Ionic liquids as surfactants

Problems of self-assembling in systems containing ionic liquids (ILs) are discussed. Main attention is paid to micellization in aqueous solutions of dialkylimidazolium ILs and their mixtures with classical surfactants. Literature data are reviewed, the results obtained by the authors and co-workers are presented. Thermodynamic aspects of the studies and problems of molecular-thermodynamic modeling receive special emphasis. It is shown that the aggregation behavior of dialkylimidazolium ILs is close to that of alkyltrimethylammonium salts (cationic surfactants) though ILs have a higher ability to self-organize, especially as it concerns long-range ordering. Some aspects of ILs applications are outlined where their common features with classical surfactants and definite specificity are of value.     

Ionic liquids in electrocatalysis

The performance of an electrocatalyst, which is needed e.g. for key energy conversion reactions such as hydrogen evolution, oxygen reduction or CO2 reduction, is determined not only by the inherent structure of active sites but also by the properties of the interfacial structures at catalytic surfaces. Ionic liquids(ILs), as a unique class of metal salts with melting point below 100 ℃, present themselves as ideal modulators for manipulations of the interfacial structures. Due to their excellent properties such as good chemical stability, high ionic conductivity, wide electrochemical windows and tunable solvent properties the performance of electrocatalysts can be substantially improved through ILs. In the current minireview, we highlight the critical role of the IL phase at the microenvironments created by the IL, the liquid electrolyte, catalytic nanoparticles and/or support materials, by detailing the promotional effect of IL in electrocatalysis as reaction media, binders, and surface modifiers. Updated exemplary applications of IL in electrocatalysis are given and moreover, the latest developments of IL modified electrocatalysts following the "Solid Catalyst with Ionic Liquid Layer(SCILL)" concept are presented.     

Ionic liquids in microemulsions

Ionic liquids (ILs) are being increasingly studied in many different chemical application areas, particularly in green solvent applications that are extending into microemulsion applications. We summarize herein these initial microemulsion formulations and applications where ILs are used as oil substitutes, water substitutes, co-surfactants (additives), and surfactants.     

New generation ionic liquids: cations derived from amino acids

Two families of a new generation of ionic liquids, in which the chiral cations are directly derived from naturally occurring alpha-amino acids and alpha-amino acid ester salts, have been obtained via very simple preparations.     

Ionic liquids from Car-Parrinello simulations, part I: liquid AlCl3

The properties of isolated AlCl3 clusters and the bulk system are investigated by means of static and dynamic electronic structure methods. We find important structural motifs with the edge connectivity dominant in a dimer and the corner connectivity dominant in a trimer. Furthermore, the trimer cluster exhibits an interesting ring structure with large cooperative effects relative to the dimer. Comparing the found structural motifs in isolated molecule calculations with the structure of the liquid allows us to determine the dominance of edge connectivity in the liquid. The size of the clusters present in the liquid indicates indeed that the dimer is the most abundant species, but there are also trimers, tetramers, and pentamers present. From the local dipole analysis both for the isolated clusters as well as for the liquid, further proof for the edge connectivity is given. However, all results point to the fact that there is also some small percentage of corner connectivity present that might be attributed to the most stable corner-connected cluster, namely the trimer. Importantly, we find that energetic considerations of isolated (static) clusters only do not represent the findings in liquid phase. Instead, a quantum cluster equilibrium approach or simulations are needed.     

Ionic liquids in analytical chemistry

Ionic liquids (ILs) are composed entirely of ions and they possess fascinating properties, including low volatility, tunable viscosity and miscibility, and electrolytic conductivity, which make ILs unique and useful for many applications in chemical analysis. The dramatic increase in the number of publications on ILs is indicative of the tremendous interest in this field from analytical chemists. This review summarizes recent efforts in the major subdisciplines of analytical chemistry, including extractions, gas chromatography, liquid chromatography, capillary electrophoresis, mass spectrometry, electrochemistry, sensors, and spectroscopy.     

Ionic liquids in sample preparation

Due to their unique properties, their good extractabilities for various target analytes, and the fact that many compounds are highly soluble in them, room-temperature ionic liquids (ILs) are used as promising alternatives to the traditional organic solvents employed in sample preparation. ILs have been used as extraction solvents for a wide range of analytes, from environmental contaminates to biomacromolecules and nanomaterials, and as dissolution solvents for various detection techniques. In this paper, the main applications of ILs in sample preparation are reviewed, and the problems and challenges in this area are described.     

Ionic liquids in confined geometries

Over recent years the Surface Force Apparatus (SFA) has been used to carry out model experiments revealing structural and dynamic properties of ionic liquids confined to thin films. Understanding characteristics such as confinement induced ion layering and lubrication is of primary importance to many applications of ionic liquids, from energy devices to nanoparticle dispersion. This Perspective surveys and compares SFA results from several laboratories as well as simulations and other model experiments. A coherent picture is beginning to emerge of ionic liquids as nano-structured in pores and thin films, and possessing complex dynamic properties. The article covers structure, dynamics, and colloidal forces in confined ionic liquids; ionic liquids are revealed as a class of liquids with unique and useful confinement properties and pertinent future directions of research are highlighted.     

Ionic liquids in separation techniques

The growing interest in ionic liquids (ILs) has resulted in an exponentially increasing production of analytical applications. The potential of ILs in chemistry is related to their unique properties as non-molecular solvents: a negligible vapor pressure associated to a high thermal stability. ILs found uses in different sub-disciplines of analytical chemistry. After drawing a rapid picture of the physicochemical properties of selected ILs, this review focuses on their use in separation techniques: gas chromatography (GC), liquid chromatography (LC) and electrophoretic methods (CE). In LC and CE, ILs are not used as pure solvents, but rather diluted in aqueous solutions. In this situation ILs are just salts. They are dual in nature. Too often the properties of the cations are taken as the properties of the IL itself. The lyotropic theory is recalled and the effects of a chaotropic anion are pointed out. Many results can be explained considering all ions present in the solution. Ion-pairing and ion-exchange mechanisms are always present, associated with hydrophobic interactions, when dealing with IL in diluted solutions. Chromatographic and electrophoretic methods are also mainly employed for the control and monitoring of ILs. These methods are also considered. ILs will soon be produced on an industrial scale and it will be necessary to develop reliable analytical procedures for their analysis and control.     

基于离子液体的绿色催化过程

离子液体为构建绿色催化反应过程提供了新途径.本文简要评述了离子液体在几个代表性催化反应中的研究进展,如CO2羰基化、烷基化、酯交换、氧化、CO2加氢、共聚以及PET降解等;分析讨论了离子液体的特点和优势,如提高反应活性、降低废物排放以及简化分离等,并对离子液体催化反应的未来发展方向进行了展望.     

Ionic liquids with herbicidal anions

Ionic liquids with herbicidal anions (named herbicidal ionic liquids—HILs) were synthesized and characterized. The combination of two active chemicals as the [cation][anion] form in a single moiety reduced the number of additional chemicals required per application. HILs ([cation][MCPA]) exhibited higher biological activity than currently used salts of MCPA, and involved pesticides of a multidirectional activity ([plant growth regulator][MCPA]). Acute toxicity of HILs could be controlled by appropriate selection of cation type. These salts had chemical and thermal stability, and showed substantially lower water solubility than starting herbicides, thus reducing soil and groundwater mobility.     

Ionic liquids: a pathway to environmental acceptability

Ionic liquids were initially proposed as replacements for conventional organic solvents; however, their chemistry has developed remarkably and offers unexpected opportunities in numerous fields, ranging from electrochemistry to biology. As a consequence of ionic liquids advancing towards potential and actual applications, a comprehensive determination of their environmental, health and safety impact is now required. This critical review aims to present an overview of the current understanding of the toxicity and environmental impact of the principal ionic liquid groups, and highlights some emerging concerns. Each cation type is considered separately, examining the significance of the biological data, and identifying the most critical questions, some yet unresolved. The need for more, and more detailed, studies is highlighted (176 references).     

Ionic liquids in microemulsions: Formulation and characterization

In the last few decades ionic liquids (ILs) have been widely considered as a “green solvents” and they are used in various fields. ILs can be used in the formation of microemulsion as a dispersed medium, polar domain and recently as a surfactant. In this particular review our discussion is about the novel IL-based aqueous and non-aqueous microemulsions which are quite fascinating and interesting research field for scientists. Synthesis of double and triple chain containing surface active ionic liquid (SAILs) and formation of microemulsion as a surfactant with ILs as a polar core have been elaborated in this review. ILs with a certain surface activity having long alkyl chain substituents can self-aggregate and form ILs microemulsion with high-temperature stability and temperature insensitivity. Characterization of these ILs in oil microemulsion and different ultrafast processes which are performed inside these characterized systems are documented very well. We have highlighted the similarities and differences between the nonaqueous microemulsions and the aqueous microemulsions. Addition of water and effect of temperature are quite important in case of the ILs containing microemulsions.     

Ionic liquids and CE combination

This paper reviews and discusses the analytical combination of ionic liquids (IL) with CE. On the one hand, it shows CE as a powerful technique to separate impurities from IL as well as being capable to determine physical and chemical properties of IL. On the other hand, it also shows how IL are employed in CE separations to enhance resolution, peak efficiency and peak symmetry. Specifically, IL are used as additives in CZE, NACE, and MEKC and as support coatings of the capillary wall in electrochromatography. The integrity of the IL in the electrophoretic system as well as the roles of the cations and anions of the IL in the electrophoretic separation are also discussed.     

Ionic liquids as hypergolic fuels

In propellant systems, fuels of choice continue to be hydrazine and its derivatives, even though they comprise a class of acutely carcinogenic and toxic substances which exhibit rather high vapor pressures and require expensive handling procedures and costly safety precautions. Only recently (2008), ionic liquids (salts with melting points less than 100 °C) with the dicyanamide anion were shown to exhibit hypergolic properties (instantaneous ignition when contacted with oxidizers (100 % nitric acid, WFNA)). Such liquids tend to have low volatilities, and high thermal and chemical stabilities, and often exhibit long liquid ranges which could allow utilization of these substances as bipropellant fuels over a variety of conditions. A new family of dicyanoborates is presented, which can be synthesized in water, with substituted N‐acyclic, N‐cyclic, and azolium cations has met nearly all of the desired important criteria needed for well‐performing fuels.     

Ionic liquids in solid-phase microextraction: a review

Solid-phase microextraction (SPME) has undergone a surge in popularity within the field of analytical chemistry in the past two decades since its introduction. Owing to its nature of extraction, SPME has become widely known as a quick and cost-effective sample preparation technique. Although SPME has demonstrated extraordinary versatility in sampling capabilities, the technique continues to experience a tremendous growth in innovation. Presently, increasing efforts have been directed towards the engineering of novel sorbent material in order to expand the applicability of SPME for a wider range of analytes and matrices. This review highlights the application of ionic liquids (ILs) and polymeric ionic liquids (PILs) as innovative sorbent materials for SPME. Characterized by their unique physico-chemical properties, these compounds can be structurally-designed to selectively extract target analytes based on unique molecular interactions. To examine the advantages of IL and PIL-based sorbent coatings in SPME, the field is reviewed by gathering available experimental data and exploring the sensitivity, linear calibration range, as well as detection limits for a variety of target analytes in the methods that have been developed.     

Ionic liquids in microextraction techniques

The tremendous potential of room temperature ionic liquids as an alternative to environmentally harmful ordinary organic solvents is well recognized. Due to their unique properties, such as low volatility, tunable viscosity and miscibility, and electrolytic conductivity, ionic liquids have attracted extensive attention and gained popularity in many areas of analytical chemistry including modern sample preparation techniques.     

Ionic liquids with perfluorinated alkoxyaluminates

Ionic liquids with the weakly coordinating perfluoroalkoxyaluminate anions, Al(ORF)4-, are obtained by a metathesis reaction of LiAl(ORF)4 and [bmim]Cl or [bmpyr]Cl in high yields. The compounds [bmim][Al(hfip)4] and [bmpyr][Al(hfip)4] have surprisingly low viscosities at elevated temperatures (60 degrees C) and an exceptionally high electrochemical window, which might render them useful for certain applications.     

Ionic liquids form ideal solutions

An understanding of the activity of a solute in solution is vital for utilising the full potential of a reactive species. In this work we determine the activity of metal salts in a variety of ionic liquids. Some solutions behave like classical non-polar solvents whereas other are practically ideal solutions up to 1 mol kg(-1) which allows standard redox potentials to be determined.     

Ionic liquids for tetraarylporphyrin preparation

In place of widely used dichloromethane, a series of ionic liquids, ILs, was employed as a reaction medium for the one-flask preparation of tetraarylporphyrins. The porphyrin yield in the IL was comparable to that in the dichloromethane, as long as both the water content and the fluidity were conditioned to be in the optimum state. When acidic IL, [C₄-SAbim][CF₃SO₃] possessing a sulfonic acid moiety was used as the reaction medium, nothing but a black tarry by-product was obtained due to its strong acidity. However, using the acidic IL in a biphasic mode together with dichloromethane enabled porphyrins to form, even at a high reactant concentration. Furthermore, the phase-separated acidic IL was reusable for at least 10 times without any loss of catalytic activity.