Room Temperature Ionic Liquids Research Articles

Flipping Water Orientation at the Surface of Water-in-Salt and Salt-in-Water Solutions.

Salt-in-water and water-in-salt mixtures are promising for battery applications and fine-tuning of room-temperature ionic liquid (RTIL) properties. Although critical processes take place at interfaces of these systems, including charge transfer and heterogeneous catalytic reactions, the microscopic interfacial structures remain unclear. Here, we apply heterodyne-detected sum-frequency generation spectroscopy to aqueous solutions of imidazolium-based RTILs to unveil the microscopic structure of the interfaces of these solutions with air. Our results show that, under salt-in-water conditions, the orientation of the OH group hydrogen-bonded to the other water molecules flips from the OH group pointing down into the liquid for pure water to up due to the accumulation of anions in the cation-rich interfacial region. However, under the water-in-salt condition, the interfacial water molecules are confined by RTIL, and their orientation is down. Details of the water organization depend critically on the alkyl chain length of the imidazolium cation. Our results demonstrate that the surface structure can be tuned by altering the molecular structure and concentration of the RTIL.

Untapping the Coal Reserves: Green Desulfurization Using Phosphonium Based Ionic Liquids

Thar coalfields of Pakistan are the 16th largest lignite coal reserves in the world. This untapped fuel source has high density for energy production. However, sulfur content limits its cleaner use the present research is a green practice for desulfurization of bituminous and lignite coal. For this purpose tetrabutylphosphonium hydroxide with anions precursor perchloric acid, dimethyl sulfate, and trifloromethanesulfonic acid was refluxed separately at room temperature to produce tetrabutylphosphonium trifloromethanesulfonate [P4444+][CF3SO3−], tetrabutylphosphonium perchlorate [P4444+][ClO4−], and tetrabutylphosphonium methyl sulfate [P4444+][MeSO4−]. The synthesized acidic nature phosphonium based room temperature ionic liquids (PRTILs) were characterized using standardized analytical techniques of FTIR, 1H-NMR, 13C-NMR, HPLC and TGA/DSC. TD50 order of PRTILs was 47 ºC< 253 ºC < 292 ºC for [P4444+][CF3SO3−], [P4444+][ClO4−], [P4444+][MeSO4−] respectively. The proximate and ultimate analysis of coal samples from Balochistan coal field indicated low moisture and high carbon content along with gross calorific value of 6938-7589 Kcal/Kg. The coal samples from Shahrig and Sor-range coal mines with highest sulfur content (6.9-11.8%) were selected for desulfurization procedures by using PRTILs and assessed through FTIR, HPLC and CHNS analyzer. The solvents were found more effective in removal of thiophene, benzothiophene, and dibenzothiophene in an oxidative environment along with an increase of GCV of coal samples to 7204-7792 Kcal/Kg. The regeneration of spent PRTILs for three cycles in 25% ethanol reveal them as sustainable solvents for the coal desulfurization process.

Tough and temperature-resistant mask-based separator realized by K-β“-Al2O3 protective layer for stabilizing NaK liquid metal batteries

The development of low-cost, high-temperature-resistant separators is crucial for optimizing the reaction interface and improving the safety performance of liquid NaK metal batteries. This paper presents a novel separator with a solid electrolyte layer, Mask@40 %β-Al2O3, primarily composed of K-β“-Al2O3 known for its exceptional ionic conductivity and high-temperature resistance. Specifically designed for room-temperature liquid NaK metal batteries, the Mask@40 %β-Al2O3 separator effectively transforms the unstable liquid–liquid interface between liquid NaK metal electrodes and traditional organic electrolytes into a stable solid–liquid interface. This transformation prevents short-circuiting caused by area collapse under high-temperature conditions. Moreover, the Bare Mask component can adsorb a conventional organic electrolyte to construct a stable solid–liquid interface on the cathode side, thereby reducing the typically observed high interfacial resistance associated with conventional solid electrolytes. The cost-effective nature and simple preparation process of the Mask@40 %β-Al2O3 separator address cost concerns while presenting an encouraging new direction for applying room-temperature liquid NaK metal batteries in extreme conditions.

The Role of Asymmetry of Perfluoro anion in Ionic Liquids: From Basic Physical Properties to the Application in Lithium Batteries

Room-temperature ionic liquids (RTILs) have attracted significant attention as non-volatile, non-flammable electrolytes over the past three decades. While the synthesis of cationic species is relatively well-established through the quaternization reaction of tertiary amines, the synthesis of perfluoro anions is much more difficult, resulting in a more limited variety compared to cations. In this study, we explore the influence of anionic species on both fundamental properties, such as thermal properties and transport properties, and on the performance of lithium-ion batteries, particularly their rate capabilities. Furthermore, we highlight how novel anionic species not only improve the properties of RTILs but also lead to the development of unique electrolyte systems, such as organic ionic plastic crystals and medium-low temperature lithium molten salts. Through our research results, we would like to demonstrate the importance of developing new anionic species from fundamental studies to practical applications in RTILs.

Selective Co(II) and Ni(II) Separation Using the Trihexyl(tetradecyl)phosphonium Decanoate Ionic Liquid

The room temperature ionic liquid trihexyl(tetradecyl)phosphonium decanoate ([P66614][Dec]) was employed in the liquid-liquid extraction of Co(II) from hydrochloric acid solutions in the presence of Ni(II). The extraction performance in liquid-liquid separations showed a strong dependence on the acid content of the feed aqueous solution. The best performance in terms of extracted cobalt and selectivity was obtained when the feed contained a HCl concentration above 6 M On the contrary, when the experiment was performed in absence of HCl, a lower extraction and Co/Ni selectivity were obtained. This behavior has been rationalized by considering the protonation of the [Dec]− anion and the different Co(II)/Ni(II) speciation in HCl media. Moreover, polymer inclusion membranes (PIMs) were prepared using PVC and [P66614][Dec] at different weight rations. Only the PIM formulated with a 30:70/PVC:[P66614][Dec] weight ratio demonstrated effective extraction of Co(II) from the HCl solution. The extraction efficiency and selectivity of the PIM was comparable to that from biphasic liquid experiments at 8 M HCl. The results of this study constitute a promising background for further practical developments of carboxylate-based ILs applied in Co/Ni separations.

Understanding the effect of alkyl chain on extraction of Np4+ and Pu4+ with hexaalkyl nitrilotriacetamides into an ionic liquid vis-à-vis a molecular solvent

Extraction of actinides using exotic ligands in room temperature ionic liquids is one of the most preferred areas of research these days. Though the amides are well studied for the extraction of actinides from nitric acid feeds, multiple amides (such as tripodal amides) are of recent origin, and reports on solvent extraction with these ligands in room temperature ionic liquids are very rare. In this work, the extraction of Np4+ and Pu4+ was studied with a series of N,N,N′,N′,N″,N″-hexaalkyl nitrilotriacetamides (NTAamides) in an ionic liquid with an objective to understand the effect of the alkyl chains length on their extraction ability. Bumim⋅Tf2N was chosen as ionic liquid due to its favourable viscosity for distribution studies. The extraction of tetravalent actinides Np4+ and Pu4+ increased linearly with increasing the alkyl chain of the NTAamides from n-butyl via n-hexyl to n-octyl. The extraction pattern was surprisingly opposite to the most observed extraction patterns in an ionic liquid, where the extraction generally decreases sharply upon increasing the feed acidity. The extracted species were ascertained as M(NO3)5⋅L (LH), where M = Np4+ or Pu4+, for each ligand. Consequent to the formation of an entirely divergent extracted complex, the extraction pattern is completely different than that expected in an ionic liquid.

Investigation of PVDF‐co‐HPF based ultrafiltration polymer inclusion membrane for the extraction of cadmium ions

AbstractUltrafiltration polymer inclusion membranes (UPIMs) have become increasingly significant for the separation and purification of heavy metals from industrial wastes and wastewater due to their convenience compared to other liquid membranes. A novel process for cadmium separation and recovery has been developed using biodegradable ion carriers, specifically room temperature ionic liquids with various molecular structures. This innovation has greatly enhanced the efficiency and application of UPIMs for cadmium separation, while also providing the membranes with unique functional properties. In this study, various UPIMs were produced using polyvinyl fluoride hexafluoropropylene (PVDF‐co‐HPF) as the base polymer, different plasticizers, and symmetric room temperature ionic liquids as ion carriers. The ability of these membranes to extract cadmium ions was evaluated, demonstrating a removal rate of 9.70 μmol s−1 from a 25 ppm Cd(II) solution under optimum conditions. The selectivity and stability of the optimized UPIM were examined under different conditions to obtain a deeper insight into of its performance. The morphological characteristics of the optimized UPIM were examined using scanning electron microscopy and atomic force microscopy techniques.

Recent Advances in Synthesis and Applications of Organic Ionic Saltsbased Sensor Arrays

Abstract: Sensor arrays contain a group of sensors, improve observations with new dimensions, provide better estimations, and additional parameters in comparison to the individual selective sensor. The array-based sensing technique provides good performance to respond to various gaseous or liquid analytes. Room temperature ionic liquids (RTILs) (melting point &lt;25oC) and Group of uniform materials based on organic salts (GUMBOS) (melting point =25-250oC) are organic ionic salts, composed of an oppositely charged pair of bulky organic cations and bulky organic/inorganic anion and shows interesting tunable physicochemical properties. In this review article, we will discuss the sensing performance of ILs- and GUMBOS-based sensor arrays. ILs-based sensor arrays have been used in electrochemical gas sensing, solvent discrimination, colorimetric gas sensing, sensing of organic compounds, optoelectronic sensing of vapors and solutions, and vapour sensing through IL/QCM systems. GUMBOS-based sensor arrays have been employed in vapour sensing through the GUMBOS/QCM method, detection, and discrimination of proteins.

Imminent prognosis for piperazinium-based ionic liquids applications for coal desulfurization

Sulfur is one of the most important quality parameters for coal rank and utility in power generation. Combustion of coal having high sulfur content leads to SOx emissions which have detrimental impacts on the environment and human health. For sulfur remediation, N-methyl piperazinium-based room temperature ionic liquids (RTILs) were synthesized with two acidic anions precursors’ dimethyl sulfate and Perchloric acid. These novel RTILs were characterized using standardized analytical techniques of FTIR, 1H NMR, 13C NMR, HPLC, and TGA/DSC. Thermal stability of dimethyl piperazinium methyl sulfate [DMPI+][MeSO4−] and methyl piperazinium perchlorate [MPI+][ClO4−] was 284 °C and 256 °C. The proximate and ultimate analysis of coal samples collected from block II of the Thar coal field shows high moisture content (29–47 %) and gross calorific value between 5006–6660 Btu/lb suggesting it is Lignite-B type fuel. Total sulfur content in coal samples was 1–4.1 % reflecting variable degree of sulfurization. Coal cleansing through oxidative extractive desulfurization theme using nifty combinations of these acidic RTILs was verified by HPLC, FTIR, CHNS Elemental Analyzer, and X-ray Florescence (XRF) techniques. Sulfur leaching from the coal matrix was higher for methyl piperazinium perchlorate and an 85 % decrease in the sulfur part of coal along with increased heat content through this study suggests cleaner and sustainable use of coal.

Effects of Heterogeneous Mixing of Imidazolium-Based Ionic Liquids with Alcohols on Complex Formation of Ni(II) Ion.

Understanding the complex formation of metal ions in room-temperature ionic liquids (ILs) is essential for the application of ILs in solvent extraction. Nevertheless, the research on metal complex formation in ILs lags behind other applications. The complex formation equilibria may be influenced by specific interactions among the metal ion, ligand molecule, and IL cation and anion. In the present investigation, the complex formation of Ni2+ with ethanol (EtOH) and methanol (MeOH) molecules in ILs, 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([CNmim][TFSA], where N represents the alkyl chain lengths of 2 and 8) was discussed in terms of the microscopic interactions among alcohol molecules, [CNmim]+ and [TFSA]-, and the mesoscopic mixing states of alcohols in [CNmim][TFSA], with N = 2-12. The microscopic interaction of alcohol molecules with the imidazolium ring H atoms in the ILs was evaluated by using ATR-IR and 1H and 13C NMR spectroscopies. The self-hydrogen bonding of alcohol molecules was clarified from the O-H stretching vibration of alcohol molecules. MeOH molecules can be more strongly hydrogen-bonded with themselves than EtOH molecules due to the less steric hindrance and the weaker dispersion force of MeOH with the IL cation's alkyl chain. In fact, small-angle neutron scattering (SANS) experiments revealed the more heterogeneous mixing of MeOH with the ILs by the self-hydrogen bonding among MeOH molecules than EtOH. The longer the IL cation's alkyl chain, the more the MeOH clusters significantly form. In contrast, the formation of EtOH clusters becomes weaker with elongating the alkyl chain. Ultraviolet (UV)-visible spectroscopic measurements on Ni2+-[CNmim][TFSA]-alcohol solutions with N = 2 and 8 revealed that di-, tetra-, and hexa-alcohol-Ni2+ complexes are formed in both the ILs. With N = 2, the stabilities of Ni2+-EtOH and Ni2+-MeOH complexes are comparable in the IL. However, with N = 8, the complexes are more stable in the EtOH solutions than in the MeOH solutions. This is because the less heterogeneous mixing of EtOH molecules with the IL results in the larger enthalpic contribution in the complex formation, as shown by the thermodynamic parameters estimated by the van't Hoff plots on the stability constants at several temperatures.

Yttrium Separation from Phosphorite Extract Using Liquid Extraction with Room Temperature Ionic Liquids Followed by Electrochemical Reduction

Yttrium Separation from Phosphorite Extract Using Liquid Extraction with Room Temperature Ionic Liquids Followed by Electrochemical Reduction

Revelation of room temperature liquid crystallinity and yellow-orange electroluminescence (EQE>7%) in a columnar self-assembled N-annulated perylene bisimide

The synthesis of highly fluorescent compounds is a critical necessity to facilitate cost-effective and metal-independent production of organic light-emitting diodes (OLEDs). This investigation introduces a readily soluble, electron-deficient N-annulated perylene bisimide (PBI-NST) equipped with a swallow tail, exhibiting room temperature columnar oblique mesophase with a low clearing point and high photoluminescence quantum yield, positioning it as a promising candidate for efficient OLEDs. Leveraging the luminescent properties of PBI-NST, a series of OLED devices were fabricated with PBI-NST as the sole emitter and at various concentrations in CBP host material. Impressively, doped devices employing the compound at 0.5 wt% emitter within the host material CBP displayed an exceptional external quantum efficiency (EQE) of 7.2 %, accompanied by a luminance of 2689 cd/m2. Further, a voltage dependent emission tuning was also noticed. The notable increase in EQE is mainly attributed to the contributions of hybrid local and charge transfer (HLCT) and triplet–triplet annihilation (TTA) process. The substantial enhancement in EQE marks a significant advancement in the application of multifunctional columnar self-assembled materials for OLED development.

Effect of Structural Modification in β Diketone on the Mutual Separation of Nd and Pr into Room-Temperature Ionic Liquid

Effect of Structural Modification in β Diketone on the Mutual Separation of Nd and Pr into Room-Temperature Ionic Liquid

Flexible Aluminum-Air Batteries

Wearable and flexible electronics have a wide range of applications. Making a flexible power source for them is essential. Aluminum-air batteries are attractive for powering portable, lightweight devices due to their inexpensive, light, and powerful energy source. In this project, the Al-air battery was made using activated carbon and aluminum electrodes, chloride-based electrolytes with ionic liquid additives. Various mixtures of 1-ethyl-3-methylimidazolium chloride, aluminum chloride, sodium hydroxide, and sodium chloride were studied. Fundamental properties of room-temperature ionic liquids, such as lower conductivity and density, improved the performance of aluminum-air batteries. Cell capacity, cyclic voltammetry behavior, and cell interfacial impedance with various electrolytes were optimized using the design of experiments. The battery's electrical power output and cell capacity were lower than those obtained using an activated carbon air cathode. The cell capacity over repeated electrochemical reactions was stable. The Al-air battery had regular cyclic voltammetry behavior. Aluminum hydroxide was not found on the anode electrode when an ionic liquid electrolyte was used. The interfacial cell impedance did not decrease after electrochemical reactions over a long time.

Room-Temperature Liquid Crystalline Tetraphenylethylene-Surfactant Complex with Chiral Supramolecular Structure and Tunable Circularly Polarized Luminescence.

A novel room-temperature liquid crystal of tetraphenylethylene derivative (TPE-DHAB) was synthesized using an ionic self-assembly strategy. The TPE-DHAB complex exhibits typical aggregation-induced emission properties and a unique helical supramolecular structure. Moreover, the generation and handedness inversion of circularly polarized luminescence (CPL) can be achieved through further chiral solvation, providing a facile approach to fabricate room-temperature liquid crystalline materials with controllable supramolecular structures and tunable CPL properties through a synergistic strategy of ionic self-assembly and chiral solvation process.

An inclusive comparison regarding aggregation of surface active ionic liquid and conventional surfactant with a cationic dye Acridine Red exposed in view of spectroscopic and theoretical study

The investigation was conducted on the interaction of acridine red (AR) with sodium dodecyl sulfate (SDS) and 1-butyl-3-methyl imidazolium octyl sulfate (BMImOS) in both premicellar and post micellar concentrations. The interaction between AR and room temperature ionic liquid (RTIL) 1-butyl-3-methyl imidazolium bromide (BMImBr) was studied to understand the effect of imidazolium cation on micellization. Spectroscopic experiments, such as UV–visible absorption spectroscopy, steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy, and dynamic light scattering, have been introduced. Various important parameters like spectral shifts, anisotropy, and aggregation number have been determined spectroscopically. However, a fresh insight into density functional theory calculations has also been provided. The observed results have been explained in terms of the aggregation behavior of the amphiphiles. A prominent redshift accompanied by a change in intensity is observed in the presence of surfactant and SAIL. However, in the case of BMImBr, no such spectral shift has been observed; only a decrease in spectral intensity highlights the quenching ability of the imidazolium cation. Average lifetime also provides some additional information regarding the difference in the formation of aggregates by SDS and BMImOS, which is further established from particle size density obtained from DLS. The salt like role of 1-butyl-3-methyl imidazolium cation also has been logically explained by anisotropy measurement and the determination of aggregation number. Using Gauss View 5.0 and Gaussian 09 package, the energy of optimization of each set of amphiphiles along with dye has been determined to follow the interaction at the molecular level. TDDFT calculations have also been performed to determine the structure of HOMO and LUMO.

Single-Particle Imaging Reveals the Electrical Double-Layer Modulated Ion Dynamics at Crowded Interface.

The dynamics of ion transport at the interface is the critical factor for determining the performance of an electrochemical energy storage device. While practical applications are realized in concentrated electrolytes and nanopores, there is a limited understanding of their ion dynamic features. Herein, we studied the interfacial ion dynamics in room-temperature ionic liquids by transient single-particle imaging with microsecond-scale resolution. We observed slowed-down dynamics at lower potential while acceleration was observed at higher potential. Combined with simulation, we found that the microstructure evolution of the electric double layer (EDL) results in potential-dependent kinetics. Then, we established a correspondence between the ion dynamics and interfacial ion composition. Besides, the ordered ion orientation within EDL is also an essential factor for accelerating interfacial ion transport. These results inspire us with a new possibility to optimize electrochemical energy storage through the good control of the rational design of the interfacial ion structures.

Understanding the Decamethylferrocene FeIII/IV Oxidation Process in Tris(pentafluoroethyl)trifluorophosphate-Containing Ionic Liquids at Glassy Carbon and Boron-Doped Diamond Electrodes.

Under voltammetric conditions, the neutral decamethylferrocene ([Me10Fc]) to cationic ([Me10Fc]+) FeII/III process is a well-known reversible outer-sphere reaction. A companion cationic [Me10Fc]+ to dicationic [Me10Fc]2+ FeIII/IV process has been reported under direct current (DC) cyclic voltammetric conditions at highly positive potentials in liquid SO2 at low temperatures and in a 1.5:1.0 AlCl3/1-butylpyridinium chloride melt. This study demonstrates that in room-temperature ionic liquids containing the hard to oxidize and hydrophobic tris(pentafluoroethyl)trifluorophosphate anion, the [Me10Fc]+/2+ process can be detected as a quasi-reversible reaction at glassy carbon (GC) and boron-doped diamond (BDD) electrodes. Large amplitude Fourier-transformed alternating current (FT-AC) voltammetry minimizes background current contributions occurring at potentials similar to those of the FeIII/IV process in the second and higher-order harmonics. This enables a straightforward determination of the thermodynamics and kinetics for both the FeII/III and FeIII/IV processes. Unlike the ideal outer-sphere FeII/III process, the parameters of the FeIII/IV process may be impacted by ion-interaction effects. For the faster FeII/III process, heterogeneous rate constants are approximately 10 times smaller at BDD than those at GC electrodes. This electrode dependence is less pronounced for the slower FeIII/IV process. The slower BDD kinetics may be attributed in part to a density of states lower than that at GC.

Solvation vs concentration fluctuations: confined dilute electrolytes near demixing at constant potential

In a recent paper, the effect of concentration fluctuations in a simple fully symmetric model of dilute electrolyte, confined between two planar electrodes, was investigated using constant charge simulations in the vicinity of the solute-solvent demixing transition. In agreement with previous theoretical findings it was shown that the total capacitance was enhanced by the occurrence of concentration fluctuations. In this work we will resort to constant potential simulations to show that the same effect is to be found in the differential capacitance. Additionally, here we will consider the effects of ion solvation by a polar solvent modelled by TIP4P/2005 water. Finally, the original fully symmetric ionic solute will be replaced by a three-site coarse grained model for a well know room temperature ionic liquid, 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMI] + [BF 4 ] − )). Our results show the presence of strong local fields within the capacitor due to incomplete local screening, and a marked asymmetry in the charge distribution. The expected capacity enhancement due to concentration fluctuations is completely mitigated by solvation effects and the response of the polar solvent to the external field.

Benzo-12-crown-4 and β-diketone bi-functionalized ionic liquids for highly selective lithium extraction from alkaline solution

Indeed, the efficient and sustainable recovery of lithium from highly concentrated sodium-containing mother liquors of Li2CO3 and salt-lake brines remains a significant challenge. Herein, two typical Li+ recognition receptors, namely benzo-12-crown-4 and thenoyltrifluoroacetone, were separately introduced into the cationic and anionic parts to successfully synthesize novel bi-functionalized task-specific ionic liquids [(B12C4)Cnim][TTA] (n = 4, 6, 8). A new, green, and high-efficiency extraction system has been developed by dissolving [(B12C4)C6im][TTA] in commercial room-temperature ionic liquid 1-hexyl-3-methyl-imdazolium bis(trifluromethylsulfonyl)imide [C6mim][NTf2], without the addition of any other co-extractants. The newly developed [(B12C4)C6im][TTA]-[C6mim][NTf2] extraction system exhibited a wide pH working range (4.0–11.0), high lithium extraction efficiency (95.4 %), as well as superior separation factors of Li/Na (βLi/Na = 2154.0) and Li/K (βLi/K=757.2). The extraction mechanism involving cation exchange was determined through slope analysis, ion chromatography, UV–vis spectroscopy and FT-IR spectra measurement, indicating that one [(B12C4)C6im][TTA] molecule can interact with two lithium ions and form a 1:2 complex. Moreover, the [(B12C4)C6im][TTA]-[C6mim][NTf2] extraction system also demonstrated fast extraction kinetics, facile stripping and regeneration, along with good cycling performance. Furthermore, a multi-stage countercurrent extraction process to extract lithium from the simulated mother liquor of Li2CO3 was evaluated. When the volume ratio (O/A) of oil phase (O) to water phase (A) was 1.0, only two theoretical extraction stages were needed to extract 91.4 % of lithium into the organic phase. Thus, the [(B12C4)C6im][TTA]-[C6mim][NTf2] extraction system is promising for lithium extraction from mother liquor of Li2CO3 and salt-lake brines. This study also opens the avenue for designing cationic and anionic bi-functionalized ionic liquids for metal ion separation.