Layer Of Sodium Dodecyl Sulfate Research Articles

Enhanced formation of methane hydrate from active ice with high gas uptake

Gas hydrates provide alternative solutions for gas storage & transportation and gas separation. However, slow formation rate of clathrate hydrate has hindered their commercial development. Here we report a form of porous ice containing an unfrozen solution layer of sodium dodecyl sulfate, here named active ice, which can significantly accelerate gas hydrate formation while generating little heat. It can be readily produced via forming gas hydrates with water containing very low dosage (0.06 wt% or 600 ppm) of surfactant like sodium dodecyl sulfate and dissociating it below the ice point, or by simply mixing ice powder or natural snow with the surfactant. We prove that the active ice can rapidly store gas with high storage capacity up to 185 VgVw−1 with heat release of ~18 kJ mol−1 CH4 and the active ice can be easily regenerated by depressurization below the ice point. The active ice undergoes cyclic ice−hydrate−ice phase changes during gas uptake/release, thus removing most critical drawbacks of hydrate-based technologies. Our work provides a green and economic approach to gas storage and gas separation and paves the way to industrial application of hydrate-based technologies.

Influence of Dodecylsulfate Adsorption on the Stability of Cerium Oxide Nanoparticle-Based Colloidal Aqueous Dispersions

In this contribution, the influence of the adsorption of dodecylsulfate, an anionic surfactant, on the stability of colloidal aqueous dispersions containing ceria (CeO2) nanoparticles (NPs) was investigated using zetametry, UV-visible spectrophotometry, and potentiometry involving an ionic surfactant-selective electrode (ISSE). In particular, thanks to absorbance follow-ups carried out as a function of time, aqueous dispersions containing a given loading of CeO2 NPs were found simultaneously to stabilize more quickly with time and to adopt a higher opacity and a more pronounced light-yellow color as the sodium dodecylsulfate (SDS) concentration increased. Knowing that this absorbance was attributed undoubtedly to CeO2 NPs, the fact that the measured absorbance is lower for a higher amount of CeO2 NPs in suspension, as revealed by a higher opacity of the studied dispersions, is somewhat counterintuitive. Besides the higher opacity of the dispersions, a shield effect of the adsorbed SDS layer toward UV-visible light may also explain this observation. The adsorption of dodecylsulfate on CeO2 NPs was indeed demonstrated using zetametry measurements in the presence of SDS and the potentiometric method combined with an ISSE. This latter method did not only allow the accurate determination of impoverishment in freely diffusing dodecylsulfate (DS) anions resulting from DS adsorption on CeO2 NPs but it also showed that this latter obeys a Freundlich isotherm.

Bovine Serum Albumin and Fibrinogen Adsorption at the 316L Stainless Steel/Aqueous Interface.

The binding of bovine serum albumin (BSA) to a 316L stainless steel surface from a buffer solution has been characterized using neutron reflectometry and quartz crystal microbalance measurements; coverage at all concentrations up to a near-physiological concentration was found to be relatively low (<20%); the protein followed a two-step isotherm adsorption model type and the overall thickness at the higher concentrations (around 80 Å) suggested possible multilayering and/or protein unfolding. As it has been postulated that BSA may inhibit the further adsorption of another blood plasma protein-fibrinogen-the effects of preadsorbing BSA on fibrinogen adsorption were examined, first by prior physisorption of BSA to the stainless steel surface and second by pretreating the stainless steel with a layer of sodium dodecyl sulfate (SDS) to render it more hydrophobic. Although the preadsorption of BSA to an untreated stainless steel surface did slightly decrease the amount of fibrinogen adsorbed initially, it had no inhibiting effect if a solution containing solely fibrinogen subsequently flowed through. In contrast, the SDS-treated surface yielded both an increased BSA adsorption and consistently decreased fibrinogen adsorption.

Ultrafast excited state deactivation channel of thioflavin T adsorbed on SDS micelle: A combined femtosecond fluorescence and transient absorption study

Abstract In this contribution, we have presented the dynamics of molecular rotor dye thioflavin T (ThT) in Stern layer of sodium dodecyl sulfate (SDS) micelle using femtosecond fluorescence up-conversion and broadband transient absorption spectroscopy. ThT being a positively charged molecule is expected to remain in the Stern layer of micelle due to columbic attraction with the negatively charged surfactant head groups. The restriction imposed by the environment slows down the rotation of molecular fragments, which increases its quantum yield ∼8 times compared to pure water. We have confirmed the dual relaxation channel of ThT (LE → TICT1 and LE → TICT2) and found that the lifetime of the three states namely LE, TICT1 and TICT2 are 0.5, 3.1 and 15.7 ps respectively in 40 mM SDS.

Influence of Boron-Doped Diamond Surface Termination on the Characteristics of Titanium Dioxide Anodically Deposited in the Presence of a Surfactant

Boron-doped diamond (BDD) films were subjected to cathodic or anodic pre-treatments to achieve hydrogen-terminated (BDD-H) or oxygen-terminated (BDD-O) surfaces and then used as supports for surfactant-assisted anodic deposition of titanium oxide. Cyclic voltammetry and EIS experiments have shown that, unlike BDD-O case, at the BDD-H surface a stable layer of sodium dodecyl sulfate (SDS) is formed, which hinders TiO2 overall deposition process, as demonstrated by linear sweep voltammetry. SEM measurements revealed that this sluggish process leads to a better uniformity and to a higher roughness of the oxide coatings. When deposited on BDD-H, TiO2 also exhibited a light to dark current ratio with ca. 28% higher than that enabled by the use of a BDD-O substrate, indicating a better efficiency of charge carrier separation.

Sodium Dodecyl Sulfate Adsorption onto Positively Charged Surfaces: Monolayer Formation With Opposing Headgroup Orientations

The adsorption and structure of sodium dodecyl sulfate (SDS) layers onto positively charged films have been monitored in situ with vibrational sum-frequency-generation (SFG) spectroscopy and surface plasmon resonance (SPR) sensing. Substrates with different charge densities and polarities used in these studies include CaF2 at different pH values as well as allylamine and heptylamine films deposited onto CaF2 and Au substrates by radio frequency glow discharge deposition. The SDS films were adsorbed from aqueous solutions ranging in concentration from 0.067 to 20 mM. In general the SFG spectra exhibited well resolved CH and OH peaks. However, at SDS concentrations between 1 and 8 mM the SFG CH and OH intensities decreased close to background levels. Combined data sets from molecular conformation, orientation, and order sensitive SFG with mass sensitive SPR suggest that the observed changes in SFG intensities above 0.2 mM are related to structural arrangements in the SDS layer. A model is proposed where the SFG intensity minimum between 1 and 8 mM is associated with a monolayer containing two headgroup orientations, one pointing toward the substrate and one pointing toward the solution phase. The SFG peaks observed at concentrations below 0.2 mM are dominated by the presence of adsorbed contaminants such as fatty alcohols (e.g., dodecanol), which are more surface active than SDS. As SDS solution concentration is increased above 1 mM SDS molecules are incorporated in the surface layer, with dodecanol continuing to be present in the surface layer for solution concentrations up to at least the critical micelle concentration.

Friction properties of acrylic-carboxylated latex films. 2: Effect of post added surfactant

The second part of this work aiming at investigating how specificities of thin films prepared from aqueous polymer colloids (latexes) influence their friction properties is devoted to the role of surfactants. Two acrylic latexes containing either 1wt% or 4wt% of acrylic acid were used, to which 0 to 9wt% of sodium dodecyl sulfate (SDS) was post added before film formation by drying. Bulk mechanical properties were also studied in order to improve interpretation of friction results. Increasing the amount of SDS in the films has the effect of increasing Young's and shear storage moduli and decreasing tanδ. SDS, forming crystallized aggregates in the bulk of the films, behaves like a reinforcing filler, except at 9wt% where the SDS phase percolates under stress and allows film deformation by shear bands at very low stress. Friction coefficients dramatically decrease with increasing SDS concentration, especially at high strain rate. Surface shear stress is strongly decreased due to lubrication by SDS having migrated to the film surface. In order to gain more insight in the lubrication mechanisms, SDS layers were deposited on glass in increasing amounts. This part of the study seemed to indicate that organization of the SDS surface layers has more impact than their amount.

Vesicle formation induced by layered double hydroxides in the catanionic surfactant solution composed of sodium dodecyl sulfate and dodecyltrimethylammonium bromide

In this paper, it is reported that positively charged Mg3Al layered double hydroxide (LDH) nanoparticles can induce the spontaneous formation of vesicles in micelle solution of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) with a mass ratio of 8:2. The formation of vesicles was demonstrated by negative-staining transmission electron microscopy observations. The size of the vesicles increased with the increase in the concentration of Mg3Al-LDH nanoparticles. A composite of LDH nanoparticles encapsulated in vesicles was formed. A possible mechanism of LDH-induced vesicle formation was suggested. The positively charged LDH surface attracts negatively charged micelles or free amphiphilic molecules, which facilitates their aggregation into bilayer patches. These bilayer patches connect to each other and finally close to form vesicles. It was also found that an adsorbed compound layer of SDS and DTAB micelles or molecules on the LDHs surface played a key role in vesicle formation.

Structure of the Sodium Dodecyl Sulfate Surfactant on a Solid Surface in Different NaCl Solutions

Studies of molecular dynamics simulations of sodium dodecyl sulfate (SDS) molecules adsorbed on a graphite surface in different salt (NaCl)/water solutions were conducted. The results showed the formation of hemicylindrical aggregates, at different salt concentrations, in agreement with atomic force microscopy (AFM) results. However, the hemicylinders exhibited different structures as the salt concentration was increased. At low concentrations, the internal structure of the hemicylinder formed well-defined SDS layers, parallel to the surface. However, when the amount of salt was increased, the top layer became less pronounced until it disappeared at the highest concentration. Density profiles of the SDS headgroups were also analyzed, and those profiles were found to become sharper as the NaCl concentration increased. The phenomenon was investigated in terms of how the aggregates wet the solid surface.

Horizontally aligned carbon nanotube field emitters fabricated on ITO glass substrates

Horizontally aligned carbon nanotube (CNT) field emitters, in which electrons are emitted from the side of CNTs, are fabricated on indium tin oxide (ITO) glass substrates by electrophoretic deposition and fissure formation techniques. A thin film of CNTs is deposited onto an ITO glass plate using an aqueous mixture of CNTs and the cationic detergent cetyltrimethylammonium bromide by applying a negative voltage to the ITO glass plate. Then, an additional layer of sodium dodecyl sulfate (SDS), an anionic detergent, is deposited on the CNT film. This is done using an aqueous solution of SDS by applying a positive voltage. Through the process of firing, CNTs with a clean surface are exposed in the fissures produced. No further treatment is needed to initiate or augment field emission. The CNT field emitters show relatively good field-emission properties such as high current density (11 mA/cm 2 at an applied electric field of 4.3 V/μm), low turn-on field (2.2 V/μm), and good stability (98 h for 10% degradation of current density from 400 μA/cm 2).

Electrically Driven Motion of an Air Bubble on Hemispherical Oil/Water Interface by Three-Phase Boundary Reactions

Our electrochemical cell consisted of a ferrocene-included hemispherical nitrobenzene (NB) droplet on the glassy carbon (GC) electrode which was immersed in the aqueous solution including sodium sulfate and sodium dodecyl sulfate (SDS). When an air bubble was injected near the boundary between the oil and the aqueous phase, it stayed at the top of the hemisphere on the boundary so that the lower half of the bubble was put in oil and the other half was in water. From the force balance of surface tension and buoyancy of the bubble, the bubble took an energetic minimum at the interface. It sank into the oil phase when ferrocene in the oil was electrochemically oxidized through the GC electrode by the three-phase boundary reaction. The electrochemical reduction caused the bubble to move back toward the aqueous phase. The motion of the bubble was synchronized with the redox reaction of ferrocene. The potential step oxidation showed such a rapid response that the motion could not be attributed to diffusion of ferricenium ion from the three-phase boundary to the bubble. Our idea of explaining the rapidity was the translational motion of the SDS layer along the boundary, which was driven by the difference in the surface concentration of SDS caused by the electrochemical generation of the ferricenium ion. The motion of the SDS layer was demonstrated by the shrinkage of the oil layer spread on the water surface when SDS solution was dropped on the oil layer. The spreading velocity was close to the velocity of propagating the oxidation of ferrocene to the bubble.

Polyelectrolyte Adsorption onto a Surface-Confined Surfactant

Using sodium dodecyl sulfate (SDS) as a surfactant and poly(diallyldimethylammonium chloride) (PDDA) as a polyelectrolyte, we formed a surfactant−polymer complex on a model surface of a positively charged 2-aminoethanethiol (cysteamine) self-assembled monolayer on gold. The complex formation is achieved by first SDS adsorption on cysteamine and subsequent adsorption of PDDA on the preformed SDS layer. Successful deposition of the PDDA layer on SDS without noticeable surfactant desorption shows that the complex formation is a fast process. The presence of SDS−PDDA complex on a cysteamine-modified gold substrate was observed by surface plasmon resonance (SPR) and Fourier transformed infrared spectroscopy. The thicknesses obtained from the SPR data were 1.5 nm for SDS and 1.1 nm for PDDA. Concentrations of SDS and PDDA in the parent solutions necessary to yield the complex upon adsorption were determined.

Agglomeration of magnetic particles and breakup of magnetic chains in surfactant solutions

This study investigates the transition from reversible secondary to irreversible primary-minimum aggregation of superparamagnetic particles in surfactant solutions. The magnetic induction at which this transition occurs is experimentally determined by visualization of chain formation under a magnetic field and chain breakup after the field is removed. The value of the theoretical transitional magnetic induction is calculated from the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, which includes van der Waals, electrostatic, and magnetic-dipole forces, as well as non-DLVO steric repulsion. Experimental results show that the transitional magnetic induction increases with higher concentrations of sodium dodecyl sulfate (SDS). When the surfactant concentration is high, the theoretical value of transitional magnetic induction agrees well with the experimental value. Only when the surface of the particles is completely covered by surfactant molecules can the secondary-minimum chains break up quickly to form a uniformly dispersed particle suspension after the magnetic force is removed. Moreover, such investigations reveal that the primary-minimum chains are shorter when they are formed in solutions of higher concentrations of SDS. This phenomenon occurs because the nonequilibrium steric repulsion between adsorbed SDS layers on the surface of the particles allows the transition from secondary- to primary-minimum aggregation for some of the particles in a chain. When the SDS segments are not adequately compressed, long chains formed in SDS solutions break up at points of secondary-minimum aggregation after removal of the magnetic force. At these points, the adsorbed SDS layers keep particles away from the primary-minimum, leading to the breakup of long chains and formation of short primary-minimum magnetic chains.

Effects of nonionic surfactant and sodium dodecyl sulfate layers on electroacoustics of hexadecane/water emulsions

Hexadecane-in-water emulsion droplets were formed in a homogeniser in the presence of a mixture of an anionic surfactant (sodium dodecyl sulfate, SDS) and nonionic surfactants of various chain lengths [nonylphenol ethoxylate (C9φEN, N=100, 40 and 30) or an alcohol ethoxylate (Brij35)]. The dynamic mobility of the oil droplets was then measured using a flow-through version of an AcoustoSizer. Large changes were observed in the dynamic mobility of the particles formed with the mixed surfactants compared to particles formed with SDS alone. O'Brien's “gel layer” model was employed to interpret the data. The characteristics of the adsorbed layer appeared to be similar whether the nonionic surfactant was adsorbed concurrently with the SDS as the emulsion formed or was merely added afterwards to the emulsion established. The particle size, the charge and the molar fraction of SDS had virtually no effect. The layers formed with the nonionic surfactants decreased in thickness with decreasing molecular weight as expected. Passage through the homogeniser itself had no effect on the properties of the largest nonionic surfactant and, hence, on the adsorption layer formed with it.

Adsorption of Sodium Dodecyl Sulfate to a Polystyrene/Water Interface Studied by Neutron Reflection and Attenuated Total Reflection Infrared Spectroscopy

Spun-cast layers of polystyrene have been transferred to large silicon crystals as substrates for neutron reflectivity studies and to prisms for infrared-attenuated total reflection measurements of surfactant adsorption. This paper describes an investigation of the adsorption from aqueous solutions of sodium dodecyl sulfate (SDS) to this interface of aqueous solution and polystyrene. The structure and amount of adsorbate is described and discussed. The adsorption isotherm shows that both the thickness and volume fraction of the SDS layer increase to plateau values above the critical micelle concentration (cmc) where the area per molecule is approximately 42 A2. Above the cmc, there is a decrease in the total amount of adsorbed material unless SDS of very high purity is used. This unusual behavior is explained by the presence of dodecan-1-ol from hydrolysis of SDS which is highly surface active but can be solubilized in micelles of SDS.

Adhesion of latex films. Part IV. Dominating interfacial effect of the surfactant

Our aim was to study the effect of various surfactants on the adhesion properties of latex films. For this purpose, a model monodisperse, surfactant-free, core-shell latex was synthesized. The core was a random copolymer of styrene and butyl acrylate. The shell consisted of a styrene/butyl acrylate/methacrylic acid terpolymer with 10 wt% of methacrylic acid. Sodium dodecyl sulfate (SDS) and various ethoxylated nonionic surfactants were post-added to the latex at increasing concentrations. The adhesion of the corresponding films was measured by peeling at 180°. The shapes of the curves relating the peel energy to the surfactant concentration were similar, irrespective of the nature of the surfactant, namely a decrease to a constant plateau level. This means that in these systems, the influence of a weak boundary layer at the interface dominates all other possible effects of the surfactant. This was confirmed by surface analysis and peel experiments with surfactant-free films contacted with spin-coated SDS layers of increasing thickness. The reasons why the deleterious interfacial effect of the surfactant overwhelms all others are discussed.

Spectroscopic Investigation of Sodium Dodecyl Sulfate Adsorbed to a Trimethylsiloxane Monolayer on Silica

The adsorption of premicellar sodium dodecyl sulfate (SDS) onto methylated (C 1 ) silica surfaces was investigated spectroscopically to explore the physical origin of premicellar adsorption. Methylation was done to provide a hydrophobic surface without interpenetration of the SDS chains into the monolayer. The premicellar adsorption maxima were found to be smaller for the C 1 surface than for the n-octadecylsiloxane (C 18 ) surface, which implicates interpenetration as an important factor in premicellar adsorption maxima. Roughness was found to increase the premicellar adsorption maximum on the C 1 surface. The rotational diffusion behavior of acridine orange on the C 1 and C 18 surfaces points to a structural transition in the adsorbed SDS layer as the origin of the large premicellar adsorption maximum of SDS on C 18 .

FTIR-ATR study of the co-adsorption of benzophenone with sodium dodecyl sulfate and sodium dodecylbenzenesulfonate using Al 2O 3-coated optics

The adsorption of sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SLABS), and the co-adsorption of those surfactants with a “probe” species — benzophenone (BPN) — at the Al 2O 3/aqueous solution interface were examined via polarized Fourier transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy. The internal reflection element (IRE) was ZnSe, coated with 0.1–0.25 μm of Al 2O 3 deposited by r.f. sputtering. This technique allows in situ determination of adsorption isotherms and adsorbate structures from IR-ATR spectra of the surfactants. Spectra of the surfactant head groups may be analyzed at energies down to about 900 cm −1. The interface remains in contact with surfactant solution while the spectra are obtained. Solvation-induced band shifts for BPN co-absorbed with SDS or with SLABS, compared with band positions in various solvents, indicated that BPN resided in the alkyl region of the SDS or SLABS surface layer. The extent of co-adsorption was a function of pH and ionic strenght. The presence of the BPN reduced the adsorption density of both SDS and SLABS. Orientation of the probe molecules within the adsorbed SDS layer was determined from the linear dichroic ratios exhibited by polarized ATR spectra. The orientation of the BPN molecules changed significantly with solution conditions, but generally the long axis of the BPN molecules was normal to long axes of the surfactant alkyl chains. The surfactant alkyl chains were found to be inclined to the surface normal at angles of 42–50, and the phenyl rings of SLABS were inclined at 38–45, depending upon the conditions. The implications of these results for the IR spectral analysis of adsorbate structures are discussed.

Reorientation of acridine orange in a sodium dodecyl sulfate monolayer at the water-hexadecane interface

A macroscopically oriented layer of sodium dodecyl sulfate (SDS) at the interface of water and n-hexadecane was investigated using acridine orange as a fluorescent probe. The range of angles through which the hindered out-of-plane reorientation occurs for the probe was found to correspond closely to the surface roughness predicted by the capillary wave model through the interfacial tension. The in-plane reorientation of the probe was found to be significantly slower than that in the absence of SDS, with little dependence on the SDS concentration. The in-plane and out-of-plane rotations of acridine orange appear to correspond to the two decay components measured for acridine orange in micellar solution, indicating that these macroscopically oriented surfactant monolayers can provide detailed insight into solute-micelle interactions

Influence of detergent builders on surface properties of sodium dodecyl sulfate solutions under dynamic and static conditions

The effects of various detergent builders on surface properties of sodium dodecyl sulfate (SDS) solutions have been investigated by measuring the equilibrium surface tension and hysteresis curves of surface pressure vs surface area under dynamic conditions. While the adsorbed layer of SDS under static conditions is in the liquid‐expanded state, a two‐dimensional phase transition of the adsorbed layer from liquid‐expanded to condensed‐film can be observed on compression at higher rates beyond the saturated adsorption. For the SDS solution containing excess NaCl (1×10−1 M), the adsorbed layer of SDS is already in the condensed state under static condition due to a depression in the dissociation of SDS.It has been found that some polyelectrolytes, as well as conventional ionic builders, contribute to increasing the surface excess concentration of SDS together with promoting micelle formation and also to stabilizing the adsorbed layer of SDS. On the other hand, poly(vinyl alcohol) (PVA) as a nonionic polymer is adsorbed at the air‐water interface in preference to SDS. In this case, the hysteresis of the dynamic surface behavior of the mixed solution can be attributed to the structural change of the adsorbed layer of PVA rather than SDS, which is different from the other ionic builders.