Eutectics: formation, properties, and applications

Regioselective synthesis of 4-arylamino-1,2-naphthoquinones in eutectogel as a confined reaction medium using LED light

Predicting selectivity and conversion in a confined reaction medium under photochemical conditions is highly challenging as compared to the corresponding conventional synthesis. Herein, we report the use of a simple carbohydrate-derived eutectogel to facilitate LED-light-induced regioselective synthesis of 4-arylamino-1,2-naphthoquinones in good yield. This methodology, by including a reusable reaction medium, proved to have the potential of affording the regioselective formation of various desired products in good yields.

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.

Hydrocarbon Extraction with Ionic Liquids

Separation and reaction processes are key components employed in the modern chemical industry, and the former accounts for the majority of the energy consumption therein. In particular, hydrocarbon separation and purification processes, such as aromatics extraction, desulfurization, and denitrification, are challenging in petroleum refinement, an industrial cornerstone that provides raw materials for products used in human activities. The major technical shortcomings in solvent extraction are volatile solvent loss, product entrainment leading to secondary pollution, low separation efficiency, and high regeneration energy consumption due to the use of traditional organic solvents with high boiling points as extraction agents. Ionic liquids (ILs), a class of designable functional solvents or materials, have been widely used in chemical separation processes to replace conventional organic solvents after nearly 30 years of rapid development. Herein, we provide a systematic and comprehensive review of the state-of-the-art progress in ILs in the field of extractive hydrocarbon separation (i.e., aromatics extraction, desulfurization, and denitrification) including (i) molecular thermodynamic models of IL systems that enable rapid large-scale screening of IL candidates and phase equilibrium prediction of extraction processes; (ii) structure-property relationships between anionic and cationic structures of ILs and their separation performance (i.e., selectivity and distribution coefficients); (iii) IL-related extractive separation mechanisms (e.g., the magnitude, strength, and sites of intermolecular interactions depending on the separation system and IL structure); and (iv) process simulation and design of IL-related extraction at the industrial scale based on validated thermodynamic models. In short, this Review provides an easy-to-read exhaustive reference on IL-related extractive separation of hydrocarbon mixtures from the multiscale perspective of molecules, thermodynamics, and processes. It also extends to progress in IL analogs, deep eutectic solvents (DESs) in this research area, and discusses the current challenges faced by ILs in related separation fields as well as future directions and opportunities.

High-Performance Flexible Ionically Conductive Superhydrophobic Papers via Deep Eutectic Polymer-Enhanced Interfacial Interactions

Endowing paper with highly flexible, conductive, and superhydrophobic properties will effectively expand its applications in fields such as green packaging, smart sensing, and paper-based electronics. Herein, a multifunctional superhydrophobic paper is reported in which a highly flexible transparent conductive substrate is prepared by introducing a hydrophobic deep eutectic polymer into the ethylcellulose network via a matrix swelling-polymerization strategy, and then the substrate is modified using fluorinated silica to impart superhydrophobicity. By introducing soft deep eutectic polymers, (1) the superhydrophobic paper can efficiently dissipate energy during deformation, (2) intrinsically ion-conducting deep eutectic polymers can endow the material with good electrical sensing properties, and (3) meanwhile, enhanced interfacial interactions can anchor inorganic particles, thereby improving the coating stability. The prepared superhydrophobic paper has an ultrahigh water contact angle (contact angle ≈ 162.2°) and exhibits a stable electrical response signal to external deformation/pressure, and the electrical properties are almost unaffected by external water molecules. In addition, the superhydrophobic paper was able to withstand 5000 bending-recovery cycles at a large angle of 150°, exhibiting stable electrical performance. The design concepts demonstrated here will provide insights into the development of superhydrophobic paper-based flexible electronic devices.

Novel ferrofluid based on water-based deep eutectic solvents: application in dispersive liquid-liquid microextraction of naphthalene-derived plant growth regulators in edible oil

A new ferrofluid extractant (Fe3O4 @SiO2-WDES) was ingeniously prepared by coating magnetic Fe3O4 @SiO2 microspheres with water-based deep eutectic solvent (WDES) and used for dispersive liquid-liquid microextraction (DLLME) and HPLC determination of naphthalene-derived plant growth regulators (PGRs, i.e., 1-naphthylacetic acid, 2-naphthylacetic acid, 1-naphthoxy acetic acid, 2-naphthyloxyacetic acid and 1-naphthylacetamide) in edible oil. Herein, mass transfer of the analytes in DLLME was significantly enhanced via increasing the contact surface by employing the microspheres as the supporter and dispersant of WDES, and phase separation can be efficiently achieved using an external magnet rather than centrifugation in traditional DLLME. Response surface methodology (RSM) based on Box-Behnken design (BBD) was employed for the optimization of core experimental conditions, and Analytical Eco-Scale and Analytical GREEnness Metric Approaches were adopted to evaluate the degree of greenness of the procedure. Under the optimal conditions, satisfactory performances of linearity ranged from 5 to 100 μg/L (R2 ≥ 0.9982), limit of detection (0.58-0.91 μg/L), limit of quantitation (1.9-3.0 μg/L), precision (RSDs ≤ 5.5%), recovery (81.3%-108.1%) and negligible matrix effect were achieved, which introduced a promising alternative route for the determination of naphthalene-derived plant growth regulators in edible oil.

Quantification of alkalinity of deep eutectic solvents based on (H-) and NMR

Alkaline deep eutectic solvents (DESs) have been widely employed across diverse fields. A comprehensive understanding of the alkalinity data is imperative for the comprehension of their performance. However, the current range of techniques for quantifying alkalinity is constrained. In this investigation, we formulated a series of alkaline DESs and assessed their basicity properties through a comprehensive methodology of Hammett functions alongside 1H NMR analysis. A correlation was established between the composition, structure and alkalinity of solvents. Furthermore, a strong linear correlation was observed between the Hammett basicity (H-) of solvents and initial CO2 adsorption rate. Machine learning techniques were employed to predict the significant impact of alkaline functional components on alkalinity levels and CO2 capture capacity. This study offers valuable insights into the design, synthesis and structure-function relationship of alkaline DESs.

Environmental Sustainability of π-Electron Donor-Based Deep Eutectic Solvents for Toluene Absorption: A Life-Cycle Perspective

The novel π-electron donor-based deep eutectic solvents (DESs) have been shown to be a promising type of absorbent with excellent performance on toluene absorption. However, their greenness or sustainability is still unclear. Thus, to bridge the gap and give a comprehensive evaluation for their industrialization potential, the life cycle assessment (LCA) was used to evaluate the potential environmental impacts incurred from their production and usage for absorbing toluene. The environmental profiles are also compared with that of popular choline chloride (ChCl) based DES, common organic solvent triethylene glycol (TEG) and ionic liquid ([EMIM][Tf2 N]). The results indicate that among the involved hydrogen bond acceptors (HBAs), TEBAC generally imparts lower environmental impacts than other HBAs but has higher impacts than ChCl. Although TEBAC-PhOH is not the most environmentally friendly absorbent during the production stage, its outstanding absorption performance minimizes the environmental impact when absorbing the same mass of toluene. Furthermore, the environmental impacts of the toluene absorption process using TEBAC-PhOH is significantly lower than that of [EMIM][Tf2 N], slightly lower than TEG. Therefore, considering both absorption performance and environmental impacts, TEBAC-PhOH can be used as a promising "green and sustainable" toluene absorbent to traditional absorbents and ionic liquids.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Gallium-Based Liquid Metals in Rechargeable Batteries: From Properties to Applications

Gallium-based (Ga-based) liquid metals have attracted considerable interest due to their low melting points, enabling them to feature both liquid properties and metallic properties at room temperature. In light of this, Ga-based liquid metals also possess excellent deformability, high electrical and thermal conductivity, superior metal affinity, and unique self-limited surface oxide, making them popular functional materials in energy storage. This provides a possibility to construct high-performance rechargeable batteries that are deformable, free of dendrite growth, and so on. This review primarily starts with the property of Ga-based liquid metal, and then focuses on the potential applications in rechargeable batteries by exploiting these advantages, aiming to construct the correlation between properties and structures. The glorious applications contain interface protection, self-healing electrode construction, thermal management, and flexible batteries. Finally, the opportunities and obstacles for the applications of liquid metal in batteries are presented.

Optimization of Deep Eutectic Solvents Enables Green and Efficient Cryopreservation

Cryopreservation presents significant opportunities for biomedical applications including cell therapy, tissue engineering, and assisted reproduction. Dimethyl sulfoxide (DMSO), the most commonly used cryoprotectant (CPA), can be added to cells to prevent cryogenic damage. However, the toxicity of cryoprotectants restrains its further development in many areas with safety concerns such as clinical treatment. Therefore, the development of low-toxicity cryoprotectants is essential for medical research. This work reports deep eutectic solvents (DES) as naturally biocompatible osmoprotectants for green and efficient cryopreservation of human umbilical cord mesenchymal stem cells (HuMSC), which may be an ideal alternative to DMSO. The six types of DESs were explored for thermal properties, toxicity, and permeability in cells. Raman spectroscopy and viscosity studies showed that DES exhibited an improved hydrogen-bonding system as the temperature decreased. By optimizing the freezing process (cooling rate, incubation time, and loading procedure) of DES, the viability of mouse embryonic fibroblast cells (NIH-3T3) after thawing was significantly improved. The HuMSC were successfully preserved with no significant difference (p > 0.05) in cell viability (94.65%) after thawing compared with DMSO, which preserved the cell differentiation function and improved the cell proliferation rate. The mechanism of DES in cryopreservation was investigated, and it was found that DES could bind water molecules and effectively inhibit the growth of ice crystals during ice recrystallization, reducing mechanical damage to cells. This study highlights the excellent performance of DES as a low-toxicity CPA for stem cell preservation, which may be a significant advance for future clinical cell therapy.

Comprehensive Understandings of Hydrogen Bond Chemistry in Aqueous Batteries

Aqueous batteries are emerging as highly promising contenders for large-scale grid energy storage because of uncomplicated assembly, exceptional safety, and cost-effectiveness. The unique aqueous electrolyte with a rich hydrogen bond (HB) environment inevitably has a significant impact on the electrode materials and electrochemical processes. While numerous reviews have focused on the materials design and assembly of aqueous batteries, the utilization of HB chemistry is overlooked. Herein, instead of merely compiling recent advancements, this review presents a comprehensive summary and analysis of the profound implication exerted by HB on all components of the aqueous batteries. Intricate links between the novel HB chemistry and various aqueous batteries are ingeniously constructed within the critical aspects, such as self-discharge, structural stability of electrode materials, pulverization, solvation structures, charge carrier diffusion, corrosion reactions, pH sensitivity, water splitting, polysulfides shuttle, and H2 S evolution. By adopting a vantage point that encompasses material design, binder and separator functionalization, electrolyte regulation, and HB optimization, a critical examination of the key factors that impede electrochemical performance in diverse aqueous batteries is conducted. Finally, insights are rendered properly based on HB chemistry, with the aim of propelling the advancement of state-of-the-art aqueous batteries.

Green preparation of β-chitins from squid pens by using alkaline deep eutectic solvents

Based on the assumption that protein could be removed by the combined mechanism of alkaline induced degradation and strong hydrogen bond interactions of deep eutectic solvents (DESs), β-chitins were successfully prepared from squid pens by using alkaline DESs formed by potassium carbonate and glycerol. The chemical structures of the DESs were investigated by 1H nuclear magnetic resonance (1H NMR), attenuated total reflection Fourier transform infrared (ATR-FTIR) and molecular modeling, and the physicochemical property of the prepared β-chitins were characterized. The preparation yields was about 32 %, and DESs with K2CO3/glycerol of 1/10 could be reused for three times while maintaining high preparation yields (31 %-32 %) and degree of deacetylation of 66.9 %-76.9 %. The mechanisms of deproteinization and demineralization by the alkaline DESs were proposed to follow the degradation and dissolution steps, and proteins and minerals were removed from squid pens through the synergistic actions of alkaline degradation and hydrogen bonding interactions. This alkaline DESs are promising to be used as a green and efficient approach for commercial production of β-chitin.

Recycling of waste lithium-ion batteries via a one-step process using a novel deep eutectic solvent

Deep eutectic solvents (DESs) possess excellent solubility and selectivity, making them suitable for extracting valuable metals and serving as a green alternative in the recycling process. This work introduces a low-viscosity DES consisting of dimethylthetin, oxalic acid, and water for the comprehensive recovery of cathode materials from LIBs. Leaching parameters such as ratio (1:1), leaching temperature (60 °C), and reaction time (15 min) for were systematically optimized, resulting in a selective separation efficiency of 99.98 % for lithium ions. Furthermore, in-situ regeneration of the precursor can be achieved during the leaching process. Charge-discharge tests indicate that the initial charge and discharge capacities of the regenerated battery are 166.8 mAh/g and 138.4 mAh/g, respectively. The DES demonstrates stability and can be easily recycled by replenishing the consumed components. This proposed strategy facilitates the reintroduction of nonrenewable resources into the supply chain and reduces the environmental impact of heavy metals, aligning with the principles of a circular economy.

A Review on 1-D Nanomaterials: Scaling-Up with Gas-Phase Synthesis

Nanowire-like materials exhibit distinctive properties comprising optical polarisation, waveguiding, and hydrophobic channelling, amongst many other useful phenomena. Such 1-D derived anisotropy can be further enhanced by arranging many similar nanowires into a coherent matrix, known as an array superstructure. Manufacture of nanowire arrays can be scaled-up considerably through judicious use of gas-phase methods. Historically, the gas-phase approach however has been extensively used for the bulk and rapid synthesis of isotropic 0-D nanomaterials such as carbon black and silica. The primary goal of this review is to document recent developments, applications, and capabilities in gas-phase synthesis methods of nanowire arrays. Secondly, we elucidate the design and use of the gas-phase synthesis approach; and finally, remaining challenges and needs are addressed to advance this field.

Construction of Poly(hydrophobic deep eutectic solvent)/Ethylcellulose Composite Films for Green Recyclable Tapes

Constructing green recyclable cellulose-based tapes with high transparency, mechanical robustness, and strong wet adhesion using natural components is highly desirable but challenging. Herein, novel cellulose-based self-adhesive tapes were reported by coating a polymerizable hydrophobic deep eutectic solvent (DES) on ethylcellulose followed by photopolymerization. The prepared ethylcellulose-based self-adhesive tape (ECSAT) exhibited an optical transmittance of up to ∼88% and could provide strong adhesion by interfacial intermolecular interactions without obstructing information. Due to the hydrophobic nature of the overall structure, ECSAT does not exhibit significant adhesive strength and mechanical degradation under water, acid, and alkali environments. Notably, ECSAT can be completely dissolved in the resultant DES and furthermore reused as a self-adhesive coating. The recycled ECSAT still maintained good optical transparency, mechanical strength, and wet adhesion. We believe that ECSATs with all-around performances have a wide range of applications in packaging and other engineering fields.

Polyprenols in Ginkgo biloba; a review of their chemistry (synthesis of polyprenols and their derivatives), extraction, purification, and bioactivities

The Ginkgo biloba L. (GB) contains high bioactive compounds. To date, flavonoids and terpene trilactone have received the majority of attention in GB studies, and the GB has been utilized globally in functional food and pharmacological firms, with sales > $10 billion since 2017, while the other active components, for instance, polyprenols (a natural lipid) with various bioactivities have received less attention. Hence, this review focused on polyprenols' chemistry (synthesis of polyprenols and their derivatives) extraction, purification, and bioactivities from GB for the first time. The various extractions and purification methods (nano silica-based adsorbent, bulk ionic liquid membrane, etc.) were delved into, and their advantages and limitations were discussed. Besides, numerous bioactivities of the extracted Ginkgo biloba polyprenols (GBP) were reviewed. The review showed that GB contains some polyprenols in acetic esters' form. Prenylacetic esters are free of adverse effects. Besides, the polyprenols from GB have numerous bioactivities such as anti-bacterial, anti-cancer, anti-viral activity, etc. The application of GBPs in the food, cosmetics, and drugs industries such as micelles, liposomes, and nano-emulsions was delved into. Finally, the toxicity of polyprenol was reviewed, and it was concluded that GBP was not carcinogenic, teratogenic, or mutagenic, giving a theoretical justification for using GBP as a raw material for functional foods. This article will aid researchers to better understand the need to explore GBP usage.

CO2 Capture Mechanism by Deep Eutectic Solvents Formed by Choline Prolinate and Ethylene Glycol

The choline prolinate ([Ch][Pro]) as a hydrogen bond acceptor and ethylene glycol (EG) as a hydrogen bond donor are both used to synthesize the deep eutectic solvents (DESs) [Ch][Pro]-EG to capture CO₂. The CO₂ capacity of [Ch][Pro]-EG is determined, and the nuclear magnetic resonance (NMR) and infrared (IR) spectrum are used to investigate the CO₂ capture mechanism. The results indicate that CO₂ reacts with both the amino group of [Pro]^- anion and the hydroxyl group of EG, and the mechanism found in this work is different from that reported in the literature for the [Ch][Pro]-EG DESs.

Exploration of the interaction mechanism of lignocellulosic hybrid systems based on deep eutectic solvents

The interactions of three deep eutectic solvents (DES) choline chloride-glycerol (ChCl-GLY), ChCl-lactic acid (ChCl-LA) and ChCl-urea (ChCl-U) with cellulose-hemicellulose and cellulose-lignin hybrid systems were investigated using the simulated computational approach. Aiming to simulate DES pretreatment of real lignocellulosic biomass in nature. DES pretreatment could disrupt the original hydrogen bonding network structure among the lignocellulosic components and reconstruct the new DES-lignocellulosic hydrogen bonding network structure. ChCl-U had the highest intensity of action on the hybrid systems, removing 78.3% of the hydrogen bonds between cellulose-4-O-methyl Gluconic acid xylan (cellulose-Gxyl) and 68.4% of the hydrogen bonds between cellulose-Veratrylglycerol-b-guaiacyl ether (cellulose-VG), respectively. The increase of urea content facilitated the interaction between DES and lignocellulosic blend system. Finally, the addition of appropriate water (DES:H₂O = 1:5) and DES formed the new DES-water hydrogen bonding network structure more favorable for the interaction of DES with lignocellulose.

Unlocking the Potential of Deep Eutectic Solvents for C-H Activation and Cross-Coupling Reactions: A Review

Green chemistry principles have underpinned the development of deep eutectic solvents (DESs). In this brief overview, we discuss the potential of DESs as a greener alternative to volatile organic solvents for cross-coupling and C-H activation reactions in organic chemistry. DESs offer numerous benefits, such as easy preparation, low toxicity, high biodegradability, and the potential to replace volatile organic compounds. The ability of DESs to recover the catalyst-solvent system enhances their sustainability. This review highlights recent advances and challenges in utilizing DESs as a reaction media, as well as the impact of physicochemical properties on the reaction process. Several types of reactions are studied to highlight their effectiveness at promoting C-C bond formation. Aside from demonstrating the success of DESs in this context, this review also discusses the limitations and future prospects of DESs in organic chemistry.

Fine-tuning the Basicity of Deep Eutectic Solvents by Substituting Guanidine for Urea in Reline

The physicochemical properties of deep eutectic solvents (DESs) depend on the combination of hydrogen bond acceptors and hydrogen bond donors used. The basicity of a DES significantly influences its performance in CO₂ chemical absorption, biomass and protein dissolution, and catalytic reactions. To the best of our knowledge, a strategy for fine-tuning the basicity of DESs has not yet been reported. Therefore, in this study, we substituted the base urea (Ur) in reline, which is a 1:2 mixture of choline chloride (ChCl) and Ur, with the superbase guanidine (Gu) to fine-tune its basicity. Binary (2Gu-ChCl) and ternary (Gu-Ur-ChCl) DESs were prepared, and their CO₂ absorption capacities were investigated at 313.2 K. The equimolar mixture Gu-Ur-ChCl absorbed CO₂ gas up to the molar ratio [CO₂]/[ChCl] ≈ 1.0. Therefore, the basicity of ChCl-based DES can be continuously varied by substituting more molecules of Ur with Gu. Our strategy of combining functional and non-functional molecules with similar structures to vary the basicity of DESs has potentially wide applications that utilize DESs in the future.

Evaluating the status quo of deep eutectic solvent in food chemistry. Potentials and limitations

Conventional organic solvents (e.g., methanol, ethanol, ethyl acetate) are widely used for extraction, reaction, and separation of valuable compounds. Although these solvents are effective, they have disadvantages, including flammability, toxicity, and persistence in the environment. Deep eutectic solvents (DESs) are valued for their biodegradability/low impact on the environment, low cost, and ease of manufacture. The objective of this review was to provide an overview of applications of DES in food chemistry, specifically in regard of extraction of polyphenols (e.g., anthocyanin, rutin, kaempferol, quercetin, resveratrol), protein, carbohydrates (e.g., chitin, pectins), lipids and lipid-soluble compounds (e.g., free fatty acids, astaxanthin, β-carotene, terpenoids), biosensor development, and use in food safety (pyrethroids, Sudan I, bisphenol A, Pb²⁺, Cd²⁺, etc.) over the past five years. A comprehensive analysis and discussion of DES types, preparation, structures, and influencing factors is provided. Furthermore, the potential and disadvantages of using DESs to extract biomolecules were assessed. We concluded that DES is a viable alternative for extracting polyphenols, carbohydrates, and lipids as well as use in food safety monitoring and biosensor development. However, more work is needed to address shortcomings, and determine whether using compounds extracted with DES can be consumed safely.

Encapsulating eutectogels for stretchable humidity-resistant strain sensors

Eutectogels are stretchable ionic conductors extensively developed in recent years, owing to their distinct advantages of low cost, non-volatility, non-toxicity, and outstanding biocompatibility. However, the susceptibility to humidity caused by the exchange of water molecules between the interiors of eutectogels and the external environment greatly restricts their practical applications. Here, a dip-coating strategy is proposed to fabricate a P(MEA-co-IBA) elastomer-coated P(AAC-co-AAM) eutectogel to achieve satisfactory humidity-resistant capability. The hydrophobic elastomer coating significantly suppresses water exchange without harming the stretchability (>500%) and conductivity of the eutectogel. Strong adhesion forms at the eutectogel-coating interface due to the formation of an interpenetrating layer. The superior electromechanical performances of encapsulated eutectogels enable stretchable ionotronic devices with stable electrical performance (>1 h) and remarkable water-droplet/moist resistances during static/dynamic loadings. A humidity-resistant encapsulated eutectogel-based wearable strain sensor is further demonstrated. The proposed humidity-resistant eutectogels are promising candidates for soft and wearable ionotronics for practical applications.

Advances in green solvents for production of polysaccharide-based packaging films: Insights of ionic liquids and deep eutectic solvents

The problems with plastic materials and the good film-forming properties of polysaccharides motivated research in the development of polysaccharide-based films. In the last 5 years, there has been an explosion of publications on using green solvents, including ionic liquids (ILs), and deep eutectic solvents (DESs) as candidates to substitute the conventional solvents/plasticizers for preparations of desired polysaccharide-based films. This review summarizes related properties and recovery of ILs and DESs, a series of green preparation strategies (including pretreatment solvents/reaction media, ILs/DESs as components, extraction solvents of bioactive compounds added into films), and inherent properties of polysaccharide-based films with/without ILs and DESs. Major reported advantages of these new solvents are high dissolving capacity of certain ILs/DESs for polysaccharides (i.e., up to 30 wt% for cellulose) and better plasticizing ability than traditional plasticizers. In addition, they frequently display intrinsic antioxidant and antibacterial activities that facilitate ILs/DESs applications in the processing of polysaccharide-based films (especially active food packaging films). ILs/DESs in the film could also be further recycled by water or ethanol/methanol treatment followed by drying/evaporation. One particularly promising approach is to use bioactive cholinium-based ILs and DESs with good safety and plasticizing ability to improve the functional properties of prepared films. Whole extracts by ILs/DESs from various byproducts can also be directly used in films without separation/polishing of compounds from the extracting agents. Scaling-up, including costs and environmental footprint, as well as the safety and applications in real foods of polysaccharide-based film with ILs/DESs (extracts) deserves more studies.

Discovery, disassembly, depolymerization and derivatization of catechyl lignin in Chinese tallow seed coats

The search for feedstock of catechyl lignin (C-lignin) is great interest and importance, as C-lignin featuring homogeneity and linearity is considered as an "ideal lignin" archetype for valorization and exits in only a few plant seed coats. In this study, naturally occurring C-lignin is first discovered in the seed coats of Chinese tallow, which has the highest content of C-lignin (15.4 wt%) as compared with other known feedstocks. An optimized extraction procedure by ternary deep eutectic solvents (DESs) enables the complete disassembly of C-lignin and G/S-lignin coexisted in Chinese tallow seed coats, and characterizations revealed that the as-separated C-lignin sample is abundant in benzodioxane units with no observation of β-O-4 structures from G/S-lignin. Catalytic depolymerization of C-lignin results in a simplex catechol product in 129 mg per gram seed coats, being higher than other reported feedstocks. Derivatizing the "black" C-lignin via the nucleophilic isocyanation of benzodioxane γ-OH leads to a "whitened C-lignin" with uniform laminar structure and excellent crystallization ability, being conducive to fabricating functional materials. Overall, this contribution showed that Chinses tallow seed coats are suitable feedstock for acquiring C-lignin biopolymer.

Effective fractionation of lignocellulose components and lignin valorization by combination of deep eutectic solvent with ethanol

Introduction: A combination of deep eutectic solvent with ethanol was developed for pretreatment of Broussonetia papyrifera to effectively extract lignin and promote the subsequent enzymatic hydrolysis. Methods: In order to further explore the optimal conditions for enzymatic hydrolysis, a central composite design method was applied. Results and Discussion: The correlation between each factor and glucose yield was obtained, and the optimal conditions was 160°C, 60 min, the ratio of DES to E was 1/1 (mol/mol). The results showed that compared with control, the glucose yield increased by 130.67% under the optimal pretreatment conditions. Furthermore, the specific surface area of biomass was increased by 66.95%, and the content of xylan and lignin was decreased by 86.71% and 85.83%. The correlation between xylan/lignin removal and enzymatic hydrolysis showed that the removal of lignin facilitated the glucose yield more significantly than that of xylan. To further explore the lignin valorization, the structural and antioxidant analysis of recovered lignin revealed that high temperature was favorable for lignin with good antioxidant performance. This pretreatment is a promising method for separating lignin with high antioxidant activity and improving cellulose digestibility.

Natural Deep Eutectic Solvents in the Synthesis of Inorganic Nanoparticles

Natural deep eutectic solvents (NDESs), as a new type of green solvent, are used in many fields, including industry in extraction processes, medicine, pharmaceuticals, metallurgy, electrodeposition, separations, gas capture, biocatalysis and nanotechnology. Mainly due to their properties, such as simple preparation, environmental friendliness, biocompatibility and multifunctionality, they are being used in various fields of industry. This review aims to provide insight into the applications of natural deep eutectic solvents, specifically in nanotechnology processes. It focuses on the description of NDES and how their physicochemical properties are used to obtain functional nanomaterials, including metals, metal oxides and salts. It highlights how the use of NDESs to obtain a wide range of inorganic nanoparticles enables the elimination of disadvantages of traditional methods of obtaining them, including reducing energy consumption and functionalising nanoparticles in situ. In conclusion, recent advances and future directions in the development and applications of NDESs in nanotechnology are discussed with the aim of identifying unexplained scientific questions that can be investigated in the future.

Room Temperature Halide-Eutectic Solid Electrolytes with Viscous Feature and Ultrahigh Ionic Conductivity

A viscous feature is beneficial for a solid electrolyte with respect to assembling solid-state batteries, which can change the solid-solid contacts from point to face. Here, novel halide-based deep eutectic solid electrolytes (DESEs) prepared by a facile ball milling method is reported. The mixture of halides triggers the deep eutectic phenomena by intermolecular interactions, leading to diverse morphologies and viscous statuses in terms of composition. Chemical- and micro-structure analyses via the cryogenic technique reveal that the LiCl and LiF nanoparticles are dispersed in an amorphous halide matrix, which endow freely mobile ions for fast ion transport. The optimized DESE thus achieves low activation energy and high ionic conductivity of 16 mS cm^-1 at room temperature, one of the highest values among various electrolytes so far. By integrating with the active materials to form a composite cathode, the viscous DESE yields a super-dense composite pellet which possesses intensively enhanced ionic conductivity in contrast to those formed by the sulfide-based electrolyte additives, demonstrating an attractive application prospect.

Progress, Key Issues, and Future Prospects for Li-Ion Battery Recycling

The overuse and exploitation of fossil fuels has triggered the energy crisis and caused tremendous issues for the society. Lithium-ion batteries (LIBs), as one of the most important renewable energy storage technologies, have experienced booming progress, especially with the drastic growth of electric vehicles. To avoid massive mineral mining and the opening of new mines, battery recycling to extract valuable species from spent LIBs is essential for the development of renewable energy. Therefore, LIBs recycling needs to be widely promoted/applied and the advanced recycling technology with low energy consumption, low emission, and green reagents needs to be highlighted. In this review, the necessity for battery recycling is first discussed from several different aspects. Second, the various LIBs recycling technologies that are currently used, such as pyrometallurgical and hydrometallurgical methods, are summarized and evaluated. Then, based on the challenges of the above recycling methods, the authors look further forward to some of the cutting-edge recycling technologies, such as direct repair and regeneration. In addition, the authors also discuss the prospects of selected recycling strategies for next-generation LIBs such as solid-state Li-metal batteries. Finally, overall conclusions and future perspectives for the sustainability of energy storage devices are presented in the last chapter.

Deep Eutectic Solvent-Mediated Electrocatalysts for Water Splitting

As green, safe, and cheap solvents, deep eutectic solvents (DESs) provide tremendous opportunities to open up attractive perspectives for electrocatalysis. In this review, the achievement of DESs in the preparation of catalysts for electrolytic water splitting is described in detail according to their roles combined with our own work. DESs are generally employed as green media, templates, and electrolytes. A large number of hydrogen bonds in DESs result in supramolecular structures which have the ability to shape the morphologies of nanomaterials and then tune their performance. DESs can also serve as reactive reagents of metal electrocatalysts through directly participating in synthesis. Compared with conventional heteroatom sources, they have the advantages of high safety and designability. The "all-in-one" transformation strategy is expected to realize 100% atomic transformation of reactants. The aim of this review is to offer readers a deeper understanding on preparing DES-mediated electrocatalysts with higher performance for water splitting.

Mechanism study of ternary deep eutectic solvents with protonic acid for lignin fractionation

This paper investigated the fractionation of lignin by ternary DES of different polyols using simulation calculation. ChCl-EG-PTSA showed the highest degradability of lignin with the absolute value of total interaction energy of -8023.80 kJ/mol, and the total number of hydrogen bonds was 91.4. The highest degradability was observed for ChCl:EG: PTSA = 2:4:1. The results show that CL^- plays a dominant role in lignin fractionation and readily forms hydrogen bonds with γ-OH. The difference is that the polyol preferred to form hydrogen bonds with α-OH in lignin. The addition of PTSA provided protons to the original system. It formed a new π-π stacking interaction with the lignin benzene ring, which destroyed the π-π stacking interaction between the original lignin. And increased the interaction of DES on lignin from -39.73 kcal/mol to -58.15 kcal/mol based on DFT.

Biodegradable Lubricant with High-Temperature and Ionic-Contamination Resistance: Deep Eutectic Solvent ChCl-PEG

Drilling fluid lubricants guarantee safe and fast drilling. When drilling high-temperature or NaCl/CaCl₂-containing formations, there is an urgent need to develop environmentally friendly lubricants that are resistant to high temperature and ionic contamination. In this study, a deep eutectic solvent (DES) ChCl-PEG lubricant for a water-based drilling fluid was designed and prepared. ChCl-PEG is a kind of biodegradable material with high thermal stability formed by hydrogen bonding between choline chloride (ChCl) and polyethylene glycol (PEG). Within 240 °C, ChCl-PEG significantly improved the lubricating properties of drilling fluids and mud cakes. The lubrication coefficient (K) was controlled within 0.2, and the reduction rate of the adhesion coefficient (Δf) was higher than 40%. The salt and calcium resistances of ChCl-PEG at high temperature (150 °C) are as high as 36% NaCl and 20% CaCl₂. Under these conditions, ChCl-PEG maintains a low value of K: 0.097-0.157 (5-36% NaCl) and 0.145-0.162 (5-20% CaCl₂), respectively. Also, it maintains higher values of Δf, which can reach up to 51.6% and 80%. The lubricating mechanism of ChCl-PEG can be summarized as the adsorption of ChCl and the formation of a large number of hydrated molecules.

Deep Eutectic Solvent-Induced In Situ Etching and Phosphorization to Form Nickel Phosphides for Electrooxidation of 5-Hydroxymethylfurfural

The development of catalysts with relatively high current densities at low potentials for the electrooxidation of 5-hydroxymethylfurfural (HMF) is still challenging. In this study, an in situ deep eutectic solvent (DES) etching phosphorization strategy is developed to prepare nickel phosphides encapsulated in P,O-codoped carbon nanosheets (Ni-P@POC). The DES serves not only as an etchant to extract Ni²⁺ from the nickel foam, but also as a phosphorus source to form nickel phosphides in situ uniformly embedded in the carbon films to produce a sheet structure. The electrooxidation performance is further greatly improved by implementing an electrochemical activation step to transform Ni-P@POC into NiOOH/Ni-P@POC (t-Ni-P@POC). t-Ni-P@POC exhibits a low onset potential of 1.20 V vs. RHE and a high current density of 200 mA cm^-2 at 1.33 V vs. RHE for HMF electrooxidation, outperforming most reported catalysts. The as-developed DES etching phosphorization strategy offers a facile, flexible, and universal route for the design of high-performance catalysts with specific nanostructures.

A Critical Review of Emerging Hydrophobic Deep Eutectic Solvents' Applications in Food Chemistry: Trends and Opportunities

Due to their low cost, biodegradability, and ease of preparation, deep eutectic solvents (DESs) are considered promising green alternatives to conventional solvents, as exploiting green solvents has been a research focus for achieving sustainable development goals. Most DESs in published studies are hydrophilic. On the other hand, the DES's hydrophilicity restricts its practical applicability to just polar molecules, which is a vital disadvantage to this extractant. Hydrophobic DES (HDES) has been developed as a new extractant adept at extracting nonpolar inorganic and organic compounds from aqueous systems. Although there has been little research on HDESs (HDES publications account for <10% of DES), specific intriguing applications have been discovered, requiring investigation and comparisons. As a result, this review covers the applications of emerging HDES in detecting pesticide residues, food additives, contaminants in food packaging, heavy metals, separation and extraction processes in food. According to the available literature, HDESs have the potential to overcome the limitations of hydrophilic DESs and be used in a broader range of applications in food with greater efficiency, which has received little attention. HDES is expected to substitute a lot of harmful organic extractants used for analytical reasons (food chemistry) in the future. Besides, the limitations of HDES were reviewed, and future studies were provided. This will serve as a reference for green chemistry advocates and practitioners in food science who want to minimize pollution and improve efficiency and benefit from the further development of HDESs.

Lipase-mediated Baeyer-Villiger oxidation of benzylcyclopentanones in ester solvents and deep eutectic solvents

This work presents the chemo-enzymatic Baeyer-Villiger oxidation of α-benzylcyclopentanones in ester solvents as well as deep eutectic solvents (DES). In the first part of the work the effect of selected reaction conditions on the reaction rate was determined. The oxidation process was most effective in ethyl acetate at 55 °C, with the use of lipase B from Candida antarctica immobilized on acrylic resin and UHP as oxidant. Ultimately, these preliminary studies prompted the development of an effective method for the implementation of lipase-mediated Baeyer-Villiger oxidation of benzylcyclopentanones in DES. The highest conversion was indicated when the oxidizing agent was a component of DESs (minimal DESs). The fastest conversion of ketones to lactones was observed in a mixture of choline chloride with urea hydrogen peroxide. In this case, after 3 days, the conversion of the ketones to lactones products exceeded 92% for all substrates. As a result, two new lactones were obtained and fully characterized by spectroscopic data.

Deep eutectic solvent assisted fabrication of zirconium phytate thin nanosheets for important biomass transformations

Utilization of naturally occurring resources to construct functional catalytic materials is significantly important, and facile and environmental-benign strategies are highly desired to afford the materials having a specific structure and good catalytic activity. Herein, we reported an innovative deep eutectic solvent (DES)-assisted strategy to synthesize zirconium phytate with a thin nanosheet structure (denoted as Zr-Phy-DES) using plant-originated phytic acid (PhyA) as the renewable building block. This strategy was eco-friendly and adjustable owing to the designability of DESs. The Zr-Phy-DES as an acidic catalyst showed high activity on two important biomass transformations, i.e., dehydration of carbohydrates and Meerwein-Ponndorf-Verley reduction of ethyl levulinate. Interestingly, Zr-Phy-DES showed higher catalytic performance than the zirconium phytates prepared in ethylene glycol and N,N-dimethylformamide, confirming the advantage of DESs for preparing functional materials. Notably, the unique feature of this proposed strategy is that renewable catalysts are prepared in an environmental-benign solvent for efficiently catalyzing biomass transformation.

•

An eco-friendly strategy for preparing catalytic materials with a specific structure

•

The catalytic activity of the prepared materials varied with the type of solvents

•

The material prepared in deep eutectic solvent showed better performance

•

Catalytic materials from natural resources and green solvents to convert biomass