Typical Liquids Research Articles

Correction to “Life Cycle Thinking-Based GREENNESS Framework for Advancing Green Chemistry: Case Study with Typical Ionic Liquids for Cellulose Dissolution and Regeneration”

Correction to “Life Cycle Thinking-Based GREENNESS Framework for Advancing Green Chemistry: Case Study with Typical Ionic Liquids for Cellulose Dissolution and Regeneration”

An Electronic “Tongue” Based on Multimode Multidirectional Acoustic Plate Wave Propagation

This paper theoretically and experimentally demonstrates the possibility of detecting the five basic tastes (salt, sweet, sour, umami, and bitter) using a variety of higher-order acoustic waves propagating in piezoelectric plates. Aqueous solutions of sodium chloride (NaCl), glucose (C6H12O6), citric acid (C6H8O7), monosodium glutamate (C5H8NO4Na), and sagebrush were used as chemicals for the simulation of each taste. These liquids differed from each other in terms of their physical properties such as density, viscosity, electrical conductivity, and permittivity. As a total acoustic response to the simultaneous action of all liquid parameters on all acoustic modes in a given frequency range, a change in the propagation losses (ΔS12) of the specified wave compared with distilled water was used. Based on experimental measurements, the corresponding orientation histograms of the ΔS12 were plotted for different types of acoustic waves. It was found that these histograms for different substances are individual and differ in shape, area, and position of their extremes. Theoretically, it has been shown that the influence of different liquids on different acoustic modes is due to both the electrical and mechanical properties of the liquids themselves and the mechanical polarization of the corresponding modes. Despite the fact that the mechanical properties of the used liquids are close to each other, the attenuation of different modes in their presence is not only due to the difference in their electrical parameters. The proposed approach to creating a multi-parametric multimode acoustic electronic tongue and obtaining a set of histograms for typical liquids will allow for the development of devices for the operational analysis of food, medicines, gasoline, aircraft fuel, and other liquid substances without the need for detailed chemical analysis.

Revealing capacitive behaviors of graphene in ionic liquids using molecular dynamics simulation

Abstract This work reveals the capacitive behaviors of graphene nanomaterials in typical ionic liquids of [BMI+] [BF4 −] using molecular dynamics simulations. It is found that the charging process induces a structural transition from disordered to partially ordered and then ordered multilayer structures of [BMI+][BF4 −] electrolyte, yielding a multiple layer-by-layer packing structure of BMI+ cation and BF4 − anion. Especially, a counterion-adsorption-dominated Helmholtz layer is revealed at a high charge density of 16 μC/cm2, which is primarily responsible for the superior capacitance results. Besides, the differential capacitance of [BMI+][BF4 −] exhibits a symmetric convexity-shaped curve, showing a maximal capacitance value of 4.83 μF/cm2. The as-obtain simulation results help to understand the microscopic charge storage mechanisms of graphene in ionic liquids.

Efficient photocatalytic degradation of 24 imidazolium ionic liquids in an N-ZnO/simulated sunlight irradiation system and its mechanism

An efficient nitrogen (N)-ZnO photocatalytic composite was synthesized and well characterized to demonstrate its superior photocatalytic performance as well as the degradation kinetics of 24 ILs in an N-ZnO/Xe lamp irradiation system, as well as the pathways and mechanisms of the photocatalytic degradation (PCD) of typical ionic liquids [OMIm]Br was systematically studied. To investigate the catalytic effect, nitrogen was synthesized from various inorganic and organic nitrogen compounds to ZnO. The NH4NO3-ZnO composite calcined at 300 °C with a molar ratio of NH4NO3 to Zn(NO3)2·6H2O of 10:1 exhibited superior catalytic performance as assessed by SEM, TEM, FT-IR, UVDRS, BET surface area, XPS, and XRD characterizations. After 24 h of exposure to Xe lamp irradiation, all 24 ILs were significantly degraded by the introduction of 0.125 g/L of catalyst, whereas simulated sunlight alone resulted in minimal degradation. The pseudo-first-order rate coefficients (k) for PCD were closely related to the carbon chain length of the alkyl substituents and the type of anion. Multiple linear regression analysis indicated no linear correlation between the parameters E, H°, Eth, and Cv° from the Gaussian calculation and k. Conversely, a positive correlation was observed for EHOMO (B=0.742, β = 1.282, P = 0.011), qH+ (B=1.040, β = 3.284, P = 0.006), and G° (B=0.001, β = 5.400, P = 0.007) with k. Mass spectrometry analysis revealed that the primary PCD pathway for [OMIm]Br involved C-N and/or C-C bond breaking, mono-, di-, and tri-hydroxylation, single and double oxygen transfer, and bromo-substitution reactions.

Liquid-like clusters in glassy solids as a unique state of matter: Dissipative but non-diffusive

The field of glassy studies has long speculated about the existence of liquid-like regions within solid amorphous states. However, limited evidence from indirect investigations has left the question of their presence unanswered. In this study, we propose a computational approach to analyze dissipation characteristics at the atomic level. Our findings reveal the actual existence of localized liquid-like dissipation clusters in the glassy state, demonstrating a damping factor similar to liquids and a vanishing shear modulus. Surprisingly, these clusters are only observed at low temperatures and do not involve diffusive motions, unlike typical liquids. This unique state of condensed matter is dissipative but non-diffusive. In metallic glasses, we show that these clusters are responsible for the recently discovered β' relaxation. Our results provide a solid basis for the longstanding concept of liquid-like region in glassy materials and provide a new perspective on establishing structure-property correlations.

Bioethanol fermentation in the presence of ionic liquids: mini review

Ionic liquids are efficient pretreatment solvents for cellulosic biomass, but typical cellulose-dissolving ionic liquids are toxic to microorganisms, hindering the fermentation process for bioethanol production. Here I summarize the mechanisms of toxicity and how to overcome the toxicity.

Non-contact viscoelasticity measurements based on impulsive stimulated Brillouin spectroscopy

The mechanical properties of cells and tissues play a crucial role in determining biological functions. As a label-free and non-contact mechanical imaging method, Brillouin spectroscopy can characterize viscoelastic changes in samples with high spatial resolution. To sensitively identify small mechanical differences among biological systems, it is important to improve Brillouin scattering efficiency while combining various viscoelastic contrast mechanisms in measurement. This paper presents a high-speed Brillouin spectroscopy based on impulsive stimulated Brillouin scattering. The acoustic oscillation can be excited in a single shot with a pulsed pump laser and detected by a continuous probe laser in the time domain. This time-domain signal can then be transferred to the frequency-domain Brillouin spectrum with high precision. With this method, various viscoelastic information including sound velocity, sound attenuation coefficient, elastic longitudinal storage modulus, and loss modulus can be obtained simultaneously based on derived spectral information. Owing to stimulated scattering and time-domain detection, spectra with a signal-to-noise ratio of 26 dB can be achieved within a millisecond-level spectral integration time. The average measurement precision for storage modulus and loss modulus of the longitudinal elastic modulus are 0.1% and 1%, respectively. With this method, the Brillouin spectra and viscoelastic parameters of typical liquids and polymer materials are measured and compared, providing a comprehensive reference for viscoelastic parameters. We also study the elastic changes in different curing stages of PDMS and make a comparison of viscoelasticity with agarose gel. Moreover, six edible oils are identified based on various viscoelastic contrast mechanisms, which not only provides a new perspective for material identification but also expands the measurement capabilities of Brillouin spectroscopy and enhances the sensitivity of viscoelasticity measurements.

Calculating Thermodynamic Factors for Diffusion Using the Continuous Fractional Component Monte Carlo Method.

Thermodynamic factors for diffusion connect the Fick and Maxwell-Stefan diffusion coefficients used to quantify mass transfer. Activity coefficient models or equations of state can be fitted to experimental or simulation data, from which thermodynamic factors can be obtained by differentiation. The accuracy of thermodynamic factors determined using indirect routes is dictated by the specific choice of an activity coefficient model or an equation of state. The Permuted Widom's Test Particle Insertion (PWTPI) method developed by Balaji et al. enables direct determination of thermodynamic factors in binary and multicomponent systems. For highly dense systems, for example, typical liquids, it is well known that molecular test insertion methods fail. In this article, we use the Continuous Fractional Component Monte Carlo (CFCMC) method to directly calculate thermodynamic factors by adopting the PWTPI method. The CFCMC method uses fractional molecules whose interactions with their surrounding molecules are modulated by a coupling parameter. Even in highly dense systems, the CFCMC method efficiently handles molecule insertions and removals, overcoming the limitations of the PWTPI method. We show excellent agreement between the results of the PWTPI and CFCMC methods for the calculation of thermodynamic factors in binary systems of Lennard-Jones molecules and ternary systems of Weeks-Chandler-Andersen molecules. The CFCMC method applied to calculate the thermodynamic factors of realistic molecular systems consisting of binary mixtures of carbon dioxide and hydrogen agrees well with the NIST REFPROP database. Our study highlights the effectiveness of the CFCMC method in determining thermodynamic factors for diffusion, even in densely packed systems, using relatively small numbers of molecules.

Rheological Properties of Wood Plastic Composites Based on Polypropylene and Birch Plywood Residues - Sanding Dust

This article summarizes the investigation results of the rheological and thermal stability properties of industrially prepared wood plastic composites based on virgin polypropylene (PP) and birch plywood production waste product, plywood sanding dust (PSD). Wood plastic composites (WPCs) PP+40 wt.% PSD contain different modifiers, such as functional lubricant Struktol TWP, antioxidant 1010, thermal stabilizer 168, ultraviolet (UV) stabilizer 770, and pigment concentrate based on low density polyethylene (LDPE). According to these studies, it was concluded that rheological properties studied by the capillary rheometry method depend on WPC composition and the parameters of rheological measurements. On the contrary, melt flow index (MFI) values did not change so much and fluctuated in the range of 1.52–1.66 g/10 min. The presence of thermal and antioxidant stabilizers promoted an increase in the thermal stability of WPCs, as determined by the thermal gravimetric analysis (TGA) method. The characteristics of fluidity curves indicated the character of typical pseudo-plastic liquids, in which viscosity not only depends on temperature, shear stress, and shear deformation rate but also decreases with an increase in shear deformation rate. That also confirmed the values of the fluidity index (n), which for pseudo-plastic polymer melts are always smaller than 1.

Miscibility studies on carboxymethyl chitosan and poly(N-vinylpyrrolidone) mixtures

The production of polymer mixtures is a widely used method to improve polymer performance, as such mixtures can combine advantageous properties from each component. In this study, mixtures based on carboxymethyl chitosan (CMCh) and poly(N-vinylpyrrolidone) (PVP) were characterized using steady shear measurements, viscometry, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and atomic force microscopy. Viscometry and steady shear studies were performed on solutions of the native polymers and their mixtures with various weight proportions (80/20, 50/50, and 20/80%w/w). The rheological tests revealed that the apparent viscosity of solutions of CMCh/PVP mixtures was higher than that of the native polymer solutions. The rheological data showed that CMCh solutions and their mixtures were typical pseudoplastic liquids, which could be accurately described by the Cross and power law models. Viscometric parameters were determined using the method proposed by Garcia et al., which indicated good miscibility between CMCh and PVP in aqueous solution. Furthermore, the morphology, structure, and thermal properties of CMCh films changed when PVP was added. The obtained analytical data showed the formation of stable mixtures of CMCh and PVP, with a high miscibility ratio between these polymers, through intermolecular interactions between the polymer chains.

Different Ignition Modes and Temperature Evolution of Typical Hypergolic Ionic Liquids

The hypergolic ignition behaviors of three ionic liquids [BMIm][DCA], [EMIm][DCA], and [EMIm][CDB] reacting with white fuming nitric acid (WFNA) were investigated using the drop test approach. Two high-speed cameras with/without a long-distance microscope and a time-resolved infrared camera were used to simultaneously record the hypergolic ignition process and the reaction region temperature evolution. Results showed two distinct hypergolic ignition modes. Specifically, for [BMIm][DCA] and [EMIm][DCA], some “vapor smoke” is generated after the fuel droplet contacts the WFNA pool, followed by sudden ejection of liquids induced by microexplosion. The measured temperature in the observation window is found to first increase, then decrease, and rise again. For [EMIm][CDB], no microexplosion is observed and the temperature monotonically increases before hypergolic ignition. It is inferred that microexplosion is caused by sufficient accumulation of gaseous intermediates or products underneath the liquid surface, and the monotonic or nonmonotonic increasing temperature is a characteristic of ignition modes. A conceptual model is proposed to illustrate the two ignition modes. In addition, the droplet impact velocity (U0) was varied from 1.1 to 2.1 m/s in the experiment. It is found that the vapor delay time (VDT), explosion delay time (EDT), and ignition delay time (IDT) are all reduced with U0 by at most 50%. For a given U0, the three time scales decrease in the order [BMIm][DCA], [EMIm][DCA], and [EMIm][CDB] (IDT as low as 14.4 ms).

Thermal stability and flammability of several quaternary ammonium ionic liquids

With the development of potential large-scale industrial application of quaternary ammonium ionic liquids in the fields of gas separation, high-temperature lubricants and even rocket propellants, deep investigations are required to reveal the possible hazards of thermal decomposition, the flammability and the hazardous gaseous products. In this study, the thermal stability of five typical quaternary ammonium ionic liquids, [N2222][NTF2], [N2222][PF6], [N2222]Br, [N4444]Br and [N4444][PF6], were studied using thermogravimetric analyser (TGA). The results show that the thermal stability of ionic liquids follows an order of [N2222][NTF2] > [N2222][PF6] > [N4444][PF6] > [N2222]Br > [N4444]Br, indicating that the thermal stability is obviously affected by the anion, with an order of [NTF2]− > [PF6]− > Br−. Besides, increasing the alkyl chain length in the cation will reduce the thermal stability. In addition, Fire Testing Technology (FTT) cone calorimeter was used to investigate the flammability and found that the longer alkyl chains of quaternary ammonium ionic liquids make great contribution on larger the total heat release, the peak value of heat releasing rate and shorter ignition time. Moreover, with the same cation, [N2222]Br and [N4444]Br were shortened the ignition time and produced larger amount of heat than [N2222][PF6] and [N4444][PF6], respectively. It clearly shows that the risk of fire is also affected by the anion, with an order of Br− > [PF6]− > [NTF2]−. Finally, the decomposition products were measured by thermogravimetry coupled with Fourier-transform infrared spectroscopy (TG-FTIR), and it is deduced that the nucleophilic Br− from [Nmmmm]Br (m = 2,4) and F− from the [NTF2]− and [PF6]− during decomposition will attack the alkyl chain of the cation, which generated gaseous products such as fluoroalkanes, bromoalkanes, olefins, etc.

Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model.

Based on our preliminary 11C-nicotine positron emission tomography (PET) imaging studies in humans, we speculated that greater deposition of nicotine in the respiratory tract from electronic cigarettes compared to combustible cigarettes could result from the alkaline pH of typical aerosol-producing electronic cigarette liquids (e-liquids). To address this hypothesis, we assessed the effect of e-liquid pH on the retention of nicotine in vitro using 11C-nicotine, PET, and a human respiratory tract model of nicotine deposition. A single 2-second 35-mL puff was delivered to a human respiratory tract cast from a 2.8-Ohm cartomizer at 4.1 volts. Immediately after the puff, a 2-second 700-mL air wash-in volume was administered. E-liquids (glycerol and propylene glycol 50/50 vol/vol) containing 24 mg/mL nicotine were mixed with 11C-nicotine. Deposition (retention) of nicotine was assessed using a GE Discovery MI DR PET/CT scanner. Eight e-liquids with different pH values (range 5.3-9.6) were investigated. All experiments were performed at room temperature and at a relative humidity of 70%-80%. Retention of nicotine in the respiratory tract cast was pH dependent and the pH-sensitive component of the retention was well described by a sigmoid curve. In total, 50% of the maximal pH-dependent effect was observed at pH 8.0, which is close to the pKa2 of nicotine. The retention of nicotine in the respiratory tract conducting airways is dependent on the e-liquid pH. Lowering the e-liquid pH reduces retention of nicotine. Nonetheless, reduction of the pH below 7 has little effect, consistent with the pKa2 of protonated nicotine. Similar to combustible cigarettes, the retention of nicotine in the human respiratory tract from consumption of electronic cigarettes may have some health consequences and affect nicotine dependence. Here we demonstrated that the retention of nicotine in the respiratory tract is dependent on the e-liquid pH, and lowering pH reduces retention of nicotine in conducting airways of the respiratory tract. Therefore, e-cigarettes with low pH values would result in reduced respiratory tract nicotine exposure and faster delivery of nicotine to the central nervous system (CNS). The latter can be associated with e-cigarette abuse liability and the effectiveness of e-cigarettes as substitutes for combustible cigarettes.

Heat transfer performance of nanofluids in heat exchanger: a review

Energy is a key aspect of any country’s economic development. Improving heat transfer performance leads to saving energy. Nanotechnology has a key role to play in optimizing heat exchangers. Fluids containing nanosized particles are called nanofluids. Nanofluids have higher thermal conductivity than typical liquids. This paper outlines current research on convective heat transfer performance, thermophysical properties, particle size, and volume concentration effects in nanofluid studies. M easurement m ethods f ort h ermal conductivity and correlations used by earlier researchers to determine thermal conductivity are also encompassed. The main applications of nanofluids as liibricants a nd radiator systems to improve the efficiency of he at removal fr om ve hicle en gines ha ve al so be en emphasized. Results suggest that by using a larger size of particle some drawbacks include particle sedimentation, clogging, erosion, stability, and increasing pressure drop. Enhancing thermal conductivity with optimum volume concentration. Improving the efficiency of heat exchange systems is one of the possible ways to reduce energy consumption. The need for optimum concentration of nanofluids is required. The Problem of stability, corrosion, and erosion arrived by increasing the volume concentration of nanoparticles in a nanofluid.

Experimental examination of the properties of Fe3O4/water nanofluid, and an estimation of a correlation using an artificial neural network

Currently, considering that the addition of solid particles to normal fluids directs to a considerable increase in thermal conductivity, the utilization of nanofluids rather than typical liquids is extremely customary. This paper provides an experimental evaluation of the viscosity and thermal conductivity of Fe3O4/water nanofluid and provides an estimation model using an artificial neural network (ANN) and margin of deviation. For this purpose, Fe3O4 nanoparticles were synthesized by the co-precipitation method, and the size of nanoparticles was investigated by the XRD test. Also, the Fe3O4/water nanofluid was prepared in a two-step method and the stability of the nanofluid was evaluated by the zeta potential test. Then, thermal conductivity and viscosity of nanofluid were measured at temperatures of 25, 30, 35, 40, 45, and 50°Celsius and volume fractions of 0.1, 0.2, and 0.3%. The outcomes of this experiment indicated that the volume fraction of nanoparticles and temperature have an immediate relationship with the thermal conductivity coefficient of nanofluids because, with the increase of these two parameters, the thermal conductivity coefficient increases and vice versa. Also, the viscosity of the nanofluid decreases with the decrease in volume fraction of nanoparticles and increases with the decrease in temperature.Because of the absence of an exact and proper correlation to predict the viscosity and thermal conductivity of this nanofluid, two correlations are presented as a subordinate of temperature and volume fraction. Also, a analogy was made among the results of the experiment and the output of the proposed relationship and it was found that the maximum margin of deflection for thermal conductivity is equal to 0.42% and for viscosity is 0.06%. Toward the end of this research, the laboratory results were analyzed by neural networks. The designed neural network was compared with the values obtained from the suggested relationship and the outcomes indicated that in predicting the viscosity and thermal conductivity of nanofluids, the neural network has fewer blunders and higher accuracy.

Molecular Simulation-Guided Spectroscopy of Imidazolium-Based Ionic Liquids and Effects of Methylation on Ion-Cage and -Pair Dynamics.

Classical molecular dynamics simulations were performed to assess an atomistic interpretation of the ion-probe structural interactions in two typical ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BDimIm][NTf2] through computational ultrafast spectroscopy. The nitrile stretching vibrations of the thiocyanate anion, [SCN]-, serve as the local mode of the ultrafast system dynamics within the imidazolium-based ionic liquid environment. The wavelet transform of classical trajectories determines the time-varying fluctuating frequencies and the stretch spectral signatures of SCN- in the normalized distribution. However, computational modeling of the two-dimensional (2D) spectra from the wavelet-derived vibrational frequencies yields time evolution of the local molecular structure along with the varied time-dependent dynamics of the spectral diffusion process. We calculated the frequency-frequency correlation functions (FFCFs), time correlations associated with the ion-pair and -cage dynamics, and mean square displacements as a function of time, depicting diffusive dynamics. The calculated results based on the pair correlation functions and the distribution of atomic density suggest that the hydrogen and methylated carbon at the two-position of the imidazolium ring of [BMIm] and [BDimIm] cations, respectively, strongly interact with the probe through the N of the thiocyanate anion rather than the S atom. The center-of-mass center-of-mass (COM-COM) cation-probe radial distribution functions (RDFs) in conjunction with the site-specific structural analysis further reveal well-structured interactions of the thiocyanate ion and [BMIm]+ cation rather than the [BDimIm] cation. In contrast, the anion-probe COM-COM RDFs depict weak interactive associations within the vibrational probe [SCN]- and [NTf2]- ions. Methylation at the two-position of the imidazolium ring predicts slower structural reorganization and breaking and reformation dynamics of the ion pairs and cages within the ionic liquid framework.

Space-time rigidity and viscoelasticity of glass forming liquids: The case of chalcogenides

The viscoelasticity of glass-forming fluids contains sustantial information about space-time rigidity. Viscoelasticity and rheology provide alternative experimental, computational and theoretical ways to asses chemical composition effects in the relaxation of supercooled liquids near the glass transition. In particular, the transverse current correlation and transversal dynamical structure factor contain space-time information allowing to relate the dynamical gap of transversal vibrational modes with floppy modes and relaxation times in the liquid. Here, a short revision is made of the subject, including simulations of Tellurium, a typical chalcogenide glass. Our results are similar to those obtained for typical metallic liquids. To rationalize this result, an statistical mechanics analysis in the strain ensemble is performed by using a model that incorporates flexibility and hard-core potentials. This shows that the entropy is akin to a hard-cord fluid as angular bonds only renormalize the entropy if they are not substantially affected by temperature effects. Finally, a comparison is made with Selenium, where bond breaking effects do not allow such a straight-forward treatment. • Relation between dynamical gap of transversal vibrational modes and floppy modes. • Developing a model that incorporates flexibility and hard-core potentials. • Longitudinal and transversal current correlation analysis in liquid tellurium. • Longitudinal and transversal dispersion relationship for tellurium.

Weakly pinned skyrmion liquid in a magnetic heterostructure

Magnetic skyrmions are topological quasiparticles that can be formed in systems with particular magnetic interactions. Here, the authors study dense arrays of skyrmions in a thin film heterostructure, showing that the skyrmions form a liquid, the properties of which depend strongly on the size and density of the skyrmions. The presence of pinning sites alters the behavior of the skyrmion liquid compared to typical liquids, but these pinning sites are shown to have a narrow energy distribution compatible with proposed applications.

The effect of oxidation state and tert-butyl substituents on the thermal behavior and thin-film morphology of cobalt-complexes (FK 102 and FK 209)

This work reports the thermodynamic and morphological study and characterization of four salts consisting of a divalent/trivalent cobalt complex with pyrazole-pyridine ligands (FK 102 and FK 209 samples) and bis(trifluoromethylsulfonyl)imide (TFSI) moieties as counter anions. The oxidation state of the central metal (Co(II) or Co(III)) and the presence of tert-butyl (t-Bu) groups in the ligand structure were found to have a strong impact on the thermal behavior, phase stability, heat capacities, and thin-film morphology of each salt. The Co(II) complexes exhibited good thermal stability up to 600 K. Lower thermal stability was observed for the Co(III) congeners. The FK209 Co(III) displayed a higher melting temperature but a partial decomposition during or above melting was detected. The higher melting temperatures observed for the Co(III) complexes were found to be entropically driven. However, the addition of t-Bu in the ligand (FK 209) leads to an increase in the melting temperature, which is driven by the enthalpy of fusion. The four compounds studied evidenced a large glass-forming ability. Moreover, the thermal stability of the glassy state was clearly increased when the ligands comprised t-Bu groups. The contribution of the t-Bu group for the molar heat capacity in the solid phase, at T = 298.15 K, was found to be (110 ± 3) J·K−1·mol−1 and (98 ± 4) J·K−1·mol−1 for the Co(II) and Co(III) complexes, respectively. These results are in good agreement with the contribution of the t-Bu group observed for both solid and liquid phases in other materials, indicating that the t-Bu groups are relatively unhindered in the crystalline phase of the salts. The morphological behavior of the thin films of FK 102 samples was found to be quite similar to the observed for typical ionic liquids, with the formation of micro- and nanodroplets onto different substrates. The introduction of t-Bu substituents in the ligand structure was found to have a strong impact on the formation of homogeneous and compact nanofilms for the FK 209 salts.

Fundamental investigations at the nexus of ionic liquids and mass spectrometry

Ionic liquids are an interesting class of compounds, with distinct properties compared to both high melting point crystalline ionic compounds and typical molecular liquids. Given such unique properties—and the tunability of these properties through cation and anion structural changes and pairings—ionic liquids have found use in an ever-growing list of applications, from spacecraft propulsion to pharmaceutical preparations. Fundamental studies of ionic liquid properties are ongoing to gain a full understanding of how these compounds behave, including at an ionic/molecular level. There is great interest in using such fundamental studies (1) to build a knowledge base to support efforts toward the rational design of task-specific compounds and (2) to benchmark and improve computational chemistry methods toward more confident in silico results. Mass spectrometry is a natural tool for solving the first problem for gas-phase applications and work is underway on several fronts to determine in what ways and to what extents mass spectrometric data correlate with bulk properties. Toward the second goal, mass spectrometric platforms allow for the direct comparison of isolated, gas-phase measurements with calculations on isolated ions/clusters, so there is likewise a natural fit there. This feature provides an overview of ionic liquids and their applications, a discussion of notable mass spectrometric contributions toward fundamental understanding, including those from the author's research, and commentary on future directions.