Mixtures Of Deep Eutectic Solvents Research Articles

Graph neural networks for CO[formula omitted] solubility predictions in Deep Eutectic Solvents

Deep Eutectic Solvents (DESs) are a promising class of solvents for CO2 capture. DESs are complex mixtures that can be designed to optimize CO2 solubility and overall capture process efficiency. However, the vast design landscape of DES mixtures makes experimental investigation prohibitive; as such, there is a need for computational models that can quickly and efficiently navigate the design space and inform data collection efforts. In this work, we propose Graph Neural Network (GNN) models for predicting CO2 solubility for DESs; the GNN leverages a mixture graph representation that captures the molecular structure of the DES components as well as their intermolecular interactions. We compare the GNN framework against alternative architectures (neural networks, graph convolution networks, and random forests) and data representations (molecular fingerprints, sigma profiles, and graphs). We show that the proposed approach offers superior predictive performance; specifically, we show that solubility can be predicted reliably directly from molecular structure (without the need of using sigma profiles as proposed in previous studies). This result is important, as obtaining sigma profiles requires expensive density functional theory computations. We also explored the ability of GNNs to predict solubility for new DES mixtures and operating conditions. We found that the model extrapolates across temperature reliably. However, we also found deficiencies in the ability of the model to predict solubility for DES mixtures, pressures, and molar ratio not included in the training sets; we show that this is due to an inherent lack of chemical diversity in datasets available in the literature. The proposed computational capabilities can thus help navigate the design space of DES and inform data collection efforts. Our models, data, and benchmarks are shared as Python code implemented in Jupyter notebooks.

DIFFERENT APPROACHES TO AGAROSE SULFATION WITH SULFAMIC ACID

Sulfated polysaccharides are important promising biologically active substances with anticoagulant properties. Biological activity is affected by the method of preparation, as well as the type of the polysaccharide and its molecular structure. In this work, we have considered various methods for the synthesis of promising anticoagulants – polysaccharide sulfates using the example of obtaining agarose sulfate. We compared various sulfating agents: chlorosulfonic acid, sulfamic acid, with various activators, and a deep eutectic solvent mixture of sulfamic acid with urea (in the melt). It has been shown that when urea is used as an activator of the process of sulfation of agarose with sulfamic acid in 1,4-dioxane, agarose sulfate with a high sulfur content (up to 14.5 wt%) is formed, which is close to the use of chlorosulfonic acid as a sulfating agent (with the production of agarose sulfate with 15.0 wt% sulfur). The use of solid catalysts in the process of sulfation of agarose with sulfamic acid leads to the production of agarose sulfate with a sulfur content of up to 14.1 wt% (for a catalyst based on the oxidized carbonaceous material Sibunit-4®). Sulfation of agarose in a deep eutectic solvent – a mixture of sulfamic acid with urea – leads to the production of agarose sulfate with a sulfur content of up to 13.7 wt%. The resulting agarose sulfates were characterized by FTIR spectroscopy, X-ray diffraction, elemental analysis, atomic force microscopy and DFT.

Interfacial Nanostructure and Hydrogen Bond Networks of Choline Chloride and Glycerol Mixtures Probed with X-ray and Vibrational Spectroscopies.

The molecular distribution at the liquid-vapor interface and evolution of the hydrogen bond interactions in mixtures of glycerol and choline chloride are investigated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Nanoscale depth profiles of supersaturated deep eutectic solvent (DES) mixtures up to ∼2 nm measured by ambient-pressure XPS show the enhancement of choline cation (Ch+) concentration by a factor of 2 at the liquid-vapor interface compared to the bulk. In addition, Raman spectral analysis of a wide range of DES mixtures reveals the conversion of gauche-conformer Ch+ into the anti-conformer in relatively lower ChCl concentrations. Finally, the depletion of Ch+ from the interface (probing depth = 0.4 nm) is demonstrated by aerosol-based velocity map imaging XPS measurements of glyceline and water mixtures. The nanostructure of liquid-vapor interfaces and structural rearrangement by hydration can provide critical insight into the molecular origin of the deep eutectic behavior and gas-capturing application of DESs.

Hydrogen Bond Donors Dictate the Frictional Response in Deep Eutectic Solvents.

Deep eutectic solvents (DESs) show promise as boundary lubricants between sliding surfaces, taking advantage of their physical stability, chemical stability, and tunability. Here, we study friction forces across nanofilms of two archetypal DES mixtures: choline chloride + ethylene glycol and choline chloride + glycerol. Using a surface force balance, we control the film thickness (to subnanometer precision) and determine the friction force simultaneously. Measurements are made at different mole fractions of the choline chloride salt and the molecular solvent, allowing us to determine the role of each species in the observed behavior. We find that the nature of the molecular solvent is dominant in determining the lubrication behavior, while the fraction of ChCl is relatively less important. By analyzing the steps in friction and the gradient of friction with load as the layers squeeze away from between the surfaces, we learn various mechanistic aspects of lubrication across the DES nanofilms of relevance to design and optimization of these promising fluids.

Effect of glucose–citric acid deep eutectic solvent on the vapor–liquid equilibrium of an aqueous ethanol solution

Objectives. To study the effect of a deep eutectic solvent (DES) based on glucose and citric acid on the vapor–liquid equilibrium of an aqueous solution of ethanol.Methods. A qualitative and quantitative analysis of the conditions of vapor–liquid equilibrium in an ethanol–water–DES ternary mixture was performed based on the open evaporation method and the measurement of TPxy data using a Świętosławski ebulliometer. Since the volatility of the DES is negligible in comparison with that of water and ethanol, the composition of the vapor phase was measured by means of Karl Fischer titration. The conditions of vapor–liquid phase equilibrium were modeled using the UNIFAC model.Results. The open evaporation method was used to determine the curves of residual concentrations for the ethanol–water–DES mixture at various DES concentrations and compositions (glucose–citric acid ratios). TPxy data was obtained for the mixture produced by adding 30 wt % DES to an aqueous solution of ethanol at atmospheric pressure. Studies show that DES based on glucose and citric acid has a significant effect on the relative volatility of ethanol in aqueous solution, leading to the disappearance of the azeotropic point. This effect is due to only the presence of glucose. Citric acid does not change the composition of the equilibrium phases, but rather increases the solubility of glucose in aqueous ethanol solutions. This is especially important at high ethanol concentrations, since glucose is poorly soluble in ethanol.Conclusions. Addition of DES based on glucose and citric acid to an aqueous solution of ethanol leads to the disappearance of the azeotropic point. DES can thus be considered as a promising entrainer for extracting ethanol from aqueous solutions using extractive distillation. Modeling of the conditions of vapor–liquid equilibrium in the ethanol–water–DES system using the UNIFAC model showed a satisfactory level of accuracy. The error in the calculated data increases with increasing the glucose concentration, while remaining acceptable for practical use.

High-pressure carbon dioxide solubility in a deep eutectic solvent (Choline Chloride/MDEA) + sulfolane—Experimental study and thermodynamic modeling using PC-SAFT equation of state

In recent years, releasing post-combustion CO2 into the atmosphere has led to global warming. Air contamination has appeared as a challenge for governments, so several approaches have been used to overcome this issue. So far, physical and chemical solvents have been employed by researchers for CO2 capture. These years deep eutectic solvents (DES) have emerged as an alternative to traditional solvents. In this study, we have investigated a mixture of DES + a physical solvent for the CO2 solubility measurement using a static vapor-liquid equilibrium cell. In this work, the DES was composed of Choline Chloride and MDEA in a molar ratio of 1 to 6 which is blended with sulfolane in weight percentages of 5,10, and 15. We performed the experiments at temperatures of 323.15, 333.15, and 343.15 K and a pressure range of up to 5 MPa. In our previous work, we had already investigated the influence of piperazine on the present DES that led to enhancing CO2 absorption in the mixture, while adding sulfolane to the DES in the present work does not present a positive effect on CO2 solubility in the DES. Enhancing pressure and reducing temperature also led to increasing CO2 solubility. Finally, we modeled the solubility data with the PC-SAFT equation of state. The modeling results were in excellent agreement with the experimental data for DES-CO2, DES-sulfolane-CO2, and DES-piperazine-CO2 systems, so the PC-SAFT EoS successfully estimated the carbon dioxide solubility in the present systems with the absolute average deviation percent of less than unity.

An eminent approach towards next generation solvents for sustainable packaging and stability of enzymes: a comprehensive study of ionic liquid and deep eutectic solvent mixtures.

Hybrid ionic fluids (HIFs) are newly emerging and fascinating sustainable solvent media, which are attracting a great deal of scientific interest in protecting the native structure of proteins. For a few decades, there has been a demand to consider ionic liquids (ILs) and deep eutectic solvents (DESs) as biocompatible solvent media for enzymes; however, in some cases, these solvent media also show limitations. Therefore, this work focuses on synthesising novel HIFs to intensify the properties of existing ILs and DESs by mixing them. Herein, HIFs have been synthesised by the amalgamation of a deep eutectic solvent (DES) and an ionic liquid (IL) with a common cation or anion. Later on, the stability and activity of hen's egg white lysozyme (Lyz) in the presence of biocompatible solvent media and HIFs were studied by various techniques such as UV-vis, steady-state fluorescence, circular dichroism (CD), Fourier transform infrared spectroscopy (FT-IR) and dynamic light scattering (DLS) measurements. This work emphasises the effect of a DES (synthesised using 1 : 2 choline chloride and malonic acid) [Maline], ILs (1-butyl-3-methylimidazolium chloride [BMIM]Cl or choline acetate [Chn][Ac]) and their corresponding HIFs on the structure and functionality of Lyz. Moreover, we also studied the secondary structure, thermal stability, enzymatic activity and thermodynamic profile of Lyz at pH = 7 in the presence of varying concentrations (0.1 to 0.5 M) of [BMIM]Cl and [Chn][Ac] ILs, Maline as a DES, and Maline [BMIM]Cl (HIF1) and Maline [Chn][Ac] (HIF2). Spectroscopic results elucidate that ILs affect the activity and structural stability of Lyz. In contrast, the stability and activity are inhibited by DES and are enhanced by HIFs at all the studied concentrations. Overall, the experimental results studied explicitly elucidate that the structure and stability of Lyz are maintained in the presence of HIF1 while these properties are intensified in HIF2. This study shows various applications in biocompatible green solvents, particularly in the stability and functionality of proteins, due to their unique combination where the properties counteract the negative effect of either DESs or ILs in HIFs.

From Hemp Waste to Bioactive Nanofiber Composites: Deep Eutectic Solvents and Electrospinning in Upcycling Endeavors.

Natural fibers have attracted increasing interest as an alternative to produce environmentally friendly and sustainable materials. Particularly, hemp fibers have been widely used in various industrial applications due to their extremely unique properties. However, hemp can generate a large amount of agro-waste, and it results in an attractive source of biopolymers for the development of low-cost materials as an alternative to the raw materials and conventional petroleum-based plastics. In addition, deep eutectic solvents (DESs), a new type of truly green solvents, have been shown to remove gums, lignin, and other non-cellulosic components from hemp fibers. Reusing these components dissolved into the DESs to fabricate new materials directly by electrospinning is a very attractive but still unexplored endeavor. Thus, this innovative research to venture new upcycling pathways is focused on the fabrication of composite nanofibers by electrospinning of a gel-based blend of Poly(vinyl alcohol) (PVA) and hemp agro-waste (HW) dissolved into choline chloride (ChCl):Glycerol (1:2) and ChCl:Urea (1:2) DES mixtures. The results obtained revealed that the produced nanofibers displayed uniform appearance with diameters ranging from 257.7 ± 65.6 nm to 380.8 ± 134.0 nm. In addition, the mechanical properties of the electrospun composite nanofibers produced from the gel-based blends of HW dissolved in DESs and PVA (HW-DESs_PVA) were found to be superior, resulting in an enhanced tensile strength and Young's modulus. Furthermore, the incorporation of HW into the nanofibers was able to provide bioactive antioxidant and antibacterial properties. Overall, this study demonstrated a promising, more sustainable, and eco-friendly way to produce electrospun composite nanofibers using HW in a circular economy perspective.

Hydrophobicity as the key to understanding the nanostructural behavior of eutectic mixtures upon apolar cosolvent addition

The influence of the addition of the apolar n-hexane (HEX) cosolvent on the structural arrangement of eutectic mixtures with different degrees of hydrophobicity, namely butylated hydroxytoluene (BHT), L-menthol (MEN), thymol (TYM), and choline chloride (ChCl), has been studied with a combined approach using small- and wide-angle X-ray scattering and molecular dynamics simulations. The cosolvent introduction has a similar impact on the molecular scale-length aggregation in BHT:MEN:HEX, TYM:MEN:HEX, and ChCl:TYM:HEX mixtures at different 1:3:H, 1:2:H, and 1:7:H molar ratios, specifically a dramatic perturbation of the main interactions present in the pure eutectics where hydrogen-bonds dominate. On larger scale-lengths, HEX addition results in a homogeneous electron-density distribution in the BHT:MEN:HEX and TYM:MEN:HEX mixtures due to a high affinity of the cosolvent for the BHT, MEN, and TYM components. Conversely, the presence of the more hydrophilic ChCl compound in the ChCl:TYM 1:7 system is the driving force for the segregation mechanism of this component which causes the formation of nano-scale inhomogeneities at high HEX concentrations, before macroscopic phase separation. The different degree of hydrophobicity is therefore key to understanding the nanostructural behavior of these eutectics in the presence of an apolar cosolvent. These findings have important implications for the employment of deep eutectic solvent mixtures, as the formation of pseudo-phase aggregates can help explaining the macroscopic behavior of these alternative media in applications like extraction procedures.

Interactions between components of choline chloride/propylene glycol or ethylene glycol deep eutectic solvents in the presence of water by determination of amlodipine besylate solubility profile

Improving amlodipine besylate (AMB) solubility as a poorly water-soluble drug is one of the biggest limits in preparation of different formulations in the pharmaceutical industry. Aiming to increase the aqueous AMB solubility, its solubility in choline chloride/propylene glycol (ChCl/PG) or choline chloride/ethylene glycol (ChCl/EG) deep eutectic solvents (DESs)-water mixtures was determined here using a shake-flask way at 293.2 K–313.2 K and ambient pressure (≈85 kPa) and correlated by models of van't Hoff, Jouyban-Acree and Jouyban-Acree-van't Hoff. In these mixtures, the maximum molarities of AMB (0.297 and 0.150 mol L−1) were determined at 313.15 K when the mass fraction of ChCl/PG and ChCl/EG were 0.8 and 1.0. The maximum AMB solubility in water was (0.008 mol L−1) at 313.15 K and observed an increment of 36.7-fold and 18.5-fold in ChCl/PG + water and ChCl/EG + water, respectively. The water effect on the stability of ChCl-PG or EG hydrogen bonding interactions was investigated by measuring the molarity of AMB in ternary mixtures of ChCl + PG or EG + water at 298.15 K. Comparing the obtained results for the above-mentioned binary and ternary mixtures presented that there is no real binary mixtures of DES and water when the water mass fraction was between 0.9 to 0.4 for ChCl/PG and 0.9 to 0.2 for ChCl/EG DESs, respectively. From correlation of AMB solubility with the selected cosolvency models, the mean percentage deviations were obtained between 3.4 % to 12.3 % which are on the acceptable range. Moreover, the consequences of apparent thermodynamic analysis demonstrated an endothermic and entropy-driven dissolution of AMB in all portions of ChCl/PG or ChCl/EG + water pseudo-binary mixtures.

Ultra-Tough and Highly Stretchable Dual-Crosslinked Eutectogel Based on Coordinated and Non-Coordinated Two Types Deep Eutectic Solvent Mixture.

Eutectogels are gaining attention in flexible device applications for their superior ionic conductivity, stability, biocompatibility, and cost-effectiveness. However, most existing eutectogels suffer from low strength and toughness. Herein, ultra-tough and highly stretchable polyacrylamide (PAM) eutectogels featuring a dual-crosslinked network comprising chemical cross-linking and physical cross-linking facilitated by metal coordination bonds and hydrogen bonds are developed. This is achieved through a controlled strategy involving polymerization of acrylamide in a coordinated metal salt-type deep eutectic solvent (DES) combined with a non-coordinated choline chloride (ChCl)-type DES mixture. By varying the molar ratio of these two types of DES, exceptional and adjustable mechanical properties of the resulting eutectogel are achieved, including a high tensile strength ranging from 2.9 to 8.2MPa and elongation at break ranging from 1725 to 747%, at a 70 wt% DES content. Furthermore, the reversible non-covalent crosslinking in these eutectogels enables self-recovery and self-healing capabilities of eutectogels. The prepared eutectogels also exhibit outstanding ionic conductivity (3.56 mS cm-1 ), making them well-suited for use as strain sensors in human motion detection. The toughening strategy is universally effective for creating tough eutectogels using coordinated metal salt-type DES with various metal ions, as well as a diverse range of coordinatable polymers.

Electrosynthesis of deep eutectic solvent assisted NiFe nanoparticles on stainless steel mesh for electrocatalytic water splitting reactions

This work focuses on the use of a deep eutectic solvent mixture to deposit nanoparticles of nickel and iron onto a surface of stainless steel (SS) mesh. The study was used to assess the performance of NiFe@SS nanoparticles in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting (OWS) reactions in a 1.0 M KOH solution. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were the materials characterization techniques that were used to examine the structure and physical properties of the NiFe@SS alloy deposited on the SS mesh. Electrochemical active surface area (ECSA) calculations were used for estimating the surface area of the electrode actively participating in the electrochemical reactions. The stability and durability of NiFe@SS nanoparticles were investigated through chronopotentiometry, chronoamperometry, and cyclic voltammetry. The results of the HER, OER, and OWS reactions brought out the significant electrocatalytic performance of NiFe@SS. The benchmark catalyst afforded overpotential values of −0.138 V and 0.234 V towards the HER and OER, respectively. The overall water-splitting cell voltage was about 1.56 V. The outperformed catalyst of NiFe@SS had an ECSA value of 32.75 mF/cm2 and showed more activity in HER, OER, and OWS reactions.

Upcycling Wool Waste into Keratin Gel-Based Nanofibers Using Deep Eutectic Solvents.

Millions of tons of wool waste are produced yearly by textile industries, which may become a serious environmental hazard in the near future. Given this concern, it is crucial to explore strategies to reduce the amount of wool waste generated worldwide and adopt more sustainable practices for dissolving and regenerating wool keratin (WK) from textile waste. Most traditional methods involve the use of expensive, toxic, harmful, and poorly biodegradable compounds. To overcome these limitations and facilitate the reuse of wool waste through a cascade valorization strategy, researchers have started testing the use of deep eutectic solvents (DES) as a more sustainable and eco-friendly alternative for WK dissolution and regeneration. In this study, the potential of two different DES mixtures, Choline chloride (ChCl): Urea and L-Cysteine (L-Cys): Lactic acid (LA), was explored for dissolving wool waste. Subsequently, the gels obtained based on DES-WK were blended with polyvinyl alcohol (PVA) in different ratios to produce nanofibers using the electrospinning technique. The PVA/L-Cys: LA DES-WK proved to be the most effective DES mixture for fabricating WK gel-based nanofibers. Furthermore, their antioxidant and antimicrobial abilities were evaluated, thus confirming their bioactivity. The results obtained revealed that this approach to valorizing textile waste offers a unique avenue for the development of sustainable functional materials with potential applications in various biomedical and industrial fields.

Thermodynamic Properties, Activity Coefficients at Infinite Dilution and Cosmo‐SAC Modelling of Deep Eutectic Solvents at Different Temperatures

AbstractA deep understanding of the solute‐ deep eutectic solvent (DESs) interactions is required for an appropriate selection of DESs as absorption media in the extraction of binary mixtures. As a result, these studies are done to evaluate the values of the activity coefficients at infinite dilution ( ), allowing us to define and understand the nature of these intermolecular interactions comprising DES mixtures with volatile organic solvents at different temperatures using gas liquid chromatography technique to determine the for 34 solutes in DESs [zinc chloride+acetic or phosphoric acid] prepared at 1 : 2 molar ratio for the temperature range (313.15–353.15) K. The thermal stability of the prepared DESs was determined by a thermogravimetric analyser. Excess thermodynamic parameters [partial molar excess enthalpies and Gibbs free energies ] were derived from the data. The selectivity and capacity values for the industrial separations were calculated and compared with the literature values of other DESs, ionic liquids, and sulfolane to assess the suitability of the investigated DESs for possible applications as extracting solvents. The selectivity and capacity values are high and therefore, [zinc chloride+acetic or phosphoric acid] can be used as a potential solvent to replace the currently used conventional solvents in the separation of the selected azeotropes. COSMO‐SAC predictions were qualitatively in very good agreement with the experimental data.

A new green approach for Lavandula stoechas aroma recovery and stabilization coupling supercritical CO2 and natural deep eutectic solvents

This work investigated a green approach to obtain and stabilize Lavandula stoechas L. volatile organic compounds with sensory aroma characteristics by using alternative solvents, namely supercritical carbon dioxide (scCO2) and deep eutectic solvents (DES). The CO2 extracts were dispersed in different DES mixtures (betaine:ethylene glycol (1:3), betaine:glycerol (1:2), and glycerol:glucose (4:1)) and their stability was monitored during 6 months of storage at room temperature by monitoring the headspace (HS) profile. The CO2 extract was used as the control. It was initially determined that there was a dominant presence of oxygenated monoterpenes (67.33–77.50%) in the extracts. During storage, significant changes occurred in the samples’ HS, such as the decrease in terpene hydrocarbons which also affected the presence of oxygenated terpenes, which increased in certain cases. Moreover, the highest formation of new components was recorded in the control which could be an indicator of decreased stability. The DESs-CO2 were more stable than the CO2 control and among them, betaine:ethylene glycol stood out as the most adequate systems for maintaining the stability of L. stoechas HS components. For the visual estimation of similarities and dissimilarities among the samples, chemometric pattern recognition approaches were applied including the hierarchical cluster analysis, principal component analysis, and sum of ranking differences.

Electrochemical preparation of nanostructure zinc oxide in emulsion deep eutectic solvents mixtures

Deep eutectic solvents (DESs) offer important advantages over classical nano-metal oxides based on eutectic systems as a result of important characteristics based on forming significant molecular design and appropriate diminution molecules; they can be candidates as fundamental materials in electrochemistry applications, such as batteries, nanogenerators, and solar cells. In this study, an ethaline: oxaline 1:1 M ratio was successfully applied to synthesize uniform nano zinc oxide using polyaniline polymer molecules as an additive. The deep eutectic solvent system exhibited new and novel active media for synthesising ZnO nanoparticles. The addition of aniline and water molecules to DES media significantly supported the formation of zinc oxide nanoparticles. Nano zinc oxide was synthesised from extracted olive leaves. The olive leaves were extracted using digestion systems in aniline: ethaline: oxaline deep eutectic solvent systems. Deep eutectic solvent emulsions have been assessed as effective synthesis media in current electrochemical processes because they are inexpensive and environmentally friendly. They produce ZnO nanocrystals with 37 nm diameters dispersed in homogeneous reagents, whereas the morphology of ZnO nanocomposites prepared in a microemulsion exhibits significant structure and 50–100 nm ZnO nanoparticles. In electrochemical synthesis conditions, when using the electrochemical method, microemulsion systems were found to serve as enhancement media for forming special structures of ZnO nanocomposite cooperate together with aniline, exhibiting excellent electrochemical activity.

Enhanced Polyphenols Recovery from Grape Pomace: A Comparison of Pressurized and Atmospheric Extractions with Deep Eutectic Solvent Aqueous Mixtures.

Deep eutectic solvents (DES) are emerging as potent polyphenol extractors under normal atmospheric conditions. Yet, their effectiveness in hot pressurized liquid extraction (HPLE) must be studied more. We explored the ability of various water/DES and water/hydrogen bond donors (HBDs) mixtures in both atmospheric solid liquid extraction (ASLE) and HPLE (50%, 90 °C) for isolating specific polyphenol families from Carménère grape pomace. We assessed extraction yields based on total polyphenols, antioxidant capacity, and recovery of targeted polyphenols. The HBDs ethylene glycol and glycerol outperformed DES in atmospheric and pressurized extractions. Ethylene glycol exhibited a higher affinity for phenolic acids and flavonols, while flavanols preferred glycerol. Quantum chemical computations indicated that a high-water content in DES mixtures led to the formation of new hydrogen bonds, thereby reducing polyphenol-solvent interactions. HPLE was found to be superior to ASLE across all tested solvents. The elevated pressure in HPLE has caused significant improvement in the recovery of flavanols (17-89%), phenolic acids (17-1000%), and flavonols (81-258%). Scanning electron microscopy analysis of post-extraction residues suggested that high pressures collapse the plant matrix, thus easing polyphenol release.

Choline Fluoride-Ethylene glycol deep eutectic solvent mixture – Synthesis and physicochemical properties

A critical factor in achieving tunability in DESs is varying the type of hydrogen bond acceptors (HBAs) and donors (HBDs). Choline halides (ChX), such as ChCl and ChBr, have been studied to investigate the effect of the choline anion on DESs. However, ChF-based DESs have been underrepresented in scientific research. ChF has excellent potential, such as high electron affinity, ionization potential, and strong hydrogen bond interactions. Moreover, ChF-based DES can lead to a deeper understanding of DESs due to the NMR-active 19F nuclear spin nature. We report the first synthesis and characterization of choline fluoride-EG (1:2, ChF:EG) DES, which we named “EthalineF.” We studied this mixture using various spectroscopic techniques, including NMR, FT-IR, Raman, and UV–vis spectroscopies. Polarity, density, viscosity, and conductivity measurements were collected as well. Transient absorption spectroscopy (TAS) was used to study the solvation dynamics of EthalineF. 19F NMR indicated that some fluoride anions (∼15%) are coordinated to the choline cation. In EthalineF, the new type of observed fluoride anions is proposed to be a tight-binding choline-fluoride ion pair. Further, EthalineF has a larger solvodynamic radius than Ethaline. This can explain the lower conductivity for EthalineF compared to Ethaline despite the higher fluidity and solvation dynamics for EthalineF.

Single-Molecule Junction Formation in Deep Eutectic Solvents with Highly Effective Gate Coupling.

The environment surrounding a molecular junction affects its charge-transport properties and, therefore, must be chosen with care. In the case of measurements in liquid media, the solvent must provide good solvation, grant junction stability, and, in the case of electrolyte gating experiments, allow efficient electrical coupling to the gate electrodes through control of the electrical double layer. We evaluated in this study the deep eutectic solvent mixture (DES) ethaline, which is a mixture of choline chloride and ethylene glycol (1:2), for single-molecule junction fabrication with break-junction techniques. In ethaline, we were able to (i) measure challenging and poorly soluble molecular wires, exploiting the improved solvation capabilities offered by DESs, and (ii) efficiently apply an electrostatic gate able to modulate the conductance of the junction by approximately an order of magnitude within a ∼1 V potential window. The electrochemical gating results on a Au-VDP-Au junction follow exceptionally well the single-level modeling with strong gate coupling (where VDP is 1,2-di(pyridine-4-yl)ethene). Ethaline is also an ideal solvent for the measurement of very short molecular junctions, as it grants a greatly reduced snapback distance of the metallic electrodes upon point-contact rupture. Our work demonstrates that DESs are viable alternatives to often relatively expensive ionic liquids, offering good versatility for single-molecule electrical measurements.

Predicting the CO2 Capture Capability of Deep Eutectic Solvents and Screening over 1000 of their Combinations Using Machine Learning

Deep eutectic solvents (DESs) are a new class of environmentally friendly solvents that have attracted the attention of many researchers. Since DESs have several practical applications in CO2 capture, knowledge of their CO2 solubility is crucial. In this study, the CO2 solubility of DESs was predicted via a multilayer perceptron (MLP) using molecular descriptors derived from the Conductor-like Screening Model for Real Solvents (COSMO-RS). An extensive database of 2327 data points was created from 94 unique DES mixtures made from 2 anions, 17 cations, and 39 hydrogen bond donors (HBDs) at 150 different compositions and operating conditions of temperatures and pressures. Several statistical tests were performed, and after thorough hyperparameter tuning, it was found that the best MLP architecture predicted the CO2 solubility with an R2 value of 0.986 ± 0.002 and an average absolute relative deviation (AARD) of 4.504 ± 0.507. The MLP has also been loaded into an accessible Excel spreadsheet included in the Supporting Information. Thereafter, in order to guide DES molecular design for achieving high CO2 solubilities, the MLP was utilized for the high-throughput screening of 1320 DES combinations. This model encourages the creation of robust and accurate models to predict the CO2 solubility of novel DESs, which will minimize the need for conducting costly and time-consuming experiments.