Volatile Organic Solvents Research Articles

Insight into the influence of natural deep eutectic solvents on the extraction of phenolic compounds from poplar type propolis: Composition and in vitro biological activity

Natural deep eutectic solvents (NADESs) have been considered promising to replace traditional volatile and toxic organic solvents for the extraction of biologically active substances from natural sources. This work applied an efficient and ethanol-exclusion strategy for extraction of phenolic compounds from poplar type propolis using five known NADESs (lactic acid:1,2-propanediol 1:1, lactic acid:fructose 5:1, choline chloride:1,2-propanediol 1:3, choline chloride:1,2-propanediol:water 1:1:1 and betaine:malic acid:water 1:1:6). The selected NADESs' extractability was evaluated by measuring the concentrations of total phenolics and total flavones and flavonols in the propolis extracts obtained, which qualitative chemical composition was further determined in detail by gas chromatography-mass spectrometry (GC-MS) analysis. It demonstrated that the chemical profiles of NADES and 70% ethanolic propolis extracts are similar. To expand the knowledge about the role of the applied solvents in the poplar propolis extraction process, the in vitro antimicrobial, cytotoxic and genotoxic activity of both NADESs and liquid NADES extracts were evaluated. The results revealed that the use of the selected NADESs as an extraction media for phenolic compounds from poplar propolis not only delivered a good extraction yield in some cases, but generally led to the preservation of propolis extracts' biological activity and even to the enhancement of their antimicrobial effect in comparison with the hydroethanolic one. Besides, the tested NADESs except for lactic acid:fructose and betaine:malic acid:water exerted low to negligible toxicity against normal cells treated and apart from lactic acid:fructose the remaining solvents demonstrated concentration-dependent moderate to subtle genotoxicity. There is a probability that not the supramolecular structure of the NADESs, but their components, played a key role for the observed biological effects. The present study has demonstrated an alternative approach for extracting the biologically active complex from poplar type propolis using NADESs, which could be useful for further pharmaceutical and cosmeceutical applications.

Physicochemical properties of ammonium acetate / propionic acid as a novel deep eutectic solvent and its binary mixtures with water in (298.15–353.15) K range

Emergence of deep eutectic solvents as potential replacements for volatile organic solvents has attracted interest of the scientific community in diverse fields of applications. Compared to ionic liquids, which exhibit similarity in many respects with this new class of green solvents, deep eutectic solvents (DESs) show low toxicity, and are easy to prepare from cheap and abundantly available starting materials. Knowledge of physicochemical properties of DESs is a prerequisite for their safe applications in technological fields and to understand the nature of interactions present in these systems. Although physicochemical properties of choline chloride based DESs are widely investigated, similar information on ammonium acetate based DESs is scant.In this work, a novel ammonium acetate/propionic acid deep eutectic solvent (AA/PA DES) is reported which is prepared by mixing ammonium acetate (AA) and propionic acid (PA) in the 1:3 mol ratio and characterized by FTIR, 1H and 13C NMR, TGA and DSC techniques. The density (ρ), sound velocity (u), viscosity (η) and conductivity (κ) of the pure DES and its binary mixtures with water are investigated over the entire composition range and temperatures (298.15–353.15) K. The excess properties, VmE, KSE, Δη, and ΔG*E are calculated and corelated using Redlich-Kister equation (RKE). Temperature dependence of conductivity and viscosity is satisfactorily described by the Vogel – Fulcher – Tamman (VFT) equation rather than Arrhenius equation. The pure DES shows a wide electrochemical potential window ranging from – 1000 mV to + 1000 mV, which coupled with its better solubilizing characteristics, could be exploited for electrochemical work.

Ionic Liquids as Green Solvents: A Comprehensive Review

Common reaction media, volatile organic solvents (VOS), contribute significantly to air pollution and pose challenges in separation and recycling processes. As environmental awareness grows, researchers are focusing on developing alternative, eco-friendly solvent systems to replace these traditional VOS. Ionic liquids (ILs) have emerged as promising "green" solvents due to their extremely low vapor pressure and high thermal stability, providing advantages in containment, product recovery, and recyclability. ILs exhibit varying stability to moisture and miscibility with molecular liquids, and their properties like density, melting point, and viscosity can be tailored by selecting appropriate cation and/or anion components. Beyond their role in chemical reactions, ILs find applications in separations, extractions, electroanalytical processes, and chemical sensing. The high ionic character of ILs significantly enhances reaction rates in various chemical processes. These versatile features position ILs as potential alternatives to VOS in a wide range of industrial applications. Moreover, their use as industrial solvents can have economic, social, and ecological impacts by influencing human health and environmental factors. In summary, the exploration of ILs as green solvents represents a crucial step towards addressing environmental concerns associated with traditional volatile organic solvents in industrial chemical processes.

Solvent-Free Fabrication of Anisotropic Microparticles with Precise 3D Shape Control Using Dipping-Based Micromolding.

We present an innovative solvent-free micromolding technique for rapidly fabricating complex polymer microparticles with three-dimensional (3D) shapes utilizing a surface tension-induced dipping process. Our fabrication process involves loading a photocurable solution into micromolds through mold dipping. The loaded solution, induced by surface tension, undergoes spatial deformation upon mold removal caused by surface forces, ultimately acquiring an anisotropic shape before photopolymerization. Results show that the amount of photocurable solution loaded depends on the degree of capillary penetration, which can be adjusted by varying the dipping time and mold height. It enables the production of polymer particles with precisely controlled 3D shapes without diluting them with volatile organic solvents. Sequential micromolding enables the spatial stacking of the polymer domain through a bottom-up approach, facilitating the creation of complex multicompartmental microparticles with independently controlled compartments. Finally, we demonstrated the successful simultaneous conjugation of multiple model-fluorescent proteins through the biofunctionalization of microparticles, indicating functional stability and effective conjugation of hydrophilic molecules such as proteins. We also extend our capacity to create bicompartmental microparticles with distinct functionalities in each compartment, revealing spatially controlled functional structures. In summary, these findings demonstrate a straightforward, rapid, and reliable method for producing highly uniform complex particles with precise control over the 3D shape and compartmentalization, all accomplished without the use of organic solvents.

Multifunctional Biomass-Based Ionic Liquids/CuCl-Catalyzed CO2-Promoted Hydration of Propargylic Alcohols: A Green Synthesis of α-Hydroxy Ketones.

α-Hydroxy ketones are a class of vital organic skeletons that generally exist in a variety of natural products and high-value chemicals. However, the traditional synthetic route for their production involves toxic Hg salts and corrosive H2SO4 as catalysts, resulting in harsh conditions and the undesired side reaction of Meyer-Schuster rearrangement. In this study, CO2-promoted hydration of propargylic alcohols was achieved for the synthesis of various α-hydroxy ketones. Notably, this process was catalyzed using an environmentally friendly and cost-effective biomass-based ionic liquids/CuCl system, which effectively eliminated the side reaction. The ionic liquids utilized in this system are derived from natural biomass materials, which exhibited recyclability and catalytic activity under 1 bar of CO2 pressure without volatile organic solvents or additives. Evaluation of the green metrics revealed the superiority of this CuCl/ionic liquid system in terms of environmental sustainability. Further mechanistic investigation attributed the excellent performance to the ionic liquid component, which exhibited multifunctionality in activating substrates, CO2 and the Cu component.

Preparation of PLGA Microspheres Using the Non-Toxic Glycofurol as Polymer Solvent by a Modified Phase Inversion Methodology.

Poly(D,L-lactide-co-glycolide is a biodegradable copolymer that can release pharmaceuticals. These pharmaceuticals can provide local therapy and also avert the clinical issues that occur when a drug must be given continuously and/or automatically. However, the drawbacks of using poly(D,L-lactide-co-glycolide include the kinetics and duration of time of poly(D,L-lactide-co-glycolide drug release, the denaturing of the drug loaded drug, and the potential clinical side effects. These drawbacks are mainly caused by the volatile organic solvents needed to prepare poly(D,L-lactide-co-glycolide spheres. Using the non-toxic solvent glycofurol solvent instead of volatile organic solvents to construct poly(D,L-lactide-co-glycolide microspheres may deter the issues of using volatile organic solvents. Up to now, preparation of such glycofurol spheres has previously met with limited success. We constructed dexamethasone laden poly(D,L-lactide-co-glycolide microspheres utilizing glycofurol as the solvent within a modified phase inversion methodology. These prepared microspheres have a higher drug load and a lower rate of water diffusion. This prolongs drug release compared to dichloromethane constructed spheres. The glycofurol-generated spheres are also not toxic to target cells as is the case for dichloromethane-constructed spheres. Further, glycofurol-constructed spheres do not denature the dexamethasone molecule and have kinetics of drug release that are more clinically advantageous, including a lower drug burst and a prolonged drug release.

Phosphorus-Containing Polymer Electrolytes for Li Batteries

Lithium-ion polymer batteries, also known as lithium-polymer, abbreviated Li-po, are one of the main research topics nowadays in the field of energy storage. This review focuses on the use of the phosphorus containing compounds in Li-po batteries, such as polyphosphonates and polyphosphazenes. Li-po batteries are mini-devices, capable of providing power for any portable gadget. From a constructive point of view, Li-po batteries contain an anode (carbon), a cathode (metal oxide), and a polymer electrolyte, which could be liquid electrolytes or solid electrolytes. In general, a divider is used to keep the anode and cathode from touching each other directly. Since liquid electrolytes have a generally high ionic conductivity, they are frequently employed in Li-ion batteries. In the last decade, the research in this field has also focused on solving safety issues, such as the leakage of electrolytes and risk of ignition due to volatile and flammable organic solvents. The research topics in the field of Li-po remain focused on solving safety problems and improving performance.

Keto-Adamantane-Based Macrocycle Crystalline Supramolecular Assemblies Showing Selective Vapochromism to Tetrahydrofuran

Here, we report the synthesis of adamantane-based macrocycle 2 by combining adamantane building blocks with π-donor 1,3-dimethoxy-benzene units. An unpredictable keto-adamantane-based macrocycle 3 was obtained by the oxidation of 2 using DDQ as an oxidant. Moreover, a new type of macrocyclic molecule-based CT cocrystal was prepared through exo-wall CT interactions between 3 and DDQ. The cocrystal material showed selective vapochromism behavior towards THF, specifically, among nine volatile organic solvents commonly used in the laboratory. Powder X-ray diffraction; UV-Vis diffuse reflectance spectroscopy; 1H NMR; and single crystal X-ray diffraction analyses revealed that color changes are attributed to the vapor-triggered decomplexation of cocrystals.

Solvent- and Catalyst-Free Synthesis of gem-Difluorinated and Polyfluoroarylated Compounds with Nucleophilic or Electrophilic Fluorine-Containing Reaction Partners, Respectively

A novel, efficient and environmentally friendly solvent-free and catalyst-free approach for the synthesis of structurally diverse gem-difluorinated and polyfluoroarylated derivatives with readily available nucleophilic and electrophilic fluorine-containing reaction partners, difluoroenoxysilane and pentafluorobenzaldehyde, is described. This neat protocol is induced by the direct hydrogen-bond interactions between fluorinated and non-fluorinated reactants without the use of heavy metal catalysts or volatile organic solvents and with no need for column chromatographic separation for most cases.

Full bio-based phenalkamine prepared by one-pot process used for preparing solvent-free protective coating

The utilization and conversion of renewable biomass is a promising strategy to attain sustainable society. Herein, full bio-based phenalkamine (FBA) was prepared using three bio-based raw materials, which were cardanol, furfural and 1,5-pentanediamine, by one-pot process based on Mannich reaction without catalyst and solvent. Then, FBA was used to cure epoxy under the condition of solvent-free, which can eliminate the negative effect of volatile organic solvents (VOCs). Attributed to the long chain, large steric hindrance and strong hydrophobicity of FBA, solvent-free FBA/epoxy coating had appropriate curing speed, non-defects morphologies, high flexibility (impact resistance height: 100 cm, bending resistant shaft diameter: 2 mm), low water absorption (0.65 wt%), and long-term protective performance (|Z|0.01Hz = 1.23 × 109 Ω·cm2 after 100 d immersion under harsh environment). Compared with partial bio-based phenalkamine (MD1041)/epoxy coating and petroleum-based phenalkamine (T31)/epoxy coating, FBA/epoxy coating had satisfactory underwater-cured protective properties (|Z|0.01Hz>106 Ω·cm2 after directly cured and immersed for 100 d in 5 wt% NaCl solution) based on the strong hydrophobicity and dense crosslink networks. Notably, FBA/epoxy coating had improved performance compared with purified FBA (PFBA)/epoxy coating, which was related to the high crosslink density coming from the residual 1,5-pentanediamine. This work provided some enlightenment to prepare solvent-free coating using full bio-based materials.

Potential of Deep Eutectic Solvents in the Extraction of Organic Compounds from Food Industry By-Products and Agro-Industrial Waste

Global food waste has a huge impact on the environment, as it is a source of greenhouse gas emissions and wasted natural resources. Across the world, over 30% of food is lost or wasted each year. Aside from this, the food industry, as well, is one of the biggest sources of agro-industrial waste and by-products, which can be valorized and used for different purposes. Such waste is a good source of bioactive organic compounds that can be extracted without altering their properties, where deep eutectic solvents can serve as green solvents and as an excellent replacement for volatile organic solvents. Isolated compounds can be used in innovative food production, chemical production, cosmetics and other industries. Deep eutectic solvents have attracted extraordinary attention due to their advantages such as environmental friendliness, availability and easy preparation, easy handling and utilization of non-toxic components for their formation. Due to these properties, they are a greener alternative to classic organic solvents for many processes, including extractions. In this paper, we review the utilization of deep eutectic solvents as potential green media for the extraction of organic compounds such as polyphenols, carbohydrates, proteins and alkaloids from by-products of the food industry and from agro-industrial waste.

Progress in waterborne polymer dispersions for coating applications: commercialized systems and new trends

Modern polymer coatings are shifting away from dispersion in volatile organic solvents towards waterborne, minimizing harmful environmental emissions.

Rheological and radioactive decontamination properties of ethyl cellulose sols in green solvents at a temperature below 0 °C.

Strippable film decontamination has been considered one of the best prospects for radioactive surface decontamination due to its high decontamination effect and less secondary pollution. However, research into strippable films has until now focused on radioactive decontamination at room temperature. Therefore, it is vital to seek a suitable degradable material for preparing strippable films in removing contaminants in an extremely cold region, as it will face the problem of the freezing of the detergent. Ethyl cellulose (EC) is a kind of degradable biopolymer which is easily dissolved in volatile green organic solvents to form a sol below 0 °C which is advantageous for forming a film. Therefore, it would be the best choice for preparing a strippable film detergent. In this study, EC sols were obtained by placing EC powder into the green solvents anhydrous ethanol and ethyl acetate. The steady and dynamic rheological behavior of EC sols was investigated with a rotary rheometer with the temperature ranging from -10 °C to 0 °C to disclose their spraying performance. Moreover, the radioactive decontamination effect of EC sols and the mechanism were also investigated. The results showed that the EC sols were pseudoplastic fluids which obeyed the Ostwald-de Waele power law below 0 °C. Furthermore, the viscosity of EC sols could be reduced by stirring, which is convenient for large-area spraying during decontamination below 0 °C. At -10 °C, the comprehensive decontamination rates of all plates were over 85%. Therefore, EC sols could be used as a basic material for strippable film decontamination below 0 °C.

Green synthesis and antitumor activity of (E)-diethyl 2-styrylquinoline-3,4-dicarboxylates.

In this work, a green, efficient and catalyst-free synthesis of a series of structurally novel (E)-diethyl 2-styrylquinoline-3,4-dicarboxylates via a direct olefination reaction between diethyl 2-methylquinoline-3,4-dicarboxylate and various aromatic aldehydes was successfully accomplished by employing eco-friendly 1,3-dimethylurea/l-(+)-tartaric acid (DMU/LTA) as an inexpensive, non-toxic and reusable reaction medium. This methodology has the attractive advantages of mild reaction conditions, simple experimental operation, and the absence of any dangerous catalysts or unsafe volatile organic solvents, with satisfactory to good yields. Subsequently, a primary in vitro evaluation for their anti-proliferative activity against human cancer cell lines A549, HT29 and T24 revealed that the compound with the 3,4,5-trimethoxystyryl moiety exhibited potent anti-tumor activity with IC50 values of 2.38, 4.52 and 9.86 μmol L-1, respectively, thereby being equipotent or even better than the reference cisplatin.

Multifaceted properties of an engineered three-dimensional Zn(ii)–metal–organic coordination polymer: synthesis, crystal structure, efficient photocatalytic degradation of an organic dye and selective luminescent sensing

Luminescent sensing of volatile organic solvents (VOCs), anions, cations, etc., and photocatalysts for aromatic dyes are two of the many emerging applications for metal-organic frameworks and coordination polymers (MOFs/CPs).

Comparison of the effectiveness of two piperazine based nano-catalysts in the synthesis of benzoxazoles and benzimidazoles and use of the powerful one in the N-Boc protection of amines.

In this work, a comparison between the catalytic activity of two piperazine based ionic liquids immobilized on ZnO NPs and SiO2 NPs is presented in the synthesis of benzoxazoles and benzimidazoles. These reactions are performed under solvent free conditions during appropriate reaction times with high yields. The catalyst obtained from ZnO-NPs (PINZS), as the more efficient one, is used for the efficient promotion of the N-Boc protection of amines. High chemoselectivity, no by-products, facile separation of the catalyst, short reaction times and no need for volatile organic solvents are the best features of the proposed methods.

Addition of allyl Grignard to nitriles in air and at room temperature: experimental and computational mechanistic insights in pH-switchable synthesis.

A straightforward and selective conversion of nitriles into highly substituted tetrahydropyridines, aminoketones or enamines by using allylmagnesium bromide as an addition partner (under neat conditions) and subsequent treatment with different aqueous-based hydrolysis protocols is reported. Refuting the conventional wisdom of the incompatibility of Grignard reagents with air and moisture, we herein report that the presence of water allows us to promote the chemoselective formation of the target tetrahydropyridines over other competing products (even in the case of highly challenging aliphatic nitriles). Moreover, the careful tuning of both the reaction media employed (acid or basic aqueous solutions for the hydrolysis protocol) and the electronic properties of the starting nitriles allowed us to design a multi-task system capable of producing either β-aminoketones or enamines in a totally selective manner. Importantly, and for the first time in the chemistry of main-group polar organometallic reagents in non-conventional protic solvents (e.g., water), both experimental and computational studies showed that the excellent efficiency and selectivity observed in aqueous media cannot be replicated by using standard dry volatile organic solvents (VOCs) under inert atmosphere conditions.

Label-Free Detection of Unbound Bilirubin and Nitrophenol Explosives in Water by a Mechanosynthesized Dual Functional Zinc Complex: Recognition of Picric Acid in Various Common Organic Media.

High levels of unconjugated bilirubin (UB) in serum lead to asymptomatic and neonatal jaundice and brain dysfunctions. Herein, we have reported the detection of UB at as low as 1 μM in an aqueous alkaline medium using a Zn(II) complex. The specificity of the complex has been validated by the HPLC in the concentration window 6-90 μM, which is rare. The sensory response of the probe at physiological pH against nitro explosives developed it as an instant-acting fluorosensor for picric acid (PA) and 2,4-dinitrophenol (2,4-DNP). Spectroscopic titration provided a binding constant of 4×105 M-1 with PA. The naked eye detection was found to be 15 μM. The solid-state photoluminescent nature of the complex enabled it for PA sensing in the solid phase. Interestingly, the probe remained fluorescent in various volatile and non-volatile organic solvents. As a result, it can also detect PA and 2,4-DNP in a wide range of common organic media. NMR studies revealed the coordination of PA, 2,4-DNP, and UB to the Zn(II) center of the probe, which is responsible for the observed quenching of the probe with the analytes.

Kinetics of Charge Transfer at Carbon-Based Counter Electrodes for Dye-Sensitized Solar Cells with Aqueous Electrolytes

Dye-sensitized solar cells (DSSCs) might provide a highly sustainable alternative for next generation photovoltaics. This is due to their low-energy production from abundant materials, short energy payback time, high efficiency under low illumination intensities (i.e., diffuse light or indoor conditions), and versatile concepts of applications. However, some commonly used electrolyte components are environmentally problematic. Acetonitrile or other volatile organic solvents, e.g., as well as carcinogenic cobalt complexes should not leak from DSSCs. Sealing foils, however, which are typically used to prevent such leakage, carry a risk of long-term failure.Replacing the organic solvent by water offers several advantages, as it is environmentally benign, less volatile and the cell function, further, cannot be damaged by the intrusion of water vapor. Instead of Co-complexes, e.g., the stable organic radical TEMPO (2,2,6,6-tretramethylpiperidine-1-oxyl) can serve as an alternative redox mediator with a highly positive redox potential (0.71 V vs. NHE). Using TEMPO, power conversion efficiencies (PCE) of up to 4.3% and high open-circuit voltages (V oc = 0.955 V) have been reported.[1] However, the use of TEMPO is limited by its solubility in water (C max < 0.15 M). Its derivative 4-hydroxy-TEMPO (OH-TEMPO) possesses a significantly higher solubility in water (C max > 2 M) and a more positive redox potential (0.81 V vs. NHE), making it a promising candidate as a redox mediator.In this work, we built DSSCs with TEMPO and OH-TEMPO based aqueous electrolytes, Y123-sensitized TiO2 photoanodes, and counter electrodes coated with poly(3,4-ethylenedioxythiphene) (PEDOT). For OH-TEMPO, the short-circuit current density (j sc) and open-circuit voltage were higher than with TEMPO, but the fill factor (FF) and the PCE were significantly lower. By impedance studies, large charge transfer resistances at the counter electrode (R CE) were obtained for OH-TEMPO in combination with additives such as 1-methylbenzimidazole (MBI), indicating a strong kinetic limitation of the OH-TEMPO+ reduction. However, we found that such additives as MBI or other organic compounds, are necessary to suppress recombination at the photoanode/electrolyte interface. Thus, we subsequently studied different counter electrode materials, such as platinum (reference), conducting polymers, and carbon materials, in contact to OH-TEMPO electrolytes with MBI to determine R CE and find suitable materials for the application in DSSCs.[1] Yang, W., Söderberg, M., Eriksson, A. I. K. & Boschloo, G. Efficient aqueous dye-sensitized solar cell electrolytes based on a TEMPO/TEMPO+ redox couple. RSC Advances 5, 26706–26709 (2015).

An Overview on Polymer-Based Electrolytes with High Ionic Mobility for Safe Operation of Solid-State Batteries

Liquid electrolytes used in commercial Li-ion batteries are generally based on toxic volatile and flammable organic carbonate solvents, thus raising safety concerns in case of thermal runaway. The most striking solution at present is to switch on all solid-state designs exploiting polymer materials, films, ceramics, low-volatile, green additives, etc. The replacement of liquids component with low-flammable solids is expected to improve the safety level of the device intrinsically. Moreover, a solid-state configuration is expected to guarantee improved energy density systems. However, low ionic conductivity, low cation transport properties and issues in cell manufacturing processes must be overcome [1].Electrochemical performance in lab-scale devices can be readily improved using different RTILs or specific low-volatile additives. Here, an overview is offered of the recent developments in our labs on innovative polymer-based electrolytes allowing high ionic mobility, particularly attractive for safe, high-performing, solid-state Li-metal batteries, and obtained by different techniques, including solvent-free UV-induced photopolymerization. Cyclic voltammetry and galvanostatic charge/discharge cycling coupled with electrochemical impedance spectroscopy exploiting different electrode materials (e.g., LFP, Li-rich NMC, LNMO, Si/C) demonstrate specific capacities approaching theoretical values even at high C-rates and stable operation for hundreds of cycles at ambient temperature [2,3]. Direct polymerization procedures on top of the electrode films are also used to obtain an intimate electrode/electrolyte interface and full active material utilization in both half and full-cell architectures. In addition, results of composite hybrid polymer electrolytes [4] and new single-ion conducting polymers [5] are shown, specifically developed to attain improved ion transport and high oxidation stability for safe operation with high voltage electrodes even at ambient conditions.