Fat crystals: A tool to inhibit molecular transport in W/O/W double emulsions

Water-in-oil-in-water (W/O/W) double emulsions are a promising technology for encapsulation applications of water soluble compounds with respect to functional food systems. Yet molecular transport through the oil phase is a well-known problem for liquid oil-based double emulsions. The influence of network crystallization in the oil phase of W/O/W globules was evaluated by NMR and laser light scattering experiments on both a liquid oil-based double emulsion and a solid fat-based double emulsion. Water transport was assessed by low-resolution NMR diffusometry and by an osmotically induced swelling or shrinking experiment, whereas manganese ion permeation was followed by means of T₂-relaxometry. The solid fat-based W/O/W globules contained a crystal network with about 80% solid fat. This W/O/W emulsion showed a reduced molecular water exchange and a slower manganese ion influx in the considered time frame, whereas its globule size remained stable under the applied osmotic gradients. The reduced permeability of the oil phase is assumed to be caused by the increased tortuosity of the diffusive path imposed by the crystal network. This solid network also provided mechanical strength to the W/O/W globules to counteract the applied osmotic forces.     

W／O／W乳液的渗透溶胀与夹带溶胀

研究了W/O/W乳液的溶胀,实验结果表明,渗透溶胀随内外相溶液间的渗透压差、表面活性剂及载体浓度的增大而增加,但随膜粘度的增加而降低,渗透压差较高时,水渗透的影响大于夹带的影响;膜相中含氧化合物对溶胀的影响大于含氮化合物,采用Span 80作乳化剂时,比采用E 644渗透溶胀约高6倍,夹带溶胀也较高;重复聚结再分散使夹带溶胀急剧增加,因而多级混合澄清槽对液膜操作似不适用。     

Alterations in phospholipid bilayers caused by sodium dodecyl sulphate/triton X-100 mixed systems

The mechanisms governing the subsolubilizing and solubilizing interaction of sodium dodecyl sulphate (SDS)/Triton X-100 mixtures and phosphatidylcholine liposomes were investigated. Permeability alterations were detected as a change in 5(6)-carboxy-fluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light-scattered by liposome suspensions. Three parameters were described as the effective surfactant/lipid molar ratios (Re) at which the surfactant system a) resulted in 50% of CF release (Re _50%CF); b) saturated the liposomes (Re _SAT;c) led to a complete solubilization of these structures (Re _SOL). From these parameters the corresponding surfactant partition coefficientsK _50%CF,K _SAT andK _SOL were determined. The free surfactant concentrationsS _W were lower than the mixed surfactant CMCs at subsolubilizing level, whereas they remained similar to these values during saturation and solubilization of bilayers in all cases. Although theRe increased as the mole fraction of the SDS rose (X _SDS), theK parameters showed a maximum atX _SDS values of about 0.6, 0.4 and 0.2 forK _50%CF,K _SAT andK _SOL respectively. Thus, the higher the surfactant contribution in surfactant/lipid system, the lower theX _SDS at which a maximum bilayer/water partitioning of mixed surfactant systems added took place and, consequently, the lower the influence of the SDS in this maximum bilayer/water partitioning.Abbreviations PC Phosphatidylcholine - PIPES piperazine-1,4 bis (2-ethanesulphonic acid) - SDS sodium dodecyl sulphate - X _SDS mole fraction of sodium dodecyl sulphate in the mixed system - CF 5(6)-carboxyfluorescein - Re effective surfactant/lipid molar ratio - Re _50%CF effective surfactant/lipid molar ratio for 50% CF release - Re _SAT effective surfactant/lipid molar ratio for bilayer saturation - Re _SOL effective surfactant/lipid molar ratio for bilayer solubilization - S _W surfactant concentration in the aqueous medium - S _{W, 50%CF} surfactant concentration in the aqueous medium for 50% CF release - S _{W, SAT} surfactant concentration in the aqueous medium for bilayer saturation - S _{W, SOL} surfactant concentration in the aqueous medium for bilayer solubilization - S _B surfactant concentration in the bilayers - K bilayer/aqueous phase surfactant partition coefficient - K _50%CF bilayer/aqueous phase surfactant partition coefficient for 50% CF release - K _SAT bilayer/aqueous phase surfactant partition coefficient for bilayer saturation - K _SOL bilayer/aqueous phase surfactant partition coefficient for bilayer solubilization - PL phospholipid TLC-FID, thin-layer chromatography/flame ionization detection system - PI polydispersity index - CMC critical micellar concentration - r ² regression coefficient     

The structural chemistry of Bi14MO24 (M=Cr, Mo, W) phases: bismuth oxides containing discrete MO4 tetrahedra

The phases Bi₁₄MO₂₄ (M=Cr, Mo, W) have been studied using differential scanning calorimetry, variable temperature X-ray powder diffraction and neutron powder diffraction. All three compounds were found to undergo a phase change, on cooling, from the previously reported tetragonal symmetry (I4/m) to monoclinic symmetry (C2/m). Transition temperatures were determined to be ∼306 K (M=W) and ∼295 K (M=Mo), whereas a gradual transition between 275 and 200 K was observed for M=Cr. The high and low temperature structures are very similar, as indicated by the relationship between the monoclinic and tetragonal unit cell parameters: a_m=√2a_t, b_m=c_t, c_m=a_t, β∼135°. High-resolution neutron powder diffraction data, collected at 400 and 4 K, were used to establish the nature of the transition, which was found to involve a reduction in the statistical possibilities for orientation of the MO₄ tetrahedra. However, in both tetragonal and monoclinic variants, a degree of orientational disorder of the tetrahedra occurs to give partially occupied sites in the average unit cell.     

Dynamic surface tension,critical micelle concentration,and activity coefficients of aqueous solutions of nonyl phenol ethoxylates

Dynamic surface tensions, σ(t) for aqueous solutions of nonyl phenol ethoxylates (NPEOs) at the temperature 298.15 K were measured using a Lauda drop volume tensiometer. The non-ionic surfactants analyzed in this work were Tergitol NP-9, NP-35 and NP-40. By using the classical Ward and Torday equation, the diffusion coefficient for each bulk surfactant concentration was calculated. The equilibrium surface tension values were determined by extrapolating the dynamic surface tension to t → ∞ on the σ(t) vs. t^−1/2 curves. These values were used to determine the critical micelle concentrations (CMC) of the surfactant aqueous solutions as well as to calculate the infinite dilution activity coefficient of the surfactant, following a model that combines the Volmer surface equation of state and the Gibbs adsorption equation.     

Wearable membranes from zirconium-oxo clusters cross-linked polymer networks for ultrafast chemical warfare agents decontamination

The urgent need for immediate personal protection against chemical warfare agents （CWAs） spurs the requirement on robust and highly efficient catalytic systems that can be conveniently integrated to wearable devices.Herein,as a new concept for CWA decontamination catalyst design,sub-nanoscale,catalytically active zirconium-oxo molecular clusters are covalently integrated in flexible polymer network as crosslinkers for the full exposure of catalytic sites as well as robust framework structures.Th...     

Response surface methodology for the modelling of copper removal from aqueous solutions using micellar-enhanced ultrafiltration

Response surface methodology (RSM) was used to study the cumulative effect of the various parameters, namely surfactant (sodium dodecyl sulphate (SDS), anionic) concentration, pH, and surfactant/metal molar ratio and to optimise the process conditions for the maximum removal of copper from aqueous solutions via micellar-enhanced ultrafiltration (MEUF). For obtaining the mutual interaction between the variables and optimising these variables, a central composite design (CCD) by use of response surface methodology was employed. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant. The model was statistically tested and verified by experimentation. Values of pH at the range of ca. 7.5 were very successful for the separation. The maximum rejection coefficient of 98.4% was obtained for the following optimal conditions: SDS/Cu²⁺ molar ratio *r = 7.85, *pH 7.36, *C_surf = 6.82 g/l SDS. A modification of micellar-enhanced ultrafiltration for the removal of copper from aqueous solutions was studied by the implementation of sodium dodecyl sulphate–polyethylene glycol (PEG) aggregates. A full factorial design (FFD) was employed for studying the effect of molar ratio of surfactant/metal, pH and mass ratio of surfactant/polymer at a constant concentration of surfactant equal to 5 g/l. The comparison of the two systems in the region of their common factors showed that the addition of polyethylene glycol caused a slight increase in rejection coefficient of copper but also could function as ‘scavenger’ for surfactant species.     

Synthesis and characterization of PbS nanorods in W/O microemulsion system

PbS nanorods have been successfully synthesized in water-in-oil (W/O) microemulsion containing non-ionic surfactant OP, n-pentanol, cyclohexane, and aqueous solution. The effects of the molar ratio of water to surfactant (ω₀), the concentration of reactants and the ageing time on the morphologies of PbS nanoparticles were investigated. The microstructures, morphologies and properties of the synthesized products were characterized by means of X-ray diffraction, transmission electron microscopy, and ultraviolet-visible (UV-VIS) absorption spectroscopy, respectively. The results showed that the synthesized rod-like products are composed of cubic phase PbS. These nanorods have an average diameter of about 100 nm, and an average length of about 500 nm. In the UV-VIS absorption spectrum, the absorption edge of PbS nanorods exhibit a blue shift compared with that of bulk PbS, indicating the quantum confinement effect of PbS nano-particles     

A general synthesis for ditungsten tetracarboxylates. Preparation of WW quadruple bonds by reductive-elimination (alkyl group disproportionation) from 1,2-diethyl compounds with WW triple bonds

A general high yield synthesis for W₂(O₂CR)₄ compounds is proposed based on eqn (1), wherein a WW triple bond is converted to a quadruple bond, and this has been established for RMe, Et and t-Bu.W₂Et₂(NMe₂)₄ + 4RCOOCOR → W₂(O₂CR)₄ + 4RCONMe₂ + C₂H₄ + C₂H₆ (1)     

Swelling and network parameters of crosslinked thermoreversible hydrogels of poly(N-ethylacrylamide)

Samples of Poly(N-ethylacrylamide) (PEA) have been synthesized by free radical polymerization in water using N,N′-methylene bis-acrylamide (BIS) as crosslinker. Hydrogels obtained by swelling them in water, 15 wt% KCl and 1 wt% sodium dodecyl sulphate (SDS) were examined by gravimetric, dimensional and compression-strain measurements to afford values of swelling ratio, polymer-solvent interaction parameters, elastic moduli and effective crosslinking density ν_e. Crosslinking inefficiency is evidenced by the low value (0.23) of ν_e relative to the theoretical crosslinking density ν_t based on the content of BIS in the synthesis. A small but finite extrapolated value of ν_e at ν_t = 0 is indicative of hydrophobic physical interactions. In water at 298 K increasing the content of BIS leads to a decrease in swelling and increases in values of elastic moduli and polymer-water interaction parameter. At a fixed content of BIS the values of ν_e and the elastic moduli exhibit an unusual increase with temperature, the crosslinking thus being thermally reversible. It is proposed that this results from a balance between hydrophobic interaction and breakage of hydrophilic hydrogen bonding. Although KCl in the medium decreases the swelling compared with that in water, the opposite effect occurs on incorporation of SDS, which is assumed to confer some polyelectrolyte character to the PEA chains. The finding, that these two swelling media reduce the values of ν_e and elastic moduli cf the value in water, has not been resolved satisfactorily.     

Assembly properties of Triton X-100/phosphatidylcholine aggregates during liposome solubilization

The assembly properties of the nonionic surfactant Triton X-100 and phosphatidylcholine (PC) aggregates during the overall solubilization process of PC liposome were investigated. Permeability alterations were detected as a change in 5(6)-carboxyfluorescein (CF) released from the interior of vesicles and bilayer solubilization as a decrease in the static light scattered by liposome suspensions. A direct dependence was established between the bilayer/aqueous phase surfactant partition coefficients (K), the growth of vesicles and the leakage of entrapped CF in the initial interaction steps (surfactant to phospholipid molar ratioRe up to 0.2). These changes may be related to the increasing presence of surfactant molecules in the outer monolayer of vesicles. In theRe range 0.2–0.35 the coexistence of a low vesicle growth with a constant increase of CF release may be correlated with the decrease inK (increased rate of flip-flop of surfactant molecules). Furthermore, in theRe range between 0.64 and 2.0 (lytic levels) almost a linear dependence was detected between the composition of these aggregates (Re) and the decrease in both the surfactant-PC aggregate size and the static light scattered by the system. This dependence was not observed in the last solubilization steps (Re range 2.0–2.60) possibly due to the increased formation of mixed micelles in this interval. The fact that the free Triton X-100 concentration at sublytic and lytic levels showed respectively lower and similar values than its critical micelle concentration confirms that permeability alterations and solubilization were determined respectively by the action of surfactant monomer and by the formation of mixed micelles.Abbreviations PC phosphatidylcholine - PIPES piperazine-1,4 bis(2-ethanesulphonic acid) - T_X-100 Triton X-100 - CF 5(6)-carboxyflucrescein - Re enective surfactant/lipid molar ratio - Re _SAT effective surfactant/lipid molar ratio for bilayer saturation - Re _SOL enective surfactant/lipid molar ratio for bilayer solubilization - S _W surfanctant concentration in the aqueous medium - S _B surfactant concentration in the bilayers - S _T total surfactant concentration - K bilayer/aqueous phase surfactant partition coefficient - K _SAT bilayer/aqneous phase surfactant partition coefficient for bilayer saturation - K _SOL bilayer/aqueous phase surfactant partition coefficient for bilayer solubilization - PL phospholipid - TLC-FID thinlayer chromatography/flame ionization detection system - PI polydispersity index - CMC critical micellar concentration - r ² regression coefficient     

Preparation and characterization of shuttle-like α-Fe2O3 nanoparticles by supermolecular template

Shuttle-like α-Fe₂O₃ nanoparticles have been successfully synthesized via a new soft-template route using polyethylene glycol (PEG) as polymer, cetyltrimethylammonium bromide (CTAB) as surfactant and FeCl₃·6H₂O as iron source materials. Meanwhile, spherical α-Fe₂O₃ nanoparticles are also fabricated under the similar conditions without surfactant and polymer. The resultant products are characterized by means of thermalgravimetric analysis (TGA), powder X-ray diffraction (XRD), infrared (IR) spectroscopy, transmission electron micrograph (TEM), X-ray photoelectron spectra (XPS) and magnetization measurements. The homogeneous α-Fe₂O₃ nanoparticles with shuttle-like shape have an average length of 120 nm and a mean diameter of about 50 nm in the middle part (an average aspect ratio of about 2.5) whereas spherical α-Fe₂O₃ nanoparticles have a mean particle diameter of about 35 nm. Magnetic hysteresis measurements reveal that shuttle-like α-Fe₂O₃ nanoparticles display normal ferromagnetic behaviors while spherical α-Fe₂O₃ nanoparticles exhibit weak ferromagnetic behaviors at room temperature. The two types of α-Fe₂O₃ exhibit hysteretic features with the remanence and coercivity of 0.156 emu/g and 664 Oe, 0.048 emu/g and 110 Oe, respectively. The higher remanent magnetization and coercivity of shuttle-like α-Fe₂O₃ nanoparticles may be associated with the aspect ratio of α-Fe₂O₃ since shape anisotropy would exert a tremendous influence on their magnetic properties.     

Thermodynamic behaviour of binary mixture of 1,3-dimethoxyimidazolium bis(trifluoromethyl-sulfonyl)imide and water

The osmotic coefficient value of binary aqueous solution containing ionic liquid was obtained by using vapour-pressure osmometry technique. The change in activity and vapour pressure depression of solvent on addition of 1,3-dimethoxyimidazolium bis(trifluoromethylsulfonyl) imide ((OMe)₂Im:NTf₂) to water have been estimated at two different temperatures (T =313 K and 323 K). The experimental osmotic coefficient values of (OMe)₂Im:NTf₂ at different molality were correlated by extended Pitzer model of Archer and the ion interaction parameters were evaluated. The correlation coefficients obtained from this model were used to estimate the mean molal activity coefficient, and excess Gibbs free energy of this mixture. The osmotic coefficient values were decreased with increase in molality of the ionic liquid within the solution. The osmotic coefficient values were found to be increased with increase in temperature of the system.     

Preparation and characterization of W/O/W double emulsions containing MgCl2

The aim of present study is to design food-grade W/O/W double emulsions encapsulating Mg²⁺ and investigate their stability and release properties. Prepared emulsions were characterized in terms of global stability, particle size, rheological properties, and interfacial tension. The double emulsions were sensitive to the presence of magnesium salt. The mean droplet size and viscosity of emulsions was positively correlated to MgCl₂ concentration. The microscopic pictures confirmed that the water transfer between two aqueous phases caused the reduced stability of double emulsions. It was suggested that swelling breakdown was the main mechanism in controlling the release of encapsulated Mg²⁺.     

Vanadotungstate isopolyanions with V: W = 4: 2 in aqueous solutions and in crystalline salts

Polycondensation in solutions containing HVO ₄ ^2? and WO ₄ ^2? ions in the 4: 2 ratio and the overall concentration c _v+w ⁰ = 5 × 10^?3 mol/l is studied. Speciation diagrams for individual and mixed vanadium(V) and tungsten(VI) polyanions are plotted based on the results of simulation for pHs 2–13 (Z = 0–3.50) on the nitrate ion background. The 6-isopolyvanadotungstate formed in the solutions retain the initial V: W ratio. The concentration formation constants for the vanadotungstate isopolyanions in aqueous solutions are determined. Compounds Tl₆V₄W₂O₁₉ · 5H₂O, Pr₂V₄W₂O₁₉ · 14H₂O, and Na₅HV₄W₂O₁₈ · 27H₂O are synthesized. Their formulas are identified using chemical analysis and IR spectroscopy.     

Order-disorder in In perovskites: The example of A(In2/3B″1/3)O3 (A=Ba, Sr; B″=W, U)

We describe the preparation and structural characterization of four In-containing perovskites from neutron powder diffraction (NPD) and X-ray powder diffraction (XRPD) data. Sr₃In₂B″O₉ and Ba(In_2/3B″_1/3)O₃ (B″=W, U) were synthesized by standard ceramic procedures. The crystal structure of the W-containing perovskites and Ba(In_2/3U_1/3)O₃ have been revisited based on our high-resolution NPD and XRPD data, while for the new U-containing perovskite Sr₃In₂UO₉ the structural refinement was carried out from high-resolution XRPD data. At room temperature, the crystal structure for the two Sr phases is monoclinic, space group P2₁/n, where the In atoms occupy two different sites Sr₂[In]_2d[In_1/3B″_2/3]_2cO₆, with a=5.7548(2) Å, b=5.7706(2) Å, c=8.1432(3) Å, β=90.01(1)° for B″=W and a=5.861(1) Å, b=5.908(1) Å, c=8.315(2) Å, β=89.98(1)° for B″=U. The two phases with A=Ba should be described in a simple cubic perovskite unit cell (S.G. Pm3¯m) with In and B″ distributed at random at the octahedral sites, with a=4.16111(1) Å and 4.24941(1) Å for W and U compounds, respectively.     

Hydrophilic and hydrophobic nano-sized Mn3O4 particles

Mn₃O₄ Hausmanite nanoparticles were prepared in aqueous solution by using metallic salt and hydrazine as precursor and reducing agent, respectively. The crystallite sizes ranged from 10 to 20 nm and the particle diameter distribution was very narrow and estimated between 20 and 30 nm. Influence of some parameters such as temperature, time of reaction, surfactant nature was studied for a synthesis in an aqueous medium. The as-made manganese oxides particles could be dispersed in an organic solvent containing stabilizing agents, according to perform the synthesis in an H₂O/n-hexan two-phase medium. These nanoparticles were characterized by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopies and nitrogen absorption measurements.     

Enthalpies of transfer of pentanol from water to sodium dodecylsulfate-dodecyl-dimethylamine oxide-water mixtures

At a given surfactant-surfactant ratio, the enthalpies of transfer ΔH (W→W+S) of pentanol 0.03m from water to sodium dodecylsulfate (NaDS)-dodecyldimethylamine oxide-water mixtures as functions of the surfactants mixture concentration (m _t) were determined. ForX _NaDS=0.9, ΔH (W→W+S) increases monotonically withm _t such as observed for pure surfactants. ForX _NaDS=0.12 and 0.3, ΔH (W→W+S) increases withm _t up to 0.12m beyond which it decreases withm _t. AtX _NaDS=0.6, two monotonic curves can be distinguished in the ΔH (W→W+S)vs. m _t trend. Experimental data were fitted through an equation previously reported for additives in pure surfactants derived by assuming the pseudo-phase transition model for the micellization and a mass action model for the distribution of the additive between the aqueous and the micellar phases. This method did permit to simultaneously obtain the distribution constant of the alcohol between the aqueous and the micellar phase (and, then, the standard free energy of transfer) and its enthalpy of transfer from the aqueous to the micellar phases. By combining these properties the standard entropies of transfer were calculated. From these results, the excess properties of pentanol in the mixed micelles were calculated as a function of the mixture composition. The excess enthalpies and entropies are positive and compensate with each other leading to null values for the excess free energies in the whole range of the mixed micelles composition.     

Structural investigation of tetraperoxo complexes of Mo(VI) and W(VI): X-ray and theoretical studies

The family of very unstable tetraperoxo compounds has been prepared from aqueous solutions containing H₂O₂ and salts of Mo(VI) or W(VI). The crystal structures of Na₂[Mo(O₂)₄]·4H₂O and Na₂[W(O₂)₄]·4H₂O have been determined from single-crystal data, while the crystal structures of Rb₂[Mo(O₂)₄], Cs₂[Mo(O₂)₄], Rb₂[W(O₂)₄] and Cs₂[W(O₂)₄] have been determined from powder X-ray diffraction data. The compounds were also characterised by IR spectroscopy and the number of peroxo groups was determined by titration methods. By means of the density functional theory (DFT) method, the geometry and stability of tetraperoxo complexes have been studied. Even though in all tetraperoxo complexes the central atom Mo(VI), W(VI) or V(V) is surrounded by four peroxo groups and the geometry of the [Me(O₂)₄]ⁿ⁻ anion is essentially the same, the investigated compounds differ in stability and colour and crystallise in different crystallographic systems.     

ESR study on the stability of W/O gel-emulsions

W/O gel-emulsions (high-internal-phase-volume-ratio emulsions) form in water (or brine) /tetraethyleneglycol dodecyl ether/heptane system above the HLB (hydrophile-lipophile balance) temperature of the system. A salt, which largely decreases cloud temperature in a water-nonionic surfactant system, makes the surfactant film rigid and the gel-emulsions hence become very stable. The effect of aded salt on the apparent order parameter S, and the isotropic hyperfine splitting constant a _N in gel-emulsions was determined by the ESR spin probe method using 5-doxyl stearic acid as the spin probe. The apparent order parameter S, and the isotropic hyperfine splitting constant a _N increase with increasing salinity in Na₂SO₄, CaCl₂, and NaCl systems. It is considered that the surfactant molecules are tightly packed in these systems and this tendency is highly related to the stability of gel-emulsions. The salt dehydrates the hydrophilic moiety of surfactant and hence the lateral interactions of surfactant molecular layer at the water-oil interface increases.The observed difference in the apparent order parameter between the ordinary emulsions and the gel-emulsions suggests that most of the surfactant molecules are adsorbed at the oil-water interface (the surface of the water droplet) in gel-emulsions.