Development of Cholinium-Based API Ionic Liquids with Enhanced Drug Solubility: Biological Evaluation and Interfacial Properties

We report an efficient sustainable two-step anion exchange synthetic procedure for the preparation of choline API ionic liquids (Cho-API-ILs) that contain active pharmaceutical ingredients (APIs) as anions combined with choline-based cations. We have evaluated the in vitro cytotoxicity for the synthesized compounds using three different cells lines, namely, HEK293 (normal kidney cell line), SW480, and HCT 116 (colon carcinoma cells). The solubility of APIs and Cho-API-ILs was evaluated in water/buffer solutions and was found higher for Cho-API-ILs. Further, we have investigated the antimicrobial potential of the pure APIs, ILs, and Cho-API-ILs against clinically relevant microorganisms, and the results demonstrated the promise of Cho-API-ILs as potent antimicrobial agents to treat bacterial infections. Moreover, the aggregation and adsorption properties of the Cho-API-ILs were observed by using a surface tension technique. The aggregation behavior of these Cho-API-ILs was further supported by conductivity and pyrene probe fluorescence. The thermodynamics of aggregation for Cho-API-ILs has been assessed from the temperature dependence of surface tension. The micellar size and their stability have been studied by dynamic light scattering, transmission electron microscopy, and zeta potential. Therefore, the duality in the nature of Cho-API-ILs has been explored with the upgradation of their physical, chemical, and biopharmaceutical properties, which enhance the opportunities for advances in pharmaceutical sciences.

New ionic liquids based on 5-fluorouracil: Tuning of BSA binding and cytotoxicity

In this work, we describe the synthesis, interactions with bovine serum albumin, and cytotoxicity of new ionic liquids based on 5-fluorouracil (API-ILs) with different cations (imidazolium, choline, isoquinolinium, guanidinium). The secondary and tertiary structure of BSA in solutions with different concentrations of API-ILs was monitored by the circular dichroism (CD) technique. The addition of API-ILs does not lead to structural changes in BSA. A quenching of fluorescence spectra intensity of BSA in presence of all API-ILs was observed, allowing the quantification of binding between API-ILs and BSA. The preferred localization of both ions in API-ILs differs significantly depending on the structure of the cation according to molecular docking. The aggregation of BSA in presence of API-ILs was analyzed by the dynamic light scattering (DLS) method, revealing a moderate increase in particle size. Cytotoxicity and selectivity of API-ILs on cancer and normal cell lines were estimated, showing a clear modification of the pharmaceutic activity of ionic liquid compared to 5-fluorouracil.

Shear-induced phase transition in the aqueous solution of an imidazolium-based ionic liquid

An ionic liquid (IL) is a salt in the liquid state that consists of a cation and an anion, one of which possesses an organic component. Because of their non-volatile property, these solvents have a high recovery rate, and, hence, they are considered as environment-friendly green solvents. It is necessary to study the detailed physicochemical properties of these liquids for designing and processing techniques and find suitable operating conditions for IL-based systems. In the present work, the flow behavior of aqueous solutions of an imidazolium-based IL, 1-methyl-3-octylimidazolium chloride, is investigated, where the dynamic viscosity measurements indicate non-Newtonian shear thickening behavior in the solutions. Polarizing optical microscopy shows that the pristine samples are isotropic and transform into anisotropic after shear. These shear thickened liquid crystalline samples change into an isotropic phase upon heating, which is quantified by the differential scanning calorimetry. The small angle x-ray scattering study revealed that the pristine isotropic cubic phase of spherical micelles distort into non-spherical micelles. This has provided the detailed structural evolution of mesoscopic aggregates of the IL in an aqueous solution and the corresponding viscoelastic property of the solution.

Amphiphilic Ionic Liquids Capable to Formulate Organized Systems in an Aqueous Solution, Designed by a Combination of Traditional Surfactants and Commercial Drugs

The present review describes the state of the art in the conversion of pharmaceutically active ingredients (API) in amphiphilic Ionic Liquids (ILs) as alternative drug delivery systems. In particular, we focus our attention on the compounds generated by ionic exchange and without original counterions which generate different systems in comparison with the simple mixtures. In water, these new amphiphiles show similar or even better properties as surfactants in comparison with their precursors. Cations such as 1-alkyl-3-methyl-imidazolium and anions such as dioctyl sulfosuccinate or sodium dodecyl sulfate appear as the amphiphilic components most studied. In conclusion, this work shows interesting information on several promissory compounds and they appear as an interesting challenge to extend the application of ILs in the medical field.

Ibuprofen molecular aggregation by direct back-face transmission steady-state fluorescence

Direct back-face transmission steady-state fluorescence was successfully applied to the study of aggregation of ibuprofen and ibuprofenate anion in solution taking advantage of its own fluorescence. The analysis of the experimental data involves the use of the differential reabsorption model to account for re-absorption phenomenon and the closed association model to describe aggregation. The fluorescence quantum yield of ibuprofenate increases when it aggregates in the presence of sodium, but it markedly decreases when 1-butyl-3-methylimidazolium is used as counterion. The proposed methodology allows the accurate determination of the critical aggregation concentrations and the mean aggregation numbers. Results were supported by complementary techniques such as time-resolved fluorescence, ¹H-NMR and small-angle neutron and X-ray scattering. The developed technique constitutes a promising strategy to characterize the aggregation of poorly fluorescent surfactants that aggregates at high concentrations and hence at high absorbance values, conditions in which the most common right-angle configuration for fluorescence acquisition is troublesome due to re-absorption.

Ionic liquids as a useful tool for tailoring active pharmaceutical ingredients

Ionic liquids (ILs) have been widely used in biomedical and pharmaceutical fields as solvents or permeation enhancers. Recently, more and more researchers focused on optimizing the physicochemical properties of active pharmaceutical ingredient (API) by ILs technology. Converting APIs into ILs (API-ILs) has shown great potential for drug delivery by eliminating polymorphism, tailoring solubility, improving thermal stability, increasing dissolution, controlling drug release, modulating the surfactant properties, enhancing permeability of APIs and modulating cytotoxicity on tumor cells. In addition, API-ILs are also used in various formulations as active ingredients, such as solutions, emulsions, even tablets or nanoparticles. This paper aims to review current status of API-ILs, including the rational and design, preparation and characterization, the improvement on the physicochemical characteristics of APIs, the compatibility of API-ILs with various formulations, and the future prospects of API-ILs in biomedical and pharmaceutical fields.

Ionic Liquid-Based Surfactants: Recent Advances in Their Syntheses, Solution Properties, and Applications

The impetus for the expanding interest in ionic liquids (ILs) is their favorable properties and important applications. Ionic liquid-based surfactants (ILBSs) carry long-chain hydrophobic tails. Two or more molecules of ILBSs can be joined by covalent bonds leading, e.g., to gemini compounds (GILBSs). This review article focuses on aspects of the chemistry and applications of ILBSs and GILBSs, especially in the last ten years. Data on their adsorption at the interface and micelle formation are relevant for the applications of these surfactants. Therefore, we collected data for 152 ILBSs and 11 biamphiphilic compounds. The head ions of ILBSs are usually heterocyclic (imidazolium, pyridinium, pyrrolidinium, etc.). Most of these head-ions are also present in the reported 53 GILBSs. Where possible, we correlate the adsorption/micellar properties of the surfactants with their molecular structures, in particular, the number of carbon atoms present in the hydrocarbon "tail". The use of ILBSs as templates for the fabrication of mesoporous nanoparticles enables better control of particle porosity and size, hence increasing their usefulness. ILs and ILBSs form thermodynamically stable water/oil and oil/water microemulsions. These were employed as templates for (radical) polymerization reactions, where the monomer is the "oil" component. The formed polymer nanoparticles can be further stabilized against aggregation by using a functionalized ILBS that is co-polymerized with the monomers. In addition to updating the literature on the subject, we hope that this review highlights the versatility and hence the potential applications of these classes of surfactants in several fields, including synthesis, catalysis, polymers, decontamination, and drug delivery.

Freire CS, Silvestre AJD, Freire MG. The Role of Ionic Liquids in the Pharmaceutical Field: An Overview of Relevant Applications

Solubility, bioavailability, permeation, polymorphism, and stability concerns associated to solid-state pharmaceuticals demand for effective solutions. To overcome some of these drawbacks, ionic liquids (ILs) have been investigated as solvents, reagents, and anti-solvents in the synthesis and crystallization of active pharmaceutical ingredients (APIs), as solvents, co-solvents and emulsifiers in drug formulations, as pharmaceuticals (API-ILs) aiming liquid therapeutics, and in the development and/or improvement of drug-delivery-based systems. The present review focuses on the use of ILs in the pharmaceutical field, covering their multiple applications from pharmaceutical synthesis to drug delivery. The most relevant research conducted up to date is presented and discussed, together with a critical analysis of the most significant IL-based strategies in order to improve the performance of therapeutics and drug delivery systems.

In Vitro Evaluation of Self-Nano-Emulsifying Drug Delivery Systems (SNEDDS) Containing Room Temperature Ionic Liquids (RTILs) for the Oral Delivery of Amphotericin B

Amphotericin B (AmpB), one of the most commonly used agents in the treatment of severe fungal infections and life-threatening parasitic diseases such as visceral Leishmaniasis, has a negligible oral bioavailability, primarily due to a low solubility and permeability. To develop an oral formulation, medium chain triglycerides and nonionic surfactants in a self-nano-emulsifying drug delivery system (SNEDDS) containing AmpB were combined with room temperature ionic liquids (RTILs) of imidazolium. The presence of ionic liquids significantly enhanced the solubility of AmpB, exhibited a low toxicity and increased the transport of AmpB across Caco-2 cell monolayers. The combination of RTILs with a lipid formulation might be a promising strategy to improve the oral bioavailability of AmpB.

Physicochemical characterization, released profile, and antinociceptive activity of diphenhydraminium ibuprofenate supported on mesoporous silica

The thermal, physical, and morphological properties of diphenhydraminium ibuprofenate ([DIP][IBU]) adsorbed onto mesoporous silica (SiO₂-60 Å and SiO₂-90 Å) from solution were determined. The thermal, physical, and morphological properties of [DIP][IBU] supported on silica were determined. The adsorption of [DIP][IBU] on the pores and surface of silica was proven by N₂ adsorption/desorption isotherms. Additionally, release profiles were determined for all systems, and the antinociceptive activity of neat [DIP][IBU] and [DIP][IBU] supported on silica were determined. The interaction of [DIP][IBU] and silica was dependent on pore size, with the formation of a [DIP][IBU] monolayer on SiO₂-60 and a multilayer on SiO₂-90. The release profile was sustained and slow and dependent on the pore size of the silica, in which the smaller the pore size, the faster the release. The nociceptive evaluation showed that [DIP][IBU] presents a greater (99.21 ± 0.85%) antinociceptive effect than the ibuprofen (46 ± 4.3%). Additionally, [DIP][IBU] on SiO₂-60 (90 ± 5.8%) had a greater antinociceptive effect than on SiO₂-90 (73 ± 13.2%), which indicates that in vivo tests are in accordance with the in vitro experiments.

Impact of Aromatic Counter-Ions Charge Delocalization on the Micellization Behavior of Surface-Active Ionic Liquids

The nature of counter-ions governs the micellar and structural characteristics of surface-active ionic liquids (SAILs). Especially, the introduction of aromatic counter-ions significantly increases their surface adsorption and induces the formation of various types of aggregates like prolate ellipsoidal micelles, rodlike micelles, vesicles, lamellars, etc. The present study reports the role of charge delocalization of two different aromatic counter-ions in the micellization behavior of their respective SAILs in aqueous medium. For this purpose, we have synthesized two SAILs, namely, 1-tetradecyl-3-methylimidzolium phenolate [C₁₄mim][PO] and 1-tetradecyl-3-methylimidzolium benzoate [C₁₄mim][BZ]. The O-atom of phenolate (PO^-) possesses negative charge, which is delocalized on its phenyl ring. Conversely, the negative charge of benzoate (BZ^-) is not delocalized on its phenyl ring. The more hydrophobic BZ^- counter-ion increases the hydrophobic interactions and reduces the electrostatic repulsions more efficiently as compared to PO^-, which results in a lower critical micelle concentration (cmc) of [C₁₄mim][BZ] than that of [C₁₄mim][PO]. Interfacial properties obtained by tensiometry reveal better surface activity and absorption efficiency of [C₁₄mim][BZ] as compared to [C₁₄mim][PO]. The increase of cmc and degree of counter-ion binding (β) with the rise of temperature for both SAILs has been observed by conductometry. The decrease in the polarity of pyrene microenvironment explains the higher compactness of [C₁₄mim][BZ] aggregates than that of [C₁₄mim][PO], observed by fluorimetry. The position of PO^- and BZ^- is in the stern and palisade layers of C₁₄mim⁺ aggregates, respectively, located by ¹H NMR. The existence of prolate ellipsoidal micelles for both SAILs has been established by small-angle neutron scattering measurements. Thus, the interfacial and bulk properties of [C₁₄mim][PO] lie somewhere in between those of the SAILs having perfect aromatic counter-ions, [C₁₄mim][BZ], and the SAILs having regular inorganic counter-ions like Cl^-, Br^-, etc.

Aggregation and Morphological Aptitude of Drug-Based Ionic Liquids in Aqueous Solution

Here, we present how replacing the usual inorganic counter ion with a pharmaceutically active aromatic one can greatly affect the interfacial as well as bulk properties of ionic liquids (ILs). We have synthesized a series of novel drug-based ILs, namely, 1-alkyl-3-methylimidazolium diclofenate ([C _n mim][DF]; n = 6, 8, 10, 12, and 14) abbreviated as DF-ILs, wherein DF^- is a well-recognized analgesic and nonsteroidal anti-inflammatory drug. We show strong synergistic interactions between C _n mim⁺ and aromatic DF^- attributed to reduced electrostatic repulsions and increased hydrophobicity from their incorporation, reflecting a 300-fold smaller critical aggregation concentration than that of their Cl^- analogue [C _n mim][Cl]. Interfacial properties for such strongly associating systems are discussed and clearly established to have remarkably improved properties than those of their Cl^- analogues. The decreasing polarity of the cybotactic region of pyrene with increase in the chain length "n" indicates an increased extent of packing of cationic head groups in the Stern layer. DF^- ion seems to play a vital role in the formation of the resulting aggregates, as probed by small angle neutron scattering and transmission electron microscopy. The thermodynamical insights of the aggregation process have been studied using isothermal titration calorimetry and temperature-dependent conductivity experiments. Unilamellar vesicles are formed at extremely low concentration, and also it is the first report that puts into picture the formation of vesicles for [C₆mim][DF] with such a short chain.

Biological Activity of Ionic Liquids and Their Application in Pharmaceutics and Medicine

Ionic liquids are remarkable chemical compounds, which find applications in many areas of modern science. Because of their highly tunable nature and exceptional properties, ionic liquids have become essential players in the fields of synthesis and catalysis, extraction, electrochemistry, analytics, biotechnology, etc. Apart from physical and chemical features of ionic liquids, their high biological activity has been attracting significant attention from biochemists, ecologists, and medical scientists. This Review is dedicated to biological activities of ionic liquids, with a special emphasis on their potential employment in pharmaceutics and medicine. The accumulated data on the biological activity of ionic liquids, including their antimicrobial and cytotoxic properties, are discussed in view of possible applications in drug synthesis and drug delivery systems. Dedicated attention is given to a novel active pharmaceutical ingredient-ionic liquid (API-IL) concept, which suggests using traditional drugs in the form of ionic liquid species. The main aim of this Review is to attract a broad audience of chemical, biological, and medical scientists to study advantages of ionic liquid pharmaceutics. Overall, the discussed data highlight the importance of the research direction defined as "Ioliomics", studies of ions in liquids in modern chemistry, biology, and medicine.

Surfactant and Gelation Properties of Acetylsalicylate Based Room Temperature Ionic Liquid in Aqueous Media

An amphiphilic room temperature ionic liquid (RTIL) containing acetylsalicylate anion of type 1-dodecyl-1-methylpiperidinium acetylsalicylate, [C₁₂mpip][AcSa], is synthesized from the precursor [C₁₂mpip][Cl] by an ion exchange process. The sample is characterized, and its surface active and aggregation behavior in water has been studied and explained. The critical aggregation concentrations (CACs) are determined by a variety of methods, namely, electrical conductivity, surface tension, steady state florescence, and isothermal titration calorimetry (ITC) at different temperatures. As compared to its precursor, [C₁₂mpip][AcSa] has low CAC values, indicating enhanced favorable interactions between the [alkylmpip]⁺ cation···bulky [AcSa]^- anion and also hydrogen bonding of both of the ions with water. The free energy of aggregation ΔG⁰_a is always negative, and both enthalpy and entropy of aggregation drive the aggregation process. The micelle-like aggregates are ellipsoidal in shape. The aggregation numbers are determined from translational diffusion coefficients and florescence quenching measurements. Aggregates of [C₁₂mpip][AcSa] are larger than those of its precursor IL with chloride anion. Therefore, it is evident that the close interactions between the ion pairs of [C₁₂mpip]⁺···[AcSa]^- facilitate packing of more molecules in an aggregate. The steady state and oscillatory rheology measurements in aqueous solutions consisting of mixtures of [C₁₂mpip][AcSa] and sodium salicylate (SS), an hydrotope additive, were carried out. The analysis of zero shear viscosity and moduli properties as a function of concentration and temperature reveals that the addition of SS promotes the growth of small ellipsoid aggregates into large worm-like structures with a typical viscoelastic gel behavior. The moduli properties vs temperature profiles are complex and no hysteresis was produced in heating and cooling modes, suggesting the thermoirreversibile and complex nature of the network structures. The release of the acetylsalicylate anion from the gels could be triggered by simple dilution, and the release occurs due to surface erosion and demicellization.

Factors influencing the formation of polybromide monoanions in solutions of ionic liquid bromide salts

Six different bromide salts - tetraethylammonium bromide ([N2,2,2,2]Br, Br), 1-ethyl-1-methylpiperidinium bromide ([C2MPip]Br, Br), 1-ethyl-1-methylpyrrolidinium bromide ([C2MPyrr]Br, Br), 1-ethyl-3-methylimidazolium bromide ([C2MIm]Br, Br), 1-ethylpyridinium bromide ([C2Py]Br, Br), and 1-(2-hydroxyethyl)pyridinium bromide ([C2OHPy]Br, Br) - were studied in regards to their capacity to form polybromide monoanion products on addition of molecular bromine in acetonitrile solutions. Using complementary spectroscopic and computational methods for the examination of tribromide and pentabromide anion formation, key factors influencing polybromide sequestration were identified. Here, we present criteria for the targeted synthesis of highly efficient bromine sequestration agents.

Surface-active ionic liquids in micellar catalysis: impact of anion selection on reaction rates in nucleophilic substitutions

A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions.

Self-encapsulation of a drug-containing ionic liquid into mesoporous silica monoliths or nanoparticles by a sol–gel process

Mesoporous silica monoliths and nanospheres were obtained using the same ionic liquid acting as a templating agent and catalyst.

Aggregation Behaviours of Surface-Active Ionic Liquids 1-Alkyl-3-methylimidazolium Bis(2-ethylhexyl)sulfosuccinate

The systematic investigation of the aggregation behaviours of newly synthesised surface-active ionic liquids 1-alkyl-3-methylimidazolium bis(2-ethylhexyl)sulfosuccinate ([Cnmim][AOT], n = 2, 3, 5, 6, 7) by various techniques is reported. The critical aggregation concentrations (CACs) and the standard Gibbs free energies of aggregation () were determined from measurements on conductivity, fluorescence, and surface tension, which suggested a stronger self-assembly ability in the bulk solution for [Cnmim][AOT] surfactants with longer alkyl chain cations. An interesting structure transition driven by the penetration of the imidazolium cation into the aggregate when n > 4 was found by analysis of the variations of the values of CAC, , the degree of counter ion binding (β), and the micropolarity (I1/I3) immediately after the CAC with changing alkyl chain length of the imidazolium cation, which was further confirmed by 1H NMR measurements.

'Pro et contra' ionic liquid drugs - Challenges and opportunities for pharmaceutical translation

Ionic liquids (ILs) are organic salts with a melting point below 100°C. Active pharmaceutical ingredients (APIs) are transformed into ILs by combining them with typically large yet charged counterions. ILs hold promise to build a large design space for relevant pharmaceutical parameters, particularly for poorly water soluble drugs. It is for this wide design space that ILs may be the entry into the fascinating vision of modifying physico-chemical properties without the need to structurally modify the active pharmaceutical ingredient itself. This extremely intriguing pharmaceutical option is critically discussed including its potential and limitations. The review is starting off with an introduction to the metathesis and characterization of ILs, and leads over to examples for pharmaceutical application, including enhancement of dissolution rate and kinetic solubility and hygroscopicity adaptation, respectively. Tuning biopharmaceutics and toxicology by proper IL design is another focus. The review connects the interrelated chemical, physical, pharmaceutical, and toxicological outcome of API-ILs, serving as guidance for the formulation scientist who aims at expanding ones armamentarium for poorly water soluble APIs while avoiding structural modification, thereof.

Aggregation behavior and total miscibility of fluorinated ionic liquids in water

In this work, novel and nontoxic fluorinated ionic liquids (FILs) that are totally miscible in water and could be used in biological applications, where fluorocarbon compounds present a handicap because their aqueous solubility (water and biological fluids) is in most cases too low, have been investigated. The self-aggregation behavior of perfluorosulfonate-functionalized ionic liquids in aqueous solutions has been characterized using conductometric titration, isothermal titration calorimetry (ITC), surface tension measurements, dynamic light scattering (DLS), viscosity and density measurements, and transmission electron microscopy (TEM). Aggregation and interfacial parameters have been computed by conductimetry, calorimetry, and surface tension measurements in order to study various thermodynamic and surface properties that demonstrate that the aggregation process is entropy-driven and that the aggregation process is less spontaneous than the adsorption process. The novel perfluorosulfonate-functionalized ILs studied in this work show improved surface activity and aggregation behavior, forming distinct self-assembled structures.

Ionic liquid-mediated transcutaneous protein delivery with solid-in-oil nanodispersions

We report a novel ionic liquid (IL)-mediated transcutaneous vaccine formulation consisting of a solid-in-oil nanodispersion of antigen coated with pharmaceutically accepted surfactants dispersed in IL-containing oil. The introduction of IL in the formulation significantly enhanced the skin permeability of ovalbumin, a model antigen.

Gels and lyotropic liquid crystals: using an imidazolium-based catanionic surfactant in binary solvents

The self-assembly behavior of an imidazolium-based catanionic surfactant, 1-butyl-3-methylimidazolium dodecylsulfate ([C4mim][C12H25SO4]), was investigated in water-ethylammonium nitrate (EAN) mixed solvents with different volume ratios. It is particular interesting that this simple surfactant could not only form lyotropic liquid crystals (LLC) with multimesophases, i.e., normal hexagonal (H1), lamellar liquid crystal (Lα), and reverse bicontinuous cubic phase (V2), in the water-rich environment but also act as an efficient low-molecular-weight gelator (LMWG) which gelated EAN-abundant binary media in a broad concentration range. The peculiar nanodisk cluster morphology of gels composed of similar bilayer units was first observed. FT-IR spectra and density functional theory (DFT) calculations reveal that strong H bonding and electrostatic interactions between EAN and the headgroups of [C4mim][C12H25SO4] are primarily responsible for gelation. The self-assembled gels displayed excellent mechanical strength and a thermoreversible sol-gel transition. It is for the first time that a rich variety of controllable ordered aggregates could be observed only by simply modulating the concentration of a single imidazolium-based catanionic surfactant or the ratio of mixed solvents. This environmentally friendly system is expected to have broad applications in various fields, such as materials science, drug delivery systems, and supramolecular chemistry.

Surfactant behavior of ionic liquids involving a drug: from molecular interactions to self-assembly

Aggregates formed in an aqueous medium by three ionic liquids CnMImIbu made up of 1-alkyl-3-methyl-imidazolium cation (n = 4, 6, 8) and ibuprofenate anion are investigated. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), (1)H nuclear magnetic resonance measurements, and atom-scale molecular dynamics simulations are used to shed light on the main interactions governing the formation of the aggregates and their composition. At high concentration, mixed micelles are formed with a composition that depends on the imidazolium alkyl chain length. For the shortest alkyl chain, micelles are mainly composed of ibuprofenate anions with some imidazolium cations intercalated between the anions. Upon increasing the alkyl chain length, the composition of the aggregates gets enriched in imidazolium cations and aggregates of stoichiometric composition are obtained. Attractive interactions between these aggregates led to the formation of larger aggregates. As suggested by molecular simulations, these larger aggregates might constitute the early stage of phase separation. Transitions from micelles to vesicles or ribbons are observed due to dilution effects and changes in the chemical composition of the aggregates. We also show that aggregation can be probed using simple microscopic quantities such as radial distribution functions and average solvation numbers.

Micellar transitions in catanionic ionic liquid–ibuprofen aqueous mixtures; effects of composition and dilution

Interactions between 1-dodecyl-3-methylimidazolium chloride and ibuprofen molecules in aqueous solution form catanionic mixtures, with morphologies of mixed micelles dependent on solution composition.

Alkyl imidazolium ionic-liquid-mediated formation of gold particle superstructures

The development of new methodologies for controlling the organization of quantum materials in multiple dimensions is crucial to the advancement of device fabrication. By using a self-assembly route using selected imidazolium ionic liquids bearing long alkyl chains (C(n)Imida, n = 8, 10, 12) as ligands, we have achieved a tunable assembly of quantum-sized gold nanoparticles. The initial stabilizer of the gold nanoparticles was partially or wholly substituted depending on the concentration and alkyl chain length. π-π interactions between imidazolium rings also promote the generation of spatially controlled aggregates from the nanometer to micrometer size regimes. In particular, in the case of an imidazolium ionic liquid with decyl chains, gold particles assemble into a core-shell spherical superstructure induced by the aggregation of imidazolium ionic liquid molecules during ligand exchange. Conceptually, the assemblies of nanoparticles mimic biological systems and provide strategies for the organization of single-component nanomaterials into functional assemblies for potential applications. Our approach is general and can be applied to other types of nanomaterials for facile manipulation of the assembly processes, permitting an exploration of physicochemical properties as well as technological applications.