Surface Active Ionic Liquids Research Articles

Salts and Ph Effects on the Enhanced Oil Recovery with a Homologous Series of Gemini Surface Active Ionic Liquids

Gemini surface active ionic liquids (SAILs) with high interfacial activity and environmental friendly nature have excellent potential in the enhanced oil recovery (EOR). Here, effects of salts and pH, within a wide range of 2.5 - 9.5, on the crude oil-water system were studied in the presence of a homologous series of imidazolium-based Gemini SAILs, {[Cnim-C4-imCn2], n = 4, 8, and 12}. By using the medium and long alkyl chain SAILs, NaCl and MgCl2 and their mixture could reduce the interfacial tension (IFT) and the critical micelle concentration (CMC) to, respectively, 93.1 and 52.6% more than achievements with no salt. It was while, for the short alkyl chain SAIL, the IFT and CMC found 55.7 and 58.6% more reductions and then increased slightly with salt concentration. On the other hand, IFT variations with pH revealed the high stability of the Gemini SAILs and achieving up to 79.2% more reductions compared to natural pH. Studies on the emulsification of crude oil-salty water showed emulsification indices within 40 - 85% after one day and only 2 - 11% decrease on it after one week. Meanwhile, emulsification indices up to 92% was achieved after one day under pH=9.5. Thus, Gemini SAILs can be good candidates for EOR.

Surface active ionic liquid assisted metal-free electrocatalytic-carboxylation in aqueous phase: a sustainable approach for CO2 utilization paired with electro-detoxification of halocarbons

Electrocarboxylation of halocarbons in aqueous micellar solutions of Imidazolium based surface active ionic liquids offers a promising green strategy for capture, fixation and utilization of CO2 for the synthesis of high-added value compounds.

Effect of Single/Mixed Surfactant Systems on Orientations of Liquid Crystals and Interaction of Proteins with Surfactants at Fluid Interfaces

A series of single surfactant systems, i.e, quaternary ammonium-based gemini surfactants with different spacers and alkyl chain lengths (m-n-m; m = 12, n = 2, 3, 4, 6; n = 3, m = 12, 14, 16), halogen-free surface-active ionic liquid (HF-SAILs) with different symmetries ([Cnmim][C12H25SO4]; n = 6, 8, 10, 12), and single-chain cationic surfactants including 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) and dodecyltrimethylammonium bromide (DTAB), along with certain combinations of different surfactants (12-3-12/[C12mim]Br and 12-3-12/DTAB) were applied to an aqueous/liquid crystal interface (ALI). All the surfactants could induce an orientational transition of liquid crystals (LCs) from a planar to homeotropic state, which caused a bright-to-dark optical shift. It was proved that double-chain surfactants and the mixed surfactants inclined to adsorb at the ALI triggering the orientational transition. Inspiringly, a quicker and more sensitive dark-to-bright optical response was observed for mixed surfactant system-decorated interfaces in contact with proteins (such as bovine serum albumin (BSA), lysozyme, and trypsin) as opposed to the single surfactant systems. The ALI decorated by the 12-3-12/[C12mim]Br system was particularly efficient and exhibited the most sensitive optical response for BSA (0.01 ng mL−1). The order parameters (SCD) of surfactants tails at the interface and the free energy of proteins with 12-3-12 and [C12mim]Br were calculated, respectively. The results explain that the 12-3-12/[C12mim]Br-laden ALI shows a quicker and more sensitive optical response for BSA. This work inspired us to study mixed surfactant systems-decorated LC interfaces and further provides new insights for different chemical and biological applications.

Surface Active Ionic Liquids Based Coatings as Subaerial Anti-Biofilms for Stone Built Cultural Heritage

New surface active ionic liquids (SAILs), based on cholinium cations and dodecylbenzenesulfonate as anion, have been synthesized and their potential application as antimicrobial colonization agents on cultural heritage (CH)stone materials investigated. The biocidal activity and antifouling capabilities were, preliminarily, evaluated by a screening on pure Gram (+) and Gram (−) bacteria strain cultures, yeasts, hyphomycetes and single-celled algae. Tests on stone materials (marble and tufa) vs. a stabilized community, constituted by a mixture of microbial strains, revealed that some SAILs display both antimicrobial and preventive antibiofilm action against new colonization. Analogous tests have been performed on the cholinium@halide precursors.

Synthesis and complexation of a new caffeine based surface active ionic liquid with lysozyme in aqueous medium: Physicochemical, computational and antimicrobial studies

A new biodegradable, caffeine and dioctyl sulfosuccinate (AOT) based surface active ionic liquid (SAIL) has been synthesized and investigated for its complexation with lysozyme (LYZ) to develop antimicrobial SAIL-LYZ colloidal complexes with enhanced activity. Interfacial properties of the formed SAIL-LYZ colloidal complexes in the aqueous medium have been investigated using tensiometry, while the complexation in bulk has been monitored with dynamic light scattering, zeta-potential and turbidity measurements. Fluorescence and circular dichroism studies have been employed to gain insight about the structural modification of LYZ on complexation with SAIL. Isothermal titration calorimetry has been employed to monitor the thermodynamics of complexation of SAIL with LYZ, whereas the binding behavior of SAIL with LYZ has been investigated using molecular docking. Further, the antimicrobial activity of SAIL-LYZ complexes has been investigated against Gram-positive and Gram-negative bacteria. Fascinatingly, depending upon the concentration of SAIL, SAIL-LYZ colloidal complexes have been found to exhibit enhanced antimicrobial activity as compared to control and the known antibiotics. It is anticipated that the present study of new colloidal complexes of SAIL with enzymes would be helpful in various biomedical applications.

Aqueous micellar solutions of Imidazolium based surface active ionic liquids: Promising solvent systems to boost the electrocatalytic performance of Vitamin B12 toward eco-green electro-detoxification of halocarbons

Vitamin B12 (VB12) is considered as a promising molecular catalyst for a diverse range of important industrial, synthetic and environmental electrochemical transformations. However, the low turnover frequency (TOF) and the solubility concerns pose serious challenges in harnessing the electrocatalytic potential of VB12 for these applications. Herein, we demonstrate that aqueous micellar solutions of SAILs viz. 1-dodecyl-3-methylimidazolium chloride ([DDMIM][Cl]) and 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIM][DS]) enhance by several orders the electrocatalytic efficiency of VB12 toward electroreduction of bromoacetonitrile. Our extensive voltammetric investigations, as recommended for the benchmarking of molecular catalysts, viz. Foot of Wave Analysis, catalytic Tafel plots and the resulting estimates of electrocatalytic parameters like TOF and TOF at zero overpotential, clearly establish that [DDMIM][Cl] and [BMIM][DS] micellar solutions enhance the electrocatalytic performance of VB12 by 106 and 104 times respectively. The presented study is of significant importance in light of some recent reports that have demonstrated the aptness of aqueous SAIL micellar solutions for aqueous phase eco-green electro-detoxification of water insoluble halocarbons.

Investigations on the micellization behavior and thermodynamic characteristics of synthesized surface active ionic liquids [C14mim] [Br] and [C15mim] [Br] in the presence of oral antidiabetic drug metformin hydrochloride

The present examination focuses on understanding the micellization behavior of surface active ionic liquids 1-tetradecyl-3-methylimidazolium bromide [C14mim] [Br] and 1-pentadecyl-3-methylimidazolium bromide [C15mim] [Br] in presence of antidiabetic drug metformin hydrochloride by employing conductivity measurements and IR spectroscopy. The CMC value and value of counter ion dissociation (α) has been calculated by utilizing conductivity measurements. The dependency of CMC value evaluated from conductivity measurements in aqueous medium and presence of different weight percentage (0.03, 0.05 & 0.07) of drug metformin hydrochloride in aqueous medium and at different temperatures (298.15, 308.15 & 318.15) has been employed to calculate various thermodynamic parameters such as standard free energy of micellization (ΔGm0), standard enthalpy of micellization (ΔHm0), and standard entropy of micellization (ΔSm0). There is a significant increase in CMC value with the rise in temperature signifying delay in micellization process with increasing temperature. Further, the structural alterations prevailing in the selected system (ionic liquid-drug) has been determined by FT-IR Spectroscopy.

Effect of ionic liquid additives on temperature and pressure fluctuations during water flow boiling in microchannels

Overheating of high-performance electronic devices is undesired for long-term reliability. In this regard, two-phase microchannel heat sinks promise high heat dissipation within small temperature budgets using the latent heat of vaporization of the boiling fluid. However, geometrical confinement induces thermofluidic fluctuations and prohibits the use of two-phase microchannel heat sinks in practical applications. Here we for the first-time report flow boiling experiments with surface-active ionic liquid (SAIL) as an additive in water. This concept is inspired by our results of pool boiling wherein bubble coalescence was avoided with SAIL. In comparison to the water where fluctuations were apparent in the slug flow regime, temperature and pressure fluctuations were nearly mitigated up to the heat flux of 700 kW/m2 with an ionic liquid solution. The suppression of instabilities is attributed to the delay in the formation of a big vapor bubble at the inlet of microchannels due to the non-coalescing nature of bubbles formed with the SAIL solution.

Insights into the interaction of Bovine Serum Albumin with Surface-Active Ionic Liquids in aqueous solution

The unique physicochemical properties of Ionic liquids (ILs) make them very desirable for biomedical applications, namely as surface active ionic liquids (SAILs). SAILs surface activity, intrinsically higher than conventional surfactants, allows them to enhance drug permeability across biomembranes and, thus, become better drug carriers than current solutions. To harvest the full potential of these materials, in-depth studies of ILs interactions with model proteins are necessary to understand the mechanisms controlling these biological processes. Albumin, a key protein of blood serum, is of particular relevance, namely in drug carrier applications. Thus, here we characterize the interaction of bovine serum albumin (BSA) with fluorinated ionic liquids which are SAILs that possess fluorous tags equal to or longer than four carbon atoms. Their impact on BSA stability and structure was evaluated using different biophysical techniques. Differential scanning fluorimetry (DSF) and calorimetry (DSC), as well as circular dichroism (CD), yielded insights on the stabilization and secondary structure of BSA upon incubation with the ILs. Binding dynamics of the interaction were studied by conductimetry and isothermal titration calorimetry (ITC), which give the values of critical aggregation concentration (CAC) of the BSA-IL complex formation, as well as thermodynamic parameters. The results presented herein support the hypothesis that BSA is stabilized and encapsulated in the presence of FILs. Thus, the FILs studied in this work have potential for uses in biomedical applications.

Studies on the self-aggregation, interfacial and thermodynamic properties of a surface active imidazolium-based ionic liquid in aqueous solution: Effects of salt and temperature

The influence of four sodium salts (NaCl, NaBr, Na2SO4, and Na3PO4) on the self-aggregation, interfacial, and thermodynamic properties of a surface active ionic liquid (1-hexadecyl-3-methylimidazolium chloride, C16MImCl) has been explored in aqueous solutions by conductometry, tensiometry, spectrofluorimetry, isothermal titration calorimetry and dynamic light scattering (DLS). Analyses of the critical micellar concentration (cmc) values indicate that the anions of the added salts promote the self-aggregation of C16MImCl in the order: Cl− < Br− < PO43−< SO42−. Dehydration of imidazolium head groups, in general, governs the process of micellization of aqueous C16MImCl in presence of the investigated salts within the investigated temperature range (298.15–318.15 K), while the melting of iceberg takes the leading role below 303.15 K for the C16MImCl-Na3PO4 system. The results indicate that addition of salt leads to a greater spontaneity of micellization, and that exothermicity prevails in these systems. Differential effect of the salts on the interfacial properties of C16MeImCl has been interpreted on the basis of the coupled influence of the electrostatic charge neutralization of surfactants at the interface, and the van der Wa-als repulsion of surfactant tails and electrostatic repulsion of surfactant head groups. C16MeImCl has been predicted to form spherical micelles in presence of varying amounts of NaCl, Na2SO4 and Na3PO4, while there occurs probably a transition in the micellar geometry from spherical to non-spherical shape when added NaBr concentration exceeds 0.01 mol.kg−1. Fluorescence studies demonstrate that a combined quenching mechanism is operative for the quenching of pyrene fluorescence in the investigated C16MImCl-salt systems. Micellar aggregation numbers obtained from Steady State Fluorescence Quenching method have always been found be somewhat smaller than those estimated from Time Resolved Fluorescence Quenching method. The order of instability of the C16MImCl-micelles ascertained from Zeta potential measurements conform to what has been inferred from the cmc values. The hydrodynamic diameters of C16MImCl-micelles, obtained from DLS studies, have been found to increase with increasing salinity of the solutions.

The Role of Imidazolium-Based Surface-Active Ionic Liquid to Restrain the Excited-State Intramolecular H-Atom Transfer Dynamics of Medicinal Pigment Curcumin: A Theoretical and Experimental Approach.

The naturally occurring polyphenolic compound curcumin has shown various medicinal and therapeutic effects. However, there are various challenges associated with curcumin, which limits its biomedical applications, such as its high degradation rate and low aqueous solubility at neutral and alkaline pH. In the present study, efforts have been directed towards trying to resolve such issues by encapsulating curcumin inside the micelles formed by imidazolium-based surface-active ionic liquid (SAIL). The shape and size of the micelles formed by the SAIL have been characterized by using DLS analysis as well as TEM measurements. The photo-physics of curcumin in the presence of ionic liquid (IL) and also with the addition of salt (NaCl) has been explored by using different optical spectroscopic tools. The time-dependent absorption studies have shown that there is relatively higher suppression in the degradation rate of curcumin after encapsulation by the imidazolium-based SAIL in an aqueous medium. The TCSPC studies have revealed that there is deactivation in the nonradiative intramolecular hydrogen transfer process of curcumin in the presence of IL micelles as well as with the addition of salt. Furthermore, the time-dependent fluorescence anisotropy measurement has been carried out to figure out the location of curcumin inside the micellar system. In order to correlate all experimental findings, density functional theory (DFT) and classical molecular dynamics (MD) simulations at neutral pH media have been performed. It has been found that the van der Waals force of interactions plays a major role in the stabilization of curcumin in the micelles rather than the coulombic forces. It also has been observed that the van der Waals interactions remain unaffected in the presence of salt. However, as revealed by the MD simulation results, the micelles are found to be more compact in size after the addition of salt. The RMSD results show that the micelles formed by the SAIL achieve greater stability after a particular time constraint. Our results have divulged that the SAIL could act as a promising drug delivery system.

Formation and potential application of micelles composed of biocompatible N-lauroyl-amino acid ionic liquids surfactant

Surface-active ionic liquid (SAIL) surfactants have attracted attention as promising alternatives to conventional surfactants because of their tailor-made and tunable properties. SAILs also address the limitations associated with conventional surfactants including toxicity and formation of unstable micelles. Here, we investigated the aggregation behavior of three biocompatible choline N-lauroyl-amino acid (NLAA)-based ILs with different amino acid side chains in aqueous solutions. The micellar behaviors of NLAA-ILs were investigated using surface tensiometry, conductometry, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The critical micellar concentration (CMC) of the NLAA-ILs was found to be 2 to 4-fold lower compared with the conventional surfactant sodium dodecyl sulfate (SDS). The thermodynamic behavior confirmed that the micelle formation of NLAA-ILs was stable, spontaneous and entropy driven at room temperature. DLS and TEM studies revealed that the size and shape of the micelles depended on the presence of an N‑hydrogen group in the head group of the anion. Choline N-lauroyl glycinate ([Cho][NLG]) and dicholine N-lauroyl aspartate ([Cho]2[NLA]) were predominantly produced as unilamellar vesicles in water whereas choline N-lauroyl sarcosinate ([Cho][NLS]) formed small spherical micelles. Importantly, SAIL [Cho][NLG] showed lower toxicity toward mammalian cells compared with the analogous ILs or the conventional surfactant SDS and similar toxicity to the conventional surfactant Tween 80. SAIL [Cho][NLG] was more efficient at forming hydrophobic ion pairs with the macromolecular drug heparin compared with SAIL [Cho][NLS]. These results clearly suggest that the biocompatible NLAA-ILs represent promising potential substitutes for conventional surfactants in various biomedical applications.

Concentration- and Temperature-Responsive Reversible Transition in Amide-Functionalized Surface-Active Ionic Liquids: Micelles to Vesicles to Organogel.

A ubiquitous example of DNA and proteins inspires the scientific community to design synthetic systems that can construct various self-assembled complex nano-objects for high-end physiological functions. To gain insight into judiciously designed artificial amphiphilic structures that through self-assembling form various morphological architectures within a single system, herein, we have studied self-aggregation of amide-functionalized surface-active ionic liquids (AFSAILs) with different head groups in the DMSO/water mixed system. The AFSAIL forms stimuli-responsive reversible micelle and vesicle configurations that coexist with three-dimensional (3D) network structures, the organogel in the DMSO/water mixed system. The self-assembly driving forces, self-organization patterns, network morphologies, and mechanical properties of these network structures have been investigated. With the proven biodegradability and biocompatibility, one can envisage these AFSAILs as the molecules with a new dimension of versatility.

Microwave-mediated synthesis of surface-active ionic liquid-capped ZnS quantum dots: morphological studies and their applicability for fluorometric sensing of ascorbic acid

In this paper, we have synthesized surface active ionic liquid (SAIL)-capped zinc sulfide (ZnS) quantum dots (QDs) with an average size of approximately 3.03 nm using a systematic and facile microwave-irradiation method in aqueous solution. The imidazolium-based SAIL, 1-dodecyl-3-ethylimidazolium bromide was acted as a capping agent and was found to modulate the morphology and properties of ZnS QDs. The synthesized ZnS QDs were examined via different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL) and cyclic voltammetry (CV). TGA confirmed the thermal stability of capped ZnS QDs. To investigate the fluorometric application, the synthesized ZnS quantum dots were tested for the sensing of ascorbic acid (AA). The fluorescence intensity was found to be directly proportional to the concentration of AA in the range of 50–476 µM and the limit of detection was 63.11 µM. It has been observed that the synthesized capped ZnS QDs selectively sense AA and calculated limit of detection (LOD) of AA was found to be lower than that of other reported systems using the fluorescence technique. To understand the role of capping agent in the synthesis of ZnS QDs, density functional theory (DFT) using B3LYP (Becke’s three-parameter exchange functional with Lee–Yang–Parr correlation energy) and 6-311 + G (d, p) basis set was employed. The DFT results showed that the SAIL played a vital role in the size-controlled synthesis of ZnS QDs.

Exploration of the soluting-out effect of carbohydrates on the micellization and surface activity of long-chain imidazolium ionic liquid in the aqueous medium

In order to elucidate the role of polyhydroxy compounds (PHC) in modifying the micellization and interfacial behaviour of surface-active ionic liquids (SAILs), system consisting of 1-tetradecyl-3-methylimidazolium bromide ([C14mim][Br]) in water and in aqueous solutions of D(+)-Xylose and D(+)-Glucose as additives at (298.15, 303.15 and 308.15) K using specific conductance, UV–visible spectroscopy, FT-IR spectroscopy, surface tension measurement was investigated. From the electrical conductivity measurements, various parameters such as critical micelle concentration (CMC), degree of ionization of the counterion on the micelles (α), the standard Gibbs energy of micellization (ΔG0m), etc. have been evaluated for different concentrations of carbohydrates at different temperatures. FT-IR spectroscopy is utilized to record the structural changes occurring in the studied systems at below CMC, at CMC, and above CMC concentrations. The various surface parameters including CMC, surface tension at CMC (γcmc), surface pressure at the interface (ᴨcmc), the maximum surface excess concentration (Γmax), and the minimum area per surfactant molecule at the surface, Amin have also been obtained using surface tension measurements. The results obtained indicated that the CMC value of the IL in the presence of different concentrations of carbohydrates decreases in the order; D(+)-Glucose > D(+)-Xylose demonstrating that carbohydrates have a soluting-out effect and their tendency to lower the CMC value of IL increases with an increase of hydrophilicity of carbohydrates.

Unveiling the thermodynamic signature underlying the interaction of human serum albumin with sub-micellar concentrations of a surface active ionic liquid

The interaction of the transport protein human serum albumin (HSA) has been studied with sub-micellar concentrations of the surface active ionic liquid 1-butyl-3-methylimidazolium octylsulfate ([BMIM][OS]). The prominent quenching of intrinsic Trp fluorescence of HSA together with a discernible hypsochromic shift of the maximum fluorescence wavelength from λem ~ 347 nm in native HSA to λem ~ 335 nm in the presence of ~15.6 mM of the [BMIM][OS] suggests disruption of the native protein conformation following interaction with the ionic liquid. This is further substantiated from far-UV circular dichroism spectroscopy which reveals the denaturing influence of [BMIM][OS] through lowering of α-helicity content of the protein. However, the major impetus of the present work lies in a detailed calorimetric investigation of the HSA-[BMIM][OS] interaction process. The isothermal titration calorimetry results delineates the predominant role of hydrophobic effect governing the interaction as characterized by negative change of heat capacity (∆Cp = − 160.65 ± 8.5 J mol−1 K−1). However, the temperature-dependent calorimetric results show an enthalpy-driven (ΔH < 0, exothermic) hydrophobic effect with gradually decreasing contribution from the entropy counterpart with increasing temperature. These results are counterintuitive to the notion of classical hydrophobic effect characterized by favorable entropy contribution (ΔS > 0) and unfavorable enthalpy contribution (ΔH > 0, endothermic), and are rationalized in terms of the ‘nonclassical hydrophobic effect’.

Catanionic mixtures of surface-active ionic liquids and N-lauroyl sarcosinate: Surface adsorption, aggregation behavior and microbial toxicity

The surface activity and aggregation behavior of catanionic mixtures of imidazolium- or pyridinium-based surface-active ionic liquids (SAILs) and sodium N-lauroyl sarcosinate (Na-LS) in aqueous solution were investigated. The effects of the alkyl chain length, the polar head group and functional groups in the SAIL molecule on the interfacial properties and self-assembly of the catanionic mixtures were evaluated by surface tension and dynamic light scattering measurements. In addition, the toxicity of the catanionic surfactant mixtures against bacteria and fungi was studied. The SAIL-LS mixed systems reduced water surface tension with high effectiveness and efficiency, and had a lower critical aggregation concentration compared to the individual components. In all the catanionic systems investigated, synergistic effects caused by strong electrostatic and hydrophobic interactions resulted in negative interaction parameter values, which increased with the alkyl chain length and in the order of non-functionalized < amide-functionalized < ester-functionalized SAILs. The structure of the mixed aggregates in the SAIL-LS catanionic systems depended on the hydrophobicity of the SAIL, the micelle-vesicle transition being driven by the alkyl chain length. The catanionic systems exhibited similar microbial toxicity to that of individual SAIL components and behaved like broad-spectrum antimicrobials.

Mixed Micelles of Surface Active Ionic Liquid (SAIL)–Octylphenol Ethoxylate: A Novel Reaction Medium for Selective Oxidation of Toluene to Benzaldehyde

AbstractIonic liquids have been found to be suitable alternatives to volatile organic solvents in chemical transformation. Through a proper choice of cations and anions, the properties of an ionic liquid can be tuned so that it resembles an amphiphile. Such specially designed molecules are known as surface‐active ionic liquids (SAIL). Like conventional surfactants, SAIL also form aggregates in an aqueous medium. Studies show that the mixing of SAIL with conventional surfactants leads to synergistic micellization. However, very few reports are available on the application of such systems as reaction media. Present study focuses on the application of mixed micelles of 1‐tetradecyl‐3‐methylimidazol‐1‐ium bromide, ([C14mim]Br) with nonionic surfactant, Octylphenol ethoxylate with 10 moles of ethylene oxide (OPE‐10). Enhanced solubilization and selective catalytic oxidation of toluene using hydrogen peroxide as an oxidant and tungstic acid as a catalyst have been studied in detail using this system.

Building on Surface-Active Ionic Liquids for the Rescuing of the Antimalarial Drug Chloroquine.

Ionic liquids derived from classical antimalarials are emerging as a new approach towards the cost-effective rescuing of those drugs. Herein, we disclose novel surface-active ionic liquids derived from chloroquine and natural fatty acids whose antimalarial activity in vitro was found to be superior to that of the parent drug. The most potent ionic liquid was the laurate salt of chloroquine, which presented IC50 values of 4 and 110 nM against a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum, respectively, corresponding to an 11- and 6-fold increase in potency as compared to the reference chloroquine bisphosphate salt against the same strains. This unprecedented report opens new perspectives in both the fields of malaria chemotherapy and of surface-active ionic liquids derived from active pharmaceutical ingredients.

Aqueous solubilization and extraction of curcumin enhanced by imidazolium, quaternary ammonium, and tropine ionic liquids, and insight of ionic liquids-curcumin interaction

The limited water solubility of curcumin becomes an obstacle in its preparation, processing, and application. Ionic liquids (ILs) were wildly applied as “green” solvents possessing design flexibility. Three types of ILs with different cations or anions were employed in the solubilization and extraction of curcumin. It seems that the hydrophobic chain of ILs plays a key role. Superior solubilization and extraction capacity were achieved with surface-active ionic liquids (SAILs), which contain long alkyl chain and a charged hydrophilic head group, resulting in their ability of aggregation and micelle formation. To put an insight into the ILs-curcumin interaction and the solubilization mechanism, UV–vis spectroscopic studies, density functional theory (DFT) calculation, and 1H NMR studies were carried out. At first, curcumin undergoes diketone-enol tautomerism with the binding of ILs monomer. Then, SAILs begin to aggregate and form micelle with the increased concentration, meanwhile, the solubility of curcumin is remarkably enhanced. The solubilized curcumin is located in the palisade of micelle in which a hydrophobic environment is provided.