Water Microemulsion System Research Articles

Investigation of interfacial composition and thermodynamic stability of 14-n-14/alcohol/oil/water microemulsions by dilution method

The interfacial composition and thermodynamic parameters of W/O 14-n-14/alcohol/oil/water microemulsions were investigated by dilution method in terms of the number of linking groups n (n = 3–6), water content, alcohol and oil types. The gemini/alcohol/oil/water microemulsion system formed spontaneously with negative Gibbs free energy at 25 ℃. The long carbon chain of alcohol facilitated the formation of W/O microemulsion. With increasing carbon chain length of the oil phase, the absolute value of the Gibbs free energy initially increased and subsequently decreased. With an increasing number of linking groups in gemini surfactants, the amount of alcohol that was required in the interfacial layer increased, thereby hindering alcohol movement from the continuous phase to the interface layer, and the absolute value of the Gibbs free energy also decreased, suggesting that a small value of n is beneficial to the stability of microemulsions.

Synthesis of Ni/CaO-γ-Al2O3@Ru Core Shell via Micro-Emulsion Method for Bio-oil Steam Reforming of Empty Fruit Bunch

Hydrogen production from bio-oil steam reforming plays an important role in the development of renewable hydrogen from biomass to produce the cleanest fuel. However, the existence of coke and low carbon conversion are problems that have been found in some studies. The purpose of this study was to reduce coke formation and to enhance carbon conversion by using core shell nanoparticle catalysts that could increase of surface area, support interaction and its catalytic activity for hydrogen production from bio-oil steam reforming of empty fruit bunch (EFB). Ni/CaO-γ-Al2O3@Ru core shells were prepared by CTAB/n-hexanol/n-hexane/water micro-emulsion system. The catalysts were characterized by means XRD, BET, FESEM-EDS and TEM. Bio-oil aqueous fraction was analyzed by using GC-MS. Carbon conversion and hydrogen yield by using Ni/CaO-γ-Al2O3@Ru core shell are resulted more 68.4 % and 18.6% than using Ni/CaO-γ-Al2O3 catalyst, respectively. The highest hydrogen yield by using Ni/CaO-γ-Al2O3@Ru core shell for steam reforming bio-oil is 5.6% in minute 10 with 0.07 g of coke deposit. The study concludes that the effect of Ni/CaO-γ-Al2O3@Ru core shell is more efficient in hydrogen production, carbon conversion and coke deposit compared to Ni/CaO-γ-Al2O3 catalyst

Multifunctional SA-PProDOT Binder for Lithium Ion Batteries.

An environmentally benign, highly conductive, and mechanically strong binder system can overcome the dilemma of low conductivity and insufficient mechanical stability of the electrodes to achieve high performance lithium ion batteries (LIBs) at a low cost and in a sustainable way. In this work, the naturally occurring binder sodium alginate (SA) is functionalized with 3,4-propylenedioxythiophene-2,5-dicarboxylic acid (ProDOT) via a one-step esterification reaction in a cyclohexane/dodecyl benzenesulfonic acid (DBSA)/water microemulsion system, resulting in a multifunctional polymer binder, that is, SA-PProDOT. With the synergetic effects of the functional groups (e.g., carboxyl, hydroxyl, and ester groups), the resultant SA-PProDOT polymer not only maintains the outstanding binding capabilities of sodium alginate but also enhances the mechanical integrity and lithium ion diffusion coefficient in the LiFePO4 (LFP) electrode during the operation of the batteries. Because of the conjugated network of the PProDOT and the lithium doping under the battery environment, the SA-PProDOT becomes conductive and matches the conductivity needed for LiFePO4 LIBs. Without the need of conductive additives such as carbon black, the resultant batteries have achieved the theoretical specific capacity of LiFePO4 cathode (ca. 170 mAh/g) at C/10 and ca. 120 mAh/g at 1C for more than 400 cycles.

Relaxation Modes in a TX100 Microemulsion System

We have studied oil in water microemulsion system comprising Triton X-100 (TX100) as surfactant, cosurfactant (octanol) and oil (decane) by dynamic light scattering at various concentration. In diluted regime, the autocorrelation function exhibits a nearly mono-exponential relaxation. The best fit is obtained by using the method of cumulant up to order 2. The apparent hydrodynamic radius RHapp and polydispersity index σD were deduced. In concentrated regime, the DLS correlation function exhibit two relaxation modes. According to Pusey and Weissman, the fast one corresponds to collective diffusion coefficient (number density fluctuations) and the slow one corresponds to self diffusion coefficient (polydispersity fluctuation). The variation of Dc and Ds with volume fraction Φ reflects that the droplets interact via an overall repulsive potential.

Effects of Additives on Water Solubilization Capacity and Intermicellar Interaction in Heptane/Hexanol/Tritonx-100/Water Microemulsion

The water solubilization capacity (W0) of microemulsion system determines its physicochemical properties and interior structures. In this study, the effects of different kinds of additives such as inorganic salt, nonaqueous polar solvent, organic salt, amino acid, and polyethylene glycols (PEG series) on the water solubilization behavior of heptane/hexanol/TritonX-100/water microemulsion system have been studied in detail. The influence mechanism of every additive on W0 has also been proposed and discussed. Furthermore, the droplet size distribution and the interaction among the droplets have been investigated by dynamic light scattering technique with the presence of additives. The result shows that the hydrodynamic diameter of microemulsion droplet and the attractive interaction between the droplets increase with the increase of the water content and the additive concentration. This work presents a facile method to adjust the structure parameters and the interface strength of microemulsion system by adding additive to the system, and to direct the applications of microemulsion system in nanomaterials preparation and drug controlled release.

Microencapsulation of an acrylate monomer in silica particles by sol–gel process

The sol–gel synthesis strategies combined with the templated growth of organic–inorganic hybrid networks provide access to an immense new area of innovative multi-functional advanced materials. One possible way to prepare such new advanced materials is to encapsulate liquid active agents (such as monomers, dyes, catalysts and hardeners) in microcapsules. Silica microcapsules of tetraethylortosilicate (TEOS) and 3-(trimethoxysilyl)propyl methacrylate (MPTS) were prepared in a precursor-monomer/NH4OH water microemulsion system. Trimethylolpropane triacrylate (TMPTA)—a trifunctional monomer useful in manufacturing of coatings, inks and adhesives—and a corresponding photoinitiator (DAROCUR 1173) were entrapped inside the obtained microcapsules. MPTS was used to increase compatibility between TMPTA and the sol–gel precursors. As stability agent we added a “home made” product resulted from functionalization of poly (ethylene glycol) methyl ether (MPEG) with (3-isocyanatopropyl) triethoxysilane (NCOTEOS). Were obtained microcapsules containing incorporated monomer and having average particle size in range of 0.5–50 μm. Thermal analysis, morphology study and the increase of the silica microcapsules average diameter, measured by DLS technique confirm the monomer encapsulation.

Phase diagrams and chemical physical properties of dodecyl sulfobetain/alcohol/oil/water microemulsion system

The HLB plane equation was deduced according to the mass balance relation in microemulsion systems for the first time. The δ-γ fishlike phase diagram was plotted and the composition of the interfacial layer was calculated for dodecyl sulfobetain/alcohol/oil/water microemulsion system. The solubilities of dodecyl sulfobetian and alcohol and the solubilization capacity for the middle-phase microemulsion were examined. The effects of different alcohols, oils, and aqueous solution composition (NaCl content and pH values) on the phase behavior and the related parameters were also investigated. The phase behavior for dodecyl sulfobetain-based microemulsion system was compared with corresponding phase behavior for lauric-N-methylglucamide-based and sodium dodecyl sulfatebased systems.

Development and antifungal evaluation of a food-grade U-type microemulsion

Food-grade microemulsions have been of increasing interest to researchers as potential delivery systems for bioactive compounds. However, food-grade microemulsions are difficult to formulate and no microemulsion has been documented for antifungal purpose. The physicochemical characterization of a food-grade glycerol monolaurate (GML)/ethanol (EtOH)/Tween 80/potassium sorbate (PS)/water microemulsion system and the antifungal activities against Aspergillus niger and Penicillium italicum have been studied in this paper. The influence of EtOH and PS on oil solubilization capability was clearly reflected in the phase behaviour of U-type microemulsion systems. One dilution-stable formulation ME (GML/EtOH/Tween 80/PS/water = 3 : 3 : 3.5 : 10.5 : 16) was selected. After 4 days of incubation, ME showed 80%A. niger growth inhibition at 0.2% and 72%P. italicum growth inhibition at 0.1%, respectively, and a delay of conidiation of 2 days compared with the control. In the antifungal activities of the microemulsion, GML and PS made major contributions with similar antifungal activities at a GML/PS weight ratio of 1: 3.5. Food-grade dilution-stable microemulsions prepared with GML as oil phase for antifungal purpose are feasible and solubilization of a hydrotrope contributes to the formation of microemulsions and enhanced antifungal activities. The present report represents the first to develop a food-grade microemulsion system for antifugal purpose.

Polypyrrole–multi-walled carbon nanotube nanocomposites synthesized in oil–water microemulsion

An oil–water microemulsion system, having been successfully used for synthesizing polypyrrole (PPy) nanoparticles, is introduced for preparing PPy–multi-walled carbon nanotube (MWCNT) nanocomposites via in situ chemical oxidative polymerization. The structures and the physical properties of the PPy–MWCNT nanocomposites are also investigated. The studies show that PPy can coat MWCNTs to form core–shell structure. The backbone structure of PPy is not damaged by the introduction of MWCNTs, and the PPy in the PPy–MWCNT nanocomposites is still amorphous as pure PPy. The conductivities of PPy–MWCNT nanocomposites are higher than that of pure PPy and are enhanced with the increase in the MWCNT–monomer mass ratio. Furthermore, a model is supposed to be used for illustrating the mechanism for PPy–MWCNT nanocomposite formation via in situ microemulsion synthesis.

Characterization and synergistic antimicrobial activities of food-grade dilution-stable microemulsions against Bacillus subtilis

Abstract The physicochemical characterization of a food-grade glycerol monolaurate (GML)/ethanol/Tween 20/sodium lactate (SL)/water microemulsion system and the antimicrobial activities against Bacillus subtilis have been studied in this paper. The influence of ethanol and SL on oil solubilization capability was clearly reflected in the phase behavior of these systems. The addition of ethanol in GML/Tween 20/water system greatly improved the oil solubilization and induced the formation of a U-type microemulsion system, while a transition from U-type to S-type microemulsion system was observed with the increasing concentration of sodium lactate. Two microemulsion formulations were obtained and remained stable by physical stability studies. Antimicrobial results showed that the microemulsions were effective in inhibiting the viable bacteria cells and the bacteria growth. Later it was found that the microemulsions had synergistic antimicrobial activities with a major contribution of GML and the solubilization of SL enhanced the antimicrobial effects. This work indicated that microemulsions are promising delivery vectors for antimicrobial applications in food industry.

Characterization and Photoluminescence of CdS Nanoparticles Synthesized in Diethyl Ether–Sodium Dioctylsulfosuccinate–Water Microemulsion System

Spherical cadmium sulfide (CdS) nanoparticles, 4–5 nm in diameter, were synthesized using an aqueous cadmium nitride [Cd(NO3)2·4H2O] and sodium sulfide [Na2S·9H2O] solution in a microemulsion system. The effects of the water to surfactant molar ratio (W = [water]/[surfactant]), the concentration of precursors, the Cd to S precursor ratio, and the density of the ultrasonic wave on the properties of the CdS nanoparticles were examined. The luminescent properties and the size effect of the nanoparticles were characterized using UV–vis absorption and photoluminescence (PL) spectra. The PL emission intensity did not change significantly with an increase in precursor and surfactant concentrations. The absorption edge and PL peak energy of the CdS nanoparticles shifted to shorter wavelengths with an increase in cadmium nitride concentration owing to a phase change and a decrease in CdS nanoparticle size.

Production of drug-loaded lipid nanoparticles based on phase behaviors of special hot microemulsions

The phase behaviors of special hot microemulsion were studied and used to realize the controllable production of drug-loaded nanostructured lipid carriers (NLCs). The home-made detection instrument of phase diagram which includes a very important thermostatic unit was applied to monitor the phase change of polyoxyethylene(40)stearate (S40)/polyoxyethylene-b-polyoxypropylene (F68)/glycerol monostearate (GMS)+oleic acid (OA)/water microemulsion system. The several main phase regions, such as oil-in-water (O/W) microemulsion, water-in-oil (W/O) microemulsion, and liquid crystal region, were all founded in the phase diagram of the above-mentioned system. The O/W microemulsion region was the most important region for the preparation of lipid nanoparticles. The drug-free GMS/OA-NLCs and retinoid acid (RA)-loaded RA-GMS/OA-NLCs were produced by direct cooling of hot microemulsions which were obtained according to the component ratio in the corresponding O/W microemulsion region in their phase diagrams. The two obtainable NLC suspensions were all transparent and clear due to the very smaller average diameter of 10.2±0.2nm of both NLCs by means of photon correlation spectroscopy (PCS) measurements. TEM images showed that both SLNs were all irregular spherical particles with the diameter of about 10nm. Zeta potential of both NLCs were in the range of −40.7±0.8mV, showing the good stability of both NLCs. Such NLCs could be used as not only drug carriers, but also other healthy-related products such as nanoscale carriers of nutrients and cosmetics additives.

The catalytic properties and mechanism of cyclohexane/DBSA/water microemulsion system for esterification

A model esterification reaction of hexanol and hexanoic acid in the cyclohexane/dodecylbenzenesulfonic acid (DBSA)/water microemulsion system has been investigated. Compared with cyclohexane/AOT/water microemulsion system and organic medium system, esterification reaction in the cyclohexane/DBSA/water system can perform relatively rapidly whether catalyzed by Candida cylindracea lipase (Ccl) or not, this demonstrated that DBSA itself can act as a kind of acid catalyst. Comparison of conversion in several acid-catalyzed reaction systems were also performed and the results showed that the conversion in DBSA system was the most highest, which proved the key factor affecting the conversion was not the acid strength, but the attribute of DBSA as a kind of surfactant. Furthermore, we also perform transesterification reaction of butanol and ethyl butyrate (and methyl butyrate) in the DBSA reverse microemulsion system; however, it cannot get remarkably high conversion like esterification, this reason may be alcohol produced during the transesterification cannot easily enter water droplet like water produced by the esterification. Comparison of conversion in the DBSA system with conversion in the O/W emulsion system DBSA as an emulsion agent also indicated that the conversion in the DBSA reverse microemulsion was much higher. Finally, the mechanism of reaction was also explored. After realizing that DBSA is both acid catalyst and surfactant, we concluded that it was concurrent function of acid catalyst and surfactant that played an important role in improving reaction rate and conversion of esterification.

Microencapsulation of Oil in Organically Modified Silicate Glass by Sol-Gel Process

AbstractMicroencapsulation provides protection and sustained or controlled release of active core agents. The sol-gel process has opened up a new way for encapsulating oil droplets within an inorganic capsule. Silica microcapsules were prepared in silica precursor-oil mixtures/NH4OH water microemulsion system. In this step, the formation of capsules incorporating oil depended strongly on the type of silica precursor. A spherical silica microsheres were only obtained when oligomer, synthesized by the hydrolysis and co-condensation of equiweight of TEOS (tetraethylorthosilicate) and MTMS (methyltrimethoxysilane), was used as the wall materials. The particles size of silica microcapsules was in the range of 1 ∼ 100 μm, depending on processing parameter such as a shear rate and O/W ratio etc. In controlled release system, the shell porosity is important to give an appropriate permeability, corresponding to the release rate. The pore structure, responsible for permeability, was adjusted by doping alkyl silane, and investigated with nitrogen sorption measurement.

Electronic switching properties in nanometer-sized Cu-(TCNQ) 2 powder compactions

Nanometer sized particles of Cu-(TCNQ) 2 were synthesized in a Triton X-100--butanol--cyclohexane--water microemulsion system. In this system, the aqueous cores were used as constrained microreactors for the precipitation of Cu-(TCNQ) 2. The particle size and size distribution were determined by transmission electron microscope and scanning electron microscope. The powder compactions of these particles were further characterized by the measurement of electric switching properties. The “ON”-“OFF” recycling number could be more than 650 times and the transition from high to low impedance state occurs with switching time of approximately 2ms.

Preparation of submicron spherical particles of silica by the water-in-oil microemulsion method

Submicron spherical particles of colloidal silica were prepared by the hydrolysis of sodium silicate in a Triton X-100—hexanol—cyclohexane—water microemulsion system. The average diameter of the silica particles obtained was about 30 nm. The formation of a microemulsion by using a cyclohexane solution of Triton X-100 was described. The effects of temperature and the concentration of the aqueous Na 2SiO 3 solution on the solubilization were investigated and the results showed that the solubilization decreased with increasing concentration of Na 2SiO 3 and that an optimum temperature existed for the system.

Microstructure of the CTAB–butanol–octane–water microemulsion system: effect of dissolved salts

Download options Please wait... Article information DOI https://doi.org/10.1039/FT9938903585 Article type Paper Download Citation J. Chem. Soc., Faraday Trans., 1993,89, 3585-3589 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Microstructure of the CTAB–butanol–octane–water microemulsion system: effect of dissolved salts P. Ayyub, A. Maitra and D. O. Shah, J. Chem. Soc., Faraday Trans., 1993, 89, 3585 DOI: 10.1039/FT9938903585 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Pushan Ayyub Amarnath Maitra Dinesh O. Shah

Vapor-pressure measurements of an oil in water microemulsion system

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVapor-pressure measurements of an oil in water microemulsion systemJohn L. Cavallo and Henri L. RosanoCite this: J. Phys. Chem. 1986, 90, 26, 6817–6821Publication Date (Print):December 1, 1986Publication History Published online1 May 2002Published inissue 1 December 1986https://doi.org/10.1021/j100284a021RIGHTS & PERMISSIONSArticle Views130Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (688 KB) Get e-Alerts

Reactions in microemulsions. 4. Kinetics of chlorophyll sensitized photoreduction of methyl red and crystal violet by ascorbate

The photoreduction of adsorbed dye (methyl red and crystal violet) sensitized by chlorophyll a in an anionic mineral oil in water microemulsion system has been investigated. The 100-A microdroplets occupy 40% of the total volume, and at the pigment concentrations employed (less than or equal to 10 ..mu..M) there is on the average less than one chlorophyll molecule per drop. Using ascorbate as the water-soluble reducing agent, the reaction exhibits a pseudo-first-order dependence on crystal violet, but a pseudo-zero-order dependence on methyl red. The chlorophyll fluorescence is quenched by methyl red, but not by crystal violet. The effect of sensitizer and of ascorbate concentration and light intensity on the quantum yield has also been examined. From the results of these and auxiliary studies, a reaction mechanism is proposed which involves the formation of a chlorophyll-dye triplet exciplex rather than the initial formation of an oxidized or reduced pigment species. Based on this scheme, a number of rate constants have been estimated.

Reactions in microemulsions. 3. Photodegredation of chlorophyll

The anionic oil in water microemulsion system composed of sodium cetyl sulfate/1-pentanol/mineral oil/water has been employed as a medium for the investigation of the photochemical behavior of chlorophyll and added oxidants and reductants at a microscopic oil-water interface. The chlorophyll, located in the surface region, undergoes photodegradation and slow dark pheophytinization. The photoreaction is accelerated by added oxidants and reductants, probably by different mechanisims. A complete redox system prevents degradation,and the azobenzene/hydrazobenzene couple can be cycled in the presence of oxygen to protect the chlorophyll.