Ionic liquid based microemulsions: A review

A novel biological antibacterial polyvinyl alcohol/polyionic liquid hydrogel for wound dressing

The release of antibiotics or anions by traditional bacteriostatic agents led to the development of bacterial drug resistance and environmental pollution. Ionic liquids (ILs) have become important choices for antibacterial agents because of their excellent physical, chemical and biological properties. In this paper, the bioactivities of 1-vinyl-3-butylimidazolium chloride ([VBIM]Cl, IL) and poly (1-vinyl-3-butylimidazolium chloride) (P[VBIM]Cl, PIL) were evaluated, and the potential antibacterial material was used to synthesize hydrogels. Using the colony formation assay and the Oxford cup method, antibacterial effect of IL and PIL were tested. Cell-Counting-Kit-8 (CCK-8) experiments were used to study the IC50 (half maximal inhibitory concentration) values of IL and showed 1.47 mg/mL, 0.35 mg/mL and 0.33 mg/mL at 24 h, 48 h and 72 h, respectively. The IC50 value of PIL were 12.15 μg/mL, 12.06 μg/mL and 11.76 μg/mL at 24 h, 48 h and 72 h, respectively. The PIL is further crosslinked with polyvinyl alcohol (PVA) to form a novel hydrogel through freeze-thaw cycles. The newly fabricated hydrogel exhibited a high water content, excellent water absorption properties and outstanding mechanical performance. Using the colony formation assay and the inhibition zone assay, the hydrogels exhibited favorable antibacterial effects (against E.coli and S.aureus) such that nearly 100% of the bacteria were killed in liquid medium while cultivating with H4 (synthesized by 0.5 g PIL and 1g PVA). In addition, the cytotoxicity of PIL was significantly reduced through hydrogen bond crosslinking. H4 showed the highest antibacterial activity and a good biocompatibility. The results indicated that the PVA&PIL hydrogels had great potential for wound dressing.

Ionic Liquid Crystals as Chromogenic Materials

Ionic liquid crystals (ILCs), a class of soft matter materials whose properties can be tuned by the wise pairing of the cation and anion, have recently emerged as promising candidates for different applications, combining the characteristics of ionic liquids and liquid crystals. Among those potential uses, this review aims to cover chromogenic ILCs. In this context, examples of photo-, electro- and thermochromism based on ILCs are provided. Furthermore, thermotropic and lyotropic ionic liquid crystals are also summarised, including the most common chemical and phase structures, as well as the advantages of confining these materials. This manuscript also comprises the following main experimental techniques used to characterise ILCs: Differential Scanning Calorimetry (DSC), Polarised Optical Microscopy (POM) and X-Ray Powder Diffraction (XRD). Chromogenic ILCs can be interesting smart materials for energy and health purposes.

Formulation of a stable diesel microemulsion using eco-friendly ionic liquids and investigation of particle size and fuel properties as an alternative fuel

Ecofriendly ionic liquids (ILs) were synthesized through amidation of ricinoleic acid, the main fatty acid in castor oil, followed by a quaternization reaction to solubilize ethanol in IL/diesel blends at different ratios. As a result, stable and highly renewable, low viscous microemulsion biofuels with high oxygen content were prepared. The prepared fuel samples combine the advantages of green ionic liquids and microemulsion properties. The chemical structures of ILs were confirmed with the aid of NMR and FTIR spectroscopy. DLS analysis revealed that the ethanol particles ranged in size from 8 to 18.1 nm in all samples. As ILs ratios decrease in microemulsion from 37 to 69%, the ethanol particle sizes increase from 10 to 25%. Ethanol shows good solubilization in diesel and IL-1 is more effective than IL-2 in ethanol solubilization at low percentages of ethanol due to more oxygen atoms besides three hydroxyl groups. The ternary phase diagram indicated that the microemulsion area in the case of using IL-1 is larger than that of IL-2. The fuel properties of the prepared microemulsions are nearly close to those of neat diesel and fall within the permitted range of ASTM D975. The viscosity and density values at low ratios of ILs are found to be very close to the values of the neat diesel at different temperatures. The prepared samples show a slight decrease in cetane number and heating value compared to diesel. However, they have improved flash points, cloud points, sulfur content, and acid value. The particle sizes were checked every week and the prepared samples showed high stability with the aid of the synthesized ILs. Moreover, the prepared microemulsions stayed in a transparent appearance for more than a year and no phase separation was observed.

Ionic liquid based surfactant-free microemulsion as a new protocol for preparation of visible light active poly(methyl methacrylate)/TiO2 nanocomposite

The practical application of sensitized TiO2 nanocomposites is very satisfying due to their high photon utilization in visible light, simple recovery without affecting the photocatalytic performance, high energy efficiency, low potential environmental risk, and low operational costs. The objective of this study is developing the ionic liquid (IL)-based surfactant-free microemulsion, as a soft template, for preparation of a novel type of sensitized poly(methyl methacrylate)/TiO2 nanocomposite (PMMA/TiO2/IL). For this purpose, a series of visible light-responsive PMMA/TiO2/IL transparent nanocomposites were prepared in microemulsion composed of methyl methacrylate monomer, 1-buthyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and 1-buthanol as amphi-solvent. Techniques such as diffuse reflectance spectroscopy (DRS)), attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray analysis (EDX) were used to characterize prepared nanocomposites. Photocatalytic degradation of methyl orange dye under visible light illumination, as an application in wastewater treatment, with the investigation of the influence of TiO2 content in the nanocomposite, pH, and nanocomposite reusability on photodegradation efficiency was studied and maximum value of 93.9% obtained at optimum conditions. The FESEM analysis indicated that the utilization of a relatively low amount of ionic liquid and also in absence of the surfactant ensures the monodispersity of the visible light sensitized TiO2 nanoparticles in the polymer matrix.

Mechanisms of Biological Effects of Ionic Liquids: From Single Cells to Multicellular Organisms

The review presents a detailed discussion of the evolving field studying interactions between ionic liquids (ILs) and biological systems. Originating from molten salt electrolytes to present multiapplication substances, ILs have found usage across various fields due to their exceptional physicochemical properties, including excellent tunability. However, their interactions with biological systems and potential influence on living organisms remain largely unexplored. This review examines the cytotoxic effects of ILs on cell cultures, biomolecules, and vertebrate and invertebrate organisms. Our understanding of IL toxicity, while growing in recent years, is yet nascent. The established findings include correlations between harmful effects of ILs and their ability to disturb cellular membranes, their potential to trigger oxidative stress in cells, and their ability to cause cell death via apoptosis. Future research directions proposed in the review include studying the distribution of various ILs within cellular compartments and organelles, investigating metabolic transformations of ILs in cells and organisms, detailed analysis of IL effects on proteins involved in oxidative stress and apoptosis, correlation studies between IL doses, exposure times and resulting adverse effects, and examination of effects of subtoxic concentrations of ILs on various biological objects. This review aims to serve as a critical analysis of the current body of knowledge on IL-related toxicity mechanisms. Furthermore, it can guide researchers toward the design of less toxic ILs and the informed use of ILs in drug development and medicine.

Interaction and antibacterial activity of ciprofloxacin with choline based ionic liquid and CTAB: A comparative spectroscopic study

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).

Green solvent systems for material syntheses and chemical reactions

It is of great significance to develop environmentally benign, non-volatile and recyclable green solvents for different applications. This feature article overviews the properties of green solvent systems (e.g., ionic liquids, supercritical carbon dioxide, deep eutectic solvents and mixed green solvent systems) and their applications in (1) framework material syntheses, including metal-organic frameworks, covalent organic frameworks and hydrogen-bonded organic frameworks, and (2) CO2 conversion reactions, including photocatalytic and electrocatalytic reduction reactions. Finally, the future perspective for research on green solvent systems is proposed from different aspects.

Dielectric Depiction of 1-Butyl-3-methylimidazolium Tetrafluoroborate/1-Butyl-3-methylimidazolium 1,4-Bis(2-ethylhexyl) Sulfosuccinate/Benzene Microemulsions: Percolation, Interface Polarization, and Electrical Parameters

Two dielectric relaxations located at approximately 10 and 300 MHz were analyzed in the microemulsion composed of the polar ionic liquid (PIL) 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), the surface-active ionic liquid (SAIL) 1-butyl-3-methylimidazolium 1,4-bis(2-ethylhexyl) sulfosuccinate ([bmim][AOT]), and benzene. The curve of the dc conductivity vs PIL weight fraction shows two inflection points, namely, 16.69 and 27.90 wt %, which are used to divide the PIL/O, bicontinuous (B.C.), and O/PIL subregions. The critical exponents of percolation u = 0.75, 0.79, and 0.80 are suggested from the scaling dependence of dc conductivity on the PIL weight fraction, together with frequency dependences of both permittivity and loss angle, which all infer that static percolation occurs in the microemulsion. Only one dielectric relaxation at high frequency was observed in the PIL/O subregion, when the concentration increased to the boundary between the PIL/O and B.C. subregions; the second dielectric relaxation appeared at low frequency. The high-frequency relaxation is caused by interfacial polarization. The low-frequency relaxation is attributed to the dipole-oriented polarization of AOT-. When the oil content of the system was reduced, the interface became softer to allow more AOT- to rotate, and the cation shifted from moving around its long axis to rotating along its short axis. The static dielectric constant of [bmim][AOT] was given. The dielectric constants and conductivity of the dispersed and continuous phases in the PIL/O and O/PIL subregions were calculated from the dielectric parameters of high-frequency relaxation.

Synthesis and Characterization of New Polymeric Ionic Liquids as Corrosion Inhibitors for Carbon Steel in a Corrosive Medium: Experimental, Spectral, and Theoretical Studies

A novel series of polymeric ionic liquids (ILs) based on benzimidazolium chloride derivatives, namely, 1,3-diheptyl-2-(2-phenyl-propyl)-3H-benzimidazol-1-ium chloride (IL1), 1,3-dioctyl-2-(2-phenyl-propyl)-3H-benzimidazol-1-ium chloride (IL2), and 1,3-Bis-decyl-2-(2-phenyl-propyl)-3H-benzoimidazol-1-ium chloride (IL3), were synthesized and chemically elucidated by Fourier transform infrared spectroscopy, 1H NMR, 13C NMR, and elemental analysis. Their influence as corrosion suppressors were investigated for C-steel corrosion in 1 M HCl, by weight loss (WL), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) methods, revealing that their exclusive addition decreased corrosion with mounting concentrations. These assays demonstrated that novel ILs are efficient inhibitors at relatively low dosages. The efficacy of the synthesized ILs reached 79.7, 92.2 and 96.9%, respectively, at 250 ppm and 303 K. Parameters for activation and adsorption were calculated and are discussed. The Tafel polarization results demonstrated that the investigated ILs support the suppression of both cathodic and anodic reactions, acting as mixed type inhibitors. Langmuir's adsorption isotherm was confirmed as the best fitted isotherm, describing the physical-chemical adsorption capability of used ILs on the C-steel surface with the change in the free energy of adsorption, ΔG°ads = 32.6-37.2 kJ mol-1. The efficacy of the synthesized ILs was improved by increasing the doses, and the temperature reached 86.6, 96.1, and 98.4%, respectively, at 318 K. Surface morphology was proved by Fourier Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM), and then, changes in test solutions were checked by Ultraviolet-visible spectroscopy. Theoretical modeling (density functional theory and Monte Carlo) revealed the correlation between the IL's molecular chemical structure and its anticorrosive property.

Expeditious Discovery of Small-Molecule Thermoresponsive Ionic Liquid Materials: A Review

Ionic liquids (ILs) are a class of low-melting molten salts (<100 °C) constituted entirely of ions, and their research has gained tremendous attention in line with their remarkably growing applications (>124,000 publications dated 30 August 2023 from the Web of ScienceTM). In this review, we first briefly discussed the recent developments and unique characteristics of ILs and zwitterionic liquids (ZILs). Compared to molecular solvents and other conventional organic compounds, (zwitter) ionic liquids carry negligible volatility and are potentially recyclable and reusable. For structures, both ILs and ZILs can be systematically tailor-designed and engineered and are synthetically fine-tunable. As such, ionic liquids, including chiral, supported, task-specific ILs, have been widely used as powerful ionic solvents as well as valuable additives and catalysts for many chemical reactions. Moreover, ILs have demonstrated their value for use as polymerase chain reaction (PCR) enhancers for DNA amplification, chemoselective artificial olfaction for targeted VOC analysis, and recognition-based affinity extraction. As the major focus of this review, we extensively discussed that small-molecule thermoresponsive ILs (TILs) and ZILs (zwitterionic TILs) are new types of smart materials and can be expeditiously discovered through the structure and phase separation (SPS) relationship study by the combinatorial approach. Using this SPS platform developed in our laboratory, we first depicted the rapid discovery of N,N-dialkylcycloammonium and 1,3,4-trialkyl-1,2,3-triazolium TILs that concomitantly exhibited LCST (lower critical solution temperature) phase transition in water and displayed biochemically attractive Tc values. Both smart IL materials were suited for applications to proteins and other biomolecules. Zwitterionic TILs are ZILs whose cations and anions are tethered together covalently and are thermoresponsive to temperature changes. These zwitterionic TIL materials can serve as excellent extraction solvents, through temperature change, for biomolecules such as proteins since they differ from the common TIL problems often associated with unwanted ion exchanges during extractions. These unique structural characteristics of zwitterionic TIL materials greatly reduce and may avoid the denaturation of proteins under physiological conditions. Lastly, we argued that both rational structural design and combinatorial library synthesis of small-molecule TIL materials should take into consideration the important issues of their cytotoxicity and biosafety to the ecosystem, potentially causing harm to the environment and directly endangering human health. Finally, we would concur that before precise prediction and quantitative simulation of TIL structures can be realized, combinatorial chemistry may be the most convenient and effective technology platform to discover TIL expeditiously. Through our rational TIL design and combinatorial library synthesis and screening, we have demonstrated its power to discover novel chemical structures of both TILs and zwitterionic TILs. Undoubtedly, we will continue developing new small-molecule TIL structures and studying their applications related to other thermoresponsive materials.

Ionic Liquid-in-Water Emulsions Stabilized by Molecular and Polymeric Surfactants

Ionic liquids have drawn notable attention for their unique solvent properties and use in applications such as batteries and chemical separations. While many ionic liquids are water-soluble, there are numerous examples of ionic liquids that are sufficiently hydrophobic to remain phase separated from water. However, relatively little is known about the stability and properties of ionic liquid-in-water emulsions. Here, we survey a series of ionic liquid-in-water emulsions stabilized by a range of ionic and nonionic molecular surfactants and polymers. To assess droplet stability and dynamics, we characterize the ionic liquid-surfactant interfacial tension, describe qualitative coarsening rates, and quantify droplet solubilization rate. In some instances, we observe unexpected spontaneous formation of complex double and triple emulsions. Our observations highlight approaches for ionic liquid emulsion formulation and provide insight into how to address challenges surrounding stabilization of ionic liquid-in-water droplets with molecular surfactants.

Impact of Processing Parameters on Contactless Emulsification via Corona Discharge

A contactless emulsification method is presented using corona discharge. The corona discharge forms using a pin-to-plate configuration, creating a non-uniform electric field. This results in a simultaneous electrohydrodynamic (EHD) pumping of silicone oil and an electroconvection of water droplets that accelerate and submerge inside the oil, leading to a continuous water-in-oil (W/O) emulsion formation process. The impact of the oil viscosity and corona generating AC and DC electric fields (i.e., voltage and frequency) on the characteristics of the emulsions is studied. The emulsification power consumption using the AC and DC electric fields is calculated and compared to traditional emulsion formation methods. While using the DC electric field results in the formation of uniform emulsions, the AC electric field is readily available and uses less power for the emulsification. This is facile, contactless, and energy-efficient for the continuous formation of W/O emulsions.

Multiple-Stimuli-Responsive Surfactant-Free Microemulsions Based on Hydrophobic Deep Eutectic Solvents

Hydrophobic deep eutectic solvents (HDESs) have been applied to colloidal systems such as microemulsions, despite the development of stimulus-responsive HDESs still being in a preliminary stage. Here, menthol and indole were hydrogen bonded to form CO₂-responsiveness HDES. A surfactant-free microemulsion constituted of HDES (menthol-indole) as the hydrophobic phase, water as the hydrophilic phase, and ethanol as the double solvent was demonstrated to be CO₂- and temperature-responsive. Dynamic light scattering (DLS) proved the single-phase region of the phase diagram, while conductivity and polarity probing techniques confirmed the kind of microemulsion. The ternary phase diagram and DLS methods were used to investigate the responsiveness of CO₂ and effect temperature on the microemulsion drop size and behavior of the phase of the HDES/water/ethanol microemulsion. The findings revealed that when temperature increased, the homogeneous phase region increased. The droplet size in the homogeneous phase region of the associated microemulsion may be reversibly and accurately adjusted by adjusting the temperature. Surprisingly, a slight temperature change can cause a significant phase inversion. Furthermore, in the system, there was no demulsification in time for the CO₂/N₂ responsiveness process but rather the production of a homogeneous and pellucid aqueous solution.

Ionic liquid-assisted synthesis of mesoporous polymers and carbon materials: the self-assembly mechanism

Soft-templating synthesis has been widely employed to fabricate ordered mesoporous polymer and carbon materials with effectively tuneable pore sizes. However, the commonly used templating agents, block copolymers, are normally decomposed during the process, thus are barely recyclable; this increases the costs and hampers the scale-up feasibility. Therefore, it becomes imperative to seek promising alternatives; amphiphilic ionic liquids (ILs) are excellent candidates due to their good recyclability. This study explored the templating behaviour of IL templates for preparing mesoporous polymers and carbons. In details, the self-assembly of ternary systems (comprising of IL templates, precursors and solvent) were investigated by a combination of coarse-grained molecular dynamics (CGMD) simulations, density function theory (DFT) calculations and experimental techniques. The results indicate that the morphologies of IL templates are tuneable not only by the adjustment of water content in the mixture but also by the selection of suitable precursors. Material precursors containing increasing numbers of hydroxyl moieties also induce various precursor-template spatial correlations, resulting in different topological structures of nanomaterials. This work presents a fundamental investigation into the mechanisms of templating synthesis with amphiphilic ILs as recyclable templates and gives insight into the effective design of coveted carbon nanomaterials for targeted applications.

Recent Developments in Ionic Liquid-Assisted Topical and Transdermal Drug Delivery

Ionic liquids (ILs) have attracted growing interest as designer solvents/materials for exploring unrealized functions in many areas of research including drug formulations and delivery owing to their inherent tunable physicochemical and biological properties. The use of ILs in the pharmaceutical industry can address challenges related to the use of conventional organic solvent-based chemical permeation enhancers. Their tunability in forming ion pairs with a diverse range of ions enables the task-specific optimization of ILs at the molecular level. In particular, ILs comprising second- and third-generation cations and anions have been extensively used to design biocompatible drug delivery systems to address the challenges related to conventional topical and transdermal drug delivery, including limited permeability, high cytotoxicity, and skin irritation. This review highlights the progress in IL-related research with particular emphasis on the very recent conceptual developments in transdermal drug delivery. Technological advancement and approaches for the formation of IL-based topical and transdermal delivery systems, as well as their promising application in drug delivery, are also discussed.

Separation and determination of basic orange II, acid orange II and auramine O in soybean products based on ionic liquid reverse micelle microextraction and ultra-high-performance liquid chromatography

A new analytical method was developed for the separation and determination of basic orange II, acid orange II and auramine O in soybean products. The technique was focused on ionic liquid reverse micelle microextraction (IL-RMME) followed by analysis and determination by ultra-high performance liquid chromatography (UHPLC) with photodiode array detector of three chemical dyes. In this method, IL-RMME solution consisting of ionic liquid [Omim]BF6 and surfactant GenapolX-080 was used as extractant. Important parameters affecting IL-RMME efficiency, such as extraction solvent type and volume, sample solution pH, salt effect, centrifugation speed and time were investigated. Under the optimal condition, the linearity of the method was in the range of 0.1-10 ng mL-1with correlation coefficient above 0.9994 and the limits of detection below 0.03 ng mL-1. At the same time, relative standard deviations of the developed procedure for intra- (n = 5) and inter-day (n = 5) precision were in the range of 5.04-8.50%. The results demonstrated that a simple fast environmentally friendly efficient method was successfully applied in the separation and determination of three chemical dyes in soybean products.

Ionic Liquids Assisted Topical Drug Delivery for Permeation Enhancement: Formulation Strategies, Biomedical Applications, and Toxicological Perspective

Topical drug delivery provides several benefits over other conventional routes by providing localizing therapeutic effects and also avoids the gastrointestinal tract circumventing the first-pass metabolism and enzymatic drug degradation. Being painless, the topical route also prevents the difficulties linked with the parenteral route. However, there are limitations to the current topical systems which necessitate the need for further research to find functional excipients to overcome these limitations. This review deals in depth with the ionic liquids concerning their physicochemical properties and applicability as well as their role in the arena of topical drug delivery in permeation enhancement, bioavailability enhancement of the drugs by solvation, and drug moiety modification. The review gives a detailed insight into the recent literature on ionic liquid-based topical formulations like ionic liquid-based emulsions, active pharmaceutical ingredient-ionic liquids, ionic liquid-based bacterial cellulose membranes, topical small interfering RNA (siRNA) delivery, and ionogels as a possible solutions for overcoming the challenges associated with the topical route. This review also takes into account the toxicological aspects and biomedical applications of ionic liquids.

Improvement of solubility, stability and antioxidant activity of carotenoids using deep eutectic solvent-based microemulsions

Natural carotenoids have been widely used as colorants and antioxidants in process of food, medicine, and cosmetic. However, the carotenoids have low bioactivity in vivo due to poor water-solubility. To enhance the solubility, stability and antioxidant activity of carotenoids, novel microemulsions (MEs) composed with deep eutectic solvents (DESs), tween 80 and water were developed as alternatives to organic solvents. The phase diagrams and physicochemical properties (viscosity, pH, and diameter) of the DES-based MEs were investigated at different temperatures. Then the solubility distribution, storage stability and DPPH free radical-scavenging activity of three carotenoids (astaxanthin, astaxanthin ester and lutein) in the MEs were evaluated. Compared with ethanol, methanol, and acetone, all the DES-based MEs studied significantly enhanced the solubility of the carotenoids due to the stronger hydrogen bonding and Van der Waals interactions. The highest solubilities of 0.27, 473.63, and 12.50 mg/mL for astaxanthin, astaxanthin ester and lutein, respectively, were observed in the MEs containing DES (DL-menthol:acetic acid = 1:2) at 35 ℃. Moreover, astaxanthin ester can be well preserved in the MEs containing DES (DL-menthol:octanoic acid = 1:2) with a half-life of more than 69 days. In addition, the DPPH scavenging capacities of the three carotenoids in all the MEs were higher than the organic solvents. The results revealed that the DES-based MEs with low viscosity (<0.2 Pa•s) and mild acidic pH (4-5) are potential solvents for natural carotenoids in food processing and storage, medicine making, as well as biomaterials processing.

Antifungal Activity and Stability of Fluconazole Emulsion Containing Ionic Liquids Explained by Intermolecular Interactions

This research reports accelerated stability experiments, the evaluation of intermolecular interactions, and antifungal assays for fluconazole emulsions prepared using ultrasound (US) and magnetic stirring (MS) in the presence of ionic liquids derived from 1,n-(3-methylimidazolium-1-yl)alkane bromide ([CnMIM]Br; n = 12 or 16). The goals of the investigation are to quantify the stability, identify the forces that drive the formation and stability, and determine the antifungal activity of fluconazole-containing emulsions, and corroborate the data from our previous results that indicated that the emulsion based on [C16MIM]Br seemed to be more stable. In this study, accelerated stability experiments evidenced a considerable stability for the [C16MIM]Br emulsions at two temperatures (25 and 37 °C)—the instability index increased in the following order: US40% < US20% < MS. The 1H NMR data showed that the ILs interacts differently with medium-chain triglycerides (MCT). Two distinct interaction mechanisms were also observed for [C12MIM]Br and [C16MIM]Br with fluconazole, in which the latter formed more compact mixed aggregates than the former. The result was corroborated by diffusion data, which showed that ILs suffered a decrease in diffusion in the presence of fluconazole. The antifungal assay showed that emulsions containing ILs displayed superior activity compared with fluconazole alone. The emulsions also showed potent activity in inhibiting a resistant species (C. glabrata—CG34) to FLZ. All emulsions showed weak irritant potential in HET-CAM assay.

Contactless Method of Emulsion Formation Using Corona Discharge

Electroemulsification methods use electrohydrodynamic (EHD) forces to manipulate fluids and droplets for emulsion formation. Here, a top-down method is presented using a contactless corona discharge for simultaneous emulsion formation and its pumping/collection. The corona discharge forms using a sharp conductive electrode connected to a high-voltage source that ionizes water vapor droplets (formed by a humidifier) and creates an ionic wind (electroconvection), dragging them into an oil medium. The nonuniform electric field induced by the corona discharge also drives the motion of the oil medium via an EHD pumping effect utilizing a modulated bottom electrode geometry. By these two effects, this contactless method enables the immersion of the water droplets into the moving oil medium, continuously forming a water-in-oil (W/O) emulsion. The impact of corona discharge voltage, vertical and horizontal distances between the two electrodes, and depth of the silicone oil on sizes of the formed emulsions is studied. This is a low-cost and contactless process enabling the continuous formation of the W/O emulsions.

Phase studies of ethyl ammonium nitrate (EAN)/sugar surfactant microemulsions: effect of chain length of alkanes and length of the hydrophobic chain of the non-ionic surfactant

Microemulsions were formulated with the ionic liquid ethylammonium nitrate (EAN) used instead of water as the polar phase, hydrocarbon solvents (n-alkanes) and sugar-based non-ionic surfactants, and their phase behaviour and microstructure were investigated. The sugar-based non-ionic surfactants used are non-toxic, biodegradable and environmentally friendly. Due to these properties, their use in microemulsion systems is a clear alternative to the conventionally used non-ionic surfactants from the class of alkyl polyoxyethylene ethers (C i E j ). The influence of n-alkanes with different chain lengths and of sugar-based nonionic surfactants with hydrophobic chains of different lengths on the microemulsion system was also investigated. The results obtained for the microemulsions with EAN described here are similar to those obtained for microemulsion systems formulated with water as the polar solvent. Liquid crystalline (LC) phases were observed in microemulsion systems with sugar-based nonionic surfactants having longer hydrocarbon chains, at lower temperatures and higher surfactant mass fraction.

Isolation of single crystals of a homoleptic UO22+-diglycolamide complex from a room temperature ionic liquid: X-ray crystallography and complexation studies

Complexation and structural investigations of the solid complex of UO22+ ion and TMDGA isolated from an ionic liquid for the first time revealed that the nature and structural features of the complex are identical with those of the complex isolated from the aqueous medium.

Engineering encapsulated ionic liquids for next-generation applications

Ionic liquids (ILs) have attracted considerable attention in several sectors (from energy storage to catalysis, from drug delivery to separation media) owing to their attractive properties, such as high thermal stability, wide electrochemical window, and high ionic conductivity. However, their high viscosity and surface tension compared to conventional organic solvents can lead to unfavorable transport properties. To circumvent undesired kinetics effects limiting mass transfer, the discretization of ILs into small droplets has been proposed as a method to increase the effective surface area and the rates of mass transfer. In the present review paper, we summarize the different methods developed so far for encapsulating ILs in organic or inorganic shells and highlight characteristic features of each approach, while outlining potential applications. The remarkable tunability of ILs, which derives from the high number of anions and cations currently available as well as their permutations, combines with the possibility of tailoring the composition, size, dispersity, and properties (e.g., mechanical, transport) of the shell to provide a toolbox for rationally designing encapsulated ILs for next-generation applications, including carbon capture, energy storage devices, waste handling, and microreactors. We conclude this review with an outlook on potential applications that could benefit from the possibility of encapsulating ILs in organic and inorganic shells.

Encapsulated ionic liquids (ILs) are candidate materials for several applications owing to the attractive properties of ILs combined with the enhanced mass transfer rate obtained through the discretization of ILs in small capsules.

Fundamentals and Design-Led Synthesis of Emulsion-Templated Porous Materials for Environmental Applications

Emulsion templating is at the forefront of producing a wide array of porous materials that offers interconnected porous structure, easy permeability, homogeneous flow-through, high diffusion rates, convective mass transfer, and direct accessibility to interact with atoms/ions/molecules throughout the exterior and interior of the bulk. These interesting features together with easily available ingredients, facile preparation methods, flexible pore-size tuning protocols, controlled surface modification strategies, good physicochemical and dimensional stability, lightweight, convenient processing and subsequent recovery, superior pollutants remediation/monitoring performance, and decent recyclability underscore the benchmark potential of the emulsion-templated porous materials in large-scale practical environmental applications. To this end, many research breakthroughs in emulsion templating technique witnessed by the recent achievements have been widely unfolded and currently being extensively explored to address many of the environmental challenges. Taking into account the burgeoning progress of the emulsion-templated porous materials in the environmental field, this review article provides a conceptual overview of emulsions and emulsion templating technique, sums up the general procedures to design and fabricate many state-of-the-art emulsion-templated porous materials, and presents a critical overview of their marked momentum in adsorption, separation, disinfection, catalysis/degradation, capture, and sensing of the inorganic, organic and biological contaminants in water and air.

Good's buffer ionic liquid tunes the phase behavior of an anionic surfactant SDBS-stabilized n-octane-water microemulsion and the stability of the solubilized horseradish peroxidase

A Good's buffer ionic liquid (GB-IL) composed of quaternary ammonium cations and Good's buffer anions is first introduced into a microemulsion system as a self-buffering and biocompatible electrolyte. The effects of the constituting ions of a GB-IL and their concentrations on the phase behavior of the anionic surfactant SDBS stabilized n-octane-H₂O microemulsion system were studied for the first time using the ε-β fish-like phase diagram method. The result indicates that the phase behavior of the above microemulsion system is greatly affected by GB-IL cations with a longer alkyl chain on the cation being more favorable for phase inversion. Compared with NaCl, a GB-IL of the same concentration is more efficient for achieving phase inversion, due to the dual role of an electrolyte and a co-alcohol. In addition to the phase behavior, the stability of horseradish peroxidase (HRP) solubilized in an SDBS stabilized bicontinuous microemulsion is also affected by a GB-IL. It is found that the variation of the cationic alkyl chain has a negligible effect on the microemulsion microstructure, but has a significant influence on the stability of the solubilized HRP. At a fixed concentration of the GB-IL, the quaternary ammonium cation with a longer alkyl chain is better for the stabilization of the HRP activity. For a given GB-IL, a higher level of the GB-IL results in a better HRP stability. More importantly, the GB-IL-buffered microemulsion, at the same level of the buffering salt, is more advantageous than the phosphate-buffered one for the stabilization of the HRP activity. This advantage is more pronounced for higher concentrations of the GB-IL. This difference in the HRP stability, caused by the buffering salts, should be ascribed to the microemulsion microstructure effect as well as the Hofmeister effect. The present study provides a guideline for the construction of a bicontinuous microemulsion with a simplified composition and stabilizing effect on the solubilized enzyme.

Tri-tert-butyl(n-alkyl)phosphonium Ionic Liquids: Structure, Properties and Application as Hybrid Catalyst Nanomaterials

A series of sterically hindered tri-tert-butyl(n-alkyl)phosphonium salts (n-CnH2n+1 with n = 1, 3, 5, 7, 9, 11, 13, 15, 17) was synthesized and systematically studied by 1H, 13C, 31P NMR spectroscopy, ESI-MS, single-crystal X-ray diffraction analysis and melting point measurement. Formation and stabilization palladium nanoparticles (PdNPs) were used to characterize the phosphonium ionic liquid (PIL) nanoscale interaction ability. The colloidal Pd in the PIL systems was described with TEM and DLS analyses and applied in the Suzuki cross-coupling reaction. The PILs were proven to be suitable stabilizers of PdNPs possessing high catalytic activity. The tri-tert-butyl(n-alkyl)phosphonium salts showed a complex nonlinear correlation of the structure–property relationship. The synthesized family of PILs has a broad variety of structural features, including hydrophobic and hydrophilic structures that are entirely expressed in the diversity of their properties

Nanoscale Advancement Continues-From Catalysts and Reagents to Restructuring of Reaction Media

Comprehensive studies dedicated to the search for specific properties of matter at the micro- and nanoscales have greatly enriched the fields of chemistry and materials science. From the point of view of synthetic chemistry, discoveries in the field of nanoscale catalysis, in which the size effects of active centers are used to accelerate the reactions, are of particular importance. However, another approach for the promotion of chemical transformations based on the micro- or nanoconfinement of reacting molecules or even on the structuring of the reaction media as a whole is gaining interest as a highly valuable tool. Herein, we highlight the example of an increase in the efficiency of phenol alkylation and tert-butylation of benzyl alcohol in reaction media based on ionic liquids by the creation of acidic microdomains in the presence of small molecule additives.