Mixture Of Choline Chloride Research Articles

Electrochemical Surface Treatment to Enhance Corrosion Resistance and Bioresistance of Medical-Grade Stainless Steels

The room-temperature eco-friendly electrochemical surface treatment of medical-grade stainless steels in ethaline, a eutectic mixture of choline chloride and ethylene glycol in a molar ratio of 1:2, is investigated in this work. High levels of brightness, smoothness and corrosion resistance of the surfaces of the stainless steels Mn AISI, AISI 316Ti, and AISI 304 can be achieved by using the technique of anodic treatment in ethaline. The surface smoothing of the steel samples due to the dissolution of defects and inhomogeneities, and the enrichment of the electropolished surfaces with chromium and nickel, resulted in increased corrosion resistance and bioresistance. The results of the experiments demonstrated that with anodic treatment in ethaline it is possible to decrease the amount of the Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans microorganisms on the surfaces of the steel samples by a factor of up to 75. Thus, the deep eutectic solvent ethaline is a highly promising medium for significantly improving corrosion resistance and bioresistance of medical-grade stainless steels by anodic treatment.

Electrochemical Synthesis of Polypyrrole and Polypyrrole-Indomethacin Coatings on NiCr Alloys Involving Deep Eutectic Solvents

There is an increased interest in the use of the deep eutectic solvents (DESs) as electrolytic media for electrochemical synthesis of conducting polymers, which could influence their characteristics. Moreover, the polypyrrole layers represent an attractive route for pharmaceutical drug release. The paper presents several experimental results regarding the electrodeposition of polypyrrole and of polypyrrole-indomethacin coatings on nickel-chromium NiCr alloy substrates widely used in dentistry, involving DES-based electrolytes, namely eutectic mixtures of choline chloride and malonic acid. This type of electrolyte also allowed an enhanced dissolution of indomethacin as compared to aqueous ones. The electropolymerization process has been investigated by cyclic voltammetry and chronoamperometry. The obtained indomethacin containing polymeric coatings have been thoroughly characterized involving scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, contact angle measurements in simulated body fluid (SBF) and indomethacin release studies. Adherent and uniform polypyrrole-indomethacin layers have been obtained on NiCr alloy substrates. The release tests showed that the polypyrrole coatings containing indomethacin may deliver the drug molecules for longer periods of at least 17 days. The maximum released amount was around 99.6% suggesting these layers may act as an active reservoir for indomethacin. Kinetics analysis based on the Korsmeyer–Peppas model suggested the diffusion of the drug out of the polymer layer as the most probable mechanism governing the release.

Electropolymerization of pyrrole from a deep eutectic solvent for supercapacitor applications

In this study, polypyrrole was electroplated onto graphite surface electrochemically from a urea and choline chloride mixture of deep eutectic solvent as the deposition solution. SEM, Raman and FTIR analysis showed that pyrrole was electrochemically polymerized homogeneously as the polypyrrole (PPy) on the graphite surface. Surface morphology of PPy/graphite composite electrode synthesized from the deep eutectic solvent electrolyte medium resembled blistered structures. Electroplated PPy-based composite electrodes were transferred to water containing LiClO4, acetonitrile containing LiClO4 and pure Reline deep eutectic solvent electrolytes to examine their electrochemical properties in different electrolytes. PPy displayed capacitance behavior in all these cycling electrolytes. PPy/graphite composite electrode was reached to 535 F g−1 in aqueous and organic electrolyte. Rate limiting reaction of PPy modified electrodes in three different electrolyte baths is between surface and diffusional controlled mechanism. Electropolymerization of pyrrole from deep eutectic solvent electrolyte media was electrochemically active in three different electrolyte media and is a promising material for supercapacitor applications.

Corrosion behavior of AA2024-T6 and AA6065-T6 alloys in reline

Deep eutectic solvents have been widely acknowledged as ionic liquid analogues, since they share many characteristics and properties with ionic liquids. The two major application areas of deep eutectic solvents have been metal processing and synthesis media; however, plenty of other applications have already been reported and predicted for these liquids. Reline, an eutectic mixture of choline chloride and urea, is a well known representative of deep eutectic solvents. Despite their importance in the contemporary technologies, the knowledge about the corrosivity of deep eutectic solvents is remarkably scarce. This article reports the results on the corrosivity of reline towards two Al alloys, namely AA2024-T6 and AA6065-T6. To measure the corrosion rates and characterize the passive film on the alloys in reline, electrochemical impedance and inductively coupled plasma optical emission spectroscopy methods were used, and the corrosion product composition was analyzed by X-ray photoelectron spectroscopy. Surface morphology and Volta potential were imaged by scanning electron microscopy, atomic force microscopy and scanning Kelvin probe force microscopy. The corrosion tests show that the two alloys are extremely stable in reline, and the passive layer is formed in the first three hours of immersion in the corrosive media. There is no evidence that electrolyte species are incorporated into the Al oxide protective layer through chemical bonding.

Molecular Features of Reline and Homologous Deep Eutectic Solvents Contributing to Nonideal Mixing Behavior.

Deep eutectic solvents based on choline chloride and a series of urea derivatives are studied by molecular dynamics simulations with the aim to identify molecular features contributing to nonideal mixing behavior of these compounds. In case of reline, a mixture of choline chloride and urea in 1:2 ratio, urea molecules provide sufficient hydrogen bond donor sites to take up the chloride anions into their polar network. Replacing any of the hydrogen atoms of urea by a methyl group strongly pushes the anion to interact with these alkyl chains, resulting in a positive deviation of the activity coefficients of choline chloride compared to reline. Furthermore, the oxygen atom of urea can interact with the nitrogen atom of the cation. This enables the chloride anion to move off-center of the cation toward the hydrogen atom of its hydroxyl group, possessing stronger directional Coulomb interactions than the nitrogen atom of the cation. The substitution of urea's hydrogen atoms in cis position to the carbonyl group as in 1,3-dimethylurea, pushes the newly introduced nonpolar alkyl chains toward the nitrogen atom of the cation. This effect can be responsible for the experimentally observed increase of the activity coefficient of the urea derivative compared to urea. Additionally, indications for formation of nonpolar domains within the liquid and, thus, nanoscale segregation is visible as soon as one hydrogen atom of urea is replaced by an alkyl group.

Treatment effects of choline chloride-based deep eutectic solvent on the chemical composition of red pine (Pinus densiflora)

Effects of deep eutectic solvent (DES) treatment were determined for the chemical composition of the sapwood and heartwood of red pine (Pinus densiflora). Two DES systems were made from the mixture of choline chloride (ChCl) and two different hydrogen bond donors (HBDs), namely, lactic acid (LA) and glycerin (GLY), with different molar ratios (1:2, 1:6, and 1:10). The yield of the solid residue after DES treatment decreased with an increase in the HBD concentration and treatment time, indicating that the water-soluble fraction was increased. The amount of solid residue was lower in the DES with LA than in DES with GLY, and higher in sapwood than in heartwood during both DES treatments. There was no substantial change in the lignin content of the samples, each being 24.7 to 29.5 wt.%, based on the mass of the treated product. Similar to the yield of the solid residue, cellulose and hemicellulose content in the treated product decreased with an increase in the HBD concentration and treatment time, and it was higher in sapwood than in heartwood. The cellulose crystallinity exhibited a slight increase with increasing treatment time, but there was no difference among the treatments using different molar ratios and between sapwood and heartwood.

Deep eutectic solvent-based ultrasound-assisted emulsification microextraction for the rapid determination of benzotriazole and benzothiazole derivatives in surface water samples

This work describes a simple and environmental-friendly method for the simultaneous determination of five benzotriazole derivatives (BTRs) and four benzothiazole derivatives (BTs) that are frequently found in surface water. The target analytes were efficiently extracted from water samples using a “green” deep eutectic solvent (DES) as the extraction solvent based- ultrasound-assisted emulsification microextraction (DES-USAEME), and their determination were performed by ultrahigh-performance liquid chromatography and electrospray ionization (+)-quadrupole time-of-flight mass spectrometry (UHPLC-ESI(+)-QToF-MS). The DES was composed of a mixture of choline chloride and phenol (molar ratio 1:2). The DES-USAEME factors were optimized by a Box-Behnken Design coupled response surface methodology. The developed method was validated, providing limits of quantitation (LOQs; 02 μg L−1), high precisions (1–8%), and satisfactory mean spiked recoveries (72–104 %). Relatively high total concentrations of the target analytes were found in samples collected from a reservoir (47.2–101.3 μg L−1), which may have been released from tire-wear particles and scrap tires from buses and old tires that were strung alongside the shuttle boats to prevent the boats from coming into contact with each other or from impacting against the dock during docking. This is the first study on the occurrence of BTRs and BTs in reservoir samples.

From Salt in Solution to Solely Ions: Solvation of Methyl Viologen in Deep Eutectic Solvents and Ionic Liquids.

Solvation and transport properties of methly viologen dichloride (MVCl2) in 1:2, 1:4, and 1:6 molar mixtures of choline chloride (ChCl) and ethylene glycol (EG), including the deep eutectic solvent (DES) ethaline (1:2 mixture), were studied through the application of the hole theory to measured physical properties, cyclic voltammetry, and Raman spectroscopy. The ChCl:EG mixtures were compared to the ionic liquid (IL) 1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl) imide ([PYR13][TFSI]) and choline bis(trifluoromethylsulfonyl)imide (ChTFSI) EG mixtures with the same molar ratios in order to understand the impact of the anion and hydrogen bond donor on solvation. Exchanging the chloride anion with TFSI is found to increase the fluidity of the solvent and promote stronger solute-solvent interactions. Raman spectroscopy suggests MVCl2 is strongly solvated by EG in ChTFSI:EG solutions and interstitially accommodated in holes in ChCl:EG mixtures and [PYR13][TFSI]. Complex solvents such as ILs and DESs are regarded as "designer solvents", and it is demonstrated here that the physical properties and solvation characteristics of these fluids strongly depend on the choice of the anion.

A study of non-ideal mixtures of ethanol and the (1 choline chloride +2 ethylene glycol) deep eutectic solvent for their volumetric behaviour

In the present study, the volumetric behaviour of mixtures of (Ethaline + ethanol) was investigated for the first time. Ethaline, which is the mixture of choline chloride and ethylene glycol at a molar ratio of 1:2, is among the most well-known Deep Eutectic Solvents (DESs). Because of its rather low viscosities as compared to many DESs, it has gained the interest of researchers for use in different applications. In this work, isobaric densities of the mixtures of Ethaline + ethanol were measured and presented over the entire mixture concentration range within the temperature range of (293.15–333.15) K. Using the measured data, excess molar volumes of the mixtures were calculated and analysed. The negative values of excess molar volumes suggested the stronger interactions of hydrogen bonds in the mixture with respect to the pure states of its constituents. Additionally, partial molar volumes and excess partial molar volumes, as well as the corresponding values at infinite dilution, were calculated and analysed. It was found that both Ethaline and ethanol have the tendency to be solvated by the mutual unlike-molecule in the mixture, and this tendency is stronger for Ethaline. It is also suggested that within the established hydrogen bond networks in the mixture, the Ethaline pseudo-molecules are probably located at central positions, being mostly surrounded by ethanol molecules.

Electropolishing of two kinds of bronze in a deep eutectic solvent (Ethaline)

Electropolishing of bronze was investigated in this work in an electrolyte based on a deep eutectic solvent, Ethaline (a eutectic mixture of choline chloride and ethylene glycol in a 1:2 M ratio, respectively). Two kinds of bronzes were used: AMPCO® 22 alloy (containing Al and Fe as alloying components) and AMPCO® 712 alloy (containing Sn, Ni, Pb and Zn as alloying components). Electrochemical responses of bronze in Ethaline were studied by cyclic voltammetry technique. It was established that the electropolishing of both bronzes can be performed at the temperature of 25 °C and anode electrode potential of 2.5 V (vs. Ag pseudo-reference electrode). The surface leveling and dissolution of microdefects were confirmed by atomic force microscopy and scanning electron microscopy. The electrochemical polishing of the surfaces of AMPCO® 22 and AMPCO® 712 bronzes was shown to result in an improvement in their corrosion resistance. Electrolytes based on deep eutectic solvents seem to be a promising replacement for traditional corrosive and environmentally hazardous acid aqueous solutions for electropolishing of copper alloys.

NADES-based fractionation of biomass to produce raw material for the preparation of cellulose acetates

Waste biomass (agave bagasse) and native birch wood were used as raw materials for a novel fractionation and derivation process to produce cellulose acetates (CAs). During the first stage of the fractionation process, a significant amount of hemicelluloses and lignin were dissolved from the biomass using a natural deep eutectic solvent (NADES) that consisted of a mixture of choline chloride and lactic acid with the molar ratio of 1:9. Then, the residual solid material was delignified by bleaching it with a mixture of acetic acid and sodium chlorite. The fractionation process generated differently purified pulps (celluloses) which were converted to CAs. The crystallinity index, polymerization degree, chemical composition, and thermal properties of the differently purified pulps and CAs were analyzed to evaluate the efficacy of the acetylation process and to characterize the CAs. The chemical derivation of the differently purified cellulose samples generated CAs with different degrees of substitution (DSs). The more purified the cellulose sample was, the higher its DS was. Moreover, some differences were observed between the acetylation efficiencies of birch and agave bagasse. Typically, cellulose purified from birch by treating it with NADES followed by bleaching was acetylated more completely (DS = 2.94) than that derived from agave bagasse (DS = 2.45). These results revealed that using green solvents, such as NADES, to treat both agave bagasse (waste biomass) and birch wood, allowed pure fractions to be obtained from biomass, and thus, biomass could be valorized into products such as CAs, which present a wide range of applications.

(Keynote) Nanoscale Structuring of Aniline-based Electroactive Polymer Films by Co-polymerisation and Particulate Inclusion

Electroactive polymer films derived from aniline and substituted derivatives have attracted huge interest, as a consequence of their electronic, optical, chemical and charge storage properties. Surprisingly, there has been limited translation of these characteristics into practical devices. Two factors that have impeded progress here are an inability to deliver and optimise multiple characteristics in a single material and the absence of control of internal film structure. The latter is particularly difficult to maintain for soft matter, whose molecular geometry and spatial disposition at the mesoscopic scale necessarily changes in response to solvent influx/efflux during redox switching. These solvation phenomena have been variously described in terms of activity (thermodynamic) effects, volume constraints (polymer mechanical properties) and mobility (kinetic) effects. Quite generally, the dominant factor depends on the timescale, a feature of the experiments reported here.In this presentation, we explore strategies aimed at understanding and controlling internal film structure and solvation for polymer films based on aniline-type monomers. From a chemical perspective, we explore the effects of three factors: the nature of the solvent / electrolyte, extension from homopolymers to co-polymers, and the inclusion of geometrically distinct particulate species to generate hybrid organic/inorganic materials.In the first instance, we compare film deposition and subsequent redox chemistry when exposed to a conventional protic solvent (water) or to the aprotic ionic liquid Ethaline (a mixture of choline chloride and ethylene glycol). As an intermediate case, we consider film deposition and redox chemistry in the protic ionic liquid Oxaline (a mixture of choline chloride and oxalic acid). Quantitative nanogravimetric (QCM) measurements during deposition from ionic liquid reveal that the polymer film has substantially greater solvent content than if deposited from aqueous medium. A recognised phenomenon for electroactive polymer films is an anomalous response for the first redox cycle; this is generally attributed to solvation effects. This phenomenon is manifested quite differently for polyaniline films in water and Ethaline. In water, film evolution occurs over a number of cycles, while in Ethaline (in which the film is more highly solvated) the transition is complete with a single cycle.In the second instance, we consider copolymerization of aniline with o-toluidine or with o-aminophenol. Counter ion coordination by the hydrogen bond donors results in substantive differences in the effectively transferred entity. In the cases of Ethaline and Oxaline, the counter ion is no longer a small, mobile chloride ion, but rather a large hydrogen bond donor-coordinated species. In pursuit of possible environmental applications, we consider the extreme case of fluoride as a counter ion. Surprisingly, the relatively small changes in polymer composition effected by co-polymerisation with o-toluidine or o-aminophenol result in substantial changes in fluoride uptake.Finally, we explore the effect of inclusion of particulates, chosen so as to influence different aspects of film behaviour. Specifically, we chose multi-walled carbon nanotubes (MWCNT), graphite flakes and molybdenum oxide particles as examples of 1D, 2D and 3D entities, respectively. Electrochemical and imaging data will be presented to demonstrate their substantive effects on film structure and dynamics.The outcomes of these studies provide insights relevant to practical applications. A particular case is that of medium transfer experiments, in which a film is deposited from one medium (aqueous or ionic liquid), redox cycled in the second and then returned to the first. We discuss the responses in terms of a “nature vs nurture” competition, in which the “nature” of a film is dictated by the conditions (medium) of deposition, and “nurture” is represented by the conditions to which it is exposed. Nanogravimetric (EQCM) responses of films subjected to water / ionic liquid / water and ionic liquid / water / ionic liquid transfer experiments reveal that films do retain some memory of their deposition conditions, but that extended redox cycling results in slow evolution that reflects the immediate medium of exposure. We discuss this in terms of slow polymer structural relaxation.

Brillouin Spectroscopy as a Suitable Technique for the Determination of the Eutectic Composition in Mixtures of Choline Chloride and Water.

Deep eutectic solvents (DESs) resulting from the right combination between a hydrogen-bond donor (HBD) and a hydrogen-bond acceptor (HBA) are becoming quite popular in number of applications. More recently, natural DESs (NADESs) containing sugars, natural organic acids, and amino acids as HBDs and ChCl as HBA have received great attention because of their further environmental sustainability as compared to regular DESs. Within this context, mixing water in controlled amounts has been widely accepted as a simple and practical way of altering DES chemical and thermodynamic properties, with viscosity and conductivity experiencing the most significant changes. However, the number of papers describing eutectic mixtures with water as the only HBD is scarce and basically none has been done in fundamental terms. Herein, we investigated mixtures composed of water as the only HBD and ChCl as the HBA using differential scanning calorimetry (DSC) as well as 1H nuclear magnetic resonance (NMR) and Brillouin spectroscopies. We found the aqueous dilution of ChCl/2H2O with a ChCl/2H2O content of ca. 80 wt % was an eutectic. Interestingly, this mixture could be considered a NADES according to its eutectic distance (ΔTme), in range to eutectics obtained in aqueous dilutions of salt hydrates.

Biodiesel purification in microextractors: Choline chloride based deep eutectic solvents vs water

Nowadays, the production of biodiesel by transesterification is a common process. On the other hand, once the biodiesel is produced, the purification of crude biodiesel to the extent that satisfies international standard norms still presents a significant challenge. One of the biggest challenges is the removal of glycerol. In this paper, the total of seven different deep eutectic solvents (DESs) based on a mixture of choline chloride and ethylene glycol or a mixture of choline chloride and glycerol were prepared and applied for biodiesel purification, using three microextractors of different sizes. The obtained results were compared with the results of biodiesel purification by wet washing in the same microextractor type. For the residence time of only 13.61 s, by using a ChCl:Gly1:2.5 DES, glycerol was almost completely removed from the biodiesel. So, the obtained result clearly justifies the application of DESs in microextractors for glycerol removal during biodiesel purification.

Encapsulation of β-Carotene by Emulsion Electrospraying Using Deep Eutectic Solvents.

The encapsulation β-carotene in whey protein concentrate (WPC) capsules through the emulsion electrospraying technique was studied, using deep eutectic solvents (DES) as solvents. These novel solvents are characterized by negligible volatility, a liquid state far below 0 °C, a broad range of polarity, high solubilization power strength for a wide range of compounds, especially poorly water-soluble compounds, high extraction ability, and high stabilization ability for some natural products. Four DES formulations were used, based on mixtures of choline chloride with water, propanediol, glucose, glycerol, or butanediol. β-Carotene was successfully encapsulated in a solubilized form within WPC capsules; as a DES formulation with choline chloride and butanediol, the formulation produced capsules with the highest carotenoid loading capacity. SEM micrographs demonstrated that round and smooth capsules with sizes around 2 µm were obtained. ATR-FTIR results showed the presence of DES in the WPC capsules, which indirectly anticipated the presence of β-carotene in the WPC capsules. Stability against photo-oxidation studies confirmed the expected presence of the bioactive and revealed that solubilized β-carotene loaded WPC capsules presented excellent photo-oxidation stability compared with free β-carotene. The capsules developed here clearly show the significant potential of the combination of DES and electrospraying for the encapsulation and stabilization of highly insoluble bioactive compounds.

Impregnating deep eutectic solvent choline chloride:urea:polyethyleneimine onto mesoporous silica gel for carbon dioxide capture

Development of green sorbents to capture carbon dioxide (CO2) whilst minimising their environmental impacts has gained interest among scientists. Deep eutectic solvent has been proposed as a promising green solvent for CO2 separation. In this study, a solid composite adsorbent based on mesoporous silica-gel (SG200) and deep eutectic solvent (DES) mixture of choline chloride:urea:polyethyleneimine (ChCl:U:PEI) was prepared by wet impregnation technique. The surface chemistry, thermal stability, surface porosity, CO2 adsorption capacity, and the effect of temperature on CO2 uptake by the adsorbents were studied. The highest CO2 adsorption of 51 mg/g at 25 °C and 1 bar was achieved by adsorbent with 25%ChCl:U:PEI loading, followed by 22%PEI (48 mg/g) and 24%ChCl:PEI (43 mg/g) loadings. Increased temperature was found to reduce the CO2 adsorption capacity. In addition, results from X-ray photoelectron spectroscopy (XPS) revealed the presence of cabamate ion after CO2 adsorption. This study revealed that the ternary DES, ChCl:U:PEI impregnated onto mesoporous silica sorbent has a promising potential to capture CO2.

Recovery of Silver and Gold From Electronic Waste by Electrodeposition in Ethaline Ionic Liquid

The recycling of metals from electronic equipment waste (e-waste) is of great concern today. The work described in the article focuses on the application of ionic liquids (ILs) to selectively recover of precious metals (Ag and Au) from the anodic slime obtained at the anodic dissolution of cast e-waste. The ingots obtained from molten and cast anodic slime were selectively dissolved in ILs. Silver and gold compositions of the ingots: 39.7 wt.% and respectively 18.9 wt.%. The IL used was an eutectic mixture of choline chloride with ethylene glycol in a 1:2 molar ratio. As catalytic/oxidizing agent, there was used pure iodine in a concentration of 0.1-0.2 moldm-3 at 298-303 K. Cyclic voltammetry was employed for the determination of the electrochemical windows of ILs as well as of the dissolution and electrodeposition potentials of principal metals present in the ingot (anode). For Ag and Au, the deposition potentials determined were 0.074 V and respectively 0.696 V. The XRD and SEM-EDX analyses revealed that the content of precious metals in the cathodic deposits was 99 wt.% for Ag and respectively ]70 wt.% for Au. We demonstrated that ILs electrolytes could be a solution to selective recovery of precious metals from e-waste.

Structural Properties and Hydrogen-Bonding Interactions in Binary Mixtures Containing a Deep-Eutectic Solvent and Acetonitrile.

Deep-eutectic solvents (DESs) are a new class of green solvents. Here, we report the hydrogen bonding and structural properties of the archetypal DES ethaline, a mixture of choline chloride (ChCl) and ethylene glycol (EG) of a 1:2 molar ratio, and its pseudo-binary mixtures with acetonitrile. The investigations were carried out employing Fourier-transform infrared (FTIR) spectroscopy combined with quantum chemical calculations. Excess and two-dimensional (2D)-correlation spectroscopies were used to identify favorable species in the solutions and to explore the heterogeneity. The results show that the mixing process is the transformation from ethaline and CH3CN dimer to the complexes of ethaline-1CH3CN and ethaline-2CH3CN, together with the increased percentages of the EG dimer, EG trimer, and CH3CN monomer with respect to their total amounts in the mixtures. Theoretical calculations show that, for ChCl, the positive charge is located at the methyl groups and methylenes, rendering their ability to form hydrogen bonds. Adding CH3CN to ethaline can hardly break apart the doubly ionic hydrogen bonds between Ch+ and Cl-. The cosolvent molecules mainly surround the core structure of ethaline, forming noncovalent hydrogen bonds with hydroxyl groups of EG/Ch+ but not Cl-. These in-depth studies on the properties of ethaline and CH3CN/CD3CN mixed solvents may shed light on exploring their applications.

New Green Adsorbent for Capturing Carbon Dioxide by Choline Chloride:Urea-Confined Nanoporous Silica

Green nanocomposite adsorbent based on nanoporous silica (NS) and deep eutectic solvent (DES) mixture of choline chloride–urea (ChCl:U) was synthesized as an alternative for carbon dioxide (CO2) adsorption. The nanocomposite adsorbent was prepared by sol–gel technique with the variations of ChCl:U (mole ratio 1:2) content in NS at 5–15% (w/w). Fourier transform infrared attenuated total reflectance (ATR-FTIR) results revealed the successful confinement of ChCl:U into NS from the presence of C=O carbonyl stretching, N–H scissoring bending, CH2 bending and C–N stretching peaks. The peaks intensity increased with increasing weight percentage of confined ChCl:U. In contrast, thermogravimetric analysis (TGA) showed decrement of thermal stability of the adsorbent when ChCl:U was confined into NS. The nitrogen physisorption demonstrated a decrease in specific surface areas of the sorbents with increasing ChCl:U weight percentage due to the transformation of micropores to mesopores. The CO2 adsorption capacity was found to be reduced when the weight percentage of ChCl:U was increased. The optimum adsorption capacity of 23.0 mg/g was achieved by 10% ChCl:U/NS sample. The mechanism of the adsorption was deduced from the ATR-FTIR and XPS spectra for 10%CuCl:U/NS showing that physisorption and chemisorption occurred during CO2 adsorption with the presence of carbamate ion.

Nanolubrication in deep eutectic solvents.

We report surface force balance measurements of the normal surface force and friction between two mica surfaces separated by a nanofilm of the deep eutectic solvent ethaline. Ethaline, a 1 : 2 mixture of choline chloride and ethylene glycol, was studied under dry conditions, under ambient conditions and with added water, revealing surface structural layers and quantised frictional response highly sensitive to water content, including regions of super-lubric behaviour under dry conditions and with added water. We also report exceptionally long-ranged electrostatic repulsion far in excess of that predicted by Debye-Hückel theory for a system with such high electrolyte content, consistent with previously reported observations of "underscreening" in ionic liquid and concentrated aqueous electrolyte systems [Smith et al., J. Phys. Chem. Lett., 2016, 7(12), 2157].