Physicochemical properties of deep eutectic solvents: A review

First truly deep eutectic solvent (DES) based stationary phase for high-performance liquid chromatography (HPLC)

Deep eutectic solvents (DESs) have gained significant attention due to their environmentally friendly properties and versatile applications in various fields, including analytical chemistry. This study investigates the use of a deep eutectic solvent (DES) composed of l-proline protonated with hydrochloric acid and xylitol as a surface modifier for silica-based stationary phases in high-performance liquid chromatography (HPLC). The DES was successfully immobilized on silica, and its impact on chromatographic performance was evaluated in normal-phase liquid chromatography (NP-HPLC). It was observed that DES immobilized layer acted as a real liquid stationary phase. The DES-modified columns exhibited improved selectivity, resolution for polar analytes, and shorter retention times for non-polar compounds compared to unmodified silica columns. Additionally, the DES-modified phase demonstrated long-term stability over multiple chromatographic cycles. These results highlight the potential of DESs as customizable, environmentally friendly stationary phase modifiers for enhancing chromatographic efficiency and selectivity, particularly in separating polar analytes, opening new avenues for the development of advanced chromatographic materials and contributing to greener and more efficient separation techniques. The robust preparation method also facilitates easy scalability for large-scale applications, such as the isolation of valuable compounds and the purification of complex mixtures, including phenols, amines, and nitro-derivatives.

Unlocking the potential of deep eutectic solvents for sustainable pectin extraction

Pectin is a heterogeneous polysaccharide mainly found in the cell walls of plants. Owing to its unique biological and functional properties, pectin is widely used across various industrial sectors, including the food, pharmaceutical, and cosmetic industries. The conventional method of industrially extracting pectin from plant materials is to use prolonged heating under highly acidic conditions. This process poses several drawbacks, including system corrosion, high energy consumption, and environmental concerns. This review article evaluates the potential application of deep eutectic solvents (DESs) as green alternatives to conventional solvents for pectin extraction, due to their exceptional extraction efficiency, minimal toxicity, low cost, eco-friendliness, and reusability. The classification, synthesis procedures, and physicochemical properties of DESs are reviewed. Additionally, the application of DESs for pectin extraction is discussed, both alone and in combination with other emerging extraction techniques, such as ultrasonic, microwave or high-pressure methods. Finally, the advantages and disadvantages of using DESs for pectin extraction are discussed. DESs has already shown considerable potential for the sustainable extraction of pectin from various plant sources, while preserving its functional attributes. The wide range of substances available for preparing DESs enables their extraction properties to be tailored for particular applications, allowing them to meet the specific needs for pectin extraction. DESs can be used in combination with other emerging extraction technologies to improve its pectin extraction efficiency. Therefore, the optimization of DES-assisted extraction techniques may lead to new sustainable methods for isolating pectin.

Deep eutectic solvent extraction of polyphenol from plant materials: Current status and future prospects in food applications

The increasing environmental concerns related to biomass waste have led to the exploration of sustainable methods for extracting bioactive compounds from plant materials, especially polyphenols, which are valued for their health benefits and use in functional foods and natural additives. These bioactive compounds are abundant in fruits, vegetables, tea, and herbs, and encompass flavonoids, phenolic acids, tannins, stilbenes, and lignans. Traditional extraction methods often rely on harmful petrochemical solvents, which pose significant environmental and health risks. In contrast, Deep Eutectic Solvents (DESs) have emerged as an eco-friendly alternative, offering advantages such as low toxicity, cost-efficiency, and a wide range of solubility. This review focused recent advancements in DES-based polyphenol extraction, emphasizing their applications in the food industry. It highlights the potential of DES to efficiently extract polyphenols, improving their bioavailability and stability, and exploring future prospect for enhancing food quality, safety, and functionality through functional foods and natural preservatives.

Highly Efficient Recovery of Cobalt-Ion Containing Waste Deep Eutectic Electrolytes: A Sustainable Solvent Extraction Approach

Efficient recovery of metals from secondary resources is essential to address resource shortages and environmental crises. The development of a cheap, environmentally friendly, and highly efficient recovery pathway is essential for resource retrieval. In this study, we propose a high-efficiency extraction approach utilizing bis(2,4,4-trimethylpentyl) phosphonic acid (Cyanex272) to recover cobalt from waste choline chloride/ethylene glycol (Ethaline) electrolyte containing Co(II) ions. By adjusting the water content of the system to modify the ligand of Co(II) ions, combined with pH adjustment, we achieved an extraction efficiency exceeding 99.9 % for Co(II) ions. Subsequently, oxalic acid (OA) was added as a stripping agent to achieve a recovery efficiency of over 99.4 % for cobalt. The extractant can be recycled more than 15 times after stripping. Impressively, more than 98.3 % of the water-diluted Ethaline extraction raffinate was recovered through reduced pressure distillation while maintaining the structure of recovered Ethaline unchanged. This work provides an economical, efficient, and sustainable pathway for treating waste Ethaline electrolyte-containing metal ions.

Cytotoxic potential of sunflower meal NaDES and liquid-liquid extracts

Sunflower meal, a by-product rich in proteins and phenolic compounds, has potential applications in food and healthcare due to its bioactive phenolic compounds. However, challenges arise in extracting these compounds, as phenol-protein complexes can reduce digestibility and nutritional value. This study explored phenolic compound extraction from sunflower meal using NaDES and hydroethanolic extract, followed by liquid-liquid extraction (LLE) with organic solvents to recover target compounds. Cytotoxicity assays were performed on breast cancer cell lines and pathogenic bacteria. Acetonitrile was the most effective solvent for phenolic recovery in Choline Chloride:Glycerol and Urea:Glycerol solvents, achieving 80 % and 63 % recovery, respectively. These NaDES combinations reduced cell viability by up to 78.4 % in MCF-7 cells and 74 % in MDA-MB-231 cells. Hydroethanolic extracts showed the highest antimicrobial activity, with up to 100 % bacterial viability reduction. This study confirms NaDES as effective green solvents and highlights their bioactivity, stressing the need for optimal extraction parameters.

A study of simultaneous electrodeposition of Cu and S in choline chloride-ethylene glycol deep eutectic solvents: a pathway to the synthesis of copper sulfide hexagons

Copper sulfides, with their tunable semiconductor properties, are promising materials for electronic and optoelectronic devices. Among the various synthesis techniques, electrodeposition stands out as a particularly effective method, offering precise control over the structure and composition of these compounds. In this study, we demonstrate the feasibility of co-electrodeposition of copper and sulfur on a carbon substrate using deep eutectic solvents (DESs) based on choline chloride and ethylene glycol. The effects of electrodeposition potential and electrochemical bath composition on the electroreduction process of CuCl2·2H2O and Na2S2O3 mixtures in DESs were investigated. By controlling the electrochemical deposition parameters, we successfully obtained various structures, including Cu clusters, S-doped Cu clusters, and copper sulfide (CuxS) hexagons. The morphology and composition of the obtained materials were characterized using scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) techniques. Our findings indicate that co-electrodeposition of Cu and S requires potentials more negative than -0.84 V vs. Pt. Furthermore, the formation of CuxS hexagons was achieved by acidifying electrochemical baths with H2SO4. Interestingly, the electrodeposition of Cu from DESs was favored under all investigated synthesis conditions. Consequently, the average atomic percentage of S in the obtained Cu-S materials was a maximum of 9.36 at%, while EDS point analyses revealed that individual copper sulfide hexagons contained 22.7 to 23.8 at% of S. These results provide valuable insights into the co-electrodeposition of Cu and S from choline chloride-ethylene glycol DESs and pave the way for the future development of novel copper sulfide-based materials.

Ultrasound-assisted ternary temperature-responsive deep eutectic solvents for extraction of carotenoids from tomato samples

As new green solvents, the low volatility of deep eutectic solvents (DESs) limits their development in natural product extraction. In this work, a series of novel lower critical solution temperature (LCST) type temperature-responsive DESs (TRDESs) were prepared and applied to the extraction of carotenoids from tomato. The highest yields (408.85 ± 4.97 μg/g of lycopene, 68.78 ± 2.00 μg/g of β-carotene) were obtained under the following conditions: extractant DES-16 (methyl 1-benzylpiperidine-4-carboxylate: valeric acid: heptanoic acid = 2:1:1), solid-liquid ratio 1:58 g/mL, extraction temperature 68 °C, and extraction time 44 min. Utilizing the temperature response characteristics of TRDESs, the separation of carotenoids and TRDESs was achieved in a mild way. Upon analysis, hydrophilic polysaccharides were simultaneously extracted and retained in water through the recovery experiment. Green Analytical Procedure Index (GAPI) proved the greenness of the method. This work provides new ideas for DESs in the extraction of natural products.

Deep Eutectic Solvents Based on N-Methyltrifluoroacetamide and Lithium Bis(trifluoromethanesulfonyl)imide as New Electrolytes with Low Viscosity and High Ionic Conductivity

In this work, we present a study on the thermal/transport properties of a novel deep eutectic solvent (DES) obtained by using N-methyltrifluoroacetamide (FNMA) as the hydrogen bond donor (HBD) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the hydrogen bond acceptor (HBA). The binary phase diagram, thermal stability, flammability, viscosity and ionic conductivity of the as-prepared DESs were investigated at atmospheric pressure. The binary phase diagram shows a range of eutectic molar ratios (xLiTFSI = 0.2~0.33), with the lowest deep eutectic temperature of -84 °C. At xLiTFSI = 0.2 (i.e., FNMA:LiTFSI = 4:1 and denoted as DES-4:1). The as-prepared DES composition exhibits high thermal stability (onset temperature of weight loss = 78 °C), a low viscosity (η = 48.9 mPa s at 25 °C), relatively high ionic conductivity (σ = 0.86 mS cm-1 at 25 °C) and non-flammability. The transport properties, including ionic conductivity and viscosity, as a function of temperature are in accordance with the Vogel-Fulcher-Tammann (VFT) equations. With increasing molar ratio of HBD vs. HBA, the viscosity decreases, and the ionic conductivity increases at a given temperature between 25 °C and 80 °C. The roughly equal pseudo-activation energies for ion transport and viscous flow in each composition imply a strong coupling of ion transport and viscous flow. Walden plots indicate vehicular transport as the main ion transport mechanism for the DES-4:1 and DES-3:1 compositions; meanwhile, it was confirmed that the ionic conductivity and viscous flow are strictly coupled. The present work is expected to provide strategies for the development of wide-temperature-range and safer electrolytes with low salt concentrations.

Porogenic Solvents in Molecularly Imprinted Polymer Synthesis: A Comprehensive Review of Current Practices and Emerging Trends

The versatility of molecularly imprinted polymers (MIPs) has led to their integration into applications like biosensing, separation, environmental monitoring, and drug delivery technologies. This diversity of applications has resulted in a plethora of synthesis approaches to precisely tailor the materials' properties to the specific demands. A critical, yet often overlooked, factor in MIP synthesis is the choice of porogen. Porogens play a pivotal role in defining the morphology, surface properties, swelling behavior, and binding efficiencies of the resulting MIPs. While aprotic solvents have traditionally been the standard in molecular imprinting, recent developments have expanded the variety of employed porogens accompanied by notable improvements in MIP performance. Therefore, this review aims to highlight both traditional and emerging types of porogens used in molecular imprinting, their influence on polymer properties and sorption performance, and their application across various sensing and extraction applications.

Physicochemical and Biological Properties of Menthol and Thymol-Based Natural Deep Eutectic Solvents

Seven hydrophobic deep eutectic solvents (hDESs) were characterised to evaluate their potential applicability in different industries and their environmental impact. Standard physicochemical properties were determined, yielding polarity and density values that were slightly higher for thymol-based hDESs than menthol-based ones, whereas for viscosity, the trend was opposite. Regarding biologically relevant activities, the antioxidative capacity and antimicrobial activity of hDESs were determined. Thymol-based hDESs are more potent as potential antioxidants, especially the one with coumarin as a hydrogen bond acceptor, which had the highest Oxygen Radical Absorbance Capacity (ORAC) value. Antimicrobial activity was assessed on four bacterial strains and one yeast strain. Calculated minimal inhibitory concentrations (MICs) showed that all hDESs possess this activity, and even the antimycotic effect against C. albicans was observed. Furthermore, to ensure the safety of these solvents for human use, in vitro cytocompatibility was determined. hDESs were tested on three human cell lines (HaCaT, CaCo-2, and HeLa), with no cytotoxic effect observed up to 1000 mg L-1. Finally, the environmental impact by the phytotoxicity test and in vitro antioxidative assay on wheat was determined for three selected hDESs, which were found to be slightly toxic, with different effects on plant defence mechanisms against induced antioxidative stress. Overall, the tested terpene-based hDESs demonstrate potential as alternative solvents for various industries, including food production, cosmetics, and pharmaceuticals, with thymol-based variants exhibiting a slight advantage in relation to the parameters evaluated in this study.

The Physicochemical Properties and Plausible Implication of Deep Eutectic Solvents in Analytical Techniques

Volatile organic solvents and fluoride-containing ionic liquids (ILs) have few drawbacks like toxicity, non-biodegradability, and environmental issues. Even though ILs are considered as new safest solvent for their lower volatility. They pose toxicity and sustainability concerns. Deep eutectic solvents (DESs) have garnered significant attention as substitutes for these solvents, addressing their drawbacks and aligning with specific principles of green chemistry, such as reduced toxicity, biodegradability, and the use of renewable resources. This review thoroughly explains the emergence and inception of DESs through their development. It deals with the physicochemical properties like density, polarity, and viscosity. The factors dealing with variation in density and viscosity of DES have been discussed. The preparation and operation of DESs, encompassing their various variants such as hydrophobic and hydrophilic types are examined to provide a comprehensive grasp of their chemical properties. Beyond basic characteristics, the article delves into a few specific DES applications to demonstrate their flexibility. DESs show promising multifarious utility, ranging from acting as extractant to critical roles in sorbent-based extractions, solvent-based extractions, and their role in various analytical techniques. The article covers the opportunities and difficulties associated with DESs, offering a prospective viewpoint on future advancements and difficulties. The review outlines different facets of DES research, emphasizing the level of knowledge at the moment and their potential influence in the emerging subject of DESs.

Enhanced microdialysis based on hydrophobic deep eutectic solvents for sampling of eugenol in Glyptocidaris crenularis

BACKGROUND

Microdialysis is an in vivo technique for dynamically analyzing biochemical components in tissues and fluids. Traditional microdialysis systems are primarily designed for low molecular weight polar compounds, resulting in lower recoveries for hydrophobic compounds. This study aimed to develop a greener, cost-effective, and enhanced microdialysis method for recovering eugenol, isoeugenol, and methyl isoeugenol, utilizing hydrophobic deep eutectic solvents as the perfusate, with the method's feasibility verified through in vivo experiments.

RESULTS

Among the 19 types of deep eutectic solvents evaluated, thymol-levulinic acid was identified as the most suitable for eugenol compounds based on liquid-liquid microextraction and microdialysis experiments, showing an in vitro microdialysis recovery approximately 100 times higher than that of water. The optimization of microdialysis parameters was conducted, including molar ratio of HBA:HBD, temperature, flow rate, and semi-permeable membrane length. In the in vivo microdialysis experiments, the temporal concentration of eugenol, which was used as an anesthetic in Glyptocidaris crenularis, was detected by GC-MS/MS and calibrated using ex vivo recovery. When the concentration of eugenol in artificial seawater was maintained at 100 μg mL-1, the eugenol levels in the coelomic fluid of Glyptocidaris crenularis rose from 0 to 6.89 ± 0.38 μg mL-1 within 60 min, then stabilized in next 80 min.

SIGNIFICANCE

The findings demonstrate that deep eutectic solvents enhanced microdialysis provides high recoveries and enables real-time monitoring of drug concentration changes in biological systems, making this method a valuable tool for pharmacokinetic studies and environmental monitoring.

Optimization of leaching of lithium and cobalt from spent lithium-ion batteries by the choline chloride-citric acid/malonic acid DES using response surface methodology

Deep eutectic solvents (DESs) are eco-friendly leaching agents which have emerged as potential candidate for recovery of valuable metals from spent LIBs (lithium-ion batteries). Earlier reports show use of more mount of chemicals, long leaching duration and less efficiency. The present work has been carried out to observe the leaching efficiency of two DES-water blend systems such as ChCl:CA(2:1) +30% H2O and ChCl:MA(1:1)+20% H2O for the leaching of Li and Co from cathodic material of spent LIBs using design of experiments and optimization through CCD (central composite design) of Response surface methodology(RSM) approach. Polynomial quadratic model for ChCl:CA (2:1)+35% H2O and the linear model for ChCl:MA(1:1)+20% H2O were selected on the basis statistical parameter values.The physico chemical properties like density, viscosity, conductivity and refractive index of DES-water blend have been determined in the temperature range 298.15-328.15K. The influence of temperature, leaching duration and stirring speed on the leaching efficiency has been scrutinized. Cobalt leaching efficiency (99.83%) was higher as compared to that of lithium (96.51%) using citric acid based DES-water blend under the conditions temperature 353 K, leaching time 117 min and stirring speed 920 rpm. FTIR and UV-Vis spectra of DES-water blend before and after leaching were recorded. DLS and Zeta potential results confirm higher leaching efficiency of choline chloride-citric acid based DES-water blend.

Ethanolamine-mediated microstructural transitions within terpenoid- and fatty acid-based deep eutectic solvents

Deep eutectic solvents (DESs) have emerged as solubilizing media of intense interest due partly to their easily tailorable physicochemical properties. Extensive H-bonding between the constituents in a two-constituent system is the major driving force for the formation of the DES. Addition of ethanolamine (MEA), a compound having H-bonding capabilities, to the DESs composed of a terpene [menthol (Men) or thymol (Thy)] and a fatty acid [n-decanoic acid (DA)] results in an unprecedented increase in dynamic viscosity due to the extensive rearrangement in the H-bonding network and other interactions within the system, while the liquid mixture still behaves as a Newtonian fluid. For the non-DA DES constituted of Men and Thy, this behavior is not observed. Visual color appearance, density and electrical conductivity measurements, UV-Vis and FTIR absorbance, differential scanning calorimetry, and empirical Kamlet-Taft parameters of the MEA-added DA-based DESs reveal the microstructural changes effectively. Cybotactic regions of the fluorescent microfluidity probes [1,3-bis(1-pyrenyl)propane - an intramolecular excimer forming probe, as well as perylene and 1,6-diphenylhexatriene - well-established anisotropy probes] also manifest the unprecedented increase in the viscosity of the DA-based DES system upon MEA addition. The carboxylic acid functionality of the DA plays a crucial role in bringing microstructural changes within the system as MEA is added. Physicochemical properties of DES systems can be effectively manipulated by not only changing the constituents and their compositions, but also by judicious addition of a co-solute/co-solvent. This work offers an easy and efficient way to favorably tailor the properties of interest of these environmentally-benign media.

Fractionation of High-Yield Noncondensed Lignin and Glucan Oligomers from Lignocellulose in a Novel Biphasic System

Effective fractionation of lignocellulose into hemicellulose, cellulose, and lignin is the precondition for full-component valorization. Generally, harsh reaction conditions are used to improve fractionation efficiency, which leads to severe lignin condensation and inhibits its value-added applications. To address this issue, a novel biphasic system consisting of molten salt hydrates (MSHs) and n-butanol was developed for birch fractionation. After the removal of hemicellulose in dilute acid, the solid residue composed of cellulose and lignin was carried out in biphasic system conversion. Cellulose was selectively converted into 73.3% yield of glucan oligomers and 16.8% glucose in the MSH phase, while lignin was in situ-extracted into the n-butanol phase with a high yield of 98.1%. Mechanism studies revealed that the in situ extraction together with Cα-OH group modification by n-butanol synchronously protected lignin β-O-4 linkages from cleavage, resulting in a high β-O-4 content of 53.7%, indicating that 87.7% of β-O-4 linkages in birch has been preserved. After depolymerization, a promising monophenol yield of 22.4% was obtained, which was 81.5% of the theoretical maximum monophenol yield obtained from birch. This fractionation strategy can also be used in softwood and herbaceous, showing a splendid separation efficiency as well as a high yield of noncondensed lignin production.

Impact of choline choride and sugar natural deep eutectic solvents on structure and functionality of treebean (Parkia timoriana) seed protein

This study explores the impact of natural deep eutectic solvents (NADES) on the structure and functionality of treebean (Parkia timoriana) seed protein, a novel approach to enhancing protein stability and functionality for sustainable bioprocessing. The research aims to evaluate the dynamic interactions between protein and choline chloride-sugar-based NADES, focusing on their effects on thermal properties, emulsification behaviour, and rheological characteristics. NADES were formulated using different sugars, and protein-NADES dispersions were analysed for their physicochemical and functional properties. Key findings include improved thermal stability, with sorbitol-based NADES showing the highest onset temperature (124.2 °C) and peak degradation temperature (330 °C), indicative of enhanced resistance to high-temperature processing. The sorbitol-NADES-protein dispersion also exhibited superior emulsification activity (50.42%) and stability (42.55%) compared to other formulations. Rheological analysis demonstrated non-Newtonian shear-thinning behaviour, with sorbitol-NADES providing the highest zero-shear viscosity (14.32 mPa s) and relaxation time (3.17 s). These results highlight the ability of NADES to stabilize protein structures while maintaining functionality under processing conditions. The novelty of the study lies in demonstrating the potential of NADES to sustainably enhance the structural and functional attributes of plant proteins, paving the way for innovative applications in food and bioprocessing industries. By employing green solvents, this study presents a sustainable solution for high-temperature food processing, addressing environmental concerns associated with conventional solvents.

CO2 adsorption in natural deep eutectic solvents: insights from quantum mechanics and molecular dynamics

CO2 capture is an important process for mitigating CO2 emissions in the atmosphere. Recently, ionic liquids have been identified as possible systems for CO2 capture processes. Major drawbacks of such systems are mostly in the high cost of synthesis of such liquids and poor biodegradability. Natural deep eutectic solvents, a class of eutectic solvents using materials of natural origin, have been developed, which compared to ionic liquids are low-cost and more environmentally benign. However, very little is known on the details at a molecular level that govern the CO2 adsorption in these systems and what the limits are of the adsorption features. Elucidating such aspects would represent a step forward in the design and implementation of such promising systems in mitigating CO2 emissions. Herein, we report a computational study on the mechanisms and characteristics of CO2 adsorption in natural deep eutectic solvents containing arginine/glycerol mixtures. We establish details of the hydrogen bonding effects that drive the carbon dioxide capture in systems composed of L-arginine and glycerol using molecular dynamics and quantum mechanics simulations. Our findings indicate that, although both arginine and glycerol contain multiple atoms capable of acting as hydrogen bond donors and hydrogen bond acceptors, L-arginine primarily functions as the hydrogen bond acceptor while glycerol serves as the hydrogen bond donor in most interactions. Furthermore, both compounds contribute hydrogen bond donors that participate in CO2 binding. This study provides valuable insights into the behaviour of CO2 adsorption in natural deep eutectic solvents and enhances our understanding from the perspective of hydrogen bonding interactions.

"One Pot" Enzymatic Synthesis of Caffeic Acid Phenethyl Ester in Deep Eutectic Solvent

Caffeic acid phenethyl ester (CAPE) represents a valuable ester of caffeic acid, which, over time, has demonstrated remarkable pharmacological properties. In general, the ester is obtained in organic solvents, especially by the esterification reaction of caffeic acid (CA) and 2-phenylethanol (PE). In this context, the purpose of this study was the use of the "one pot" system to synthesize CAPE through biocatalysis with various lipases in a choline-chloride-based DES system, employing the "2-in-1" concept, where one of the substrates functions as both reactant and solvent. The synthesis process of CAPE is contingent on the molar ratio between CA and PE; thus, this factor was the primary subject of investigation, with different molar ratios of CA and PE being studied. Furthermore, the impact of temperature, time, the nature of the biocatalyst, and the water loading of the DES system was also examined. This 'green' synthesis method, which has demonstrated encouraging reaction yields (%), could secure and maintain the therapeutic potential of CAPE, mainly due to the non-toxic character of the reaction medium.

Deep Eutectic Solvent-Assisted Synthesis of Ni-Graphene Composite Supported on Screen-Printed Electrodes for Biogenic Amine Detection

Deep eutectic solvents (DES) have emerged as versatile, sustainable media for the synthesis of nanomaterials due to their low toxicity, tunability, and biocompatibility. This study develops a one-step method to modify commercially available screen-printed electrodes (SPE) using laser-induced pyrolysis of DES, consisting of choline chloride and tartaric acid with dissolved nickel acetate and dispersed graphene. The electrodes were patterned using a 532 nm continuous-wave laser for the in situ formation of Ni nanoparticles decorated on graphene sheets directly on the SPE surface (Ni-G/SPE). The synthesis parameters, specifically laser power and graphene concentration, were optimized using the Nelder-Mead method to produce modified Ni-G/SPEs with maximized electrochemical response to dopamine. Electrochemical characterization of the developed sensor by differential pulse voltammetry revealed its broad linear detection range from 0.25 to 100 μM and high sensitivity with a low detection limit of 0.095 μM. These results highlight the potential of laser-assisted DES synthesis to advance electrochemical sensing technologies, particularly for the detection of biogenic amines.

Effect of deep eutectic solvents on activity, stability, and selectivity of enzymes: Novel insights and further prospects

Deep eutectic solvents (DESs) have been extensively concerned since 2008 as reaction media in biocatalysis because of their excellent solvent performances. Here, we try to clarify the effects of DESs on the catalytic properties, structure, and conformation of enzymes. Through comprehensive analysis, it is found that the catalytic properties of enzymes can be designed in different DESs through modulating the hydrogen bond acceptors, hydrogen bond donors, and their molar ratio. Structural changes of different enzymes in various DESs are not always consistent, which may be attributed to the original structure of enzymes, DES composition, and the interactions between enzymes and DESs. Moreover, we try to elucidate how DESs interact with varying amounts of water, and furthermore how water in DES affects the catalytic properties of enzymes. The available researches indicate that proper amount of water can integrate into the network of DESs and strengthen the hydrogen-bonding interactions while excessive water will destroy the integrity of DESs. Water affects the performance of enzymes in two possible ways: 1) affecting enzyme affinity and structure directly; 2) influencing the properties of DESs, thus modulating the efficiency of enzymes. This review paves road for researchers to design DESs with desired properties for specific applications.

Breaking barriers in electrodeposition: Novel eco-friendly approach based on utilization of deep eutectic solvents

This review article provides a comprehensive examination of the innovative approaches emerging from using deep eutectic solvents (DESs) in electrodeposition techniques. Through an in-depth exploration of fundamental principles, the study highlights the advantages of DESs as electrolytes, including reduced toxicity, enhanced control over deposition parameters, and specific influences on morphology. By showcasing specific studies and experimental findings, the article offers tangible evidence of the superior performance of DES-based electrodeposition methods. Key findings reveal that DESs utilization enables eco-friendly electrodeposition of noble metal and transition metal coatings, coatings of their alloys and composites, as well as electrodeposition of semiconductor and photovoltaic alloy coatings; while also addressing challenges such as hydrogen evolution in conventional electrolytes. Notably, DES-based electrolytes facilitate the formation of electrodeposits with unique nanostructures and improve the stability of colloidal systems for composite coatings. The article contains invaluable tables detailing electrolyte compositions, electrodeposition conditions, and deposition results for a diverse array of metals, alloys, and composites, serving as a practical handbook for researchers and industry practitioners. In conclusion, the review underscores the transformative impact of DESs on electrodeposition techniques and emphasizes the prospects for future advancements in surface modification and material synthesis.

A comprehensive study of experimental and theoretical characterization and in silico toxicity analysis of new molecules

In this study, for the first time in the literature, a 2-(3-methoxyphenylamino)-2-oxoethyl acrylate (3MPAEA) molecule was synthesized in two steps, and a 2-chloro-N-(3-methoxyphenyl)acetamide (m-acetamide) was obtained in the first step. Experimental results were obtained using FTIR, 1H, and 13C NMR spectroscopy methods for m-acetamide and 3MPAEA compounds created in the laboratory environment and compared with theoretical results. Band gap (BG) energy, chemical hardness, electronegativity, chemical potential, and electrophilicity index were calculated. With vibration spectroscopic analysis, atom-molecule vibrations of the theoretical and experimental peaks of the spectrum were observed. The locations of C and H atoms were determined by nuclear magnetic resonance spectroscopy. The green, blue, and red regions of the potential energy map (MEP) map were examined. Some observed that the energy thermal, heat capacity, and entropy graphs increased in direct proportion to increasing the temperature in Kelvin, which is known as thermochemistry. The changes in the rotation, translation, and vibration of the molecule as its temperature increased were examined. When the thermochemistry surface map was examined, some observed that the temperature was high in the middle binding site of the molecules. Covalent interactions were graphed using the non-covalent interactions (NCIs) calculation method. In silico toxicity studies were carried out for m-acetamide and 3MPAEA molecules: fathead minnow LC50 (96 h), Daphnia magna LC50 (48 h), Tetrahymena pyriformis IGC50 (48 h), oral rat LD50, water solubility, bioconcentration factor, developmental toxicity, mutation, normal boiling point, flash point, melting point, density, thermal conductivity, viscosity, vapor pressure, etc. parameters were investigated.

Exploration of the Solubility Hyperspace of Selected Active Pharmaceutical Ingredients in Choline- and Betaine-Based Deep Eutectic Solvents: Machine Learning Modeling and Experimental Validation

Deep eutectic solvents (DESs) are popular green media used for various industrial, pharmaceutical, and biomedical applications. However, the possible compositions of eutectic systems are so numerous that it is impossible to study all of them experimentally. To remedy this limitation, the solubility landscape of selected active pharmaceutical ingredients (APIs) in choline chloride- and betaine-based deep eutectic solvents was explored using theoretical models based on machine learning. The available solubility data for the selected APIs, comprising a total of 8014 data points, were collected for the available neat solvents, binary solvent mixtures, and DESs. This set was augmented with new measurements for the popular sulfa drugs in dry DESs. The descriptors used in the machine learning protocol were obtained from the σ-profiles of the considered molecules computed within the COSMO-RS framework. A combination of six sets of descriptors and 36 regressors were tested. Taking into account both accuracy and generalization, it was concluded that the best regressor is nuSVR regressor-based predictive models trained using the relative intermolecular interactions and a twelve-step averaged simplification of the relative σ-profiles.

A Comprehensive Review on Deep Eutectic Solvents: Their Current Status and Potential for Extracting Active Compounds from Adaptogenic Plants

Deep eutectic solvents (DESs) have attracted attention from researchers as novel compounds for extracting active substances because of their negligible toxicity, polarity, and ability to be tailored depending on the experiment. In this review, we discuss deep eutectic solvents as a promising medium for the extraction of adaptogenic compounds. In comparison to traditional methods, extraction with the use of DESs is a great alternative to the excessive usage of harmful organic solvents. It can be conducted in mild conditions, and DESs can be designed with different precursors, enhancing their versatility. Adaptogenic herbs have a long medicinal history, especially in Eastern Asia. They exhibit unique properties through the active compounds in their structures, including saponins, flavonoids, polysaccharides, and alkaloids. Therefore, they demonstrate a wide range of pharmaceutical effects, such as anti-inflammatory, antibacterial, and anticancer abilities. Since ancient times, many different adaptogenic herbs have been discovered and are well known, including Panax ginseng, Scutellaria baicalensis, and Schisandra chinensis. Active compounds can be extracted using standard methods, such as hydrolyzation, maceration, and conventional reflux extraction. However, due to the limitations of classical processing technologies, there has been a need to develop new and eco-friendly methods. We focus on the types of solvents, extraction efficiency, properties, and applications of the obtained active compounds. This review highlights the potential of DESs as eco-friendly alternatives for extracting bioactive compounds.

Microextraction techniques with deep eutectic solvents for gas chromatographic analysis: a minireview

Sample pretreatment is one of the key steps in sample analysis. The design and development of new materials promote advancements in sample pretreatment technology. Deep eutectic solvents (DESs) are a novel material that have been developed in recent years. They possess characteristics such as low toxicity, good thermal stability, simple preparation methods, and low cost. DESs have the potential to replace traditional organic extraction solvents. DESs are formed from a hydrogen bond donor (HBD) and acceptor (HBA). Changing the type of HBA and HBD or their ratio leads to variations in the structure and properties of the resulting DESs. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) are the primary analytical techniques used in laboratories. This paper analyzes the selection relationship between DESs and analytes, as well as the steps of sample pretreatment, based on the characteristics of GC instruments, and utilizing DES extractants and extraction materials for sample pretreatment. This paper summarizes the progress of DES-based microextraction methods for GC. It introduces the different classifications of liquid and solid-phase microextraction and the application of DESs in them. The theoretical mechanism and extraction/separation mechanism of DESs are analyzed, and potential application of DESs in extraction/separation technology is discussed.

Exploring Deep Eutectic Solvents as Pharmaceutical Excipients: Enhancing the Solubility of Ibuprofen and Mefenamic Acid

Objectives: The study explores the potential of various deep eutectic solvents (DESs) to serve as drug delivery systems and pharmaceutical excipients. The research focuses on two primary objectives: evaluating the ability of the selected DES systems to enhance the solubility of two poorly water-soluble model drugs (IBU and MFA), and evaluating their physicochemical properties, including density, viscosity, flow behavior, surface tension, thermal stability, and water dilution effects, to determine their suitability for pharmaceutical applications. Methods: A range of DES systems containing pharmaceutically acceptable constituents was explored, encompassing organic acid-based, sugar- and sugar alcohol-based, and hydrophobic systems, as well as menthol (MNT)-based DES systems with common pharmaceutical excipients. MNT-based DESs exhibited the most significant solubility enhancements. Results: IBU solubility reached 379.69 mg/g in MNT: PEG 400 (1:1) and 356.3 mg/g in MNT:oleic acid (1:1), while MFA solubility peaked at 17.07 mg/g in MNT:Miglyol 812®N (1:1). In contrast, solubility in hydrophilic DES systems was significantly lower, with choline chloride: glycerol (1:2) and arginine: glycolic acid (1:8) showing the best results. While demonstrating lower solubility compared to the MNT-based systems, sugar-based DESs exhibited increased tunability via water and glycerol addition both in terms of solubility and physicochemical properties, such as viscosity and surface tension. Conclusions: Our study introduces novel DES systems, expanding the repertoire of pharmaceutically acceptable DES formulations and opening new avenues for the rational design of tailored solvent systems to overcome solubility challenges and enhance drug delivery.

Greening Separation and Purification of Proteins and Peptides

The increasing awareness of environmental issues and the transition to green analytical chemistry (GAC) have gained popularity among academia and industry in recent years. One of the principles of GAC is the reduction and replacement of toxic solvents with more sustainable and environmentally friendly ones. This review gives an overview of the advances in applying green solvents as an alternative to the traditional organic solvents for peptide and protein purification and analysis by liquid chromatography (LC) and capillary electrophoresis (CE) methods. The feasibility of using greener LC and CE methods is demonstrated through several application examples; however, there is still plenty of room for new developments to fully realize their potential and to address existing challenges. Thanks to the tunable properties of designer solvents, such as ionic liquids and deep eutectic solvents, and almost infinite possible mixtures of components for their production, it is possible that some new designer solvents could potentially surpass the traditional harmful solvents in the future. Therefore, future research should focus mainly on developing new solvent combinations and enhancing analytical instruments to be able to effectively work with green solvents.

Deep eutectic solvent: Synthesis, classification, properties and application in macromolecular substances

Deep eutectic solvent (DES) is a kind of solvent prepared by mixing hydrogen bond donors and hydrogen bond acceptors, and have become a hot topic in ecological civilization construction due to its low toxicity and sustainability. Its excellent properties such as low volatility, thermal stability and biodegradability make it stand out among many organic solvents and widely used in fields including medicine, chemical industry and agriculture, with broad development prospects. In recent years, the application of DES in the food field has mostly focused on the extraction of small molecular substances, and there are few summaries on the application of DES in macromolecular substances. In this review, we introduced the synthesis, classification and properties of DES, and summarized the application of DES in the food industry for macromolecular substances, including the extraction of macromolecular substances such as chitosan and pectin, as well as the preparation of related macromolecular substrate films. At the same time, we analyzed the characteristics of DES and its advantages and limitations in application, and provided prospects for future development.

Delamination and Evaluation of Multilayer PE/Al/PET Packaging Waste Separated Using a Hydrophobic Deep Eutectic Solvent

This research concerns the development and implementation of ground-breaking strategies for improving the sorting, separation, and recycling of common flexible laminate packaging materials. Such packaging laminates incorporate different functional materials in order to achieve the desired mechanical performance and barrier properties. Common components include poly(ethylene) (PE), poly(propylene) (PP), and poly(ethylene terephthalate) (PET), as well as valuable barrier materials such as poly(vinyl alcohol) (PVOH) and aluminium (Al) foils. Although widely used for the protection and preservation of food produce, such packaging materials present significant challenges for established recycling infrastructure and, therefore, to our future ambitions for a circular economy. Experience from the field of ionic liquids (ILs) and deep eutectic solvents (DESs) has been leveraged to develop novel green solvent systems that delaminate multilayer packaging materials to facilitate the separation and recovery of high-purity commodity plastics and aluminium. This research focuses on the development of a hydrophobic DES and the application of a Design of Experiments (DoE) methodology to investigate the effects of process parameters on the delamination of PE/Al/PET laminate packaging films. Key variables including temperature, time, loading, flake size, and perforations were assessed at laboratory scale using a 1 L filter reactor vessel. The results demonstrate that efficient separation of PE, Al, and PET can be achieved with high yields for material and solvent recovery. Recovered plastic films were subsequently characterised via Fourier-transform infra-red (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) to qualify the quality of plastics for reuse.

A Review on the Application of Deep Eutectic Solvents in Polymer-Based Membrane Preparation for Environmental Separation Technologies

The use of deep eutectic solvents (DESs) for the preparation of polymer membranes for environmental separation technologies is comprehensively reviewed. DESs have been divided into five categories based on the hydrogen bond donor (HBD) and acceptor (HBA) that are involved in the production of the DESs, and a wide range of DESs' physicochemical characteristics, such as density, surface tension, viscosity, and melting temperature, are initially gathered. Furthermore, the most popular techniques for creating membranes have been demonstrated and discussed, with a focus on the non-solvent induced phase separation (NIPS) method. Additionally, a number of studies have been reported in which DESs were employed as pore formers, solvents, additives, or co-solvents, among other applications. The addition of DESs to the manufacturing process increased the presence of finger-like structures and macrovoids in the cross-section and, on numerous occasions, had a substantial impact on the overall porosity and pore size. Performance data were also gathered for membranes made for various separation technologies, such as ultrafiltration (UF) and nanofiltration (NF). Lastly, DESs provide various options for the functionalization of membranes, such as the creation of various liquid membrane types, with special focus on supported liquid membranes (SLMs) for decarbonization technologies, discussed in terms of permeability and selectivity of several gases, including CO2, N2, and CH4.

Formation of Self-Healing Granular Eutectogels through Jammed Carbopol Microgels in Supercooled Deep Eutectic Solvent

Typically, gel-like materials consist of a polymer network structure in a solvent. In this work, a gel-like material is developed in a deep eutectic solvent (DES) without the presence of a polymer network, achieved simply by adding microgels. The DES is composed of choline chloride and citric acid and remains stably in a supercooled state at room temperature, exhibiting Newtonian fluid behavior with high viscosity. When the microgel (Carbopol) concentration exceeds 2 wt %, the DES undergoes a transition from a liquid to a soft gel state, characterized as a granular eutectogel. The soft gel characteristics of eutectogels exhibit a yield stress, and their storage moduli exceed the loss moduli. The yield stress and storage moduli are observed to increase with increasing microgel concentration. In contrast, the ion conductivity decreases with increasing microgel concentration but eventually levels off. Because the eutectogel can dissolve completely in excess water, it is a physical gel-like material, attributed to the densely packed structure of microgels in the supercooled DES. Due to the absence of networks, the granular eutectogel has the capability to self-heal simply by being pushed together after being cut into two pieces.

Tuning Ferulic Acid Solubility in Choline-Chloride- and Betaine-Based Deep Eutectic Solvents: Experimental Determination and Machine Learning Modeling

Deep eutectic solvents (DES) represent a promising class of green solvents, offering particular utility in the extraction and development of new formulations of natural compounds such as ferulic acid (FA). The experimental phase of the study undertook a systematic investigation of the solubility of FA in DES, comprising choline chloride or betaine as hydrogen bond acceptors and six different polyols as hydrogen bond donors. The results demonstrated that solvents based on choline chloride were more effective than those based on betaine. The optimal ratio of hydrogen bond acceptors to donors was found to be 1:2 molar. The addition of water to the DES resulted in a notable enhancement in the solubility of FA. Among the polyols tested, triethylene glycol was the most effective. Hence, DES composed of choline chloride and triethylene glycol (TEG) (1:2) with added water in a 0.3 molar ration is suggested as an efficient alternative to traditional organic solvents like DMSO. In the second part of this report, the affinities of FA in saturated solutions were computed for solute-solute and all solute-solvent pairs. It was found that self-association of FA leads to a cyclic structure of the C28 type, common among carboxylic acids, which is the strongest type of FA affinity. On the other hand, among all hetero-molecular bi-complexes, the most stable is the FA-TEG pair, which is an interesting congruency with the high solubility of FA in TEG containing liquids. Finally, this work combined COSMO-RS modeling with machine learning for the development of a model predicting ferulic acid solubility in a wide range of solvents, including not only DES but also classical neat and binary mixtures. A machine learning protocol developed a highly accurate model for predicting FA solubility, significantly outperforming the COSMO-RS approach. Based on the obtained results, it is recommended to use the support vector regressor (SVR) for screening new dissolution media as it is not only accurate but also has sound generalization to new systems.

Valorization and protection of anthocyanins from strawberries (Fragaria×ananassa Duch.) by acidified natural deep eutectic solvent based on intermolecular interaction

This study introduces an innovative approach for the valorization and protection of anthocyanins from 'Benihoppe' strawberry (Fragaria × ananassa Duch.) based on acidified natural deep eutectic solvent (NADES). Choline chloride-citric acid (ChCl-CA, 1:1) was selected and acidified to enhance the valorization and protection of anthocyanins through hydrogen bond. The optimal conditions (ultrasonic power of 318 W, extraction temperature of 61 °C, liquid-to-solid ratio of 33 mL/g, ultrasonic time of 19 min), yielded the highest anthocyanins of 1428.34 μg CGE/g DW. UPLC-Triple-TOF/MS identified six anthocyanins in acidified ChCl-CA extract. Stability tests indicated that acidified ChCl-CA significantly increased storage stability of anthocyanins in high temperature and light treatments. Molecular dynamics results showed that acidified ChCl-CA system possessed a larger diffusion coefficient (0.05 m2/s), hydrogen bond number (145) and hydrogen bond lifetime (4.38 ps) with a reduced intermolecular interaction energy (-1329.74 kcal/mol), thereby efficiently valorizing and protecting anthocyanins from strawberries.

A new DES-mediated synthesis of Henna-based benzopyranophenazines and benzoxanthenetriones

MTPPBr/THFTCA-DES was prepared as a new deep eutectic solvent (DES) from a mixture (molar ratio 7:3) of methyltriphenyl-phosphonium bromide (MTPPBr) and tetrahydrofuran-2,3,4,5-tetra-carboxylic acid (THFTCA), and characterized with various spectroscopic techniques, densitometer, and eutectic point. Then, it was used as a new and powerful catalyst for the synthesis of two sets of biologically important compounds, namely the Henna-based benzopyranophenazines and benzoxan-thenetriones. Solvent-free conditions, short reaction time, high efficiency, and easy recycling and separation of the DES catalyst are among the most important features of the presented method. Also, there is a nice consistency between the proposed structure of the DES compound, the integration values of the 1H NMR peaks, and the ratio of MTPPBr to THFTCA obtained from the eutectic point phase diagram. In addition, the reduction of peak splitting patterns in DES compared to the two primary materials can be good evidence of the formation of hydrogen bonds between the two components.

Experimental Study on the Transport Properties of 12 Novel Deep Eutectic Solvents

Deep eutectic solvents (DESs) are complex substances composed of two or three components, wherein hydrogen bond donors and acceptors engage in intricate interactions within a hydrogen bond network. They have attracted extensive attention from researchers due to their easy synthesis, cost-effectiveness, broad liquid range, good stability, and for being green and non-toxic. However, studies on the physical properties of DESs are still scarce and many theories are not perfect enough, which limits the application of DESs in engineering practice. In this study, twelve DESs were synthesized by using choline chloride and betaine as HBAs, and ethylene glycol, polyethylene glycol 600, o-cresol, glycerol, and lactic acid as HBDs. The variation rules of their thermal conductivity and viscosity with temperature at atmospheric pressure were systematically investigated. The experimental results showed that the thermal conductivity of the 1:4 choline chloride/glycerol solvent was the largest at 294 K, reaching 0.2456 W·m-1·K-1, which could satisfy the demand for high efficiency heat transfer by heat-transferring workpieces. The temperature-viscosity relationship of the DESs was fitted using the Arrhenius model, and the maximum average absolute deviation was 6.77%.

Deep eutectic solvents for the extraction of polyphenols from food plants

Deep Eutectic Solvents (DESs) offer a promising, sustainable alternative for extracting polyphenols from food plants, known for their health benefits. Traditional extraction methods are often costly and involve toxic solvents. This review discusses the basic concepts, preparation techniques, and factors influencing the effective and safe use of DESs in polyphenol extraction. DESs' adaptability allows integration with other green extraction technologies, such as microwave- and ultrasound-assisted extractions, enhancing their efficiency. This adaptability demonstrates the potential of DESs in the sustainable extraction of bioactive compounds. Current research indicates that DESs could play a significant role in the sustainable procurement of these compounds, marking an important advancement in food science research and development. The review underscores DESs as a realistic, eco-friendly alternative in the realm of natural extraction technologies, offering a significant contribution to sustainable practices in food science.

Switchable deep eutectic solvent as green and efficient media for liquid-phase microextraction of phenoxyacetic acid herbicides in water and food matrices

In this work, a switchable deep eutectic solvent (SDES) based on fatty acid and polyetheramine ion pair was prepared for liquid-phase microextraction (LPME) of phenoxyacetic acid herbicides in drinking water, beverage and honey matrices. The as-synthesized SDES equipped with an interesting characteristic of fast and reversible polarity switching, achieving homogeneous extraction and rapid bi-phase separation simultaneously. Several key parameters affecting the extraction performance were investigated comprehensively by Box-Behnken design. Under the optimal conditions, the method exhibited excellent linearity (15-4000 μg L-1), low detection limits (3-5 μg L-1), desirable precision (RSD < 8.1 %), and satisfactory recovery (72.6-98.7 %). More importantly, the introduction of SDES can simplify the pre-treatment procedure, shorten extraction time (4 min), and avoid the usage of traditional organic solvent during the whole extraction process. In addition, the switching mechanism of SDES was characterized by FT-IR and 1H NMR, and the forming mechanism of SDES was investigated using density-functional theory. The green of the method was estimated using the analytical ecological scale, the analytical green calculator, and the green analytical procedure index. The cytotoxicity of SDES was investigated and the result displayed that toxicity of the SDES was very low with the EC50 > 500 mg/L. Therefore, the proposed method was green and efficient and revealed considerable application prospects for the extraction of trace analytes from complex materials.

Experimental and Machine-Learning-Assisted Design of Pharmaceutically Acceptable Deep Eutectic Solvents for the Solubility Improvement of Non-Selective COX Inhibitors Ibuprofen and Ketoprofen

Deep eutectic solvents (DESs) are commonly used in pharmaceutical applications as excellent solubilizers of active substances. This study investigated the tuning of ibuprofen and ketoprofen solubility utilizing DESs containing choline chloride or betaine as hydrogen bond acceptors and various polyols (ethylene glycol, diethylene glycol, triethylene glycol, glycerol, 1,2-propanediol, 1,3-butanediol) as hydrogen bond donors. Experimental solubility data were collected for all DES systems. A machine learning model was developed using COSMO-RS molecular descriptors to predict solubility. All studied DESs exhibited a cosolvency effect, increasing drug solubility at modest concentrations of water. The model accurately predicted solubility for ibuprofen, ketoprofen, and related analogs (flurbiprofen, felbinac, phenylacetic acid, diphenylacetic acid). A machine learning approach utilizing COSMO-RS descriptors enables the rational design and solubility prediction of DES formulations for improved pharmaceutical applications.

Corrosion inhibition activity of a natural polysaccharide from Dysosma versipellis using tailor-made deep eutectic solvents

In this work, a total of 18 types of choline chloride, betaine, and L-proline-based deep eutectic solvents (DESs) were synthesized to determine the extraction yield of a natural polysaccharide (PSA) from Dysosma versipellis using an ultrasound-assisted extraction method. Results indicate that the choline-oxalic acid-based DES has the best extraction yield for PSA due to the proper physical-chemical properties between PSA and DES. To evaluate the optimal extraction conditions, a response surface methodology was carried out. Under the optimal conditions, the extraction yield of PSA reaches 10.37 % (± 0.03 %), higher than the conventional extraction methods. Findings from FT-IR and NMR suggest that the extracted PSA belongs to a neutral polysaccharide with (1 → 6)-linked α-d-glucopyranose in the main chain. Interestingly, results from various electrochemical measurements show the extracted PSA exhibits excellent corrosion inhibition performance for mild steel (MS) in a 0.5 M HCl solution, with 90.8 % of maximum corrosion inhibition efficiency at 210 mg L-1. SEM and XPS measurements reveal the formation of a protective layer on the MS surface. The adsorption behaviour of extracted PSA well obeys the Langmuir adsorption isotherm containing the chemisorption and physisorption. Additionally, theoretical calculations validate the experimental findings.

Experimental and Theoretical Insights into the Intermolecular Interactions in Saturated Systems of Dapsone in Conventional and Deep Eutectic Solvents

Solubility is not only a crucial physicochemical property for laboratory practice but also provides valuable insight into the mechanism of saturated system organization, as a measure of the interplay between various intermolecular interactions. The importance of these data cannot be overstated, particularly when dealing with active pharmaceutical ingredients (APIs), such as dapsone. It is a commonly used anti-inflammatory and antimicrobial agent. However, its low solubility hampers its efficient applications. In this project, deep eutectic solvents (DESs) were used as solubilizing agents for dapsone as an alternative to traditional solvents. DESs were composed of choline chloride and one of six polyols. Additionally, water-DES mixtures were studied as a type of ternary solvents. The solubility of dapsone in these systems was determined spectrophotometrically. This study also analyzed the intermolecular interactions, not only in the studied eutectic systems, but also in a wide range of systems found in the literature, determined using the COSMO-RS framework. The intermolecular interactions were quantified as affinity values, which correspond to the Gibbs free energy of pair formation of dapsone molecules with constituents of regular solvents and choline chloride-based deep eutectic solvents. The patterns of solute-solute, solute-solvent, and solvent-solvent interactions that affect solubility were recognized using Orange data mining software (version 3.36.2). Finally, the computed affinity values were used to provide useful descriptors for machine learning purposes. The impact of intermolecular interactions on dapsone solubility in neat solvents, binary organic solvent mixtures, and deep eutectic solvents was analyzed and highlighted, underscoring the crucial role of dapsone self-association and providing valuable insights into complex solubility phenomena. Also the importance of solvent-solvent diversity was highlighted as a factor determining dapsone solubility. The Non-Linear Support Vector Regression (NuSVR) model, in conjunction with unique molecular descriptors, revealed exceptional predictive accuracy. Overall, this study underscores the potency of computed molecular characteristics and machine learning models in unraveling complex molecular interactions, thereby advancing our understanding of solubility phenomena within the scientific community.

Synergistic Applications of Graphene-Based Materials and Deep Eutectic Solvents in Sustainable Sensing: A Comprehensive Review

The recently explored synergistic combination of graphene-based materials and deep eutectic solvents (DESs) is opening novel and effective avenues for developing sensing devices with optimized features. In more detail, remarkable potential in terms of simplicity, sustainability, and cost-effectiveness of this combination have been demonstrated for sensors, resulting in the creation of hybrid devices with enhanced signal-to-noise ratios, linearities, and selectivity. Therefore, this review aims to provide a comprehensive overview of the currently available scientific literature discussing investigations and applications of sensors that integrate graphene-based materials and deep eutectic solvents, with an outlook for the most promising developments of this approach.

Preparation of nanochitin using deep eutectic solvents

Chitin is an abundant and renewable non-wood biopolymer. Nanochitin is formed by the assembly of chitin molecules, which has the advantages of large tensile strength, high specific surface area, and biodegradability, so it has been widely used. However, the traditional methods of preparing nanochitin have many drawbacks. As the new generation of green solvents, deep eutectic solvents (DESs) have been successfully applied in the fields of chitin dissolution, extraction, and nanochitin preparation. In this review, the relevant knowledge of chitin, nanochitin, and DESs was first introduced. Then, the application status of DESs in the fields of chitin was summarized, with a focus on the preparation of nanochitin using DESs. In conclusion, this review provided a comprehensive analysis of the published literature and proposed insights and development trends in the field of preparation of nanochitin using DESs, aiming to provide guidance and assistance for future researchers.

Deep eutectic solvents as a green alternative for trace element analysis in food and beverage samples: Recent advances and challenges

Metals and metalloids have different effects on human health even at trace levels. Some of them are essential for living organisms while others can be toxic. Therefore, the determination of trace elements in food and beverage is highly important to understand their impact in human health. A new generation of solvents named deep eutectic solvents (DES) has emerged as a green alternative for trace element analysis, owing to their low toxicity, biodegradability, and high extraction capacity. In recent years, the application of DES in extraction techniques for trace element analysis in food and beverage samples has increased significantly. This review summarizes recent advances and challenges on the application of DES to develop microextraction techniques useful for the analysis of samples with complex matrices. The importance of the use of biodegradable substances instead of classic organic solvents, which are toxic, volatile, and flammable in methods for elemental analysis with a positive environmental impact is also highlighted. Finally, conclusions and future challenges arising from the use of DES in microextraction techniques are discussed.

Capillary electrophoresis separations with deep eutectic solvents as greener separation media: A proof-of-concept study

Capillary electrophoresis (CE) has conventionally been classified into aqueous and non-aqueous categories based on the types of buffer solvents employed. Traditionally, non-aqueous CE has always been associated with the use of organic solvents, which are considered hazardous to health and environmentally detrimental. In this work, we introduce deep eutectic solvents (DESs) as CE separation media for the first time, presenting a novel and environmentally friendly approach to CE separations. The DES employed consists of proline and urea (Proline:Urea, PU), both of which are naturally occurring compounds that are readily available, cost-effective, and environmentally benign. Various fundamental aspects of the DES-type CE media were investigated, including thermal property, viscosity, electroconductivity, Joule heating effect, and compatibility with detectors. A simulated complex mixture of ten naphthalene-based compounds with varied charges and sizes was separated using the DES-based medium in capillary zone electrophoresis (CZE) mode. Moreover, we also established a DES-based micellar electrokinetic chromatography (MEKC) system utilizing Tween-20 as the surfactant. Six structurally similar naphthalene derivatives (isomers) that couldn't be resolved by CZE were effectively separated due to their strong hydrophobic interaction with Tween-20 micelles within the DES medium. Given that DESs are "designer" solvents with highly tunable properties and environmentally friendly characteristics, this study demonstrates the potential of employing DESs as an alternative to organic solvents for greener CE separations.

Natural Oleanolic Acid-Tailored Eutectogels Featuring Multienvironment Shape Memory Performance

Shape memory gels, one of the primary modern smart materials, hold great promise in a myriad of applications spanning from soft robotics to medical devices. Nevertheless, most shape memory gels rely on water, organic solvents, and ionic liquids as dispersion mediums, posing the risks of freezing, dehydration, and toxicity to humans or environment. Herein, we have developed a thermoresponsive shape memory eutectogel by introducing an oleanolic acid-modified polyacrylamide network into a deep eutectic solvent (DES). The resulting eutectogel shows a fracture strength of 4.46 MPa along with elongation of 345%, Young's modulus of 14.83 MPa, and toughness of 9.51 MJ m-3. Thanks to the low freezing point and low volatility inherited from DES, this eutectogel possesses good antifreezing and long-term storage stability, which facilitate the shape memory behavior both in silicone oil and in air. The shape fixity and shape recovery ratios of this eutectogel maintain almost 90% during 10 cycles in silicone oil and more than 70% during four cycles in air that cannot be realized in hydrogels. By virtue of shape memory effect and conductivity, the eutectogel can be further used as a thermoswitch. This work presents a simple approach to fabricating shape memory eutectogels and imparts exciting prospects to smart eutectogels.

Antibacterial and antifungal activities of natural deep eutectic solvents

The increasing antibiotic resistance towards a panel of microorganisms is one of the public health concerns. For this reason, the search for alternatives to the widely used antibiotic has been undertaken. In the era of sustainable chemistry, deep eutectic solvents (DESs) have emerged as promising antimicrobial agents. These solvents possess several advantages such as low volatility, low flammability, ease of preparation, and typically low cost of production. These properties make DES suitable for various applications, including extraction of biomolecules and preparation of cosmetics. Natural DESs (NADESs) are special category of DESs prepared from natural sources, which matched the recent trends of leaning back to nature, and decreasing dependence on synthetic precursors. NADES can be prepared by heating and stirring, freeze-drying, evaporation, grinding, and ultrasound-assisted and microwave-assisted synthesis. Utilizing NADESs as an alternative to traditional antibiotics, which become ineffective over time due to bacterial resistance, holds great promise for these reasons. This review aims to discuss the antimicrobial properties of multiple NADESs, including antibacterial and antifungal activities. To the best of our knowledge, this review is the first literature survey of the antimicrobial activities of NADESs. KEY POINTS: • Natural deep eutectic solvents are promising antimicrobial alternative to antibiotics • NADES holds high potential for their activity against bacterial resistance • NADES have also substantial antifungal activities.

How Can Deep Eutectic Systems Promote Greener Processes in Medicinal Chemistry and Drug Discovery?

Chemists in the medicinal chemistry field are constantly searching for alternatives towards more sustainable and eco-friendly processes for the design and synthesis of drug candidates. The pharmaceutical industry is one of the most polluting industries, having a high E-factor, which is driving the adoption of more sustainable processes not only for new drug candidates, but also in the production of well-established active pharmaceutical ingredients. Deep eutectic systems (DESs) have emerged as a greener alternative to ionic liquids, and their potential to substitute traditional organic solvents in drug discovery has raised interest among scientists. With the use of DESs as alternative solvents, the processes become more attractive in terms of eco-friendliness and recyclability. Furthermore, they might be more effective through making the process simpler, faster, and with maximum efficiency. This review will be focused on the role and application of deep eutectic systems in drug discovery, using biocatalytic processes and traditional organic chemical reactions, as new environmentally benign alternative solvents. Furthermore, herein we also show that DESs, if used in the pharmaceutical industry, may have a significant effect on lowering production costs and decreasing the impact of this industry on the quality of the environment.

Deep eutectic solvents for the determination of endocrine disrupting chemicals

The harmful effects of endocrine disrupting chemicals (EDCs) to humans and other organisms in the environment have been well established over the years, and more studies are ongoing to classify other chemicals that have the potential to alter or disrupt the regular function of the endocrine system. In addition to toxicological studies, analytical detection systems are progressively being improved to facilitate accurate determination of EDCs in biological, environmental and food samples. Recent microextraction methods have focused on the use of green chemicals that are safe for analytical applications, and present very low or no toxicity upon disposal. Deep eutectic solvents (DESs) have emerged as one of the viable alternatives to the conventional hazardous solvents, and their unique properties make them very useful in different applications. Notably, the use of renewable sources to prepare DESs leads to highly biodegradable products that mitigate negative ecological impacts. This review presents an overview of both organic and inorganic EDCs and their ramifications on human health. It also presents the fundamental principles of liquid phase and solid phase microextraction methods, and gives a comprehensive account of the use of DESs for the determination of EDCs in various samples.