Ionic Liquid-based Surfactant Research Articles

Modulation of Phase Behavior and Microscopic Dynamics in Cationic Vesicles by 1-Decyl-3-methylimidazolium Bromide.

Synthetic cationic lipids have garnered significant attention as promising candidates for gene/DNA transfection in therapeutic applications. The phase behavior of the vesicles formed by these lipids is intriguing, revealing intricate connections to the structure and dynamics of the membrane. These phenomena emerge from the complex interplay between hydrophobic and electrostatic interactions of the lipids. In this study, we explore the impact of an ionic liquid-based surfactant, 1-decyl-3-methylimidazolium bromide (DMIM[Br]), on the structural, dynamical, and phase behavior of cationic dihexadecyldimethylammonium bromide (DHDAB) vesicles. Our investigations indicate that the addition of DMIM[Br] increases the vesicle size while thinning the membrane. Further, DMIM[Br] also induces substantial changes in the membrane phase behavior. At 10 and 25 mol %, DMIM[Br] eliminates the pre-transition from coagel to intermediate crystalline (IC) phase and decreases the onset temperature of the main phase transition to the fluid phase. In the cooling cycle, the addition of DMIM[Br] further induces the formation of an intermediate gel phase. This behavior is reminiscent of the non-synchronous ordering observed in the DODAB membrane, a longer-chain counterpart of DHDAB. Interestingly, at 40 mol % of DMIM[Br], the formation of the intermediate gel phase is largely suppressed. Neutron scattering data provide evidence that the addition of DMIM[Br] enhances lipid mobility in coagel and fluid phases, suggesting that DMIM[Br] acts as a plasticizer, enhancing membrane fluidity across all of the phases. Our findings infer that DMIM[Br] modulates the membrane's phase behavior and fluidity, two essential ingredients for the efficient transport of cargo, by controlling the balance of electrostatic and hydrophobic interactions.

Effects of head-group volume on the thermodynamic parameters and species distribution of ionic liquid-based surfactants in water: 1-(n-hexadecyl)-3-alkylimidazolium bromides and chlorides

The following series of ionic liquid-based surfactant halides was studied: 1-(n-hexadecyl)-3-Cm-imidazolium bromides and chlorides (C16CmImBr and C16CmImCl, respectively) where Cm = C1-C4. Using isothermal titration calorimetry, we calculated the enthalpy of micelle formation (ΔH⁰mic) at 25 °C for both halide surfactants, and from 15 to 70 °C for C16CmImCl. Values of ΔH⁰mic were then employed to calculate the entropy of micelle formation (ΔS⁰mic) from the corresponding free energy (ΔG⁰mic); the latter was calculated from the critical micelle concentration (cmc) and the degree of counter-ion dissociation (αmic). Values of ∣ΔG⁰mic∣ increase as a function of increasing Cm, although this increase is smaller than that of the previously studied series CnC1ImCl, where Cn = C10 to C16. This is attributed to the difference in dehydration of the surfactant segments that accompanies micelle formation, which is much larger for the increase in the hydrophobic chain (CnC1ImCl) than for the head-group (C16CmImCl). The calculated enthalpograms (ΔH⁰dilution versus [surfactant]) for C16C4ImBr showed deviation from ideal solution behavior, this was attributed to the formation of premicellar aggregates. The latter conclusion was corroborated by Pulsed Field Gradient (PFG)-NMR experiments of C16CmImCl in D2O. Thus, a model based on the presence of the following species in solution fitted satisfactorily the dependence of the observed surfactant diffusion coefficients on [surfactant]: free surfactant molecules; premicellar aggregates and micellized surfactant. The concentration of the premicellar aggregates increases noticeably as a function of increasing Cm, due to hydrophobic interactions between the Cm groups. The solubilization of (anionic) thymol blue indicator by C16CmImBr was studied using UV–Vis spectroscopy. The solubilization power (=moles of solubilized molecule/mole of micellized surfactant) was calculated, and compared with our previous data on the solubilization of (hydrophobic) Sudan IV dye and (less hydrophobic) drug nitrendipine by C16CmImBr. In all cases, the solubilization power decreases as a function of increasing Cm, albeit to different degrees, due to a combination of steric hindrance by the head-group, and decreased micelle size, both acting in the same direction.

Biocompatible magnetite nanoparticles coated with ionic liquid-based surfactant as a hydrophilic sorbent for dispersive solid phase microextraction of cephalosporins prior to their quantitation by HPTLC

Extraction of highly hydrophilic compounds from biological fluids including urine or plasma samples is a dilemma due to high hydrophilicity of the matrix itself. The main aim of the current work is to explore the competence of ionic liquid (IL)-based surfactant-coated mineral oxide nanoparticles (NPs) in dispersive solid-phase microextraction (d-SPME) of highly hydrophilic analytes taking cefoperazone (CPZ) as a model analyte for the study. The IL-based surfactant coated Fe3O4 NPs is utilized as an innovative adsorbent for the separation and pre-concentration of CPZ after intramuscular injection (I.M) in rabbits. The utilized magnetite NPs were synthesized via simple and reliable co-precipitation procedure, which doesn’t require any air-free environment and depends on a single iron (III) salt. Characterization of the as-synthesized NPs was achieved by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX). Surface area measurements show that Fe3O4 NPs have large surface area of 75 m2 g−1. The developed approach utilizes the unique properties of the IL-based surfactant including multiple polar interaction types provided by the polar head in addition to merits of Fe3O4 nanoparticles, which include large adsorptive capacity and magnetic properties, to improve separation, save time, and achieve satisfactory recovery. Comprehensive study was developed for the factors, that affect the adsorption capacity such as pH, NPs amount, IL-based surfactant concentration, ionic strength, adsorption time, and desorption conditions. Moreover, the adsorption data was fitted to Langmuir and second-order kinetic models as reflected by the reasonable determination coefficients of 0.9319 and 0.9726, respectively. Under the optimized conditions, the developed approach achieves good correlation coefficient of 0.9975, and 0.9981 over linearity range of 0.7–12.0 and 4.0–50.0 µg mL−1 for both CPZ standard solutions and spiked rabbit plasma, respectively. It also provides good sensitivity expressed by the low values of limit of detection (LOD) of 0.2 and 1.2 µg mL−1 and limit of quantitation (LOQ) of 0.7 and 4.0 µg mL−1 for both the standard solutions and spiked plasma, respectively. The developed approach was also applied successfully for monitoring CPZ in rabbit plasma samples with satisfactory recovery % (83–110). In addition, a detailed pharmacokinetic study is performed where pharmacokinetic parameters of CPZ in rabbit plasma samples were calculated.

Determination of the Nucleoside Reverse Transcriptase Inhibitors Lamivudine, Stavudine, and Didanosine in Human Urine by Micellar Electrokinetic Chromatography Using the Ionic Liquid-Based Cationic Surfactant 1-Tetradecyl-3-Methylimidazolium Bromide

Micellar electrokinetic chromatography (MEKC) with ultraviolet detection was employed for the simultaneous determination of the nucleoside reverse transcriptase inhibitors lamivudine, stavudine and didanosine with the ionic liquid-based cationic surfactant 1-tetradecyl-3-methylimidazolium bromide ([C14MIm]Br) as the pseudostationary phase. The composition, pH, and concentration of running buffer, surfactant concentration, separation voltage, and injection time were optimized. In comparison with conventional cationic surfactants, improved separation was observed using [C14MIm]Br. The applicability of the method was demonstrated by the analysis of human urine. The method exhibited wide linear ranges with limits of quantitation of 0.5, 0.3, and 1.0 μg/mL for lamivudine, stavudine, and didanosine, respectively. The intra-day and inter-day accuracies were from 91.5% to 114.0%. The precision, expressed as relative standard deviation (RSD), was less than 12.6% for the peak area. The recoveries of the analytes in the samples were between 91.8% and 97.3%. This approach is convenient, rapid, and economical for these analytes in biological samples.

Sodium Salicylate Mediated Ionic Liquid Based Catanionic Coacervates as Membrane‐Free Microreactors for the Selective Sequestration of Dyes and Curcumin

AbstractDesigning artificial protocells to sequester the biomolecules within its compartments is a challenging task and can be achieved through the use of surfactant‐based coacervates. Surfactant structures could be tailored to achieve the highest sequestration through coacervate droplets, irrespective of the polarity, charge and type of the analytes. Herein, we designed a morpholinium‐based ester‐functionalized ionic‐liquid‐based surfactant (ILBS) with a higher surface activity than its analogous conventional surfactant to form complex catanionic coacervates over the broad range of sodium salicylate (NaSal) concentrations. The spherically shaped micellar aggregates of the investigated ILBS are transformed into cylindrical shapes and again in the spherically shaped micellar aggregates depending on the NaSal concentration, which forms the coacervate droplets. The complex catanionic coacervates have been studied for their stability in the presence of mono and divalent cations, pH, temperature, viscosity and with respect to time. The microfluidic channel of 100 μm internal diameter was designed to obtain coacervate droplets with a maximum size of 100 μm. The coacervates were designed based on the NaSal concentration; cationic, neutral and anionic to exhibit selective and non‐selective encapsulation of the model charged dyes. We speculate that the strategically designed coacervate droplets could mimic membrane‐free protocells, which are applicable in multiple biomimetic operations.

Imidazolium-based ionic liquid surfactants as pseudostationary in combination with a chiral selector in micellar electrokinetic chromatography.

In recent years, ionic liquid-based surfactants have drawn more and more attention. As a new promising brand of surfactants, ionic liquid-based surfactants have their unique properties and superior aggregation behavior, which can be introduced as micellar pseudostationary in MEKC mode. In this paper, a novel ionic liquid-based surfactant, 1-butyl-3-methylimidazolum dodecyl sulfate [C4MIm][C12SO4], was synthesized through ion exchange reaction and applied for the first time to form micellar as pseudostationary phase for chiral separation with clindamycin phosphate as chiral selector. As observed, compared with conventional non-ionic liquid anionic surfactant, improved separation of tested drug enantiomers was obtained in the established MEKC system with ionic liquid-based surfactant. Parameters such as concentration of ionic liquid-based surfactants, type and proportion of organic modifier, concentration of chiral selector, and pH of buffer solution were systematically investigated to optimize the ionic liquid-based surfactant MEKC system. Graphical abstract.

Ionic Liquid-Based Catanionic Coacervates: Novel Microreactors for Membrane-Free Sequestration of Dyes and Curcumin.

Surfactant-mediated coacervates are termed as the new age microreactors for their ability to spontaneously sequester the molecules with varied polarities and functionalities. Efforts to emulate this applicability of coacervates through synthetic control of surfactant structures are finding success; however, there is little understanding of how to translate these changes into tailor-made properties. Herein, we designed 3-methyl-1-(octyloxycarbonylmethyl)imidazolium bromide (C8EMeImBr), an ester-functionalized ionic liquid-based surfactant, which shows better surface active properties than the nonfunctionalized and conventional cationic surfactant and forms complex coacervates over the broad range of concentration with sodium salicylate (NaSal). Mono- and divalent cations as well as ionic strength, viscosity, and time-dependent stability of the coacervates had also been addressed in order to study whether these coacervates could work as microreactors to encapsulate various molecules. The anionic charged complex coacervates with sponge morphology and honey comb-like interior show good efficiency to sequester cationic dyes from water because of electrostatic and hydrophobic interactions and good encapsulation efficiency for curcumin owing to their high surface area. Results suggest that ionic liquid-based coacervates studied here could be exploited as a novel low-cost, effective, and environmentally benign alternative to sequester dyes from the contaminated water and their recovery.

Thermo-Switchable de Novo Ionic Liquid-Based Gelators with Dye-Absorbing and Drug-Encapsulating Characteristics.

An ionic liquid-based surfactant with ester functionality self-aggregates in an aqueous medium and forms ionogels at 8.80% (w/v) concentration at physiological pH. The ionogel exhibited a remarkable change in its appearance with temperature from fibrillar opaque to transparent because of the dynamic changes within its supramolecular structure. This gel-to-gel phase transition occurs below the melting point of the solid ionic liquid. The ionogels were investigated using turbidity, differential scanning calorimetry, scanning electron microscopy (SEM), field emission SEM (FE-SEM), inverted microscopy, transmission electron microscopy imaging, Fourier transform infrared spectroscopy, and rheological measurements. The fibrillar opaque ionogel and transparent ionogel were studied for their ability to absorb dyes (methyl orange and crystal violet) and to encapsulate drugs (diclofenac sodium and imatinib mesylate).

Utility of Ionic Liquid-based Surfactant in Enhancement of Oxidation Peak Signal of Atorvastatin at Pencil Graphite Electrode

Utility of Ionic Liquid-based Surfactant in Enhancement of Oxidation Peak Signal of Atorvastatin at Pencil Graphite Electrode

A guanidinium ionic liquid-based surfactant as an adequate solvent to separate and preconcentrate cadmium and copper in water using in situ dispersive liquid–liquid microextraction

A guanidinium ionic liquid-based surfactant to preconcentrate cadmium and copper in water using in situ dispersive liquid–liquid microextraction.

Soluting-out effect of carbohydrates on the surface active ionic liquid 1-decyl-3-methylimidazolium bromide in aqueous solutions

Herein, with the aim of shedding light on the effect of non-ionic co-solute (carbohydrate) stereochemistry on the aggregation and surface behaviour of ionic liquid-based surfactant 1-decyl-3-methylimidazolium bromide ([C10mim][Br]) in aqueous solution, we studied the surface tension, electrical conductivity, volumetric and compressibility properties for the aqueous solutions of [C10mim][Br] in the presence of different sugars containing pentose monosaccharides (xylose, ribose and arabinose), hexose monosaccharides (glucose, and mannose), disaccharides (sucrose and lactose) and trisaccharide (raffinose) at different temperatures. From the electrical conductivity measurements, the values of the degree of ionization of the counter ion on the micelles (α) and thermodynamic properties of micellization (ΔGm) for [C10mim][Br] in aqueous carbohydrate solutions were obtained. The various parameters such as apparent molar volume (Vϕ), isentropic compressibility (κs), apparent molar isentropic compressibility (Kϕ) and the change of apparent molar properties upon micellization (ΔVϕ,m and ΔKϕ,m) were derived from the experimental density and speed of sound data. The surface tension measurements provided a series of parameters, including surface tension at the cmc (γcmc), effectiveness of surface tension reduction (Πcmc), maximum surface excess concentration (Γmax) and minimum surface area per molecule (Amin) at interface of air/solution for the investigated surfactant in the presence of different sugars at 298.15K. All the investigated carbohydrates have soluting-out effect (favouring the micelle formation) and their abilities to reduce the cmc of [C10mim][Br] in aqueous solutions increase with an increase in the hydrophilicity of the carbohydrate.

Ionic Liquid-Based Surfactant Extraction Coupled with Magnetic Dispersive μ-Solid Phase Extraction for the Determination of Phthalate Esters in Packaging Milk Samples by HPLC

A highly selective sample cleanup procedure combining ionic liquid-based surfactant extraction (ILSE) and magnetic dispersive μ-solid phase extraction (MD-μ-SPE) was triumphantly developed for the synchronously extraction of four phthalate acid esters (PAEs) in packaging milk samples prior to high-performance liquid chromatography coupled with photodiode array detector (HPLC-DAD). In this ionic liquid (IL)-based surfactant method, 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM] [PF6]) was used as extraction solvent, anionic surfactant sodium linear alkylbenzene sulfonate (LAS) was used as auxiliary extraction solvent, and then sodium chloride (NaCl) was mixed to drive phase separation. The synthesized hydrophobic diatomaceous earth-supported Fe3O4 magnetic nanoparticles (DSMNPs) were applied as an efficient adsorbent to retrieve the analyte-containing IL and LAS. Under the optimal extraction situations, good linearity of the approach was obtained in the concentration range from 10 to 1000 ng/mL for target analytes, and the preconcentration process was rapidly accomplished in 5 min. The limits of detection (LODs) based on a signal-to-noise ratio (S/N = 3) were ranged from 1.42 to 3.57 ng/mL with the relative standard deviations (RSDs) over the range of 1.84–3.56% (n = 5). The above-mentioned method was applied to the trace analysis of four PAEs including benzyl butyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-n-butyl phthalate (DBP), and di-n-octyl phthalate (DNOP) in packaging milk samples, and recoveries were between 89.8 and 99.7%.

Phase Behavior of Castor Oil-Based Ionic Liquid Microemulsions: Effects of Ionic Liquids, Surfactants, and Cosurfactants

Castor oil-based ionic liquid microemulsions are promising alternatives for petroleum-based biolubricant basestocks. This study presents the phase behavior of castor oil-based ionic liquid microemulsions through phase manifestation, and the areas of the single-phase domain (SME) were calculated accordingly to further illustrate the phase-forming capacities of the designed microemulsions. The results indicated that the phase-forming capacities of castor oil-based ionic liquid microemulsions depended largely on the ionic liquid ions, surfactant types, and cosurfactant chain lengths. The SME of different anion-based ionic liquid microemulsions showed the following sequences: [BMIM][Tf2N]-based > [BMIM][PF6]-based > [BMIM][BF4]-based. The longer carbon chain of ionic liquid cations in single surfactant-based systems and the larger percentage of ionic liquid-based surfactant in mixed surfactants-based systems both gave rise to the phase-forming capacities of castor oil-based ionic liquid microemulsions. Given ...

Formation of a sheet-like hydrogel from vesicles via precipitates based on an ionic liquid-based surfactant and β-cyclodextrin

Alkyl triphenylphosphonium bromide (C16TPB), an ionic liquid-based surfactant, and β-cyclodextrin were found to be able to form into a supramolecular complex, which could further aggregate into vesicles in an aqueous solution. The vesicles transformed into precipitates as the concentration of both β-CD and the surfactant increased. Interestingly, a sheet-like hydrogel with multiple responsive properties formed upon the addition of inorganic salts. The morphology and size distribution of the supramolecular aggregates were characterized in detail by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and dynamic light scattering (DLS). A possible transformation mechanism was suggested based on the results of 1H NMR, FT-IR and powder X-ray diffraction (XRD). The research might be of value in applications of biochemistry and design of smart materials.

Application of ionic liquid-based surfactants in the microwave-assisted extraction for the determination of four main phloroglucinols fromDryopteris fragrans

An ionic liquid-based surfactant combined with microwave-assisted extraction method, followed by RP-HPLC-diode array detection (DAD) with a core shell column, was successfully applied in extracting and quantifying four major phloroglucinols from Dryopteris fragrans. Eight ionic liquids with different cation and anion were investigated, and 1-octyl-3-methylimidazolium bromide presented the best relative extraction efficiency for four phloroglucinols. The optimum conditions of this method were as follows: ionic liquid concentration 0.75 M, liquid/solid ratio 12:1 mL/g, extraction time 7 min, extraction temperature 50°C, and irradiation power 600 W. The quality analytical parameters of the method were obtained based on the linearity, precision, accuracy, detection, and quantification limits. The recoveries were between 96.90 and 103.5% with standard deviations not higher than 4.7%. Compared with ionic liquid-based heat reflux extraction, ultrasonic-assisted extraction, negative-pressure cavitation extraction, and conventional microwave-assisted extraction, the relative extraction efficiencies of the proposed method for four phloroglucinols increased 1.5-40.4%. The method was successfully applied for the quantification of four major phloroglucinols from D. fragrans. All these results suggest that the developed method represents an excellent alternative for the extraction and quantification of phloroglucinols in other plant materials.

Dispersion of multiwalled carbon nanotubes by ionic liquid-type Gemini imidazolium surfactants in aqueous solution

Butyl-α,β-bis(dodecylimidazolium bromide) ([C 12-C 4-C 12im]Br 2) is a new type ionic liquid-based Gemini surfactant. Multiwalled carbon nanotubes (MWCNTs) can be dispersed effectively in [C n -C 4-C n im]Br 2 aqueous solutions due to its special molecular structure, including two imidazole ring head groups and two hydrophobic chains. The resulted MWCNT suspensions are stable for more than one month and no precipitation is observed. Both UV-vis-NIR and transmission electron microscopy (TEM) studies indicate that the MWCNTs dispersed in solutions are present as individual. The dispersed amount of MWCNTs first increased and then decreased with increasing the concentration of [C 12-C 4-C 12im]Br 2. Compared with single-chain ionic liquid-based surfactant 1-butyl-3-alkylimidazolium bromide ([C n mim]Br), [C n -C 4-C n im]Br 2 has stronger ability of dispersing CNTs, which is also ascribed to its molecular structure. It was also found that the [C n -C 4-C n im]Br 2 with a longer hydrocarbon chain demonstrated a stronger dispersion ability. The ζ-potential measurements show that the MWCNTs dispersed in [C 12-C 4-C 12im]Br 2 aqueous solution have relatively high positive charges, which can conclude that it is the Coulomb force between CNTs that makes them stable. Based on these, the possible dispersion mechanism has been proposed.