Surfactant Micelles Research Articles

Mesoporous platinum nanoparticles as a peroxidase mimic for the highly sensitive determination of C-reactive protein.

The generation of a mesoporous structure in platinum nanoparticles can effectively enhance physical and chemical properties. In this study, mesoporous platinum nanoparticles (MPNs) were synthesized by a soft template-mediated one-pot chemical method. To develop a mesoporous structure, Pluronic F-127 was employed. The Pluronic F-127 surfactant forms self-assembled micelles, and the micelles act as the pore-directing agents in the synthesis of nanoparticles. Scanning electron microscopy results revealed that the MPN had a uniform size of 70nm on average and a distinct mesoporous structure. The development of a concave mesoporous structure on the surface of the MPNs can increase the surface area and facilitate the efficient transport of reactants. The synthesized MPNs exhibited peroxidase-like activity. Furthermore, the MPNs showed excellent catalytic efficiency compared to HRP, due to the high surface area derived from the presence of the mesoporous structure. The peroxidase-like MPNs were applied to the enzyme-linked immunosorbent assay (ELISA) of C-reactive protein (CRP). The MPN-based ELISA exhibited sensitive CRP detection in the range from 0.24 to 7.8ng/mL with a detection limit of 0.13ng/mL. Moreover, the recoveries of the CRP concentrations in spiked human serum were 98.6% and 102%. These results demonstrate that as a peroxidase mimic, the MPNs can replace the natural enzymes in conventional ELISA for sensitive CRP detection.

Effect of spacer length on the micellization of cationic trisiloxane surfactants

Siloxane surfactants, hydrophobic (poly)siloxane chain and hydrophilic polar headgroup linking with spacer ((CH2)3 or (CH2)3S(CH2)3), exhibit peculiarly chemical and physical properties. The aggregation behavior and surface properties of siloxane surfactant can be influenced by the hydrophobicity of spacer. Cationic trisiloxane surfactants ([Si3-C3-Min]Br, [Si3-C4-Min]Br, and [Si3-C5-Min]Br) with the same imidazolium group, hydrophobic heptamethyltrisiloxane, and spacer (different number of methylene) were synthesized. The effect of the spacer on micellization in aqueous solution was investigated. Compared with 1-methyl-3- trisiloxaneimidazolium chloride ([Si3Min]Cl), critical micelle concentration (CMC), effectiveness (πCMC), and minimum area occupied by a surfactant molecule (Αmin) values of the investigated surfactants decrease with increase the number of methylene in spacer, while, γCMC value increases as the length of spacer increase. The micellization process was enthalpy driven. The ΔHm0 value becomes more exothermic for [Si3-C5-Min]Br attributed to the increasing hydrophobicity of spacer. The ΔHm0 of [Si3-C3-Min]Br is less exothermic than that of [Si3-C4-Min]Br and [Si3-C5-Min]Br. Spherical aggregates with the range of 20–500 nm were formed in aqueous solution at 2 times CMC.

Photometric Determination of Novocaine with Preconcentration in Surfactant Micelles

Photometric Determination of Novocaine with Preconcentration in Surfactant Micelles

Influence of head group structure of cationic surfactants on the desorption of cesium from clays and clay minerals

The role of cationic surfactants head group for cesium (Cs) desorption from clays and clay minerals was investigated in this study by using two surfactants having similar hydrocarbon chain lengths but different head group types. Two surfactants used were dodecyltrimethylammonium bromide (DTAB) with linear structure and benzyldodecyldimethylammonium bromide (BDAB) containing bulkier head group. The results indicated that Cs desorption from bentonites using both surfactants was accompanied by interlayer expansion. In the case of Na-bentonite, BDAB showed higher Cs desorption efficiency than DTAB due to larger interlayer expansion after intercalation of BDAB. In contrast, the amount of desorbed Cs from Ca-bentonite was comparable, corresponding to the almost identical interlayer expansion after intercalation of both surfactants. It was because Ca ions present in Ca-bentonite must associate with two negatively charged interlayers, hence limiting its expansion. Cs desorption from kaolinite was more governed by surfactant micelles. When the surfactant micelles were formed earlier at low concentration, considerable desorption of Cs was achieved. In this regard, BDAB more efficiently desorbed Cs compared to DTAB owing to rapid formation of BDAB micelles at lower concentrations caused by the increase in head group size. For Cs desorption from illite, both surfactants even exhibited similar insignificant results with HCl used as a control of desorbent. Frayed edge sites in illite probably provoked strong Cs retention causing the difficulty in desorbing Cs. Furthermore, desorption kinetic data of Cs from all samples using both surfactants fitted well with pseudo-second order model, suggesting the occurrence of chemical desorption by involving ion-exchange mechanism.

Thermal detection of second critical micelle concentration in SDS and CTAB aqueous solutions using a modified Lewis-Nielsen effective thermal model

When surfactant molecules are in solution, they self-assemble into various configurations, with the structural conformation changing upon concentration, temperature, and pH. The thermal transport of aqueous solutions containing anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant hexadecyltrimethylammonium bromide (CTAB) was investigated using the thermal wave resonant cavity (TWRC) technique. We use the Lewis-Nielsen effective thermal conductivity model to explain the observed behavior in a new way. We consider that the form factor of the Lewis-Nielsen model relies entirely on surfactant concentration rather than being a constant, as initially was proposed by Lewis and Nielsen. Our findings indicate that the proposed method can detect the transition between spherical and rod-like surfactant micelles. Additionally, this technique could be used to calculate the thermal conductivity of surfactant molecules in water.

Interaction between meso-tetra-(4-hydroxyphenyl)porphyrin and SDS in aqueous solutions: Premicellar porphyrin-surfactant J-aggregate formation

Interactions between meso-tetra(4-hydroxyphenyl)porphyrin (THPP) and anionic sodium n-dodecyl sulfate (SDS) in a wide surfactant concentration range (0.5–50 mM) have been studied by UV–vis absorption and fluorescence spectroscopy, resonance light scattering (RLS), spin probe EPR spectroscopy and dynamic light scattering (DLS). J-type aggregate formation has been observed for THPP within 2–5 mM surfactant concentration range, accompanied by a significant bathochromic shift of the absorption bands, fluorescence quenching and emergence of an intense RLS signal. Porphyrin binding to the surfactant micelles above the cmc and aggregate formation below the cmc have been observed in SDS solutions containing THPP by DLS and EPR spectroscopy. SEM and optical microscopy revealed a rod-like morphology of the microparticles crystallized from an air dried suspension of THPP J-aggregates. The results obtained contribute to understanding of the mechanism of porphyrin-surfactant interactions both below and above the surfactant cmc.

Analytical modeling of micelle growth. 5. Molecular thermodynamics of micelles from zwitterionic surfactants

HypothesisThe critical micelle concentration, aggregation number, shape and length of spherocylindrical micelles in solutions of zwitterionic surfactants can be predicted by knowing the molecular parameters and surfactant concentrations. This can be achieved by upgrading the quantitative molecular thermodynamic model with expressions for the electrostatic interaction energy between the zwitterionic dipoles and micellar hydrophobic cores of spherical and cylindrical shapes. TheoryThe correct prediction of the mean micellar aggregation numbers requires precise calculations of the free energy per molecule in the micelles. New analytical expressions for the dipole electrostatic interaction energy are derived based on the exact solutions of the electrostatic problem for a single charge close to a boundary of spherical and cylindrical dielectric media. The obtained general theory is valid for arbitrary ratios between dielectric constants, radii of spheres and cylinders, positions, and orientations of dipoles. FindingsThe detailed numerical results show quantitatively the effects of the micelle curvature and dielectric properties of the continuum media on the decrease of the dipole electrostatic interaction energy. Excellent agreement was achieved between the theoretical predictions and experimental data for the critical micelle concentration, size and aggregation number of zwitterionic surfactant micelles. This study can be extended to mixed micelles of zwitterionic and ionic surfactants in the presence of salt to interpret and predict the synergistic effect on the rheology of solutions.

The synthesis of quaternary N-alkyl tropinium cationic surfactants and study on their properties: effect of temperature, hydrophobic chain length and anions

• A series of quaternary N-alkyl tropinium cationic surfactants (TILS) with different anion were synthesized and characterized. • By changing counter ions, the krafft point was significantly reduced (from 313.15 K to below 273.15 K) • By increasing the hydrophobicity of anions, the critical micelle concentration ( CMC ) value of TILS decreased about 4-5 times (being compared with bromide). • The effects of temperature, hydrophobic chain length, and anions on the micellar properties of TILS were investigated. A series of quaternary N-alkyl tropinium cationic surfactants (TILS) were synthesized and characterized. The effect of temperature, hydrophobic chain length and anions on their properties were studied. By changing the structure of anion, the krafft point was significantly reduced (from 313.15 K to below 273.15 K) and wide temperature window was obtained. The critical micelle concentration ( CMC ) value of TILS based on electrical conductivity method was found to be decreased about 4-5 times by increasing hydrophobicity of anions. At lower temperature and longer hydrophobic chain, TILS had lower CMC value and better surface activity. The thermodynamic properties of micellization Gibbs free energy Δ G mic , enthalpy Δ H mic and entropy T Δ S mic of micelles were obtained by Mass action model. The result indicates that the micellization process of the TILS was spontaneous and more stable with the increase of anionic hydrophobicity. In addition, with the increase of hydrophobic side chain length, the driving force of surfactant micellization may be enthalpy driven at higher temperature and entropy driven at lower temperature. The micro-environment of TILS solution with different concentrations was studied by UV spectrophotometry with curcumin as a probe and the change of micro-environment was used to determine the CMC of TILS. The CMC values were similar obtained by two methods.

Thermodynamic parameters of ibuprofen micellization with tween 60 at different temperature

Surfactant micellization of Non-steroidal anti-inflammatory drugs (NSAIDs) such as Ibuprofen carrying by surface active agent as polyethylene glycol sorbitan monostearate (Tween 60) was determined by measuring the surface tension as a function of molar concentration in aqueous solution at different temperature ranged from 20°C to 50°C to investigate the critical micelle concentration (CMC). The values of the Gibbs surface excess concentration( Γmax ), minimum area occupied per molecule( Amin. ), surface pressure at CMC (Πcmc) was determined on basis of the standard Gibbs free energy of adsorption (ΔG°ads). The results indicated that CMC increased by temperature increasing for Tween 60, and inversely for micelle of Ibuprofen with Tween 60. The thermodynamic parameters as standard Gibbs free energy(ΔG°), enthalpy(ΔH°), and the entropy(ΔS°) of drug-surfactant of micellization were evaluated using changing of CMC at different temperature. The results based on thermodynamic parameters investigated the spontaneously of micelle formation and that increase the possibility to predict the wettability of Ibuprofen.

Photometric Determination of Novocaine with Preconcentration in Surfactant Micelles

Photometric Determination of Novocaine with Preconcentration in Surfactant Micelles

Mesoscale Modeling of Micellization and Adsorption of Surfactants and Surfactant-Like Polymers in Solution: Challenges and Opportunities

Surfactants and surfactant-like amphiphilic polymers play important roles in many industrial processes (e.g., home and personal care, laundry, paints and coatings, and biopharmaceuticals). In the past two decades, significant progress has been achieved in understanding and modeling crucial surfactant properties (e.g., critical micellization concentration [CMC], cloud points, adsorption, and stabilization of colloidal particles against flocculation), but many challenges still remain. In this review, several popular data-driven, atomistic, and coarse-grained modeling approaches are described that are used to study surfactant properties. Then, specific examples of how these approaches are used for specific applications are provided. Finally, opportunities and challenges for surfactant theory and modeling are discussed.

Surfactant–solid complex for enhancing the flow in pipelines: an experimental approach

BackgroundViscoelastic soluble polymeric additives have been used successfully for a long time as drag reducers in pipelines carrying commercial liquids like crude oil. Most of these polymers suffer from irreversible degradation when exposed to high shearing zones as in valves, elbows, and pumps which reduces, or eliminates, its flow enhancement effect. Insoluble additives were proven to be an effective drag reducer that overcomes the degradation drawback of soluble additives. On the other hand, insoluble additives suffer from the lack of viscoelasticity which limits their use as flow enhancers. The creation of complexes from soluble and insoluble additives is a field of research that is rarely explored despite its importance in introducing new flow enhancement methods for a higher drag reduction performance. The present work introduces a new surfactant–solid complex as a drag-reducing agent for turbulent flow in pipelines.ResultsThe surfactant, solid, and their complexes’ drag reduction performance was tested in a closed-loop turbulent flow liquid circulation system, while rheological characteristics of the soluble additives were tested using a standard rheometer. All the surfactant solutions showed non-Newtonian shear thinning behavior in all the investigated concentrations that ranged between 500 and 1300 wppm. The initial experimental result indicated that the surfactant solution's drag reduction performance was higher than that of the solid suspensions. On the other hand, the drag reduction performance was enhanced by 52% when creating a 1300 wppm surfactant–2000 wppm solid complex. This improvement in the drag reduction performance is due to the formation of surfactant–solid-enforced aggregates with high resistance to shear forces and high turbulence suppression efficiency.ConclusionsThe present work introduces a new drag reduction solid–surfactant complex by creating aggregates combining the viscoelastic properties of surfactants with the resistance to high shear forces exerted by the solid particles. The polar nature of the surfactant micelles that form in single-phase flow systems contributed significantly to trapping the solid's micro-particles as enforcement to resist the shearing forces applied by the turbulent flow system.

Micellization of conventional and gemini surfactants in aquoline: A case of exclusively water based deep eutectic solvent

Deep eutectic solvents (DES) based on water as the only hydrogen bond donor (HBD) have been introduced recently (aquoline). There is not a single report on surfactant association behaviour in aquoline. This study deals with the determination of physical properties (rheology, specific conductance, pH, micro polarity and apparent dielectric constant) of pure aquoline (with different molar ratios of choline chloride (ChCl): water, DES I - DES IV) and association behaviour of ionic surfactants in such aquoline systems. DESs were found Newtonian and highly polar / conducting fluids with nearly neutral pH (6.9–7.1). Micellization behaviour of different ionic surfactants (sodium dodecyl sulphate (SDS), sodium dodecane-1-sulphonate (SDSo), sodium dodecyl benzene sulphonates (SDBS), P, P'-1,4-butanedieyl, P, P'-didodecylester, disodium salt (12-4-12A), cetyltrimethylammonium ammonium bromide (CTAB) or dodecyl trimethyl ammonium bromide (DTAB)) has been studied fluorometrically in various aquolines and compare data with an aqueous medium. In most of the cases, critical micelle concentration (CMC) values have been found lower than water which may be due to the presence of choline chloride (ChCl, one of the components of aquoline), which can interact micelle electrostatically and hydrophobically. For different head groups in anionic surfactant, CMC follows the order 12-4-12A < SDBS < SDS < SDSo, which fits in the Hoffmeister like series of head groups. For cationic surfactants (CTAB and DTAB), CMC shows a similar chain length effect as observed in water. Overall, CMC data allow to propose that CMC decreases with an increase in molar content of water in a typical aquoline under eutectic limit. Micellar aggregation number (Nm), Stern-Volmer constant, micellar polarity, and apparent dielectric constant were also computed. It has been observed that micelles of lower Nm, with high polarity, are formed in a typical aquoline system (DES III). The study may find applications where organized assemblies are required in highly polar solvents.

Effect of SDS Micelles on Actinomycin D - DNA Complexes.

DNA thermal denaturation was evaluated as a measure of the effect of antitumor drug actinomycin D on the stability of the double helix and also the effect of SDS micelles on actinomycin D - DNA complexes. The results indicated that the melting temperature of DNA was dependent on drug concentration, increasing with actinomycin D concentration. High thermal stabilization (about 10 °C) of the DNA helix after the association with actinomycin D clearly demonstrates the intercalative binding mode. The presence of SDS micelles leads to the release of intercalated actinomcyin D molecules from DNA double helix and their further relocation in surfactant micelles. These results highlighted that the drug release can be controlled in time and by varying the concentration and nature of surfactant.

Influence of divalent ion concentration on the adhesion behaviour of sulfonate self-assembled monolayers (SAM)

Surfactant-assisted oil recovery is usually employed for the production of residual oil after primary and secondary recovery techniques have been exhausted. The loss of injected surfactants via adsorption on to the porous media surfaces impede the efficiency of the procedure and greatly impact process economics. To address this issue, the choice of surfactant and aqueous fluid composition are varied. In particular, the divalent ion concentration is a property that potentially influences surfactant adsorption significantly. It is this aspect which has been addressed in this study. In this study, atomic force microscope (AFM). tips were functionalised with a self-assembled monolayer (SAM) of the alkanethiol, sodium 11-mercaptoundecanesulfonate (otherwise known as MUS) with the –SO3-headgroups oriented outwards towards the aqueous solutions, this is a model for the well-studied surfactant, sodium dodecyl sulfate, SDS. The adhesion forces between these “surfactant-functionalised” tips and Bandera Brown sandstone surfaces were measured in brine solutions of varying CaCl2 concentrations. Observations deviate from previous studies where adsorption of surfactant headgroups in the bulk solution is enhanced via Ca2+ bridging with the surface. Rather, measured adhesion forces decreased with increase in CaCl2 concentration. The results are reversible and also occurs in a reducing environment when the iron in the Bandera brown is reduced for iron (III) to iron (II). The observed behaviour is interpreted in terms of Ca2+ preferentially bridging between neighbouring headgroups on the tip due to the dense packing of molecules non-representative of respective bulk behaviours and acting as a barrier to adhesive contact. Thus, this supposed micellization at the tip aided by the formation of Ca2+ salt bridges between alternate headgroups more closely mimics a surfactant micelle, rather than dispersed individual monomers. The findings of this study provide insight into nanoscale anionic surfactant interactions in general and within sandstone reservoirs in particular where surfactant adsorption is driven largely by monomers rather than micelles. Investigating surfactant adsorption using microscopic techniques such as AFM allow for the determination of interactions at mineral-fluid interfaces and constitute an effective screening methodology for ascertaining enhanced oil recovery process feasibility.

The effect of cosolvents and surfactants on the solubility of sulfasalazine

ABSTRACT Sulfasalazine is a BSC class 4 poorly soluble sulphonamide, and the objective of this work is to employ cosolvents, surfactants, and pH change to improve its solubility. Cosolvents including ethanol, 1,2-propanediol, glycerol, methanol, acetone, and polyethylene glycol (PEG) 400 were utilised to study drug solubility in aqueous solvent mixtures. The effect of surfactant micellization is also investigated using cationic, anionic, and non-ionic surfactants. Moreover, some cosolvency models were used to represent the results as a mathematical model. PEG-400 created the highest enhancement in drug solubility and caused a 317-fold increase relative to its aqueous solubility. Results of the micellization study indicate that the drug is most efficiently dissolved in cationic surfactant followed by anionic surfactant, and it is least dissolved by non-ionic surfactant. Computational modelling shows good reliability of the combined nearly ideal binary solvent/Redlich–Kister and the Jouyban–Acree models for solubility prediction in the binary solvent mixtures.

Binding of Perfluorooctanoate to Poly(ethylene oxide)

To inform the design of polymer-based adsorbent materials for sequestration of per- and polyfluoroalkyl substances (PFAS) from aqueous solution, we report here on the critical aggregation concentration (CAC), shape, size, composition, and interactions of assemblies formed in water between perfluorooctanoic acid ammonium salt (PFOA) and the nonionic polymer poly(ethylene oxide) (PEO), obtained from complementary experiments (conductivity, surface tension, pyrene fluorescence, viscosity, and small-angle neutron scattering (SANS)) and atomistic molecular dynamics (MD) simulations. PEO–PFAS binding commences at concentrations lower than the PFOA critical micelle concentration (CMC) and is driven by PEO localizing on the micelle surface and shielding the fluorocarbon parts of PFOA from contact with water. PFOA + PEO mixed micelles have a 10% higher association number and are 40% more elongated compared to polymer-free PFOA micelles. This is the first investigation on the structure of polymer + fluorocarbon surfactant mixed micelles and contributes fundamental insights into the association of water-soluble polymers with PFAS surfactants.

New insights into the synergism between silica nanoparticles and surfactants on interfacial properties: Implications for spontaneous imbibition in tight oil reservoirs

Nanofluids, a new cost-effective chemical additive for enhanced oil recovery (EOR) applications, have attracted increasing attention in the development of tight oil reservoirs. However, the underlying role of nanofluids in the EOR processes has yet to be identified. In this work, the synergistic effects between various surfactant molecules and silica NPs at oil/water, solid/liquid, or oil/water/solid three-phase system were systematically studied, and their effects on EOR in the tight sandstone reservoir were explored. Several silica-based nanofluids were prepared by dispersing silica nanoparticles (NPs) and surface-modifying chemical agents (i.e., anionic, nonionic, anion-nonionic, and amphoteric surfactants) in deionized (DI) water, and the properties of these nanofluids were further evaluated via dispersion stability, interfacial tension (IFT), wettability, spontaneous imbibition and nuclear magnetic resonance (NMR) tests at 60 °C. The experimental results showed that the imbibition efficiency potentials of stable nanofluids modified by different surfactants was: anionic-nonionic > anionic > nonionic > amphoteric. Micropores and mesopores contributed to majority of the imbibition recovery. The appropriate IFTs and oil contact angles for EOR potential were more than 1 mN/m and 140°, respectively. Anionic-nonionic and anionic surfactant nanofluids were suggested as better fracturing additives or EOR agents for sandstone reservoirs. In addition, it was proven that the IFT reduction and wettability alteration were mainly attributed to the synergistic effects of silica NPs and surfactant micelles. This research provides new insights into the underlying mechanism between surfactant nanofluids to interfacial interactions and EOR applications.

Effect of Ionic and Non-Ionic Surfactant on Bovine Serum Albumin Encapsulation and Biological Properties of Emulsion-Electrospun Fibers.

Emulsion electrospinning is a method of modifying a fibers’ surface and functional properties by encapsulation of the bioactive molecules. In our studies, bovine serum albumin (BSA) played the role of the modifier, and to protect the protein during the electrospinning process, the W/O (water-in-oil) emulsions were prepared, consisting of polymer and micelles formed from BSA and anionic (sodium dodecyl sulfate–S) or nonionic (Tween 80–T) surfactant. It was found that the micelle size distribution was strongly dependent on the nature and the amount of the surfactant, indicating that a higher concentration of the surfactant results in a higher tendency to form smaller micelles (4–9 µm for S and 8–13 µm for T). The appearance of anionic surfactant micelles reduced the diameter of the fiber (100–700 nm) and the wettability of the nonwoven surface (up to 77°) compared to un-modified PCL polymer fibers (100–900 nm and 130°). The use of a non-ionic surfactant resulted in better loading efficiency of micelles with albumin (about 90%), lower wettability of the nonwoven fabric (about 25°) and the formation of larger fibers (100–1100 nm). X-ray photoelectron spectroscopy (XPS) was used to detect the presence of the protein, and UV-Vis spectrophotometry was used to determine the loading efficiency and the nature of the release. The results showed that the location of the micelles influenced the release profiles of the protein, and the materials modified with micelles with the nonionic surfactant showed no burst release. The release kinetics was characteristic of the zero-order release model compared to anionic surfactants. The selected surfactant concentrations did not adversely affect the biological properties of fibrous substrates, such as high viability and low cytotoxicity of RAW macrophages 264.7.

Surfactantes iônicos e não-iônicos: micelas, micelas reversas e sistemas micro heterogêneos

Surfactants are surface-active agents which belong to the category of amphiphilic molecules. Indeed, surfactants are characterized for the presence of polar and apolar domains in the same compound. They can form different types of aggregates, such as those known as micelles, being that the concentration at which they form these micelles is called critical micellar concentration (cmc). The different aggregation states of the surfactant (monomer, pre-micellar aggregate, micelle, and liposomes) can present different properties in terms of capability of chemical interaction. The presence of these different configurations and/or the variation of concentration of each one alters the physicochemical properties of the chemical systems with ionic and non-ionic surfactants. The micro heterogenous systems originated by these surfactants have been widely studied in literature to infer several aspects related to similar media that are encountered in the biological tissues.