Ionic liquids synthesis and applications: An overview

Preparation of a novel environmentally friendly hydrophobic deep eutectic solvent ChCl-THY and its application in removal of hexavalent chromium from aqueous solution

A liquid-liquid extraction methodology was developed for the removal of Cr(VI) from contaminated water using a novel green hydrophobic deep eutectic solvent (DES) as an efficient sole extracting agent. The hydrophobic DES was obtained by mixing choline chloride and thymol in 1:4 molar ratio at 70°C for 10 min and was denoted as ChCl-THY(1:4). The ChCl-THY(1:4) works efficiently for removal of high (20 mg/L) and low (500 µg/L) concentration of Cr(VI) from artificially contaminated natural water with >95% extraction efficiency (E%) at optimized reaction conditions (pH 2-6, 40°C). The DES was characterized by ¹ H NMR and FTIR spectroscopy, and the data suggest that interaction occurs between Cl^- ion of choline chloride and H atoms of thymol molecules. Physicochemical properties such as density, melting point, moisture, and solubility were studied and discussed. Herein, no sharp melting point was observed for ChCl-THY(1:4) in DSC curve. DES was regenerated using 0.1 M NaOH as stripping agent, and 50%-60% extraction efficiency could be attained in the next cycle. A plausible mechanism of interaction between Cr(VI) species and DES was also explored with the help of FTIR spectroscopy. PRACTITIONER POINTS: A novel hydrophobic DES (ChCl-THY) is prepared by mixing choline chloride and thymol at 1:4 molar ratio. ChCl-THY(1:4) is employed for the first time as sole extracting agent to remove the Cr(VI) from contaminated aqueous solution. >95% extraction efficiency was achieved by ChCl-THY(1:4) in natural water conditions at µg/L and mg/L level of contamination. Both the component used to prepare the DES are naturally abundant; hence, DES is not toxic for biota. The element present in natural water did not show any interference with extraction of Cr(VI).

Advances Achieved by Ionic-Liquid-Based Materials as Alternative Supports and Purification Platforms for Proteins and Enzymes

Ionic liquids (ILs) have been applied in several fields in which enzymes and proteins play a noteworthy role, for instance in biorefinery, biotechnology, and pharmaceutical sciences, among others. Despite their use as solvents and co-solvents, their combination with materials for protein- and enzyme-based applications has raised significant attention in the past few years. Among them, significant advances were brought by supported ionic liquids (SILs), in which ILs are introduced to modify the surface and properties of materials, e.g., as ligands when covalently bond or when physiosorbed. SILs have been mainly investigated as alternative supports for enzymes in biocatalysis and as new supports in preparative liquid chromatography for the purification of high-value proteins and enzymes. In this manuscript, we provide an overview on the most relevant advances by using SILs as supports for enzymes and as purification platforms for a variety of proteins and enzymes. The interaction mechanisms occurring between proteins and SILs/ILs are highlighted, allowing the design of efficient processes involving SILs. The work developed is discussed in light of the respective development phase and innovation level of the applied technologies. Advantages and disadvantages are identified, as well as the missing links to pave their use in relevant applications.

Validation of Structural Grounds for Anomalous Molecular Mobility in Ionic Liquid Glasses

Ionic liquid (IL) glasses have recently drawn much interest as unusual media with unique physicochemical properties. In particular, anomalous suppression of molecular mobility in imidazolium IL glasses vs. increasing temperature was evidenced by pulse Electron Paramagnetic Resonance (EPR) spectroscopy. Although such behavior has been proven to originate from dynamics of alkyl chains of IL cations, the role of electron spin relaxation induced by surrounding protons still remains unclear. In this work we synthesized two deuterated imidazolium-based ILs to reduce electron-nuclear couplings between radical probe and alkyl chains of IL, and investigated molecular mobility in these glasses. The obtained trends were found closely similar for deuterated and protonated analogs, thus excluding the relaxation-induced artifacts and reliably demonstrating structural grounds of the observed anomalies in heterogeneous IL glasses.

Salicylate-Based Ionic Liquids as Innovative Ingredients in Dermal Formulations

The identification and characterization of novel compounds with improved functionality and safety is of great importance. Ionic liquids are potential candidates for use in dermal formulation as multifunctional components with a large variability potential. The behavior of Ionic Liquids (ILs) in aqueous solutions has an impact on their functionality in the formulation as well as on their biological activity. Therefore, the solutions of selected ILs containing salicylate anions were investigated in the present work. The alkyl chain length of the cation determined most of the studied parameters. Thus, the surface activity, the antimicrobial activity, and cytotoxicity were directly proportional to the chain length. The salicylate anion did not affect the surface activity significantly, but had an important influence on the biological activity, especially for ILs with short chain lengths. It was found that the antimicrobial activity of benzalkonium-based ILs was mainly dependent on the cation, and the minimal inhibitory concentration (MIC) values were three order of magnitude lower than those of salicylic acid. Nevertheless, the slightly lower MIC values of benzalkonium salicylate, compared to benzalkonium chloride, might indicate a synergistic effect resulting from different modes of action of the two ions. N-hexyl nicotinamide salicylate also showed a higher antimicrobial activity than salicylic acid and, at the same time, a very good skin tolerance at concentrations up to 5% w/w. Based on our investigations N-hexyl nicotinamide salicylate was identified as potential emulsifiers / co-emulsifiers with antimicrobial properties for dermal formulations.

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.

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton exchange membrane fuel cells (PEMFCs) to work at low and moderate temperatures. The design of new conductive membranes and nanoparticles (NPs) whose morphology directly affects their catalytic properties is of utmost importance. Nanoparticle morphologies, like cubes, octahedrons, icosahedrons, bipyramids, plates, and polyhedrons, among others, are widely studied for catalysis applications. The recent progress around the high catalytic activity has focused on the stabilizing agents and their potential impact on nanomaterial synthesis to induce changes in the morphology of NPs.

Microwave-Assisted Ionic Liquid-Catalyzed Selective Monoesterification of Alkylphosphonic Acids-An Experimental and a Theoretical Study

It is well-known that the P-acids including phosphonic acids resist undergoing direct esterification. However, it was found that a series of alkylphoshonic acids could be involved in monoesterification with C2-C4 alcohols under microwave (MW) irradiation in the presence of [bmim][BF4] as an additive. The selectivity amounted to 80-98%, while the isolated yields fell in the range of 61-79%. The method developed is a green method for P-acid esterification. DFT calculations at the M062X/6-311+G (d,p) level of theory (performed considering the solvent effect of the corresponding alcohol) explored the three-step mechanism, and justified a higher enthalpy of activation (160.6-194.1 kJ·mol-1) that may be overcome only by MW irradiation. The major role of the [bmim][BF4] additive is to increase the absorption of MW energy. The specific chemical role of the [BF4] anion of the ionic liquid in an alternative mechanism was also raised by the computations.

Promising Nanoparticle-Based Heat Transfer Fluids-Environmental and Techno-Economic Analysis Compared to Conventional Fluids

Providing optimal operating conditions is one of the major challenges for effective heating or cooling systems. Moreover, proper adjustment of the heat transfer fluid is also important from the viewpoint of the correct operation, maintenance, and cost efficiency of these systems. Therefore, in this paper, a detailed review of recent work on the subject of conventional and novel heat transfer fluid applications is presented. Particular attention is paid to the novel nanoparticle-based materials used as heat transfer fluids. In-depth comparison of environmental, technical, and economic characteristics is discussed. Thermophysical properties including thermal conductivity, specific heat, density, viscosity, and Prandtl number are compared. Furthermore, the possible benefits and limitations of various transfer fluids in the fields of application are taken into account.

A Method for Preparing Superhydrophobic Paper with High Stability and Ionic Liquid-Induced Wettability Transition

In this study, the polymer PTSPM-PMETAC with anion adsorption properties was prepared by a one-step method, then the amino-modified nano-SiO2 was grafted onto the polymer to improve the roughness of the surface and enhance the stability of superhydrophobic properties, and a high-stability superhydrophobic paper with ion-induced wettability transition properties was successfully prepared. The study found that the paper can realize the reversible control of surface wettability through the exchange between the anions PF6- and Cl- adsorbed on the surface of PMETAC, and further investigation of the effect of different solvents on the ion exchange properties found that water was the poor solvent for ion exchange, while the mixtures of methanol, acetone, and methanol & water were the good solvent. On the whole, the preparation of superhydrophobic paper by this method not only simple in preparation process, low in cost and strong in universality, but also the prepared superhydrophobic paper has high transparency and good stability, which has great application potential in industrial production.

Preparation and Chiral Applications of Optically Active Polyamides

Chirality is omnipresent in nature and plays vital roles in living organism, and has become a hot research topic across multidisciplinary fields including chemistry, biology, physics, and material science. Meanwhile, polyamides constitute an important class of polymers and have received significant attention owing to their outstanding properties and wide-ranging applications in many areas. Judiciously introducing chirality into polyamides will undoubtedly obtain attractive chiral polymers, namely, optically active polyamides. This review describes the preparation methods of chiral polyamides, including solution polycondensation, interfacial polycondensation, ring-open polymerization, and others; the newly emerging categories of chiral polyamides, i.e., helical polyamides, chiral polyamide-imides, are also presented. The applications of optically active polyamides in chiral research fields including asymmetric catalysis, membrane separation, and enantioselective crystallization are also summarized. In addition, current challenges in chiral polyamides are further presented and future perspectives in the field are proposed.

Ether-Functionalized Pyrrolidinium-Based Room Temperature Ionic Liquids: Physicochemical Properties, Molecular Dynamics, and the Lithium Ion Coordination Environment

The physicochemical properties of room temperature ionic liquids (RTILs) consisting of bis(trifluoromethanesulfonyl)amide (TFSA^- ) combined with 1-hexyl-1-methylpyrrolidinium (Pyr_1,6 ⁺ ), 1-(butoxymethyl)-1-methylpyrrolidinium (Pyr_1,1O4 ⁺ ), 1-(4-methoxybutyl)-1-methyl pyrrolidinium (Pyr_1,4O1 ⁺ ), and 1-((2-methoxyethoxy)methyl)-1-methylpyrrolidinium (Pyr_1,1O2O1 ⁺ ) were investigated using both experimental and computational approaches. Pyr_1,1O2O1 TFSA, which contains two ether oxygen atoms, showed the lowest viscosity, and the relationship between its physicochemical properties and the position and number of the ether oxygen atoms was discussed by a careful comparison with Pyr_1,1O4 TFSA and Pyr_1,4O1 TFSA. Ab initio calculations revealed the conformational flexibility of the side chain containing the ether oxygen atoms. In addition, molecular dynamics (MD) calculations suggested that the ion distributions have a significant impact on the transport properties. Furthermore, the coordination environments of the Li ions in the RTILs were evaluated using Raman spectroscopy, which was supported by MD calculations using 1000 ion pairs. The presented results will be valuable for the design of functionalized RTILs for various applications.

Development of an automated yeast-based spectrophotometric method for toxicity screening: Application to ionic liquids, GUMBOS, and deep eutectic solvents

Saccharomyces cerevisiae has been used as a eukaryotic model organism for studying the toxic effects of various compounds. In this context, an automated spectrophotometric method based on the enzymatic reduction of methylene blue dye to a colorless product by living yeast cells was implemented in a sequential injection analysis system. Loss of yeast viability/impaired metabolic activity was monitored by an increase in optical density at 664 nm. To prove the usefulness of this approach, the toxicity of ILs (ionic liquids), GUMBOS (group of uniform materials based on organic salts), and DESs (deep eutectic solvents) was examined. Differences obtained between IC₅₀ values confirmed the impact of structural elements on each compounds' toxicity. While DESs appeared to be less toxic than ILs, GUMBOS were found to be among the most toxic compounds to yeast cells and thus can be viewed as promising antimicrobial candidates. The automated methodology showed satisfactory repeatability and reproducibility (RSD < 9%), which is in good agreement with Green Chemistry principles. In fact, the method required consumption of only 40 μL of reagents and produced less than 2 mL of effluents per cycle. Thus, the developed assay can be used as an alternative tool for toxicity screening.

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

The ceaseless increase of pollution cases due to the tremendous consumption of fossil fuels has steered the world towards an environmental crisis and necessitated urgency to curtail noxious sulfur oxide emissions. Since the world is moving toward green chemistry, a fuel desulfurization process driven by clean technology is of paramount significance in the field of environmental remediation. Among the novel desulfurization techniques, the oxidative desulfurization (ODS) process has been intensively studied and is highlighted as the rising star to effectuate sulfur-free fuels due to its mild reaction conditions and remarkable desulfurization performances in the past decade. This critical review emphasizes the latest advances in thermal catalytic ODS and photocatalytic ODS related to the design and synthesis routes of myriad materials. This encompasses the engineering of metal oxides, ionic liquids, deep eutectic solvents, polyoxometalates, metal-organic frameworks, metal-free materials and their hybrids in the customization of advantageous properties in terms of morphology, topography, composition and electronic states. The essential connection between catalyst characteristics and performances in ODS will be critically discussed along with corresponding reaction mechanisms to provide thorough insight for shaping future research directions. The impacts of oxidant type, solvent type, temperature and other pivotal factors on the effectiveness of ODS are outlined. Finally, a summary of confronted challenges and future outlooks in the journey to ODS application is presented.

Carotenoids obtained from an ionic liquid-mediated process display anti-inflammatory response in the adipose tissue-liver axis

Ionic liquids (ILs) have been proposed as more efficient and sustainable solvents to replace volatile organic solvents (VOSs). However, the drawbacks associated with their use are still limiting the regular application of bioactive compounds obtained from the processes they mediate as food ingredients. It is true that the number of ILs approved by the Food and Drug Administration for food applications is still low and mainly focused on the ones from the quaternary ammonium family. However, this trend is changing, judging from the evidence that industries are surpassing overgeneralization about ILs (on price and toxicity) and starting to consider the potential and performance of ILs as solvents. Despite the examples of industries applying ILs in their processes, the use of bioactive compounds obtained from IL-based processes as ingredients in food formulations is still a big challenge. The positive influence of carotenoids on diseases associated or originating from the inflammatory scenario including, among others, obesity, is not new. Moreover, it is also well known that the poorest population worldwide does not have the recommended intake of carotenoids, especially those pro-vitaminic A. In an attempt to help answer this issue, dietary supplements containing adequate doses of natural carotenoids are expected to be the solution, or at least, part of the solution for a healthier life, but also, to reduce hunger. Thus, complete studies evaluating the toxicological potential and the real viability of adding these bioactive compounds in food formulations proving (or not!) their safety to consumers and handlers are highly demanded. This work proposes to investigate the potential of carotenoids extracted from Bactris gasipaes feedstocks mediated by an ethanolic solution of an imidazolium-based IL. Thus, male Wistar rats were randomized in six different groups, supplemented or not by carotenoids extracted by IL or VOS, and fed by control- and/or high-fat-diets (HFD). The adipose tissue-liver axis was studied as a model to investigate the influence of the carotenoids on the levels of inflammation and oxidative stress markers. The main results showed that animals supplemented with carotenoids extracted with IL displayed improvements in serum parameters, besides lower metabolic efficiency, and antioxidant response on the liver, even when fed with HFD. However, animals supplemented with carotenoids extracted by VOS showed higher levels of pro-inflammatory markers and huge oxidative stress on the liver.

Highly Soluble Imidazolium Ferrocene Bis(sulfonate) Salts for Redox Flow Battery Applications

Redox flow batteries (RFBs) are scalable devices that employ solution-based redox active components for scalable energy storage. To maximize energy density, new highly soluble catholytes and anolytes need to be synthesized and evaluated for their electrochemical performance. To that end, we synthesized a series of imidazolium ferrocene bis(sulfonate) salts as highly soluble catholytes for RFB applications. Six salts with differing alkyl chain lengths on the imidazolium cation were synthesized, characterized, and electrochemically analyzed. While aqueous solubility was significantly improved, the reactivity of the imidazolium cation and the increased viscosities of the salt solutions in water (which increase with increasing imidazolium chain length) limit the applicability of these materials to RFB design.

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

Rare earth elements (REEs) are becoming more and more significant as they play crucial roles in many advanced technologies. Therefore, the development of optimized processes for their recovery, whether from primary resources or from secondary sources, has become necessary, including recovery from mine tailings, recycling of end-of-life products and urban and industrial waste. Ionic solvents, including ionic liquids (ILs) and deep-eutectic solvents (DESs), have attracted much attention since they represent an alternative to conventional processes for metal recovery. These systems are used as reactive agents in leaching and extraction processes. The most significant studies reported in the last decade regarding the recovery of REEs are presented in this review.

Expanding the Chemical Space of Benzimidazole Dicationic Ionic Liquids

Benzimidazole dicationic ionic liquids (BDILs) have not yet been widely explored in spite of their potential. Therefore, two structurally related families of BDILs, paired with either bromide or bistriflimide anions and bearing alkyl spacers ranging from C3 to C6, have been prepared. Their thermal properties have been studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), while their electrical properties have been assessed by cyclic voltammetry (CV). TG analysis confirmed the higher stability of the bistriflimide BDILs over the bromide BDILs, with minor variation within the two families. Conversely, DSC and CV allowed for ascertaining the role played by the spacer length. In particular, the thermal behavior changed dramatically among the members of the bistriflimide family, and all three possible thermal behavior types of ILs were observed. Furthermore, cyclic voltammetry showed different electrochemical window (C3(C1BenzIm)2/2Tf2N < C4(C1BenzIm)2/2Tf2N, C5(C1BenzIm)2/2Tf2N < C6(C1BenzIm)2/2Tf2N) as well as a reduction peak potential, shape, and intensity as a function of the spacer length. The results obtained highlight the benefit of accessing a more structurally diverse pool of compounds offered by dicationic ILs when compared to the parent monocationic ILs. In particular, gains are to be found in the ease of fine-tuning their properties, which translates in facilitating further investigations toward BDILs as designer solvents and catalysts.

Bioaccessibility and Cellular Uptake of Carotenoids Extracted from Bactris gasipaes Fruit: Differences between Conventional and Ionic Liquid-Mediated Extraction

Currently, on an industrial scale, synthetic colorants are used in many fields, as well as those extracted with conventional organic solvents (COSs), leading to several environmental issues. Therefore, we developed a sustainable extraction and purification method mediated by ionic liquids (IL), which is considered an alternative high-performance replacement for COSs. Carotenoids are natural pigments with low bioaccessibility (BCT) and bioavailability (BV) but with huge importance to health. To investigate if the BCT and cellular uptake of the carotenoids are modified by the extraction method, we conducted a comparison assay between both extraction procedures (IL vs. COS). For this, we used the Amazonian fruit Bactris gasipaes, a rich source of pro-vitamin A carotenoids, to obtain the extract, which was emulsified and subjected to an in vitro digestion model followed by the Caco-2 cell absorption assay. The bioaccessibility of carotenoids using IL was better than those using COS (33.25%, and 26.84%, respectively). The cellular uptake of the carotenoids extracted with IL was 1.4-fold higher than those extracted using COS. Thus, IL may be a feasible alternative as extraction solvent in the food industry, replacing COS, since, in this study, no IL was present in the final extract.

Structure-Property Relation of Trimethyl Ammonium Ionic Liquids for Battery Applications

Ionic liquids are attractive and safe electrolytes for diverse electrochemical applications such as advanced rechargeable batteries with high energy densities. Their properties that are beneficial for energy storage and conversion include negligible vapor-pressure, intrinsic conductivity as well as high stability. To explore the suitability of a series of ionic liquids with small ammonium cations for potential battery applications, we investigated their thermal and transport properties. We studied the influence of the symmetrical imide-type anions bis(trifluoromethanesulfonyl)imide ([TFSI]−) and bis(fluorosulfonyl)imide ([FSI]−), side chain length and functionalization, as well as lithium salt content on the properties of the electrolytes. Many of the samples are liquid at ambient temperature, but their solidification temperatures show disparate behavior. The transport properties showed clear trends: the dynamics are accelerated for samples with the [FSI]− anion, shorter side chains, ether functionalization and lower amounts of lithium salts. Detailed insight was obtained from the diffusion coefficients of the different ions in the electrolytes, which revealed the formation of aggregates of lithium cations coordinated by anions. The ionic liquid electrolytes exhibit sufficient stability in NMC/Li half-cells at elevated temperatures with small current rates without the need of additional liquid electrolytes, although Li-plating was observed. Electrolytes containing [TFSI]− anions showed superior stability compared to those with [FSI]− anions in battery tests.

Advantages of Electrochemical Polishing of Metals and Alloys in Ionic Liquids

Electropolishing of metal surfaces is a benign alternative to mechanical treatment. Ionic liquids are considered as green electrolytes for the electropolishing of metals. They demonstrate a number of advantages in comparison with acid aqueous solutions and other methods of producing smooth or mirror-like surfaces that are required by diverse applications (medical instruments, special equipment, implants and prostheses, etc.). A wide window of electrochemical stability, recyclability, stability and tunability are just a few benefits provided by ionic liquids in the title application. An overview of the literature data on electropolishing of such metals as Ti, Ni, Pt, Cu, Al, U, Sn, Ag, Nb, stainless steel and other alloys in ionic liquids is presented.

Determination of Chlorides in Ionic Liquids by Wavelength Dispersive X-ray Fluorescence Spectrometry

The synthesis of ionic liquids (ILs) usually involves two steps: (i) quaternization of a precursor followed by (ii) a salt metathesis reaction to introduce the desired anion. A consequence of the second step is that most ILs still contain some amount of the initial anion, often chloride. In this work, wavelength dispersive X-ray fluorescence (WDXRF) spectrometry is presented for the direct measurement of chlorides in ILs. The WDXRF settings were optimized, and the system was calibrated for the detection of chloride in several analogues of the commercially available IL Aliquat 336, [A336][X] (with X = I-, Br-, NO3 -, or SCN-). The Cl Kα intensity showed excellent linearity for samples with a conversion >0.80 (approximately Cl < 8000 ppm). Synthetic quality control samples showed that the instrumental error and deviations induced by the calibration procedure were small with maximum values of 1 and 5%, respectively. Detection and quantification limits depended strongly on the matrix (i.e., anion system and dilution) but were relatively low: 42-191 and 127-578 ppm Cl, respectively. Compared with other analytical techniques used for this purpose, the strengths of WDXRF include its ease of use, rapid measurements, the near absence of sample preparation steps, and versatility in terms of anion systems and chloride concentration range.

Selective separation of main flavonoids by combinational use of ionic liquid-loaded microcapsules from crude extract of Tartary buckwheat

For selective adsorption of main flavonoids from crude Tartary buckwheat extract (rutin, 0.021 mg/mL; quercetin, 0.030 mg/mL; and kaempferol, 0.011 mg/mL), new ionic liquid-based sorbents were successfully prepared by encapsulating [Bmim]Br and [Bmim]Pro in regular spherical non-magnetic and magnetic microcapsules with polysulfone content of 8%, respectively. After appropriate loading process, the microcapsules were comprehensively characterized by infrared spectroscopy, thermogravimetry analysis and scanning electron microscopy. Then the separation strategy was designed to separate rutin and quercetin from kaempferol by combinational use of two kinds of IL-loaded microcapsules (ILLMs). The effects of solid-liquid ratio of ILLMs and extract, pH, time and adsorption temperature were all investigated. The experimental data fit well with the quasi-second-order kinetics model and Langmuir model. After desorption, target flavonoids were well recovered and the ILLMs showed good stability. As the result, a new IL-based separation technology for main flavonoids from food crop was developed for the first time.

Application of Ionic Liquids for Batteries and Supercapacitors

Nowadays, the rapid development and demand of high-performance, lightweight, low cost, portable/wearable electronic devices in electrical vehicles, aerospace, medical systems, etc., strongly motivates researchers towards advanced electrochemical energy storage (EES) devices and technologies. The electrolyte is also one of the most significant components of EES devices, such as batteries and supercapacitors. In addition to rapid ion transport and the stable electrochemical performance of electrolytes, great efforts are required to overcome safety issues due to flammability, leakage and thermal instability. A lot of research has already been completed on solid polymer electrolytes, but they are still lagging for practical application. Over the past few decades, ionic liquids (ILs) as electrolytes have been of considerable interest in Li-ion batteries and supercapacitor applications and could be an important way to make breakthroughs for the next-generation EES systems. The high ionic conductivity, low melting point (lower than 100 °C), wide electrochemical potential window (up to 5-6 V vs. Li+/Li), good thermal stability, non-flammability, low volatility due to cation-anion combinations and the promising self-healing ability of ILs make them superior as "green" solvents for industrial EES applications. In this short review, we try to provide an overview of the recent research on ILs electrolytes, their advantages and challenges for next-generation Li-ion battery and supercapacitor applications.

A Review on Ionic Liquids-Based Membranes for Middle and High Temperature Polymer Electrolyte Membrane Fuel Cells (PEM FCs)

Today, the use of polymer electrolyte membranes (PEMs) possessing ionic liquids (ILs) in middle and high temperature polymer electrolyte membrane fuel cells (MT-PEMFCs and HT-PEMFCs) have been increased. ILs are the organic salts, and they are typically liquid at the temperature lower than 100 °C with high conductivity and thermal stability. The membranes containing ILs can conduct protons through the PEMs at elevated temperatures (more than 80 °C), unlike the Nafion-based membranes. A wide range of ILs have been identified, including chiral ILs, bio-ILs, basic ILs, energetic ILs, metallic ILs, and neutral ILs, that, from among them, functionalized ionic liquids (FILs) include a lot of ion exchange groups in their structure that improve and accelerate proton conduction through the polymeric membrane. In spite of positive features of using ILs, the leaching of ILs from the membranes during the operation of fuel cell is the main downside of these organic salts, which leads to reducing the performance of the membranes; however, there are some ways to diminish leaching from the membranes. The aim of this review is to provide an overview of these issues by evaluating key studies that have been undertaken in the last years in order to present objective and comprehensive updated information that presents the progress that has been made in this field. Significant information regarding the utilization of ILs in MT-PEMFCs and HT-PEMFCs, ILs structure, properties, and synthesis is given. Moreover, leaching of ILs as a challenging demerit and the possible methods to tackle this problem are approached in this paper. The present review will be of interest to chemists, electrochemists, environmentalists, and any other researchers working on sustainable energy production field.

Ionic Liquid-Derived Carbon-Supported Metal Electrocatalysts as Anodes in Direct Borohydride-Peroxide Fuel Cells

Three different carbon-supported metal (gold, platinum, nickel) nanoparticle (M/c-IL) electrocatalysts are prepared by template-free carbonization of the corresponding ionic liquids, namely [Hmim][AuCl4], [Hmim]2[PtCl4], and [C16mim]2[NiCl4], as confirmed by X-ray diffraction analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and Raman spectroscopy. The electrochemical investigation of borohydride oxidation reaction (BOR) at the three electrocatalysts by cyclic voltammetry reveals different behavior for each material. BOR is found to be a first-order reaction at the three electrocatalysts, with an apparent activation energy of 10.6 and 13.8 kJ mol−1 for Pt/c-IL and Au/c-IL electrocatalysts, respectively. A number of exchanged electrons of 5.0, 2.4, and 2.0 is obtained for BOR at Pt/c-IL, Au/c-IL, and Ni/c-IL electrodes, respectively. Direct borohydride-peroxide fuel cell (DBPFC) tests done at temperatures in the 25–65 °C range show ca. four times higher power density when using a Pt/c-IL anode than with an Au/c-IL anode. Peak power densities of 40.6 and 120.5 mW cm−2 are achieved at 25 and 65 °C, respectively, for DBPFC with a Pt/c-IL anode electrocatalyst.