Interfacial Properties of Double Salt Ionic Liquids: A Molecular Dynamics Study

The behavior of ionic liquids containing more than one cation or anion, double salt ionic liquids, at the interfaces with vacuum and relevant acid gases (CO₂ and SO₂) was studied using classic molecular dynamics simulations. The [1-butyl-3-methylimidazolium]­[Cl]_1–<i>x</i>[Tf₂N]_<i>x</i> double salt ionic liquids were considered in which the effect of ionic molar ratio was investigated in the entire composition range. Molecular dynamics simulations using large model systems and simulation times of 200 ns allowed a detailed characterization of the structuring at the investigated interfaces, showing the possibility of tuning the interfacial behavior through the ratios of involved ions in double salt ionic liquids, which opens a new option for controlling relevant industrial processes involving ionic liquids, such as acid gas capture

Interfacial Properties of Deep Eutectic Solvents Regarding to CO₂ Capture

The interfacial properties of deep eutectic solvents based on choline cloride plus urea, glycerol, or malonic acid in contact with gas phases composed by pure CO₂, pure SO₂, and a model flue gas, along with the liquid–vacuum interface, were studied using molecular dynamics simulations. The works provide insights on the mechanisms of acid gases capture at relevant interfaces and at atomistic level. The structural rearrangements on the molecules and ions composing the solvents at the solvent upon contact with the studied gas phases is studied together with the adsorption of gas molecules at the surface, the diffusion rates across the surface boundary, and the strength of intermolecular forces in the surface. This work provides a detailed analysis on the interfacial mechanism controlling acid gases captured by deep eutectic solvents

Water Effect on Acid-Gas Capture Using Choline Lactate: A DFT Insight beyond Molecule–Molecule Pair Simulations

The suitability of CO₂ and SO₂ capture by using choline lactate ionic liquid as a sorbent and the effect of water content for acid-gas absorption were investigated through density functional theory (DFT) simulations in this work. Simulations that contain model systems considering up to four molecules (cholinium, lactate, water, and CO₂/SO₂) have been analyzed, and compositional effects on small cluster(s) formed by four ionic pairs and variable number of water molecules have been studied in this work. Assessment of the effect of water content on acid-gas capture that uses exotic ionic liquids is a rare study, and our results showed that water presence hinders CO₂/SO₂ affinity and solubility dramatically, mainly due to the dominated affinity between the ionic pair and water molecule rather than the CO₂/SO₂ molecule. Moreover, our studies also showed that affinity between ionic liquid and CO₂ is hindered by more than ionic liquid and SO₂ rich system with the presence of water in the environment

Theoretical Study on the Solvation of C60 Fullerene by Ionic Liquids

The solvation of C60 fullerene by 24 different ionic liquids belonging to the imidazolium, piperazinium, and cholinium families was analyzed from a nanoscopic viewpoint using classic molecular dynamics simulations and Density Functional Theory (DFT) methods. Charge transfer between the ions and fullerene were computed by DFT. Force field parametrization used in molecular dynamics simulations was corrected to reproduce DFT ion–C60 interaction mechanism. Structural, dynamic, and energetic factors were analyzed to infer the role of the studied ions on the behavior of fullerenes in ionic liquids. The intermolecular ion–C60 interaction energy controls the behavior of these fluids, leading to prevailing roles by interaction mechanism through the π system of C60 nanoparticle, both for anions and cations

Theoretical Study on the Solvation of C₆₀ Fullerene by Ionic Liquids II: DFT Analysis of the Interaction Mechanism

As a continuation of our previous work (<i>J. Phys. Chem. B</i>, <b>2014</b>, <i>118</i>, 11330) on the solvation of C₆₀ by ionic liquids (ILs) using Molecular Dynamic simulations, this paper reports a systematic density functional theory (DFT) analysis on the interaction mechanism between C₆₀ and 24 different ionic liquids (belonging to the imidazolium, piperazinium, and cholinium groups). Properties such as binding energies, charge distributions, intermolecular interactions, or electronic structure were analyzed as a function of the selected ILs. The stronger IL-C₆₀ interactions would be related with π–π stacking between the C₆₀ surface and anions such as salycilate ([SA]). Likewise, the electronic structure analysis pointed to a well-defined relationship between the energetics of IL-C₆₀ systems and IL features. Therefore, ILs with deep HOMO energies as well as weak interaction between both ions would be a priori good candidates for C₆₀ solvation. Although only short-range interactions are studied in the framework of DFT, this work provides useful information for the rational design of ILs that could exhibit suitable features as C₆₀ solvents

Theoretical Study of Renewable Ionic Liquids in the Pure State and with Graphene and Carbon Nanotubes

The <i>N</i>-ethyl-<i>N</i>-(furan-2-ylmethyl)­ethanaminium dihydrogen phosphate ionic liquid was studied as a model of ionic liquids which can be produced from totally renewable sources. A computational study using both molecular dynamics and density functional theory methods was carried out. The properties, structuring, and intermolecular interactions (hydrogen bonding) of this fluid in the pure state were studied as a function of pressure and temperature. Likewise, the adsorption on graphene and the confinement between graphene sheets was also studied. The solvation of single walled carbon nanotubes in the selected ionic liquid was analyzed together with the behavior of ions confined inside these nanotubes. The reported results show remarkable properties for this fluid, which show that many of the most relevant properties of ionic liquids and their ability to interact with carbon nanosystems may be maintained and even improved using new families of renewable compounds instead of classic types of ionic liquids with worse environmental, toxicological, and economical profiles

Thermoelectric Properties of Doped-Cu₃SbSe₄ Compounds: A First-Principles Insight

This work reports the first systematic study of the effects of substitutional doping on the transport properties and electronic structure of Cu₃SbSe₄. To this end, the electronic structures and thermoelectric parameters of Cu₃SbSe₄ and Cu₃Sb_1–<i>x</i>M_<i>x</i>Se₄ (M = Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Bi) were systematically investigated by using density functional theory and the Boltzmann semiclassical transport theory. Substitutional doping at Sb site with IIIA (M = Al, Ga, In, Tl) and IVA (M = Si, Ge, Sn, Pb) elements considerably increases the hole carrier concentration and consequently the electrical conductivity, while doping with M = Bi would be adequate to provide high <i>S</i> values. Changes in calculated thermoelectric parameters are explained based on the effects of the dopant element on the electronic band structure near the Fermi level. We also present an extensive comparison between thermoelectric parameters here calculated and available experimental data. Our results allow us to infer significant insights into the search for new materials with improved thermoelectric performance by modifying the electronic structure through substitutional doping

Deep Eutectic Solvents: Physicochemical Properties and Gas Separation Applications

Sustainable technologies applied to energy-related applications should develop a pivotal role in the next decades. In particular, carbon dioxide capture from flue gases emitted by fossil-fueled power plants should play a pivotal role in controlling and reducing the greenhouse effect. Therefore, the development of new materials for carbon capture purposes has merged as central research line, for which many alternatives have been proposed. Ionic liquids (ILs) have emerged as one of the most promising choices for carbon capture, but in spite of their promising properties, some serious drawbacks have also appeared. Deep eutectic solvents (DESs) have recently been considered as alternatives to ILs that maintain most of their relevant properties, such as task-specific character, and at the same time avoid some of their problems, mainly from economic and environmental viewpoints. DES production from low-cost and natural sources, together with their almost null toxicity and total biodegradability, makes these solvents a suitable platform for developing gas separation agents within the green chemistry framework. Therefore, because of the promising characteristics of DESs as CO₂ absorbents and in general as gas separating agents, the state of the art on physicochemical properties of DESs in relationship to their influence on gas separation mechanisms and on the studies of gas solubility in DESs are discussed. The objective of this review work is to analyze the current knowledge on gas separation using DESs, comparing the capturing abilities and properties of DESs with those of ILs, inferring the weaknesses and strengths of DESs, and proposing future research directions on this subject

Theoretical Study of Amino Acid-Based Ionic Liquids Interacting with Carbon Nanosystems

The properties of 1-ethyl-3-methylimidazolium glycinate ionic liquid regarding fullerenes, graphene, and single-walled carbon nanotubes are studied using classical molecular dynamics simulations. Endohedral fullerenes forming C60 to C540 containing a variable number of confined ions are studied, and the solvation of these systems by bulk liquid phases is also studied. The adsorption of the ionic liquid on top of graphene sheets and the confinement between two sheets are also analyzed as a function of intersheet separation. Likewise, confinement inside single-walled nanotubes as a function of nanotube diameter is analyzed together with ionic mobility in comparison with bulk phases. External solvation, densification, and layering around the nanotubes are also considered. The properties of these systems involving amino acid-based ionic liquids are compared with available studies involving classical imidazolium ionic liquids with other types of ions

Characterization of Amide–Alkanediol Intermolecular Interactions

The properties of formamide + 1,2-alkanediol binary liquid systems were studied both at the macro- and microscopic levels using a combined experimental and computational methodology. Physicochemical properties, infrared spectroscopy, and solvatochromic studies together with classic molecular dynamics and quantum chemistry calculations allowed the main characteristics of these binary fluids to be inferred with regard to the variations of hydrogen bonding with formamide and 1,2-alkanediol molecular structures, mixture composition, and temperature. The complexity of these liquid systems arising from the presence of three different functional groups, which may act as hydrogen bond donors and acceptors, is analyzed, allowing a detailed picture to be inferred of the studied systems which is of relevance both for basic liquid state theory and for industrial purposes