ANZ JOURNAL OF SURGERY, Issue 6 2000
Y. Chen
Background: It has been speculated that the formation of surgical adhesions must be preceded by physical adhesion of the two surfaces, a process normally prevented by a lining of adsorbed surface-active phospholipid (surfactant) acting as both a superb boundary (solid-to-solid) lubricant and a release (antistick) agent. Animal trials administering exogenous surfactant as a dry powder (ALECÔ) have previously demonstrated a reduction of 80% in abdominal adhesions. Methods: Incubation of rat peritoneum (both live and excised) with radiolabelled dipalmitoyl phosphatidylcholine (DPPC) has been used to demonstrate adsorption; while the normal lining of surfactant in the human abdominal cavity has been confirmed by epifluorescence microscopy using Phosphin E as the hydrophobic probe. Aims: The overall aim is to confirm that peritoneal mesothelium has a lining of surfactant known for its lubricating and release properties, and that this lining can be enhanced by the adsorption of exogenous material. Results: Adsorption of DPPC to peritoneal mesothelium was 470 ng/cm 2 (n = 8) ex vivo and 598 ng/cm 2 (n = 18) in vivo, these rates being enhanced by EggPG by 62%ex vivo and 47%in vivo to reach the equivalent of almost three close-packed monolayers. Conclusions: These results can explain the reduction in surgical adhesions previously reported in animals by administering ALECÔ (7:3 DPPC:EggPG) as a highly surface-active dry powder, although it is now used in saline suspension to treat respiratory distress syndrome in newborns, in whom it has no side-effects. These findings would appear to justify clinical trials for dry ALECÔ in suppressing surgical adhesions with minimal risk of an adverse reaction. The results of these trials are also discussed and found to be compatible with the known ability of surfactant to resist physical adhesion by fibronectin, the tacky ,glue' by which fibroblasts attach to surfaces as the first step in formation of fibrinous adhesions. [source]

Electrochemical Behavior of Catecholamines and Related Compounds at In Situ Surfactant Modified Carbon Paste Electrodes

ELECTROANALYSIS, Issue 2-3 2007
M.Carmen Blanco-López
Abstract The voltammetric characteristics of catecholamines: epinephrine (E) and norepinephrine (NE) and related compounds: isoproterenol, metanephrine, L -dopa, methyldopa, vanillylmandelic acid (VMA), and homovanillic acid (HVA) at unmodified and in situ surfactant- modified carbon paste electrodes were comparatively evaluated. For the basic and amphoteric compounds the modification of the electrode surface with submicellar concentrations of anionic surfactants (sodium dodecylsulfate, sodium decylsulfate or sodium dodecylsulfonate) produce an important current enhancement in its oxidation and reduction peak current together with the improvement in the reversibility of the processes. These effects were explained in basis on electrostatic and hydrophobic interactions. On the other hand, the oxidation of acidic metabolites, HVA and VMA, was studied at electrodes modified in situ with cationic surfactants. Under certain conditions the surfactant could stabilise some of the electrochemical reaction intermediates, thus explaining the different voltammetric behaviour of HVA and VMA. [source]

New Strategy for Dehydrogenase Amperometric Biosensors Using Surfactant to Enhance the Sensitivity of Diaphorase/Ferrocene Modified Carbon Paste Electrodes for Electrocatalytic Oxidation of NADH

ELECTROANALYSIS, Issue 13 2003
César Ramírez-Molina
Abstract A carbon paste electrode (CPE) modified with diaphorase (DAP) and ferrocene (FcH) has been developed for determination of NADH at low working potential. The sensitivity and operational stability, towards the detection of the reduced form of the nicotinamide adenine dinucleotide (NADH) in flow injection analysis (FIA), were greatly improved (5 times) upon adding Tween 20 into the electrode matrix. The magnitude of the amperometric signal was dependent on DAP, FcH and surfactant loading, into the modified carbon paste electrode. A rapid and repeatable response was observed to the variation of NADH concentration in the vicinity of the electrode surface. Such advantages of the DAP/FcH/Tween 20 modified carbon paste were successfully used in the construction of L -lactate dehydrogenase modified electrodes. The use of this new approach can be generalized to other dehydrogenases and represents a decisive step for a versatile preparation method of amperometric biosensors. [source]

Direct Preparation of N-Glycosidic Bond-Linked Nonionic Carbohydrate-Based Surfactant (NICBS) via Ritter Reaction,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2007
Zerong Daniel Wang
Abstract The Ritter reaction has been successfully extended to the direct preparation of N-glycosidic bond-linked nonionic carbohydrate-based surfactants from carbohydrates and nitriles in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and silver perchlorate (AgClO4) on a high-speed mechanical shaker. The new surfactant molecules have the features of low toxicity, environmental compatibility and biodegradability. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Development of a Novel Oxidative Hair Color Based on a System with an Optimized Ratio of Higher Alcohol to Cationic Surfactant

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2006
T. Yamashita
Oxidative hair color, the most commonly used for coloring hair, is characterized by its bleaching effect. This effect enables dark hair to be dyed in various bright colors. In order to enhance this bleaching effect, the concentration of either the alkalizing or oxidizing agent in the hair color base is generally increased. However, this method causes chemical damage to the hair. With the aim of finding methods to obtain an improved bleaching effect without increasing the amount of bleaching ingredients, the authors investigated the permeation mechanism. Cationic bases showed the highest bleaching effect and allowed greater penetration, permitting bleaching ingredients to enter the cortex of the hair more easily and diffuse more quickly. In addition, the molar ratios of higher alcohol (A) to cationic surfactant (C) as a function of the bleaching effect were also evaluated. The results showed an optimum range for this A/C ratio. The smoothness of the hair was also evaluated, revealing an optimum range for the A/C ratio. Based on these findings, a product with an A/C ratio that maximizes the bleaching effect and the smoothness of the hair was successfully developed. Comparison of this newly developed product with a conventional product verified that the new product has a greater bleaching effect and gives a beautiful depth of color while maintaining the silky smoothness of the texture of the hair. Part of this study was presented at the 23rd IFSCC Congress 2004, Orlando, Florida USA. [source]

Surfactant assisted polymerization of tetrafluoroethylene in supercritical carbon dioxide with a pilot scale batch reactor

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008
Alberto Giaconia
Abstract Chain-free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO2), at 50 °C and 121,133 bar, with tertiary -amyl-per-pivalate as a free radical initiator, using a 5-L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant-free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200,500 ,m. Quite interestingly, when the free acid surfactant was used, a clear acceleration of the polymerization rate was observed and smaller polymer particles with more regular quasi-spherical morphology were obtained. Melt fusion crystallinity of as-polymerized poly(TFE) seemed not substantially affected by the presence of the stabilizers and was rather high (80,86%) suggesting that polymerization mainly occurs at polymer particle surface. All these elements suggest that FLUOROLINK® 7004H PFPE carboxylic acid decreases coagulation of primary polymer particles leading to an increase in polymer surface area. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 257,266, 2008 [source]

Preparation of Highly Dispersed Ultrafine Barium Titanate Powder by Using Microbial-Derived Surfactant

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2003
Hidehiro Kamiya
To uniformly disperse ultrafine BaTiO3 particles with a stoichiometric composition and several tens of nanometers in diameter to primary particles during the sol,gel synthesis process, a new aqueous surfactant with a high hydrophilic group density and special cis-structure was prepared from a microbial product and added to solution before the sol,gel synthesis reaction. Because of the rapid formation of large and porous aggregates which were 30,50 ,m in diameter in suspension without addition of this unique structural surfactant, the prepared ultrafine BaTiO3 particles caused rapid sedimentation in suspension. The addition of the surfactant in the range of 7.1 wt% for the synthesized BaTiO3 particles made it possible to decrease the size of the aggregates in suspension as well as the sedimentation velocity while maintaining the stoichiometric composition. The optimum additive content to obtain the minimum aggregate size of about 100,200 nm in diameter and the highest dispersion stability in suspension while maintaining the stoichiometric composition of prepared ultrafine BaTiO3 particles without other phases was determined at about 7.1 wt%. Because the excess addition of this surfactant at more than 8.5 wt% inhibited the uniform synthesis of BaTiO3 particles, an amorphous phase with a highly specific surface area and a BaCO3 phase formed in the synthesized particles. [source]

Role of Lung Surfactant in Respiratory Disease: Current Knowledge in Large Animal Medicine

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 2 2009
U. Christmann
Lung surfactant is produced by type II alveolar cells as a mixture of phospholipids, surfactant proteins, and neutral lipids. Surfactant lowers alveolar surface tension and is crucial for the prevention of alveolar collapse. In addition, surfactant contributes to smaller airway patency and improves mucociliary clearance. Surfactant-specific proteins are part of the innate immune defense mechanisms of the lung. Lung surfactant alterations have been described in a number of respiratory diseases. Surfactant deficiency (quantitative deficit of surfactant) in premature animals causes neonatal respiratory distress syndrome. Surfactant dysfunction (qualitative changes in surfactant) has been implicated in the pathophysiology of acute respiratory distress syndrome and asthma. Analysis of surfactant from amniotic fluid allows assessment of fetal lung maturity (FLM) in the human fetus and exogenous surfactant replacement therapy is part of the standard care in premature human infants. In contrast to human medicine, use and success of FLM testing or surfactant replacement therapy remain limited in veterinary medicine. Lung surfactant has been studied in large animal models of human disease. However, only a few reports exist on lung surfactant alterations in naturally occurring respiratory disease in large animals. This article gives a general review on the role of lung surfactant in respiratory disease followed by an overview of our current knowledge on surfactant in large animal veterinary medicine. [source]

Synthesis of High Solid-Content Latex using Alkali-Soluble Resin as Sole Surfactant

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004
Marcelo do Amaral
Abstract Summary: A novel polymerization procedure to synthesize latex stabilized by alkali-soluble resin (ASR) is detailed. According to this process, latexes with a high solid content and low viscosity are obtained using a substantially lower amount of ASR when compared with existing techniques. Similar rewet properties were found for the latexes obtained by a standard process and for the one obtained by the process described in this work. Comparison of the particle size distributions obtained by conventional emulsion polymerization (,) and by miniemulsion polymerization (,). [source]

Integration of CdSe quantum dots with GaN optoelectronic materials

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
J. G. Pagan
Abstract Material structures on the nanoscale can enable enhancement of optoelectronic device performance. For example, in the InGaN active layers of MOCVD grown blue light emitting diodes, indium segregation plays a critical role in the interplay between blue luminescent channels and non-radiative recombination centers such as crystal defects. Unfortunately, high efficiency luminescence of InGaN does not extend into the "deep green" spectral region, around the wavelength of peak human eye response. We are investigating whether commercially available luminescent nanostructures such as CdSe quantum dots can be incorporated into III-nitride devices to extend their high-efficiency performance into the "deep green". Surfactant stabilized CdSe particles in liquid dispersions are drop-cast onto HVPE grown GaN. Physical properties of resultant CdSe surface structures are examined. Luminescence is reported before and after subsequent growth of GaN. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Effects of surfactant and molecular weight of polyol on grating formation and switching of holographic PDLC

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008
S. S. Shim
Abstract The interposition of surfactants between polymer and liquid crystal (LC) droplets was theoretically predicted by the positive spreading coefficient (0,<,,31) and utilized to interpret the morphology, grating formation kinetics, diffraction efficiency, and switching of the holographic polymer dispersed liquid crystal (HPDLC), prepared from various types (octanoic acid, poly oxyethylene octyl phenyl ether, and perfluoro-1-butanesulfonyl fluoride) and amounts (0,9 wt%) of surfactant and molecular weights of polyol (PPG). Regardless of the surfactant type, diffraction efficiency increased with the addition and increasing amount of surfactant, a tendency consistent with increasing value of spreading coefficient, which is determined by the formulations of grating formation. In contrast, diffraction efficiency showed a maximum with the polypropylene glycol (PPG) molecular weight. Surfactant effectively reduced the anchoring energy and electrically drove the film which otherwise was not driven. Overall, surfactant with greater ,31 gave smaller droplet, greater diffraction efficiency, driving voltage, contrast ratio, and smaller response time. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Pharmaceutical Nano-Cocrystals: Sonochemical Synthesis by Solvent Selection and Use of a Surfactant,

ANGEWANDTE CHEMIE, Issue 40 2010
John R. G. Sander
Nanopharmazeutika: Sonochemie und die Anwendung eines Tensids (Span-85) wurden eingeführt, um pharmazeutische Cokristalle mit nanoskaligen Abmessungen herzustellen. Auf diese Art lässt sich der Löslichkeitsunterschied zwischen dem pharmazeutischen Wirkstoff (hier: Coffein) und dem Cokristallbildner (2,4-Dihydroxybenzoesäure) beseitigen (siehe Bild). [source]

Protein Refolding Mediated by Reverse Micelles of Cibacron Blue F-3GA Modified Nonionic Surfactant

BIOTECHNOLOGY PROGRESS, Issue 2 2006
Xiao-Yue Wu
An affinity-based reverse micellar system formulated with nonionic surfactant was applied to the refolding of denatured-reduced lysozyme. The nonionic surfactant of sorbitan trioleate (Span 85) was modified with Cibacron Blue F-3GA (CB) as an affinity surfactant (CB-Span 85) to form affinity-based reverse micelles in n -hexane. The water content of 15 was found optimal for lysozyme refolding in the reverse micellar system of 62.7 mmol/L Span 85 with coupled CB of 0.3 and 0.5 mmol/L. In addition, the operating conditions such as pH and the concentrations of urea and redox reagents were optimized. Under the optimized conditions, complete renaturation of lysozyme at 3,3.5 mg/mL was achieved, whereas dilution refolding in the bulk aqueous phase under the same conditions gave much lower activity recovery. Moreover, the secondary structure of the refolded lysozyme was found to be the same as the native lysozyme. Over 95% of the refolded lysozyme was recovered from CB-Span 85 reverse micelles by a stripping solution of 0.5 mol/L MgCl2. Thus, the present system is advantageous over the conventional reverse micellar system formed with ionic surfactants in the ease of protein recovery. [source]

ChemInform Abstract: Three-Component Reaction of 2-Alkynylbenzaldehyde, Amine, and Nucleophile Using Lewis Acid Surfactant Combined Catalyst in Water.

CHEMINFORM, Issue 36 2008
Yang Ye
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Light-Emitting meso-Structured Sulfides with Hexagonal Symmetry: Supramolecular Assembly of [Ge4S10]4- Clusters with Trivalent Metal Ions and Cetylpyridinium Surfactant.

CHEMINFORM, Issue 4 2001
K. Kasthuri Rangan
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Stability of Anion Binding with Monomers of a Cationic Surfactant

CHEMPHYSCHEM, Issue 6 2008
Anna Jakubowska Dr.
Competitive binding: Electrospray ionisation mass spectrometry is used to probe the binding ability of different anions with a cationic surfactant. Bond strengths are estimated from plots of the intensity of the peak assigned to a given complex ion in the mass spectrum versus the cone voltage applied to induce the abstraction of the counterions from the monomers (see graph). [source]

Effect of Sodium Halide on Dynamic Surface Tension of a Cationic Surfactant

CHINESE JOURNAL OF CHEMISTRY, Issue 8 2005
Lü Feng-Feng
Abstract The equilibrium and dynamic surface tension (DST) of the novel cationic surfactant, 3-(p -nonylphenoxy)-2-hydroxylpropyl trimethyl ammonium bromide, abbreviated as RTAB, were studied. The effect of sodium halide such as NaCl, NaBr and NaI on the DST behavior of the RTAB solution below its CMC was studied in detail. Due to the preferential adsorption, the effect of hydration and salting out, the ability to reduce the DST values at the same concentration was in the order of NaI>NaBr>NaCl. Attributed to its high surface activity, the equilibrium time of the DST of the surfactant solution was insensitive to the ionic strength. [source]

Surfactant/I2/Water: An Efficient System for Deprotection of Oximes and Imines to Carbonyls under Neutral Conditions in Water.

CHEMINFORM, Issue 31 2005
Pranjal Gogoi
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Cleansing without compromise: the impact of cleansers on the skin barrier and the technology of mild cleansing

DERMATOLOGIC THERAPY, Issue 2004
K. P. Ananthapadmanabhan
ABSTRACT:, Cleanser technology has come a long way from merely cleansing to providing mildness and moisturizing benefits as well. It is known that harsh surfactants in cleansers can cause damage to skin proteins and lipids, leading to after-wash tightness, dryness, barrier damage, irritation, and even itch. In order for cleansers to provide skin-care benefits, they first must minimize surfactant damage to skin proteins and lipids. Secondly, they must deposit and deliver beneficial agents such as occlusives, skin lipids, and humectants under wash conditions to improve skin hydration, as well as mechanical and visual properties. While all surfactants tend to interact to some degree with lipids, their interaction with proteins can vary significantly, depending upon the nature of their functional head group. In vitro, ex vivo, and in vivo studies have shown that surfactants that cause significant skin irritation interact strongly with skin proteins. Based on this understanding, several surfactants and surfactant mixtures have been identified as "less irritating" mild surfactants because of their diminished interactions with skin proteins. Surfactants that interact minimally with both skin lipids and proteins are especially mild. Another factor that can aggravate surfactant-induced dryness and irritation is the pH of the cleanser. The present authors' recent studies demonstrate that high pH (pH 10) solutions, even in the absence of surfactants, can increase stratum corneum (SC) swelling and alter lipid rigidity, thereby suggesting that cleansers with neutral or acidic pH, close to SC-normal pH 5.5, may be potentially less damaging to the skin. Mildness enhancers and moisturizing agents such as lipids, occlusives, and humectants minimize damaging interactions between surfactants, and skin proteins and lipids, and thereby, reduce skin damage. In addition, these agents play an ameliorative role, replenishing the skin lipids lost during the wash period. The present review discusses the benefits of such agents and their respective roles in improving the overall health of the skin barrier. [source]

Bismuth/Polyaniline/Glassy Carbon Electrodes Prepared with Different Protocols for Stripping Voltammetric Determination of Trace Cd and Pb in Solutions Having Surfactants

ELECTROANALYSIS, Issue 2 2010
M. Wang
Abstract To improve reproducibility, stability and sensitivity, a bismuth (Bi) thin film was coated on glassy carbon (GC) substrates which surfaces were modified with a porous thin layer of polyaniline (PANI) via multipulse potentiostatic electropolymerization to form Bi/PANI/GC electrodes (Bi/PANI/GCEs). The Bi/PANI/GCEs were used successfully for simultaneous detection and determination of Cd2+ and Pb2+ ions, and various parameters were studied with reference to square wave anodic stripping voltammetric (SWASV) signals. The experimental results depicted that the environment-friendly Bi/PANI/GCEs had the ability to rapidly monitor trace heavy metals even in the presence of surface-active compounds. [source]

Surface Resistance and Potentiometric Response of Polymeric Membranes Doped with Nonionic Surfactants

ELECTROANALYSIS, Issue 19 2004
Liya Muslinkina
Abstract The influence of lipophilic, electrically neutral surfactants added to the membrane on the ion transfer resistance between an aqueous sample and a polymeric ion-selective membrane has been studied by electric impedance spectroscopy and potentiometry. An increase in the surface resistance and a shift of the apparently super-Nernstian response to lower sample ion activities has been observed when using the nonpolar bis(2-ethylhexyl) sebacate as plasticizer. [source]

Comparison of synthetic surfactants and biosurfactants in enhancing biodegradation of polycyclic aromatic hydrocarbons

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003
Randhir S. Makkar
Abstract Polycyclic aromatic hydrocarbon (PAH) contamination of the environment represents a serious threat to the health of humans and ecosystems. Given the human health effects of PAHs, effective and cost-competitive remediation technologies are required. Bioremediation has shown promise as a potentially effective and low-cost treatment option, but concerns about the slow process rate and bioavailability limitations have hampered more widespread use of this technology. An option to enhance the bioavailability of PAHs is to add surfactants directly to soil in situ or ex situ in bioreactors. Surfactants increase the apparent solubility and desorption rate of the PAH to the aqueous phase. However, the results with some synthetic surfactants have shown that surfactant addition can actually inhibit PAH biodegradation via toxic interactions, stimulation of surfactant degraders, or sequestration of PAHs into surfactant micelles. Biosurfactants have been shown to have many of the positive effects of synthetic surfactants but without the drawbacks. They are biodegradable and nontoxic, and many biosurfactants do not produce true micelles, thus facilitating direct transfer of the surfactant-associated PAH to bacteria. The results with biosurfactants to date are promising, but further research to elucidate surfactant,PAH interactions in aqueous environments is needed to lead to predictive, mechanistic models of biosurfactant-enhanced PAH bioavailability and thus better bioremediation design. [source]

Molecular Tailored Histidine-Based Complexing Surfactants: From Micelles to Hydrogels

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2009
Patrick Gizzi
Abstract Novel histidine-based complexing surfactants, designed as AA-His-EOm -Cn, containing trifunctional moduli (peptidic/hydrophilic/hydrophobic) were synthesized by a modular step-by-step procedure, which allowed easy structural changes, and consequently correlations between their molecular structures and their self-assembling properties could be established. Thus, micelles or hydrogels could be obtained by simply modifying the hydrophobic tail lengths or the junction between the different moduli of the designed compounds. At low pH values, all compounds were surface active in aqueous solutions. At higher pH values, in the range 8,10, micellization took place for decyl compounds (n = 10), whereas hydrogelation occurred for longer chain lengths (n = 12, 14), and this, at very-low concentrations of surfactant (<0.3 wt.-%), could thus act as low molecular weight gelator (LMWG). The driving forces for gel formation were noncovalent intermolecular interactions such as ,-stacking and hydrophobic and hydrogen-bonding interactions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Deprotonation of Indole Derivatives in Aqueous Cationic Surfactants

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2004
Nicoletta Spreti
Abstract Deprotonations of 5-nitroindole, 1a, and its 2-carboxylate ion, 2a, have been monitored in 0.01, 0.1, and 0.5 M NaOH in micellar solutions of cetyl trialkylammonium bromide, alkyl = Me, Et, nPr, nBu, CTABr, CTEABr, CTPABr, CTBABr. Extents of deprotonation (% f) have been fitted using the pseudophase model of micellar effects with interionic competition described by ion exchange or by independent association constants. Both treatments indicate that base dissociation constants in dilute OH, are lower than in water by factors of ca. 3,11, and decrease with increasing bulk of the head groups, and that these factors increase modestly as the OH, concentration increases to 0.5 M. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and Electrochromism

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Tierui Zhang
Abstract A variety of functional nanostructured organic/inorganic hybrid materials from the europium-exchanged derivative of a Preyssler-type polyoxometalate (POM), [EuP5W30O110]12,, and functional organic surfactants were prepared by the ionic self-assembly (ISA) route. The effect of organic surfactants on the structure, photoluminescent, electrochemical and electrochromic properties of the POM anions was investigated in detail. All obtained hybrid materials are amphotropic, i.e., exhibit both thermotropic and lyotropic liquid-crystalline phase behaviour. Investigations of their photophysical properties have shown that the interactions of the various surfactants with the polyanions influence the coordination environments and site symmetry of Eu3+ in different ways. The functional groups in the organic surfactants significantly influence the electrochromic properties and photoluminescence of POMs. Different from normal and pyridine-containing complexes, no photoluminescence and no electrochromism were observed from the ferrocene-containing complexes. This may be explained in view of charge transfer between the POM anion and the ferrocenyl group. [source]

Colloid Surfactants for Emulsion Stabilization,

ADVANCED MATERIALS, Issue 17 2008
Jin-Woong Kim
Colloid surfactants are fabricated with precisely controlled geometry and used for emulsion stabilization. These amphiphilic dimer particles (left) combine the benefits of emulsion stabilization of particles and the amphiphilicity of molecular surfactants to afford better emulsion stabilization. Remarkably, these colloidal surfactants stabilize not only spherical emulsion droplets but also nonspherical ones (right). [source]

pH-induced alterations in stratum corneum properties

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2003
K. P. Ananthapadmanabhan
Synopsis Skin-cleansing compositions based on alkyl carboxylates (soaps) have a higher irritation potential than those based on syndet surfactants such as alkyl isethionates or alkyl ether sulphates. Contributing factors include inherent differences in the irritation potential of soaps and syndet surfactants, pH-induced changes in surfactant solution chemistry, and the direct effects of pH on the physical properties of the stratum corneum (SC). Past work has not directly addressed the effect of solution pH on the SC itself and its potential role in cleanser-induced skin irritation. In the current work, alterations to SC properties induced by buffered pH solutions and two strongly ionizable surfactants, sodium dodecyl sulphate and sodium lauryl ether sulphate, at different pH values are measured. By utilizing optical coherence tomography (OCT) and infrared (IR) spectroscopy we have directly measured physical changes in SC proteins and lipids. Our results indicate that SC swelling, which reflects alterations to SC structural proteins, is increased significantly at pH 10, compared to pH 4 and 6.5. The transition temperature (Tm) of SC lipids is found to increase at pH 10, compared to pH 4 and 6.5, suggesting a more rigid SC lipid matrix. Surfactants cause a further increase in swelling and lipid rigidity. Some aspects of what these results mean for SC physical properties as well as their implications to potential mechanisms of surfactant-induced skin irritation are discussed. Résumé Les compositions nettoyantes pour la peau à base d'alkyl carboxylates (savons) ont un potentiel irritant supérieur à celles à base de syndet tensioactifs tels que les alkyl isothionates ou les alkyl ether sulfates. Les facteurs en cause comprennent les différences de potentiel irritant inhérentes aux savons et aux syndet tensioactifs, les modifications de la chimie de la solution de tensioactif dues aux pH, et les effets directs du pH sur les propriétés physiques de la couche cornée (CC). Les travaux antérieurs n'ont pas traité directement l'effet du pH de la solution sur la couche cornée elle-même et son rôle potentiel dans l'irritation de la peau due à la solution nettoyante. Dans la présente étude on a mesuré les altérations des propriétés de la CC causées par des solutions à pH tamponné et deux tensioactifs fortement ionisables, le dodecyl sulfate de sodium et le lauryl ether sulfate de sodium, à différentes valeurs de pH. En utilisant la tomographie optique (OCT) et la spectroscopie à infrarouge (IR) on a mesuré directement les modifications physiques des protéines et des lipides de la CC. Nos résultats montrent que le gonflement de la CC, qui traduit des altérations des protéines structurales de la CC, augmente significativement à pH 10, par comparaison au pH 4 et 6.5. On observe que la température de transition (Tm) des lipides de la CC augmente à pH 10, par comparaison au pH 4 et 6.5, suggérant une matrice lipidique de la CC plus rigide. Les tensioactifs provoquent une augmentation plus importante du gonflement et de la rigidité lipidique. On aborde certains aspects de la signification de ces résultats vis-à-vis des propriétés physiques de la couche cornée ainsi que leurs conséquences sur les mécanismes potentiels de l'irritation de la peau causée par les tensioactifs. [source]

Low-Temperature Synthesis of Star-Shaped PbS Nanocrystals in Aqueous Solutions of Mixed Cationic/Anionic Surfactants,

ADVANCED MATERIALS, Issue 3 2006
N. Zhao
Uniform, well-defined star-shaped PbS nanocrystals with tunable sizes (40,100,nm, see Figure), as well as octahedral PbS nanocrystals, have been readily synthesized in aqueous solutions containing a mixture of the surfactants cetyltrimethylammonium bromide/ sodium dodecyl sulfate (CTAB/SDS) at low temperature (80,°C). The size of the PbS nanostars can be accurately controlled by adjusting the reaction time. This result may open new avenues for the green chemical synthesis of shape-controlled semiconductor nanocrystals. [source]

Effect of surfactants and liquid hydrocarbons on gas hydrate formation rate and storage capacity

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2003
Zhigao Sun
Abstract Hydrate formation rate plays an important role in making hydrates for the storage and transport of natural gas. Micellar surfactant solutions were found to increase gas hydrate formation rate and storage capacity. With the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation reduced. Surfactants (an anionic surfactant, a non-ionic surfactant and their mixtures) and liquid hydrocarbons (cyclopentane and methylcyclohexane) were used to improve hydrate formation. The experiments of hydrate formation were carried out in the pressure range 3.69,6.82 MPa and the temperature range 274.05,277.55 K. The experimental pressures were kept constant during hydrate formation in each experimental run. The effect of anionic surfactant (sodium dodecyl sulphate (SDS)) on natural gas storage in hydrates is more pronounced compared to a non-ionic surfactant (dodecyl polysaccharide glycoside (DPG)). The induction time of hydrate formation was reduced with the presence of cyclopentane (CP). Cyclopentane and methylcyclohexane (MCH) could increase hydrate formation rate, but reduced hydrate storage capacity The higher methylcyclohexane concentration, the lower the hydrate storage capacity. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Surfactants, skin cleansing protagonists

JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 1 2010
M Corazza
Abstract The correct choice of cosmetic products and cleansers is very important to improve skin hydration, to provide moisturizing benefits and to minimize cutaneous damage caused by surfactants. In fact, surfactants may damage protein structures and solubilize lipids. Soaps, defined as the alkali salts of fatty acids, are the oldest surfactants and are quite aggressive. Syndets (synthetic detergents) vary in composition and surfactant types (anionic, cationic, amphotheric, non-ionic). These new skin cleansing products also contain preservatives, fragrances, and sometimes emollients, humectants and skin nutrients. We present a revision of the literature and discuss recent findings regarding skin cleansers. [source]