Common Ionic Liquids Research Articles

MD simulations of mixtures of charged Gay-Berne and Lennard-Jones particles as models of ionic liquid crystals

ABSTRACTWe use a simple model of Ionic Liquid Crystals represented by mixtures of positively charged ellipsoidal Gay-Berne particles and negatively charged spherical Lennard-Jones particles. This system will model common ionic liquid crystals, for example those based on symmetrically substituted imidazolium halide salts. The system has been studied using Molecular Dynamics simulations for three different values of the scaled charge (0.0, 0.5, 2.0) at two different number densities (0.30, 0.36) in the NVT ensemble. Radial distribution functions and orientational order parameters have been calculated in order to get more insights on the phase segregation and organization of domains together with a comparison of the van der Waals and coulombic terms of the total interaction energy.

Thermal rheology and microstructure of shear thickening suspensions of silica nanoparticles dispersed in the ionic liquid [C4mim][BF4

A stable dispersion of silica nanoparticles in a common ionic liquid [C4mim][BF4] that exhibits significant shear thickening is formulated by controlling the strength of hydrogen bonding between the nanoparticle surface and the anion of [C4mim][BF4]. Colloidal stability is demonstrated to be due to the formation of solvation layers, the properties of which are determined by scattering measurements. Time-temperature superposition measurements and the onset of yielding behavior in steady shear indicate the increase of particle-particle attraction and loss of stability of colloidal dispersions above 30 °C. Small angle neutron scattering and dynamic light scattering measurements confirm the reduction in solvation layering at elevated temperatures, leading to a transition from stable dispersion to unstable, attractive gel with increasing temperature (i.e., an inverse melting transition). It is demonstrated how controlling specific surface-anion interactions through chemical functionality can be used to formula...

Synthesis and characterization of ionic liquid based mixed matrix membrane for acid gas separation

This work evaluates the potential of a mixed matrix membrane synthesized with 1-ethyl-3-methylimmidazolium-ethylsulphate [EMIM][EtSO4] a common ionic liquid (IL) blended with poly (ether-block-amide) (PEBA) elastomer to separate either hydrogen sulphide (H2S) or carbon dioxide (CO2) or both acid gasses (H2S and CO2) from its streams. Layer-by-layer deposition method was used to synthesize the defect-free blended membrane. The prepared membranes were characterized by field emission scanning electron microscopy (FESEM), fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) for physical and thermal properties. Several experiments were conducted by varying pressure and ionic liquid concentration at normal temperature for pure gases (H2S/CO2/CH4/Air). The presence of ionic liquid (5 wt%) shows higher H2S permeability of 540 barrer and a comparatively low CO2 permeability of 55 barrer at pressure of 7 kg/cm2 through the blended membrane due to higher H2S solubility (1.5 times more than CO2) in the same IL. The trend of permeability for different single gases was observed in the pattern following: H2S > CO2>Air > CH4. Ideal selectivity was 66.0 for H2S/CH4 and 24.0 for H2S/Air which is much higher than those for CO2 binary mixture such as CO2/CH4 (4.6) and CO2/Air (2.4). The addition of ionic liquid in the membrane matrix enhances the permeability of acid gases compared to pure PEBA membrane. Robeson’s diagram also shows the promising trends for the experimental points either crossing the upper bound line or getting nearer which highlight the pivotal role of IL in blended membrane.

Solubilities and Thermodynamic Properties of Carbon Dioxide in Guaiacol-Based Deep Eutectic Solvents

In this work, the solubility data of CO2 in three kinds of guaiacol-based deep eutectic solvents (DESs) at 293.15, 303.15, 313.15, and 323.15 K and pressures below 600.0 kPa were determined. The DESs were prepared from guaiacol and quaternary ammonium salts (QASs, including choline chloride, acetylcholine chloride, and diethylamine hydrochloride) with a molar ratio of guaiacol to QAS of 3:1, 4:1, and 5:1. Henry’s law was used to correlate the solubility data, and the thermodynamic properties, such as standard Gibbs free energy, standard enthalpy, and standard entropy of these systems were derived. The solubility of CO2 increased with increasing molar ratio of guaiacol to QAS in each kind of DES. The dissolution enthalpies were negative at all conditions. The dissolution capacities of present DESs for CO2 were further compared with those of other DESs and several common ionic liquids.

A transparent solid-state ion gel for supercapacitor device applications

A feasibility study of the synthesis of gel polymer electrolytes based in methyl methacrylate (MMA) and 1-vinyl-2-pyrrolidone (VP) using [HEMIm][BF4] as common ionic liquid has been done. A novel PVP/[HEMIm][BF4] solid-state and self-standing ion gel electrolyte has been successfully prepared. The thermal degradation of PVP/[HEMIm][BF4] ion gel occurs in two steps with the first one at above 200 °C and the main one over 390 °C. This solid-state ion gel is transparent, showing an optical transmittance with a maximum value of 90% in the visible wavelength region from 370 to 770 nm. The synthesized PVP/[HEMIm][BF4] solid-state ion gel exhibits an electrochemical stability window of ca. 5.0 V and an acceptable ionic conductivity of σ = 5.7 10−3 S cm−1 at room temperature. A symmetrical pseudocapacitive supercapacitor has been assembled and characterized using this PVP/[HEMIm][BF4] solid-state ion gel—glass/ITO/PEDOT/PVP/[HEMIm][BF4]/PEDOT/ITO/glass. It is found that the supercapacitor shows a typical areal specific capacitance of 3.1 mF cm−2, a maximum energy density of 2.5 μWh cm−2, and an areal specific power density of ca. 1 mW cm−2.

Characterization of inclusion complexes of organic ions with hydrophilic hosts by ion transfer voltammetry with solvent polymeric membranes

The quantitative characterization of inclusion complexes formed in aqueous phase between organic ions and hydrophilic hosts by ion-transfer voltammetry with solvent polymeric membrane ion sensors is studied, both in a theoretical and experimental way. Simple analytical solutions are presented for the determination of the binding constant of the complex from the variation with the host concentration of the electrochemical signal. These solutions are valid for any voltammetric technique and for solvent polymeric membrane ion sensors comprising one polarisable interface (1PI) and also, for the first time, two polarisable interfaces (2PIs). Suitable experimental conditions and data analysis procedures are discussed and applied to the study of the interactions of a common ionic liquid cation (1-octyl-3-metyl-imidazolium) and an ionisable drug (clomipramine) with two hydrophilic cyclodextrins: α-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. The experimental study is performed via square wave voltammetry with 2PIs and 1PI solvent polymeric membranes and in both cases the electrochemical experiments enable the detection of inclusion complexes and the determination of the corresponding binding constant.

Valence band photoelectron spectra of [EMIM][BF4] ionic liquid vapor: Evidences of electronic relaxation

Experimental ultraviolet photoelectron spectra of [EMIM][BF4] molecules were recorded and analyzed. The low binding energy tail of the HOMO peak in the UPS spectrum is about 7.5eV, in agreement with previous estimations of the liquid phase HOMO-LUMO gap. These gas-phase spectra reveal detailed information about the electronic structure of the molecules of this common ionic liquid and enable comparison with ab initio calculation methods like density functional theory (DFT) and Møller–Plesset perturbation theory (MP2). The ab initio calculations are able to explain most of the features in the spectra.

(Invited) Ferrocene-Modified Electroactive Ionic Liquids to Prevent Self-Discharge of Redox-Active Electrolyte Capacitors

Introduction: Redox-active electrolyte supercapacitors (RESC) are obtained by dissolving electroactive species in the electrolyte as a mean to increase the energy density of carbon-based capacitors.[1-3] RESCs are most often using aqueous electrolytes due to a higher solubility of redox molecules in water compared to organic solvents. For the same reason, ionic liquids (ILs) have not been extensively studied as electrolyte in RESCs despite the fact that they could present the advantage of an increased maximum operating voltage. So far, a compromise must be done between fast transport and high solubility of the redox molecule (obtained in aqueous electrolytes) and a high cell voltage (obtained with organic solvents and ionic liquids). RESCs may benefit from the development of electroactive electrolytes specifically formulated for this purpose, and which should i) allow high concentrations in redox species, ii) present a high maximum voltage, and iii)include a self-discharge suppression mechanism. This work demonstrates that electroactive ionic liquids, in which a redox moiety is covalently linked to one of the ions, may be used to meet these challenges. Experimental: Electroactive ILs were obtained by modifying the common ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [EMIm][NTf2], with ferrocene. The ferrocene redox unit was linked either to the cation ([FcEIm][NTf2]) or the anion ([EMIm][FcNTf]) (Fig. 1). The ionic liquids were then used as the electrolyte in symmetrical cells using activated carbon (80 wt.%) as the active material. The cells were studied to evaluate the energy density and self-discharge to evaluate the effect of the ionic liquid structure on performance. Results and discussion: Cyclic voltammetry was used in first place to evaluate the response of the cells containing an electrolyte composed of 80 wt.% of either [EMIm][NTf2], [FcEIm][NTf2] or [EMIm][FcNTf] ILs in acetonitrile. The oxidation and reduction of the ferrocenyl unit on the IL results in the presence of peaks on the CV curves (Fig. 1). These faradaic reactions increase the amount of energy stored in the device by accumulating charges in the electrolyte which is a the heart of redox-active electrolyte supercapacitors. Galvanostatic charge-discharge (GCD) experiments were carried out to evaluate the energy density of the devices employing the electroactive ionic liquids. The gravimetric specific energy values, based on total weight of both electrodes for the RESCs presented here, are (at I = 2 mA) 13.2 and 9.0 Wh kg-1 for [EMIm][FcNTf] and [FcEIm][NTf2], respectively. These values represent a significant increase from equivalent double-layer devices using either the unmodified ionic liquid [EMIm][NTf2] (Wg = 7.2 Wh kg-1) or the conventional electrolyte 1 M TBAP in CH3CN (Wg = 6.4 Wh kg-1). Self-discharge (SDC) represents a major issue with RESCs because a shuttle discharge mechanism (reduction oxidized species at the negative electrode) adds up to the diffusion-based SDC.[4] The profiles of individual electrodes demonstrate that after an initial decrease due to ohmic drop, the potential of the positive electrode remained constant for three hours. SDC suppression in RESC based on redox IL with the Fc-modified anion is explained by the formation of a film at the positive electrode upon oxidation of [FcNTf]- to [Fc+NTf-]0that prevent the shuttling of the charged species to the negative electrode. Conclusions: The functionalization of an ionic liquid with ferrocene led to high concentrations of redox moieties in the electrolyte (2.4 M) and a large maximum operating voltage (2.5 V). An energy density of up to 13.2 Wh per kg (both electrodes) was obtained which represents an 83 % increase vs. the unmodified ionic liquid. When the ionic liquid’s anion is modified with ferrocene, the self-discharge at the positive electrode is fully suppressed due to the deposition of a film on the electrode. While the rate dependency of the specific energy and stability could be improved, these findings suggest that electroactive ionic liquids are particularly well-suited for use in redox-active electrolyte supercapacitors. References 1) E. Frackowiak et al. Chemsuschem, 5 (2012) 1181-1185; 2) S. Roldan et al. Angew. Chem. Int. Ed., 50 (2011) 1699-1701; 3) S.T. Senthilkumar et al. J. Mater. Chem. A, 1 (2013) 12386-12394; 4) L.B. Chen et al. Energy Environ. Sci., 7 (2014) 1750-1759. Figure 1

"Solvate" Ionic Liquids, "Solvent-in-salt" Ionic Liquids, and "Deep Eutectic" Ionic Liquids. What are the Relationships - and the Ionicities?

Recently, in the search for alkali metal-containing electrolytes with higher conductivities than available in common ionic liquid systems, some interesting systems have shown up. The most interesting ones are those that also have wide electrochemical windows and high alkali metal transport numbers, and when non-flammability is also included, the interest has indeed run high1 , 2. The aqueous systems ("water-in-salt" electrolytes) are the most recent on the scene, and are of special importance for obvious reasons, but they are closely related in principle to other also successful systems developed independently in different labs and so given different designations. All are characterized by being extremely concentrated in ions but modulated in properties by the presence of one or other type of molecular constituent in molar proportions up to 50% and in some cases greater. Some other examples, are the "solvate ionic liquids" of the Watanabe3 and Henderson4 laboratories in which Li+ ions exist 1:1 with polyglyme molecules, and the "deep eutectic" liquids used by Abbott and coworkers5 for the electrodeposition of higher valent metals, where again the autoionization of the multivalent ions is induced by equimolar proportions of a favorable (often oxygenic) ligand. Both are special cases of the more general "solvent-in-salt" class of electrolyte from the Chen-Armand collaboration6. In this talk we will review the relationship between these different types of ionic systems and examine their relative ionicities, ionic mobilities, and other key characteristic properties. 1 Suo, L. et al. “Water-in-salt” electrolyte enables high-voltage aqueous lithium-ion chemistries. Science 350, 938-943 (2015).2 Suo, L. et al. Advanced High Voltage Aqueous Li-ion Battery Enabled by “Water-in-Bisalt” Electrolyte. Angewandte Chemie Int. Ed. (printed online) DOI (2016).3 Ueno, K. et al. Glyme−Lithium Salt Equimolar Molten Mixtures: Concentrated Solutions or Solvate Ionic Liquids? J. Phys. Chem. B 116, 11323-11331 dx.doi.org/11310.11021/jp307378j (2012).4 Henderson, W. A. Glyme-lithium salt phase behavior. . J. Phys. Chem. 110, 13177-13183 (2006).5 Abbott, A. P., Barron, J. C., Rydere, K. S. & Wilson, D. Chem.–Eur. J. 13, 6495. (2007).6 Suo, L., Hu, Y.-S., Armand, M. & Chen, L. A new class of Solvent-in-Salt electrolyte for high-energy rechargeable metallic lithium batteries. . Nat. Commun. 4, 1481 (2013).

Evaluation of density, viscosity, surface tension and CO2 solubility for single, binary and ternary aqueous solutions of MDEA, PZ and 12 common ILs by using artificial neural network (ANN) technique

In this study, density, viscosity, surface tension and CO2 solubility for single, binary and ternary aqueous solutions of N-methyldiethanolamine (MDEA), piperazine (PZ) and 12 common ionic liquids (ILs) were predicted by applying artificial neural network (ANN) technique. The input data included operating temperature (293.15–373.15K) and pressure (0.177–3938.400kPa) in addition to the weight fractions of aqueous solutions of MDEA, PZ and ILs which were respectively in the range of (0.0–1.0), (0.0–0.09) and (0.0–1.0) as well as the molecular weight of ILs (148.18–505.00g/mol) and their acentric factors (0.325–1.261). More than 2600 experimental data points for density, viscosity, surface tension and CO2 solubility were collected from literature. By using the Levenberg-Marquardt back-propagation and tan-sigmoid as learning algorithm and transfer function, respectively, four ANN models were examined to treat these data. It was found that the best ANN architectures for predicting these properties were respectively (7:3:0:1), (7:6:0:1), (7:4:0:1) and (7:10:0:1). The calculated properties were compared with the corresponding experimental data which indicated a negligible error.

Amphiphile self-assembly based on ionic liquids

Ionic liquids (ILs), as a class of compounds composed of ions with melting points at or near room temperature, have unusual physicochemical properties including low volatility, high temperature stability, high ionic conductivity and easy recyclability. Thus ILs have been applied widely in the range of organic synthesis, catalysis, chromatography, analytical chemistry, biochemistry and so on. Perhaps the most unique capability of ILs is to support the self-assembly of amphiphiles. Due to the extraordinary properties of ILs, the self-assembled aggregates based on ILs have attracted a lot of attentions during the last decades. ILs are now not only considered as important alternative solvents, but also as materials with unique and tuneable properties which can be easily adjusted by suitable selection of cations and anions for a specific function. Based on the unique designability of ILs, it will be expected to achieve the controllability of the nanostructures and properties of IL-based self-assembled aggregates by tailoring the structures of ILs. Here, the research progress of amphiphile self-assembly based on ILs was reviewed. Firstly, the room-temperature ILs can be considered as solvents to participate in the self-assembly process and classified as protic ionic liquids (PILs) and aprotic ionic liquids (AILs), respectively. Up to now, a number of AILs based on imidazolium cations and many alkylammonium PILs, such as ethylammonium nitrate (EAN), have been used as self-assembly media to support amphiphile to form various aggregates including micelles, vesicles, microemulsions and liquid crystals. Different from AILs, the PILs can build up hydrogen-bonding networks which are similar to water molecules due to their protic nature and general properties. The different solvent properties of PILs and AILs have significant influence on the aggregation behavior of amphiphilic molecules. Secondly, the long chain analogues of common ionic liquids, named as surfactive ionic liquids (SAILs), could possess inherent surface active properties and self-assemble to form different aggregates with specific structures, shapes and properties in aqueous solutions like traditional amphiphilic molecules. Various long-chain SILs with different cationic headgroups based on imidazolium, pyrrolidinium, piperidinium etc. have been synthesized and investigated. Except for cationic SAILs, the aggregation behaviors of a series of anionic SAILs based on organic surfactant anions and imidazolium cations have also been studied to expand the application of SAILs in the filed of colloid and interface chemistry. SILs, as a novel kind of surfactants, can self-assembly into different kinds of aggregates driven by intermolecular interactions including hydrophobic interaction, electrostatic interaction, hydrogen bonding and so on. Thus, the type of cations, the alkyl chain length, and the nature of the counterions have key effect on the aggregation behavior of SAILs. Thirdly, the physicochemical properties of the given surfactant solutions can also be modified by the addition of external ionic liquids. Due to the tailoring properties of ILs, “task-specific” ILs (TSILs) have emerged by introducing functional groups as a part of substituent to impart a particular capability to ILs and further modulate the aggregation behavior of surfactant solutions. This is also a practical way for us to determine the role of one specific intermolecular interaction on the self-assembly process. The present work summarized the amphiphile self-assembly based on ILs, including room-temperature ILs as solvents, long-chain ILs as amphiphiles and ILs as external additives. Our aim is to establish the dependence of aggregation behavior of amphiphiles on the unique structures of ILs. This review is helpful to achieve the controllability and functionalization of traditional self-assembled aggregates by the incorporation of functional ILs.

Thermogravimetric measurement of deep eutectic solvents vapor pressure

Knowledge of volatility of solvents in general and ionic liquids analogues in particular is crucial for thermodynamic modelling and proper solvent selection. In this study, the vapor pressure of a selected set of ionic liquids analogues known as deep eutectic solvents (DES) was investigated by thermogravimetric analysis (TGA). The experimental measurements were conducted for the practical temperature range of 343.15 to 393.15K. In general, measurements revealed that DESs have low but detectable vapor pressure. Compared to some common ionic liquids, DESs have higher vapor pressure. It is interesting to know that the vapor pressure-temperature relationship of DESs is more complex than that of molecular liquids as well as that of most ionic liquids. The conventional Antoine model was not able to explain the variation of vapor pressure with temperature. However, the vapor pressure was found to exhibit a noticeable trend with the DES critical temperature which was estimated theoretically. The Wagner vapor pressure model was able to predict the vapor pressure with an average %AAD of 2.89%.

Long-Range Ordering of Ionic Liquid Fluid Films.

We report the transformation of ionic liquid films from isotropic bulk to a fluid-ordered state over micrometer length scales. Data from infrared and nonlinear spectroscopy measurements show clear transitions that, for varying ionic liquids, occur over time frames of 10 min to 2 h. These maturation times depend linearly on the chosen ionic liquids' bulk viscosities. Interestingly, the ionic liquids do not form solids upon ordering but do exhibit strong preferential alignments of molecules that persist throughout the fluid films' thicknesses. Our measurements characterize this ordering process and show that it is largely insensitive to substrate surface chemistry or small amounts of absorbed water. Additional experiments show the transition is observed across several of the most common ionic liquid cations and that the process is completely reversible. The driving force for this organization is attributed to electrostatic and steric forces combined with a slow shearing of the viscous ionic liquid. These interactions work together to slowly bring the molecules within the film to a preferred, global orientation. The physical length and time scales of this transformation are unexpected and intriguing and invite additional studies to develop an understanding and control of ionic liquid materials' behavior, particularly near surfaces, to benefit their uses in lubrication, capacitive energy storage, and heterogeneous catalysis.

Synthesis of 5-tert-butyl-1,2,3-trimethylbenzene catalyzed by [Et3NH]Cl–AlCl3

Common Lewis acids and Lewis acidic ionic liquid catalysts were applied in the synthesis of 5-tert-butyl-1,2,3-trimethylbenzene from 1,2,3-trimethylbenzene and 2-chloro-2-methylpropane, where [Et3NH]Cl–AlCl3 demonstrated the most promising catalytic potential. The effects of reaction time, temperature, catalyst composition and dosage have been systematically studied in the presence of [Et3NH]Cl–AlCl3. The maximum selectivity of 90.32% was achieved upon heating at 10°C for 5 h with a mass fraction of [Et3NH]Cl–AlCl3 to 1,2,3-trimethylbenzene of 10%. Activity of the ionic liquid catalyst remained high after several cycles.

Ionic liquid-doped polyaniline and its redox activities in the zwitterionic biological buffer MOPS

The electropolymerization of aniline in several common imidazolium-based ionic liquids has been accomplished successfully with the potentiodynamic method. Considering the fact that imidazolium-based ionic liquids are acidic, they have been selected as the electrolyte for the electropolymerization of aniline, eliminating the usage of extra inorganic or organic acids. The ionic liquids not only serve as the reaction media, exerting the unique favorable π-π interactions between the imidazolium rings and benzene rings of aniline monomer or the growing polymer, but also act as the dopants to render different properties to the resulting polyaniline. Among the tested imidazolium-based ionic liquids, [BMIM][BF4], [BMIM][PF6], [BMIM][NTf2], [EMIM][ES] and [HMIM][FAP], polyaniline doped by the hydrophilic ionic liquid [BMIM][BF4] displays the good electrochemical responses in the biologically important MOPS (3-(N-Morpholino)-propanesulfonic acid) solution with 2.34×10−3M of sulfuric acid additive. NMR, UV–vis and electrochemical impedance experiments were performed to further characterize the polyaniline/[BMIM][BF4] composite. In contrast, polyaniline that is doped by the hydrophobic ionic liquid [BMIM][PF6] is electroactive in the MOPS solution in the absence of the acid additive, with a pH of 5, extending the working pH range of polyaniline, which is typically electroactive in the solutions with the pH values less than 3. It is suggested that the effective hydrogen bonding interactions between BF4 anion and water facilitate its hydrolysis in the microenvironment of the polymer backbone to provide the acidic protons, which are beneficial to the adjustment of the microenvironments of the polyaniline system and thus renders its observed well-resolved reversible pair of redox peaks in the MOPS solution. PF6 anion, on the other hand, with its larger size and less basicity, has the weaker interaction with water, thus releasing the protons in a relatively slow manner, which gives some “buffer” capacities and rendering the [BMIM][PF6]-doped polyaniline electroactive in the pH 5 of MOPS solution without the acid additive.

Understanding the Solubility of Acetaminophen in 1-n-Alkyl-3-methylimidazolium-Based Ionic Liquids Using Molecular Simulation.

During the manufacturing of pharmaceutical compounds, solvent mixtures are commonly used, where the addition of a cosolvent allows for the tuning of the intermolecular interactions present in the system. Here we demonstrate how a similar effect can be accomplished using a room temperature ionic liquid. The pharmaceutical compound acetaminophen is studied in 21 common ionic liquids composed of a 1-n-alkyl-3-methylimidazolium cation with 1 of 7 anions. Using the acetate anion, we predict a large enhancement in solubility of acetaminophen relative to water. We show how this is caused by a synergistic effect of favorable interactions between the ionic liquid and the phenyl, hydroxyl and amide groups of acetaminophen, demonstrating how the ionic liquid cation and anion may be chosen to preferentially solvate different functional groups of complex pharmaceutical compounds. Additionally, while the use of charge scaling in ionic liquid force fields has previously been found to have a minute effect on ionic liquid structural properties, we find it appreciably affects the computed solvation free energy of acetaminophen, which in turn affects the predicted solubility.

Enhancing extraction ability by rational design of phosphoryl functionalized ionic liquids and mechanistic investigation on neodymium (III) extraction

AbstractFour ionic liquids (ILs): 3-(diethoxyphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3P(OEt)2][PF6] (IL-1), 3-(ethoxyphenylphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3PPh(OEt)][PF6] (IL-2), 3-(diphenylphosphoryl)propyl triphenylphosphinium hexafluorophosphate [Ph3PC3P(Ph)2][PF6] (IL-3), and 3-(diethoxyphosphoryl)propyl triphenylphosphinium bis(trifluoromethanesulfonyl)imide [Ph3PC3P(OEt)2][NTf2] (IL-4) were synthesized and characterized by IR and 31P, 1H, 13C NMR spectroscopy. The liquid-liquid extraction of neodymium(III) by these phosphorus functionalized ionic liquids (PFILs) diluted with common room temperature ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C6mim][NTf2] was studied. The extraction percentage of Nd(III) was measured as a function of various parameters, such as the initial pH of aqueous phase, equilibrium time, temperature, and concentration of PFIL extractant. The influence of the nature of diluents and salting-out reagents on extraction was also investigated. The results indicated that the extraction process was exothermical and the extraction percentage of Nd(III) by IL-1 was the highest among the PFILs investigated. A possible metal complexation mechanism was proposed for the present PFIL/IL extraction system. And the loaded Nd(III) ions by PFIL could be stripped completely from the ionic liquid phase by 1 mol/L nitric acid.

Life-Cycle Perspectives on Aquatic Ecotoxicity of Common Ionic Liquids.

This study compares the aquatic ecotoxicity impacts of production- and use-phase release of five common ionic liquids (ILs). Integrating toxicity data, physical properties, and fate and transport parameters with the USEtox model, we report, for the first time, the freshwater ecotoxicity characterization factors for [Bmim](+)[Br](-), [Bmim](+)[Cl], [Bmim](+)[BF4](-), [Bmim](+)[PF6](-), and [BPy](+)[Cl](-) as 624, 748, 823, 927, and 1768 CTUe/kg, respectively. IL Production life cycle inventories were modeled and utilized to estimate their production-side ecotoxicity impacts. Literature on environmental aspects of ILs propagates either their green characteristics (no air emissions and high recyclability) or their nongreen aspects due to toxicity concerns of their release to water. This study adds a third dimension by showing that the upstream ecotoxicity impacts of producing ILs could outweigh the potential ecotoxicity impacts of direct release during use. Furthermore, for the studied ILs, an average of 83% of ecotoxicity impacts associated with their production can be linked to chemicals and materials released during the upstream synthesis steps, while only 17% of ecotoxicity impacts relate to life-cycle energy consumption. The findings underscore the need to develop sustainable synthesis routes, tight control over chemical releases during production, and careful selection of precursor materials and production processes.

Application of Alkylphosphate Ionic Liquids as Lubricants for Ceramic Material

Three kinds of alkylphosphate ionic liquids were synthesized and evaluated as lubricants for silicon nitride–silicon nitride and silicon nitride–zirconium oxide contacts under different test conditions. The results show that silicon nitride substrates exhibit better load-bearing capability compared with zirconium oxide because of their special physical properties and chemical activity. Meanwhile, alkylphosphate ionic liquids exhibit better friction-reducing and antiwear properties than the common ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (L-P104) and the base oil poly(α-olefin) (PAO). Scanning electron microscopy and X-ray photoelectron spectroscopy results indicate that tribochemical reactions occur between the alkylphosphate ionic liquids and ceramic substrates without corrosion during the friction process. When this is combined with the test results for contact angles, it can be concluded that the excellent lubricity of alkylphosphate ionic liquids is ascribed to the synergistic effe...

Intramolecular Excimer Formation Dynamics of 1,3-Bis-(1-pyrenyl)propane within 1-Butyl-3-methylimidazolium Hexafluorophosphate and Its Polyethylene Glycol Mixtures.

Mixtures of ionic liquid with polyethylene glycol (PEG) have shown interesting features as solubilizing media. Intramolecular excimer formation dynamics of 1,3-bis-(1-pyrenyl)propane [1Py(3)1Py] is investigated within mixtures of a common and popular ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) with PEGs of average molecular weight (MW) 200 (PEG200), average MW 400 (PEG400), number-average MW Mn 570-630 (PEG600), and number-average MW Mn 950-1050 (PEG1000) over the complete composition range at a 10° interval in the temperature range 10-90 °C. Irrespective of the composition of the medium and the temperature, excited-state intensity decay of the excimer fluorescence best fits to a three-exponential decay function, suggesting the presence of one excited-state monomer and two kinetically distinguishable excimers where both excimers are populated simultaneously by the excited monomer with no interconversion between the two excimers. In neat PEGs for temperatures ≤ 50 °C, intensity decay data of monomer fluorescence best fits to a single-exponential decay function, which implies the dissociation of both excimers back to the monomer to be insignificant. As the temperature is increased, the fits become closer to a double-exponential decay function, implying dissociation of one of the excimers to become significant. In neat [bmim][PF6], while a double-exponential decay function is required to fit the monomer excited-state intensity decay data at lower temperatures, three exponentials are required to satisfactorily fit the data at higher temperatures, suggesting both excimers significantly dissociate back to the monomer at higher temperatures within the ionic liquid. Within long-chain PEG-containing ([bmim][PF6] + PEG) mixtures, PEG as opposed to [bmim][PF6] controls the excimer formation dynamics by supposedly wrapping around the excimer, thus hindering dissociation back to the monomer. The overall rate constant of the excimer formation within ([bmim][PF6] + PEG) mixtures is found to scale better with the microviscosity rather than the bulk viscosity of the mixtures.