Deep eutectic solvent mediated synthesis of pyrazolo[3,4-b]- and pyrimido[4,5-b]quinolines

Alkaline anion exchange membrane fuel cells (AEMFC) have gained interest due to their potential as electrochemically energy conversion devices and a competitive alternative to the more extensively studied commercialized proton exchange membrane fuel cells (PEMFCs). Nevertheless, their development impedes the limited ion conductivity, chemical and mechanical stability in an alkaline medium of anion exchange membranes (AEMs). The ionic conductivity of AEM is lower than that of a proton exchange membrane (PEM) because the mobility of hydroxide ions is inherently lower than that of protons [1]. Deep eutectic solvents (DESs) as green solvents can overcome this issue.The main idea of this research is to fabricate a deep eutectic solvent-supported polymer-based AEM for alkaline fuel cell application by electrospinning technique. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of AEM due to its water solubility, biodegradability, high fiber forming ability, non-toxicity, and high chemical and thermal stability [2]. This work aims to achieve high ionic conductivity, chemical and mechanical stability by two methods: swelling polyvinyl alcohol (PVA)-based nanofibers into DES and encapsulating DES inside the PVA-nanofibers together with optimizing fabrication methods.In this study, polymer electrolytes as potential AEMs were first prepared using the swelling method, where electrospun PVA nanofibers were fabricated via the electrospinning technique, followed by swelling in a series of DESs. To prepare the DES solutions, choline chloride (ChCl) and ethylene glycol (EG) were mixed at different molar ratios. The cross-linking of pure PVA fibers with glutaraldehyde in ethanol (see Figure 1B) and DES uptake and the presence of voids as channels for ion conduction (see Figure 1C) were successfully confirmed with a scanning electron microscopy (SEM, Crossbeam500, Zeiss). The ionic conductivity of swelled in DES PVA-based membranes were evaluated by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature and was equal to 0.336 mS/cm. The presence of DES in the membrane was confirmed with FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10): a slight C-N+ peak at 953 cm-1 from ChCl has proven interaction between PVA and DES with FTIR spectroscopy, meaning that DES is present in the fiber. In addition, the nitrogen content in the obtained membrane was determined by CHNS elemental analysis (Elemental Vario micro cube) as 3.32 wt.%.In order to overcome high weight loss in the swelling method, the encapsulation method was suggested as an alternative option, which is based on the encapsulation of DES into the PVA solution by mixing them, varying the amount of DES added, and then preparing fibers using electrospinning. Observing the morphology of DES-encapsulated PVA nanofibers with a scanning electron microscope (SEM, Crossbeam500, Zeiss), as the content of DES in the solution increased, there was an observed rise in the average diameter of the nanofibers (see Figure 1D). Encapsulation of DES in PVA nanofibers was primarily confirmed by transmission electron microscope (TEM, JEM -1400 Plus, JEOL): PVA appears lighter due to its decreased density, proving that DES is present inside the fibers. Also, the same tendency was observed with the results of FTIR spectroscopy (FT-IR spectrometer, Nicolet iS10) as for the swelling method, meaning that DES is present in the fiber. According to CHNS elemental analysis (Elemental Vario micro cube), nitrogen content was lower than for the swelling method - 0.70 wt.%. The ionic conductivity was evaluated as 0.364 mS/cm by electrochemical impedance spectroscopy (Metrohm Autolab) at room temperature, which was almost the same as for the swelling method.As a result, very flexible and visually transparent electrospun DES-supported PVA-based AEMs were obtained via the swelling and encapsulation method.

Commercial coolants such as water, ethylene glycol and triethylene glycol possess very low thermal conductivity, high vapor pressure, corrosion issues and low thermal stability thus limiting the thermal enhancement of the nanofluids. Thus, a new type of base fluid known as deep eutectic solvents (DESs) is proposed in this work as a potential substitute for the conventional base fluid due to their unique solvent properties such as low vapor pressure, high thermal stability, biodegradability and non-flammability. In this work, 33 different DESs derived from phosphonium halide salt and ammonium halide salts were synthesised. Carbon nantubes (CNTs) with different concentrations (0.01 wt%–0.08 wt%) were dispersed into DESs with the help of sonication. Stability of the nanofluids were determined using both qualitative (visual observation) and quantitative (UV spectroscopy) approach. In addition, thermo-physical properties such as thermal conductivity, specific heat, viscosity and density were investigated. The stability results indicated that phosphonium based DESs have higher stability (up to 4 d) as compared to ammonium-based DESs (up to 3 d). Thermal enhancement of 30% was observed for ammonium based DES-CNT nanofluid whereas negative thermal enhancement was observed in phosphonium based DES-CNT nanofluid.

Sodium-ion batteries (SIBs) are a potential cost-effective alternative for lithium-ion batteries (LIBs) in applications which require large-scale energy storage. In these applications, low cost and sustainability are of prime importance. The extensive use of LIBs for large-scale storage would drive up lithium prices because of the latter’s limited production. As the lightest and smallest alkali metal after lithium, sodium is abundant and widely available, and is therefore more cost-efficient and sustainable. SIBs can use light and inexpensive aluminum current collectors for both the anode and cathode, as opposed to LIBs, which usually require more expensive copper current collectors for the anodes. This further increases the SIB's viability in applications where cost and sustainability are the most crucial factors.Viable battery electrolytes should have sufficient ionic conductivity, be electronically insulating, have a large electrochemical and thermal stability window, and not show reactivity with the other components of the battery. They should be safe, non-toxic, and inexpensive. Ionic liquids, defined as materials which consist entirely out of ions and which remain liquid below 100 °C, were previously studied as electrolytes for SIBs as they have a high intrinsic ionic conductivity, can dissolve high amounts of salt, are non-flammable and have a high thermal and (electro)chemical stability. Ionic liquids are typically expensive due the difficulty of their synthesis. Deep eutectic solvents (DESs) are closely related to ionic liquids and consist of a mixture of Lewis/Brönsted acids and bases, where the melting temperature of the mixture is below that of the individual components. Whereas DESs and ionic liquids can have similar physical properties, DESs can have additional advantages such as ease of preparation and wide availability of reagents, although this depends on the exact composition. Binary and ternary mixtures of different XFSI (FSI = bis(fluorosulfonyl)imide) and XTFSI (TFSI = bis(trifluoromethanesulfonyl)imide) inorganic salts were previously applied as DES electrolyte in sodium-ion half cells, which were constrained to operation at 80 °C or higher because of their relatively high melting points.1,2 These cells showed high reversibility and high Coulombic efficiency.Other DESs may also offer an increase of the stability of battery operation, and may be used at less stringent temperature conditions (with acceptable ionic conductivity even at room temperature). This stability problem is particularly pronounced at 55 °C or higher for conventional electrolytes, where battery performance rapidly degrades when linear carbonates are used as electrolyte solvent.3 Our series of DESs as SIB electrolytes were based on the dissolution of NaTFSI in an amide which is solid at room temperature. For each electrolyte, the effect of the solution structure on its electrochemical properties was studied. The amide was spontaneously reduced when contacted with sodium metal. By increasing the salt concentration, we observe a lower reactivity with sodium metal, a broader electrochemical stability window and a decreased ionic conductivity due to the strong Coulombic interactions among the amide molecules, Na+, and TFSI- ions (Figure). The sample containing 10 mol% of NaTFSI shows an anodic stability limit of ~3.6 V vs Na+/Na and a conductivity of 10.3 mS cm-1 at 55 °C. A DES with 30 mol% NaTFSI is stable up to ~4.6 V vs Na+/Na and has a conductivity of 3.8 mS cm-1 at 55 °C. The variation of conductivity with temperature of both DESs could be fitted with the Vogel-Tamman-Fulcher equation. At 55 °C, (Na3V2(PO4)3/C)/(Na2+x Ti4O9/C) full cells containing DES as electrolyte demonstrate a considerably higher durability and Coulombic efficiency than cells containing a conventional organic solvent-based electrolyte. As such, these DESs form a new class of electrolytes for application in sodium-ion batteries, offering a more durable performance at 55 °C than conventional systems.References(1) Nohira, T.; Ishibashi, T.; Hagiwara, R. Properties of an Intermediate Temperature Ionic Liquid NaTFSA – CsTFSA and Charge – Discharge Properties of NaCrO2 Positive Electrode at 423 K for a Sodium Secondary Battery. J. Power Sources 2012, 205, 506–509.(2) Fukunaga, A.; Nohira, T.; Kozawa, Y.; Hagiwara, R. Intermediate-Temperature Ionic Liquid NaFSA-KFSA and Its Application to Sodium Secondary Batteries. J. Power Sources 2012, 209, 52–56.(3) Yan, G.; Dugas, R.; Tarascon, J. The Na3V2(PO4)2F3/Carbon Na-Ion Battery: Its Performance Understanding as Deduced from Differential Voltage Analysis. J. Electrochem. Soc. 2018, 165 (2), 220–227. Figure 1

Microwave irradiation was postulated to reduce time and energy for deep eutectic solvent (DES) production which is in line with the principle of green chemistry. In this study, the choline chloride (ChCl)‐malic acid (MA) DES was prepared using microwave‐assisted (DES‐Mic) and conventional (DES‐Con) approaches. Microwave was a relatively greener approach as it was rapid (5 min) and consumed 92.8 % energy less than DES‐Con. Moreover, DES‐Mic and DES‐Con exhibited similar physicochemical profiles (pH, solubility, density) and rheological properties. Structural profiling through FTIR analysis suggested hydrogen bond formation between the functional groups of ChCl and MA. The FTIR spectra also did not show structural differences in the DES synthesized using different methods. DES‐Mic and DES‐Con exhibited superior 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) (80.8±0.1 and 83.2±0.3 %, respectively) free radical scavenging activities than ChCl (15.6±0.8 %), MA (20.0±1.4 %) and ChCl:MA aqueous mixture without subjected to DES synthesis conditions (ChCl:MA aq ; 23.3±0.8 %). Both DES were also proven as more efficient solvents for the extraction of polysaccharides from ramie leaf, as they recorded higher yields (21.4±1.9 and 22.2±1.0 %, respectively) than equimolar of MA (17.7±2.6 %) and ChCl (6.4±0.2 %). Overall, microwave was proven as a more sustainable approach for DES preparation compared to conventional method, which could be further improvised for industrial applications.

The subtle but substantial distinction between ammonium- and phosphonium-based deep eutectic solvents

Extraction and characterization of lignin from lignocellulose biomass using citric acid and fructose-based NADES.

Mineral processing is one of the important methods of resource utilization, and flotation and leaching are the main methods of mineral processing. The conventional reagents used in these methods usually show that they may lead to health, environment, safety, and other related problems. In order to make these methods safer and cleaners, it is necessary to explore the use of more green and environmentally friendly reagents. Ionic liquids (ILs) and deep eutectic solvents (DESs) are known as green solvents because of their wide liquid temperature range, good solubility, high thermal and chemical stability, almost nonvolatile and low toxicity. The application of ILs and DESs as agents in mineral flotation and extraction of valuable metal can provide new alternatives to traditional methods and processes and realize green and clean production. ILs and DESs have been successfully used to high-efficient float some minerals that are difficult to float, such as rare-earth minerals, quartz, and quartz hematite, as well as carbonate asphalt during recent years. Here we focus on the application progress, existing problems, and development direction of ILs and DESs in mineral processing. We introduced characteristics of ILs and DESs, and the research progress of ILs and DESs in green flotation of rare-earth ore, quartz and quartz hematite. The research works of ILs and DESs in the green leaching of chalcopyrite, sulfide ore, gold, and silver ore is summarized. Interactions of ILs and DESs with common minerals of soil also discussed to help understand the impact of ionic liquids on soil and groundwater. Compared with the traditional flotation and leaching reagents, the amount of ILs and DESs used is obviously smaller, and the selectivity and efficiency are better than that of the traditional system. After further research and optimization, it is expected to be developed into a new efficient and green mineral processing technology.

Critical overview on the use of hydrophobic (deep) eutectic solvents for the extraction of organic pollutants in complex matrices

This study investigates the effect of using water as a low-viscosity component in ternary amine-based deep eutectic solvents (DESs) on the physicochemical properties, thermal stability, and CO2 absorption capacity of the resulting DESs. It should be emphasized that water is a component of the ternary DES. The effect of water content in the DES, type of hydrogen bond acceptors (HBAs), hydrogen bond donors (HBDs), and HBA:HBD ratio on the above parameters was investigated. Moreover, the effect of temperature and pressure on the CO2 absorption capacity of DESs was predicted using the predictive model COSMO-RS. This model was also used to predict the CO2 solubility in the DESs and the results were compared with the experimental values. The results showed that the addition of small amounts of water, e.g., 5 and 10 wt% during preparation, can significantly decrease the viscosity of the resulting DESs, up to 25% at room temperature, while maintaining the high CO2 absorption capacity and high thermal stability. The ternary DESs based on MEA exhibited a high CO2 absorption capacity of 0.155–0.170 g CO2 / g DES. The ternary DESs were found to be thermally stable with a decomposition temperature of 125°C, which promotes the use of such solvents in post-combustion capture processes. Finally, COSMO-RS proved to be a suitable tool for qualitative prediction of CO2 solubility in DESs and demonstration of trends related to the effects of temperature, pressure, molar ratio, water content, HBD and HBA on CO2 solubility.

High-performance donor–acceptor electron acceptors containing 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN)-type terminals are labile toward photooxidation and basic conditions, and ...

Recent cutting-edge approaches to the integration of solid-liquid extraction with deep eutectic solvents: Toward a greener procedure for biomass valorization

Anhydrous metal nanoparticle suspensions using deep eutectic solvents (DES) – Green approach to metal nanoparticles production

Deep eutectic solvents (DESs) have emerged as an alternative to both common organic solvents and ionic liquids (ILs). DESs share physicochemical properties with ILs such as low vapor pressure, high thermal stability, high viscosity while offering advantages such as low toxicity, lower cost, and ease of preparation. Moreover, DESs are attractive candidates for electrochemical applications due to their large voltage windows and solubility properties. DESs as a solvent class share a general composition of a hydrogen bond donor (HBD), typically a polyol, amide, or acid, and a hydrogen box acceptor (HBA), usually a quaternary ammonium or phosphonium salt. At a specific molar composition of a HBD and HBD, the DES forms a eutectic mixture resulting in a large melting point depression due to extensive hydrogen bonding between the components.Despite being widely studied, the microscopic structures of DESs have remained largely uncharacterized. Herein, we present a multitechnique NMR study of two DESs: glyceline (glycerol + choline chloride) and ethaline (ethylene glycol + choline chloride). Fast-field cycling 1H relaxometry, pulsed field gradient diffusion, nuclear Overhauser effect spectroscopy (NOESY), 13C NMR relaxation, and pressure-dependent NMR experiments are deployed to sample a range of frequencies and modes of motion of the polyol and choline components of the DES. Generally, translational and rotational diffusion of polyols are more rapid than those of choline while short-range rotational motions observed from 13C relaxation indicate slow local motion of glycerol at low choline chloride (ChCl) content. We show how the additional hydroxyl group present in glycerol contributes to not only higher viscosities, but a larger perturbation of the hydrogen bonding network by the addition of ChCl.Additionally, we have investigated the solubility properties of several lithium salts (LiTFSI, LiFSI, LiPF6, LiBF4, and LiOAc) in these DESs and utilized the same suite of NMR techniques to understand how they act as solvents. We observe that due to anion effects, the heterogeneities present in DES result in differential solvation for some species where there is a distinction of lithium salts co-existing in these holes as well as the bulk. The large changes in the structural organization of DESs that result from the presence of lithium salts will serve as a guide to the design of a new class of electrolytes for lithium-ion batteries.

The existing CO2 absorption by deep eutectic solvents is limited by the unavoidable water absorption problem during use. In this study, we prepared three deep eutectic solvents with different alcohol aminations and added different water contents to discuss the effect of water content on the absorption of carbon dioxide by deep eutectic solvents. All deep eutectic solvents have a low melting point at room temperature as a liquid and have high thermal stability, where the choline chloride-diethanolamine deep eutectic solvents have a high viscosity. Anhydrous choline chloride-monoethanolamine deep eutectic solvents have the largest CO2 absorption, reaching 0.2715 g g−1, and the absorption of CO2 by anhydrous choline chloride-N-methyldiethanolamine deep eutectic solvents is only 0.0611 g g−1. Water content inhibited the absorption of CO2 in primary amine and secondary amine systems, whereas it enhanced the absorption of CO2 in tertiary amine systems, which was related to the reaction process of deep eutectic solvent and CO2.

Functional biodegradable agar based films from polyphenol-rich matcha extracts via deep eutectic solvents: From microstructure to bioactivity.