Deep eutectic solvents (DESs) and their applications

A new ternary deep eutectic solvent for electropolymerization of thionine on glassy carbon electrodes modified with multiwalled carbon nanotubes for the determination of ascorbic acid

The phenazine redox dye, thionine (Th), was used to prepare poly(thionine) (PTh) polymer film modified electrodes. PTh was electrodeposited on glassy carbon electrodes (GCE) and on GCE modified with multiwalled carbon nanotubes (MWCNT) by potential cycling electropolymerization in the ternary deep eutectic solvent composed of choline chloride (ChCl), thymol (Thy), ethylene glycol (EG), ChCl-Thy-EG (1:1:4) with the addition of different doping acids. The MWCNT promote greater polymer growth, conductivity and increased stability of the polymer films. The modified electrodes, PTh/MWCNT/GCE, were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and the morphology of its surface by scanning electron microscopy. PTh/MWCNT/GCE was used in the determination of ascorbic acid (AA) using fixed potential amperometry with a linear range of 2.5 μM-100 μM and a detection limit of 0.68 μM. The proposed sensor was tested on commercial pharmaceutical samples successfully with good sensitivity, repeatability and reproducibility.

Valorization of waste tomato leaves with natural deep eutectic solvents

Waste produced during cultivation of edible plants can be a valuable source of bioactive molecules. Herein, we present the valorization of tomato leaves to obtain biologically active extracts. Deep eutectic solvents (DESs), composed of natural ingredients, were applied as extracting solvents. The extracts were rich in bioactive chemicals such as phenolics and flavonoids, with rutin as the main component (∼6 mg/g of biomass). The obtained extracts showed high antioxidative potential. Moreover, it was possible to recycle DES for subsequent extractions. Evaluation of the antimicrobial activity of the extracts against selected bacteria (Escherichia coli and Staphylococcus epidermidis) and yeast (Candida albicans) revealed that it showed strong antifungal activity, while the pure solvent did not exhibit such properties. The study revealed that by adhering to the principles of the circular economy and extracting waste tomato leaves using natural DESs, valuable antioxidants and antimicrobial agents can be obtained with high yields.

Highly ionic conductive, elastic, and biocompatible double-network composite gel for epidermal biopotential monitoring and wearable sensing

Soft ionic conductors are promising candidates for epidermal electrodes, flexible sensors, ionic skins, and other soft iontronic devices. However, their inadequate ionic conductivity and mechanical properties (such as toughness and adhesiveness) are still the main constraints for their wide applications in wearable bioelectronics. Herein, an all-biocompatible composite gel with a double-network (DN) strategy is proposed. Compared to the single network, introducing a double-helix structured ι-carrageenan facilitates the DN gel with greatly enhanced mechanical properties and higher ionic conductivity (16.0 mS cm-1). Moreover, the DN gels exhibit high transparency (>92 %), high stretchability (1660 %), and sufficient adhesion. Benefiting from the above unique features, the DN gels successfully serve as biopotential electrodes, which can dynamically monitor human electrophysiological signals with a higher signal-to-noise ratio and superior environmental stability than the commercial electrode. Additionally, they can be employed as resistive strain sensors for accurate human movement monitoring. Our multifunctional DN composite gels offer a feasible platform for on-skin bioelectronics and human-machine interactions.

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.

Valorization of wheat straw through enhancement of cellulose accessibility, xylan elimination and lignin removal by choline chloride:p-toluenesulfonic acid pretreatment

Different molar ratio of choline chloride (ChCl) and p-toluenesulfonic acid (p-TsOH) (2:1, 1:1 and 1:2, mol:mol) were used to prepare deep eutectic solvents (ChCl:p-TsOH) for pretreating cellulose fibers to elevate cellulose accessibility, enhance xylan elimination, increase lignin removal and promote enzymatic digestion. ChCl:p-TsOH (1:1, mol:mol) could effectually destroy the dense layout of wheat straw (WS) at 80 °C for 60 min. Cellulose crystallinity declined from 43.4 % to 25.5 %, and the lignin surface area and hydrophobicity were reduced to 182.6 m2/g and 3.2 L/g, respectively. While cellulose accessibility in WS was significantly improved to 523.9 mg/g. The delignification and xylan removal reached 72.4 % and 90.5 %, respectively. The enzymatic digestibility reached 89.3 %. Furthermore, molecular dynamics simulation and quantum chemistry calculation were conducted on the lignocellulose model. The van der Waals interaction between ChCl:p-TsOH and lignin and the dispersion interaction between ChCl and lignin were identified. Accordingly, the interaction between biomass and ChCl:p-TsOH was elucidated at the molecular level. It provided a comprehensive understanding of lignocellulosic biomass valorization through the highly efficient pretreatment by ChCl:p-TsOH.

Tuning the nanostructure and tribological properties of a non-ionic deep eutectic solvent with water addition

HYPOTHESIS

The addition of water to a non-ionic N-oxide deep eutectic solvent(DES) composed of phenylacetic acid (PhAA) and N-dodecylmorpholine-N-oxide(MO-12) in a 1:1 M ratio(PhAA/MO-12) will promote interfacial nanostructure formation due to increased proton transfer and solvophobic interactions, leading to reduced friction.

EXPERIMENTS

The interfacial structure and friction of PhAA/MO-12 with water content up to 41.9 wt% were investigated at mica surfaces. Atomic force microscopy(AFM) was used to measure normal force-separation profiles, lateral images, and nanoscale friction.

FINDINGS

Conductivity increases over twentyfold with the addition of 23.6 wt% water. AFM force curves reveal that increasing water content in PhAA/MO-12 leads to a more pronounced interfacial structure with steps extending further into the bulk. High-resolution near-surface images show a well-defined sponge-like nanostructure at 23.6 wt% water, which is absent in the neat DES. The enhanced nanostructure is attributed to increased proton transfer from PhAA to MO-12 and segregation of polar and apolar domains driven by water-strengthened solvophobic interactions. Friction reduces up to 72 % for ≥7.0 wt% water compared to the neat DES, due to a more robust boundary layer facilitated by water.

Supramolecular cyclodextrin deep eutectic solvent-strengthened chitosan eutectogel as a novel percutaneous delivery system of resveratrol for anti-psoriasis

Psoriasis is a chronic and incurable inflammatory skin disease usually requiring long-term disease management. Natural phytochemical resveratrol (RES) has been known for high efficiency and low toxicity, exhibiting good anti-psoriasis potential. However, its biological activity is limited by poor solubility, chemical instability, and insufficient skin retention. Herein, we developed an adhesive eutectogel loaded with RES constructed through electrostatic and hydrogen bonding cross-linking between cyclodextrin-levulinic acid supramolecular deep eutectic solvent (DES) and chitosan (CS). A series of characterizations combined with molecular dynamics simulations demonstrated that such DES not only significantly increased the solubility and stability of RES, but also acted as the cross-linker and plasticizer in eutectogel preparation. When applied to the skin surface, the eutectogel formed a soft film in situ that established tight contact with the skin, thereby enhancing RES sustained penetration into the skin. In an imiquimod-induced psoriasis-like mice model, the eutectogel effectively alleviated psoriasis symptoms, inhibited the excessive proliferation of keratinocytes, and regulated the expression of IL-23/IL-17 axis-related factors, whose therapeutic effect was better than that of commercially available calcipotriol ointment. Overall, The DES-strengthened eutectogel offers a promising topical drug delivery platform for psoriasis treatment and expands the applications of green polysaccharide medical materials.

A functional eutectogel based on ultrahigh-molecular weight polymers: Physical entanglements in deep eutectic solvent

Eutectogels have emerged as a promising material for wearable devices due to its superior ionic conductivity, non-volatility, and low cost. Despite numerous efforts, only a limited number of polymers and gelling mechanisms have been successfully employed in the fabrication of eutectogels. In this study, an effective three-dimensional network is developed based on the entanglements of polymer chains, facilitating the formation of an entangled eutectogel. The fabrication process involves directly dissolving ultra-high molecular weight polyvinylpyrrolidone (PVP) in deep eutectic solvent (reline) through a simple heating-cooling method. The resulting eutectogel, containing 40 wt% PVP, exhibits excellent stretchability of 1410 % strain, toughness of 544.8 kJ/m3, and ionic conductivity of 0.015 S/m. It also generates a reliable resistance signal suitable for strain-sensing applications. Furthermore, this entangled eutectogel displays self-healing capabilities, enabled by the diffusion and re-entanglement of polymer chains. This work not only demonstrates a facile fabrication approach for an entangled eutectogel but also provides the first investigation into employing long chain entanglements in the development of eutectogels.

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.

Deep eutectic solvents in analysis, delivery and chemistry of pharmaceuticals

Deep eutectic solvents (DES) have an emerging scientific role, assisting modern pharmaceutics. They are uniquely supporting the resolution of crucial issues, such as the effective extraction and isolation of bio-actives. They act as media and catalysts for pharmaceutical drug synthesis, and as green solvents and modifiers in pharmaceutical analysis. Their role in pharmaceutical formulation and drug delivery is also up-and-coming, for instance, as alternative drug-solubilizing agents, drug stabilizers and functional additives, as therapeutic deep eutectic solvents, deep eutectic API, and monomers and reaction media for the synthesis of biomaterials for advanced drug delivery. The DES also help transforming medicinal/pharmaceutical chemistry. Although DES were described in 1918, their first pharmaceutical use is only reported in 1960. In view of their broad applicability in pharmaceutics, it may be interesting to review their history, origin, evolution, potential advantages, limitations, and specific applications as green solvents. A chronological and comparative study of the literature showed the important role of DES in green approaches for modern pharmaceuticals. The concepts, applications, and outcomes of DES in pharmaceutical analysis, formulation/drug delivery, and pharmaceutical/medicinal chemistry are presented. A comprehensive outline of the atypical applications of DES as effective green solvents in pharmaceutical bioactive extraction was assessed. Efforts to present classifications of DES explored in pharmaceuticals were also made. The present manuscript also covers computational trend, adds on commercial aspects with potential future applications of DES in pharmaceutical sciences.

Mechanism of dissolution of cellulose in quaternary ammonium phosphate/dimethyl sulfoxide

Finding of new environmentally friendly cellulose solvent system is critical for efficient usage of cellulose. In this paper, cellulose solvent based on the mixture of di-tetrabutylammonium hydrogen phosphate and dimethyl sulfoxide (TBA2HPO4/DMSO) was developed. We found that TBA2HPO4/DMSO system has excellent solubility of cellulose. The solubility of cellulose in the system depends on TBA2HPO4/DMSO mass ratio. The increase of DMSO content leads to the faster dissolution of cellulose in TBA2HPO4/DMSO. Microcrystalline cellulose can be dissolved in TBA2HPO4/DMSO (30/70, w/w) within 5 min at 60 °C. The highest solubility of cellulose, 14.5 wt%, was achieved in TBA2HPO4/DMSO (68/32, w/w). Dissolution mechanism investigation indicated that TBA2HPO4 itself cannot dissolve cellulose. The addition of DMSO resulted the dissociation of TBA2HPO4 to release TBA+ and HPO42- in the system. The HPO42- is an excellent hydrogen bond acceptor, which can form hydrogen bonds with hydroxy groups of cellulose to destroy the hydrogen-bonding network of cellulose. The solvated TBA+ cations by DMSO attracted around cellulose chains via the ionic bond with HPO42- anions that bounded to cellulose chains to isolate cellulose chains to result homogeneous cellulose solution. The TBA2HPO4/DMSO is a promising system for the preparation of regenerated cellulose materials.

Coffee husk valorization through choline chloride/lactic acid (1:10) green catalyst extraction for lignin monomers recovery

The processing of coffee consists on the separation of the grains from other parts of the fruit, then roasted and extracted to obtain the beverage that is so appreciated worldwide. Several studies have dedicated efforts to treat the residue from coffee processing, while recovering lignols of industrial interest. Given this scenario, the nutrients in the coffee husk can enhance microbial growth, providing optimal conditions for the microorganisms to produce metabolites that may have medicinal properties. Deep eutectic solvents (DES) are a class of solvents and/or catalysts designed on demand for specific uses, being used to enhance extraction processes of coffee husk. Our present study was successful establishing conditions where the coffee husk enhanced the growth of microorganisms from two Brazilian biomes, the endophytic fungus from Cerrado and the actinomycete, from Atlantic Rainforest in Boraceia, São Paulo. The DES composed by ChCl/LA (1:10) was selected as cosolvent for the extraction, while it also optimized microbial cultivation conditions. Coffee husk was an excellent supplement for culture media, once the fungus FE316 produced Fumiquinazoline A, Tripprostatin B and Pseurotin A, while the actinomycete AC154 produced Trichorozin-IV as metabolites only expressed when in addition to the coffee husk. UHPLC-MS/MS analysis enabled the annotation of lignin monomer compounds, such as alkaloids, phenylpropanoids and terpenoids present in the coffee husk, more specifically, caffeic acid, isochlorogenic acid B, chlorogenic acid and coniferyl aldehyde, underscoring the value of this biomass.

Self-association of cyclodextrin inclusion complexes in a deep eutectic solvent enhances guest solubility

Cyclodextrins are widely used pharmaceutical excipients known to increase the solubility of drug compounds through formation of inclusion complexes. A prominent limitation of common cyclodextrins is their own scarce solubility in water, which renders them unsuitable for many drug formulations. Cyclodextrin solubility can be enhanced in appropriate media such as Deep Eutectic Solvents (DESs). However, DESs can also reduce the equilibrium constant for host-guest complexation, making it challenging to optimize drug solubility using cyclodextrin. To determine the impact and mechanism of cyclodextrin complexation in DES, we tracked changes in the solubility of methyl orange (MO), serving as a hardly soluble model compound, in the presence of β-cyclodextrin (CD) in hydrated urea-choline chloride DES. The highest achievable MO solubility is obtained in concentrated CD-in-DES mixtures at low hydration, resulting from the higher solubility of CD⊃MO complexes in DES compared to water as a solvent. Combining our results with molecular dynamics simulations, we provide evidence that CD⊃MO complexes self-associate into dimers and larger oligomers. This self-association of complexes greatly enhances MO solubilization by CD beyond that expected from the canonical 1:1 binding stoichiometry. This newly unraveled solubilization mechanism via cyclodextrins and its facilitation by DES should aid the design of future drug formulations.

Microextraction of steroidal hormones from urine samples using natural deep eutectic solvents: insights into chemical interactions using molecular dynamics simulations

Natural deep eutectic solvents (NADES) are gaining significant attention in analytical chemistry due to attractive physico-chemical properties associated with sustainable aspects. They have been successfully evaluated in different fields, and applications in sample preparation have increased in the last years. However, there is a limited knowledge related to chemical interactions and mechanism of intermolecular action with specific analytes. In this regard, for the first time, this study exploited a computational investigation using molecular dynamics (MD) predictions combined with experimental data for the extraction/determination of steroidal hormones (estriol, β-estradiol, and estrone) in urine samples using NADES. The ultrasound-assisted liquid-liquid microextraction (UALLME) approach followed by high-performance liquid chromatography with diode array detection (HPLC-DAD) was employed using menthol:decanoic acid as extraction solvent. Experimental parameters were optimized through multivariate strategies, with the best conditions consisting of 3 min of extraction, 150 μL of NADES, and 3 mL of sample (tenfold diluted). According to molecular dynamics predictions confirmed by experimental data, a molar ratio that permitted the highest efficiency consisted of menthol:decanoic acid 2:1 v/v. Importantly, computational simulations revealed that van der Waals interactions were the most significant contributor to the interaction energy of analytes-NADES. Using the optimized conditions, limits of detection (LOD) ranged from 3 and 8 μg L-1, and precision (n = 3) varied from 8 to 19%. Intraday precision was evaluated at 3 concentrations: low (LOQ according to each analyte), medium (100 μg L-1), and high (750 μg L-1). Accuracy was successfully assessed through recoveries that ranged from 82 to 98%. In this case, molecular dynamics simulations proved to be an important tool for in-depth investigations of interaction mechanisms of DES with different analytes.

Lignin nano/micro-particles from agricultural biomasses: Developing direct precipitation for integrated biorefinery

The state-of-the-art, simple and scalable methods for lignin micro-/nano-particles recovery from agricultural biomasses were evaluated in this review. Being non-wood biomasses, these materials can be easily fibrillated, supporting the usage of mild soda or organic solvent pretreatment. Different approaches in particle recovery were compared to conclude that the bottom-up approach facilitates smaller particles towards the nano-size range whereas mechanical treatment can act as a supporting method to increase uniformity and reduce particle sizes after bottom-up precipitation. By combining with the pretreatment steps, direct one-pot lignin micro-/nano-particle recovery can be achieved using the lignin-containing black liquor or organosolv liquor. These lignin micro-/nano-particles can then be applied as high-value functional products in cosmetics, pharmaceuticals, environmental remediation, and energy sectors. The systematic evaluation of lignin micro-/nano-particles recovery from agricultural biomasses in this review can support the full utilization of these natural resources to aim towards a circular agriculture.

Gel-Based Electrolytes for Organic Electrochemical Transistors: Mechanisms, Applications, and Perspectives

Organic electrochemical transistors (OECTs) have emerged as the core component of specialized bioelectronic technologies due to their high signal amplification capability, low operating voltage (<1 V), and biocompatibility. Under a gate bias, OECTs modulate device operation via ionic drift between the electrolyte and the channel. Compared to common electrolytes with a fluid nature (including salt aqueous solutions and ion liquids), gel electrolytes, with an intriguing structure consisting of a physically and/or chemically crosslinked polymer network where the interstitial spaces between polymers are filled with liquid electrolytes or mobile ion species, are promising candidates for quasi-solid electrolytes. Due to relatively high ionic conductivity, the potential for large-scale integration, and the capability to suppress channel swelling, gel electrolytes have been a research highlight in OECTs in recent years. This review summarizes recent progress on OECTs with gel electrolytes that demonstrate good mechanical as well as physical and chemical stabilities. Moreover, various components in forming gel electrolytes, including different mobile liquid phases and polymer components, are introduced. Furthermore, applications of these OECTs in the areas of sensors, neuromorphics, and organic circuits, are discussed. Last, future perspectives of OECTs based on gel electrolytes are discussed along with possible solutions for existing challenges.

Hydrophobic deep eutectic solvent-ferrofluid microextraction followed by liquid chromatography-mass spectrometry for the enantioselective determination of chiral agrochemicals in natural waters

The increasing use of chiral agrochemicals sold as racemic formulations raises concern for the negative impacts that inactive enantiomers can have on aquatic life and human health. The present work just focuses on the determination of ten chiral pesticides in river water samples by applying a ferrofluid-based microextraction followed by their stereoselective liquid chromatography analysis. To develop the ferrofluid, magnetite nanoparticles were prepared and coated with oleic acid and then dispersed in a hydrophobic natural deep eutectic solvent (NaDES), composed of L-menthol and thymol (1:1). The stable colloidal dispersion was characterised by scanning electron microscopy, thermogravimetric analysis, energy-dispersive X-ray spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. The analyte microextraction from 5 ml river samples was performed using 50 µl of ferrofluid, while acidified acetonitrile (150 µl) was used to break down the ferrofluid and solubilise the NaDES containing the analytes. All the extracts were analysed by high-performance liquid chromatography-tandem mass spectrometry. For each analyte, the baseline separation of isomers was achieved on a Lux i-Amylose-3 column (amylose tris(3-chloro-5-methylphenylcarbamate) working in reversed-phase mode; the combination with mass spectrometry detection allows the overall separation of 24 isomers (ten chiral analytes among which eight containing a single (one) chiral centre, one with two chiral centres and the last one existing in four stereoisomeric forms, due to the presence of two regioisomers with a chiral carbon) within 37 min. The method showed very good figures of merit in terms of recoveries (77.7-97.5%), intra-day and inter-day precision (2.7-7.7% and 6.9-14.9%, respectively), limit of detection (0.01-0.35 µg/L), limit of quantitation (0.03-1.20 µg/L), linear dynamic range, and intra-day and inter-day accuracy (1.2-14.8% and 1.8-15.0%, respectively). The presented method was able to detect 14 out of 24 isomers at the preventive limit established by the Italian legislation for single pesticide (that for a chiral pesticide is the sum of all its isomers) in surface waters, set at 0.1 µg/l. Finally, the method was evaluated using AGREEprep and ComplexGAPI metrics, compared with other ferrofluid-based methods, and applied to the analysis of water samples from two Italian rivers (the Nera River and the Tiber River), providing to be sustainable and reliable for the application to real river matrices.

Recent perspective of synthesis and modification strategies of cellulose nanocrystals and cellulose nanofibrils and their beneficial impact in scaffold-based tissue engineering: A review

Outstanding properties of nanocellulose provide opportunities for novel applications in various fields, particularly tissue engineering. Despite of numerous useful characteristics of nanocellulose, its production methods suffer from the lack of control of morphology, high cost, and the use of organic solvents. On the other hand, hydrophilicity of nanocellulose is a significant challenge for its dispersion as a reinforcement in hydrophobic polymers matrix. Therefore, sustainable production methods and well-tuning interfacial characteristics of nanocellulose have been identified as critical steps in their development. This review article discusses the numerous preparation methods and surface modification strategies of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) to help nanocellulose users obtain the appropriate material for their desired application. We also cover various polymer/nanocellulose scaffolds that are reported in the literature and investigate the effect of CNC and CNF on their mechanical, thermal and biological properties. Moreover, we provide several scientific figures and tables for a better understanding of the explored topics. Finally, we evaluate the opportunities and challenges of nanocellulose industrialization in the field of tissue engineering. Overall, this review guides researchers towards a deeper understanding of nanocellulose production processes, changing their properties using surface modification methods, and subsequently their performance in scaffold-based tissue engineering.

Advances and challenges in green extraction of chitin for food and agriculture applications: A review

Chitin, the second most abundant polysaccharide in nature, offers numerous practical applications due to its versatile functional properties. However, its utilization is constrained by significant challenges in extraction, as well as low solubility and high crystallinity. While traditional chemical and biological fermentation methods can achieve high-purity chitin, these processes are often environmentally harmful or time/energy-consuming. Ionic liquids and deep eutectic solvents have emerged as more sustainable alternatives for chitin extraction, though both methods still face certain limitations, which are comprehensively discussed in this review. Besides extraction, chitin or modified chitin is increasingly being used to create a variety of biomaterials, which have shown considerable potential in food applications, including food packaging, preservation, stabilization, and nutrient encapsulation and delivery. Furthermore, the applications of chitin-based biomaterials are also reviewed in agriculture, where they are utilized as fertilizers, biocides, the elicitation of plants, or to treat seeds. This review not only provides a deeper understanding of the advancements and limitations in green chitin extraction methods but also highlights the broad potential of chitin-based biomaterials in both food and agriculture.

Room-temperature and recyclable preparation of cellulose nanofibers using deep eutectic solvents for multifunctional sensor applications

Cellulose nanofibers (CNFs) have gained increasing attention due to their robust mechanical properties, favorable biocompatibility, and facile surface modification. However, green and recyclable CNF production remains challenging. Herein, a green, low-cost and room-temperature strategy was developed to exfoliate CNFs using deep eutectic solvents. A high average yield (~90 %) of CNFs was achieved during the recycling process. The resultant CNFs delivered favorable dispersion in water with an average length of ~5.3 μm and an average diameter of ~44 nm. The application of the resultant CNFs for multifunctional sensors was explored by fabricating the composite films of poly(vinyl alcohol) (PVA), tannic acid-decorated CNFs (CNF@TA) and Ag nanoparticles (AgNPs). As a stretchable strain sensor, the PVA/CNF@TA/AgNPs sample exhibited superior sensitivity (GF = 46.42), low detection limit (<1 %) and fast response (80 ms). This sensor possessed excellent temperature sensing performance with good accuracy (0.1 °C), high TCR (29.84/°C) in the body temperature region of 34-42 °C and desirable linearity (R2 = 0.981). In addition, the sensor could be used to monitor real-time skin moisture information. This simple and economical preparation strategy may facilitate potential applications of CNFs in the development of multifunctional sensors for wearable electronic devices.

Dynamics of Deep Eutectic Mixtures of Tetraethylammonium Halides/Ethylene Glycol Investigated with Ultrafast Infrared Spectroscopy

Health and environmental risks posed by volatile organic solvents create an incentive to develop safer, less volatile solvents with the appropriate functionality. Deep eutectic solvents and other low-volatility organic mixtures offer a highly tunable alternative through a mixture composition selection. However, a significant gap exists in understanding the relationship between molecular-level properties and the resulting solvation and transport properties. Using ultrafast infrared (IR) polarization-selective pump-probe (lifetimes and orientational relaxation) spectroscopy, we investigated the dynamics of 1:3 molar mixtures of tetraethylammonium bromide (TEABr) and chloride (TEACl) with ethylene glycol (EG) and of pure EG using the anionic vibrational probe, the CN stretch of SeCN-. The very high salt concentrations are in many respects analogous to water-in-salt solutions, e.g., LiBr and LiCl. These ion/water mixtures can have extremely high ratios of ions to solvating neutral molecules, similar to the 1:3TEABr and 1:3TEACl mixtures studied here. In 1:3TEABr/EG and 1:3TEACl/EG solutions, there are far too few EGs to solvate the ions. Therefore, like water-in-salt, 1:3TEABr/EG and 1:3TEACl/EG solutions will have solvent-separated ion pairs, contact ion pairs, and large ion/EG clusters, forming extended ion/solvent networks. The orientational dynamics experiments on 1:3TEABr/EG and 1:3TEACl/EG show striking similarities to experiments from the literature on 1:4 LiBr and LiCl aqueous solutions, even though the cations and solvents in the deep eutectic mixtures are vastly different.

Recent progress of multifunctional nanocellulose-based pharmaceutical materials: A review

In the pharmaceutical industry, ongoing research and development focus on discovering new drug formulations that align with regulatory approvals. Recently, innovative drug delivery systems have been used to maximize therapeutic efficacy with a precision of sustained drug delivery in the disease management system. Nanocellulose (NCs) synthesized from abundant cellulose, have attracted wide attention for potential pharmaceutical applications due to their unique properties, such as biocompatibility, high surface area-to-volume ratio, extensive drug loading and binding capacity, controlled drug release efficiency, strength, and availability with various treatments and modification ability. Nevertheless, research on nanocarriers (NCs) in the pharmaceutical field faces several limitations and challenges. Key areas requiring further exploration include chemical consumption, energy intensity, effluent management, recovery processes from acid hydrolysis, reaction times, ecotoxicology, and overall development progress. This overview provides the applications of emerging nanocellulose. It gives a clue on the synthesis of sustainable NCs related to their different sources, pre- and post-modifications of NCs, and key properties in pharmaceutical sectors. Furthermore, it gives an overview of the current advancements, life cycle analysis, biosafety, and key property performance with a summary of challenges and future perspectives.

Green DES-mediated preparation of the rose-shaped S-scheme heterojunction photocatalyst (β-Bi2O3/Bi2O2.33)/TiO2 to boost antibiotics degradation

Here, the rose-shaped S-scheme heterojunction photocatalyst (β-Bi2O3/Bi2O2.33)/TiO2 was successfully prepared by a new, green and simple deep eutectic solvent-mediated strategy, which not only exhibits exceptional photocatalytic activity for tetracycline degradation, but also displays good stability, excellent universality and superior hydrogen evolution activity.

A size-dependent ideal solution model for liquid-solid phase equilibria prediction in aqueous organic solutions

Predictive synthesis of aqueous organic solutions with desired liquid-solid phase equilibria could drive progress in industrial chemistry, cryopreservation, and beyond, but is limited by the predictive power of current solution thermodynamics models. In particular, few analytical models enable accurate liquidus and eutectic prediction based only on bulk thermodynamic properties of the pure components, requiring instead either direct measurement or costly simulation of solution properties. In this work, we demonstrate that a simple modification to the canonical ideal solution theory accounting for the entropic effects of dissimilar molecule sizes can transform its predictive power. Incorporating a Flory-style entropy of mixing term that includes both the mole and volume fractions of each component, we derive size-dependent equations for the ideal chemical potential and liquidus temperature, and use them to predict the binary phase diagrams of water and 10 organic solutes of varying sizes. We show that size-dependent prediction outperforms the ideal model in all cases, reducing average error in the predicted liquidus temperature by 59% (to 5.6 K), eutectic temperature by 45% (to 9.7 K), and eutectic composition by 43% (to 4.7 mol%), as compared to experimental data. Furthermore, by retaining the ideal assumption that the enthalpy of mixing is zero, we demonstrate that, for aqueous organic solutions, much of the deviation from ideality that is typically attributed to molecular interactions may in fact be explained by simple entropic size effects. These results suggest an underappreciated dominance of mixing entropy in these solutions, and provide a simple approach to predicting their phase equilibria.

A blessing and a curse: impact of urea derivatives on the secondary building unit of Ca-MOFs prepared in deep eutectic solvents

Deep eutectic solvents (DESs) based on a 1 : 2 combination of choline chloride with either urea or e-urea (2-imidazolidinone) have been studied as media for the preparation of Ca(II) metal-organic frameworks (Ca-MOFs). In particular, the impact of the urea derivative on the secondary building unit (SBU) has been investigated by exploring the formation of Ca-MOFs with a series of ten di- and tetra-carboxylic acids, varying in length, steric hindrance and the number and relative orientation of coordinating units. While several of these ligands have, to the best of our knowledge, not been previously reported to form Ca-MOFs, eleven new materials could be prepared and characterized by single-crystal and powder diffraction, elemental and thermogravimetric analyses as well as absorption and emission spectroscopy. The DES incorporating e-urea was found to be especially prone to the formation of crystalline materials. However, a recurrent one-dimensional SBU based on bridging carboxylate moieties and the carbonyl unit of e-urea was observed. Coordination of the solvent molecule is assisted by hydrogen bonding of the NH groups, leading to a strongly stabilizing motif preventing these materials from thermal activation without loss of crystallinity.

An unconventional separation method of α-Terpineol from its isomer 1,8-Cineole via in situ-association formation of deep eutectic solvent and machine learning

α-Terpineol and 1,8-cineole are two important compounds in essential oils. This study developed an efficient method to recover α-terpineol from model oil (MO) based on association extraction by in situ formations of deep eutectic solvent (DES) between α-terpineol and some quaternary ammonium salts (QASs) by hydrogen-bond (HB) interaction. Such interaction could be broken almost completely by the introduction of water, due to the stronger HB interaction between water and QASs, which could release α-terpineol by liquid-liquid separation and save the organic solvents consumption. QASs were screened by gaussian energy calculation and experimental verification. Subsequently, the effect of physicochemical properties of the quaternary ammonium salts on the weak interaction between QASs and α-Terpineol was also screened using random forests model. Tetrabutylammonium chloride (TBAC) was proved to form DES with α-terpineol but not with 1,8-cineole, which was proved by FT-IR and 1H nuclear magnetic resonance (1H NMR) spectroscopy. After response surface methodology (RSM) and Genetic Algorithm-Back Propagation (GA-BP) neural network optimization, the distribution ratio and selectivity of α-terpineol to 1,8-cineole could reach a high value of 29.6 and 42.2. The α-terpineol could achieve a purity up to 99.6 % with a recovery of 88.8 % by the two-step back-extractions using n-hexane and water. Furthermore, camphor leaf essential oil was used to demonstrate the reliability of the method for further application. In this separation process, all reagents including organic salt, n-hexane and water could be recovered and reused. It provides an alternative and promising method for the economical and green treatment of essential oils.

Eco-friendly extraction and recovery of triterpenoids from persimmon leaves (Diospyros kaki L.f.) using ultrasound-assisted deep eutectic solvents and macroporous resins

Triterpenoids are known for their promising biological activities, and there is a growing focus on green extraction methods for these compounds. In this study, ultrasound-assisted deep eutectic solvents were employed to extract triterpenoids from persimmon leaves, with choline chloride-lactic acid identified as an effective green solvent. The extraction conditions were carefully optimized using response surface methodology, resulting in an extraction efficiency of 12.41%, which is 1.54 times higher than that achieved with conventional organic solvents such as methanol. The triterpenoids were then successfully recovered using a solid-liquid extraction method based on AB-8 macroporous resins, achieving a 94.01% recovery rate with a final product triterpenoid content of 81.87%. These findings provide a strong foundation for the sustainable extraction of triterpenoids and other valuable compounds from biomass.

Weakly Solvating Cyclic Ether-Based Deep Eutectic Electrolytes for Stable High-Temperature Lithium Metal Batteries

Deep eutectic electrolytes (DEE) have emerged as an innovative approach to address the instability and safety issues of lithium metal batteries at elevated temperatures. However, in practice, there is often an undesirable incompatibility between the eutectic mixture and electrodes, and also an insufficient reduction stability of DEE due to the increased Li+ concentration. Herein, we designed a new DEE by utilizing weakly solvating tetrahydropyran (THP) solvent. Due to the high reduction resistance of THP and concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), this DEE demonstrates enhanced compatibility with Li metal anode and high temperature tolerance with LiMn2O4 cathode. The Li||LiMn2O4 cell (1.6 mAh cm-2) shows a high capacity retention of 96.02 % after 600 cycles at room temperature. More importantly, this Li||LiMn2O4 cell achieves a remarkable high-temperature performance with a high capacity retention of 91.72 % after 120 cycles and low self-discharge after storage for 240 hours at a high temperature of 55 °C, which is critical for LiMn2O4 cathode. Overall, this electrolyte design provides an alternative pathway for the development of DEEs for high-temperature and high-voltage lithium metal batteries, which can also be expanded to other batteries.

Designed Reactive Natural Deep Eutectic Solvents for Lipase-Catalyzed Esterification

Natural deep eutectic solvents (NADESs) are a sustainable, green option for extraction and reaction media in biorefineries and various chemical and biotechnological applications. Particularly, enzymatic reactions profit from NADES applications, as these solvents help to maintain high substrate solubility while improving both enzyme stability and efficiency. Recent studies confirmed that NADESs can perform multiple functions simultaneously, as reaction media for biocatalytic conversions, but also as substrates and catalysts for reactions, fulfilling the role of a reactive solvent. This study reports the beneficial effect of designed reactive natural deep eutectic solvents (R-NADESs) on the esterification activity and thermal stability of free and immobilized lipases in the synthesis of polyol- and carbohydrate-based biosurfactants. We manufactured and characterized 16 binary and ternary R-NADES systems with choline chloride (ChCl) as the hydrogen bond acceptor (HBA) and carbohydrate polyols; mono-, di-, and oligosaccharides; urea (U); N-methyl urea (MU); and water as the hydrogen bond donors (HBDs), in different combinations and molar ratios, most of which are reported for the first time in this paper. We determined their physicochemical, thermal, and molecular properties, including among others viscosity, polarizability, and the number of hydrogen bonds, and we showed that these properties are controlled by composition, molar ratio, molecular properties, temperature, and water content. Many lipases, both native and immobilized, showed high stability and remarkable catalytic performance in R-NADESs during esterification reactions.

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.

A review on the role of deep eutectic solvents in mango (Mangifera indica) extraction

The present review attempts to evaluate the applicability of deep eutectic solvents (DES) as a green technique for the extraction of phytochemicals from Mangifera indica L. and their therapeutic potential. Mango has been reported to show numerous therapeutic activities, which are attributed to its abundant source of bioactive compounds. Thus, the therapeutic potential of phytochemicals in mangoes is reviewed based on different reported bioactivity tests. The use of DESs is considered a green approach for the extraction of bioactive compounds from natural sources utilizing two or more components and a safe alternative for application in the nutritional, pharmaceutical and other sectors. The trends in the extraction of phytochemicals from mango using different DES components and different extraction parameters of the optimum protocol are reviewed. Hence, DESs are considered potential solvents with selective and efficient properties for extracting bioactive ingredients from mango. However, there are several knowledge gaps that need to be assessed for DES-based bioactive compound extraction from mango such as information on the local and specific varieties of mangoes, standardization of the extraction protocols and use of other parts of the mango plant as alternatives to its peel as bioactive sources. Accordingly, the extraction of bioactive compounds from mango using DESs will provide useful information for subsequent agricultural, pharmaceutical and nutraceutical applications in the future.

Beneficial Effects of FEC on an In-Situ Polymerized Deep Eutectic Electrolyte for Solid-State Batteries

Eutectic-based polymer electrolytes have emerged as promising solid electrolytes because of their ionic liquid-like properties, while modifications are essential to further increase their ionic conductivity at room temperature and solve their compatibility with lithium anode. In this work, an in situ polymerized composite electrolyte is modified by the addition of fluoroethylene carbonate (FEC) whose beneficial effect is systematically investigated in different contents. Poly(ethylene glycol) diacrylate (PEGDA), deep eutectic solvent (LiTFSI:N-methylacetamide = 1:3), and alumina fiber work as the monomer, solvent, and three-dimensional skeleton, respectively. In adjusting FEC content, ionic conductivity at room temperature is dramatically raised by three times to 8.93 × 10-4 S cm-1, with a 4-fold increase in lithium-ion transference number to 0.405. Meanwhile, the electrochemical window is widened from 3.5 to 4.8 V. The FEC addition also helps in improving the stability with Li anode, which comes from LiF-rich interphases formed at interfaces. The dynamics of LiFePO4 is significantly enhanced with higher reversibility in full cells, so that fast capacity decay is inhibited with a specific capacity of 124.1 mAh g-1 obtained after 300 cycles at 1 C. These results provide an effective modification for the deep eutectic electrolyte, which will boost its development in solid-state batteries.

Green Manufacture of Hydrated Polymers Coatings with On-Demand Mechanics and Lubricity Based on Novel Biobased Polymerizable Deep Eutectic Solvents

The aging population necessitates a critical need for medical devices, where polymers-based surface lubrication coating is essential for optimal functionality. In fact, lubrication and mechanical requirements vary depending on the service environment of different medical devices. Until now, key mean is still blank for general preparation of hydrophilic polymers-based lubrication coatings with on-demand mechanics and lubricity. This study introduces a novel hydrophilic lubrication coating with tunable mechanical properties and lubricity, derived from eco-friendly polymerizable deep eutectic solvents (PDESs) containing betaine, hydroxyethyl acrylate, glycerol, and tannic acid. Unlike traditional high molecular weight polymers, this approach leverages small-molecule, high-biobased PDESs, thereby simplifying the synthesis process. The resulting coating demonstrates exceptional adhesion to a range of medical device materials─including glass, stainless steel, polyvinyl chloride, and polyurethane─thanks to the high content of hydroxyl groups and pyrogallol motifs from tannic acid. It also enables the precise tuning of mechanical strength, modulus, adhesion, hydrophilicity, and lubrication properties by varying the amounts of glycerol and tannic acid. Furthermore, the coating undergoes a hydration-induced transition from high-strength, high-friction to low-strength, low-friction states, maintaining repeatable performance. Additionally, the synergistic effects of betaine and tannic acid in the PDES contribute to its notable antimicrobial properties. In summary, these PDESs demonstrate significant potential for enhancing lubrication in a range of biomedical devices.

Molecular Understanding of CO2 Absorption by Choline Chloride/Urea Confined within Nanoslits

Clarifying the potential relationship between the microstructure of nanoconfined choline chloride/urea (ChClU) and CO2 absorption performance is key to understanding the abnormal increase in CO2 under nanoconfinement. In this study, we used molecular dynamics simulations and grand canonical Monte Carlo (GCMC) to systematically study the mechanism underlying the absorption of CO2 by ChClU within nanoslits. According to the spatial distribution, ChClU can form two different laminar regions within nanoslits, namely, the interfacial region (region I) and beyond region I (region II). In region II, the interface induces rearrangement of ChClU, resulting in an increase in free volume and subsequent increase in CO2 solubility. In region I, changing the interface from hydrophobic to hydrophilic (e.g., S_I to S_IV) by setting the appropriate charge patterns, the urea molecules gradually change from "disordered" to "ordered standing" relative to the solid surface. The preferential orientation of the urea molecules causes competition between the ChClU's free volume and urea molecules, resulting in a non-monotonic change in CO2 solubility. Specifically, from S_I to S_III, the increase in urea molecules enhances the CO2 solubility. In S_IV, space for CO2 absorption is insufficient due to the accumulation of urea molecules, and thus CO2 solubility decreases.

Advanced Eutectogel Electrolyte for High-Performance and Wide-Temperature Flexible Zinc-Air Batteries

Despite ongoing challenges, achieving further breakthroughs in the development of gel polymer electrolytes with a wide temperature range, excellent liquid retention capability and enhanced anode compatibility in flexible zinc-air batteries (FZABs) remains a significant objective. This study presents a significant advancement in the development of choline chloride/ethylene glycol-polyvinyl alcohol (ChCl/EG-PVA) eutectogel electrolyte, tailored for high-performance operation across a wide temperature range. Systematic in-situ and ex-situ characterizations and theoretical simulations confirm the formation of robust hydrogen bonding and denser polymer cross-linked networks within the prepared eutectogel, leading to enhanced liquid retention ability (93.7 % after 96 h exposure to air) and ion transport capacity (ionic conductivity of 171.3 mS cm-1). Additionally, the zincophilicity nature of the choline cation in eutectogel effectively suppresses dendrites growth. The assembled FZAB utilizing this eutectogel electrolyte achieves a peak power density of 109.3 mW cm-2 and a cycle life of 90 h. Notably, the power density of FZAB is maintained as high as 38.2 mW cm-2 at -40 °C and 63.2 mW cm-2 at 50 °C, demonstrating its prominent suitability for applications in extreme temperature conditions. The design of eutectogel provides a novel way to achieve the high-performance FZAB.

A feasible approach to chromophores removal and color reduction in industrial lignin via deep eutectic solvent/isopropanol treatment

The dark coloration of industrial lignin significantly limits its potential for applications in high-value products. This work reported a practical strategy for lignin color reduction through the synergistic treatment of acidic deep eutectic solvent and isopropanol (DES-IPA). The results showed that the DES-IPA treatment could effectively remove the p-coumarate units and methoxy groups in lignin. Meanwhile, the condensation reaction in lignin was effectively inhibited. The color of lignin was reduced to an acceptable range while retaining the aromatic ring structure and reactive activity of lignin. Additionally, the DES-IPA treatment endowed lignin with other superior properties, including higher relative molecular weight, narrower molecular weight distribution, and higher purity. Moreover, sunscreen containing 2 wt% light-colored lignin could effectively block ultraviolet light in the wavelength range of 200-400 nm. Overall, the process expanded the application scenarios of lignin, thereby increasing the value of lignin by-products.

Phosphonium chloride-based deep eutectic solvents inhibit pathogenic Acanthamoeba castellanii belonging to the T4 genotype

Herein, we investigated the anti-amoebic activity of phosphonium-chloride-based deep eutectic solvents against pathogenic Acanthamoeba castellanii of the T4 genotype. Deep eutectic solvents are ionic fluids composed of two or three substances, capable of self-association to form a eutectic mixture with a melting point lower than each substance. In this study, three distinct hydrophobic deep eutectic solvents were formulated, employing trihexyltetradecylphosphonium chloride as the hydrogen bond acceptor and aspirin, dodecanoic acid, and 4-tert-butylbenzoic acid as the hydrogen bond donors. Subsequently, all three deep eutectic solvents, denoted as DES1, DES2, DES3 formulations, underwent investigations comprising amoebicidal, adhesion, excystation, cytotoxicity, and cytopathogenicity assays. The findings revealed that DES2 was the most potent anti-amoebic agent, with a 94% elimination rate against the amoebae within 24 h at 30 °C. Adhesion assays revealed that deep eutectic solvents hindered amoebae adhesion to human brain endothelial cells, with DES2 exhibiting 88% reduction of adhesion. Notably, DES3 exhibited remarkable anti-excystation properties, preventing 94% of cysts from reverting to trophozoites. In cytopathogenicity experiments, deep eutectic solvent formulations and dodecanoic acid alone reduced amoebae-induced human brain endothelial cell death, with DES2 showing the highest effects. Lactate dehydrogenase assays revealed the minimal cytotoxicity of the tested deep eutectic solvents, with the exception of trihexyltetradecylphosphonium chloride, which exhibited 35% endothelial cell damage. These findings underscore the potential of specific deep eutectic solvents in combating pathogenic Acanthamoeba, presenting promising avenues for further research and development against free-living amoebae.

Rapid and Environmentally-Friendly Synthesis of Thiazolidinone Analogues in Deep Eutectic Solvent Complemented with Computational Studies

A greener, safer, and more efficient methodology for the synthesis of (Z)-5-benzylidene-2-thioxothiazolidin-4-ones (3 a-u) and (Z)-5-benzylidenethiazolidine-2,4-diones (4 a-i) has been developed. The deep eutectic solvent (DES) ZnCl2/urea used as a greener solvent as well as a catalyst in this study accelerated the condensation of rhodanine and thiazolidine-2,4-dione with different aldehydes to afford the target scaffolds in excellent yields (88-98 %). The reaction methodology adopted offered significant advantages such as mild reaction conditions, functional group tolerance, quick reaction time, column-free isolation, catalytic recyclability, and applicability to gram-scale production. Moreover, density function theory calculations were carried out to investigate the global reactivity and stability profiles of these compounds. Finally, the green metrics analysis supported the greener nature of the present methodology.

Innovative formaldehyde adsorption with optimized deep eutectic solvents: An experiment and multilevel computational chemistry approach

Formaldehyde, a hazardous gas that is exposed to everyone every day, has been proven to pose an elevated risk of respiratory problems, allergies, and chronic diseases. Adsorption technologies have proven to be a straightforward and labor-saving method to reduce indoor formaldehyde levels. Currently, extensive research has been conducted utilizing Deep Eutectic Solvents (DES) as adsorbents for harmful gases, yet the adsorption and conversion mechanisms for formaldehyde remain unclear. In this study, we highlighted the adsorption and transformation mechanisms of formaldehyde with DES employing quantum chemical and molecular dynamics calculations. Initially, thermodynamic software (CosmoTherm) was employed to calculate the logarithmic activity coefficients (LAC) of formaldehyde and determine the solid-liquid equilibrium (SLE) for 416 combinations of DES. On the basis of the eutectic point and LAC of DES, potential formaldehyde adsorbents were screened. In the second step, the DES screened out has a good formaldehyde adsorption capacity through the experiment. Finally, the reactive sites, reaction pathways, van der Waals interactions, and hydrogen bonds of DES of L-cysteine/diethanolamine (CYS-DEA) and formaldehyde were studied through a theoretical approach. This study comprehensively elucidates the screening of formaldehyde adsorbents, experimental adsorption, and adsorption mechanisms. Significantly shortens the development cycle of DES as formaldehyde adsorbents.

Porous Deep Eutectic Solvents-Unfulfilled Dream or the Next Breakthrough in Scientific Innovation?

Porous deep eutectic solvents (PDES) are capturing the imagination of scientists, promising a revolutionary leap in material science. These innovative materials, blending the versatility of deep eutectic solvents (DES) with the intricate architectures of porous structures, offer an exciting array of applications-from green chemistry and catalysis to energy storage and environmental remediation. However, the journey from laboratory curiosity to industrial application is fraught with challenges. This perspective article analyzes the realm of PDES, scrutinizing the cutting-edge advancements and the challenges that lie ahead. By exploring their synthesis, unique properties, and diverse application potential, the critical question is asked: are PDES an unfulfilled dream or the next big breakthrough in scientific innovation? A comprehensive analysis reveals a "landscape" ripe with opportunity, suggesting that with targeted research and development, PDES can indeed become a cornerstone technology, driving progress across multiple scientific domains.

Recommended Practices for the Electrochemical Recovery of Cobalt from Lithium Cobalt Oxide: A Case Study of the Choline Chloride:Ethylene Glycol Deep Eutectic Solvent

We recommend best practices for the recovery of cobalt from LiCoO2 (LCO) lithium-ion battery (LIB) cathodes by (i) leaching using green deep eutectic solvents (DES) and (ii) subsequent electrodeposition, through a case study of the choline chloride (ChCl):ethylene glycol (EG) DES. DES physical properties (conductivity, viscosity, and surface tension) were tailored by varying the composition between mole ratios of 1 : 2 and 1 : 5 (ChCl:EG). Examined along with leaching process parameters (temperature, duration), increasing the fraction of hydrogen bond donors (HBDs) decreased DES surface tension and enhanced leaching. Complete Co recovery was achieved using 1 : 5 ChCl:EG DES at 160 °C and 48 h. Leaching temperatures >160 °C are discouraged due to DES thermal degradation. The electrodeposition process was optimized for selective Co recovery with high faradaic efficiency. The leaching ability of the DES was antithetical to the stability of electrodeposition cell components and required operational parameter adjustment to minimize degradation. The optimized system (copper cathode and stainless-steel anode) employing 1 : 5 DES leachate exhibited a faradaic efficiency of ~80 %, specific Co recovery of ~0.8 mg hr Collapse

Key Words

• Cobalt
• Deep eutectic solvents
• Electrodeposition.
• Lithium-ion battery
• Recycling

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MESH Headings Collapse

Grants Collapse

Affiliation(s)

Mohamed Shahid Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA Department of Chemical Engineering, University of Petroleum and Energy Studies, Dehradun, 248007, India
Suchithra Ashoka Sahadevan Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Missouri, USA
Vijay Ramani Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Missouri, USA
Shrihari Sankarasubramanian Department of Biomedical Engineering and Chemical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA

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Task-Specific Deep Eutectic Solvent for Efficient Dissolution and Further Accelerating Alkaline Hydrolysis of Polyesters Into Their Monomers

Polyester plastics have brought great convenience to modern society. However, the continuous accumulation of their production increasingly threatens human health. Polyethylene terephthalate (PET) is one of the largest type of polyester plastics and its recycling is a major challenge. In this work, deep eutectic solvent (DES) composed of thenyl alcohol and choline chloride (ChCl) was designed for efficient dissolution of PET at 165 °C for 20 min, and further accelerating complete alkaline hydrolysis of PET into its monomer terephthalic acid (TPA) and ethylene glycol (EG) with a high TPA monomer yield (98.2 %) in 25 min at 100 °C. Moreover, the designed DES is also efficient for dissolution and alkaline hydrolysis of other polyester plastics, including poly(trimethylene terephthalate) (PTT) and poly(ethylene furanoate) (PEF) into their monomers. This work provides a feasible and sustainable solution for the recycling of polyester wastes.

Development of smart films based on soy protein and cow horn dissolved in a deep eutectic solvent: Physicochemical and environmental assessment

With the urge to reduce the use of petroleum-based materials, the aim of this work is to valorize biowaste to develop smart films through a sustainable fabrication way. In this regard, choline chloride/urea (1:2) deep eutectic solvent (DES) at different concentrations (25, 40, 50 and 75 wt%) was used to dissolve cow horn, used as reinforcement agent in soy protein films. The film fabrication was carried out by compression molding, a fast and cost-effective. As proved by SEM/EDX, cow horn was well-dispersed in the films, suggesting a homogeneous distribution of the sulfur from the cysteine present in keratin, the main component of cow horn. FTIR spectroscopy suggested interactions between the components of the formulation, which reduce the water uptake from 180 % to 140 %. Additionally, the films could be heat-sealed. With the aim of developing smart films, blueberry extract was incorporated into the formulation. This extract provided the films with pH sensitivity, which was followed by the film color change in presence of ammonia vapor. In particular, it is worth noting the ability of those films prepared with 40 wt% Horn/DES and 15 wt% blueberry extract to detect food spoilage. Finally, the environmental assessment of the films showed a minimal environmental impact of the procedure, with DES preparation and soybean production as the main relative contributors of the environmental load.

Tough and Stretchable Zwitterionic Eutectogels via Copolymerization-Induced Phase Separation in a Targeted Deep Eutectic Solvent

Deep eutectic solvent (DES)-based eutectogels show significant promise for flexible sensors due to their high ionic conductivity, non-volatility, biocompatibility, and cost-effectiveness. However, achieving tough and stretchable eutectogels is challenging, as the highly polar DES tends to screen noncovalent bonds, such as hydrogen and ionic bonds, between polymer chains, limiting their mechanical strength. In this work, this issue is addressed by leveraging the limited solubility of zwitterionic polymers in a specific DES to induce phase separation, promoting dipole-dipole interactions between polymer chains. These interactions improve energy dissipation under mechanical stress, allowing the creation of tough and stretchable P(MAA-co-VIPS)/TBAC-EG eutectogels through a copolymerization-induced phase separation approach. Methacrylic acid (MAA) and sulfobetaine vinylimidazole (VIPS) are copolymerized within a tetrabutylammonium chloride-ethylene glycol (TBAC-EG) DES, resulting in a bicontinuous network. The bicontinuous structure consists of a PVIPS-rich phase that enhances toughness via dipole-dipole interactions, and a PMAA solvent-rich phase that enables high stretchability. The resulting eutectogel demonstrates excellent mechanical properties, including a strength of 1.76 MPa, toughness of 16.61 MJ m⁻3, and remarkable stretchability of 1293%, along with self-recovery, self-healing, and shape-memory capabilities. The zwitterionic polymer-specific DES design opens up broad application potential for these eutectogels in diverse fields.

Application of Hansen solubility parameters in the eutectic mixtures: difference between empirical and semi-empirical models

Hansen Solubility Parameters (HSPs) are widely used as a tool in solubility studies. Given the variety of existent approaches to predict these parameters, this investigation focused on estimating the HSPs of a set of Natural Deep Eutectic Systems (NADES), using empirical (EM) and semi-empirical models (SEM), and then understanding their differences/similarities. Although these theoretical models are designed and recommended mostly for simple molecules or simple solutions, they are still being used in eutectic systems studies, mainly empirical ones. Thus, a preliminary test was conducted with a set of conventional solvents, in which their experimental values of HSPs are known. Besides the confirmation of the EM as the most suitable for these kinds of regular solvents, the results found also showed a very similar behaviour to what was observed in NADES, i.e., in terms of suggesting the EM and SEM with the highest/lowest similarity. Furthermore, it was concluded that although there is a large discrepancy between the estimated values of the hydrogen bond parameter, especially for systems with a higher polar character, there is still a good similarity for the other parameters. In fact, it was observed that, when combining the semi-empirical models, it was possible to obtain a value of the hydrogen bond parameter more similar to the empirical ones.

Deep eutectic solvent-assisted carbon quantum dots from biomass Triticum aestivum: A fluorescent sensor for nanomolar detection of dual analytes mercury (Ⅱ) and glutathione

Deep eutectic solvents (DESs) have attracted significant attention in recent years due to its environment friendly characteristics and its participation in the multi-heteroatom doping of carbon quantum dots (CQDs). In this work, we present a simple, fast, and environment-friendly microwave synthesis approach for the synthesis of DES-assisted nitrogen and chloride co-doped CQDs (N,Cl-CQDs) using a choline chloride-urea based DES. A biomass-based precursor, i.e., wheatgrass (Triticum aestivum), has been used as a carbon source. Transmission electron microscopy (TEM) showed the spherical shape with average 1.75 nm particle diameter of prepared CQDs. The surface functionality and chemical composition of prepared N,Cl-CQDs were determined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopic techniques. The N,Cl-CQDs obtained a high quantum yield (QY), i.e., 36 %, compared to undoped CQDs, which were synthesized in an aqueous medium (QY = 15 %). The prepared N,Cl-CQDs showed significant properties such as excellent photostability, favorable water solubility, and high optical stability. N,Cl-CQDs were used as sensing platform for the detection of Hg2+ ions and GSH with LOD value of 39 nM and 43 nM, respectively. The fluorescence quenching mechanism was confirmed by several photophysical parameters, such as average lifetime values, radiative rate constant (k r ), non-radiative rate constant (knr) and others. Furthermore, the current sensing system's viability is also tested in a river water sample for the detection of Hg2+. The N,Cl-CQDs prepared in this study exhibited a reduced detection limit and a broad linear range by an easy, environmentally friendly, and rapid method for detecting GSH and Hg2+ ions.

Structural and Dynamic Heterogeneity of Deep Eutectic Solvents Composed of Choline Chloride and Ortho-Phenol Derivatives

Structural, thermal, and dynamic properties of four deep eutectic solvents comprising choline chloride paired with ortho-phenolic derivative hydrogen-bond donors were probed using experiments and molecular simulations. The hydrogen-bond donors include phenol, catechol, o-chlorophenol, and o-cresol, in a 3:1 mixture with the hydrogen-bond acceptor choline chloride. Density, viscosity, and pulsed-field gradient NMR diffusivity measurements were conducted over a range of temperatures. Classical and ab initio molecular dynamics simulation results match experimental data reasonably well. The simulation results were then used to perform a more detailed analysis of the local structure and dynamics of these systems.

Exploring Dynamics and Intermolecular Interactions in Binary Mixtures of Reline and DMSO: An Investigation Using Nuclear Magnetic Resonance and Infrared Spectroscopic Techniques

Reline, which is composed of choline chloride and urea in a molar ratio of 1:2, is the first and most extensively studied deep eutectic solvent (DES). In certain applications, reline is blended with organic solvents, dimethyl sulfoxide (DMSO) in most cases, to gain improved properties. Therefore, it is crucial to have a profound understanding of the impact of DMSO on the dynamics and structures of the species in the binary mixtures. In this study, neat reline and ten reline/DMSO mixtures, with DMSO molar fraction ranging from 0.1 to 0.95, were investigated primarily through a combined approach utilizing nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopic techniques. Based on our investigation, we probed a significant transition of the binary mixtures from large molecule solutions or viscous liquids to nonviscous small-molecule solutions at a DMSO molar fraction of 0.7. Specifically, upon analyzing the self-diffusion coefficient, 1H T1 and 1H T2, we observed a notable increase in the molecular mobility of the species within the reline/DMSO system, particularly when the DMSO molar fraction exceeded 0.7. Drawing upon the FT-IR findings, we suggest that the enhanced molecular mobility, as evidenced by NMR analysis, is correlated with the disruption of molecular hydrogen-bonding interactions involving the -NH2 and -OH groups. Furthermore, based on 1D 1H, 1D 15N, and 2D 1H-1H COSY spectra, it was revealed that the interaction between urea and choline remains relatively stable until the DMSO fraction exceeds 0.7, whereupon it exhibited a notable weakening as the DMSO fraction increases from 0.7 to 0.95. In the meantime, DMSO molecules predominantly engage in hydrogen bond interactions with urea and choline when the DMSO molar fraction exceeds 0.7. Our results align well with previous molecular dynamics (MD) simulation studies and provide profound insights into the significant transition in the reline/DMSO mixture system.

Introduction and characterization of a novel Cu(ii)-based quaternary deep eutectic solvent and its application in the efficient synthesis of triazoles and tetrazoles under mild conditions as an inexpensive, reusable, benign, and dual solvent/catalyst medium

Deep eutectic solvents consist of hydrogen bond donor and acceptor components. They are a new type of ionic liquids, and they have attracted the attention of many chemists in recent years. In this work, a quaternary deep eutectic solvent (QDES) was prepared using choline chloride, glycerol, l-arginine, and copper acetate. Its physicochemical properties were determined by Fourier transform infrared spectroscopy (FT-IR), thermal analysis (TGA), differential scanning calorimetry (DSC), hydrogen potential (pH), cyclic voltammetry (CV), viscosity, density, refractive index, ionic conductivity and spectrophotometer ultraviolet-visible (UV-Vis). Further, as a novel benign solvent/catalyst for the synthesis of 1,4-disubstituted-1,2,3-triazole, 4-substituted-1H-1,2,3-triazole, and 5-substituted-1H-tetrazole derivatives were used in a click reaction strategy. The special features of this method include mild conditions, a non-toxic environment, short reaction time, easy operation, biodegradability, deep eutectic solvent/catalyst recovery, access to cheaper raw materials, and environmental compatibility.

"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.