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• Effects of gas components on SDBS foam were investigated at multiple length scales. • The increase of alkane chain enhances the foamability and stability of the foam. • Effects of alkanes on interfacial adsorption of surfactant molecules were clarified. • Pathway by which alkanes alter gas–liquid interfacial tension was discovered. The foam drainage technique is considered to be a promising measure for solving the problem of liquid accumulation in natural gas wells and gathering pipelines. However, differences in gases can greatly affect the performance of surfactant foam, thus limiting the application of this technology. To elucidate the mechanism of natural gas components influencing foam properties, the interfacial properties of hydrocarbon gas-surfactant-water system were analyzed thermodynamically and kinetically by combining molecular dynamics simulations and foaming experiments. The results show that with the increasing alkane chain length, the foaming volume and half-life of the foam are gradually rising, while the gas–liquid interfacial tension is decreasing, which is consistent with the results of molecular dynamics simulations. Compared with air, hydrocarbon gases are more beneficial for foam generation and stabilization. The interfacial adsorption of alkane molecules and the interaction between alkanes and surfactants are the main factors affecting the interfacial tension and film stability of different systems. [ABSTRACT FROM AUTHOR]

• Effects of gas components on SDBS foam were investigated at multiple length scales. • The increase of alkane chain enhances the foamability and stability of the foam. • Effects of alkanes on interfacial adsorption of surfactant molecules were clarified. • Pathway by which alkanes alter gas–liquid interfacial tension was discovered. The foam drainage technique is considered to be a promising measure for solving the problem of liquid accumulation in natural gas wells and gathering pipelines. However, differences in gases can greatly affect the performance of surfactant foam, thus limiting the application of this technology. To elucidate the mechanism of natural gas components influencing foam properties, the interfacial properties of hydrocarbon gas-surfactant-water system were analyzed thermodynamically and kinetically by combining molecular dynamics simulations and foaming experiments. The results show that with the increasing alkane chain length, the foaming volume and half-life of the foam are gradually rising, while the gas–liquid interfacial tension is decreasing, which is consistent with the results of molecular dynamics simulations. Compared with air, hydrocarbon gases are more beneficial for foam generation and stabilization. The interfacial adsorption of alkane molecules and the interaction between alkanes and surfactants are the main factors affecting the interfacial tension and film stability of different systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel viscoelastic enhanced air foam for enhanced oil recovery was developed. • Viscoelastic surfactants have the dual characteristics of "polymer and surfactant". • The elasticity of liquid film hinders the diffusion of the gas. • The self-assembly of viscoelastic surfactant makes foam liquid easy to inject. • Supramolecular self-assembly makes air foam suitable for low permeability formation. Polymer has been widely studied as an effective means to improve foam stability in reservoir exploitation. Nevertheless, the deployment of this technology in low-permeability reservoirs may prove challenging and could potentially result in formation damage. The innovation of this study is the utilization of viscoelastic surfactants to create enhanced air foam with wormlike micelles and three-dimensional network structures. This can result in a synergy between the properties of fluidity control and oil washing efficiency, thereby enhancing the strength of the foam. The supramolecular self-assembly property facilitates the injection of the foam into the formation while preserving its original structure and properties, thereby enhancing the stability of the foam and markedly improving the recovery of low permeability reservoirs. The viscoelastically enhanced air foam system is composed of the zwitterionic surfactant erucylamido propyl betaine (EHSB) and the anionic surfactant sodium dodecyl sulfate (SDS), which has been designated EHSB-SDS. The foam performance was evaluated using the Waring Blender method and rheological behavior, with foam fluid viscosity, initial foam volume (V 0), half-life for drainage (t d) and foam half-life (t f) serving as the evaluation indicators. The influence of temperature, salinity and oil content on foam performance is considered to explore the reservoir adaptability. The dynamic/micro stability, macro rheological properties, interfacial viscoelasticity and Zeta potential of the enhanced air foam system were further studied to clarify the stability mechanism of enhanced air foam system. The t d , t f and composite index of EHSB-SDS is 56.6 min, 36 h and 648000 mL·min, respectively. The viscoelastic surfactants form wormlike micelles, which increase the foam solution viscosity. This results in a slow drainage speed and the rupture of the bubbles. The adsorption of surfactant at the gas/liquid interface results in an increase in surface activity, interfacial expansion modulus and zeta potential, which serves to enhance the strength of the liquid film and the electrostatic repulsion among bubbles. These three factors are primarily responsible for the stability of the foam. The research establishes a theoretical basis for the effective development of low permeability reservoirs and new foam flooding technology. [ABSTRACT FROM AUTHOR]

The decomposition of monolayers prepared with anionic surfactants, sodium dodecyl sulfate (SDS), or cationic ones, dodecyltrimethylammonium bromide (DTAB), at the water/air interface was studied when biosurfactants (surfactin) are added to the films. Molecular dynamics simulations were carried out for monolayers with a fixed number of SDS or DTAB molecules and a different amount of biosurfactants to form SDS/surfactin and DTAB/surfactin mixtures. It is found that the presence of the biosurfactant modifies interfacial and structural properties of the ionic monolayers at the interface; the DTAB monolayer is distorted even for a few surfactin molecules, whereas the SDS monolayer remains steady up to a given amount of biosurfactant. In both monolayers the surface tension decreases with the number of biosurfactants, however while for the DTAB/surfactin the values seem to fluctuate, for the SDS/surfactin mixture the values decay linearly, with a discontinuity for a given surfactin concentration. The linear behaviour of the surface tension for the SDS/surfactin allows us to evaluate free energies for the monolayers and a two-dimensional equation of state. The structure of the monolayers was analyzed in terms of density profiles, order parameters, thickness of the interfaces and the data show that the DTAB/surfactin is more distorted than the SDS/surfactin by the presence of few surfactin molecules. The results indicate that SDS surfactants are more likely to form longer lasting films with fewer surfactin molecules than DTAB.   • Monolayer of anionic and cationic surfactant with a biosurfactant show different behaviour at the water/air interface. • Mixtures of SDS with biosurfactants (surfactin) produce stable monolayers at low surfactin concentrations. • Mixtures of DTAB with surfactin produce distorted monolayers even for a small number of biosurfactant molecules. • SDS-surfactin interactions make softer monolayers than the DTABsurfactin interactions at the water/air interface. [ABSTRACT FROM AUTHOR]

• Ionic surfaces enhance polar hydrocarbons adsorption via electrostatic interactions. • Graphite surface enhances polar hydrocarbons adsorption via π-π interactions. • Cation distribution impacts polar oil adsorption; free cations inhibit, surface cations enhance. • Multicomponent hydrocarbons exhibit competitive adsorption, with polar components advantaged. • Molecular mass and polarity significantly influence hydrocarbon diffusivity on shale surfaces. Understanding shale oil adsorption in reservoir nanopores is essential for efficient extraction. This study used MD simulations to analyze the adsorption and diffusion of two- and multi-component hydrocarbons (Aromatics, Alkanes, Resin) on various shale surfaces (Calcite, Montmorillonite, Quartzite, Organic) at 353 K and 25 MPa. Hydrocarbons formed a bilayer adsorption structure comprising a high-concentration adsorption layer (L1, 0.35–0.90 g/cm3) and a low concentration weak adsorption layer (L2), with adsorption density ranked as Resin > Aromatics > Alkanes. Reservoir surfaces were classified as ionic (e.g., calcite, montmorillonite) and non-ionic (e.g., quartz, graphite), and polar hydrocarbons exhibited higher adsorption densities and energies on ionic surfaces due to combined electrostatic and van der Waals interactions, while non-ionic surfaces showed smaller adsorption differences. For multicomponent hydrocarbons, adsorption layer densities followed the order: graphite > MMT-SiO > quartz > calcite > MMT-Na, with competitive adsorption observed. The polar component exhibited a greater adsorption advantage on the calcite, MMT-SiO side and graphite surfaces due to electrostatic interactions and π-π interactions, and a lesser advantage on the MMT-Na side and quartz surfaces. Hydrocarbon diffusivity was influenced by molecular mass and polarity and ordered as Alkanes > Aromatics ≫ Resin. Polar molecules had a weaker diffusion than nonpolar molecules at similar molecular masses. Among the multicomponent hydrocarbons, the self-diffusion coefficient (Self-D) of Resin increased, while that of lighter components decreased compared to two-component systems. These findings offer strategies for improving shale oil recovery by tailoring injection fluids to reservoir types, anionic surfactants or chelating agents may be used to reduce electrostatic interactions in carbonate and clay reservoirs, while nonionic surfactants may be more effective in quartz reservoirs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption at air–water interface depends on diamine and surfactant structure. • All diamines result in enhanced adsorption of SDS, MES and SLES. • Multilayer adsorption for butanediamine / SDS (MES) • Multilayer formation independent of solution pH. • Only monolayer adsorption with ethoxylated diamines. The biogenic amines, polyamines, such as putrescine and cadavarine, are small flexible polycations. They interact with charged biological species and have a range of important biological functions. Their strong interaction with anionic surfactants results in enhanced adsorption at interfaces. Aspects of the impact of the polyamine molecular weight and structure on the pattern of surfactant adsorption at the air–water interface have been explored previously using neutron reflectivity, NR, and surface tension, ST. However there is limited evidence for the extent to which surfactant adsorption can be manipulated and the impact of the diamine structure and surfactant headgroup structure on surfactant adsorption at the air–water interface is reported here. The addition of putrescine [1,4 diaminobutane or butanediamine] over the pH range 3 to 10 enhances significantly the adsorption of sodium dodecyl sulfate, SDS, sodium dodecyl diethylene sulfate, SLES, and sodium tetradecyl methyl ester sulfonate, MES. For SDS and to a lesser extent MES there are regions where surface multilayer adsorption occurs at both pH 3 and 10, and this extends significantly the range of polyamine structures for which this is observed. Modifying the diamine spacer with ethylene oxide groups of varying length still results in enhanced adsorption for SDS and MES, but the enhancement is less pronounced and depends upon the size of the ethylene oxide group. However the incorporation of the ethylene oxide group does suppresses the formation of the more complex surface multilayered structures. [ABSTRACT FROM AUTHOR]

• The quaternary ammonium gemini surfactant containing with perfluorobranched short chain is synthesized. • The deviation between the PBFS/SOS mixture and the ideal mixture is investigated. • There is the strong interaction between PBFS and SOS. • The solution of PBFS/SOS mixture shows excellent surface property. • The PBFS/SOS solution could wet PTFE plates at the concentration of 0.0625 mmol/L. The hydrophobic and oleophobic properties of perfluorobranched short chains are similar to those long chain fluorocarbons (fluorocarbon chain length ≥ 7), and their environmentally friendly properties make them good alternatives to traditional perfluorooctyl derivatives. For this purpose, a novel perfluorinated branched short chain quaternary ammonium gemini surfactant (PBFS) with high surface activity was synthesized, and the surface properties, aggregation behavior, wetting performance and adsorption performance of the complex system of PBFS and sodium octyl sulfate (SOS) were systematically studied. PBFS exhibited superior surface activity in aqueous solution with the critical micelle concentration (CMC) of 0.1667 mmol/L and the corresponding surface tension (γ CMC) of 20.17 mN/m. Moreover, despite the fact that the mixing of PBFS and SOS was not ideal, the two still had the good synergistic effect: the CMC of the compounding solution was reduced to 0.0072 mmol/L and γ CMC was 16.01 mN/m when the compounding ratio (CF: CH) was 1:8. And the composite solution could completely wet low surface energy polytetrafluoroethylene (PTFE) plates at 1 mmol/L, and could also wet PTFE plates at extremely low concentrations (0.0625 mmol/L), showing good wetting performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doping of SDS in NLC leads to increased dielectric anisotropy with red-shift • The diffusion coefficient decreases by 80.77 % when the concentration of anionic surfactant increases from 0 to 3.0 wt%. • LC cells with 3.0 wt% anionic surfactant show 30 % decrease in rotational viscosity and 64 % decrease in response time. • A bathochromic shift of 31 nm in UV–Vis spectrum and PL quenching of 64 % is observed with 3.0 wt% dispersion of SDS. Modern research has long focused on controlling and optimizing the dielectric, electro-optical and optical attributes of liquid crystals (LCs) to increase their technological value. Numerous approaches have been investigated for this reason in an effort to overcome various issues such as high response time, high driving voltage requirements, low dielectric anisotropy and limited operating temperature range, etc. The strategy utilizing binary/multicomponent systems is the most investigated and seems to have the most potential out of all the other techniques. In keeping with the same subject, the influence of anionic surfactant on the dielectric, electro-optical, and optical properties of nematic LC (NLC) has been examined. Precisely, dodecane-1-sulfonic acid sodium salt (SDS) which is an anionic surfactant was dispersed in a room temperature NLC E7 at various concentrations. Our findings reveal a significant alteration in the electro-optical behavior resulting from the introduction of an anionic surfactant, extending well beyond the instance of electrode polarization, albeit with a detrimental impact on performance within the low-frequency range as a result of increased ionic contribution. The main findings of this study include a 17.5%% increase in dielectric anisotropy, an appreciable reduction of about 30%% in threshold voltage and rotational viscosity, and approximately 64% reduction in response time in the host NLC due to the addition of anionic salt in it. A significant photoluminescence quenching of about 64%% is observed after dispersion of 3.0% by weight anionic surfactant in E7. These findings offer potential pathways for the development of future technologies in various domains, including photonic devices, biological imaging, light-emitting diodes (LEDs), and luminescent markers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co(OH) 2 synthesised in reverse micellar core of SPAN 80/1-butanol/water/toluene. • O/W Pickering emulsion is developed by Co(OH) 2 , in situ hydrophobized with SDS. • An ambiguous phase separation of Pickering emulsion is noticed at 4.3 mM SDS. • Hydrophobic interaction through tail-to-tail mode leads nanoplates-like architect. • Hydrophilic surface from both ends result to loss of amphiphilic character. The present study employs reverse micellar-templated Co(OH) 2 nanospheres, in situ hydrophobized with SDS in Pickering emulsion formulations and unlocking the mechanism of ambiguous phase separation at a certain surfactant concentration (4.3 mM). Co(OH) 2 is synthesised in the core of reverse micelle: SPAN 80/1-butanol/water/toluene. Novel O/W Pickering emulsions have been developed with the help of positively charged (ς = 4.47 mV) Co(OH) 2 (0.05 wt%) and an adequate amount of an anionic surfactant, SDS. An ambiguous phase separation of Pickering emulsion at 4.3 mM SDS is noticed within just 4 hr of standings, whereas, surprisingly stable O/W Pickering emulsions are found above and below these SDS concentrations. Upon addition of 2.6 mM SDS to the aqueous colloidal dispersion of Co(OH) 2 , the particles converted to amphiphilic one and stabilized the Pickering emulsion. However, these monolayer adsorbed surfactants face a hydrophobic interaction through tail-to-tail mode after adding 4.3 mM SDS to the colloidal dispersion. Consequently, they achieve a nanoplates-like architect and regain the extreme hydrophilic surface from both ends and eventually leads to the ambiguous phase separation through inter-droplet coalescence. The contact angle value altering from 44.9° (for 2.6 mM SDS) to 19.6° (for 4.3 mM SDS) confirms that the surface has changed from being amphiphilic to becoming extremely hydrophilic. Yet, again an increase in SDS (6.06 mM and onwards) suggest that surfactant molecules further adsorbed in either any of the two hydrophilic ends and revolving the particles to its previous amphiphilic state and eventually started to stabilise the emulsion droplets. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile method was used to prepare multifunctional zwitterionic surfactants. • Surfactants were applied for demulsification of Arabian crude oil emulsions. • The effect of sulfone functionalization on the demulsification process was studied. • Multifunctional zwitterionic surfactants showed high and fast demulsification efficiency. We report an easy process to prepare new anionic and zwitterionic surfactants to break water in Arabian heavy crude oil emulsions (W/O) with different compositions (10/90, 30/70 and 50/50 vol%). Surfactants were prepared in only two stages using simple methodology. Diethylenetriamine was interacted with three moles of glycidyl 4-nonyl ether followed by the interaction with 3 and 8 mol of 1,3-propanesultone to yield TNDTS-3 and TNDTS-8 respectively. FTIR and NMR spectroscopies were carried out to substantiate the chemical structures of surfactants. Relative solubility number (RSN), surface activity and solubility properties were determined. Demulsification efficiencies and interfacial tension (IFT) of the prepared surfactants were investigated. Our findings demonstrated that increasing propyl sulfonate groups in the surfactant structure improved water solubility, IFT activity and demulsification efficiency. TNDTS-8 achieved 100 % demulsification activities in all W/O emulsions (10/90, 30/70 and 50/50 vol%). [ABSTRACT FROM AUTHOR]

The thermodynamic behavior of mixed systems containing the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant polyethylene glycol dodecyl ether (Brij L4) in aqueous solutions was investigated. Electrical conductivity and interfacial tension measurements were employed to investigate the concentration-dependent properties of these surfactant mixtures. Two main experiments were conducted: i) constant ratio experiment: the overall surfactant concentration was varied while maintaining a fixed ratio between SDS and Brij L4. It was shown that the critical micelle concentration (CMC) determined from electrical conductivity measurements does not indicate the formation of the first mixed micelles as observed using tensiometry, but the point from which the adsorption of counterions by the existing micelles became important. By using the Regular Solution Theory (RST), it was found that the interaction between SDS and Brij L4 is synergistic, driven by dipole-ion interactions of the hydrophilic regions of the two surfactants. ii) Fixed SDS concentration while increase the Brij L4 concentration: the resulting electrical conductivity exhibited non-trivial behavior which complexity arose from simultaneous phenomena of incorporation of free SDS molecules into the micelles as Brij L4 concentration increased, leading to a decrease in electrical conductivity; liberation of some adsorbed counterions from the mixed micelles to the solution, which increases the conductivity and increase of viscosity due to Brij L4 further addition that leads to a sequential decrease in electrical conductivity. • Sodium dodecyl sulfate and Brij forms mixed micelles with synergetic interactions. • Tensiometry evidences the micelle formation and conductivity the adsorption of ions. • Adding Brij promotes the incorporation of SDS and counterions at low concentration. • Higher concentration of Brij dilutes SDS and liberates the incorporated counterions. • Further addition of Brij increases the viscosity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Drug-SDS/CTAB-water ternary system has been investigated. • The trends in φ v values indicate the dominance of ion-ion/ion-hydrophilic interactions. • ECT shows stronger solute–solvent interactions. • φ v / φ κ of SDS increase in pre-micellar region thereafter shows almost constant variation. • φ v / φ κ of CTAB decrease sharply near about at 0.9 mmol∙kg−1 in pre-micellar region. The present study deals with the interactions of Emtricitabine and Lamivudine (anti-HIV drugs) with anionic surfactant sodium dodecylsulphate (SDS) and cationic surfactant cetyltrimethylammonium bromide (CTAB) at (298.15–313.15) K temperature range by volumetry, compressibility and viscometric approach. The experimental values of sound velocity and density are used to compute various parameters such as apparent molar volume (φ v), isentropic compressibility (κ s), and apparent molar adiabatic compression (φ κ) by employing cosphere overlap model. Relative viscosity parameter (η r) evaluated from viscosity data also helps to understand various interactions prevalent in surfactant-drug-water ternary system. This attempt of extracting information about various physicochemical interactions of anti-HIV drugs with surfactants can prove beneficial to develop novel anti-HIV agents with better viral resistance activity. [ABSTRACT FROM AUTHOR]

• By combining macroscopic experiments and microscopic simulations, the optimal combination of composite ionic surfactant solutions is derived, which can realize the efficient enhancement of the effect of dust reduction on coal dust. • The dynamic changes of surface tension and contact angle of different solutions were observed, and the microscopic wetting principles of each surfactant were characterized from their structural features by establishing their molecular models. • By constructing adsorption models containing two different ions, it was concluded that the nonionic and anionic surfactants had the most obvious longitudinal distribution between coal and water after compounding, which could form a tighter adsorption layer and allow water molecules to penetrate into the coal molecules, thus enhancing the wetting effect on coal dust. To improve surfactant wetting action on coal dust in the process of mine spray dust reduction, this paper adopts a combination of experiments and molecular simulation to study the wetting properties and mechanism of different kinds of active agents on coal dust and selects the compounded surfactants with better dust reduction effect. The results show that: fatty alcohol polyoxyethylene ether can reduce the surface tension to 34.16 mN·m−1, which is 35.84 mN·m−1 comparatively less than that of pure water; dodecylphenol polyoxyethylene ether and poly(ethylene glycol) octyl phenyl ether have the maximum electrostatic potentials of 0.0892 a.u and 0.0908 a.u, which exceed that of water molecules, which indicate that the nonionic active agents are the most polar, and it is easy for them to form the hydrogen bonding with water, and the ability to reduce surface tension is superior to other types of active agents; molecular simulation results show that the non + anionic complex system can form a tighter adsorption layer between coal and water, so that the water molecules move more vigorously, moving from the molecules of water to those of coal, thus producing a better wetting effect than the monomer active agent. In addition, dust settling experiments and particle size experiments were conducted to verify the reasonableness of the microscopic simulation. The study's findings can provide a reference for identifying and designing compounded surfactants with excellent wetting performance to improve the dust reduction effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catanionic niosomes, composed of cationic and anionic surfactants, are multifunctional carriers for anticancer drugs. • CTAB and SDS were utilized as positively and negatively charged surfactants, respectively. • The behavior of Cabozantinib, an FDA-approved c-Met inhibitor, as the drug sample, was studied in the bilayer. • The influence of cationic/anionic molar ratios on the bilayer features was investigated. Niosomes are adaptable nanocarriers for the delivery and controlled release of anticancer drugs. The addition of ionic surfactants could easily functionalize these carriers. Catanionic niosomes that are comprised of cationic and anionic surfactants are effective drug-delivery vehicles. Here, we aim to evaluate the impact of the cationic/anionic ratio on the noisome characteristics. A novel approach utilizing molecular modeling was utilized to analyze some characteristics of catanionic niosomes, showing great potential as a vehicle for anticancer drugs. The nonionic surfactant SPAN60, along with cholesterol as the stabilizer, was utilized in the study. Moreover, CTAB and SDS were used as positively and negatively charged surfactants, respectively. An FDA-approved c-Met inhibitor, cabozantinib, was selected as the drug. Several significant parameters associated with the cabozantinib molecule and its properties within the bilayer like hydrogen bonding, total energy, radius of gyration (Rgyr), diffusion coefficient, and radial distribution function (RDF). The findings suggest that the cabozantinib's hydrogen bonding plays a vital role in the drug's movement through the bilayer. The CTAB-rich niosomes showed a higher number of hydrogen bonds compared to the SDS-rich formulations. The diffusion coefficient was in agreement with the number of H-bonding, and this value increased from 3.12 × 10-12 (m2/s) in CTAB-rich niosome to 7.66 × 10-12 (m2/s) in SDS-rich niosime. The total binding energy between the drug and bilayer components can control drug release. The computational approach could sufficiently describe the influence of cationic/anionic molar ratios on the bilayer features, and the characteristics of catanionic niosomes could be easily adjusted for the controlled release of anticancer drugs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The bioavailability of the weakly water-soluble AZI could have been enhanced by the CAPB-STS mixed micelle. • The AZI binding constant values were found maximum of 3.144 at α CAPB 0.1of mixed micelle. • Aqueous solubility of AZI 0.0032 mmol/L were enhanced up to 0.048 mmol/L in the presence of mixed micelles. • At α CAPB 0.1 mixed micelles, the controlled release of AZI in PBS at pH 7.4 was found to be 30.77%. The study highlights the importance of mixed micelles in enhancing the binding and solubilization properties of partially water-soluble medications, using zwitterionic cocoamidopropyl betaine (CAPB) and anionic sodium tetradecyl sulfate surfactants. Surface tension and fluorescence spectroscopy evaluated the critical micelle concentration (CMC) of CAPB-STS mixed micelle. The thermodynamic parameters were assessed using Clint, Rubingh, and Motomura's approach, which showed a synergistic interaction between the CAPB and STS. UV spectroscopy technique was used to evaluate the applicability of mixed micelle to enhance the solubility and binding constant (K b) of antibiotic azithromycin dihydrate (AZI). K b values of AZI were increased from 2.301 to 3.415 and molar solubilization ratio (MSR) values of AZI were increased from 0.228 to 0.801 by decreasing α CAPB from 0.9 to 0.1. The result indicated that zwitterionic CAPB was an electrostatic interaction consisting of both attractive (−CH 2 COO¯ group) and repulsive (−N+ group) interactions with AZI (−NH+ group), causing AZI molecules to reside in the Stern layer. While STS consisted of a negative −SO 4 ¯ head group, it caused increased electrostatic interaction, and AZI penetrated the palisade layer of mixed micelles. At 7.00 mmolL-1 concentration of α CAPB 0.1, the solubility of AZI in water was increased to 2.77 mmol/L from 0.0032 mmol/L. Additionally, after 8 h, the controlled release of AZI in PBS at pH 7.4 was 95.58 % and decreased up to 30.77 % at α CAPB 0.1 mixed micelles. The observation of controlled AZI release from α CAPB 0.9 to 0.1 indicates that AZI molecules were strongly bound to mixed micelles by both hydrophobic and electrostatic interactions. In the end, a mixed micelle of CAPB-STS could serve as a useful drug-solubilizing agent in pharmaceutical applications. [ABSTRACT FROM AUTHOR]

• A seawater-based zwitterionic/anionic surfactant compound was formulated, and its interfacial properties and enhanced oil recovery potential were evaluated. • The underlying mechanisms were systematically studied based on the intermolecular interactions through molecular dynamics simulations. • The impacts of surfactant formula, salinity and cation types on intermolecular interactions were discussed. • The arrangement of surfactant molecules at the heavy oil/seawater interface was studied and the adsorption features were identified. • The interactions between the surfactant molecules and the heavy oil components were systematically analyzed. Zwitterionic/anionic surfactant mixtures can produce many synergistic effects that benefit heavy oil production. In this work, a seawater-based zwitterionic/anionic surfactant compound was prepared using cocoamidopropyl betaine (CAB) and alkyl polyoxyethylene ether sodium sulfate (AES), emphasizing their synergistic effects in enhancing conventional heavy oil recovery. First, the emulsification capability and the oil displacement efficiency of the surfactant compound were tested through laboratory experiments. Then the impacts of salinity, cation types, surfactant formulation and solution pH on surfactant-surfactant or surfactant-heavy oil interactions were systematically explored through molecular dynamics simulations to unveil the underlying mechanisms of enhanced oil recovery. The results showed that, (1) in a seawater-based system, when the AES/CAB concentration ratio was 1:1, a large wormlike micelle was formed due to the cation bridging of Ca2+ and Mg2+ ions, which not only strengthened the attractive interactions between the AES-SO 4 − and the CAB-N+ functional groups, but also screened the repulsive interactions between the AES-SO 4 − and the CAB-COO− functional groups. (2) Through mixed adsorption, the arrangement of AES/CAB molecules at the aqueous/heavy oil interface was more compact. (3) By incorporating the AES/CAB mixture into the associative structures of asphaltene and resins, it could effectively weaken the attraction interactions between the asphaltenes and the resins. Through these synergies, an additional oil recovery of 24.93 % was yielded by combining AES/CAB flooding and subsequent seawater flooding, compared to 19.38 % in the pure AES case. This study provides important insights into the microscopic mechanisms of zwitterionic/anionic surfactant mixtures, which can facilitate the effective development of heavy oil reservoirs and guide the complex formulation of cost-effective surfactant compounds. [ABSTRACT FROM AUTHOR]

Surfactants are crucial in chemical enhanced oil recovery, but high adsorption onto rocks reduces their efficiency and economic viability. Sacrificial agents, such as alkalis, nanoparticles, and polymers have been investigated to mitigate this issue but they in turn present drawbacks such as poor oil interaction, compatibility issues, pore plugging, and increased costs. Binary surfactant systems, due to their favorable potential synergistic interactions, are proposed as solutions for reducing surfactant adsorption. Static adsorption experiments were conducted to assess the effect of the binary surfactants on adsorption efficiency, and the impact of salinity on the adsorption process equilibrium was also studied. Five core flooding experiments under reservoir temperature (41 ∘C), reservoir pressure (21 MPa), and high salinity (23.4 wt.%) were conducted to evaluate dynamic adsorption. The surfactant concentrations in supernatant and effluent, after the adsorption process were determined via interfacial tension tests using a spinning drop method. The results showed a significant reduction in surfactant adsorption on carbonate rocks, from 9.99 mg/g-rock to 0.68 mg/g-rock for anionic surfactants and from 5.38 mg/g-rock to 0.19 mg/g-rock for zwitterionic surfactants, with corresponding dynamic reductions of 61% and 89%. Our results were further evidenced by the little to no changes in the differential pH curves in the adsorption process of the binary surfactant systems. This study presents a cost-effective approach for significantly reducing surfactant adsorption on carbonate rocks and aids in designing surfactant formulations for adsorption reduction in high-temperature, high-salinity carbonate reservoirs. • Core flooding experiments were conducted to evaluate dynamic adsorption. • Static and dynamic adsorption tests were conducted at high salinity (23 wt.%). • Nonionic surfactant was crucial to reducing the adsorption values in binary surfactants by at least 60%. • The decrease in adsorption for binary surfactants was linked with their monolayer adsorption mechanism. [ABSTRACT FROM AUTHOR]

• Synergistic effects can be formed between sodium erucate and short chain cationic surfactants. • The phase transition between wormlike micelle and vesicle can be triggered by temperature. • The components and concentrations of mixed system affects rheological properties of wormlike micelles. • NaOEr/HTAB wormlike micelles system has good carrying sand and gel breaking properties. Clean fracturing fluids are widely used in reservoir stimulation and increasing production due to their characteristics of simple preparation, no residue, easy flowback, and low damage. At present, clean fracturing fluids are mainly prepared by cationic surfactants as main agent and inorganic or organic salts as additives, which can lead to unavoidable losses of cationic surfactants due to their adsorption in the formation. Anionic-cationic surfactants composite system can not only compensate for the shortcomings of a single surfactant system, but also improve the reservoir adaptability of the surfactant system. In this paper, a clean fracturing fluid was prepared with long-chain anionic surfactant, Sodium erucate (NaOEr), as main agent and a series of cationic surfactants with different as additive. Then, the aggregation behavior of mixed system was determined by visual appearance, rheology experiments, differential scanning calorimetry and cryogenic transmission electron microscopy. The phase transition mechanism induced by temperature was proposed, and the performance of the mixed system as a fracturing fluid was evaluated. The results showed the mixed systems could self-assemble into wormlike micelles when the length of hydrophobic carbon chains of cationic surfactant was 6 and 8. Increasing the length of the hydrophobic carbon chain could enhance the electrostatic effect, leading to precipitation in the mixed system. When the ratio of cationic surfactant was between 0.5 and 0.6 and the concentration was between 68 and 175 mmol∙L-1, the mixed systems tended to form three-dimensional structures by entangling and stacking wormlike micelles, showing high viscoelasticity and viscosity. The aggregation structure of the mixed system transformed from vesicles to wormlike micelles at 46.8 °C, which is attributed to the transition of carbon chains of NaOEr from non-flexible to flexible. Finally, the mixed system as a fracturing fluid has good shear resistance and temperature resistance. The viscosity of NaOEr/HTAB can reach above 50 mPa⋅s after sheared for 60 min at the conditions of 170 s−1 and 80 °C. This study provides an anionic clean fracturing fluid and broaden the application of viscoelastic surfactants in oilfield development. [ABSTRACT FROM AUTHOR]

• A novel surfactant-polymer (SP) combined system was successfully developed for heavy oil reservoirs. • The in-situ emulsification performance and synergistic collaboration mechanisms of SP system were systematically investigated. • The enhanced oil recovery (EOR) effect and mechanisms of SP system were identified with dual viscosity reduction and mobility controllability. Surfactant-polymer (SP) combined systems is an effective nonthermal method to enhance the heavy oil recovery, through in-situ emulsification and mobility control mechanisms. In this study, a novel SP system was developed using 0.2 wt% anionic surfactant (alkyl naphthol polyoxyethylene ether sulfonate, ANES) and 0.1 wt% polymer (partially hydrolyzed polyacrylamide, HPAM). The SP system had viscosity reduction rate of ∼ 98 %, viscosity ratio of oil to displaced water (μ o / μ d) of ∼ 3.95 and IFT of ∼ 0.29 mN/m, beneficial for decreasing the mobility ratio of water to heavy oil. Then, the applied performances including emulsion morphologies and stability, wettability alteration ability were systematically characterized. The results showed that the freshly O/W emulsions formed by SP system displayed uniform droplet size distribution, as well as high stability with tight interfacial film. In addition, the SP system exhibited excellent wettability alteration property with low contact angle of 18.3°. The synergistic collaboration mechanisms of surfactant and polymer include heavy oil–water interfacial tension reduction, in-situ emulsification, oil-viscosity reduction and water-viscosity increase. Finally, the static oil washing and dynamic sand-pack flooding experiments showed that the SP system exhibited high oil washing efficiency (62.89 %) and enhanced oil recovery efficiency (56.9 %) with improving the mobility controllability after the primary water-flooding process. This study indicated that the synergistic collaborations between surfactant and polymer had great potential to enhance the heavy oil recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism of action of anionic complex surfactants on coal was investigated by AFM and DFT. • The interaction mechanism between the anionic complex surfactant and the coal surface is electrostatic attraction. • The effect of anionic complex surfactants on the wettability of coal surfaces was investigated. • Anionic complex surfactants exhibit better performance on coal surfaces than any single surfactant. The objective of this study was to elucidate the cooperative modification mechanism of anionic composite pharmaceuticals on coal substrates. Composite pharmaceuticals were synthesized using sodium hexametaphosphate (SHMP) and sodium polycarboxylate to reduce coal hygroscopicity. The mesoscopic alteration process between the coal surfaces and the compound pharmaceuticals was examined via atomic force microscopy (AFM). AFM showed that SHMP was multilayer-adsorbed on coal via electrostatic and hydrogen bonding, while sodium polycarboxylate was single layer-adsorbed at the SHMP layer via electrostatic interactions. Composite pharmaceutical adhesion to coal was lower than that for individual pharmaceuticals, indicating synergistic effects. The mechanism underpinning the microscopic synergistic effect of complex pharmaceuticals on the coal surface was further examined using density functional theory (DFT) at the molecular scale. DFT calculations showed that the adsorption energy of SHMP binding to a sodium polycarboxylate molecule was greater than that of SHMP binding to two identical pharmaceutical molecules. The SHMP portion generally interacted with the aromatic coal nucleus via its ring structure, exposing the sodium polycarboxylate carbon chain to maximize the adsorption energy. Combining DFT and AFM provided insight into the composite pharmaceutical function, and a theoretical framework for coal flotation separation was established. [ABSTRACT FROM AUTHOR]

[Display omitted] • Smart hydrogels prepared using anionic surfactant and anionic photoresponsive additive. • Hydrogels prepared based on hydrogen bonding and steric hindrance regulation strategy. • Hydrogels exhibit the stimulus-responsiveness of both NaDC and trans -NaOMCA. • Bridging hydrogen bonds between DC− and trans -OMCA− lead to their synergistic effect. • Release of model drug from the prepared hydrogels was triggered by external stimuli. Developing natural biosurfactant-based smart hydrogels with low-toxicity, biocompatibility and multi-stimulus-responsiveness is of great importance in fundamental and applied science. Based on the strategy of hydrogen bonding and steric hindrance regulation, multi-stimulus-responsive hydrogels were constructed using electrostatically repulsive sodium deoxycholate (NaDC) and sodium salt of trans -ortho-methoxycinnamic acid (trans -NaOMCA). The rheological and DLS techniques, TEM, optical microscopy, 1H NMR, FT-IR and UV–vis spectrometers were used to investigate the stimulus-responsiveness and the controlled release of model drug. Molecular dynamics (MD) simulations were performed to provide molecular insights into the effect of stimuli on self-assembly, type and number of hydrogen bonds, etc. This study provides a new method to construct multi-stimulus-responsive hydrogels using anionic surfactant and anionic photoresponsive additive. The NaDC/ trans -NaOMCA/H 2 O mixed system exhibits reversible pH- and CO 2 -responses. FT-IR and 1H NMR spectra results and MD simulations reveal that, the formation and breaking of bridging hydrogen bonds involving H 3 O+ (including the acid salt structures) play key roles in reversible sol ⇌ gel transition, and the bridging hydrogen bonds between DC− and trans -OMCA− lead to a synergistic effect during the formation of HAc- and CO 2 -induced hydrogels. In addition, the HAc-induced hydrogels are thermosensitive and photoresponsive, exhibiting the stimulus-responsiveness of both NaDC and trans -NaOMCA. The stimulus-responsive mechanism has been proposed. The investigation of the release of methylene blue from the prepared hydrogels will provide guidance for practical applications. [ABSTRACT FROM AUTHOR]

• Synergistic effect regulates the CO 2 -responsive mechanism. • DTAB does not interfere with the original CO 2 -responsive mechanism. • SDS favors the formation of a compact surfactant layer. • TX-100 enhances the interface activity of the mixture. • The distinct CO 2 -responsive mechanisms require a delicate formulation design. CO 2 -responsive surfactants are a promising technology with potential applications in various fields. Therefore, the design of their formulations must be carefully considered to ensure their effectiveness in each specific application. Herein, we employed molecular dynamics simulations to investigate an oil/water (O/W) interface stabilized by a surfactant mixture containing a CO 2 -responsive cationic primary surfactant and another co-surfactant. It has been discovered that formulating the CO 2 -responsive cationic surfactant with a typical anionic surfactant (sodium dodecyl sulfate, SDS) can lead to a distinct CO 2 -responsive mechanism of the surfactant mixture. To compare, the CO 2 -responsive mechanism remains unchanged if the CO 2 -responsive cationic surfactant is formulated with a typical cationic surfactant (dodecyl trimethylammonium bromide, DTAB). A nonionic co-surfactant can enhance the interface activity of the surfactant mixture but the synergistic effect is not strong enough to lead to a different CO 2 -responsive mechanism. The distinct phase behavior between two surfactant mixtures suggests that the CO 2 -responsive mechanism is dominated by the type of surfactants formulated with the CO 2 -switchable surfactant. [ABSTRACT FROM AUTHOR]

• In this paper, a new formulation of nanoemulsion composed of two surfactants containing benzene rings was proposed, and compared with micelle for spontaneous imbibition displacement experiments. • In this paper, it was found that the nanoemulsion had good solubilization and enhanced oil recovery performance. • It is of great significance to select the best oil displacement agent and promote the application of oil displacement agent in oilfield. Nanoemulsion has a wide range of applications in oilfield chemistry due to its unique nanoscale size, excellent kinetic stability and high specific surface area. In this paper, a novel nanoemulsion oil flooding system was prepared using anionic surfactant sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactant alkylphenol ethoxylates (OP-10), kerosene, n-butanol and deionized water. The particle size, Zeta potential, interfacial tension (IFT) and wettability properties were evaluated in the laboratory. The displacement performance of nanoemulsion was evaluated by the spontaneous imbibition experiment. Meanwhile, it compared with the same concentration of SDBS + OP-10 + n-butanol (SOB) system. The results showed that the particle size of the nanoemulsion was 70 ∼ 100 nm. When the concentration of nanoemulsion was 0.10 %, the oil–water IFT could reach 0.091 mN/m. The spontaneous imbibition oil recovery of the nanoemulsion (0.10 wt%) could reach 33.20 %, which was 23.02 % higher than that of SOB system. We also research the spontaneous imbibition displacement mechanism of nanoemulsion and micelle in low-permeability reservoirs. This paper will help to select the best oil displacement agent for the design of enhanced oil recovery (EOR) projects and promote the application of oil displacement agent in oilfield. [ABSTRACT FROM AUTHOR]

[Display omitted] • α-amylase activity decreases with time/temperature; non-ionic surfactants enhance it. • EO/surfactants increase protease activity at 35 °C; decrease at higher temperatures. • Enzyme-EO-surfactant interactions improve performance of multifunctional solutions. This study investigates the stability of α-amylase and protease in disinfectant formulations incorporating essential oils (EOs), anionic surfactants (linear alkylbenzene sulfonate), non-ionic surfactants (alkylpolyglucosides and ethoxylated fatty alcohols), and mixtures of them, analysing the influence of the composition, temperature, and time using shelf-life assays. EOs reduce α-amylase activity showing first-order deactivation kinetics, and surfactants were found not to significantly affect its activity. However, protease activity increases with the presence of EOs, and it was also observed that the use of surfactants does not significantly affect protease activity either. This work represents a step forward in the development of environmentally friendly multifunctional detergents with high disinfectant and detersive capacity. [ABSTRACT FROM AUTHOR]

• The synthetic route of FS had the mild reaction conditions and simple operation. • The FS showed excellent surface activity (γ cmc was 15.33 mN/m, CMC was 0.002 mol/L). • The synergistic effect between FS and SOS was obvious. • The compound solution could completely wet the PTFE plate at low concentration. Traditional perfluorooctane sulfonic acid (PFOS) fluorocarbon surfactants endangered human health and environment. Therefore, an environmentally friendly quaternary ammonium cationic fluorocarbon surfactant (PFAS-IEt) was synthesized, and surface activities, aggregation behavior, adsorption properties and wettability of PFAS-IEt/sodium n-octyl sulfate (SOS) mixtures in dilute solutions were systematically investigated. The results demonstrated that PFAS-IEt possessed excellent surface activity in aqueous solution. Surprisingly, its surface tension was only 15.33 mN/m and critical micelle concentration (CMC) was 0.002 mol/L. It could be used as a potential substitute for PFOS. In addition, PFAS-IEt had the good synergistic effect with SOS. The PTFE plate with low surface energy could be completely wetted by the binary compound solution at low concentration (0.04 mol/L) (contact angle was 0°), which was superior to the reported long chain quaternary ammonium non-ionic fluorocarbon surfactants (MN-2C 9 F 19 and EN-2C 9 F 19). [ABSTRACT FROM AUTHOR]

• The copolymer P(BA-AA) was synthesized as a polymeric surfactant via a continuous polymerization process. • The synthesized polymeric surfactant P(BA-AA) exhibited a low critical micelle concentration (CMC). • Polymeric surfactants were applied to the polymerization of acrylic PSAs, and enhanced the adhesive properties of the PSAs. Low molecular weight polymers with hydrophobic-carboxyl groups have been usually used as anionic surfactants in emulsion polymerization for coatings. However, such polymeric surfactants usually have low acid values below 200, because it is difficult to make high acid-value polymeric surfactants using a normal batch reactor. In this work, we polymerized high acid value polymeric surfactant having high acid values successfully up to 380 using CSTR (continuous stirring tank reactor). The synthesized polymeric surfactant was a random copolymer of P(BA-AA) and we applied them as anionic surfactants in making emulsion-type acrylic PSAs (Pressure-Sensitive Adhesives) to investigate the effects of high acid values on the adhesive properties. This CSTR can effectively control the composition and molecular weight of polymeric surfactants through varying monomer ratios, retention time, and initiator concentrations. The surface tension analysis and emulsion stability test indicated that the synthesized polymeric surfactants exhibited a similar levels of critical micelle concentration (CMC) and emulsion stability with other conventional anionic surfactants. Also, the adhesion property analysis showed that the PSA used high acid value polymeric surfactant resulting in superior adhesive properties and heat resistance than the PSAs used low acid value polymeric surfactant or conventional low molecular weight surfactant. It was very notable that polymeric surfactants having unusually high acid values above 300 because of their high contents of carboxylic acid groups could result in superior adhesive properties and heat resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Di(2-ethylhexyl)phosphoric acid salt was used as a surfactant for SUPRAS formation. • Inorganic electrolytes were shown to serve as coacervation agents in this system. • Sodium carbonate and sodium phosphate created alkaline medium to form amphiphiles. • Density, viscosity and pH values of the novel SUPRASs were obtained. • Liquid-phase microextraction approach for determination of antipyrine in saliva. In this study, di(2-ethylhexyl)phosphoric acid salt was investigated as a double-chain anionic surfactant for supramolecular solvent formation in a liquid-phase microextraction procedure for the first time. Inorganic electrolytes (sodium salts) were shown to be coacervation agents, due to their salting-out property in solution of sodium di(2-ethylhexyl)phosphate, obtained by deprotonation of the acid. The physico-chemical properties of the newly synthesised solvents were studied. Sodium carbonate and sodium phosphate were found to be the most suitable coacervation agents, due to their alkaline nature and low viscosity of the supramolecular solvent phases they produce. The extraction ability of the novel solvent was demonstrated in liquid-phase microextraction of a colored derivative of antipyrine from saliva for further spectrophotometric determination. The extraction recovery was found to be 70 %. The proposed green sample preparation technique enabled the exclusion of traditional toxic solvents and reduction of reagent consumption. The satisfactory analytical performance of the procedure was validated with real sample analysis. The calibration graph was linear over the concentration range of 0.03 to 0.5 mmol/L. The limit of detection (3σ) and limit of quantification (10σ), calculated from blank tests, were 0.01 and 0.03 mmol/L, respectively. [ABSTRACT FROM AUTHOR]

• Ultra-fast mechanochemical strategy to obtain stable colloidal dispersions of MWCNT in hydrophilic media: never has been so easy. • An ultra-fast and easy mechanochemical strategy for MWCNT dispersion is showed. • Reproducible non-covalent functionalization of MWCNT with surfactants (cationic, anionic or neutral). • Preservation of the pristine sp2 hybrid state of the carbon atoms. • Long-term stable MWCNT colloids in hydrophilic media are achieved. In this paper, we present a new protocol that allows the dispersion of multi-wall carbon nanotubes (MWCNT) in the form of stable colloids in a hydrophilic medium up to concentrations of ca. 0.06 % (w/w). The strategy involves using a combination of mechanochemical treatment and surfactants. In this study, we processed MWCNTs with surfactants in a ball mill without using any solvents. The mechanochemical treatment consists of processing mixtures of MWCNTs (0.35 g) with different surfactants (4.5 g of CTAB, 3.6 g of SDS and 4.5 g of F127 as cationic anionic and neutral surfactants, respectively) in a ball mill for only 20 min at 300 rpm. The resulting black powder is then used directly to prepare dispersions in hydro-alcoholic media, which maintain colloidal stability for at least 25 days. Although various strategies for dispersal have been proposed in the literature, many involve time-consuming and multi-step processes with low yields. The MWCNTs modified non-covalently using our protocol are synthesised in a single step with a 100 % yield without any loss of reagents. MWCNT have shown potential in many emerging applications of great interest. Its use necessarily implies the achievement of a good dispersion in different solvents, and this aspect, in the case of hydrophilic media, still does not have a satisfactory answer. The absence of solvent during the mechanochemical treatment is the key aspect of our strategy. This small change represents a significant improvement. We demonstrate the outstanding stability of the obtained suspensions and the preservation of the nano-/microstructure of the MWCNTs, which remains unaltered during their preparation. Furthermore, using environmentally friendly solutions for dispersion makes this protocol a Green Chemistry approach. [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the acid-base properties of the indicator dye methyl yellow in water–ethanol solutions with a volume fraction of alcohol of 10 % and 50 %. The influence of the addition of NaCl salts and tetrabutylammonium chloride, as well as the anionic surfactant sodium dodecylsulfate (SDS) on the acidity constant of the indicator, was evaluated. Under the chosen conditions, ethanol additives have a more significant effect on the p K a value. For the first time, using the dynamic light scattering method, the particle sizes, polydispersity index, and ζ-potential of colloidal particles in pure aqueous and mixed water–ethanol solutions of methyl yellow (φ alcohol from 0.2 % to 50 %) in the presence of NaCl and SDS were estimated. In solutions with φ alcohol = 50 % colloidal particles were not found. It has been shown that the hardened gelatin gel of photographic film can be used as a convenient sorbent for methyl yellow. In the process of dye extraction into a gelatin film from water-alcohol solutions containing SDS and NaCl, the acid-base properties of the methyl yellow remained almost unchanged. The difference between the p K a values obtained for the indicator both in solution and in the film did not exceed the measurement error. [ABSTRACT FROM AUTHOR]

• Ionic surfactants have significant impact on the nucleation of gold and gold@silver nanoparticles. • Yellow to orange color gold sols were prepared with CTAB surfactant. • Cyanidin-3,5-di-O-glycoside acted as reducing as well as capping agent. • Electrostatic and hydrophobic interactions are responsible for different morphology. Cyanidin-3, 5-di-O-glycoside (anthocyanin) was extracted from the red rose flower petals in an aqueous media. Anthocyanin was used as reductant to the preparation of gold nanoparticles with cationic and anionic surfactants. UV–visible absorption spectroscope, transmission electron microscope, scanning electron microscope, and energy dispersive X-ray spectroscope were employed to determine absorption bands of anthocyanin, surface Plasmon resonance (SPR) band, and morphology of the gold and gold@silver nanoparticles. Anthocyanin exhibited two absorption peaks at 284 and 518 nm, and one shoulder at 328 nm in the UV–visible spectrum. The intensity of these peaks decreases with time after the addition of HAuCl 4. The color and the position of SPR band of gold nanoparticles depend on the concentration of gold salt with and without cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). The anionic and cationic head groups of SDS and CTAB micelles have significant impact of the morphology of gold nanoparticles. Seedless co-reduction method was used for the synthesis of gold@silver nanoparticles. TEM images clearly indicate the formation of bimetallic gold@silver core-shell nanoparticles. The antioxidant power of AuNPs and gold@silver nanoparticles were tested in terms of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity as a function of different concentrations of nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PO group is a premise for obtaining higher interfacial activity for short hydrophobe extended anionic surfactant. • Short hydrophobe extended anionic surfactant have stronger salt resistance, calcium and magnesium resistance. • Short hydrophobe extended anionic surfactant shows similar interfacial behavior to that with long alkyl chain. Extended surfactant is a new type of oil displacement agent with excellent performance in enhanced oil recovery (EOR). In this paper, the novel extended surfactants with short hydrophobe (ethylhexyl) have been studied. The dynamic interfacial tensions (IFTs) between extended surfactant (C 8 P x E y C) solutions and n-alkanes were measured by the spinning drop method. The effect of surfactant concentration, polyoxypropylene (PO) numbers, polyoxyethylene (EO) numbers and electrolyte on the IFTs were investigated. The experimental results show that the interfacial activity of the extended surfactants mainly depends on the PO groups, and the short hydrophobe extended anionic surfactant shows the similar behavior of reducing IFT to that of long alkyl chain one. The IFTs decrease with an increase of the PO numbers against n-alkanes, and an increase of the EO numbers leads to the destruction of the tight arrangement of the adsorption film because the size of EO group is smaller than that of PO group, which results in an increase of IFT. The addition of electrolyte can reduce the IFTs by weakening the electrostatic repulsion between surfactant molecules at the interface, but it has little effect on its HLB. The long EO chain of extended surfactant prevents divalent cation from binding two surfactant counterions, which results in the little effect on reducing IFT. This study is of great significance for the insight of extended surfactants and their application in high-salt reservoirs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experiments and simulation combine to investigate the interaction of Gemini surfactant with lignite. • The modification mechanism of the Gemini surfactant on lignite was investigated. • The wettability of the Gemini surfactant on lignite was investigated. In this study, the nonionic Gemini surfactant S465 was used for regulating the wettability of the lignite surface. The adsorption characteristics of the surfactant on the lignite surface are discussed, and the mechanism of adsorption is explained from a microscopic viewpoint. The adsorption experiments show that the adsorption of S465 on the lignite surface is consistent with predictions made by the Langmuir adsorption isotherm. Furthermore, it indicates that the adsorption process is spontaneous and exothermic. X-ray photoelectron spectroscopy (XPS) analysis shows that the oxygen-containing functional groups content (CO, C = O, and O = C-O) on the lignite surface decreases after the adsorption of the surfactant, which enhances the hydrophobicity of the lignite surface. It is found from molecular dynamics (MD) simulation that the polar ethoxy groups of the surfactant touch the lignite surface, and the nonpolar groups (alkyl chains) entwine closely with each other, forming a protective layer, which keeps water away from the surface of the lignite. The mobility of water molecules is higher in the lignite/surfactant/water system compared to the system without surfactants, and the adsorption of surfactants results in the lignite interaction with water being weaker, therefore, the hydrophobicity of lignite is improved after the adsorption of the surfactant. [ABSTRACT FROM AUTHOR]

• Surfactant-enhanced soil washing is a promising approach for soil decontamination. • Structure and concentration of surfactants affected the solubilisation of HCHs. • α- and γ-HCH isomers were more easily solubilised than β- and δ-HCH. • Blends of surfactants influenced the critical micelle concentration. Surfactant-enhanced remediation of soil can increase the solubility of hydrophobic organic contaminants in water and improve their removal. In this study, the effect of 24 traditional surfactants and surface-active ionic liquids (SAILs) on the solubility of hexachlorocyclohexane isomers (α-, β-, γ-, δ-HCH) was evaluated in batch-type experiments. The combination of two different proportions of a cationic SAIL and an anionic surfactant was also assessed. The solubilisation capacity of the surfactant varied depending on its concentration and structure, but also the HCH isomer considered. In general, the anionic surfactants yielded the best results, increasing solubilisation of HCH up to 2.4 times compared to the control (pure water). α-HCH and γ-HCH isomers were more easily solubilised than β-HCH and δ-HCH regardless of the surfactant's type. The main advantage of ionic liquids being their tunability, some clues are given for formulating surfactants to enhance the solubilisation of HCH. The combination of a traditional surfactant and a SAIL influenced the critical micelle concentration, but not the solubilisation of the contaminant. Further studies on the use of blends for this application are required. The increase of solubility achieved with the studied surfactants encourages their application in washing HCH-contaminated soils through solubility enhancement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption behavior of mixtures of surfactant and polymer at the solid/water interface is studied by computational simulations. • After adding polymers, the adsorption conformations are changed to spherical micelle or multilayer. • The adsorption energy of the anionic surfactant is weakened by the polymer at the solid/water interface. • The negatively charged PCA has a strongly competitive adsorption with surfactants. • HPMC with great content of hydroxyl groups strongly interact with the hydrophilic groups of surfactants. In cementitious system, surfactant is used as air-entraining agents, which is often incompatible with other chemical admixtures, such as superplasticizers. The adsorption of surfactants at solid–liquid interface is critical for the bubble stability. The measurement of adsorption properties of surfactant in fresh cement or concrete is very difficult. In this study, classical molecular dynamics simulations is used to analysis the influence of two polymers (call as HPMC and PCA, respectively) on the adsorption behaviors of the two anionic surfactants (call as HSO4 and HPO4, respectively) at the C3A/water and ettringite/water interfaces. At solid/water interface, both of HSO4 and HPO4 molecules form a monolayer with hydrophilic head groups adsorbed on the solid surfaces. After adding polymers, the adsorption conformations are changed to spherical micelle or multilayer. The electrostatic interaction between oxygen atoms of hydrophilic head groups and calcium atoms of solid surface plays a decisive role. Therefore, the value of adsorption energy of HPO4 with more negatively charged hydrophilic head groups is greater than that of HSO4. The adsorption energies of the two surfactants are weakened by the two polymers, but the adsorption energy value of HPO4 is always greater. The influence mechanism of HPMC and PCA is different. The negatively charged PCA has a strongly competitive adsorption with the surfactants. The neutral HPMC has a weak adsorption capacity but it carries many hydroxyl groups to interact with the hydrophilic head groups of surfactants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synergism is observed in a mixed system comprising two anionic surfactants. • A large negative interaction parameter confirms the strong synergistic interaction at low α S D S. • The addition of SO induces ellipsoidal to vesicle transition of SDS micelles. Mixed micellar systems play a pivotal role in numerous scientific and industrial applications due to their inimitable solution properties and potential for enhancing solubilization and emulsification processes. The present study unveils the mixed micellization behavior of two anionically charged surfactants, sodium dodecyl sulfate (SDS) and sodium oleate (SO), in aqueous solutions through a combination of solution viscosity, tensiometric and small-angle neutron scattering (SANS) techniques. The dynamic changes in the interfacial properties of the mixed micellar system as a function of the SDS-to-SO ratio are evaluated from surface tension measurements. The results offer an insight into the formation of the stable mixed micelles with the alteration in the critical micelle concentration (CMC) as a function of the composition of both surfactants and the nature of the interaction. Surface tension data disclose the thermodynamic aspects of micelle formation and the influence of surfactant interactions on the surface activity of the system. Complementing the surface tension measurements, SANS analysis was conducted to clarify the structural aspects of the SDS-SO mixed micelles. SANS inferred the micellar size, shape, and aggregation number (N agg), thereby shedding light on the nanoscale organization of the micellar aggregates in the aqueous solution. By combining SANS and surface tension data, a comprehensive understanding of the mixed micellization behavior of SDS and SO is achieved, addressing both interfacial and structural aspects. A computational simulation approach has also been employed to obtain the optimized parameters, which provide a better understanding of the correlation of SDS and SO molecular orbital energy levels. The results underscore the importance of surface tension and structural characterization techniques to comprehend the behavior of mixed micelles fully. [ABSTRACT FROM AUTHOR]

[Display omitted] • New surfactant-like 5-alkyl-1,2,4-triazole-3-thiones were synthesized. • CMC was estimated using the conductivity method and the 1H NMR technique. • Samples of triazole-stabilized spherical silver nanoparticles were obtained. • The synthesized triazoles show moderate antifungal activity against C. albicans. • DFT calculations support similar electronic structure for all the new triazoles. New 5-alkyl-1,2,4-triazole-3-thiones containing structural fragments of anionic surfactants have been synthesized and examined as stabilizers in the wet chemistry synthesis of silver nanoparticles (AgNPs). The synthesis of the new 1,2,4-triazole-3-thiones was done via the cyclization reaction of 4-acyl-thiosemicarbazides in basic conditions. The structure of the new surfactant was analyzed by spectroscopic (infrared and nuclear magnetic resonance) and theoretical DFT methods. The surface activity characteristic, such as critical micelle concentration, was estimated using the conductivity method and the 1H NMR technique. The structural peculiarities of the new compounds testify to their surfactant properties, which is why they were explored as stabilizers in the chemical synthesis of silver nanoparticles from silver nitrate in an aqueous solution. The UV–VIS spectroscopy technique confirmed the formation of AgNPs in aqueous solutions of 5-alkyl-1,2,4-triazole-3-thiones. The stable AgNPs were obtained only using 1,2,4-triazole-3-thiones with longer alkyl chains (pentadecyl and heptadecyl), whereas the 5-pentyl-1,2,4-triazole-3-thione and the 5-heptyl-1,2,4-triazole-3-thione have not shown considerable stabilization activity. To better understand the interaction of the 1,2,4-triazole-3-thiones with AgNPs, Raman spectra analysis, quantum chemical modeling, and force field molecular dynamics were performed. The new triazoles were studied for their antifungal activity by the determination of minimal inhibition concentrations and docking studies. [ABSTRACT FROM AUTHOR]

• Anionic natural surfactant was successfully fabricated from peanut oil through trans -esterification and sulfonation. • Conductivity and surface tension confirmed 2000 ppm as the CMC of newly proposed surfactant. • Developed natural surfactant reduced the IFT to 0.35 mN/m and further to 0.068 mN/m with the formation water. • Developed natural surfactant altered the wettability to water wet at 44° contact angle. • Injection of natural surfactant enabled additional 19.3% OOIP from sandstone rock. Nowadays, there is a growing inclination towards the environmentally friendly and economically viable materials in the field of chemical enhanced oil recovery including the surfactant flooding. This study investigates the performance of a newly developed anionic surfactant derived from peanut oil in enhanced oil recovery (EOR) applications. The validity of the formulated surfactant using the esterification and sulfonation methods was verified through FTIR, 1H NMR, and TGA analytical techniques. According to the outputs of conductivity and surface tension from developed surfactant solutions at 500 and 4000 ppm, the concentration of 2000 ppm was identified as the critical micelle concentration (CMC). Several experimental tests were applied on the surfactant solutions and more specifically at CMC range, such as IFT measurement, wettability estimation, foamability, oil displacement and emulsification. The surfactant solution at CMC (optimal surfactant solution) reduced the IFT from an initial value of 15.5 to 6.8 × 10−2 mN/m at the optimum concentration of formation water (15,000 ppm). Wettability alteration was examined on sandstone and carbonate rock samples, and the optimal surfactant solution successfully altered both rock surfaces from strongly oil-wet to water-wet, resulting in a decrease in contact angle from 144° to 58° on carbonate rock and from 138° to 44° on sandstone rock. In addition, the emulsion test results revealed a significant ability of the peanut surfactant to create emulsions. Examination of microscopic images demonstrated that the emulsion remained stable for approximately 90 days with a high compatibility under high saline conditions. Hence, the developed natural surfactant enabled to displace extra 19.3 % and 15.64 % original oil in place (OOIP) from the sandstone and carbonate core plugs, respectively, with shifting the relative permeability curves towards the lift side. [ABSTRACT FROM AUTHOR]

• Discuss interactions of three ionic surfactants with antibiotic drug cloxacillin sodium (ClxNa) at different temperatures. • The ClxNa disfavors the micellization of CTAB and TTAB whereas it favors SDS at higher [ClxNa]. • The CMC values show a U-shaped curve against temperature for all the studied systems. • Thermodynamic parameters reveal that the micellization of studied surfactant–ClxNa systems is entropically driven. The physicochemical properties and interactions of surfactant–drug aggregates are regarded as essential features to achieve optimum therapeutic action of the drug. In this article, the effect of various concentrations of anionic antibiotic drug cloxacillin sodium (ClxNa) on the micellization of cationic surfactants such as cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB) and anionic surfactant sodium dodecyl sulphate (SDS) have been investigated using electrical conductance measurement at different temperatures (288.15 K, 293.15 K, 298.15 K, 303.15 K, 308.15 K, and 313.15 K). The results suggest an increase in critical micelles concentration (CMC) values for cationic surfactants (CTAB/TTAB) with a rise in drug concentration (0 mM up to 10 mM) whereas anionic surfactant SDS shows a decrease in CMC at higher drug concentrations (from 2.5 mM up to 10 mM) at all the studied temperatures. The degree of counterion dissociation (α) values for TTAB aggregates show a slight increase with [ClxNa], except at a few lower temperature ranges whereas such a regular trend was not obtained for CTAB and SDS aggregates. Temperature-dependent CMC values show a nonlinear nature with a rise in temperatures and follow a U-shaped curve for all studied pure surfactant and surfactant–ClxNa systems. Micellization for all surfactant-drug systems is found to be spontaneous. Investigation of other temperature-dependent thermodynamic parameters such as change in standard enthalpy ( Δ H m 0), and entropy ( Δ S m 0) of micellization suggest that surfactant–drug interactions are both endothermic ( Δ H m 0 < 0, particularly at lower temperatures) and exothermic ( Δ H m 0 < 0, at higher temperatures), whereas micellization is largely entropically driven ( Δ S m 0 > Δ H m 0). [ABSTRACT FROM AUTHOR]

• Sesame oil was used as a natural substance for the synthesis of a new anionic surfactant. • Thermal stability and characterization of the surfactant were shown by TGA, FTIR, and 1H NMR analysis. • The crude oil–water IFT was achieved to a low value by the surfactant and the rock wettability was shifted to water-wet. • The surfactant was able to generate a stable foam and emulsion. • A 16.18% increase in oil recovery was achieved by optimal fluid flooding. This study is centered on creating an anionic surfactant using edible sesame oil for enhanced oil recovery (EOR) objects. The surfactant was synthesized under esterification and sulfonation processes. Characterization analyses were performed to describe the surfactant and evaluate its temperature stability. Related experiments were conducted to investigate phase behavior, surface activity, and EOR implications of the surfactant. A chemical flooding experiment was carried out. This involved injecting the surfactant along with the appropriate levels of salinity and alkalinity, into a carbonate plug. Additionally, the ability of the surfactant to generate and maintain foam and emulsion was examined. The surface tension values were reduced from 64 to 33.07 mN/m, and the interfacial tension (IFT) values dropped from 21 to 0.81 mN/m. Through these experiments, the critical micelle concentration (CMC) of the surfactant was determined to be 800 ppm. Upon reaching the CMC, the IFT further decreased to 0.38 and 0.14 mN/m at optimal salinity and alkalinity levels respectively. The previously hydrophobic carbonate surface underwent significant improvement in wettability, transitioning to hydrophilic behavior. This shift was evident as the contact angle decreased from 130.2° to 58.8° within a brief 60-minute equilibration period, representing a suitable wettability state for EOR. The surfactant exhibited an emulsion and foam stability period lasting 35 days. Additionally, its ability to function effectively in the presence of sodium chloride (NaCl) ions was verified with compatibility demonstrated at salinity levels below 100000 ppm. Ultimately, the flooding outcomes displayed a notable 16.18 % enhancement in oil recovery when employing the optimum fluid. [ABSTRACT FROM AUTHOR]

• The AdEr/KCl wormlike micelles demonstrate remarkable temperature resistance. • Molecular dynamics (MD) simulations provided a deep exploration of the temperature-dependent rheological response. • Environmentally friendly AdEr/KCl wormlike micelles was first applied in the fracturing fluid. Ionic liquid surfactant (ILS) presents a promising alternative for balancing the conflicting relationship of hydrophobicity and water solubility in anionic surfactants. Despite this potential, the utilization of ultra-long chain anionic ILS in viscoelastic surfactant (VES) fracturing fluids has been infrequently reported. In our previous research, we successfully prepared a viscoelastic wormlike micelles (WLMs) by employing an ultra-long chain ILS known as Adamantyl trimethyl ammonium erucate (AdEr) with potassium chloride (KCl). This novel system opens up promising avenues for its application in fracturing fluids. This study aims to comprehensively investigate the impact of temperature on the behavior of AdEr/KCl wormlike micelles, thereby evaluating the fracturing fluid performance. In rheological experiments, we observed that the zero-shear viscosity (η 0) of AdEr/KCl WLMs remains at ∼103mPa·s at 90 °C, demonstrating excellent thermal resistance. Molecular dynamic (MD) simulations demonstrated that, as the temperature increased, it initially resulted in the disintegration of the aggregate structure, followed by a remarkable reformation of the same structure. This observed behavior can be attributed to the gradual decrease in polarity of the adamantyl groups as the temperature increases. Finally, the AdEr/KCl-based fracturing fluids, AE-1 and AE-2, not only exhibit outstanding temperature resistance (90 °C and 130 °C, respectively) but also demonstrate exceptional proppant-carrying and oil-induced gel-breaking capabilities. This study promotes the utilization of anionic ILSs in the formulation of environmentally-friendly fracturing fluids, emphasizing the crucial role of understanding temperature-induced changes through MD simulations. [ABSTRACT FROM AUTHOR]

• Highly emissive carbon quantum dots synthesized from citric acid in DMF medium. • Fluorescence property investigated inside micelles formed by different types of surfactants like cationic (CPC, CTAB), anionic (SDS) and neutral (TX 100, BRIJ-35) • CPC interacts with greater extent and formed co-assembly with negatively-charged carbon quantum dots (CQDs) and no other surfactants, that we studied, interact with CQDs. • Formation of a non-fluorescent vesicle without any phase separation over the large concentration barrier of the CPC surfactant. • No vesicle formation takes place for another cationic surfactant CTAB excluding the role of only electrostatic interaction. The tuning of photo physical properties of highly emissive carbon quantum dots which was synthesized from citric acid in DMF medium through solvothermal method is investigated inside micelles formed by different types of surfactants like cationic surfactant cetylpyridinium chloride (CPC), cetrimonium bromide (CTAB), anionic surfactant sodium dodecyl sulfate (SDS) and neutral surfactant polyethylene glycol tert -octyl phenyl ether (TX100), polyoxoethylene lauryl ether (BRIJ-35). Interestingly, only CPC interacts with greater extent and formed co-assembly with negatively-charged carbon quantum dots (CQDs) whereas other surfactants like CTAB, SDS, TX100 and BRIJ-35 do not alter the fluorescence intensity extensively. This results in the formation of a non fluorescent vesicle. No phase separation was observed over the large concentration barrier of the CPC surfactant. However, no such vesicle formation takes place for another cationic surfactant CTAB excluding the role of only electrostatic interaction. The synthesized vesicle is characterized by various techniques including HRTEM, DLS. For the aqueous solution of CQDs having concentration of 0.5 mg/ml, addition of CPC leads to formation of different sized vesicles of size 40 nm to 100 nm. The driving force behind this formation of non-fluorescent vesicles is oxidative photo induced electron transfer which is revealed by the highest occupied molecular orbital (HOMO) –lowest unoccupied molecular orbital (LUMO) interaction between the donor (CQDs) and the acceptor (CPC). We trust such type vesicle can be a suitable alternative for drug carriers, biomarkers and other various applications also. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interaction of nimesulide with CTAB, HDPC, SDS and Triton X-100 micelles is investigated. • The binding constant, K b value follows the order: HDPC > CTAB > Triton X-100 > SDS. • Nimesulide partitions significantly more in CTAB micelles. • Bioinformatic tools were used to predict the relationship between chemical structure - pharmacokinetic/pharmacodynamic features of studied compounds. The present work reports the interaction of anti-inflammatory drug nimesulide with cationic (CTAB, HDPC), anionic (SDS) and non-ionic (Triton X-100) surfactant micelles. The drug-micelles systems were studied by UV–Vis absorption spectroscopy to estimate the binding constant (K b), partition coefficient (K x) and the free energy of binding and partition (ΔG b , ΔG x). The values of K b indicate a stronger interaction between nimesulide and cationic micelles due to cumulative electrostatic and hydrophobic forces. Also, the higher values of K x obtained for HDPC and CTAB micelles point out a higher drug concentration in cationic micelles than in the surrounding aqueous medium, as against SDS and Triton X-100 micelles. The bioinformatic methods were used to evaluate the pharmacokinetic, pharmacogenomic and pharmacodynamic profiles of the nimesulide, CTAB, HDPC, SDS, and Triton X-100. Our results showed that all compounds exhibit good intestinal absorption, good BBB and CNS permeabilities, and low toxicity features. Also, the ecotoxicity of compounds was quantified. Various pharmacogenomic features of compounds were recorded. Supplementary, we conducted an extensive analysis based on various aspects of the structural and functional features of compounds, such as their electronic (dipole moment, frontiers orbital energies), steric, and hydrophobic features. Experimental and theoretical results show that CATB and HDPC cationic micelles may be better drug delivery agents for nimesulide. [ABSTRACT FROM AUTHOR]

[Display omitted] • The presence of Fe 3 O 4 nanoparticles in low concentrations of a mixture of anionic-amphoteric surfactant (<0.15 wt%) increases IFT. • There is no significant change in IFT at high concentrations of a mixture of anionic-amphoteric surfactant (≥ 0.15 wt%) and Fe 3 O 4 nanoparticles. • 0.15 wt% surfactant mixtures and Fe 3 O 4 nanoparticles provide the optimum result in wettability to more water-wet. • Combining 0.01 wt% Fe 3 O 4 nanoparticles in 0.15 wt% surfactant mixtures enhanced the oil recovery of 63.17%. This study investigates the effects of individual and combined systems on interfacial tension (IFT) and wettability alteration characteristics of a combination mixture of colloidal Fe 3 O 4 nanoparticles and amphoteric-anionic surfactant. Combining a binary of amphoteric-anionic surfactants has resulted in an IFT reduction compared to brine alone. Furthermore, the addition of Fe 3 O 4 nanoparticles at concentrations lower than the critical micelle concentration (CMC) of binary surfactant mixes (<0.15 wt%) resulted in an observed increase in IFT values. However, there is no significant change in IFT around or above the CMC (≥ 0.15 wt%). The alteration in wettability can be observed through a reduction in contact angle when amphoteric-anionic surfactants and Fe 3 O 4 nanoparticles are combined, resulting in a change from water-wet to strongly water-wet conditions. The findings of the imbibition test also demonstrated that adding 0.01 wt% Fe 3 O 4 colloidal nanoparticles in the surfactant mixture provided an optimal recovery efficiency of 63.17%. The results of this study indicate that a notable improvement in recovery can be observed when the primary mechanism of wettability alteration is achieved and simultaneously supported by IFT reduction. [ABSTRACT FROM AUTHOR]

• A series of anionic-nonionic Gemini surfactant were synthesized. • The molecular structure has a great influence on the surface activity and the thermodynamic properties of micelles. • The molecular polarity index can be used to evaluate the surface activity of Gemini surfactants. In this work, Gemini surfactants with different hydrophobic tails and spacer groups were designed and synthesized. The structures were verified by 1H NMR spectrum and mass spectrometry. The modulation of the experimental results of micellar thermodynamics and surface activity by the molecular structure has been thoroughly discussed and studied. Furthermore, the electrostatic potential results explain Gemini surfactants have a very efficient ability to reduce surface tension. The molecular polarity index (MPI) has been shown to be used to cost-effectively evaluate the surface activity of Gemini surfactants. It is hoped that the work will promote the structural design and industrial application of Gemini surfactants. [ABSTRACT FROM AUTHOR]

Herein, we have shown the mixed micelle formation between anionic benzene sulphonate (viz., sodium 4,4′-(16,25-dioxo-15,17,24,26-tetraaza-hexatriacontane15,26-diyl) dibenzenesulphonate [BSC14-C6-14CSB] and sodium 4,4′-(18,27-dioxo-17,19,26,28-tetraaza-tetracontane15,26-diyl) dibenzenesulphonate [BSC16-C6-16CSB]) with conventional anionic surfactant (sodium dodecyl sulphate [SDS]) by conductivity and fluorometry methods. The conductivity measurements were done over a range of mole fractions of SDS at different temperatures to study the mixed micellization and thermodynamic parameters, while fluorescence measurements were performed over entire range of mole fraction of SDS in order to observe the aggregation and micro-polarity. The conductometric study confirms the synergism in all mole fractions of SDS with [BSC14-C6-14CSB] and [BSC16-C6-16CSB] at all temperatures. The Rubinghs regular solution theory (RST) was employed to evaluate micellar mole fraction, X 1 , ideal micellar mole fraction, X ideal , interaction parameter (β), activity coefficients (f 1 , and f 2) for both mixed micelles systems and Gibbs excess free energy (G E ). The G E values are negative for entire mole fraction range suggesting the formation of stable mixed micelles. In addition to this, other thermodynamic parameters like Gibbs free energy change of micellization (Δ G mic), enthalpy change of micellization (Δ H mic) and entropy change of micellization (Δ S mic) were evaluated. Also, the aggregation number (N agg) in micelles was calculated using pyrene probe fluorescence measurement. The binding constant, dielectric constant and micropolarity of mixed systems of SDS + [BSC14-C6-14CSB] and SDS + [BSC16-C6-16CSB] binary mixtures were obtained from the ratio of peak strength (I 1 / I 3) from the pyrene probe fluorescence emission spectra. Unlabelled Image • Mixed micellization behaviour of SDS–[BSC14-6-14CSB]/[BSC16-6-16CSB] • The synergistic interaction was observed. • The process of micellization is entropy driven. [ABSTRACT FROM AUTHOR]

Due to the high surface activity and low critical micelle concentration (CMC) of metallogemini-surfactants (MGSs), in this work various magnetic MGSs (MMGS 1 s) were prepared by simple grinding of low-cost hydrated salts of Fe3+, Co2+, Mn2+ and Ni2+ with GS 1 synthesized by an improved solvent-free method. These new MMGS 1 s, which are complexes of 2FeCl 4 −, CoCl 4 2−, MnCl 4 2−, and NiCl 4 2− with GS 1 , were characterized by UV–Vis, FT-IR, and melting point (mp) analyses. So, the maximum UV–Vis absorption wavelength was due to the GS 1 2+·CoCl 4 2− and the minimum mp and pH were due to the GS 1 2+ ·2FeCl 4 − (MFeGS 1). The results of the catalytic activities of MMGS 1 s in solvent-free synthesis of anticancer O , O ′-diethyl-α-(benzothiazole-2-yl)amino(phenylmethyl) phosphonate (ACBTAP) revealed the superiority of MFeGS 1 , although catalysts were isolated as aqueous magnetic liquids (MLs) by addition of water. The aqueous MLs were further prepared in 0.01 and 0.1 molar concentration and analyzed by pH, surface tension (ᵞ), superconducting quantum interface device magnetometer (SQUID), and magnetic tests. Similar to GS 1 , all MMGS 1 s reduced the ᵞ of water by a half time ratio, while the magnetic activity of their aqueous MLs confirmed by magnetic drop-deviation and drop-movement over organic phase. The SQUID analysis of the aqueous MLs supported ferromagnetic properties for solution of MCoGS 1 , MNiGS 1 , and MMnGS 1 in water and paramagnetic properties for the aqueous solution of GS 1 2+·2FeCl 4 −. The as-prepared MLs are novel polar alternatives for organic solvents, water-treatment sorbents, and magnetic delivery of biomaterials. Unlabelled Image • Improved solvent-free synthesis of gemini-surfactant (GS 1) in 96% yield • MMGS 1 s gave by co-grinding of GS 1 and low-cost hydrated metal halides. • Upgraded preparation of magnetic metallogeminisurfactants (MMGS 1 s) • New aqueous magnetic liquids (MLs) by solubilizing of MMGS 1 s in water • The GS 1 2+·2FeCl 4 2− is a talented catalyst for synthesis of anticancer ACBTAP drug. [ABSTRACT FROM AUTHOR]

Abstract Enhanced oil recovery (EOR) especially surfactant slug injection has received a great attention as an oil recovery technique. Surfactants are capable in reducing the interfacial tension (IFT) and altering the wettability of rock from subsurface reservoir. Here, a new anionic surfactant was synthesized from Madhuca longifolia (Mahua) oil. The surfactant was characterized using FTIR, GC–MS, FE-SEM and EDX analysis and tested rigorously using IFT, wettability and flooding experiments for its application in EOR. The surfactant showed an ultralow IFT value around 1 × 10−2 at optimal salinity. Thermodynamic parameters were calculated using surface tension as a function of temperature and the studies showed that adsorption of molecules at the interface is favorable over micellization. The surfactant was found to be thermally stable by TGA analysis for its application at high temperature reservoir conditions. It showed the ability to alter the wettability of oil-wet sandstone rock surface to water-wet. The core-flooding experiments were conducted using individual surfactant slug and surfactant-polymer slug injection, which showed an additional recovery of almost 20% over convention water flooding. The experimental results were simulated using computational fluid dynamics (CFD) analysis. The results obtained after simulation study and core-flooding experiment results are very much comparable. The comprehensive evaluation of thermal, interfacial and oil recovery studies provides grounds for potential application in EOR. Graphical abstract Unlabelled Image Highlights • Synthesis of natural surfactant from Madhuca longifolia • Ultralow IFT achieved by surfactant in presence of salt and alkali • Rock wettability is altered using surfactant from oil-wet to water-wet. • Core flooding experiments recovered up to 20% additional recoveries. • Simulation studies of experimental data using computational fluid dynamics [ABSTRACT FROM AUTHOR]

Abstract The micellization behavior of N -Lauryl sarcosine sodium (NLS, an anionic surfactant) and Dodecyltrimethylammonium bromide (DOTAB, a cationic surfactant) in aqueous solution is investigated by UV–vis spectrophotometric and conductometric methods at 298.15 K. A critical micelle concentration (CMC) were obtained for pure NLS and DOTAB as well as mixed micelles [NLS(1) + DOTAB(2)]. The CMC values of the studied system at different mole fractions (y i) are much less than that of individual surfactants (due to the strong electrostatic attraction between components after mixing). In this work, the tautomers of 1-phenyl-1, 3-butadione (or benzoylacetone) were used to obtain the mixed CMC of anionic surfactant systems by UV–Vis technique. The deviations of critical micelle concentration (CMC) from the ideal values show the interaction between NLS and DOTAB. The micellar mole fraction values (X 1 m and X 2 m ) according to Rubingh approach were calculated and the results obtained reveal the same composition in the mixed micellization at most mole fraction(y 1) even when the initial mixing ratio is far from equimolar. The activity coefficients of components were less than unity (f 1 m < < 1 and f 2 m < < 1) and the values of the interaction parameter (β m ) are negative in all compositions, which indicate the strong synergistic interaction between NLS and DOTAB. The Gibbs free energy of micellization (ΔG mic 0) and the excess free energy of micellization (G mic E ) values are found to be negative in this system demonstrated the stability of the mixture. All of the evaluated results imply a strong synergism between components. Graphical abstract Unlabelled Image Highlights • Interaction between cationic and anionic surfactants has been investigated. • The maximum synergism point for DOTAB-NLS, has been observed at the same mole fraction of components. • The mixed micelle composition and the interaction parameter were calculated using RST theory. • Thermodynamic parameters of micellization (ΔG mic 0 and G mic E ) were calculated. [ABSTRACT FROM AUTHOR]

Abstract In search of a substance able to function as an anionic surfactant applied for the electrically-induced anchoring transitions in liquid crystals, the compound 4-heptyloxybenzoate benzyl dodecyldimethylammonium (HOBBDDA) has been synthesized. Its orienting influence on nematic liquid crystal 4-pentyl-4′-cyanobiphenyl (5CB) has been tested. HOBBDDA dissolved up to 1.4% in 5CB droplets dispersed in polymer film does not change the tangential surface anchoring inherent to polyvinyl alcohol matrix used. Homeotropic surface anchoring is realized if the HOBBDDA content exceeds 1.7%. The molecules of the surfactant in 5CB dissociate into anions and cations. The anions modify the surface anchoring under the action of DC electric field both in the normal and inverse mode. The mixture of HOBBDDA and cetyltrimethylammonium bromide can function as a binary ionic-cationic surfactant which significantly expands the prospects for using the ionic-surfactant method to control liquid crystal materials. Highlights • The anionic surfactant suitable for electrically controlled modification of surface anchoring in nematic was synthesized. • The electrically induced anchoring transition in nematic droplets doped with the anionic surfactant is demonstrated. • The binary mixture of cationic and anionic surfactants was prepared to allow modifying anchoring at both parts of drople. [ABSTRACT FROM AUTHOR]

Abstract Adsorption isotherms of five ionic liquid surfactants belonging to different families and diverse structures, namely: 1-dodecyl-3-methylimidazolium chloride, [C 12 C 1 im]Cl; 1-dodecyl methylpyrrolidinium bromide, [C 12 C 1 Pyrr]Br; 1-dodecyl methylpyridinium chloride, [C 12 C 1 Py]Cl; 1-dodecyl methylpiperidiniumm bromide, [C 12 C 1 Pip]Br; and 1-octyl-3-methylimidazolium octylsulfonate, [C 8 C 1 im][C 8 SO 3 ] on a gold surface have been studied using a quartz crystal microbalance with dissipation (QCM-D). All surfactants show critical micelles concentrations (CMCs) in 10–20 mM range. Simultaneous adsorption and dissipation measurements were made in pre- and post-micellar concentration regions at 298.15 K. Peculiar results were obtained for all the IL surfactants. Frequency measurements show that the adsorbed amounts in the pre-micellar region are small and, as soon as the aggregates formation takes place, the adsorbed amount increases significantly. Dissipation measurements indicate the formation of rigid layers with very low values in the pre-micellar region. However, in the post-micellar region, with the increase of concentration (up to 75 mM~5xCMC) the dissipation significantly increases demonstrating the presence of loosely bound structures/multilayers on the gold surface. Graphical abstract Adsorption and viscoelastic behavior of ionic liquid surfactants (SILs) on gold surfaces studied using QCM-D revealed that with increasing SILs concentration I the adsorbed amount increases and distinct structural changes occurred depending mainly on the C/CMC ratio. Unlabelled Image Highlights • QCM-D study reveals that SILs adsorbed readily at gold surfaces. • SILs adsorption depends on the ratio of working concentration and CMC. • Viscoelastic modeling reveals formation of multilayers at higher concentrations. [ABSTRACT FROM AUTHOR]