Glycine Anion Research Articles

Self-Assembled Oligomers Facilitate Amino Acid-Driven CO2 Capture at the Air-Aqueous Interface.

Direct air capture of CO2 using amino acid absorbents, such as glycine or sarcosine, is constrained by the relatively slow mass transfer of CO2 through the air-aqueous interface. Our recent study showed a marked improvement in CO2 capture by introducing CO2-permeable oligo-dimethylsiloxane (ODMS-MIM+) oligomers with cationic (imidazolium, MIM+) headgroups. In this work, we have employed all-atom molecular dynamics simulations in combination with subensemble analysis using network theory to provide a detailed molecular picture of the behavior of CO2 and the glycinate anions (Gly-) at the ODMS-MIM+ decorated air-aqueous interfaces. We show that the cationic head groups of the surfactants enhance the concentration and lifetime of Gly- in the interfacial region, while ODMS tails promote the physisorption of CO2 in the interfacial region. Together, these two factors increase the effective region of contact and the probability of interactions between CO2 and Gly- compared to that of the pure air-aqueous interface. The fundamental insights gained in this work establish essential foundations for developing hybrid systems with oligomer-decorated interfaces to maximize the overall CO2 capture rates.

The Role of Nonequilibrium Solvent Effects in Enhancing Direct CO2 Capture at the Air-Aqueous Amino Acid Interface.

Direct air capture (DAC) technologies are limited by the poor understanding of the dynamic role of interfaces in modulating the chemisorption of CO2 from air into solutions. While the reactivity of aqueous amine-based solvents in the bulk environment is strongly inhibited by nonequilibrium solvent effects, promoting DAC at interfaces posits a possibility to reduce the coupling with the solvent and significantly accelerate DAC. Building on an experimentally proven concept to bring an anionic glycine absorbent to the interface through ion-pairing interactions with a positively charged surfactant, we establish the fundamental time scales for key elementary steps involved in DAC with rate theory and enhanced-sampling ab initio molecular dynamics simulations. We elucidate the mechanism by which water influences the free energy barriers and dynamical crossing-recrossing of those barriers, affecting the reaction rates. We find that water reorganizes to partially dehydrate [-NH2], facilitating SN2-based CO2 conversion to a zwitterion, which then releases a proton via overhydration of [-NH2]. The low-density interfacial water favors dehydration over overhydration, leading to a comparatively higher barrier (slower kinetics) for proton release. The barrier-recrossing events neutralize this effect, letting both steps occur at the same time scale (sub-microseconds) and making the overall DAC process faster at the interface than in the bulk water. Such an understanding of environment-sensitive solvent effects on the reaction kinetics will help design tailored interfaces for enhanced CO2 capture kinetics via control of solvation and ion paring.

Analysis of Anodic Linear Sweep Voltammograms Considering Insufficient Lability of Cu|Cu(II), Glycine System

Anodic LS voltammograms of the alkaline Cu|Cu(II), glycine system were converted into mass-transport corrected Tafel plots considering that the glycinate anion L− takes part in the first stage of copper ionization. The anodic current density was normalized relative to the surface concentration of L− species, which was determined using the mass transfer model of chemically interacting species. The lability of the system was assessed based on available kinetic characteristics and specific experimental data. To linearize the Tafel plots, corrections were made to account for the insufficient mobility of the proton attached to glycine amino group. Obtained Tafel constants indicate that the second step of copper ionization, involving the oxidation of the intermediate copper(I)-glycine complex, is the rate-determining step.

Coupling of anode reactions in the process of electrooxidation of glycine anion on gold

Electrochemical processes involving organic substances are complex multi-stage reactions. In our opinion, it is incorrect to describe their kinetics using the principle of independent partial processes (or their individual stages) since electrode reactions can be coupled due to competition for active surface sites, due to common intermediate stages, or through an electron. In this case, the theory of coupled reactions or the graph-kinetic method should be used to provide the kinetic description of the process. In general, graph theory makes it possible to identify the relationship between the “structure” and the kinetic behavior of complex systems by means of graphical analysis. In the case of electrochemical reactions, structural elements are substances adsorbed on the metal surface and (or) a set of substances interacting in the reactions. The relationship between their concentrations can be characterized quantitatively by a transformation law, for example,the law of effective masses. Thus, a graph is a set of reacting substances and a sequence of reactions represented graphically. Graphs allow setting a system of kinetic equations and analyzing them by associating a certain behavior of the system with the structure of the corresponding graph. Under the assumption that one intermediate particle is involved in each elementary stage, the kinetic expressions will be linear, which corresponds to the first-order reaction model. Graph-kinetic analysis of the processes within the Au|Gly–,OH–,H2O system confirmed that the partial multi-stage reactions of anode oxidation of glycine and hydroxyl anions are kinetically coupled. We obtained expressions for partial currents of electrooxidation of hydroxide ions and glycine anions during the anodic process occurring on gold in an alkaline glycinecontaining solution. It was shown that with an increase in the anode potential, the nature of the limiting stage of the anodicprocess changes. Formal constants of rates and equilibria of electrochemical reactions involving particles of background electrolyte and glycinate ion were calculated. It was found that the rates of partial oxidation reactions of adsorbed OH particles and O H are significantly higher than those of organic anions (Gly- and HCOO–). This indicates that the kinetics of the electrooxidation processes of Glyis in the Au|Gly-,OH–,H2O system are determined by the kinetic features of the electrooxidation reactions of hydroxide ions

A computational study of the ternary mixtures of NaPF6-EC and choline glycine ionic liquid.

This study investigates the structural and dynamic properties of ternary mixtures composed of NaPF6, ethylene carbonate (EC), and the ionic liquid choline glycine (ChGly), with a focus on their potential as electrolytes for supercapacitors. The combination of NaPF6-EC, known for its high ionic conductivity, with the biodegradable and environmentally friendly ChGly offers a promising approach to enhancing electrolyte performance. Through molecular simulations, we analyze how the inclusion of small concentrations of ChGly affects key properties such as density, cohesive energy, and ion mobility. Our findings demonstrate that the NaPF6-EC-ChGly mixture exhibits a complex network of electrostatic interactions and hydrogen bonding, with the glycine anion significantly influencing the liquid structure. In mixtures with small additions of ChGly, we observed an optimal balance of diffusion and ionic mobility. These results highlight the potential of ChGly as a green additive to conventional electrolytes, paving the way for more sustainable and high-performance energy storage devices.

Revaluing Anion Effects on Maillard Reaction Catalysis as a Relevant Feature for Kinetic Predictions

The influence of organic and inorganic anions on the Maillard reaction (MR) in glucose–glycine systems at 100 °C and pH close to neutrality was analyzed. The progress of MR markers was followed at the intermediate and final stages by spectrophotometric, pH changes, and colorimetric measurements. Two different trends were found depending on the nature of the anion. Systems with anions displaying basic properties showed an exponential correlation between the MR kinetic constants and their basicity constant values. On the other hand, systems containing anions with no acid–base properties exhibited a linear correlation between water dissolution enthalpies of their sodium salts and MR constants, indicating both a zwitterionic glycine–anion interaction catalytic effect and a relationship with their Jones–Dole viscosity constants. Finally, at a given heating time, the present anion defined the chromatic aspects of the samples, provided that the rest of the compositional variables were constant.

Analytical solutions for the injection of wettability modifiers in carbonate reservoirs based on a reduced surface complexation model

The potential of tuned-composition waterflooding to enhance oil recovery from carbonate reservoirs has been widely investigated, where wettability alteration is the dominant mechanism. It is hypothesized that the sulfate in seawater adsorbs on the rock surface, removing acidic hydrocarbon species adsorbed thereon. Glycine, the simplest amino acid, has also been investigated as a wettability modifier for carbonates that acts similarly to sulfate.Wettability alteration by the adsorption of sulfate ion and glycine anion has been satisfactorily modeled by extending calcite's surface complexation model (SCM) based on zeta potential measurements. However, determining the relevance of the individual geochemical reactions is obscured by the complexity of the SCM. Moreover, the large number of equilibrium constants and their associated uncertainty result in many degrees of freedom when matching corefloods and spontaneous imbibition experiments.This research determines the chemical reactions in the calcite's SCM that govern wettability alteration and the incremental oil recovery by glycine-enhanced waterflooding in carbonate reservoirs. We found that the wettability alteration by SCM can be approximated by two anion exchange reactions between the wettability modifiers, sulfate and glycine anions, and the carboxylic acids adsorbed on the rock surface. Moreover, the wettability of the system described by the adsorption of carboxylic acids and the incremental oil recovery by waterflooding are linearly correlated with the K value of the reaction of carboxylic acids with the carbonate surface and the concentration of carboxylic acids in the system, which is a function of the total acid number.We present analytical solutions for the two-phase, multicomponent reactive-transport model coupled with anion exchange reactions. To the best of our knowledge, this is the first time the presented analytical solutions are applied to describe enhanced waterflooding in carbonate reservoirs where more than one wettability modifier is injected. The analytical solutions showed that glycine injection enhances oil recovery over waterflooding by the formation of two wettability alteration waves. The number of waves and their types (rarefaction or shock) depend on glycine's and sulfate's concentration at the injection. The improvement in oil recovery by wettability alteration mainly occurs because the more favorable mobility ratio increases the displacement efficiency with no reduction in residual oil saturation. A synergy was found between glycine and sulfate, where the presence of glycine promotes the formation of a wettability-alteration shock by sulfate that improves the displacement efficiency.

Adsorption of gold and silver glycinate on graphene and graphene oxide surface: A DFT study

The non-toxicity and efficiency of glycinate make it an attractive alternative for cyanide in the extraction of gold and silver from ores. In this study, the adsorption behavior of gold and silver complexes with cyanide and glycinate anions on graphene and graphene oxide surfaces was investigated based on the density functional theory calculations. Contrary to cyanide complexes, glycinate complexes prefer parallel orientation to graphene and graphene oxide surfaces. Based on the obtained adsorption energies, interaction of all complexes with graphene oxide surface is stronger than with graphene surface. The adsorption energies of Au(gly)2- and Ag(gly)2- on the graphene surface are −1.46 and −1.11 eV, whereas Au(CN)2- and Ag(CN)2- adsorb on this surface with energies of −0.62 and −0.51 eV. PDOS diagram analysis confirms that the hydroxyl group is responsible for strong interaction between complexes and graphene oxide surface. The adsorption energies of Au(gly)2- and Ag(gly)2- complexes on the GO2 and GO3 surfaces are −2.19 and −1.85 eV, respectively, which implies the applicability of graphene oxide surface at recovering gold and silver ions from the leaching solution. Charge density difference and Mulliken population analyses show charge transfer occurs from the adsorbed complex to the surface which is intensified by adding functional groups to the surface.

Cation functional group effect on SO2 absorption in amino acid ionic liquids.

Introduction: The effect of the functional group of the cation on SO2 acidic gas absorption by some designed amino acid ionic liquids (AAILs) was studied. Methods: An isolated pair of glycinate anion and pristine imidazolium-based cation, as well as decorated cation functionalized by hydroxyl (OH), amine (NH2), carboxylic acid (COOH), methoxy (OCH3), and acetate (CH3COO) groups, were structurally optimized by density functional theory (DFT) using split-valence triple-zeta Pople basis set. Results and Discussion: The binding and Gibbs free energy (ΔGint) values of SO2 absorption show the AAIL functionalized by the COOH group is the most thermodynamically favorable green solvent and this functional group experiences the closest distance between anion and captured SO2 and vice versa in the case of cation … SO2 which may be the main reason for being the best absorbent; in addition, the highest net charge-transfer amount of SO2 is observed. Comparing the non-covalent interaction of the systems demonstrates that the strongest hydrogen bond between captured gas and anion, as well as π-hole, and van der Waals (vdW) interaction play critical roles in gas absorption; besides, the COOH functional group decreases the steric effect while the CH3COO functional group significantly increases steric effect after absorption that declines the hydrogen bond.

Tracing the Effect of Replacing [Gly]- with [Ala]- and Hydroxylation of [emim]+ on the Fine-Tuning of the Transport Properties of the Corresponding Amino Acid-Based Ionic Liquids Using MD Simulation.

Natural amino acid-based ionic liquids (AAILs) composed of deprotonated amino acids, [AA]-, as anions and hydroxylated imidazolium cations provide an eco-friendly nontoxic IL family with the growing number of chemical and biochemical revolutionary applications. In this paper, the transport properties of four AAILs composed of 1-(2-hydroxyethyl)-3-methylimidazolium ([HOemim]+) and 1-ethyl-3-methylimidazolium ([emim]+) cations with alaninate and glycinate anions were studied by molecular dynamics (MD) simulations. A nonpolarizable all-atom force field with the scaled charge (±0.8e) on each of the ions was applied and compared with the unit charge model in some cases. The tunable effects of the presence of the hydroxyl group in the side chain of the imidazolium cation, the type of amino acid anion, and the varied temperature on the dynamical behavior of AAILs were investigated in detail. The experimentally compatible trends of the simulated ionic self-diffusion coefficients, ionic conductivity, and ionicity were found to be inverse to the viscosity and ionic association of these ILs as [emim][Gly] > [emim][Ala] > [HOemim][Gly] > [HOemim][Ala]. The main reason behind these trends is the higher ability of the hydroxylated cation for the hydrogen-bond formation with [AA]-. The mean square displacement (MSD), self-diffusion, and transference number of imidazolium cations are larger than those of [AA]- anions, except in the case of [HOemim][Gly]. It was found that the activation energy for diffusion of [AA]- is lower than that of [HOemim]+ but higher than that of [emim]+ in [HOemim][AA] and [emim][AA] ILs, respectively. The computed velocity autocorrelation function (VACF) showed that [Gly]-, as the lightest ion, has the shortest mean collision time and velocity randomization time among the ions, especially in the [HOemim][Gly] IL. Replacing [emim]+ with [HOemim]+, similar to the effect of decreasing temperature, causes significant decreasing of the ionic self-diffusion and increasing of the well depth of the first minimum of the ionic VACFs. Current findings show that introducing suitable functional groups in the side chain of imidazolium cations can be a viable approach for efficient engineering design and fine-tuning of the transport properties of these AAILs.

Reaction Mechanism of CO2 with Choline-Amino Acid Ionic Liquids: A Computational Study.

Carbon capture and sequestration are the major applied techniques for mitigating CO2 emission. The marked affinity of carbon dioxide to react with amino groups is well known, and the amine scrubbing process is the most widespread technology. Among various compounds and solutions containing amine groups, in biodegradability and biocompatibility perspectives, amino acid ionic liquids (AAILs) are a very promising class of materials having good CO2 absorption capacity. The reaction of amines with CO2 follows a multi-step mechanism where the initial pathway is the formation of the C-N bond between the NH2 group and CO2. The added product has a zwitterionic character and can rearrange to give a carbamic derivative. These steps of the mechanism have been investigated in the present study by quantum mechanical methods by considering three ILs where amino acid anions are coupled with choline cations. Glycinate, L-phenylalanilate and L-prolinate anions have been compared with the aim of examining if different local structural properties of the amine group can affect some fundamental steps of the CO2 absorption mechanism. All reaction pathways have been studied by DFT methods considering, first, isolated anions in a vacuum as well as in a liquid continuum environment. Subsequently, the role of specific interactions of the anion with a choline cation has been investigated, analyzing the mechanism of the amine-CO2 reaction, including different coupling anion-cation structures. The overall reaction is exothermic for the three anions in all models adopted; however, the presence of the solvent, described by a continuum medium as well as by models, including specific cation- -anion interactions, modifies the values of the reaction energies of each step. In particular, both reaction steps, the addition of CO2 to form the zwitterionic complex and its subsequent rearrangement, are affected by the presence of the solvent. The reaction enthalpies for the three systems are indeed found comparable in the models, including solvent effects.

Enhanced structural stability of insulin aspart in cholinium aminoate ionic liquids

Cholinium aminoates [Ch][AA] have gained tremendous interest as a promising ionic liquid medium for the synthesis and storage of proteins. However, high alkalinity of [Ch][AA] limits its usage with pH-sensitive proteins. Here, we probed the structure, stability, and interactions of a highly unstable therapeutic protein, insulin aspart (IA), in a range of buffered [Ch][AA] (b-[Ch][AA]) using a combination of biophysical tools and in silico pipeline including ultraviolet-visible, fluorescence, and circular dichroism spectroscopies, dynamic light scattering measurements and molecular docking. b-[Ch][AA] used in the study differed in concentrations and their anionic counterparts. We reveal information on ion and residue specific solvent–protein interactions, demonstrating that the structural stability of IA was enhanced by a buffered cholinium prolinate. In comparison to the glycinate and alaninate anions, the hydrophilic prolinate anions established more hydrogen bonds with the residues of IA and provided a less polar environment that favours the preservation of IA in its active monomeric form, opening new opportunities for utilizing [Ch][AA] as storage medium.

Adsorption of CO2 with tetraethylammonium glycine ionic liquid modified alumina in the Rotating Adsorption Bed

CO2 capture and reuse have become the crucial task for controlling severe climate changes. Based on the practical application problems related to high viscosity of the ionic liquids (ILs) in the CO2 absorption process, the new adsorbent was obtained by loading the tetraethylammonium glycine (N2222Gly) on millimeter-scale microspheres of alumina (Al2O3) with ultrasonic impregnation-filtration method in this text. The results shown that the N2222Gly was successfully and uniformly loaded on the surface and pore structure of the Al2O3 by the electrostatic interaction between glycine anion and the positively charged Al2O3 interface. The prepared adsorbent (N2222Gly-Al2O3) were filled in the Rotating Adsorption Bed (RAB), and a rapidly updated gas-solid interface area was formed when the RAB was rotating under the drive of the motor. Under the rotating dynamic environment, more active sites of N2222Gly-Al2O3 were exposed to CO2 and the mass transfer effect between gas-solid was effectively enhanced. The adsorption capacity in the RAB was equal to 15.94 mg·g−1, and was about 4.63 mg·g−1 higher than in the fixed bed. In addition, the RAB showed a seductive strengthening effect with the decrease in adsorption capacity of only 14.5% after six desorption operations (much less than the 30.5% decrease in the fixed bed). Interestingly, as a new type of adsorption device, the RAB enhanced the internal and external diffusion rates of the adsorption process, providing a new idea for the effective adsorption of CO2 at low partial pressure with presence of the N2222Gly-Al2O3.

Equilibration processes in alkaline Cu | Cu(II), glycine system

The nature and kinetics of the equilibrium processes at the interface between the copper electrode and the alkaline solution containing glycine complexes of Cu(II) have been studied. The material balance equations that consider the formation of Сu(I) complexes were used to calculate the composition of the equilibrium system. It was found that the amount of Сu(I) compounds increases with increasing the pH and ligand concentration. Using the EQCM method it was found that the electrochemical dissolution of Cu electrode proceeds under open circuit conditions at potentials 60–70 mV higher than their equilibrium values. The generation of Cu+ ions obeys the laws of pseudo-first order processes at a rate constant of ~2 × 10–4 s–1. It is assumed that the final product of the equilibration is a monoligand complex of CuL (L– is a glycinate anion). Besides, there is a thermodynamic probability of the formation of cuprous oxide in the system.

An Electrokinetic Study of Amino Acid and Potential-Determining Ions for Enhanced Waterflooding in Carbonate Reservoirs

Summary Reservoir rock wettability plays an important role in waterflooding especially in fractured carbonate reservoirs because oil recovery tends to be inefficient from the mixed-wet or oil-wet rock matrix. Improved oil recovery has been observed by adjusting the concentrations of potential-determining ions (PDIs) to alter the wettability of carbonate rocks. Our previous study showed that the oil recovery from carbonate reservoirs by waterflooding can be enhanced by the addition of glycine, the simplest amino acid. The interaction of glycine anion and oil-wet carbonate surfaces was confirmed in contact angle measurements and yielded the incremental oil recovery in imbibition experiments. This paper presents a surface complexation model (SCM) for the interaction between glycine and oil-wet carbonate surfaces that considers the impact of temperature, pH, salinity, and the concentrations of PDIs. The proposed SCM was tuned based on the zeta potential (ZP) data reported for synthetic calcite in glycine solutions. The tuned model predicts that the strong affinity of glycine for the oil-wet carbonate surface causes the carboxylic acids to desorb from the surface. The concentration of adsorbed carboxylic acids was in qualitative agreement with the water-wetting state of carbonate rocks inferred from the reported contact angle and spontaneous imbibition experiments. Moreover, the model indicates that glycine’s performance as a wettability alteration agent improves significantly at high temperatures. It also suggests that enhanced oil recovery (EOR) by formation brine (FB) with 1 to 3 wt% glycine at high temperatures should be similar to the injection of low-salinity seawater (LSW). The proposed SCM supports glycine’s potential to change the wettability of oil-wet carbonates at high salinity, high hardness, and high temperature.

Milliampere-level direct current enhance cyanogenic capability of bacteria during the bioleaching of precious metals from waste printed circuit boards

For the conservation and sustainable utilization of metallic resources, recovering precious metals from the vast quantity of waste printed circuit boards is an attractive avenue. Bioleaching has been proved as an environment-friendly and suitable recovery technology. However, the limited cyanogenic capability restricts the industrialization of this technology. To break this bottleneck, in this paper, an innovative bioleaching technology assisted by milliampere-level direct current was developed to enhance cyanogenic capability. Experimental results indicated 10 mA current was the most beneficial for cyanide production. At 10 mA, the cyanide concentration reached 5.05 mg/L, 1.48 times that of without electric current. With the assistance of milliampere-level direct current, the total energy required for the reaction from glycine anion to cyanide was decreased by 101.81 kcal/mol. Meanwhile, the added direct current reduced the relative abundance of Pseudomonadaceae but enriched Enterobacteriaceae. Clusters of orthologous groups function classification revealed that some functions involved in cyanide production such as secondary metabolites biosynthesis, transport and catabolism were more powerful. This work proposes a novel approach to break the bottleneck of low cyanogenic capability in bioleaching technology, providing crucial scientific information for the industrialization of bioleaching.

Impact of pH on the Anodic Current-Voltage Characteristics of the Alkaline Cu ∣ Cu (II), Glycine System

Anodic voltammograms using rotating disc electrode (RDE) and linear sweep (LS) techniques were obtained for alkaline (9 < pH < 11.2) Cu (II)-glycine solutions. The nature and properties of the RDE anodic pseudo-limiting currents i lim and LS peak currents i p were considered within the framework of a theoretical model, taking into account the peculiarities of mass transfer of chemically interacting species. Both i lim and i p increase with solution pH and vary linearly with the concentration of glycinate anion l−. The degree of irreversibility of the process significantly affects the i p values, but has only small influence on i lim. Both characteristic current densities could serve as a measure of deprotonated ligand species, which is capable of forming stable Cu (II) complexes. The applications of modified equations, which were derived for i p in the case of simple redox systems, are discussed in detail.

The impact of glycine on the zeta potential of calcite at different temperatures and brine compositions

This study presents zeta potential (ZP) measurements of synthetic calcite in glycine solutions using the electrophoretic method. We tested samples with glycine concentrations of 1, 3, and 5 wt% at 25°C, while the ZP of 5 wt% glycine solutions was also measured at 50 and 75°C. The first set of measurements consisted of single-component brines prepared with CaCl2, MgCl2, Na2SO4, and NaCl salts with an ionic strength of 0.05 M. The second set of measurements consisted of formation brine (FB) with an ionic strength of 6.37 M and FB diluted 2-, 10-, and 100-times (2dFB, 10dFB, 100dFB, respectively). Results show that the effect of glycine on calcite’s ZP depended on its initial ZP value. Moreover, the increase in temperature significantly decreased calcite’s ZP in most samples. The ZP values in CaCl2 and MgCl2 brines were initially positive and decreased with the addition of glycine. Conversely, the ZP values of calcite in NaCl and Na2SO4 brines were initially negative and increased with the addition of glycine. The trends of ZP versus glycine concentration for 2dFB and 10dFB were analogous to the ones with CaCl2 and MgCl2 brines. Similar trends were observed between 100dFB, NaCl, and Na2SO4 brines. Finally, the increase of temperature from 25°C to 50°C and 70°C significantly reduced the ZP of calcite’s particles in CaCl2, Na2SO4, and NaCl brines, while the ZP of FB and its dilutions slightly decreased at 50°C. This is the first time the ZP measurements of calcite in glycine solutions were reported, to the best of our knowledge. Results are mainly explained by (1) the adsorption of glycine anion onto the calcite’s surface, (2) the decrease of the brine’s pH from the addition of glycine, and (3) the complex formation of glycine with divalent ions. Given the ubiquity and abundance of calcite in nature, we expect this study to increase the understanding of the electrostatic interactions between amino acids and calcite in phenomena such as wettability alteration and biomineralization.

Structure of cholinium glycinate biocompatible ionic liquid at graphite electrode interface.

We use constant potential molecular dynamics simulations to investigate the interfacial structure of the cholinium glycinate biocompatible ionic liquid (bio-IL) sandwiched between graphite electrodes with varying potential differences. Through number density profiles, we observe that the cation and anion densities oscillate up to ∼1.5 nm from the nearest electrode. The range of these oscillations does not change significantly with increasing electrode potential. However, the amplitudes of the cation (anion) density oscillations show a notable increase with increasing potential at the negative (positive) electrode. At higher potential differences, the bulkier N(CH3)3CH2 group of cholinium cations ([Ch]+) overcomes the steric barrier and comes closer to the negative electrode as compared to oxygen atom (O[Ch]+ ). We observe an increase in the interaction between O[Ch]+ and the positive electrode with a decrease in the distance between them on increasing the potential difference. We also observe hydrogen bonding between the hydroxyl group of [Ch]+ cations and oxygens of glycinate anions through the simulated tangential radial distribution function. Orientational order parameter analysis shows that the cation (anion) prefers to align parallel to the negative (positive) electrode at higher applied potential differences. Charge density profiles show a positive charge density peak near the positive electrode at all the potential differences because of the presence of partially positive charged hydrogen atoms of cations and anions. The differential capacitance (Cd) of the bio-IL shows two constant regimes, one for each electrode. The magnitude of these Cd values clearly suggests potential application of such bio-ILs as promising battery electrolytes.

Experimental and theoretical study of CO2 sorption in biocompatible and biodegradable cholinium-based ionic liquids

Biocompatible choline-based amino acid ionic liquids ([Cho][AA]s) were synthesized using neutralization choline hydroxide with amino acids. The sorption of carbon dioxide gas in three [Cho][AA]s, cholinium glycinate ([Cho][Gly]), cholinium alaninate ([Cho][Ala]), and cholinium valinate ([Cho][Val]) were investigated by quartz crystal microbalance (QCM) at temperatures from 288.15 to 318.15 K and pressures up to 4 bar. According to the sorption mechanism, the experimental CO2 sorption in [Cho][AA]s was correlated by a reaction equilibrium thermodynamic model. The thermodynamic parameters including reaction equilibrium constant, Henry’s law constant, enthalpy of physical sorption were calculated and compared with assessing the CO2 sorption performance in [Cho][AA]s. The results indicate that [Cho][AA]s with glycinate anion has better performance than others in carbon dioxide sorption. FT-IR spectra of [Cho][AA]s after CO2 sorption reveals that the chemical sorption of CO2 was take placed via carbamate formation. Density functional theory (DFT) calculations have been performed to affirm sorption energy of CO2 onto three [Cho][AA]s with different anions.