Effect Of Sodium Dodecyl Sulfate Concentration Research Articles

Structural, mechanical, and tribological studies of Ni-B-TiN composite coating: effect of SDS concentration

In industrial applications, it has been desired to be durable and used for a long time in harsh working conditions. As an alternative study, the effects of surfactants on TiN particle distribution, particle content in the coating, microstructure, surface morphology, hardness, and wear resistance were investigated. Scanning electron microscopy (SEM) was used to characterize the surface and cross-section images of Ni-B-TiN composite coatings. The SDS concentration in the electrolyte affects the TiN particle distribution, resulting in a uniformly distributed surface morphology of the composite coating. The crystal properties of the elements in the composite coating were examined using X-ray diffraction (XRD). The surfactant directed the Ni crystal in the (111) plane, affecting the preferred direction of the grains. The distribution of TiN particles in the Ni-B alloy matrix with Zeta potential was investigated. The mechanical properties of composite coatings were evaluated over average values by performing tests from different zones under a max. 50 mN load using the Nanoindentation technique. The tribological behavior of Ni-B-TiN composite coatings sliding towards Al2O3 balls (Ø 6 mm) was investigated with a CSM tribometer device void of lubrication at room temperature. In this study, the usability of SDS (sodium dodecyl sulfate)-anionic surfactant for Ni-B-TiN metal matrix composites deposited on mild steel substrates by the electrodeposition method has been explained.

Effect of Surfactants on Gas Holdup in Shear-Thinning Fluids

In this study, the gas holdup of bubble swarms in shear-thinning fluids was experimentally studied at superficial gas velocities ranging from 0.001 to 0.02 m·s−1. Carboxylmethyl cellulose (CMC) solutions of 0.2 wt%, 0.6 wt%, and 1.0 wt% with sodium dodecyl sulfate (SDS) as the surfactant were used as the power-law (liquid phase), and nitrogen was used as the gas phase. Effects of SDS concentration, rheological behavior, and physical properties of the liquid phase and superficial gas velocity on gas holdup were investigated. Results indicated that gas holdup increases with increasing superficial gas velocity and decreasing CMC concentration. Moreover, the addition of SDS in CMC solutions increased gas holdup, and the degree increased with the surfactant concentration. An empirical correlation was proposed for evaluating gas holdup as a function of liquid surface tension, density, effective viscosity, rheological property, superficial gas velocity, and geometric characteristics of bubble columns using the experimental data obtained for the different superficial gas velocities and CMC solution concentrations with different surfactant solutions. These proposed correlations reasonably fitted the experimental data obtained for gas holdup in this system.

Modulation of the Mechanical Properties of Hydrophobically Modified Supramolecular Hydrogels by Surfactant-Driven Structural Rearrangement

A combination of rheology and small-angle neutron scattering (SANS) experiments revealed the mechanism by which a surfactant can stiffen or soften physically cross-linked hydrogels. Here, the structure and rheological properties of a supramolecular hydrogel based on a random copolymer of N,N-dimethylacrylamide (DMA) and 2-(N-ethylperfluorooctane-sulfonamido)ethyl methacrylate (FOSM) were modified by the addition of sodium dodecyl sulfate (SDS). The effect of SDS concentration on the microstructure and properties of the hydrogel was determined by two types of experiments: (1) adding SDS by time-dependent, radial diffusion and (2) using samples where uniform loadings, i.e., no concentration gradient, of the SDS were achieved. Nanodomains consisting of FOSM aggregates were responsible for the physical cross-links in the hydrogel, but the formation of an equilibrium supramolecular network of the hydrogel was limited by conformational pinning of the water-swollen polymer segments by the relatively immobile FOS...

Effect of concentration and addition of ions on the adsorption of sodium dodecyl sulfate on stainless steel surface in aqueous solutions

The adsorption characteristics of sodium dodecyl sulfate (SDS) on stainless steel surface in aqueous solutions as well as the effect of added NaClO4 on adsorption are investigated. The stainless steel surface is hydrophobic when wetted by water and negatively charged in SDS solutions, which was characterized by performing open circuit potential (EOCP) and zero charge potential (EPZC) measurements. The adsorption isotherm of SDS on stainless steel surface in SDS aqueous solutions was measured by quartz crystal microbalance (QCM). The results indicate a four-stage adsorption process according to the micellization of SDS molecules both in bulk solution and on stainless steel surface. With the increase of SDS concentration, the mass of the adsorbed SDS molecules increases, while the structure of the adsorbed layer changes from monomers to hemimicelles. In the presence of NaClO4 as background electrolyte, the adsorption isotherm shifts to lower SDS concentration regime, mainly as a result of changing in electrostatic interactions both by the binding of Na+ on micelles and by the changing of ionic strength of the solution. The ionic strength effect is shown to be of vital importance in the change in electrostatic interactions between adsorbed hemimicelles mimicked by recording force-distance curves between a negatively charged tip and the hemimicelles using atomic force microscope (AFM). All the effects of SDS concentration and addition of NaClO4 on adsorption are clarified based on hydrophobic interactions and electrostatic interactions both between SDS molecules and between SDS molecules and stainless steel surface.

Effect of SDS concentration on colloidal suspensions of Ag and Au nanoparticles

We present a kinetic study of the effects of sodium dodecyl sulfate (SDS) concentration on reduction and aggregation of Ag+ and Au3+ ions in aqueous solutions. There are distinct differences between the surface plasmon absorption bands of Ag nanoparticles at different concentrations of SDS. The results reveal the existence of two competing SDS-induced processes: stabilization of the Ag nanoparticles due to adsorption and aggregation of the Ag nanoparticles due to increase in ionic strength. However, SDS induced aggregation of Au nanoparticles is negligible because of less surface passivity as evident from eaq− reaction with AuCl4−. Nevertheless, the average size of the Ag and Au nanoparticles remains almost similar at all SDS concentrations. UV–Vis spectrophotometry and transmission electron microscopy are used to characterize the nanoparticles. Moreover, it is shown that these SDS-capped Ag, Au and Au/Ag bimetallic nanoparticles could function as catalysts for the reduction of o-nitro aniline in the presence of NaBH4.

Concentration of sodium dodecyl sulfate used in occlusion body extraction affects Spodoptera littoralis nucleopolyhedrovirus biological activity

Efficacy of a baculovirus as a biological control agent is evaluated according to biological parameters, median lethal dose (LD_{50}) of the virus, and median lethal time (LT_{50}) of infected larvae. Sodium dodecyl sulfate (SDS) is commonly used in concentrations of 0.1%-1% to extract infective units of the baculoviruses, occlusion bodies (OBs), from infected cadavers. Although several studies have shown disruption of OB structure by SDS, the effects of SDS concentrations on baculovirus biological parameters are not well known. Indeed, it is essential to detect the optimum SDS concentration for OB extraction to compare the activity of baculoviruses accurately. In our study, the effects of SDS (0.1%-2%) on baculoviral biological activity were examined using Spodoptera littoralis nucleopolyhedrovirus in third instar Spodoptera littoralis (Lepidoptera: Noctuidae) larvae. Use of 1% SDS in OB extraction caused the lowest LD_{50}, while higher concentrations than 1% significantly increased the LD_{50}. The differences between LT_{50} values at 0.1%-1% SDS were found to be insignificant; however, higher concentrations (>1.0%) caused significant loss of biological activity. Therefore, 0.1%-1.0% SDS could be used for OB extraction; however, evaluation of LD_{50} and LT_{50} values together suggests that 1% SDS provides the best biological activity. The mode of action of SDS on baculovirus biological activity is discussed further.

Effects of sodium dodecyl sulfate on the oriented growth of nesquehonite whiskers

In this study, nesquehonite MgCO3·3H2O whiskers with long length and high aspect ratio were synthesized through reactive crystallization, in which MgCl2 and Na2CO3 precipitated in the presence of sodium dodecyl sulfate (SDS). The effects of SDS concentration, reactive temperature and reactants concentration were investigated. SEM, XRD and FT-IR were used to character morphology and structure of the products. It was found that the presence of SDS in the mixed aqueous solution was an important parameter for the morphology and size of nesquehonite crystals. The morphology of nesquehonite crystals changed from rod-like to bundle-like with increasing SDS concentration. The average length of nesquehonite whiskers was about 87–180μm while the aspect ratio was 18–45. The longest length reached 250μm and the biggest aspect ratio was about 100. The reactive temperature and reactant concentration also affect the size even the crystal type. It is concluded that SDS was beneficial for oriented growth of one-dimensional nesquehonite whiskers based on the formation process of the nesquehonite whiskers. The possible mechanism of SDS in nesquehonite whiskers precipitation was ascribed to physical adsorption of SDS on the individual amorphous nanoparticles or crystallites. The critical point of oriented growth occurred when the SDS concentration was about 4.33mM.

Aggregation Kinetics and Transport of Single-Walled Carbon Nanotubes at Low Surfactant Concentrations

Little is known about how low levels of surfactants can affect the colloidal stability of single-walled carbon nanotubes (SWNTs) and how surfactant-wrapping of SWNTs can impact ecological exposures in aqueous systems. In this study, SWNTs were suspended in water with sodium dodecylsulfate (SDS) as a surface-active dispersing agent. The effect of SDS concentration on SWNT suspension stability was investigated with time-resolved dynamic light scattering (TRDLS) initial aggregation studies utilizing both monovalent (Na(+)) and divalent (Ca(2+)) cations. The critical coagulation concentration (CCC) values increased with SDS concentration for the Na(+) treatments, but the Ca(2+) treatments were less sensitive to SDS concentration changes. Longer term stability studies with SDS concentrations orders of magnitude below the SDS critical micelle concentration demonstrated that SWNTs remained suspended for over six weeks in a surface water. Transport studies in a freshwater sediment similarly showed a SDS concentration-dependent mobility of SDS-wrapped SWNTs in that SWNTs showed a relatively greater retention at lower SDS concentrations (0.001%-0.05% w/v) than at a higher SDS concentration (0.1%). It is hypothesized that the stability and mobility of SWNT suspensions is directly related to the surface coverage of SDS on the SWNT surface that simultaneously increases electrosteric repulsion and decreases surface chemical heterogeneity. Overall, these studies demonstrate that low levels of surfactant are effective in stabilizing and mobilizing SWNTs in environmental media.

Measuring Local Equilibrium Flavor Distributions in SDS Solution Using Headspace Solid-Phase Microextraction

Solid-phase microextraction (SPME) sampling of the headspace above an aqueous micellar solution of sodium dodecyl sulfate (SDS) was shown to be effective for quantifying the equilibrium partitioning of limonene solute between water and SDS micellar aggregates. Concentrations in the headspace were determined from the amount absorbed by the SPME fiber during 1 min extractions, with the quantity on the fiber determined using gas chromatography/mass spectrometry (GC/MS). Headspace concentrations as a function of surfactant concentration were fit to a mass balance to yield the partition coefficient and critical micelle concentration. When the total limonene in the system was low enough that it could be completely dissolved by water in the absence of micelles, a constant value for the partition coefficient of 1700 M(-1) was obtained, independent of the limonene concentration. However, at higher total limonene concentrations, the partition coefficient became a function of the amount of limonene in the micelles, as confirmed by separate experiments in which either limonene or SDS concentration was varied. The observed increase in partition coefficient with increasing limonene likely signals a shift from micelles to swollen micelles and ultimately to microemulsion droplets. The effect of SDS concentration on the aqueous solubility limit of limonene could also be observed in HS-SPME experiments where either SDS or limonene was varied.

Sodium dodecyl sulfate-modified carbon paste electrodes for selective determination of dopamine in the presence of ascorbic acid

A carbon paste electrode (CPE) modified by a monolayer film of sodium dodecyl sulfate (SDS) was used for detection of dopamine (DA). Cyclic voltammetry demonstrated improved response of the DA sensor. This suggests the effectivity of surface modification of CPE by SDS. Impedance spectroscopy was used for the characterization of CPE surface properties. The effect of SDS concentration on the electrode quality also reveals that SDS formed a monolayer on CPE surface with a high density of negative-charged end directed outside the electrode. As a result, the carbon paste electrode modified with SDS (SDS/CPE) exerted discrimination against ascorbic acid in physiological circumstance. Thus, it can selectively determine dopamine even in the presence of 220-fold AA combined with differential pulse stripping voltammetry. In pH 7.40 phosphate buffer solution, the oxidation peak current on differential pulse voltammograms increases linearly with the concentration of DA in the range of 5.0 × 10 − 7 to 8.0 × 10 − 4 mol · L − 1 with a detection limit of 5.0 × 10 − 8 mol · L − 1 . Satisfying results are achieved when detecting the DA in injection and simulated biology sample.

Histochemical and biochemical evidences of the reversibility of tyrosinase activation by SDS

Terfezia claveryi ascocarps present a fully latent tyrosinase, whose activity can be measured only after activation with sodium dodecyl sulfate (SDS) or trypsin. The effect of SDS concentration on tyrosinase activity is represented by a sigmoidal curve, while activation shows a hyperbolic response. The progress curves obtained when the reaction was started by the addition of low amounts of trypsin or SDS revealed a lag phase. The stability of T. claveryi tyrosinase with both activating agents was also studied, and different profiles were obtained for trypsin and SDS. The first in vivo evidence that SDS activation of tyrosinase is a reversible process in contrast with the irreversibility of trypsin activation is reported in this paper for the first time.

Quantitative Analysis of Seven Triazine Herbicides by On-Line Micellar Electrokinetic Chromatography-Electrospray Ionization Mass Spectrometry

This paper presents a successful demonstration of the on-line coupling of MEKC (micellar electrokinetic chromatography) to ESIMS (electrospray ionization mass spectrometry) for the quantitative analysis of seven s-triazine herbicides. The on-line MEKC-ESIMS was used to determine the structure of CE-separated peaks of seven triazine herbicides. The mixture of triazine herbicides was separated in a 20 mM sodium borate buffer (pH 8.5) containing 15 mM sodium dodecylsulfate (SDS) by using a bare fused-silica capillary. Electrospray ionization mass spectrometer was operated in the positive-ion mode when the mass spectra of seven triazine herbicides were observed from each peak, and the solution of water-methanol-formic acid (50/49/1 v/v/v) was used as a sheath liquid. The effects of SDS concentration, the run buffer pH, and the electric field on the separation of seven s-triazine herbicides were investigated. The MEKC-ESIMS detection showed 5 to 10 times higher sensitivity compared to the MEKC-UV detection. In addition, it did not need any pretreatment step.

Analysis of catechins in extracts of Cistus species by microemulsion electrokinetic chromatography

A microemulsion electrokinetic chromatographic (MEEKC) method was developed for the separation of six catechins, specific marker phytochemicals of Cistus species. The MEEKC method involved the use of sodium dodecyl sulfate (SDS) as surfactant, heptane as organic solvent and butan-1-ol as co-solvent. In order to have a better stability of the studied catechins, the separation was performed under acidic conditions (pH 2.5 phosphate buffer). The effects of SDS concentration and of the amount of organic solvent and co-solvent on the analyte resolution were evaluated. The optimized conditions (heptane 1.36% (w/v), SDS 2.31% (w/v), butan-1-ol 9.72% (w/v) and 50 m M sodium phosphate buffer (pH 2.5) 86.61% (w/v)) allowed a useful and reproducible separation of the studied analytes to be achieved. These conditions provided a different separation profile compared to that obtained under conventional micellar electrokinetic chromatography (MECK) using SDS. The method was validated and applied to the determination of catechin and gallocatechin in lyophilized extracts of Cistus incanus and Cistus monspeliensis.

Diffusion coefficients of sodium dodecyl sulfate in water swollen cross-linked polyacrylamide membranes

Diffusion of aqueous sodium dodecyl sulfate (SDS) across cross-linked polyacrylamide hydrogel membranes has been studied by electrical conductivity measurements. Initial rapid sorption of SDS (as unimer) into the membranes is observed. The effect of SDS concentration, and of cross-linker fraction on the degree of swelling of the gels is studied and associated with binding of the surfactant to the polymer, with surface bound water suggested to be involved in these interactions. Below the surfactant critical micelle concentration, volume collapse of less cross-linked membranes is observed, and associated with aggregate formation. Fluorescence measurements using pyrene as a probe show that micellar aggregates do not diffuse through the membrane, and only overall unimer diffusion is observed. The effect of cross-linking on the diffusion process is discussed.

Adhesion strength of sodium dodecyl sulfate-modified soy protein to fiberboard

Thermal and rheological properties of sodium dodecyl sulfate (SDS)-modified soy protein isolate (SPI) adhesives were studied using differential scanning calorimetry (DSC) and rheometry. The ordered structure of native SPI was denatured as SDS concentration increased, and thermal stability of native SPI decreased at high SDS concentration. The enthalpy of SPI denaturation decreased significantly with increasing SDS concentration. Apparent viscosity of the SPI adhesives increased as SDS concentration increased. The SPI adhesives modified by high concentrations of SDS exhibited characteristics of a Newtonian-type flow. The SDS-modified SPI adhesives were applied to fiberboard, and effects of SDS concentration, press conditions, and assembly time on bond strength were investigated. Shear strength of the SPI adhesives increased with SDS concentration, reaching its maximum value at 3 wt% of SDS, and then decreased significantly. The shear strength increased as press time and/or press temperature increased. High press temperature (100 °C) and long press time (5 min) are needed to achieve relatively good adhesion properties. The shear strength also increased as assembly time increased. The shear strength of the SDS-modified SPI adhesives decreased after soaking in water for 24 h.