Adsorption Of Sodium Dodecyl Sulfate Research Articles

Colloidal Silica based High Selectivity Shallow Trench Isolation (STI) Chemical Mechanical Polishing (CMP) Slurry

AbstractAmong various properties of chemical mechanical polishing (CMP) slurry, selectivity plays a key role in global planarization of high density and small pattern size shallow trench isolation (STI) process. Lack of adequate selectivity can lead to defects such as dishing and erosion. To improve the selectivity of STI CMP process, CMP characteristics of silica and silicon nitride wafer were investigated using colloidal silica slurry as a function of slurry pH. Sodium dodecyl sulfate (SDS), an anionic surfactant, was added to increase the selectivity of the slurry. As a result, selectivity increased from 3 to 25. It was concluded that selective passivation layer formed on silicon nitride wafer surface at acidic slurry pH range was responsible for the observed selectivity increase. Adsorption characteristics of SDS on silica and silicon nitride were measured as a function of slurry pH and concentration of SDS. As indicated by zeta potential behavior under acidic pH conditions, SDS adsorption on silicon nitride was significantly higher han silica due to the electrostatic forces. Significantly higher SDS coating on silicone nitride seems to have resulted in lubrication layer leading to increased polishing selectivity.

Ionic surfactant adsorption onto activated carbons.

The adsorption of sodium dodecyl sulfate onto a set of activated carbons from aqueous solutions has been studied in the low concentration range. The adsorption isotherms are reasonably well fitted by a double Langmuir equation but the calorimetry of adsorption enthalpies shows a rather wide distribution of energies. This distribution is related to direct adsorbate-adsorbent interactions in pores of different size, without noticeable contributions from the chemical nature of the surface. The adsorbate-adsorbent interaction free energy through water is evaluated using the model proposed by van Oss and co-workers for the interfacial free energy. The obtained results indicate that the calculated free energy is in good agreement with that found from application of the double Langmuir equation to the adsorption isotherms.

In Situ Mechanistic Study of SDS Adsorption on Hematite for Optimized Froth Flotation

An in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) technique has been developed to study the adsorption of sodium dodecyl sulfate (SDS) onto pure, colloidal hematite as a function of both concentration and pH. The absorption bands of methyl and methylene groups are most reliable for quantifying adsorption unambiguously. The infrared spectral results have been correlated with ζ-potential studies to establish an absence of adsorption above the iso-electric point of 7.3, and to indicate that the mechanism of adsorption is physical, involving reversible electrostatic and hydrophobic forces. In the same way, there is no evidence for the existence of chemisorption. This is supported in the spectral results by the absence of shifts in relative band intensities and the absence of new adsorption bands. At low pH and high SDS concentrations, the adsorption is sufficient to cause a reversal in sign of the ζ-potential. Spectral absorption measurements should be made under in situ conditions to obtain unambiguous results. Studies of adsorption on natural hematite indicate a high depletion of SDS from solution at low pH; the measurements are consistent with precipitation losses due to the presence of calcium and ferric ions. This precipitation leads to a drop in flotation recovery. At high pH, adsorption occurs onto mineral particles which have become coated with carbonate mineral, leading to a flat variation of recovery with pH. The results have enabled optimum flotation conditions to be defined. Recovery can be directly related to adsorption density at moderate pH below the iso-electric point. The optimum pH for flotation is 5; extremes of pH are detrimental to flotation recovery of pure mineral and should be avoided. Low pH causes surfactant precipitation, while high pH will lead to surface transformation of the mineral. A collector concentration of 0.05 times the critical micelle concentration, corresponding to partial monolayer coverage on the hematite surface, is sufficient to ensure good recovery.

Surfactant Adsorption at Solid−Aqueous Interfaces Containing Fixed Charges: Experiments Revealing the Role of Surface Charge Density and Surface Charge Regulation

The charge on the solid−liquid interface affects both the amount of ionic surfactant and the organization of the surfactant adsorbed at the solid−liquid interface. For most solids, the surface charge is not fixed; it is regulated by the adsorption or desorption of ions. The aim of this work is to study surfactant adsorption to surfaces that have a controlled and fixed density of covalently bound surface charges. The desired surface charge density is achieved by the use of gold−thiol self-assembled monolayers (SAMs) of different ω-groups (−OH and −N+(CH3)3). The mole fraction of −N+(CH3)3 on the mixed SAM dictates the density of covalently bound charges. The charge on −N+(CH3)3 is fixed and does not self-regulate, but the total surface charge can be changed through adsorption of other ions. We have studied the adsorption of sodium dodecyl sulfate (SDS) to the interface between these model surfaces and aqueous solutions of SDS. Atomic force microscopy (AFM) of the adsorbed surfactant reveals no surface micelles above the critical micelle concentration, cmc, over a wide variety of −N+(CH3)3 densities. This leads us to hypothesize that lateral mobility of ions other than surfactant at the interface is important for the formation of surface micelles of ionic surfactants. Adsorption isotherms of SDS (with no added salt) measured by surface plasmon resonance (SPR) show a plateau region that ends at about cmc/25. In this plateau region, the surface excess of SDS is equal to the known fixed surface charge. There is a second plateau region above the cmc. In this concentration range, the surface excess is approximately twice the fixed surface charge. Desorption experiments starting above the cmc show rapid desorption of SDS into water until the surface excess is equal to the fixed surface charge. The rapid desorption is followed by a much slower desorption.

Formation and stability of drug nanoparticles obtained from drug/PVP/SDS ternary ground mixture

The purpose of this study was to investigate the stability and the formation mechanism of drug nanoparticles obtained from a ternary system consisting of poorly water-soluble drug, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS). The physical state of drug nanoparticles was investigated by powder X-ray diffraction and zeta potential measurements. Poorly water-soluble drug, PVP K17 and SDS were mixed at a weight ratio of 1:3:1 and ground for 30 min by vibrational rod mill. Most of the poorly water-soluble drugs used in this study provided the nano- particle formation in the submicron region after the ternary ground mixtures (GMs) were dispersed into distilled water. Stability and mechanism of drug nanoparticle formation were investigated by focusing on phenytoin, probucol and griseofulvin. The drug nanoparticle formation was also observed when the ternary GMs were dispersed in the dissolution media. The mean particle size of the dispersed particles was still less than 250 nm after storage at 25°C for one month, indicating the long-term stability of drug nanoparticles. The quantitative determination of drug content demonstrated that more than 93% of the drug was recovered as fine particles smaller than 0.8 ^m from the ternary GMs, whereas the nanoparticles were hardly gained from binary GMs, drug with PVP K17 or SDS. Powder X-ray diffraction analysis for the dispersed particles accumulated by ultracentrifugation indicated that the dispersed particles existed as fine crystals. The zeta potential measurement revealed that the obtained nanoparticles were stable in aqueous media because the particle agglomeration was effectively inhibited by the adsorption of both PVP and SDS onto the particle surface.

Transparent SiC thin films by PEG–SDS-assisted self-assembly of SiC nanoparticles

Transparent SiC thin films were fabricated on polyethylene oxide monolayer (PEOM) on a glass substrate at room temperature through self-assembly process of dispersed SiC nanoparticles in aqueous solution. By simply adding sodium dodecylsulfate (SDS) into the solution containing the PEOM glass substrate at room temperature and pH 3, SiC nanoparticles were slowly self-assembled onto the substrate and grown into the thin films due to adsorption of SDS on the surfaces of PEOM-modified substrate and SiC nanoparticles. Photoluminescence (PL) studies of the films showed a strong peak at 640 nm at room temperature.

Interaction Forces on α-Alumina Surfaces with Coadsorption of Anionic/Nonionic Surfactant Mixtures

Direct measurement of interaction forces between α-alumina surfaces with coadsorbed anionic sodium dodecyl sulfate (SDS) and nonionic hexaoxyethylenedodecyl ether (C12E6) at pH 3.5 is carried out by colloidal probe atomic force microscopy. The strength of interaction forces is found to be dependent on the initial SDS concentrations, whereas the addition of C12E6 alone causes negligible effects on the interaction. This is due to the absence of attractive interactions between C12E6 molecules and α-alumina. On the other hand, the interaction forces are remarkably different for the simultaneous addition of the two surfactants. At lower C12E6 concentrations the observed repulsion induced by the electric double layer is larger than that in the corresponding single SDS solution, suggesting the stronger SDS adsorption as a consequence of the reduction of the electrostatic repulsion between the ionic headgroups of SDS admicelles. By the further addition of C12E6 a steric stabilizing force is detected from the separation of approximately 5 nm. This is attributed to the formation of a closely packed adlayer comparing with the case of the single SDS admicelles. The effects of sequential addition of C12E6 to the α-alumina preadsorbed hydrophobically with SDS are also investigated to understand the complex phenomena that occur at the interface.

Adsorption of Polymer/Surfactant Mixtures at the Air−Water Interface: Ethoxylated Poly(ethyleneimine) and Sodium Dodecyl Sulfate

The adsorption of the polymer/surfactant mixture of ethoxylated poly(ethyleneimine) (PEI) and sodium dodecyl sulfate (SDS) at the air−water interface has been studied by specular neutron reflectivity and surface tension. PEI is a strong polyelectrolyte at low pH and behaves like a neutral polymer at high pH. The variation in the concentration dependence of the SDS adsorption at the interface and the corresponding surface tension behavior, in the presence of 20 ppm PEI and at different pHs, reflect the changing nature of the polymer with pH. At SDS concentrations of <0.5 mM, the SDS adsorption increases with decreasing pH, whereas for SDS concentrations of >0.5 mM it is essentially independent of pH. This change in adsorption behavior with concentration corresponds roughly to the concentration at which the PEI no longer adsorbs at the interface. Furthermore, at the lower SDS concentrations PEI adsorbs at the interface, and the PEI adsorption increases with decreasing pH. The pattern of SDS and PEI adsorption is indicative of a strong polymer/surfactant interaction at low pH, which decreases with increasing pH. The surface tension behavior at different pHs shows neither the classical dependence on surfactant concentration of weakly interacting polymer/surfactant mixtures, such as poly(vinylpyrrolidone)/SDS, nor the more complex behavior of charged polymer/oppositely charged surfactant mixtures. Although the ethoxylation of the PEI avoids phase separation in concentrated PEI/surfactant solutions, the adsorption data and surface tension demonstrate that it provides, in addition to pH, a modification to the effect of the strength of the interaction between the PEI and the SDS. In addition to the increasingly favorable interaction between PEI and SDS with decreasing pH, there is also an element of competitive adsorption arising from the inherent surface activity of the PEI.

Analytical investigation of the self-desorption of the oligomers of mixtures of a polydisperse ethoxylated surfactant with sodium dodecylsulfate from a silica/water interface

The adsorption isotherms onto a hydrophilic silica of mixtures of sodium dodecylsulfate (SDS) and of all the oligomers of a polydisperse nonylethylene glycol n-dodecyl ether (C 12E 9) surfactant were determined using a high-performance liquid chromatography (HPLC) technique. Incorporation of the anionic surfactant to the negatively charged silica surface is favored by the adsorption of the nonionic surfactant. Comparison between the adsorption isotherms of mixtures of SDS with a monodisperse C 12E 9 and a polydisperse C 12E 9 shows that the adsorption of SDS at the silica/water interface is stronger with the latter material than with the former in a large surface coverage domain. The composition of the surface aggregates and the variation of the oligomer distribution in these aggregates were determined. The previously described phenomena called self-desorption which was observed for the global C 12E 9 and SDS surfactant mixtures was confirmed: increasing the total concentration at a fixed surfactant ratio induces at high concentration a desorption of the anionic surfactant and all of the less polar oligomers from the solid/water interface. An interpretation scheme is proposed which assumes that the interaction of SDS is larger with the less polar oligomers than with the polar ones. The self-desorption effect could then be considered as the consequence of the polydispersity of the nonionic surfactant and to the net repulsion interaction between SDS and the silica surface as the mole fraction of SDS in the surfactant mixture increases.

Influence of the temperature in the adsorption of sodium dodecyl sulfate on phosphatidylcholine liposomes

The influence of the temperature on the adsorption of monomeric and micellar solutions of the anionic surfactant sodium dodecyl sulfate (SDS) on phosphatidylcholine (PC) liposomes was investigated using the fluorescent probe 2-( p-toluidinyl)-naphthalene-6-sodium sulfonate (TNS). The number of adsorbed molecules was quantified by measuring changes in the electrostatic potential ( Ψ o) of the liposomes/probe during an incubation with SDS at varying temperatures. At low surfactant concentrations (from 0.05 to 0.25 mM), the increase in temperature reduced the number of surfactant molecules incorporated per vesicle regardless of the incubation time, whereas at high surfactant concentrations (from 0.50 to 1.0 mM) the incubation time has an opposite effect on this process. Thus, after 10 s, the surfactant adsorption decreased with temperature, yet it increased progressively with time. The adsorption was linear with temperature below critical micellar concentration (CMC) of SDS and this linear tendency did not change above CMC. This suggests an adsorption of SDS monomers regardless of the surfactant concentration.

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.

Nanoparticle formation of poorly water-soluble drugs from ternary ground mixtures with PVP and SDS.

Poorly water-soluble drugs N-5159, griseofulvin (GFV), glibenclamide (GBM) and nifedipine (NFP) were ground in a dry process with polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). Different crystallinity behavior of each drug during grinding was shown in the ternary Drug/PVP/SDS system. However, when each ternary Drug/PVP/SDS ground mixture was added to distilled water, crystalline nanoparticles which were 200 nm or less in size were formed and had excellent stability. Zeta potential measurement suggested that the nanoparticles had a structure where SDS was adsorbed onto the particles that were formed by the adsorption of PVP on the surface of drug crystals. Stable existence of crystalline nanoparticles was attributable to the inhibition of aggregation caused by the adsorption of PVP and SDS on the surface of drug crystals. Furthermore, the electrostatic repulsion due to the negative charge of SDS on a shell of nanoparticles could be assumed to contribute to the stable dispersion.

Kinetics of Sodium Dodecyl Sulfate Adsorption on and Desorption from Self-Assembled Monolayers Measured by Surface Plasmon Resonance

By use of a flow cell in conjunction with surface plasmon resonance, experimental results are obtained for the intrinsic kinetics of sodium dodecyl sulfate (SDS) adsorption on and desorption from self-assembled monolayers (SAMs) on gold. When the flow of the bulk surfactant solution in the flow cell is increased, conditions are reached where the surface kinetics are rate controlling and mass transfer limitations in the bulk solution are negligible. The SDS adsorption and desorption rates increase with the bulk surfactant concentration in the monomer regime. At and above the critical micelle concentration of SDS, the adsorption and desorption rates become nearly constant. It is shown that SDS needs to be recrystallized to remove minute impurities. The results suggest that the SDS monomers play a dominant role in adsorption and desorption on SAMs. Sodium dodecyl sulfate has a greater affinity for hydrophobic SAMs than for charged, hydrophilic SAMs. The data also suggest that the kinetics of adsorption and s...

The Adsorption of Anionic Surfactants by Iron(III) and Aluminium Hydroxides

The adsorption of sodium dodecyl sulphate and sulphanol NP-3 by iron(III) and aluminium hydroxides was studied. The applicability of the Langmuir, Freundlich and Hill–de Boer adsorption equations for the description of the adsorption isotherms obtained experimentally was verified. Values of various parameters characterising the adsorption of the anionic surfactants investigated by iron(III) and aluminium hydroxides have been calculated. These allowed assumptions to be made about the adsorption mechanism. The possibility of using air as an adsorbent for anionic surfactants was studied.

Micrometer to Nanometer Patterns of Polypyrrole Thin Films via Microphase Separation and Molecular Mask

We report a new method to control both the nucleation and growth of polypyrrole (Ppy) for the formation of the patterns from micrometer to nanometer sizes using adsorbed sodium dodecyl sulfate bilayers as a molecular mask. Polystyrene (PS) and poly(4-vinylpyridine) blend and block poly(styrene-b-4-vinylpyridine), which have microphase-separated domains in micrometer and nanometer scales, respectively, were used as templates. With the molecular mask, the resulting Ppy can be selectively grown up to 50 nm only along the PS domains.

REMOVAL OF AN IONIC SURFACTANT FROM WASTEWATER BY CARBON BLACKS ADSORPTION

The adsorption of an ionic surfactant, sodium dodecyl sulfate (SDS), from aqueous solution onto six carbon blacks with different surface characteristics has been studied in various ranges of low concentrations. The process can be related to types of interactions that are always the same since the adsorption in these systems depends mainly on the porosity of the samples but not on the chemical composition of the surface. However, adsorption progresses follows two processes: the first one related to the adsorption of SDS into the narrowest pores with a suitable width, and the second one related to adsorption of SDS onto a more open surface.

Simultaneous Adsorption of Poly(1-vinylpyrrolidone-co-acrylic acid) and Sodium Dodecyl Sulfate at Alumina/Water Interface

The simultaneous adsorption of poly( 1-vinylpyrrolidone-co-acrylic acid) (PVcA) and sodium dodecyl sulfate (SDS) on positively charged alumina particles is carried out at pH 5.2 by measuring the amount of PVcA and SDS adsorbed, ζ potential, and sedimentation rate of alumina suspensions. In addition, conformation of PVcA and SDS adsorbed using their corresponding spin-labeled ones is estimated. The amount of PVcA adsorbed increases sharply and becomes a plateau with an increase of PVcA concentration, while a typical adsorption isotherm of SDS is obtained. In the simultaneous adsorption of PVcA and SDS under fixed initial concentrations of PVcA, the amount of PVcA adsorbed increases and reaches a maximum, and then decreases with SDS concentration. The enhancement in the adsorption is due to the interaction between SDS and PVcA as confirmed by surface tensiometry. The dispersion stability of alumina suspensions by the simultaneous adsorption of PVcA and SDS is considerably high compared with that by SDS adsorption alone. The high dispersion stability is due to the extended conformation of the adsorbed PVcA and the electrostatic repulsion force. Further, the mobility of SDS molecules in the PVcA-SDS adsorbed layer is found to be more restricted than that in the SDS adsorbed layer alone.

An Experimental System for Imaging the Reversible Adsorption of Amphiphiles at Aqueous−Liquid Crystal Interfaces

We report an experimental system that permits optical imaging of the reversible adsorption of amphiphiles at stable, planar interfaces formed between aqueous phases and immiscible thermotropic liquid crystals. Copper grids (hole sizes of 19−292 μm and thicknesses of 18−20 μm) supported on glass surfaces treated using octadecyltrichlorosilane were impregnated with nematic 4-cyano-4‘-pentylbiphenyl (5CB). Films of 5CB confined within the grids were stable (did not dewet the grid) to immersion into either water, aqueous solutions of sodium dodecyl sulfate (SDS), or aqueous solutions of SDS containing NaCl. Whereas the anchoring of 5CB on the copper grid dominated the appearance of the 5CB when using grids with hole sizes of 19 μm, reversible changes in the orientation of the liquid crystal (observed using polarized light) caused by adsorption of SDS at the liquid crystal−aqueous interface were readily observed when using grids with hole sizes larger than 19 μm. With increasing concentrations of SDS in the aqueous phase, a series of reproducible and distinct surface-driven distortions were observed within the 5CB confined to the grid. We also observed the effects of added NaCl on the distortions induced within the liquid crystal to be consistent with increased adsorption of SDS caused by screening of the electrostatic interactions between the SDS adsorbed at the interface. This result suggests that the orientation of the 5CB is influenced by the areal density of SDS molecules at the liquid crystal−aqueous interface (probably through steric interactions). Because the aqueous phase contacting the liquid crystal can be exchanged (thus permitting the addition and removal of reactants), this experimental system is a simple and broadly useful one for investigations in which liquid crystals are used to amplify interfacial phenomena at fluid interfaces into optical images.

Polypyrrole-coated natural rubber latex by admicellar polymerization

Admicellar polymerization has been used for the preparation of an electrically conductive polypyrrole coating on latex particles. An anionic surfactant, sodium dodecyl sulfate (SDS), was adsorbed onto natural rubber (NR) latex particles to form the surfactant bilayers after adjusting the pH below the point of zero charge of the latex surface. Adsorption of SDS and pyrrole adsolubilization were determined as a function of pyrrole and sodium chloride concentrations. Pyrrole caused a decrease in SDS adsorption at equilibrium. Sodium chloride increased the surfactant adsorption and the pyrrole adsolubilization. Thermogravimetric results showed the presence of polypyrrole. The conductivity of the polypyrrole-coated NR latex film prepared by admicellar polymerization without salt was the lowest; however, with salt addition, the conductivity of the film improved significantly. The oxidative polymerization technique resulted in a relatively higher conductivity than oxidative admicellar polymerization.

Impedance analysis of an electrode-separated piezoelectric sensor as a surface monitoring technique for surfactant adsorption on quartz surface.

This paper describes the measurement of the kinetics of adsorption of sodium dodecyl sulfate (SDS), an anionic surfactant, onto a quartz surface with a pre-adsorbed layer of Ca2+ as an ion bridge, using an electrode-separated piezoelectric sensor (ESPS). An impedance analysis method was employed to characterize the responses of the ESPS. The impedance and frequency parameters of the ESPS were examined as functions of the conductivity, permittivity, viscosity and density of the liquid. The adsorption process of SDS onto the quartz surface resulted in an increase in both the mass and energy dissipation of the oscillating quartz crystal. The adsorption densities could be estimated by the ESPS method after taking into consideration the effects of surface viscosity and roughness. The adsorption and desorption rate constants of SDS onto the quartz surface were calculated as ka = (88.1 +/- 0.26) mol(-1) L s(-1) and kd = (4.92 +/- 0.53) x 10(-3) s(-1), respectively, based on the Langmuir model. ESPS was shown to be a powerful means of examining anionic surfactant adsorption to the solid/liquid interface.