Single Ionic Liquid Research Articles

How to detect possible pitfalls in ePC-SAFT modelling: Extension to ionic liquids

An ion-specific electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) has been developed to describe the thermodynamic and transport properties of ionic liquids (ILs) for developing IL-based technologies to separate CO2 from gas mixtures. However, as it has been pointed out previously, SAFT-based models can lead to a pitfall, manifesting as an additional fictitious liquid-liquid critical line connected to an additional mechanically stable critical point when modeling pure substances. In this work, a method for detecting a pitfall in ILs was developed, where an expression with ionic term for calculating the critical point with ePC-SAFT was derived and an algorithm for detecting the additional fictitious phase equilibrium for ILs was proposed. The pitfall occurrence for an extended set ILs taken from our previous work was investigated. It shows that a pitfall occurs only for one single IL among all 96 ILs in the temperature and pressure range of interest. For [C8mpy][BF4], at 290.27–291.78 K, a pitfall may occur at the pressures of interest; at 273.15–290.20 K, it may occur at any given pressure. The ion-specific ePC-SAFT parameters for [C8mpy]+ may therefore need to be modified in the future when more reliable experimental results are available for parameter fitting.

Simultaneous preconcentration of toxic elements in eye makeup products through single drop ionic liquid based non-dispersive microextraction method using narrow glass column: Multivariate application

An innovative and simple single drop ionic liquid based non-dispersive microextraction (SDILNDµE) method has been proposed for enrichment of arsenic (As), cadmium (Cd), nickel (Ni) and lead (Pb) in eye makeup products prior to analysis with electrothermal atomic absorption spectrometry (ETAAS). A narrow glass column was used to provide more contact area by enhancing the phase transfer ratio between two media (extractive and aqueous). Improved recoveries of the hydrophobic complexes of metals and metalloid with ammonium pyrrolidinedithiocarbamate (APDC) extracted into the 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim] [PF6] were achieved. Several parameters were systematically optimized. At optimum conditions, limit of detection (LOD) for Cd, As, Pb and Ni was attained as 0.086, 0.049, 0.126 and 0.262 μgL−1, correspondingly with relative standard deviation < 5%. Spike recovery study was carried out in the real samples to check the precision of proposed methodology. The proposed method was productively practiced on the real sample for simultaneous enrichment of toxic elements (As, Ni, Pb and Cd) in eye makeup products. Principal component analysis (PCA) was applied to assess the various levels of toxic elements as chief causes of variation in the data sets and to find the relation among samples (eye makeup products) and toxic elements (variables). Hierarchical cluster analysis (HCA) was used to explore the grouping of various eye makeup products on the basis of toxic element contents as additional statistics to the output attained by PCA.

Biopolymer based ionogels as active layers in low-cost gas sensors for electronic noses

Electronic noses are formed by an array of gas sensors connected to a pattern recognition computational system and have been applied in a wide range of fields. In this work we describe chemiresistive gas sensors produced by the deposition of ionogels onto metallic interdigitated electrodes. Three ionogels were formed by a single ionic liquid, EMIMDCA, and three different biopolymers (gelatine, agar and sodium alginate). As a proof of concept, this nose was tested with five organic volatile compounds (methanol, ethanol, acetone, ethyl acetate and hexane) having different polarities and different room temperature vapour pressures. Principal components analysis (PCA) was used for dimensionality reduction and to represent the separation of these solvents. Applying five different machine learning classification algorithms and two cross-validation methods (leave-one-out and K-fold), the accuracy of the e-nose was evaluated in discriminating the solvents studied. Hit rates of at least 96% were obtained.

Room‐Temperature Reversible and Nonvolatile Tunability of Electrical Properties of Cr‐Doped In2O3 Semiconductor Thin Films Gated by Ferroelectric Single Crystal and Ionic Liquid

AbstractIntegration of different functional materials into a device in which the physical properties can be tuned using an electric field in a reversible and nonvolatile manner is highly desired for the fabrication of compact and energy‐efficient multifunctional electronic devices. The integration of In2O3‐based semiconductor thin films with ferroelectric 0.71PbMg1/3Nb2/3O3‐0.29PbTiO3 (PMN‐0.29PT) single crystals in ferroelectric‐field‐effect‐transistor devices that allow for the tuning of carrier density, carrier type, Fermi level, and their related properties in a reversible and nonvolatile manner, is reported. Specifically, gating of In2–x Crx O3 (x = 0, 0.02, 0.05, 0.08, 0.11) films with a PMN‐0.29PT layer provides a means to reversibly tune and modulate the resistivity of the films up to an on‐and‐off ratio of 5.2 × 104% in a nonvolatile manner at room temperature. Such resistivity modulation is associated with reversible and nonvolatile transformation of the carrier type between n‐type and p‐type due to polarization switching. Additionally, reversible switching of resistivity is realized utilizing DEME‐TFSI ionic liquid as a top‐gate material. These results demonstrate that electrical‐voltage control of physical properties using PMN‐xPT as both substrate and gating material provides a highly effective approach to study the carrier‐density/type‐related physical properties of semiconductor films.

Flame-retardant plant thermoplastics directly prepared by single ionic liquid substitution

Grass and wood biomass (bagasse, cedar, and eucalyptus) was directly converted into flame-retardant thermoplastics by dissolution in an ionic liquid mixture and successive precipitation. During dissolution, the hydroxy groups of the biomass were substituted with a phosphonate-type ionic liquid. The three resulting biomass samples were formed into thin films by hot pressing at 140–160 °C. They also self-extinguished a fire by forming foamed char layers after contacting the fire in an alcohol lamp. In this method, more than 86% of the hydroxy groups were maintained after ionic liquid substitution because the single phosphonate-type ionic liquid acted as a plasticizer and flame retardant in the plant biomass. Therefore, plant biomass-derived flame-retardant thermoplastics have the potential for further functionalization. We developed flame-retardant thermoplastics directly from biomass just by dissolution into ionic liquids and precipitation. During the dissolution, a phosphonate-type ionic liquid adducted on the polymers included in biomass such as cellulose through reaction of the hydroxyl groups. In this method, more than 86% of the hydroxy groups were maintained after ionic liquid substitution because the single phosphonate-type ionic liquid acted as a plasticizer and flame retardant in the plant biomass. Therefore, the plant biomass-derived flame-retardant thermoplastics have the potential for further functionalization.

Tissue-Engineered Trachea Consisting of Electrospun Patterned sc-PLA/GO- g-IL Fibrous Membranes with Antibacterial Property and 3D-Printed Skeletons with Elasticity.

In this study, a tissue-engineered trachea, consisting of multilevel structural electrospun polylactide (PLA) membranes enveloping 3D-printed thermoplastic polyurethane (TPU) skeletons, was developed to create a mechanically robust, antibacterial and bioresorbable graft for the tracheal reconstruction. The study design incorporated two distinct uses of stereocomplex PLA: patterned electrospun fibers to enhance tissue integration compared to the random layered fibers, meanwhile possessing good antibacterial property; and 3D-printed TPU scaffold with elasticity to provide external support and protection. Herein, ionic liquid (IL)-functioned graphene oxide (GO) was synthesized and presented enhanced mechanical and hydrophilicity properties. More interesting, antibacterial activity of the GO- g-IL modified PLA membranes were proved by Escherichia coli and Staphylococcus aureus, showing superior antibacterial effect compared to single GO or IL. The synergistic antibacterial effect could be related to that GO break cytomembrane of bacteria by its extremely sharp edges, while IL works by electrostatic interaction between its cationic structures and electronegative phosphate groups of bacteria membranes, leading to the loss of cell electrolyte and cell death. Hence, after L929 fibroblast cells were seeded on patterned fibrous membranes with phenotypic shape, further effective cell infiltration, cell proliferation and attachment were observed. In addition, the tissue-engineered trachea scaffolds were implanted into rabbit models. The in vivo result confirmed that the scaffolds with patterned membranes manifested favorable biocompatibility and promoted tissue regeneration.

Isobaric vapor-liquid equilibria for tert-butanol + water with single and mixed ionic liquids as solvents at 101.3 kPa

Ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([C2mim][DCA]) and a mixture of ionic liquids [C2mim][DCA] + 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) were used as extractive distillation solvents to separate tert-Butyl alcohol (TBA) + water. The vapor-liquid equilibria for TBA + water + [C2mim][DCA] and TBA + water + [C2mim][DCA] + [C2mim][OAc] were measured at 101.3 kPa. The NRTL model was employed to correlate the vapor-liquid equilibrium data, and the binary interaction parameters were obtained. The experimental results show that both of the solvents can improve the relative volatility of TBA to water, and completely destroy the azeotropic point of TBA-water. There is no synergistic effects between [C2mim][DCA] and [C2mim][OAc], and the selectivity of [C2mim][OAc] is higher than that of [C2mim][DCA], but the viscosity of [C2mim][DCA] is lower.

Flame-retardant thermoplastics derived from plant cell wall polymers by single ionic liquid substitution

We proposed flame retardant thermoplastics derived from plant-based polymers by substitution with a single phosphonate-type ionic liquid species.

Estimation of safe environmental concentrations of ionic liquids towards bacteria by chemical toxicity distribution method

Ionic Liquids (ILs) are considered as the potential replacement of industrial organic solvents because of their salient physical and chemical properties, for example, ionic nature, low vapor pressure, and good solubility properties. These properties make ILs feasible for potential application. Industrialization of ILs has a potential to adversely affect and pose risk to the ecosystem because of their toxic nature. However, the conventional research on the ILs is mainly carried out by performing acute the toxicity assessment of individual species for individual ILs which is termed as effect assessment. Effect assessment for individual ILs is insufficient for the ecotoxicological risk assessment of ILs. Subsequently, effect assessment of single ILs on one species is not sufficient to evaluate risk. The main objective of the current research was to estimate the safe environmental concentrations (SECs) of ILs towards three bacterial strains V fischeri, E coli and S vacuolatus by Chemical Toxicity Distribution (CTD) method. CTDs provided the SECs for a group Imidazolium NTf2 ILs toward three bacteria. E coli was the most sensitive species amongst three species when exposed to the selected group of ILs with 2.976 × 10−4 mmol/L as SEC.

Mechanistic study on metal-free acetylene hydrochlorination catalyzed by imidazolium-based ionic liquids

A novel green approach to acetylene hydrochlorination yielding vinyl chloride is presented using 1-alkyl-3-methyimidazolium-based ionic liquids (ILs) as single component metal-free catalysts. The effects of anion species and substituent group in the imidazolium cation on the reaction are investigated. Through the catalytic performance and computational simulation, the catalytic mechanism of single component ILs for metal-free acetylene hydrochlorination is proposed. It is suggested that ILs as single component metal-free catalysts must consist of chloride anion, which is participate in the reaction process of acetylene hydrochlorination to form [HCl2]− through the activation of HCl molecule. Notably, the structural modification of conjugated cation will be the key factor to further improve the catalytic efficiency. The mechanistic understanding has an important significance to modify the metal-free catalytic efficiency of ILs for acetylene hydrochlorination.

Ionic Liquids Catalysis for Carbon Dioxide Conversion With Nucleophiles.

Carbon dioxide, as a promising C1 synthon, has attracted great interest in organic synthesis. Due to the thermodynamic stability and kinetic inertness of CO2, developing efficient strategies for CO2 activation and subsequent conversion is very crucial. In this context, Ionic liquids (ILs) show great potential for capturing and activating CO2 owing to their unique structures and properties, making them become ideal alternatives to volatile organic solvents and/or catalysts for CO2 transformation. This minireview aims at summarizing ILs-promoted reactions of CO2 with N-nucleophiles (primary amines)/O-nucleophiles (primary alcohols, water). Two catalytic systems i.e., metal/ILs binary systems such as Cu/ILs systems and Ag/ILs systems as well as single ILs systems including anion-functionalized ILs and bifunctionalized ILs have been developed for CO2 catalytic conversion, for instance, carboxylative cyclization of nucleophiles e.g., propargylic alcohols, amines, 2-aminobenzonitriles and o-aminobenzenethiol, and formylation of amines or 2-aminothiophenols with hydrosilanes to afford various value-added chemicals e.g., cyclic carbamates, unsymmetrical organic carbonates, α-hydroxyl ketones, and benzimidazolones. In a word, IL could provide a powerful tool for efficient CO2 utilization.

Lipophilic polymethacrylate ionic liquids as lubricant additives

Despite the growing research field of polymeric ionic liquids used as materials for electrolytes and energy materials, catalysts, separation aides, and carbon materials, reports of lipophilic polymeric ionic liquids for lubricants are essentially nonexistent. Oil-miscible single molecule ionic liquids (ILs) are reported to perform well as neat lubricants and as additives in lubricating base oils. In this work, methacrylate type ionic liquid monomers containing ammonium or imidazolium cations and two different counter-anions were synthesized and used as co-monomers to obtain functional poly(alkyl methacrylates) (PAMAs) as viscosity index improvers (VII) additives for lubricants. The structure of the IL, including the cation, the anion, and the spacer’s length separating the IL from the methacrylate group, plays an important role in the resulting polymer solubility in PAO (poly-alpha olefin), solution rheology, friction, and wear behavior. Depending on the IL structure, VIIs containing up to 20% mol IL are soluble in PAO (grade 4), and demonstrate frictionandwear reduction, compared to a conventional oil-soluble PAMA. Notably, wear volume reduction of up to 80% compared to the oil-soluble control poly(dodecyl methacrylate) is observed.

Aggregation behavior and antimicrobial activity of a micellar system of binary ionic liquids

Ionic liquid (IL) surfactants have attracted great attention as potential alternatives to conventional surfactants because of their unique tailor-made physicochemical properties. However, in most cases, the aggregations formed by single IL surfactants in aqueous media are unstable, even when using a large amount of surfactant. To address this limitation, here we investigated the aggregation behavior of binary IL surfactant micelles composed of the ILs choline oleate ([Cho][Ol]) and choline laurate ([Cho][Lau]) in aqueous media using tensiometry and dynamic light scattering measurements. Micellar and interfacial parameters including critical micelle concentration (cmc), micellar interaction parameters (β), activity coefficients (f1 and f2), surface excess concentration (Гmax), minimum surface area per molecule (Amin), and the size of surfactant aggregates were studied. In addition, various thermodynamic parameters such as the Gibbs free energy of micellization (∆Gomic), standard Gibbs free energy of adsorption (∆Goad), molar free energy (Gmin), and the excess Gibbs free energy of micellization (ΔGex) were also evaluated. A non-ideal synergistic interaction was observed for the mixed IL surfactant system, which formed larger micelles (105–120 nm) compared with those formed with a single IL (86–102 nm). The formed micelles were found to be thermodynamically stable with regards to all the mole ratio of ILs system. The antimicrobial activity of the single as well of the mixed IL system against Gram-positive and -negative bacteria displayed a low toxicity profile that fell in the range of “practically harmless” (100–1000 mg L−1). The results suggested that the micellar system composed of mixed IL surfactants provides unique physical, chemical, and biological properties may offer novel opportunities for various applications such as oil dispersants.

Evaluation of the usefulness of a novel electrochemical sensor in detecting uric acid and dopamine in the presence of ascorbic acid using a screen-printed carbon electrode modified with single walled carbon nanotubes and ionic liquids

A novel sensor was developed in order to determine dopamine (DP) and uric acid (UA) by adsorptive voltammetry, using optimal amounts of single walled carbon nanotubes (SWCNT) dispersed in chitosan solution (cs) and deposited on a screen-printed carbon electrode (SPCE). The electrode surface (cs-SWCNT/SPCE) was treated with the ionic liquid (IL) 1 butyl-3-metilimidazolium tetrafluorborate (BMIMBP4). The electro-catalytic properties of the cs-SWCNT-IL/SPCE were studied with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrode surface was studied using scanning electron microscopy (SEM). Anodic peak currents for DP and UA with BMIMBP4 in the presence of ascorbic acid (AA) increased by 17.0 and 70.0% respectively. Optimal parameters were (pH 2.4; adsorption time; tADS 100s and adsorption potential; EADS -0.10 V). Anodic peak currents were proportional to the concentration between 0.5 and 5.0 μmol L−1 using standard solutions of PD and UA respectively, and 0.50–30.0 μmol L−1 for DP and 0.50–1000 μmol L−1 for UA with real samples. Detection limits were 0.16 μmol L−1 for DP and 0.17 μmol L−1 for UA. The sensor was used in the determination of AU and DP in human urine samples spiked with quantities of DP with recovery between 85 and 102% for DA and UA respectively.

Mixtures of ionic liquids as more efficient media for cellulose dissolution

The ability to dissolve cellulose, by using mixtures of ionic liquids, has been studied and compared with results obtained for the corresponding single ionic liquids. The ionic liquid mixtures tested were a 3:7mol/mol mixture of 1-ethyl-3-methylimidazolium chloride ([C2mim]Cl) and 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]), and the eutectic mixture (i.e., a 5.1:4.9mol/mol ratio) of [C2mim]Cl and 1-butyl-3-methylimidazolium chloride (C4mim]Cl). The amount of dissolved cellulose was investigated at three different temperatures (323, 348, and 373K) for each system. The greatest amount of dissolved cellulose was obtained for the [C2mim]Cl+[C2mim][OAc] mixture, at 373K, and it was 40g per 100g of solvent. Moreover, attempts were made to lower the viscosity of the resulting systems and improve the dissolution capacity by addition of dimethylsulfoxide (DMSO) as co-solvent. Results showed that addition of DMSO at 50mol% allows the dissolution of even greater amounts of cellulose (up to 43g per 100g of solvent). To the best of our knowledge, this is the largest ever reported amount of dissolved cellulose in ionic liquid media. Additionally, physical properties (density, surface tension, and viscosity) of the investigated ionic liquid mixtures were determined and compared with the values of the corresponding parent salts. The dissolved cellulose could be easily reconstituted from its solution in ionic liquid mixtures by addition of water. The regenerated cellulose was characterized by powder X-ray diffraction (pXRD), thermogravimetric analysis (TGA), and optical microscopy. The analyses confirmed the conversion of the crystal structure of cellulose from cellulose I to cellulose II during the dissolution and regeneration process.

Measurement and modeling of CO2 solubility in [bmim]Cl – [bmim][Tf2N] mixed-ionic liquids for design of versatile reaction solvents

In this work, mixtures of 1-butyl-3-methylimidazolium chloride ([bmim]Cl) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) were chosen to study because [bmim]Cl is suitable for processing biomass and [bmim][Tf2N] is suitable for increasing carbon dioxide (CO2) solubility in the ionic liquid phase. Solubilities of CO2 in mixed ionic liquid systems ([bmim]Cl and [bmim][Tf2N]) were measured at (353–393) K and at pressures up to 15MPa with a magnetic suspension balance technique. Mixed ionic liquids were prepared at mole ratios, [bmim]Cl: [bmim][Tf2N] of 0.75: 0.25, 0.50: 0.50 and 0.25: 0.75. CO2 solubility in mixed ionic liquids changed regularly from that in single [bmim]Cl to that in single [bmim][Tf2N]. By assuming mixed ionic liquids as a mixture of two ionic liquids, the ε*-modified Sanchez-Lacombe equation of state could predict CO2 solubility data with pure component parameters of single ionic liquids and interaction parameters for [bmim]Cl-CO2, [bmim][Tf2N]-CO2 and [bmim]Cl-[bmim][Tf2N] to within an average relative deviation of 2.4%.

Using Ionic Liquid Mixtures To Improve the SO2 Absorption Performance in Flue Gas

The functional ionic liquids (ILs) [NH2emim][OAc] and [NH2emim][BF4] were synthesized for SO2 capture. Although functional ILs have potential advantages in SO2 absorption, the high viscosity of a single IL markedly affects the SO2 absorption separation process. To improve the SO2 absorption performance, [NH2emim][OAc] and [NH2emim][BF4] were mixed with low-viscosity imidazolium-based ILs [bmim][OH]/[bmim][BF4]. When the mole ratio of [NH2emim][OAc]/[bmim][OH] is about 1:1, the binary mixture has the best SO2 absorption capacity. The SO2 absorption performance was investigated in the simulated flue gas, where SO2 partial pressure was about 0.2 kPa. Under the low SO2 partial pressure, the absorption capacity of the [NH2emim][OAc] + [bmim][OH] mixture was more than 0.7 mol of SO2/mol of IL, which was superior to that of a single IL. The regeneration test of [NH2emim][OAc] + [bmim][OH] showed that the binary mixture had high reversibility and the SO2 absorption capacity almost kept constant after 12 recycles....

Modeling Carbon Dioxide Vibrational Frequencies in Ionic Liquids: I. Ab Initio Calculations.

This work elucidates the molecular binding mechanism of CO2 in [C4C1IM][PF6] ionic liquid (IL) and its interplay with the CO2 asymmetric stretch frequency ν3, and establishes computational protocols for the reliable construction of spectroscopic maps for simulating ultrafast 2D-IR data of CO2 solvated in ILs. While charge transfer drives the static frequency shift between different ionic liquids ( J. Chem. Phys. 2015 , 142 , 212425 ), we find here that electrostatic and Pauli repulsion effects dominate the dynamical frequency shift between different geometries sampled from the finite-temperature dynamics within a single ionic liquid. This finding is also surprising because dispersion interactions dominate the CO2-IL interaction energies, but are comparably constant across different geometries. An important practical consequence of this finding is that density functional theory is expected to be sufficiently accurate for constructing potential energy surfaces for CO2 in [C4C1IM][PF6], as needed for accurate anharmonic calculations to construct a reliable spectroscopic map. Similarly, we established appropriate computational and chemical models for treating the extended solvent environment. We found that a QM/MM treatment including at least 2 cation-ion pairs at the QM level and at least 32 pairs at the MM level is necessary to converge vibrational frequencies to within 1 cm-1. Using these insights, this work identifies a computational protocol as well as a chemical model necessary to construct accurate spectroscopic maps from first principles.

Nitrogen and sulfur co-doped porous carbon – is an efficient electrocatalyst as platinum or a hoax for oxygen reduction reaction in acidic environment PEM fuel cell?

Non-precious, heteroatom doped carbon is reported to replace commercial Pt/C in both alkaline and acidic half-cell rotating disc electrode study; however the real world full cell measurements with the metal-free electrocatalysts overcoming the practical troubles in acidic environment proton exchange membrane fuel cell (PEMFC) are almost negligible to confirm the claim. Nitrogen and sulfur co-doped porous carbon (DPC) was synthesized in a one step, high yield process from single source ionic liquid precursor using eutectic salt as porogens to achieve porosity. Structural characterization confirms 7.03% nitrogen and 1.68% sulfur doping into the high surface area, porous carbon structure. As the cathode oxygen reduction reaction (ORR) catalyst, metal-free DPC and Pt nanoparticles decorated DPC (Pt/DPC) shows stable and high exchange current density by four electron transfer pathway in acidic half–cell liquid environment due to the synergistic effect of nitrogen and sulfur doping and porous nature of DPC. In an actual solid state full cell measurement, Pt/DPC shows higher performance comparable to commercial Pt/C; however DPC failed to reciprocate the half-cell performance due to blockage of active sites in the membrane electrode assembly fabrication process.

Feasible study of polypyrrole film in single and double cationic ionic liquids as novel electrolytes for energy storage applications

We report the supercapacitive performance of p-toluene sulfonic acid (pTS) doped polypyrrole (PPy) thin film tested in series of ionic liquid (IL) salt electrolytes based on single and double imidazolium IL. The IL salt electrolytes were prepared by dissolving 0.1M of the total salt concentration in deionized water and their ionic conductivity was measured. The electrochemical properties of pTS doped PPy film as an active material in single and double cationic IL electrolytes were evaluated using cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy analysis. It is observed that the effects of the number of cation in IL salts are significant in determining their potential applications for supercapacitors. The results showed that the pTS doped PPy film in double cationic IL electrolytes exhibited higher specific capacitance value than that of single cationic IL electrolytes. Among double cationic IL electrolyte, C4(MIm)2(BF4)2 was most promising candidate for supercapacitor because of their higher specific capacitance value (222Fg−1) and enhanced rate capability induced due to lower solution resistance of the electrolyte.