Room Temperature Ionic Liquids Research Articles

Flow mechanisms and their influence on the properties of EGaIn-graphene-poly(ethylene) oxide composites during material extrusion-based additive manufacturing

Polymer composites featuring room temperature liquid alloy particles complimenting other conductive fillers enable unique thermal and electrical properties. Direct-ink-writing approach is an intriguing processing path for these material systems, offering high resolution microstructural and property control. This paper investigates the composition-process-property relationships for material extrusion-based additive manufacturing of EGaIn-Graphene-Poly(ethylene) Oxide composites. Particularly, the influence of composite composition, printing nozzle size and flow rate on electrical conductivity is studied through a mechanistic approach. In that, capillary rheometry and flow modeling was performed to describe the contribution of shear flow and wall slip to the ink flow and how they drive the conductivity of printed structures for various composite ink compositions and process parameters. Influence of composition on material property and process driven conductivity were separately analyzed. Results indicate that EGaIn particles hinder material property-driven baseline average conductivity at high graphene loading. Shear flow and wall slip both increase conductivity. Graphene and total active material concentration increase wall slip and decrease shear flow, leading to a net negative effect of total active material concentration on conductivity. These findings will contribute to composite and process design towards additive manufacturing of composites with as-designed properties.

Ionogel hybrid polymer electrolytes encompassing room-temperature ionic liquids for 4V-class Li-metal batteries operating at ambient temperature

ABSTRACT In this study, we prepare ionogels composed of bisphenol A ethoxylate dimethacrylate, poly(ethylene glycol) methyl ether methacrylate, lithium bis(trifluoromethanesulfonyl)imide, and 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide or 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ionic liquids via rapid, scalable, solvent-free UV-induced polymerization. The various hybrid polymer electrolyte formulations are thoroughly characterized using a comprehensive set of physico-chemical and electrochemical methods, including gel content, FTIR, rheology, DTMA, TGA, SEM, cycling voltammetry, impedance spectroscopy, and galvanostatic cycling in laboratory-scale Li-metal cells. We particularly focus on the influence of using two different ionic liquids as reaction medium on the properties of the resulting materials and their electrochemical behaviors. Our results indicate that viscosity affects the polymerization kinetics of the ionogels, which in turn might affect their thermal stability and galvanostatic cycling behavior. In the purpose of promoting overall performance of solid-state batteries, we also present the results of composite electrolytes obtained by introducing Li7La3Zr2O12 (LLZO) into ionogels and following in-situ UV-polymerisation. The addition of LLZO ceramic results in more porous solid networks, leading to enhanced charge/discharge stability at ambient temperature and higher C-rates featuring 4V-class NMC cathodes, enlightening the promising prospects of the developed materials to be successfully implemented as stable, durable, and efficient electrolytes in next-generation Li-metal cells.

Measuring the Capacitance of Carbon in Ionic Liquids: From Graphite to Graphene.

The physical electrochemistry of the carbon/ionic liquids interface underpins the processes occurring in a vast range of applications spanning electrochemical energy storage, iontronic devices, and lubrication. Elucidating the charge storage mechanisms at the carbon/electrolyte interface will lead to a better understanding of the operational principles of such systems. Herein, we probe the charge stored at the electrochemical double layer formed between model carbon systems, ranging from single-layer graphene to graphite and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI). The effect of the number of graphene layers on the overall capacitance of the interface is investigated. We demonstrate that in pure EMIM-TFSI and at moderate potential biases, the electronic properties of graphene and graphite govern the overall capacitance of the interface, while the electrolyte contribution to the latter is less significant. In mixtures of EMIM-TFSI with solvents of varying relative permittivity, the complex interplay between electrolyte ions and solvent molecules is shown to influence the charge stored at the interface, which under certain conditions overcomes the effects of relative permittivity. This work provides additional experimental insights into the continuously advancing topic of electrochemical double-layer structure at the interface between room temperature ionic liquids and carbon materials.

Stereoselective Catalytic Synthesis of Bioactive Compounds in Natural Deep Eutectic Solvents (NADESs): A Survey across the Catalytic Spectrum

Deep eutectic solvents (DESs) are a mixture of two or more components, and at a particular composition, they become liquids at room temperature. When the compounds that constitute the DESs are primary metabolites namely, amino acids, organic acids, sugars, or choline derivatives, the DESs are called natural deep eutectic solvents (NADESs). NADESs fully represent green chemistry principles. These solvents are highly welcome, as they are obtained from renewable resources, and gratifyingly are biodegradable and biocompatible. They are an alternative to room-temperature ionic liquids (RTILs). From the pharmaceutical industry’s point of view, they are highly desirable, but they unfortunately have been rarely used despite their enormous potential. In this review, we look at their impact on the asymmetric catalytic synthesis of key target molecules via metal-based catalysis, biocatalysis, and organocatalysis. In many cases, the NADESs that have been used are chiral and can even promote enantioselective reactions; this crucial and very exciting aspect is also discussed and analyzed.

New Trend of Amperometric Gas Sensors Using Atomic Gold-Decorated Platinum/Polyaniline Composites

The Amperometric Gas Sensor (AGS) uses an electrode as the transducer element which converts its signal into a current from the electrochemical reaction of analytes taking place at the electrode surface. Many attempts to improve AGS performance, such as modifying the working electrode, applying a particular gas-permeable membrane, and selecting the proper electrolyte, etc., have been reported in the scientific literature. On the other hand, in the materials community, atomic gold has gained much attention because its physicochemical properties dramatically differ from those of gold nanoparticles. This paper provides an overview of the use of atomic gold in AGSs, both in a bulky AGS and a miniaturized AGS. In the miniaturized AGS, the system must be redesigned; for example, the aqueous electrolyte commonly used in a bulky AGS cannot be used due to volatility and fluidity issues. A Room Temperature Ionic Liquid (RTIL) can be used to replace the aqueous electrolyte since it has negligible vapor pressure; thus, a thin film of RTIL can be realized in a miniaturized AGS. In this paper, we also explain the possibility of using RTIL for a miniaturized AGS by incorporating a quartz crystal microbalance sensor. Several RTILs coated onto modified electrodes used for isomeric gas measurement are presented. Based on the results, the bulky and miniaturized AGS with atomic gold exhibited a higher sensor response than the AGS without atomic gold.

Structure-Dependence and Mechanistic Insights into the Piezoelectric Effect in Ionic Liquids.

We reported recently that two imidazolium room-temperature ionic liquids (RTILs) exhibit the direct piezoelectric effect (J. Phys. Chem. Lett., 2023, 14, 2731-2735). We have subsequently investigated several other RTILs with pyrrolidinium and imidazolium cations and tetrafluoroborate and bis(trifluoromethylsulfonyl)imide anions in an effort to gain insight into the generality and mechanism of the effect. All the RTILs studied exhibit the direct piezoelectric effect, with a magnitude (d33) and threshold force that depend on the structures of both the cation and anion. The structure-dependence and existence of a threshold force for the piezoelectric effect are consistent with a pressure-induced liquid-to-crystalline solid phase transition in the RTILs, and this is consistent with experimental X-ray diffraction data.

Utilizing Room-Temperature Ionic Liquids in the Analysis of Volatile Hazardous and Noxious Substances in Marine Sediments

Utilizing Room-Temperature Ionic Liquids in the Analysis of Volatile Hazardous and Noxious Substances in Marine Sediments

Extraction of Palladium from Spent Nuclear Fuel Reprocessing Solutions

New solvent systems for selective separation of palladium from nuclear wastes represent a prospective way to reduce the total waste volume and induce this metal’s extraction. For this purpose, the potential of modern green solvent room-temperature ionic liquid was assessed with diamide-type extractants based on N-heterocycles and S-donating thiodiglicolic acid. The N-donating heterocyclic extractants demonstrate structure-dependent high selectivity toward palladium in the presence of various impurity metals (such as Zr, Cs, Sr, Mo, Ce, Fe, and Cr) from spent nuclear fuel. Palladium is extracted into the organic phase quite selectively with a separation factor greater than a thousand for all extractants. Ionic liquid media are capable of selective palladium separation from platinum group metals and synergetically increase the selectivity of the extractants.

Efficient microwave-assisted synthesis of 1-hexylpyridin-1-ium bromide: Anion exchange to acetate and fundamentals tools to probe its interaction with RuCl3

The study presents a robust and efficient method for synthesizing high-purity 1-hexylpyridin-1-ium acetate (1-HP-Ac), a room-temperature ionic liquid (RTIL), using microwave synthesis. The study also explores its interaction with ruthenium trichloride (RuCl3). Initially, we employed classical solvothermal methods to obtain 1-hexypyridin-1-ium bromide (1-HP-Br), a precursor for 1-HP-Ac. Issues related to impurity and time constraints necessitated a transition to microwave-assisted synthesis, which emerged as an eco-friendly, energy-efficient approach. Microwave synthesis proved superior by delivering shorter reaction times (30 min), higher yields, and eliminating the need for solvents or inert atmospheres. Various characterization techniques (1H NMR, 13C NMR, FTIR, TGA, and HRMS) and matching quantum mechanical NMR predictions confirmed the successful synthesis of the hexylpyridinium cation and anion exchange transforming 1-HP-Br into its acetate form. The interaction between the synthesized RTIL and RuCl3 was monitored through NMR-based titrations and molecular dynamics (MD) modeling. The study explored the effects of increasing amounts of either RTIL or RuCl3 with the critical inflection point at a 1:2 ratio of 1-HP-Ac to RuCl3 for effective interactions and potential changes in average molecular conformation. Specifically, examining Karplus J-coupling constants provided information about dihedral angles within 1-HP-Ac. The data suggested that RuCl3 has a discernible influence on these angles, particularly for aliphatic protons. With thermal stability up to 200 °C, 1-HP-Ac is a fitting candidate for high-temperature reactions. MD simulation quantifies the solvation environment created by the IL as well as elucidates interactions of 1-HP-Ac with the RuCl3 crystal structure. The insights gained from our research into 1-HP-Ac's interaction with RuCl3, combined with the efficiency of microwave-assisted synthesis, open new avenues for further studies in catalysis, material science, and related fields..

Electrochemical framework for dynamic tracking of Soil Organic Matter

Soil Health parameters serve as excellent surrogate measures towards assessing environmental quality and understanding effects of climate change mitigation via carbon sequestration. Soil Organic Matter (SOM) is a parameter that is synonymous to soil health and understanding SOM is a key metric to building and influencing good soil and agronomic practices by impacting soil aggregation and water withholding capacity. It is a vital regulator of soil nutrient cycling and uptake as well as a factor in the global carbon cycle and is hence more advantageous than just carbon monitoring. While it is understood that soil health cannot be analyzed directly, the use of an efficient indicator that can relay information about the soil physico-chemical and biological characteristics is highly desirable since it offers the ability to analyze soil information over time and build patterns in terms of geographical location.The proposed sensing system offers an in-situ electroanalytical approach to survey various electroactive substances present in the soil matrix. Utilizing this experimental framework- A mechanism of interaction between the RTIL (Room Temperature Ionic-Liquid) modified electrode and the OM functional moieties based on hydrogen bonding and pi-pi interactions captured using electrochemical impedance spectroscopy method is utilized to build a first-of-a-kind electrochemical SOM sensor.

Enhanced Water Flux of Aromatic Polyamide Membranes by Grafting Imidazolium‐Type Ionic Liquids Containing Silsesquioxane Frameworks

AbstractAn imidazolium‐type room‐temperature ionic liquid containing silsesquioxane frameworks is successfully prepared. The polar ionic liquid products are grafted onto the surface of prepared aromatic polyamide (PA) membranes to improve water flux of PA membranes. Membranes grafted with an ionic liquid exhibit a water flux of 1.89 L m−2 h−1 bar−1), 48% higher than that of pure PA membranes while the salt rejection still remains at 96%. This improvement can be attributed to the enhanced hydrophilicity of the membrane surface, as evidenced by the reduced water contact angle.

Effect of different parameters utilized for image guided endodontic root canal preparation on temperature changes: an in vitro study

BackgroundNavigated endodontics is a cutting-edge technology becoming increasingly more accessible for dental practitioners. Therefore, it is necessary to clarify the ideal technical parameters of this procedure to prevent collateral damage of the surrounding tissues. There is a limited number of studies available in published scientific literature referencing the possible collateral thermal damage due to high-speed rotary instruments used in guided endodontic drilling. The aim of our study was to investigate the different drilling parameters and their effect upon the temperature elevations measured on the outer surface of teeth during guided endodontic drilling.MethodsIn our in vitro study, 72 teeth with presumably narrow root canals were prepared using a guided endodontic approach through a 3D-printed guide. Teeth were randomly allocated into six different test groups consisting of 12 teeth each, of which, four parameters affecting temperature change were investigated: (a) access cavity preparation prior to endodontic drilling, (b) drill speed, (c) cooling, and (d) cooling fluid temperature. Temperature changes were recorded using a contact thermocouple electrode connected to a digital thermometer.ResultsThe highest temperature elevations (14.62 °C ± 0.60 at 800 rpm and 13.76 °C ± 1.24 at 1000 rpm) were recorded in the groups in which drilling was performed without prior access cavity preparation nor without a significant difference between the different drill speeds (p = 0.243). Access cavity preparation significantly decreased temperature elevations (p < 0.01) while drilling at 800 rpm (8.90 °C ± 0.50) produced significantly less heating of the root surface (p < 0.05) than drilling at 1000 rpm (10.09 °C ± 1.32). Cooling significantly decreased (p < 0.01) temperature elevations at a drill speed of 1000 rpm, and cooling liquid temperatures of 4–6 °C proved significantly (p < 0.01) more beneficial in decreasing temperature elevations (1.60 °C ± 1.17) than when compared with room temperature (21 °C) liquids (4.01 °C ± 0.22).ConclusionsBased on the results of our study, guided endodontic drilling at drill speeds not exceeding 1000 rpm following access cavity preparation, with constant cooling using a fluid cooler than room temperature, provides the best results in avoiding collateral thermal damage during navigated endodontic drilling of root canals.

Sulfur-rich MoS3 cathode for high-performance room-temperature liquid and solid-state lithium metal batteries

Sulfur-based compounds have been considered one of the most attractive cathode materials for next-generation batteries owing to their high energy density and environmental benignity. Among them, metal sulfides like MoS2 show high conductivity as well as intrinsic catalytic activity, however, the sulfur content and specific capacity are relatively low. In this article, we proposed a sulfur-rich amorphous molybdenum trisulfide‑carbon nanotubes (MoS3-CNT) cathode via in situ deposition. Benefiting from the enhanced electrical conductivity and enriched abundant reactive sites, the cathode exhibits impressive performance when assembled as liquid and solid-state lithium metal batteries at room temperature. In liquid lithium metal batteries, optimized MoS3-CNT20% cathode exhibits an impressive high specific capacity of 900.7 mAh/g in the first cycle, while the cycling stability is poor (35.4% after 50 cycles) owing to severe shuttle effect. When fabricated with polymer solid-state electrolyte, the cycling stability could be significantly improved to 85.7% after 50 cycles with an initial capacity of 314.2 mAh/g. This study provides a rational strategy for developing high-performance metal sulfide cathodes thus helping sustainable development.

Imidazole ionic liquids-based ultra-broadband metamaterial absorbers from cross-architecture design

Room temperature ionic liquids (ILs) characterized by high dielectric loss factors and conductivity emerge as promising candidates for liquid-based metamaterial absorbers (LMMAs). In this work, the IL 1-ethyl-3-methyl-imidazolium dicyanamide was employed to construct an IL-based LMMA, leveraging a cross-architecture (C-A) design paradigm. Numerical analyses reveal that the C-A ILMMA achieves an absorption efficiency exceeding 90% within the frequency range of 7.5–57.8 GHz, translating to a relative absorption bandwidth of 153%. Moreover, the symmetrical configuration of the C-A ILMMA ensures its robust performance across a comprehensive range of polarization angles (0° to 90°), thereby underscoring its polarization insensitivity. Even with an increased incident angle of 60°, the C-A ILMMA sustains an absorption rate above 85% within the frequency intervals of 9.0–13.3 GHz and 24.7–60.0 GHz, highlighting its broad incident angle absorption capability. Owing to the superior thermal stability of the IL, the C-A ILMMA consistently maintains an absorption rate of over 90% across a temperature gradient from 20 °C to 100 °C. Mechanistic investigations reveal that the optimal absorption of the C-A ILMMA predominantly stems from dielectric polarization loss and the ionic current induced within the ILs. Subsequent experimental evaluations corroborate that the C-A ILMMA exhibits an absorptivity in excess of 90% over an ultra-broadband frequency spanning 10–40 GHz, aligning closely with numerical predictions. This IL-based C-A ILMMA not only augments the absorption bandwidth substantially but also enhances the adaptability of ILMMA in more rigorous environments, attributed to the commendable physicochemical properties of ILs.

Impact of Surface Chemistry on Emulsion-Electrode Interactions and Electron-Transfer Kinetics in the Single-Entity Electrochemistry.

Single-entity electrochemistry (SEE) provides powerful means to track a single particle, single cell, and even single molecule from the nano to microscale. The electrode serves as not only the detector of collision but also the surface supplier in SEE, and the fundamental understanding of the electrode surface chemistry on the dynamic particle-electrode interactions and electrochemical responses of a single particle still remains unexplored, particularly for soft particles. Herein, dynamic interactions of microemulsions and the interaction-controlled electron-transfer (ET) kinetics are studied employing SEE and fluorescence spectroscopy. The o/w-type nitrobenzene emulsions were prepared with the surfactant-type room temperature ionic liquids (RTILs). Biased the electrode potential for the reduction of 7,7,8,8-tetracyanoquinodimethane within emulsions, it is surprising to see the distinct collision current signals on the carbon fiber ultramicroelectrode (C UME) and Au ultramicroelectrode (Au UME) in the late stage of chronoamperometric measurements. Theoretical understanding was made to determine the ET kinetics behind the disparate current signals. It is believed that the electrode surface chemistry, i.e., the surface energy, has a great influence on the dynamic emulsion-electrode interactions and ET kinetics. On the hydrophilic surface of Au UME, emulsions tend to decompose/detach from the electrode surface immediately after colliding. In contrast, on the lipophilic surface of C UME with lower surface energy, a layer of oil phase accumulated by the coalescence of emulsions and the migration of the precedent colliding emulsions, which would serve as a barrier to block ET via tunneling as manifested by the gradual slowdown of ET rate and the reduced collision frequency in the late stage of measurement. The impacts of the emulsion size and amphiphilicity of RTILs on the C UME-emulsion interactions and ET kinetics were also investigated.

Machine learning-driven investigation of the structure and dynamics of the BMIM-BF4 room temperature ionic liquid.

Room-temperature ionic liquids are an exciting group of materials with the potential to revolutionize energy storage. Due to their chemical structure and means of interaction, they are challenging to study computationally. Classical descriptions of their inter- and intra-molecular interactions require time intensive parametrization of force-fields which is prone to assumptions. While ab initio molecular dynamics approaches can capture all necessary interactions, they are too slow to achieve the time and length scales required. In this work, we take a step towards addressing these challenges by applying state-of-the-art machine-learned potentials to the simulation of 1-butyl-3-methylimidazolium tetrafluoroborate. We demonstrate a learning-on-the-fly procedure to train machine-learned potentials from single-point density functional theory calculations before performing production molecular dynamics simulations. Obtained structural and dynamical properties are in good agreement with computational and experimental references. Furthermore, our results show that hybrid machine-learned potentials can contribute to an improved prediction accuracy by mitigating the inherent shortsightedness of the models. Given that room-temperature ionic liquids necessitate long simulations to address their slow dynamics, achieving an optimal balance between accuracy and computational cost becomes imperative. To facilitate further investigation of these materials, we have made our IPSuite-based training and simulation workflow publicly accessible, enabling easy replication or adaptation to similar systems.

Evaluating the contributions to conductivity in room temperature ionic liquids.

The conductivity of room temperature ionic liquids is not described adequately by the Nernst-Einstein equation, which accounts only for Brownian motion of the ions. We report on the conductivity of the ionic liquid 1-butyl-3-methylimidazolum bis(trifluoromethylsulfonyl) imide (BMIM TFSI), comparing the known conductivity of this RTIL to the diffusion constants of the cationic and anionic species over a range of length scales, using time-resolved fluorescence depolarization and fluorescence recovery after photobleaching (FRAP) measurements of chromophores in the RTIL. Our data demonstrate that the diffusional contribution to molar conductivity is ca. 50%. Another mechanism for the transmission of charged species in RTILs is responsible for the "excess" molar conductivity, and we consider possible contributions.

Cationic micelles in deep eutectic solvents: effects of solvent composition.

Deep eutectic solvents (DES) are mixtures of hydrogen bond donors and acceptors that form strongly hydrogen-bonded room temperature liquids. Changing the H-bonding components and their ratios can alter the physicochemical properties of deep eutectic solvents. Recent studies have shown p-toluenesulfonic acid (pTSA) forms room temperature liquids with choline chloride (ChCl) at different molar ratios: 1 : 1, 1 : 2 and 2 : 1 [Rodriguez Rodriguez et al., ACS Sustain. Chem. Eng., 2019, 7(4), 3940]. They also showed that the composition affects the physical properties of these liquids and their ability to dissolve metal oxides. In this work we evaluate the solubility and self-assembly of cationic surfactants alkyltrimethyl ammonium bromides (CnTAB) in these pTSA/ChCl based liquids. CnTABs are insoluble in 1pTSA : 2ChCl, whereas in 1pTSA : 1ChCl and 2pTSA : 1ChCl they form micelles. We characterise CnTAB (n = 12, 14, 16) micelles using small angle neutron scattering and also look at interaction of water with the micelles. These studies help determine the interaction of DES components with the surfactant and the influence of varying pTSA and water ratios on these interactions. This provides potential for controlled surfactant templating and for tuning rheology modification in such systems.

Temperature-dependent hole mobility in pyrene-thiophene-based room-temperature discotic liquid crystals.

π-Conjugated pyrene-thiophene-based room-temperature discotic liquid crystals armed with four peripheral aliphatic chains are reported to study their potential use in a hole-transporting organic semiconductor. The charge carrier mobility studies using the ToF method revealed room temperature hole mobility in the order of 10-4 cm2 V-1 s-1 for both mesogens. However, the mobility values for compound 1a were observed in the order of 10-3 cm2 V-1 s-1 at high temperatures. Such molecular systems can potentially be used in nonlinear organic electronic applications.

Room-temperature ferroelectric nematic liquid crystal showing a large and diverging density.

The ferroelectric nematic phase (NF) is a recently discovered phase of matter in which the orientational order of the conventional nematic liquid crystal state is augmented with polar order. Atomistic simulations suggest that the polar NF phase would be denser than conventional nematics owing to contributions from polar order. Using an oscillating U-tube densitometer, we obtain detailed temperature-dependent density values for a selection of conventional liquid crystals with excellent agreement with earlier reports. Having demonstrated the validity of our method, we then record density as a function of temperature for M5, a novel room-temperature ferroelectric nematic material. We present the first experimental density data for a NF material as well as density data for a nematic that has not previously been reported. We find that the room-temperature NF material shows a large (>1.3 g cm-3) density at all temperatures studied, notably including phases without polar order. An increase in density at phase transitions is observed. The magnitude of the increase for the intermediate-to-ferroelectric nematic (NX-NF) transition is an order of magnitude smaller than the isotropic-nematic (I-N) transition. We then probe potential consequences that may result from an elevated density through measurement of the refractive indices (no and ne). The navg of M5 is compared with 5CB and polar smectic liquid crystals. We observe how the highly polar nature of the system counteracts the effects of an increase in density. With knowledge of experimental density, we are able to derive an approximation that yields the polar order parameter, 〈P1〉, from polarisation measurements. Present results may be typical of ferroelectric nematic materials, potentially guiding material development, and is especially relevant for informing ongoing studies into this emerging class of materials.