Water-soluble Ionic Liquids Research Articles

Green extraction of chitin from hard spider crab shells

A green protocol to extract chitin from crab shells using water soluble ionic liquids (ILs) is here reported. Compared to conventional multistep acid-base extraction methods, this one-pot procedure achieves pulping of recalcitrant crustacean waste shells by employing ammonium acetate, ammonium formate and hydroxylammonium acetate as water-soluble, low-cost and easy to prepare ILs. An extensive parametric analysis of the pulping process has been carried out with different ILs, different ratios, temperature and time. The optimized protocol provides a high-quality chitin comparable, if not better, to commercial chitin. The best results were obtained at 150 °C with ammonium formate prepared in-situ from aqueous ammonia and formic acid: chitin was isolated in a 17 wt% yield (based on dried crab shells as starting biowaste), a degree of acetylation (DA) > 94 %, a crystallinity index of 39–46 %, a molecular weight up to 6.6 × 105 g/mol and a polydispersity of ca 2.0.

Compartmentalization into Outer and Inner Shells of Hollow Nanospheres for Antibiosis Based on Chemistry and Physical Damages.

There is a substantially ascending demand for nonantibiotic strategies to overcome the resistance of bacterial infections. Here, the discovery of a distinctive antibacterial structure is reported. The novel structure of nanoparticle strategy is proposed for appreciable bacteria killing by the smart design of the delayed addition of crosslinkers into the reaction mixture. [2-(methacryloyloxy)ethyl]trimethylammonium chloride solution (MTCl), a water-soluble ionic liquid (IL), has narrow-size material distribution, good whiteness, and high weather resistance. The quaternary ammonium salt is utilized to efficiently permeate cell membranes through electrostatic interaction, accordingly, boasting a beneficiary of antibacterial properties. More importantly, it allows bacteria to attach the nanomaterials easily, especially the double-shelled nanosphere. In light of the introduction of 9-amino(9-deoxy)ep-quinine (QNNH2) on its inner shell, it blocks the nucleic acid and glucose metabolism in bacteria, which is betterment of the antibacterial activity of double-shelled structure nanoparticle compared to other structure of nanomaterials. This physical/chemical/biological triple antibacterial process eliminates the need for traditional antibiotics, and the fabrication strategies and material properties described here provide insights into the design of antibacterial nanomaterials based on chemical and physical effects.

Tribological performance of fatty acid ammonium ionic liquids as anti-wear additives in water-based fluids

In this study, we synthesized eight water-soluble ionic liquids (ILs) and investigated their tribological performance as additives in water-diethylene glycol (WDG) base fluids. The results of the tribological test suggested that these ILs additives demonstrate promising capabilities in friction reduction and anti-wear for water lubricated contacts. The ILs with the longest carboxylic chain length, namely C10MIPA and C10DIPA in this work, displayed superior tribological performances. Observations on the abraded surfaces showed that the IL forms a monolayer adsorption through self-assembly, and upon rubbing it creates a continuous and stable tribo-film with an uneven thickness of 30–60 nm through tribo-chemical reactions. The tribo-film mainly consists of iron oxides. The proposed lubrication mechanisms include adsorbed film and formed tribo-films, which work effectively to reduce the shear stress and thus sliding friction.

Skin-Friendly Flexible Ultraviolet Detectors Based on Reversibly Deformable Worm-Like Polymer Nanoparticles.

Flexible ultraviolet (UV) light detection technology has important applications in wearable devices, smart sensors, and other fields and attracts much attention in recent years. However, for most semiconductor-based UV detectors, the elastic modulus between rigid semiconductors and flexible substrates is mismatched, which makes it difficult to fabricate UV detectors that meet the needs of wearable devices. Herein, a fully flexible, large-scale, skin-friendly UV photodetector component centered on photo-responsive worm-like polymer nanoparticles (NPs) is developed, and the resulting device can quantitatively detect UV illumination. Skin-friendly poly(vinyl alcohol) (PVA), amphiphilic azobenzene-containing polymer NPs (AzNPs), and water-soluble ionic liquids (IL) are formed into (AzNPs-IL)/PVA fabrics by electrospinning. There are interactions such as hydrogen bonding among PVA, AzNPs, and IL, which make the material system stable. The UV detector made of the fabric realizes UV sensing through the illuminance-mechanical stress-electrical signal conversion mechanism. It is capable of achieving a response time of 9 s, a detection range of 10-150mW cm-2 , and stability for 1000 cycle tests upon 365nm UV irradiation. Moreover, it has good skin affinity, and the water contact angle of the fabric is only 23.57°, which holds great promise for wearable smart devices.

Pullulan-1-Ethyl-3-Methylimidazolium Tetrafluoroborate Composite as a Water-Soluble Active Component of a Vibration Sensor.

In recent years, the issue of electronic waste production has gained significant attention. To mitigate the environmental impact of e-waste, one approach under consideration involves the development of biodegradable electronic devices or devices that dissolve in the environment at the end of their life cycle. This study presents results related to the creation of a sensor that effectively addresses both criteria. The device was constructed using a composite material formed by impregnating a pullulan membrane (a biodegradable water-soluble biopolymer) with 1-Ethyl-3-Methylimidazolium tetrafluoroborate (a water-soluble ionic liquid) and coating the product with a conductive silver-based varnish. Capitalizing on the piezoionic effect, the device has demonstrated functionality as a vibration sensor with a sensitivity of approximately 5.5 × 10-5 V/mm and a resolution of about 1 mm. The novelty of this study lies in the unique combination of materials. Unlike the use of piezoelectric materials, this combination allows for the production of a device that does not require an external potential difference generator to function properly as a sensor. Furthermore, the combination of a biopolymer, such as pullulan, and an ionic liquid, both readily soluble in water, in creating an active electronic component represents an innovation in the field of vibration sensors.

Synthesis of water soluble ionic liquid copolymers based on acrylamide and investigation of their properties in flocculating of clay suspensions

To overcome water absorption and swelling by clay mineral layers, it is very important to develop stabilizing additives for water-based drilling fluids, where organic polymers are used as raw materials. Acrylamide copolymers, acting as flocculating agents, have the potential to separate minerals such as montmorillonite. In this study, three water-soluble copolymers containing acrylamide-amphoter, acrylamide-amphoter-anion, and acrylamide-amphoter-cation were synthesized and characterized using various analytical techniques, including Fourier-transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, and derivative thermal gravimetric techniques. These copolymers were employed as flocculants to treat water suspensions containing montmorillonite particles, and a range of analytical methods, such as sedimentation volume measurement, scanning electron microscopy analysis, X-ray diffraction analysis, and contact angle measurement, were employed to identify the relationship between inhibitive performance. The flocculation of montmorillonite plates was attributed to the electrostatic attractions between montmorillonite and the synthesized copolymers. High molecular weight copolymers offer greater thermal stability and better flocculation characteristics for water-based drilling fluids. Among the tested copolymers, the acrylamide-amphoter-anion sample, with the highest molecular weight, exhibited the best performance as a coagulant when compared to the other copolymers.

Ionic liquid additive enabling anti-freezing aqueous electrolyte and dendrite-free Zn metal electrode with organic/inorganic hybrid solid electrolyte interphase layer

• [BMIM]OTF ionic liquid is used as the electrolyte additive for zinc-ion batteries. • The modified electrolyte can offer very large ionic conductivity at –40°C. • The [BMIM]OTF enables the formation of an organic/inorganic hybrid SEI layer. • The Zn deposition process is homogenized and parasitic side reactions are inhibited. • The full battery with [BMIM]OTF exhibits excellent performances even at −30°C. Benefiting from intrinsic safety, low cost, and competitive energy density, aqueous zinc-ion batteries (AZIBs) have attracted tremendous research interest, whereas suffering from low stability of Zn metal anode in aqueous electrolytes. Herein, 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]OTF), a water-soluble ionic liquid with very low melting point, is used as the electrolyte additive. The addition of [BMIM]OTF only slightly influences the ionic conductivity of 3 M Zn(OTF) 2 aqueous electrolyte at room temperature, while considerably improving the tolerance to low temperatures. This additive is also found to be preferentially adsorbed on the Zn electrode, tune the solvation sheath of hydrated Zn 2+ ions, reduce the corrosion activity of Zn electrode, and enable the formation of an organic/inorganic hybrid solid electrolyte interphase (SEI) layer. Such SEI layer is zincophilic and hydrophobic, thereby decreasing the nucleation overpotential of Zn plating, enhancing the interfacial charge transfer kinetics, homogenizing the Zn deposition behavior, and inhibiting parasitic side reactions. With the [BMIM]OTF-modified electrolyte, the Zn//Zn symmetric cell offers good cyclability even under extremely large areal capacity of 25 mAh cm −2 . And the assembled AZIB with an Al-vanadate cathode material exhibits excellent performances even at −30°C. This work provides new insights into stabilizing aqueous batteries.

Polyzwitterionic double-network ionogel electrolytes for supercapacitors with cryogenic-effective stability

Although hydrogel electrolytes have been widely used in the field of energy storage devices, additional conductive fillers with mismatched structural characteristics will inevitably reduce their both mechanical and electrochemical properties. How to achieve high ionic conductivity together with good mechanical strength is still a challenge. Herein, a high strength double-network polyzwitterionic electrolyte is designed by introducing water-soluble ionic liquids (EMIM-BF4) into a zwitterionic hydrogel through the superfast solvent exchange. The resulting polyzwitterionic electrolytes are superior to traditional polyzwitterionic hydrogels or polyvinyl alcohol (PVA) hydrogels with respect to their better tensile strength (1.9 MPa), higher ionic conductivity (7.24 mS/cm), and wider temperature adaptability (−60 to 50 °C). More importantly, the optimized symmetric assembled supercapacitor delivers high areal capacitance of 227.7 mF/cm2 at 0.5 mA/cm2, excellent rate capability, and high energy/power densities, greatly surpassing the performances of the system without polyzwitterions. It could be anticipated that the performance of this novel polyzwitterionic electrolyte-based supercapacitors will be further greatly improved with better structural electrodes. Moreover, we also implanted designed energy-storage systems to the subcutaneous tissue of the experimental rats and exhibited potential “on–off” variation of fault indicator LED. This work provides an effective method for the development of robust supercapacitors suitable for harsh environments, showing a great potential for real wearable and implanted applications in some extreme circumstances.

Water-soluble ionic liquid as a fluorescent probe towards distinct binding and detection of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol in aqueous medium

Owing to the escalating threat of criminal activities and pollution aroused by 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP), development of a proficient sensor for the detection of these explosives is highly demanded. Herein, a water-soluble ionic liquid-tagged fluorescent probe, 1-ethyl-3-(3-formyl-4-hydroxybenzyl)-1H-benzimidazol-3-ium chloride (EB-IL) has been designed and synthesized for the detection of TNT and TNP in 100% aqueous medium. The EB-IL fluorescent probe displayed strong cyan-blue fluorescence at 500 nm which gets quenched upon the addition of TNT/TNP over other concomitant nitro-compounds. The distinct binding response of EB-IL towards TNT could be due to the formation of hydrogen bonding between the acidic proton of benzimidazolium (C2–H) and nitro group of TNT. Meanwhile, the selective binding of TNP with EB-IL could be due to the exchange of counter Cl− anion of EB-IL with picrate anion. The fluorescence quenching of EB-IL by TNT could be attributed to the resonance energy transfer (RET) and that of TNP is ascribed to the anion-exchange process. The developed sensor is extremely selective and sensitive towards TNT and TNP with high quenching constants of 1.94 × 105 M−1 and 2.32 × 106 M−1 and shows a lower detection limit of 159 nM and 282 nM, respectively.

A highly-effective ionic liquid flame retardant towards fire-safety waterborne polyurethane (WPU) with excellent comprehensive performance

The flame-retardant waterborne polyurethane (WPU) has attracted more and more attentions from academia and industry. However, the addition of conventional flame retardants into WPU will damage the emulsion stability and introduce the potential further risk to demulsification and preparation failure. In this work, a novel flame-retardant approach is proposed, demonstrating outstanding efficiency, excellent compatibility and minimized side effect. A water-soluble ionic liquid 1-methyl-3-((6-oxidodibenzo[c,e] (Akindoyo et al., 2016; Chattopadhyay and Raju, 2007) [1,2]oxaphosphinin-6-yl)methyl)-1-H-imidazol-3-ium-4-methylbenzenesulfonate ([Dmim]Tos) is applied as the additive flame retardant for the WPU dispersions. The resulting WPUs (WPU/[Dmim]Toses) display excellent flame retardancy via a low loading content (max 6.0 wt%) and potential adhesion applicable to industries, while maintaining the major comprehensive performance, including storage stability, mechanical property, thermal stability, transparency, hydrophobicity, etc. Effort from this work, besides of overcoming the explicit drawback, also serves as reference of novel methodologies to solve the compatibility issue between additive agents and WPU.

Concentrating water-soluble ionic liquids from aqueous solutions: Osmotic distillation with hydrophobic membranes

Ionic liquids (ILs) show a wide range of applications as “green” solvents in the new era and the recovery of water-soluble ILs has become an urgent issue. Herein, for the first time, osmotic distillation is applied to concentrate and recover water-soluble ILs with a series of hydrophobic membranes. Poly(vinylidene fluoride) membrane with vertically oriented pores and stainless steel mesh were hydrophobically modified and then compared with commercial membranes to demonstrate the influence of different pore structures on the osmotic distillation concentration process. With the vapor pressure difference between two sides of the membrane being the driving force, the dilute aqueous solutions of ILs can be concentrated to about 84 wt% after 24 h with a water flux of 7.8 kg m−2 h−1. It is also able to achieve ultra-high rejections to ILs and MgCl2 (>99.99%) by this osmotic distillation process. Although there exists a limitation for dewatering the ILs solutions with very high concentrations and thus the final ILs purity cannot reach 100%, this method is promising for practical applications benefiting from its high rejection to ions, easy operability at ambient temperature and remarkable universality in terms of hydrophobic membranes used.

Osmotic pressure as driving force for recovering ionic liquids from aqueous solutions

An emerging challenge occurs for recovering ionic liquids (ILs) because of their exponential growth in academic and industrial applications. We report for the first time to reclaim water-soluble ILs from their aqueous solutions by osmotically driving water to spontaneously permeate through semi-permeable membranes. Theoretical simulation indicates a weak hydrability of ILs and a tendency to form micelles in water. We thus demonstrate a significant difference in osmotic pressures between the aqueous solutions of ILs and inorganic salts. Four categories of broadly representative ILs are continuously recovered from their diluent aqueous solutions (~1 wt%) with semi-permeable membranes. Eventually, a record-high concentration up to 58–78 wt% is achieved in this work. Our strategy integrates superiorities of low energy consumption, universal applicability toward ILs, diversified selection of semi-permeable membranes, almost unattenuated water flux and high rejection to ions, hopefully providing new insights into the authentic “green” industrial applications of ILs.

Synthesis of new water-soluble ionic liquids and their antibacterial profile against gram-positive and gram-negative bacteria

A series of imidazolium bromide salts (NIM-Br 1a, 1b and 1c) bearing different lengths of alkyl chains were synthesized and theirin vitro antibacterial activities were determined by measuring the minimum inhibitory concentration (MIC) values for Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. In addition, these imidazolium derivatives were also evaluated against biofilm produced by these bacterial strains. All compounds were found to be effective against Gram-positive and Gram-negative bacteria, and also more effective on the S. aureus biofilm production than the others.

Viscoelastic Properties of Polyelectrolyte Multilayers Swollen with Ionic Liquid Solutions.

Polyelectrolyte multilayers (PEM) obtained by layer-by-layer assembly can be doped with ionic liquid (IL) via the swelling of the films with IL solutions. In order to examine the mechanical properties of IL-containing PEM, we implement a Kelvin-Voigt model to obtain thickness, viscosity and elastic modulus from the frequency and dissipation shifts determined by a dissipative quartz crystal microbalance (QCM-D). We analyze the changes in the modeled thickness and viscoelasticity of PEI(PSS/PADMAC)4PSS and PEI(PSS/PAH)4PSS multilayers upon swelling by increasing the concentration of either 1-Ethyl-3-methylimidazolium chloride or 1-Hexyl-3-methylimidazolium chloride, which are water soluble ILs. The results show that the thickness of the multilayers changes monotonically up to a certain IL concentration, whereas the viscosity and elasticity change in a non-monotonic fashion with an increasing IL concentration. The changes in the modeled parameters can be divided into three concentration regimes of IL, a behavior specific to ILs (organic salts), which does not occur with swelling by simple inorganic salts such as NaCl. The existence of the regimes is attributed to a competition of the hydrophobic interactions of large hydrophobic ions, which enhance the layer stability at a low salt content, with the electrostatic screening, which dominates at a higher salt content and causes a film softening.

A simple method for assessing chemical toxicity of ionic liquids on Vibrio fischeri through the structure of cations with specific anions

Both water and non-water soluble ionic liquids (ILs) may be toxic where ILs soluble in water can be released into aquatic ecosystems. Toxicity of ILs can be determined as effective nominal concentration EC50 because it is important to assess the toxicity of ILs by an inhibition assay, which can evaluate the toxicological danger of ILs. A novel model is introduced for desk calculations of chemical toxicity of ILs based on Vibrio fischeri with more reliance on their answers as one could attach to the more complex outputs. It requires only specific elemental compositions of cations and anions as well as the presence of some molecular fragments in cations with particular anions. The measured values of logEC50(/μM) for 187 ILs corresponding to 250 experimental data were used to derive and test of the new model. For 153 ILs (203 datapoints), where the reported values of logEC50(/μM) as training and test sets by one of the best quantitative structure-activity relationship (QSAR) were available, the new method gives more reliable predictions. The present simple method is also tested with further 34 (47 datapoints), which confirm good forecasting reliability of the new model.

Characterization of Ionic Liquid Aqueous Two-Phase Systems: Phase Separation Behaviors and the Hydrophobicity Index between the Two Phases.

1-Allyl-3-methylimidazolium chloride [Amim][Cl] and 1-butyl-3-methylimidazolium chloride [Bmim][Cl] are water-soluble ionic liquids (ILs) that can from an aqueous two-phase system (ATPS) when mixed with specific salts. Herein, we prepared [Amim][Cl]- and [Bmim][Cl]-ATPSs by adding the salts (K2CO3, K2HPO4). To investigate the phase separation behavior of the IL-ATPSs, binodal curves were drawn at different temperatures and the length and slope of the tie lines were analyzed. The [Bmim][Cl]/K2HPO4 system underwent two-phase separation at lower temperature conditions, suggesting that the phase separation might depend on the salting-out effect in the bottom phase. Using the IL-ATPS, the distribution coefficients, Kaa, of amino acids were determined and used to characterize the hydrophobicity index (HF) between the top and bottom phases, which is a good indicator to understand the molecular partitioning behaviors in conventional ATPSs. The HF values of the IL-ATPSs were in the range 0.13-0.41 mol/kJ; these values were almost the same as the HF values reported for an ATPS composed of poly(ethylene glycol) and salt.

Tribological Investigations of Silicon Nitride Lubricated by Ionic Liquid Aqueous Solutions

Water-lubricated ceramic components are promising material combinations for tribological applications because they are wear resistant and can exhibit low coefficients of friction under different loads. The aim of the work was to show in model tribological experiments with silicon nitride that the lubricating properties of water can be improved by adding water-soluble ionic liquids (ILs). The geometry used and the experimental parameters were selected to approximately simulate a piston ring–cylinder liner contact. We found that the addition of 1% IL tributyl methyl phosphonium acetate [P4441][OAc] leads to a reduction of the maximum friction work by 58% compared to pure water lubrication and even by 96% compared to oil-lubricated steel. It was shown that suitable running-in conditions and sufficient cooling by the lubricant at an early stage are important prerequisites for achieving low friction and wear values. In addition, the chemical interaction of water and IL with silicon nitride strongly affects the tribological behavior. As increasing demands on sustainability (green tribology) become more important due to environmental aspects, this work provides important insights for the development of novel water-based lubricant systems.

Tribological properties and surface interaction of novel water-soluble ionic liquid in water-glycol

Abstract Two kinds of novel water-soluble ILs were synthesized and applied as lubricant additives in water-glycol. ILs, as the multifunctional and high efficiency additive, could drastically improve antiwear, friction-reducing and extreme pressure properties of water-glycol. SEM and EDS results indicated that the sample lubricated by PEG600MO phosphate-ammonium IL (P1) acquires higher active element content in the area with heavy wear, while that lubricated by PEG600MO phosphite-ammonium IL (P2) is relatively homogeneous on the worn surface with heavy and mild wear. L-edge XANES results showed that the tribofilm is composed of polyphosphate, and the increase of the polyphosphate chain length could improve the tribological properties. Additionally, the additive concentration, the rubbing time and the load could change the chain length of polyphosphate.

Small Size Rh Nanoparticles in Micelle Nanostructure by Ionic Liquid/CTAB for Acceptorless Dehydrogenation of Alcohols Only in Pure Water

Ultrasmall size Rh nanoparticles were synthesized and stabilized by the complex of cetyltrimethylammonium bromide and water-soluble ionic liquid molecules. The new catalytic system shows excellent catalytic activity in the oxidation of alcohols to aldehydes or ketones only in pure water through acceptorless dehydrogenation. It is atom economic, clean and green in the synthesis of aldehydes or ketones and H2 production at the same time.

Influence of an ionic liquid on rheological and filtration properties of water-based drilling fluids at high temperatures

Ionic liquids have attracted significant research interest due to their unique thermal stability. In this paper, the influence of a water-soluble ionic liquid on the rheological and filtration properties of water-based drilling fluids at high temperature is investigated. The drilling fluids are evaluated by means of rheological and filtration tests following the American Petroleum Institute (API) standards, submitted to an aging process or at high temperature. The experimental results show that the rheological behavior of water-based drilling fluids is improved and enhanced in the presence of low concentration of ionic liquid (as low as 0.05mass%) at high temperatures (even up to 240°C). Meanwhile, the high-temperature and high-pressure (HTHP) filtration volumes are reduced by as much as 52% compared with that of polymer water-based drilling fluids without ionic liquid. The study of the mechanism demonstrates that the water-soluble ionic liquid have an excellent capacity to improve the rheological and filtration properties of water-based drilling fluids at high temperatures due to the high thermal stability and cation exchange ability of the ILA.