Review of the role of ionic liquids in two-dimensional materials

Ionic liquids (ILs) are expected to be used as readily available “designer” solvents, characterized by a number of tunable properties that can be obtained by modulating anion and cation combinations and ion chain lengths. Among them, its high ionicity is outstanding in the preparation and property modulation of two-dimensional (2D) materials. In this review, we mainly focus on the ILs-assisted exfoliation of 2D materials towards large-scale as well as functionalization. Meanwhile, electric-field controlled ILs-gating of 2D material systems have shown novel electronic, magnetic, optical and superconducting properties, attracting a broad range of scientific research activities. Moreover, ILs have also been extensively applied in various field practically. We summarize the recent developments of ILs modified 2D material systems from the electrochemical, solar cells and photocatalysis aspects, discuss their advantages and possibilities as “designer solvent”. It is believed that the design of ILs accompanying with diverse 2D materials will not only solve several scientific problems but also enrich materials design and engineer of 2D materials.     

Electrolyte based on fluorinated cyclic quaternary ammonium ionic liquids

Ionic liquids, ILs, based on fluorinated pyrrolidinium and piperidinium ammonium cations and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs including melting point, glass transition and degradation temperatures, viscosity, ionic conductivity, and electrochemical stability were determined and compared to alkyl pyrrolidinium and piperidinium ILs. The incorporation of a CF₃ group instead of a CH₃ induces an increase of the IL viscosity, thus a conductivity decrease. However, good ionic conductivity is obtained with fluorinated pyrrolidinium IL. Cyclic amine ILs with propyl alkyl chain or fluorinated ammonium exhibit very high electrochemical stability toward oxidation. The effect of the addition of LiTFSI on the IL properties was studied with the same methodology.     

Electrochemical performance of lead acid battery using ammonium hydrogen sulphate with different alkyl groups

In this work, the application of ionic liquids (ILs)??mono-, bicycyclohexyl, monohexyl and tetrahexyl ammonium hydrogen sulphate??as electrolyte additives on the electrochemical performance of lead acid batteries is proposed. The electrochemical behaviour of Pb?C1.66% Sb?C0.24% Sn alloy in sulphuric acid solution is investigated in the presence of the mentioned ILs with different numbers of alkyl or cycloalkyl chains. Particularly, the hydrogen and oxygen evolution potential and anodic layer characteristics were studied using cyclic and linear sweep voltammetric methods. The obtained results indicate that hydrogen evolution overpotential of Pb/Sb/Sn alloy in the presence of ILs increases. This overpotential mainly depends on the concentration of ILs and the number of alkyl and cycloalkyl chains on the cations. Also, the difference between the oxygen oxidation potential in anodic and cathodic scans (?E) decreases using different ILs.     

Physicochemical properties of ionic liquids based on imidazolium/pyrrolidinium cations and maleate/phthalate anions

Ionic liquids (ILs) based on imidazolium/pyrrolidinium cations and maleate/phthalate anions can be used as excellent electrolyte materials for electrolytic capacitors. In this study, we synthesized four ILs of this family and investigated their thermal behaviors, ionic conductivities and sparking voltages. The four ILs have high thermal stability for capacitor requirements. The conductivities of imidazolium ILs are slightly higher than those of pyrrolidinium analogs and the conductivities of maleate anion-based ILs are higher than those of corresponding phthalate anion-based ILs. Besides, the long-term thermal stability of imidazolium ILs in conductivity is superior to that of pyrrolidinium analogs. Whereas the long-term thermal stability of phthalate anion-based ILs is better than that of corresponding maleate anion-based ILs. The influence of cationic structure of the ILs on conductivity was analyzed. The temperature dependence of conductivity was also discussed in this work. The Vogel–Tammann–Fulcher (VTF) equation accurately describes the temperature dependence of conductivity for the ILs. In addition, the result of sparking voltage measurement shows that neither Ikonopisov nor Albella model is valid for the ILs.     

A short review on stable metal nanoparticles using ionic liquids,supported ionic liquids,and poly(ionic liquids)

Metal nanoparticles (NPs) are a subject of global interest in research community due to their diverse applications in various fields of science. The stabilization of these metal NPs is of great concern in order to avoid their agglomerization during their applications. There is a huge pool of cations and anions available for the selection of ionic liquids (ILs) as stabilizers for the synthesis of metal NPs. ILs are known for their tunable nature allowing the fine tuning of NPs size and solubility by varying the substitutions on the heteroatom as well as the counter anions. However, there has been a debate over the stability of metal NPs stabilized by ILs over a long period of time and also upon their recycling and reuse in organocatalytic reactions. ILs covalently attached to solid supports (SILLPs) have given a new dimension for the stabilization of metal NPs as well as their separation, recovery, and reuse in organocatalytic reactions. Poly(ILs) (PILs) or polyelectrolytes have created a significant revolution in the polymer science owing to their characteristic properties of polymers as well as ILs. This dual behavior of PILs has facilitated the stabilization of PIL-stabilized metal NPs over a long period of time with negligible or no change in particle size, stability, and size distribution upon recycling in catalysis. This review provides an insight into the different types of imidazolium-based ILs, supported ILs, and PILs used so far for the stabilization of metal NPs and their applications as a function of their cations and counter anions.     

Solvent effect in sonochemical synthesis of metal-alloy nanoparticles for use as electrocatalysts

Nanomaterials are now widely used in the fabrication of electrodes and electrocatalysts. Herein, we report a sonochemical study of the synthesis of molybdenum and palladium alloy nanomaterials supported on functionalized carbon material in various solvents: hexadecane, ethanol, ethylene glycol, polyethylene glycol (PEG 400) and Ionic liquids (ILs). The objective was to identify simple and more environmentally friendly design and fabrication methods for nanomaterial synthesis that are suitable as electrocatalysts in electrochemical applications. The particles size and distribution of nanomaterials were compared on two different carbons as supports: activated carbon and multiwall carbon nanotubes (MWCNTs). The results show that carbon materials functionalized with ILs in ethanol/deionized water mixture solvent produced smaller particles sizes (3.00 ± 0.05 nm) with uniform distribution while in PEG 400, functionalized materials produced 4.00 ± 1 nm sized particles with uneven distribution (range). In hexadecane solvents with Polyvinylpyrrolidone (PVP) as capping ligands, large particle sizes (14.00 ± 1 nm) were produced with wide particle size distribution. The metal alloy nanoparticles produced in ILs without any external reducing agent have potential to exhibit a higher catalytic activity due to smaller particle size and uniform distribution.     

Organosilicon functionalized quaternary ammonium ionic liquids as electrolytes for lithium-ion batteries

Organosilicon-functionalized quaternary ammonium ionic liquids (ILs) with oligo(ethylene oxide) substituent are designed and synthesized. Such properties as viscosity, conductivity, and thermal/electrochemical stability of these ILs are characterized. These ILs are miscible with the commercial carbonate electrolyte (EC: DEC?=?1:1(w/w), 1 M LiPF₆) and are used as cosolvents to form hybrid electrolytes in proportions up to 30 vol%. By using such hybrid electrolytes, the LiFePO₄/Li half cells exhibit no deterioration in specific capacity and cyclability, and the graphite/Li half cells show improved compatibility in the presence of lithium oxalyldifluoroborate. These hybrid electrolytes exhibit less flammability compared with the commercial baseline electrolyte, and thus improved safety for use in lithium-ion batteries.     

Phase behaviors of ionic liquids attributed to the dual ionic and organic nature

Ionic liquids (ILs), also known as room-temperature molten salts, are solely composed of ions with melting points usually below 100 °C. Because of their low volatility and vast amounts of species, ILs can serve as ‘green solvents' and ‘designer solvents' to meet the requirements of various applications by fine-tuning their molecular structures. A good understanding of the phase behaviors of ILs is certainly fundamentally important in terms of their wide applications. This review intends to summarize the major conclusions so far drawn on phase behaviors of ILs by computational, theoretical, and experimental studies, illustrating the intrinsic relationship between their dual ionic and organic nature and the crystalline phases, nanoscale segregation liquid phase, IL crystal phases, as well as phase behaviors of their mixture with small organic molecules.     

Microwave-assisted synthesis using ionic liquids

The research and application of green chemistry principles have led to the development of cleaner processes. In this sense, during the present century an ever-growing number of studies have been published describing the use of ionic liquids (ILs) as solvents, catalysts, or templates to develop more environmentally friendly and efficient chemical transformations for their use in both academia and industry. The conjugation of ILs and microwave irradiation as a non-conventional heating source has shown evident advantages when compared to conventional synthetic procedures for the generation of fast, efficient, and environmental friendly synthetic methodologies. This review focuses on the advances in the use of ILs in organic, polymers and materials syntheses under MW irradiation conditions.     

Ionic liquids screening for desulfurization of natural gasoline by liquid–liquid extraction

Seventy five ionic liquids (ILs) were tested as a sequestering agent of sulfured compounds in natural gasoline (NG). Desulphurization of NG was performed by means of liquid–liquid extraction method at room temperature and atmospheric pressure. Experimental ILs containing imidazolium, pyridinium, and ammonium cations along with organic and inorganic anions were synthesized conventionally and under microwave and sonochemical conditions. The effect of the molecular structure of ILs on the desulfurization efficiency of NG with high sulfur content was evaluated. Analysis indicated that the anion type played a more important role than the cation on the desulphurization process. ILs based on halogen–ferrates and halogen–aluminates exhibited the highest efficiency in sulfur removal, and their efficiency is further improved when there is an excess of metallic salt in a ratio of at least 1:1.3 during the synthesis of the corresponding IL. An explanation for the ability of metallic ILs to remove sulfur-containing compounds from natural gasoline based on the ratio of the ionic charge to the atomic radius is proposed. Furthermore, a method to recover and reuse water-sensitive to halogenated precursors is described.     

2018年4期电子期刊

稀土有机配合物具有优异的发光性能,但其内在缺陷如较低的稳定性和较差的加工性等则限制了它们的实际应用。离子液体稳定性和溶解性能均较好,将稀土配合物和离子液体结合可以有效地弥补上述不足,同时可以赋予材料更多奇特和优异的性能,从而增强它们的实用性。本文主要介绍了一些典型的含离子液体和稀土配合物的发光材料体系,阐明了离子液体在这些体系中的地位及作用,并对这类材料未来的应用及发展前景作了展望。     

Electrochemical conversion of carbon dioxide in a solid oxide electrolysis cell

Carbon dioxide is one of the greatest concerns worldwide, since it is not only a major greenhouse gas but also expected to be an important, sustainable resource for fuels and chemicals. The electrochemical conversion of carbon dioxide, based on solid electrolyte membrane reactors, has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion and kinetics, relatively low selectivity and high energy consumption. In this review, electrocatalysts and solid oxide electrolytes, both proton and oxide ion conductors as core materials in an electrochemical ceramic membrane reactor have been reviewed and particular emphasis is placed on their application to synthesize carbon monoxide and hydrogen.     

A perturbed hard-sphere equation of state extended to imidazolium-based ionic liquids

A perturbed hard-sphere equation of state (EOS) has been previously employed to predict pressure–volume–temperature properties of some ionic liquids (ILs) with phosphonium-, pyridinium-, and pyrrolidinium cations. In this work, we have extended the considered EOS to another class of ILs in compressed states. This class consists of 14 imidazolium-based ILs. The predicted densities were compared with those obtained from the experiment, over a broad pressure range from 0.1 to 200 MPa. From 1,122 data points examined for the aforementioned ILs, the total average absolute deviation was found to be 1.05%.     

硝基苯在BMimPF6中的紫外光谱及电还原特性

应用紫外光谱和循环伏安法研究了硝基苯和离子液体BMim PF6的相互作用及其电还原特性。结果表明,硝基苯与紫外光谱受离子液体作用的影响,硝基的吸收峰红移,末端吸收消失。硝基苯电还原的传递系数α随浓度变化而减小。扩散系数D随浓度升高先降低后稍升高。     

Self‐Assembly of Ag6 Clusters into Nanowires for Nonenzymatic Electrochemical Sensing of Glucose

Self‐assembly of metal nanoclusters into 3D ordered superstructures and the exploration of their electrochemical properties are highly significant for fundamental research and practical application. In this study, atomically precise Ag₆(NALC)₅ nanoclusters are successfully synthesized and their structure is determined carefully. It is interesting that the prepared Ag₆(NALC)₅ nanoclusters can be self‐assembled into ultrafine nanowires, long ribbons, and finally 3D porous network in the mixed solution of water and ethanol, which can be attributed to the solvent polarity, static electricity interaction between ligands, and the possible Van der Waals attractions. Such assembly phenomenon lays a foundation for the future fabrication of silver clusters‐based nanodevices. In addition, the synthesized silver nanoclusters can be used for electrochemical sensing of glucose with high detection sensitivity, selectivity, and low limit of detection. This work is expected to be helpful for the synthesis of atomically precise metal nanoclusters and their applications in fabrication of nanodevices for chemical sensors.     

Solvophobic solvation and interaction of small apolar particles in imidazolium-based ionic liquids

We report results of molecular dynamics simulations characterizing the solvation and interaction of small apolar particles such as methane and xenon in imidazolium-based ionic liquids (ILs). The simulations are able to reproduce semiquantitatively the anomalous temperature dependence of the solubility of apolar particles in the infinite dilution regime. We observe that the "solvophobic solvation" of small apolar particles in ILs is governed by compensating entropic and enthalpic contributions, very much like the hydrophobic hydration of small apolar particles in liquid water. In addition, our simulations clearly indicate that the solvent mediated interaction of apolar particles dissolved in ILs is similarly driven by compensating enthalpic and entropic contributions, making the "solvophobic interaction" thermodynamically analogous to the hydrophobic interaction.     

Unexpected acceleration of Ultrasonic-Assisted iodide dosimetry in the catalytic presence of ionic liquids

This study investigates the potential of using small amounts of ionic liquids (IL) to enhance ultrasound-assisted extraction of lipids content from green microalgae. Three imidazolium-based ILs (butyl, octyl and dodecyl), each of them with two anions (bromide and acetate) were tested as additives. Viscosity and surface tension of the ILs aqueous mixtures were analyzed to determine the influence of ILs’ anions and alkyl chain length, whereas KI dosimetry experiments were used as an indicator of radicals formation. A key finding suggests that the small addition of ILs improves the ultrasonication either by enhancing the viscosity and reducing the water surface tension, leading to a more powerful acoustic cavitation process or by increasing HO° production likely to oxidize the microalgae cells membranes, and consequently disrupting them on a more efficient manner. KI dosimetry also revealed that long ILs alkyl chain is detrimental. This experimental observation is confirmed thus strengthened as the yield of extracted lipids from green microalgae has shown an incremental trend when the IL concentration also increased. These hypotheses are currently under investigation to spot detailed impact of ILs on cavitation process.     

Modification of Tao–Mason equation of state to ionic liquids

In our previous paper, we extended the Tao and Mason equation of state (TM EOS) to refrigerant fluids, using the speed of sound data. Here, we predict the equation of state for ionic liquids (ILs). The considered ILs are [Bmim][PF₆], [C₂mim][NtF₂], [C₃mim][NtF₂], [C₆mim][NtF₂], [C₇mim][NtF₂], [C₂mim][EtOSO₃], [Bmim][MeSO₄], [Bmim][OcSO₄], and [C₄mim][dca]. The equation of state consists of three temperature-dependent parameters: the second virial coefficient, a constant for scaling the softness of repulsive force, and an effective hard-sphere diameter equivalent to the van der Waals co-volume. The second virial coefficients of ILs are scare and there is no accurate potential energy function to allow their theoretical calculation. In this work, the second virial coefficient have been calculated using corresponding states correlation based on temperature and density at normal boiling point. The other two parameters of the equation of state can be calculated using a scaling rule. Analysis of our predicted results shows that the Tao?CMason equation of state is capable of accurately predicting the density of ILs at any temperature and pressure. The overall average absolute deviation densities for 1,633 data points are 2.05%. Also, the density of ILs obtained from the TM EOS has been compared with those calculated from vdW?CCS?C?? and Peng?CRobinson (PR) equation of state. Our results are in favor of the preference of the TM EOS over the two other equations of state. The overall average absolute deviation for 1,633 data points calculated by vdW?CCS?C?? and PR equation of state are 6.63% and 12.19%, respectively.     

Improved equation of state for ionic liquids using surface tension

The major objective of this work was the development of a reliable model to describe volumetric properties of ionic liquids (ILs). In this regard, we have applied the Ihm–Song–Mason equation of state (EOS) to some phosphonium- and imidazolium-based ILs. Three temperature-dependent parameters in the equation of state have been scaled based on the surface tension and the liquid density at room temperature. In order to improve the predictive power of the mentioned EOS for ILs, we have proposed using a simple modification. We have taken 1,228 experimental points to show the reliability of the improved EOS. The comparison of predicted densities with literature data over a broad range of temperature, 293–472 K, and pressures up to 200 MPa led to encouraging results. The average absolute deviation of calculated densities from literature values was found to be 0.75%.