The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kai Sundmacher - One of the best experts on this subject based on the ideXlab platform.
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decrease of droplet size of the reverse Microemulsion 1 butyl 3 methylimidazolium tetrafluoroborate triton x 100 cyclohexane by addition of water
Journal of Physical Chemistry B, 2008Co-Authors: Yanan Gao, Kai Sundmacher, Liane Hilfert, A VoigtAbstract:In the present contribution, results concerning the role of small amounts of water in the 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4)-in-cyclohexane ionic liquid (IL) reverse Microemulsions are reported. Dynamic light scattering (DLS) revealed that the size of Microemulsion droplets decreased remarkably with increasing water content although water is often used as a polar component to swell reverse Microemulsions. It was thus deduced that the number of Microemulsion droplets was increased which was confirmed by conductivity measurements. The states of dissolved water were investigated by Fourier transform IR (FTIR) spectroscopic analysis showing that water molecules mainly act as bound water. 1H NMR along with two-dimensional rotating frame nuclear Overhauser effect (NOE) experiments (ROESY) further revealed that water molecules were mainly located in the periphery of the polar core of the Microemulsion droplets and behave like a chock being inserted in the palisade layer of the droplet. This ...
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analysis of a technical grade w o Microemulsion and its application for the precipitation of calcium carbonate nanoparticles
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Frank Rauscher, Peter Veit, Kai SundmacherAbstract:Abstract For a directed synthesis of inorganic nanoparticles in water-in-oil (w/o)-Microemulsions the detailed investigation of the Microemulsion system is of particular importance. This study illustrates that the phase behavior of the ternary as well as of the quaternary mixture (with reactants) has to be analyzed to identify Microemulsion regions suitable for particle synthesis. Besides detailed phase prism investigations the Microemulsion, consisting of water/reactant, cyclohexane and Marlipal O13/40, was further characterized. Dynamic light scattering studies have been conducted for determining the droplet size and viscosity measurements have been undertaken to clarify the internal structure. A time scale analysis of the involved processes during particle formation (e.g., droplet exchange, reaction, nucleation, growth and mixing) points out, that the utilization of w/o-Microemulsions for precipitation reactions is an effective way to overcome mixing problems, which usually are present in bulk precipitation. This is demonstrated for the precipitation of CaCO3 from two Microemulsions containing dissolved Na2CO3 and CaCl2, respectively. The influence of Microemulsion composition, initial reactant concentration and holding time on the final particle size and shape was investigated. The resulting CaCO3 nanoparticles have been characterized by means of a transmission electron microscope. Depending on the applied reaction conditions it is shown that different particle sizes and morphologies can be obtained.
Mads Kreilgaard - One of the best experts on this subject based on the ideXlab platform.
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influence of Microemulsions on cutaneous drug delivery
Advanced Drug Delivery Reviews, 2002Co-Authors: Mads KreilgaardAbstract:In attempt to increase cutaneous drug delivery, Microemulsion vehicles have been more and more frequently employed over recent years. Microemulsion formulations have been shown to be superior for both transdermal and dermal delivery of particularly lipophilic compounds, but also hydrophilic compounds appear to benefit from application in Microemulsions compared to conventional vehicles, like hydrogels, emulsions and liposomes. The favourable drug delivery properties of Microemulsions appear to mainly be attributed to the excellent solubility properties. However, the vehicles may also act as penetration enhancers depending on the oil/surfactant constituents, which involves a risk of inducing local irritancy. The correlation between Microemulsion structure/composition and drug delivery potential is not yet fully elucidated. However, a few studies have indicated that the internal structure of Microemulsions should allow free diffusion of the drug to optimise cutaneous delivery from these vehicles.
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nmr characterisation and transdermal drug delivery potential of Microemulsion systems
Journal of Controlled Release, 2000Co-Authors: Mads Kreilgaard, Erik Jonas Pedersen, Jerzy W. JaroszewskiAbstract:Abstract The purpose of this study was to investigate the influence of structure and composition of Microemulsions (Labrasol/Plurol Isostearique/isostearylic isostearate/water) on their transdermal delivery potential of a lipophilic (lidocaine) and a hydrophilic model drug (prilocaine hydrochloride), and to compare the drug delivery potential of Microemulsions to conventional vehicles. Self-diffusion coefficients determined by pulsed-gradient spin-echo NMR spectroscopy and T 1 relaxation times were used to characterise the Microemulsions. Transdermal flux of lidocaine and prilocaine hydrochloride through rat skin was determined in vitro using Franz-type diffusion cells. The formulation constituents enabled a broad variety of Microemulsion compositions, which ranged from water-continuous to oil-continuous aggregates over possible bicontinuous structures, with excellent solubility properties for both lipophilic and hydrophilic compounds. The Microemulsions increased transdermal flux of lidocaine up to four times compared to a conventional oil-in-water emulsion, and that of prilocaine hydrochloride almost 10 times compared to a hydrogel. A correlation between self-diffusion of the drugs in the vehicles and transdermal flux was indicated. The increased transdermal drug delivery from Microemulsion formulations was found to be due mainly to the increased solubility of drugs and appeared to be dependent on the drug mobility in the individual vehicle. The Microemulsions did not perturb the skin barrier, indicating a low skin irritancy.
Liqiang Zheng - One of the best experts on this subject based on the ideXlab platform.
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Microemulsions of n alkylimidazolium ionic liquid and their performance as microreactors for the photocycloaddition of 9 substituted anthracenes
Langmuir, 2009Co-Authors: Jin Zhang, Liqiang Zheng, Bin Chen, Bin Dong, Chenho TungAbstract:The phase behavior of the ternary system consisting of an ionic liquid (1-tetradecyl-3-methylimidazolium bromide [C14mim]Br), p-xylene, and water were investigated. Depending on the composition of the ternary system, formation of hexagonal and lamellar liquid crystals as well as Microemulsions was observed. 1H NMR spectroscopy study, 2D ROESY spectroscopic analysis, and rheological measurements of the Microemulsions indicated that p-xylene is preferably located in the hydrophobic core and the palisade shells of the Microemulsions. The sizes of the Microemulsion droplets for the samples with water/[C14mim]Br ratio of 78:22 are measured by both dynamic light scattering (DLS) and transmission electron microscopy with the freeze−fracture technique (FF-TEM). Upon change of the mole ratio of the solubilized xylene to [C14mim]Br from 0 to 2.4, the diameters of the Microemulsion droplets increase from ca. 20 to 90 nm and size distribution gets broad. These Microemulsions can solubilize and preorientate anthracene...
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second virial coefficient of bmimbf4 triton x 100 cyclohexane ionic liquid Microemulsion as investigated by microcalorimetry
Langmuir, 2008Co-Authors: Shaohua Zhang, Liqiang Zheng, Yanan GaoAbstract:The second virial coefficient of the ionic liquid (IL) Microemulsion was obtained for the first time using microcalorimetry. The heat of dilution of the Microemulsion solutions was measured by isothermal titration microcalorimetry (ITC), and the second virial coefficient was derived from the heat of dilution and the number density of the IL Microemulsion solutions on the basis of a hard-sphere interaction potential assumption and as a function of the second-order polynomial. The validity of the second virial coefficient was confirmed by the percolation behavior of different ionic liquid Microemulsion solutions of Triton X-100 in cyclohexane with or without added salts. The information obtained from the second virial coefficient shows that the interactions between ionic liquid Microemulsion droplets are much stronger than those for traditional Microemulsions, which may be attributed to the relatively larger size of the Microemulsion droplets.
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a cyclic voltammetric technique for the detection of micro regions of bmimpf6 tween 20 h2o Microemulsions and their performance characterization by uv vis spectroscopy
Green Chemistry, 2006Co-Authors: Na Li, Liqiang Zheng, Xueyan Zhao, Shaohua Zhang, Ganzuo LiAbstract:As green solvents, ionic liquids (ILs) can be substitutes for traditional organic solvents, and form useful Microemulsions with water. Microemulsions consisting of the IL, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), the non-ionic surfactant Tween 20 and water were formed at 30.0 °C, and the phase behavior of the ternary system was investigated. Three regions of the Microemulsions: water-in-bmimPF6 (W/IL), bicontinuous, and bmimPF6-in-water (IL/W) were identified by cyclic voltammetry using potassium ferrocyanide K4Fe(CN)6 as an electroactive probe. The polarity of the Microemulsion environment was investigated by UV-Visible spectroscopy using methyl orange as a probe. Use of the ionic compound K3Fe(CN)6 in UV-Visible measurements revealed that the bmimPF6/Tween 20/H2O Microemulsions could solubilize salt species into the Microemulsion droplets. Moreover, the solubilization of riboflavin in the Microemulsions was also shown by UV-Visible spectra. These results show that these IL-based Microemulsions have potential in the production of metal nanomaterials, in biological extractions or as solvents for enzymatic reactions.
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structural studies of 1 butyl 3 methylimidazolium tetrafluoroborate tx 100 p xylene ionic liquid Microemulsions
ChemPhysChem, 2006Co-Authors: Jin Zhang, Xinwei Li, Hongyan Xu, Liqiang Zheng, Xueyan Zhao, Li YuAbstract:The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4 ) forms nonaqueous Microemulsions with p-xylene, with the aid of the nonionic surfactant TX-100. The phase behavior of the ternary system is investigated, and three microregions of the Microemulsions-ionic liquid-in-oil (IL/O), bicontinuous, and oil-in-ionic liquid (O/IL)-are Identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O Microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF 4 ), which is a similar phenomenon to that observed for typical water-in-oil (W/O) Microemulsions, suggesting the formation of IL/O Microemulsions. The microstructural characteristics of the Microemulsions are investigated by FTIR and 1 H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX-100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF 4 into the core of the TX-100 aggregates. In addition, the micropolarity of the Microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the Microemulsion droplets is obtained in the IL Microemulsion. Finally, a plausible structure for the IL/O Microemulsion is presented.
Nissim Garti - One of the best experts on this subject based on the ideXlab platform.
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microstructure considerations of new five component winsor iv food grade Microemulsions studied by pulsed gradient spin echo nmr conductivity and viscosity
Langmuir, 2003Co-Authors: Anan Yaghmur, And Brian Antalek, Abraham Aserin, Nissim GartiAbstract:The microstructure of an unusual Winsor IV isotropic region of five-component Microemulsions based on nonionic surfactants was studied. The Microemulsions are composed of R(+)-limonene, water, propylene glycol (PG), ethanol (EtOH), and polyoxyethylene sorbitan monostearate (Tween 60) with a 1:1:3 R(+)-limonene/ethanol/surfactant weight ratio. The phase diagrams of the system are characterized by an extended single continuous isotropic region starting from an oil-rich solution containing no aqueous phase (reverse micelles) to the water/propylene glycol (1/1) corner (swollen direct micelles). The Microemulsions seem to be attractive for food applications. The microstructure changes gradually, smoothly, and continuously upon increasing the aqueous phase content. The Microemulsion transforms from a water-in-oil (W/O) Microemulsion to a bicontinuous phase and to an oil-in-water (O/W) Microemulsion. The microstructure of the Microemulsion along a selected dilution line, is probed using pulsed gradient spin−echo...
Jin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Microemulsions of n alkylimidazolium ionic liquid and their performance as microreactors for the photocycloaddition of 9 substituted anthracenes
Langmuir, 2009Co-Authors: Jin Zhang, Liqiang Zheng, Bin Chen, Bin Dong, Chenho TungAbstract:The phase behavior of the ternary system consisting of an ionic liquid (1-tetradecyl-3-methylimidazolium bromide [C14mim]Br), p-xylene, and water were investigated. Depending on the composition of the ternary system, formation of hexagonal and lamellar liquid crystals as well as Microemulsions was observed. 1H NMR spectroscopy study, 2D ROESY spectroscopic analysis, and rheological measurements of the Microemulsions indicated that p-xylene is preferably located in the hydrophobic core and the palisade shells of the Microemulsions. The sizes of the Microemulsion droplets for the samples with water/[C14mim]Br ratio of 78:22 are measured by both dynamic light scattering (DLS) and transmission electron microscopy with the freeze−fracture technique (FF-TEM). Upon change of the mole ratio of the solubilized xylene to [C14mim]Br from 0 to 2.4, the diameters of the Microemulsion droplets increase from ca. 20 to 90 nm and size distribution gets broad. These Microemulsions can solubilize and preorientate anthracene...
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structural studies of 1 butyl 3 methylimidazolium tetrafluoroborate tx 100 p xylene ionic liquid Microemulsions
ChemPhysChem, 2006Co-Authors: Jin Zhang, Xinwei Li, Hongyan Xu, Liqiang Zheng, Xueyan Zhao, Li YuAbstract:The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4 ) forms nonaqueous Microemulsions with p-xylene, with the aid of the nonionic surfactant TX-100. The phase behavior of the ternary system is investigated, and three microregions of the Microemulsions-ionic liquid-in-oil (IL/O), bicontinuous, and oil-in-ionic liquid (O/IL)-are Identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O Microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF 4 ), which is a similar phenomenon to that observed for typical water-in-oil (W/O) Microemulsions, suggesting the formation of IL/O Microemulsions. The microstructural characteristics of the Microemulsions are investigated by FTIR and 1 H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX-100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF 4 into the core of the TX-100 aggregates. In addition, the micropolarity of the Microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the Microemulsion droplets is obtained in the IL Microemulsion. Finally, a plausible structure for the IL/O Microemulsion is presented.