Class Of Surfactants Research Articles

Novel Gemini Surfactant for Binding Eu(III)-Polyoxometalate into Hydrogels and Polymer Latexes.

The incorporation of rare-earth ions into polymer matrices can lead to useful materials in various fields such as biomarkers, lasers, luminescent devices, optical storage materials, and so on. Methods of incorporation are either extremely simple, such as mixing the polymer and the ion of interest in adequate solvents, or more sophisticated such as synthesizing predesigned monomers that contain the rare-earth ion or binding the ion on an already formed polymer chain. Cationic gemini surfactants represent a class of surfactants that can be used to incorporate metal-oxygen cluster compounds by means of strong electrostatic interactions. In this study, first, a novel cationic gemini surfactant having double bonds on both side chains was designed and prepared. After characterization, the surfactant was used to synthesize hydrogels with different degrees of crosslinking and also as a surfmer in emulsion polymerization of methyl methacrylate. The resulted polymer matrices were able to bind europium-polyoxometalate Na9[EuW10O36].32H2O. In case of luminescent lanthanide ions, changing the microenvironment around the metal ion also changes the intensity of some emission peaks as well as other luminescent parameters. Investigation of emission spectra of Eu3+ indicates a decrease in the symmetry of the microenvironment, when the polyanions pass from water to latex, to surfactant solution, and to hydrogel.

Surface activity, micellization, and application of nano-surfactants—amphiphilic carbon dots

For nano-surfactants, a new class of surfactants, the unique surface properties, micellization, and application of amphiphilic carbon dots (CDs) have been investigated carefully. Amphiphilic CDs (C12-CDs and C12-SCDs) were synthesized under mild reaction conditions. These CDs exhibit higher surface activity than conventional surfactants (APG12 and SDBS), whereas hydrophilic CDs have negligible surface activity. Above the critical micelle concentration, C12-CDs aggregate into an irregular spherical structure like micelle with an average diameter of about 100 nm, whereas C12-SCDs do not form aggregates. The surface tension of C12-CDs and C12-SCDs reaches the minimum at pH = 3, which is close to the isoelectric point of CDs. As pH increases, the water solubility of CDs increases, and thus the surface tension increases. C12-CDs can still maintain high activity at cNaCl = 250 g/L, but their resistance to CaCl2 is poor. The addition of the sulfonate groups enhances the tolerance of CDs to both NaCl and CaCl2. At cNaCl = 360 g/L and cCaCl2 = 750 g/L, C12-SCDs still have high surface activity.The removal efficiency of oil film and contact angle experiments show that compared to the traditional surfactant SDBS, C12-CDs and C12-SCDs have an excellent wettability alternation due to their abundant hydroxyl, carboxyl, amine, and sulfonate groups. Among them, the wettability alternation of C12-SCDs is better than that of C12-CDs due to their hydrophilic sulfonate groups. Furthermore, the Pickering emulsions stabilized by C12-SCDs have rapid pH and CO2 response performance. In addition, compared to the traditional surfactants SDBS and APG12, CDs have an excellent dispersion performance to MWCNTs. Different from the dispersion mechanism of cationic surfactant CPC (strong electrostatic attraction), CDs are adsorbed on the surface of MWCNTs through their hydrophobic effect and π-π stacking effect to achieve effective dispersion. Among them, because the sulfonate groups have high steric resistance and electrostatic repulsion, the dispersion performance of C12-SCDs is better than that of C12-CDs.

Symmetry (Asymmetry) of the Molar Excess Gibbs Free Energy Function of the Binary Mixed Micelles of Bile Acid Anion and Classical Cationic Surfactant: Influence of Sterically Shielded and Sterically Unshielded Polar Groups of the Steroid Skeleton

Binary mixtures of surfactants build a binary mixed micelle in which the ratio of surfactants usually differs from the initial ratio of surfactants in their binary mixture. The thermodynamic stabilization of the binary mixed micellar pseudophase about the hypothetical ideal state (intermolecular interactions between the different particles and the conformational states of the particles are identical to those of monocomponent states) is described by the molar excess Gibbs free energy (gE). The dependence of gE on the molar fraction of surfactant i (xi) from the binary mixed micelle can be described by a symmetric function (symmetry is described to the line parallel to the y-axis and passes through xi = 0.5) or by an asymmetric function. Theoretical analysis (canonical partition function, conformational analysis) examines how the presence of different polar functional groups, some of which are sterically shielded from the steroid skeleton of bile salts (surfactant), affect the symmetry of the function gE of the binary mixed micelle of the cholic acid anion (bile salts) and classic cationic surfactant (hydrophobic tail and polar head). Suppose the steroid skeleton of the bile salt contains non-sterically shielded polar groups (or the temperature is relatively high). In that case, gE is a symmetric function. At the same time, if the steroid skeleton also contains sterically shielded polar groups, then the gE function is asymmetric.

Adsorption of extended anionic surfactants at the water- polymethylmethacrylate interface: The effect of polyoxyethylene groups

Wetting of solid surfaces is a typical phenomenon in daily life and manufacturing. The wettability of solid surfaces can be efficiently altered by certain surfactants. Extended surfactants, a novel class of surfactant with a unique structure, have a potent potential to convert neutral surfaces into hydrophilic surfaces. To deeply understand the influence of EO groups on the adsorption mechanism of surfactants at solid surfaces, the wettability of the extended anionic surfactants sodium cetyl (oxyethylene)3 carboxylate (C16EO3C), sodium cetyl (oxyethylene)5 carboxylate (C16EO5C), and sodium cetyl (oxyethylene)7 carboxylate (C16EO7C) on polymethylmethacrylate (PMMA) surfaces was investigated. Surface tension and contact angle experiments were used to determine adsorption characteristics such as adhesion tension, PMMA-liquid interface tension, and adhesion work. The experimental results show that the adsorption amounts of C16EOnC at the liquid-air interface are obviously larger than those at the PMMA-liquid interface. Below CMC, all three extended surfactant molecules adsorb at the PMMA-liquid interface via polar interactions and hydrophobic part towards the aqueous phase, which results in an increase of γSL. However, the decrease of γLV and the increase of γSL have opposite effects on the contact angle, resulting in almost constant values below CMC. With an increase in EO number, the hydrophobic modification ability increases because longer EO chains provide stronger polar interactions between C16EOnC molecules and the PMMA surface. Above CMC, C16EOnC molecules continue to adsorb at the PMMA-liquid interface and form a bilayer film. Conclusively, the contact angle abruptly decreased due to the hydrophilic modification of the PMMA surface. With an increase of EO number, the hydrophilic modification ability increases because surfactants with a larger EO number endow the second layer with a more hydrophilic nature.

Preparation of Elastin Membranes Based on Surfactants and Separation Mechanism

The influence of a classical surfactant – palmitoyl-glycylglycine and bola amphiphilic – demecarium bromide upon the elastin membrane preparation and separation mechanism of turmeric from aqueous solutions was studied by: UV-VIS spectroscopy, scanning electron microscopy, dynamic light scattering and separation rates. The tensile strength and hydrophobic property were improved by introducing a surfactant (classic or bola). In this research the influence of surfactants upon the microporous structure and retention of turmeric from aqueous solutions was studied. The biomembranes were produced by a casting-solvent evaporation technique. The elastin powder was dissolved in a water-acetic acid (70:30 v/v) solution with and without plasticizer: glycerol and surfactant (classic or bola), constant continuous stirring for 5-7 hrs. at 60°C, then degassed the solution for 2 hrs. The solution was poured and afterwards maintained in the oven at 45-55°C for 5-8 hrs. Ecological biomembranes are obtained from a biodegradable biopolymer – elastin, and can be used successfully in removing turmeric from wastewaters.

Synthesis and properties of sodium fatty acyl lactylates

Sodium fatty acyl lactylates (Cn lactylates), which are a class of biomass-based surfactants, were synthesized from fatty acids and lactic acid via a two-step reaction. The equilibrium surface tensions, dynamic surface tensions, and application performances of synthesized surfactants with various hydrophobic chain lengths were studied and compared. With the increasing of alkyl chain length, the Cn lactylates exhibited better surface activity along with excellent foaming and emulsificationproperties, and the wettability on paraffin film and stain removal ability on carbon black-stained cloth improved. Moreover, C10 lactylate showed superior antibacterial ability against E. coli, whereas C12 lactylate demonstrated the best wetting property on canvas sheets and the best decontaminability on sebum-soiled cloths. These results showed that the properties of Cn lactylates can be tuned by modifying the chain length.

Synthesis of branched surfactant via ethoxylation of oleic acid derivative and its surface properties

A class of bio-based nonionic surfactants with double hydrophilic head groups (DMOE n ) was obtained from the waste cooking oil. • A new strategy for the preparation of branched surfactants from renewable oleic acid in waste cooking oil was proposed, and a class of bio-based nonionic surfactants with double hydrophilic head groups (DMOE n ) was obtained. • The ethoxylation reaction process of DMO and its reaction kinetic were both systematically optimized and studied. • The surface activities, aggregation and adsorption behaviors of DMOE n were investigated, and it was discovered that DMOE n had the characteristics of typical branched surfactant with good wetting performance, low foaming and strong defoaming ability. A new series of bio-based branched nonionic surfactants (ethoxylated dihydroxy stearic acid methyl ester, DMOE n ) was synthesized and characterized. DMOE n was based on a hydroxyoctadecanoic acid methyl ester, which was obtained from renewable oleic acid in waste cooking oil. These new polyoxyethylene surfactants contained double hydrophilic and hydrophobic chains, which shows the surface properties of the branched surfactant. The synthesis rules and reaction kinetics were studied in detail. The physicochemical properties and surface properties of the DMOE n with different degrees of ethoxylation at various concentrations were investigated. Furthermore, the surface tension results indicate that DMOE n reduced the surface tension reduction and increased the diffusion rate in an aqueous solution. The dynamic contact angle, wettability, foaming properties, and emulsifying capacity tests showed that DMOE n exhibited good wetting performance, low foaming, fast defoaming, and excellent emulsifying ability, which shows that the surfactant has potential application in industrial cleaning.

Linear instability of a surfactant-laden shear imposed falling film over an inclined porous bed

The influence of externally imposed shear on a surfactant-laden gravity-driven fluid flow over an inclined porous substrate is studied using the linear perturbation theory. The hydrodynamic instability of the flow system corresponding to infinitesimal disturbances is examined in the framework of the Orr–Sommerfeld (OS) boundary value problem. Furthermore, the generalized OS model is obtained by including the Marangoni stress and external shear on the flow dynamics. The formulated stability problem is solved as an eigenvalue problem by the Chebyshev spectral collocation technique. The analysis encounters the existence of different classes of unstable modes, namely, the surface, surfactant, and shear modes. The surface mode instability occurs in the low range of Reynolds number and is the dominant mode of instability in particular parameter ranges. The imposed shear at the top surface along and opposite to the flow direction induces possible destabilization and stabilization of the flow, respectively. The permeability and porosity of the porous medium have a mixed impact on the surface mode instability. The temporal growth rate of the surface mode enhances for a thicker porous medium. The surface mode of the flow contaminated by an insoluble surfactant is less unstable than that of the clean free surface flow. This is due to the co-existence of the damped surfactant mode together with the unstable surface mode. On the other hand, the shear mode instability is identified at higher Reynolds numbers for a very small inclination angle, and the shear mode propagates faster for stronger imposed shear in the downstream direction. This trend is reversed for the upstream imposed shear. Moreover, the Marangoni effects exhibit the stabilizing influence on the shear mode. Conclusively, the external shear force would be helpful in regulating the instability of the surfactant-laden film flow down a porous medium.

Biosensor based on laccase-halloysite nanotube and imidazolium zwitterionic surfactant for dopamine determination

Zwitterionic surfactants incorporated nanomaterials and biomolecules structures offers enhanced catalytic activities and stabilities in biosensing. Herein, we present the construction of biosensors using graphite, a class of imidazolium zwitterionic surfactants, 3-(1-alkyl-3-imidazolio)-propane-sulfonate (ImS3-n; n = 10, 12, 14, 16) and laccase (Lac) immobilized on clay halloysite nanotube (HNT) in a carbon paste electrode (CPE). The Lac-HNT-ImS3–14/CPE showed to be the most promising biosensor due to the low capacitance and fastest electronic charge transfer using the probe hexacyanoferrate. Therefore, the surfactant ImS3–14 was characterized by spectroscopic techniques such as 1H, 13C NMR and ESI-MS. The developed biosensor was used to create a novel electroanalytical method for the determination of dopamine by square-wave voltammetry (SWV). Under optimized conditions, the calibration plot showed a linear range for dopamine of 0.99–67.8 µmol L−1 using SWV. The limit of detection calculated was 0.252 µmol L−1. The biosensor was successfully applied in the determination of dopamine contained in pharmaceutical samples, and the new proposed sensor was obtained with a recovery range from 97.6% to 108.7 % (n = 3). The Lac-HNT-ImS3–14/CPE biosensor is presented here as a new laccase-based biosensor with outstanding characteristics, which offered an elegant way for interfacing the electrochemical biosensor at the molecular level. It also plays a significant role in electronic signal transduction and biological recognition processes.

Lipase-Mediated Mechanoenzymatic Synthesis of Sugar Esters in Dissolved Unconventional and Neat Reaction Systems.

Mechanochemical and biocatalytic approaches in modern research are two major assets to develop greener processes. In the present study, these modular tools of sustainability are pointed toward the production of versatile and daily employed compounds such as surfactants. Toward this aim, glycolipids, a class of nonionic surfactants composed of ubiquitous and primary metabolites such as sugar and fatty acid moieties, represent a promising alternative to petroleum-derived surface-active agents. Therefore, the combination of biocatalysis with mechanochemistry aiming at glycolipid synthesis seemed a logical step that was taken in this study for the first time. The monoacylated model compound glucose-6-O-decanoate was synthesized with the help of a bead mill apparatus using two different unconventional dissolved reaction systems, namely, menthol-based hydrophobic deep eutectic solvents and 2-methyl-2-butanol, thus reaching up to 12% yield in the latter based on the conversion of vinyl decanoate, after only 90 min of reaction. In addition, a neat reaction system using an excess of vinylated fatty ester as an adjuvant allowed a 27 mM/h space-time yield. The overall significant increase in productivities, up to 6 times, compared to standard heating and shaking methods, shows the tremendous potential of mechanoenzymatic synthesis.

Influence of electrolytes on the structural and viscosity properties of mixed anionic–nonionic–zwitterionic surfactants in detergent formulations

AbstractCleaning products have a global market of around $33 billion in 2020 and play an essential role in daily life, providing consumers with important public health benefits. Surfactants are the main ingredients of cleaning products and they can effectively remove dirt, germs, and other contaminants from surfaces. Understanding the role of each surfactant class in a detergent formulation and their interaction with NaCl is of utmost importance for formulating efficient and sustainable cleaning products. This paper describes the study of ternary surfactant systems consisting of surfactants (sodium lauryl ether sulfate, alkyl polyglycoside, or betaine, three of the most commonly used surfactants in detergent formulations), water, and NaCl. The effects of concentration on critical micelle concentration, aggregate size, and rheological behavior were evaluated by dynamic light scattering and rheology techniques.

A molecular study on the behavior of polyethoxylated alkyl ethers surfactants in a water/n-alkane interface

Advanced oil recovery in oil/water and water/oil emulsions is a scientific and technological challenge, and efficient technologies depend on the water/oil interface properties. Due to their amphiphilic nature, surfactants are used to modify these interfacial properties to increase oil recovery and stabilize droplets in emulsification processes. Poly-(oxyethylene) alkyl ethers are a class of non-ionic surfactants often used as reference detergents due to their relatively simple structure compared to typical commercial surfactants. This tunable structure allows a design to tailor the substance’s properties to the desired application. Here, we conduct molecular dynamics simulations to obtain both macroscopic and microscopic properties of water/n-heptane interfacial systems in the presence of these surfactants. We evaluated the effect of both temperature and modifications to the structure of the surfactant model, varying the number of ethylene oxide units in the head group. We verify that their structural properties are specific to maximize stabilizing interactions such as hydrogen bonds with water molecules, adopting a folded structure and parallel orientation in regards to the interface. We analyze the Potential of Mean Force (PMF) that shows the affinity of the surfactant to the interface is enhanced as the number of ethoxylated units increases, which is related to the decrease in interfacial tension.

New Biobased Sulfonated Anionic Surfactants Based on the Esterification of Furoic Acid and Fatty Alcohols: A Green Solution for the Replacement of Oil Derivative Surfactants with Superior Proprieties.

The surfactant market represents a key sector of the chemical industry and encompasses many diverse applications. Their sustainability in terms of feedstock used, synthetic procedure, biodegradability, and formulation are crucial parameters to assessing the environmental impact of the surfactant. The anionic surfactant linear alkyl benzene sulfonates have proven successful to date because of their high performance, low cost, and extensive studies within formulations to optimize performance, allowing usage in a large variety of applications, especially in cleaning. Due to their advantageous properties and extensive research and development, their substitution with a biobased surfactant such as sodium dodecyl sulfate has struggled to succeed. Furan surfactants have been reported as valuable candidates for the implementation of green alternatives to traditional anionic sulfonated surfactants with a perfect trade-off between performances and green credentials. However, their implementation suffers of scalability and high cost in producing the final product due to feedstock availability and low yields of the final product. Herein, we report a new class of furan surfactants, sulfonated alkyl furoates, which are derived from the esterification of furoic acid and fatty alcohols, followed by a sulfonation step. Compared to traditional surfactants, they showed more favorable behavior in basic proprieties (such as critical micelle concentration, ecotoxicity, hard water resistance, surface tension water/oil), which gives a good prospective for the introduction of a new biobased chemical with superior performances.

Experimental investigation of N-lauroyl sarcosine and N-lauroyl-L-glutamic acid as green surfactants for enhanced oil recovery application

The vast deployment of surfactants worldwide in various industries has an intense impact on the environment. This led to the quest for surfactants with high performance but less environmental footprint. Therefore, bio-based surfactants derived from renewable sources have evolved as greener alternatives to conventionally deployed surfactants. Amino acid-based surfactants (AAS) prove to be a promising class of biodegradable and biocompatible surfactants with better safety profiles that meet both physiological and ecological requirements. Nevertheless, they are yet to be deployed in enhanced oil recovery (EOR) application due to limited investigation into their EOR potential. Owing to the recent report on the satisfactory performance of sodium cocoyl alaninate in terms of its EOR potential, this current study investigates the EOR potential of N-lauroyl sarcosine (NLS) and lauroyl glutamic acid (LGA). The study encompasses their surface and aggregation behavior, interfacial tension reduction and wettability alteration capability, emulsification, adsorption behaviour and oil displacement test. NLS proved to be more surface-active than LGA due to the additional carboxylate in the head group of LGA. Both surfactants showed high tolerance to salt and hardness, especially at high-temperature conditions. Furthermore, NLS showed superior IFT reduction capability with a minimum IFT of 0.07 mN/m while LGA only attained a minimum IFT of 0.14 mN/m. This results in better emulsifying power of NLS, yet LGA yielded more stable emulsions. In agreement to their high salt tolerance both surfactants exhibited improved performance in IFT reduction at high salinity condition. NLS and LGA also showed good wetting power on the quartz surface, hence altering rock surface wettability. Both surfactants achieved significant oil recovery after waterflooding, with NLS attaining additional oil recovery of 43% and LGA attaining 25%. The optimistic recoveries are due to the low waterflood recovery. NLS and LGA, therefore, prove to be superb alternatives to conventionally deployed EOR surfactants due to satisfactory performances coupled with their environmentally benign nature.

Characterization of radicals in polysorbate 80 using electron paramagnetic resonance (EPR) spectroscopy and spin trapping

Polysorbates are an important class of nonionic surfactants that are widely used to stabilize biopharmaceuticals. The degradation of polysorbate 20 and 80 and the related particle formation in biologics are heavily discussed in the pharmaceutical community. Although a lot of experimental effort was spent in the detailed study of potential degradation pathways, the underlying mechanisms are only sparsely understood. Besides enzymatic hydrolysis, another proposed mechanism is associated with radical-induced (auto)oxidation of polysorbates. To characterize the types and the origin of the involved radicals and their propagation in bulk material as well as in diluted polysorbate 80 solutions, we applied electron paramagnetic resonance (EPR) spectroscopy using a spin trapping approach. The prerequisite for a meaningful experiment using spin traps is an understanding of the trapping rate, which is an interplay of (i) the presence of the spin trap at the scene of action, (ii) the specific reactivity of the selected spin trap with a certain radical as well as (iii) the stability of the formed spin adducts (a slow decay rate). We discuss whether and to which extent these criteria are fulfilled regarding the identification of different radical classes that might be involved in polysorbate oxidative degradation processes. The ratio of different radicals for different scenarios was determined for various polysorbate 80 quality grades in bulk material and in aqueous solution, showing differences in the ratio of present radicals. Possible correlations between the radical content and product parameters such as the quality grade, the manufacturing date, the manufacturer, the initial peroxide content according to the certificate of analysis of polysorbate 80 are discussed.

Effect of SiO2 nanoparticles + 1-dodecyl-3-methyl imidazolium chloride on the IFT and wettability alteration at the presence of asphaltenic-synthetic oil

Using nanoparticles (NPs) in different industries such as enhanced oil recovery processes increased during the past decade due to its significant effects on the wettability alteration and IFT reduction to some extent. On the other side, ionic liquids (ILs) are proposed a new class of solvents that introduce considerable advantages in different areas of sciences. In this way, a hybrid method based on the NPs and ILs is proposed in the current investigation. So, silicon dioxide (SiO2) as one of the most effective NPs on the wettability alteration and 1-dodecyl-3-methyl imidazolium chloride ([C12mim][Cl]) as a new class of surfactants are used to find their effects on the interfacial tension (IFT) reduction and wettability alteration at the presence of asphaltenic synthetic oil for the first time. In this way, the stability of SiO2-NPs at the presence of and absence of IL is examined which revealed stability of SiO2-NPs for more than one month at the presence of IL while fast precipitation was observed if no IL existed in the solution. After that, the effect of IL and SiO2-NPs on the IFT reduction and wettability alteration is investigated by changing the concentration of these chemicals between 0 and 2000 ppm and ranging the asphaltene content between 2 and 10%wt. The results revealed that for all of the examined concentrations of IL and asphaltene fraction, reduction in IFT is inevitable as the concentration increases. Besides, the results demonstrate that there is a threshold value for asphaltene content (6%wt) in which for the values below or higher than this threshold, the effect of IL on the IFT reduction reduces leading to the vanishing of a sharp reduction in IFT and determining a distinguished critical micelle concentration (CMC). According to findings, for asphaltenic synthetic oil (ASO) with 6%wt asphaltene content CMC value of 250 ppm is obvious while for the other ASO, no obvious and distinguished CMC values exist. Moreover, the results reveal that the IFT reduces to the value of 0.48 mN/m as the IL concentration increases to 2000 ppm while the asphaltene content is kept constant at 6%wt. Further IFT measurements demonstrate the negligible effect of SiO2-NPs on the IFT reduction while the concomitant existence of SiO2-NPs and IL with the concentration of 1000 ppm moves the wettability of the rock surface toward strongly water-wet with contact angle (CA) of 33.1°. The worth mentioning point is that the entire amount of reduction in the CA from 156.3° (initial condition) to 33.1° at the presence of hybrid solution is not completely due to the presence of SiO2-NPs and it is the cumulative effect of IL and SiO2-NPs presence. Finally, several core flooding experiments are performed using different chemical formulations which reveal that using a hybrid solution of SiO2-NPs + IL with a concentration of 1000 ppm for each chemical increases the tertiary oil recovery to 15.2%wt based on OOIP for the ASO/formation brine with asphaltene content of 10%wt.

Whole-cell electric sensor for determination of sodium dodecyl sulfate.

Linear alkyl sulfates are a major class of surfactants that have large-scale industrial application and thus wide environmental release. These organic pollutants threaten aquatic environments and other environmental compartments. We show the promise of the use of a whole-cell electric sensor in the analysis of low or residual concentrations of sodium dodecyl sulfate (SDS) in aqueous solutions. On the basis of bioinformatic analysis and alkylsulfatase activity determinations, we chose the gram-negative bacterium Herbaspirillum lusitanum, strain P6–12, as the sensing element. Strain P6–12 could utilize 0.01–400 mg/L of SDS as a growth substrate. The electric polarizability of cell suspensions changed at all frequencies used (50–3000 kHz). The determination limit of 0.01 mg/L is much lower than the official requirements for the content of SDS in potable and process water (0.5 and 1.0 mg/L, respectively), and the analysis takes about 1–5 min. The promise of H. lusitanum P6–12 for use in the remediation of SDS-polluted soils is discussed.Graphical abstract

Emulsifying properties of sugar-based surfactants prepared by chemoenzymatic synthesis

Sugar Fatty Acid Esters (SFAEs) are a class of non-ionic surfactants that can be synthesized from inexpensive natural resources. Depending on carbon chain length and nature of the sugar head group, SFAEs cover a wide range of hydrophilic–lipophilic balance (HLB) values, which result in tunable tenside properties and in turn relevant for a wide variety of industrial applications. Three sugar-based surfactants (6-O-lauroyl-, 6-O-palmitoyl- and 6-O-stearoyl-1-O-butyl glucopyranosides) have been prepared by a lipase-catalyzed esterification of isomeric mixture of n-butyl glucosides. Specifically, their interfacial features together with W/O emulsifying properties and stability over time have been finely evaluated (interfacial tension (IFT) values, W/O emulsion turbidity and water droplet size distribution), resulting 6-O-palmitoyl- and 6-O-stearoyl-1-O-butyl glucopyranosides as the most efficient ones.

Dynamic interfacial tension and adsorption kinetics of nonionic surfactants during microfluidic droplet formation process

Surfactant adsorption plays an important role in the microfluidic droplet formation process, which manifested as dynamic interfacial tension phenomenon. Due to rapid droplet expansion and convection flow around the droplet, traditional methods of interfacial tension measurement are difficult to investigate the surfactant adsorption kinetics in microfluidic process. We thus developed a differential pressure based microfluidic platform and proposed an in-situ method to determine time-evolving interfacial tension during microfluidic droplet formation according to Young-Laplace equation in this research. Four classical nonionic surfactants: Triton X-100, Tween 20, Brij 56, and Brij 58 were tested with classical n-octant/water as the working system. The concentrations of these surfactants at interface were further determined from the measured interfacial tension based on Frumkin adsorption model. The adsorption rates of surfactant showed that increasing surfactant concentration in the bulk solution and flow rate of continuous phase both promoted surfactant adsorption in the cases of Tween 20, Brij 56, and Brij 58, indicating the mass transfer-controlled mechanism of adsorption kinetics. The average thickness of mass transfer boundary layer ranged from 0.1 to 5 μm was determined from the mass transfer rate and a correlation equation was proposed to predict the thickness. However, the adsorption mechanism of Triton X-100 turned to be kinetics-controlled for its high critical micelle concentration, which helped to determine the adsorption and desorption rate constants.

Monoalkyl Phosphinic Acids as Ligands in Nanocrystal Synthesis.

Ligands play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that monoalkyl phosphinic acids are another interesting ligand class, forming metal complexes with a reactivity that is intermediate between the traditional carboxylates and phosphonates. We first present the synthesis of n-hexyl, 2-ethylhexyl, n-tetradecyl, n-octadecyl, and oleylphosphinic acid. These compounds are suitable ligands for high-temperature nanocrystal synthesis (240-300 °C) since, in contrast to phosphonic acids, they do not form anhydride oligomers. Consequently, CdSe quantum dots synthesized with octadecylphosphinic acid are conveniently purified, and their UV-vis spectrum is free from background scattering. The CdSe nanocrystals have a low polydispersity and a photoluminescence quantum yield up to 18% (without shell). Furthermore, we could synthesize CdSe and CdS nanorods using phosphinic acid ligands with high shape purity. We conclude that the reactivity toward TOP-S and TOP-Se precursors decreases in the following series: cadmium carboxylate > cadmium phosphinate > cadmium phosphonate. By introducing a third and intermediate class of surfactants, we enhance the versatility of surfactant-assisted syntheses.