The application of deep eutectic solvent-based magnetic nanofluid in analytical sample preparation

Natural deep eutectic solvents (NADES) have gained significant attention as green solvents due to their unique properties, such as high solubility, low volatility, low toxicity, and tunability. Liquid phase microextraction (LPME) is a sample preparation technique that plays a crucial role in analytical chemistry, and the use of NADES as extraction solvents in LPME offers numerous benefits compared to traditional solvents. NADES can effectively extract bioactive compounds from natural sources without damaging their structure and activity. They can also serve as solvents and catalysts in organic reactions, enhancing the bioavailability of natural compounds. In addition, NADES can be utilized as mobile or stationary phases in chromatographic techniques for separating and analyzing natural compounds. The review highlights the efficiency of NADES in terms of extraction ability, analyte stabilization capacity, and detection compatibility. Moreover, the availability of their components, ease of preparation, low toxicity, cost-effectiveness, and biodegradability make NADES attractive for researchers in the field of analytical chemistry. The applications of NADES in LPME contribute to the principles of green analytical chemistry and green sample preparation by providing a sustainable and environmentally friendly approach to sample preparation. A comprehensive overview of the applications of NADES in liquid phase microextraction is provided, emphasizing their potential for advancing green practices in analytical chemistry.

The zinc secondary batteries (ZIBs) are promoting as one of the next-generation batteries using zinc with a high theoretical capacity as a negative electrode. However, the dendrite growth due to repeated charging and discharging are disadvantages. Deep eutectic solvents (DESs), which are obtained by mixing two or more compounds consisting of a hydrogen bond acceptor and a hydrogen bond donor, have suppressed dendrite growth.[1] Mixing Zn (ClO4)2・6H2O (solid) and sulfolane (SL, melting point 27.5 ℃) yields a DES and the DES prevents dendrite growth. However, the whisker-like Zn deposition is observed at high current density, suggesting that the DES cannot inherently prevent dendrite growth.[2] On the other hand, Dokko et al. have reported that the Li+ hopping conduction occurs in SL based super-concentrated electrolyte solution, suppressing concentration polarization.[3] Liquid structure plays a crucial role in the Li+ hopping conduction. In this work, to develop a DES that prevents dendrite growth by suppressing the concentration polarization, we prepared the SL based DESs consisting of various anions.Zn(ClO4) DES was prepared by mixing Zn (ClO4)2・6H2O and SL. We also prepared the DES with the anion changed to Zn (TfO)2. The liquid structures of Zn-SL DES were observed using a laser Raman spectrophotometer NRS-4500. The chronoamperometry of the Zn-symmetric cell was measured at room temperature. An electrochemical measurement system (SP-150, Bio-logic) was used for the electrochemical measurement.In the Raman spectrum of neat SL, a Raman band assigned to the scissoring vibration of SO2 is observed at 567 cm-1. This Raman bands appears at 571 cm-1 and 574 cm-1 in the Raman spectrum for Zn (ClO4)2 DES and Zn (TfO)2 DES, respectively. In addition, the FWHM of the band of Zn (TfO)2 DES is larger than that of Zn (ClO4)2 DES. In high concentration Li-SL electrolyte, Li+ interacts not only with SL but also with anions to form the contact ion pairs (CIP) and aggregates (AGG) in which the anion cross-links Li+. As these liquid structure form, the Raman band shifts to the high wavenumber and broadens. Therefore, the CIP and AGG may be easily formed in Zn (TfO)2 DES. This is expected to suppress concentration polarization and dendrite growth. In the case of migration-controlled Zn2+ transport, the current should increase with increasing the applied voltage. For the Zn (ClO4)2 DES, there was no increase in current density of the symmetric cell with increasing applied voltage. In contrast, for the Zn (TfO)2 DES, the current value increased continuously with increasing applied voltage, reaching a high value of 10.8 mA cm-2 at 600 mV. In addition, despite the low conductivity of Zn (TfO)2 DES, the high current density was observed upon polarization. We believe that this is due to the rapid transport of zinc by forming CIP and AGG. However, for Zn (TfO)2 DES, the current decay due to concentration polarization is observed at large polarization. To suppress the concentration polarization, Zn2+ concentration was increased and then the chronoamperometry measurements was conducted again. In the Zn (TfO)2 DES, there was no increase in the current density of the symmetric cell with increasing the applied voltage. On the other hand, the current density of the symmetric cell with Zn (ClO4)2 DES suddenly increased from 300 mV. This may be due to a change in electrode area caused by the formation of dendrites.４．References[1] Funian Mo, Guojin Liang, Qiangqiang Meng, et. al. Energy Environ. Sci., 706-715 (2019)[2] Xidong Lin, Guodong Zhou, Matthew J. Robson, et. al. Adv.Funct.Mater. 2109322 (2021)[3] Kaoru Dokko, Daiki Watanabe, et. al. J.Phys.Chem. B, 122, 10736–10745, (2018)

Deep eutectic solvents-based adsorbents in environmental analysis

The effects of a hydrogen bond acceptor and hydrogen bond donor on carbon dioxide absorption via natural deep eutectic solvents were studied in this work. Naturally occurring non-toxic deep eutectic solvent constituents were considered; choline chloride, b-alanine, and betaine were selected as hydrogen bond acceptors; lactic acid, malic acid, and fructose were selected as hydrogen bond donors. Experimental gas absorption data were collected via experimental methods that uses gravimetric principles. Carbon dioxide capture data for an isolated hydrogen bond donor and hydrogen bond acceptor, as well as natural deep eutectic solvents, were collected. In addition to experimental data, a theoretical study using Density Functional Theory was carried out to analyze the properties of these fluids from the nanoscopic viewpoint and their relationship with the macroscopic behavior of the system, and its ability for carbon dioxide absorption. The combined experimental and theoretical reported approach work leads to valuable discussions on what is the effect of each hydrogen bond donor or acceptor, as well as how they influence the strength and stability of the carbon dioxide absorption in deep eutectic solvents. Theoretical calculations explained the experimental findings, and combined results showed the superiority of the hydrogen bond acceptor role in the gas absorption process, with deep eutectic solvents. Specifically, the cases in which choline chloride was used as hydrogen bond acceptor showed the highest absorption performance. Furthermore, it was observed that when malic acid was used as a hydrogen bond donor, it led to low carbon dioxide solubility performance in comparison to other studied deep eutectic solvents. The cases in which lactic acid was used as a hydrogen bond donor showed great absorption performance. In light of this work, more targeted, specific, deep eutectic solvents can be designed for effective and alternative carbon dioxide capture and management.

Green solvents (GSs) has gained significant attention in recent years due to their potential as safer and more sustainable alternatives to traditional organic solvents. Solvents are used in a wide range of applications, from industrial processes to everyday products. Solvent emissions and losses can have a significant impact on the environment and human health, which is why many initiatives are being undertaken to get rid of or switch to eco-friendly alternatives. A key area of green chemistry that led to the concept of “green” solvents is the development of alternative solvents that are less toxic and more environmentally friendly than traditional organic solvents. The advantages of using green solvents over conventional ones are their environmental friendliness, biocompatibility, biodegradability, and simplicity of preparation. Different sample preparation techniques have successfully utilized green solvents to offer a sustainable separation media for the extraction of a variety of inorganic and organic compounds which are crucial for research in environmental samples. Recent developments in green analytical chemistry (GAC) have focused on how to prepare and use samples using environmentally sustainable solvents. The current study covers the advance and currently used green solvents with an emphasis on environmentally friendly sample preparation methods. This review aims to briefly summarize the current state of knowledge about the use of green solvents particularly ionic liquids, deep eutectic solvents and switchable solvents (SSs) with the perspective of GAC in sample preparation methods.

The pretreatment or disruption of a cellulose I \(\beta \) crystallite by four deep eutectic solvents (DES): choline-chloride ethylene glycol, choline-chloride oxalic acid, choline-chloride urea, and choline-chloride levulinic acid, was described from the atomistic interactions observed in molecular dynamics and ab-initio (NCI-AIM) studies. The cellulose I \(\beta \) disruption was studied considering plausible correlations between the Kamlet-Taft (α and β) solvent parameters, and a series of thermodynamic, structural, and energetic properties. It was found that the Kamlet-Taft parameters correlated with the thermodynamic properties of the DES, as well as their variations after the addition of the cellulose crystallite. Structural analysis revealed that the weaker the interactions within the molecules of the solvent, the stronger the interactions between the hydroxyl group from cellulose with the chloride anion and with the hydrogen bond donor. Further analysis indicated that the \(R-CO-R\) moieties in the hydrogen bond donor within the solvent, displayed best interplaying with the cellulose. The hydrogen bond occupancies within the cellulose crystallite, evidenced that the main \(O6-H6\cdots O2/O3\) and \(O2-H2\cdots O6\) interchain hydrogen bonds in the glucan located at the edge of the solute, were replaced by weak \(O6-H6\cdots O4\) hydrogen bonds in all solvents. This effect was related to the \({O/Cl}_{DES}\cdots H-donor\) and \({O}_{DES}-{H}_{DES}\cdots acceptor\) HBs between cellulose and DES molecules, and it was confirmed by the non-covalent interactions obtained through DFT calculations. The energetic interactions and the atomistic degree of disruption of the cellulose crystallite, were not completely described by the Kamlet-Taft β or α parameters when considered separately. Surprisingly, by using the net basicity (\(\beta -\alpha \)) definition such correlations were improved, suggesting that both parameters must be considered together to develop new, green, and sustainable solvents for cellulose pretreatment process.Graphic abstract

Separation of aromatics from aliphatics is challenging because of the close range of their boiling points and the formation of several combinations of azeotropes. Until now, no feasible separation process is available for aromatic concentrations below 20 wt%. In this work, we have investigated the possibility of using selected Deep Eutectic Solvents (DESs) for the liquid-liquid extraction of aromatics. DESs have emerged as green solvents that may offer several industrial alternatives. The DESs used in this work were synthesized from ammonium salt with ethylene glycol, lactic acid and sulfolane as Hydrogen Bond Donor (HBD). Equilibrium data for the ternary system consisting of ethylbenzene and n-octane with all DESs were measured at 25°C and atmospheric pressure. The results showed comparable distribution ratio and selectivity with commercial solvents. The absence of the HBD in the hydrocarbon layer, means the reduction of the number of separation stages. In addition, the Non-Random Two Liquid (NRTL) model was successfully used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems.

In recent years, green chemistry has focused on the search for green solvents to replace the toxic organic solvents traditionally used in sample preparation. Ionic liquids (ILs) and deep eutectic solvents (DESs), which belong to neoteric liquids, are environmentally friendly solvents widely used for the extraction and subsequent determination of bioactive molecules and contaminants. ILs are semi-organic molten salts at temperature below 100 °C, composed by organic cations and organic or inorganic anions. DESs are a greener evolution of ionic liquids, consisting of a quaternary ammonium salt that acts as a hydrogen bond acceptor molecule and organic acids, sugars, amines, or polyalcohols that can be used as hydrogen bond donor molecules. DES components, when combined in a specific molar ratio, form an eutectic mixture that is liquid at room temperature. Both DESs and ILs have been widely applied in several extraction procedures, including matrix solid-phase dispersion (MSPD) extraction. MSPD is an extraction technique based on a homogenization phase between a solid sample and a solid dispersing material that has the function of breaking the sample, increasing analytes extraction yield. Three possible uses of neoteric solvents in MSPD extraction were investigated: (i) as extraction solvents to replace traditional organic solvents; (ii) as an adjuvant of MSPD extraction, to be added to the sample and dispersing material during the homogenization step; (iii) as an element to create innovative and highly selective dispersing materials. This review aims to describe and discuss in detail the use of neoteric solvents in the MSPD process in their various applications.

Ionic liquids (ILs) are organic salts with a melting temperature lower than the boiling point of water, while deep eutectic solvents (DESs) are usually composed of two or more components that can associate with each other through hydrogen bonds, and the resulting melting point of the mixture is lower than each of the components. These two classes of solvents share many remarkable properties, such as low volatility, non- flammability, wide liquidous range, and tunability; moreover, DESs are more inexpensive and environmentally friendlier. In addition to the fundamental scientific interest in these types of materials, our modeled systems are relevant to practical applications such as dye- sensitized solar cells and gas separations, as well as developing nanomaterials based on ILs. We first performed molecular dynamics (MD) simulations to study the structure and dynamics of DESs and ILs confined inside slit-like graphite and titania [rutile (110)] nanopores. Our results show that hydrogen bond donor (HBD) molecules of modeled DESs can form long-lived hydrogen bonds with the oxygen atoms in the rutile walls, consequently the rutile walls are coated by HBD layers that are almost depleted of ions, which exhibiting a liquid structure that departs from that of the bulk DES and with very slow dynamics. In contrast, for DESs inside graphitic pores, all species are present in the fluid layers near the carbon walls, the local liquid structure everywhere is similar to that of a bulk DES, and the overall dynamics are faster than those observed inside rutile pores of the same pore size. When the pore size is reduced, in general the hydrogen bonds formed can exist for longer time, a larger proportion of the hydrogen bonds involve the walls (in the case of a rutile pore), and the overall dynamics of the confined DES become slower. We then performed MD simulations of confined DESs or ILs in contact with gas phases containing CO2, and later a binary mixture of CO2 and CH4. When the amount of DES in the pore is varied, in the absence of DES, CO2 adsorbs to the pore walls, but increasing amounts of DES inside the pores quickly displace carbon dioxide into the gas/liquid interfaces, and into dissolution within the confined DES. As the amount of DES inside the pores increases, the diffusivity of CO2 reaches a maximum in partially filled pores and decays to the values observed in pores filled with DES, which are similar to the diffusion coefficients of CO2 in the bulk DES. The average number densities of CO2 near the confined DES (i.e., dissolved in the DES, and adsorbed at the pore walls and at the gas/liquid interface) are significantly larger than the corresponding value observed in the bulk DES. Furthermore, the solubility selectivity, diffusion selectivity and permselectivity of CO2 over CH4 inside the pore will alter with different pore materials, the properties of confined DESs or ILs, the loadings of solvents in the nanopores. Additionally, biased MD simulations have been performed to model the heterogeneous nucleation of IL [dmim+][Cl-] near a graphitic surface from its supercooled liquid phase. As nucleation is a rare event, a combination of techniques (i.e. the string method in collective variables and Markovian milestoning with Voronoi tessellations) has been used to obtain a minimum free energy path connecting the supercooled liquid and crystal phases, and determine the free energy and the rates involved in the nucleation process. It is found that when the subcooled liquid phase is in contact with a graphitic disk, the free energy barrier becomes about 42% smaller (~49 kcal/mol), and the critical nucleus formed is about 17% smaller (~3.0 nm) than the one observed for homogeneous nucleation.

Purification of biodiesel prior to utilizing it as an alternative fuel is an essential industrial practice. Low glycerol content is one of the important pointers needed for passing the EN 14214 and ASTM D6751 international biodiesel standards. In this study, choline chloride (ChCl) as salt and ethylene glycol and 2,2,2-Trifluoroacetamide as hydrogen bond donors (HBDs) were employed to synthesize two ammonium salt-non glycerol based Deep Eutectic Solvents (DES). The physical properties of the synthesized DESs were measured and analyzed. These DESs were utilized to remove all the free glycerol from the palm oil-based biodiesel. The results indicated that all the tested DESs were able to remove all free glycerol successfully. The Central Composite Design (CCD) of the Response Surface Methodology (RSM) was used to to experiment design and optimization of total glycerol removal using ethylene glycol-based DESs and 2,2,2-Trifluoroacetamide-based DESs. The maximum total glycerol removal by ethylene glycol-based DESs was obtained at 0.66 ethylene glycol mole fraction and at DES/biodiesel molar ratio of 3 with removal efficiency of 23.85% as well as by 2,2,2-Trifluoroacetamide-based DESs at 0.60 2,2,2-Trifluoroacetamide mole fraction and at DES/biodiesel molar ratio of 2.93 with removal efficiency of 29.29%. The reusability of these DESs for removing free glycerol and total glycerol content from palm oil-based biodiesel was also investigated. This study proves that both ammonium salt-non glycerol based DESs can be successfully employed to remove the glycerol from palm oil-based biodiesel.

Novel chemistry of Deep Eutectic Solvents (DES) is a matter of current interest as the unusual properties of these solvents make them a versatile medium for a variety of reactions. In particular, they provide media with a wide potential window and high ionic strength for the redox chemistry of metals. A wide range of type II DES (Metal halide (MX) + Hydrogen Bond Donor (HBD)) with AlCl3 (MX) have been synthesised, where hydrogen bond donors (HBD) included acetamide, methyl-, dimethyl-, trimehylacetamide, urea, di- and tetramethylurea. The ratio of AlCl3 - HBD was maintained at 1.5:1 throughout. Viscosity and conductivity of these novel DES, have been related to the melting point of HBD as well as to the availability of proton exchanging groups. Mechanisms of aluminium deposition/dissolution from room temperature chloroaluminate melts were studied in order to elucidate the effects of amines type on the properties of these novel electrolytes. Mass transport and speciation were investigated by means of Electrochemical Quartz Crystal Microbalance (in dispersive mode), UV-Vis and NMR. It was found that although the higher deposition rate was proportional to the higher conductivity of the respective DES, the rate of the stripping process was related to the type of HBD used. Creation of an aluminium based battery requires a balance between current efficiency and deposition rate and this can be achieved by a choice of suitable HBD. The influence of surface tension of DES on their electrochemical properties, and ultimately availability of proton exchanging groups to participate in liquid formation is currently under investigation. Figure 1

Global warming is a critical issue resulting partly from increasing carbon dioxide emissions. Technologies have been developed to capture carbon dioxide followed by storage or utilization, yet techniques are limited by the use of toxic solvents and the generation of harmful by-products. Research in green chemistry has designed green solvents which are non-toxic, efficient and environmentally friendly. Here we review green solvents employed for carbon capture, with emphasis on ionic liquids, deep eutectic solvents and liquid polymers. Solvent performance depends on temperature, density and viscosity. Deep eutectic solvents appear as the most advanced solvents with capacities reaching up to 4.292 g CO2 per g of solvent. Ionic liquids have shown CO2 uptakes of 4.72 mol of CO2/mol of solvent, but are less efficient on average. Liquid polymers display capacities of up to 1.357 mol of CO2/mol of solvent.

Background: The 4-thiazolidinone-5-carboxylic acid and its derivatives have diverse applications in agriculture, industrial and pharmaceutical fields. Therefore, the synthesis of this heterocyclic compound attracted much attention from researchers with green chemistry protocols. In this research work, we have introduced the green protocol for the synthesis of 4-thiazolidinone- 5-carboxylic acid by keeping the parameters in mind like cost-effective, environmentally benign, short reaction time and easy work-up procedure. Methods: Initially, we irradiated the mixture of substituted aldehyde, thiosemicarbazide and furan 2-5-dione in the presence of choline chloride-thiourea-based Deep Eutectic Solvent [DES] as a green medium. The reaction optimization was performed in different solvents like ethanol, glycerol, and PEG-400. Results: The DES, which was used as a green solvent, produced an excellent result in context to short reaction time, yield, easy workup, mild reaction condition and cost-effective protocol. All the results are discussed. Conclusion: The DES-mediated synthesis of 4-thiazolidinone-5-carboxylic acid is found to be an excellent protocol, which followed green chemistry principles. This method has specific features like mild reaction conditions, environmentally benign, cost-effective and easy workup procedure.

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

Prediction of glycerol removal from biodiesel using ammonium and phosphunium based deep eutectic solvents using artificial intelligence techniques