Journal of Ionic Liquids最新文献

Here we present the heat capacity (C_p) of a series of ten imidazolium based ionic liquids (ILs), mono- and dicationic, with chemical formula C_nMIMBr (n = 2, 4, 6, 8, 10, 12, 14, and 16) and C_n(MIM)₂Br₂, (n = 4 and 8), respectively. The heat capacity values of eight ILs were determined using modulated differential scanning calorimetry (MDSC) in the temperature range of (358.15 to 378.15) K and compared with the results obtained from theoretical models found in the literature and molecular modeling calculations. For this set of ILs the C_p values were found to be in the range of (189.3 to 985.7) J mol⁻¹ K⁻¹. A linear increase in heat capacity with temperature was observed for all ILs. The C_p predicted by theoretical models and molecular modeling calculations showed reasonable agreement with the experimental C_p values for the majority of the studied ILs. The heat capacity increased with the addition of methylene groups in the side and spacer chains for both mono- and dicationic ILs. Consistent with the literature, it is observed that the additional methylene groups have a larger effect on the heat capacity at higher temperature.

It has been increasingly common to investigate dynamic and thermodynamic properties of green solvents at atomistic scales with molecular simulation. In this work, we present a detailed evaluation of the widely used fixed-charge regime, i.e., the combination of scaled RESP charges and GAFF derivatives. The benchmark set contains three ionic liquids formed by cations 1-butyl-3-methylimidazolium and 1-hexyl-3-methylimidazolium and anions bis(trifluoromethylsulfonyl)imide and PF6. For the charge scaling issue, two physical properties including the mass density and the solvation free energies of external agents in ionic liquids are selected as the criteria. Large-scale fast-growth solvation free energy simulations are performed to obtain the solvation thermodynamics, and the results are further combined with hydration data to form a water-ionic-liquids transfer dataset, which considers the partition of solutes between water and ionic liquids. It is observed that the density-derived charge scaling factor is always smaller than that derived from solvation/partition thermodynamics, which supports the use of a slightly larger scaling factor to obtain a balanced description of solute-solvent and solvent-solvent interactions. For the bonded-terms assessment, we refit the transferable GAFF2 derivatives with generalized force-matching in a molecule- and component-specific manner. The results suggest that the bond-stretching and angle-bending terms in GAFF derivatives are often problematic, while the torsional potential shows satisfactory reproduction of ab initio results. Finally, combining the extensive computational perspectives accumulated in our series works, general guidelines for molecular modelling of ionic liquids with fixed-charge force fields are summarized.

The accuracy of vapor pressure calculations is essential because it is used as a basis to estimate the thermal and equilibrium properties in energy industries. In this research work, a new empirical model for predicting the vapor pressure of ionic liquids is presented. The model was derived from 383 experimental data points of the vapor pressure of 32 different ionic liquids, as a function of temperature, critical pressure, critical temperature, acentric factor, critical compressibility factor, the number of carbons of the second alkyl group of the cation, mass connectivity index and molecular weight. The computational parameters have been determined using extended group contribution methods. The accuracy of the new model has been calculated by the absolute relative deviation percent (AARD%) of 6.82. The comparison between the current study and previous studies indicates that the proposed method provides more accurate results compared to other methods.

A new all-atom force field for the tris(pentafluoroethyl)trifluorophosphate ([FAP]${}^{-}$) anion was developed and paired with an existing force field for 1-n-hexyl-3-methylimidazolium ([C${}_6$C${}_1$im]${}^{+}$). Molecular dynamics simulations were employed to compute the density, shear viscosity, self-diffusivity, local dynamics, and liquid structure of [$C_6$$C_1$im][FAP]. Computed densities, isothermal compressibility, isobaric expansivity, and shear viscosities all agree well with experimental data. The octahedral geometry of the [FAP]${}^{-}$ anion results in facial ([fFAP]${}^{-}$) and meridional ([mFAP]${}^{-}$) isomers. Simulations with varying ratios of the two [FAP]${}^{-}$ isomers show modest but non-negligible differences in properties as a function of isomer composition.

Surface active ionic liquids (SAILs) with stimuli-responsive properties is among the class of Ionic liquids (ILs) that have tailor made structures and enormous application potential than the traditional surfactants. The impetus for studying the functionalized (pH and light responsive) SAILs is their dynamic properties added with enormous scope of potential applications, e.g., in decontamination, nanotechnology, polymer chemistry, and drug delivery to name a few. The progress in the field of SAILs rests on a clear understanding of the relationship between their molecular structure, functionality or stimuli responsive group involved within the head group, tail and within the anion and its solution properties at the air-solution interface. This review article constitutes the synthetic strategies adopted by different groups to design functionalized (pH and Light-responsive) SAILs and elaborates their physico-chemical properties including surface-active properties and their ability to form self-assembled structures that are relevant to applications. Out of the wide spectrum of applications, our interest is limited to the decontamination and drug delivery, and nanotechnology.

In this study, Graphene Ionanofluid (INF) was prepared and investigated in the temperature range of 30–60 °C for stability, pH, density, specific heat, viscosity, thermal, and electrical conductivity. These new fluids are produced by dispersing the Graphene NPs in ionic liquid (IL) 1-ethyl-3-methylimidazolium chloride [EMiM]Cl in the concentration range of 0.05–0.5 wt.%. The obtained data is compared to the classical models available in the literature. The pH of the INFs lies in the range of 8.2–9.0. The results reveal that the density, electrical and thermal conductivity (TC) of INF improves with concentration. At the same time, the viscosity of INF decreases with concentration. The minimum enhancement in thermal conductivity at 30 °C is about 4.9% at a concentration of 0.05 wt.%. The most significant thermal conductivity enhancement is 27.6%, achieved at 60 °C with a concentration of 0.5% by weight. Specific heat, thermal and electrical conductivity of INF increases as temperature rises, whereas viscosity and density decrease. Furthermore, the prepared INF has a lower viscosity than the base fluid. The new correlations are formulated to determine the viscosity and thermal conductivity of INF in the studied temperature and concentration range with R² values of 0.98 and 0.96, respectively.

Ionic liquids (ILs) have found applications in the pretreatment of waste lignocellulosic biomass by interacting with the carbohydrate molecules present in the biomass materials. Pretreatment is essential before biomass conversion into valuable chemicals, fuels, and many other value-added products. This comparative study mainly focused on the pretreatment ability of four ILs having acetate or triflate as a common anion with different cations. Among various studied ILs, diazabicyclo[5.4.0]undec-7-ene (DBU)-based acidic ionic liquid when used as a dual solvocatalyst showed significant structural modifications of the rice straw (RS) sample, through C₆-O bond breakage assisted by the tertiary nitrogen in DBU cation. Structural modifications due to the pretreatment were confirmed through SEM, PXRD, and FTIR analysis. The elemental analysis confirmed that carbon content in original RS is reduced to 29% and 20% upon ionothermal treatment of RS with IL at 90 °C and 120 °C, respectively. Additionally, TGA indicated that further pyrolysis could be easier with the pretreated rice straw yielding biochar up to 9% thereby reducing wastes. Conversion of RS was found to be 60% which reduced marginally to 50% after three cycles of recycling the IL. The findings of this work provide the proof of concept that studied IL with high thermal stability and recyclability should act as a potential solvocatalyst in sustainable pretreatment and other biomass applications.

Ionic liquids have developed as a new class of low-temperature molten salts which are formed of weakly corresponding cations and anions. Efforts to extend the ionic liquids applications across different research arenas have grown in recent years with growths in understanding and tailoring their physical, chemical, and biological properties. The use of ionic liquids as a source/media for the synthesis and stabilization of metal nanostructures has gained more popularity recently owing to their ability to be personalized in varying sizes, and morphologies. The metal nanostructures synthesized in the presence of ionic liquids are employed in cancer diagnosis and therapy. The current review describes the different ionic liquids and their role in the synthesis of metal nanostructures for cancer diagnosis and therapy. In the end, the perspective and new directions for developing ionic liquid-mediated synthesis of metal nanostructures for cancer diagnostic and therapy are highlighted.