Search results for "microemulsion"

Spin-crossover nanocrystals with magnetic, optical, and structural bistability near room temperature.

2008

TiO2 nanocrystalline powders by W/O microemulsion synthesis

2012

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids

2021

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1–5 μm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 μm) and catalyzes Brönsted rather …

Physico-chemical properties of dense water/copper(II) bis(2-ethylhexyl) sulfosuccinate/CCl4 microemulsions

2007

Measurements of some physico-chemical properties (density, viscosity, conductance, infra-red spectra) of water/copper(II) bis(2-ethylhexyl) sulfosuccinate (Cu(DEHSS)2)/CCl4 microemulsions, as a function of the volume fraction O of the dispersed phase (0 < O < 0.6) and of the molar ratio R (R = [water]/[DEHSS−]), have been performed at 25 °C. At each value of R, the density of the micellar phase is practically independent of O whereas the viscosity of microemulsions diverges above threshold O values. A divergent behavior for the electrical conductivity has also been observed but only at certain R values. These results, together with those from infra-red spectra, suggest that in percolated mi…

Modulation of retention and selectivity in oil-in-water microemulsion liquid chromatography: A review

2019

Microemulsions (MEs) are stable, isotropically clear solutions consisting of an oil and water stabilized by a surfactant and a co-surfactant. Oil-in-water microemuslion liquid chromatography (MELC) is a relatively new chromatographic mode, which uses an O/W ME as mobile phase. Retention, selectivity and efficiency can be modified by changing the concentration of the ME components and the ratio between the aqueous and oil phases. This work makes a critical survey on the information found in the literature about the mobile phase compositions that lead to the creation of successful O/W ME mobile phases, as well as the effect of pH for ionizable compounds and temperature. The viability of perfo…

Physicochemical Investigation of Nanostructures in Liquid Phases: Ytterbium Nitrate Ionic Clusters Confined in Ytterbium Bis(2-ethylhexyl) Sulfosucci…

2007

The confinement of finite amounts of ytterbium nitrate in the nanoscopic space of ytterbium bis(2-ethylhexyl)sulfosuccinate (Yb(DEHSS) 3 ) reversed micelles dispersed in n-heptane has been investigated by UV-vis-NIR, FT-IR, and SAXS. The analysis of the experimental data is consistent with the hypothesis that Yb(NO 3 ) 3 is distributed among reversed micelles as small size ionic clusters surrounded by the Yb 3+ surfactant counterions and anionic heads while the surfactant alkyl chains point toward the solvent medium. As a consequence of confinement and interfacial effects, the ionic clusters display photophysical properties different from those in the bulk state or isolated species. Moreove…

Physicochemical Investigation of the Solubilization of Ytterbium Nitrate in AOT Reverse Micelles and Liquid Crystals

2006

A wide investigation of the solubilization of the water-soluble salt Yb(NO3)(3) in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles and AOT liquid crystals has been carried out. After saturation of water/AOT/organic solvent w/o microemulsions with pure Yb(NO3)(3), the Yb(NO3)(3)/AOT composites were prepared by complete evaporation under vacuum of the volatile components (water and organic solvent) of the salt-containing microemulsions. It was observed that these composites can be totally dissolved in pure n-heptane or CCl4, allowing the solubilization of a noticeable amount of Yb(NO3)(3) in quite dry apolar media. By UV-vis-NIR, FT-IR, and H-1 NMR spectroscopies, some informati…

Oil-In-Water Microemulsion Liquid Chromatography

2018

Oil-in-water microemulsions (O/W MEs) are obtained spontaneously by mixing two immiscible liquids (water and oil) in the presence of a surfactant. A co-surfactant is also often needed for ME stabil...

Preparation and characterisation of Na 2 S and ZnSO 4 nanoparticles in water/sodium bis(2-ethylhexyl)sulphosuccinate/ n -heptane microemulsions

2001

The preparation procedure for nanoparticles of the water-soluble salts Na2S and ZnSO4, two commonly used reagents to synthesise ZnS nanoparticles, by evaporation of volatile components of salt-containing water-in-oil microemulsions is described. In suitable conditions, the evaporation leads to the formation of dry salt–surfactant composites and to the formation of Na2S or ZnSO4 nanoparticles. It was found that the salt–surfactant composites can be totally redissolved in a dry apolar organic solvent allowing the formation of virtually water-free solutions containing a considerable amount of the water-soluble salts. The presence of nanoparticles in these solutions and in the composites has be…

Quasi-elastic light scattering in polymer-containing microemulsion

1996

Abstract Quasi-elastic light scattering (QELS) was performed in dilute water in oil microemulsion stabilized by AOT surfactant. The water-soluble polyethylene oxide (PEO) with low molecular weight (8000) added to the microemulsion seems to be confined within the aqueous microphase, since PEO is insoluble in oil (n-heptane). The measurements by QELS of diffusion coefficient, at dilute concentrations, allow determination of the size of the droplets. The phase diagram of the microemulsion undergoes remarkable changes on addition of the polymer. The results show that at fixed R ( water surfactant ratio) the droplets decrease their size as the concentration of polymer increases. This occurrence …