Sodium Dodecyl Sulfate Molecules Research Articles

Enhanced Power Output of a Triboelectric Nanogenerator using Poly(dimethylsiloxane) Modified with Graphene Oxide and Sodium Dodecyl Sulfate.

In this work, a new approach to modifying poly(dimethylsiloxane) (PDMS) as a negative triboelectric material using graphene oxide (GO) and a sodium dodecyl sulfate (SDS) surfactant was reported. A porous PDMS@GO@SDS composite triboelectric nanogenerator (TENG) could deliver an output voltage and current of up to 438 V and 11 μA/cm2, respectively. These values were 3-fold higher than those of the flat PDMS. The superior performance is attributed to the intensified negative charges on PDMS from the oxygen functional groups of GO and anionic head groups of the SDS molecules. The outstanding performance and straightforward, low-cost fabrication process of the PDMS@GO@SDS TENG would be beneficial for the further development of powerful NGs integrated into wearable electronics and self-charging power cells.

Effect of silica sand size and saturation on methane hydrate formation in the presence of SDS

Abundant reserves of natural gas hydrates are hosted in the pores of sediment layers, and the hydrate-based technology could be widely used in industry. In this work, the formation kinetics of methane hydrate in a complex system containing silica sand and 300-ppm sodium dodecyl sulfate (SDS) solution were investigated at 275.15 K and 7 MPa. The hydrate was formed in different-saturated silica sand with particle sizes of 100, 150, 200, 300, and 400 mesh. The results indicated that in both the 50%- and 100%-saturated sand, a larger particle size exhibited a better methane storage capacity. In the complex system, the presence of SDS molecules significantly enhanced the hydrate formation process and weakened the effect of particle size on the hydrate formation rate. The difference in hydrate gas uptake formed in the differently saturated silica sand indicted that with an increase in saturation, the smaller-sized silica sands caused a more marked inhibitory effect. Finally, the different hydrate distributions in the 50%- and 100%-saturated silica sand revealed that a hydrate film formed quickly and preferentially on the surface of the silica sand, which was attributed to the adsorption of the SDS active groups and the presence of the silica sand surface. With the thickening of the hydrate film, the resulting volume expansion and stronger capillary force led to the migration of the liquid phase, which resulted in the hydrate distributions observed in the differently saturated silica sands.

A Liquid‐Crystal‐Based System for Differentiating Structurally Related Analytes

AbstractWe report a new approach for differentiating structurally related analytes using a liquid crystal (LC) based system. In this work we have combined two principles (analyte‐surfactant interactions and host‐guest inclusion) at LC/aqueous interface to differentiate structurally related analytes methyl red (MR) and methyl orange (MO). On introducing MR/MO in aqueous solution containing sodium dodecyl sulfate (SDS), the optical response of 4‐cyano‐4′‐pentylbiphenyl (5CB) changes from dark to bright in presence of MR but remains same in the presence of MO. This observation implies interaction of analyte (MR) and surfactant (SDS), thus effectively displacing SDS adsorbed at the 5CB/aqueous interface. Further, competitive inclusion complex formation of β‐cyclodextrin (β‐CD) with SDS or with analyte (dye, MR/MO) was visualized through changes in the optical response of 5CB at SDS‐laden 5CB/aqueous interface. On addition of MR/MO to the SDS‐β‐CD complex solution the optical response of 5CB changes from bright to dark in presence of MO but remains same in the presence of MR. This implicates that homeotropic orientation of 5CB resulted due to the reorganization of displaced SDS molecules from β‐CD cavity at the 5CB/aqueous interface. Overall, this LC based system demonstrates differentiation of structurally related analytes in the absence and presence of β‐CD.

Online Removal of Sodium Dodecyl Sulfate via Weak Cation Exchange in Liquid Chromatography-Mass Spectrometry Based Proteomics.

Biological research often requires the use of sodium dodecyl sulfate (SDS) to solubilize protein samples; however, this detergent is not compatible with direct mass spectrometry (MS) analysis. Here, we report an online high-throughput proteomics method that permits standard in-solution digestion of SDS-containing samples followed by direct liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis using weak cation-exchange chromatography (WCX). This approach, called the online removal of sodium dodecyl sulfate (Online reSDS), exploits the properties of WCX in a highly organic and mildly acidic medium to retain positively charged peptides by both hydrophilic interaction and electrostatic attraction while simultaneously repelling negative SDS molecules. This method was optimized to successfully analyze complex samples that contain up to 1% of SDS. Furthermore, online reSDS improves the identification of peptides with post-translational modifications (PTMs), such as deamidation and phosphorylation, without preliminary enrichment. In conclusion, we show that reSDS can facilitate research in proteomics by allowing the use of SDS in a wide range of LC-MS/MS applications with simplified sample-processing procedures.

Effect of Sodium Dodecyl Sulfate Surfactant on Methane Hydrate Formation: A Molecular Dynamics Study.

In experimental studies, it has been observed that the presence of sodium dodecyl sulfate (SDS) significantly increases the kinetics of hydrate formation and the final water-to-hydrate conversion ratio. In this study, we intend to understand the molecular mechanism behind the effect of SDS on the formation of methane hydrate through molecular dynamics simulation. Hydrate formation conditions similar to that of laboratory experiments were chosen to study hydrate growth kinetics in 1 wt % SDS solution. We also investigate the effect of interactions with isolated SDS molecules on methane hydrate growth. It was observed that the hydrophobic tail part of the SDS molecule favorably interacts with the growing hydrate surface and may occupy the partial hydrate cages while the head groups remain exposed to water.

The Role of Electrostatic Repulsion on Increasing Surface Activity of Anionic Surfactants in the Presence of Hydrophilic Silica Nanoparticles

Hydrophilic silica nanoparticles alone are not surface active. They, however, develop a strong electrostatic interaction with ionic surfactants and consequently affect their surface behavior. We report the interfacial behavior of n-heptane/anionic-surfactant-solutions in the presence of hydrophilic silica nanoparticles. The surfactants are sodium dodecyl sulfate (SDS) and dodecyl benzene sulfonic acid (DBSA), and the diameters of the used particles are 9 and 30 nm. Using experimental tensiometry, we show that nanoparticles retain their non-surface-active nature in the presence of surfactants and the surface activity of surfactant directly increases with the concentration of nanoparticles. This fact was attributed to the electrostatic repulsive interaction between the negatively charged nanoparticles and the anionic surfactant molecules. The role of electrostatic repulsion on increasing surface activity of the surfactant has been discussed. Further investigations have been performed for screening the double layer charge of the nanoparticles in the presence of salt. Moreover, the hydrolysis of SDS molecules in the presence of silica nanoparticles and the interaction of nanoparticles with SDS inherent impurities have been studied. According to our experimental observations, silica nanoparticles alleviate the effects of dodecanol, formed by SDS hydrolysis, on the interfacial properties of SDS solution.

Neutral and acid-adapted fatty acid vesicles of conjugated linoleic acid.

FAVs (fatty acid vesicles), originated from natural biomass and created available biointerface, have advantages of biocompatibility, low-cost, and easy self-assembly in aqueous solution due to their dynamic feature. However, there is no example of applying FAVs in contact with human body since they are inherently alkaline-adapted and pH windows for the FAV formation and application are very narrow and far away from the physiological pH range. In this work an attempt to turn the alkaline-adapted FAVs into neutral and acid-adapted ones was made by fabricating the amphiphile-hybrid vesicles of CLA (conjugated linoleic acid) with a typical cosmetic emulsifier SDS (sodium dodecylsulfate) and/or a co-emulsifier DA (dodecyl alcohol). pH windows for the SDS- and/or DA-hybrid FAV formation of CLA were judged by using dynamic light scattering criterion, and confirmed by small-angle X-ray scattering and room temperature transmission electron microscopy. The experimental results show that with the aid of H-bonding and ion-dipole forces among molecules of CLA, SDS and DA within the hybrid vesicle walls that were identified by Fourier transform infrared analysis, much wider pH windows of 2.5-11.7 for the hybrid FAVs were obtained by expansion from 8.0-9.0 for FAV of CLA alone, which was composition-dependent and made the hybrid FAVs become neutral and acid-adapted.

Thermodynamic compatibility between cyclodextrin supramolecular complexes and surfactant

Supramolecular structures based on cyclodextrins have been extensively used for drug delivery systems over decades. However, combining host and guest molecules in a pharmaceutical formulation is not a trivial process, being one of the majors concern the inclusion complex compatibility with other excipients presented in the final formulation. Herein, experimental and theoretical calculations were used to investigate the competition of sodium dodecyl sulfate (SDS) with atenolol (ATE) or losartan (LOS), antihypertensive drugs widely used in the treatment of hypertension. Our findings, using nuclear magnetic resonance and isothermal titrations calorimetry experiments and molecular dynamic simulations demonstrated that LOS remain included into CD cavity after excipient (SDS) addition, which was not verified for ATE ternary system, being the drug displaced by SDS molecule.

Thermochemistry of the Dissolution of Dipeptides Containing DL-α-Alanine in Aqueous Solutions of Sodium Dodecyl Sulfate at 298.15 K

Enthalpies of the dissolution of DL-α-alanylglycine (AlaGly), DL-α-alanyl-DL-α-alanine (AlaAla), DL-α-alanyl-DL-α-valine (AlaVal), and DL-α-alanyl-DL-norleucine (AlaNln) in an aqueous solution of sodium dodecyl sulfate (SDS) at SDS concentration of m = 0–0.07 mol kg−1 and temperature Т = 298.15 K are measured via calorimetry. The standard values of the enthalpy of dissolution (ΔsolH m ) and the transfer of dipeptides (ΔtrH m ) from water to aqueous SDS solutions are calculated using the experimental data. The dependences of ΔsolH m and ΔtrH m the SDS concentration at a constant concentration of dipeptide are established. Thermochemical characteristics of the transfer of AlaGly, AlaAla, AlaVal, and AlaNln in the investigated range of SDS concentrations are compared. The results are interpreted by considering ion–ion, ion–polar, and hydrophobic–hydrophobic interactions between SDS and dipeptide molecules.

Controlling direct contact force for wet adhesion with different wedged film stabilities

In solid–liquid–solid adhesive systems, wedged films often feature instability at microscopic thicknesses, which can easily disrupt the adhesive strength of their remarkable direct contact force. Here, sodium dodecyl sulfate (SDS) was employed to tune the instability of adhesion in wedged glass–water–rubber films, achieving controllable direct contact. Experimental results showed that the supplement of SDS molecules significantly weakened the direct contact force for wet adhesion and eliminated it at high concentrations. The underlying reason was suggested to be the repulsive double-layer force caused by SDS molecules, which lowers the instability of the wedged film and balances the preload, disrupting the direct contact in wet adhesion.

Ab Initio Study on Electronic Sorting of Single-Wall Carbon Nanotubes Using Sodium Dodecyl Sulfate

How differently sodium dodecyl sulfate (SDS) surfactants behave on metallic and semiconducting carbon nanotubes (CNTs) is one of the fundamental questions in the science and application of CNTs. In this study, we investigate the adsorption of SDS surfactants onto single-wall CNTs (SWCNTs) using ab initio methods to clarify the mechanism of metal/semiconductor separation of SWCNTs. We found that dodecyl sulfate (DS) ions are more likely to adsorb onto SWCNTs than sodium (Na) ions or SDS molecules, whereas the adsorption energy of SDS molecules becomes stronger as the diameter of the SWCNTs increases, the adsorption energy of DS ions for metallic (5, 5) CNTs is much stronger than those for semiconducting (6, 5) or (10, 3) CNTs, causing a larger aggregation number of DS ions on metallic SWCNTs and a separation of SWCNTs by electronic type. In actual multiple surfactant simulations, for a few DS ions, it is preferred that all DS ions adsorb on metallic (5, 5) CNTs; however, for more than eight DS ions, one or...

Facilely control the SDS ability to reduce the interfacial tension via the host-guest recognition

Supramolecular chemistry provides a facile and feasible method to construct desired compounds via noncovalent interactions. Based on the host-guest recognition, the surfactant/cyclodextrin (CD) inclusion exhibited the excellent performance in potential application of various fields. The sodium dodecyl sulfate (SDS)/β-CD inclusion was introduced to chemical enhanced oil recovery. The fabrication of SDS/β-CD inclusion seriously affected the SDS ability to reduce the interfacial tension (IFT) between a model oil (toluene and n-decane, v/v=1:1) and water, which may be the key factor to reduce the adsorption loss of SDS molecules via the addition of β-CD molecules. To reactivate the interfacial activity of SDS molecules, we employed the adamantanamine chloride (AD) to the SDS/β-CD inclusion solutions. Interestingly, the electrostatic attraction between AD/β-CD inclusion and SDS molecule dominated the change tendency of IFT values, which was further verified by the systematical investigations on the salinity and temperature effects on the IFT.

The Molecular Basis of the Sodium Dodecyl Sulfate Effect on Human Ubiquitin Structure: A Molecular Dynamics Simulation Study

To investigate the molecular interactions of sodium dodecyl sulfate (SDS) with human ubiquitin and its unfolding mechanisms, a comparative study was conducted on the interactions of the protein in the presence and absence of SDS at different temperatures using six independent 500 ns atomistic molecular dynamics (MD) simulations. Moreover, the effects of partial atomic charges on SDS aggregation and micellar structures were investigated at high SDS concentrations. The results demonstrated that human ubiquitin retains its native-like structure in the presence of SDS and pure water at 300 K, while the conformation adopts an unfolded state at a high temperature. In addition, it was found that both SDS self-assembly and the conformation of the resulting protein may have a significant effect of reducing the partial atomic charges. The simulations at 370 K provided evidence that the SDS molecules disrupted the first hydration shell and expanded the hydrophobic core of ubiquitin, resulting in complete protein unfolding. According to these results, SDS and temperature are both required to induce a completely unfolded state under ambient conditions. We believe that these findings could be useful in protein folding/unfolding studies and structural biology.

Thixotropic bulk elasticity versus interfacial elasticity in Xanthan Gum surfactant mixed solutions

Dynamic surface behavior and interfacial rheology of Xanthan Gum (XG) polymer and surfactant mixed aqueous solutions have been investigated in this work using Profile Analysis Tensiometry (PAT). The interactions of XG with anionic sodium dodecyl sulfate (SDS) and nonionic triton X100 surfactants were studied. The results demonstrate a significant influence of the XG thixotropic bulk rheology behavior on dynamic surface tension measurements. The time dependent thixotropic force (due to the movement and rearrangement of XG molecules under applied shear and relaxation time afterwards) was evaluated using a high precision buoyancy force measurement system. This extra thixotropic force can affect the expected balance of gravity and surface forces in the Gauss-Laplace equations and causes an abnormal increasing dynamic surface tension for aqueous XG solutions versus time in absence of surfactants. It is shown that the thixotropic property of this polymer can also induce an additional surface elasticity which can be measured by drop oscillation experiments via PAT. Therefore, surface elasticity measurements can be proposed as a novel method for determining the extent of fluid thixotropy. The results also showed strong interaction between XG and SDS molecules. At SDS concentrations below critical micelle concentration (CMC), the equilibrium surface tension of XG-SDS solution decreased considerably with increasing XG concentration. This interaction originates from the anionic nature of both XG and SDS molecules. The surface tension behavior of mixed solutions of XG and Triton X100 molecules did not show significant interactions. The obtained results allow improving the ability of the Gauss-Laplace Equation to calculate more accurately the dynamic surface tension of thixotropic fluids.

Electrochemical oxidation of As(iii) on Pd immobilized Pt surface: kinetics and sensing performance.

Pd nanoparticles were electrochemically immobilized on a Pt surface in the presence of sodium dodecyl sulfate (SDS) molecules to study the electrokinetics of arsenite oxidation reactions and the corresponding sensing activities. The X-ray photoelectron spectroscopy (XPS) analysis showed that on the Pt surface, Pd atoms exist as adatoms and the contents of Pd(0) and Pd(ii) were 75.72 and 24.28 at%, respectively, and the particle sizes were in the range of 61–145 nm. The experimental results revealed that the catalytic efficiency as well as the charge transfer resistance (at the redox potential of the Fe(ii)/Fe(iii) couple) increased in the order of Pt < Pt–Pd < Pt–Pdsds. A Pt–Pdsds electrode exhibited an open circuit potential (OCP) of 0.65 V in acidic conditions; however, when 50.0 mM NaAsO2 was present, the OCP value shifted to 0.42 V. It has been projected that the As(iii) oxidation proceeds using a sequential pathway: As(iii) → As(iv) → As(v). After optimization of the square wave voltammetric data, the limits of detection of As(iii) were obtained as 1.3 μg L−1 and 0.2 μg L−1 when the surface modification of the Pt surface was executed with Pd particles in the absence and presence of the SDS surfactant, respectively. Finally, real samples were analyzed with excellent recovery performance.

Superlow Friction of Graphite Induced by the Self-Assembly of Sodium Dodecyl Sulfate Molecular Layers.

Two-dimensional (2D) layered materials usually exhibit superlow friction properties when the shear occurs between incommensurate interface lattices. In this work, we propose a new method, which is different from the traditional structure superlubricity, to achieve the superlow friction of graphite. This method involves attaching sodium dodecyl sulfate (SDS) molecular layers on the friction surfaces by self-assembly and sliding across the aqueous medium. The friction coefficient between graphite and silica can be reduced to approximately 0.005 at a maximal contact pressure of 31 MPa by this method. The mechanism of the superlow friction was investigated by using an atomic force microscopy and can be attributed to the extremely weak interaction between graphite and SDS molecules. It forms a shear plane of SDS molecules/graphite with extremely low shear strength and extremely low adhesion. This finding provides new insights into the molecular mechanisms underlying an efficient lubrication of 2D layered materials in liquid.

Triblock-Copolymer-Assisted Mixed-Micelle Formation Results in the Refolding of Unfolded Protein.

The present work reports a new strategy for triblock-copolymer-assisted refolding of sodium dodecyl sulfate (SDS)-induced unfolded serum protein human serum albumin (HSA) by mixed-micelle formation of SDS with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer EO20PO68EO20 (P123) under physiological conditions. The steady-state and time-resolve fluorescence results show that the unfolding of HSA induced by SDS occurs in a stepwise manner through three different phases of binding of SDS, which is followed by a saturation of interaction. Interestingly, the addition of polymeric surfactant P123 to the unfolded protein results in the recovery of ∼87% of its α-helical structure, which was lost during SDS-induced unfolding. This is further corroborated by the return of the steady-state and time-resolved fluorescence decay parameters of the intrinsic tryptophan (Trp214) residue of HSA to the initial nativelike condition. The isothermal titration calorimetry (ITC) data also substantiates that there is almost no interaction between P123 and the native state of the protein. However, the mixed-micelle formation, accompanied by substantial binding affinities, removes the bound SDS molecules from the scaffolds of the unfolded state of the protein. On the basis of our experiments, we conclude that the formation of mixed micelles between SDS and P123 plays a pivotal role in refolding the protein back to its nativelike state.

Intermolecular Interactions in Self-Assembly Process of Sodium Dodecyl Sulfate by Vertically Polarized Raman Spectra

Molecular self-assembly is extremely important in many fields, but the characterization of their corresponding intermolecular interactions is still lacking. The C—H stretching Raman band can reflect the hydrophobic interactions during the self-assembly process of sodium dodecyl sulfate (SDS) in aqueous solutions. However, the Raman spectra in this region are seriously overlapped by the OH stretching band of water. In this work, vertically polarized Raman spectra were used to improve the detection sensitivity of spectra of C—H region for the first time. The spectral results showed that the first critical micelle concentration and the second critical micelle concentration of SDS in water were 8.5 and 69 mmol/L, respectively, which were consistent with the results given by surface tension measurements. Because of the high sensitivity of vertically polarized Raman spectra, the critical micelle concentration of SDS in a relatively high concentration of salt solution could be obtained in our experiment. The two critical concentrations of SDS in 100 mmol/L NaCl solution were recorded to be 1.8 and 16.5 mmol/L, respectively. Through comparing the spectra and surface tension of SDS in water and in NaCl solution, the self-assembly process in bulk phase and at interface were discussed. The interactions among salt ions, SDS and water molecules were also analyzed. These results demonstrated the vertically polarized Raman spectra could be employed to study the self-assembly process of SDS in water.

Label-free detection of allergens in food via surfactant-induced signal amplification using a field effect transistor-based biosensor

In recent years, food safety concerning food allergy has received increasing attention globally. A simple and sensitive detection method should be developed to measure trace amounts of allergens in foods. Here, we propose a label-free field effect transistor (FET)-based biosensing system for the detection of a buckwheat allergenic protein, BWp16, by surfactant-induced signal amplification. BWp16 could be detected by coupling with an anionic surfactant, sodium dodecyl sulfate (SDS), as this coupling enhanced the net charge of the protein, enough to be detected by FET biosensors. A significant response was observed when the allergen was coupled with SDS, while the responses were decreased or unchanged when it was coupled with a cationic or non-ionic surfactant, suggesting that the SDS coupling maintains the antibody recognition ability of the target allergen, and it would be useful to enhance the sensor responses. The fluorescence spectroscopic measurement revealed that the SDS molecules were successfully coupled with target allergenic protein BWp16, resulting in an increase in its net charge. Furthermore, we demonstrated that the FET biosensor enables specific detection of the allergen in food at the desired concentration levels for food safety analysis, suggesting that it could be used as an alternative food allergen analyzer, both industrially and domestically.

Interactions of Cationic, Anionic and Nonionic Surfactants with Cresol Red Dye in Aqueous Solutions: Conductometric, Tensiometric, and Spectroscopic Studies

Abstract The interaction of cresol red (CR) with cetylpyridinium bromide (CPB), sodium dodecyl sulphate (SDS), and Triton X-100 (TX-100) was studied in aqueous solutions employing conductometric, tensiometric, and spectroscopic methods. Various micellar and interfacial parameters were calculated in absence and in presence of CR. The interactions suggest the formation of a CR-CPB adduct, an association of CR with the micelle of TX-100 while no adduct is formed between CR and SDS. Appreciably low critical micelle concentration, CMC value of TX-100 compared with those of CPB and SDS in pure water and drastic reduction of CMC of CPB (about one-twelfth of its value in pure water) than SDS and TX-100 in the presence of CR were observed. Higher negative values of Gibbs free energy of micellization, ΔG m 0, for all the three surfactants indicate that micellization process is spontaneous. The values of maximum surface excess concentration, Γ max, and minimum area per molecule, A min, suggest that in the presence of CR, the air-solution interface is closely packed and the orientation of surfactant molecules is almost perpendicular to the surface. UV-visible spectra suggest the formation of ion-pair complex between the dye CR and the monomers of CPB in the pre-micellar region, while above the CMC a breaking up of the ion-pair complex takes place and the dye is solubilized in the micelles of CPB. In the case of SDS the absorption spectra indicate weak interaction between CR and SDS molecules formation of H-bonding, short range dispersive forces, and hydrophobic interactions between CR and TX-100 molecules in the solution.