Different Concentrations Of Ionic Liquid Research Articles

Binding Study of Antibacterial Drug Ciprofloxacin with Imidazolium-Based Ionic Liquids Having Different Halide Anions: A Spectroscopic and Density Functional Theory Analysis.

Herein, we have shown the interaction of an antibiotic drug ciprofloxacin (CIP) with three surface-active ionic liquids (ILs), having the same cation and different anions, namely, 1-decyl-3-methylimidazoliumtetrafluoroborate [C10mim][BF4], 1-decyl-3-methylimidazolium bromide [C10mim][Br], and 1-decyl-3-methylimidazolium chloride [C10mim][Cl]. This study has been performed by exploiting various spectroscopic techniques such as steady-state fluorescence, time-resolved fluorescence, and UV-visible spectroscopy. The fluorescence emission study of CIP with ILs was performed at various concentrations of all the three ILs. The emission spectra of CIP decreased in the presence of ILs, suggesting complex formation between CIP-IL. The effect of different concentrations of ILs on the emission spectra of CIP was exploited in terms of quenching and binding parameters. Further, fluorescence emission study was validated by the time-resolved fluorescence technique by measuring the average lifetime (τavg) of CIP in the presence of all the three ILs. The τavg value of the drug changed with the addition of ILs, which suggests complex formation between the drug and ILs. This complex formation was also confirmed by UV-visible spectroscopy results of CIP with all the three ILs. Further, for evaluating the thermodynamic parameters of the CIP-IL interactions, isothermal titration calorimetry (ITC) was performed. The ITC experiment yielded the thermodynamic parameters, ΔH (change in the enthalpy of association), ΔG (Gibbs free energy change), ΔS (entropy change), and binding constant (Ka). The binding parameters driven by ITC revealed that CIP-IL interactions are spontaneous in nature and enthalpy-driven, involving hydrophobic forces. Further, the classical density functional theory (DFT) calculations were performed, which provided deep insight for CIP-IL complex formation.

Studies on the Interaction between Model Proteins and Fluorinated Ionic Liquids.

Proteins are inherently unstable, which limits their use as therapeutic agents. However, the use of biocompatible cosolvents or surfactants can help to circumvent this problem through the stabilization of intramolecular and solvent-mediated interactions. Ionic liquids (ILs) have been known to act as cosolvents or surface-active compounds. In the presence of proteins, ILs can have a beneficial effect on their refolding, shelf life, stability, and enzymatic activities. In the work described herein, we used small-angle X-ray scattering (SAXS) to monitor the aggregation of different concentrations of ILs with protein models, lysozyme (Lys) and bovine serum albumin (BSA), and fluorescence microscopy to assess micelle formation of fluorinated ILs (FILs) with Lys. Furthermore, coarse-grained molecular dynamics (CG-MD) simulations provided a better understanding of Lys-FIL interactions. The results showed that the proteins maintain their globular structures in the presence of FILs, with signs of partial unfolding for Lys and compaction for BSA with increased flexibility at higher FIL concentrations. Lys was encapsulated by FIL, thus reinforcing the potential of ILs to be used in the formulation of protein-based pharmaceuticals.

Effect of imidazolium ionic liquids as microwave absorption media for the intensification of microwave-assisted extraction of Citrus sinensis peel essential oils

Ionic liquid-based microwave-assisted extraction (MAE-IL) has been applied for the separation of essential oils (EOs) from Citrus sinensis var. Valencia peels. Two imidazolium ionic liquids, 1-ethyl-3-methyl imidazolium acetate ([C2mim]OAc) and 1-butyl-3-methyl imidazolium chloride ([C4mim]Cl), were investigated for extraction efficiency, thermal behavior of the process, and chemical composition of the EOs obtained. During extractions, two different concentrations of ionic liquids (ILs) were studied (5% or 10 %), and the proposed MAE-IL was evaluated in comparison with usual microwave-assisted extraction (MAE) using water as solvent. Results indicated that both concentrations of ILs influenced EO extraction, thermal behavior, and chemical composition. However, [C2mim]OAc was more efficient, increasing extraction velocity by 10 times, enhancing extraction efficiency of EOs (39 %), and increasing the presence of oxyterpene compounds in the EOs. However, the great ability of ILs to interact with microwaves had an impact on the thermal history of the sample, reaching almost 110 °C, promoting the presence of compounds related to thermal effect.

Improving Ramie Fibers Softness Using Ionic Liquid Treatment

ABSTRACT Ramie fiber as the longest natural cellulose fiber in the world has been widely used in textile production. However, the rigidity of ramie fiber greatly restricts its application in high value-added garments. The softening treatment of ramie fibers is therefore essential. In this study, four different concentrations of ionic liquid (IL) solutions, [Emim]OAc(1-ethyl-3-methylimidazolium acetate), were used to treat degummed ramie fibers. The fiber fineness, mechanical properties, moisture absorption, and liberation ability were tested, and the fibers were also examined with Scanning Electron Micorscope (SEM), Gel Permeation (GPC), and X-ray diffraction (XRD). The results showed that the fiber modulus after 90% IL treatment was decreased to 31% of its original value while the breaking tenacity was decreased to 50% of its original value, these mechanical properties of treated ramie fiber were similar to cotton fiber and much softer than regular ramie fibers. Moreover, with the IL treatment, the ramie fiber presented higher water absorption and breaking elongation. It is believed that with the proper IL treatment, the ramie fiber will show better potential for textile production.

Role of Additives for High Performance Polymer Electrolytes

Today, the progress of polymer electrolytes with high ambient ionic conductivity, better mechanical and thermal properties, has become the main objective in the field of polymer science because of their requirements in super capacitors, rechargeable batteries, fuel cells and other electrochemical devices. Many kinds of polymer electrolytes have been developed, however main drawback is the low ionic conductivity, which is inadequate for most of the device applications. Efforts have also been made to enhance the ionic conductivity of polymer electrolytes to meet the demand for different devices. Although polymer electrolytes with high value of ionic conductivity (∼10−3-10−4 S/cm) have been developed but these also suffer from poor mechanical properties. Incorporation of plasticizers as well as nano fillers in polymer electrolytes, is of great importance for enhancing their performance in devices. In the recent years, researchers came up with an idea to make the use of ionic liquids in polymer electrolytes to address the problem of low ionic conductivity of polymer electrolytes at room temperatures as well as to keep good electrochemical and mechanical properties. The optimized ionic conductivity value of the order of ∼10−3 S/cm has been observed by different workers at different concentrations of ionic liquids. Also, polymer gel electrolytes have been reported to possess high ionic conductivity (of the order of ∼ 10−2 S/cm) at ambient temperature. However, despite possessing high value of ionic conductivity these gel electrolytes have poor mechanical and thermal properties. Hence, the modified polymer /gel electrolytes having optimized properties, are described in this review paper. An attempt has also been made to highlight the work of different researchers in the form of synthesis, characterization and analysis of different modified polymer electrolytes for their use in different ionic devices.

Characterization of polysulfone/diisopropylamine 1‐alkyl‐3‐methylimidazolium ionic liquid membranes: high pressure gas separation applications

AbstractMembrane separation is gaining great attention in many applications, especially in gas separation. Polysulfone (PSF) is the most widely studied polymeric membrane material for CO2 in its pure or modified state. Ionic liquids supported membrane technology (SILMs) are now widely applied due to their unique properties at room temperatures. In our previous study, we proved the enhanced ability of ionic liquid enhanced PSF for the separation of CO2 from gas streams. In this study, the dielectric measurements (BDS) extending up to 107 Hz for different concentrations of ionic liquid into PSF matrix, are presented. Thermogravimetric analysis measurement (TGA), differential scanning calorimeter (DSC), dynamic mechanical analysis, and the tensile properties of the membranes are studied in order to optimize the efficiency of separating CO2 from CO2/N2 mixture and CO2/CH4. TGA showed that pure PSF is a highly thermostable polymer, of which the 5% weight loss temperature is above 150°C. DSC traces show that the Tg of PSF was 149.5°C and decreases gradually for the composites. This behavior was confirmed with BDS analyses, which also revealed important information about the chain motions dynamics and the fragility index. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Molecular structure characterization of lignite treated with ionic liquid via FTIR and XRD spectroscopy

In order to characterize the effect of ionic liquid concentration on the molecular structure of lignite, the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) experiments were performed on lignite coal samples treated with different concentrations of ionic liquids. The results show that with the increase of IL concentrations, the apparent aromaticity fa increases gradually. The chemical bonds on both sides of the alkyl groups are destroyed, the alkyl chains become shorter, and the molecular structure become more compact. The C-O groups such as alcohol, phenol and ether groups are converted to CO groups such as carbonyl, aldehyde and carboxy groups. The inter-layer spacing (d002) ranges from 0.374 to 0.379, which is slightly higher than that in pure graphite. It indicates that the crystalline order in coal samples is in a lower degree. The La ranges from 3.05 to 4.05 nm and Lc ranges from 0.98 to 1.11 nm, which indicates the crystallite size increases further and the order degree of coal samples gradually approaches graphitization. The results of this paper can provide some reference for studying the characteristics of molecular structure change of coal.

Interaction of imidazolium based ionic liquids with aqueous Triton X-100 surfactant: Clouding, fluorescence and NMR studies

The micellar environment of aqueous Triton X-100 is dependent on its concentration and is driven by changes in the surfactant-water interactions. A mutual solubility curve is observed in clouding of Triton X-100 with a lower critical solution temperature at 339.5 K. Thermodynamic analysis indicate that the clouding process is entropy and enthalpy controlled below and above the lower critical solution temperature respectively. Enthalpy-entropy compensation effect has been invoked to discuss the clouding process. Addition of imidazolium based ionic liquids with variable alkyl chain length affect the micellar structure differently. The effect of different concentrations of ionic liquids on clouding of 2% Triton X-100 is studied to gauge their influence on the clouding process. The observed variations in clouding can be attributed to the hydrophobicity of the alkyl chain length of ionic liquids where, the hexyl and octyl alkyl chains results in substantial increase in cloud point for 2% Triton X-100. Fluorescence, 1H NMR and DLS studies are conducted to authenticate the changes occurring in the micellar systems. While fluorescence studies have shown a decrease in polarity of the micellar environment with increase in alkyl chain length, 1H NMR studies confirm the penetration of long alkyl chain ionic liquid in the micelles. DLS measurements show that ionic liquids are adsorbed on the micellar surface.

SPEEK-based proton exchange membranes modified with MOF-encapsulated ionic liquid

Ionic liquids (ILs) 1-butyl-3-methylimidazolium hydrogensulfate (BMI.HSO4), 1-butylimidazole hydrogensulfate (BImH.HSO4) and 3-triethylammonium propane sulfonic hydrogensulfate (TEA-PS.HSO4) were encapsulated in UiO-66 (Zr-MOF) framework. These samples were incorporated into sulfonated poly (ether ether ketone) (SPEEK) polymer in different concentrations of IL. The influence of ionic liquid concentration encapsulated in Zr-MOF was evaluated through the morphology and thermal and chemical stability of the modified membranes. The incorporation of 7.5 wt% Zr-MOF in SPEEK produced membranes with high proton conductivity, making this the best mass ratio for the incorporation of the ionic liquids. Contact angle and swelling analysis indicate that the presence of these ionic liquids provides stability to the membrane, preventing it from absorbing high amounts of water. Mass ratios of 2.5 and 5.0 wt% of encapsulated ILs in Zr-MOF were also used. Proton conductivity results show that a higher concentration of ionic liquid generates agglomerates, limiting proton mobility in the membranes. Among the three ionic liquids tested, TEA-PS.HSO4 presents the best proton conductivity values, between 92 and 140 mS cm−1. These results indicate that the Zr-MOF/TEA-PS.HSO4 sample is a good candidate for use in proton exchange membrane for fuel cells.

Imidazolium ionic liquids-based salting-out extraction of 2,3-butanediol from fermentation broths

Abstract Salting-out extraction is an efficient technique for the separation of bio-based chemicals from fermentation broths. So far, salting-out extraction of 2,3-butanediol has mainly focused on systems composed of organic solvents and salts, while less attention has been given to the green solvent ― ionic liquids. In this research, imidazolium ionic liquids were used to examine the recovery of 2,3-butanediol from fermentation broths. The influences of the temperature and concentration of 2,3-butanediol on phase formation were determined using two systems of 1-butyl-3-methylimidazolium chloride ([C4mim][Cl])-K2HPO4 and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2mim][CF3SO3])-K2HPO4. The partition behaviors of 2,3-butandiol and ionic liquids, and the selectivity of 2,3-butanediol over glucose and organic acids were investigated and compared at different concentrations of ionic liquids and K2HPO4. Most of 2,3-butanediol and ionic liquids were distributed to the top phase, whereas different trends of partition coefficient variation were observed. Under the condition of 25% [C2mim][CF3SO3]-30% K2HPO4 (w/w), the recovery of 2,3-butanediol and [C2mim][CF3SO3] was 95.7% and 99.5%, respectively, and selectivity for glucose, succinic acid and lactic acid was 2.59, 115 and 20.8, respectively.

Effect of Some Aluminum Salts - Amine Ionic Liquids on Several Serum Human Parameters and Bacterial Growth of Klebsiella pneumoniae and Staphylococcus aureus

The advantages of pharmaceutics and biological activity of some ionic liquids (ILs) on human serum (HS) and bacterial growth were studied. The effect of aluminum nitrate-acetamide (AN-Ac) and aluminum ammonium sulfate-urea (ammonium alum-urea) ionic liquids were studied on two types of bacterial species gram negative (K.pneumoniae) and gram positive (Staph.aureus). The results showed that the key factors of inhibition are the type, structures, kind of anion and cation of ILs, water miscibility and concentration of ILs and the type of microorganism in both solid and liquid media. Inhibition of bacteria growth was observed to be decreased with decreasing the quantities of (AN-Ac) and (ammonium alum-urea) ILs. The inhibition zone (The Kirby-Bauer Disk Diffusion Test), beside the optical density were measured at 600 nm for bacterial broth incubated at 37 oC for 24hrs with different concentrations of ionic liquids of (2, 5, 10, 20)% (v/v). Subsequently, the results of optical densities were calculated as colony forming units (CFUs). The concentration of ILs was calculated practically until it reached the optimal concentration of 2% (v/v). This concentration caused no variation on serum parameters likes sugar, lipid profile, protein, liver functions, kidney functions, and electrolytes, obtained by using Automatic biochemistry analyzers technique.

Application of Mobile Phases Containing Ionic Liquid for HPLC Analysis of Selected Isoquinoline Alkaloids.

An HPLC procedure on a polar reversed-phase column with mobile phases containing ionic liquid (IL) was developed for the analysis of selected alkaloids from different chemical groups. We aimed to obtain optimal conditions for the separation of alkaloids because widely used silica-based stationary phases exhibit a silanol effect, rendering analysis of basic analytes extremely difficult. Retention, separation selectivity, peak symmetry, and system efficiency were examined in various eluent systems containing different concentrations of IL and acetonitrile. The obtained results revealed substantial influence from the concentrations of IL, the organic modifier, and temperature on the retention behavior of the investigated alkaloids. The most selective and efficient chromatographic systems were applied for the analysis of several alkaloids in a plant extract.

Cholesterol affects the interaction between an ionic liquid and phospholipid vesicles. A study by differential scanning calorimetry and nanoplasmonic sensing

The present work aims at studying the interactions between cholesterol-rich phosphatidylcholine-based lipid vesicles and trioctylmethylphosphonium acetate ([P8881][OAc]), a biomass dissolving ionic liquid (IL). The effect of cholesterol was assayed by using differential scanning calorimetry (DSC) and nanoplasmonic sensing (NPS) measurement techniques. Cholesterol-enriched dipalmitoyl-phosphatidylcholine vesicles were exposed to different concentrations of the IL, and the derived membrane perturbation was monitored by DSC. The calorimetric data could suggest that the binding and infiltration of the IL are delayed in the vesicles containing cholesterol. To clarify our findings, NPS was applied to quantitatively follow the resistance of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine incorporating 0, 10, and 50mol% of cholesterol toward the IL exposure over time. The membrane perturbation induced by different concentrations of IL was found to be a concentration dependent process on cholesterol-free lipid vesicles. Moreover, our results showed that lipid depletion in cholesterol-enriched lipid vesicles is inversely proportional to the increasing amount of cholesterol in the vesicles. These findings support that cholesterol-rich lipid bilayers are less susceptible toward membrane disrupting agents as compared to membranes that do not incorporate any sterols. This probably occurs because cholesterol tightens the phospholipid acyl chain packing of the plasma membranes, increasing their resistance and reducing their permeability.

A study on carbon dioxide removal by blending the ionic liquid in membrane synthesis

Abstract The attention in ionic liquids (IL) is driven by its distinctive properties, such as negligible vapour pressure, thermal stability, and tunability of properties. To further grow its application in the separation field, the ionic liquid membranes (ILMs) and its separation technology have been proposed and developed rapidly. This paper presents details of recent research involving the blending of ionic liquid in membrane synthesis for Carbon Dioxide (CO2) removal from Methane (CH4). The low CO2/CH4 separation factor through commercialized membranes is due to the lack of CO2 affinity towards the polymeric membranes and the presence of interfacial voids in the mixed matrix membranes (MMM). The main objective is to study the influence of ionic liquid (IL) addition into the polymer and polymer-inorganic filler towards the membrane properties and performances. This was achieved by blending different concentrations of ILs at a fixed polyethersulfone (PES) and PES-SAPO-34 composition. The membranes were synthesized using dry-phase inversion technique to prevent the voids formation. The synthesized membranes were physico-chemically characterized and the performances of these membranes were evaluated in term of permeance and selectivity. The synthesized membranes were found to have dense and voids-free structure with lower polymer decomposition temperature (∼410 °C) as compared with pure PES membrane. The presence of ILs in the membranes had significantly increased the permeance of CO2 due to enhanced affinity effect. However, the permeance of CH4 is at the reverse trend due to less CH4 pathway within the membranes. Experimental results showed that both ILs have significant improvement on the ideal selectivity of the synthesized membranes. This significant improvement indicated that ionic liquid is worth to be explored as an alternative material to enhance the CO2 affinity in membranes for CO2 separation from CO2/CH4 mixture.

Efficiency of Ionic Liquid 1-Ethyl-3-Methyl-Imidazolium Acetate ([EMIM][Ac]) in Enhanced Medium Oil Recovery

Chemical flooding is one of the most efficient methods for Enhanced Oil Recovery (EOR). This study demonstrates the efficiency of mixing different concentrations of Ionic Liquid (IL), 1-Ethyl-3-Methyl-Imidazolium Acetate ([EMIM][Ac]), with Weyburn brine to improve a medium oil recovery, Weyburn oil, from an unconsolidated sand pack sample at room conditions. Effects of Slug Size (SS), IL + brine slug initiation time, and combining IL with alkali on the Recovery Factor (RF) were investigated. This study showed that the optimum concentration of ([EMIM][AC]) was 1000 ppm and the most efficient injection time of the chemical slug was at the beginning of the flooding procedure (as secondary flooding mode). In addition, it was proved that the potential of injecting a slug of IL + brine is much better than that of introducing a slug of alkali + brine. Besides, the combination of IL and alkali (AIL) resulted in better RF than injecting either of them alone. Finally, the Surface Tension (SFT), pH, wettability alteration, and viscosity of the displacing phases were measured.

Tuning of hydrophilic ionic liquids concentration: A way to prevent enzyme instability

Ionic liquids (ILs) are considered as green alternatives to organic solvents in various enzymatic biotechnological processes. A wide variety of hydrophilic and hydrophobic ionic liquids have been synthesized in order to investigate their effects on both enzyme activity and stability. In most cases, hydrophobic ILs such as those containing PF6⿿ anion have shown better performances in enzymatic reactions. In the present work, the effect of alkyl chain length of [CnMIM][Br] (n=2, 4, 6, 12) on hydrolytic activity of Thermoanaerobacter thermohydrosulfuricus lipase (TTL), as a model enzyme, was evaluated and compared with [C4MIM][PF6] as a hydrophobic ionic liquid. Moreover, effect of hydrophilic ILs on the activity and thermal stability of TTL in different concentrations of ionic liquids was studied. The results showed that TTL had the highest lipase activity in the presence of 0.3M [C2MIM][Br], 1M [C4MIM][Br] and 0.3M [C6MIM][Br]. However, no significant effect was revealed in the presence of [C12MIM][Br]. A comparison between the effects of [C4MIM][PF6] and [C4MIM][Br] on the TTL thermostability at 85°C and 90°C revealed that the hydrophobic anion PF6⿿ provided a good stabilizing effect for TTL; although the influence of hydrophilic functions is also promising. According to the findings, it could be concluded that the TTL and probably similar enzymes can be used for several biotransformation reactions by tuning the hydrophilic ionic liquids concentrations as solvents.

Effect of [C n mim][Br] Based Ionic Liquids on the Aggregation Behavior of Tetradecyltrimethylammonium Bromide in Aqueous Medium

In order to gain insight into the role of environmentally benign imidazolium based ionic liquids (ILs) to alter the physicochemical properties of single chain cationic surfactants, we have investigated the effect of 1-hexyl-3-methylimidazolium bromide ([C6mim][Br]) and 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) on the aggregation behavior of aqueous tetradecyltrimethylammonium bromide (TTAB). The critical micelle concentration (CMC) of TTAB at different concentrations of ILs was determined through conductance, surface tension, spectral change of a dye by UV–Vis measurement, and the pyrene fluorescence probe measurement techniques at 298.15 K. Decreasing of the CMC of aqueous TTAB with increasing ILs concentration proves the micellization is favorable. The effect of ILs on the properties of TTAB was verified by using NaBr. Surface tension measurements complimented by dynamic light scattering (DLS) data revealed the packing density of TTAB aggregates at different concentrations of ILs. The effective area of TTAB molecules at the air/water interface was calculated by the Gibbs adsorption isotherm and found to decrease up to 0.6 wt% of ILs followed by an increase at higher concentration. DLS data revealed an increase in micellar size of TTAB at higher concentration of IL with decrease in the aggregation number (N agg), determined by the fluorescence quenching method.

Imidazolium chloride‐based ionic liquid‐assisted improvement of lipase activity in organic solvents

AbstractThe activity of a lipase from a newly isolated Pseudomonas sp. was investigated in the presence of organic solvents and imidazolium chloride‐based ionic liquids (IL) such as BMIM[Cl] and HMIM[Cl]. The lipase activity in the presence of IL was higher compared to that in common organic solvents such as methanol and 2‐propanol. A possible explanation for the enzyme activation might be the structural changes induced in the protein in organic systems. Since IL quench the intensity of fluorescence emission, it was not possible to investigate the major factor that influences the enzyme behavior in these new organic salts. Furthermore, the enzyme exhibited excellent activity in buffer mixtures containing both organic solvent and IL. The stability of the lipase at 50°C was considerably increased in the presence of 20% BMIM[Cl] compared with the untreated lipase in aqueous medium. The light scattering method clearly showed that prevention of aggregation could be the reason for thermal stabilization at 50°C in reactions containing IL. Kinetic analysis of the enzyme in the presence of different concentrations of IL showed that the Km value increased from 0.45 mM in aqueous buffer to 2.4 mM in 50% v/v BMIM[Cl]/buffer. The increase in Km indicates that IL can significantly reduce the binding affinity of the substrate to the enzyme. Also, a linear correlation was observed between the BMIM[Cl] concentration and Vmax of the enzyme. As the concentration of BMIM[Cl] increased from 10 to 50% v/v, the Vmax value increased from 1.8 to 46 μM/min.