Dodecyl Sulfate Ions Research Articles

Tumor necrosis factor interaction with gold nanoparticles

We report on a systematic investigation of molecular conjugation of tumor necrosis factor-α (TNF) protein onto gold nanoparticles (AuNPs) and the subsequent binding behavior to its antibody (anti-TNF). We employ a combination of physical and spectroscopic characterization methods, including electrospray-differential mobility analysis, dynamic light scattering, polyacrylamide gel electrophoresis, attenuated total reflectance-Fourier transform infrared spectroscopy, fluorescence assay, and enzyme-linked immunosorbent assay. The native TNF used in this study exists in the active homotrimer configuration prior to conjugation. After binding to AuNPs, the maximum surface density of TNF is (0.09 ± 0.02) nm(-2) with a binding constant of 3 × 10(6) (mol L(-1))(-1). Dodecyl sulfate ions induce desorption of monomeric TNF from the AuNP surface, indicating a relatively weak intermolecular binding within the AuNP-bound TNF trimers. Anti-TNF binds to both TNF-conjugated and citrate-stabilized AuNPs, showing that non-specific binding is significant. Based on the number of anti-TNF molecules adsorbed, a substantially higher binding affinity was observed for the TNF-conjugated surface. The inclusion of thiolated polyethylene glycol (SH-PEG) on the AuNPs inhibits the binding of anti-TNF, and the amount of inhibition is related to the number ratio of surface bound SH-PEG to TNF and the way in which the ligands are introduced. This study highlights the challenges in quantitatively characterizing complex hybrid nanoscale conjugates, and provides insight on TNF-AuNP formation and activity.

Diffusion Interactions of Some Biologically Important Transition Metal Complexes on Micellar Properties of Sodium Dodecyl Sulphate

The specific conductance of aqueous solutions of sodium dodecyl sulphate (SDS) was measured from 20 to 35 ºC with an interval of 5 °C in the absence and presence of metal complexes such as [Cr(acac)2(H2O)2]Cl, K3[Fe(C2O4)3] and (NH4)4[Co(C6H5O7)2] at concentrations ranging from 2.0 × 10-4 to 8.0 x 10-4 M. The specific conductance rapidly increased at the pre-micellar region with increasing of temperature and concentration of SDS, but after critical micelle concentration (CMC) the rate of increase was slower. As the concentrations of metal complexes [Cr(acac)2(H2O)2]Cl, K3[Fe(C2O4)3] and (NH4)4[Co(C6H5O7)2] increased, the CMC of SDS decreased exponentially, which was sharp with increasing temperature. The CMC decreases due to the formation of pre-micellar aggregates of the positive counter ions of the complexes with dodecyl sulphate ions (DS-) and hydrophobic interaction between ligands of complexes and hydrophobic tail of SDS. The pre-micellar aggregate formation was essentially influenced by the counter ions binding abilities to the anionic micelle. The effect of metal complexes on lowering the CMC of SDS was found to follow the order [Cr(acac)2(H2O)2]Cl < K3[Fe(C2O4)3] < (NH4)4[Co(C6H5O7)2]. Thermodynamics of metal complexes with SDS and parameters of micellization ΔG°mic, ΔH°mic and TΔS°mic were calculated.Keywords: Surfactants; Sodium dodecyl sulphate; Critical micelle concentration; Pre-micellar aggregate; Hydrophobic interaction.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i1.7989J. Sci. Res. 4 (1), 135-141 (2012)

Thermodynamic studies on thin liquid films IV. Foam film stabilized by sodium dodecyl sulfate

Thermodynamic treatment of thin liquid films in Part III of this series was applied to foam films stabilized by sodium dodecyl sulfate. Miscibility of sodium chloride and sodium dodecyl sulfate in the adsorbed films at the film surfaces and transition between the black films were studied by measuring film thickness and contact angle. A discontinuous change in the thickness and a break on the contact angle vs. concentration curve appeared at the transition. Judging from the phase diagram of adsorption, sodium chloride and sodium dodecyl sulfate are a little miscible in the adsorbed films. The miscibility was ascribed to specific interaction between sodium ion and dodecyl sulfate ion in the adsorbed films. The miscibility in an adsorbed film was compared between the film surface and meniscus and between the common black and Newton black films.

Electrochemical synthesis of bilayer coatings of poly( N-methylaniline) and polypyrrole on mild steel and their corrosion protection performances

Homopolymer and bilayer coatings of poly( N-methylaniline) (P NMA) and polypyrrole-dodecylsulfate (PPy-DS) have been electropolymerized on a mild steel (MS) surface by the potentiodynamic method in aqueous oxalic acid solutions. In order to include dodecylsulfate ion as dopant in the polypyrrole, sodium dodecylsulfate was also added to the polymerization solution of pyrrole. Characterization of coatings was carried out by the cyclic voltammetry, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). Corrosion behavior of the polymer coated MS electrodes was investigated in highly aggressive 0.5 M HCl solution by the Tafel test and electrochemical impedance spectroscopy (EIS) techniques. Corrosion test revealed that among the protective coatings obtained, the P NMA/PPy-DS bilayer exhibited the best corrosion resistance at all immersion times.

Composition Driven Monolayer to Bilayer Transformation in a Surfactant Intercalated Mg−Al Layered Double Hydroxide

The structure and organization of dodecyl sulfate (DDS) surfactant chains intercalated in an Mg-Al layered double hydroxide (LDH), Mg(1-x)Alx(OH)2, with differing Al/Mg ratios has been investigated. The Mg-Al LDHs can be prepared over a range of compositions with x varying from 0.167 to 0.37 and therefore provides a simple system to study how the organization of the alkyl chains of the intercalated DDS anions change with packing density; the Al/Mg ratio or x providing a convenient handle to do so. Powder X-ray diffraction measurements showed that at high packing densities (x ≥ 0.3) the alkyl chains of the intercalated dodecyl sulfate ions are anchored on opposing LDH sheets and arranged as bilayers with an interlayer spacing of ∼27 Å. At lower packing densities (x < 0.2) the surfactant chains form a monolayer with the alkyl chains oriented flat in the galleries with an interlayer spacing of ∼8 Å. For the in between compositions, 0.2 ≤ x < 0.3, the material is biphasic. MD simulations were performed to understand how the anchoring density of the intercalated surfactant chains in the Mg-Al LDH-DDS affects the organization of the chains and the interlayer spacing. The simulations are able to reproduce the composition driven monolayer to bilayer transformation in the arrangement of the intercalated surfactant chains and in addition provide insights into the factors that decide the arrangement of the surfactant chains in the two situations. In the bilayer arrangement, it is the dispersive van der Waals interactions between chains in opposing layers of the anchored bilayer that is responsible for the cohesive energy of the solid whereas at lower packing densities, where a monolayer arrangement is favored, Coulomb interactions between the positively charged Mg-Al LDH sheets and the negatively charged headgroup of the DDS anion dominate.

Protein Structural Change in a Mixed System of Ionic and Zwitterionic Surfactants

The secondary structure of bovine serum albumin (BSA) in the binary surfactant system of anionic sodium dodecyl sulfate (SDS) and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) was examined at 25°C. The helicity of BSA decreased from 66% to 55% in a solution of DDAPS alone and decreased to 50% in a solution of SDS alone. However, the late addition of DDAPS reformed the helical structure of BSA, which was initially disrupted by SDS. The reformation required higher DDAPS concentrations as the initial SDS concentration increased. A maximum helicity of 63% was attained by this reformation. On the other hand, the helical structure of the protein, which was first affected by DDAPS denaturation, was also reformed to the same degree by the late addition of certain amounts of SDS. Although attention was paid to the additive order of these two surfactants to BSA, the final helicity of the protein depended on the final concentrations of these two surfactants, irrespective of the additive order. These phenomena may be attributed to the predominance of mixed micelle formation over complex formation between BSA and the two surfactants below the mixing ratio of DDAPS ([DDAPS]/([DDAPS]+[SDS])) of 0.95. The predominance of the mixed micelle formation distinctly appeared in mixing ratios between 0.50 and 0.75. In this range, the mixed micelle formation accompanied the removal of dodecyl sulfate (DS) ions bound to BSA upon the late addition of DDAPS to the BSA-SDS mixture, whereas, upon the late addition of SDS to the BSA-DDAPS mixture, the mixed micelle formation was accelerated by the coexistence of DDAPS which disturbed the binding of DS ions to the protein.

Ion-Selective Electrode for Anionic Surfactants Using Hexadecyl Trimethyl Ammonium Bromide-Sodium Dodecylsulfate as an Active Ionophore

The construction and characteristic performance of PVC membrane electrode responsive to sodium dodecylsulfate (SDS) are described in this paper. The electrode is based on hexadecyl trimethyl ammonium bromide-Sodium dodecylsulfate (CTA+DS−) ion pair as ionophore in PVC membrane, which displays a Nernstian slope of −58 ± 0.9 mV/decade in a 5.0 × 10−6to 2.5 × 10−3 mol L−1concentration range and a limit of detection of 2.9 × 10−6 mol L−1. The electrode can be used for 3 months without showing significant changes in the value of slope or working range. Also the electrode has wide pH range of application and short response time. The electrode shows a selective response to SDS and a poor response to common inorganic anions. The selective sequence found was SDS &gt; HCO3 −&gt; CH3COO−&gt; Cl−&gt; I−&gt; NO3 −≈Br−&gt; F−&gt; CO3 2−&gt; C6H5O7 3−&gt; C2O4 2−&gt; SO4 2−&gt; C4H4O6 2−&gt; SO3 2−&gt; PO4 3−. The potentiometric selectivity coefficients determined are indicating that common anions would not interfere in the SDS determination. The electrode has been utilized as an end point indicator electrode for potentiometric titration involving hyamine as titrant.

Layered Cobalt Hydroxide Nanocones: Microwave‐Assisted Synthesis, Exfoliation, and Structural Modification

Layered cobalt hydroxide nanocones intercalated with dodecyl sulfate (DS) ions (see scheme; OH− blue, Co green dots, DS ions red) could be synthesized by the microwave-assisted rolling of lamellar structures. The cones could be exfoliated into cobalt hydroxide nanosheets and converted into CoOOH and Co3O4 nanocones.

ELECTROCHEMICAL SYNTHEZIS AND CHARACTERIZATION OF POLYPYRROLE FOR DODECYLSULFATE SENSOR MEMBRANE

A conducting polymer, polypyrrole, has been electrochemically synthesized from pyrrole monomer using cyclic voltammetry technique in aqueous solution in the presence of HDS dopant and KNO3 supporting electrolyte. The polymer was deposited on the surface of an Au-wire and the modified electrode obtained was then used as dodecylsulfate (DS-) ion sensor electrode. The best performance PPy-DS modified-Au electrode conditioned in the air system without HDS or SDS solution gave linear potential response for the concentration range of 1.0 x 10-5 - 1.0 x 10-3 M, sensitivity of 54.5 mV/decade, detection limit of 1.0 x 10-5 M, and response time of 23 - 30 second. The electrode showed good selectivity towards other anions, therefore can be used to determine SDS concentration in real samples system without any change of the samples matrix. Keywords: polypyrrole, SDS, cyclic voltammetry

Preparation and shape evolution of cuprous oxide in the solution phases of copper (II) dodecyl sulfate

In this paper, the functionalized surfactant of copper dodecyl sulfate [Cu(DS) 2] was used both as the metal ion source and as the modifier to investigate the preparation and shape evolution of cuprous oxide (Cu 2O). The increase of Cu(DS) 2 concentration from 0.27 to 6.82 mM caused the morphological change of Cu 2O crystals from the truncated cubic to the cuboctahedral, then to the coexistence of the cubic and the truncated octahedral, and finally to the truncated octahedrons. As an experimental control, the inorganic salt of copper (II) chloride was also used as the metal ion source to conduct the precipitation of Cu 2O. These results indicate that the special adsorption of organic counterions (i.e., dodecyl sulfate ions) exerted a great influence on the shape control of Cu 2O crystals, especially at a relatively low concentration. Meanwhile, the d-glucose concentration and the incubation time of crystals were also considered. In conclusion, the competitive adsorption of surfactant ions and d-glucose molecules onto crystalline faces, as well as the aging time, accounted jointly for the shape control of Cu 2O crystals.

Interaction of cationic monomer with sodium dodecyl sulfate in dilute aqueous solutions: ESR study

The effect of a cationic monomer (N,N,N,N-trimethyl[methacryloxyethyl]ammonium methyl sulfate) on the formation, structure, and local dynamics of associates resulted from the interaction of the monomer with sodium dodecyl sulfate in aqueous solutions was studied by ESR spectroscopy. In the presence of the monomer, micelles are formed at concentrations much lower than the CMC of the pure surfactant with the monomer molecules that form a condensed layer of counterions around a micelle of sodium dodecyl sulfate. The binding of surfactant micelles with the cationic monomer causes a significant decrease in the local molecular mobility of dodecyl sulfate ions.

Imaging of the Liquid−Liquid Interface under Electrochemical Instability Using Confocal Fluorescence Microscopy

The onset of the electrochemical instability has been imaged at the 1,2-dichloroethane (DCE)|water (W) interface modified with a fluorescent phospholipid using confocal fluorescence microscopy (CFM). Heterogeneously fluorescent images are recorded successively under the transfer of dodecyl sulfate ions (DS-) across the interface, which induces the irregularly increased current in a voltammogram. The commencement of the hydrodynamic movement of the solutions due to the electrochemical instability has been detected as the appearance of dark domains at the edge of the interface, that is, the three-phase contact of the DCE-W-glass wall confining the interface. In the potential region around the midpoint potential of the transfer of DS-, the area of the dark domains fluctuates and gradually grows with time. These locally confined unstable domains give rise to slightly augmented current in the simultaneously recorded voltammogram. The interface in this potential range appears to be globally stable at the expense of small unstable domains. In the potential region where the irregularly increased current is visible in the voltammogram, the entire interface becomes unstable and the dark and bright regions move vertiginously due to the Marangoni convection of the adjacent solution phases.

The Impact of Electrolyte on the Aggregation of the Complexes of Hyperbranched Poly(ethyleneimine) and Sodium Dodecyl Sulfate

The aggregation of the negatively charged complexes of hyperbranched poly(ethylenimine) (PEI) and sodium dodecyl sulfate (SDS) has been investigated at different sodium chloride (NaCl) concentrations using coagulation kinetics, electrophoretic mobility and dynamic light scattering measurements. The observed variation of the initial rate of coagulation with NaCl concentration indicates the formation of kinetically stable colloid dispersions in the investigated composition and pH range. These dispersions are electrostatically stabilized due to the adsorption of excess dodecyl sulfate ions on the surface of the polyelectrolyte/surfactant particles. Because of the enhanced adsorption of the anionic surfactant, the kinetic stability of the PEI/SDS dispersions increases with increasing SDS concentration and decreasing pH. Finally, we rationalize the effect of salt on the phase behavior and surface properties of polyelectrolyte/surfactant mixtures in terms of the salt-induced aggregation features of polyelectrolyte/surfactant particles.

Influence of EMAA compatibilizer on the structure and properties of HDPE/hydrotalcite nanocomposites prepared by melt mixing

AbstractHigh‐density polyethylene (HDPE)/hydrotalcite nanocomposites were prepared and characterized with a partially neutralized sodium ionomer of poly(ethylene‐co‐methacrylic acid) (EMAA) as a compatibilizer. Moreover, nanocomposites based on this ionomer were characterized as patterns to analyze the interactions between the hydrotalcite sheets and the methacrylic groups on the ionomer. Hydrotalcite particles were organically modified with sodium dodecyl sulfate ions. Their presence in the interlayer space was confirmed by means of Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD). Morphological analysis carried out with XRD and transmission electron microscopy (TEM) revealed the partially exfoliated/intercalated structure achieved in the nanocomposites. The mechanical properties of the HDPE nanocomposites mainly depended on the nature of the polymer matrix. Higher values of the tensile strength and Young's modulus were found in the EMAA nanocomposites. Thermogravimetric analysis (TGA) showed that hydrotalcite particles improved the thermal stability and delayed the onset decomposition temperature of both HDPE and EMAA nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Application of a membrane contactor for a simultaneous removal of p -cresol and Cr(III) ions from water solution

The aim of the study was to investigate the simultaneous removal of p-cresol and Cr(III) ions using a membrane contactor enhanced by a micellar solubilization. The investigations of solutes removal were performed taking advantage a polysulfone capillary membrane contactor in a counter-current mode and a micellar sodium dodecyl sulfate ions solution. The coefficients for a resistance in series mass transfer model were determined.

Continuous Treatment of Bisphenol A and Diethyl Phthalate Solutions Using Dodecylsulfate-Intercalated Mg-Al Layered Double Hydroxide Particles Packed in Column

Dodecylsulfate ion (DS ― )-intercalated Mg-Al layered double hydroxide (DS·Mg-Al LDH) particles packed in a column has been investigated to continuously treat bisphenol A and diethyl phthalate solutions. The effluents obtained by passing bisphenol A and diethyl phthalate solutions through the column are constantly measured by using a photomultiplier detector in order to analyze residual bisphenol A and diethyl phthalate. During the flow of bisphenol A and diethyl phthalate solutions, no absorbance was detected in the effluents for a certain amount of time. This suggests that bisphenol A and diethyl phthalate were continuously taken up by the DS·Mg-Al LDH particles in the column due to the hydrophobic interactions with intercalated DS ― until the shortage of its accommodation in the interlayer of the LDH. DS ― was rigidly fixed in the interlayers of DS·Mg-Al LDH during the flow of bisphenol A and diethyl phthalate solutions. Furthermore, the cycle of the uptake of bisphenol A from an aqueous solution and the elution of taken-up bisphenol A by ethanol was repeated by the alternately passing bisphenol A solution and ethanol through the column until the column ruptured by the swelling of the DS·Mg-Al LDH particles.

Synthesis of Hexagonal Nickel Hydroxide Nanosheets by Exfoliation of Layered Nickel Hydroxide Intercalated with Dodecyl Sulfate Ions

One-nanometer-thick nickel hydroxide nanosheets were prepared by exfoliation of layered nickel hydroxides intercalated with dodecyl sulfate (DS) ions. The shape of the nanosheets was hexagonal, as was that of the layered nickel hydroxides intercalated with DS ions. The nickel hydroxide nanosheets exhibited charge-discharge properties in strong alkaline electrolyte. The morphology of the nanosheet changed during the electrochemical reaction.

Development of a molecularly imprinted polymer for pyridoxine using an ion-pair as template

One of the main challenges in the molecularly imprinted polymers (MIP) field is the proper MIP design for water-soluble compounds because of appearance of serious drawbacks in polar solvents and insolubility of those compounds in non-polar solvents which are commonly used for MIP synthesis. In this work a novel and simple method for synthesis of molecularly imprinted polymers for a water-soluble compound was introduced. Pyridoxine was chosen as a target molecule and the ion-pair complex formed between pyridoxine ion (Py +) and dodecyl sulfate ion (DS −) was transferred into the chloroform via liquid–liquid extraction. Then polymerization was carried out in chloroform. The molecular mechanics and density functional theory were proposed to screen proper monomer. Binding energy, Δ E, of a template and a monomer as a measure of their interaction was considered. Ion-pair [Py +-DS −] was supposed as a template molecule and acrylic acid, methacrylic acid, allyamine, vinylpridine and 2-hydroxy ethyl methacrylate were as tested monomers. The MIP synthesized using acrylic acid showed the highest selectivity to pyridoxine as predicted from the Δ E calculation. The obtained MIP showed very high affinity against vitamin B6 in comparison to non-imprinted polymers (NIP). It was proved that the obtained MIP with introduced method was much better than that prepared in methanol as porogen. It was showed that the MIP prepared by this new method could be used as an adsorber for extraction and determination of pyridoxine in real and synthetic samples.

PVC matrix membrane sensor for potentiometric determination of dodecylsulfate

The construction and performance characteristics of a new potentiometric PVC membrane sensor for the determination of sodium dodecyl sulfate (SDS) are described. The sensor was based on the use of an N-cetyl-N,N,N trimethyl ammonium (CTA) dodecyl sulfate (DS) ion pair as ion exchange sites in PVC matrix in the presence of o-nitrophenyl octylether as plasticiser. The sensor exhibited a fast, stable, and near-Nernstian response for SDS over the concentration range of 1 × 10−3 to 10−6 M at 25°C and the pH range 4–8.5 with anionic slope of 52.5 ± 0.5 mV decade−1. The lower detection limit was 3 × 10−6 M, and the response time was 25 s. Selectivity coefficients of SDS with respect to a number of different species were investigated. There were negligible interferences caused by most of the investigated anions. The determination of 1.0–280.0 µg mL−1 of SDS in aqueous solutions showed an average recovery of 99.1%, and the mean relative standard deviation was 1.4 at 100 µg mL−1. The results obtained in the determination of SDS in liquid soap, water and in some pharmaceutical preparations compared favourably with those obtained by the Methylene Blue active substance method (MBAS). In the present investigation, the DS sensor has been used as an end-point indicator electrode for some precipitation titration reactions, e.g. titration of SDS with CTMABr and cetylpyridinium chloride with SDS.

Polylactide (PLA)/layered double hydroxides composite fibers by electrospinning method

Inorganic nanosized layered double hydroxides (LDHs) modified with dodecyl sulfate (DS) ions were incorporated into semi-crystalline polylactide (PLA) nanofiber non-woven membranes by combining a nanocomposite technique and the solution electrospinning process. The structure, morphology and thermal property of the electrospun membranes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential thermal analysis (DTA). It was found that the melting point of PLA decreased upon the increase of LDHs content in the membranes.