkyl chain, hydration level, and corneocyte cells of the stratum corneum (SC). Results reveal that the ME interacts with a component of the SC and perturbs its architectural structure. The extent of perturbation in the SC depends on the concentration of water and AOT in the ME. Preliminary dermal toxicity studies indicate that the AOT/water/isopropylmyristate ME be safe for the transdermal permeation of 5-FU. PMID:15698753

  7. Investigation on the conformations of AOT in water-in-oil microemulsions using 2D-ATR-FTIR correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Lai, Zuliang; Wu, Peiyi


    The carbonyl groups of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in the water-in-oil (W/O) microemulsions of AOT/tetrachloromethane/water were investigated by using two-dimensional attenuated total reflection Fourier transform infrared (2D-ATR-FTIR) correlation spectroscopy under a perturbation of temperature. The results of a traditional curve fitting method were compared with the 2D correlation spectra results. The peaks at 1718 and 1736 cm -1 were assigned to different carbonyl groups in trans conformation and gauche conformation of AOT molecules, respectively. With the increase of temperature, the trans conformation increased quickly at the lower temperature below 35 °C and decreased slowly at the higher temperature. The special phenomenon owed to the composition and decomposition of the hydrogen bonding between water of the inner polar core and carbonyl groups of AOT molecules. Two new peaks at 1707 and 1747 cm -1 in the 2D correlation spectra implied the process of the transition of AOT molecule conformation and the deviation of correlation coefficients of curve fitting method. 2D-ATR-FTIR correlation spectroscopy exhibited the superiority over the traditional curve fitting method.

  8. Micellar interactions in water-AOT based droplet microemulsions containing hydrophilic and amphiphilic polymers

    NASA Astrophysics Data System (ADS)

    Appel, Markus; Spehr, Tinka Luise; Wipf, Robert; Moers, Christian; Frey, Holger; Stühn, Bernd


    We investigate the influence of addition of hydrophilic and amphiphilic polymer on percolation behavior and micellar interactions in AOT-based water-in-oil droplet microemulsions. We focus on two series of samples having constant molar water to surfactant ratio W = 20 and constant droplet volume fraction Φ = 30%, respectively. From dielectric spectroscopy experiments, we extract the bending rigidity of the surfactant shell by percolation temperature measurements. Depending on droplet size, we find stabilization and destabilization of the surfactant shell upon addition of hydrophilic poly(ethylene glycol) (PEG) (Mn = 3100 g mol-1) and amphiphilic poly(styrene)-b-poly(ethylene glycol) copolymer with comparable length of the hydrophilic block. Complementary small angle X-ray scattering experiments corroborate the finding of stabilization for smaller droplets and destabilization of larger droplets. Subsequent analysis of dielectric spectra enables us to extract detailed information about micellar interactions and clustering by evaluating the dielectric high frequency shell relaxation. We interpret the observed results as a possible modification of the inter-droplet charge transfer efficiency by addition of PEG polymer, while the amphiphilic polymer shows a comparable, but dampened effect.

  9. Enzyme hyperactivity in AOT water-in-oil microemulsions is induced by 'lone' sodium counterions in the water-pool.


    Oldfield, Christopher; Freedman, Robert B; Robinson, Brian H


    Water-in-oil microemulsions are thermodynamically stable single-phase dispersions of water and surfactant within a continuous oil phase. The classical ternary system, based on the surfactant sodium bis(2-ethylhexyl)sulfosuccinate ('AOT'), water and an alkane such as n-heptane, is an optically transparent monodispersion of spherical water-droplets coated with a close-packed surfactant monolayer and the droplet radius is, to a good first approximation, directly proportional to the molar water: surfactant ratio, R. Enzymes dissolved in the water droplets retain activity and stability. These systems have attracted interest as media for biotransformations. Principally based upon studies in AOT-stabilized w/o microemulsions, a peculiar feature of the kinetics of enzyme-catalyzed reactions has long been apparent: the reaction rate characteristically increases from around zero at R=3, through a maximum, in the range R= 10-20, and thereafter decreases again, so that plots of rate vs. R are characteristically 'bell-shaped'. Furthermore, at optimal R, enzymes seem to be 'hyperactive', i.e., they are more active, by a modest but significant factor of 2-3-fold, than in aqueous solution. In this paper we propose the hypothesis that this kind of R-dependence arises because of the presence of freely mobile lone surfactant counterions (Na+) within the water-pool. These ions have no charge partners within the water pool and consequently have a high electrochemical potential. According to our model, lone counterions facilitate the hydrolysis of ester or amide substrates, for example, by stabilizing the tetrahedral intermediate formed during the reaction through ion-pairing with the carbonyl oxygen of the substrate, thus facilitating transfer of negative charge from the carbonyl carbon as it is attacked by the incoming nucleophile. An expression for the relationship between the concentration of free counterions in the water-pool and the compositional parameter R leads directly

  10. Synthesis of Ag and AgI quantum dots in AOT-stabilized water-in-CO2 microemulsions.


    Liu, Juncheng; Raveendran, Poovathinthodiyil; Shervani, Zameer; Ikushima, Yutaka; Hakuta, Yukiya


    Silver and silver iodide nanocrystals have been synthesized in the water-in-CO(2) reverse microemulsions formed by the commonly used surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT), in the presence of 2,2,3,3,4,4,5,5-octafluoro-1-pentanol as cosurfactant. The nanometer-sized aqueous domains in the microemulsion cores not only act as nanoreactors, but the surfactant interfacial monolayer also helps the stabilization of the metal and semiconductor nanoparticles. The transmission electron microscopy results show that silver and silver iodide nanocrystals with average diameters of 6.0 nm (standard deviation, SD=1.3 nm) and 5.7 nm (SD=1.4 nm), respectively, were formed. The results indicate that the method can be utilized as a general and economically viable approach for the synthesis of metal and semiconductor quantum dots in environmentally benign supercritical carbon dioxide. PMID:15685712

  11. Ionic liquid-in-oil microemulsions composed of double chain surface active ionic liquid as a surfactant: temperature dependent solvent and rotational relaxation dynamics of coumarin-153 in [Py][TF2N]/[C4mim][AOT]/benzene microemulsions.


    Rao, Vishal Govind; Mandal, Sarthak; Ghosh, Surajit; Banerjee, Chiranjib; Sarkar, Nilmoni


    In the recent past, nonaqueous microemulsions containing ionic liquids (ILs) have been utilized for performing chemical reactions, preparation of nanomaterials, and synthesis of nanostructured polymers and in drug delivery systems. The most promising fact about IL-in-oil microemulsions is their high thermal stability compared to that of aqueous microemulsions. In our earlier publication (Rao, V. G.; Ghosh, S.; Ghatak, C.; Mandal, S.; Brahmachari, U.; Sarkar, N. J. Phys. Chem. B 2012, 116, 2850-2855), we presented for the first time the possibility of creating huge number of IL-in-oil microemulsions, just by replacing the inorganic cation, Na(+), of NaAOT by any organic cation and using different ionic liquids as the polar core. In this manuscript we are interested in exploring the effect of temperature on such systems. We have characterized the phase diagram of the [Py][TF2N]/[C4mim][AOT]/benzene ternary system at 298 K. We have shown that in the experimental temperature range employed in this study, the microemulsions remain stable and a slight decrease in the size of the microemulsions is observed with increasing temperature. We have reported the detailed study of solvent and rotational relaxation of coumarin 153 (C-153) in neat IL, N-methyl-N-propylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide ([Py][TF2N]), and in [Py][TF2N]/[C4mim][AOT]/benzene microemulsions using steady state and picosecond time-resolved spectroscopy. We have monitored the effect of (i) varying the [Py][TF2N]/[C4mim][AOT] molar ratio (R value) and (ii) temperature on solvent and rotational relaxation of C-153. The features observed in absorption and emission spectra clearly indicate that (i) the probe molecules reside at the polar interfacial region of the [Py][TF2N]/[C4mim][AOT]/benzene microemulsions and (ii) with increasing R value the probe molecules move toward the polar IL-pool of the microemulsion. We have shown that the increase in solvation time on going from neat [Py][TF2N] to

  12. The catalytic efficiency of lipase in a novel water-in-[Bmim][PF6] microemulsion stabilized by both AOT and Triton X-100.


    Xue, Luyan; Li, Ying; Zou, Feixue; Lu, Lu; Zhao, Yin; Huang, Xirong; Qu, Yinbo


    In the water-in-[Bmim][PF(6)] microemulsion stabilized by both AOT and Triton X-100, the lipase-catalyzed hydrolysis of 4-nitrophenyl butyrate (p-NPB) was investigated to evaluate the catalytic efficiency of lipase in this novel microemulsion. The structural parameters of the microemulsion and the conditions of the enzymatic reaction affect the catalytic activity of lipase, especially the concentration of Tris-HCl buffer. Under optimum conditions, the catalytic activity of lipase in the present microemulsion is much higher than that in H(2)O saturated [Bmim][PF(6)]. When the partitioning of the substrate in the microemulsion is taken into account, the catalytic efficiency of lipase in this novel microemulsion is 14.3 times that in H(2)O saturated [Bmim][PF(6)] due to the significant decrease of the Michaelis constant in the microemulsion. Due to the large interface, high water activity, and probably the activating effect of the imidazolium cation in the water pool, the present microemulsion is demonstrated to be a promising medium for the lipase-catalyzed hydrolytic reaction. To demonstrate an important biocatalytic application in the IL-based microemulsion, the lipase-catalyzed synthesis of the flavoring agent benzyl acetate via transesterification of vinyl acetate with benzyl alcohol was also studied in the medium. Due to the high dispersion of lipase, large interface and removal of the byproduct, a maximum yield of 94% was obtained, indicating that the novel microemulsion is really important and useful. PMID:22218335

  13. A small-angle neutron scattering study of intermicellar interactions in microemulsions of AOT, water, and near-critical propane

    SciTech Connect

    Kaler, E.W. ); Billman, J.F. ); Fulton, J.L.; Smith, R.D. )


    Small-angle neutron scattering (SANS) measurements of high-pressure solutions of propane/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/D{sub 2}O have demonstrated that a water-in-oil microemulsion phase can be formed in propane. The dispersed droplets are, within experimental error, the same size as those formed in conventional microemulsions at the same water-to-surfactant ratio, and the size does not depend on propane density. The interdroplet interaction potential was modeled as a hard-core repulsion augmented by a strong and extremely short range attraction. This model describes droplets whose hydrocarbon tails are strongly attractive to the hydrocarbon tails of adjacent droplets. The SANS fit shows that the magnitude of the tail-tail attractive interactions may be much stronger than the longer range van der Waals type attractive interactions between the water cores of the droplets. These findings confirm results of IR and UV-vis spectroscopic studies of near-critical and supercritical fluid microemulsions.

  14. Temperature control of pattern formation in the Ru(bpy)(3)(2+)-catalyzed BZ-AOT system.


    McIlwaine, Rachel; Vanag, Vladimir K; Epstein, Irving R


    Using temperature as a control parameter, we observe a transition from stationary Turing patterns at T = 15-20 degrees C to traveling waves at T = 50 degrees C (and above) in the Ru(bpy)(3)(2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction incorporated into the water nanodroplets of a water-in-oil aerosol OT (AOT) microemulsion. At constant chemical composition, molar ratio and droplet fraction, the transition takes place via a series of stable patterns, including oscillatory Turing patterns (at 35-40 degrees C) and reversed oscillatory Turing patterns (at 50 degrees C). We attribute the pattern transitions to a temperature-induced percolation transition of the BZ-AOT microemulsion, implying a change from isolated water nanodroplets to a system-spanning network of water channels. PMID:19240935

  15. Spraying enzymes in microemulsions of AOT in nonpolar organic solvents for fabrication of enzyme electrodes.


    Shipovskov, Stepan; Trofimova, Daria; Saprykin, Eduard; Christenson, Andreas; Ruzgas, Tautgirdas; Levashov, Andrey V; Ferapontova, Elena E


    A new technique suitable for automated, large-scale fabrication of enzyme electrodes by air-spraying enzymes in organic inks is presented. Model oxidoreductases, tyrosinase (Tyr) and glucose oxidase (GOx), were adapted to octane-based ink by entrapment in a system of reverse micelles (RM) of surfactant AOT in octane to separate and stabilize the catalytically active forms of the enzymes in nonpolar organic media. Nonpolar caoutchouk polymer was also used to create a kind of "dry micelles" at the electrode/solution interface. Enzyme/RM/polymer-containing organic inks were air-brushed onto conductive supports and were subsequently covered by sprayed Nafion membranes. The air-brushed enzyme electrodes exhibited relevant bioelectrocatalytic activity toward catechol and glucose, with a linear detection range of 0.1-100 microM catechol and 0.5-7 mM glucose; the sensitivities were 2.41 A M(-1) cm(-2) and 2.98 mA M(-1) cm(-2) for Tyr and GOx electrodes, respectively. The proposed technique of air-brushing enzymes in organic inks enables automated construction of disposable enzyme electrodes of various designs on a mass-production scale. PMID:16255612

  16. Relaxation Times of Microemulsion Systems From Electro-Optical Measurements

    NASA Astrophysics Data System (ADS)

    Edwards, Matthew


    Relaxation Times of Microemulsion Systems from Electro-Optical Measurements Matthew Edwards (Spelman College) Relaxation measurements, as determined from electro-optically induced birefringence, have been made on ternary microemulsion systems of AOT, water, and octane. Loci of 22 samples, representing displacements along the 90oil concentration line in the three-component phase diagram, were prepared having weight fractions ranging from 0to AOT+water to 60times, at room temperature, changed by more than an order of magnitude in this phase diagram displacement, going from 2.55x10(-7)at 0The methodology for determing each sample's relaxation time was to fit the raw data of polarized - transmitted laser intensity as a function of time, as generated from using the standard Kerr effect. The raw data sample sets were fitted to within 8exponentially decaying function. The single exponential decay mechanism that is thought to be "effective rotational relaxation." This supports our earlier measurements (1) which indicate clustering of composite droplets within the microemulsion samples following the onset of the applied electric field. 1. Edwards, M.E. et, Physical Review E, 57, No. 797 (1998)

  17. Microemulsion fuel system

    SciTech Connect

    Hazbun, E.A.; Schon, S.G.; Grey, R.A.


    A microemulsion fuel composition is described comprising: (a) a jet fuel, fuel oil or diesel hydrocarbon fuel; (b) about 3.0 to about 40% by weight water and/or methanol; and (c) a surface active amount of a combination of surface active agents consisting of: (1) tertiary butyl alcohol; and (2) at least one amphoteric; anionic, cationic or nonionic surfactant.

  18. Protein extraction by Winsor-III microemulsion systems.


    Gomez del Rio, Javier A; Hayes, Douglas G


    Proteins (bovine serum albumin (BSA), α-chymotrypsin, cytochrome c, and lysozyme) were extracted from 0.5 to 2.0 g L(-1) aqueous solution by adding an equal volume of isooctane solution that contained a surfactant mixture (Aerosol-OT, or AOT, and a 1,3-dioxolane (or cyclic ketal) alkyl ethoxylate, CK-2,13-E5.6), producing a three-phase (Winsor-III) microemulsion with a middle, bicontinuous microemulsion, phase highly concentrated in protein (5-13 g L(-1)) and small in volume (12-20% of entire volume). Greater than 90% forward extraction was achieved within a few minutes. Robust W-III microemulsion systems were formulated at 40°C, or at 25°C by including a surfactant with shorter ethoxylate length, CK-2,13-E3 , or 1.5% NaCl (aq). Successful forward extraction correlated with high partitioning of AOT in the middle phase (>95%). The driving force for forward extraction was mainly electrostatic attractions imposed by the anionic surfactant AOT, with the exception of BSA at high ionic strength, which interacted via hydrophobic interactions. Through use of aqueous stripping solutions of high ionic strength (5.0 wt %) and/or pH 12.0 (to negate the electrostatic attractive driving force), cytochrome c and α-chymotrypsin were back extracted from the middle phase at >75% by mass, with the specific activity of recovered α-chymotrypsin being >90% of its original value. PMID:21695808

  19. Particle interactions in microemulsion systems

    SciTech Connect

    Brouwer, W.M.; Nieuwenhuis, E.A.; Kops-Werkhoven, M.M.


    This study obtains information about the type of interactions between microemulsion particles as a function of their composition using time averaged and dynamic light scattering and sedimentation measurements and checks the consistency of the experimental data with respect to the generalized Einstein relation. Interactions between microemulsion particles are affected by the flexibility of the soap chains. The more flexible the soap chains, the lesser the attraction forces between the particles. The lack of consistency in the interaction behavior as obtained from different experimental techniques is an important observation, which leads to the conclusion that care should be taken in the determination of the interaction behavior in microemulsion systems from one or 2 experimental techniques. 24 referernces.

  20. A theoretical approach for estimation of ultimate size of bimetallic nanocomposites synthesized in microemulsion systems

    NASA Astrophysics Data System (ADS)

    Salabat, Alireza; Saydi, Hassan


    In this research a new idea for prediction of ultimate sizes of bimetallic nanocomposites synthesized in water-in-oil microemulsion system is proposed. In this method, by modifying Tabor Winterton approximation equation, an effective Hamaker constant was introduced. This effective Hamaker constant was applied in the van der Waals attractive interaction energy. The obtained effective van der Waals interaction energy was used as attractive contribution in the total interaction energy. The modified interaction energy was applied successfully to predict some bimetallic nanoparticles, at different mass fraction, synthesized in microemulsion system of dioctyl sodium sulfosuccinate (AOT)/isooctane.

  1. Processes for microemulsion polymerization employing novel microemulsion systems


    Beckman, Eric J.; Smith, Richard D.; Fulton, John L.


    This invention is directed to a microemulsion system comprising a first phase including a low-polarity fluid material which is a gas at standard temperature and pressure, and which has a cloud-point density. It also includes a second phase including a polar fluid, typically water, a monomer, preferably a monomer soluble in the polar fluid, and a microemulsion promoter for facilitating the formation of micelles including the monomer in the system. In the subject process, micelles including the monomer are formed in the first phase. A polymerization initiator is introduced into the micelles in the microemulsion system. The monomer is then polymerized in the micelles, preferably in the core of the micelle, to produce a polymeric material having a relatively high molecular weight.

  2. Exploring the locations of different groups of a cationic surface-active 3 H-indole probe molecule in AOT-based water-in-oil microemulsions

    NASA Astrophysics Data System (ADS)

    Li, Jian; Shen, Xinghai; Gao, Hongcheng


    We report herein the spectral and photophysical studies of the locations of different groups of a probe molecule, i.e., [2-( p-hexylamino)phenyl-3,3-dimethyl-5-ethoxycarbonyl-3 H-indole]methyldioctadecylammonium iodide ( 1) in the microemulsion of sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Two models were suggested: (1) the aliphatic chains, the hexyl group together with the part from the amino nitrogen to indolic nitrogen penetrate into the interface of the microemulsion, while the part from the indolic nitrogen to the right side resides outside the interface; (2) the aromatic main chain of 1 lies flat at the inner interface. The measured spectral characteristics, micropolarity, and fluorescence lifetime of 1 support the two models.

  3. Microemulsions based transdermal drug delivery systems.


    Vadlamudi, Harini C; Narendran, Hyndavi; Nagaswaram, Tejeswari; Yaga, Gowri; Thanniru, Jyotsna; Yalavarthi, Prasanna R


    Since the discovery of microemulsions by Jack H Schulman, there has been huge progress made in applying microemulsion systems in plethora of research and industrial process. Microemulsions are optically isotropic systems consisting of water, oil and amphiphile. These systems are beneficial due to their thermodynamic stability, optical clarity, ease of preparation, higher diffusion and absorption rates. Moreover, it has been reported that the ingredients of microemulsion can effectively overcome the diffusion barrier and penetrate through the stratum corneum of the skin. Hence it becomes promising for both transdermal and dermal drug delivery. However, low viscosity of microemulsion restrains its applicability in pharmaceutical industry. To overcome the above drawback, the low viscous microemulsions were added to viscous gel bases to potentiate its applications as topical drug delivery systems so that various drug related toxic effects and erratic drug absorption can be avoided. The present review deals with the microemulsions, various techniques involved in the development of organic nanoparticles. The review emphasized on microemulsion based systems such as hydrogels and organogels. The physicochemical characteristics, mechanical properties, rheological and stability principles involved in microemulsion based viscous gels were also explored. PMID:25466399

  4. Interactions and phase transitions in micellar and microemulsion systems studied by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin


    Owing to their amphiphilic nature, surfactant molecules spontaneously self-assemble into various forms of aggregates in aqueous and hydrocarbon solvents. These aggregates are often so well defined and sufficiently uniform in size that the suspension can be treated effectively as one- or two-component supramolecular liquids. Ionic surfactants such as sodium dodecyl sulfate (SDS) form normal micelles in water. These micelles together with their counterions can be regarded as a strongly coupled two-component coulomb fluid. On the other hand sodium di-2-ethylhexylsulfosuccinate (AOT) forms reverse micelles in hydrocarbons (oils). These reverse micelles can solubilize large amounts of water and become microemulsions. These microemulsion droplets bear no net charge and interact with each other via Van der Waals forces analogous to atoms in simple liquids. Thus, AOT microemulsion system shows a gas-liquid type phase transition. By exploiting the existing liquid theories the SANS spectra can be satisfactorily analysed in terms of wel-defined interparticle interactions. For ionic micelles one can obtain the surface charge and aggregation number at arbitrary concentrations and for microemulsions one obtains the range and depth of the attractive interaction near the critical point.

  5. Metallic nanoparticle synthesis within reverse micellar microemulsion systems

    NASA Astrophysics Data System (ADS)

    Kitchens, Christopher Lawrence

    The synthesis of metallic nanoparticles is integral for the advancement of the field of nanotechnology. Solution based nanomaterial synthesis is an effective method for the production of nanomaterials, particularly with the use of surfactants and other materials for directed assembly allowing control over the nanomaterials' physical properties. This dissertation presents research performed to study the synthesis of metallic nanoparticles within reverse micelle systems. A fundamental approach has been taken to carefully examine the role of each component of the reverse micelle system, specifically the surfactant, bulk solvent, and the aqueous micelle core. The role of the sodium bis(2-ethylhexyl) sulfosuccinate (AOT) surfactant is two fold. Initially, the surfactant forms reverse micelles, nano-sized water pools dispersed within the bulk organic solvent which act as nano-reactors for the chemical reduction of the metallic precursors and metallic nanoparticle synthesis. The surfactant also acts as a stabilizing agent, effectively dispersing synthesized particles in solution, preventing agglomeration. Previously it was thought that spherical reverse micelles acted as templates for nanoparticle synthesis despite the negligible effect of the initial micelle diameter on the on the diameter of nanoparticles synthesized. Rather the initial micelle diameter influences the nanoparticle growth rate. In contrast, the properties of the bulk organic solvent do influence the nanoparticle diameter. The nature of solvent interactions with the AOT surfactant tails in various liquid alkane solvents, compressed propane, and supercritical ethane demonstrates that steric stabilization of the metallic nanoparticles by the AOT surfactant determines the particle sizes synthesized, rather than the previously accepted templating effect. Time resolved UV-vis spectroscopy was used to study the kinetics of particle synthesis, Neutron Spin Echo spectroscopy and Small Angle Neutron Scattering

  6. Time-dependent solubilization of IgG in AOT-brine-isooctane microemulsions: role of cluster formation.


    Gerhardt, N I; Dungan, S R


    The stability and structure of protein-containing water-in-oil (w/o) microemulsions were investigated by using the large protein immunoglobulin G (IgG, MW 155,000) in a mixture comprised of brine, sulfosuccinic acid bis [2-ethylhexyl]ester (sodium salt), and isooctane. We explored factors affecting the initial uptake of IgG into the w/o microemulsion and its subsequent release to a solid (precipitate) phase, and the kinetics of the latter process. Influences of such parameters as pH, ionic strength, and protein concentration on the solubilization and precipitation of bovine IgG in the organic phase are described. The structure and dynamics in microemulsions containing bovine IgG were probed by using dynamic light scattering, and it was found that the presence of IgG in the microemulsion induced strong attractive forces between the droplets. Based on results obtained by using these various experimental approaches, a model for protein solubilization and release is proposed. In this model, we propose the formation of clusters within which bovine IgG resides and which substantially slow the kinetics of protein release from the droplets to the precipitate phase. PMID:11857282

  7. Rheology, Morphology and Phase Behavior in Amphiphilic Block Copolymer/microemulsion Systems

    NASA Astrophysics Data System (ADS)

    Gottlieb, Moshe; Braun, Liora; Zhang, Zeng-Rong


    Joining together by means of covalent bonds hydrophobic and hydrophilic entities on the same molecule gives rise to materials with interesting properties in aqueous systems or in the presence of mixed solvents such as water/oil microemulsions. In this paper we describe the rheological properties of a synthetic amphiphilic block copolymer dissolved in a water-in-oil microemulsion. The block copolymer is an ABA type copolymer composed of poly(oxyethylene) (PEO) as the hydrophilic A block and poly(dimethyl siloxane) (PDMS) as the hydrophobic center B block. Different polymers have been prepared with a B block of D_p=160 and three different sizes of the A blocks with D_p= 10, 45, and 120 respectively. The resulting copolymer is insoluble in water and hardly soluble in decane (good solvent for the PDMS). In the presence of water in oil microemulsion stabilized by the small molecular weight surfactant AOT a one-phase region is maintained when the copolymer is added. Yet, peculiar rheological behavior is observed. For constant water-microemulsion concentration (φ) addition of polymer increases the system viscosity as expected. Yet, the lower φ the higher the viscosity and at high φ the effect of polymer addition is quite low.

  8. Determination of ultra trace amounts of protein by 4-chlorosulfo-(2'-hyaroxylphenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] as the fluorescence spectral probe in AOT microemulsion

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Wei, Qin; Cai, Yanyan; Han, Yanyan; Zhao, Yanfang; Du, Bin


    Experiments indicated that protein can enhance the fluorescence of the 4-chlorosulfo-(2'-hydroxylophenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] in the presence of bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) microemulsion. Based on this, a sensitive and reproducible fluorometric method for the determination of micro amount protein was developed. The calibration curves of four proteins were given. Under the optimum experimental conditions, the enhanced fluorescence intensity of the system was in proportional to the concentration of protein in the range of 0.1-11 μg mL -1 for bovine serum albumin (BSA), 1.0-10 μg mL -1 for human serum albumin (HSA), 1.0-50 μg mL -1 for ovalbumin (Ova) and 2.5-18 μg mL -1 for γ-globulins (γ-G). Their detection limits were 0.070, 0.071, 0.33 and 0.22 μg mL -1, respectively. The ClSARP-Ti(IV) complex as a spectral probe can be used to the determination of protein in milk powder and oatmeal yielding with satisfactory results. Therefore, the proposed method is one of the most sensitive methods available. In addition, the interaction mechanism of this system is studied by multi-techniques.

  9. New phases found in reverse micelle systems with high concentrations of AOT.


    Lai, Wei-Chi; Lai, Po-Hsiang


    This paper discusses the phase behavior, rheology, and structure of self-assembled sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle systems at high AOT concentrations. When the amount of AOT and w(o) (the molar ratio of water to AOT) were changed, many different phases were found, a fact which is not discussed in the literature. Opaque gel-like phase (phase separation) occurred with high concentrations of AOT in organic solvents without water. When the AOT concentration and w(o) were increased to 18-72 m and 2, respectively, the samples were gel-like and translucent. Dynamic rheological results indicate that the viscoelastic transition agreed with a multirelaxation time model. Small-angle X-ray scattering (SAXS) results imply that these samples showed a hexagonally close-packed cylindrical structure in which the diameter of a cylinder was ~2.5-3.0 nm, depending on the water contents. Moreover, these AOT cylinders self-assembled into fiber bundles with a diameter of 1-10 μm, as determined using a polarized optical microscope. As w(o) was increased to 2-6 in 72 m AOT samples, similar rheological and SAXS results were obtained. However, a different type of viscoelastic transition occurred, from multirelaxation to single-relaxation, when w(o) was increased to 7-11. The samples were in the transparent gel-like phase, and the structures determined by SAXS were a combination of hexagonally packed cylindrical and lamellar structure. The close-packed cylindrical structures had larger radii and shorter lengths with increasing w(o). Furthermore, when w(o) was increased to 12, the gel-like phase disappeared and a highly viscous solution was observed. This is because all the cylindrical structures collapsed and transformed into lamellar structures when the amount of water was further increased. PMID:23879569

  10. REVIEWS OF TOPICAL PROBLEMS: Waves and patterns in reaction-diffusion systems. Belousov-Zhabotinsky reaction in water-in-oil microemulsions

    NASA Astrophysics Data System (ADS)

    Vanag, Vladimir K.


    Advances in nonequilibrium pattern formation in reaction-diffusion systems are reviewed. Special emphasis is placed on patterns found in the spatially extended Belousov-Zhabotinsky reaction dispersed in aerosol OT water-in-oil microemulsions (BZ-AOT system): Turing patterns, packet and standing waves, antispirals and segmented spirals, and accelerating waves and oscillons. All experimental results are explained theoretically and reproduced in computer simulations.

  11. Size and diffusion phenomena of AOT/alcohol/water system in the presence of morin by dynamic light scattering.


    Bhattarai, Ajaya; Wilczura-Wachnik, Hanna


    Presented paper is a continuation of our studies on morin interaction with AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reversed micelles solutions in two solvents: ethanol and n-decanol. Now we focused on morin influence on size and diffusion phenomena in the system morin/solvent/AOT/water. In this paper precise measurements of dynamic light scattering (DLS) of the effects of temperature, solvents (alcohols), water on the size and diffusion of AOT reversed micelles in the morin/AOT/alcohol/water system are reported. The concentrations of AOT were varied from 0.51 to 0.78mol/L. Morin concentration in during auto-correlation function registration was not the same in each solvent because of its different solubility depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=(H2O)/(AOT) and was equal 0 and 30 in ethanol, and 0 in n-decanol. DLS measurements were done at 298.15 and 308.15K. DLS experiment involved on detection two relaxation modes (fast and slow) in the systems containing AOT reversed micelles, water, morin and solvents (ethanol and n-decanol). The DLS data clearly show the solvent influence as well as morin presence on AOT reversed micelles size and consequently their diffusion coefficients. Contrary to n-decanol strong competition between morin and ethanol molecules in AOT reversed micelles palisade layer has been found. It suggests that morin molecules replaced ethanol in AOT reversed micelles and locate in their palisade layer strongly increasing AOT reversed micelles size. Furthermore, it was found a sharp increase in correlation radii of slow modes of AOT reversed micelles containing morin molecules and their diffusion coefficients diminishing. PMID:25448557

  12. Designing a new strategy for the formation of IL-in-oil microemulsions.


    Rao, Vishal Govind; Ghosh, Surajit; Ghatak, Chiranjib; Mandal, Sarthak; Brahmachari, Udita; Sarkar, Nilmoni


    Due to the increasing applicability of ionic liquids (ILs) as different components of microemulsions (as the polar liquid, the oil phase, and the surfactant), it would be advantageous to devise a strategy by which we can formulate a microemulsion of our own interest. In this paper, we have shown how we can replace water from water-in-oil microemulsions by ILs to produce IL-in-oil microemulsions. We have synthesized AOT-derived surface-active ionic liquids (SAILs) which can be used to produce a large number of IL-in-oil microemulsions. In particular, we have characterized the phase diagram of the [C(4)mim][BF(4)]/[C(4)mim][AOT]/benzene ternary system at 298 K. We have shown the formation of IL-in-oil microemulsions using the dynamic light scattering (DLS) technique and using methyl orange (MO), betaine 30, and coumarin-480 (C-480) as probe molecules. PMID:22329703

  13. Design and Evaluation of Microemulsion Gel System of Nadifloxacin

    PubMed Central

    Shinde, Ujwala; Pokharkar, Sharda; Modani, Sheela


    Topical microemulsion systems for the antiacne agent, nadifloxacin were designed and developed to overcome the problems associated with the cutaneous delivery due to poor water solubility. The solubility of nadifloxacin in oils, surfactants and cosurfactants was evaluated to screen the components of the microemulsion. Various surfactants and cosurfactants were screened for their ability to emulsify the selected oily phase. The pseudoternary diagrams were constructed to identify the area of microemulsion existence. The influence of km (surfactant/cosurfactant) ratio on the microemulsion existence region was determined and optimum systems were designed. The systems were assessed for drug-loading efficiency and characterised for optical birefringence, pH and refractive index, robustness to dilution, globule size, drug content and thermodynamic stability. Optimised microemulsion systems were formulated into gel form and evaluated for viscosity, spreadability, drug content, ex vivo skin permeation and antibacterial activity. The maximum solubility of nadifloxacin in the microemulsion system was found to be 0.25%. The nadifloxacin microemulsions had a small and uniform globule size (67.3-121.23 nm). The stability results revealed that all formulations showed a stable globule size and the polydispersity index under stress conditions. Incorporation of nadifloxacin in microemulsion gel increased the ex vivo skin permeation and antibacterial activity when compared to marketed cream. PMID:23439454

  14. Phase behavior of microemulsion systems studied by positron annihilation techniques

    SciTech Connect

    Serrano, J.; Reynoso, R.; Lopez, R.; Olea, O.; Fucugauchi, L.A.


    The positron annihilation technique was applied to the study of phase behavior of sodium stearate (or oleate)-alcohol-oil-water microemulsion systems. The positron annihilation parameters revealed a dependence of the water/oil ratio at which microemulsion formation occurs on the hydrocarbon chain length of both alcohol cosurfactant and solvent as well as surfactant concentration. Dynamic laser light scattering has been utilized for substantiating the phase transitions determined in the different microemulsion systems by positron annihilation. The difference in the behavior between saturated and unsaturated surfactants is the most remarkable result of the investigation. Thus, replacing sodium stearate by sodium oleate in the surfactant-1-hexanol-isooctane systems obviated microemulsion formation. This behavior has been rationalized by considering packing and kink presence in microemulsion formation. 26 references.

  15. The synthesis of silica and silica-ceria, core-shell nanoparticles in a water-in-oil (W/O) microemulsion composed of heptane and water with the binary surfactants AOT and NP-5.


    Chung, Sang-Ho; Lee, Dae-Won; Kim, Min-Sung; Lee, Kwan-Young


    In this study, a strategy was developed for the synthesis of nano-sized, silica-ceria, core-shell composites in a water-oil (W/O) microemulsion consisting of water, heptane and the binary surfactants AOT (sulfosuccinic acid bis (2-ethylhexyl) ester sodium salt) and NP-5 (polyoxyethylene (5) nonylphenyl ether). The core-shell, silica-ceria particles were prepared in a stepwise procedure: (1) the precipitation of the core-silica particles in a W/O microemulsion and (2) the surface precipitation of ceria on the core silica dispersed over the microemulsion. The composition of the binary surfactant greatly influenced the growth rate of the core-silica particles. The virial coefficient of diffusion was utilized to estimate the effect of the surfactant composition on the degree of intermicellar interaction that is important for the growth rate of the silica along with the flexibility of the micellar interface and the structure of the water domain. The deposition of the ceria on the core silica was not straightforward because the bulk and surface precipitation competed with each other. The promotion of surface precipitation was attempted by: (1) chemically modifying the silica surface with an organoamine group and (2) slowing down the precipitation rate of the ceria in a semi-batch operation. These attempts successfully produced the nano-sized silica-ceria, core-shell particles, which were evidenced through the TEM, XPS and zeta potential analysis. PMID:21211804

  16. Noncritical microemulsion as nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Vicari, Luciano R. M.; Barone, A. C.


    Water in oil microemulsions are systems of spherical droplets of water coated by a monolayer of surfactant molecules, immersed in oil. Initially we have studied the optical nonlinear behavior of water in oil microemulsion by the Self-Phase-Modulation of a gaussian laser beam by an optically thin film. The material is WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) far from critical points and near the percolative transition from electrically insulating to electrically conducting. We have observed optical nonlinearity in the L2 area of the phase diagram, near the percolation line and far from the one-phase two-phase boundary line. In this point, the material turbidity is very low. Strong optical nonlinearity has been reported. Nonlinear optical effects in a Water/AOT/Decane (WAD) microemulsion have been experimentally studied also in a pump probe configuration. We detect the variation of the on axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. Results seem to suggest the hypothesis of a chain like shape of the clusters.

  17. Bidisperse colloids: nanoparticles and microemulsions in coexistence.


    Tabor, Rico F; Eastoe, Julian; Dowding, Peter J; Grillo, Isabelle; Rogers, Sarah E


    Mixed 'hard-soft' colloidal systems have been generated in which the 'hard' components (80 nm diameter silica nanoparticles) coexist with a population of 'soft' microemulsion droplets, both structures stabilised by the anionic surfactant sodium bis(ethylhexyl)sulfosuccinate (AOT) with toluene as solvent. The addition of water to swell the inverse micelles to form microemulsion droplets appears to increase attractive interactions between the silica particles (determined by DLS), possibly due to adsorption of some water at the silica-toluene interface; however, long-term stability of the dispersions is maintained. Small-angle neutron scattering was used to examine the structures present in these new colloidal systems. PMID:20144832

  18. Cytarabine-AOT catanionic vesicle-loaded biodegradable thermosensitive hydrogel as an efficient cytarabine delivery system.


    Liu, Jing; Jiang, Yue; Cui, Yuting; Xu, Chuanshan; Ji, Xiaoqing; Luan, Yuxia


    Carrier with high drug loading content is one of the most important issues in drug delivery system. In the present work, an ion-pair amphiphilic molecule composed of anticancer drug cation and surfactant anion is used for straightforward fabricating vesicles for cancer therapy. Anticancer drug (cytarabine hydrochloride) and anionic surfactant (AOT) are selected for the fabrication of ion-pair amphiphilic molecule. One amphiphilic molecule contains one drug cation, thus the drug loading content is 50% (mol/mol) in theory. The in vitro drug release study shows that the release time of cytarabine is about 3 times of the pure cytarabine solution and the permeability of cytarabine has been improved about 160 times tested by parallel artificial membrane permeability assay model. However, the hemolytic toxicity is largely decreased in the studied concentration range. The in vitro cytotoxicity results show that cytarabine-AOT amphiphiles have a much lower IC50 (drug concentration resulting in 50% cell death) value and a higher cell inhibition rate comparing with their respective components, indicating its effective therapy for leukemic cells. To obtain a longer and a convenient drug release system, the prepared vesicles are further incorporated into the thermosensitive PLGA-PEG-PLGA hydrogel to prepare a subcutaneous administration. The in vivo drug release results indicate that cytarabine-AOT vesicle-loaded hydrogel is a good injectable delivery system for controlled release of cytarabine for cancer therapy. PMID:25066076

  19. Study of the alkaline fading of phenolphthalein in microemulsions.


    Mao, Shiyan; Chen, Zhiyun; An, Xueqin; Shen, Weiguo


    The reactions of the alkaline fading of phenolphthalein (PN) have been studied in water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane microemulsions by monitoring the absorbance changes of PN in the system with the time and the results compared with those found for the same reactions in aqueous solutions. It was found that the values of the equilibrium constants and the forward reaction rate constants in the microemulsions were significantly larger than that in aqueous solutions and decreased with increasing the molar ratio of water to AOT (ω), except for that with low ω. The temperature dependence of the reaction rate constant was analyzed to obtain the values of free energy, enthalpy, and entropy of activation, which suggests the existence of an isokinetic relationship and a common mechanism for the reactions occurring in the microemulsions with different ω. It was also observed that the competition between the reactions of the alkaline fading of PN and the hydrolyzation of AOT in water/AOT/isooctane microemulsions when the reaction time was sufficiently long. PMID:21574587

  20. A reliable and reproducible method for the lipase assay in an AOT/isooctane reversed micellar system: modification of the copper-soap colorimetric method.


    Kwon, Chang Woo; Park, Kyung-Min; Choi, Seung Jun; Chang, Pahn-Shick


    The copper-soap method, which is based on the absorbance of a fatty acid-copper complex at 715 nm, is a widely used colorimetric assay to determine the lipase activity in reversed micellar system. However, the absorbance of the bis(2-ethylhexyl) sodium sulfosuccinate (AOT)-copper complex prevents the use of an AOT/isooctane reversed micellar system. An extraction step was added to the original procedure to remove AOT and eliminate interference from the AOT-copper complex. Among the solvents tested, acetonitrile was determined to be the most suitable because it allows for the generation of a reproducible calibration curve with oleic acid that is independent of the AOT concentrations. Based on the validation data, the modified method, which does not experience interference from the AOT-copper complex, could be a useful method with enhanced accuracy and reproducibility for the lipase assay. PMID:25842332

  1. W/O microemulsions as dendrimer nanocarriers: an EPR study.


    Rokach, Shifra; Ottaviani, Maria Francesca; Shames, Alexander I; Nir, Ido; Aserin, Abraham; Garti, Nissim


    A complex system, based on a dendrimer solubilized in the aqueous core of water-in-oil microemulsion, may combine the advantages of both dendrimers and microemulsions to provide better control of drug release. We report for the first time the use of EPR technique to determine the effect of solubilized dendrimer on the structure of the microemulsion. The solubilized poly(propyleneimine) (PPI-G2) interacts with sodium bis(2-ethylhexyl) sulfosuccinate (AOT). EPR analysis provided information on polarity, microviscosity, and molecular order of the systems. Polarity and microviscosity increased from unloaded water-in-oil microemulsion to the system loaded with 0.2 wt % PPI-G2, but remained unchanged with higher PPI-G2 loads. The degree of order also increased with 0.2 wt % PPI-G2 with only minor additional increase with larger quantities (25 wt %) of PPI-G2. Variations in pH only slightly affected the structure of microemulsion in the absence and presence of the loaded dendrimers. Aliphatic oils with longer lipophilic chains enhanced the structural order of the microemulsion. On increasing water content, polarity and degree of order increased. PPI-G2 dendrimer in small loads is attracted by the negatively charged AOT and thus intercalates in the interface of the droplets. Yet, at higher PPI-G2 loads, the excess molecules are solubilized in the water core. PMID:22989387

  2. Formulation of microemulsion systems for dermal delivery of silymarin.


    Panapisal, Vipaporn; Charoensri, Sawitree; Tantituvanont, Angkana


    Silymarin is a standardized extract from Silybum marianum seeds, known for its many skin benefits such as antioxidant, anti-inflammatory, and immunomodulatory properties. In this study, the potential of several microemulsion formulations for dermal delivery of silymarin was evaluated. The pseudo-ternary phase diagrams were constructed for the various microemulsion formulations which were prepared using glyceryl monooleate, oleic acid, ethyl oleate, or isopropyl myristate as the oily phase; a mixture of Tween 20®, Labrasol®, or Span 20® with HCO-40® (1:1 ratio) as surfactants; and Transcutol® as a cosurfactant. Oil-in-water microemulsions were selected to incorporate 2% w/w silymarin. After six heating-cooling cycles, physical appearances of all microemulsions were unchanged and no drug precipitation occurred. Chemical stability studies showed that microemulsion containing Labrasol® and isopropyl myristate stored at 40°C for 6 months showed the highest silybin remaining among others. The silybin remainings depended on the type of surfactant and were sequenced in the order of: Labrasol® > Tween 20® > Span 20®. In vitro release studies showed prolonged release for microemulsions when compared to silymarin solution. All release profiles showed the best fits with Higuchi kinetics. Non-occlusive in vitro skin permeation studies showed absence of transdermal delivery of silybin. The percentages of silybin in skin extracts were not significantly different among the different formulations (p > 0.05). Nevertheless, some silybin was detected in the receiver fluid when performing occlusive experiments. Microemulsions containing Labrasol® also were found to enhance silymarin solubility. Other drug delivery systems with occlusive effect could be further developed for dermal delivery of silymarin. PMID:22350738

  3. Coexisting aggregates in mixed aerosol OT and cholesterol microemulsions.


    Sedgwick, Myles A; Trujillo, Alejandro M; Hendricks, Noah; Levinger, Nancy E; Crans, Debbie C


    Dynamic light scattering and NMR spectroscopic experimental evidence suggest the coexistence of two compositionally different self-assembled particles in solution. The self-assembled particles form in solutions containing water, Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) surfactant, and cholesterol in cyclohexane. In a similar series of studies carried out in 1-octanol only one aggregate type, that is, reverse micelles, is observed. Dynamic light scattering measurements reveal the presence of two different types of aggregates in the microemulsions formed in cyclohexane, demonstrating the coexistence of two compositionally distinct structures with very similar Gibbs energies. One particle type consists of standard AOT reverse micelles while the second type of particle consists of submicellar aggregates including cholesterol as well as small amounts of AOT and water. In microemulsions employing 1-octanol as the continuous medium, AOT reverse micelles form in a dispersed solution of cholesterol in 1-octanol. Although the size distribution of self-assembled particles is well-known for many different systems, evidence for simultaneous formation of two distinctly sized particles in solution that are chemically different is unprecedented. The ability to form microemulsion solutions that contain coexisting particles may have important applications in drug formulation and administration, particularly as applied to drug delivery using cholesterol as a targeting agent. PMID:21188993

  4. Microemulsion systems studied by positron annihilation techniques

    SciTech Connect

    Boussaha, A.; Djermouni, B.; Fucugauchi, L.A.; Ache, H.J.


    The formation of thermalized positronium atoms is greatly reduced if increasing amounts of water become solubilized in reversed micelles formed by sodium bis(2-ethylhexyl) sulfosuccinate in apolar solvents. Similar observations have been made if the surfactant is Triton X-100. The application of the positron annihilation technique to the study of microemulsions consisting of potassium oleate-alcohol-oil-water mixtures indicates, consistent with previous results, that microemulsion formation requires a certain water/oil ratio if the oil is a long-chain aliphatic hydrocarbon such as hexadecane. This ratio is 0.4 in the case of a 1-pentanol- and 0.2 for a 1-hexanol-containing mixture. This minimum water content is strongly reduced if the oil is an aromatic hydrocarbon. The positron annihilation data also sensitively reflect structural rearrangements in these solutions occurring upon further addition of water, such as the transition of spherical aggregates to a disk-like lamellae structure.

  5. Solvent effect on the size of platinum nanoparticle synthesized in microemulsion systems

    NASA Astrophysics Data System (ADS)

    Salabat, Alireza; Far, Mina Rahmati


    In this research work, the effect of solvent on the size of paltinum nanoparticles synthesized by microemulsion method was investigated. Platinum nanoparticles have been prepared by the reduction of H2PtCl6 with hydrazine in water-in-oil (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfo-succinate (AOT) and solvents n-hexane, cyclohexane and n-nonane. The size of the platinum nanoparticles was measured using transmission electron microscopy (TEM). It was verified that, for reduction of H2PtCl6 by hydrazine in microemulsion with different organic solvents, the solvents are arranged by their influence on nanoparticle sizes as follows: n-nonane > cyclohexane > n-hexane.

  6. Microemulsions: Structure and dynamics

    SciTech Connect

    Friberg, S.E.; Bothorel, P.


    This book covers the state-of-the-art in stability, structure, applications, and dynamics representation of microemulsion systems. An international group of reviewers discuss the introductory investigations into macroemulsions and interfacial free energy, the derivation of the microemulsion systems from micellar solutions, and the correlation between structure and dynamics. Future developments in this area are also considered. The book presents following: contents; phase diagrams and pseudophase assumption; phase diagram and critical behavior of a quaternary microemulsion system; non-aqueous microemulsions; nonionics; molecular diffusion in microemulsions; dynamics of microemulsions; low interfacial tensions in microemulsion systems; oil recovery and microemulsions.

  7. Structure study of a microemulsion system with an ionic liquid.


    Kang, Tae Hui; Jeon, Yoonnam; Kim, Mahn Won


    We found that an ionic liquid (IL) with a long alkyl chain moiety, 1-tetradecyl-3-methylimidazolium chloride (C14MIM·Cl), forms a single crystal after the addition of octanol in an alkane solvent. But the solution exhibits a structural change after adding a small amount of water. An optically clear solution is found within limits, and it is stable for several months. Since the IL molecule has an amphiphilic property, it behaves as a surfactant in the microemulsion system. But the IL formed a single crystal rather than a lyotropic liquid crystalline structure, unlike a typical surfactant. Therefore, it is important to understand the structure of the microemulsion system. We used the small angle neutron scattering (SANS) technique to investigate the structure. The scattering intensity was analyzed using a spherical core-shell model with the Schultz size distribution, and a contrast matching method was used to study the internal structure. The structure of the solution is confirmed to be a water-in-oil microemulsion system, and the swelling law is obeyed in the microemulsion system. PMID:26439624

  8. Viscoelastic behavior of dense microemulsions

    NASA Astrophysics Data System (ADS)

    Cametti, C.; Codastefano, P.; D'arrigo, G.; Tartaglia, P.; Rouch, J.; Chen, S. H.


    We have performed extensive measurements of shear viscosity, ultrasonic absorption, and sound velocity in a ternary system consisting of water-decane-sodium di(2-ethylhexyl)sulfo- succinate(AOT), in the one-phase region where it forms a water-in-oil microemulsion. We observe a rapid increase of the static shear viscosity in the dense microemulsion region. Correspondingly the sound absorption shows unambiguous evidence of a viscoelastic behavior. The absorption data for various volume fractions and temperatures can be reduced to a universal curve by scaling both the absorption and the frequency by the measured static shear viscosity. The sound absorption can be interpreted as coming from the high-frequency tail of the viscoelastic relaxation, describable by a Cole-Cole relaxation formula with unusually small elastic moduli.

  9. Characteristics of spontaneously formed nanoemulsions in octane/AOT/brine systems.


    Kini, Gautam C; Biswal, Sibani Lisa; Wong, Michael S; Miller, Clarence A


    Nanoemulsions were formed spontaneously by diluting water-in-oil (W/O) or brine-in-oil (B/O) microemulsions of a hydrocarbon (octane), anionic surfactant (Aerosol-OT or AOT) and water or NaCl brine in varying levels of excess brine. The water-continuous nanoemulsions were characterized by interfacial tension, dynamic light scattering, electrophoresis, optical microscopy and phase-behavior studies. The mechanism of emulsification was local supersaturation and resulting nucleation of oil during inversion. For nanoemulsions formed at low salinities with Winsor I phase behavior, octane drops grew from initial diameters of 150-250 nm to 480-1000 nm over 24h, depending on salinity. Growth was caused by mass transfer but seemed to approach the asymptotic stage of Ostwald ripening described by the Lifshitz-Slyozov-Wagner (LSW) theory only for dilution with salt-free water. Near the higher cross-over salinity (Winsor III), the nanoemulsions showed much slower growth with droplet size consistently remaining below 200 nm over 24h and reaching 250 nm after 1 week. Birefringence indicated the presence of liquid crystal for these conditions, which could have contributed to the slow growth rate. At even higher salinity levels in the Winsor II domain, W/O/W multiple emulsions having drops greater than 1 μm in diameter were consistently recorded for the first 5-7h, after which size decreased to values below 1 μm. The number and size of internal water droplets in multiple emulsion drops was found to decrease over time, suggesting coalescence of internal droplets with the continuous water phase and mass transfer of water from internal droplets to continuous phase as possible mechanisms of the observed drop shrinkage. Electrophoresis studies showed the nanoemulsions to be highly negatively charged (zeta potentials of -60 mV to -120 mV). The high charge on octane droplets helped assure stability to flocculation and coalescence, thereby allowing mass transfer to control growth in the

  10. Microemulsion to liquid crystal transition in two anionic surfactant systems

    SciTech Connect

    Hackett, J.L.; Miller, C.A.


    The phase behavior of two anionic surfactant systems, one containing a commercial alpha olefin sulfonate (AOS) and the other containing pure sodium dodecyl sulfate (SDS), was determined in the region where a transition from microemulsion to liquid-crystalline phases occurred with decreasing alcohol content and temperature. A general and rather complex pattern of phase behavior was seen that included a four-phase coexistence region of brine, microemulsion, lamellar liquid crystal, and oil, and two three-phase regions containing both microemulsion and liquid crystal. In much of the four-phase region, complete separation of the phases did not occur even after equilibration for 1 year or more at constant temperature. Instead, oil and brine were observed to coexist with stable birefringent dispersions that (for some compositions at least) apparently contained three phases: microemulsion, liquid crystal, and oil. Solubilization of brine was uniformly low in the phases making up the dispersions. The dispersions in the SDS system exhibited non-Newtonian behavior with apparent viscosities in the range of 50 to 100 mPa . s (50 to 100 cp) at a shear rate of 10 seconds/sup -1/. Microemulsion viscosities in the same system were about an order of magnitude lower. No plugging or other adverse behavior was seen when such dispersions flowed at a velocity of 10/sup -5/ m/s (3 ft/D) through a model porous medium having pore sizes comparable with those in reservoirs. In preliminary experiments, selected dispersions appeared to be capable of displacing oil from the same model porous medium.

  11. Oil Induced Spontaneous Flow in Water- Bis(2-ethylhexyl)Sulfosuccinat (AOT) system

    NASA Astrophysics Data System (ADS)

    Kalakonda, Parvathalu

    Instability and evaporation rates of oils within the layers of vesicles of a surfactants trigger the spontaneous (second flow) flow. The incorporation of oils into bis(2-ethylhexyl)sulfosuccinat (AOT) system remains incompletely characterized. We show that the second flow has a finite size that show a minimum at a particular concentration (mM) of surfactant solution. As a result, the layers are destabilized lead to ``explode'' and create the second flow. The fluorescence emission spectra and evaporation rates show that the oil diffuses into the layers of vesicles of a surfactant. We have characterized evaporation rates of oils on various concentrations (mM) of surfactant solution and observed that oils evaporation rates depend on volume and remain constant as the function of concentration of surfactant. We believe that second flow is new feature and brings a new insight into the fluid flow dynamics.

  12. Synthesizing metallic to superconducting ceramic nanoparticles using optimized microemulsion systems

    NASA Astrophysics Data System (ADS)

    Li, Fang

    A microemulsion system with cetyltrimethylammonium bromide (CTAB) as surfactant, 1-butanol as cosurfactant and n-octane as the oil phase was optimized to produce nanoparticles. Based on the results of conductivity and droplet size, oil/surfactant weight ratio of 1.5 was chosen to perform the study due to its higher solubilization and droplet stability. Nanoparticles of monometallic Fe, bimetallic Fe/Ni, oxide Y2O3, complex oxide Y 2BaCuO5 (Y211) and YBa2Cu3O7-x (Y123) have been successfully synthesized using the water-in-oil microemulsion method. The size of amorphous Fe, Fe/Ni nanoparticles were about 10 nm and 5 nm respectively. The reduction rate of trichloroethylene (TCE, a model contaminant) by the Fe produced from the microemulsion system was the highest compared to the solution product and the commercial product. In the case of Fe/Ni nanoparticles, the initial degradation rate is four times faster than for Fe nanoparticles. Nanocrystalline Y2O3 particles were flake shaped with dimension in the range of 16--30 nm. Y2BaCuO5 and YBa2Cu3O7-x nanoparticles (˜110 nm) produced using the microemulsion method had lower processing temperature than other processing methods due to their smaller particle size. As the reaction time was shortened, the Y211 particle size reduced from larger than 100 nm to the 30--100 nm range. Superconductivity of Y123 nanoparticles was verified using magnetic measurements and the critical transition temperature was 91 K. In the melt-textured Y123 disk, a single domain with a maximum trapped field of 0.14 T was successfully fabricated with the addition of 30% Y211 nanoparticles produced by the microemulsion method. The JC and size distribution of Y211 grain in the Y123 matrix were slightly better than in conventional samples.

  13. Phase equilibrium of sodium bis(2-ethylhexyl) phosphate/water/n-heptane/sodium chloride microemulsion

    SciTech Connect

    Shioi, Akihisada; Harada, Makoto; Matsumoto, Keishi )


    The microemulsion phase diagram for the sodium bis(2-ethylhexyl) phosphate (SDEHP)/water/n-heptane/sodium chloride system is reported. The salinity effects on the phase diagram are discussed in detail. Cylindrical aggregates were found to exist in the oil-rich region and disklike aggregates in the brine-rich region. The middle-phase microemulsion in equilibrium with both the excess brine and oil phases was concluded to be composed of these microstructures. Sodium bis(2-ethylhexyl) phosphate has a common hydrocarbon tail with sodium bis(2-ethylhexyl) sulfosuccinate (AOT), but the phase equilibrium and the structures of the microemulsion phases in SDEHP system were much different from those in the AOT case. The differences were attributed to those in the shapes of aggregates for the two cases.

  14. A novel water-in-ionic liquid microemulsion and its interfacial effect on the activity of laccase.


    Xue, Luyan; Qiu, Huajun; Li, Ying; Lu, Lu; Huang, Xirong; Qu, Yinbo


    It is of great significance to develop an appropriate water-in-ionic liquid (W/IL) microemulsion suitable for the expression of the catalytic activity of a given enzyme. In this paper, the phase diagram of a new AOT/Triton X-100/H(2)O/[Bmim][PF(6)] pseudo ternary system is presented. With the aid of nonionic surfactant Triton X-100, AOT could be dissolved in hydrophobic ionic liquid [Bmim][PF(6)], forming a large single phase microemulsion region. The water-in-[Bmim][PF(6)] (W/IL) microemulsion domain was identified electrochemically by using K(3)Fe(CN)(6) as a probe. The existence of W/IL microemulsions was demonstrated spectrophotometrically by using CoCl(2) as a probe. New evidences from the FTIR spectroscopic study, which was first introduced to the W/IL microemulsion by substituting D(2)O for H(2)O to eliminate the spectral interference, demonstrated that there existed bulk water at larger ω(0) values (ω(0) was defined as the molar ratio of water to the total surfactant) in the W/IL microemulsion, which had remained unclear before. In addition to the inorganic salts, biomacromolecule laccase could be solubilized in the W/IL microemulsion. The laccase hosted in the microemulsion exhibited a catalytic activity and the activity could be regulated by the composition of the interfacial membrane. PMID:20951007

  15. [Water in oil microemulsions containing NaCl for transdermal delivery of fluorouracil].


    Xiao, Yan-Yu; Liu, Fang; Chen, Zhi-Peng; Ping, Qi-Neng


    This study is to prepare the W/O microemulsion containing NaCl and fluorouracil (5-Fu) as a model drug to investigate the transdermal characteristics and skin irritation of the microemulsion in vitro. Isopropylmyristate (IPM) acting as oil phase, Aerosol-OT (AOT) as surfactant, Tween 85 as cosurfactant, NaCl solution was added dropwise to the oil phase to prepare W/O microemulsion at room temperature using magnetic stirring, and then 5-Fu powder was added. According to the area of microemulsion based on the pseudo-tertiary phase diagrams, the optimum formulation was screened initially. And the permeation flux of fluorouracil across excised mice skin was determined in vitro using Franz diffusion cells to study the influence of the amount of water and the drug loading capacity and optimize the formulation further. Refer to 5-Fu cream, the irritation of microemulsion on the rat skin was studied. The optimum formulation was composed of 0.7% (w/v) 5-Fu, 50% NaCl solution (0.05 mol x L(-1)), 20% mix-surfactant (AOT/Tween 85, K(m) = 2) and 29.3% oil (IPM). The cumulative amount of fluorouracil permeated in 12 h was (2 013.4 +/- 41.6) microg x cm(-2), 20.23 folds and 10.38 folds more than 0.7% fluorouracil aqueous solution and 2.5% (w/w) fluorouracil cream, respectively. Microemulsion exhibited some irritation, but could be reversed after drug withdrawal. The addition of NaCl significantly increased the content of water and the drug loading in microemulsion systems. The NaCl/AOT-Tween 85/IPM microemulsion system promoted the permeation of fluorouracil greatly, which may be a promising vehicle for the transdermal delivery of fluorouracil and other hydrophilic drug. PMID:21882535

  16. Effect of Dipalmitoylphosphatidylcholine on a microemulsion

    NASA Astrophysics Data System (ADS)

    Sharifi, Soheil; Nasrollahi, Aboozar


    In this work, the dynamic behavior of droplets under addition of Dipalmitoylphosphatidylcholine (lipid) and CTAB (salt) is studied by photon correlation spectroscopy. The collective diffusion coefficient ( D c ) of Brownian motion of droplets/salt and droplets/lipid was explored by photon correlation spectroscopy (PCS). The PCS experiment demonstrated that D c of AOT/H2O/ n-decane microemulsion increased with increase of lipid and CTAB. For understanding the dynamic of droplets, we investigated viscosity and droplet interaction in Lipid/AOT/H2O/ n-decane microemulsion. This system illustrated a well-known maximum in relative viscosity as a function of water/AOT molar ratio near X = 7. The maximum of viscosity can be varied by adding lipid at different concentration. Small angle X-ray scattering measurements revealed that the morphology of droplets changed from cylindrical to spherical with increase of lipid amount in the droplets. The same effect was observed in the mixture of water droplets with CTAB.

  17. Ultrafast energy transfer in water-AOT reverse micelles.


    Cringus, Dan; Bakulin, Artem; Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S; Wiersma, Douwe A


    A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model system for nanoscopic water droplets surrounded by a soft-matter boundary. Femtosecond nonlinear infrared spectroscopy in the OH-stretching region of H2O fully confirms the core/shell model, in which the entrapped water molecules partition onto two molecular subensembles: a bulk-like water core and a hydration layer near the ionic surfactant headgroups. These two distinct water species display different relaxation kinetics, as they do not exchange vibrational energy. The observed spectrotemporal ultrafast response exhibits a local character, indicating that the spatial confinement influences approximately one molecular layer located near the water-amphiphile boundary. The core of the encapsulated water droplet is similar in its spectroscopic properties to the bulk phase of liquid water, i.e., it does not display any true confinement effects such as droplet-size-dependent vibrational lifetimes or rotational correlation times. Unlike in bulk water, no intermolecular transfer of OH-stretching quanta occurs among the interfacial water molecules or from the hydration shell to the bulk-like core, indicating that the hydrogen bond network near the H2O/AOT interface is strongly disrupted. PMID:18047308

  18. Food grade microemulsion systems: canola oil/lecithin:n-propanol/water.


    Abbasi, Soleiman; Radi, Mohsen


    In this study, the capability of a natural surfactant, lecithin, and the influence of ionic strength, pH, and temperature on some properties of a food grade microemulsion system were evaluated. For this purpose, the pseudoternary phase diagrams of canola oil/lecithin:n-propanol/water microemulsions in the presence of different salts (NaCl and CaCl2), ionic strengths, pHs, and temperatures were constructed. Our findings showed that the presence of salts slightly increased the W/O areas on the phase diagrams, whereas pH variation was not effective on the microemulsion formation. The expansion of microemulsion areas with temperature indicated the greater triglycerides solubilization capacity of lecithin based microemulsions at higher temperatures. These findings revealed the efficiency of lecithin-based microemulsion system for solubilization of triglycerides which can potentially be used for extraction of edible vegetable oils particularly canola oil. PMID:26471642

  19. Kinetics and mechanism of the cutinase-catalyzed transesterification of oils in AOT reversed micellar system.


    Badenes, Sara M; Lemos, Francisco; Cabral, Joaquim M S


    The kinetics of the enzymatic transesterification between a mixture of triglycerides (oils) and methanol for biodiesel production in a bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane reversed micellar system, using recombinant cutinase from Fusarium solani pisi as a catalyst, was investigated. In order to describe the results that were obtained, a mechanistic scheme was proposed, based on the literature and on the experimental data. This scheme includes the following reaction steps: the formation of the active enzyme-substrate complex, the addition of an alcohol molecule to the complex followed by the separation of a molecule of the fatty acid alkyl ester and a glycerol moiety, and release of the active enzyme. Enzyme inhibition and deactivation effects due to methanol and glycerol were incorporated in the model. This kinetic model was fitted to the concentration profiles of the fatty acid methyl esters (the components of biodiesel), tri-, di- and monoglycerides, obtained for a 24 h transesterification reaction performed in a stirred batch reactor under different reaction conditions of enzyme and initial substrates concentration. PMID:21739170

  20. Analysis and antibacterial activity of Nigella sativa essential oil formulated in microemulsion system.


    Shaaban, Hamdy A; Sadek, Zainab; Edris, Amr E; Saad-Hussein, Amal


    The Essential oil (EO) of Nigella sativa (black cumin) was extracted from the crude oil and the volatile constituents were characterized using gas chromatographic analysis. The EO was formulated in water-based microemulsion system and its antibacterial activity against six pathogenic bacteria was evaluated using the agar well diffusion method. This activity was compared with two other well known biologically active natural and synthetic antimicrobials namely eugenol and Ceftriaxone(®). Results showed that N. sativa EO microemulsion was highly effective against S. aureus, B. cereus and S. typhimurium even at the lowest tested concentration of that EO in the microemulsion (100.0 μg/well). Interestingly, the EO microemulsion showed higher antibacterial activity than Ceftriaxone solution against S. typhimurium at 400.0 μg/well and almost comparable activity against E. coli at 500.0 μg/well. No activity was detected for the EO microemulsion against L. monocytogenes and P. aeruginosa. Eugenol which was also formulated in microemulsion was less effective than N. sativa EO microemulsion except against P. aeruginosa. The synthetic antibiotic (Ceftriaxone) was effective against most of the six tested bacterial strains. This work is the first report revealing the formulation of N. sativa EO in microemulsion system and investigating its antibacterial activity. The results may offer potential application of that water-based microemulsion in controlling the prevalence of some pathogenic bacteria. PMID:25748382

  1. Illuminating microemulsions: ionic liquid-CdS quantum dots hybrid materials as potential white light harvesting systems.


    Damarla, Krishnaiah; Bharmoria, Pankaj; Rao, K Srinivasa; Gehlot, Praveen Singh; Kumar, Arvind


    Microemulsions (MEs) comprising of 2-hydroxyethylammonium formate, (HO-EAF), isooctane and dioctylsulfosuccinate proliniumisopropylester ([ProC3]AOT) have been constructed and used to prepare and stabilize CdS Quantum Dots (QDs) at room temperature. Such hybrid materials exhibited tunable light emission wherein the photoluminescence chromaticity could be precisely adjusted to pure white with a quantum efficiency (QE) of ∼43%, by adjusting the droplet size of MEs. PMID:27087045

  2. Process of forming compounds using reverse micelle or reverse microemulsion systems


    Linehan, John C.; Fulton, John L.; Bean, Roger M.


    The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

  3. Microemulsions in supercritical hydrochlorofluorocarbons

    SciTech Connect

    Jackson, K.; Fulton, J.L.


    We report the properties of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsions formed in supercritical hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons, and flourocarbons. The fluids used in this study include compounds that are of low toxicity and flammability and that are expected to remain environmentally acceptable well into the next century (e.g., 1,1,1, 2-tetrafluoroethane (R134a) and chlorodifluoromethane (R22)). We show that it is possible to form a water-in-oil type of microemulsion in a low molecular weight HCFC (R22). In addition to these HCFCs, We also review the ability to form microemulsions in 14 other fluids (ethane, propene, propane, n-butane, n-pentane, n-haxane, isobutane, isooctane, difluoromethane, trifluoromethane, hexafluoroethane, sulfur haxafluoride, xenon, and carbon dioxide) at conditions just above or below the critical point (0.75 < T/T{sub c} <1.1) of the solvent. We report extensively the phase behavior of AOT and didodecyldimethylammonium bromide microemulsions formed in a supercritical HCFC, R22. We show that microemulsions in HCFCs are practical alternatives to other fluids, such as supercritical carbon dioxide. 56 refs., 7 figs., 1 tab.

  4. Microemulsion Drug Delivery System: For Bioavailability Enhancement of Ampelopsin

    PubMed Central

    Solanki, Shailendra Singh; Sarkar, Brajesh; Dhanwani, Rakesh Kumar


    Ampelopsin, one of the most common flavonoids, reported to possess numerous pharmacological activities and shows poor aqueous solubility. The purpose of this study was to enhance the dissolution rate and bioavailability of this drug by developing a novel delivery system that is microemulsion (ME) and to study the effect of microemulsion (ME) on the oral bioavailability of ampelopsin. Capmul MCM-based ME formulation with Cremophor EL as surfactant and Transcutol as cosurfactant was developed for oral delivery of ampelopsin. Optimised ME was evaluated for its transparency, viscosity, percentage assay and so forth. Solubilisation capacity of the ME system was also determined. The prepared ME was compared with the pure drug solution and commercially available tablet for in vitro drug release. The optimised ME formulation containing ampelopsin, Capmul MCM (5.5%), Cremophor EL (25%), Transcutol P (8.5%), and distilled water showed higher in vitro drug release, as compared to plain drug suspension and the suspension of commercially available tablet. These results demonstrate the potential use of ME for improving the bioavailability of poor water soluble compounds, such as ampelopsin. PMID:22830055

  5. Effect of Protein Incorporation on the Nanostructure of the Bicontinuous Microemulsion Phase of Winsor-III Systems: A Small-Angle Neutron Scattering Study

    SciTech Connect

    Hayes, Douglas G.; Gomez del Rio, Javier A.; Ye, Ran; Urban, Volker S.; Pingali, Sai Venkatesh; O’Neill, Hugh M.


    Small-angle neutron scattering (SANS) analysis using the Teubner₋Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oil from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOTs sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. We find that the results of this study demonstrate the importance of ionic strength to modulate proteinsurfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.

  6. Effect of Protein Incorporation on the Nanostructure of the Bicontinuous Microemulsion Phase of Winsor-III Systems: A Small-Angle Neutron Scattering Study


    Hayes, Douglas G.; Gomez del Rio, Javier A.; Ye, Ran; Urban, Volker S.; Pingali, Sai Venkatesh; O’Neill, Hugh M.


    Small-angle neutron scattering (SANS) analysis using the Teubner₋Strey model has been employed to evaluate the effect of protein incorporation into the middle, bicontinuous microemulsion (BμE) phase of Winsor-III (WIII) systems formed by an aerosol-OT (AOT)/alkyl ethoxylate mixed surfactant system to understand better the extraction of proteins into and out of BμEs and to study the effect of proteins on a system that serves as a biomimetic analog of cell membranes. Under conditions of high salinity, the incorporation of positively charged proteins cytochrome c, lysozyme, and α-chymotrypsin, near their solubilization limit in the BμEs promoted the release of water and oilmore » from the BμEs, a decrease in the quasi-periodic repeat distance (d), an increase in ordering (a decrease in the amphiphilicity factor, fa) for the surfactant monolayers, and a decrease in the surface area per surfactant headgroup, suggesting that the proteins affected the self-assembly of components in the BμE phase and produced Debye shielding of AOTs sulfonate headgroup. For WIII systems possessing lower salinity, cytochrome c reduced the efficiency of surfactant in the BμE phase, noted by increases in d and fa, suggesting that the enzyme and AOT underwent ion pairing. We find that the results of this study demonstrate the importance of ionic strength to modulate proteinsurfactant interactions, which in turn will control the release of proteins encapsulated in the BμEs, relevant to WIII-based protein extraction and controlled release from BμE delivery systems, and demonstrate the utility of BμEs as a model system to understand the effect of proteins on biomembranes.« less

  7. Counterion exchange selectivity coefficients at water-in-oil microemulsion interface.


    Gonçalves, Saulo A P; De Pauli, Silvia H; Tedesco, Antonio C; Quina, Frank H; Okano, Laura T; Bonilha, João B S


    The counterion binding at a water/Aerosol-OT (AOT)/heptane microemulsion interface was treated in the context of the pseudo-phase ion exchange formalism. Two approaches were used to determine the selectivity coefficient for copper/sodium counterion binding at the AOT microemulsion interface: measurements of the Cu(II) concentration taken up by the reverse micelle in a Winsor II microemulsion system and steady-state emission quenching measurements of an anionic water-solubilized probe, the tris-(4,4'-dicarboxy-2,2'-bipyridine) ruthenium (II) ion. In addition, the selectivity coefficient for methyl viologen/sodium at the microemulsion surface was determined by the same photophysical technique. The value for copper (II)/sodium exchange (K(Cu/Na)) is 1.1+/-0.3 and that for methyl viologen/sodium (K(MV/Na)) is 0.9+/-0.3. The results show that the pseudo-phase ion exchange model can be used to obtain the selectivity coefficient in a microemulsion system. PMID:14583227

  8. Characterization of a water-in-oil microemulsion containing a concentrated ammonium ferric sulfate aqueous phase

    SciTech Connect

    Darab, J.G.; Pfund, D.M.; Fulton, J.L.; Linehan, J.C. ); Capel, M. ); Ma, Y. )


    A water-in-oil (w/o) microemulsion containing high concentrations of ammonium ferric sulfate in solution was characterized by SAXS, EXAFS, electrical conductivity, and viscosity measurements and by its phase behavior. The nanometer-sized aqueous droplets are microemulsified by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in an isooctane continuous phase. Addition of small amounts of sodium dodecyl sulfate (SDS) as a cosurfactant greatly aids in the solubilization of the inorganic electrolyte-laden aqueous phase. For this five-component system there is a large region of the composition phase space that exists as a clear, stable w/o microemulsion. A portion of this w/o microemulsion phase space can be characterized as spherically shaped aqueous nanometer-sized droplets. A simple relationship between the total surfactant concentration and the amount of water on the droplet size was established. This relationship has the same form as the well-known relationship for the ternary system, AOT/water/isooctane. True thermodynamic equilibrium was not established in this microemulsion study because the reaction times for the various ferric oxyhydroxide species are prohibitively long. As a result, pseudoequilibria for this ammonium ferric sulfate microemulsion are reported. 31 refs., 7 figs., 1 tab.

  9. Biocatalysis in water-in-ionic liquid microemulsions: a case study with horseradish peroxidase.


    Moniruzzaman, M; Kamiya, N; Goto, M


    In this article we report the first results on the enzymatic activity of horseradish peroxidase (HRP) microencapsulated in water-in-ionic liquid (w/IL) microemulsions using pyrogallol as the substrate. Toward this goal, the system used in this study was composed of anionic surfactant AOT (sodium bis(2-ethyl-1-hexyl)sulfosuccinate)/hydrophobic IL [C(8)mim][Tf(2)N] (1-octyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide)/water/1-hexanol. In this system, the catalytic activity of HRP was measured as a function of substrate concentrations, W(0) (molar ratio of water to surfactant), pH, and 1-hexanol content. The curve of the activity-W(0) profile was found to be hyperbolic for the new microemulsion. The apparent Michaelis-Menten kinetic parameters (k(cat) and K(m)) were estimated and compared to those obtained from a conventional microemulsion. Apparently, it was found that HRP-catalyzed oxidation of pyrogallol by hydrogen peroxide in IL microemulsuions is much more effective than in a conventional AOT/water/isooctane microemulsion. The stability of HRP solubilized in the newly developed w/IL microemulsions was examined, and it was found that HRP retained almost 70% of its initial activity after incubation at 28 degrees C for 30 h. PMID:19113810

  10. Microemulsion of babassu oil as a natural product to improve human immune system function

    PubMed Central

    Pessoa, Rafael Souza; França, Eduardo Luzia; Ribeiro, Elton Brito; Lanes, Patrícia Kelly Dias; Chaud, Natalina Galdeano Abud; Moraes, Lucélia Campelo Albuquerque; Honorio-França, Adenilda Cristina


    Background The aim of this study was to develop and characterize a babassu oil microemulsion system and determine the effect of this microemulsion on the functional activity of phagocytes. Methods The microemulsion was formulated using distilled water, babassu as the oil phase component, Sorbitan monooleate-Span 80® (SP), Polysorbate 80-Tween 80® (TW), and 1-butanol (BT). Pseudoternary diagrams were prepared, and microemulsion diagram regions were preselected. Rheological characterization and preliminary and accelerated stability tests were performed. The effect of the microemulsion on the interactions between leukocytes and bacteria was determined by superoxide release, phagocytosis, and microbicidal activity. Results The developed formulation SP/TW/BT (4.2/4.8/1.0) was classified as oil/water, showed a Newtonian profile, and had linear viscosity. When we assessed the interaction of the microemulsion or babassu oil with phagocytes, we observed an increase in superoxide, phagocytosis, and microbicidal activity. Conclusion The babassu oil microemulsion system is an option for future applications, including for vaccine delivery systems. Babassu oil is a natural product, so is an alternative for future immunotherapy strategies, in particular for infectious diseases. PMID:25565770

  11. Solubility dynamic of methyl yellow and carbon black in microemulsions and lamellar liquid crystal of water, non ionic surfactants and cyclohexane system

    NASA Astrophysics Data System (ADS)

    Amran, A.; Harfianto, R.; Dewi, W. Y.; Beri, D.; Putra, A.


    Solubility dynamics of methyl yellow and carbon black in microemulsions and liquid crystals of water, non-ionic surfactants and cyclohexane system, have been investigated. Actually, solubility dynamics of these dyes both in microemulsion (w/o microemulsions) and the lamellar liquid crystal (LLC) were strongly related to the chemical composition, nature and characteristics of microemulsions and the lamellar liquid crystals.

  12. Formulation, physicochemical characterization and stability study of lithium-loaded microemulsion system.


    Mouri, Abdelkader; Legrand, Philippe; El Ghzaoui, Abdeslam; Dorandeu, Christophe; Maurel, Jean Claude; Devoisselle, Jean-Marie


    Lithium biocompatible microemulsion based on Peceol(®), lecithin, ethanol and water was studied in attempt to identify the optimal compositions in term of drug content, physicochemical properties and stability. Lithium solubilization in microemulsion was found to be compatible with a drug-surfactant binding model. Lithium ions were predominantly solubilized within lecithin head group altering significantly the interfacial properties of the system. Pseudo-ternary phase diagrams of drug free and drug loaded microemulsions were built at constant ethanol/lecithin weight ratio (40/60). Lithium loaded microemulsion has totally disappeared in the Peceol(®) rich part of phase diagram; critical fractions of lecithin and ethanol were required for the formation of stable microemulsion. The effect of lithium concentration on the properties and physical stability of microemulsions were studied using microscopy, Karl Fischer titrations, rheology analyses, conductivity measurements and centrifugation tests. The investigated microemulsions were found to be stable under accelerated storage conditions. The systems exhibited low viscosity and behaved as Newtonian fluid and no structural transition was shown. PMID:26836707

  13. Determination of the interaction enthalpy between microemulsion droplets by isothermal titration microcalorimetry.


    Zheng, Peizhu; Ma, Yuanming; Peng, Xuhong; Yin, Tianxiang; An, Xueqin; Shen, Weiguo


    A new experimental design for the measurement of the real heat of dilution of the microemulsion droplets by isothermal titration microcalorimetry (ITC) has been reported and used to study the interaction enthalpies of the droplets for the system of water/sodium bis(2-ethylhexyl)-sulfosuccinate (AOT)/toluene. The results are in good agreement with those determined from light-scattering experiments. PMID:21913718

  14. A new hydrate form of diflunisal precipitated from a microemulsion system.


    Sung, Hsuan-Lei; Fan, Yueh-Lin; Yeh, Kimberly; Chen, Yen-Fu; Chen, Li-Jen


    Three microemulsion systems were applied as solvents for polymorph screening of seven active pharmaceutical ingredients (APIs): carbamazepine, piroxicam, sulfaguanidine, nitrofurantoin, theophylline, quercetin, and diflunisal. All the recrystallized compounds were examined by using powder X-ray diffractometry, differential scanning calorimetry, elemental analysis, Karl Fischer titration and dissolution rate. A new crystal form of diflunisal hydrate was discovered by the cooling method of recrystallization in a water-in-oil microemulsion system, composed of water, alkane and dioctyl sodium sulfosuccinate. The new hydrate form of diflunisal was characterized and confirmed to be a stoichiometry of diflunisal:water of 1:1. The other two microemulsion systems were able to convert the anhydrous diflunisal Form I to Form III. The dissolution rate of diflunisal hydrate is unexpectedly much higher than that of anhydrous ones (Forms I and III). All the other six APIs (carbamazepine, piroxicam, sulfaguanidine, nitrofurantoin, theophylline and quercetin) recrystallized from the microemulsion systems were all converted into hydrate form. PMID:23624616

  15. Size-selective extraction of polycyclic aromatic hydrocarbons from a microemulsion system using cyclodextrins

    SciTech Connect

    Elliot, N.B.; Prenni, A.J.; Warner, I.M. ); Ndou, T.T. )


    A procedure for the size-selective extraction of polycyclic aromatic hydrocarbons (PAHs) from an oil-in-water microemulsion system is reported. This extraction is achieved through a precipitation/extraction process involving cyclodextrins (CDs) and select PAHs in the microemulsion. Results are confirmed by fluorescence analysis of supernatant and precipitate. The size relationship between the PAH and CD cavity appears to be a major factor in the selectivity of the process. For example, after extraction with [beta]-CD, the fluorescence intensity of naphthalene in the microemulsion is reduced to 3.7% of its original value, whereas with [alpha]- or [gamma]-CD the intensity remains unchanged. In studies of a model system, the microemulsion involves a three- component mixture of PAHs; [alpha]-, [beta]-, and [gamma]-CD are investigated for their extraction capabilities for these three PAHs.

  16. Partitioning behavior of an acid-cleavable, 1,3-dioxolane alkyl ethoxylate, surfactant in single and binary surfactant mixtures for 2- and 3-phase microemulsion systems according to ethoxylate head group size

    SciTech Connect

    Gomez Del Rio, Javier A; Hayes, Douglas G; Urban, Volker S


    Partition coefficients for a pH-degradable 1,3-dioxolane alkyl ethoxylate surfactant, 4-CH{sub 3}O (CH{sub 2}CH{sub 2}O){sub 5.6}-CH{sub 2}, 2,2-(CH{sub 2}){sub 12}CH{sub 3}, 2-(CH{sub 2}) CH{sub 3}, 1,3-dioxolane or ''cyclic ketal'' surfactant, CK-2,13-E{sub 5.6,ave}, between isooctane- and water-rich phases of 2- and 3-phase microemulsion systems (K{sub n}) were determined as functions of the ethoxylate size, n, and temperature for the neat surfactant and its binary surfactant mixtures, to understand the partitioning of alkyl ethoxylates possessing a broad distribution of ethoxylate size and to determine conditions required for formation of 3-phase microemulsion systems at an optimal temperature where phase separation occurs rapidly, important for protein purification via proteins selective partitioning to the middle phase, driven by affinity to the second surfactant of the binary mixture. A semi-empirical thermodynamic mathematical model described the partitioning data well, provided optimal temperature values consistent with phase diagrams and theory, and demonstrated that the tail region of CK-2,13-E{sub 5.6,ave} is more polar than the hydrophobes of fatty alcohol ethoxylates. The addition of Aerosol-OT (AOT) removed the temperature sensitivity of CK-2,13-E{sub 5.6,ave}s partitioning, producing 3-phase microemulsion systems between 20 C and 40 C. Analysis of the bottom phases of the 2- and 3-phase microemulsion systems formed by CK-2,13-E{sub 5.6,ave} via small-angle neutron scattering demonstrated the presence of spherical, monodisperse oil-in-water microemulsions.

  17. Systemic delivery of insulin via the nasal route using a new microemulsion system: In vitro and in vivo studies.


    Sintov, Amnon C; Levy, Haim V; Botner, Shafir


    The main purpose of this study was to investigate the nasal absorption of insulin from a new microemulsion spray preparation in rabbits. The bioavailability of insulin lispro via the nasal route using a W/O microemulsion was found to reach 21.5% relative to subcutaneous administration, whereas the use of an inverse microemulsion as well as a plain solution yielded less than 1% bioavailability. The profile of plasma glucose levels obtained after nasal spray application of the microemulsion (1IU/kg lispro) was similar to the subcutaneous profile of 0.5IU/kg at the first 90min after application and resulted in a 30-40% drop in glucose levels. The microemulsion system was characterized by DLS, TEM, viscosity measurements, and by construction of pseudo-ternary phase diagram. The average droplet size of an insulin-unloaded and insulin-loaded microemulsions containing 20% aqueous phase (surfactants-to-oil ratio=87:13) was 2nm and 2.26nm in diameter, respectively. In addition, the effect of the microemulsion on FITC-labeled insulin permeation was examined across the porcine nasal mucosa in vitro. The permeability coefficient of FITC-insulin via the microemulsion was 0.210±0.048cm/h with a lag time of 10.9±6.5min, whereas the permeability coefficient from a plain solution was 0.082±0.043cm/h with a lag time of 36.3±10.1min. In view of the absorption differences of insulin between 20%, 50% water-containing microemulsions and an aqueous solution obtained in vitro and in vivo, it has been concluded that the acceleration in the intramucosal transport process is the result of encapsulating insulin within the nano-droplet clusters of a W/O microemulsion, while the microemulsion ingredients seems to have no direct role. PMID:20709120

  18. Preparation and evaluation of microemulsion systems containing salicylic acid.


    Badawi, Alia A; Nour, Samia A; Sakran, Wedad S; El-Mancy, Shereen Mohamed Sameh


    Microemulsions (MEs) are clear, thermodynamically stable systems. They were used to solubilize drugs and to improve topical drug availability. Salicylic acid (SA) is a keratolytic agent used in topical products with antimicrobial actions. The objective of this work was to prepare and evaluate SA ME systems. Different concentrations of SA were incorporated in an ME base composed of isopropyl myristate, water, and Tween 80: propylene glycol in the ratio of 15:1. Three ME systems were prepared: S2%, S5%, and S10% which contain 2%, 5%, and 10% of SA, respectively. Evaluation by examination under cross-polarizing microscope, measuring of percent transmittance, pH measurement, determination of the specific gravity, assessment of rheological properties, and accelerated stability study were carried out. The data showed that the addition of SA markedly affected the physical properties of the base. All systems were not affected by accelerated stability tests. Stability study for 6 months under ambient conditions was carried out for S10%. No remarkable changes were recorded except a decrease in the viscosity value after 1 month. The results suggested that ME could be a suitable vehicle for topical application of different concentrations of SA. PMID:19757081

  19. Preparation and in vitro evaluation of an ilomastat microemulsion gel by a self-microemulsifying system.


    Senhao, Li; Dongqin, Quan


    The purpose of this study was to construct a microemulsion gel formulation by a self-microemulsifying system for transdermal topical delivery of ilomastat. The optimum formulations were screened by penetration evaluation in vitro. Ilomastat microemulsion gel was prepared by drawing a ternary phase diagram and Pluronic F127 was added as gel matrix for the formulation. The optimal formulations had wide microemulsion existent field and good self-microemulsifying efficiency. The droplet size was within 100 nm. Statistical comparison of the permeation throughout 24 h showed that the two microemulsion gel preparations of ilomastat provided higher permeation than that of the normal gel which had only a low cumulative amount of ilomastat (6.03 microg x cm(-2)) 24 h after application. Cumulative amount of ilomastat from microemulsion gels A and B was 2.2 times and 1.8 times that of the normal gel at 24 h respectively. These results indicate that the microemulsion gel may be a promising vehicle for topical delivery of ilomastat. PMID:22512086

  20. Formation and cleansing performance of bicontinuous microemulsions in water/poly (oxyethylene) alkyl ether/ester-type oil systems.


    Aramaki, Kenji; Tawa, Kosuke; Shrestha, Lok Kumar; Iwanaga, Tetsuro; Kamada, Miho


    Phase behaviors in water/poly(oxyethylene) dodecyl ether (C₁₂EO(n), n = 4, 6, 8)/cetyl isooctanoate (CIO) systems were studied. In the C₁₂EO₆ and C₁₂EO₈ systems, self-assembled structures with positive curvatures, such as O/W microemulsions, and micellar cubic and hexagonal phases, were observed. A wider region of a lamellar liquid-crystalline phase, which included a narrow microemulsion region joined by a miscibility gap, was observed in the C₁₂EO₄ system. The structure of the microemulsion phase in the C₁₂EO₄ system was characterized by pulsed-field-gradient NMR (PFG-NMR) and small angle X-ray scattering (SAXS) techniques. PFG-NMR measurements indicated that the structure of the microemulsion was bicontinuous; both water and oil phases were continuous within the microemulsion. Pair-distance distribution function, p (r), and structure factors obtained by Generalized Indirect Fourier Transformation (GIFT) analysis of the SAXS data showed that the microemulsion domain sizes decreased with an increase in the oil content. The structure of the bicontinuous microemulsion was consistent with the results of a detergency test, in which the microemulsion samples were applied to lipstick dirt on an artificial skin plate. Detergency was observed to be better for the microemulsion at lower oil contents because of the larger oil domain size at these low concentrations. PMID:24088518

  1. Transport properties of diluted inverted micelles and microemulsions

    SciTech Connect

    Lalanne, J.R.; Pouligny, B.; Sein, E.


    Experimental results concerning 3 transport properties are discussed: viscosity, mass diffusion, and heat transfer in the ternary system sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/CCl4. Thermal conductivity has been investigated by a thermal lens technique using a single laser pulse in the microsecond range. The results are discussed and compared by using a model based upon the kinetic theory of fluids. The study shows how such investigations can lead to an original determination of the intermicellar potential in microemulsions. 99 references.

  2. In vitro permeation and in vivo whitening effect of topical hesperetin microemulsion delivery system.


    Tsai, Yi-Hung; Lee, Ko-Feng; Huang, Yaw-Bin; Huang, Chi-Te; Wu, Pao-Chu


    Hesperetin is one of the flavonoids and possess anti-inflammatory, UV-protecting and antioxidant effects. Permeation issues for topical delivery systems of such effects are occasionally problematic, and in view of the fact that microemulsions are potential carriers for transdermal delivery system, the objective of this study was to design an optimal microemulsion formulation by in vitro permeation study for hesperetin topical dosage form and determine its topical photoprotective effect and skin irritation by in vivo study. The hesperetin-loaded microemulsion showed an enhanced in vitro permeation compared to the aqueous and isopropyl myristate (IPM) suspension dosage form of hesperetin. In comparison, the effect of co-surfactant on the drug permeation capacity, propylene glycol showed highest permeation rate, followed by ethanol, glycerol and polyethylene glycol (PEG 400). Sunscreen agent padimate O, as a transdermal enhancer could increase the permeation rate of hesperetin. In case of in vivo study, the hesperetin-loaded microemulsion showed significant topical whitening effect and diminished skin irritation when compared with the non-treatment group, indicating that the hesperetin microemulsion could be used as an effective whitening agent. PMID:20060453

  3. Investigation of microemulsion system for transdermal delivery of itraconazole

    PubMed Central

    Chudasama, Arpan; Patel, Vineetkumar; Nivsarkar, Manish; Vasu, Kamala; Shishoo, Chamanlal


    A new oil-in-water microemulsion-based (ME) gel containing 1% itraconazole (ITZ) was developed for topical delivery. The solubility of ITZ in oils and surfactants was evaluated to identify potential excipients. The microemulsion existence ranges were defined through the construction of the pseudoternary phase diagrams. The optimized microemulsion was characterized for its morphology and particle size distribution. The optimized microemulsion was incorporated into polymeric gels of Lutrol F127, Xanthan gum, and Carbopol 934 for convenient application and evaluated for pH, drug content, viscosity, and spreadability. In vitro drug permeation of ME gels was determined across excised rat skins. Furthermore, in vitro antimycotic inhibitory activity of the gels was conducted using agar-cup method and Candida albicans as a test organism. The droplet size of the optimized microemulsion was found to be <100 nm. The optimized Lutrol F 127 ME gel showed pH in the range of 5.68±0.02 and spreadability of 5.75±1.396 gcm/s. The viscosity of ME gel was found to be 1805.535±542.4 mPa s. The permeation rate (flux) of ITZ from prepared ME gel was found to be 4.234 μg/cm/h. The release profile exhibited diffusion controlled mechanism of drug release from ME ITZ gel. The developed ME gels were nonirritant and there was no erythema or edema. The antifungal activity of ITZ showed the widest zone of inhibition with Lutrol F127 ME gel. These results indicate that the studied ME gel may be a promising vehicle for topical delivery of ITZ. PMID:22171289

  4. Spinodal decomposition of a three-component water-in-oil microemulsion system

    SciTech Connect

    Mallamace, F.; Micali, N.; Trusso, S.; Chen, S.H. ||


    We have performed a series of spinodal decomposition measurements of a three-component microemulsion system made of a surfactant Aerosol OT, water, and decane. The measurements were made by a temperature jump from a one-phase droplet microemulsion to a two-phase droplet microemulsion along the critical isovolume fraction line (10%) using a time resolved light scattering intensity measurement technique. All three stages of the evolution were studied. Time evolution of intensities for the initial stage follows closely the linearized theory. On the other hand, time evolution of the characteristic wave vector, the maximum scattering intensity, and the intensity distributions in the intermediate and late stages are in good agreement with recent dynamic scaling theories.

  5. Reverse micelle and microemulsion phases in supercritical fluids

    SciTech Connect

    Fulton, J.L.; Smith, R.D.


    The surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to form reverse micelle and microemulsion phases in supercritical ethane and propane for systems consisting of 80-100% alkane by weight. Phase diagrams obtained from view cell studies of microemulsion phases formed in supercritical fluids are reported and shown to be strongly dependent on pressure. The properties of these solutions were also characterized by conductivity, density, and surfactant solubility measurements. The solubility of AOT in ethane and propane over a range of pressures shows behavior typical of solids in supercritical fluids. The maximum water-to-surfactant ratio (W/sub 0/) increased dramatically in both ethane and propane systems as pressure was increased. At 300 bar and 103/sup 0/C, the supercritical propane-surfactant system is capable of solubilizing much more water (W/sub 0/ = 12) than the supercritical ethane-surfactant system (W/sub 0/ = 4) at 300 bar and 37/sup 0/C. Some of the important thermodynamic contributions that are likely responsible for this pressure-dependent phase behavior are discussed, and potential applications of this new class of solvents are considered.

  6. Stability and comparative analysis of AOT/water/isooctane reverse micelle system using dynamic light scattering and molecular dynamics.


    Vasquez, V R; Williams, B C; Graeve, O A


    We use molecular dynamics (MD) and dynamic light scattering (DLS) measurements to analyze the size of reverse micellar structures in the AOT-water-isooctane system at different water-to-surfactant ratios at ambient temperature and pressure. We find good qualitative agreement for the size and morphology behavior of the reverse micelle structures between molecular dynamics calculations and DLS measurements; however, the average values for the reverse micelle size distributions are systematically larger for the DLS measurements. The latter tends to capture the average hydrodynamic size of the structures based on self-diffusion rather than the average physical size as measured in MD simulations, explaining the systematic deviations observed. The combination of MD with DLS allows a better interpretation of the experimental results, in particular for conditions where the structures are nonspherical, commonly observed at lower water-to-surfactant ratios. We also present and analyze the effect of zirconyl chloride on the micellar size distributions in this system. These type of salts are common for reverse micellar synthesis processes. We find that zirconyl chloride affects significantly the size distributions. PMID:21384835

  7. Theory for dynamical self arrest and gelation in microemulsions and the block copolymer systems

    SciTech Connect

    Wu, Sangwook


    The main purpose of this work is to investigate the glassy behavior of microemulsions and block copolymers. The origin of glassy behavior in microemulsions and block copolymers is frustration due to a competition between short-range interaction and long range interaction. According to the charge frustrated Ising model, the competition between ferromagnetic interaction and antiferromagnetic interaction is the origin of frustration in microemulsions. The competition between entropic effects and stoichiometric constraints responsible for the formation of micelles in microemulsions can lead to the emergence of a self generated glassy behavior in these systems. In the block copolymer, the competition between the repulsive short range interaction between monomers in polymer chains and the long range interaction by chemical bonds can lead to the emergence of a self generated glassy behavior. The criteria for the fluctuation induced first order transition and our microemulsion and block copolymer glasses are essentially the same. Both are a consequence of the large phase space of low energy excitations (14) (62) (all states with momenta q which fulfill |q| = q{sub m}) and are of at the most a moderate supercooling of the liquid state is required. This is strongly supported by the observation in Ref. (14) that the metastable states which are first to appear at a fluctuation induced first order transition are the ones build by a superposition of large amplitude waves of wavenumber q{sub m}, but with random orientations and phases, i.e. just the ones which form the metastable states of our microemulsion and block copolymer glass. (38)

  8. Partitioning of polymeric plutonium(IV) in Winsor II microemulsion systems

    SciTech Connect

    Chaiko, D.J. )


    The hydrolysis and polymerization of Pu(IV) can cause serious problems during the aqueous processing of spent fuel and nuclear wastes. Several studies describing the liquid/liquid extraction behavior of polymeric Pu(IV) have been reported in the literature. In many cases, poor plutonium extraction was accompanied by the appearance of an interfacial crud or third phase. Invariably, poor mass balances were observed during the extraction of aged, colloidal Pu(IV). Extraction of colloidal Pu(IV) by microemulsion-based solvent extraction systems, however, is capable of attaining bulk phase mass balances for Pu of 100%. The Winsor II microemulsions discussed in this paper consisted of sodium bis(2-ethylhexyl) sulfosuccinate in hexane with either octylphenyl-N,N-diisobutylcarbamoylmethylphosphine oxide or tributyl phosphate as coextractant. Backextraction of plutonium from microemulsion phases was achieved by Pu encapsulation in silica particles that were produced by the acid-catalyzed hydrolysis and polymerization of tetraethoxysilane within the aqueous microdroplets of the microemulsion.

  9. Integral physicochemical properties of reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

    NASA Astrophysics Data System (ADS)

    Fedyaeva, O. A.; Shubenkova, E. G.; Poshelyuzhnaya, E. G.; Lutaeva, I. A.


    The effect the degree of hydration has on optical and electrophysical properties of water/AOT/ n-hexane system is studied. It is found that AOT reverse micelles form aggregates whose dimensions grow along with the degree of hydration and temperature. Aggregation enhances their electrical conductivity and shifts the UV spectrum of AOT reverse emulsions to the red region. Four states of water are found in the structure of AOT reverse micelles.

  10. Formation of microemulsions for using as cosmeceutical delivery systems: effects of various components and characteristics of some formulations.


    Wuttikul, Krisada; Boonme, Prapaporn


    Microemulsions are interesting formulations for cosmeceutical applications due to their good appearance, high solubilization power, thermodynamic stability, and enhancement of skin penetration. In addition, they can spontaneously form when suitable types and amounts of components are simply mixed. In this study, the phase behavior of the nonionic systems with various parameters was studied by construction of phase diagrams using titration method. Natural oils, i.e., coconut oil (CO), rice bran oil (RBO), and palm oil (PO), were analyzed for their fatty acid compositions and then mixed with blends of nonionic surfactants (Tween80: Span80) and water or mixtures of water and a cosolvent, propylene glycol (PG), to find the microemulsion regions. Subsequently, some microemulsions were selected for physical characterization. The largest microemulsion regions which were obtained from CO, RBO, and PO covered the sizes of 11.65, 9.84, and 9.24 %, respectively. The surfactant mixture at weight ratio of 1:1 was the most suitable for CO and PO, but for RBO, it was 2:1. PG could increase the microemulsion regions of PO from 9.24 to 15.33 %, depending on PG concentrations. Hence, the sizes of the microemulsion regions were related to oil types, surfactant mixtures, and ratios between water and PG. The studied microemulsions were water-in-oil (w/o) type, and their internal droplets were in the nanosize range. They exhibited Newtonian flow behavior and their mean viscosity values were from 247.53 to 690.35 cP which were correlated with the types and concentrations of the components in the formulations. In conclusion, natural oils could form w/o microemulsions with nonionic surfactants. The microemulsion formation and characteristics were related to many parameters of the components. PMID:26813671

  11. Volume properties of reverse micellar systems AOT/ n-heptane/DMSO-water

    NASA Astrophysics Data System (ADS)

    Sargsyan, A. R.; Shahinyan, G. A.; Markarian, S. A.


    The volume properties of reverse micellar systems bis(2-ethylhexyl) sulfosuccinate sodium salt/ n-heptane/dimethyl sulfoxide-water are studied via densitometry. The presence of dimethyl sulfoxide and the increase in its amount in a dimethyl sulfoxide-water mixed solvent raise the apparent volume of the polar phase. This increase is also observed when the degree of hydration of the polar core and the temperature are raised.

  12. Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.


    Sostarecz, Audra G; Gaidamauskas, Ernestas; Distin, Steve; Bonetti, Sandra J; Levinger, Nancy E; Crans, Debbie C


    We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats. PMID:24615733

  13. Microemulsion system for topical delivery of thai mango seed kernel extract: development, physicochemical characterisation and ex vivo skin permeation studies.


    Leanpolchareanchai, Jiraporn; Padois, Karine; Falson, Françoise; Bavovada, Rapepol; Pithayanukul, Pimolpan


    A microemulsion system containing Thai mango seed kernel extract (MSKE, cultivar "Fahlun") was developed and characterised for the purpose of topical skin delivery. The MSKE-loaded microemulsions were prepared by using the spontaneous emulsification method. Isopropyl myristate (IPM) was selected as the oil phase. A polyoxyethylene sorbitan monooleate and sorbitan monododecanoate (1:1, w/w) system was used as the surfactant phase; an aqueous mixture of different cosurfactants (absolute ethanol, 96.3% v/v ethanol, 1-propanol, 2-propanol or 1,2-propanediol) at a weight ratio of 1:1 was used as the aqueous phase. Among the cosurfactants studied, the 1-propanol aqueous mixture had the largest microemulsion region (48.93%) in the pseudo-ternary phase diagram. Microemulsions containing 1% MSKE demonstrated good physicochemical stability during a six-month study period at 25 ± 2 °C/60% ± 5% RH. The ex vivo skin permeation study demonstrated that the microemulsions exhibited a potent skin enhancement effect allowing MSKE to penetrate skin layers up to 60-fold higher compared with the control. Neither skin irritation nor skin corrosion was observed in ex vivo studies. The present study revealed that IPM-based microemulsion systems may be promising carriers to enhance skin penetration and delivering MSKE for topical treatment. PMID:25347456

  14. Delivery systems for biopharmaceuticals. Part II: Liposomes, Micelles, Microemulsions and Dendrimers.


    Silva, Ana C; Lopes, Carla M; Lobo, José M S; Amaral, Maria H


    Biopharmaceuticals are a generation of drugs that include peptides, proteins, nucleic acids and cell products. According to their particular molecular characteristics (e.g. high molecular size, susceptibility to enzymatic activity), these products present some limitations for administration and usually parenteral routes are the only option. To avoid these limitations, different colloidal carriers (e.g. liposomes, micelles, microemulsions and dendrimers) have been proposed to improve biopharmaceuticals delivery. Liposomes are promising drug delivery systems, despite some limitations have been reported (e.g. in vivo failure, poor long-term stability and low transfection efficiency), and only a limited number of formulations have reached the market. Micelles and microemulsions require more studies to exclude some of the observed drawbacks and guarantee their potential for use in clinic. According to their peculiar structures, dendrimers have been showing good results for nucleic acids delivery and a great development of these systems during next years is expected. This is the Part II of two review articles, which provides the state of the art of biopharmaceuticals delivery systems. Part II deals with liposomes, micelles, microemulsions and dendrimers. PMID:26278524

  15. Efficacy of Different Block Copolymers in Facilitating Microemulsion Phases in Polymer Blend Systems

    NASA Astrophysics Data System (ADS)

    Pandav, Gunja; Ganesan, Venkat


    Polymeric microemulsions are formed in a narrow range of phase diagram when a blend of immiscible homopolymers is compatibilized by copolymers. In this study, we consider the ternary blend system of A and B homopolymers mixed with block copolymers containing A and B segments, and probe the efficacy of different copolymer configurations in promoting the formation of microemulsion phases. Specifically, we consider: (a) Monodisperse diblock copolymers; (b) Diblock copolymers with bidisperse molecular weights (MW); (c) Block copolymers having MW polydispersity in one of the blocks; (d) Diblock copolymers having monodisperse MW but bidispersity in average composition; and (e) Gradient copolymers exhibiting a linear variation in the average composition. Using single chain in mean field simulations effected in two dimensions, we probe the onset of formation and the width of the bicontinuous microemulsion channel in the ternary phase diagram of homopolymer blended with compatibilizer. We rationalize our results by explicitly quantifying the interfacial activity and the influence of fluctuation effects in the respective copolymer systems.

  16. Nanostructured diffusion-limited-aggregation crystal pattern formation in a reactive microemulsion system

    NASA Astrophysics Data System (ADS)

    Srivastava, Rohit; Srivastava, P. K.


    Nanostructured diffusion-limited-aggregation (DLA) crystal pattern formation in microemulsion consisting of water, styrene, cetyltrimethylammonium chloride (CTACl), potassium persulphate and an oscillating Belousov-Zhabotinsky (BZ) reactant is reported. A variety of spatiotemporal patterns like concentric wave, spatial (stripe) and chaotic patterns appear. A colloidal phase composed of numerous nano-sized particles has been observed. The solid phase nucleation has been found to occur in the colloidal phase and has been found to grow in a symmetric crystal pattern with the progress of the reaction finally exhibiting DLA structures. We show that the formation of a nanostructured DLA crystal pattern is governed by spatial structures emerging in the BZ microemulsion system. Without any spatial structure in the microemulsion system only hydrogel of high viscosity is formed. A nano-sized branched crystal pattern was formed with a particle diameter in the range of 60-100 nm, as evident by transmission electron microscope, powder x-ray diffraction and particle size analyser studies.

  17. Characterization of Microemulsion Systems Formed by a Mixed 1,3-Dioxolane Ethoxylate / Octyl Glucoside Surfactant System

    SciTech Connect

    Alkhatib, Mayson H; Hayes, Douglas G; Urban, Volker S


    The phase behavior of microemulsion systems containing water (or 1.0 wt% NaCl{sub aq}), isooctane, and the binary surfactant system consisting of n-octyl-{beta}-D-glucopyranoside, C{sub 8}{beta}G{sub 1}, and the acid-cleavable alkyl ethoxylate, 4-CH{sub 3}O (CH{sub 2}CH{sub 2}O){sub 7.2}, 2-(CH{sub 2}){sub 12}CH{sub 3}, 2-(CH{sub 2})CH{sub 3}, 1,3-dioxolane, or 'cyclic ketal' ('CK-2,13'), was determined. Large temperature-insensitive one, two, and three-phase microemulsion-phase regions were obtained when equal masses of the two surfactants were employed, suggesting that C{sub 8}{beta}G{sub 1} reduces the temperature sensitivity of CK-2,13's ethoxylate group. Addition of C{sub 8}{beta}G{sub 1} to CK-2,13 greatly improves the latter's low efficiency, evidenced by the formation of a three-phase microemulsion system for surfactant concentrations at low fractions of total surfactants for systems with equal mass ratios of water to oil and CK-2,13 to C{sub 8}{beta}G{sub 1}. Analysis of the phase diagrams also suggests that CK-2,13 and C{sub 8}{beta}G{sub 1} impart hydrophobic and hydrophilic character, respectively, to the surfactant mixture, and that addition of salt further increases the hydrophilicity of C{sub 8}{beta}G{sub 1}, presumably because of the salting-in of the latter. Analysis of small-angle neutron scattering data revealed that the mixed surfactant system formed spherical oil-in-water microemulsions, and that increasing the CK-2,13 fraction among the surfactants reduced the critical microemulsion concentration but slightly increased the nanodroplet size.

  18. Solubilization of a dendrimer into a microemulsion.


    Nir, Ido; Aserin, Abraham; Libster, Dima; Garti, Nissim


    The present work investigates, for the first time, a system comprising a dendrimer incorporated into the water core of water-in-oil (W/O) microemulsion (ME). A second generation (G-2) poly(propyleneimine) dendrimer (PPI) was solubilized into W/O ME composed of AOT (sodium bis(2-ethylhexyl)sulfosuccinate), heptane, and water. Such a model system possessing the benefits of both dendrimers and ME, can potentially offer superior control of drug administration. The localization of PPI within the system, its specific interactions with the components of the carrier, and its effect on the ME structure was explored by SAXS, DSC, ATR-FTIR, and electrical conductivity measurements. Considerable water binding by PPI, accompanied by partial dehydration of AOT polar heads, was detected by ATR-FTIR and DSC analysis, suggesting that PPI acted as a "water pump". In addition, SAXS measurements showed periodicity increase and disordering of the droplets. Hence, localization of PPI within the core and interfacial regions of the droplets was assumed. Direct electrostatic interactions between PPI and the sulfonate group were not noticed, since the dendrimer molecules were mostly not protonated in the current basic environment at pH 12. However, slight hydrogen bonding between PPI and the S=O groups allowed the dendrimer to behave as a "spacer" between sodium and sulfonate ions. This affected the electrical conductivity behavior of the system, revealing that PPI favored the percolation process. Most likely, PPI decreased the rigidity of the interfacial layer, facilitating the diffusion of sodium ions through the channels. The characterized model system can be advantageously utilized to design specific delivery vehicles, allowing administration of dendrimers as a therapeutic agent from host MEs. PMID:21126032

  19. Optical Properties of Silica-Encapsulated ZnSe Nanocrystals Prepared with Water-in-Oil Microemulsions

    NASA Astrophysics Data System (ADS)

    Liu, Kang; Kim, Ji Hyeon; Park, Sang Joon


    Silica-encapsulated ZnSe nanocrystals (NCs) were prepared by a safe and simple synthesis method, utilizing a sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/water/cyclohexane microemulsion system and characterized by UV-vis analysis, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). For the encapsulations, two reverse micellar solutions [one for tetraethyl orthosilicate (TEOS) and the other for ZnSe] containing different water volumes were employed. The size of silica particles containing ZnSe NCs could be controlled from 13-37 nm by varying the water content W (W=[H2O]/[AOT]). On the other hand, the size of encapsulated ZnSe NCs was almost unchanged (about 2.5 nm) even though the size of the silica particles was increased. At W = 7, the maximum PL efficiency of 6% was obtained and the photostability was increased markedly after ZnSe NCs were encapsulated by silica.

  20. Electron microscopic study of a glass-forming water/oil pseudo-three-component microemulsion system

    SciTech Connect

    Green, J.L. )


    The development of microemulsion systems that do not break down during cooling and in which neither dispersed nor matrix phases crystallize during the cooling process opens the way to direct studies of the microemulsion structure and also the investigation of the dispersed liquid in unusual states. The authors report the first water-in-oil example of this type of system. It was obtained by partial replacement of water by glycerol and total replacement of normal paraffin by ethylcyclohexane, in the water/oil/didodecyldimethylammonium bromide three-component system. The phase diagram at 25{degree}C indicates a remarkably wide range of clear-phase compositions. A dispersed droplet structure for the water-rich range is unequivocally established by direct electron microscope imaging of the vitrified microemulsion, using the freeze-fracture technique.

  1. High aspect ratio CdS nanowires synthesized in microemulsion system

    SciTech Connect

    Fu Xun . E-mail:; Wang Debao; Wang Jing; Shi Huaqiang; Song Caixia


    CdS nanowires with typical length more than 8 {mu}m and width of 30 nm on average have been successfully synthesized through Cd(NO{sub 3}){sub 2} reacting with CS{sub 2} and ethylenediamine in microemulsion system of sodium dodecylbenzene sulfonate (SBDS). The microstructures of the as-synthesized CdS nanowires were characterized using XRD, transmission electron microscopy (TEM) and HRTEM. The possible formation mechanism was discussed. The morphologies of CdS sample strongly depend on the concentration of surfactant in solutions.

  2. Reversed micellar solution-to-bicontinuous microemulsion transition in sodium bis(2-ethylhexyl) phosphate/n-heptane/water system

    SciTech Connect

    Yu, Z.J.; Neuman, R.D.


    The solution structures in the three-component system sodium bis(2-ethylhexyl) phosphate (NaDEHP)/n-heptane/water have been investigated by dynamic and static light-scattering, electrical conductivity, and {sup 31}P-NMR spectroscopic and viscometric measurements. A transition in the physicochemical properties was observed over a rather narrow range of W{sub o} (molar ratio of water to NaDEHP) values. Rodlike reversed micelles and swollen rodlike reversed micelles form when W{sub o}< 4. Beyond this W{sub o} range, phase separation occurs at low NaDEHP concentrations, and homogeneous one-phase microemulsions form at high NaDEHP concentrations. It is suggested that the n-heptane-continuous solution of water-swollen reversed micelles transforms to a bicontinuous microemulsion when W{sub o} increases beyond W{sub o} {approx} 4. The bicontinuous microemulsion region ranges between two local viscosity maxima at W{sub o}{approx} 4 and W{sub o}{approx} 100, and an oil-in-water (O/W) microemulsion exists when W{sub o}> 100. Local dynamic domain structures consistent with the bicontinuous microemulsion behaviors are proposed and discussed. 29 refs., 7 figs., 1 tab.

  3. Preparation of iron oxide nanoparticles from FeCl3 solid powder using microemulsions

    NASA Astrophysics Data System (ADS)

    Nassar, Nashaat; Husein, Maen


    Nanoparticles of iron oxide were prepared by subjecting iron chloride powder to (w/o) microemulsions consisting of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), isooctane and water. FeCl3 was first dissolved in the water pools of the microemulsion, and then reacted with NaOH added as an aqueous solution to form iron oxide. The amount of NaOH solution was limited so that single microemulsion phase is obtained. This technique serves as an in-situ nanoparticle preparation technique aimed at minimizing particle aggregation associated with particle transportation to required sites. In this study, the effects of AOT concentration and water to AOT mole ratio on the nanoparticle size were investigated. UV/Vis spectrophotometry and transmission electron microscopy (TEM) were used to measure the particle size distribution.

  4. Characterization and in vitro permeation study of microemulsions and liquid crystalline systems containing the anticholinesterase alkaloidal extract from Tabernaemontana divaricata.


    Chaiyana, Wantida; Rades, Thomas; Okonogi, Siriporn


    The aims of the present study were to characterize the microstructure and study the skin permeation enhancement of formulations containing the alkaloidal extract from Tabernaemontana divaricata. The extract was loaded in the formulations composed of Zingiber cassumunar oil, Triton X-114, ethanol and water with the oil:surfactant ratios of 1:5 and 2:5. The formulations were characterized by photon correlation spectroscopy, polarizing light microscopy, differential scanning calorimetry, and viscosity measurement. A reverse micellar phase, w/o microemulsions, liquid crystalline systems, liquid crystal in microemulsion systems and coarse emulsions were formed along the aqueous dilution line of both oil:surfactant ratios. Formulations with the ratio of 1:5 containing 0.1 μg/ml extract showed a significantly higher acetylcholinesterase inhibition than those with the ratio of 2:5. The skin of stillborn piglet was used in the permeation study. The liquid crystalline and microemulsion systems significantly increased the transdermal delivery of the extract within 24h. It was concluded that the alkaloidal extract from T. divaricata stem loaded in liquid crystalline or microemulsion systems comprising Z. cassumunar oil/Triton X-114/ethanol/water may act as an alternative percutanous formulations for enhancing the acetylcholine level in Alzheimer's patients. PMID:23680734

  5. Electron processes in AOT reverse micelles. Part 2. Influence of oil phase. Pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Gebicki, J. L.; Bednarek, P.


    Reverse micellar systems formed of AOT, i.e. sodium bis(2-ethyl-1-hexyl) sulfo-succinate, in different hydrocarbons, without water, dry micelles, and in the presence of water, wet micelles, have been studied by means of pulse radiolysis. Different localization sites of hydrated electron within wet reverse micelle including a triad e aq-/Na +/SO 3- rad (absorption band peaking around 610 nm) are proposed and discussed to explain the influence of the ratio [water]/[AOT] and of the kind of alkane on the position and half-width of the absorption spectrum of the hydrated electron. Sulfite radical, necessary to form such triad, is released as a result of electron interaction with AOT molecule within reverse micelles (RM) containing water. A product of direct electron attachment to AOT molecule, AOT radical anion, has been observed spectrophotometrically only in dry AOT RM at ambient temperature (absorption band peaking around 330 nm).

  6. Recovery of oil using microemulsions

    SciTech Connect

    Puerto, M.C.


    This patent describes a method of recovering hydrocarbons from a subterranean reservoir formation containing formation hydrocarbons and formation water. It comprises determining the effective reservoir water/hydrocarbon bank viscosity and the reservoir salinity; determining the proper oil molar volume for a micro-emulsion; determining the proper oil or mixture of oils to be used to create an optimal microemulsion; tailoring a microemulsion in the one phase region of the ternary diagram of an optimum microemulsion system that is optimum at the reservoir salinity; injecting the microemulsion into the formation through at least one injection means to displace the hydrocarbons toward at least one production means, and recovering hydrocarbons with the production means.

  7. Design and control of patterns in reaction-diffusion systems

    NASA Astrophysics Data System (ADS)

    Vanag, Vladimir K.; Epstein, Irving R.


    We discuss the design of reaction-diffusion systems that display a variety of spatiotemporal patterns. We also consider how these patterns may be controlled by external perturbation, typically using photochemistry or temperature. Systems treated include the Belousov-Zhabotinsky (BZ) reaction, the chlorite-iodide-malonic acid and chlorine dioxide-malonic acid-iodine reactions, and the BZ-AOT system, i.e., the BZ reaction in a water-in-oil reverse microemulsion stabilized by the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT).

  8. Design and control of patterns in reaction-diffusion systems

    SciTech Connect

    Vanag, Vladimir K.; Epstein, Irving R.


    We discuss the design of reaction-diffusion systems that display a variety of spatiotemporal patterns. We also consider how these patterns may be controlled by external perturbation, typically using photochemistry or temperature. Systems treated include the Belousov-Zhabotinsky (BZ) reaction, the chlorite-iodide-malonic acid and chlorine dioxide-malonic acid-iodine reactions, and the BZ-AOT system, i.e., the BZ reaction in a water-in-oil reverse microemulsion stabilized by the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

  9. Hydrated Electrons in a Quaternary Microemulsion System: A Pulse Radiolysis Study


    Adhikari; Joshi; Gopinathan


    Using the technique of pulse radiolysis, hydrated electrons have been produced and studied in quaternary microemulsion (sodium lauryl sulfate (NaLS)/water/cyclohexane/1-pentanol) system. Remarkably high lifetimes ( approximately 20 &mgr;s) for hydrated electrons have been obtained. In general, these are two orders of magnitude higher than those reported earlier in reverse micelles. The water droplet sizes and location of the probes have been determined from the decay kinetics of hydrated electrons. The yields and half-lives (t 1/2 ) of the hydrated electrons vary smoothly as the water droplet sizes are changed. We believe that these studies will be useful not only in interpreting electron transfer reactions occurring in small water pockets in biological systems but also in the production of metal nanoclusters by radiation chemical method. PMID:9241228

  10. [Preparation of self-microemulsion drug delivery system of the mixture of paeonol and borneol based on Xingbi Fang].


    Lü, Feng-Qin; Li, Huang; Xu, Wei; Zhang, Xun; Huang, Ming-Qing; Zheng, Jian; Chu, Ke-Dan


    The aim of this study is to prepare self-microemulsifying drug delivery system (SMEDDS) of the mixture of paeonol (Pae) and borneol (Bor). Solubility test, ternary phase diagrams and simplex lattice method were employed to screen and optimize the formulation of the mixture of Pae and Bor-loaded SMEDDS. After formed into microemulsions, the particle diameter (PD) was determined and a TEM was employed to observe the microemulsions' morphology. The contents of Pae and Bor were determined by gas chromatography. As a result, while ethyl oleate (EO) as the oil phase, cremophor EL35 (EL35) as surfactant and Transcutol HP (HP) as cosurfactant, the range of the microemulsion on the ternary phase diagram was larger than other combinations. And at a ratio of 20:45:35, the microemulsions' PD was about 34 nm and the polydispersity index (PI) was about 0.2. There were 16% of Pae, 2% of Bor, 16% of EO, 37% of EL35 and 29% of HP in the prepared SMEDDS. The preparation process of the Pae and Bor-loaded SMEDDS based on Xingbi Fang is simple and feasible. This study provides a reference for the researches on the related traditional Chinese medicine and the related components. PMID:24417089

  11. Microemulsions in technical processes

    SciTech Connect

    Schwuger, M.J.; Stickdorn, K.; Schomaecker, R.


    The aim of this review is to present once again the basic properties of microemulsions and to relate them to some already established applications and also to show further potential fields of application. This review will survey this area, focusing mainly on the last decade. Earlier publications on the technical relevance of microemulsions and reverse micelles were reviewed by Langevin in 1982. The most important properties of these systems, which are of significance for technical applications, will be described. The applications discussed are: enhanced oil recovery; liquid-liquid extraction; extraction from chemically contaminated soils; lubricants and cutting oils; pharmaceuticals and cosmetics; washing; impregnation and textile finishing; and chemical reactions in microemulsions. 143 refs.

  12. Conductivity in nonpolar media: experimental and numerical studies on sodium AOT-hexadecane, lecithin-hexadecane and aluminum(III)-3,5-diisopropyl salicylate-hexadecane systems.


    Schmidt, Jochen; Prignitz, Rodolphe; Peschka, Dirk; Münch, Andreas; Wagner, Barbara; Bänsch, Eberhard; Peukert, Wolfgang


    The conductivity behavior of doped hydrocarbon systems is studied by applying impedance spectroscopy. In the case of 3,5-diisopropyl salicylato aluminum (III) the charge carriers are formed by dissociation of the compound and their concentration is proportional to the square root of the solute concentration. In hydrocarbon systems that consist of micelle forming compounds (sodium AOT/ lecithin) a linear dependence of charge carrier concentration on solute concentration is observed in the concentration regime where micelles are present. The conduction mechanisms are studied by numerical solution of a Poisson-Nernst-Planck system that describes the charge transport. We follow two different approaches to extract the degree of micelle dissociation from the impedance data. Firstly, by computing the response of a linear approximation of the Poisson-Nernst-Planck model, and secondly by computing the fully nonlinear response from direct numerical simulations using finite elements. For high and moderate frequencies both approaches agree very well with the experimental data. For small frequencies the response becomes nonlinear and the concept of impedance fails. Furthermore, the numerically computed values for the degree of dissociation are of the same order of magnitude as the values obtained with classical formulas, but still differ by a factor of about 1/3. The direct numerical simulation allows new insight into the conduction mechanisms for different frequency regimes. PMID:22925119

  13. Fourier transform infrared spectroscopic study on microemulsion systems of alkali metal salts of 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester

    NASA Astrophysics Data System (ADS)

    Zhou, Weijin; Shi, Nai; Xu, Zhen-hua; Wu, JinGuang


    There has recently been a growing interest in the reverse micelle and microemulsion formation in the solvent extraction process. In our previous papers, the formation of W/O type microemulsions in the organic phase of sodium or potassium salt of 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester was investigated by using the subtraction technique on FTIR. In this paper, the conductance and the FTIR spectroscopic study on the microemulsion systems of Li, Na, and K salts of this acidic extractant was reported.

  14. Size Dependent Ultrafast Cooling of Water Droplets in Microemulsions by Picosecond Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Seifert, G.; Patzlaff, T.; Graener, H.


    The ultrafast thermal relaxation of reversed micelles in n-octane/AOT/water (where AOT denotes sodium di-2-ethylhexyl sulfosuccinate) microemulsions was investigated by time-resolved infrared pump-probe spectroscopy. This picosecond cooling process can be described in terms of heat diffusion, demonstrating a new method to determine the nanometer radii of the water droplets. The reverse micelles are stable against transient temperatures far above the equilibrium stability range. The amphiphilic interface layer (AOT) seems to provide an efficient heat contact between the water and the nonpolar solvent.

  15. Temperature and Pressure Effects on the Bending Modulus of Monolayers in a Ternary Microemulsion

    NASA Astrophysics Data System (ADS)

    Kawabata, Y.; Nagao, M.; Seto, H.; Komura, S.; Takeda, T.; Schwahn, D.; Yamada, N. L.; Nobutou, H.


    We performed small-angle neutron scattering and neutron spin echo experiments on a ternary microemulsion composed of ionic surfactant AOT, water, and decane. Thermal fluctuations of monolayers have been investigated as a function of temperature and pressure. The amphiphilic monolayers become more flexible with increasing temperature and more rigid with increasing pressure. These results are consistent with the microscopic picture that the head-head repulsion of the AOT molecules is enhanced at high temperature while an attractive interaction between the hydrophobic tails of the AOT molecules increases at high pressure.

  16. Hardware and software system for automatic microemulsion assay evaluation by analysis of optical properties

    NASA Astrophysics Data System (ADS)

    Maeder, Ulf; Schmidts, Thomas; Burg, Jan-Michael; Heverhagen, Johannes T.; Runkel, Frank; Fiebich, Martin


    A new hardware device called Microemulsion Analyzer (MEA), which facilitates the preparation and evaluation of microemulsions, was developed. Microemulsions, consisting of three phases (oil, surfactant and water) and prepared on deep well plates according to the PDMPD method can be automatically evaluated by means of the optical properties. The ratio of ingredients to form a microemulsion strongly depends on the properties and the amounts of the used ingredients. A microemulsion assay is set up on deep well plates to determine these ratios. The optical properties of the ingredients change from turbid to transparent as soon as a microemulsion is formed. The MEA contains a frame and an imageprocessing and analysis algorithm. The frame itself consists of aluminum, an electro luminescent foil (ELF) and a camera. As the frame keeps the well plate at the correct position and angle, the ELF provides constant illumination of the plate from below. The camera provides an image that is processed by the algorithm to automatically evaluate the turbidity in the wells. Using the determined parameters, a phase diagram is created that visualizes the information. This build-up can be used to analyze microemulsion assays and to get results in a standardized way. In addition, it is possible to perform stability tests of the assay by creating special differential stability diagrams after a period of time.

  17. Dielectric depolarisation and concerted collective dynamics in AOT reverse micelles with and without ubiquitin.


    Schmollngruber, Michael; Braun, Daniel; Oser, Daniel; Steinhauser, Othmar


    In this computational study we present molecular dynamics (MD) simulations of reverse micelles, i.e. nano-scale water pools encapsulated by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and dissolved in isooctane. Although consisting of highly polar components, such micro-emulsions exhibit surprisingly low dielectric permittivity, both static and frequency-dependent. This finding is well supported by experimental dielectric measurements. Furthermore, the computational dielectric spectra of reverse micelles with and without the polar protein ubiquitin are almost identical. A detailed component analysis of our simulated systems reveals the underlying mechanism of the observed dielectric depolarisation. While each component by itself would make a remarkable contribution to the static dielectric permittivity, mutual compensation leads to the observed marginal net result. This compensatory behavior is maintained for all but the highest frequencies. Dielectric model theory adapted to the peculiarities of reverse micelles provides an explanation: embedding a system in a cavity engulfed by a low dielectric medium automatically leads to depolarization. In this sense experiment, simulation and theory are in accordance. PMID:26751837

  18. Fourier transform infrared study on microemulsion system of potassium salt of bis(2-ethylhexyl) phosphinic acid (HA)

    NASA Astrophysics Data System (ADS)

    Zhou, Weijin; Shi, Nai; Wang, Yi; Chang, Zhiyuan; Wu, JinGuang


    To study microemulsion formation in a solvent extraction system is to probe into some basic principles of extraction chemistry in the light of combining extraction chemistry with surface chemistry. In our previous investigations, the microemulsions of the salts of HDEHP and PC88A have been studied systematically by FT-IR. In the experiment, we observed the change of peak positions and intensities of P equals O, P-O-C and P-O-H groups during saponification and hydration, and discovered that the peak of P-O-C splits apart into 1045 and 1075 cm-1. The vibration frequency of the P-O-C group in HDEHP and PC88A is quite close to the symmetric stretching frequency of the POO- group, and thus causes difficulties in the study of their peak position and absorbance variation. For this reason we synthesized bis(2-ethylhexyl) phosphinic acid without the P-O-C group. Infrared spectra in the range of 800 - 4000 cm-1 of this microemulsion system was studied.

  19. FT-IR and dielectric study of water/AOT liquid crystals

    NASA Astrophysics Data System (ADS)

    Calandra, P.; Caponetti, E.; Chillura Martino, D.; D'Angelo, P.; Minore, A.; Turco Liveri, V.


    In order to explore the influence of microwave radiation on highly viscous microheterogeneous systems, the evolution of structural and dynamical properties of the water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT) liquid crystals as a function of the molar ratio R ( R=[water]/[AOT]) has been investigated by FT-IR spectroscopy and time domain reflectometry. The study emphasises how the progressive hydration of the surfactant head groups is mainly responsible for the structural and dynamical evolution of water/AOT liquid crystals. In particular, it has been found that the state of water at lower R values is strongly perturbed, bulk-like water appears only at R>23 and the water/AOT interface polarisation is controlled by the fast translational dynamics of sodium counterions and the slow orientational dynamics of the AOT ionic head groups.

  20. Evaluation of Microemulsion and Lamellar Liquid Crystalline Systems for Transdermal Zidovudine Delivery.


    Carvalho, André Luis Menezes; Silva, José Alexsandro da; Lira, Ana Amélia Moreira; Conceição, Tamara Matos Freire; Nunes, Rogéria de Souza; de Albuquerque Junior, Ricardo Luiz Cavalcanti; Sarmento, Victor Hugo Vitorino; Leal, Leila Bastos; de Santana, Davi Pereira


    This study proposed to investigate and to compare colloidal carrier systems containing Zidovudine (3'-azido-3'-deoxythymidine) (AZT) for transdermal administration and optimization of antiretroviral therapy. Microemulsion (ME) and lamellar phase (LP) liquid crystal were obtained and selected from pseudoternary diagrams previously developed. Small-angle X-ray scattering and rheology analysis confirmed the presence of typical ME and liquid crystalline structures with lamellar arrangement, respectively. Both colloidal carrier systems, ME, and LP remained stable, homogeneous, and isotropic after AZT addition. In vitro permeation study (using pig ear skin) showed that the amount of permeated drug was higher for ME compared to the control and LP, obtaining a permeation enhancing effect on the order of approximately 2-fold (p < 0.05). Microscopic examination after in vivo skin irritation studies using mice suggested few histological changes in the skin of animals treated with the ME compared to the control group (hydrogel). Thus, ME proved to be adequate and have promising effects, being able to promote the drug permeation without causing apparent skin irritation. On the order hand, LP functioned as a drug reservoir reducing AZT partitioning into the skin. PMID:27220471

  1. Reactions in microemulsion formed by sodium dodecyl sulfate, water, and hexanol

    SciTech Connect

    Valaulikar, B.S. . Chemistry Div.)


    The reactions, oxidation of iodide by persulfate and basic hydrolysis of crystal violet, were investigated in the w/o microemulsion formed by sodium dodecyl sulfate, water, and hexanol. The second order rate constants were measured as a function of emulsion formed by sodium dodecyl sulfate, water, and hexanol. The second order rate constants were measured as a function of water to surfactant molar ratio and hexanol content. The increased rates were attributed to the smaller droplet size of the water pools. The rates are shown to be controlled by the water content as well as the hexanol content. It is shown that the manner in which the rate is affected applies to the catalyzed as well as the retarded reactions. This system is shown to be more effective than the AOT/water/decane system.

  2. Nonlinear effects of electric fields in the Belousov-Zhabotinsky reaction dissolved in a microemulsion

    NASA Astrophysics Data System (ADS)

    Dähmlow, Patricia; Müller, Stefan C.


    Labyrinth-like Turing patterns are investigated under the influence of an electric field. The patterns form in the ferroin-catalyzed Belousov-Zhabotinsky reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion. For two different values of the droplet fraction above and below the percolation transition of the system, the electric field induced drift of the patterns is different. Above the percolation transition, a linear increase of the drift velocity with increasing electric field strength is found. However, below the percolation transition, this increase shows an exponential behavior. The patterns are also observed to reorient under high electrical field strength, such that they are arranged perpendicular with respect to the field lines.

  3. Preparation of ZnSe Nanocrystals Using Water-in-Oil Microemulsions

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Soo; Kim, Jong Sung; Park, Sang Joon


    ZnSe nanocrystals were prepared using a safe and simple synthetic method by employing a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/oil microemulsion system with aqueous ZnSO4 and Se2- solutions, and characterized by X-ray diffraction (XRD) analysis, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). To control the diameter of nanocrystals in the quantum confinement region, the synthesis was performed with different oil phases (heptane and cyclohexane) and various water-to-surfactant ratios, W ([H2O]/[surfactant]). Cubic zinc blende ZnSe nanocrystals were synthesized and their size was controlled in the range from 2.5 to 17 nm. The maximum PL efficiency was 14% for the smallest ZnSe nanocrystal.

  4. Nonlinear effects of electric fields in the Belousov-Zhabotinsky reaction dissolved in a microemulsion.


    Dähmlow, Patricia; Müller, Stefan C


    Labyrinth-like Turing patterns are investigated under the influence of an electric field. The patterns form in the ferroin-catalyzed Belousov-Zhabotinsky reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion. For two different values of the droplet fraction above and below the percolation transition of the system, the electric field induced drift of the patterns is different. Above the percolation transition, a linear increase of the drift velocity with increasing electric field strength is found. However, below the percolation transition, this increase shows an exponential behavior. The patterns are also observed to reorient under high electrical field strength, such that they are arranged perpendicular with respect to the field lines. PMID:25933665

  5. TOPICAL REVIEW: Mesoscale structures in microemulsions

    NASA Astrophysics Data System (ADS)

    Komura, S.


    Due to the existence of intermediate mesoscopic internal structures, soft matter exhibits various fascinating non-linear and non-equilibrium phenomena. In this review article, we focus on microemulsions consisting of water, oil, and surfactant from the viewpoint of soft matter physics. Microemulsions exhibit a rich phase behavior as the composition and/or the temperature is varied. In the middle phase, oil and water mix in the presence of surfactant molecules to form a mesoscopic bicontinuous structure. To explain the complex behavior of microemulsions, it is useful to employ phenomenological approaches such as the Ginzburg-Landau theory or the membrane theory. We discuss the Ginzburg-Landau theory and also review the Teubner-Strey model, the Gompper-Schick model, and the two-order-parameter model. Based on these models, we discuss the structure of the middle phase and its wetting transition. The membrane theory proposed by Helfrich is also useful for describing the physical properties of microemulsions. Various structures in microemulsions, such as droplets, bicontinuous and network structures, are properly accounted for by the curvature elasticity model. We focus on the Exxon model which clarifies the physical origin of the middle phase. Within the phenomenological level of description, we review the dynamical aspects of droplet and bicontinuous microemulsions. We also give an overview of microemulsions found in multicomponent polymeric systems (polymeric microemulsions). A discussion on recent applications of microemulsions completes the review.

  6. Influence of microemulsion structure on cystine reactivity with keratin fibres.


    Solans, C; Parra, J L; Erra, P; Azemar, N; Clausse, M; Touraud, D


    Summary The activity of thioglycolic acid, incorporated in a microemulsion, towards cystine residues present in keratin proteins has been investigated. In an attempt to relate the structural state of the microemulsions to cystine reactivity, an appropriate model system showing a large microemulsion domain with diverse structures was chosen. The realm of preferentially hydrocarbon-continuous microemulsion-type media was found to induce the highest activity. PMID:19456980

  7. Pressure-induced protein unfolding in the ternary system AOT-octane-water is different from that in bulk water.


    Meersman, Filip; Dirix, Carolien; Shipovskov, Stepan; Klyachko, Natalia L; Heremans, Karel


    In a cellular environment, the presence of macromolecular cosolutes and membrane interfaces can influence the folding-unfolding behavior of proteins. Here we report on the pressure stability of alpha-chymotrypsin in the ternary system bis(2-ethylhexyl)sodium sulfosuccinate-octane-water using FTIR spectroscopy. The ternary system forms anionic reverse micelles which mimic cellular conditions. We find that inclusion of a single protein molecule in a reverse micelle does not alter its conformation. When pressurized in bulk water, alpha-chymotrypsin unfolds at 750 MPa into a partially unfolded structure. In contrast, in the ternary system, the same pressure increase induces a random coil-like unfolded state, which collapses into an amorphous aggregate during the decompression phase. It is suggested that the unfolding pathway is different in a cell-mimicking environment due to the combined effect of multiple factors, including confinement. A phase transition of the reverse micellar to the lamellar phase is thought to be essential to provide the conditions required for unfolding and aggregation, though the unfolding is not a direct result of the phase transition. Our observations therefore suggest that membranes may cause the formation of alternative conformations that are more susceptible to aggregation. PMID:15807607

  8. Phospholipid structured microemulsion as effective carrier system with potential in methicillin sensitive Staphylococcus aureus (MSSA) involved burn wound infection.


    Chhibber, Tanya; Wadhwa, Sheetu; Chadha, Parul; Sharma, Gajanand; Katare, Om Prakash


    Burn wounds are foremost site for bacterial colonization and multiplication. Staphylococcus aureus is one of the most predominant pathogen found in burn wounds. Fusidic acid (FA) is widely employed in the treatment of complicated skin infections caused by Staphylococcus aureus. Hence, the aim of this study was to investigate the usefulness and efficacy of topical FA (2% w/w) loaded biocompatible microemulsion-based-system (FA-ME) in eradicating MSSA bacterial infections which otherwise was less effective when dealt with conventional formulations. For construction of pseudoternary phase diagram, ratio of oil (IPM):water:Smix is 20:30:50% w/w and proportion of Smix (Phospholipid:Tween 80 (T80):Ethanol) is in the ratio of 1:2:1, respectively. The hypothesis relates here to the role of phospholipids as part of the nano-scale structure of microemulsion systems to overcome the hurdles of drug delivery. The prepared FA-ME system was evaluated for its therapeutic efficacy and carrier-specific characteristics such as globule size, % transmittance, transmission electron microscopy, drug content and stability. Selected microemulsion system was incorporated into gel form and evaluated for texture analysis, drug permeation in 24 h and treatment of burn wounds. Burn wound infection was established with MSSA ATCC 25923 in BALB/c mice and the process of wound healing as well as bacterial loading in the wound was estimated. The developed nanosized FA-ME system demonstrated improved wound healing, better spreadability and enhanced therapeutic efficacy due to the changes in the behavior of the drug molecules by way of carrier-characteristics. PMID:26004269

  9. Preparation of starch nanoparticles in water in oil microemulsion system and their drug delivery properties.


    Wang, Xinge; Chen, Haiming; Luo, Zhigang; Fu, Xiong


    In this research, 1-hexadecyl-3-methylimidazolium bromide C16mimBr/butan-1-ol/cyclohexane/water ionic liquid microemulsion was prepared. The effects of n-alkyl alcohols, alkanes, water content and temperature on the properties of microemulsion were studied by dilution experiment. The microregion of microemulsion was identified by pseudo-ternary phase diagram and conductivity measurement. Then starch nanoparticles were prepared by water in oil (W/O) microemulsion-cross-linking methods with C16mimBr as surfactant. Starch nanoparticles with a mean diameter of 94.3nm and narrow size distribution (SD=3.3) were confirmed by dynamic light scattering (DLS). Scanning electron microscope (SEM) data revealed that starch nanoparticles were spherical granules with the size about 60nm. Moreover the results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) demonstrated the formation of cross-linking bonds in starch molecules. Finally, the drug loading and releasing properties of starch nanoparticles were investigated with methylene blue (MB) as drug model. This work may provide an efficient pathway to synthesis starch nanoparticles. PMID:26794752

  10. USPIO assisting degradation of MXC by host/guest-type immobilized laccase in AOT reverse micelle system.


    Yang, Yu-Xiang; Pi, Na; Zhang, Jian-Bo; Huang, Yan; Yao, Ping-Ping; Xi, Yan-Jie; Yuan, Hong-Ming


    The laccase and ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) have been assembled inside the tubular mesoporous silica via co-adsorption technology to prepare host/guest-type immobilized laccase, which is applied to degrade methoxychlor (MXC) in aqueous and reverse micelle environments. The effects of various parameters on degradation of MXC were studied. Under the optimum conditions, the degradation rate could reach maximum value of 45.6 % and remain at 20.8 % after seven cycles. Moreover, the addition of small molecular compound 2, 2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) to the system could greatly improve the degradation efficiency. The MXC degradation process is a first-order reaction, and the activation energy of MXC degradation catalyzed by immobilized laccase (41.46 kJ mol(-1)) is relatively lower than that catalyzed by free laccase (44.91 kJ mol(-1)). Based on the degradation products measured by gas chromatograph-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR), the degradation mechanism of MXC has also been proposed. PMID:27023821

  11. Liquid-crystalline and microemulsion phase behavior in alcohol-free aerosol-OT/oil/brine systems

    SciTech Connect

    Ghosh, O.; Miller, C.A.


    The phase behavior of systems containing the pure anionic surfactant Aerosol OT or sodium bis(2-ethylhexyl) sulfosuccinate was studied as a function of salt concentration, surfactant concentration, alkane carbon number, and water-to-oil ratio. Since the hydrophilic and lipophilic properties of Aerosol OT are nearly balanced, the surfactant forms microemulsions with water and oil in the absence of cosurfactant, allowing for simplified representation of phase behavior. In particular, this property aided in the understanding of transitions between the aqueous surfactant phase behavior and the well-studied oil-rich microemulsion regime. With the addition of salt to dilute alcohol-free surfactant-water mixtures, transitions in the liquid-crystalline phases similar to those seen previously for systems containing petroleum sulfonates and other anionic surfactants with alcohol cosurfactants were found. When hydrocarbons of various chain lengths were equilibrated with the aqueous surfactant solutions, again behavior similar to that of anionic surfactants with alcohol cosurfactants was observed. Pseudoternary diagrams of surfactant-brine-oil were constructed at various brine salinities with n-dodecane as the oil. The assumption that brine acts as a pseudocomponent was found to work best at salinities well below and well above the optimum and at low surfactant concentrations. In any case, the results provide extensive information on phase behavior of a four-component system containing a pure anionic surfactant, a pure hydrocarbon, and sodium chloride brine over a region of considerable interest for enhanced oil recovery and other applications.

  12. Pore Scale Dynamics of Microemulsion Formation.


    Unsal, Evren; Broens, Marc; Armstrong, Ryan T


    Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (<10(-2) mN m(-1)) that is required for miscibility to occur. Many studies focus on microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound

  13. Ionic liquid tunes microemulsion curvature.


    Liu, Liping; Bauduin, Pierre; Zemb, Thomas; Eastoe, Julian; Hao, Jingcheng


    Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of [bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size has an average radius of 360 A and the ionic liquid induces softening of the charged catanionic film. Most interestingly, the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly systems. PMID:19161325

  14. Gelled polymerizable microemulsions. 2. Microstructure.


    Stubenrauch, Cosima; Tessendorf, Renate; Salvati, Anna; Topgaard, Daniel; Sottmann, Thomas; Strey, Reinhard; Lynch, Iseult


    Using bicontinuous microemulsions as templates opens a new field for the design of novel structures and thus novel materials, but has significant challenges due to the very small composition and temperature windows in which microemulsions are bicontinuous. In previous work we had shown that we can take a ternary base system (water-n-dodecane--C 13/15E 5), add monomer and cross-linker ( N-isopropylacrylamide and N, N'-methylenebisacrylamide) to the water phase, and add a gelator (12-hydroxyoctadecanoic acid) to the oil phase while remaining in the one-phase region of the phase diagram. It was also possible to allow the gelator to form an organogel by changing the temperature such that we crossed the sol--gel line, which fell within the one-phase region. In this work, we show conclusively that addition of the monomers and the gelator does not affect the microemulsion microstructure and that, even in the gelled state, the polymerizable microemulsion is indeed bicontinuous. 1H NMR self-diffusion, conductivity, and small-angle neutron scattering measurements all confirm the bicontinuous nature of the gelled polymerizable microemulsion. PMID:18558728

  15. Preparation of silica-encapsulated ZnSe nanocrystals by mixed surfactant microemulsions.


    Liu, Kang; Ma, Sung Jin; Kim, Ji Hyeon; Choi, Hyung Wook; Kim, Kyung Hwan; Park, Sang Joon


    Silica-encapsulated ZnSe nanocrystals (NCs) have been prepared by employing sodium (2-ethylhexyl)sulfonate (AOT)/water/cyclohexane microemulsions containing ZnSe quantum dots with polyoxyethylenenonylphenylether (NP5)/water/cyclohexane microemulsions containing tetraethylorthosilicate (TEOS). Size tunable silica nanoparticles were achieved by using various water-to-surfactant ratios, W ([H2O]/[surfactant]). In order to characterize as-synthesized nanocrystals, photoluminescence (PL) spectroscopy, UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) were employed. Cubic zinc blende quantum dots (QDs) (2.5 nm in diameter) were successfully encapsulated by silica nanoparticles (14.3-28.9 nm in diameter). The enhanced photoluminescence efficiency about 10% has been observed when compared with the results from the similar work using AOT microemulsions. The entire size of the silica-encapsulated nanocrystals increased with increasing W, then decreased slightly when free water exists in the core of the NP5/AOT microemulsion. On the other hand, the ZnSe NCs in the silica did not change their size during the synthesis. In addition, the possible mechanisms for growth of silica particles and the kinetics of silica particles formation were discussed. PMID:24245247

  16. Stability and disperse composition of water-in-oil microemulsions in a tributyl phosphate-nitric acid system

    SciTech Connect

    Vinogradov, I.V.; Zakharkin, V.S.; Shepel'kov, S.V.


    An investigation has been made of the influence of the concentrations of tributyl phosphate (TBP) and nitric acid on the surface and bulk distribution, the stability, and the disperse composition of water-in-oil microemulsions. A correlation has been established between the interphase tension and the time for complete stratification of the microemulsions. The process of forming stable microemulsions is interpreted on the basis of views on the surfactant properties of TBP hydratosolvates.

  17. Isomeric and concentration effects of C4-cosurfactants on four-component microemulsions investigated by neutron spin-echo and small-angle scattering

    NASA Astrophysics Data System (ADS)

    Zambrano, E.; Kotlarchyk, M.; Langner, A.; Faraone, A.


    Neutron spin-echo spectroscopy and small-angle scattering measurements were performed to determine how the isomeric structure and concentration of C4-cosurfactants (i.e. butyl alcohols) influence structure and dynamics in four-component water-in-oil microemulsions. The system investigated was AOT/butanol/water/n-octane at room temperature (AOT denotes sodium di-2-ethyl hexylsulfosuccinate), deuterated to achieve contrast of the surfactant/cosurfactant film. At a fixed volume fraction of 0.06 and a fixed molar ratio of [water]/[AOT] = 20, we studied the effects of increasing the molar ratio of [butanol]/[AOT] from 0 to 30. Data from samples containing the cosurfactant n-butyl alcohol were compared with samples prepared with tert-butyl alcohol and, in a few cases, sec-butyl alcohol. Data were analysed using a core-shell model for polydisperse spherical droplets, allowing for the presence of shape fluctuations. It was found that all structural isomers of the cosurfactant led to a similar decrease in droplet size with increasing alcohol content. In all cases, droplet size and shape fluctuations were observed to increase with alcohol content; however, the effect was most pronounced for size fluctuations (i.e. polydispersity) in the presence of tert-butanol. The data indicates that tert-butanol has a higher degree of penetration into the water core, leading to a reduced influence on the effective area per surfactant head group on the droplet surface. There is also evidence that an increased droplet-droplet attraction upon adding tert-butanol drives phase separation in the system.

  18. Enthalpies of solution and volumes of water in reversed AOT micelles

    SciTech Connect

    D'Aprano, A.; Lizzio, A.; Liveri, V.T.


    Molar enthalpies of solution and apparent molar volumes of water in the sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane system as a function of the molar ratio R = (water)/(AOT) were determined at 25 /sup 0/C. The dependence of these experimental data on R has been rationalized in terms of a semiempirical model based on water partitioning between two states. The positive enthalpies of solution of water indicate that the insertion of water in reversed AOT micelles (unfavorable from an enthalpic point of view) is mainly driven by a favorable change on entropy. An increase of the maximum number of water molecules solvating AOT with increasing concentration of surfactant has also been observed and discussed.

  19. Intramolecular charge transfer reaction, polarity, and dielectric relaxation in AOT/water/heptane reverse micelles: pool size dependence.


    Biswas, Ranjit; Rohman, Nashiour; Pradhan, Tuhin; Buchner, Richard


    Intramolecular charge transfer (ICT) reaction in a newly synthesized molecule, of 4-(1-morpholenyl) benzonitrile (M6C), in AOT/water/heptane reverse micelles at different pool sizes has been studied by using steady-state and time-resolved fluorescence emission spectroscopy. The pool size dependences of the reaction equilibrium constant and reaction rate have been explained in terms of the average polarity of the confined solvent pools estimated from the fluorescence emission Stokes shift of a nonreactive probe, coumarin 153, dissolved in these microemulsions. The complex permittivity measurements in the frequency range 0.01microemulsions at different pool sizes (0AOT concentrations (0.1AOT headgroup and n-heptane. The reorientation of these interfacial water molecules is probably responsible for the nanosecond component observed in numerous polar solvation dynamics experiments in these reverse micelles. Subsequently, the estimated polarity and the measured reorientational time scale have been used to explain the dramatic slowing down of the ICT reaction rate and its dependence on pool size in these confined environments. PMID:18630864

  20. Pressure-induced structural phase transition of dense droplet microemulsions studied by small-angle x-ray scattering

    NASA Astrophysics Data System (ADS)

    Seto, Hideki; Nagao, Michihiro; Kawabata, Youhei; Takeda, Takayoshi


    A small-angle x-ray scattering (SAXS) study of dense water-in-oil droplet microemulsions composed of water, decane, and AOT [sodium bis(2-ethylhexyl) sulfosuccinate] was performed in order to clarify phase behavior with applied pressure and the corresponding structural phase transitions. SAXS spectra were collected for pressures between ambient pressure (0.1 MPa) and 80 MPa and droplet volume fraction, φ, from 0.40 to 0.70. With increasing φ, the mean radius of droplets decreased slightly and polydispersity increased. With increasing pressure, the droplet structure transformed to a two-phase system with coexistence of lamellar and droplet structures, independent of the droplet volume fraction. These results suggest that, with increasing pressure, the increasing inter-droplet attractive force controls the pressure variation of the structure.

  1. Water-in-ionic liquid microemulsion formation in solvent mixture of aprotic and protic imidazolium-based ionic liquids.


    Kusano, Takumi; Fujii, Kenta; Hashimoto, Kei; Shibayama, Mitsuhiro


    We report that water-in-ionic liquid microemulsions (MEs) are stably formed in an organic solvent-free system, i.e., a mixture of aprotic (aIL) and protic (pIL) imidazolium-based ionic liquids (ILs) containing the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT). Structural investigations using dynamic light, small-angle X-ray, and small-angle neutron scatterings were performed for MEs formed in mixtures of aprotic 1-octyl-3-methylimidazolium ([C8mIm(+)]) and protic 1-alkylimidazolium ([CnImH(+)], n = 4 or 8) IL with a common anion, bis(trifluoromethanesulfonyl)amide ([TFSA(-)]). It was found that the ME structure strongly depends on the mixing composition of the aIL/pIL in the medium. The ME size appreciably increases with increasing pIL content in both [C8mIm(+)][TFSA(-)]/[C8ImH(+)][TFSA(-)] and [C8mIm(+)][TFSA(-)]/[C4ImH(+)][TFSA(-)] mixtures. The size is larger for the n = 8 system than that for the n = 4 system. These results indicate that the shell part of MEs is composed of both AOT and pIL cation, and the ME size can be tuned by pIL content in the aIL/pIL mixtures. PMID:25226398

  2. Preparation and evaluation of aceclofenac topical microemulsion.


    Ramesh Shah, Rohit; Shripal Magdum, Chandrakant; Shivagonda Patil, Shitalkumar; Shanawaj Niakwade, Nilofar


    A topical preparation containing aceclofenac was developed using an o/w microemulsion system. Isopropyl myristate was chosen as the oil phase as it showed a good solubilising capacity. Pseudo-ternary phase diagrams were used to obtain the concentration ranges of the oil, surfactant (Labrasol) and co-surfactant (plurol oleique) for microemulsion formation. Five different formulations were formulated with various amount of the oil (5-25%), water (10-50%), and the mixture of surfactant and co-surfactant at the ratio of 4 (45-65%). In vitro permeability of aceclofenac from the microemulsions was evaluated using Keshary Chien diffusion cells with 0.45-μm cellulose acetate membrane. The amount of the aceclofenac permeated was analyzed by HPLC and the droplet size and zeta potential of the microemulsions was determined using a Zetasizer Nano-ZS. The mean diameters of the microemulsion droplets approximately ranged between 154 - 434 nm, and the permeability of aceclofenac incorporated into the microemulsion systems was 3 folds higher than that of the marketed formulation. These results indicate that the microemulsion system studied is a promising tool for percutaneous delivery of aceclofenac. PMID:24363700

  3. Fourier transform infrared spectroscopy of azide and cyanate ion pairs in AOT reverse micelles

    NASA Astrophysics Data System (ADS)

    Owrutsky, Jeffrey C.; Pomfret, Michael B.; Barton, David J.; Kidwell, David A.


    Evidence for ion pair formation in aqueous bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles (RMs) was obtained from infrared spectra of azide and cyanate with Li+, Na+, K+, and NH4+ counterions. The anions' antisymmetric stretching bands near 2000 cm-1 are shifted to higher frequency (blueshifted) in LiAOT and to a lesser extent in NaAOT, but they are very similar to those in bulk water with K+ and NH4+ as the counterions. The shifts are largest for low values of wo=[water]/[AOT] and approach the bulk value with increasing wo. The blueshifts are attributed to ion pairing between the anions and the counterions. This interpretation is reinforced by the similar trend (Li+>Na+>K+) for producing contact ion pairs with the metal cations in bulk dimethyl sulfoxide (DMSO) solutions. We find no evidence of ion pairs being formed in NH4AOT RMs, whereas ammonium does form ion pairs with azide and cyanate in bulk DMSO. Studies are also reported for the anions in formamide-containing AOT RMs, in which blueshifts and ion pair formation are observed more than in the aqueous RMs. Ion pairs are preferentially formed in confined RM systems, consistent with the well established ideas that RMs exhibit reduced polarity and a disrupted hydrogen bonding network compared to bulk water and that ion-specific effects are involved in mediating the structure of species at interfaces.

  4. Microemulsion-based drug delivery system for transnasal delivery of Carbamazepine: preliminary brain-targeting study.


    Patel, Rashmin Bharatbhai; Patel, Mrunali Rashmin; Bhatt, Kashyap K; Patel, Bharat G; Gaikwad, Rajiv V


    This study reports the development and evaluation of Carbamazepine (CMP)-loaded microemulsions (CMPME) for intranasal delivery in the treatment of epilepsy. The CMPME was prepared by the spontaneous emulsification method and characterized for physicochemical parameters. All formulations were radiolabeled with (99m)Tc (technetium) and biodistribution of CMP in the brain was investigated using Swiss albino rats. Brain scintigraphy imaging in rats was also performed to determine the uptake of the CMP into the brain. CMPME were found crystal clear and stable with average globule size of 34.11 ± 1.41 nm. (99m)Tc-labeled CMP solution (CMPS)/CMPME/CMP mucoadhesive microemulsion (CMPMME) were found to be stable and suitable for in vivo studies. Brain/blood ratio at all sampling points up to 8 h following intranasal administration of CMPMME compared to intravenous CMPME was found to be 2- to 3-fold higher signifying larger extent of distribution of the CMP in brain. Drug targeting efficiency and direct drug transport were found to be highest for CMPMME post-intranasal administration compared to intravenous CMP. Rat brain scintigraphy also demonstrated higher intranasal uptake of the CMP into the brain. This investigation demonstrates a prompt and larger extent of transport of CMP into the brain through intranasal CMPMME, which may prove beneficial for treatment of epilepsy. PMID:24825492

  5. Solubilization of water in water-in-oil microemulsions of kerosene

    SciTech Connect

    Andheria, A.P.; Bhagwat, S.S.


    The incorporation of water into fuels formulated as microemulsions can offer several advantages such as fire resistance, increased flash point, and improved air-fuel contact. To this end, phase equilibria of kerosene microemulsions employing ionic and nonionic surfactants such as sodium di-(2-ethylhexyl) sulfosuccinate (AOT), lauryl diethanolamide (LDEA), nonylphenol EO-4.5 (NPEO-4.5), sorbitan monolaurate (Span-20), and cetyltrimethylammonium bromide (CTAB), as well as cosurfactants such as n-pentanol, n-hexanol, and n-heptanol, were studied. The effect of the aromaticity of the oil phase on the solubilization of water was also investigated.

  6. Nose to brain microemulsion-based drug delivery system of rivastigmine: formulation and ex-vivo characterization.


    Shah, Brijesh M; Misra, Manju; Shishoo, Chamanlal J; Padh, Harish


    Alzheimer's disease (AD) is a progressive neurodegenerative disorder leading to irreversible loss of neurons, cognition and formation of abnormal protein aggregates. Rivastigmine, a reversible cholinesterase inhibitor used for the treatment of AD, undergoes extensive first-pass metabolism, thus limiting its absolute bioavailability to only 36% after 3-mg dose. Due to extreme aqueous solubility, rivastigmine shows poor penetration and lesser concentration in the brain thus requiring frequent oral dosing. This investigation was aimed to formulate microemulsion (ME) and mucoadhesive microemulsions (MMEs) of rivastigmine for nose to brain delivery and to compare percentage drug diffused for both systems using in-vitro and ex-vivo study. Rivastigmine-loaded ME and MMEs were prepared by titration method and characterized for drug content, globule size distribution, zeta potential, pH, viscosity and nasal ciliotoxicity study. Rivastigmine-loaded ME system containing 8% w/w Capmul MCM EP, 44% w/w Labrasol:Transcutol-P (1:1) and 48% w/w distilled water was formulated, whereas 0.3% w/w chitosan (CH) and cetyl trimethyl ammonium bromide (as mucoadhesive agents) were used to formulate MMEs, respectively. ME and MMEs formulations were transparent with drug content, globule size and zeta potential in the range of 98.59% to 99.43%, 53.8 nm to 55.4 nm and -2.73 mV to 6.52 mV, respectively. MME containing 0.3% w/w CH followed Higuchi model (r(2) = 0.9773) and showed highest diffusion coefficient. It was free from nasal ciliotoxicity and stable for three months. However, the potential of developed CH-based MME for nose to brain delivery of rivastigmine can only be established after in-vivo and biodistribution study. PMID:24467601

  7. Correlation between AERONET AOT and VIIRS EDR AOT: A new EDR cell

    NASA Astrophysics Data System (ADS)

    Molinie, J.; Henry, J. L.; Clement, J.; Euphrasie-Clotilde, L.; Brute, F. N.


    Every year, a huge mass of desert dusts lifted from Saharan and sub Saharan regions is injected over the Atlantic Ocean and bring to the Caribbean and the American continent. Guadeloupe a West Indies island, is affected by the presence of dusts particles which impact the air quality and acts on human health. The effect produced by the particles in the atmosphere can be observed by satellite. VIIRS is one the latest tools provided by NASA, to help scientific community to have a better understanding of aerosol behavior. In this job we try to found a link between ground measurement AOT and VIIRS data.In Guadeloupe, AOT measurements have been performed with sun photometer of AERONET network. We calculated AOT at 500 nm mean daily sun photometer data in order to compare them with AOT EDR 550 data computed by NOAA Aerosol calibration and validation team. Three AOT EDR cells, located over the ocean and close to the East coast of the island of have been chosen to evaluate the correlation between ground and satellite data. We obtained using data performed from May to December 2012, correlation coefficient range between 0.8 and 0.87. We observed numerous AOT EDR 550 have been computed with a number of IP pixel, nAOT very low. We proposed to used only cases with nAOT equal or higher than 10. The correlation coefficients improved and reached 0.9. However, those good results have been obtained with a day number reduced by almost 50 per cent.In order to keep a good correlation and a higher number of day we rebuilt a cell by merging two cells. We obtained a new cell with an AOT EDR value equal to the mean AOT EDR of the two parents' value and a nAOT the sum of the previous nAOTs. The results with the new nAOT equal of higher than 10 is, r =0.91 and we keep 75 per cent of the cases.

  8. Microemulsions as carriers for therapeutic molecules.


    Mehta, Surinder K; Kaur, Gurpreet


    The thrust for finding newer drug delivery systems for exiting therapeutic molecules has opened a wide window for colloidal systems. Due to the presence of different domains of variable polarity in the microemulsion systems, they show a huge potential to be used as drug delivery vehicles for a variety of drugs. The use of microemulsion as drug delivery vehicles through a number of routes has engaged a large number of research groups in this area. Microemulsion media finds several applications ranging from drug delivery to drug nanoparticle templating due to its ability to enhance solubility, stability and bioavailability. This review on patent articles recounts the patent literature dealing with different kind of microemulsion carriers used via different routes, solubility and permeability enhancement and its use as a template for nanoparticle synthesis. PMID:19807681

  9. Sizing of reverse micelles in microemulsions using NMR measurements of diffusion.


    Law, Susan J; Britton, Melanie M


    This paper reports the size of reverse micelles (RMs) in AOT/octane/H(2)O and CTAB/hexanol/H(2)O microemulsions using magnetic resonance (MR) pulsed field gradient (PFG) measurements of diffusion. Diffusion data were measured using the pulsed gradient stimulated echo (PGSTE) experiment for surfactant molecules residing in the RM interface. Inverse Laplace transformation of these data generated diffusion coefficients for the RMs, which were converted into hydrodynamic radii using the Stokes-Einstein relation. This technique is complementary to those previously used to size RMs, such as dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS), but also offers several advantages, which are discussed. RM sizes, determined using the PGSTE method, in the AOT (sodium bis(2-ethylhexyl) sulfosuccinate) and CTAB (cetyltrimethylammonium bromide) microemulsions were compared with previous DLS and SAXS data, showing good agreement. Methods for determining number distributions from the PGSTE data, through the use of scaling factors, were investigated. PMID:22794150

  10. Interfacial hydrodynamic instabilities driven by cross-diffusion in reverse microemulsions

    NASA Astrophysics Data System (ADS)

    Budroni, M. A.; Carballido-Landeira, J.; Intiso, A.; De Wit, A.; Rossi, F.


    When two microemulsions are put in contact in the gravity field along a horizontal contact line, cross-diffusion can trigger the transport of one species in the presence of a gradient in concentration of another species. We show here theoretically that such cross-diffusion effects can induce buoyancy-driven convective instabilities at the interface between two solutions of different compositions even when initially the less dense solution lies on top of the denser one. Two different sources of convective modes are identified depending whether positive or negative cross-diffusion is involved. We evidence the two predicted cross-diffusion driven instabilities experimentally using a two-layer stratification of Aerosol-OT (AOT) water-in-oil microemulsions solutions with different water or AOT composition.

  11. Block-copolymer-induced structure formation in microemulsions

    SciTech Connect

    Hilfiker, R.; Eicke, H.F.; Steeb, C.; Hofmeier, U. )


    Transient electric birefringence measurements were performed on water/AOT (sodium bis(2-ethylhexyl) sulfosuccinate)/isooctane microemulsions with various amounts of block-copoly(oxyethylene/isoprene/oxyethylene) added. The authors could show that addition of the copolymer leads to a formation of nanodroplet (ND)-copolymer-aggregates. The contributions of NDs and aggregates to the induced birefringence could easily be separated because the NDs exhibited a negative and the aggregates a positive induced birefringence and because the time scales corresponding to the two processes were different.

  12. Effect of alpha-lactalbumin on the phase behavior of AOT-brine-isooctane mixtures: role of charge interactions.


    Shimek, Justin W; Rohloff, Catherine M; Goldberg, Jessica; Dungan, Stephanie R


    We have found that both electrostatic and hydrophobic interactions are involved in the ability of the protein alpha-lactalbumin (alpha-LA) to affect the self-assembly of the anionic surfactant sodium bis(ethylhexyl) sulfosuccinate (AOT, 3.5 wt %) in equivolume mixtures of organic and aqueous solutions. The composition and size of AOT phase structures that form in the presence of 0.35 wt % protein were evaluated as a function of pH and ionic strength. In the absence of protein, AOT forms water-in-oil microemulsion droplets for all pH and salt concentrations studied here. The presence of the protein in the water-in-oil microemulsion phase boosts water solubilization and droplet size, as the spontaneous curvature of the surfactant interface becomes less negative. Aggregates of protein, surfactant, and oil also form in the water-continuous phase. The size and composition of structures in both phases can be tuned in the presence of protein by varying the pH and ionic strength. alpha-LA induces the appearance of an anisotropic surfactant phase at pH <5.8. At intermediate salt concentrations, a third isotropic, viscous aqueous phase appears that contains 55-60% of the protein, 10-14% of the surfactant, and significant amounts of oil. Circular dichroism and fluorescence spectroscopy indicate that the protein contains enhanced alpha-helical secondary structure when self-assembling with surfactant, and has a loosened tertiary structure. The protein does not interact with the surfactant as an unfolded random coil. Although the conformation of alpha-LA in aqueous salt solutions is known to depend on pH, when self-assembling with AOT the protein adopts a structure whose features are quite pH insensitive, and likely reflect an intrinsic interaction with the interface. PMID:15952844

  13. FT-IR Spectroscopic Evidence Of Phase Transition For NaA-ROH-Kerosine-H2O Microemulsion System Containing Nd3+ Ions

    NASA Astrophysics Data System (ADS)

    Liao, Hua; Xu, Zhen-Hua; Shi, Nai; Wu, Jin-Guang; Xu, Guang-Xian


    In the previous investigation, the saponification of naphthenic acid extractant system has been proved to be a process of the formation of a microemulsion of 14/0 type, and its full extraction of rare earths is a process of destruction of the W/O microemulsion[1]. When NdCl3 is partially extracted with NaA (sodium naphthenate) secoctylalcohol-- kerosine-- water microemulsion system (ME), both the NdA3 and the NaA co-exist in the same organic phase. However,the formation mechanism of microemulsion containing neodymium has not been much studied. In this paper, 10 aliquots of fully saponificated extractants were equilibrated with various amounts of NdC13 solutions respectively, then ten organic phases with different extraction efficiencies of neodymium from 094 to 9094 were obtained. After extraction,the volume of neodymium containing organic phase increased by 5 to 4594, because of the transfer of water molecules. The appearance of these organic phase still remained clear and transparent. The average hydrodynamic radius of the drops were found to be 100-300 Angstrom by using light scattering techniques. The results give a direct evidence of the microemulsion formation in the organic phase. Their FT-IR spectra were measured with CaFa liquid cells utilizing a Nicolet 7199B FT-IR spectrometer. The presence of various amounts of water in the organic phases was clearly detected from the relative intensity changes of 1644 cm-I, which is assigned to the bending mode of 1110 molecules. Fig.1 shows the change of water contents to the percent extraction of neodymium. Comparsion with the FT-IR spectra, it is seen that the 1560 cm-1 peak of the full saponificated extractant is attributed to the asym. stretching vibration of COO''' group, it shifted to 1536 for 100% extration of Nd ions, indicating the formation of neodymium naphthenate (NdA ) from ionic sodium naphthenate. The sym. strethching vibration of COO''' located at 1406 cm-1, it shifted to 1408 cm in 45% Nd extration

  14. Reverse micelles and microemulsions in near-critical and supercritical fluids

    SciTech Connect

    Smith, R.D.; Fulton, J.L.; Blitz, J.P.; Tingey, J.M. )


    Reverse micelle and water-in-oil (w/o) microemulsion phases can be formed in near-critical and supercritical fluids, giving rise to uniquely pressure dependent phase behavior. The solvating power of reverse micelles formed from the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in fluids with moderate critical temperatures (e.g., ethane, propane, or xenon) depends largely upon the water-to-surfactant ratio of the micelle phase (W{sub m}), which at large W{sub m} can approach that of bulk water. The maximum water-to-surfactant ratio (W{sub 0}), which defines the boundary between a one-phase and a two-phase fluid system (where a second, predominantly aqueous phase exists), is strongly pressure dependent. The physical size of a reverse micelle in one-phase AOT/H{sub 2}O systems at constant W{sub m} has been shown to be nearly independent of the continuous-phase identity and pressure. In contrast, the apparent hydrodynamic size increases dramatically as W{sub 0} is approached due to increased micelle-micelle attractive interactions (e.g., clustering). The maximum reverse micelle size (W{sub m} {proportional to} diameter) increases with pressure for fluids such as ethane and propane, approaching W{sub m} = 40, corresponding to a droplet size of {approximately} 17 nm. Significant micelle densities are obtained for two phase systems, even at relatively low pressure (< 100 bar). These systems can be used to efficiently extract hydrophilic substances, including proteins, from dilute aqueous solution with substantial selectivity without the need for any chemical change to the system.

  15. Interaction between morin and AOT reversed micelles--studies with UV-vis at 25 °C.


    Bhattarai, Ajaya; Wilczura-Wachnik, H


    The precise measurements of morin absorbance in presence of surfactant/solvent/water systems at 25 °C by UV-vis technique are reported. The surfactant used in presented study was sodium bis(2-ethylhexyl) sulfosuccinate called Aerosol-OT or AOT. The solvents selected were: ethanol, ethylene glycol, and n-decanol. The concentrations of AOT were varied between 0.001 and 0.4 mol/kg. Morin concentration in quvette during UV-vis registration was not equals in all solvent because of its different solubility and absorption intensity depending on the solvent. Water concentration in the studied systems was defined by R parameter according to relation: R=[H2O]/[AOT] and was equal 0, 30 and 40 in ethanol; 0, 10, 20 and 30 in ethylene glycol and 0, 10, 20, 30, and 40 in n-decanol. In presented work a Nernstian distribution of morin between the organic and micellar phases was assumed. The intensity of morin absorbance as a function of AOT concentration was analyzed. Using Non-linear Regression Procedure (NLREG) morin binding constant (K' [mol/kg]), and morin distribution constant (K) between organic phase and AOT micellar phase have been calculated. The experimental results have shown a significant influence of solvent, surfactant and water presence on morin UV-vis spectrum. Calculated data pointed out on different transfer of morin molecules from the organic to micellar phase depending on the solvent. Moreover, results of calculations indicate on competition between morin and water molecules interacting with AOT polar heads. Morin molecules privileged location in AOT reversed micelles strongly depends on the solvent. In case of systems with ethylene glycol as solvent is possible morin molecules location in polar cores of AOT reversed micelles as results of strong interaction between AOT polar heads and morin hydroxyl groups, whereas in case of ethanol and n-decanol morin molecules are located in palisade layer. PMID:24239834

  16. Microregion detection of ionic liquid microemulsions.


    Gao, Yanan; Wang, Suqing; Zheng, Liqiang; Han, Shuaibing; Zhang, Xuan; Lu, Deming; Yu, Li; Ji, Yongqiang; Zhang, Gaoyong


    Nonaqueous ionic liquid (IL) microemulsion consisting of IL, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF(4)), surfactant TX-100, and toluene was prepared and the phase behavior of the ternary system was investigated. Electrical conductivity measurement was used for investigating the microregions of the nonaqueous IL microemulsions. On the basis of the percolation theory, the bmimBF(4)-in-toluene (IL/O), bicontinuous, and toluene-in-bmimBF(4) (O/IL) microregions of the microemulsions were successfully identified using insulative toluene as the titration phase. However, this method was invalid when conductive bmimBF(4) acted as the titration phase. The microregions obtained by conductivity measurements were further proved by electrochemical cyclic voltammetry experiments. The results indicated that the conductivity method was feasible for identifying microstructures of the nonaqueous IL microemulsions. PMID:16765365

  17. Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown

    SciTech Connect

    Mankamo, T.; Kim, I.S.; Samanta, P.K.


    When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested.

  18. Risk-based evaluation of Allowed Outage Times (AOTs) considering risk of shutdown

    SciTech Connect

    Mankamo, T. ); Kim, I.S.; Samanta, P.K. )


    When safety systems fail during power operation, Technical Specifications (TS) usually limit the repair within Allowed Outage Time (AOT). If the repair cannot be completed within the AOT, or no AOT is allowed, the plant is required to be shut down for the repair. However, if the capability to remove decay heat is degraded, shutting down the plant with the need to operate the affected decay-heat removal systems may impose a substantial risk compared to continued power operation over a usual repair time. Thus, defining a proper AOT in such situations can be considered as a risk-comparison between the repair in frill power state with a temporarily increased level of risk, and the altemative of shutting down the plant for the repair in zero power state with a specific associated risk. The methodology of the risk-comparison approach, with a due consideration of the shutdown risk, has been further developed and applied to the AOT considerations of residual heat removal and standby service water systems of a boiling water reactor (BWR) plant. Based on the completed work, several improvements to the TS requirements for the systems studied can be suggested.

  19. Kinetics of the oxidation of iodide ion by persulfate ion in the critical water/bis(2-ethylhexyl) sodium sulfosuccinate/n-decane microemulsions.


    Yin, Handi; Du, Zhongyu; Zhao, Jihua; Shen, Weiguo


    In this work, we studied the kinetics of the oxidation of iodide ion by persulfate ion in the critical water/bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/n-decane microemulsions with the molar ratios of water to AOT being 35.0 and 40.8 via the microcalorimetry at various temperatures. It was found that the Arrhenius equation was valid for correlating experimental measurements in the noncritical region, but the slowing down effect existed significantly in the near critical region. We determined the values of the critical slowing down exponent and found it to be 0.187 ± 0.023 and 0.193 ± 0.032, respectively, which agreed well with the theoretical value of 0.207 predicted by the Griffiths-Wheeler rule for the singularity of the dimer/monomer droplet equilibrium in the critical AOT/water/n-decane microemulsions. PMID:25348218

  20. The application of artificial neural networks in the prediction of microemulsion phase boundaries in PEG-8 caprylic/capric glycerides based systems.


    Djekic, Ljiljana; Ibric, Svetlana; Primorac, Marija


    The objective of this study was to develop artificial neural network (ANN) model suitable to predict successfully the borders of the microemulsion region in the quaternary system PEG-8 caprylic/capric glycerides (Labrasol)/cosurfactant/isopropyl myristate/water, in order to minimise experimental effort. In our preliminary investigations of phase behaviour, two cosurfactants were used, PEG-40 hydrogenated castor oil (Cremophor) RH 40) and polyglyceryl-6 isostearate (Plurol Isostearique). Microemulsion existance area in pseudo-ternary phase diagrams was determined using titration method at constant: (a) oil-to-water ratio (alpha=50%, w/w); (b) surfactant-to-cosurfactant ratio (Km) 4:6; (c) Km 5:5; or (d) Km 6:4. It was found that the phase behaviour of systems involving polyoxyethylene type of cosurfactant depends significantly on oil-to-surfactant/cosurfactant mixture mass ratio (O/SCoS) but it is Km-independent. The formation of microemulsions in Labrasol/polyglyceryl-6 isostearate based systems was a complex function of Km and O/SCoS and there was employed a Generalized Regression Neural Network (GRNN) with four layers as a predictive mathematical model, using data obtained from the phase behaviour study (the surfactant concentration in surfactant/cosurfactant mixture (S, %, w/w), the oil concentration in the mixture with tensides (O, %, w/w) as two input variables, and the water solubilization limit (W(max), %, w/w) as output data). After network training, six independent pairs of input/output data were used for network testing. The resulting GRNN was tested statistically and found to be of quality predictive power. This results confirmed that the trained GRNN could be effective in predicting the size of the microemulsion area providing valuable tool in formulation of this type of colloidal vehicles. PMID:18571348

  1. Microemulsion-based organogels as matrices for lipase immobilization.


    Zoumpanioti, Maria; Stamatis, Haralambos; Xenakis, Aristotelis


    Organogels based on water-in-oil microemulsions can be formed using various natural polymers such as gelatin, agar or cellulose derivatives. Enzymes entrapped in the water core of the microemulsion can keep their activity and enhance their stability within the gel matrix. The importance of the microemulsion based organogels (MBGs) leans on their numerous potential biotechnological applications. An important example is the use of various lipase microemulsion systems for hydrolytic or synthetic reactions. In this review, several MBGs are being evaluated as immobilization matrices for various enzymes. The main subject focuses on the parameters that affect the use of MBGs as media for bioorganic reactions using lipases as catalysts. PMID:20156546

  2. Cyclodextrin and Meglumine-Based Microemulsions as a Poorly Water-Soluble Drug Delivery System.


    Aloisio, Carolina; G de Oliveira, Anselmo; Longhi, Marcela


    Cyclodextrins (CDs) and meglumine (MEG) are pharmaceutical excipients widely used to improve solubility of poorly water-soluble drugs. The purpose of this work was to study the effect of CDs or MEG on the internal microstructure of soya oil-based O/W microemulsions (MEs) and on the modulation of the solubility and release rate of Class II model hydrophobic drugs, sulfamerazine and indomethacin. The pseudoternary phase diagrams revealed that higher proportions of oil phase, as well as the presence of β-cyclodextrin (ßCD), methyl-ßCD, and MEG, favored the incorporation of the drugs. The conductivity studies, particle size, and zeta potential analysis showed that the O/W ME structure remained unaffected and that the ME presented reduced droplet sizes after the incorporation of the ligands. The drug-component interactions were assessed by proton nuclear magnetic resonance studies. The highest incorporations of sulfamerazine (35.6 mg/mL) and indomethacin (73.1 mg/mL) were obtained with the ME with W = 5%, MEG and W = 1.8% ßCD in a phosphate buffer solution of pH 8, respectively. In addition, the ligands in ME significantly enhanced the released amount of the drugs, probably due to a solubilizing effect that facilitates the drug to penetrate the unstirred water layer adjacent to membranes. PMID:26886337

  3. Formation and characterization of ordered bicontinuous microemulsions.


    Kogan, Anna; Shalev, Deborah E; Raviv, Uri; Aserin, Abraham; Garti, Nissim


    Ordered bicontinuous microstructures formed in a fully water-dilutable, pseudoternary unique nonionic microemulsion were obtained and characterized. The concentrate contained a mixture of triacetin/d-alpha-tocopherol acetate/ethanol/Tween 60. Upon dilution, the concentrate was transformed from a reversed micellar system to oil-in-water microemulsion droplets. The transformation occurred through an intermediate phase of ordered bicontinuous structures. The factors that governed the construction of this unique phase, and its physical and structural properties, were characterized in detail. The techniques used included small angle X-ray scattering (SAXS), self-diffusion and quantum filtered NMR, differential scanning calorimetry, rheology measurements, electrical conductivity, and dynamic light scattering. This mesophase displays microemulsion properties along with some characteristics of lyotropic liquid crystals (but is not a mixture of the two). Similar to microemulsions, the structures were transparent and spontaneously formed and exhibited thermodynamic stability. Yet, unlike microemulsions, they showed short-range order at room temperature. Additionally, the microstructures exhibited non-Newtonian flow behavior, characteristic of lamellar structures. The bicontinuous ordered microemulsions were obtained upon heating (to 25 degrees C) from the lamellar phase existing at low temperatures (5 degrees C). The main feature governing the bicontinuous mesophase formation was the amphiphilic nature of oil blends composed of d-alpha-tocopherol acetate and triacetin. The oils functioned as cosurfactants, altering the packing parameter of the surfactant and leading to the construction of bicontinuous structures with short-range order. These unique structures might have drug or nutraceutical delivery advantages. PMID:19719271

  4. Polymeric bicontinuous microemulsions

    NASA Astrophysics Data System (ADS)

    Krishnan, Kasiraman

    Rheology of complex fluids has been a topic of considerable interest recently. Bicontinuous microemulsions (BmuE), made by mixing appropriate amounts of oil, water and a surfactant, form a unique class of complex fluids. They possess a characteristic nanostructure consisting of undulating surfaces with vanishingly small interfacial curvature. BmuEs can also be generated in polymers by mixing appropriate amounts of two homopolymers and their corresponding diblock copolymer. The main objective of the present research is to study effects of shear on a model polymeric BmuE. Scattering is used as a predominant tool with in situ flow devices, along with optical microscopy and rheology. The model BmuE consists of a ternary blend of poly(ethyl ethylene) (PEE), poly(dimethyl siloxane) (PDMS) and a PEE-PDMS diblock copolymer. Steady shear experiments reveal four regimes as a function of shear rate. At low shear rates (regime I), Newtonian behavior is observed; there is onset of shear thinning at higher rates (regime II). In regime III, the stress is independent of shear rate, whereas it increases with shear rate once again in regime IV. Morphological characterization was carried out for each of these four regimes using scattering and microscopy, the key result being the evidence for flow-induced phase separation in regime III. Transient rheological measurements were conducted for startup and step changes in shear rate, and the BmuE exhibits features similar to worm-like micellar colloidal systems. Time-resolved light scattering and microscopy also reveal interesting characteristics. Dynamic mechanical spectroscopy indicates similarities with neat block copolymers near the order-disorder transition. The equilibrium rheological behavior is intriguing and detailed comparisons are made with Landau-Ginzburg theoretical models. Other areas of research as a part of this thesis include study of structural dynamics of BmuEs with dynamic light scattering, and the rheological

  5. The use of novel ionic liquid-in-water microemulsion without the addition of organic solvents in a capillary electrophoretic system.


    Cao, Jun; Qu, Haibin; Cheng, Yiyu


    In this work, a new ionic liquid-in-water (IL/W) microemulsion without requiring toxic organic solvents was investigated as a pseudostationary phase (PSP) in CE. As observed during the IL/W microemulsion system, a fast and an efficient separation of eight phenolic acids was achieved using 1-butyl-3-methylimidazolivmhexa fluorophosphate (bmimPF(6)) as oil drops, Tween 20 as the surfactant, and borate as the BGE. The effects of oil phase, surfactant, buffer and pH on the separation were explored in detail to evaluate the novel PSP. In contrast, the detection efficiency of these same analytes was markedly decreased using oil-in-water (O/W) MEEKC. We have also validated the practicality of the IL/W microemulsion method by quantitative determination of acidic compounds in pharmaceutical injection. The results obtained indicated that an additional association between the IL cations and analytes tested seemed to play a prominent role in the separation mechanism exhibited by this novel PSP compared with the conventional O/W MEEKC. PMID:20922759

  6. Electrocatalysis with vitamin B sub 12 in water-in-oil microemulsions at carbon-fiber microelectrodes

    SciTech Connect

    Owlia, A.


    Microemulsions are clear, thermodynamically stable dispersions containing oil, surfactant and water. They are crude models of biological membranes and can be used to investigate some of the organizational influence of membranes in lipid and protein synthesis, energy transduction, ion and group transport, etc. This thesis concerns the investigation of microemulsion properties as media in which catalytic reduction of vicinal dibromides can take place with the electrochemically generated Co(I) form of Vitamin B{sub 12}. Methods to study fundamental properties of resistive w/o AOT/H{sub 2}O/isoctane were developed. Microelectrodes of approximate radius of 6 {mu}m were prepared and characterized. Nonlinear regression was applied to the analysis of steady state voltammograms obtained at carbon-fiber microelectrodes. Reversible regression models were used to analyze data for oxidation of ferrocene in acetonitrile with and without added electrolyte. An estimate of cell resistance in highly resistive media was obtained by including ohmic drop in the model for reversible electron transfer. The electrocatalytic reduction of 1,2-dibromoethane (EDB), 1,2-dibromobutane (DBB), and trans-1,2-dibromocyclohexane (DBCH) with Vitamin B{sub 12} in pH {le} 3 water MeCN and w/o microemulsions of AOT/H{sub 2}O/isoctane at carbon fiber microelectrode was investigated. The microviscosity of w/o microemulsions were estimated from the Stokes-Einstein equation using ferrocene as a probe. Results show that the diffusion of molecules in the microemulsions are similar to their diffusion in organic phase (isoctane). Nonlinear regression analysis of the data for AOT w/o microemulsions describing the dependence of D{prime} on C{sub x} enables an estimate of micelle diffusion coefficients.

  7. Flow Properties of Multilamellar Droplets in AOT/Brine/Glycerol Mixtures

    NASA Astrophysics Data System (ADS)

    Ishii, Akiko; Pons, Ramon; Ushiki, Hideharu; Rouch, Jacques; Letamendia, Louis


    The properties of lamellar solutions formed in a quaternary mixture made of brine, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), and glycerol have been studied under shear flow. As in AOT, brine pseudo-ternary system, the lamellar solutions exhibit a structural transition above a threshold shear rate, and form quasi-monodispersed multilamellar droplets. In this regime, the solutions are shear thinning. Both the viscosity and the droplet size scale with the shear rate with exponents respectively equal to -0.7 and -0.4. This last value is smaller than the one, 0.5, reported in the ternary systems. Tentative explanations of our experimental results are given.

  8. Spatiotemporal Pattern Formation and Chaos in the Belousov-Zhabotinsky Reaction in a Reverse Microemulsion

    NASA Astrophysics Data System (ADS)

    Epstein, Irving R.; Vanag, Vladimir K.


    We study the spatiotemporal behavior of the oscillatory Belousov-Zhabotinsky (BZ) reaction in a reverse microemulsion consisting of water, octane and the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT). By varying the microemulsion composition, we can "tune" its structure, specifically the size and spacing between the nanometer-sized water droplets in which the polar BZ reactants reside. We find a remarkable array of pattern formation as the microemulsion structure and BZ chemistry are varied. Behaviors observed include stationary Turing patterns, traveling and standing waves, spirals, targets, antispirals and antitargets (which travel into rather than out from their center), and spatiotemporal chaos. A simple reaction-diffusion model, which accounts for the BZ chemistry and the differential diffusion of species within water droplets and in the bulk oil phase, is able to reproduce nearly all of the observed behavior.

  9. Higher order structure of proteins solubilized in AOT reverse micelles.


    Naoe, Kazumitsu; Noda, Kazuki; Kawagoe, Mikio; Imai, Masanao


    The higher order structure of proteins solubilized in an bis(2-ethylhexyl) sulfosuccinate sodium (AOT) reverse micellar system was investigated. From circular dichroic (CD) measurement, CD spectra of cytochrome c, which is solubilized at the interface of reverse micelles, markedly changed on going from buffer solution to the reverse micellar solution, and the ellipticity values in the far- and near-UV regions decreased with decreasing the water content (W0: molar ratio of water to AOT), indicating that the secondary and tertiary structures of cytochrome c changed with the water content. The ellipticity of ribonuclease A, which is solubilized in the center of micellar water pool, in the near-UV region was dependent on W0 and became minimum when W0 of ca. 8 while the ellipticity in the far-UV region was almost constant, indicating that the tertiary structure of ribonuclease A was affected by the water content, but the secondary structure was conserved. The degree of curvature of the micellar interface appears to influence the protein structure because the reverse micelle size is linearly proportional to the W0 value. As evidence of this, when the micelle size was comparable to the protein's dimensions, the structures were more affected by the water content. Judging from the dependence of the factor influencing the protein structure on the protein species, the location of solubilized protein in reverse micelles is significantly related to whether the protein structure in the system is affected by the micellar interface. In the cases of cytochrome c and lysozyme, the ellipticity against W0 was dependent on the AOT concentration. In contrast, ribonuclease A gave very similar ellipticity values whatever the AOT concentration. In the n-hexane micellar system, cytochrome c exhibited lower ellipticity values and ribonuclease A in the lower W0 range (W0

  10. Lignin amine microemulsions

    SciTech Connect

    DaGue, M.G.


    This patent describes a method of recovering hydrocarbons from an underground hydrocarbon formation having at least one injection well and at least one production well. It comprises injecting into the formation through an injection well a microemulsion comprising an internal phase of a primary amine having from about 8 to about 22 carbon atoms, lignin, a water soluble anionic surfactant, a solubilizer and an oil; and an external phase of brine comprising greater than about 90% by weight of the microemulsion; driving the microemulsion through the formation; and producing hydrocarbons through a production well.

  11. Preparation of starch nanoparticles in a water-in-ionic liquid microemulsion system and their drug loading and releasing properties.


    Zhou, Gang; Luo, Zhigang; Fu, Xiong


    An ionic liquid microemulsion consisting of 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim]PF₆), surfactant TX-100, 1-butanol, and water was prepared. The water-in-[Bmim]PF₆ (W/IL), bicontinuous, and [Bmim]PF₆-in-water (IL/W) microregions of the microemulsion were identified by conductivity measurements. Starch nanoparticles with a mean diameter of 91.4 nm were synthesized with epichlorohydrin as cross-linker through W/IL microemulsion cross-linking reaction at 50 °C for 4 h. Fourier transform infrared spectroscopy (FTIR) data demonstrated the formation of cross-linking bonds in starch molecules. Scanning electron microscopy (SEM) revealed that starch nanoparticles were spherical and that some particles showed aggregation formation. Furthermore, drug loading and releasing properties of starch nanoparticles were investigated with mitoxantrone hydrochloride as a drug model. This work provides an efficient and environmentally friendly approach for the preparation of starch nanoparticles, which is beneficial to their further application. PMID:25069988

  12. Surface chemistry of surfactant AOT-stabilized SnO(2) nanoparticles and effect of temperature.


    Luwang, Meitram N; Ningthoujam, Raghumani S; Singh, Naorem S; Tewari, Raghvendra; Srivastava, Sri K; Vatsa, Rajesh K


    SnO(2).xH(2)O nanoparticles were prepared at room temperature by the microemulsion route. Sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used as a surfactant to stabilize the nanoparticles. These nanoparticles show green luminescence at 510nm, which has been assigned to oxygen vacancies. Infrared spectra of samples heated in the temperature range 500-900 degrees C show bond formation between SnO(2) nanoparticles and SO(4)(2-), which arises from oxidation of SO(3)(-) present in AOT. This was further supported by X-ray diffraction. Shape transformations of the particles from triangular to spherical and then to rectangular was observed as the heat-treatment temperature was increased, and this is related to the surface energy of particles. An enhancement in emission intensity of Eu(3+) was observed when Eu(3+) ions were doped into the SnO(2) nanoparticles due to significant energy transfer from SnO(2) (or Eu-O) to Eu(3+) through surface-mediated energy transfer as compared to direct excitation of Eu(3+) at 397nm. Interestingly, these nanoparticles are dispersible in water, and can be incorporated into polymer-based materials such as polyvinyl alcohol to give homogeneous films, giving rise to blue and red emissions. PMID:20557894

  13. Nonlinear optical characterization of cluster dynamic in water in oil microemulsion by a pump probe laser beam technique

    NASA Astrophysics Data System (ADS)

    Vicari, L.


    We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters, of the kind already reported with the application of strong electric field, could justify this result.

  14. Nonlinear optical characterization of cluster dynamic in water in oil microemulsion by a pump probe laser beam technique.


    Vicari, L


    We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters, of the kind already reported with the application of strong electric field, could justify this result. PMID:15010903

  15. Structure and rheology of associative triblocks in microemulsion solutions

    NASA Astrophysics Data System (ADS)

    Bhatia, Surita Rani

    This thesis describes our theoretical and experimental work on the rheology, static structure, and phase behavior of associative solutions. Our theoretical efforts have centered on solving the diffusion equation model of Dolan and Edwards for ideal associative triblocks between surfaces to yield the segment density profile and free energy. We have shown that polymers between two spheres cause an O(kT) attraction, similar to that calculated by Milner and Witten for associative polymer brushes between flat plates. The attraction we calculate is weaker than that given by the Derjaguin approximation, and excluded volume moderates the attraction and softens the repulsion between spheres. The free energy was used to estimate an interparticle potential, which in turn was used to compute structure factors for solutions of associative polymers via Monte Carlo simulations. As a model system for our experiments, we have chosen PEO-PI-PEO triblocks in an AOT/water/decane microemulsion. Upon dilution with decane, the solutions phase separate into a dense, high viscosity phase and a dilute, low viscosity phase. We have performed both small-angle neutron scattering (SANS) and rheology on these solutions. Structure factors derived from our SANS data agree fairly well with those predicted by our theory and indicate that the droplets reside in an attractive minimum. The rheology of these solutions shows several interesting features that are not predicted by classical reversible network theory. Data from oscillatory experiments indicate a single relaxation time at low polymer concentrations but show evidence of a slower relaxation for higher concentrations. In addition, some solutions exhibit a maximum in the high shear viscosity. Some of our observations are predicted by the flowerlike micelle theory developed by Semenov and co-workers; however, our data is not completely consistent with the theoretical predictions. The high frequency modulus scales roughly quadratically with

  16. Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT).


    Xu, Jingjiang; Wei, Xiaoming; Yu, Luoqin; Zhang, Chi; Xu, Jianbing; Wong, K K Y; Tsia, Kevin K


    Enabled by the ultrahigh-speed all-optical wavelength-swept mechanism and broadband optical amplification, amplified optical time-stretch optical coherence tomography (AOT-OCT) has recently been demonstrated as a practical alternative to achieve ultrafast A-scan rate of multi-MHz in OCT. With the aim of identifying the optimal scenarios for MHz operation in AOT-OCT, we here present a theoretical framework to evaluate its performance metric. In particular, the analysis discusses the unique features of AOT-OCT, such as its superior coherence length, and the relationship between the optical gain and the A-scan rate. More importantly, we evaluate the sensitivity of AOT-OCT in the MHz regime under the influence of the amplifier noise. Notably, the model shows that AOT-OCT is particularly promising when operated at the A-scan rate well beyond multi-MHz--not trivially achievable by any existing swept-source OCT platform. A sensitivity beyond 90 dB, close to the shot-noise limit, can be maintained in the range of 2 - 10 MHz with an optical net gain of ~10 dB. Experimental measurement also shows excellent agreement with the theoretical prediction. While distributed fiber Raman amplification is mainly considered in this paper, the theoretical model is generally applicable to any type of amplification schemes. As a result, our analysis serves as a useful tool for further optimization of AOT-OCT system--as a practical alternative to enable MHz OCT operation. PMID:25321720

  17. Improvement in extraction and catalytic activity of Mucor javanicus lipase by modification of AOT reverse micelle.


    Talukder, Mahabubur Rahman; Susanto, Diana; Feng, Gao; Wu, Jinchuan; Choi, Won Jae; Chow, Yvonne


    Reverse micelles are formed in apolar solvents by spontaneous aggregation of surfactants. Surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) is most often used for the reverse micellar extraction of enzymes. However, the inactivation of enzyme due to strong interaction with AOT molecules is a severe problem. To overcome this problem, the AOT/water/isooctane reverse micellar system was modified by adding short chain polyethylene glycol 400 (PEG 400). The modified AOT reverse micellar system was used to extract Mucor javanicus lipase from the aqueous phase to the reverse micellar phase. The extraction efficiency (E) increased with the increase in PEG 400 addition and the maximum E in PEG 400 modified system was twofold higher than that in the PEG 400-free system. Upon addition of PEG 400, the water activity (a(w)) of aqueous phase decreased, whereas a(w) of reverse micellar phase increased. The circular dichroism spectroscopy analysis revealed that PEG 400 changes the secondary and tertiary structure of lipase. The maximum specific activity of lipase extracted in PEG 400-modified reverse micellar system was threefold higher than that in the PEG-free system. PMID:17639532

  18. Overcoming the cutaneous barrier with microemulsions.


    Lopes, Luciana B


    Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system. PMID:24590260

  19. Overcoming the Cutaneous Barrier with Microemulsions

    PubMed Central

    Lopes, Luciana B.


    Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system. PMID:24590260

  20. Microemulsion Synthesis of Nanoparticle PZT Powder

    NASA Astrophysics Data System (ADS)

    Amiriyan, M.; Nemati, Z. A.; Rahmanifar, M. S.; Ramesh, S.; Meenaloshini, S.; Tolouei, R.


    Nanocrystalline lead zirconate titanate (PZT) powders have been synthesized using microemulsion processing route. Microemulsion is one of the major processing techniques to synthesize a nanosize, homogenous, and almost agglomerate free ceramic powders. The ternary microemulsion system is consisted of cyclohexane as the oil phase, Triton X100 as the nonionic surfactant phase, and an aqueous phase containing 0.619 M Pb2+, 0.325 M Zr4+, and 0.3 M Ti4+, representing a Pb2+: Zr4+: Ti4+ molar ratio of 1:0.52:0.48. The ratio of these cations has been adjusted using Inductively Coupled Plasma (ICP) technique. After coprecipitation of metallic hydroxides by adding ammonia solution in microemulsion system, the PZT precursor was obtained. PZT powders have been prepared upon calcination of precursor at 800° C. Prepared powders was characterised using techniques such as X-ray diffraction, differential thermal analysis, and scanning electron microscopy. The characteristics of microemulsion processed powder is discussed, with emphasis on the presence of nano scaled PZT powder with a composition near to morphotropic phase boundary (MPB) without formation of any intermediate phases.

  1. Structural and dynamical transformations between neighboring dense microemulsion phases

    SciTech Connect

    Kotlarchyk, M. ); Sheu, E.Y. ); Capel, M. )


    A small-angle x-ray scattering (SAXS) study of dense AOT-water-decane microemulsions (AOT denotes sodium bis(2-ethylhexyl) sulfosuccinate) was undertaken in order to delineate clearly the phase behavior and corresponding structural transitions for AOT-plus-water volume fractions ranging from {phi}=0.60 to 0.95. Spectra were collected for temperatures between {ital T}=3 and 65 {degree}C. The resulting {ital T}-vs-{phi} phase diagram indicates three distinct structural domains when the water-to-AOT molar ratio is fixed at {ital W}=40.8, namely, the previously investigated {ital L}{sub 2} droplet phase, a high-temperature {ital L}{sub {alpha}} lamellar phase, and a low-temperature {ital L}{sub 3} phase consisting of randomly connected lamellar sheets. A significantly wide coexistence region accompanies the droplet-to-lamellar phase transition, which is demonstrated to be first order. For {ital W} between 15 and 40, an analysis of the lamellar structure using a one-dimensional paracrystal model produces a Hosemann {ital g} factor indicative of an approximately constant variation in the lamellar spacing of about 8%. The SAXS study was supplemented by dielectric-relaxation, shear-viscosity, and quasielastic light-scattering measurements in order to substantiate the observed phase transitions and further our understanding of the structural and dynamical properties of the {ital L}{sub 3} phase. It was found that the {ital L}{sub 3} phase exhibits Newtonian behavior up to a shear rate of 790 s{sup {minus}1}, in contradiction to previous theoretical considerations. The phase exhibits two distinct relaxation modes. A relaxation time of {similar to}1 ms characterizes the Brownian motion of a single lamellar sheet, while the motion of the entire interconnected sheet assembly has a relaxation time on the order of 1 s.

  2. Oxidative refolding of reduced, denatured lysozyme in AOT reverse micelles.


    Fan, Jun-Bao; Chen, Jie; Liang, Yi


    The refolding kinetics of the reduced, denatured hen egg white lysozyme in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-isooctane-water reverse micelles at different water-to-surfactant molar ratios has been investigated by fluorescence spectroscopy and UV spectroscopy. The oxidative refolding of the confined lysozyme is biphasic in AOT reverse micelles. When the water-to-surfactant molar ratio (omega 0) is 12.6, the relative activity of encapsulated lysozyme after refolding for 24 h in AOT reverse micelles increases 46% compared with that in bulk water. Furthermore, aggregation of lysozyme at a higher concentration (0.2 mM) in AOT reverse micelles at omega 0 of 6.3 or 12.6 is not observed; in contrast, the oxidative refolding of lysozyme in bulk water must be at a lower protein concentration (5 microM) in order to avoid a serious aggregation of the protein. For comparison, we have also investigated the effect of AOT on lysozyme activity and found that the residual activity of lysozyme decreases with increasing the concentration of AOT from 1 to 5 mM. When AOT concentration is larger than 2 mM, lysozyme is almost completely inactivated by AOT and most of lysozyme activity is lost. Together, our data demonstrate that AOT reverse micelles with suitable water-to-surfactant molar ratios are favorable to the oxidative refolding of reduced, denatured lysozyme at a higher concentration, compared with bulk water. PMID:18377920

  3. Magnetite-Alginate-AOT nanoparticles based drug delivery platform

    NASA Astrophysics Data System (ADS)

    Regmi, R.; Sudakar, C.; Dixit, A.; Naik, R.; Lawes, G.; Toti, U.; Panyam, J.; Vaishnava, P. P.


    Iron oxide having the magnetite structure is a widely used biomaterial, having applications ranging from cell separation and drug delivery to hyperthermia. In order to increase the efficacy of drug treatments, magnetite nanoparticles can be incorporated into a composite system with a surfactant-polymer nanoparticle, which can act as a platform for sustained and enhanced cellular delivery of water-soluble molecules. Here we report a composite formulation based on magnetite and Alginate-aerosol OT (AOT) nanoparticles formulated using an emulsion-cross-linking process loaded with Rhodamine 6G [1]. We prepared two set of nanoparticles by using Ca^2+ or Fe^2+ to cross-link the alginate polymer. Additionally, we added ˜8 nm diameter Fe3O4 magnetic nanoparticles prepared by a soft chemical method to these alginate-AOT nanoparticles. The resulting composites were superparamagnetic at room temperature, with a saturation magnetization of approximately 0.006 emu/g of solution. We will present detailed studies on the structural and magnetic properties of these samples. We will also discuss HPLC measurements on Rhodamine uploading in these composites. [1] M.D.Chavanpatil, Pharmaceutical Research, vol.24, (2007) 803.

  4. Polarity of the interface in ionic liquid in oil microemulsions.


    Andújar-Matalobos, María; García-Río, Luis; López-García, Susana; Rodríguez-Dafonte, Pedro


    Ionic liquid based microemulsions were characterized by absorption solvatochromic shifts, (1)H NMR and kinetic measurements in order to investigate the properties of the ionic liquid within the restricted geometry provided by microemulsions and the interactions of the ionic liquid with the interface. Experimental results show a significant difference between the interfaces of normal water and the new ionic liquid microemulsions. Absorption solvatochromic shift experiments and kinetic studies on the aminolysis of 4-nitrophenyl laurate by n-decylamine show that the polarity at the interface of the ionic liquid in oil microemulsions (IL/O) is higher than at the interface of water in oil microemulsions (W/O) despite the fact that the polarity of [bmim][BF(4)(-)] is lower than the polarity of water. (1)H NMR experiments showed that an increase in the ionic liquid content of the microemulsion led to an increase in the interaction between [bmim][BF(4)(-)] and TX-100. The reason for the higher polarity of the microemulsions with the ionic liquid can be explained in terms of the incorporation of higher levels of the ionic liquid at the interface of the microemulsions, as compared to water in the traditional systems. PMID:21820124

  5. Microemulsions: Structures, surfactant layer properties and wetting transitions

    NASA Astrophysics Data System (ADS)

    Abillon, O.; Lee, L. T.; Langevin, D.; Wong, K.


    We review briefly the basic known features of microemulsion structures, emphasizing the importance of the surfactant layer bending elasticity. The results for water-alkane-nonionic-surfactant systems, confirming the close relationship between the maximum characteristic size in the microemulsion and the persistence length of the surfactant layer, are presented. We show that microemulsions are formed when the surfactant layer bending moduli are in a well defined range: if the bending modulus is too large, ordered lamellar phases are obtained, while if it is too small, the surfactant film cannot form, and the medium is a structureless molecular mixture. The evolution between microemulsions and molecular mixtures is continuous; its relationship with the wetting transition between the microemulsion and the two excess phases is discussed.

  6. Magnetic microemulsions based on magnetic ionic liquids.


    Klee, Andreas; Prevost, Sylvain; Kunz, Werner; Schweins, Ralf; Kiefer, Klaus; Gradzielski, Michael


    Microemulsions with magnetic properties were formed by employing a magnetic room temperature ionic liquid (MRTIL) as polar phase, cyclohexane as oil, and an appropriate mixture of ionic surfactant and decanol as a cosurfactant. By means of small-angle neutron scattering (SANS) and electric conductivity the microemulsion structure could be confirmed, where the classical structural sequence of oil-continuous-bicontinuous-polar phase continuous is observed with increasing ratio [polar phase]/[oil]. Accordingly a maximum of the structural size is observed at about equal volumes of oil and MRTIL contained. Therefore this system is structurally the same as normal microemulsions but with the magnetic properties added to it by the incorporation into the systems formulation. PMID:23060241

  7. A small angle x-ray scattering study of the droplet-cylinder transition in oil-rich sodium bis(2-ethylhexyl) sulfosuccinate microemulsions

    NASA Astrophysics Data System (ADS)

    Svergun, D. I.; Konarev, P. V.; Volkov, V. V.; Koch, M. H. J.; Sager, W. F. C.; Smeets, J.; Blokhuis, E. M.


    A method for nonlinear fitting of x-ray scattering data from polydisperse mixtures was developed. It was applied to the analysis of the structural changes in the droplet phase of oil-rich water-in-oil (w/o) sodium bis(2-ethylhexyl) sulfosuccinate (AOT) microemulsions with increasing temperature or upon addition of salt. Data were collected at different temperatures (15 to 60 °C) and salt concentrations (up to 0.6% NaCl) within the one-phase region of the L2 phase (w/o microemulsion) for different droplet sizes (water/AOT molar ratio wo=25 to 56) and concentrations (droplet weight fraction cw=2% to 20%). This allowed us to distinguish between contributions from individual scattering particles, e.g., droplets and cylinders to the total scattering intensity. The complete data set containing over 500 scattering curves could be interpreted by fitting the scattering of weighted sums of AOT covered water droplets, long cylinders, and inverse AOT micelles containing bound water only, to the experimental scattering curves. The polydispersity of the droplets and cylinders is described by Schulz distributions and the interactions between the droplets are calculated using a sticky hard-sphere potential in the Percus-Yevick approximation. The volume fractions of the components, their average sizes and polydispersity, and the stickiness of the water/AOT droplets are determined by a nonlinear fit to the experimental data.

  8. Crystallization from microemulsions ? a novel method for the preparation of new crystal forms of aspartame

    NASA Astrophysics Data System (ADS)

    Füredi-Milhofer, Helga; Garti, N.; Kamyshny, A.


    Solubilization and crystallization of the artificial sweetener aspartame (APM), in water/isooctane microemulsions stabilized with sodium diisooctyl sulfosuccinate (AOT) has been investigated. The amount of aspartame that could be solubilized depended primarily on the amount of surfactant and on the temperature. The maximum AOT/aspartame molar ratio at the w/o interface is shown to be 6.2 at 25°C. It was concluded that the dipeptide is located at the w/o interface interspersed between surfactant molecules and that it acts as a cosurfactant. A new crystal form, APM III, was obtained by cooling of hot w/isooctane/AOT microemulsions containing solubilized aspartame. The new crystal form exhibits a distinct X-ray diffraction powder pattern, as well as changes in the FTIR spectra, thermogravimetric and DSC patterns. H-NMR spectra of APM III dissolved in D 2O were identical to the spectrum of commercial aspartame recorded under the same conditions. The new crystal form has greatly improved dissolution kinetics.

  9. Reactivity of hair cystine in microemulsion media.


    Erra, P; Solans, C; Azemar, N; Parra, J L; Touraud, D; Clausse, M


    Synopsis Reduction of keratin cystine by thioglycolic acid incorporated in microemulsions of the water/sodium dodecilsulphate/n-pentanol/n-dodecane system has been determined. The results obtained have been interpreted in relation to the properties of the reaction media. Microemulsions with constant oil-to-surface active mixture weight ratios (R(o/s)) and different concentrations of water were chosen as reaction media. At low water concentrations a steep increase in reactivity with the increase of water was observed at all values of R(o/s). However it was more pronounced the higher the oil content. A relation between maximum cysteine formation and percolative behaviour of the microemulsion was found at high R(o/s) values. PMID:19456961

  10. Dendrimer-templated Pd nanoparticles and Pd nanoparticles synthesized by reverse microemulsions as efficient nanocatalysts for the Heck reaction: A comparative study.


    Noh, Ji-Hyang; Meijboom, Reinout


    Palladium nanoparticles (NPs) were prepared using a dendrimer-templated method using G4, G5 and G6 PAMAM-OH dendrimers as well as a reverse microemulsion method using the water/dioctyl sulfosuccinate sodium salt (aerosol-OT, AOT) surfactant/isooctane system with water to surfactant ratios (ω0) of 5, 10 and 13. These 6 catalysts were characterized by UV-Vis spectroscopy, TEM, EDX, and XRD. TEM micrographs showed that the average sizes of 2.74-3.32nm with narrower size distribution were achieved by using dendrimer-templated synthetic methods, whereas the reverse microemulsion method resulted in broad size distribution with an average size of 3.87-5.06nm. The influence of various reaction parameters such as base, catalyst dosing, alkene, aryl halide and temperature on the Heck C-C coupling reaction was evaluated. The activation parameters were derived from the reaction rate of each catalyst obtained at various temperatures. A correlation of catalytic activity, enthalpy of activation and particle size is discussed. Particle size changes of each catalyst were investigated after the catalytic reaction. Overall results indicated that dendrimer-templated Pd NP catalysts showed superior activity as compared to the Pd NPs synthesized by reverse microemulsions, with the dendrimer-templated G5-OH(Pd80) showing the best activity. These catalysts were also reusable for 3 cycles, retaining high yield and showing excellent yields under mild conditions. Therefore, the dendrimer-templated Pd NPs are efficient catalyst systems for the ligand-free Heck C-C coupling reaction. PMID:24267330

  11. Segmented Spiral Waves and Anti-phase Synchronization in a Model System with Two Identical Time-Delayed Coupled Layers

    NASA Astrophysics Data System (ADS)

    Yuan, Guo-Yong; Yang, Shi-Ping; Wang, Guang-Rui; Chen, Shi-Gang


    In this paper, we consider a model system with two identical time-delayed coupled layers. Synchronization and anti-phase synchronization are exhibited in the reactive system without diffusion term. New segmented spiral waves, which are constituted by many thin trips, are found in each layer of two identical time-delayed coupled layers, and are different from the segmented spiral waves in a water-in-oil aerosol sodium bis(2-ethylhexyl) sulfosuccinate (AOT) micro-emulsion (ME) (BZ-AOT system), which consists of many small segments. "Anti-phase spiral wave synchronization" can be realized between the first layer and the second one. For different excitable parameters, we also give the minimum values of the coupling strength to generate segmented spiral waves and the tip orbits of spiral waves in the whole bilayer.

  12. Transdermal delivery of curcumin via microemulsion.


    Sintov, Amnon C


    The objective of this study was to evaluate the transdermal delivery potential of a new curcumin-containing microemulsion system. Three series of experiments were carried out to comprehend the system characteristics: (a) examining the influence of water content on curcumin permeation, (b) studying the effect of curcumin loading on its permeability, and (c) assessing the contribution of the vesicular nature of the microemulsion on permeability. The skin permeability of curcumin from microemulsions, which contained 5%, 10%, and 20% of water content (1% curcumin), was measured in vitro using excised rat skin. It has been shown that the permeability coefficient of CUR in a formulation containing 10% aqueous phase (ME-10) was twofold higher than the values obtained for formulations with 5% and 20% water (Papp=0.116 × 10(-3)± 0.052 × 10(-3)vs. 0.043 × 10(-3)± 0.022 × 10(-3) and 0.047 × 10(-3)± 0.025 × 10(-3)cm/h, respectively. A reasonable explanation for this phenomenon may be the reduction of both droplet size and droplets' concentration in the microemulsion as the aqueous phase decreased from 20% to 5%. It has also been shown that a linear correlation exists between the decrease in droplet size and the increase of curcumin loading in the microemulsion. In addition, it has been demonstrated that a micellar system, S/O-mix, and a plain solution of curcumin resulted in a significantly lower curcumin permeation relative to that presented by the microemulsion, Papp=0.018 × 10(-3)± 0.011 × 10(-3), 0.005 × 10(-3)± 0.002 × 10(-3), and 0.002 × 10(-3)± 0.000 × 10(-3)cm/h, respectively, vs. 0.110 × 10(-3)± 0.021 × 10(-3)cm/h for the microemulsion. The enhancement ratio (ER=Jss-ME/Jss-solution) of CUR permeated via 1% loaded microemulsion was 55. PMID:25655717

  13. CdSe/TiO2 core-shell nanoparticles produced in AOT reverse micelles: applications in pollutant photodegradation using visible light

    PubMed Central


    CdSe quantum dots with a prominent band-edge photoluminescence were obtained by a soft AOT water-in-oil (w/o) microemulsion templating method with an estimated size of 2.7 nm. The CdSe particles were covered with a TiO2 layer using an intermediate SiO2 coupling reagent by a sol-gel process. The resulting CdSe/TiO2 core/shell nanoparticles showed appreciable photocatalytic activity at λ = 405 nm which can only originate because of electron injection from the conduction band of CdSe to that of TiO2. PMID:21711492

  14. "Snap-shooting" the interface of AOT reverse micelles: use of chemical trapping


    Srilakshmi; Chaudhuri


    The first use of the phenyl cation trapping technique in "snap-shooting" the local molar concentrations of water and sulfosuccinate head-groups in the interfacial region of AOT-2,2,4-trimethylpentane-water reverse micelles has been accomplished. Our results demonstrate that the interfacial concentrations of the sulfosuccinate head-groups in AOT (0.1 M)-2,2,4-trimethylpentane-water reverse micelles are remarkably high (2.75-2.34 M) across the W0 (the molar ratio of water to surfactant) range 12 to 44. However, the interfacial concentrations of water in AOT- 2,2,4-trimethylpentane-water reverse micelles across the same range of solution compositions are significantly lower (27.9-32.0 M) than the molar concentration of bulk water (55.5 M). The present results provide new insight on the microenvironments of interfacially located enzymes such as lipases entrapped in AOT-2,2,4-trimethylpentane-water reverse micelles, the most extensively exploited reverse-micellar system in micellar biotechnology. PMID:10985732

  15. Preparation and evaluation of fexofenadine microemulsion for intranasal delivery.


    Piao, Hong-Mei; Balakrishnan, Prabagar; Cho, Hyun Jong; Kim, Hyunjun; Kim, You Sun; Chung, Suk-Jae; Shim, Chang-Koo; Kim, Dae-Duk


    To enhance the solubility and bioavailability of poorly absorbable fexofenadine, microemulsion system composed of oil, surfactant and co-surfactant was developed for intranasal delivery. Phase behavior, particle size, viscosity and solubilization capacity of the microemulsion system were characterized. Histopathology and in vivo nasal absorption of the optimized microemulsion formulations were also investigated in rats. A single isotropic region was found in the pseudo-ternary phase diagrams developed at various ratios with Lauroglycol 90 as oil, Labrasol as surfactant and Plurol oleiqueCC49 or its mixture with PEG-400 (1:1) as cosurfactant. An increase in the microemulsion region in pseudo-ternary phase systems was observed with increased surfactant concentration. The optimized microemulsion formulations showed higher solubulization of fexofenadine, i.e., F1 (22.64mg/mL) and F2 (22.98mg/mL), compared to its intrinsic water solubility (1.51mg/mL). Nasal absorption of fexofenadine from these microemulsions was found to be fairly rapid. T(max) was observed within 5min after intranasal administration at 1.0mg/kg dose, and the absolute bioavailability (0-4h) was about 68% compared to the intravenous administration in rats. Our results suggested that these microemulsion formulations could be used as an effective intranasal dosage form for the rapid-onset delivery of fexofenadine. PMID:20685383

  16. Preparation and evaluation of fexofenadine microemulsions for intranasal delivery.


    Piao, Hong-Mei; Balakrishnan, Prabagar; Cho, Hyun-Jong; Kim, Hyunjun; Kim, You-Sun; Chung, Suk-Jae; Shim, Chang-Koo; Kim, Dae-Duk


    To enhance the solubility and bioavailability of poorly absorbable fexofenadine, microemulsion system composed of oil, surfactant and co-surfactant was developed for intranasal delivery. Phase behavior, particle size, viscosity and solubilization capacity of the microemulsion system were characterized. Histopathology and in vivo nasal absorption of the optimized microemulsion formulations were also investigated in rats. A single isotropic region was found in the pseudo-ternary phase diagrams developed at various ratios with Lauroglycol 90 as oil, Labrasol as surfactant and Plurol Oleique CC49 or its mixture with PEG-400 (1:1) as cosurfactant. An increase in the microemulsion region in pseudo-ternary phase systems was observed with increased surfactant concentration. The optimized microemulsion formulations showed higher solubulization of fexofenadine, i.e., F1 (22.64 mg/mL) and F2 (22.98 mg/mL), compared to its intrinsic water solubility (1.51 mg/mL). Nasal absorption of fexofenadine from these microemulsions was found to be fairly rapid. Tmax was observed within 5 min after intranasal administration at 1.0 mg/kg dose, and the absolute bioavailability (0-4 h) was about 68% compared to the intravenous administration in rats. Our results suggested that these microemulsion formulations could be used as an effective intranasal dosage form for the rapid-onset delivery of fexofenadine PMID:20635476

  17. Molten fatty acid based microemulsions.


    Noirjean, Cecile; Testard, Fabienne; Dejugnat, Christophe; Jestin, Jacques; Carriere, David


    We show that ternary mixtures of water (polar phase), myristic acid (MA, apolar phase) and cetyltrimethylammonium bromide (CTAB, cationic surfactant) studied above the melting point of myristic acid allow the preparation of microemulsions without adding a salt or a co-surfactant. The combination of SANS, SAXS/WAXS, DSC, and phase diagram determination allows a complete characterization of the structures and interactions between components in the molten fatty acid based microemulsions. For the different structures characterized (microemulsion, lamellar or hexagonal phases), a similar thermal behaviour is observed for all ternary MA/CTAB/water monophasic samples and for binary MA/CTAB mixtures without water: crystalline myristic acid melts at 52 °C, and a thermal transition at 70 °C is assigned to the breaking of hydrogen bounds inside the mixed myristic acid/CTAB complex (being the surfactant film in the ternary system). Water determines the film curvature, hence the structures observed at high temperature, but does not influence the thermal behaviour of the ternary system. Myristic acid is partitioned in two "species" that behave independently: pure myristic acid and myristic acid associated with CTAB to form an equimolar complex that plays the role of the surfactant film. We therefore show that myristic acid plays the role of a solvent (oil) and a co-surfactant allowing the fine tuning of the structure of oil and water mixtures. This solvosurfactant behaviour of long chain fatty acid opens the way for new formulations with a complex structure without the addition of any extra compound. PMID:27241163

  18. Ethylene glycol and the thermostability of trypsin in a reverse micelle system.


    Stupishina, E A; Khamidullin, R N; Vylegzhanina, N N; Faizullin, D A; Zuev, Yu F


    The influence of ethylene glycol (EG) on the kinetics of hydrolysis of N-alpha-benzoyl-L-arginine ethyl ether catalyzed by trypsin encapsulated in sodium bis-(2-ethylhexyl)sulfosuccinate (AOT)-based reverse micelles was studied at different temperatures. Ethylene glycol was shown to shift the range of the trypsin activity in the reverse micelles towards higher temperatures. Infrared spectroscopy showed a stabilizing effect of EG on the secondary structure of the protein in the system of reverse micelles. Electron spin resonance spectroscopy showed that the solubilized protein affected the interactions of EG with the polar head groups of AOT and altered the rigidity of the micellar matrix. The results indicate that EG increases the thermostability of the solubilized enzyme in microemulsion media by two mechanisms. PMID:16732732

  19. Factors affecting the phase behavior and antimicrobial activity of carvacrol microemulsions.


    Shaaban, Hamdy A; Edris, Amr E


    The aim of this study was to investigate some factors that can contribute to the formulation of aqueous-based carvacrol microemulsion that can potentially be used in food preservation or disinfection. For this purpose the capacity of formation of carvacrol microemulsion was first revealed by studying the phase behavior of that compound in five different non-ionic microemulsion systems. Factors affecting that phase behavior like the type of non-ionic surfactant and presence of solubilization enhancers were also studied. The fully dilutable microemulsion system that can incorporate high carvacrol amount, as revealed from the phase diagrams, was chosen for the antibacterial evaluation study. The same microemulsion system was re-formulated in a cationic form by substituting the non-ionic surfactant, Tween 20 (T20) with the cationic cetylpyridinium chloride (CPC). The disc diffusion method was used to evaluate the activity of these microemulsion systems against different pathogenic bacteria. Results of the phase behavior study showed that carvacrol is a challenging phenolic compound which did not lend itself easily for solubilization in a fully dilutable non-ionic microemulsion. Incorporation of some solubilization enhancers like propylene glycol (PG) or short chain alcohols can fulfill this purpose however high surfactant/carvacrol ratio (9:1) was still required to solubilize only 1.0 wt% carvacrol in dilutable microemulsion. The antibacterial evaluation study at that concentration revealed that non-ionic carvacrol microemulsion formulated with T20 and a solubilization enhancer did not exhibit better antimicrobial activity than the same concentration of carvacrol formulated in surfactant-free aqueous solution composed of water/PG (1:1). On the other hand, the CPC-formulated carvacrol microemulsion showed significantly higher antibacterial activity than T20-formulated microemulsion. Results of the current investigation shed the light on the solubilization capacity and

  20. Evaluation of nicotinamide microemulsion on the skin penetration enhancement.


    Boonme, Prapaporn; Boonthongchuay, Chalida; Wongpoowarak, Wibul; Amnuaikit, Thanaporn


    This study purposed to evaluate a microemulsion containing nicotinamide for its characteristics, stability, and skin penetration and retention comparing with a solution of nicotinamide in 2:1 mixture of water and isopropyl alcohol (IPA). The microemulsion system was composed of 1:1 mixture of Span80 and Tween80 as a surfactant mixture, isopropyl palmitate (IPP) as an oil phase, and 2:1 mixture of water and IPA as an aqueous phase. Nicotinamide microemulsion was prepared by dissolving the active in the aqueous phase before simply mixing with the other components. It was determined for its characteristics and stability under various conditions. The skin penetration and retention studies of nicotinamide microemulsion and solution were performed by modified Franz diffusion cells, using newborn pig skin as the membrane. The results showed that nicotinamide microemulsion could be obtained as clear yellowish liquid, was water-in-oil (w/o) type, possessed Newtonian flow, and exhibited physicochemical stability when kept at 4 °C and room temperature (≈30 ± 2 °C) during 3 months. From the skin penetration data, the microemulsion could enhance the skin penetration of nicotinamide comparing with the solution. Additionally, nicotinamide microemulsion could provide much higher amount of skin retention than that of skin penetration, resulting in suitability for a cosmeceutical product. PMID:25318786

  1. Quantitative characterization of the viscosity of a microemulsion

    NASA Technical Reports Server (NTRS)

    Berg, Robert F.; Moldover, Michael R.; Huang, John S.


    The viscosity of the three-component microemulsion water/decane/AOT has been measured as a function of temperature and droplet volume fraction. At temperatures well below the phase-separation temperature the viscosity is described by treating the droplets as hard spheres suspended in decane. Upon approaching the two-phase region from low temperature, there is a large (as much as a factor of four) smooth increase of the viscosity which may be related to the percolation-like transition observed in the electrical conductivity. This increase in viscosity is not completely consistent with either a naive electroviscous model or a simple clustering model. The divergence of the viscosity near the critical point (39 C) is superimposed upon the smooth increase. The magnitude and temperature dependence of the critical divergence are similar to that seen near the critical points of binary liquid mixtures.

  2. Development and characterization of eucalyptol microemulsions for topic delivery of curcumin.


    Liu, Chi-Hsien; Chang, Fu-Yen


    Microemulsions have received great attention for applications in transdermal drug delivery. The use of curcumin for treating various skin diseases like scleroderma, psoriasis, and skin cancer was extensively reported. The solubility of curcumin in various oils, surfactants, and cosurfactants was studied herein in order to find the optimal components for a transdermal delivery vehicle. Microemulsion systems composed of eucalyptol, polysorbate 80, ethanol, and water were developed as transdermal delivery vehicles for curcumin. Effects of the microemulsion composition on transdermal curcumin delivery were studied using Franz diffusion cells. The transdermal curcumin flux, permeability coefficient, and enhancement ratio were analyzed to evaluate the effects of eucalyptol/water ratios in the microemulsions. Pseudo-ternary phase diagrams of the eucalyptol microemulsions with various surfactant/cosurfactant ratios (1:1-1:3) were constructed to investigate their phase behaviors. Conductivity, interfacial tension, size, and viscosity data of the microemulsions were used to characterize the physicochemical properties of transdermal vehicles. The influence of the microemulsions on skin histology and on the delivery route was analyzed using hematoxylin/eosin staining and confocal laser scanning microscopy. In conclusion, microemulsions were successfully developed for transdermal curcumin delivery after screening various components and adjusting the oil/water ratios. The curcumin permeation rate of the microemulsion developed was 15.7-fold higher than that of the control (eucalyptol only). These results indicate that an eucalyptol microemulsion system is a promising tool for the percutaneous delivery of curcumin. PMID:21297295

  3. Investigating effect of microemulsion components: In vitro permeation of ketoconazole.


    Patel, Mrunali R; Patel, Rashmin B; Parikh, Jolly R; Solanki, Ajay B; Patel, Bharat G


    The purpose of this study was to evaluate the effect of oil, surfactant/co-surfactant mixing ratios and water on the in vitro permeation of ketoconazole (KTZ) applied in O/W microemulsion vehicle through intact rat skin. Lauryl Alcohol (LA) was screened as the oil phase of microemulsions, due to a good solubilizing capacity of the microemulsion system. The pseudo-ternary phase diagrams for microemulsion regions were constructed using LA as the oil, Labrasol (Lab) as the surfactant (S) and ethanol (EtOH) as the cosurfactant (CoS). The formulation which showed a highest permeation rate of 54.65 ± 1.72 µg/cm(2)/h(1) and appropriate physico-chemical properties was optimized as containing 2% KTZ, 10% LA, 20% Lab/EtOH (1:1) and 68% double distilled water (w/w). The efficiency of microemulsion formulation in the topical delivery of KTZ was dependent upon the contents of water and LA as well as Lab/EtOH mixing ratio. It was concluded that the percutaneous absorption of KTZ from microemulsions was enhanced with increasing the LA and water contents, and with decreasing the Lab/EtOH ratio in the formulation. Candida albicans was used as a model fungus to evaluate the antifungal activity of the best formula achieved, which showed the widest zone of inhibition as compared to KTZ reference. The studied microemulsion formulation showed a good stability for a period of three months. Histopathological investigation of rat skin revealed the safety of microemulsion formulations for topical use. These results indicate that the studied microemulsion formulation might be a promising vehicle for topical delivery of KTZ. PMID:20146553

  4. Molecular thermodynamic modeling of droplet-type microemulsions.


    Moreira, Livia A; Firoozabadi, Abbas


    Microemulsions are nanoheterogeneous, thermodynamically stable, spontaneously forming mixtures of oil and water by means of surfactants, with or without cosurfactants. The pledge to use small volumes of amphiphile molecules compared to large amounts of bulk phase modifiers in a variety of chemical and industrial processes, from enhanced oil recovery to biotechnology, fosters continuous investigation and an improved understanding of these systems. In this work, we develop a molecular thermodynamic theory for droplet-type microemulsions, both water-in-oil and oil-in-water, and provide the theoretical formulation for three-component microemulsions. Our thermodynamic model, which is based on a direct minimization of the Gibbs free energy of the total system, predicts the structural and compositional features of microemulsions. The predictions are compared with experimental data for droplet size in water-alkane-didodecyl dimethylammonium bromide systems. PMID:22149425

  5. Formation of microemulsion: Effect of temperature and polyacrylamide

    SciTech Connect

    John, A.C.; Rakshit, A.K. )


    The pseudoternary phase diagram of the system involving cyclohexane, sodium dodecyl sulphate, propanol, and water was constructed for an SDS-to-propanol mass ratio 1:2. The area of the monophasic microemulsion region was computed. The effects of change of temperature and change of concentration of water-soluble polyacrylamide (PAA) on the microemulsion zone as well as the conductance, viscosity, and adiabatic compressibility of the microemulsion systems were studied. It was observed that for the water system there is a critical temperature below which the microemulsion zone increases with temperature, though at higher temperature the zone decreases within the range studied. The effects of presence of polyacrylamide above and below 0.003%(w/v)also are different from each other.

  6. Form fluctuations of polymer loaded spherical microemulsions studied by neutron scattering and dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Kuttich, B.; Falus, P.; Grillo, I.; Stühn, B.


    We investigate the structure and shell dynamics of the droplet phase in water/AOT/octane microemulsions with polyethyleneglycol (MW = 1500) molecules loaded in the droplets. Size and polydispersity of the droplets is determined with small angle X-ray scattering and small angle neutron scattering experiments. Shell fluctuations are measured with neutron spin echo spectroscopy and related to the dynamic percolation seen in dielectric spectroscopy. Shell fluctuations are found to be well described by the bending modulus of the shell and the viscosities inside and outside the droplets. Addition of the polymer decreases the modulus for small droplets. For large droplets the opposite is found as percolation temperature shifts to higher values.

  7. Spectrometric study on the binding of curcumin with AOT: effect of micelle-to-vesicle transition.


    Zhou, Haibo; Yang, Qianqian; Wang, Xiaoyong


    In this work, the role of micelle-to-vesicle transition of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in the binding, stability and antioxidant activity of curcumin has been studied using absorption and fluorescence measurements. As AOT molecules aggregate into micelles and vesicles, curcumin bound with AOT often gives higher intensities of absorption and fluorescence than that of free curcumin. The most enhanced absorption and fluorescence of curcumin induced by AOT vesicles, are attributed to the location of curcumin in their lipid bilayer. The measurement of curcumin anisotropy suggests that the bilayer of AOT vesicles provides curcumin with a more hydrophobic microenvironment than the palisade layer of AOT micelles. The binding constant (Kb) of curcumin with AOT vesicles is three times that of curcumin with AOT micelles. Moreover, AOT vesicles are found to be superior to AOT micelles for enhancing the stability and radical scavenging ability of curcumin. PMID:24837931

  8. Influence of the composition of monoacyl phosphatidylcholine based microemulsions on the dermal delivery of flufenamic acid.


    Hoppel, Magdalena; Ettl, Hanna; Holper, Evelyn; Valenta, Claudia


    Although microemulsions are one of the most promising dermal carrier systems, their clinical use is limited due to their skin irritation potential. Therefore, microemulsions based on naturally derived monoacyl phosphatidylcholine (MAPL) were developed. The influence of the water, oil and surfactant content on dermal delivery of flufenamic acid was systematically investigated for the first time. A water-rich microemulsion led to significantly higher in vitro skin penetration of flufenamic acid compared to other microemulsions. The superiority of the water-rich microemulsion over a marketed flufenamic acid containing formulation was additionally confirmed. Differences in drug delivery could be explained by alterations of the microemulsions after application. Evaporation of isopropanol led to crystal-like structures of MAPL on the skin surface from the surfactant- or oleic acid-rich microemulsions. In contrast, the formation of this additional barrier was hindered in case of the water-rich microemulsion. The skin penetration of MAPL was additionally analyzed by combined ATR-FTIR and tape stripping experiments, where MAPL itself penetrated only into the initial layers of the stratum corneum, independent of the microemulsion composition. Since a surfactant must penetrate the skin to cause irritation, MAPL can be presumed as a skin-friendly emulsifier with the ability to stabilize pharmaceutically acceptable microemulsions. PMID:25178824

  9. Synthesis of nanosize silica in aerosol OT reverse microemulsions

    SciTech Connect

    Arriagada, F.J.; Osseo-Asare, K. . Dept. of Materials Science and Engineering)


    Silica nanoparticles were synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/decane/ammonium hydroxide reverse microemulsions via the base-catalyzed hydrolysis of tetraethoxysilane (TEOS). The fluorescence spectra of 1,3,6,8-pyrenetetrasulfonic acid (PTS) trapped in the water pools indicate that free water molecules do not become available until the water-to-surfactant molar ratio (R) exceeds about 10. At R values below about 4, no particles are produced. Under these conditions, the surfactant molecules are closely packed at the interface and the water molecules are strongly bound to the surfactant polar groups and the sodium counterions; the net result is to inhibit TEOS hydrolysis. As R increases from 5 to 9.5, the diameter of the resulting particles increases, and the size distribution decreases. These trends are rationalized in terms of changes in the local concentration of hydrolyzed TEOS species in the reversed micellar pseudophase, coupled with the protective action of the surfactant film. The fact that the final particle sizes exceed the diameters of the corresponding water pools indicates a role for intermicellar matter exchange in the particle growth process. The dispersions are not stable, and gel-like precipitates eventually form. The low dispersion stability is attributed to the presence of sodium ions and to the possible decrease in pH caused by the hydrolysis of the AOT surfactant molecules. This surfactant has been used in a number of applied investigations involving membrane chemistry, protein separations, metal separations, solar energy conversion, and nanoparticle synthesis.

  10. A facile construction strategy of stable lipid nanoparticles for drug delivery using a hydrogel-thickened microemulsion system.


    Chen, Huabing; Xiao, Ling; Du, Danrong; Mou, Dongsheng; Xu, Huibi; Yang, Xiangliang


    We report a novel facile method for preparing stable nanoparticles with inner spherical solid spheres and an outer hydrogel matrix using a hot O/W hydrogel-thickened microemulsion with spontaneous stability. The nanoparticles with average diameters of about 30.0 nm and 100.0 nm were constructed by cooling the hot hydrogel-thickened microemulsion at different temperatures, respectively. We explained the application of these nanoparticles by actualizing the cutaneous delivery of drug-loaded nanoparticles. The in vitro skin permeation studies showed that the nanoparticles could significantly reduce the penetration of model drugs through skin and resulted in their dermal uptakes in skin. The sol-gel process of TEOS was furthermore used in the template of HTM to regulate the particle size of nanoparticles. The coating of silica on the surface of nanoparticles could regulate the penetration of drug into skin from dermal delivery to transdermal delivery. This strategy provides a facile method to produce nanoparticles with long-term stability and ease of manufacture, which might have a promising application in drug delivery. PMID:19946154

  11. Transdermal delivery of betahistine hydrochloride using microemulsions: physical characterization, biophysical assessment, confocal imaging and permeation studies.


    Hathout, Rania M; Nasr, Maha


    Transdermal delivery of betahistine hydrochloride encapsulated in various ethyl oleate, Capryol 90(®), Transcutol(®) and water microemulsion formulations was studied. Two different kinds of phase diagrams were constructed for the investigated microemulsion system. Pseudoplastic flow that is preferable for skin delivery was recorded for the investigated microemulsions. A balanced and bicontinuous microemulsion formulation was suggested and showed the highest permeation flux (0.50±0.030mgcm(-2)h(-1)). The effect of the investigated microemulsions on the skin electrical resistance was used to explain the high permeation fluxes obtained. Confocal laser scanning microscopy was used to confirm the permeation enhancement and to reveal the penetration pathways. The results obtained suggest that the proposed microemulsion system highlighted in the current work can serve as a promising alternative delivery means for betahistine hydrochloride. PMID:23732802

  12. Unfolding and inactivation of cutinases by AOT and guanidine hydrochloride.


    Ternström, Tomas; Svendsen, Allan; Akke, Mikael; Adlercreutz, Patrick


    We present a comparative analysis of the unfolding and inactivation of three cutinases in the presence of guanidine hydrochloride (GdnHCl) and bis(2-ethylhexyl) sodium sulfosuccinate (AOT). Previous investigations have focused on the cutinase from Fusarium solani pisi (FsC). In addition to FsC, the present study includes the cutinase from Humicola insolens (HiC) and a mutant variant of HiC (muHiC) with increased activity and decreased surfactant sensitivity. Equilibrium and time-resolved denaturation by AOT were studied in aqueous solution and reverse micelles, and were compared with GdnHCl denaturation. The far-UV CD and fluorescence denaturation profiles obtained in the aqueous solutions of the two denaturants coincide for all three cutinases, indicating that unfolding is a co-operative two-state process under these conditions. In reverse micelles, the cutinases unfold with mono-exponential rates, again indicating a two-state process. The free energy of denaturation in water was calculated by linear extrapolation of equilibrium data, yielding very similar values for the three cutinases with averages of -11.6 kcal mol(-1) and -2.6 kcal mol(-1) for GdnHCl and AOT, respectively. Hence, the AOT denatured state (D(AOT)) is less destabilised than the GdnHCl denatured state (D(GdnHCl)), relative to the native state in water. Far-UV CD spectroscopy revealed that D(AOT) retains some secondary structure, while D(GdnHCl) is essentially unstructured. Similarly, fluorescence data suggest that D(AOT) is more compact than D(GdnHCl). Activity measurements reveal that both D(AOT) and D(GdnHCl) are practically inactive (catalytic activity <1% of that of the native enzyme). The fluorescence spectrum of D(AOT) in reverse micelles did not differ significantly from that observed in aqueous AOT. NMR studies of D(AOT) in reverse micelles indicated that the structure is characteristic of a molten globule, consistent with the CD and fluorescence data. PMID:15752695

  13. Low-pressure lipase-catalyzed production of mono- and diglycerides with and without N-butane and AOT surfactant.


    Valério, Alexsandra; Fiametti, Karina G; Rovani, Suzimara; Treichel, Helen; de Oliveira, Débora; Oliveira, J Vladimir


    The aim of this work is to report the production of mono- and diglycerides from olive oil at ambient condition and in pressurized n-butane as solvent medium. For this purpose, a commercial immobilized lipase (Novozym 435) was employed as catalyst and sodium (bis-2-ethyl-hexyl) sulfosuccinate (Aerosol-OT or AOT) as surfactant. The experiments were conducted in batch mode varying the temperature, pressure, and AOT concentration. Results showed that lipase-catalyzed glycerolysis either with compressed n-butane or in solvent-free system with AOT as surfactant might be a potential alternative route to conventional methods, as high contents of reaction products, especially monoglycerides ( approximately 60 wt.%), were achieved at mild temperature and pressure with a relatively low solvent to substrates mass ratio (4:1) in short reaction times (2 h). PMID:19641856

  14. Microemulsion-mediated synthesis of nanosize molybdenum sulfide particles

    SciTech Connect

    Boakye, E.; Radovic, L.R.; Osseo-Asare, K. . Dept. of Materials Science and Engineering)


    A microemulsion-based method for the synthesis of molybdenum sulfide nanoparticles is reported. Molybdenum sulfide particles in the size range 10--80 nm have been precipitated in water-in-oil microemulsions (water-containing inverse micelles) formulated with polyoxyethylene(5)nonylphenyl ether (NP-5). The particles were synthesized in the NP-5/cyclohexane/water microemulsion system by acidifying ammonium tetrathiomolybdate solubilized in the water cores of the inverse micelles. Particle characterization was accomplished by chemical analysis, transmission electron microscopy, and ultraviolet/visible spectroscopy. The small size and the cage-like nature of the microemulsion water cores limit particle growth and aggregation. The particle size was found to be a function of the water-to-surfactant molar ratio and the average number of ammonium tetrathiomolybdate ions solubilized per water core. These trends are rationalized in terms of classical nucleation theory and aggregative growth concepts.

  15. Polymeric Bicontinuous Microemulsions

    NASA Astrophysics Data System (ADS)

    Bates, Frank S.; Maurer, Wayne W.; Lipic, Paul M.; Hillmyer, Marc A.; Almdal, Kristoffer; Mortensen, Kell; Fredrickson, Glenn H.; Lodge, Timothy P.


    High molecular weight block copolymers can be viewed as macromolecular surfactants when blended with thermodynamically incompatible homopolymers. This Letter describes the formation of polymeric bicontinuous microemulsions in mixtures containing a model diblock copolymer and two homopolymers. Although we attribute development of this equilibrium morphology to the effects of fluctuations, mean-field theory provides a quantitative strategy for preparing the bicontinuous state at blend compositions near an isotropic Lifshitz point.

  16. Microstructure of microemulsion modified with ionic liquids in microemulsion electrokinetic chromatography and analysis of seven corticosteroids.


    Ni, Xinjiong; Yu, Meijuan; Cao, Yuhua; Cao, Guangqun


    In this work, the influences of ionic liquid (IL) as a modifier on microemulsion microstructure and separation performance in MEEKC were investigated. Experimental results showed that synergetic effect between IL 1-butyl-3-methylimidazolium tetrafluoro-borate (BmimBF4 ) and surfactant SDS gave a decreased CMC. With increment of IL in microemulsion, negative ζ potential of the microdroplets reduced gradually. The influence of IL on the dimensions of microdroplet was complicated. At BmimBF4 less than 8 mM, IL made microemulsion droplet smaller in size. While at BmimBF4 more than 10 mM, the size increased and reached to a maximum value at 12 mM, where the microdroplets were larger than that without IL. After that, the micreodroplet size decreased again. Relative fluorescence intensity of the first vibration band of pyrene to the third one (I1 /I3 ) enhanced as IL was added to microemulsion, which indicated that this addition increased environmental polarity in the inner core of microdroplets. Prednisone, hydrocortisone, prednisolone, hydrocortisone acetate, cortisone acetate, prednisolone acetate, and triamcinolone acetonide were analyzed with MEEKC modified with IL to evaluate the separation performance. Cortisone acetate and prednisolone acetate could not be separated at all in typical microemulsion. The seven analytes could be separated by the addition of 10 mM BmimBF4 into the microemulsion system. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for seven analytes were between 86 and 114%. This method provides accuracy, reproducibility, pretreatment simplicity, and could be applied to the quality control of cosmetics. PMID:23801369

  17. Microemulsion liquid membranes. I. Application to acetic acid removal from water

    SciTech Connect

    Wiencek, J.M.; Qutubuddin, S. )


    A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of acetic acid from an aqueous feed phase. The surfactant systems were carefully characterized in order to assure that they were truly microemulsions. The effects of mixing intensity, feed concentration, treat ratio, and microemulsion viscosity on the separation kinetics were investigated. The microemulsions did not typically display leakage and had negligible swell over 5-minute duration. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the acetate ion via a temperature change of approximately 40 C. Material balances closed to within 10% and rates of separation were faster than the sampling rates when the microemulsion was fully dispersed in the aqueous feed phase.

  18. Supramolecular assemblies obtained by mixing different cyclodextrins and AOT or BHDC reverse micelles.


    Silva, O Fernando; Correa, N Mariano; Silber, Juana J; de Rossi, Rita H; Fernández, Mariana A


    In this contribution we show the effect of the surfactant polar head and the external solvent on the incorporation of different cyclodextrins (CDs) {α-CD, β-CD, γ-CD, decenylsuccinyl-β-CD (Mod-β-CD), and hydroxypropyl-β-CD (hp-β-CD)} in different reverse micelles (RMs) {benzene/sodium 1,4-bis(2-ethylhexyl) sulfosuccinate(AOT)/water, and benzene/benzyl-n-hexadecyldimethylammonium chloride (BHDC)/water} and compare them with previous results obtained in n-heptane/AOT/water RMs. To investigate the different systems, we have used UV-vis spectrophotometry, induced circular dichroism spectroscopy (ICD), and the achiral molecular probe methyl orange (MO). The results show dramatic differences changing the external solvent and the surfactant, which are explained by considering the differences in the RMs interface composition, the water-surfactant interaction, and the CDs' location in the different media investigated. None of the CDs were incorporated into the benzene/AOT/water RMs at any [H2O]/[surfactant] ratio studied (W0) whereas it was previously shown that Mod-β-CD and hp-β-CD could be included in n-heptane/AOT/water RMs. However, all of the CDs are incorporated in benzene/BHDC/water RMs at W0 > 10 and hp-β-CD is dissolved even at W0 = 0. Different from what was found in n-heptane/AOT RMs, in BHDC RMs MO showed ICD signals with two different CDs: Mod-β-CD and hp-β-CD. The results are explained by considering the known difference in the interfacial water structure for AOT and BHDC RMs and the electron-rich region on the secondary hydroxyl (wider side of the CDs), which helps to solubilize all CDs in BHDC. This study shows that chiral cyclodextrin could be available for a guest in an organic medium such as the RMs. Therefore we have created a potentially powerful nanoreactor with two different confined regions in the same aggregate: the polar core of the RMs and the chiral hydrophobic cavity of cyclodextrin. PMID:24597759

  19. Lecithin-Linker Microemulsion Gelatin Gels for Extended Drug Delivery

    PubMed Central

    Xuan, Xiao-Yue; Cheng, Yu-Ling; Acosta, Edgar


    This article introduces the formulation of alcohol-free, lecithin microemulsion-based gels (MBGs) prepared with gelatin as gelling agent. The influence of oil, water, lecithin and hydrophilic and lipophilic additives (linkers) on the rheological properties and appearance of these gels was systematically explored using ternary phase diagrams. Clear MBGs were obtained in regions of single phase microemulsions (μEs) at room temperature. Increasing the water content in the formulation increased the elastic modulus of the gels, while increasing the oil content had the opposite effect. The hydrophilic additive (PEG-6-caprylic/capric glycerides) was shown to reduce the elastic modulus of gelatin gels, particularly at high temperatures. In contrast to anionic (AOT) μEs, the results suggest that in lecithin (nonionic) μEs, the introduction of gelatin “dehydrates” the μE. Finally, when the transdermal transport of lidocaine formulated in the parent μE and the resulting MBG were compared, only a minor retardation in the loading and release of lidocaine was observed. PMID:24300183

  20. Effects of water content and chain length of n-alkane on the interaction enthalpy between the droplets in water/sodium bis(2-ethylhexyl)-sulfosuccinate/n-alkane microemulsions.


    Fan, Dashuang; Zheng, Peizhu; Ma, Yuanming; Yin, Tianxiang; Zhao, Jihua; Shen, Weiguo


    The concentration-dependent enthalpies of mixing for water/sodium bis(2-ethylhexyl)-sulfosuccinate (AOT)/n-alkane microemulsions with different water contents ω0 and chain lengths n of n-alkane were determined by isothermal titration microcalorimetry (ITC) and flow-mixing microcalorimetry at 298.15 K and used to calculate the interaction enthalpies (-ΔH(C)) between the droplets. It was found that -ΔH(C) increased with ω0, and changed from negative to positive at about ω0 = 10. The investigation of the dependence of -ΔH(C) on n revealed that the values of -ΔH(C) were negative and had a minimum for ω0 = 5; while they were positive and had a maximum for ω0 = 15. These phenomena were discussed based on the competition of the overlapping contribution of the surfactant tails between two neighbouring droplets and the penetration contribution of the solvent molecules into the surfactant tails. These results indicated the important role of entropy in the stability of the microemulsion systems. PMID:25727484

  1. Structure and Solvent Properties of Microemulsions

    ERIC Educational Resources Information Center

    Katz, Civia A.; Calzola, Zachary J.; Mbindyo, Jeremiah K. N.


    A microscale laboratory experiment to investigate the formation and utility of microemulsions is described. Microemulsions are technologically important fluids that can reduce the use of toxic organic solvents. In the experiment, students prepare a microemulsion and compare the solubility of sudan III dye in the microemulsion and in dodecane. They…

  2. In situ microemulsion synthesis of hydroxyapatite-MgFe2O4 nanocomposite as a magnetic drug delivery system.


    Foroughi, Firoozeh; Hassanzadeh-Tabrizi, S A; Bigham, Ashkan


    In this study, an innovative synthesis process has been developed to produce hydroxyapatite-magnesium ferrite (HA-MgFe2O4) nanocomposite. In addition, the effect of calcination temperature on drug delivery behavior of produced samples was investigated. HA-MgFe2O4 nanocomposite was prepared via one-step modified reverse microemulsion synthesis route. The resulting products were characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller surface area analysis (BET). The calcined samples at 500 and 700°C demonstrated mesoporous characteristics and large specific surface areas of 88 and 32m(2)/g, respectively. TEM and VSM results showed that the nanocomposite calcined at 700°C has core-shell morphology and a maximum saturation magnetization of 9.47emug(-1). PMID:27524079

  3. Nucleation and growth mechanism of Pd/Pt bimetallic clusters in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles as studied by in situ X-ray absorption spectroscopy.


    Chen, Ching-Hsiang; Hwang, Bing-Joe; Wang, Guo-Rung; Sarma, Loka Subramanyam; Tang, Mau-Tsu; Liu, Din-Goa; Lee, Jyh-Fu


    We report in situ X-ray absorption spectroscopy (XAS) investigations on the formation of palladium-platinum (Pd/Pt) bimetallic clusters at the early stage within the water-in-oil microemulsion system of water/AOT/n-heptane. The reduction of palladium and platinum ions and the formation of corresponding clusters are monitored as a function of dosage of reducing agent, hydrazine (N(2)H(5)OH). Upon successive addition of the reducing agent, hydrazine (N(2)H(5)OH), five distinguishable steps are observed in the formation process of Pd/Pt clusters at the early stage. Both in situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis for both the Pd K-edge and Pt L(III)-edge revealed the formation of Pd/Pt bimetallic clusters. A corresponding structural model is proposed for each step to provide a detailed insight into the nucleation and growth mechanism of Pd/Pt bimetallic clusters. We also discussed the atomic distribution of Pd and Pt atoms in Pd/Pt bimetallic clusters based on the calculated XAS structural parameters. PMID:16853800

  4. Tetrakis(dimethylamino)ethylene chemiluminescence (TDE CL) characterization of the CMC and the viscosity of reversed microemulsions.


    Huang, Chien-Chang; Hohn, Keith L


    A new technique for the characterization of reversed microemulsions based on tetrakis(dimethylamino)ethylene (TDE) chemiluminescence (CL) has been explored. This method is based on the transport of quenching species from the continuous nonpolar phase to the interior of micelles. The emission intensity of TDE chemiluminescence was measured as a function of time for different concentrations of surfactant. These data were fit as an exponential decay, and the decay constant, k, was found. When k was plotted as a function of surfactant concentration, there was a clear change in the trend with surfactant concentration at a certain concentration; the concentration where this change occurred was concluded to be the critical micelle concentration (CMC). Using this method, the CMC of doctyl sulfosuccinate sodium salt (AOT) was evaluated in short-chain alkanes (including n-dodecane, n-decane, n-octane, n-heptane, and isooctane), cyclohexane, and mineral oil (light), while the CMCs of sodium dodecylbenzenesulfonate (NaDDBs) and Triton X-100 (X-100) were detected in cyclohexane. The CMC values were found to range from 0.61 to 2.10 mM, and they decreased with the carbon chain length of the alkane solvent. In addition, it was found that the emission intensity of TDE chemiluminescence is sensitive to variations in solvent viscosity. TDE CL is suggested as a fluorescent molecular rotor for measuring the viscosity of the system which is nanosized. PMID:20136086

  5. Preparation, characterization, and preliminary antibrowning evaluations of norartocarpetin microemulsions.


    Zheng, Zong-Ping; Dong, Xue; Yuan, Kun; Lan, Shan; Zhu, Qin; Wang, Mingfu; Chen, Jie


    Norartocarpetin is a flavone widely distributed in Moraceae plants with strong tyrosinase inhibitory activity. However, its poor solubility in aqueous systems and in food grade solvents (oils) limits its extensive applications. The aim of this study was to improve the solubility of norartocarpetin by developing an oil-in-water (o/w) microemulsion with food grade components. A microemulsion was developed and characterized, and its chemical and physical stabilities were also evaluated within 8 weeks. Using the construction of pseudoternary phase diagrams, the optimized formulation of 2% w/w of ethyl oleate, 12% w/w of Tween 80, 6% w/w of polyethylene glycol 400, and 80% w/w of water was obtained, with a maximum solubility of norartocarpetin up to 1.73 ± 0.21 mg/mL, at least a 1000-fold increase in solubility. The microemulsion base and norartocarpetin-loaded microemulsion were demonstrated to be stable after accelerated and long-term conditions (8 weeks). The norartocarpetin microemulsion still showed strong tyrosinase inhibitory activity and antibrowning effect on fresh-cut apple slices. These combined results indicated that norartocarpetin microemulsion may be suitable as an antibrowning agent for fresh-cut fruits. PMID:25603116

  6. Analytical applications of emulsions and microemulsions.


    Burguera, José Luis; Burguera, Marcela


    Dispersion systems like emulsions and microemulsions are able to solubilize both polar and non-polar substances due to the special arrangement of the oil and aqueous phases. The main advantages of using emulsions or microemulsions in analytical chemistry are that they do not require the previous destruction of the sample matrix or the use of organic solvents as diluents, and behave similarly to aqueous solutions, frequently allowing the use of aqueous standard solutions for calibration. However, it appears that there are many contradictory concepts and misunderstandings often related to terms definition when referring to such systems. The main aim of this review is to outline the differences between these two aggregates and to give an overview of the most recent advances on their analytical applications with emphasis on the potentiality of the on-line emulsification processes. PMID:22817921

  7. Solid lipid nanoparticle preparation by a warm microemulsion based process: influence of microemulsion microstructure.


    Fadda, P; Monduzzi, M; Caboi, F; Piras, S; Lazzari, P


    Warm microemulsions (WME) containing lipids are used as starting systems to obtain solid lipid nanoparticles (SLN) in alternative processes to those based on high pressure homogenization technique. SLN characteristics can be influenced by the microemulsion composition and the specific conditions adopted in the quenching process related to the transformation of WME into nanoparticles. To establish optimized conditions for the production of SLN starting from WME, in a first step of this work we have defined the microstructure of warm microemulsions highlighted in the lecithin (LCT)/water (W)/tripalmitin (TP)/1-butanol (B)/taurocholate sodium salt (ST) phase behavior at 70°C. Moreover, we have further studied the LCT/W/TP/B system by evaluating the effect on the microemulsion area due to the LCT/B weight ratio, the replacement of 1-butanol with different alcohols (ROH), and the addition of taurocholate sodium salt (ST) at different LCT/ST weight ratios. The microstructure of the isotropic phase region obtained in the presence of ST has been characterized by both (1)H NMR PGSE measurements and electrical conductivity. The characteristics of final nanoparticles are discussed taking into account both the microstructure of the parent WME and the conditions of the quenching process leading to SLN. The present results highlight the relevance of the microstructural characteristic of WME to assure the obtainment of SLN with average diameter in the order of 100-2000 nm and narrow size distribution. PMID:23422277

  8. Producing oil-in-water microemulsions from a microemulsion concentrate

    SciTech Connect

    Osterloh, W.T.


    This patent describes a method of recovering oil and hydrocarbons with a microemulsion from an underground hydrocarbon formation penetrated by at least one injection well and at least one production well. It comprises: injecting into a hydrocarbon formation through an injection well a homogeneous oil-in-water microemulsion comprised of oil, brine and surfactant; injecting a drive fluid into the formation through the injection well to push the microemulsion towards a production well; and recovering oil, hydrocarbon and other fluids from the production well.

  9. Hierarchically structured bicontinuous polymeric microemulsions

    SciTech Connect

    Fleury, Guillaume; Bates, Frank S.


    We recently described the synthesis and phase behavior of a new type of CECEC-P multiblock copolymer composed of glassy poly(cyclohexylethylene) (C), semicrystalline poly(ethylene) (E), and elastomeric poly(ethylene-alt-propylene) (P) with symmetric (equal volume) CECEC and P sequences (G. Fleury and F. S. Bates, Macromolecules, 2009, 42, 3598-3610). Here we report the formation and characterization of a multicontinuous structure based on the blending of CEC triblock copolymer and P homopolymer with such a hexablock copolymer along the 50:50 (CEC/P) isopleth. These materials produce a sequence of phases that are correlated with the volume fraction of CECEC-P as evidenced by SAXS and TEM measurements. A percolating bicontinuous mesostructure was identified at volume fractions of hexablock copolymer, f{sub CECEC-P} = 0.10 and 0.125, within the composition range known to result in a bicontinuous morphology in A-B/A/B systems. A solid product was formed by cooling the initially homogeneous ternary mixture from above the melting temperature of the E blocks to room temperature. Crystallization of E leads to microphase separation of C and E and simultaneous ejection of P from CEC (and CECEC) at a larger length scale. The mechanical properties of these materials are inferior to what is anticipated based on pure CEC triblock copolymer, attributable to the low molecular weight and irregular structure of the C/E region sequences. Nevertheless, this study establishes a procedure for producing bicontinuous yet structurally asymmetric materials based on the microemulsion process and extends the concept of a microemulsion to multiblock copolymers.

  10. Effect of water-in-oil microemulsions and lamellar liquid crystalline systems on the precorneal tear film of albino New Zealand rabbits

    PubMed Central

    Chan, Judy; Maghraby, Gamal M El; Craig, Jennifer P; Alany, Raid G


    The aim of this study is to investigate the effect of phase transition water-in-oil (w/o) microemulsions (ME) and liquid crystalline systems (LC) on the precorneal tear film (PCTF). The study used six albino NZ rabbits and monitored the integrity and stability of the PCTF before and after instillation of test formulations. The effects were evaluated by assessment of the PCTF lipid layer using interferometry, tear evaporation rate measurements, and indirect estimation of tear volume. Ocular application of test formulations changed the appearance of the PCTF lipid layer, indicating lipid layer disruption. The recovery time was longer in case of ME compared with an aqueous solution (SOL). The tear evaporation rate was increased after application of both ME and LC systems compared with the SOL, with the LC system showing the greatest effect. Tear volume measurement results revealed minimal changes associated with the instillation of both ME systems. Whilst phase transition w/o ME systems can interact with the PCTF lipid layer in albino New Zealand rabbits, their effect on the volume of resident tears was found to be minimal. PMID:19668396