Hydrophilic Room Temperature Ionic Liquid Research Articles

Hydrophobicity-Dependent Heterogeneous Nanoaggregates and Fluorescence Dynamics in Room-Temperature Ionic Liquids.

The hydrophobicity of room-temperature ionic liquids (RTILs) has been shown to have a very significant effect on the optical and structural properties of and in RTILs. The average excited state lifetime of neat RTILs has been shown to be increasing with increasing hydrophobicity of the RTILs. By employing pico-nanosecond-based fluorescence anisotropy decay, the volume of the nanoaggregates in neat RTILs have been calculated. The volume of these nanoaggregates have been shown to be decreasing with increase in hydrophobicity of the RTILs. Thus, hydrophobicity has been shown to have an important role, i.e., hydrophobicity can be used as a handle to tune the properties of RTILs as designer solvents. Moreover, the excited-state lifetime of red-emitting fluorophores, i.e., whose fluorescence emission is not perturbed by the inherent emission of RTILs, has been shown to increase with the increasing hydrophobicity of the RTILs. Highly hydrophobic RTILs have been shown to exhibit positive deviation and highly hydrophilic RTIL has been shown to exhibit negative deviation from the linear correlation between average solvation time (τs) versus viscosity/temperature (η/T).

Room temperature ionic liquid based extraction and recovery of Rifampicin from water and its mechanistic study

An attempt has been made to develop a fast, efficient and eco-friendly process for extraction of drug; Rifampicin (RF) from its aqueous solutions using room temperature ionic liquids (RTILs). RTILs viz. 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 2-Hydroxyethyl-trimethylammonium L-(+)-lactate ([(C2H4OH)-(CH3)3N][Lactate])/CL have been applied for removal of RF. Factors affecting removal of this contaminant from its aqueous solution such as effect of hydrophilicity/hydrophobicity of RTILs, concentration of used RTILs and effect of pH of drug solution have been studied to investigate mechanism of extraction process. Partition coefficient, of RF between RTILs and aqueous phases as well as its extraction efficiency E% have been calculated and analyzed. Results showed that hydrophobic RTILs; [BMIM][PF6] and [EMIM][NTf2] are more efficient in extraction of RF from its aqueous solutions in just 1 minute as compared to hydrophilic RTILs; [BMIM][BF4] and [(C2H4OH)-(CH3)3N][Lactate].

Measurement of Hydrogen Sulfide Concentration by use of Carbon Nanotubes and 1-allyl-3-Methylimidazolium Bromide

Objective:In this research, carboxylated multi-walled carbon nanotubes were used to construct working and counter electrodes of the electrochemical gas sensor. The 1-allyl-3- methylimidazolium bromides which is a hydrophilic room temperature ionic liquid was used as the electrolyte. Finally, the sensor was used to measure hydrogen sulfide and carbon monoxide in the air.Methods:The electrochemical method was used to measure the hydrogen sulfide concentration. To record sensor response, chronoamperometry was performed. Also, impedance spectroscopy of screen printed electrodes modified with MWCNTs-COOH was done. The working electrode was characterized by field emission scanning electron microscopy (FESEM), Energy-Dispersive X-Ray Spectroscopy (EDX) and Fourier-Transform Infrared (FTIR) spectroscopy.Results:In the range of 0.6 ppm to 10 ppm, the sensor had a linear behavior and its sensitivity was 0.3716 µA / ppm. The results of the FESEM, EDX and FTIR analysis confirm the desired structure of the working electrode. Impedance spectroscopy shows that by using ionic liquid electrolyte the impedance is less than the case of the sulfuric acid electrolyte.Conclusion:The use of ionic liquid as an electrolyte can increase the sensor sensitivity about 141% with respect to sulfuric acid as the electrolyte, in 0.6 ppm to 10 ppm concentration range of H2S gas. Also, the sensor response to hydrogen sulfide is more than one thousand times greater than its response to carbon monoxide per 1 ppm of gas.

Colorimetric Humidity Sensor Using Inverse Opal Photonic Gel in Hydrophilic Ionic Liquid.

We demonstrate a fast response colorimetric humidity sensor using a crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) in the form of inverse opal photonic gel (IOPG) soaked in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM+][BF4−]), a non-volatile hydrophilic room temperature ionic liquid (IL). An evaporative colloidal assembly enabled the fabrication of highly crystalline opal template, and a subsequent photopolymerization of PHEMA followed by solvent-etching and final soaking in IL produced a humidity-responsive IOPG showing highly reflective structural color by Bragg diffraction. Three IOPG sensors with different crosslinking density were fabricated on a single chip, where a lightly crosslinked IOPG exhibited the color change response over entire visible spectrum with respect to the humidity changes from 0 to 80% RH. As the water content increased in IL, thermodynamic interactions between PHEMA and [BMIM+][BF4−] became more favorable, to show a red-shifted structural color owing to a longitudinal swelling of IOPG. Highly porous IO structure enabled fast humidity-sensing kinetics with the response times of ~1 min for both swelling and deswelling. Temperature-dependent swelling of PHEMA in [BMIM+][BF4−] revealed that the current system follows an upper critical solution temperature (UCST) behavior with the diffraction wavelength change as small as 1% at the temperature changes from 10 °C to 30 °C.

Matrix-effect-free determination of BTEX in variable soil compositions using room temperature ionic liquid co-solvents in static headspace gas chromatography mass spectrometry

Concerns about the environmental impact of shale energy exploration (i.e., hydraulic fracturing and other well stimulation techniques) have risen due to its rapid expansion in the United States and other countries. Soils in shale basins engaged in unconventional oil and gas development can become contaminated by volatile organic compounds (VOCs), such as benzene, toluene, ethylbenzene, and xylenes (BTEX) through mishandling of chemical additives, products, and/or waste fluids. In this study, room temperature ionic liquids (RTILs) were evaluated as solvents in an effort to increase sensitivity and to reduce and normalize matrix effects associated with varying soil compositions during analysis. Headspace gas chromatography mass spectrometry (HS-GC-MS) experiments demonstrated that hydrophilic RTILs 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][ESO4], 1-ethyl-3-methylimidazolium diethyl phosphate [EMIM][DEP], and tris(2-hydroxyethyl) methylammonium methylsulfate [MTEOA][MeOSO3] normalized the response for BTEX compounds between 2 different soils, sandy loam and sandy clay loam. Furthermore, the optimization of the HS equilibration time to 30 min resulted in the reduction of matrix effects in certified reference soils of sand, clay, and loam textures. Limits of detection and limits of quantification were in the sub- to mid- pg g−1 level in soil. For determination at 1 g of certified BTEX reference soil, the relative standard deviation was within 10% and percent recoveries were above 80% for toluene, ethylbenzene, and xylenes. This method reduces the need to characterize and matrix-match soil texture for calibration purposes. It also reduces the analysis time and increases precision and accuracy for the quantification of BTEX in variable soil matrices relative to standard methods.

Transport Matters: Boosting CO2 Electroreduction in Mixtures of [BMIm][BF4 ]/Water by Enhanced Diffusion.

Room-temperature ionic liquids (RTILs) are promising new electrolytes for efficient carbon dioxide reduction. However, due to their high viscosity, the mass transport of CO2 in RTILs is typically slow, at least one order of magnitude slower than in aqueous systems. One possibility to improve mass transport in RTILs is to decrease their viscosity through dilution with water. Herein, defined amounts of water are added to 1-butyl-3methylimidazolium tetrafluoroborate ([BMIm][BF4 ]), which is a hydrophilic RTIL. Electrochemical measurements on quiescent and hydrodynamic systems both indicate enhanced CO2 electroreduction. This enhancement has its origin in thermodynamic/kinetic effects (the addition of water increases the availability of H+ , which is a reaction partner of CO2 electroreduction) and in an increased rate of transport due to lower viscosity. Electrochemically determined diffusion coefficients for CO2 in [BMIm][BF4 ]/water systems agree well with values determined by NMR spectroscopy.

An aluminum – ionic liquid interface sustaining a durable Al-air battery

A thorough study of a unique aluminum (Al)-air battery utilizing a pure Al anode, an air cathode, and hydrophilic room temperature ionic liquid electrolyte 1-ethyl-3-methylimidazolium oligofluorohydrogenate [EMIm(HF)2.3F] is reported. The effects of various operation conditions, both at open circuit potential and under discharge modes, on the battery components were discussed. A variety of techniques were utilized to investigate and study the interfaces and processes involved, including electrochemical studies, electron microscopy, spectroscopy and diffraction. As a result of this intensive study, the upon-operation voltage drop (“dip”) obstacle, occurring in the initial stages of the Al-air battery discharge, has been resolved. In addition, the interaction of the Al anode with oligofluorohydrogenate electrolyte forms an Al-O-F layer on the Al surface, which allows both activation and low corrosion rates of the Al anode. The evolution of this layer has been studied via impedance spectroscopy genetic programming enabling a unique model of the Al-air battery.

Electrodeposition and Characterization of CoP Compounds Produced from the Hydrophilic Room-Temperature Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Dicyanamide

The voltammetric behaviors of Co(II), H2PO2−, and their mixtures in four molar ratios were studied in the hydrophilic room-temperature ionic liquid (RTIL) 1-butyl-1-methylpyrrolidinium dicyanamide ([BMP][DCA]). Co(II) was introduced into the RTIL via Co-metal anodization or the addition of CoSO4, respectively, while NaH2PO2 was used as the H2PO2− source. A single redox couple of Co(II)/Co was observed in the RTIL containing Co(II). Although elemental phosphorus (P) cannot be directly electrodeposited from NaH2PO2, CoP was successfully obtained via potentiostatic electrodeposition from [BMP][DCA] containing both CoSO4 and NaH2PO2. The obtained Co and CoP electrodeposits were both characterized to study the effects of electrodeposition potential on their surface morphology, elemental composition, crystallinity, and electrocatalytic activity. The as-deposited Co and CoP both showed amorphous features in X-ray diffraction analysis, and crystalline diffraction signals were observed after they were annealed at 623 K for 2 hours. The crystalline structures of the as-deposited CoP, however, were observed using high-resolution TEM, indicating a nanometer-domain crystal size. The oxygen evolution reaction (OER) was studied at the Pt electrode, Co-, and CoP-coated copper electrodes, of which the Co∼70P30∼ electrode showed the best electrocatalytic activity toward OER.

Solubility study of tobramycin in room temperature ionic liquids: an experimental and computational based study

Herein, we present a computational and experimental study assessing the solubility of tobramycin1in a series of hydrophilic room temperature ionic liquids (RTIL).

Surface Adsorption and Micelle Formation of Polyoxyethylene-type Nonionic Surfactants in Mixtures of Water and Hydrophilic Imidazolium-type Ionic Liquid.

The interfacial properties of polyoxyethylene alkyl ether-type nonionic surfactants (CnEm) were studied in a hydrophilic room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), in the presence of water. These properties were assessed using static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The interfacial properties were strongly dependent on the solution composition. Increased water concentration lowered the critical micelle concentration (cmc). The cmc was also affected by the lengths of both the alkyl and polyoxyethylene chains, but a greater impact was observed for the alkyl chain length. These results indicate that micellization occurs as a result of solvophobic interaction between surfactant molecules in the water/bmimBF4 mixed solutions, similar to aqueous surfactant systems. The cloud point phenomenon was observed for CnEm with a relatively low hydrophilic-lipophilic balance (HLB) value, and the relationship between the cloud point and water/bmimBF4 composition exhibited a convex upward curve. Furthermore, the mixing of bmimBF4 with water increased the surfactant solubility for water-rich compositions, suggesting that bmimBF4 acts as a chaotropic salt.

Fixed-site-carrier facilitated transport of carbon dioxide through ionic-liquid-based epoxy-amine ion gel membranes

The amine functional groups in room-temperature ionic liquid (RTIL)-based epoxy-amine ion gel membranes allow for the fixed-site-carrier facilitated transport of CO2. These membranes were tested under humidified mixed-gas (CO2/N2) feeds in order to evaluate the effects of relative humidity, CO2 partial pressure, and hydrophobicity of the added free RTIL on CO2/N2 separation performance. Changes in relative humidity were found to have little effect on CO2/N2 separation performance at constant CO2 partial pressure. However, comparison to dry-gas measurements showed that the presence of water vapor is necessary to observe facilitated CO2 transport in these systems. Increased CO2 permeability and CO2/N2 selectivity were observed for these epoxy-amine ion gel membranes with decreasing CO2 partial pressure, as expected for materials operating via the fixed-site-carrier facilitated transport mechanism. The hydrophilicity of the free RTIL was found to influence CO2 transport, with a more hydrophilic RTIL able to facilitate CO2 transport at lower relative humidity. Facilitated transport enhances the CO2/N2 separation performance of these epoxy-amine ion gel membranes and enables them to exceed the 2008 Robeson plot upper bound.

Effects of Water on Solvation Layers of Imidazolium-Type Room Temperature Ionic Liquids on Silica and Mica.

Effects of the addition of water on solvation layers of imidazolium-type room temperature ionic liquids (RT-ILs) have been studied through force curve measurements of atomic force microscopy (AFM). Two kinds of RT-ILs were employed in this study; one is a hydrophilic RT-IL (1-butyl-3-methylimidazolium tetrafluoroborate, BmimBF4), and the other is a hydrophobic one (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, EmimTFSI). These RT-ILs form solvation layers on hydrophilic solid substances (i.e., silica and mica) in the absence of added water. The addition of water into BmimBF4 resulted in the disruption of the solvation layers and then the formation of an interfacial water phase on silica. In contrast, the formation of the interfacial water phase was not evidenced on mica because of the absence of hydrogen-bonding sites on the mica surface. Interestingly, the addition of water into EmimTFSI induced the formation of the interfacial water phase on the two solid surfaces. In the EmimTFSI system, importantly, significantly greater adhesion forces were observed on silica than on mica. This reflects the different formation mechanisms of the interfacial water phase on the two solid surfaces. We conclude that the hydrogen bonding is a key factor in determining whether water molecules can be adsorbed on the solid surfaces, but it is also necessary to take into account the hydrophilic/hydrophobic nature of the RT-ILs.

Different electrochemical behavior of adult and fetal hemoglobin at ionic liquid-carbon nanotube nanocomposite

The direct electrochemistry of human adult and fetal hemoglobin on the surface of nanocomposite containing the carboxylated multi-walled carbon nanotubes (MWCNTs) and a hydrophilic room temperature ionic liquid (RTIL) has been reported. The voltammetric results showed that both types of hemoglobins entrapped in RTIL-MWCNTs nanocomposite displayed a pair of well defined, quasi-reversible redox peaks, corresponding to the Fe(III)/Fe(II) redox couple of heme prosthetic group, with the formal potentials of −0.234 and −0.232 V (vs. Ag/AgCl) for human adult and fetal hemoglobin, respectively. Immobilized human fetal hemoglobin on RTIL-MWCNTs nanocomposite relative to immobilized human adult hemoglobin showed slight differences in reversibility, electron transfer rate and protein-substrate affinity toward hydrogen peroxide.

A cesium-133 nuclear magnetic resonance study of the cesium cation сomplexation by macrocyclic polyethers in hydrophobic RITLs

Thermodynamic data for cesium complexes formation with 18-crown-6 (18C6, L) in five hydrophobic room temperature ionic liquids (RTIL): trioctylmethylammonium salicylate ([TOMA][Sal]), tetrahexylammonium dihexylsulfosuccinate ([THA][DHSS]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][N(Tf)2]), 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([HMIM][N(Tf)2]) as well as with 12-crown-4 (12C4, L) and 15-crown-5 (15C5, L) in [BMIM][N(Tf)2] are measured with NMR 133Сs technique at 27–50°C. Only [Cs(18C6)]+ complexes are found for [TOMA][Sal], [THA][DHSS], [BMIM][PF6], while in [BMIM][N(Tf)2] and [HMIM][N(Tf)2] both [Cs(18C6)]+ and [Cs(18C6)2]+ species are formed. For 12C4 and 15C5 only [CsL]+ species are registered in [BMIM][N(Tf)2]. For [BMIM][N(Tf)2] the log K1 values are steadily increasing: 12C4<15C5<18C6. А comparative study of [Cs(18C6)]+ stability in RTILs is estimated to be in the range between water and acetonitrile with constants increasing in the order [THA][DHSS]<[TOMA][Sal]<[BMIM][PF6]<[BMIM][N(Tf)2]<[HMIM][N(Tf)2]. It is demonstrated that unlike hydrophilic RTIL the entropy change with an exception of [BMIM][PF6], promotes complex formation while the corresponding enthalpy change is either positive or gives rather small contribution to the complex stability.

SEM observation of the live morphology of human red blood cells under high vacuum conditions using a novel RTIL

In this study, we succeed in visualizing a ‘living’ morphology of red blood cells (RBCs) by a rapid and simple scanning electron microscope (SEM) pretreatment using a hydrophilic room temperature ionic liquid (RTIL) with asymmetrical structure. The conventional pretreatment induces size shrinkage of the cells, and the diameter observed in an SEM (less than 6 µm) was smaller than that in an optical microscope (8 µm). Though RBCs are well‐known to be easily deformed with the environmental conditions, the cells did not show the deformation when they were pretreated with our RTILs. Since the chemical structure of our RTIL resembles a ‘choline’, which is a typical bioactive material, and has biocompatibilities, they may make it avoid from the deformation of RBCs. In fact, only immersing RBCs, our novel RTIL can provide a clear SEM image without size shrinkage and deformation. Interestingly, the obtained SEM image shows 8 µm in the diameter, almost same size as that in optical microscope. Therefore, this method is expected for novel SEM pretreatment for various biological samples observation as ‘living’ matter. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Direct Evidence of Confined Water in Room-Temperature Ionic Liquids by Complementary Use of Small-Angle X-ray and Neutron Scattering.

The direct evidence of confined water ("water pocket") inside hydrophilic room-temperature ionic liquids (RTILs) was obtained by complementary use of small-angle X-ray scattering and small-angle neutron scattering (SAXS and SANS). A large contrast in X-ray and neutron scattering cross-section of deuterons was used to distinguish the water pocket from the RTIL. In addition to nanoheterogeneity of pure RTILs, the water pocket formed in the water-rich region. Both water concentration and temperature dependence of the peaks in SANS profiles confirmed the existence of the hidden water pocket. The size of the water pocket was estimated to be ∼3 nm, and D2O aggregations were well-simulated on the basis of the observed SANS data.

High-Field EPR Spectroscopic Characterization of Spin Probes in Aqueous Ionic Liquid Mixtures

Abstract Binary mixtures of the hydrophilic room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim+][BF4 -]) and water have been probed using high-field/high-frequency electron paramagnetic resonance (EPR) spectroscopy. By adding nitroxide radicals as paramagnetic tracers, the solution structure could be assessed from typical solutes' points of view. Three probe molecules, differing in charge and hydrogen bonding affinity, have been employed: the dianionic Fremy's salt, amphiphilic TEMPO, and hydrophilic TEMPOL. High-field pulse EPR spectroscopy has been used to determine hyperfine interaction tensors and g-matrices under cryogenic conditions. Polarity-proticity plots reveal the interaction of the nitroxide moiety with apolar (TEMPO) and ionic (FS) nano-domains, depending on the probe structure. Only small variations are observed on changing the water content suggesting that the probes are well shielded from aqueous subdomains. The results indicate that addition of water in fact stabilizes IL-rich mesostructures by embedding them in pools of water.

Electrochemical detection of BSA damage induced by Fenton reagents in room temperature ionic liquid

Electrochemical analysis of Fenton-mediated oxidative damage to protein was successfully investigated using a hydrophilic room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium tetrafluoroborate, as a medium. RTIL served as a nonaqueous solvent for monitoring bovine serum albumin (BSA) damage induced by hydroxyl radical. The oxidation signal of poly-o-phenylenediamine was used as a probe for the sensitive detection of BSA damage based on the attenuation of film conductivity after damage. More dramatic damage in IL compared with that in an aqueous solvent media confirmed that IL was suitable medium for the electrochemical detection of BSA damage. Dependence of damage degree on H2O2 concentration, the ratio of Fe2+ and H2O2 and the incubation time was obtained. Protection of BSA from damage by antioxidants was also investigated. The results showed that antioxidants could quench free radicals and combine with biomacromolecules in order to protect them. These conclusions proved that RTIL could be a promising application in the study of damage.

Corrosion Behavior of Carbon Steel in Alkanolamine/Room-Temperature Ionic Liquid Based CO2 Capture Systems

To address the drawbacks of aqueous alkanolamine based state-of-the-art technology for industrial scale carbon dioxide capture, among a number of options, alkanolamine/room-temperature ionic liquid (RTIL) systems are also being tested as a likely replacement. These new schemes seem to be a better alternative to hamper corrosion occurrence. Omission of the aqueous phase marks abolition of probable oxidizing species mainly responsible for corrosion in water-based chemical absorption processes. In the present study, the corrosion phenomenon in amine/room-temperature ionic liquid blends comprised of alkanolamine/s (monoethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, N-methyldiethanolamine) and hydrophilic room-temperature ionic liquid ([BMIM][BF4], [EMIM][BF4], and [EMIM][Otf]) has been investigated by systematically probing the effect of amine/RTIL type, process temperature, CO2 loading, presence/absence of oxygen in flue gas, as well as the influence of water content. The analytical techniques ex...

Effect of hydrophilicity of room temperature ionic liquids on the electrochemical and electrocatalytic behaviour of choline oxidase

In the present report, six different nano-composites contaning the same amine functionalized multi-walled carbon nanotubes (NH(2)-MWCNTs) but different room temperature ionic liquids (RTILs) were prepared. Then, the efficiency of these nano-composites as supporting materials for studying the electrochemistry and electrocatalysis of choline oxidase (ChOx) as a model enzyme were compared. The corresponding cyclic voltammetric and amperometric data showed that the electrocatalytic activity and the electroanalytical performance of immobilized ChOx depends on the degree of hydrophilicity of RTILs used in the applied nano-composite. The higher stability (180 days), higher enzyme loading (6.56 mol cm(-2)), lower detection limit (3.85 μM) and wider linear range (0.005-0.8 mM) was obtained for the most hydrophilic RTIL (1-allyl-3-methylimidazolium bromide).