Identification of polar, ionic, and highly water soluble organic pollutants in untreated industrial wastewaters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castillo, M.; Alonso, M.C.; Riu, J.

1999-04-15

This paper presents a generic protocol for the determination of polar, ionic, and highly water soluble organic pollutants on untreated industrial wastewaters involving the use of two different solid-phase extraction (SPE) methodologies followed by liquid chromatography-mass spectrometry (LC-MS). Untreated industrial wastewaters might contain natural and synthetic dissolved organic compounds with total organic carbon (TOC) values varying between 100 and 3000 mg/L. All polar, ionic and highly water soluble compounds comprising more than 95% of the organic content and with major contribution to the total toxicity of the sample cannot be analyzed by conventional gas chromatography-mass spectrometry (GC-MS), and LC-MS ismore » a good alternative. In this work two extraction procedures were used to obtain fractionated extracts of the nonionic polar compounds: a polymeric Isolute ENV + SPE cartridge for the preconcentration of anionic analytes and a sequential solid-phase extraction (SSPE) method percolating the samples first in octadecylsilica cartridge in series with the polymeric Lichrolut EN cartridge. Average recoveries ranging from 72% to 103% were obtained for a variety of 23 different analytes. Determination of nonionic pollutants was accomplished by reverse-phase liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), while anionic compounds were analyzed by ion pair chromatography-electrospray-mass spectrometry (IP-ESI-MS) and LC-ESI-MS. This protocol was applied to a pilot survey of textile and tannery wastewaters leading to the identification and quantification of 33 organic pollutants.« less

Quantifying intermolecular interactions of ionic liquids using cohesive energy densities.

PubMed

Lovelock, Kevin R J

2017-12-01

For ionic liquids (ILs), both the large number of possible cation + anion combinations and their ionic nature provide a unique challenge for understanding intermolecular interactions. Cohesive energy density, ced , is used to quantify the strength of intermolecular interactions for molecular liquids, and is determined using the enthalpy of vaporization. A critical analysis of the experimental challenges and data to obtain ced for ILs is provided. For ILs there are two methods to judge the strength of intermolecular interactions, due to the presence of multiple constituents in the vapour phase of ILs. Firstly, ced IP , where the ionic vapour constituent is neutral ion pairs, the major constituent of the IL vapour. Secondly, ced C+A , where the ionic vapour constituents are isolated ions. A ced IP dataset is presented for 64 ILs. For the first time an experimental ced C+A , a measure of the strength of the total intermolecular interaction for an IL, is presented. ced C+A is significantly larger for ILs than ced for most molecular liquids, reflecting the need to break all of the relatively strong electrostatic interactions present in ILs. However, the van der Waals interactions contribute significantly to IL volatility due to the very strong electrostatic interaction in the neutral ion pair ionic vapour. An excellent linear correlation is found between ced IP and the inverse of the molecular volume. A good linear correlation is found between IL ced IP and IL Gordon parameter (which are dependent primarily on surface tension). ced values obtained through indirect methods gave similar magnitude values to ced IP . These findings show that ced IP is very important for understanding IL intermolecular interactions, in spite of ced IP not being a measure of the total intermolecular interactions of an IL. In the outlook section, remaining challenges for understanding IL intermolecular interactions are outlined.

Quantifying intermolecular interactions of ionic liquids using cohesive energy densities

PubMed Central

2017-01-01

For ionic liquids (ILs), both the large number of possible cation + anion combinations and their ionic nature provide a unique challenge for understanding intermolecular interactions. Cohesive energy density, ced, is used to quantify the strength of intermolecular interactions for molecular liquids, and is determined using the enthalpy of vaporization. A critical analysis of the experimental challenges and data to obtain ced for ILs is provided. For ILs there are two methods to judge the strength of intermolecular interactions, due to the presence of multiple constituents in the vapour phase of ILs. Firstly, cedIP, where the ionic vapour constituent is neutral ion pairs, the major constituent of the IL vapour. Secondly, cedC+A, where the ionic vapour constituents are isolated ions. A cedIP dataset is presented for 64 ILs. For the first time an experimental cedC+A, a measure of the strength of the total intermolecular interaction for an IL, is presented. cedC+A is significantly larger for ILs than ced for most molecular liquids, reflecting the need to break all of the relatively strong electrostatic interactions present in ILs. However, the van der Waals interactions contribute significantly to IL volatility due to the very strong electrostatic interaction in the neutral ion pair ionic vapour. An excellent linear correlation is found between cedIP and the inverse of the molecular volume. A good linear correlation is found between IL cedIP and IL Gordon parameter (which are dependent primarily on surface tension). ced values obtained through indirect methods gave similar magnitude values to cedIP. These findings show that cedIP is very important for understanding IL intermolecular interactions, in spite of cedIP not being a measure of the total intermolecular interactions of an IL. In the outlook section, remaining challenges for understanding IL intermolecular interactions are outlined. PMID:29308254

Analysis of metallic nanoparticles and their ionic counterparts in complex matrix by reversed-phase liquid chromatography coupled to ICP-MS.

PubMed

Yang, Yuan; Luo, Li; Li, Hai-Pu; Wang, Qiang; Yang, Zhao-Guang; Qu, Zhi-Peng; Ding, Ru

2018-05-15

Developing quantification and characterization methodology for metallic nanoparticles (MNPs) and their ionic component in complex matrix are crucial for the evaluation of their environmental behavior and health risks to humans. In this study, reversed phase high performance liquid chromatography combined ICP-MS was established for the characterization of MNPs in complex matrix. The ionic component could be separated from NPs with the optimized parameters of aqueous mobile phase. Good linear relationship between average diameter and retention time of NPs was obtained using HPLC-ICP-MS and the size smaller than 40 nm could be determined with this method, the detected results were in accordance with TEM results. The low detection limit of AuNPs and Au(Ⅲ) (both in sub-μg/L level) showed that this method was promising for the characterization of AuNPs and Au(Ⅲ) in environmental water. The mass concentration of ionic Au(Ⅲ) in environmental water could be detected using the proposed HPLC-ICP-MS and the concentration of AuNPs was obtained by subtracting the Au(Ⅲ) concentration from the total Au (The concentration of total Au was detected by ICP-MS after microwave digestion). Furthermore this proposed HPLC-ICP-MS method and single particle-ICPMS (SP-ICP-MS) was used for the analysis of the Ag speciation in commercial antibacterial products. Copyright © 2018 Elsevier B.V. All rights reserved.

Challenges in Determining Intrinsic Viscosity Under Low Ionic Strength Solution Conditions.

PubMed

Pindrus, Mariya A; Shire, Steven J; Yadav, Sandeep; Kalonia, Devendra S

2017-04-01

To determine the intrinsic viscosity of several monoclonal antibodies (mAbs) under varying pH and ionic strength solution conditions. An online viscosity detector attached to HPLC (Viscotek®) was used to determine the intrinsic viscosity of mAbs. The Ross and Minton equation was used for viscosity prediction at high protein concentrations. Bulk viscosity was determined by a Cambridge viscometer. At 15 mM ionic strength, intrinsic viscosity of the mAbs determined by the single-point approach varied from 5.6 to 6.4 mL/g with changes in pH. High ionic strength did not significantly alter intrinsic viscosity, while a significant increase (up to 24.0 mL/g) was observed near zero mM. No difference in bulk viscosity of mAb3 was observed around pH 6 as a function of ionic strength. Data analysis revealed that near zero mM ionic strength limitations of the single-point technique result in erroneously high intrinsic viscosity. Intrinsic viscosity is a valuable tool that can be used to model baseline viscosity at higher protein concentrations. However, it is not predictive of solution non-ideality at higher protein concentrations. Furthermore, breakdown of numerous assumptions limits the applicability of experimental techniques near zero mM ionic strength conditions. For molecules and conditions studied, the single-point approach produced reliable intrinsic viscosity results at 15 mM. However, this approach must be used with caution near zero mM ionic strength. Data analysis can be used to reveal whether determined intrinsic viscosity is reliable or erroneously high.

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions.

PubMed

Rinne, Klaus F; Gekle, Stephan; Netz, Roland R

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.

Halide Ions Effects on Surface Excess of Long Chain Ionic Liquids Water Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenjie; Sung, Woongmo; Ao, Mingqi

2013-10-07

The interfacial structure and composition of water solutions with alkylimidazolium ionic liquids varying in their halide anions ([C12mim][X], X = Cl and I) were investigated by X-ray near-total-reflection fluorescence spectroscopy and X-ray reflectivity measurements. We demonstrate that X-ray fluorescence and reflectivity techniques provide a more direct measurement of surface adsorption. Furthermore, we show that for [C12mim][Cl] and [C12mim][I] solutions with mixed inorganic salts (NaI, NaCl), I– ions replace Cl– above the critical micelle concentration (CMC) of [C12mim][Cl] at much lower concentrations of NaI, whereas NaCl concentrations a hundred times higher than the CMC of [C12mim][I] only partially replace the I–more » at the interface. Our surface-sensitive X-ray diffraction and spectroscopy provide two independent tools to directly determine the surface adsorption of ionic surfactants and the interfacial composition of the surface films.« less

New insight into the environmental impact of two imidazolium ionic liquids. Effects on seed germination and soil microbial activity.

PubMed

Salgado, J; Parajó, J J; Teijeira, T; Cruz, O; Proupín, J; Villanueva, M; Rodríguez-Añón, J A; Verdes, P V; Reyes, O

2017-10-01

The next generation of ionic liquids must be synthetized taking into account structures that guarantee the suitable properties for a defined application as well as ecological data. Thus, searching of the right methodologies to know, quickly and efficiently, the ecological effects of these compounds is a preliminary task. The effects of two imidazolium based ionic liquids with different anions, 1-butyl-3-methylimidazolium tetrafluoroborate, [C 4 C 1 Im][BF 4 ], and 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 3 C 1 Im][NTf 2 ], on seedling emergence of six tree species and on the microbial behaviour of two soils were determined in this work. Results showed that the highest doses of both ionic liquids caused the total inhibition of germination for almost all the species studied and that the seeds are more sensitive to the presence of these compounds than soil microbial activity. Nevertheless, signals of stress and death are observed from the results of heat released by microorganisms after the addition of the highest doses of both ionic liquids. The novelty of this work resides in the enlargement of knowledge of toxicity of ILs on complex organisms such as arboreal species and microbial activity of soils studied for the first time through a microcalorimetric technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

Coarse-Grained Molecular Dynamics Simulation of Ionic Polymer Networks

DTIC Science & Technology

2008-07-01

AFRL-RX-WP-TP-2009-4198 COARSE-GRAINED MOLECULAR DYNAMICS SIMULATION OF IONIC POLYMER NETWORKS (Postprint) T.E. Dirama, V. Varshney, K.L...GRAINED MOLECULAR DYNAMICS SIMULATION OF IONIC POLYMER NETWORKS (Postprint) 5a. CONTRACT NUMBER FA8650-05-D-5807-0052 5b. GRANT NUMBER 5c...We studied two types of networks which differ only by one containing ionic pairs that amount to 7% of the total number of bonds present. The stress

The effect of varying the anion of an ionic liquid on the solvent effects on a nucleophilic aromatic substitution reaction.

PubMed

Hawker, Rebecca R; Haines, Ronald S; Harper, Jason B

2018-05-09

A variety of ionic liquids, each containing the same cation but a different anion, were examined as solvents for a nucleophilic aromatic substitution reaction. Varying the proportion of ionic liquid was found to increase the rate constant as the mole fraction of ionic liquid increased demonstrating that the reaction outcome could be controlled through varying the ionic liquid. The solvent effects were correlated with the hydrogen bond accepting ability (β) of the ionic liquid anion allowing for qualitative prediction of the effect of changing this component of the solute. To determine the microscopic origins of the solvent effects, activation parameters were determined through temperature-dependent kinetic analyses and shown to be consistent with previous studies. With the knowledge of the microscopic interactions in solution, an ionic liquid was rationally chosen to maximise rate enhancement demonstrating that an ionic solvent can be selected to control reaction outcome for this reaction type.

Experimental determination of lead carbonate solubility at high ionic strengths: A Pitzer model description

DOE PAGES

Xiong, Yongliang

2015-05-06

In this article, solubility measurements of lead carbonate, PbCO 3(cr), cerussite, as a function of total ionic strengths are conducted in the mixtures of NaCl and NaHCO 3 up to I = 1.2 mol•kg –1 and in the mixtures of NaHCO 3 and Na 2CO 3 up to I = 5.2 mol•kg –1, at room temperature (22.5 ± 0.5 °C). The solubility constant (log K sp) for cerussite, PbCO 3(cr) = Pb 2+ + CO 3 2- was determined as –13.76 ± 0.15 (2σ) with a set of Pitzer parameters describing the specific interactions of PbCO 3(aq), Pb(CO 3) 2more » 2-, and Pb(CO 3)Cl – with the bulk-supporting electrolytes, based on the Pitzer model. The model developed in this work can reproduce the experimental results including model-independent solubility values from the literature over a wide range of ionic strengths with satisfactory accuracy. The model is expected to find applications in numerous fields, including the accurate description of chemical behavior of lead in geological repositories, the modeling of formation of oxidized Pb–Zn ore deposits, and the environmental remediation of lead contamination.« less

Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinne, Klaus F.; Netz, Roland R.; Gekle, Stephan

2014-12-07

Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into differentmore » water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.« less

Chromatographic and spectroscopic methods for the determination of solvent properties of room temperature ionic liquids.

PubMed

Poole, Colin F

2004-05-28

Room temperature ionic liquids are novel solvents with favorable environmental and technical features. Synthetic routes to over 200 room temperature ionic liquids are known but for most ionic liquids physicochemical data are generally lacking or incomplete. Chromatographic and spectroscopic methods afford suitable tools for the study of solvation properties under conditions that approximate infinite dilution. Gas-liquid chromatography is suitable for the determination of gas-liquid partition coefficients and activity coefficients as well as thermodynamic constants derived from either of these parameters and their variation with temperature. The solvation parameter model can be used to define the contribution from individual intermolecular interactions to the gas-liquid partition coefficient. Application of chemometric procedures to a large database of system constants for ionic liquids indicates their unique solvent properties: low cohesion for ionic liquids with weakly associated ions compared with non-ionic liquids of similar polarity; greater hydrogen-bond basicity than typical polar non-ionic solvents; and a range of dipolarity/polarizability that encompasses the same range as occupied by the most polar non-ionic liquids. These properties can be crudely related to ion structures but further work is required to develop a comprehensive approach for the design of ionic liquids for specific applications. Data for liquid-liquid partition coefficients is scarce by comparison with gas-liquid partition coefficients. Preliminary studies indicate the possibility of using the solvation parameter model for interpretation of liquid-liquid partition coefficients determined by shake-flask procedures as well as the feasibility of using liquid-liquid chromatography for the convenient and rapid determination of liquid-liquid partition coefficients. Spectroscopic measurements of solvatochromic and fluorescent probe molecules in room temperature ionic liquids provide insights into solvent intermolecular interactions although interpretation of the different and generally uncorrelated "polarity" scales is sometimes ambiguous. All evidence points to the ionic liquids as a unique class of polar solvents suitable for technical development. In terms of designer solvents, however, further work is needed to fill the gaps in our knowledge of the relationship between ion structures and physicochemical properties.

Determination of the distribution constants of aromatic compounds and steroids in biphasic micellar phosphonium ionic liquid/aqueous buffer systems by capillary electrokinetic chromatography.

PubMed

Lokajová, Jana; Railila, Annika; King, Alistair W T; Wiedmer, Susanne K

2013-09-20

The distribution constants of some analytes, closely connected to the petrochemical industry, between an aqueous phase and a phosphonium ionic liquid phase, were determined by ionic liquid micellar electrokinetic chromatography (MEKC). The phosphonium ionic liquids studied were the water-soluble tributyl(tetradecyl)phosphonium with chloride or acetate as the counter ion. The retention factors were calculated and used for determination of the distribution constants. For calculating the retention factors the electrophoretic mobilities of the ionic liquids were required, thus, we adopted the iterative process, based on a homologous series of alkyl benzoates. Calculation of the distribution constants required information on the phase-ratio of the systems. For this the critical micelle concentrations (CMC) of the ionic liquids were needed. The CMCs were calculated using a method based on PeakMaster simulations, using the electrophoretic mobilities of system peaks. The resulting distribution constants for the neutral analytes between the ionic liquid and the aqueous (buffer) phase were compared with octanol-water partitioning coefficients. The results indicate that there are other factors affecting the distribution of analytes between phases, than just simple hydrophobic interactions. Copyright © 2013 Elsevier B.V. All rights reserved.

Simulation studies of ionic liquids: Orientational correlations and static dielectric properties

NASA Astrophysics Data System (ADS)

Schröder, C.; Rudas, T.; Steinhauser, O.

2006-12-01

The ionic liquids BMIM+I-, BMIM+BF4-, and BMIM+PF6- were simulated by means of the molecular dynamics method over a time period of more than 100ns. Besides the common structural analysis, e.g., radial distribution functions and three dimensional occupancy plots, a more sophisticated orientational analysis was performed. The angular correlation functions g00110(r) and g00101(r) are the first distance dependent coefficients of the pairwise orientational distribution function g(rij,Ω1,Ω2,Ω12). These functions help to interpret the three dimensional plot and reveal interesting insights into the local structure of the analyzed ionic liquids. Furthermore, the collective network of ionic liquids can be characterized by the Kirkwood factor Gκ(r ) [J. Chem. Phys. 7, 911 (1939)]. The short-range behavior (r<10Å) of this factor may be suitable to predict the water miscibility of the ionic liquid. The long-range limit of Gk∞ is below 1 which demonstrates the strongly coupled nature of the ionic liquid networks. In addition, this factor relates the orientational structure and the dielectric properties of the ionic liquids. The static dielectric constant ɛ(ω =0) for the simulated system is 8.9-9.5. Since in ionic liquids the very same molecule contributes to the total dipole moment as well as carries a net charge, a small, but significant contribution of the cross term between the total dipole moment and the electric current to ɛ(ω =0) is observed.

Per- and poly-fluoroalkyl substances (PFASs) in the urban, industrial, and background atmosphere of Northeastern China coast around the Bohai Sea: Occurrence, partitioning, and seasonal variation

NASA Astrophysics Data System (ADS)

Yao, Yiming; Chang, Shuai; Zhao, Yangyang; Tang, Jianhui; Sun, Hongwen; Xie, Zhiyong

2017-10-01

Air samples were collected using high-volume samplers at two coastal towns on the Bohai Sea in China, 320 km apart, and at a background site (North Huangcheng Island) in the Bohai Sea, 50 km from the coast. A suite of neutral and ionic per- and poly-fluoroalkyl substances (PFASs) was investigated. Urban activity was related to high levels of neutral PFASs at Tianjin while perfluorooctanoic carboxylic acid (PFOA) was dominant in the atmosphere at Weifang, possibly due to industrial sources. Polyfluoroalkyl phosphoric acid diesters (diPAPs) occurred in the particle phase only, with a total concentration range of 0.02-6.72 pg m-3. The dominant homologue was 6:2 diPAP. PFASs profiles at NHI suggested direct atmospheric transport of neutral and ionic PFASs from source regions. Temperature-dependent partitioning of fluorotelomer alcohols (FTOHs) was observed in winter, when total concentrations and particle-phase fractions of FTOHs were significantly higher as compared to those in summer. Correlation analyses suggested more active gas-phase degradation of FTOHs in summer and likely heterogeneous degradation in both seasons. Overall, it is necessary to account for ionic PFASs in both gas and particle phases and particulate matter was important for atmospheric transport and for determining the fate of PFASs, especially in areas close to a source region.

Diffusion of ionic and non-ionic contrast agents in articular cartilage with increased cross-linking--contribution of steric and electrostatic effects.

PubMed

Kulmala, K A M; Karjalainen, H M; Kokkonen, H T; Tiitu, V; Kovanen, V; Lammi, M J; Jurvelin, J S; Korhonen, R K; Töyräs, J

2013-10-01

To investigate the effect of threose-induced collagen cross-linking on diffusion of ionic and non-ionic contrast agents in articular cartilage. Osteochondral plugs (Ø=6mm) were prepared from bovine patellae and divided into two groups according to the contrast agent to be used in contrast enhanced computed tomography (CECT) imaging: (I) anionic ioxaglate and (II) non-ionic iodixanol. The groups I and II contained 7 and 6 sample pairs, respectively. One of the paired samples served as a reference while the other was treated with threose to induce collagen cross-linking. The equilibrium partitioning of the contrast agents was imaged after 24h of immersion. Fixed charge density (FCD), water content, contents of proteoglycans, total collagen, hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent) cross-links were determined as a reference. The equilibrium partitioning of ioxaglate (group I) was significantly (p=0.018) lower (-23.4%) in threose-treated than control samples while the equilibrium partitioning of iodixanol (group II) was unaffected by the threose-treatment. FCD in the middle and deep zones of the cartilage (p<0.05) and contents of Pent and LP (p=0.001) increased significantly due to the treatment. However, the proteoglycan concentration was not systematically altered after the treatment. Water content was significantly (-3.5%, p=0.007) lower after the treatment. Since non-ionic iodixanol showed no changes in partition after cross-linking, in contrast to anionic ioxaglate, we conclude that the cross-linking induced changes in charge distribution have greater effect on diffusion compared to the cross-linking induced changes in steric hindrance. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Extending the applicability of the Goldschmidt tolerance factor to arbitrary ionic compounds

PubMed Central

Sato, Toyoto; Takagi, Shigeyuki; Deledda, Stefano; Hauback, Bjørn C.; Orimo, Shin-ichi

2016-01-01

Crystal structure determination is essential for characterizing materials and their properties, and can be facilitated by various tools and indicators. For instance, the Goldschmidt tolerance factor (T) for perovskite compounds is acknowledged for evaluating crystal structures in terms of the ionic packing. However, its applicability is limited to perovskite compounds. Here, we report on extending the applicability of T to ionic compounds with arbitrary ionic arrangements and compositions. By focussing on the occupancy of constituent spherical ions in the crystal structure, we define the ionic filling fraction (IFF), which is obtained from the volumes of crystal structure and constituent ions. Ionic compounds, including perovskites, are arranged linearly by the IFF, providing consistent results with T. The linearity guides towards finding suitable unit cell and composition, thus tackling the main obstacle for determining new crystal structures. We demonstrate the utility of the IFF by solving the structure of three hydrides with new crystal structures. PMID:27032978

Extending the applicability of the Goldschmidt tolerance factor to arbitrary ionic compounds.

PubMed

Sato, Toyoto; Takagi, Shigeyuki; Deledda, Stefano; Hauback, Bjørn C; Orimo, Shin-ichi

2016-04-01

Crystal structure determination is essential for characterizing materials and their properties, and can be facilitated by various tools and indicators. For instance, the Goldschmidt tolerance factor (T) for perovskite compounds is acknowledged for evaluating crystal structures in terms of the ionic packing. However, its applicability is limited to perovskite compounds. Here, we report on extending the applicability of T to ionic compounds with arbitrary ionic arrangements and compositions. By focussing on the occupancy of constituent spherical ions in the crystal structure, we define the ionic filling fraction (IFF), which is obtained from the volumes of crystal structure and constituent ions. Ionic compounds, including perovskites, are arranged linearly by the IFF, providing consistent results with T. The linearity guides towards finding suitable unit cell and composition, thus tackling the main obstacle for determining new crystal structures. We demonstrate the utility of the IFF by solving the structure of three hydrides with new crystal structures.

High mass resolution isochronous time-of-flight spectrograph for three-dimensional space plasma measurements

NASA Technical Reports Server (NTRS)

Moebius, E.; Bochsler, P.; Ghielmetti, A. G.; Hamilton, D. C.

1990-01-01

By combining a toroidal electrostatic analyzer with a novel cylindrically symmetric isochronous time-of-flight mass spectrometer, an instrument was developed that simultaneously determines the three-dimensional distribution function of ions and differentiates species. The ion mass is determined to high resolution (M/Delta-M greater than 50) from the time of flight within a harmonic field configuration defined by hyperboloid equipotential surfaces. A second conventional time-of-flight channel makes use of particles leaving the thin entrance foil as neutrals. An additional solid state detector in which the neutrals are stopped allows the total energy and thereby the ionic charge of the incident ions to be determined as well. Information from the neutral and the ion channels can be combined to determine the total mass of an incident molecular ion and the mass of one atomic fragment.

Assessing the dispersive and electrostatic components of the cohesive energy of ionic liquids using molecular dynamics simulations and molar refraction data.

PubMed

Shimizu, Karina; Tariq, Mohammad; Costa Gomes, Margarida F; Rebelo, Luís P N; Canongia Lopes, José N

2010-05-06

Molecular dynamics simulations were used to calculate the density and the cohesive molar internal energy of seventeen different ionic liquids in the liquid phase. The results were correlated with previously reported experimental density and molar refraction data. The link between the dispersive component of the total cohesive energy of the fluid and the corresponding molar refraction was established in an unequivocal way. The results have shown that the two components of the total cohesive energy (dispersive and electrostatic) exhibit strikingly different trends and ratios along different families of ionic liquids, a notion that may help explain their diverse behavior toward different molecular solutes and solvents.

Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Wenlong

2006-01-01

This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M 2S + (0.1 Ga 2S 3 + 0.9 GeS 2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass formingmore » range for the addition of different alkalis into the basic glass forming system 0.1 Ga 2S 3 + 0.9 GeS 2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M 2S + (0.1Ga 2S 3 + 0.9 GeS 2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na 2S + B 2S 3 (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction. Similar results were obtained both in neutron and synchrotron x-ray diffraction experiments. The results provide direct structural evidence that doping B 2S 3 with Na 2S creates a large fraction of tetrahedrally coordinated boron in the glass. The final section is the general conclusion of this thesis and the suggested future work that could be conducted to expand upon this research.« less

Ionic liquids: differential scanning calorimetry as a new indirect method for determination of vaporization enthalpies.

PubMed

Verevkin, Sergey P; Emel'yanenko, Vladimir N; Zaitsau, Dzmitry H; Ralys, Ricardas V; Schick, Christoph

2012-04-12

Differential scanning calorimetry (DSC) has been used to measure enthalpies of synthesis reactions of the 1-alkyl-3-methylimidazolium bromide [C(n)mim][Br] ionic liquids from 1-methylimidazole and n-alkyl bromides (with n = 4, 5, 6, 7, and 8). The optimal experimental conditions have been elaborated. Enthalpies of formation of these ionic liquids in the liquid state have been determined using the DSC results according to the Hess Law. The ideal-gas enthalpies of formation of [C(n)mim][Br] were calculated using the methods of quantum chemistry. They were used together with the DSC results to derive indirectly the enthalpies of vaporization of the ionic liquids under study. In order to validate the indirect determination, the experimental vaporization enthalpy of [C(4)mim][Br] was measured by using a quartz crystal microbalance (QCM). The combination of reaction enthalpy measurements by DSC with modern high-level first-principles calculations opens valuable indirect thermochemical options to obtain values of vaporization enthalpies of ionic liquids.

High performance preconcentration of inorganic Se species by dispersive micro-solid phase extraction with a nanosilica-ionic liquid hybrid material

NASA Astrophysics Data System (ADS)

Llaver, Mauricio; Coronado, Eduardo A.; Wuilloud, Rodolfo G.

2017-12-01

A highly sensitive and efficient dispersive micro-solid phase extraction (D-μ-SPE) method was developed for inorganic Se speciation analysis. A novel ionic liquid (IL)-nanomaterial hybrid consisting of 1-dodecyl-3-methylimidazolium bromide-functionalized nanosilica was used for the efficient retention of Se(IV) complexed with ammonium pyrrolidine dithiocarbamate, followed by elution with an ethyl acetate/Triton X-114 mixture and determination by electrothermal atomic absorption spectroscopy. The Se(VI) species was selectively determined by difference between total inorganic Se and Se(IV) after pre-reduction. The IL-nanomaterial hybrid was characterized by Fourier transform infrared spectroscopy and transmission electronic microscopy. Likewise, Se(IV) sorption capacity of the retention material and maximum amount of IL loaded on its surface were determined. Several factors concerning the functionalization, extraction and elution steps were optimized, yielding a 100% extraction efficiency for Se(IV) under optimal conditions. A limit of detection of 1.1 ng L- 1, a relative standard deviation of 5.7% and a 110-fold enhancement factor were obtained. The D-μ-SPE method was successfully applied to several water samples from different origins and compositions, including rain, tap, underground, river and sea.

Determination of sulfonamides in butter samples by ionic liquid magnetic bar liquid-phase microextraction high-performance liquid chromatography.

PubMed

Wu, Lijie; Song, Ying; Hu, Mingzhu; Xu, Xu; Zhang, Hanqi; Yu, Aimin; Ma, Qiang; Wang, Ziming

2015-01-01

A novel, simple, and environmentally friendly pretreatment method, ionic liquid magnetic bar liquid-phase microextraction, was developed for the determination of sulfonamides in butter samples by high-performance liquid chromatography. The ionic liquid magnetic bar was prepared by inserting a stainless steel wire into the hollow of a hollow fiber and immobilizing ionic liquid in the micropores of the hollow fiber. In the extraction process, the ionic liquid magnetic bars were used to stir the mixture of sample and extraction solvent and enrich the sulfonamides in the mixture. After extraction, the analyte-adsorbed ionic liquid magnetic bars were readily isolated with a magnet from the extraction system. It is notable that the present method was environmentally friendly since water and only several microliters of ionic liquid were used in the whole extraction process. Several parameters affecting the extraction efficiency were investigated and optimized, including the type of ionic liquid, sample-to-extraction solvent ratio, the number of ionic liquid magnetic bars, extraction temperature, extraction time, salt concentration, stirring speed, pH of the extraction solvent, and desorption conditions. The recoveries were in the range of 73.25-103.85 % and the relative standard deviations were lower than 6.84 %. The experiment results indicated that the present method was effective for the extraction of sulfonamides in high-fat content samples.

Induction of Ca2+-dependent cyclosporin A-insensitive nonspecific permeability of the inner membrane of liver mitochondria and cytochrome c release by α,ω-hexadecanedioic acid in media of varying ionic strength.

PubMed

Dubinin, M V; Vedernikov, A A; Khoroshavina, E I; Samartsev, V N

2014-06-01

In liver mitochondria loaded with Ca2+ or Sr(2+), α,ω-hexadecanedioic acid (HDA) can induce nonspecific permeability of the inner membrane (mitochondrial pore) by the mechanism insensitive to cyclosporin A (CsA). In this work we studied the effect of ionic strength of the incubation medium on the kinetics of the processes that accompany Ca2+-dependent induction of the mitochondrial pore by fatty acid: organelle swelling, Ca2+ release from the matrix, changes in transmembrane potential (Δψ) and rate of oxygen consumption, and the release of cytochrome c from the intermembrane space. Two basic incubation media were used: sucrose medium and isotonic ionic medium containing KCl without sucrose. We found that 200 μM Ca2+ and 20 μM HDA in the presence of CsA effectively induce high-amplitude swelling of mitochondria both in the case of sucrose and in the ionic incubation medium. In the presence of CsA, mitochondria can rapidly absorb Ca2+ and retain it in the matrix for a while without reducing Δψ. Upon incubation in the ionic medium, mitochondria retain most of the added Ca2+ in the matrix for a short time without reducing the Δψ. In both cases the addition of HDA to the mitochondria 2 min after the introduction of Ca2+ leads to the rapid release of these ions from the matrix and total drop in Δψ. The mitochondrial swelling induced by Ca2+ and HDA in non-ionic medium is accompanied by almost maximal stimulation of respiration. Under the same conditions, but during incubation of mitochondria in the ionic medium, it is necessary to add cytochrome c for significant stimulation of respiration. The mitochondrial swelling induced by Ca2+ and HDA leads to the release of cytochrome c in a larger amount in the case of ionic medium than for the sucrose medium. We conclude that high ionic strength of the incubation medium determines the massive release of cytochrome c from mitochondria and liberates it from the respiratory chain, which leads to blockade of electron transport along the respiratory chain and consequently to disruption of the energy functions of the organelles.

Determination of triazine herbicides in juice samples by microwave-assisted ionic liquid/ionic liquid dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography.

PubMed

Su, Rui; Li, Dan; Wu, Lijie; Han, Jing; Lian, Wenhui; Wang, Keren; Yang, Hongmei

2017-07-01

A novel microextraction method, termed microwave-assisted ionic liquid/ionic liquid dispersive liquid-liquid microextraction, has been developed for the rapid enrichment and analysis of triazine herbicides in fruit juice samples by high-performance liquid chromatography. Instead of using hazardous organic solvents, two kinds of ionic liquids, a hydrophobic ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) and a hydrophilic ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate), were used as the extraction solvent and dispersion agent, respectively, in this method. The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of 1-hexyl-3-methylimidazolium hexafluorophosphate dispersed entirely into sample solution with the help of 1-butyl-3-methylimidazolium tetrafluoroborate. In addition, an ion-pairing agent (NH 4 PF 6 ) was introduced to improve recoveries of the ionic liquid phase. Several experimental parameters that might affect the extraction efficiency were investigated. Under the optimum experimental conditions, the linearity for determining the analytes was in the range of 5.00-250.00 μg/L, with the correlation coefficients of 0.9982-0.9997. The practical application of this effective and green method is demonstrated by the successful analysis of triazine herbicides in four juice samples, with satisfactory recoveries (76.7-105.7%) and relative standard deviations (lower than 6.6%). In general, this method is fast, effective, and robust to determine triazine herbicides in juice samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microscopic properties of ionic liquid/organic semiconductor interfaces revealed by molecular dynamics simulations.

PubMed

Yokota, Yasuyuki; Miyamoto, Hiroo; Imanishi, Akihito; Takeya, Jun; Inagaki, Kouji; Morikawa, Yoshitada; Fukui, Ken-Ichi

2018-05-09

Electric double-layer transistors based on ionic liquid/organic semiconductor interfaces have been extensively studied during the past decade because of their high carrier densities at low operation voltages. Microscopic structures and the dynamics of ionic liquids likely determine the device performance; however, knowledge of these is limited by a lack of appropriate experimental tools. In this study, we investigated ionic liquid/organic semiconductor interfaces using molecular dynamics to reveal the microscopic properties of ionic liquids. The organic semiconductors include pentacene, rubrene, fullerene, and 7,7,8,8-tetracyanoquinodimethane (TCNQ). While ionic liquids close to the substrate always form the specific layered structures, the surface properties of organic semiconductors drastically alter the ionic dynamics. Ionic liquids at the fullerene interface behave as a two-dimensional ionic crystal because of the energy gain derived from the favorable electrostatic interaction on the corrugated periodic substrate.

Genotoxicity, mutagenicity and cytotoxicity of carotenoids extracted from ionic liquid in multiples organs of Wistar rats.

PubMed

Larangeira, Paula Martins; de Rosso, Veridiana Vera; da Silva, Victor Hugo Pereira; de Moura, Carolina Foot Gomes; Ribeiro, Daniel Araki

2016-11-01

The ionic liquid or melted salt 1-Butyl-3-methylimidazolium is an alternative process to extract natural pigments, such as carotenoids. Lycopene represents 80-90% of total of carotenoids presents in tomatoes and it has been widely studied due its potent antioxidant action. The aim of this study was to evaluate genotoxicity, mutagenicity and cytotoxicity of carotenoids extracted from ionic liquid using experimental model in vivo. For this purpose, a total of 20 male Wistar rats were distributed into four groups (n=5), as follows: control group; received a corresponding amount of corn oil for 7days by intragastric gavage (i.g.), ionic liquid group, received 10mgkg -1 body weight for 7days by gavage; 10mg carotenoids group, received 10mgkg -1 bw dissolved in corn oil for 7days by gavage and 500mg carotenoids group, received 500mgkg -1 bw dissolved in corn oil for 7days by gavage. Rat liver treated with ionic liquid exhibited moderate histopathological changes randomly distributed in the parenchyma, such as cytoplasmic eosinophilia, apoptotic bodies, inflammatory infiltrate and focal necrosis. DNA damage was found in peripheral blood and liver cells of rats treated with ionic liquid or carotenoids at 500mg. An increase of micronucleated cells and 8-OhDG immunopositive cells were also detected in rats treated with carotenoids at 500mg. In summary, our results demonstrate that recommended dose for human daily intake of carotenoids extracted by ionic liquid did not induce genotoxicity, mutagenicity and cytotoxicity in multiple organs of rats. Copyright © 2016 Elsevier GmbH. All rights reserved.

Ionic liquids based microwave-assisted extraction of lichen compounds with quantitative spectrophotodensitometry analysis.

PubMed

Bonny, Sarah; Paquin, Ludovic; Carrié, Daniel; Boustie, Joël; Tomasi, Sophie

2011-11-30

Ionic liquids based extraction method has been applied to the effective extraction of norstictic acid, a common depsidone isolated from Pertusaria pseudocorallina, a crustose lichen. Five 1-alkyl-3-methylimidazolium ionic liquids (ILs) differing in composition of alkyl chain and anion were investigated for extraction efficiency. The extraction amount of norstictic acid was determined after recovery on HPTLC with a spectrophotodensitometer. The proposed approaches (IL-MAE and IL-heat extraction (IL-HE)) have been evaluated in comparison with usual solvents such as tetrahydrofuran in heat-reflux extraction and microwave-assisted extraction (MAE). The results indicated that both the characteristics of the alkyl chain and anion influenced the extraction of polyphenolic compounds. The sulfate-based ILs [C(1)mim][MSO(4)] and [C(2)mim][ESO(4)] presented the best extraction efficiency of norstictic acid. The reduction of the extraction times between HE and MAE (2 h-5 min) and a non-negligible ratio of norstictic acid in total extract (28%) supports the suitability of the proposed method. This approach was successfully applied to obtain additional compounds from other crustose lichens (Pertusaria amara and Ochrolechia parella). Copyright © 2011 Elsevier B.V. All rights reserved.

Visualization of Biomass Solubilization and Cellulose Regeneration during Ionic Liquid Pretreatment of Switchgrass

USDA-ARS?s Scientific Manuscript database

Auto-fluorescent mapping of plant cell walls was used to visualize cellulose and lignin in pristine switchgrass (Panicum virgatum) stems to determine the mechanisms of biomass dissolution during ionic liquid pretreatment. The addition of ground switchgrass to the ionic liquid 1-n-ethyl-3-methylimid...

Electrodialytic in-line preconcentration for ionic solute analysis.

PubMed

Ohira, Shin-Ichi; Yamasaki, Takayuki; Koda, Takumi; Kodama, Yuko; Toda, Kei

2018-04-01

Preconcentration is an effective way to improve analytical sensitivity. Many types of methods are used for enrichment of ionic solute analytes. However, current methods are batchwise and include procedures such as trapping and elution. In this manuscript, we propose in-line electrodialytic enrichment of ionic solutes. The method can enrich ionic solutes within seconds by quantitative transfer of analytes from the sample solution to the acceptor solution under an electric field. Because of quantitative ion transfer, the enrichment factor (the ratio of the concentration in the sample and to that in the obtained acceptor solution) only depends on the flow rate ratio of the sample solution to the acceptor solution. The ratios of the concentrations and flow rates are equal for ratios up to 70, 20, and 70 for the tested ionic solutes of inorganic cations, inorganic anions, and heavy metal ions, respectively. The sensitivity of ionic solute determinations is also improved based on the enrichment factor. The method can also simultaneously achieve matrix isolation and enrichment. The method was successively applied to determine the concentrations of trace amounts of chloroacetic acids in tap water. The regulated concentration levels cannot be determined by conventional high-performance liquid chromatography with ultraviolet detection (HPLC-UV) without enrichment. However, enrichment with the present method is effective for determination of tap water quality by improving the limits of detection of HPLC-UV. The standard addition test with real tap water samples shows good recoveries (94.9-109.6%). Copyright © 2017 Elsevier B.V. All rights reserved.

Comparative Investigation of the Ionicity of Aprotic and Protic Ionic Liquids in Molecular Solvents by using Conductometry and NMR Spectroscopy.

PubMed

Thawarkar, Sachin; Khupse, Nageshwar D; Kumar, Anil

2016-04-04

Electrical conductivity (σ), viscosity (η), and self-diffusion coefficient (D) measurements of binary mixtures of aprotic and protic imidazolium-based ionic liquids with water, dimethyl sulfoxide, and ethylene glycol were measured from 293.15 to 323.15 K. The temperature dependence study reveals typical Arrhenius behavior. The ionicities of aprotic ionic liquids were observed to be higher than those of protic ionic liquids in these solvents. The aprotic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, [bmIm][BF4 ], displays 100 % ionicity in both water and ethylene glycol. The protic ionic liquids in both water and ethylene glycol are classed as good ionic candidates, whereas in DMSO they are classed as having a poor ionic nature. The solvation dynamics of the ionic species of the ionic liquids are illustrated on the basis of the (1) H NMR chemical shifts of the ionic liquids. The self-diffusion coefficients D of the cation and anion of [HmIm][CH3 COO] in D2 O and in [D6 ]DMSO are determined by using (1) H nuclei with pulsed field gradient spin-echo NMR spectroscopy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Globular, Sponge-like to Layer-like Morphological Transition in 1-n-Alkyl-3-methylimidazolium Octylsulfate Ionic Liquid Homologous Series.

PubMed

Kapoor, Utkarsh; Shah, Jindal K

2018-01-11

Segregation of polar and nonpolar domains in ionic liquids for which either the cation or anion is responsible for inducing nonpolar domains is well understood. On the other hand, information regarding the nanoscale heterogeneities originating due to the presence of nonpolar content on both the ions is rudimentary at this point. The present contribution is aimed at addressing this question and focuses on a molecular dynamics simulation study to probe nanoscale structural and aggregation features of the 1-n-alkyl-3-methylimidazolium [C n mim] octylsulfate [C 8 SO 4 ] ionic liquid homologous series (n = 2, 4, 6, 8, 10, and 12). The objective of this work is to determine the effect of increasing alkyl chain length in the cation on nonpolar domain formation, especially when the alkyl chain lengths from both the ions participate in defining such domains. The results indicate that all the ionic liquids form nonpolar domains, morphology of which gradually changes from globular, sponge-like to layer-like structure with increase in the cationic alkyl chain length. The length of the nonpolar domains calculated from the total structure factor for [C 10 mim][C 8 SO 4 ] is considerably higher than that reported for other imidazolium-based ionic liquid containing smaller anions. The structure factor for [C 12 mim][C 8 SO 4 ] ionic liquid contains multiple intermediate peaks separating the charge alternation peak and pre-peak, which points to nonpolar domains of varying lengths, an observation that remains to be validated. Analysis of the heterogeneous order parameters and orientational correlation functions of the alkyl chains further suggests an increase in the spatial heterogeneity and long-range order along the homologous series. The origin of rich diversity of structures obtained by introducing nonpolar content on both the ions is discussed.

Acid-base titrations of functional groups on the surface of the thermophilic bacterium Anoxybacillus flavithermus: comparing a chemical equilibrium model with ATR-IR spectroscopic data.

PubMed

Heinrich, Hannah T M; Bremer, Phil J; Daughney, Christopher J; McQuillan, A James

2007-02-27

Acid-base functional groups at the surface of Anoxybacillus flavithermus (AF) were assigned from the modeling of batch titration data of bacterial suspensions and compared with those determined from in situ infrared spectroscopic titration analysis. The computer program FITMOD was used to generate a two-site Donnan model (site 1: pKa = 3.26, wet concn = 2.46 x 10(-4) mol g(-1); site 2: pKa = 6.12, wet concn = 6.55 x 10(-5) mol g(-1)), which was able to describe data for whole exponential phase cells from both batch acid-base titrations at 0.01 M ionic strength and electrophoretic mobility measurements over a range of different pH values and ionic strengths. In agreement with information on the composition of bacterial cell walls and a considerable body of modeling literature, site 1 of the model was assigned to carboxyl groups, and site 2 was assigned to amino groups. pH difference IR spectra acquired by in situ attenuated total reflection infrared (ATR-IR) spectroscopy confirmed the presence of carboxyl groups. The spectra appear to show a carboxyl pKa in the 3.3-4.0 range. Further peaks were assigned to phosphodiester groups, which deprotonated at slightly lower pH. The presence of amino groups could not be confirmed or discounted by IR spectroscopy, but a positively charged group corresponding to site 2 was implicated by electrophoretic mobility data. Carboxyl group speciation over a pH range of 2.3-10.3 at two different ionic strengths was further compared to modeling predictions. While model predictions were strongly influenced by the ionic strength change, pH difference IR data showed no significant change. This meant that modeling predictions agreed reasonably well with the IR data for 0.5 M ionic strength but not for 0.01 M ionic strength.

Response surface optimization of pH and ionic strength for emulsion characteristics of egg yolk.

PubMed

Kurt, S; Zorba, O

2009-11-01

Effects of pH (3.5, 4.5, 6.0, 7.5, and 8.5) and ionic strength (0.05, 0.15, 0.30, 0.45, and 0.55 M NaCl) on emulsion capacity, emulsion stability (ES), apparent yield stress of emulsion (AYS), and emulsion density (ED) of egg yolk were studied by using a model system. Ionic strength and pH had significant (P < 0.01) effects on the emulsion characteristics of egg yolk. Their interaction effects also have been found significant on ES, AYS, and ED. Predicted solutions of ES, emulsion capacity, and ED were minimum. The critical point of ES was determined to be at pH 6.08 and an ionic strength of 0.49 (M NaCl). Predicted solution for AYS was a maximum, which was determined to be at pH 6.04 and an ionic strength of 0.29 (M NaCl). Optimum values of pH and ionic strenght were 4.61 to 7.43 and 0.10 to 0.47, respectively.

A model for self-diffusion of guanidinium-based ionic liquids: a molecular simulation study.

PubMed

Klähn, Marco; Seduraman, Abirami; Wu, Ping

2008-11-06

We propose a novel self-diffusion model for ionic liquids on an atomic level of detail. The model is derived from molecular dynamics simulations of guanidinium-based ionic liquids (GILs) as a model case. The simulations are based on an empirical molecular mechanical force field, which has been developed in our preceding work, and it relies on the charge distribution in the actual liquid. The simulated GILs consist of acyclic and cyclic cations that were paired with nitrate and perchlorate anions. Self-diffusion coefficients are calculated at different temperatures from which diffusive activation energies between 32-40 kJ/mol are derived. Vaporization enthalpies between 174-212 kJ/mol are calculated, and their strong connection with diffusive activation energies is demonstrated. An observed formation of cavities in GILs of up to 6.5% of the total volume does not facilitate self-diffusion. Instead, the diffusion of ions is found to be determined primarily by interactions with their immediate environment via electrostatic attraction between cation hydrogen and anion oxygen atoms. The calculated average time between single diffusive transitions varies between 58-107 ps and determines the speed of diffusion, in contrast to diffusive displacement distances, which were found to be similar in all simulated GILs. All simulations indicate that ions diffuse by using a brachiation type of movement: a diffusive transition is initiated by cleaving close contacts to a coordinated counterion, after which the ion diffuses only about 2 A until new close contacts are formed with another counterion in its vicinity. The proposed diffusion model links all calculated energetic and dynamic properties of GILs consistently and explains their molecular origin. The validity of the model is confirmed by providing an explanation for the variation of measured ratios of self-diffusion coefficients of cations and paired anions over a wide range of values, encompassing various ionic liquid classes as well as the simulated GILs. The proposed diffusion model facilitates the qualitative a priori prediction of the impact of ion modifications on the diffusive characteristics of new ionic liquids.

Determination of organic carbon and ionic accountability of various waste and product waters derived from ECLSS water recovery tests and Spacelab humidity condensate

NASA Technical Reports Server (NTRS)

Carter, Donald L.; Cole, Harold; Habercom, Mark; Griffith, Guy

1992-01-01

The development of a closed-loop water recovery system for Space Station Freedom involves many technical challenges associated with contaminant removal. Attention is presently given to the characterization of contaminants constituting total organic carbon (TOC), and to the Hubaux and Vos (1970) statistical model for low level TOC that has been employed. A tabulation is given for TOC accountability in the case of both potable and hygiene waters.

Similarity law and critical properties in ionic systems.

NASA Astrophysics Data System (ADS)

Desgranges, Caroline; Delhommelle, Jerome

2017-11-01

Using molecular simulations, we determine the locus of ideal compressibility, or Zeno line, for a series of ionic compounds. We find that the shape of this thermodynamic contour follows a linear law, leading to the determination of the Boyle parameters. We also show that a similarity law, based on the Boyle parameters, yields accurate critical data when compared to the experiment. Furthermore, we show that the Boyle density scales linearly with the size-asymmetry, providing a direct route to establish a correspondence between the thermodynamic properties of different ionic compounds.

On the chemical stabilities of ionic liquids.

PubMed

Sowmiah, Subbiah; Srinivasadesikan, Venkatesan; Tseng, Ming-Chung; Chu, Yen-Ho

2009-09-25

Ionic liquids are novel solvents of interest as greener alternatives to conventional organic solvents aimed at facilitating sustainable chemistry. As a consequence of their unusual physical properties, reusability, and eco-friendly nature, ionic liquids have attracted the attention of organic chemists. Numerous reports have revealed that many catalysts and reagents were supported in the ionic liquid phase, resulting in enhanced reactivity and selectivity in various important reaction transformations. However, synthetic chemists cannot ignore the stability data and intermolecular interactions, or even reactions that are directly applicable to organic reactions in ionic liquids. It is becoming evident from the increasing number of reports on use of ionic liquids as solvents, catalysts, and reagents in organic synthesis that they are not totally inert under many reaction conditions. While in some cases, their unexpected reactivity has proven fortuitously advantageous in others is has been a problem, it is imperative that when selecting an ionic liquid for a particular synthetic application, attention be paid to its compatibility with the reaction conditions. Even though, more than 200 room temperature ionic liquids are known, only a few reports have commented their effects on reaction mechanisms or rate/stability. Therefore, rather than attempting to give a comprehensive overview of ionic liquid chemistry, this review focuses on the non-innocent nature of ionic liquids, with a decided emphasis to clearly illuminate the ability of ionic liquids to affect the mechanistic aspects of some organic reactions thereby affecting and promoting the yield and selectivity.

Theoretical Study of Renewable Ionic Liquids in the Pure State and with Graphene and Carbon Nanotubes.

PubMed

García, Gregorio; Atilhan, Mert; Aparicio, Santiago

2015-09-17

The N-ethyl-N-(furan-2-ylmethyl)ethanaminium dihydrogen phosphate ionic liquid was studied as a model of ionic liquids which can be produced from totally renewable sources. A computational study using both molecular dynamics and density functional theory methods was carried out. The properties, structuring, and intermolecular interactions (hydrogen bonding) of this fluid in the pure state were studied as a function of pressure and temperature. Likewise, the adsorption on graphene and the confinement between graphene sheets was also studied. The solvation of single walled carbon nanotubes in the selected ionic liquid was analyzed together with the behavior of ions confined inside these nanotubes. The reported results show remarkable properties for this fluid, which show that many of the most relevant properties of ionic liquids and their ability to interact with carbon nanosystems may be maintained and even improved using new families of renewable compounds instead of classic types of ionic liquids with worse environmental, toxicological, and economical profiles.

Surface-active ionic liquids in micellar catalysis: impact of anion selection on reaction rates in nucleophilic substitutions† †Electronic supplementary information (ESI) available: Formulae for calculating aggregation parameters and fitting of kinetic constants and copies of NMR spectra. See DOI: 10.1039/c6cp00493h Click here for additional data file.

PubMed Central

Cognigni, Alice; Gaertner, Peter; Zirbs, Ronald; Peterlik, Herwig; Prochazka, Katharina; Schröder, Christian

2016-01-01

A series of surface-active ionic liquids based on the 1-dodecyl-3-methylimidazolium cation and different anions such as halides and alkylsulfates was synthesized. The aggregation behavior of these ionic liquids in water was characterized by surface tension, conductivity measurements and UV-Vis spectroscopy in order to determine the critical micelle concentration (CMC) and to provide aggregation parameters. The determination of surface activity and aggregation properties of amphiphilic ionic liquids was accompanied by SAXS studies on selected surface-active ionic liquids. The application of these surface-active ionic liquids with different anions was tested in nucleophilic substitution reactions for the degradation of organophosphorus compounds. Kinetic studies via UV-Vis spectrophotometry showed a strong acceleration of the reaction in the micellar system compared to pure water. In addition, an influence of the anion was observed, resulting in a correlation between the anion binding to the micelle and the reaction rate constants, indicating that the careful choice of the surface-active ionic liquid can considerably affect the outcome of reactions. PMID:27121134

Fluorophotometric determination of critical micelle concentration (CMC) of ionic and non-ionic surfactants with carbon dots via Stokes shift.

PubMed

Lavkush Bhaisare, Mukesh; Pandey, Sunil; Shahnawaz Khan, M; Talib, Abou; Wu, Hui-Fen

2015-01-01

A new and facile method for the determination of critical micelle concentration (CMC) of ionic and non-ionic surfactants is proposed in this article. Carbon dots exhibited substantial fluorescence and therefore enhanced the sensitivity of this evaluation. Understanding the formation of surfactant micelles is vital for the applications of biomedicine such as drug fabrication and smart molecular vehicles in delivering therapeutic dosage to various molecular sites. The fluorescence property of carbon dots was utilized for the first time to estimate the critical micelle concentration of surfactants. The central concept of the approach is based on the Stokes shift determination of a system composed of constant amount of carbon dots with varying concentrations of ionic and non-ionic surfactants. The synthesized carbon dots were characterized by FTIR, TEM, XRD, Raman, UV, and fluorescence spectroscope. The carbon dots were excited at 280 nm so as to obtain maximum emission for the Stokes shift measurement. The CMC value of cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), Triton X-100, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide (SB-12) evaluated by this approach was found to be 0.98, 7.3, 0.19, and 3.5mM, respectively. The signals of spectra were assigned and explained in terms of both electron transitions between specific molecular orbital and the interaction with solvent. Copyright © 2014 Elsevier B.V. All rights reserved.

Determination of the solubility parameter of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate by inverse gas chromatography.

PubMed

Ma, Xiaohong; Wang, Qiang; Li, Xiaoping; Tang, Jun; Zhang, Zhengfang

2015-11-01

Thermodynamic properties of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] BF4) were determined via inverse gas chromatography (IGC). Two groups of solvents with different chemical natures and polarities were used to obtain information about [BMIM] BF4-solvent interactions. The specific retention volume, molar heat of sorption, weight fraction activity coefficient, Flory-Huggins interaction parameter as well as solubility parameter were also determined in a temperature range of 333 - 373 K. The results showed that the selected solvents n-C10 to n-C12, carbon tetrachloride, cyclohexane and toluene were poor solvents for [BMIM] BF4, while dichloromethane, acetone, chloroform, methyl acetate, ethanol and methanol were favorite solvents for [BMIM] BF4. In addition, the solubility parameter of [ BMIM] BF4 was determined as 23.39 (J/cm3)0.5 by the extrapolation at 298 K. The experiment proved that IGC was a simple and accurate method to obtain the thermodynamic properties of ionic liquids. This study could be used as a reference to the application and research of the ionic liquids.

Determination of trihalomethanes in waters by ionic liquid-based single drop microextraction/gas chromatographic/mass spectrometry.

PubMed

Aguilera-Herrador, Eva; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

2008-10-31

A simple, rapid, solventless method for the determination of trihalomethanes (THMs) (chloroform, bromodichloromethane, dibromochloromethane and bromoform) in water samples is presented. The analytes are extracted from the headspace of the aqueous matrix into a 2 microL drop of the ionic liquid 1-octyl-3-methyl-imidazolium hexafluorophosphate working at 30 degrees C for 30 min. The separation and detection of the target compounds is accomplished by gas chromatography/mass spectrometry owing to the use of an interface that efficiently transfers the analytes extracted in the ionic liquid drop to the gas chromatograph while preventing the ionic liquid from entering the column. The detection limits obtained are below the values compelled by the legislation, ranging from 0.5 microg L(-1) for chloroform and bromodichloromethane to 0.9 microg L(-1) for dibromochloromethane. The use of ionic liquid in the extraction procedure avoids the use of organic solvents and leads to relative standard deviations that range from 3.1% to 4.8%.

Beneficial effect of added water on sodium metal cycling in super concentrated ionic liquid sodium electrolytes

NASA Astrophysics Data System (ADS)

Basile, Andrew; Ferdousi, Shammi A.; Makhlooghiazad, Faezeh; Yunis, Ruhamah; Hilder, Matthias; Forsyth, Maria; Howlett, Patrick C.

2018-03-01

The plating and stripping performance of sodium metal in an ionic liquid electrolyte is improved when including water as an additive. Herein we report for the first time the trend of improved cycling behavior of Na0/+ in N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide with 500 ppm H2O. The addition of water to this ionic liquid electrolyte promotes the breakdown of the [FSI]- anion towards beneficial SEI formation. The benefits during plating and stripping of sodium is observed as lower total polarization during symmetrical cell cycling and decreased electrode/electrolyte interface impedance. Sodium metal surfaces after cycling with 500 ppm H2O are shown to be smooth in morphology in comparison to lower additive concentrations. The outcome of adventitious moisture benefiting Na0/+ cycling in an ionic liquid, contrary to conventional electrolytes, allows flexibility in ionic liquid electrolyte design to the benefit of battery manufacturers.

Ionic Liquid-Hybrid Molecularly Imprinted Material-Filter Solid-Phase Extraction Coupled with HPLC for Determination of 6-Benzyladenine and 4-Chlorophenoxyacetic Acid in Bean Sprouts.

PubMed

Han, Yehong; Yang, Chunliu; Zhou, Yang; Han, Dandan; Yan, Hongyuan

2017-03-01

A new method involving ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled to high-performance liquid chromatography (IL-HIM-FSPE-HPLC) was developed for the simultaneous isolation and determination of 6-benzyladenine (6-BA) and 4-chlorophenoxyacetic acid (4-CPA) in bean sprouts. Sample preconcentration was performed using a modified filter, with the new IL-HIM as the adsorbent, which shows double adsorption. The first adsorption involves special recognition of molecular imprinting, and the second involves ion exchange and electrostatic attraction caused by the ionic liquid. This method combines the advantages of ionic liquids, hybrid materials, and molecularly imprinted polymers and was successfully applied to determine 6-BA and 4-CPA in bean sprouts. The adsorption of 6-BA to IL-HIM is based on selective imprinted recognition, whereas the adsorption of 4-CPA is mainly dependent on ion-exchange interactions.

An elegant access to formation and vaporization enthalpies of ionic liquids by indirect DSC experiment and "in silico" calculations.

PubMed

Verevkin, Sergey P; Zaitsau, Dzmitry H; Emel'yanenko, Vladimir N; Schick, Christoph; Jayaraman, Saivenkataraman; Maginn, Edward J

2012-07-14

We used DSC for determination of the reaction enthalpy of the synthesis of the ionic liquid [C(4)mim][Cl]. A combination of DSC and quantum chemical calculations presents a new, indirect way to study thermodynamics of ionic liquids. The new procedure was validated with two direct experimental measurements and MD simulations.

Determination of the total acidity in soft drinks using potentiometric sequential injection titration.

PubMed

van Staden, J Koos F; Mashamba, M Mulalo G; Stefan, R Raluca I

2002-12-06

A potentiometric SI titration system for the determination of total acidity in soft drinks is proposed. The concept is based on the aspiration of the acid soft drink sample between two base zones into a holding coil with the volume of the first base zone twice to that of the second one and channelled by flow reversal through a reaction coil to a potentiometric sensor. A solution of 0.1 mol l(-1) sodium chloride is used as ionic strength adjustment buffer in the carrier stream. The system has been applied to the analysis of some South African soft drinks having a total acidity level of about 0.2-0.3% (w/v). The method has a sample frequency of 45 samples per h with a linear range of 0.1 and 0.6% (w/v). It is easy to use, fully computerised, and gives the results that are comparable to both automated batch titration and manual titration.

The hemolymph of caterpillars Spodoptera littoralis: physico-chemical properties and ionic composition compared to culture media.

PubMed

Smagghe, G; Van Leeuwen, T

2004-01-01

In this paper, we determined some physico-chemical properties like osmotic pressure, pH and electrical conductivity of the hemolymph from caterpillars of Spodoptera littoralis (Lepidoptera: Noctuidae) during the last larval instar. It was of interest that we observed an increase in osmotic pressure with the increase in age in the last instar that may concur with the start of histolysis at metamorphosis. These physicochemical properties were then compared to those of Grace's and modified Grace's tissue culture medium. In addition, concentrations of the cations Na, K, Ca and Mg, and the anions Cl, NO3, PO4 and SO4 were determined in the insect hemolymph of S. littoralis. The cations K and Mg reached high values with a percent of about 52% of the total amount of cations. The concentration of sodium was low. The total sum of the anions consisted about 56 meq/1, and this allows to neutralise about 45 % of the total cations.

Ionic strength and DOC determinations from various freshwater sources to the San Francisco Bay

USGS Publications Warehouse

Hunter, Y.R.; Kuwabara, J.S.

1994-01-01

An exact estimation of dissolved organic carbon (DOC) within the salinity gradient of zinc and copper metals is significant in understanding the limit to which DOC could influence metal speciation. A low-temperature persulfate/oxygen/ultraviolet wet oxidation procedure was utilized for analyzing DOC samples adapted for ionic strength from major freshwater sources of the northern and southern regions of San Francisco Bay. The ionic strength of samples was modified with a chemically defined seawater medium up to 0.7M. Based on the results, a minimum effect of ionic strength on oxidation proficiency for DOC sources to the Bay over an ionic strength gradient of 0.0 to 0.7 M was observed. There was no major impacts of ionic strength on two Suwanee River fulvic acids. In general, the noted effects associated with ionic strength were smaller than the variances seen in the aquatic environment between high- and low-temperature methods.

Microscopic characterization of tension wood cell walls of Japanese beech (Fagus crenata) treated with ionic liquids.

PubMed

Kanbayashi, Toru; Miyafuji, Hisashi

2016-09-01

Tension wood that is an abnormal part formed in angiosperms has been barely used for wood industry. In this study, to utilize the tension wood effectively by means of liquefaction using ionic liquid, we performed morphological and topochemical determination of the changes in tension wood of Japanese beech (Fagus crenata) during ionic liquid treatment at the cellular level using light microscopy, scanning electron microscopy and confocal Raman microscopy. Ionic liquid treatment induced cell wall swelling in tension wood. Changes in the tissue morphology treated with ionic liquids were different between normal wood and tension wood, moreover the types of ionic liquids. The ionic liquid 1-ethyl-3-methylimidazolium chloride liquefied gelatinous layers rapidly, whereas 1-ethylpyridinium bromide liquefied slowly but delignified selectively. These novel insights into the deconstruction behavior of tension wood cell walls during ionic liquid treatment provide better understanding of the liquefaction mechanism. The obtained knowledge will contribute to development of an effective chemical processing of tension wood using ionic liquids and lead to efficient use of wood resources. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length.

PubMed

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-10-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes.

Ionic Size Effects: Generalized Boltzmann Distributions, Counterion Stratification, and Modified Debye Length

PubMed Central

Liu, Bo; Liu, Pei; Xu, Zhenli; Zhou, Shenggao

2013-01-01

Near a charged surface, counterions of different valences and sizes cluster; and their concentration profiles stratify. At a distance from such a surface larger than the Debye length, the electric field is screened by counterions. Recent studies by a variational mean-field approach that includes ionic size effects and by Monte Carlo simulations both suggest that the counterion stratification is determined by the ionic valence-to-volume ratios. Central in the mean-field approach is a free-energy functional of ionic concentrations in which the ionic size effects are included through the entropic effect of solvent molecules. The corresponding equilibrium conditions define the generalized Boltzmann distributions relating the ionic concentrations to the electrostatic potential. This paper presents a detailed analysis and numerical calculations of such a free-energy functional to understand the dependence of the ionic charge density on the electrostatic potential through the generalized Boltzmann distributions, the role of ionic valence-to-volume ratios in the counterion stratification, and the modification of Debye length due to the effect of ionic sizes. PMID:24465094

Mixtures of the 1-ethyl-3-methylimidazolium acetate ionic liquid with different inorganic salts: insights into their interactions.

PubMed

Oliveira, Filipe S; Cabrita, Eurico J; Todorovic, Smilja; Bernardes, Carlos E S; Lopes, José N Canongia; Hodgson, Jennifer L; MacFarlane, Douglas R; Rebelo, Luís P N; Marrucho, Isabel M

2016-01-28

In this work, we explore the interactions between the ionic liquid 1-ethyl-3-methylimidazolim acetate and different inorganic salts belonging to two different cation families, those based on ammonium and others based on sodium. NMR and Raman spectroscopy are used to screen for changes in the molecular environment of the ions in the ionic liquid + inorganic salt mixtures as compared to pure ionic liquid. The ion self-diffusion coefficients are determined from NMR data, allowing the discussion of the ionicity values of the ionic liquid + inorganic salt mixtures calculated using different methods. Our data reveal that preferential interactions are established between the ionic liquid and ammonium-based salts, as opposed to sodium-based salts. Computational calculations show the formation of aggregates between the ionic liquid and the inorganic salt, which is consistent with the spectroscopic data, and indicate that the acetate anion of the ionic liquid establishes preferential interactions with the ammonium cation of the inorganic salts, leaving the imidazolium cation less engaged in the media.

Brønsted acidity of protic ionic liquids: a modern ab initio valence bond theory perspective.

PubMed

Patil, Amol Baliram; Mahadeo Bhanage, Bhalchandra

2016-09-21

Room temperature ionic liquids (ILs), especially protic ionic liquids (PILs), are used in many areas of the chemical sciences. Ionicity, the extent of proton transfer, is a key parameter which determines many physicochemical properties and in turn the suitability of PILs for various applications. The spectrum of computational chemistry techniques applied to investigate ionic liquids includes classical molecular dynamics, Monte Carlo simulations, ab initio molecular dynamics, Density Functional Theory (DFT), CCSD(t) etc. At the other end of the spectrum is another computational approach: modern ab initio Valence Bond Theory (VBT). VBT differs from molecular orbital theory based methods in the expression of the molecular wave function. The molecular wave function in the valence bond ansatz is expressed as a linear combination of valence bond structures. These structures include covalent and ionic structures explicitly. Modern ab initio valence bond theory calculations of representative primary and tertiary ammonium protic ionic liquids indicate that modern ab initio valence bond theory can be employed to assess the acidity and ionicity of protic ionic liquids a priori.

Landfills as sources of polyfluorinated compounds, polybrominated diphenyl ethers and musk fragrances to ambient air

NASA Astrophysics Data System (ADS)

Weinberg, Ingo; Dreyer, Annekatrin; Ebinghaus, Ralf

2011-02-01

In order to investigate landfills as sources of polyfluorinated compounds (PFCs), polybrominated diphenyl ethers (PBDEs) and synthetic musk fragrances to the atmosphere, air samples were simultaneously taken at two landfills (one active and one closed) and two reference sites using high volume air samplers. Contaminants were accumulated on glass fiber filters (particle phase) and PUF/XAD-2/PUF cartridges (gas phase), extracted by methyl-tert butyl ether/acetone (neutral PFCs), methanol (ionic PFCs) or hexane/acetone (PBDEs, musk fragrances), and detected by GC-MS (neutral PFCs, PBDEs, musk fragrances) or HPLC-MS/MS (ionic PFCs). Total concentrations ranged from 84 to 706 pg m -3 (volatile PFCs, gas phase), from

Ionic Graphitization of Ultrathin Films of Ionic Compounds.

PubMed

Kvashnin, A G; Pashkin, E Y; Yakobson, B I; Sorokin, P B

2016-07-21

On the basis of ab initio density functional calculations, we performed a comprehensive investigation of the general graphitization tendency in rocksalt-type structures. In this paper, we determine the critical slab thickness for a range of ionic cubic crystal systems, below which a spontaneous conversion from a cubic to a layered graphitic-like structure occurs. This conversion is driven by surface energy reduction. Using only fundamental parameters of the compounds such as the Allen electronegativity and ionic radius of the metal atom, we also develop an analytical relation to estimate the critical number of layers.

Salting-out homogenous extraction followed by ionic liquid/ionic liquid liquid-liquid micro-extraction for determination of sulfonamides in blood by high performance liquid chromatography.

PubMed

Liu, Zhongling; Yu, Wei; Zhang, Hanqi; Gu, Fanbin; Jin, Xiangqun

2016-12-01

Salting-out homogenous extraction followed by ionic liquid/ionic liquid dispersive liquid-liquid micro-extraction system was developed and applied to the extraction of sulfonamides in blood. High-performance liquid chromatography was applied to the determination of the analytes. The blood sample was centrifuged to obtain the serum. After the proteins in the serum were removed in the presence of acetonitrile, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, dipotassium hydrogen phosphate, ionic liquid 1-Hexyl-3-methylimidazolium hexafluorophosphate were added into the resulting solution. After the resulting mixture was ultrasonically shaken and centrifuged, the precipitate was separated. The acetonitrile was added in the precipitate and the analytes were extracted into the acetonitrile phase. The parameters affecting the extraction efficiency, such as volume of ionic liquid, amount of dipotassium hydrogen phosphate, volume of dispersant, extraction time and temperature were investigated. The limits of detection of sulfamethizole (STZ), sulfachlorpyridazine (SCP), sulfamethoxazole (SMX) and Sulfisoxazole (SSZ) were 4.78, 3.99, 5.21 and 3.77μgL -1 , respectively. When the present method was applied to the analysis of real blood samples, the recoveries of analytes ranged from 90.0% to 113.0% and relative standard deviations were lower than 7.2%. Copyright © 2016 Elsevier B.V. All rights reserved.

Determination of Physical Properties of Ionic Liquids Using Molecular Simulations

DTIC Science & Technology

2010-08-20

That is, most groups rely on relatively short (100-500 ps) simulations and evaluate the viscosity via conventional Green - Kubo integration . In this...and can contribute to higher than expected viscosities . The liquid structure of the energetic ionic liquid 2-hydroxyethylhydrizinium nitrate was...claimed previously that neglect of polarizability leads to inaccuracies in the computed transport properties of ionic liquids such as viscosities

Solvation structures of water in trihexyltetradecylphosphonium-orthoborate ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yong-Lei, E-mail: wangyonl@gmail.com; System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, SE-100 44 Stockholm; Sarman, Sten

2016-08-14

Atomistic molecular dynamics simulations have been performed to investigate effective interactions of isolated water molecules dispersed in trihexyltetradecylphosphonium-orthoborate ionic liquids (ILs). The intrinsic free energy changes in solvating one water molecule from gas phase into bulk IL matrices were estimated as a function of temperature, and thereafter, the calculations of potential of mean force between two dispersed water molecules within different IL matrices were performed using umbrella sampling simulations. The systematic analyses of local ionic microstructures, orientational preferences, probability and spatial distributions of dispersed water molecules around neighboring ionic species indicate their preferential coordinations to central polar segments in orthoboratemore » anions. The effective interactions between two dispersed water molecules are partially or totally screened as their separation distance increases due to interference of ionic species in between. These computational results connect microscopic anionic structures with macroscopically and experimentally observed difficulty in completely removing water from synthesized IL samples and suggest that the introduction of hydrophobic groups to central polar segments and the formation of conjugated ionic structures in orthoborate anions can effectively reduce residual water content in the corresponding IL samples.« less

Hydrogen bonding in ionic liquids.

PubMed

Hunt, Patricia A; Ashworth, Claire R; Matthews, Richard P

2015-03-07

Ionic liquids (IL) and hydrogen bonding (H-bonding) are two diverse fields for which there is a developing recognition of significant overlap. Doubly ionic H-bonds occur when a H-bond forms between a cation and anion, and are a key feature of ILs. Doubly ionic H-bonds represent a wide area of H-bonding which has yet to be fully recognised, characterised or explored. H-bonds in ILs (both protic and aprotic) are bifurcated and chelating, and unlike many molecular liquids a significant variety of distinct H-bonds are formed between different types and numbers of donor and acceptor sites within a given IL. Traditional more neutral H-bonds can also be formed in functionalised ILs, adding a further level of complexity. Ab initio computed parameters; association energies, partial charges, density descriptors as encompassed by the QTAIM methodology (ρBCP), qualitative molecular orbital theory and NBO analysis provide established and robust mechanisms for understanding and interpreting traditional neutral and ionic H-bonds. In this review the applicability and extension of these parameters to describe and quantify the doubly ionic H-bond has been explored. Estimating the H-bonding energy is difficult because at a fundamental level the H-bond and ionic interaction are coupled. The NBO and QTAIM methodologies, unlike the total energy, are local descriptors and therefore can be used to directly compare neutral, ionic and doubly ionic H-bonds. The charged nature of the ions influences the ionic characteristics of the H-bond and vice versa, in addition the close association of the ions leads to enhanced orbital overlap and covalent contributions. The charge on the ions raises the energy of the Ylp and lowers the energy of the X-H σ* NBOs resulting in greater charge transfer, strengthening the H-bond. Using this range of parameters and comparing doubly ionic H-bonds to more traditional neutral and ionic H-bonds it is clear that doubly ionic H-bonds cover the full range of weak through to very strong H-bonds.

Size and Charge Dependence of Ion Transport in Human Nail Plate

PubMed Central

Baswan, Sudhir M.; Li, S. Kevin; LaCount, Terri D.; Kasting, Gerald B.

2016-01-01

The electrical properties of human nail plate are poorly characterized, yet are a key determinate of the potential to treat nail diseases such as onychomycosis using iontophoresis. In order to address this deficiency, molar conductivities of 17 electrolytes comprising 12 ionic species were determined in hydrated human nail plate in vitro. Cation transport numbers across the nail for 11 of these electrolytes were determined by the electromotive force method. Effective ionic mobilities and diffusivities at infinite dilution for all ionic species were determined by regression analysis. The ratios of diffusivities in nail to those in solution were found to correlate inversely with the hydrodynamic radii of the ions according to a power law relationship having an exponent of −1.75 ± 0.27, a substantially steeper size dependence than observed for similar experiments in skin. Effective diffusivities of cations in nail were three-fold higher than those of comparably sized anions. These results reflect the strong size and charge selectivity of the nail plate for ionic conduction and diffusion. The analysis implies that efficient transungual iontophoretic delivery of ionized drugs having radii upwards of 5 Å (approximately MW ≥ 340 Da) will require chemical or mechanical alteration of the nail plate. PMID:26886342

Ionic liquid-based extraction followed by graphite-furnace atomic absorption spectrometry for the determination of trace heavy metals in high-purity iron metal.

PubMed

Matsumiya, Hiroaki; Kato, Tatsuya; Hiraide, Masataka

2014-02-01

The analysis of high-purity materials for trace impurities is an important and challenging task. The present paper describes a facile and sensitive method for the determination of trace heavy metals in high-purity iron metal. Trace heavy metals in an iron sample solution were rapidly and selectively preconcentrated by the extraction into a tiny volume of an ionic liquid [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] for the determination by graphite-furnace atomic absorption spectrometry (GFAAS). A nitrogen-donating neutral ligand, 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), was found to be effective in the ionic liquid-based selective extraction, allowing the nearly complete (~99.8%) elimination of the iron matrix. The combination with the optimized GFAAS was successful. The detectability reached sub-μg g(-1) levels in iron metal. The novel use of TPTZ in ionic liquid-based extraction followed by GFAAS was successfully applied to the determination of traces of Co, Ni, Cu, Cd, and Pb in certified reference materials for high-purity iron metal. © 2013 Published by Elsevier B.V.

Ions in Wine and Their Relation to Electrical Conductivity Under Ultrasound Irradiation.

PubMed

Yan, Yan-Ying; Zhang, Qing-An; Li, Er-Chun; Zhang, Ya-Feng

2017-09-01

Change in electrical conductivity is considered a potential indicator for the on-line monitoring of wine aging accelerated by ultrasound, as determined in our previous study; however, the exact mechanism of change is currently unclear. In this study, the ion content and the total ionic strength were analyzed by ion-exchange chromatography to investigate the change mechanism of the electrical conductivity of wine under ultrasound irradiation. The results indicate that the changes in wine electrical conductivity during ultrasound treatment correlate with the changes in the cations (Na+, K+, Ca2+, Mg2+, and NH4+) and in the anions from the organic acids (malic acid, citric acid, tartaric acid, oxalic acid, and formic acid) and inorganic acids (Cl-, SO42-, and PO43-), especially for the ionic strength of the wine. Overall, electrical conductivity may be used to reflect the chemical reactions related to wine aging to a certain extent because the reactions can be initiated by the conversion of cations and by the degradation or auxiliary function of organic acids.

Heterogeneous electro-Fenton catalyst for 1-butylpyridinium chloride degradation.

PubMed

Meijide, Jessica; Pazos, Marta; Sanromán, Maria Ángeles

2017-10-15

The application of the electro-Fenton process for organic compound mineralisation has been widely reported over the past years. However, operational problems related to the use of soluble iron salt as a homogeneous catalyst involve the development of novel catalysts that are able to operate in a wide pH range. For this purpose, polyvinyl alcohol-alginate beads, containing goethite as iron, were synthesised and evaluated as heterogeneous electro-Fenton catalyst for 1-butylpyridinium chloride mineralisation. The influence of catalyst dosage and pH solution on ionic liquid degradation was analysed, achieving almost total oxidation after 60 min under optimal conditions (2 g/L catalyst concentration and pH 3). The results showed good catalyst stability and reusability, although its effectiveness decreases slightly after three successive cycles. Furthermore, a plausible mineralisation pathway was proposed based on the oxidation byproducts determined by chromatographic techniques. Finally, the Microtox® test revealed notable detoxification after treatment which demonstrates high catalyst ability for pyridinium-based ionic liquid degradation by the electro-Fenton process.

Extraction of ranitidine and nizatidine with using imidazolium ionic liquids prior spectrophotometric and chromatographic detection.

PubMed

Kiszkiel, Ilona; Starczewska, Barbara; Leśniewska, Barbara; Późniak, Patrycja

2015-03-15

A new extraction medium was proposed for liquid-liquid extraction of the histamine H2 receptor antagonists ranitidine (RNT) and nizatidine (NZT). The ionic liquids with low vapor pressure and favorable solvating properties for a range of compounds such as 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C4mim][Tf2N] were tested for isolation of analytes. The extraction parameters of RNT and NZT, namely, amount of ionic liquid, pH of sample solution, shaking and centrifugation time were optimized. The isolation processes were performed with 1 mL of the ionic liquids. The extracted samples (pH values near 4) were shaken at 1750 rpm. The influence of interfering substances on the efficiency of extraction process was also studied. Methods for the histamine H2 receptor antagonists (ranitidine and nizatidine) determination after their separation using imidazolium ionic liquids by high performance liquid chromatography (HPLC) combined with UV spectrophotometry were developed. The application of ionic liquids in extraction step allows for selective isolation of analytes from aqueous matrices and their preconcentration. The above methods were applied to the determination of RNT and NZT in environmental samples (river water and wastewater after treatment). Copyright © 2014 Elsevier B.V. All rights reserved.

Comparative study of bending characteristics of ionic polymer actuators containing ionic liquids for modeling actuation

NASA Astrophysics Data System (ADS)

Kikuchi, Kunitomo; Sakamoto, Takumi; Tsuchitani, Shigeki; Asaka, Kinji

2011-04-01

Ionic polymer metal composites (IPMCs) that can operate in air have recently been developed by incorporating an ionic liquid in ionic polymers. To understand transduction in these composites, it is important to determine the role of the ionic liquid in the ionic polymer (Nafion®), to identify the counter cation, and to investigate the interaction of IPMCs with water vapor in the air. We used Fourier-transform infrared spectroscopy to analyze three Nafion® membranes, which were soaked in mixtures of water and an ionic liquid (1-ethyl-3-methyl-imidazolium tetrafluoroborate (EMIBF4), 1-buthyl-3-methyl-imidazolium tetrafluoroborate (BMIBF4), and 1-buthyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6)). The results demonstrate that only cations (EMI+ and BMI+) in the ionic liquids are taken into the Nafion® membranes as counter ions and that the water content of the membranes in air is less than ˜4% that of Nafion® swollen with water. Based on the experimental results, a transduction model is proposed for an IPMC with an ionic liquid. In this model, bending is caused by local swelling due to the volume effect of the bulky counter cations. This model can explain 30-50% of the experimentally observed bending curvature.

Electric double-layer capacitance between an ionic liquid and few-layer graphene.

PubMed

Uesugi, Eri; Goto, Hidenori; Eguchi, Ritsuko; Fujiwara, Akihiko; Kubozono, Yoshihiro

2013-01-01

Ionic-liquid gates have a high carrier density due to their atomically thin electric double layer (EDL) and extremely large geometrical capacitance Cg. However, a high carrier density in graphene has not been achieved even with ionic-liquid gates because the EDL capacitance CEDL between the ionic liquid and graphene involves the series connection of Cg and the quantum capacitance Cq, which is proportional to the density of states. We investigated the variables that determine CEDL at the molecular level by varying the number of graphene layers n and thereby optimising Cq. The CEDL value is governed by Cq at n < 4, and by Cg at n > 4. This transition with n indicates a composite nature for CEDL. Our finding clarifies a universal principle that determines capacitance on a microscopic scale, and provides nanotechnological perspectives on charge accumulation and energy storage using an ultimately thin capacitor.

Electric double-layer capacitance between an ionic liquid and few-layer graphene

PubMed Central

Uesugi, Eri; Goto, Hidenori; Eguchi, Ritsuko; Fujiwara, Akihiko; Kubozono, Yoshihiro

2013-01-01

Ionic-liquid gates have a high carrier density due to their atomically thin electric double layer (EDL) and extremely large geometrical capacitance Cg. However, a high carrier density in graphene has not been achieved even with ionic-liquid gates because the EDL capacitance CEDL between the ionic liquid and graphene involves the series connection of Cg and the quantum capacitance Cq, which is proportional to the density of states. We investigated the variables that determine CEDL at the molecular level by varying the number of graphene layers n and thereby optimising Cq. The CEDL value is governed by Cq at n < 4, and by Cg at n > 4. This transition with n indicates a composite nature for CEDL. Our finding clarifies a universal principle that determines capacitance on a microscopic scale, and provides nanotechnological perspectives on charge accumulation and energy storage using an ultimately thin capacitor. PMID:23549208

Descriptors for ions and ion-pairs for use in linear free energy relationships.

PubMed

Abraham, Michael H; Acree, William E

2016-01-22

The determination of Abraham descriptors for single ions is reviewed, and equations are given for the partition of single ions from water to a number of solvents. These ions include permanent anions and cations and ionic species such as carboxylic acid anions, phenoxide anions and protonated base cations. Descriptors for a large number of ions and ionic species are listed, and equations for the prediction of Abraham descriptors for ionic species are given. The application of descriptors for ions and ionic species to physicochemical processes is given; these are to water-solvent partitions, HPLC retention data, immobilised artificial membranes, the Finkelstein reaction and diffusion in water. Applications to biological processes include brain permeation, microsomal degradation of drugs, skin permeation and human intestinal absorption. The review concludes with a section on the determination of descriptors for ion-pairs. Copyright © 2015 Elsevier B.V. All rights reserved.

Understanding the impact of nanoscale aggregation on charge transport and structural dynamics in room temperature ionic liquids

NASA Astrophysics Data System (ADS)

Griffin, Philip; Holt, Adam; Wang, Yangyang; Sokolov, Alexei

2015-03-01

Amphiphilic room temperature ionic liquids (ILs) segregate on the nanoscale, forming intricate networks of charge-rich ionic domains intercalated with charge-poor aliphatic domains. While this structural phenomenon has been well established through x-ray diffraction studies and atomistic MD simulations, the precise effects of nanophase segregation on ion transport and structural dynamics in ILs remains poorly understood. Using a combination of broadband dielectric spectroscopy, light scattering spectroscopy, and rheology, we have characterized the ionic conductivity, structural dynamics, and shear viscosity of a homologous series of quaternary ammonium ionic liquids over a wide temperature range. Upon increasing the length and volume fraction of the alkyl side chains of these quaternary ammonium ILs, ionic conductivity decreases precipitously, although no corresponding slowing of the structural dynamics is observed. Instead, we identify the dynamical signature of supramolecular aggregates. Our results directly demonstrate the role that chemical structure and ionic aggregation plays in determining the charge transport properties of amphiphilic ILs.

Contributions of an ancient evaporitic-type reservoir to subglacial Lake Vostok chemistry

NASA Astrophysics Data System (ADS)

De Angelis, M.; Petit, J.-R.; Savarino, J.; Souchez, R.; Thiemens, M. H.

2004-06-01

We present here the first comprehensive study of the chemical composition of accretion ice from Lake Vostok. Ion chromatographic analyses were performed on samples obtained along the deeper part of the Vostok ice core. Samples were taken from 3350 down to 3611 m depth, both in glacier ice and subglacial lake ice. The total ionic contents of two accretion ice layers—a few meters thick and centered around 3540 and 3590 m depth—are several times lower than those of glacier ice. Very low concentrations were also observed in the deeper part of accretion ice, below 3609 m depth. Elsewhere, the total ionic content is variable but remains 5 to 50 times higher than in glacier ice. Whatever its total ionic content, the ionic composition of accretion ice is significantly different from what is observed in glacier ice. It is dominated by sodium chloride, homogeneously distributed throughout the ice lattice, as well as calcium and magnesium sulfate, likely located in solid inclusions, or to a lesser extent at grain boundaries. Chemical considerations combined with additional studies of sulfur and oxygen isotopes in sulfate, and iron measurements strongly suggest that glacier water recycling and bedrock hydrolysis do not play a prominent role in providing impurities to accretion ice. It is more likely that NaCl rich water carrying fine sulfate salt particles is sporadically incorporated in the ice accreting in a shallow bay upstream from Vostok. The origin of such salty water, which should also contribute to Lake salinity, is discussed.

Electrostatic Interactions Influence Protein Adsorption (but Not Desorption) at the Silica-Aqueous Interface.

PubMed

McUmber, Aaron C; Randolph, Theodore W; Schwartz, Daniel K

2015-07-02

High-throughput single-molecule total internal reflection fluorescence microscopy was used to investigate the effects of pH and ionic strength on bovine serum albumin (BSA) adsorption, desorption, and interfacial diffusion at the aqueous-fused silica interface. At high pH and low ionic strength, negatively charged BSA adsorbed slowly to the negatively charged fused silica surface. At low pH and low ionic strength, where BSA was positively charged, or in solutions at higher ionic strength, adsorption was approximately 1000 times faster. Interestingly, neither surface residence times nor the interfacial diffusion coefficients of BSA were influenced by pH or ionic strength. These findings suggested that adsorption kinetics were dominated by energy barriers associated with electrostatic interactions, but once adsorbed, protein-surface interactions were dominated by short-range nonelectrostatic interactions. These results highlight the ability of single-molecule techniques to isolate elementary processes (e.g., adsorption and desorption) under steady-state conditions, which would be impossible to measure using ensemble-averaging methods.

Mercury methylation influenced by areas of past mercury mining in the Terlingua district, Southwest Texas, USA

USGS Publications Warehouse

Gray, J.E.; Hines, M.E.; Biester, H.

2006-01-01

Speciation and microbial transformation of Hg was studied in mine waste from abandoned Hg mines in SW Texas to evaluate the potential for methyl-Hg production and degradation in mine wastes. In mine waste samples, total Hg, ionic Hg2+, Hg0, methyl-Hg, organic C, and total S concentrations were measured, various Hg compounds were identified using thermal desorption pyrolysis, and potential rates of Hg methylation and methyl-Hg demethylation were determined using isotopic-tracer methods. These data are the first reported for Hg mines in this region. Total Hg and methyl-Hg concentrations were also determined in stream sediment collected downstream from two of the mines to evaluate transport of Hg and methylation in surrounding ecosystems. Mine waste contains total Hg and methyl-Hg concentrations as high as 19,000 ??g/g and 1500 ng/g, respectively, which are among the highest concentrations reported at Hg mines worldwide. Pyrolysis analyses show that mine waste contains variable amounts of cinnabar, metacinnabar, Hg0, and Hg sorbed onto particles. Methyl-Hg concentrations in mine waste correlate positively with ionic Hg2+, organic C, and total S, which are geochemical parameters that influence processes of Hg cycling and methylation. Net methylation rates were as high as 11,000 ng/g/day, indicating significant microbial Hg methylation at some sites, especially in samples collected inside retorts. Microbially-mediated methyl-Hg demethylation was also observed in many samples, but where both methylation and demethylation were found, the potential rate of methylation was faster. Total Hg concentrations in stream sediment samples were generally below the probable effect concentration of 1.06 ??g/g, the Hg concentration above which harmful effects are likely to be observed in sediment dwelling organisms; whereas total Hg concentrations in mine waste samples were found to exceed this concentration, although this is a sediment quality guideline and is not directly applicable to mine waste. Although total Hg and methyl-Hg concentrations are locally high in some mine waste samples, little Hg appears to be exported from these Hg mines in stream sediment primarily due to the arid climate and lack of precipitation and mine runoff in this region. ?? 2006 Elsevier Ltd. All rights reserved.

Ultrasound-assisted magnetic solid-phase extraction based ionic liquid-coated Fe3O4@graphene for the determination of nitrobenzene compounds in environmental water samples.

PubMed

Cao, Xiaoji; Shen, Lingxiao; Ye, Xuemin; Zhang, Feifei; Chen, Jiaoyu; Mo, Weimin

2014-04-21

An ultrasound-assisted magnetic solid-phase extraction procedure with the [C7MIM][PF6] ionic liquid-coated Fe3O4-grafted graphene nanocomposite as the magnetic adsorbent has been developed for the determination of five nitrobenzene compounds (NBs) in environmental water samples, in combination with high performance liquid chromatography-photodiode array detector (HPLC-PDA). Several significant factors that affect the extraction efficiency, such as the types of magnetic nanoparticle and ionic liquid, the volume of ionic liquid and the amount of magnetic nanoparticles, extraction time, ionic strength, and solution pH, were investigated. With the assistance of ultrasound, adsorbing nitrobenzene compounds by ionic liquid and self-aggregating ionic liquid onto the surface of the Fe3O4-grafted graphene proceeded synchronously, which made the extraction achieved the maximum within 20 min using only 144 μL [C7MIM][PF6] and 3 mg Fe3O4-grafted graphene. Under the optimized conditions, satisfactory linearities were obtained for all NBs with correlation coefficients larger than 0.9990. The mean recoveries at two spiked levels ranged from 80.35 to 102.77%. Attributed to the convenient magnetic separation, the Fe3O4-grafted graphene could be recycled many times. The proposed method was demonstrated to be feasible, simple, solvent-saving and easy to operate for the trace analysis of NBs in environmental water samples.

Ionic size effects to molecular solvation energy and to ion current across a channel resulted from the nonuniform size-modified PNP equations.

PubMed

Qiao, Yu; Tu, Bin; Lu, Benzhuo

2014-05-07

Ionic finite size can impose considerable effects to both the equilibrium and non-equilibrium properties of a solvated molecular system, such as the solvation energy, ionic concentration, and transport in a channel. As discussed in our former work [B. Lu and Y. C. Zhou, Biophys. J. 100, 2475 (2011)], a class of size-modified Poisson-Boltzmann (PB)/Poisson-Nernst-Planck (PNP) models can be uniformly studied through the general nonuniform size-modified PNP (SMPNP) equations deduced from the extended free energy functional of Borukhov et al. [I. Borukhov, D. Andelman, and H. Orland, Phys. Rev. Lett. 79, 435 (1997)] This work focuses on the nonuniform size effects to molecular solvation energy and to ion current across a channel for real biomolecular systems. The main contributions are: (1) we prove that for solvation energy calculation with nonuniform size effects (through equilibrium SMPNP simulation), there exists a simplified approximation formulation which is the same as the widely used one in PB community. This approximate form avoids integration over the whole domain and makes energy calculations convenient. (2) Numerical calculations show that ionic size effects tend to negate the solvation effects, which indicates that a higher molecular solvation energy (lower absolute value) is to be predicted when ionic size effects are considered. For both calculations on a protein and a DNA fragment systems in a 0.5M 1:1 ionic solution, a difference about 10 kcal/mol in solvation energies is found between the PB and the SMPNP predictions. Moreover, it is observed that the solvation energy decreases as ionic strength increases, which behavior is similar as those predicted by the traditional PB equation (without size effect) and by the uniform size-modified Poisson-Boltzmann equation. (3) Nonequilibrium SMPNP simulations of ion permeation through a gramicidin A channel show that the ionic size effects lead to reduced ion current inside the channel compared with the results without considering size effects. As a component of the current, the drift term is the main contribution to the total current. The ionic size effects to the total current almost come through the drift term, and have little influence on the diffusion terms in SMPNP.

Metal-chelating active packaging film enhances lysozyme inhibition of Listeria monocytogenes.

PubMed

Roman, Maxine J; Decker, Eric A; Goddard, Julie M

2014-07-01

Several studies have demonstrated that metal chelators enhance the antimicrobial activity of lysozyme. This study examined the effect of metal-chelating active packaging film on the antimicrobial activity of lysozyme against Listeria monocytogenes. Polypropylene films were surface modified by photoinitiated graft polymerization of acrylic acid (PP-g-PAA) from the food contact surface of the films to impart chelating activity based on electrostatic interactions. PP-g-PAA exhibited a carboxylic acid density of 113 ± 5.4 nmol cm(-2) and an iron chelating activity of 53.7 ± 9.8 nmol cm(-2). The antimicrobial interaction of lysozyme and PP-g-PAA depended on growth media composition. PP-g-PAA hindered lysozyme activity at low ionic strength (2.48-log increase at 64.4 mM total ionic strength) and enhanced lysozyme activity at moderate ionic strength (5.22-log reduction at 120 mM total ionic strength). These data support the hypothesis that at neutral pH, synergy between carboxylate metal-chelating films (pKa(bulk) 6.45) and lysozyme (pI 11.35) is optimal in solutions of moderate to high ionic strength to minimize undesirable charge interactions, such as lysozyme absorption onto film. These findings suggest that active packaging, which chelates metal ions based on ligand-specific interactions, in contrast to electrostatic interactions, may improve antimicrobial synergy. This work demonstrates the potential application of metal-chelating active packaging films to enhance the antimicrobial activity of membrane-disrupting antimicrobials, such as lysozyme.

Theoretical studies on structural, magnetic, and spintronic characteristics of sandwiched Eu(n)COT(n+1) (n = 1-4) clusters.

PubMed

Zhang, Xiuyun; Ng, Man-Fai; Wang, Yanbiao; Wang, Jinlan; Yang, Shuo-Wang

2009-09-22

Europium (Eu)-cyclootetatrene (COT = C(8)H(8)) multidecker clusters (Eu(n)COT(n+1), n = 1-4) are studied by relativistic density functional theory calculations. These clusters are found to be thermodynamically stable with freely rotatable COT rings, and their total magnetic moments (MMs) increase linearly along with the number of Eu atoms. Each Eu atom contributes about 7 mu(B) to the cluster. Meanwhile, the internal COT rings have little MM contribution while the external COT rings have about 1 mu(B) MM aligned in opposite direction to that of the Eu atoms. The total MM of the Eu(n)COT(n+1) clusters can thus be generalized as 7n - 2 mu(B) where n is the number of Eu atoms. Besides, the ground states of these clusters are ferromagnetic and energetically competitive with the antiferromagnetic states, meaning that their spin states are very unstable, especially for larger clusters. More importantly, we uncover an interesting bonding characteristic of these clusters in which the interior ionic structure is capped by two hybrid covalent-ionic terminals. We suggest that such a characteristic makes the Eu(n)COT(n+1) clusters extremely stable. Finally, we reveal that for the positively charged clusters, the hybrid covalent-ionic terminals will tip further toward the interior part of the clusters to form deeper covalent-ionic caps. In contrast, the negatively charged clusters turn to pure ionic structures.

Cyclic voltammetry using silver as cathode material: a simple method for determining electro and chemical features and solubility values of CO2 in ionic liquids.

PubMed

Reche, Irene; Gallardo, Iluminada; Guirado, Gonzalo

2015-01-28

A report is presented on the use of cyclic voltammetry using silver as a working electrode. The combined electrocatalytic properties of silver and ionic liquids allow cyclic voltammetry to be turned into an ideal tool for the rapid and accurate access to diffusion coefficient values and solubility values of carbon dioxide in ionic liquids under standard conditions.

Influence of MRI contrast media on histamine release from mast cells.

PubMed

Kun, Tomasz; Jakubowski, Lucjusz

2012-07-01

Mast cells, owing to diversity of secreted mediators, play a crucial role in the regulation of inflammatory response. Together with basophils, mast cells constitute a central pathogenetic element of anaphylactic (IgE-dependent) and anaphylactoid (IgE-independent) reactions. In severe cases, generalized degranulation of mast cells may cause symptoms of anaphylactic shock. The influence of the classical, iodine-based contrast media on mastocyte degranulation has been fully described. Our objective was to determine the influence of the gadolinium-based MRI contrast media on histamine release from mast cells and to compare the activity of ionic and non-ionic preparations of contrast media. To determine the intensity of mast cell degranulation, we used an experimental model based on mastocytes isolated from rat peritoneal fluid. Purified suspensions of mast cells were incubated with various concentrations of Gd-DTPA and Gd-DTPA-BMA, and solutions of PEG 600 which served as a non-toxic osmotic stimulus. The intensity of mast cell activation was presented as mean percentage of histamine released from cells after incubation. The obtained results demonstrate that both ionic and non-ionic preparations of the MRI contrast media are able to induce mast cell degranulation in vitro. It was also proved that the non-ionic MRI contrast media stimulate mast cells markedly more weakly than ionic contrast media at identical concentration. The aforementioned results may suggest a more profitable safety profile of the non-ionic contrast preparations. We may also conclude that triggering of mast cell degranulation after incubation with the solutions of MRI contrast media results from non-specific osmotic stimulation and direct toxicity of free ionic residues.

Brain microdialysis as a tool to explore the ionic profile of the brain extracellular space in neurocritical patients: a methodological approach and feasibility study.

PubMed

Martínez-Valverde, Tamara; Vidal-Jorge, Marian; Montoya, Noelia; Sánchez-Guerrero, Angela; Manrique, Susana; Munar, Francisca; Pellegri, Maria-Dolors; Poca, Maria-Antonia; Sahuquillo, Juan

2015-01-01

Our aim is to determine whether the ionic concentration in brain microdialysate enables calculations of the actual Na(+), K(+), and Cl(-) concentrations in vitro and whether this method can be applied to determine the ionic concentrations in the brain extracellular fluid. We designed an experiment using CMA-71 probes (M Dialysis, Stockholm, Sweden) and the standard conditions used in a clinical setting. Nine CMA-71 probes were inserted in different matrices and perfused with mock cerebrospinal fluid containing 3% albumin at the standard infusion rate used in the clinical setting (0.3 μL/min). Microvials were replaced every 12 h, and the ionic concentrations, both in the dialysate and the matrix, were analyzed. For each ion, scatter plots were built, with [Na(+)], [K(+)], and [Cl(-)] in the dialysate as the predictor variables and the matrix concentrations as the outcome variables. A linear regression model allowed us to calculate the true ionic concentrations in the matrix. To demonstrate the feasibility of the method, we present the calculated ionic profile of one patient with a malignant infarction and a second with a severe traumatic brain injury. Our results confirm that the ionic concentration in microdialysate can be used to calculate the true concentrations of ions in a matrix and the actual concentrations in the extracellular fluid. Microdialysis offers the unique possibility of monitoring the dynamic changes of ions in the brain over time and opens a new avenue to explore the brain's ionic profile, its changes in brain edema, and how this profile can be modified with different therapies.

Determination of atenolol in human plasma using ionic-liquid-based ultrasound-assisted in situ solvent formation microextraction followed by high-performance liquid chromatography.

PubMed

Zeeb, Mohsen; Farahani, Hadi; Papan, Mohammad Kazem

2016-06-01

An efficient analytical method called ionic-liquid-based ultrasound-assisted in situ solvent formation microextraction followed by high-performance liquid chromatography was developed for the determination of atenolol in human plasma. A hydrophobic ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) was formed by the addition of a hydrophilic ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) to a sample solution containing an ion-pairing agent during microextraction. The analyte was extracted into the ionic liquid phase while the microextraction solvent was dispersed throughout the sample by utilizing ultrasound. The sample was then centrifuged, and the extracting phase retracted into the microsyringe and injected to liquid chromatography. After optimization, the calibration curve showed linearity in the range of 2-750 ng/mL with the regression coefficient corresponding to 0.998. The limits of detection (S/N = 3) and quantification (S/N = 10) were 0.5 and 2 ng/mL, respectively. A reasonable relative recovery range of 90-96.7% and satisfactory intra-assay (4.8-5.1%, n = 6) and interassay (5.0-5.6%, n = 9) precision along with a substantial sample clean-up demonstrated good performance of the procedure. It was applied for the determination of atenolol in human plasma after oral administration and some pharmacokinetic data were obtained. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of cloud point extraction and solid phase extraction methods for speciation of arsenic in natural water using multivariate technique.

PubMed

Baig, Jameel A; Kazi, Tasneem G; Shah, Abdul Q; Arain, Mohammad B; Afridi, Hassan I; Kandhro, Ghulam A; Khan, Sumaira

2009-09-28

The simple and rapid pre-concentration techniques viz. cloud point extraction (CPE) and solid phase extraction (SPE) were applied for the determination of As(3+) and total inorganic arsenic (iAs) in surface and ground water samples. The As(3+) was formed complex with ammonium pyrrolidinedithiocarbamate (APDC) and extracted by surfactant-rich phases in the non-ionic surfactant Triton X-114, after centrifugation the surfactant-rich phase was diluted with 0.1 mol L(-1) HNO(3) in methanol. While total iAs in water samples was adsorbed on titanium dioxide (TiO(2)); after centrifugation, the solid phase was prepared to be slurry for determination. The extracted As species were determined by electrothermal atomic absorption spectrometry. The multivariate strategy was applied to estimate the optimum values of experimental factors for the recovery of As(3+) and total iAs by CPE and SPE. The standard addition method was used to validate the optimized methods. The obtained result showed sufficient recoveries for As(3+) and iAs (>98.0%). The concentration factor in both cases was found to be 40.

Calorimetric Studies and Structural Aspects of Ionic Liquids in Designing Sorption Materials for Thermal Energy Storage.

PubMed

Brünig, Thorge; Krekić, Kristijan; Bruhn, Clemens; Pietschnig, Rudolf

2016-11-02

The thermal properties of a series of twenty-four ionic liquids (ILs) have been determined by isothermal titration calorimetry (ITC) with the aim of simulating processes involving water sorption. For eleven water-free ILs, the molecular structures have been determined by X-ray crystallography in the solid state, which have been used to derive the molecular volumes of the ionic components of the ILs. Moreover, the structures reveal a high prevalence of hydrogen bonding in these compounds. A relationship between the molecular volumes and the experimentally determined energies of dilution could be established. The highest energies of dilution observed in this series were obtained for the acetate-based ILs, which underlines their potential as working fluids in sorption-based thermal energy storage systems. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mitochondria-rich cells adjustments and ionic balance in the Neotropical fish Prochilodus lineatus exposed to titanium dioxide nanoparticles.

PubMed

Carmo, Talita L L; Azevedo, Vinícius C; Siqueira, Priscila R; Galvão, Tiago D; Santos, Fabrício A; Martinez, Cláudia B R; Appoloni, Carlos R; Fernandes, Marisa N

2018-07-01

Manufactured titanium dioxide nanoparticles (TiO 2 -NP) have been intensely applied in numerous industrial products and may be a risk for aquatic systems as they are not completely removed from domestic and industrial wastes after water treatment. This study evaluated the osmo- and ionic balance, Na + /K + -ATPase, H + -ATPase and carbonic anhydrase activities and the mitochondria-rich cells (MRC) in the gills and kidney of the Neotropical fish Prochilodus lineatus after 2 (acute) and 14 (subchronic) days of exposure to nominal 0, 1, 5, 10 and 50 mg L -1 TiO 2 -NP. The nominal concentrations corresponded to 0.0, 0.6, 1.6, 2.7 and 18.1 mg L -1 suspended TiO 2 -NP, respectively, in the water column one hour after NP introduction and were maintained for at least 24 h. Acute exposure to TiO 2 -NP decreased plasma osmolality and Ca 2+ levels. Na + /K + -ATPase, H + -ATPase and carbonic anhydrase activities were inhibited in the gills, but not in the kidney. Total MRC density did not change in gills and kidneys. At gill surface, total MRC density decreased in fish exposed to 50 mg L -1 TiO 2 -NP and the total MRC fractional surface area unchanged although, there were some changes in the fractional area of MRC with apical microvilli (MRCm) and MRC with apical sponge-like structure (MRCs). MRCm was more abundant than MRCs. After subchronic exposure, there was no change in plasma osmolality, ionic balance and enzyme activities. Total gill MRC density increased in the filament epithelium and renal tubules. In the gills, MRC contacting water exhibited some adjustments. Total MRC and fractional surface area unchanged, but there was an increase of MRCs contacting water at gill surface after exposure to10 and 50 mg L -1 TiO 2 -NP. MRC proliferation in filament epithelium and in renal tubules as well as the increasing MRCs at gill surface may have contributed to avoid change in plasma osmolality, ionic balance and enzyme activities and suggested a cellular physiological and morphological response to restore and maintain osmotic and ionic homeostasis after subchronic exposure. Copyright © 2018 Elsevier B.V. All rights reserved.

Experimental and computational study on the properties of pure and water mixed 1-ethyl-3-methylimidazolium L-(+)-lactate ionic liquid.

PubMed

Aparicio, Santiago; Alcalde, Rafael; Atilhan, Mert

2010-05-06

Ionic liquids have attracted great attention, from both industry and academe, as alternative fluids for a large collection of applications. Although the term green is used frequently to describe ionic liquids in general, it is obvious that it cannot be applied to the huge quantity of possible ionic liquids, and thus, those with adequate environmental and technological profiles must be selected for further and deeper studies, from both basic science and applied approaches. In this work, 1-ethyl-3-methylimidazolium L-(+)-lactate ionic liquid is studied, because of its remarkable properties, through a wide-ranging approach considering thermophysical, spectroscopic, and computational tools, to gain a deeper insight into its complex liquid structure, both pure and mixed with water, thus implying the main factors that would control the technological applications that could be designed using this fluid. The reported results shows a strongly structured pure ionic liquid, in which hydrogen bonding, because of the hydroxyl group of the lactate anion, develops a remarkable role, together with Coulombic forces to determine the fluid's behavior. Upon mixing with water, the ionic liquid retains its structure up to very high dilution levels, with the effect of the ionic liquid on the water structure being very large, even for very low ionic liquid mole fractions. Thus, in water solution, the studied ionic liquid evolves from noninteracting ions solvated by water molecules toward large interacting structures with increasing ionic liquid content.

Preparation of magnetic chitosan and graphene oxide-functional guanidinium ionic liquid composite for the solid-phase extraction of protein.

PubMed

Ding, Xueqin; Wang, Yuzhi; Wang, Ying; Pan, Qi; Chen, Jing; Huang, Yanhua; Xu, Kaijia

2015-02-25

A series of novel cationic functional hexaalkylguanidinium ionic liquids and anionic functional tetraalkylguanidinium ionic liquids have been synthesized, and then magnetic chitosan graphene oxide (MCGO) composite has been prepared and coated with these functional guanidinium ionic liquids to extract protein by magnetic solid-phase extraction. MCGO-functional guanidinium ionic liquid has been characterized by vibrating sample magnetometer, field emission scanning electron microscopy, X-ray diffraction spectrometer and Fourier transform infrared spectrometer. After extraction, the concentrations of protein were determined by measuring the absorbance at 278 nm using an ultra violet visible spectrophotometer. The advantages of MCGO-functional guanidinium ionic liquid in protein extraction were compared with magnetic chitosan, graphene oxide, MCGO and MCGO-ordinary imidazolium ionic liquid. The proposed method has been applied to extract trypsin, lysozyme, ovalbumin and bovine serum albumin. A comprehensive study of the adsorption conditions such as the concentration of protein, the amount of MCGO-functional guanidinium ionic liquid, the pH, the temperature and the extraction time were also presented. Moreover, the MCGO-functional guanidinium ionic liquid can be easily regenerated, and the extraction capacity was about 94% of the initial one after being used three times. Copyright © 2015 Elsevier B.V. All rights reserved.

Specialist gelator for ionic liquids.

PubMed

Hanabusa, Kenji; Fukui, Hiroaki; Suzuki, Masahiro; Shirai, Hirofusa

2005-11-08

Cyclo(l-beta-3,7-dimethyloctylasparaginyl-L-phenylalanyl) (1) and cyclo(L-beta-2-ethylhexylasparaginyl-L-phenylalanyl) (2), prepared from L-asparaginyl-L-phenylalanine methyl ester, have been found to be specialist gelators for ionic liquids. They can gel a wide variety of ionic liquids, including imizazolium, pyridinium, pyrazolidinium, piperidinium, morpholinium, and ammonium salts. The mean minimum gel concentrations (MGCs) necessary to make gels at 25 degrees C were determined for ionic liquids. The gel strength increased at a rate nearly proportional to the concentration of added gelator. The strength of the transparent gel of 1-butylpyridinium tetrafluoroborate ([C(4)py]BF(4)), prepared at a concentration of 60 g L(-1) (gelator 1/[C(4)py]BF(4)), was ca. 1500 g cm(-2). FT-IR spectroscopy indicated that a driving force for gelation was intermolecular hydrogen bonding between amides and that the phase transition from gel to liquid upon heating was brought about by the collapse of hydrogen bonding. The gels formed from ionic liquids were very thermally stable; no melting occurs up to 140 degrees C when the gels were prepared at a concentration of 70 g L(-1) (gelator/ionic liquid). The ionic conductivities of the gels were nearly the same as those of pure ionic liquids. The gelator had electrochemical stability and a wide electrochemical window. When the gels were prepared from ionic liquids containing propylene carbonate, the ionic conductivities of the resulting gels increased to levels rather higher than those of pure ionic liquids. The gelators also gelled ionic liquids containing supporting electrolytes.

Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples.

PubMed

da Silva, Meire Ribeiro; Mauro Lanças, Fernando

2018-03-10

Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enzyme activity in dialkyl phosphate ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, M.F.; Dunn, J.; Li, L.-L.

2011-12-01

The activity of four metagenomic enzymes and an enzyme cloned from the straw mushroom, Volvariellavolvacea were studied in the following ionic liquids, 1,3-dimethylimidazolium dimethyl phosphate, [mmim][dmp], 1-ethyl-3-methylimidazolium dimethyl phosphate, [emim][dmp], 1-ethyl-3-methylimidazolium diethyl phosphate, [emim][dep] and 1-ethyl-3-methylimidazolium acetate, [emim][OAc]. Activity was determined by analyzing the hydrolysis of para-nitrobenzene carbohydrate derivatives. In general, the enzymes were most active in the dimethyl phosphate ionic liquids, followed by acetate. Generally speaking, activity decreased sharply for concentrations of [emim][dep] above 10% v/v, while the other ionic liquids showed less impact on activity up to 20% v/v.

The effect of addition of primary positive salts, complex salt, on the ionic strength and rate constant at various temperatures by reaction kinetics

NASA Astrophysics Data System (ADS)

Kurade, S. S.; Ramteke, A. A.

2018-05-01

In this work, we have investigated the rate of reaction by using ionic strength at different temperatures. The main goal of this experiment is to determine the relation between ionic strength with reaction rate, reaction time and rate constant with temperature. It is observed that the addition of positive salt indicate the increasing ionic strength with increase in run time at various temperatures. Thus the temperature affects the speed of reaction and mechanism by which chemical reaction occurs and time variable plays vital role in the progress of reaction at different temperatures.

Size and Charge Dependence of Ion Transport in Human Nail Plate.

PubMed

Baswan, Sudhir M; Li, S Kevin; LaCount, Terri D; Kasting, Gerald B

2016-03-01

The electrical properties of human nail plate are poorly characterized yet are a key determinate of the potential to treat nail diseases, such as onychomycosis, using iontophoresis. To address this deficiency, molar conductivities of 17 electrolytes comprising 12 ionic species were determined in hydrated human nail plate in vitro. Cation transport numbers across the nail for 11 of these electrolytes were determined by the electromotive force method. Effective ionic mobilities and diffusivities at infinite dilution for all ionic species were determined by regression analysis. The ratios of diffusivities in nail to those in solution were found to correlate inversely with the hydrodynamic radii of the ions according to a power law relationship having an exponent of -1.75 ± 0.27, a substantially steeper size dependence than observed for similar experiments in skin. Effective diffusivities of cations in nail were 3-fold higher than those of comparably sized anions. These results reflect the strong size and charge selectivity of the nail plate for ionic conduction and diffusion. The analysis implies that efficient transungual iontophoretic delivery of ionized drugs having radii upward of 5 Å (molecular weight, ca. ≥ 340 Da) will require chemical or mechanical alteration of the nail plate. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Correlation between electrical and mechanical properties in La1-xSrxGa1-yMgyO3-δ ceramics used as electrolytes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Morales, M.; Roa, J. J.; Perez-Falcón, J. M.; Moure, A.; Tartaj, J.; Espiell, F.; Segarra, M.

2014-01-01

The relation between the electrical and the mechanical properties in Sr and Mg doped LaGaO3 ceramics, which can be used as electrolyte for solid oxide fuel cells, was investigated in terms of hardness and ionic conductivity. For this purpose, ceramic materials corresponding to the compositions of La1-xSrxGa1-yMgyO3-δ (LSGM), with x = 0.1 and y = 0.2, and x = 0.15 and y = 0.2, were prepared. LSGM powders synthesized by the ethylene glycol complex solution method were shaped into disks by isostatic pressing method. The variation in the microstructure of samples was achieved by varying the sintering temperature between 1300 and 1450 °C. While the effect of the different microstructures on the electrical properties of the LSGM electrolytes was determined by impedance spectroscopy, the influence of the hardness was extracted by instrumented indentation technique. The results showed a linear correlation between the hardness and total ionic conductivity within the temperature range of 500-660 °C, thus indicating that both properties were strongly influenced on the relative density and purity of the samples. It has a potential practical implication: by measuring the LSGM hardness at room temperature, one can achieve an approach to the ionic conductivity within the studied temperature range.

X-ray Photoelectron Spectroscopy of Pyridinium-Based Ionic Liquids: Comparison to Imidazolium- and Pyrrolidinium-Based Analogues.

PubMed

Men, Shuang; Mitchell, Daniel S; Lovelock, Kevin R J; Licence, Peter

2015-07-20

We investigate eight 1-alkylpyridinium-based ionic liquids of the form [Cn Py][A] by using X-ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake-up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic-liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8 Py][A] and analogues including 1-octyl-1-methylpyrrolidinium- ([C8 C1 Pyrr][A]), and 1-octyl-3-methylimidazolium- ([C8 C1 Im][A]) based samples, where X is common to all ionic liquids. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Removal of total cyanide in coking wastewater during a coagulation process: significance of organic polymers.

PubMed

Shen, Jian; Zhao, He; Cao, Hongbin; Zhang, Yi; Chen, Yongsheng

2014-02-01

Whether a cationic organic polymer can remove more total cyanide (TCN) than a non-ionic organic polymer during the same flocculation system has not been reported previously. In this study, the effects of organic polymers with different charge density on the removal mechanisms of TCN in coking wastewater are investigated by polyferric sulfate (PFS) with a cationic organic polymer (PFS-C) or a non-ionic polymer (PFS-N). The coagulation experiments results show that residual concentrations of TCN (Fe(CN)6(3-)) after PFS-C flocculation (TCN < 0.2 mg/L) are much lower than that after PFS-N precipitation. This can be attributed to the different TCN removal mechanisms of the individual organic polymers. To investigate the roles of organic polymers, physical and structural characteristics of the flocs are analyzed by FT-IR, XPS, TEM and XRD. Owing to the presence of N+ in PFS-C, Fe(CN)6(3-) and negative flocs (Fe(CN)6(3-) adsorbed on ferric hydroxides) can be removed via charge neutralization and electrostatic patch flocculation by the cationic organic polymer. However, non-ionic N in PFS-N barely reacts with cyanides through sweeping or bridging, which indicates that the non-ionic polymer has little influence on TCN removal.

Effects of ionic liquid to water ratio as a composite medium for the synthesis of LiFePO4 for battery

NASA Astrophysics Data System (ADS)

Tith, Rany; Dutta, Jaydeep; Jung, Kichang; Martinez-Morales, Alfredo A.

2017-05-01

LiFePO4 is a highly researched cathode material that serves as an alternative material for traditional commercial lithiumion batteries such as LiCoO2. Currently, there are a number of different methods to synthesize LiFePO4 including: hydrothermal, solid state, spray pyrolysis, and coprecipitation. Our proposed method has the potential to provide an ecologically friendly and economically competitive way to synthesize LiFePO4 by utilizing ionic liquid and water, as a composite synthesis medium. The addition of water to ionic liquid can be beneficial as it can act as a mineralizer to bring insoluble precursors to form LiFePO4 seed crystals. Furthermore, this method provides the possibility of recycling the ionic liquid for repeated synthesis processes. In this work, we study the effects of ionic liquid to water ratio on the crystallinity and morphology of the synthesized material. Our group was able to conclude a reaction medium utilizing a ratio of equal parts of 1-ethyl-3-methyl imidazolium trifluoromethane sulfonate (EMIM Otf) and water, or a slightly favored ionic liquid ratio, increases the efficacy of the synthesis route. Crystallinity and purity was determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) was used to determine morphology and crystal sizes, and energy dispersion spectroscopy (EDX) was used for elemental analysis.

The presence of functional groups key for biodegradation in ionic liquids: effect on gas solubility.

PubMed

Deng, Yun; Morrissey, Saibh; Gathergood, Nicholas; Delort, Anne-Marie; Husson, Pascale; Costa Gomes, Margarida F

2010-03-22

The effect of the incorporation of either ester or ester and ether functions into the side chain of an 1-alkyl-3-methylimidazolium cation on the physico-chemical properties of ionic liquids containing bis(trifluoromethylsulfonyl)imide or octylsulfate anions is studied. It is believed that the introduction of an ester function into the cation of the ionic liquids greatly increases their biodegradability. The density of three such ionic liquids is measured as a function of temperature, and the solubility of four gases-carbon dioxide, ethane, methane, and hydrogen-is determined between 303 K and 343 K and at pressures close to atmospheric level. Carbon dioxide is the most soluble gas, followed by ethane and methane; the mole fraction solubilities vary from 1.8 x 10(-3) to 3.7 x 10(-2). These solubilities are of the same order of magnitude as those determined for alkylimidazolium-based ionic liquids. The chemical modification of the alkyl side chain does not result in a significant change of the solvation properties of the ionic liquid. All of the solubilities decrease with increasing temperature, corresponding to an exothermal solvation process. From the variation of this property with temperature, the thermodynamic functions of solvation (Gibbs energy, enthalpy, and entropy) are calculated and provide information about the solute-solvent interactions and the molecular structure of the solutions.

[Determination of solubility parameters for asymmetrical dicationic ionic liquids by inverse gas chromatography].

PubMed

Wang, Jun; Yang, Xuzhao; Wu, Jinchao; Song, Hao; Zou, Wenyuan

2015-12-01

Inverse gas chromatographic (IGC) technology was used to determine the solubility parameters of three asymmetrical dicationic ionic liquids ([ PyC5Pi] [ NTf2]2, [MpC5Pi] [NTf2]2 and [PyC6Pi] [NTf2]2) at 343.15-363.15 K. Five alkanes were applied as test probes including octane (n-C8) , decane (n-C10), dodecane (n-C12), tetradecane (n-C14), hexadecane (n-C16). Some thermodynamic parameters were obtained by IGC data analysis, such as the specific retention volumes of the solvents (V0(g)), the molar enthalpies of sorption (ΔHs(1)), the partial molar enthalpies of mixing at infinite dilution (ΔH∞91)), the molar enthalpies of vaporization (ΔH)v)), the activity coefficients at infinite dilution (Ω∞(1)), and Flory-Huggins interaction parameters (χ∞(12)) between ionic liquids and probes. The solubility parameters (δ2) of the three dicationic ionic liquids at room temperature (298.15 K) were 28.52-32.66 (J x cm(-3)) ½. The solubility parameters (δ2) of cationic structure with 4-methyl morpholine are bigger than those of the cationic structure with pyridine. The bigger the solubility parameter (δ2) is, the more the carbon numbers of linking group of the ionic liquids are. The results are of great importance to the study of the solution behavior and the applications of ionic liquid.

High H⁻ ionic conductivity in barium hydride.

PubMed

Verbraeken, Maarten C; Cheung, Chaksum; Suard, Emmanuelle; Irvine, John T S

2015-01-01

With hydrogen being seen as a key renewable energy vector, the search for materials exhibiting fast hydrogen transport becomes ever more important. Not only do hydrogen storage materials require high mobility of hydrogen in the solid state, but the efficiency of electrochemical devices is also largely determined by fast ionic transport. Although the heavy alkaline-earth hydrides are of limited interest for their hydrogen storage potential, owing to low gravimetric densities, their ionic nature may prove useful in new electrochemical applications, especially as an ionically conducting electrolyte material. Here we show that barium hydride shows fast pure ionic transport of hydride ions (H(-)) in the high-temperature, high-symmetry phase. Although some conductivity studies have been reported on related materials previously, the nature of the charge carriers has not been determined. BaH2 gives rise to hydride ion conductivity of 0.2 S cm(-1) at 630 °C. This is an order of magnitude larger than that of state-of-the-art proton-conducting perovskites or oxide ion conductors at this temperature. These results suggest that the alkaline-earth hydrides form an important new family of materials, with potential use in a number of applications, such as separation membranes, electrochemical reactors and so on.

Pressure and temperature dependences of the ionic conductivities of the thallous halidesTlCl, TlBr, and TlI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samara, G.A.

1981-01-15

Detailed studies of the pressure and temperature dependences of the ionic conductivities of TlCl and TlBr have allowed determination of the lattice volume relaxations and energies associated with the formation and motion of Schottky defects in these crystals. The volume relaxations deduced from the conductivity are found to be comparable in magnitude with values calculated from the strain energy model and a dynamical model. The association energy of Tl/sup +/ vacancies and divalent impurities was also determined for TlBr. A particularly important result is the finding that for these CsCl-type crystals the relaxation of the lattice associated with vacancy formationmore » is outward. Earlier studies on ionic crystals having the NaCl structure have yielded a similar result. This outward relaxation thus appears to be a general result for ionic crystals of both the NaCl and CsCl types (and possibly other ionic lattice types), in disagreement with earlier theoretical calculations which show that the relaxation should be inward for all models of ionic vacancies investigated. The conductivity of TlI was studied in both the (low temperature and pressure) orthorhombic phase as well as in the cubic CsCl-type phase. There is a large electronic contribution to the conductivity in the orthorhombic phase. An interesting result for all three materials is the observation in the cubic phase of a pressure-induced transition from ionic to electronic conduction. This is in qualitative agreement with what is known about the pressure dependences of the electronic structure of these materials.« less

Ionic structures and transport properties of hot dense W and U plasmas

NASA Astrophysics Data System (ADS)

Hou, Yong; Yuan, Jianmin

2016-10-01

We have combined the average-atom model with the hyper-netted chain approximation (AAHNC) to describe the electronic and ionic structure of uranium and tungsten in the hot dense matter regime. When the electronic structure is described within the average-atom model, the effects of others ions on the electronic structure are considered by the correlation functions. And the ionic structure is calculated though using the hyper-netted chain (HNC) approximation. The ion-ion pair potential is calculated using the modified Gordon-Kim model based on the electronic density distribution in the temperature-depended density functional theory. And electronic and ionic structures are determined self-consistently. On the basis of the ion-ion pair potential, we perform the classical (CMD) and Langevin (LMD) molecular dynamics to simulate the ionic transport properties, such as ionic self-diffusion and shear viscosity coefficients, through the ionic velocity correlation functions. Due that the free electrons become more and more with increasing the plasma temperature, the influence of the electron-ion collisions on the transport properties become more and more important.

Osmotic swelling of polyacrylate hydrogels in physiological salt solutions.

PubMed

Horkay, F; Tasaki, I; Basser, P J

2000-01-01

The swelling behavior of fully neutralized sodium polyacrylate gels was investigated in aqueous solutions of alkali metal (LiCl, NaCl, KCl, CsCl) and alkaline earth metal salts (CaCl2, SrCl2, BaCl2). The total salt concentration and the ratio of monovalent to divalent cations were varied in the biologically significant range. It is found that the concentrations of both monovalent and divalent cations vary continuously and smoothly in the gel despite the abrupt change in the gel volume. The individual elastic, mixing, and ionic contributions to the free energy of the gel were separately determined as a function of the degree of network swelling to elucidate the thermodynamics of swelling. Shear modulus measurements performed at different Ca2+ concentrations suggest that Ca2+ does not form stable cross-links between the polymer chains. At low and moderate swelling ratios the concentration dependence of the shear modulus follows a power law behavior, G variation of phi n, with n = 0.34 +/- 0.03. At high swelling degrees, however, the shear modulus increases with increasing swelling. The value of the Flory-Huggins interaction parameter, chi, determined from osmotic swelling pressure and shear modulus measurements, strongly depends on the ionic composition of the equilibrium solution and increases with increasing Ca2+ concentration.

The synthesis and the chemical and physical properties of non-aqueous silylamine solvents for carbon dioxide capture.

PubMed

Rohan, Amy L; Switzer, Jackson R; Flack, Kyle M; Hart, Ryan J; Sivaswamy, Swetha; Biddinger, Elizabeth J; Talreja, Manish; Verma, Manjusha; Faltermeier, Sean; Nielsen, Paul T; Pollet, Pamela; Schuette, George F; Eckert, Charles A; Liotta, Charles L

2012-11-01

Silylamine reversible ionic liquids were designed to achieve specific physical properties in order to address effective CO₂ capture. The reversible ionic liquid systems reported herein represent a class of switchable solvents where a relatively non-polar silylamine (molecular liquid) is reversibly transformed to a reversible ionic liquid (RevIL) by reaction with CO₂ (chemisorption). The RevILs can further capture additional CO₂ through physical absorption (physisorption). The effects of changes in structure on (1) the CO₂ capture capacity (chemisorption and physisorption), (2) the viscosity of the solvent systems at partial and total conversion to the ionic liquid state, (3) the energy required for reversing the CO₂ capture process, and (4) the ability to recycle the solvents systems are reported. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Drift, Diffusion, and Reactions of Slow Ions in Gases.

DTIC Science & Technology

1980-02-28

explaining plasma chemistry ; ionic transport data are required for the accurate determination of these rate coefficients. Observations on ionic identity and...34Studies of Ion Plasma Chemistry with Drift Tube Mass Spectrometers", Third International Symposium on Plasma Chemistry , Limoges, France, (July 1977

Development and optimization of a naphthoic acid-based ionic liquid as a "non-organic solvent microextraction" for the determination of tetracycline antibiotics in milk and chicken eggs.

PubMed

Gao, Jiajia; Wang, Hui; Qu, Jingang; Wang, Huili; Wang, Xuedong

2017-01-15

In traditional ionic liquids (ILs)-based microextraction, ILs are often used as extraction and dispersive solvents; however, their functional effects are not fully utilized. Herein, we developed a novel ionic liquid 1-butyl-3-methylimidazolium naphthoic acid salt ([C4MIM][NPA]) with strong acidity. It was used as a mixed dispersive solvent with conventional [C2MIM][BF4] in "functionalized ionic liquid-based non-organic solvent microextraction (FIL-NOSM)" for determination of tetracycline antibiotics (TCs) in milk and eggs. Utilization of [C4MIM][NPA] in FIL-NOSM method increased extraction recoveries (ERs) of TCs by more than 20% and eliminated the pH adjustment step because of its strong acidity. Under optimized conditions based on central composite design, the ERs of four TCs were 94.1-102.1%, and the limitsofdetection were 0.08-1.12μgkg(-1) in milk and egg samples. This proposed method provides high extraction efficiency, less pretreatment time and requires non-organic solvents for determination of trace TC concentrations in complex animal-based food matrices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-Consistent Determination of Atomic Charges of Ionic Liquid through a Combination of Molecular Dynamics Simulation and Density Functional Theory.

PubMed

Ishizuka, Ryosuke; Matubayasi, Nobuyuki

2016-02-09

A self-consistent scheme is developed to determine the atomic partial charges of ionic liquid. Molecular dynamics (MD) simulation was conducted to sample a set of ion configurations, and these configurations were subject to density functional theory (DFT) calculations to determine the partial charges. The charges were then averaged and used as inputs for the subsequent MD simulation, and MD and DFT calculations were repeated until the MD results are not altered any more. We applied this scheme to 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide ([C1mim][NTf2]) and investigated its structure and dynamics as a function of temperature. At convergence, the average ionic charges were ±0.84 e at 350 K due to charge transfer among ions, where e is the elementary charge, while the reduced ionic charges do not affect strongly the density of [C1mim][NTf2] and radial distribution function. Instead, major effects are found on the energetics and dynamics, with improvements of the overestimated heat of vaporization and the too slow motions of ions observed in MD simulations using commonly used force fields.

Simultaneous electrochemical determination of L-cysteine and L-cysteine disulfide at carbon ionic liquid electrode.

PubMed

Safavi, Afsaneh; Ahmadi, Raheleh; Mahyari, Farzaneh Aghakhani

2014-04-01

A linear sweep voltammetric method is used for direct simultaneous determination of L-cysteine and L-cysteine disulfide (cystine) based on carbon ionic liquid electrode. With carbon ionic liquid electrode as a high performance electrode, two oxidation peaks for L-cysteine (0.62 V) and L-cysteine disulfide (1.3 V) were observed with a significant separation of about 680 mV (vs. Ag/AgCl) in phosphate buffer solution (pH 6.0). The linear ranges were obtained as 1.0-450 and 5.0-700 μM and detection limits were estimated to be 0.298 and 4.258 μM for L-cysteine and L-cysteine disulfide, respectively. This composite electrode was applied for simultaneous determination of L-cysteine and L-cysteine disulfide in two real samples, artificial urine and nutrient broth. Satisfactory results were obtained which clearly indicate the applicability of the proposed electrode for simultaneous determination of these compounds in complex matrices.

Determination of Physical Properties of Energetic Ionic Liquids Using Molecular Simulations

DTIC Science & Technology

2006-12-31

respose , trrncdu g the time for revienig istions, searc g exsting data sources. gathering and rrivntaWii thedata nestedad std comgteltng and rvedng...measure self -diffusivities for three ionic liquid systems. We then compared our calculated self -diffusivities against these data. 3.2.2 Summary of...useful measure of liquid dynamics that is amenable to both experimental and computational determination is the self -diffusivity, D,, defined as l-lim ,!Ir

Graphene/Ionic Liquid Composite Films and Ion Exchange

PubMed Central

Mo, Yufei; Wan, Yunfang; Chau, Alicia; Huang, Fuchuan

2014-01-01

Wettability of graphene is adjusted by the formation of various ionic surfaces combining ionic liquid (IL) self-assembly with ion exchange. The functionalized ILs were designed and synthesized with the goal of obtaining adjustable wettability. The wettability of the graphene surface bearing various anions was measured systematically. The effect of solvent systems on ion exchange ratios on the graphene surface has also been investigated. Meanwhile, the mechanical properties of the graphene/IL composite films were investigated on a nanometer scale. The elasticity and adhesion behavior of the thin film was determined with respected to the indentation deformation by colloid probe nanoindentation method. The results indicate that anions played an important role in determining graphene/IL composite film properties. In addition, surface wetting and mechanics can be quantitatively determined according to the counter-anions on the surface. This study might suggest an alternate way for quantity detection of surface ions by surface force. PMID:24970602

Light scattering measurements supporting helical structures for chromatin in solution.

PubMed

Campbell, A M; Cotter, R I; Pardon, J F

1978-05-01

Laser light scattering measurements have been made on a series of polynucleosomes containing from 50 to 150 nucleosomes. Radii of gyration have been determined as a function of polynucleosome length for different ionic strength solutions. The results suggest that at low ionic strength the chromatin adopts a loosely helical structure rather than a random coil. The helix becomes more regular on increasing the ionic strength, the dimension resembling those proposed by Finch and Klug for their solenoid model.

Time-of-flight measurement of ionic species generated during ablation for optimization of focusing condition at free-electron laser beamline

NASA Astrophysics Data System (ADS)

Senba, Y.; Nagasono, M.; Koyama, T.; Yumoto, H.; Ohashi, H.; Tono, K.; Togashi, T.; Inubushi, Y.; Sato, T.; Yabashi, M.; Ishikawa, T.

2013-03-01

Optimization of focusing conditions is important in free-electron laser applications. A time-of-flight mass analyzer has been designed and constructed for this purpose. The time-of-flight spectra of ionic species evolved from laser ablation of gold were measured. The yields of ionic species showed strong correlations with free-electron-laser intensity. This method conveniently allows for direct estimation of laser intensity on sample and determination of focusing position.

In silico free energy predictions for ionic liquid-assisted exfoliation of a graphene bilayer into individual graphene nanosheets.

PubMed

Kamath, Ganesh; Baker, Gary A

2012-06-14

Free energies for graphene exfoliation from bilayer graphene using ionic liquids based on various cations paired with the bis(trifluoromethylsulfonyl)imide anion were determined from adaptive bias force-molecular dynamics (ABF-MD) simulation and fall in excellent qualitative agreement with experiment. This method has notable potential as an a priori screening tool for performance based rank order prediction of novel ionic liquids for the dispersion and exfoliation of various nanocarbons and inorganic graphene analogues.

Average-atom model for two-temperature states and ionic transport properties of aluminum in the warm dense matter regime

NASA Astrophysics Data System (ADS)

Hou, Yong; Fu, Yongsheng; Bredow, Richard; Kang, Dongdong; Redmer, Ronald; Yuan, Jianmin

2017-03-01

The average-atom model combined with the hyper-netted chain approximation is an efficient tool for electronic and ionic structure calculations for warm dense matter. Here we generalize this method in order to describe non-equilibrium states with different electron and ion temperature as produced in laser-matter interactions on ultra-short time scales. In particular, the electron-ion and ion-ion correlation effects are considered when calculating the electron structure. We derive an effective ion-ion pair-potential using the electron densities in the framework of temperature-depended density functional theory. Using this ion-ion potential we perform molecular dynamics simulations in order to determine the ionic transport properties such as the ionic diffusion coefficient and the shear viscosity through the ionic velocity autocorrelation functions.

A Spectral-SAR Model for the Anionic-Cationic Interaction in Ionic Liquids: Application to Vibrio fischeri Ecotoxicity

PubMed Central

Lacrămă, Ana-Maria; Putz, Mihai V.; Ostafe, Vasile

2007-01-01

Within the recently launched the spectral-structure activity relationship (S-SAR) analysis, the vectorial anionic-cationic model of a generic ionic liquid is proposed, along with the associated algebraic correlation factor in terms of the measured and predicted activity norms. The reliability of the present scheme is tested by assessing the Hansch factors, i.e. lipophylicity, polarizability and total energy, to predict the ecotoxicity endpoints of wide types of ionic liquids with ammonium, pyridinium, phosphonium, choline and imidazolium cations on the aquatic bacteria Vibrio fischeri. The results, while confirming the cationic dominant influence when only lipophylicity is considered, demonstrate that the anionic effect dominates all other more specific interactions. It was also proved that the S-SAR vectorial model predicts considerably higher activity for the ionic liquids than for its anionic and cationic subsystems separately, in all considered cases. Moreover, through applying the least norm-correlation path principle, the complete toxicological hierarchies are presented, unfolding the ecological rules of combined cationic and anionic influences in ionic liquid toxicity.

Rapid analysis of ultraviolet filters using dispersive liquid-liquid microextraction coupled to headspace gas chromatography and mass spectrometry.

PubMed

Pierson, Stephen A; Trujillo-Rodríguez, María J; Anderson, Jared L

2018-05-29

An ionic-liquid-based in situ dispersive liquid-liquid microextraction method coupled to headspace gas chromatography and mass spectrometry was developed for the rapid analysis of ultraviolet filters. The chemical structures of five ionic liquids were specifically designed to incorporate various functional groups for the favorable extraction of the target analytes. Extraction parameters including ionic liquid mass, molar ratio of ionic liquid to metathesis reagent, vortex time, ionic strength, pH, and total sample volume were studied and optimized. The effect of the headspace temperature and volume during the headspace sampling step was also evaluated to increase the sensitivity of the method. The optimized procedure is fast as it only required ∼7-10 min per extraction and allowed for multiple extractions to be performed simultaneously. In addition, the method exhibited high precision, good linearity, and low limits of detection for six ultraviolet filters in aqueous samples. The developed method was applied to both pool and lake water samples attaining acceptable relative recovery values. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroactive polymer actuator based on a reduced graphene electrode

NASA Astrophysics Data System (ADS)

Im, Ki Hong; Choi, Hyonkwang

2014-03-01

We report an electroactive polymer (EAP) actuator using a reduced graphene electrode for a ionic polymer-metal composite actuator. Aqueous-reduced graphene is deposited to both sides of the ionic polymer membranes by using a simple inkjet printing process. The electrical and the optical properties of the reduced graphene were evaluated by using a four-point probe system, Raman spectroscopy, and Fourier-transform infrared attenuated total reflection spectroscopy. The actuator properties were evaluated from the curvatures of the ionic polymer graphene composite (IPGC) for various input voltages. From the results, we propose a new and simple isosceles trapezoidal element model for analyzing the relations among the input voltage, thickness, and curvature of IPGC.

Determination of three estrogens and bisphenol A by functional ionic liquid dispersive liquid-phase microextraction coupled with ultra-high performance liquid chromatography and ultraviolet detection.

PubMed

Jiang, Yuehuang; Tang, Tingting; Cao, Zhen; Shi, Guoyue; Zhou, Tianshu

2015-06-01

A hydroxyl-functionalized ionic liquid, 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, was employed in an improved dispersive liquid-phase microextraction method coupled with ultra high performance liquid chromatography for the enrichment and determination of three estrogens and bisphenol A in environmental water samples. The introduced hydroxyl group acted as the H-bond acceptor that dispersed the ionic liquid effectively in the aqueous phase without dispersive solvent or external force. Fourier transform infrared spectroscopy indicated that the hydroxyl group of the cation of the ionic liquid enhanced the combination of extractant and analytes through the formation of hydrogen bonds. The improvement of the extraction efficiency compared with that with the use of alkyl ionic liquid was proved by a comparison study. The main parameters including volume of extractant, temperature, pH, and extraction time were investigated. The calibration curves were linear in the range of 5.0-1000 μg/L for estrone, estradiol, and bisphenol A, and 10.0-1000 μg/L for estriol. The detection limits were in the range of 1.7-3.4 μg/L. The extraction efficiency was evaluated by enrichment factor that were between 85 and 129. The proposed method was proved to be simple, low cost, and environmentally friendly for the determination of the four endocrine disruptors in environmental water samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ionic Association Ion-Selective Electrode Experiment.

ERIC Educational Resources Information Center

Emara, Mostafa M.; And Others

1979-01-01

Describes an experiment that, using a commercially available solid-state selective electrode in conjunction with a pH-meter, determines the stability constants of sodium sulfate while varying the ionic strength of the media using sodium chloride. Detailed reproducible procedures of both the measurements and calculations are described. (BT)

Key Developments in Ionic Liquid Crystals.

PubMed

Alvarez Fernandez, Alexandra; Kouwer, Paul H J

2016-05-16

Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material?

Evolution of ferroelectricity in tetrathiafulvalene-p-chloranil as a function of pressure and temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dengl, Armin; Beyer, Rebecca; Peterseim, Tobias

2014-06-28

The neutral-to-ionic phase transition in the mixed-stack charge-transfer complex tetrathiafulvalene-p-chloranil (TTF-CA) has been studied by pressure-dependent infrared spectroscopy up to p = 11 kbar and down to low temperatures, T = 10 K. By tracking the C=O antisymmetric stretching mode of CA molecules, we accurately determine the ionicity of TTF-CA in the pressure-temperature phase diagram. At any point, the TTF-CA crystal bears only a single ionicity; there is no coexistence region or an exotic high-pressure phase. Our findings shed new light on the role of electron-phonon interaction in the neutral-ionic transition.

Key Developments in Ionic Liquid Crystals

PubMed Central

Alvarez Fernandez, Alexandra; Kouwer, Paul H. J.

2016-01-01

Ionic liquid crystals are materials that combine the classes of liquid crystals and ionic liquids. The first one is based on the multi-billion-dollar flat panel display industry, whilst the latter quickly developed in the past decades into a family of highly-tunable non-volatile solvents. The combination yields materials with a unique set of properties, but also with many challenges ahead. In this review, we provide an overview of the key concepts in ionic liquid crystals, particularly from a molecular perspective. What are the important molecular parameters that determine the phase behavior? How should they be introduced into the molecules? Finally, which other tools does one have to realize specific properties in the material? PMID:27196890

Total Synthesis of Ionic Liquid Systems for Dissolution of Lunar Simulant

NASA Technical Reports Server (NTRS)

Sharpe, Robert J.; Karr, Laurel J.; Paley, Mark S.

2010-01-01

For purposes of Space Resource Utilization, work in the total synthesis of a new ionic liquid system for the extraction of oxygen and metals from lunar soil is studied and described. Reactions were carried out according to procedures found in the chemical literature, analyzed via Thin-Layer Chromatography and 1H Nuclear Magnetic Resonance Spectroscopy and purified via vacuum distillation and rotary evaporation. Upon final analysis via 1H NMR, it was found that while the intermediates of the synthesis had been achieved, unexpected side products were also present. The mechanisms and constraints of the synthesis are described as well as the final results of the project and recommendations for continued study

Potential use of ionic species for identifying source land-uses of stormwater runoff.

PubMed

Lee, Dong Hoon; Kim, Jin Hwi; Mendoza, Joseph A; Lee, Chang-Hee; Kang, Joo-Hyon

2017-02-01

Identifying critical land-uses or source areas is important to prioritize resources for cost-effective stormwater management. This study investigated the use of information on ionic composition as a fingerprint to identify the source land-use of stormwater runoff. We used 12 ionic species in stormwater runoff monitored for a total of 20 storm events at five sites with different land-use compositions during the 2012-2014 wet seasons. A stepwise forward discriminant function analysis (DFA) with the jack-knifed cross validation approach was used to select ionic species that better discriminate the land-use of its source. Of the 12 ionic species, 9 species (K + , Mg 2+ , Na + , NH 4 + , Br - , Cl - , F - , NO 2 - , and SO 4 2- ) were selected for better performance of the DFA. The DFA successfully differentiated stormwater samples from urban, rural, and construction sites using concentrations of the ionic species (70%, 95%, and 91% of correct classification, respectively). Over 80% of the new data cases were correctly classified by the trained DFA model. When applied to data cases from a mixed land-use catchment and downstream, the DFA model showed the greater impact of urban areas and rural areas respectively in the earlier and later parts of a storm event.

Fabrication of an ionic-liquid-based polymer monolithic column and its application in the fractionation of proteins from complex biosamples.

PubMed

Zhang, Doudou; Zhang, Qian; Bai, Ligai; Han, Dandan; Liu, Haiyan; Yan, Hongyuan

2018-05-01

An ionic-liquid-based polymer monolithic column was synthesized by free radical polymerization within the confines of a stainless-steel column (50 mm × 4.6 mm id). In the processes, ionic liquid and stearyl methacrylate were used as dual monomers, ethylene glycol dimethacrylate as the cross-linking agent, and polyethylene glycol 200 and isopropanol as co-porogens. Effects of the prepolymerization solution components on the properties of the resulting monoliths were studied in detail. Scanning electron microscopy, nitrogen adsorption-desorption measurements, and mercury intrusion porosimetry were used to investigate the morphology and pore size distribution of the prepared monoliths, which showed that the homemade ionic-liquid-based monolith column possessed a relatively uniform macropore structure with a total macropore specific surface area of 44.72 m 2 /g. Compared to a non-ionic-liquid-based monolith prepared under the same conditions, the ionic-liquid-based monolith exhibited excellent selectivity and high performance for separating proteins from complex biosamples, such as egg white, snailase, bovine serum albumin digest solution, human plasma, etc., indicating promising applications in the fractionation and analysis of proteins from the complex biosamples in proteomics research. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Seasonal evolution of anionic, cationic and non-ionic surfactant concentrations in coastal aerosols from Askö, Sweden

NASA Astrophysics Data System (ADS)

Gérard, Violaine; Nozière, Barbara; Baduel, Christine

2015-04-01

Surfactants present in atmospheric aerosols are expected to enhance the activation into cloud droplets by acting on one of the two key parameters of the Köhler equation: the surface tension, σ. But because the magnitude of this effect and its regional and temporal variability are still highly uncertain [1,2], various approaches have been developed to evidence it directly in the atmosphere. This work presents the analysis of surfactants present in PM2.5 aerosol fractions collected at the coastal site of Askö, Sweden (58° 49.5' N, 17° 39' E) from July to October 2010. The total surfactant fraction was extracted from the samples using an improved double extraction technique. Surface tension measurements performed with the pendant drop technique [3] indicated the presence of very strong surfactants (σ ~ 30 - 35 mN/m) in these aerosols. In addition, these extractions were combined with colorimetric methods to determine the anionic, cationic and non-ionic surfactant concentrations [4,5], and provided for the first time interference-free surfactant concentrations in atmospheric aerosols. At this site, the total surfactant concentration in the PM2.5 samples varied between 7 to 150 mM and was dominated by anionic and non-ionic ones. The absolute surface tension curves obtained for total surfactant fraction displayed Critical Micelle Concentrations (CMC) in the range 50 - 400 uM, strongly suggesting a biological origin for the surfactants. The seasonal evolution of these concentrations and their relationships with environmental or meteorological parameters at the site will be discussed. [1] Ekström, S., Nozière, B. et al., Biogeosciences, 2010, 7, 387 [2] Baduel, C., Nozière, B., Jaffrezo, J.-L., Atmos. Environ., 2012, 47, 413 [3] Nozière, B., Baduel, C., Jaffrezo, J.-L., Nat. Commun., 2014, 5, 1 [4] Latif, M. T.; Brimblecombe, P. Environ. Sci. Technol., 2004, 38, 6501 [5] Pacheco e Silva et al., Method to measure surfactant in fluid, 2013, US 2013/0337568 A1

Numerical modeling of ultrasonic cavitation in ionic liquids

NASA Astrophysics Data System (ADS)

Calvisi, Michael L.; Elder, Ross M.

2017-11-01

Ionic liquids have favorable properties for sonochemistry applications in which the high temperatures and pressures achieved by cavitation bubbles are important drivers of chemical processes. Two different numerical models are presented to simulate ultrasonic cavitation in ionic liquids, each with different capabilities and physical assumptions. A model based on a compressible form of the Rayleigh-Plesset equation (RPE) simulates ultrasonic cavitation of a spherical bubble with a homogeneous interior, incorporating evaporation and condensation at the bubble surface, and temperature-varying thermodynamic properties in the interior. A second, more computationally intensive model of a spherical bubble uses the finite element method (FEM) and accounts for spatial variations in pressure and temperature throughout the flow domain. This model provides insight into heat transfer across the bubble surface and throughout the bubble interior and exterior. Parametric studies are presented for sonochemistry applications involving ionic liquids as a solvent, examining a range of realistic ionic liquid properties and initial conditions to determine their effect on temperature and pressure. Results from the two models are presented for parametric variations including viscosity, thermal conductivity, water content of the ionic liquid solvent, acoustic frequency, and initial bubble pressure. An additional study performed with the FEM model examines thermal penetration into the surrounding ionic liquid during bubble oscillation. The results suggest the prospect of tuning ionic liquid properties for specific applications.

In-situ ionic liquid dispersive liquid-liquid microextraction using a new anion-exchange reagent combined Fe3O4 magnetic nanoparticles for determination of pyrethroid pesticides in water samples.

PubMed

Fan, Chen; Liang, You; Dong, Hongqiang; Ding, Guanglong; Zhang, Wenbing; Tang, Gang; Yang, Jiale; Kong, Dandan; Wang, Deng; Cao, Yongsong

2017-07-04

In this work, in-situ ionic liquid dispersive liquid-liquid microextraction combined ultrasmall Fe 3 O 4 magnetic nanoparticles was developed as a kind of pretreatment method to detect pyrethroid pesticides in water samples. New anion-exchange reagents including Na[DDTC] and Na[N(CN) 2 ] were optimized for in-situ extraction pyrethroids, which showed enhanced microextraction performance. Pyrethroids were enriched by hydrophilic ionic liquid [P 4448 ][Br] (aqueous solution, 200 μL, 0.2 mmol mL -1 ) reaction in-situ with anion-exchange reagent Na[N(CN) 2 ] (aqueous solution, 300 μL, 0.2 mmol mL -1 ) forming hydrophobic ionic liquid as extraction agent in water sample (10 mL). Ultrasmall superparamagnetic iron oxide nanoparticles (30 mg) were used to collect the mixture of ionic liquid and pyrethroids followed by elution with acetonitrile. The extraction of ionic liquid strategies was unique and efficiently fulfilled with high enrichment factors (176-213) and good recoveries (80.20-117.31%). The method was successively applied to the determination of pyrethroid pesticides in different kinds of water samples with the limits of detection ranged from 0.16 to 0.21 μg L -1 . The proposed method is actually nanometer-level microextraction (average size 80 nm) with the advantages of simplicity, rapidity, and sensitivity. Copyright © 2017 Elsevier B.V. All rights reserved.

DETERMINATION OF HENRY'S LAW CONSTANTS FOR VOCS IN ROOM TEMPERATURE IONIC LIQUIDS

EPA Science Inventory

Ionic liquids (ILs) have been shown to be a newer medium for a wide variety of chemical reactions and are considered as the potential replacements for traditional volatile organic solvents. However, the separation and recovery of organic compounds from ILs has not been systematic...

Spring thaw ionic pulses boost nutrient availability and microbial growth in entombed Antarctic Dry Valley cryoconite holes

PubMed Central

Telling, Jon; Anesio, Alexandre M.; Tranter, Martyn; Fountain, Andrew G.; Nylen, Thomas; Hawkings, Jon; Singh, Virendra B.; Kaur, Preeti; Musilova, Michaela; Wadham, Jemma L.

2014-01-01

The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation age. During the initial melt there was a mean nine times enrichment in dissolved chloride relative to mean concentrations of the initial frozen holes indicative of an ionic pulse, with similar mean nine times enrichments in nitrite, ammonium, and dissolved organic matter. Nitrate was enriched twelve times and dissolved organic nitrogen six times, suggesting net nitrification, while lower enrichments for dissolved organic phosphorus and phosphate were consistent with net microbial phosphorus uptake. Rates of bacterial production were significantly elevated during the ionic pulse, likely due to the increased nutrient availability. There was no concomitant increase in photosynthesis rates, with a net depletion of dissolved inorganic carbon suggesting inorganic carbon limitation. Potential nitrogen fixation was detected in fully melted holes where it could be an important source of nitrogen to support microbial growth, but not during the ionic pulse where nitrogen availability was higher. This study demonstrates that ionic pulses significantly alter the timing and magnitude of microbial activity within entombed cryoconite holes, and adds credence to hypotheses that ionic enrichments during freeze-thaw can elevate rates of microbial growth and activity in other icy habitats, such as ice veins and subglacial regelation zones. PMID:25566210

Spring thaw ionic pulses boost nutrient availability and microbial growth in entombed Antarctic Dry Valley cryoconite holes.

PubMed

Telling, Jon; Anesio, Alexandre M; Tranter, Martyn; Fountain, Andrew G; Nylen, Thomas; Hawkings, Jon; Singh, Virendra B; Kaur, Preeti; Musilova, Michaela; Wadham, Jemma L

2014-01-01

The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation age. During the initial melt there was a mean nine times enrichment in dissolved chloride relative to mean concentrations of the initial frozen holes indicative of an ionic pulse, with similar mean nine times enrichments in nitrite, ammonium, and dissolved organic matter. Nitrate was enriched twelve times and dissolved organic nitrogen six times, suggesting net nitrification, while lower enrichments for dissolved organic phosphorus and phosphate were consistent with net microbial phosphorus uptake. Rates of bacterial production were significantly elevated during the ionic pulse, likely due to the increased nutrient availability. There was no concomitant increase in photosynthesis rates, with a net depletion of dissolved inorganic carbon suggesting inorganic carbon limitation. Potential nitrogen fixation was detected in fully melted holes where it could be an important source of nitrogen to support microbial growth, but not during the ionic pulse where nitrogen availability was higher. This study demonstrates that ionic pulses significantly alter the timing and magnitude of microbial activity within entombed cryoconite holes, and adds credence to hypotheses that ionic enrichments during freeze-thaw can elevate rates of microbial growth and activity in other icy habitats, such as ice veins and subglacial regelation zones.

Ionic Liquid Dispersive Liquid-Liquid Microextraction Method for the Determination of Irinotecan, an Anticancer Drug, in Water and Urine Samples Using UV-Vis Spectrophotometry.

PubMed

Uysal, Deniz; Karadaş, Cennet; Kara, Derya

2017-05-01

A new, simple, efficient, and environmentally friendly ionic liquid dispersive liquid-liquid microextraction method was developed for the determination of irinotecan, an anticancer drug, in water and urine samples using UV-Vis spectrophotometry. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate was used as the extraction solvent, and ethanol was used as the disperser solvent. The main parameters affecting the extraction efficiency, including sample pH, volume of the ionic liquid, choice of the dispersive solvent and its volume, concentration of NaCl, and extraction and centrifugation times, were investigated and optimized. The effect of interfering species on the recovery of irinotecan was also examined. Under optimal conditions, the LOD (3σ) was 48.7 μg/L without any preconcentration. Because the urine sample was diluted 10-fold, the LOD for urine would be 487 μg/L. However, this could be improved 16-fold if preconcentration using a 40 mL aliquot of the sample is used. The proposed method was successfully applied to the determination of irinotecan in tap water, river water, and urine samples spiked with 10.20 mg/L for the water samples and 8.32 mg/L for the urine sample. The average recovery values of irinotecan determined were 99.1% for tap water, 109.4% for river water, and 96.1% for urine.

Which iodinated contrast media is the least cytotoxic to human disc cells?

PubMed

Kim, Kyung-Hyun; Park, Jeong-Yoon; Park, Hyo-Suk; Kuh, Sung-Uk; Chin, Dong-Kyu; Kim, Keun-Su; Cho, Yong-Eun

2015-05-01

Iodinated contrast media (CM) is commonly used for various intradiscal injections such as in discography and endoscopic spinal surgery. However, CM has been shown to be toxic to renal tissue due to its ionic strength and osmolarity and as a result of iodine-induced cytotoxicity, which has raised concern over whether there are similar negative effects on disc cells. This in vitro study was designed to identify the least cytotoxic iodinated CM to the human disc cell among four different physiochemical iodinated contrast dyes. In vitro laboratory study. Intervertebral disc tissue was obtained by discectomy from a total of 10 lumbar disc patients undergoing surgery and disc cells were isolated. The human disc cells were grown in 3D alginate bead culture with 0, 0.1, 10, and 100 mg/mL CM solutions (ionic dimer, ionic monomer, non-ionic dimer, and non-ionic monomer) and mannitol as a control for 2 days. The living cells were analyzed with trypan blue staining. Fluorescence-activated cell sorting analysis was performed using Annexin V and propidium iodide (PI) and 3D alginate bead immunostaining to identify live, apoptotic, and necrotic cells. Human disc cell death was time- and dose-dependent in response to CM and more necrosis was observed than apoptosis. In addition, non-ionic dimeric CM (iodixanol) showed the least toxic effect on human disc cells, followed by non-ionic monomeric (iopromide), ionic dimeric (ioxaglate), and ionic monomeric CM (ioxithalamate). Contrast media is cytotoxic to human disc cells in a dose- and time-dependent manner. This in vitro study revealed that, among four different CM preparations, non-ionic dimeric CM is the least detrimental to human disc cell viability. Careful attention should be paid to the type of CM chosen for discography and endoscopic spinal surgery. It is also necessary to investigate the detrimental effects of CM on disc cells and disc degeneration in further in vivo studies. Copyright © 2015 Elsevier Inc. All rights reserved.

Effects of molten-salt/ionic-liquid mixture on extraction of docosahexaenoic acid (DHA)-rich lipids from Aurantiochytrium sp. KRS101.

PubMed

Choi, Sun-A; Jung, Joo-Young; Kim, Kyochan; Kwon, Jong-Hee; Lee, Jin-Suk; Kim, Seung Wook; Park, Ji-Yeon; Yang, Ji-Won

2014-11-01

In this study, lipid extraction from Aurantiochytrium sp. was performed using a molten-salt/ionic-liquid mixture. The total fatty acid content of Aurantiochytrium sp. was 478.8 mg/g cell, from which 145 mg/g cell (30.3% of total fatty acids) of docosahexaenoic acid (DHA) was obtained. FeCl3·6H2O showed a high lipid extraction yield (207.9 mg/g cell), when compared with that of [Emim]OAc, which was only 118.1 mg/g cell; notably however, when FeCl3·6H2O was mixed with [Emim]OAc (5:1, w/w), the yield was increased to 478.6 mg/g cell. When lipid was extracted by the FeCl3·6H2O/[Emim]OAc mixture at a 5:1 (w/w) blending ratio under 90 °C, 30 min reaction conditions, the fatty acid content of the extracted lipid was a high purity 997.7 mg/g lipid, with most of the DHA having been extracted (30.2% of total fatty acids). Overall, lipid extraction from Aurantiochytrium sp. was enhanced by the synergistic effects of the molten-salt/ionic-liquid mixture with different ions.

Novel double-confined polymeric ionic liquids as sorbents for solid-phase microextraction with enhanced stability and durability in high-ionic-strength solution.

PubMed

Feng, Juanjuan; Sun, Min; Xu, Lili; Wang, Shuai; Liu, Xia; Jiang, Shengxiang

2012-12-14

Because of the occurrence of ion exchange between high-ionic-strength solution and anions of polymeric ionic liquids (PILs), PILs based solid-phase microextraction (SPME) fibers were rarely used in direct immersion mode to high-salt-added samples. In this work, a novel double-confined PIL sorbent was prepared by co-polymerization of cation and anion of 1-vinyl-3-octylimidzaolium p-styrenesulfonate (VOIm(+)SS(-)). The poly(VOIm(+)-SS(-)) was chemically bonded onto functionalized stainless steel wire via surface radical chain-transfer reaction. Stability of poly(VOIm(+)-SS(-)) in high-ionic-strength solution was investigated and compared with that of poly(1-vinyl-3-octylimidzaolium benzenesulfonate) (poly(VOIm(+)BS(-))) by elemental analysis of sulfur element, and results turned out that the poly(VOIm(+)-SS(-)) was more stable. Coupled to gas chromatography (GC), the poly(VOIm(+)-SS(-)) fiber was used to extract three sorts of compounds including anilines, phenols and phthalate esters in aqueous solution. The as-established method showed good linearity, low detection limits, and acceptable repeatability. The direct immersion SPME-GC method was applied to determine the model phthalate esters in bottled mineral water. The determination results were satisfactory. Copyright © 2012 Elsevier B.V. All rights reserved.

Correlating Humidity-Dependent Ionically Conductive Surface Area with Transport Phenomena in Proton-Exchange Membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Qinggang; Kusoglu, Ahmet; Lucas, Ivan T.

2011-08-01

The objective of this effort was to correlate the local surface ionic conductance of a Nafion? 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using electrochemical impedance spectroscopy and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationshipmore » between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion? membrane was examined.« less

Friction and wear behavior of glasses and ceramics

NASA Technical Reports Server (NTRS)

Buckley, D. H.

1973-01-01

Adhesion, friction, and wear behavior of glasses and ionic solids are reviewed. These materials are shown to behave in a manner similar to other solids with respect to adhesion. Their friction characteristics are shown to be sensitive to environmental constituents and surface films. This sensitivity can be related to a reduction in adhesive bonding and the changes in surficial mechanical behavior associated with Rehbinder and Joffe effects. Both friction and wear properties of ionic crystalline solids are highly anisotropic. With metals in contact with ionic solids the fracture strength of the ionic solid and the shear strength in the metal and those properties that determine these will dictate which of the materials undergoes adhesive wear. The chemical activity of the metal plays an important role in the nature and strength of the adhesive interfacial bond that develops between the metal and a glass or ionic solid.

Dual Ionic and Organic Nature of Ionic Liquids

PubMed Central

Shi, Rui; Wang, Yanting

2016-01-01

Inherited the advantages of inorganic salts and organic solvents, ionic liquids (ILs) exhibit many superior properties allowing them promising green solvents for the future. Although it has been widely acknowledged that the unique features of ILs originate from their dual ionic and organic nature, its microscopic physical origin still remains blurry. In this work, by comparing the ion/molecule cage structures obtained from molecular dynamics simulations for seven prototypic liquids—a molten inorganic salt, four ILs, a strongly polar organic solvent, and a weakly polar organic solvent, we have revealed that the depth of the cage energy landscape characterizes the ionic nature of ILs, whereas the slope and curvature of its mimimum determine the organic nature of ILs. This finding advances our understanding of ILs and thus will help their efficient utilization as well as the systematic design of novel functionalized ILs. PMID:26782660

X‐ray Photoelectron Spectroscopy of Pyridinium‐Based Ionic Liquids: Comparison to Imidazolium‐ and Pyrrolidinium‐Based Analogues

PubMed Central

Mitchell, Daniel S.; Lovelock, Kevin R. J.

2015-01-01

Abstract We investigate eight 1‐alkylpyridinium‐based ionic liquids of the form [CnPy][A] by using X‐ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake‐up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic‐liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8Py][A] and analogues including 1‐octyl‐1‐methylpyrrolidinium‐ ([C8C1Pyrr][A]), and 1‐octyl‐3‐methylimidazolium‐ ([C8C1Im][A]) based samples, where X is common to all ionic liquids. PMID:25952131

Charge Dynamics and Bending Actuation in Aquivion Membrane Swelled with Ionic Liquids.

PubMed

Lin, Junhong; Liu, Yang; Zhang, Q M

2011-01-21

The actuation strain and speed of ionic electroactive polymer (EAP) actuators are mainly determined by the charge transport through the actuators and excess ion storage near the electrodes. We employ a recently developed theory on ion transport and storage to investigate the charge dynamics of short-side-chain Aquivion® (Hyflon®) membranes with different uptakes of ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf). The results reveal the existence of a critical uptake of ionic liquids above which the membrane exhibit a high ionic conductivity (σ>5×10(-2) mS/cm). Especially, we investigate the charge dynamics under voltages which are in the range for practical device operation (~1 volts and higher). The results show that the ionic conductivity, ionic mobility, and mobile ion concentration do not change with the applied voltage below 1 volt (and for σ below 4 volts). The results also show that bending actuation of the Aquivion membrane with 40 wt% EMI-Tf is much larger than that of Nafion, indicating that the shorter flexible side chains improve the electromechanical coupling between the excess ions and the membrane backbones, while not affect the actuation speed.

Charge Dynamics and Bending Actuation in Aquivion Membrane Swelled with Ionic Liquids

PubMed Central

Lin, Junhong; Liu, Yang; Zhang, Q. M.

2011-01-01

The actuation strain and speed of ionic electroactive polymer (EAP) actuators are mainly determined by the charge transport through the actuators and excess ion storage near the electrodes. We employ a recently developed theory on ion transport and storage to investigate the charge dynamics of short-side-chain Aquivion® (Hyflon®) membranes with different uptakes of ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf). The results reveal the existence of a critical uptake of ionic liquids above which the membrane exhibit a high ionic conductivity (σ>5×10−2 mS/cm). Especially, we investigate the charge dynamics under voltages which are in the range for practical device operation (~1 volts and higher). The results show that the ionic conductivity, ionic mobility, and mobile ion concentration do not change with the applied voltage below 1 volt (and for σ below 4 volts). The results also show that bending actuation of the Aquivion membrane with 40 wt% EMI-Tf is much larger than that of Nafion, indicating that the shorter flexible side chains improve the electromechanical coupling between the excess ions and the membrane backbones, while not affect the actuation speed. PMID:21339839

Theory and practice in the electrometric determination of pH in precipitation

NASA Astrophysics Data System (ADS)

Brennan, Carla Jo; Peden, Mark E.

Basic theory and laboratory investigations have been applied to the electrometric determination of pH in precipitation samples in an effort to improve the reliability of the results obtained from these low ionic strength samples. The theoretical problems inherent in the measurement of pH in rain have been examined using natural precipitation samples with varying ionic strengths and pH values. The importance of electrode design and construction has been stressed. The proper choice of electrode can minimize or eliminate problems arising from residual liquid junction potentials, streaming potentials and temperature differences. Reliable pH measurements can be made in precipitation samples using commercially available calibration buffers providing low ionic strength quality control solutions are routinely used to verify electrode and meter performance.

Determination of perchlorate in drinking water by ion chromatography using macrocycle-based concentration and separation methods.

PubMed

Lamb, John D; Simpson, David; Jensen, Bryce D; Gardner, Joseph S; Peterson, Quinn P

2006-06-16

Macrocycle-based ion chromatography provides a convenient, reliable method for the determination of perchlorate ion, which is currently of great interest to the environmental community. This study shows that effective perchlorate determinations can be made using standard conductimetric detection by combining an 18-crown-6-based mobile phase with an underivatized reversed-phase mobile phase ion chromatography (MPIC) column. One unique feature of this method is the flexibility in column capacity that is achieved through simple variations in eluent concentrations of 18-crown-6 and KOH, facilitating the separation of target analyte anions such as perchlorate. Using a standard anion exchange column as concentrator makes possible the determination of perchlorate as low as 0.2 ug/L in low ionic strength matrices. Determination of perchlorate at the sub-ug/L level in pure water and in spiked local city hard water samples with high background ion concentrations can be achieved this way. However, like other IC techniques, this method is challenged to achieve analyses at the ug/L level in the demanding high ionic strength matrix described by the United States Environmental Protection Agency (EPA) (1,000 mg/L chloride, sulfate and carbonate). We approached this challenge by use of the Cryptand C1 concentrator column, provided by Dionex Corporation, to effectively preconcentrate perchlorate while reducing background ion concentrations in the high ionic strength matrix. The retention characteristics of the concentrator column were studied in order to maximize its effectiveness for perchlorate determinations. The method makes possible the determination of perchlorate at the 5 ug/L level in the highest ionic strength matrix described by the EPA.

The use of cross-linked chitosan beads for nutrients (nitrate and orthophosphate) removal from a mixture of P-PO4, N-NO2 and N-NO3.

PubMed

Jóźwiak, Tomasz; Filipkowska, Urszula; Szymczyk, Paula; Kuczajowska-Zadrożna, Małgorzata; Mielcarek, Artur

2017-11-01

A hydrogel chitosan sorbent ionically cross-linked with sodium citrate and covalently cross-linked with epichlorohydrin was used to remove nutrients from an equimolar mixture of P-PO 4 , N-NO 2 and N-NO 3 . The scope of the study included, among other things, determination of the influence of pH on nutrient sorption effectiveness, nutrient sorption kinetics as well as determination of the maximum sorption capacity of cross-linked chitosan sorbents regarding P-PO 4 (H 2 PO 4 - , HPO 4 2- ), N-NO 2 (HNO 2 , NO 2 - ), and N-NO 3 (NO 3 - ). The effect of the type of the cross-linking agent on the affinity of the modified chitosan to each nutrient was studied as well. The kinetics of nutrient sorption on the tested chitosan sorbents was best described with the pseudo-second order model. The model of intramolecular diffusion showed that P-PO 4 , N-NO 2 and N-NO3 sorption on cross-linked hydrogel chitosan beads proceeded in two phases. The best sorbent of nutrients turned out to be chitosan cross-linked covalently with epichlorohydrin; with P-PO 4 , N-NO 2 and N-NO 3 sorption capacity reaching: 1.23, 0.94 and 0.76mmol/g, respectively (total of 2.92mmol/g). For comparison, the sorption capacity of chitosan cross-linked ionically with sodium citrate was: 0.43, 0.39 and 0.39mmol/g for P-PO 4 , N-NO 2 and N-NO 3 , respectively (total of 1.21mmol/g). Copyright © 2017 Elsevier B.V. All rights reserved.

13C cell wall enrichment and ionic liquid NMR analysis: progress towards a high-throughput detailed chemical analysis of the whole plant cell wall.

PubMed

Foston, Marcus; Samuel, Reichel; Ragauskas, Arthur J

2012-09-07

The ability to accurately and rapidly measure plant cell wall composition, relative monolignol content and lignin-hemicellulose inter-unit linkage distributions has become essential to efforts centered on reducing the recalcitrance of biomass by genetic engineering. Growing (13)C enriched transgenic plants is a viable route to achieve the high-throughput, detailed chemical analysis of whole plant cell wall before and after pretreatment and microbial or enzymatic utilization by (13)C nuclear magnetic resonance (NMR) in a perdeuterated ionic liquid solvent system not requiring component isolation. 1D (13)C whole cell wall ionic liquid NMR of natural abundant and (13)C enriched corn stover stem samples suggest that a high level of uniform labeling (>97%) can significantly reduce the total NMR experiment times up to ~220 times. Similarly, significant reduction in total NMR experiment time (~39 times) of the (13)C enriched corn stover stem samples for 2D (13)C-(1)H heteronuclear single quantum coherence NMR was found.

Excess plasma membrane and effects of ionic amphipaths on mechanics of outer hair cell lateral wall.

PubMed

Morimoto, Noriko; Raphael, Robert M; Nygren, Anders; Brownell, William E

2002-05-01

The interaction between the outer hair cell (OHC) lateral wall plasma membrane and the underlying cortical lattice was examined by a morphometric analysis of cell images during cell deformation. Vesiculation of the plasma membrane was produced by micropipette aspiration in control cells and cells exposed to ionic amphipaths that alter membrane mechanics. An increase of total cell and vesicle surface area suggests that the plasma membrane possesses a membrane reservoir. Chlorpromazine (CPZ) decreased the pressure required for vesiculation, whereas salicylate (Sal) had no effect. The time required for vesiculation was decreased by CPZ, indicating that CPZ decreases the energy barrier required for vesiculation. An increase in total volume is observed during micropipette aspiration. A deformation-induced increase in hydraulic conductivity is also seen in response to micropipette-applied fluid jet deformation of the lateral wall. Application of CPZ and/or Sal decreased this strain-induced hydraulic conductivity. The impact of ionic amphipaths on OHC plasma membrane and lateral wall mechanics may contribute to their effects on OHC electromotility and hearing.

Ionization-potential depression and dynamical structure factor in dense plasmas

NASA Astrophysics Data System (ADS)

Lin, Chengliang; Röpke, Gerd; Kraeft, Wolf-Dietrich; Reinholz, Heidi

2017-07-01

The properties of a bound electron system immersed in a plasma environment are strongly modified by the surrounding plasma. The modification of an essential quantity, the ionization energy, is described by the electronic and ionic self-energies, including dynamical screening within the framework of the quantum statistical theory. Introducing the ionic dynamical structure factor as the indicator for the ionic microfield, we demonstrate that ionic correlations and fluctuations play a critical role in determining the ionization potential depression. This is, in particular, true for mixtures of different ions with large mass and charge asymmetry. The ionization potential depression is calculated for dense aluminum plasmas as well as for a CH plasma and compared to the experimental data and more phenomenological approaches used so far.

Study on the temperature-dependent coupling among viscosity, conductivity and structural relaxation of ionic liquids.

PubMed

Yamaguchi, Tsuyoshi; Yonezawa, Takuya; Koda, Shinobu

2015-07-15

The frequency-dependent viscosity and conductivity of three imidazolium-based ionic liquids were measured at several temperatures in the MHz region, and the results are compared with the intermediate scattering functions determined by neutron spin echo spectroscopy. The relaxations of both the conductivity and the viscosity agree with that of the intermediate scattering function at the ionic correlation when the relaxation time is short. As the relaxation time increases, the relaxations of the two transport properties deviate to lower frequencies than that of the ionic structure. The deviation begins at a shorter relaxation time for viscosity than for conductivity, which explains the fractional Walden rule between the zero-frequency values of the shear viscosity and the molar conductivity.

Ionic association of lithium salts in propylene carbonate/ 1,2-dimethoxyethane mixed systems for lithium batteries

NASA Astrophysics Data System (ADS)

Ishikawa, Masashi; Wen, Shi-Qui; Matsuda, Yoshiharu

1993-06-01

The ionic association constants of lithium perchlorate, lithium trifluoremethylsulfate, lithium hexafluorophosphate, and lithium tetrafluoroborate have been determined experimentally (by Shedlovsky's method) in various mixtures of propylene carbonate and 1,2-dimethoxyethane as typical electrolyte systems for rechargeable lithium batteries. The association constants vary extensively for different mixing ratios of propylene to 1,2-dimethoxyethane and for different species of salts. These values are compared with the theoretical values as predicted by the Fuoss and Bjerrum equations. On the basis of this comparison and some physical properties of the solution, the variation in the ionic association constants may be ascribed to the charge of ionic association species, i.e., a contact ion-pair and a solvent-separated ion-pair.

Interaction between 2',4-dihydroxychalcone and the N, f, e conformers of bovine serum albumin: influence of temperature and ionic strength.

PubMed

Curvale, Rolando A; Debattista, Nora B; Pappano, Nora B

2012-04-01

UV-Vis spectroscopy was used to study the interaction between the 2',4- dihydroxychalcone, flavonoid which is known to have anti-tumor activity in vitro, and others biological properties, and the N, F and E conformers of bovine serum albumin at different ionic strengths and temperatures. The Klotz model was found to be adequate to determine the constants and number of binding sites. The reaction was found to be exothermic and spontaneous. The number of binding sites decreases and the reaction is more exergonic along with the increase in ionic strength and the conformational change of N to E. The reactions were necessarily hydrophobic and followed by a process of ionic character.

Effect of additives on the clouding and aggregation behavior of Triton X-100

NASA Astrophysics Data System (ADS)

Semwal, Divyam; Sen, Indrani Das; Jayaram, Radha V.

2018-04-01

The present study investigates the effect of additives such as CsNO3 and imidazolium ionic liquids on the cloud point (CP) of Triton X-100. Thermodynamic parameters of the clouding process were determined in order to understand the interactions. CP was found to increase with the increase in concentration of most of the ionic liquids studied. This increase of CP reflects the solubilization of the ionic liquids in the micellar phase1. The thermodynamic parameters on the introduction of CsNO3 in TX-100 - ionic liquid system helps in understanding the different interactions occurring in the system. All ΔG values for clouding were found to be positive and hence made the process non spontaneous.

Composition of nasal airway surface liquid in cystic fibrosis and other airway diseases determined by X-ray microanalysis.

PubMed

Vanthanouvong, V; Kozlova, I; Johannesson, M; Nääs, E; Nordvall, S L; Dragomir, A; Roomans, G M

2006-04-01

The ionic composition of the airway surface liquid (ASL) in healthy individuals and in patients with cystic fibrosis (CF) has been debated. Ion transport properties of the upper airway epithelium are similar to those of the lower airways and it is easier to collect nasal ASL from the nose. ASL was collected with ion exchange beads, and the elemental composition of nasal fluid was determined by X-ray microanalysis in healthy subjects, CF patients, CF heterozygotes, patients with rhinitis, and with primary ciliary dyskinesia (PCD). In healthy subjects, the ionic concentrations were approximately isotonic. In CF patients, CF heterozygotes, rhinitis, and PCD patients, [Na] and [Cl] were significantly higher compared when compared with those in controls. [K] was significantly higher in CF and PCD patients compared with that in controls. Severely affected CF patients had higher ionic concentrations in their nasal ASL than in patients with mild or moderate symptoms. Female CF patients had higher levels of Na, Cl, and K than male patients. As higher salt concentrations in the ASL are also found in other patients with airway diseases involving chronic inflammation, it appears likely that inflammation-induced epithelial damage is important in determining the ionic composition of the ASL. Copyright (c) 2006 Wiley-Liss, Inc.

Ultrasound-assisted temperature-controlled ionic liquid emulsification microextraction coupled with capillary electrophoresis for the determination of parabens in personal care products.

PubMed

Ma, Teng; Li, Zheng; Jia, Qiong; Zhou, Weihong

2016-07-01

We developed a CE and ultrasound-assisted temperature-controlled ionic liquid emulsification microextraction method for the determination of four parabens (methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) in personal care products including mouthwash and toning lotion. In the proposed extraction procedure, ionic liquid (IL, 1-octyl-3-methylimidazolium hexafluorophosphate) was used as extraction solvent, moreover, no disperser solvent was needed. Parameters affecting the extraction efficiency including volume of IL, heating temperature, ultrasonic time, extraction time, sample pH, ionic strength, and centrifugation time were optimized. Under the optimized conditions, the method was found to be linear over the range of 3-500 ng/mL with coefficient of determination (R(2) ) in the range of 0.9990-0.9998. The LODs and LOQs for the four parabens were 0.45-0.72 ng/mL and 1.50-2.40 ng/mL, respectively. Intraday and interday precisions (RSDs, n = 5) were in the range of 5.4-6.8% and 7.0-8.7%, respectively. The recoveries of parabens at different spiked levels ranged from 71.9 to 119.2% with RSDs less than 9.5%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High pressure far infrared spectroscopy of ionic solids

NASA Technical Reports Server (NTRS)

Lowndes, R. P.

1974-01-01

A high-pressure far-infrared cell operating at up to truly hydrostatic pressures of 8 kbar is described and used to determine the anharmonic self-energies associated with the transverse optic modes of ionic solids in which q approximately equals zero. The cell allows far-infrared studies in the spectral range below 120 reciprocal cm. The transverse optic modes were investigated to determine their mode Gruneisen constants and the pressure dependence of their inverse lifetimes in RbI, CsI, and TlCl.

Solute-Gas Equilibria in Multi-Organic Aqueous Systems

DTIC Science & Technology

1981-11-30

THIS PAGK(*7@nDae~ Kht.Eero*g) Block 20 (cont.) --z Henry’s constants for selected organic solvents were determined at ionic strengths up to 1.0 M (KC1...equili- brium, batch stripping reactor. Data were fit to a regression equation. Henry’s constants for selected organic solvents were determined at ionic...organic systems. The presence of additional or- ganics (some perhaps not even strippable ) likely to be found along with a particular volatile should be

Determination of triazine herbicides in fresh vegetables by dynamic microwave-assisted extraction coupled with homogeneous ionic liquid microextraction high performance liquid chromatography.

PubMed

Wu, Lijie; Hu, Mingzhu; Li, Zhanchao; Song, Ying; Yu, Cui; Zhang, Yupu; Zhang, Hanqi; Yu, Aimin; Ma, Qiang; Wang, Ziming

2015-02-01

A novel extraction method, dynamic microwave-assisted extraction coupled with homogeneous ionic liquid microextraction, was developed for the determination of triazine herbicides, including desmetryn, terbumeton, propazine, terbuthylazine, dimethametryn, and dipropetryn in fresh vegetable samples by high performance liquid chromatography (HPLC). In the developed method, 120 μL of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]) was added to 10 mL of aqueous solution containing 0.3 g of NaCl to obtained the extraction solvent. Six triazines could be extracted completely within 4 min by the present method. Then, [NH4][PF6] was added into the extract to form a water-insoluble ionic liquid [C4MIM][PF6] via a simple metathesis reaction, and the analytes were enriched into the ionic liquid phase. After centrifugation and dilution with acetonitrile, the resulting solution was analyzed directly by HPLC. The effects of some experimental parameters, including type and volume of ionic liquid, volume of extraction solvent, amount of ion-pairing agent [NH4][PF6], salt concentration, microwave power, and flow rate of extraction solvent on the extraction efficiency were investigated and optimized. Under the optimum experimental conditions, the linearity for determining the analytes was in the range of 2.50-250.00 μg kg(-1), with the correlation coefficients ranging from 0.9989 to 0.9999. When the present method was applied to the analysis of vegetable samples, satisfactory recoveries were obtained in the range of 76.8%-106.9%, and relative standard deviations were lower than 9.8%.

Temperature-controlled ionic liquid-based ultrasound-assisted microextraction for preconcentration of trace quantity of cadmium and nickel by using organic ligand in artificial saliva extract of smokeless tobacco products

NASA Astrophysics Data System (ADS)

Arain, Sadaf Sadia; Kazi, Tasneem Gul; Arain, Asma Jabeen; Afridi, Hassan Imran; Baig, Jameel Ahmed; Brahman, Kapil Dev; Naeemullah; Arain, Salma Aslam

2015-03-01

A new approach was developed for the preconcentration of cadmium (Cd) and nickel (Ni) in artificial saliva extract of dry snuff (brown and black) products using temperature-controlled ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction (TIL-UDLLμE) followed by electrothermal atomic absorption spectrometry (ETAAS). The Cd and Ni were complexed with ammonium pyrrolidinedithiocarbamate (APDC), extracted in ionic liquid drops, 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6]. The multivariate strategy was applied to estimate the optimum values of experimental variables influence the % recovery of analytes by TIL-UDLLμE method. At optimum experimental conditions, the limit of detection (3s) were 0.05 and 0.14 μg L-1 while relative standard deviations (% RSD) were 3.97 and 3.55 for Cd and Ni respectively. After extraction, the enhancement factors (EF) were 87 and 79 for Cd and Ni, respectively. The RSD for six replicates of 10 μg L-1 Cd and Ni were 3.97% and 3.55% respectively. To validate the proposed method, certified reference material (CRM) of Virginia tobacco leaves was analyzed, and the determined values of Cd and Ni were in good agreement with the certified values. The concentration of Cd and Ni in artificial saliva extracts corresponds to 39-52% and 21-32%, respectively, of the total contents of both elements in dry brown and black snuff products.

Charge-based characterization of nanometric cationic bifunctional maghemite/silica core/shell particles by capillary zone electrophoresis.

PubMed

d'Orlyé, Fanny; Varenne, Anne; Georgelin, Thomas; Siaugue, Jean-Michel; Teste, Bruno; Descroix, Stéphanie; Gareil, Pierre

2009-07-01

In view of employing functionalized nanoparticles (NPs) in the context of an immunodiagnostic, aminated maghemite/silica core/shell particles were synthesized so as to be further coated with an antibody or an antigen via the amino groups at their surface. Different functionalization rates were obtained by coating these maghemite/silica core/shell particles with 3-(aminopropyl)triethoxysilane and 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane at different molar ratios. Adequate analytical performances with CE coupled with UV-visible detection were obtained through semi-permanent capillary coating with didodecyldimethyl-ammonium bromide, thus preventing particle adsorption. First, the influence of experimental conditions such as electric field strength, injected particle amount as well as electrolyte ionic strength and pH, was evaluated. A charge-dependent electrophoretic mobility was evidenced and the separation selectivity was tuned according to electrolyte ionic strength and pH. The best resolutions were obtained at pH 8.0, high ionic strength (ca. 100 mM), and low total particle volume fraction (ca. 0.055%), thus eliminating interference effects between different particle populations in mixtures. A protocol derived from Kaiser's original description was performed for quantitation of the primary amino groups attached onto the NP surface. Thereafter a correlation between particle electrophoretic mobility and the density of amino groups at their surface was established. Eventually, CE proved to be an easy, fast, and reliable method for the determination of NP effective surface charge density.

Capillary ion chromatography with on-column focusing for ultra-trace analysis of methanesulfonate and inorganic anions in limited volume Antarctic ice core samples.

PubMed

Rodriguez, Estrella Sanz; Poynter, Sam; Curran, Mark; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Paull, Brett

2015-08-28

Preservation of ionic species within Antarctic ice yields a unique proxy record of the Earth's climate history. Studies have been focused until now on two proxies: the ionic components of sea salt aerosol and methanesulfonic acid. Measurement of the all of the major ionic species in ice core samples is typically carried out by ion chromatography. Former methods, whilst providing suitable detection limits, have been based upon off-column preconcentration techniques, requiring larger sample volumes, with potential for sample contamination and/or carryover. Here, a new capillary ion chromatography based analytical method has been developed for quantitative analysis of limited volume Antarctic ice core samples. The developed analytical protocol applies capillary ion chromatography (with suppressed conductivity detection) and direct on-column sample injection and focusing, thus eliminating the requirement for off-column sample preconcentration. This limits the total sample volume needed to 300μL per analysis, allowing for triplicate sample analysis with <1mL of sample. This new approach provides a reliable and robust analytical method for the simultaneous determination of organic and inorganic anions, including fluoride, methanesulfonate, chloride, sulfate and nitrate anions. Application to composite ice-core samples is demonstrated, with coupling of the capillary ion chromatograph to high resolution mass spectrometry used to confirm the presence and purity of the observed methanesulfonate peak. Copyright © 2015 Elsevier B.V. All rights reserved.

CHLORIDEDETERMINATION IN HIGH IONIC STRENGTH SOLUTION OF AMMONIUM ACETATE USING NEGATIVE ION ELECTRON SPRAY IONIZATION (HPLC/MS)

EPA Science Inventory

A precise ion chromatography method has been developed for the determination of chloride in high ionic strength ammonium acetate solutions (10-5 M-5 M) using sodium carbonate/sodium bicarbonate as eluent. Negative ion electrospray ionization (ESI) mass spectrometry was used for q...

Synthesis and characterization of ionic polymer networks in a room-temperature ionic liquid.

PubMed

Stanzione, Joseph F; Jensen, Robert E; Costanzo, Philip J; Palmese, Giuseppe R

2012-11-01

Ionic liquid gels (ILGs) for potential use in ion transport and separation applications were generated via a free radical copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and N,N'-methylene(bis)acrylamide (MBA) using 1-ethyl-3-methylimidazolium ethylsulfate (IL) as a room temperature ionic liquid solvent medium. The AMPS and MBA monomer solubility window in the IL in the temperature range of 25 to 65 °C was determined. In situ ATR-FTIR showed near complete conversion of monomers to a cross-linked polymer network. ILGs with glass transition temperatures (T(g)s) near -50 °C were generated with T(g) decreasing with increasing IL content. The elastic moduli in compression (200 to 6600 kPa) decreased with increasing IL content and increasing AMPS content while the conductivities (0.35 to 2.14 mS cm⁻¹) increased with increasing IL content and decreasing MBA content. The polymer-IL interaction parameter (χ) (0.48 to 0.55) was determined via a modified version of the Bray and Merrill equation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, S.; Ghosh, A., E-mail: sspag@iacs.res.in

We have studied ionic conductivity and dielectric permittivity of PEO-LiClO{sub 4} solid polymer electrolyte plasticized with propylene carbonate. Differential scanning calorimetry and X-ray diffraction studies confirm minimum volume fraction of crystalline phase for the polymer electrolyte with 40 wt. % propylene carbonate. The ionic conductivity exhibits a maximum for the same composition. The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. Ion-ion interactions in the polymer electrolytes have been studied using Raman spectra and the concentrations of free ions, ion-pairs and ion-aggregates have been determined. The ionic conductivity increases due to the increase of freemore » ions with the increase of propylene carbonate content. But for higher content of propylene carbonate, the ionic conductivity decreases due to the increase of concentrations of ion-pairs and ion-aggregates. To get further insights into the ion dynamics, the experimental data for the complex dielectric permittivity have been studied using Havriliak–Negami function. The variation of relaxation time with temperature obtained from this formalism follows Vogel-Tamman-Fulcher equation similar to the ionic conductivity.« less

The apparent solubility of aluminum (III) in Hanford high-level waste.

PubMed

Reynolds, Jacob G

2012-01-01

The solubility of aluminum in Hanford nuclear waste impacts on the processability of the waste by a number of proposed treatment options. For many years, Hanford staff has anecdotally noted that aluminum appears to be considerably more soluble in Hanford waste than the simpler electrolyte solutions used as analogues. There has been minimal scientific study to confirm these anecdotal observations, however. The present study determines the apparent solubility product for gibbsite in 50 tank samples. The ratio of hydroxide to aluminum in the liquid phase for the samples is calculated and plotted as a function of total sodium molarity. Total sodium molarity is used as a surrogate for ionic strength, because the relative ratios of mono-, di- and trivalent anions are not available for all of the samples. These results were compared to the simple NaOH-NaAl(OH)(4)-H(2)O system, and the NaOH-NaAl(OH)(4)-NaCl-H(2)O system data retrieved from the literature. The results show that gibbsite is apparently more soluble in the samples than in the simple systems whenever the sodium molarity is greater than 2M. This apparent enhanced solubility cannot be explained solely by differences in ionic strength. The change in solubility with ionic strength in simple systems is small compared to the difference between aluminum solubility in Hanford waste and the simple systems. The reason for the apparent enhanced solubility is unknown, but could include kinetic or thermodynamic factors that are not present in the simple electrolyte systems. Any kinetic explanation would have to explain why the samples are always supersaturated whenever the sodium molarity is above 2M. Real waste characterization data should not be used to validate thermodynamic solubility models until it can be confirmed that the apparent enhanced gibbsite solubility is a thermodynamic effect and not a kinetic effect.

The apparent solubility of aluminum (III) in Hanford high-level waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, Jacob G.

2012-12-01

The solubility of aluminum in Hanford nuclear waste impacts on the process ability of the waste by a number of proposed treatment options. For many years, Hanford staff has anecdotally noted that aluminum appears to be considerably more soluble in Hanford waste than the simpler electrolyte solutions used as analogues. There has been minimal scientific study to confirm these anecdotal observations, however. The present study determines the apparent solubility product for gibbsite in 50 tank samples. The ratio of hydroxide to aluminum in the liquid phase for the samples is calculated and plotted as a function of total sodium molarity.more » Total sodium molarity is used as a surrogate for ionic strength, because the relative ratios of mono, di and trivalent anions are not available for all of the samples. These results were compared to the simple NaOH-NaAl(OH{sub 4})H{sub 2}O system, and the NaOH-NaAl(OH{sub 4})NaCl-H{sub 2}O system data retrieved from the literature. The results show that gibbsite is apparently more soluble in the samples than in the simple systems whenever the sodium molarity is greater than two. This apparent enhanced solubility cannot be explained solely by differences in ionic strength. The change in solubility with ionic strength in simple systems is small compared to the difference between aluminum solubility in Hanford waste and the simple systems. The reason for the apparent enhanced solubility is unknown, but could include. kinetic or thermodynamic factors that are not present in the simple electrolyte systems. Any kinetic explanation would have to explain why the samples are always supersaturated whenever the sodium molarity is above two. Real waste characterization data should not be used to validate thermodynamic solubility models until it can be confirmed that the apparent enhanced gibbsite solubility is a thermodynamic effect and not a kinetic effect.« less

Surface interactions between nanoscale iron and organic material: Potential uses in water treatment process units

NASA Astrophysics Data System (ADS)

Storms, Max

Membrane systems are among the primary emergent technologies in water treatment process units due to their ease of use, small physical footprint, and high physical rejection. Membrane fouling, the phenomena by which membranes become clogged or generally soiled, is an inhibitor to optimal efficiency in membrane systems. Novel, composite, and modified surface materials must be investigated to determine their efficacy in improving fouling behavior. Ceramic membranes derived from iron oxide nanoparticles called ferroxanes were coated with a superhydrophillic, zwitterionic polymer called poly (sulfobetaine methacrylate) (polySBMA) to form a composite ceramic-polymeric membrane. Membrane samples with and without polySBMA coating were subjected to fouling with a bovine serum albumin solution and fouling was observed by measuring permeate flux at 10 mL intervals. Loss of polySBMA was measured using total organic carbon analysis, and membrane samples were characterized using x-ray diffraction, scanning electron microscopy, and optical profilometry. The coated membrane samples decreased initial fouling rate by 27% and secondary fouling rate by 24%. Similarly, they displayed a 30% decrease in irreversible fouling during the initial fouling stage, and a 27% decrease in irreversible fouling in the secondary fouling stage; however, retention of polySBMA sufficient for improved performance was not conclusive. The addition of chemical disinfectants into drinking water treatment processes results in the formation of compounds called disinfection by-products (DBPs). The formation of DBPs occurs when common chemical disinfectants (i.e. chlorine) react with organic material. The harmful effects of DBP exposure require that they be monitored and controlled for public safety. This work investigated the ability of nanostructured hematite derived from ferroxane nanoparticles to remove organic precursors to DBPs in the form of humic acid via adsorption processes. The results show that pH and ionic strength have an effect on adsorption capacity and mechanism. At lower ionic strengths, the adsorption isotherms are closely correlated with the Freundlich adsorption isotherm model, while at higher ionic strength, the isotherms are closely related to the Langmuir adsorption isotherm model. Lower pH systems facilitate better adsorption capacities than higher pH systems, and lower ionic strength systems facilitate better adsorption than higher ionic strength systems.

A Fast and Robust Poisson-Boltzmann Solver Based on Adaptive Cartesian Grids

PubMed Central

Boschitsch, Alexander H.; Fenley, Marcia O.

2011-01-01

An adaptive Cartesian grid (ACG) concept is presented for the fast and robust numerical solution of the 3D Poisson-Boltzmann Equation (PBE) governing the electrostatic interactions of large-scale biomolecules and highly charged multi-biomolecular assemblies such as ribosomes and viruses. The ACG offers numerous advantages over competing grid topologies such as regular 3D lattices and unstructured grids. For very large biological molecules and multi-biomolecule assemblies, the total number of grid-points is several orders of magnitude less than that required in a conventional lattice grid used in the current PBE solvers thus allowing the end user to obtain accurate and stable nonlinear PBE solutions on a desktop computer. Compared to tetrahedral-based unstructured grids, ACG offers a simpler hierarchical grid structure, which is naturally suited to multigrid, relieves indirect addressing requirements and uses fewer neighboring nodes in the finite difference stencils. Construction of the ACG and determination of the dielectric/ionic maps are straightforward, fast and require minimal user intervention. Charge singularities are eliminated by reformulating the problem to produce the reaction field potential in the molecular interior and the total electrostatic potential in the exterior ionic solvent region. This approach minimizes grid-dependency and alleviates the need for fine grid spacing near atomic charge sites. The technical portion of this paper contains three parts. First, the ACG and its construction for general biomolecular geometries are described. Next, a discrete approximation to the PBE upon this mesh is derived. Finally, the overall solution procedure and multigrid implementation are summarized. Results obtained with the ACG-based PBE solver are presented for: (i) a low dielectric spherical cavity, containing interior point charges, embedded in a high dielectric ionic solvent – analytical solutions are available for this case, thus allowing rigorous assessment of the solution accuracy; (ii) a pair of low dielectric charged spheres embedded in a ionic solvent to compute electrostatic interaction free energies as a function of the distance between sphere centers; (iii) surface potentials of proteins, nucleic acids and their larger-scale assemblies such as ribosomes; and (iv) electrostatic solvation free energies and their salt sensitivities – obtained with both linear and nonlinear Poisson-Boltzmann equation – for a large set of proteins. These latter results along with timings can serve as benchmarks for comparing the performance of different PBE solvers. PMID:21984876

Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling.

PubMed

Reid, Michael S; Kedzior, Stephanie A; Villalobos, Marco; Cranston, Emily D

2017-08-01

This work explores cellulose nanocrystal (CNC) thin films (<50 nm) and particle-particle interactions by investigating film swelling in aqueous solutions with varying ionic strength (1-100 mM). CNC film hydration was monitored in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

Ionic structure in liquids confined by dielectric interfaces

NASA Astrophysics Data System (ADS)

Jing, Yufei; Jadhao, Vikram; Zwanikken, Jos W.; Olvera de la Cruz, Monica

2015-11-01

The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as in the design of double-layer supercapacitors for energy storage and in the extraction of metal ions from wastewater. In this article, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric interfaces using molecular dynamics simulations and liquid state theory. We explore the effects of high electrolyte concentrations, multivalent ions, dielectric contrasts, and external electric field on the ionic distributions. We observe the presence of non-monotonic ionic density profiles leading to a layered structure in the fluid which is attributed to the competition between electrostatic and steric (entropic) interactions. We find that thermal forces that arise from symmetry breaking at the interfaces can have a profound effect on the ionic structure and can oftentimes overwhelm the influence of the dielectric discontinuity. The combined effect of ionic correlations and inhomogeneous dielectric permittivity significantly changes the character of the effective interaction between the two interfaces.

β-cyclodextrin-ionic liquid polymer based dynamically coating for simultaneous determination of tetracyclines by capillary electrophoresis.

PubMed

Zhou, Chunyan; Deng, Jingjing; Shi, Guoyue; Zhou, Tianshu

2017-04-01

Tetracyclines are a group of broad spectrum antibiotics widely used in animal husbandry to prevent and treat diseases. However, the improper use of tetracyclines may result in the presence of their residues in animal tissues or waste. Recently, great attention has been drawn towards the green solvents ionic liquids. Ionic liquids have been employed as a coating material to modify the electroosmotic flow in capillary electrophoresis. In this study, a functionalized ionic liquid, mono-6-deoxy-6-(3-methylimidazolium)-β-cyclodextrin tosylate, was synthesized and used for the simultaneous separation and quantification of tetracyclines by capillary electrophoresis. Good separation efficiency could be achieved due to the multiple functions of β-cyclodextrin derived ionic liquid, including the electrostatic interaction, the hydrogen bonding, and the cavity structure in β-cyclodextrin ionic liquid which can entrap the tetracyclines to form inclusion complex. After optimization, baseline separation achieved in 25 min with the running buffer consisted of 10 mmol/L, pH 7.2 phosphate buffer and 20 mmol/L β-cyclodextrin ionic liquid. The satisfied result demonstrated that the β-cyclodextrin ionic liquid is an ideal background electrolyte modifier in the separation of tetracyclines with high stability and good reproducibility. And it is an effective strategy to design and synthesize specific ILs as additive applied in separation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of ionic membrane properties on the performance of ionic polymer-metal composite (IPMC) actuator

NASA Astrophysics Data System (ADS)

Jho, Jae Y.; Han, Man J.; Park, Jong H.; Lee, Jang Y.; Wang, Hyuck S.

2005-05-01

On purpose to overcome the limit of conventional ionic polymer-metal composites (IPMC) using the commercial ionic membranes, novel IPMCs with radiation-grafted ion-exchange membranes were prepared. Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-co-HFP) and poly(ethylene-co-tetrafluoroethylene) (ETFE) were radiation-grafted with styrene, and then sulfonated. The properties of the membranes were modulated by controlling the amount of polystyrene sulfonic acid (PSSA) groups in the membranes. The amount of PSSA groups were tuned by controlling the total absorbed dose of γ-ray. The membranes were characterized by measuring the water-uptake, the ion-exchange capacity, and the ion conductivity. The performance of the IPMCs using these membranes were analyzed with laser displacement meter. They exhibited much larger bending displacement in comparison with Nafion-based IPMC. With increasing the amount of PSSA groups, the maximum displacement and the bending speed were remarkably increased. The results made sure that the property of ion-exchange membrane was the key element affecting the actuation performance of IPMC.

Direct Observation of Ion Distributions near Electrodes in Ionic Polymer Actuators Containing Ionic Liquids

PubMed Central

Liu, Yang; Lu, Caiyan; Twigg, Stephen; Ghaffari, Mehdi; Lin, Junhong; Winograd, Nicholas; Zhang, Q. M.

2013-01-01

The recent boom of energy storage and conversion devices, exploiting ionic liquids (ILs) to enhance the performance, requires an in-depth understanding of this new class of electrolytes in device operation conditions. One central question critical to device performance is how the mobile ions accumulate near charged electrodes. Here, we present the excess ion depth profiles of ILs in ionomer membrane actuators (Aquivion/1-butyl-2,3-dimethylimidazolium chloride (BMMI-Cl), 27 μm thick), characterized directly by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) at liquid nitrogen temperature. Experimental results reveal that for the IL studied, cations and anions are accumulated at both electrodes. The large difference in the total volume occupied by the excess ions between the two electrodes cause the observed large bending actuation of the actuator. Hence we demonstrate that ToF-SIMS experiment provides great insights on the physics nature of ionic devices. PMID:23512124

Fuel Cell Using the Protic Ionic Liquid and Rotator Phase Solid Electrolyte Principles

DTIC Science & Technology

2008-07-15

appropriate host for the ionic liquid. (a) Papers published in peer-reviewed journals (N/A for none) [1] Thompson J, Dunn P, Holmes L, Belieres J-P...Names of Post Doctorates PERCENT_SUPPORTEDNAME Jean-Philippe Belieres 0.50 Xiaoguang Sun 0.50 1.00FTE Equivalent: 2Total Number: Names of Faculty...chemical shift for transferred protons (co-worker Jean-Philippe Belieres ) This is a fundamental study of the chemical state of the proton on the cation

Ionic liquid-based single-drop microextraction/gas chromatographic/mass spectrometric determination of benzene, toluene, ethylbenzene and xylene isomers in waters.

PubMed

Aguilera-Herrador, Eva; Lucena, Rafael; Cárdenas, Soledad; Valcárcel, Miguel

2008-08-01

The direct coupling between ionic liquid-based single-drop microextraction and gas chromatography/mass spectrometry is proposed for the rapid and simple determination of benzene, toluene, ethylbenzene and xylenes isomers (BTEX) in water samples. The extraction procedure exploits not only the high affinity of the selected ionic liquid (1-methyl-3-octyl-imidazolium hexaflourophosphate) to these aromatic compounds but also its special properties like viscosity, low vapour pressure and immiscibility with water. All the variables involved in the extraction process have been studied in depth. The developed method allows the determination of these single-ring compounds in water under the reference concentration level fixed by the international legislation. In this case, limits of detection were in the range 20 ng L(-1) (obtained for benzene) and 91 ng L(-1) (for o-xylene). The repeatability of the proposed method, expressed as RSD (n=5), varied between 3.0% (o-xylene) and 5.2% (toluene).

Electronic structures of WAlO(y) and WAlO(y)(-) (y = 2-4) determined by anion photoelectron spectroscopy and density functional theory calculations.

PubMed

Mann, Jennifer E; Waller, Sarah E; Jarrold, Caroline Chick

2012-07-28

The anion photoelectron spectra of WAlO(y)(-) (y = 2-4) are presented and assigned based on results of density functional theory calculations. The WAlO(2)(-) and WAlO(3)(-) spectra are both broad, with partially resolved vibrational structure. In contrast, the WAlO(4)(-) spectrum features well-resolved vibrational structure with contributions from three modes. There is reasonable agreement between experiment and theory for all oxides, and calculations are in particular validated by the near perfect agreement between the WAlO(4)(-) photoelectron spectrum and a Franck-Condon simulation based on computationally determined spectroscopic parameters. The structures determined from this study suggest strong preferential W-O bond formation, and ionic bonding between Al(+) and WO(y)(-2) for all anions. Neutral species are similarly ionic, with WAlO(2) and WAlO(3) having electronic structure that suggests Al(+) ionically bound to WO(y)(-) and WAlO(4) being described as Al(+2) ionically bound to WO(4)(-2). The doubly-occupied 3sp hybrid orbital localized on the Al center is energetically situated between the bonding O-local molecular orbitals and the anti- or non-bonding W-local molecular orbitals. The structures determined in this study are very similar to structures recently determined for the analogous MoAlO(y)(-)/MoAlO(y) cluster series, with subtle differences found in the electronic structures [S. E. Waller, J. E. Mann, E. Hossain, M. Troyer, and C. C. Jarrold, J. Chem. Phys. 137, 024302 (2012)].

Effect of ionic strength on the thermodynamic characteristics of complexation between Fe(III) ion and nicotinamide in water-ethanol and water-dimethyl sulfoxide mixtures

NASA Astrophysics Data System (ADS)

Gamov, G. A.; Grazhdan, K. V.; Gavrilova, M. A.; Dushina, S. V.; Sharnin, V. A.; Baranski, A.

2013-06-01

Solutions of iron(III) perchlorate in water, water-ethanol, and water-dimethyl sulfoxide solvents (x_{H_2 O} = 0.7 and 0.25 mole fractions) at ionic strength values I = 0.1, 0.25, and 0.5 are studied by IR spectroscopy. Analysis of the absorption bands of perchlorate ion shows that it does not participate in association processes. It is demonstrated that in the range of ionic strength values between 0 and 0.5 (NaClO4), it affects neither the results from potentiometric titration to determine the stability constants of the iron(III)-nicotinamide complex nor the thermal effects of complexation determined via direct calorimetry in a binary solvent containing 0.3 mole fractions (m.f.) of a non-aqueous component.

Integral equation model for warm and hot dense mixtures.

PubMed

Starrett, C E; Saumon, D; Daligault, J; Hamel, S

2014-09-01

In a previous work [C. E. Starrett and D. Saumon, Phys. Rev. E 87, 013104 (2013)] a model for the calculation of electronic and ionic structures of warm and hot dense matter was described and validated. In that model the electronic structure of one atom in a plasma is determined using a density-functional-theory-based average-atom (AA) model and the ionic structure is determined by coupling the AA model to integral equations governing the fluid structure. That model was for plasmas with one nuclear species only. Here we extend it to treat plasmas with many nuclear species, i.e., mixtures, and apply it to a carbon-hydrogen mixture relevant to inertial confinement fusion experiments. Comparison of the predicted electronic and ionic structures with orbital-free and Kohn-Sham molecular dynamics simulations reveals excellent agreement wherever chemical bonding is not significant.

Controlling adsorption and passivation properties of bovine serum albumin on silica surfaces by ionic strength modulation and cross-linking.

PubMed

Park, Jae Hyeon; Sut, Tun Naw; Jackman, Joshua A; Ferhan, Abdul Rahim; Yoon, Bo Kyeong; Cho, Nam-Joon

2017-03-29

Understanding the physicochemical factors that influence protein adsorption onto solid supports holds wide relevance for fundamental insights into protein structure and function as well as for applications such as surface passivation. Ionic strength is a key parameter that influences protein adsorption, although how its modulation might be utilized to prepare well-coated protein adlayers remains to be explored. Herein, we investigated how ionic strength can be utilized to control the adsorption and passivation properties of bovine serum albumin (BSA) on silica surfaces. As protein stability in solution can influence adsorption kinetics, the size distribution and secondary structure of proteins in solution were first characterized by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and circular dichroism (CD) spectroscopy. A non-monotonic correlation between ionic strength and protein aggregation was observed and attributed to colloidal agglomeration, while the primarily α-helical character of the protein in solution was maintained in all cases. Quartz crystal microbalance-dissipation (QCM-D) experiments were then conducted in order to track protein adsorption onto silica surfaces as a function of ionic strength, and the measurement responses indicated that total protein uptake at saturation coverage is lower with increasing ionic strength. In turn, the QCM-D data and the corresponding Voigt-Voinova model analysis support that the surface area per bound protein molecule is greater with increasing ionic strength. While higher protein uptake under lower ionic strengths by itself did not result in greater surface passivation under subsequent physiologically relevant conditions, the treatment of adsorbed protein layers with a gluteraldehyde cross-linking agent stabilized the bound protein in this case and significantly improved surface passivation. Collectively, our findings demonstrate that ionic strength modulation influences BSA adsorption uptake on account of protein spreading and can be utilized in conjunction with covalent cross-linking strategies to prepare well-coated protein adlayers for improved surface passivation.

Molecular origin of high free energy barriers for alkali metal ion transfer through ionic liquid-graphene electrode interfaces.

PubMed

Ivaništšev, Vladislav; Méndez-Morales, Trinidad; Lynden-Bell, Ruth M; Cabeza, Oscar; Gallego, Luis J; Varela, Luis M; Fedorov, Maxim V

2016-01-14

In this work we study mechanisms of solvent-mediated ion interactions with charged surfaces in ionic liquids by molecular dynamics simulations, in an attempt to reveal the main trends that determine ion-electrode interactions in ionic liquids. We compare the interfacial behaviour of Li(+) and K(+) at a charged graphene sheet in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate, and its mixtures with lithium and potassium tetrafluoroborate salts. Our results show that there are dense interfacial solvation structures in these electrolytes that lead to the formation of high free energy barriers for these alkali metal cations between the bulk and direct contact with the negatively charged surface. We show that the stronger solvation of Li(+) in the ionic liquid leads to the formation of significantly higher interfacial free energy barriers for Li(+) than for K(+). The high free energy barriers observed in our simulations can explain the generally high interfacial resistance in electrochemical storage devices that use ionic liquid-based electrolytes. Overcoming these barriers is the rate-limiting step in the interfacial transport of alkali metal ions and, hence, appears to be a major drawback for a generalised application of ionic liquids in electrochemistry. Some plausible strategies for future theoretical and experimental work for tuning them are suggested.

The Effect of Ionic Liquid Pretreatment on the Bioconversion of Tomato Processing Waste to Fermentable Sugars and Biogas.

PubMed

Allison, Brittany J; Cádiz, Juan Canales; Karuna, Nardrapee; Jeoh, Tina; Simmons, Christopher W

2016-08-01

Tomato pomace is an abundant lignocellulosic waste stream from industrial tomato processing and therefore a potential feedstock for production of renewable biofuels. However, little research has been conducted to determine if pretreatment can enhance release of fermentable sugars from tomato pomace. Ionic liquids (ILs) are an emerging pretreatment technology for lignocellulosic biomass to increase enzymatic digestibility and biofuel yield while utilizing recyclable chemicals with low toxicity. In this study, pretreatment of tomato pomace with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) was investigated. Changes in pomace enzymatic digestibility were affected by pretreatment time and temperature. Certain pretreatment conditions significantly improved reducing sugar yield and hydrolysis time compared to untreated pomace. Compositional analyses suggested that pretreatment primarily removed water-soluble compounds and enriched for lignocellulose in pomace, with only subtle changes to the composition of the lignocellulose. While tomato pomace was effectively pretreated with [C2mim][OAc] to improve enzymatic digestibility, as of yet, unknown factors in the pomace caused ionic liquid pretreatment to negatively affect anaerobic digestion of pretreated material. This result, which is unique compared to similar studies on IL pretreatment of grasses and woody biomass, highlights the need for additional research to determine how the unique chemical composition of tomato pomace and other lignocellulosic fruit residues may interact with ionic liquids to generate inhibitors for downstream fermentation to biofuels.

A green ionic liquid-based vortex-forced MSPD method for the simultaneous determination of 5-HMF and iridoid glycosides from Fructus Corni by ultra-high performance liquid chromatography.

PubMed

Du, Kunze; Li, Jin; Bai, Yun; An, Mingrui; Gao, Xiu-Mei; Chang, Yan-Xu

2018-04-01

A simple and green ionic liquid-based vortex-forced matrix solid phase dispersion (IL-VFMSPD) method was presented to simultaneously extract 5-hydroxymethyl furfurol (5-HMF) and iridoid glycosides in Fructus Corni by ultra-high performance liquid chromatography. Ionic liquid was used as a green elution reagent in vortex-forced MSPD process. A few parameters such as the type of ionic liquid, the type of sorbent, ratio of sample to sorbent, the concentration and volume of ionic liquid, grinding time and vortex time, were investigated in detail and an orthogonal design experiment was introduced to confirm the best conditions in this procedure. With the final optimized method, the recoveries of the target compounds in Fructus Corni were in the range of 95.2-103% (RSD<5.0%) and the method displayed a good linearity within the range of 0.8-200 μg mL -1 for morroniside, sweroside, loganin, cornuside and 1.2-300 μg mL -1 for 5-HMF. The limits of detection ranged from 0.02 to 0.08 μg mL -1 for all compounds. The results showed that the newly established method was efficiently applied to extract and determine iridoid glycosides and 5-HMF for quality control of Fructus Corni. Copyright © 2017 Elsevier Ltd. All rights reserved.

Estimation of the ionic charge of non-metallic species into an electrical discharge through a web application

NASA Astrophysics Data System (ADS)

Pérez Gutiérrez, B. R.; Vera-Rivera, F. H.; Niño, E. D. V.

2016-08-01

Estimate the ionic charge generated in electrical discharges will allow us to know more accurately the concentration of ions implanted on the surfaces of nonmetallic solids. For this reason, in this research a web application was developed to allow us to calculate the ionic charge generated in an electrical discharge from the experimental parameters established in an ion implantation process performed in the JUPITER (Joint Universal Plasma and Ion Technologies Experimental Reactor) reactor. The estimated value of the ionic charge will be determined from data acquired on an oscilloscope, during startup and shutdown of electrical discharge, which will then be analyzed and processed. The study will provide best developments with regard to the application of ion implantation in various industrial sectors.

A computer program for geochemical analysis of acid-rain and other low-ionic-strength, acidic waters

USGS Publications Warehouse

Johnsson, P.A.; Lord, D.G.

1987-01-01

ARCHEM, a computer program written in FORTRAN 77, is designed primarily for use in the routine geochemical interpretation of low-ionic-strength, acidic waters. On the basis of chemical analyses of the water, and either laboratory or field determinations of pH, temperature, and dissolved oxygen, the program calculates the equilibrium distribution of major inorganic aqueous species and of inorganic aluminum complexes. The concentration of the organic anion is estimated from the dissolved organic concentration. Ionic ferrous iron is calculated from the dissolved oxygen concentration. Ionic balances and comparisons of computed with measured specific conductances are performed as checks on the analytical accuracy of chemical analyses. ARCHEM may be tailored easily to fit different sampling protocols, and may be run on multiple sample analyses. (Author 's abstract)

Mechanisms of the Diffusion of Nonpolar Substances in a Hydrophilic Ionic Liquid

NASA Astrophysics Data System (ADS)

Atamas', N. A.

2018-01-01

The structural-dynamic features of ionic liquid-nonpolar substance systems are studied by means of molecular dynamics using Frenkel's fundamental theory of a liquid and the phonon theory of the thermodynamics of a liquid, in combination with the DL_POLY_4.05 software package. Argon, methane, and benzene molecules serve as the dissolved substances. Model concepts are proposed and analyzed to describe the diffusion of molecules of a dissolved substance in an ionic liquid. It is shown that an increase in the mass of the molecules of a dissolved nonpolar substance correlates with their mobility in a hydrophilic ionic liquid (IL). This determines the diffusion of the components of dmim+/Cl- IL solutions and is responsible for the anomalous behavior of the solubility of nonpolar substances in them.

The Analysis of Prospective Chemistry Teachers' Cognitive Structure: The Subject of Covalent and Ionic Bonding

ERIC Educational Resources Information Center

Temel, Senar; Özcan, Özgür

2016-01-01

This study aims to analyse prospective chemistry teachers' cognitive structure related to the subject of covalent and ionic bonding. Semi-structured interviews were conducted with the participants in order to determine their cognitive structure, and the interviews were audio recorded to prevent the loss of data. The data were transcribed and…

Combination of in situ metathesis reaction with a novel "magnetic effervescent tablet-assisted ionic liquid dispersive microextraction" for the determination of endogenous steroids in human fluids.

PubMed

Wu, Jia; Xu, Zilin; Pan, Yixuan; Shi, Yi; Bao, Xiujie; Li, Jun; Tong, Yu; Tang, Han; Ma, Shuyan; Wang, Xuedong; Lyu, Jianxin

2018-05-01

Herein, a novel magnetic effervescence tablet-assisted microextraction coupled to in situ metathesis reaction of ionic liquid (IS-META-ILDM) is presented for the determination of four endogenous steroids in human urine, pregnant women's blood, and fetal umbilical cord blood. The magnetic effervescent tablets, which were composed of Fe 3 O 4 nanoparticles, sodium carbonate (alkaline source), and tartaric acid (acidic source), were used to disperse the extractant and for convenient magnetic separation. After the effervescent reaction, in situ reaction between NH 4 PF 6 and [C 6 MIM]BF 4 was adopted to change hydrophilic ionic liquid to hydrophobic liquid, which could be separated from the aqueous phase. The newly developed method has three obvious advantages: (1) combination of effervescent dispersion and magnetic nanoparticles' retrieval is cost-effective and the dispersion and collection of the extractant can be completed almost simultaneously; (2) as compared to temperature-controlled ionic liquid dispersive microextraction and cold-induced solidified microextraction, this method avoids a heating and cooling process which significantly reduces the extraction time and energy cost; and (3) the combination of adsorption by magnetic nanoparticles with extraction by in situ metathesis reaction easily produces high recoveries for target analytes. The optimized composition of effervescent tablet and experimental parameters are as follows: 0.64 g mixture of sodium carbonate and tartaric acid, 7 mg of Fe 3 O 4 (20 nm) as magnetic sorbents, 40 μL of [C 6 MIM]BF 4 as the extraction solvent, 0.15 g NH 4 PF 6 , and 300 μL of elution solvent. Under the optimized conditions, the newly developed method provided high extraction recoveries (90.0-118.5%) and low LODs (0.14-0.17 μg L -1 ) in urine and blood samples. In total, this IS-META-ILDM method provided high extraction efficiency, fast and convenient separation, and underutilization of any organic solvent, and thus it has great potential for the determination of trace endogenous steroids in complex human fluids. Graphical abstract The newly developed method has three obvious advantages: combination of effervescent dispersion and magnetic nanoparticles' retrieval is cost-effective and the dispersion and collection of the extractant can be completed almost simultaneously. It avoids a heating and cooling process which significantly reduces the extraction time and energy cost and easily produces high recoveries for target analytes.

Polarographic determination of lead hydroxide formation constants at low ionic strength

USGS Publications Warehouse

Lind, Carol J.

1978-01-01

Values of formation constants for lead hydroxide at 25 ??C were calculated from normal pulse polarographic measurements of 10-6 M lead in 0.01 M sodium perchlorate. The low concentrations simulate those found in many freshwaters, permitting direct application of the values when considering distributions of lead species. The precise evaluation of species distribution in waters at other ionic strengths requires activity coefficient corrections. As opposed to much of the previously published work done at high ionic strength, the values reported here were obtained at low ionic strength, permitting use of smaller and better defined activity coefficient corrections. These values were further confirmed by differential-pulse polarography and differential-pulse anodic stripping voltammetry data. The logs of the values for ??1??? ??2???, and ??3??? were calculated to be 6.59, 10.80, and 13.63, respectively. When corrected to zero ionic strength these values were calculated to be 6.77, 11.07, and 13.89, respectively.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

NASA Astrophysics Data System (ADS)

Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

2016-05-01

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sengwa, R. J., E-mail: rjsengwa@rediffmail.com; Dhatarwal, Priyanka, E-mail: dhatarwalpriyanka@gmail.com; Choudhary, Shobhna, E-mail: shobhnachoudhary@rediffmail.com

2016-05-06

Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF{sub 4}) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governedmore » by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10{sup −6} S cm{sup −1} which suggests the suitability of the SPE film for rechargeable lithium batteries.« less

Engineering polyelectrolyte multilayer structure at the nanometer length scale by tuning polymer solution conformation.

NASA Astrophysics Data System (ADS)

Boddohi, Soheil; Killingsworth, Christopher; Kipper, Matt

2008-03-01

Chitosan (a weak polycation) and heparin (a strong polyanion) are used to make polyelectrolyte multilayers (PEM). PEM thickness and composition are determined as a function of solution pH (4.6 to 5.8) and ionic strength (0.1 to 0.5 M). Over this range, increasing pH increases the PEM thickness; however, the sensitivity to changes in pH is a strong function of ionic strength. The PEM thickness data are correlated to the polymer conformation in solution. Polyelectrolyte conformation in solution is characterized by gel permeation chromatography (GPC). The highest sensitivity of PEM structure to pH is obtained at intermediate ionic strength. Different interactions govern the conformation and adsorption phenomena at low and high ionic strength, leading to reduced sensitivity to solution pH at extreme ionic strengths. The correspondence between PEM thickness and polymer solution conformation offers opportunities to tune polymer thin film structure at the nanometer length scale by controlling simple, reproducible processing conditions.

Molecular dynamics study of thermodynamic stability and dynamics of [Li(glyme)]+ complex in lithium-glyme solvate ionic liquids

NASA Astrophysics Data System (ADS)

Shinoda, Wataru; Hatanaka, Yuta; Hirakawa, Masashi; Okazaki, Susumu; Tsuzuki, Seiji; Ueno, Kazuhide; Watanabe, Masayoshi

2018-05-01

Equimolar mixtures of glymes and organic lithium salts are known to produce solvate ionic liquids, in which the stability of the [Li(glyme)]+ complex plays an important role in determining the ionic dynamics. Since these mixtures have attractive physicochemical properties for application as electrolytes, it is important to understand the dependence of the stability of the [Li(glyme)]+ complex on the ion dynamics. A series of microsecond molecular dynamics simulations has been conducted to investigate the dynamic properties of these solvate ionic liquids. Successful solvate ionic liquids with high stability of the [Li(glyme)]+ complex have been shown to have enhanced ion dynamics. Li-glyme pair exchange rarely occurs: its characteristic time is longer than that of ion diffusion by one or two orders of magnitude. Li-glyme pair exchange most likely occurs through cluster formation involving multiple [Li(glyme)]+ pairs. In this process, multiple exchanges likely take place in a concerted manner without the production of energetically unfavorable free glyme or free Li+ ions.

Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

PubMed

de Souza, Ranyere Lucena; de Faria, Emanuelle Lima Pache; Figueiredo, Renan Tavares; Freitas, Lisiane dos Santos; Iglesias, Miguel; Mattedi, Silvana; Zanin, Gisella Maria; dos Santos, Onélia Aparecida Andreo; Coutinho, João A P; Lima, Álvaro Silva; Soares, Cleide Mara Faria

2013-03-05

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss. Copyright © 2013 Elsevier Inc. All rights reserved.

Preparation of stir cake sorptive extraction based on polymeric ionic liquid for the enrichment of benzimidazole anthelmintics in water, honey and milk samples.

PubMed

Wang, Yulei; Zhang, Jie; Huang, Xiaojia; Yuan, Dongxing

2014-08-20

In this work, a new stir cake sorptive extraction (SCSE) using polymeric ionic liquid monolith as sorbent was prepared. The sorbent was obtained by in situ copolymerization of an ionic liquid, 1-allyl-3-methylimidazolium bis[(trifluoro methyl)sulfonyl]imide (AMII) and divinylbenzene (DB) in the presence of N,N-dimethylformamide. The influence of the content of ionic liquid and the porogen in the polymerization mixture on extraction performance was studied thoroughly. The physicochemical properties of the polymeric ionic liquid were characterized by infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry. The usefulness of SCSE-AMIIDB was demonstrated by the enrichment of trace benzimidazole anthelmintics. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of trace benzimidazoles residues in water, milk and honey samples was established by coupling SCSE-AMIIDB with high performance liquid chromatography/diode array detection (SCSE-AMIIDB-HPLC/DAD). Results indicated that the limits of detection (S/N=3) for target compounds were 0.020-0.072 μg L(-1), 0.035-0.10 μg L(-1) and 0.026-0.076 μg L(-1) in water, milk and honey samples, respectively. In addition, an acceptable reproducibility was achieved by evaluating the repeatability and intermediate precision with relative standard deviations (RSD) of less than 9% and 11%, respectively. Finally, the established AMII-SCSE-HPLC/DAD method was successfully applied for the determination of benzimidazoles residues in milk, honey and environmental water samples. Recoveries obtained for the determination of benzimidazole anthelmintics in spiking samples ranged from 70.2% to 117.6%, with RSD below 12% in all cases. Copyright © 2014 Elsevier B.V. All rights reserved.

Ionic liquid phase microextraction combined with fluorescence spectrometry for preconcentration and quantitation of carvedilol in pharmaceutical preparations and biological media.

PubMed

Zeeb, Mohsen; Mirza, Behrooz

2015-04-30

Carvedilol belongs to a group of medicines termed non-selective beta-adrenergic blocking agents. In the presented approach, a practical and environmentally friendly microextraction method based on the application of ionic liquids (ILs) was followed by fluorescence spectrometry for trace determination of carvedilol in pharmaceutical and biological media. A rapid and simple ionic liquid phase microextraction was utilized for preconcentration and extraction of carvedilol. A hydrophobic ionic liquid (IL) was applied as a microextraction solvent. In order to disperse the IL through the aqueous media and extract the analyte of interest, IL was injected into the sample solution and a proper temperature was applied and then for aggregating the IL-phase, the sample was cooled in an ice water-bath. The aqueous media was centrifuged and IL-phase collected at the bottom of the test tube was introduced to the micro-cell of spectrofluorimeter, in order to determine the concentration of the enriched analyte. Main parameters affecting the accuracy and precision of the proposed approach were investigated and optimized values were obtained. A linear response range of 10-250 μg I(-1) and a limit of detection (LOD) of 1.7 μg I(-1) were obtained. Finally, the presented method was utilized for trace determination of carvedilol in commercial pharmaceutical preparations and biological media.

Capturing the effect of [PF3(C2F5)3]-vs. [PF6]-, flexible anion vs. rigid, and scaled charge vs. unit on the transport properties of [bmim]+-based ionic liquids: a comparative MD study.

PubMed

Kowsari, Mohammad H; Ebrahimi, Soraya

2018-05-16

Comprehensive molecular dynamics simulations are performed to study the average single-particle dynamics and the transport properties of 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP], ionic liquids (ILs) at 400 K. We applied one of the most widely used nonpolarizable all-atom force fields for ILs, both with the original unit (±1) charges on each ion and with the partial charges uniformly scaled to 80-85%, taking into account the average polarizability and tracing the experimentally compatible transport properties. In all simulations, [bmim]+ was considered to be flexible, while the effect of a flexible vs. rigid structure of the anions and the effect of two applied charge sets on the calculated properties were separately investigated in detail. The simulation results showed that replacing [PF6]- with [FAP]-, considering anion flexibility, and applying the charge-scaled model significantly enhanced the ionic self-diffusion, ionic conductivity, inverse viscosity, and hyper anion preference (HAP). Both of the calculated self-diffusion coefficients from the long-time linear slope of the mean-square displacement (MSD) and from the integration of the velocity autocorrelation function (VACF) for the centers of mass of the ions were used for evaluation of the ionic transference number, HAP, ideal Nernst-Einstein ionic conductivity (σNE), and the Stokes-Einstein viscosity. In addition, for quantification of the degree of complicated ionic association (known as the Nernst-Einstein deviation parameter, Δ) and ionicity phenomena in the two studied ILs, the ionic conductivity was determined more rigorously by the Green-Kubo integral of the electric-current autocorrelation function (ECACF), and then the σGK/σNE ratio was evaluated. It was found that the correlated motion of the (cationanion) neighbors in [bmim][FAP] is smaller than in [bmim][PF6]. The relaxation times of the normalized reorientational autocorrelation functions were computed to gain a deep, molecular-level insight into the rotational motion of the ions. The geometric shape of the ion is a key factor in determining its reorientational dynamics. [bmim]+ shows faster translational and slower rotational dynamics in contrast to [PF6]-.

Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges.

PubMed

Han, Biao; Chery, Daphney R; Yin, Jie; Lu, X Lucas; Lee, Daeyeon; Han, Lin

2016-01-28

This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks - ionic cross-links and fixed charges - in determining their nanomechanical properties. The layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) network is used as the model material. The densities of ionic cross-links and fixed charges are modulated through solution pH and ionic strength (IS), and the swelling ratio, elastic and viscoelastic properties are quantified via an array of atomic force microscopy (AFM)-based nanomechanical tools. The roles of ionic cross-links are underscored by the distinctive elastic and viscoelastic nanomechanical characters observed here. First, as ionic cross-links are highly sensitive to solution conditions, the instantaneous modulus, E0, exhibits orders-of-magnitude changes upon pH- and IS-governed swelling, distinctive from the rubber elasticity prediction based on permanent covalent cross-links. Second, ionic cross-links can break and self-re-form, and this mechanism dominates force relaxation of PAH/PAA under a constant indentation depth. In most states, the degree of relaxation is >90%, independent of ionic cross-link density. The importance of fixed charges is highlighted by the unexpectedly more elastic nature of the network despite low ionic cross-link density at pH 2.0, IS 0.01 M. Here, the complex is a net charged, loosely cross-linked, where the degree of relaxation is attenuated to ≈50% due to increased elastic contribution arising from fixed charge-induced Donnan osmotic pressure. In addition, this study develops a new method for quantifying the thickness of highly swollen polymer hydrogel films. It also underscores important technical considerations when performing nanomechanical tests on highly rate-dependent polymer hydrogel networks. These results provide new insights into the nanomechanical characters of ionic polyelectrolyte complexes, and lay the ground for further investigation of their unique time-dependent properties.

Curvature dependence of the effect of ionic functionalization on the attraction among nanoparticles in dispersion

NASA Astrophysics Data System (ADS)

Jabes, B. Shadrack; Bratko, Dusan; Luzar, Alenka

2018-06-01

Solubilization of nanoparticles facilitates nanomaterial processing and enables new applications. An effective method to improve dispersibility in water is provided by ionic functionalization. We explore how the necessary extent of functionalization depends on the particle geometry. Using molecular dynamics/umbrella sampling simulations, we determine the effect of the solute curvature on solvent-averaged interactions among ionizing graphitic nanoparticles in aqueous dispersion. We tune the hydrophilicity of molecular-brush coated fullerenes, carbon nanotubes, and graphane platelets by gradually replacing a fraction of the methyl end groups of the alkyl coating by the ionizing -COOK or -NH3Cl groups. To assess the change in nanoparticles' dispersibility in water, we determine the potential-of-mean-force profiles at varied degrees of ionization. When the coating comprises only propyl groups, the attraction between the hydrophobic particles intensifies from spherical to cylindrical to planar geometry. This is explained by the increasing fraction of surface groups that can be brought into contact and the reduced access to water molecules, both following the above sequence. When ionic groups are added, however, the dispersibility increases in the opposite order, with the biggest effect in the planar geometry and the smallest in the spherical geometry. These results highlight the important role of geometry in nanoparticle solubilization by ionic functionalities, with about twice higher threshold surface charge necessary to stabilize a dispersion of spherical than planar particles. At 25%-50% ionization, the potential of mean force reaches a plateau because of the counterion condensation and saturated brush hydration. Moreover, the increase in the fraction of ionic groups can weaken the repulsion through counterion correlations between adjacent nanoparticles. High degrees of ionization and concomitant ionic screening gradually reduce the differences among surface interactions in distinct geometries until an essentially curvature-independent dispersion environment is created. Insights into tuning nanoparticle interactions can guide the synthesis of a broad class of nonpolar nanoparticles, where solubility is achieved by ionic functionalization.

Design of functional guanidinium ionic liquid aqueous two-phase systems for the efficient purification of protein.

PubMed

Ding, Xueqin; Wang, Yuzhi; Zeng, Qun; Chen, Jing; Huang, Yanhua; Xu, Kaijia

2014-03-07

A series of novel cationic functional hexaalkylguanidinium ionic liquids and anionic functional tetraalkylguanidinium ionic liquids have been devised and synthesized based on 1,1,3,3-tetramethylguanidine. The structures of the ionic liquids (ILs) were confirmed by (1)H nuclear magnetic resonance ((1)H NMR) and 13C nuclear magnetic resonance (13C NMR) and the production yields were all above 90%. Functional guanidinium ionic liquid aqueous two-phase systems (FGIL-ATPSs) have been first designed with these functional guanidinium ILs and phosphate solution for the purification of protein. After phase separation, proteins had transferred into the IL-rich phase and the concentrations of proteins were determined by measuring the absorbance at 278 nm using an ultra violet visible (UV-vis) spectrophotometer. The advantages of FGIL-ATPSs were compared with ordinary ionic liquid aqueous two-phase systems (IL-ATPSs). The proposed FGIL-ATPS has been applied to purify lysozyme, trypsin, ovalbumin and bovine serum albumin. Single factor experiments were used to research the effects of the process, such as the amount of ionic liquid (IL), the concentration of salt solution, temperature and the amount of protein. The purification efficiency reaches to 97.05%. The secondary structure of protein during the experimental process was observed upon investigation using UV-vis spectrophotometer, Fourier-transform infrared spectroscopy (FT-IR) and circular dichroism spectrum (CD spectrum). The precision, stability and repeatability of the process were investigated. The mechanisms of purification were researched by dynamic light scattering (DLS), determination of the conductivity and transmission electron microscopy (TEM). It was suggested that aggregation and embrace phenomenon play a significant role in the purification of proteins. All the results show that FGIL-ATPSs have huge potential to offer new possibility in the purification of proteins. Copyright © 2014 Elsevier B.V. All rights reserved.

Size mass distribution of water-soluble ionic species and gas conversion to sulfate and nitrate in particulate matter in southern Taiwan.

PubMed

Tsai, Jiun-Horng; Chang, Li-Peng; Chiang, Hung-Lung

2013-07-01

A Micro-Orifice Uniform Deposition Impactor (MOUDI) and a Nano-MOUDI were employed to determine the size-segregated mass distributions of ambient particulate matter (PM) and water-soluble ionic species for particulate constituents. In addition, gas precursors, including HCl, HONO, HNO3, SO2, and NH3 gases, were analyzed by an annular denuder system. PM size mass distribution, mass concentration, and ionic species concentration were measured during the day and at night during episode and non-episode periods in winter and summer. Average total suspended particle (TSP) concentrations during episode days in winter were as high as 153 ± 33 μg/m(3), and PM mass concentrations in summer were as low as one-third of that in winter. Generally, PM concentration at night was higher than that in the daytime in southern Taiwan during the sampling periods. In winter during the episode periods, the size-segregated mass distribution of PM mass concentration was mostly in the 0.32-3.2-μm range, and the PM concentration increased significantly in the range of 0.32-3.2 μm at night. Ammonium, nitrate, and sulfate were the dominant water-soluble ionic species in PM, contributing 34-48% of TSP mass. High concentrations of ammonia (12.9-49 μg/m(3)) and SO2 (2.6-27 μg/m(3)) were observed in the gas precursors. The conversion ratio was high in the PM size range of 0.18-3.2 μm both during the day and at night in winter, and the conversion ratio of episode days was 20% higher than that of non-episode days. The conversion factor was high for both nitrogen and sulfur species at nighttime, especially on episode days.

Development of a novel naphthoic acid ionic liquid and its application in "no-organic solvent microextraction" for determination of triclosan and methyltriclosan in human fluids and the method optimization by central composite design.

PubMed

Wang, Hui; Gao, Jiajia; Yu, Nana; Qu, Jingang; Fang, Fang; Wang, Huili; Wang, Mei; Wang, Xuedong

2016-07-01

In traditional ionic liquids (ILs)-based microextraction, the hydrophobic and hydrophilic ILs are often used as extractant and disperser, respectively. However, the functional effects of ILs are not utilized in microextraction procedures. Herein, we introduced 1-naphthoic acid into imidazolium ring to synthesize a novel ionic liquid 1-butyl-3-methylimidazolium naphthoic acid salt ([C4MIM][NPA]), and its structure was characterized by IR, (1)H NMR and MS. On the basis of its acidic property and lower solubility than common [CnMIM][BF4], it was used as a mixing dispersive solvent with [C4MIM][BF4] in "functionalized ionic liquid-based no organic solvent microextraction (FIL-NOSM)". Utilization of [C4MIM][NPA] in FIL-NOSM procedures has two obvious advantages: (1) it promoted the non-polar environment, increased volume of the sedimented phase, and thus could enhance the extraction recoveries of triclosan (TCS) and methyltriclosan (MTCS) by more than 10%; and (2) because of the acidic property, it can act as a pH modifier, avoiding extra pH adjustment step. By combining single factor optimization and central composite design, the main factors in the FIL-NOSM method were optimized. Under the optimal conditions, the relative recoveries of TCS and MTCS reached up to 98.60-106.09%, and the LODs of them were as low as 0.12-0.15µgL(-1) in plasma and urine samples. In total, this [C4MIM][NPA]-based FIL-NOSM method provided high extraction efficiency, and required less pretreatment time and unutilized any organic solvent. To the best of our knowledge, this is the first application of [C4mim][NPA]-based microextraction method for the simultaneous quantification of trace TCS and MTCS in human fluids. Copyright © 2016 Elsevier B.V. All rights reserved.

Ionic liquids for nano- and microstructures preparation. Part 2: Application in synthesis.

PubMed

Łuczak, Justyna; Paszkiewicz, Marta; Krukowska, Anna; Malankowska, Anna; Zaleska-Medynska, Adriana

2016-01-01

Ionic liquids (ILs) are widely applied to prepare metal nanoparticles and 3D semiconductor microparticles. Generally, they serve as a structuring agent or reaction medium (solvent), however it was also demonstrated that ILs can play a role of a co-solvent, metal precursor, reducing as well as surface modifying agent. The crucial role and possible types of interactions between ILs and growing particles have been presented in the Part 1 of this review paper. Part 2 of the paper gives a comprehensive overview of recent experimental studies dealing with application of ionic liquids for preparation of metal and semiconductor based nano- and microparticles. A wide spectrum of preparation routes using ionic liquids is presented, including precipitation, sol-gel technique, hydrothermal method, nanocasting and ray-mediated methods (microwave, ultrasound, UV-radiation and γ-radiation). It was found that ionic liquids formed of a 1-butyl-3-methylimidazolium [BMIM] combined with tetrafluoroborate [BF4], hexafluorophosphate [PF6], and bis(trifluoromethanesulfonyl)imide [Tf2N] are the most often used ILs in the synthesis of nano- and microparticles, due to their low melting temperature, low viscosity and good transportation properties. Nevertheless, examples of other IL classes with intrinsic nanoparticles stabilizing abilities such as phosphonium and ammonium derivatives are also presented. Experimental data revealed that structure of ILs (both anion and cation type) affects the size and shape of formed metal particles, and in some cases may even determine possibility of particles formation. The nature of the metal precursor determines its affinity to polar or nonpolar domains of ionic liquid, and therefore, the size of the nanoparticles depends on the size of these regions. Ability of ionic liquids to form varied extended interactions with particle precursor as well as other compounds presented in the reaction media (water, organic solvents etc.) provides nano- and microstructures with different morphologies (0D nanoparticles, 1D nanowires, rods, 2D layers, sheets, and 3D features of molecules). ILs interact efficiently with microwave irradiation, thus even small amount of IL can be employed to increase the dielectric constant of nonpolar solvents used in the synthesis. Thus, combining the advantages of ionic liquids and ray-mediated methods resulted in the development of new ionic liquid-assisted synthesis routes. One of the recently proposed approaches of semiconductor particles preparation is based on the adsorption of semiconductor precursor molecules at the surface of micelles built of ionic liquid molecules playing a role of a soft template for growing microparticles. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetical hollow fiber bar collection of extract in homogenous ionic liquid microextraction of triazine herbicides in water samples.

PubMed

Wang, Kun; Jiang, Jia; Kang, Mingqin; Li, Dan; Zang, Shuang; Tian, Sizhu; Zhang, Hanqi; Yu, Aimin; Zhang, Ziwei

2017-04-01

The homogeneous ionic liquid microextraction combined with magnetical hollow fiber bar collection was developed for extracting triazine herbicides from water samples. These analytes were separated and determined by high performance liquid chromatography. The triazines were quickly extracted into ionic liquid microdroplets dispersed in solution, and then these microdroplets were completely collected with magnetical hollow fiber bars; the pores of which were impregnated with hydrophobic ionic liquid, which makes the phase separation simplified with no need of centrifugation. Some experimental parameters, such as the type of ionic liquid, ultrasonic immersion time of hollow fiber, pH of sample solution, volume of hydrophilic ionic liquid, amount of ion-pairing agent NH 4 PF 6 , NaCl concentration, number of magnetical hollow fiber bar, stirring rate, and collection time were investigated and optimized. When the present method was applied to the analysis of real water samples, the precision and recoveries of six triazine herbicides vary from 0.1 to 9.2% and 73.4 to 118.5%, respectively. The detection limits for terbumeton, ametryn, prometryn, terbutryn, trietazine, and dimethametryn were 0.48, 0.15, 0.15, 0.14, 0.35, and 0.16 μg L -1 , respectively.

Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations.

PubMed

Zheng, Zhiqiang; Xu, Qiming; Guo, Jiangna; Qin, Jing; Mao, Hailei; Wang, Bin; Yan, Feng

2016-05-25

The structure-antibacterial activity relationship between the small molecular compounds and polymers are still elusive. Here, imidazolium-type ionic liquid (IL) monomers and their corresponding poly(ionic liquids) (PILs) and poly(ionic liquid) membranes were synthesized. The effect of chemical structure, including carbon chain length of substitution at the N3 position and charge density of cations (mono- or bis-imidazolium) on the antimicrobial activities against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by determination of minimum inhibitory concentration (MIC). The antibacterial activities of both ILs and PILs were improved with the increase of the alkyl chain length and higher charge density (bis-cations) of imidazolium cations. Moreover, PILs exhibited lower MIC values relative to the IL monomers. However, the antibacterial activities of PIL membranes showed no correlation to those of their analogous small molecule IL monomers and PILs, which increased with the charge density (bis-cations) while decreasing with the increase of alkyl chain length. The results indicated that antibacterial property studies on small molecules and homopolymers may not provide a solid basis for evaluating that in corresponding polymer membranes.

Transports of ionic liquids in ionic polymer conductor network composite actuators

NASA Astrophysics Data System (ADS)

Liu, Yang; Liu, Sheng; Lin, Junhong; Wang, Dong; Jain, Vaibhav; Montazami, Reza; Heflin, James R.; Li, Jing; Madsen, Louis; Zhang, Q. M.

2010-04-01

We investigate the influence of ionic liquids on the electromechanical performance of Ionic Polymer Conductor Network Composite (IPCNC) bending actuators. Two imidazolium ionic liquids (ILs) with one cation, which is 1-ethyl-3- methylimidazolium ([EMI+]), and two different anions, which are tetrafluoroborate ([BF4-]) and trifluoromethanesulfonate ([Tf-]), are chosen for the study. By combining the time domain electric and electromechanical responses, we developed a new model that describes the ion transports in IPCNC actuators. The time constant of excess cation and anion migration in various composite electrodes are deduced: 6s and 25s in RuO2/Nafion; 7.9s and 36.3s in RuO2/Aquivion; 4.8s and 53s in Au/PAH, respectively. NMR is also applied to provide quantitative measures of self-diffusion coefficients independently for IL anions and cations both in pure ILs and in ILs absorved into ionomers. All the results indicate that the motion of cation, in the studied pure ionic liquids, polymer matrix and conductor network composites, is faster than that of anion. Moreover, the CNC morphology is playing a crucial role in determining the ion transport in the porous electrodes.

Aerosol and snow transfer processes: An investigation on the behavior of water-soluble organic compounds and ionic species.

PubMed

Barbaro, Elena; Zangrando, Roberta; Padoan, Sara; Karroca, Ornela; Toscano, Giuseppa; Cairns, Warren R L; Barbante, Carlo; Gambaro, Andrea

2017-09-01

The concentrations of water-soluble compounds (ions, carboxylic acids, amino acids, sugars, phenolic compounds) in aerosol and snow have been determined at the coastal Italian base "Mario Zucchelli" (Antarctica) during the 2014-2015 austral summer. The main aim of this research was to investigate the air-snow transfer processes of a number of classes of chemical compounds and investigate their potential as tracers for specific sources. The composition and particle size distribution of Antarctic aerosol was measured, and water-soluble compounds accounted for 66% of the PM 10 total mass concentration. The major ions Na + , Mg 2+ , Cl - and SO 4 2- made up 99% of the total water soluble compound concentration indicating that sea spray input was the main source of aerosol. These ionic species were found mainly in the coarse fraction of the aerosol resulting in enhanced deposition, as reflected by the snow composition. Biogenic sources were identified using chemical markers such as carboxylic acids, amino acids, sugars and phenolic compounds. This study describes the first characterization of amino acids and sugar concentrations in surface snow. High concentrations of amino acids were found after a snowfall event, their presence is probably due to the degradation of biological material scavenged during the snow event. Alcohol sugars increased in concentration after the snow event, suggesting a deposition of primary biological particles, such as airborne fungal spores. Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of Inorganic Ion Profiles of Illicit Drugs by Capillary Electrophoresis.

PubMed

Evans, Elizabeth; Costrino, Carolina; do Lago, Claudimir L; Garcia, Carlos D; Roux, Claude; Blanes, Lucas

2016-11-01

A portable capillary electrophoresis instrument with dual capacitively coupled contactless conductivity detection (C 4 D) was used to determine the inorganic ionic profiles of three pharmaceutical samples and precursors of two illicit drugs (contemporary samples of methylone and para-methoxymethamphetamine). The LODs ranged from 0.10 μmol/L to 1.25 μmol/L for the 10 selected cations, and from 0.13 μmol/L to 1.03 μmol/L for the eight selected anions. All separations were performed in less than 6 min with migration times and peak area RSD values ranging from 2 to 7%. The results demonstrate the potential of the analysis of inorganic ionic species to aid in the identification and/or differentiation of unknown tablets, and real samples found in illicit drug manufacture scenarios. From the resulting ionic fingerprint, the unknown tablets and samples can be further classified. © 2016 American Academy of Forensic Sciences.

Magnetomotive room temperature dicationic ionic liquid: a new concept toward centrifuge-less dispersive liquid-liquid microextraction.

PubMed

Beiraghi, Asadollah; Shokri, Masood; Seidi, Shahram; Godajdar, Bijan Mombani

2015-01-09

A new centrifuge-less dispersive liquid-liquid microextraction technique based on application of magnetomotive room temperature dicationic ionic liquid followed by electrothermal atomic absorption spectrometry (ETAAS) was developed for preconcentration and determination of trace amount of gold and silver in water and ore samples, for the first time. Magnetic ionic liquids not only have the excellent properties of ionic liquids but also exhibit strong response to an external magnetic field. These properties provide more advantages and potential application prospects for magnetic ionic liquids than conventional ones in the fields of extraction processes. In this work, thio-Michler's ketone (TMK) was used as chelating agent to form Ag/Au-TMK complexes. Several important factors affecting extraction efficiency including extraction time, rate of vortex agitator, pH of sample solution, concentration of the chelating agent, volume of ionic liquid as well as effects of interfering species were investigated and optimized. Under the optimal conditions, the limits of detection (LOD) were 3.2 and 7.3ngL(-1) with the preconcentration factors of 245 and 240 for Au and Ag, respectively. The precision values (RSD%, n=7) were 5.3% and 5.8% at the concentration level of 0.05μgL(-1) for Au and Ag, respectively. The relative recoveries for the spiked samples were in the acceptable range of 96-104.5%. The results demonstrated that except Hg(2+), no remarkable interferences are created by other various ions in the determination of Au and Ag, so that the tolerance limits (WIon/WAu or Ag) of major cations and anions were in the range of 250-1000. The validated method was successfully applied for the analysis of Au and Ag in some water and ore samples. Copyright © 2014 Elsevier B.V. All rights reserved.

Facile synthesis of poly(ionic liquid)-bonded magnetic nanospheres as a high-performance sorbent for the pretreatment and determination of phenolic compounds in water samples.

PubMed

Bi, Wentao; Wang, Man; Yang, Xiaodi; Row, Kyung Ho

2014-07-01

Poly(ionic liquid)-bonded magnetic nanospheres were easily synthesized and applied to the pretreatment and determination of phenolic compounds in water samples, which have detrimental effects on water quality and the health of living beings. The high affinity of poly(ionic liquid)s toward the target compounds as well as the magnetic behavior of Fe3 O4 were combined in this material to provide an efficient and simple magnetic solid-phase extraction approach. The adsorption behavior of the poly(ionic liquid)-bonded magnetic nanospheres was examined to optimize the synthesis. Different parameters affecting the magnetic solid-phase extraction of phenolic compounds were assessed in terms of adsorption and recovery. Under the optimal conditions, the proposed method showed excellent detection sensitivity with limits of detection in the range of 0.3-0.8 ng/mL and precision in the range of 1.2-3.3%. This method was also applied successfully to the analysis of real water samples; good spiked recoveries over the range of 82.5-99.2% were obtained. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational and experimental characterization of a pyrrolidinium-based ionic liquid for electrolyte applications

NASA Astrophysics Data System (ADS)

Torabifard, Hedieh; Reed, Luke; Berry, Matthew T.; Hein, Jason E.; Menke, Erik; Cisneros, G. Andrés

2017-10-01

The development of Li-ion batteries for energy storage has received significant attention. The synthesis and characterization of electrolytes in these batteries are an important component of this development. Ionic liquids (ILs) have been proposed as possible electrolytes in these devices. Thus, the accurate determination of thermophysical properties for these solvents becomes important for determining their applicability as electrolytes. In this contribution, we present the synthesis and experimental/computational characterization of thermodynamic and transport properties of a pyrrolidinium based ionic liquid as a first step to investigate the possible applicability of this class of ILs for Li-ion batteries. A quantum mechanical-based force field with many-body polarizable interactions has been developed for the simulation of spirocyclic pyrrolidinium, [sPyr+], with BF4- and Li+. Molecular dynamics calculations employing intra-molecular polarization predicted larger heat of vaporization and self-diffusion coefficients and smaller densities in comparison with the model without intra-molecular polarization, indicating that the inclusion of this term can significantly effect the inter-ionic interactions. The calculated properties are in good agreement with available experimental data for similar IL pairs and isothermal titration calorimetry data for [sPyr+][BF4-].

A simple, rapid and green ultrasound assisted and ionic liquid dispersive microextraction procedure for the determination of tin in foods employing ETAAS.

PubMed

Tuzen, Mustafa; Uluozlu, Ozgur Dogan; Mendil, Durali; Soylak, Mustafa; Machado, Luana O R; Dos Santos, Walter N L; Ferreira, Sergio L C

2018-04-15

This paper proposes a simple, rapid and green ultrasound assisted and ionic liquid dispersive microextraction procedure using pyrocatechol violet (PV) as complexing reagent and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide [C 6 MIM][Tf 2 N] as ionic liquid for the detection of tin employing electrothermal atomic absorption spectrometry (ETAAS). The optimization step was performed using a two-level full factorial design involving the following factors: pH of the working media, amount reagents, ionic liquid volume and extraction time and the chemometric response was tin recovery. The procedure allowed the determination of tin with limits of detection and quantification of 3.4 and 11.3 ng L -1 , respectively. The relative standard deviation was 4.5% for a tin solution of 0.50 µg L -1 . The validation method was confirmed by analysis of rice flour certified reference material. The method was applied for the quantification of tin in several food samples. The concentration range found varied from 0.10 to 1.50 µg g -1 . Copyright © 2017 Elsevier Ltd. All rights reserved.

Determination of ionic species formed during growth of Escherichia coli by capillary isotachophoresis.

PubMed

Futschik, K; Ammann, M; Bachmayer, S; Kenndler, E

1993-08-06

The ionic species that are formed during the microbial growth of Escherichia coli were determined by capillary isotachophoresis as a function of the time of cultivation. This formation was indicated by the change in a sum parameter, the impedance of the nutrient broth, measured by a special electrode system. Based on the determination of the individual ions formed under the given conditions (identified as acetate, lactate, alpha-ketoglutarate, fumarate, ammonium and probably a simple amine), the change in conductivity was calculated and compared with that obtained by the impedance measurement of the bulk medium. From the results it can be concluded that the change in the sum parameter as a function of time is originated by the ions determined.

Extraction and Chromatographic Determination of Shikimic Acid in Chinese Conifer Needles with 1-Benzyl-3-methylimidazolium Bromide Ionic Liquid Aqueous Solutions

PubMed Central

Chen, Fengli; Hou, Kexin; Li, Shuangyang; Zu, Yuangang; Yang, Lei

2014-01-01

An ionic liquids-based ultrasound-assisted extraction (ILUAE) method was successfully developed for extracting shikimic acid from conifer needles. Eleven 1-alkyl-3-methylimidazolium ionic liquids with different cations and anions were investigated and 1-benzyl-3-methylimidazolium bromide solution was selected as the solvent. The conditions for ILUAE, including the ionic liquid concentration, ultrasound power, ultrasound time, and liquid-solid ratio, were optimized. The proposed method had good recovery (99.37%–100.11%) and reproducibility (RSD, n = 6; 3.6%). ILUAE was an efficient, rapid, and simple sample preparation technique that showed high reproducibility. Based on the results, a number of plant species, namely, Picea koraiensis, Picea meyeri, Pinus elliottii, and Pinus banksiana, were identified as among the best resources of shikimic acid. PMID:24782942

Molecular dynamics simulation of low dielectric constant polymer electrolytes

NASA Astrophysics Data System (ADS)

Wheatle, Bill; Lynd, Nathaniel; Ganesan, Venkat

Recent experimental studies measured the ionic conductivities of a series of poly(glycidyl ether)s with varying neat dielectric constants (ɛ), viscosities (η), and glass transition temperatures (Tg), as hosts for lithium bistrifluoromethanesulfonimide (LiTFSI) salt. In such a context, it was demonstrated that the ionic conductivity of these polymer electrolytes was a function of ɛ rather than Tg or η, suggesting that there may exist regimes in which ionic conductivity is not limited by slow segmental dynamics but rather by low ionic dissociation. Motivated by such results, we used atomistic molecular dynamics to study the structure and transport characteristics of the same set of host polymers. We found that the coordination number of TFSI- about Li+ in the first solvation shell and the total fraction of free ions increased as a function of ɛ, implying the polymer hosts enhanced ion dissociation. In addition, we found that increasing the dielectric constant of the host polymer enhanced self-correlated ion transport, as evidenced by an increase in the diffusion coefficients of each ion species. Overall, we confirmed that limited ion dissociation in low- ɛ polymer electrolyte hosts hampers ionic conductivity. We would like to thank the National Science Foundation Graduate Research Fellowship Program for funding this research endeavor.

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid-liquid microextraction for the separation and determination of estrogens in water samples by high-performance liquid chromatography with fluorescence detection.

PubMed

Zhang, Rui; Wang, Chuanliu; Yue, Qiaohong; Zhou, Tiecheng; Li, Na; Zhang, Hanqi; Hao, Xiaoke

2014-11-01

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid-liquid microextraction method was proposed for the extraction and concentration of 17-α-estradiol, 17-β-estradiol-benzoate, and quinestrol in environmental water samples by high-performance liquid chromatography with fluorescence detection. 1-Hexyl-3-methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion-pairing and salting-out agent NH4 PF6 was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1-hexyl-3-methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid-liquid microextraction was widened. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Fangyong; Lartey, Michael; Damodaran, Krishnan

2013-01-01

Ionic liquids are an emerging class of materials with applications in a variety of fields. Steady progress has been made in the creation of ionic liquids tailored to specific applications. However, the understanding of the underlying structure–property relationships has been slower to develop. As a step in the effort to alleviate this deficiency, the influence of side groups on ionic liquid properties has been studied through an integrated approach utilizing synthesis, experimental determination of properties, and simulation techniques. To achieve this goal, a classical force field in the framework of OPLS/Amber force fields has been developed to predict ionic liquidmore » properties accurately. Cu(I)-catalyzed click chemistry was employed to synthesize triazolium-based ionic liquids with diverse side groups. Values of densities were predicted within 3% of experimental values, whereas self-diffusion coefficients were underestimated by about an order of magnitude though the trends were in excellent agreement, the activation energy calculated in simulation correlates well with experimental values. The predicted Henry coefficient for CO{sub 2} solubility reproduced the experimentally observed trends. This study highlights the importance of integrating experimental and computational approaches in property prediction and materials development, which is not only useful in the development of ionic liquids for CO{sub 2} capture but has application in many technological fields.« less

Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Fangyong; Lartey, Michael; Damodaran, Krishnan

Ionic liquids are an emerging class of materials with applications in a variety of fields. Steady progress has been made in the creation of ionic liquids tailored to specific applications. However, the understanding of the underlying structure–property relationships has been slower to develop. As a step in the effort to alleviate this deficiency, the influence of side groups on ionic liquid properties has been studied through an integrated approach utilizing synthesis, experimental determination of properties, and simulation techniques. To achieve this goal, a classical force field in the framework of OPLS/Amber force fields has been developed to predict ionic liquidmore » properties accurately. Cu(I)-catalyzed click chemistry was employed to synthesize triazolium-based ionic liquids with diverse side groups. Values of densities were predicted within 3% of experimental values, whereas self-diffusion coefficients were underestimated by about an order of magnitude though the trends were in excellent agreement, the activation energy calculated in simulation correlates well with experimental values. The predicted Henry coefficient for CO{sub 2} solubility reproduced the experimentally observed trends. This study highlights the importance of integrating experimental and computational approaches in property prediction and materials development, which is not only useful in the development of ionic liquids for CO{sub 2} capture but has application in many technological fields.« less

Ionic strength-induced formation of smectite quasicrystals enhances nitroaromatic compound sorption.

PubMed

Li, Hui; Pereira, Tanya R; Teppen, Brian J; Laird, David A; Johnston, Cliff T; Boyd, Stephen A

2007-02-15

Sorption of organic contaminants by soils is a determinant controlling their transport and fate in the environment. The influence of ionic strength on nitroaromatic compound sorption by K+- and Ca2+ -saturated smectite was examined. Sorption of 1,3-dinitrobenzene by K-smectite increased as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorption by Ca-smectite at CaCl2 ionic strengths of 0.015 and 0.15 M remained essentially the same. The "salting-out" effect on the decrease of 1,3-dinitrobenzene aqueous solubility within this ionic strength range was <1.5% relative to the solubility in pure water. This decrease of solubility is insufficient to account for the observed increase of sorption by K-smectite with increasing KCl ionic strength. X-ray diffraction patterns and light absorbance of K-clay suspensions indicated the aggregation of clay particles and the formation of quasicrystal structures as KCI ionic strength increased. Sorption enhancement is attributed to the formation of better-ordered K-clay quasicrystals with reduced interlayer distances rather than to the salting-out effect. Dehydration of 1,3-dinitrobenzene is apparently a significant driving force for sorption, and we show for the first time that sorption of small, planar, neutral organic molecules, namely, 1,3-dinitrobenzene, causes previously expanded clay interlayers to dehydrate and collapse in aqueous suspension.

Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuzuki, Seiji, E-mail: s.tsuzuki@aist.go.jp; Shinoda, Wataru; Miran, Md. Shah

2013-11-07

The stabilization energies for the formation (E{sub form}) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G{sup **} level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E{sub form} for the [dema][CF{sub 3}SO{sub 3}] and [dmpa][CF{sub 3}SO{sub 3}] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative)more » than that for the [etma][CF{sub 3}SO{sub 3}] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl{sup −}, BF{sub 4}{sup −}, TFSA{sup −} anions. The anion has contact with the N–H bond of the dema{sup +} or dmpa{sup +} cations in the most stable geometries of the dema{sup +} and dmpa{sup +} complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E{sub form} for the less stable geometries for the dema{sup +} and dmpa{sup +} complexes are close to those for the most stable etma{sup +} complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA{sup −} anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF{sub 3}SO{sub 3}] ionic liquid.« less

Ultrasound-assisted ionic liquid-based micellar extraction combined with microcrystalline cellulose as sorbent in dispersive microextraction for the determination of phenolic compounds in propolis.

PubMed

Cao, Jun; Peng, Li-Qing; Du, Li-Jing; Zhang, Qi-Dong; Xu, Jing-Jing

2017-04-22

An ionic liquid-(IL) based micellar extraction combined with microcrystalline cellulose- (MCC) assisted dispersive micro solid-phase extraction method was developed to extract phenolic compounds from propolis. A total of 20 target compounds were identified by ultra-high- performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry. The main extraction parameters were optimized and included the ultrasonic power, ultrasonic time, sample pH, type of IL, the concentration of [C12mim]Br, extraction time, concentration of MCC, type of sorbent and type of elution solvents. Under the optimum conditions, the proposed method exhibited good linearities (r 2  ≥ 0.999) for all plant phenolic compounds with the lower limits of detection in the range of 0.21-0.41 ng/mL. The recoveries ranged from 82.74% to 97.88% for pinocembrin, chrysin and galangin. Compared with conventional solvent extraction, the present method was simpler and more efficient and required less organic solvent and a shorter extraction time. Finally, the methodology was successfully used for the extraction and enrichment of phenolic compounds in propolis. Copyright © 2017 Elsevier B.V. All rights reserved.

Heavy metal speciation and uptake in crayfish and tadpoles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bundy, K.J.; Berzins, D.; Millet, L.

1996-12-31

Developing valid pollution recording methods is central to assessing environmental damage and remediation. This often is difficult, however, because of speciation and multiphase distribution of contaminants. Polarography, an electroanalytical technique capable of detection and quantification of trace levels of elements and ionic complexes, is a promising method for analyzing environmental samples. Here, polarography has been used to determine lead concentration in water, sediment, bullfrogs, tadpoles, and adsorbed onto kaolin. It has also been used to measure hexavalent chromium concentration in crayfish. This research involves field studies and two laboratory experiments. Studies of a Louisiana swamp have shown lead`s affinity formore » sediment and water particulate phases, rather than being ionically dissolved in the aqueous phase. In swamp bullfrogs, lead was found in greater concentrations in bone compared to muscle. In the first laboratory experiment, lead uptake originating from water and sediment increased in tadpoles as exposure time and concentration increased. Also, this animal`s development was hindered at higher concentrations. The second laboratory experiment exposed crayfish to aqueous hexavalent chromium. Total chromium uptake increased with exposure time and concentration. The chromium tissue abundance was hepatopancreas > gills > muscle. A substantial portion of tissue hexavalent chromium converted to the less toxic trivalent form.« less

A MODIFIED PROTEIN ASSAY FROM MICROGRAM TO LOW NANOGRAM LEVELS IN DILUTE SAMPLES

PubMed Central

Heda, Ghanshyam D.; Kunwar, Upasana; Heda, Rajiv P.

2013-01-01

In this paper we present a modified and improved protein assay that was previously described as ‘amidoschwarz assay’ by Schaffner and Weissmann (Anal. Biochem. 56, 1973, 502–514). Our improved protein assay is user-friendly and 30 to 40 times more sensitive than the earlier method. The assay was developed into 3 formats (maco, micro, and nanoassay) with TCA as protein precipitating agent; measuring up to 96 samples. The macro and micro formats of this assay require a single reagent staining with amido black of protein dots, bound to nitrocellulose membrane with lowest protein measurements to 1 μg and 0.1 μg respectively. The nanoassay on the other hand with combination staining of amido black followed by colloidal gold can extend the detection limit to 2.5 ng of protein. Protein concentrations were determined by densitometry and/or spectrophotometry. This assay is compatible with many ionic and non-ionic detergents. This improved protein assay provides an additional choice to researchers in measuring total protein concentration accurately in dilute biological samples as low as 0.125 μg/ml, prior to their biochemical analysis such as in comparative proteomics. PMID:24135655

Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

DOE PAGES

Usher, Tedi -Marie; Levin, Igor; Daniels, John E.; ...

2015-10-01

In this study, the atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO 3 andmore » Na ½Bi ½TiO 3, and dielectric SrTiO 3. For Na ½Bi ½TiO 3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO 3 and SrTiO 3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.« less

Determining fluoride ions in ammonium desulfurization slurry using an ion selective electrode method

NASA Astrophysics Data System (ADS)

Luo, Zhengwei; Guo, Mulin; Chen, Huihui; Lian, Zhouyang; Wei, Wuji

2018-02-01

Determining fluoride ions in ammonia desulphurization slurry using a fluoride ion selective electrode (ISE) is investigated. The influence of pH was studied and the appropriate total ionic strength adjustment buffer and its dosage were optimized. The impact of Fe3+ concentration on the detection results was analyzed under preferable conditions, and the error analysis of the ISE method’s accuracy and precision for measuring fluoride ion concentration in the range of 0.5-2000 mg/L was conducted. The quantitative recovery of F- in ammonium sulfate slurry was assessed. The results showed that when pH ranged from 5.5˜6 and the Fe3+ concentration was less than 750 mg/L, the accuracy and precision test results with quantitative recovery rates of 92.0%-104.2% were obtained.

Temperature- and pressure-dependent infrared spectroscopy of 1-butyl-3-methylimidazolium trifluoromethanesulfonate: A dipolar coupling theory analysis

NASA Astrophysics Data System (ADS)

Burba, Christopher M.; Chang, Hai-Chou

2018-03-01

Continued growth and development of ionic liquids requires a thorough understanding of how cation and anion molecular structure defines the liquid structure of the materials as well as the various properties that make them technologically useful. Infrared spectroscopy is frequently used to assess molecular-level interactions among the cations and anions of ionic liquids because the intramolecular vibrational modes of the ions are sensitive to the local potential energy environments in which they reside. Thus, different interaction modes among the ions may lead to different spectroscopic signatures in the vibrational spectra. Charge organization present in ionic liquids, such as 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4mim]CF3SO3), is frequently modeled in terms of a quasicrystalline structure. Highly structured quasilattices enable the dynamic coupling of vibrationally-induced dipole moments to produce optical dispersion and transverse optical-longitudinal optical (TO-LO) splitting of vibrational modes of the ionic liquid. According to dipolar coupling theory, the degree of TO-LO splitting is predicted to have a linear dependence on the number density of the ionic liquid. Both temperature and pressure will affect the number density of the ionic liquid and, therefore, the amount of TO-LO splitting for this mode. Therefore, we test these relationships through temperature- and pressure-dependent FT-IR spectroscopic studies of [C4mim]CF3SO3, focusing on the totally symmetric Ssbnd O stretching mode for the anion, νs(SO3). Increased temperature decreases the amount of TO-LO splitting for νs(SO3), whereas elevated pressure is found to increase the amount of band splitting. In both cases, the experimental observations follow the general predictions of dipolar coupling theory, thereby supporting the quasilattice model for this ionic liquid.

Improved Activity of a Thermophilic Cellulase, Cel5A, from Thermotoga maritima on Ionic Liquid Pretreated Switchgrass

PubMed Central

Chen, Zhiwei; Pereira, Jose H.; Liu, Hanbin; Tran, Huu M.; Hsu, Nathan S. Y.; Dibble, Dean; Singh, Seema; Adams, Paul D.; Sapra, Rajat; Hadi, Masood Z.; Simmons, Blake A.; Sale, Kenneth L.

2013-01-01

Ionic liquid pretreatment of biomass has been shown to greatly reduce the recalcitrance of lignocellulosic biomass, resulting in improved sugar yields after enzymatic saccharification. However, even under these improved saccharification conditions the cost of enzymes still represents a significant proportion of the total cost of producing sugars and ultimately fuels from lignocellulosic biomass. Much of the high cost of enzymes is due to the low catalytic efficiency and stability of lignocellulolytic enzymes, especially cellulases, under conditions that include high temperatures and the presence of residual pretreatment chemicals, such as acids, organic solvents, bases, or ionic liquids. Improving the efficiency of the saccharification process on ionic liquid pretreated biomass will facilitate reduced enzyme loading and cost. Thermophilic cellulases have been shown to be stable and active in ionic liquids but their activity is typically at lower levels. Cel5A_Tma, a thermophilic endoglucanase from Thermotoga maritima, is highly active on cellulosic substrates and is stable in ionic liquid environments. Here, our motivation was to engineer mutants of Cel5A_Tma with higher activity on 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) pretreated biomass. We developed a robotic platform to screen a random mutagenesis library of Cel5A_Tma. Twelve mutants with 25–42% improvement in specific activity on carboxymethyl cellulose and up to 30% improvement on ionic-liquid pretreated switchgrass were successfully isolated and characterized from a library of twenty thousand variants. Interestingly, most of the mutations in the improved variants are located distally to the active site on the protein surface and are not directly involved with substrate binding. PMID:24244549

Improved activity of a thermophilic cellulase, Cel5A, from Thermotoga maritima on ionic liquid pretreated switchgrass.

PubMed

Chen, Zhiwei; Pereira, Jose H; Liu, Hanbin; Tran, Huu M; Hsu, Nathan S Y; Dibble, Dean; Singh, Seema; Adams, Paul D; Sapra, Rajat; Hadi, Masood Z; Simmons, Blake A; Sale, Kenneth L

2013-01-01

Ionic liquid pretreatment of biomass has been shown to greatly reduce the recalcitrance of lignocellulosic biomass, resulting in improved sugar yields after enzymatic saccharification. However, even under these improved saccharification conditions the cost of enzymes still represents a significant proportion of the total cost of producing sugars and ultimately fuels from lignocellulosic biomass. Much of the high cost of enzymes is due to the low catalytic efficiency and stability of lignocellulolytic enzymes, especially cellulases, under conditions that include high temperatures and the presence of residual pretreatment chemicals, such as acids, organic solvents, bases, or ionic liquids. Improving the efficiency of the saccharification process on ionic liquid pretreated biomass will facilitate reduced enzyme loading and cost. Thermophilic cellulases have been shown to be stable and active in ionic liquids but their activity is typically at lower levels. Cel5A_Tma, a thermophilic endoglucanase from Thermotoga maritima, is highly active on cellulosic substrates and is stable in ionic liquid environments. Here, our motivation was to engineer mutants of Cel5A_Tma with higher activity on 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) pretreated biomass. We developed a robotic platform to screen a random mutagenesis library of Cel5A_Tma. Twelve mutants with 25-42% improvement in specific activity on carboxymethyl cellulose and up to 30% improvement on ionic-liquid pretreated switchgrass were successfully isolated and characterized from a library of twenty thousand variants. Interestingly, most of the mutations in the improved variants are located distally to the active site on the protein surface and are not directly involved with substrate binding.

The lanthanum gallate-based mixed conducting perovskite ceramics

NASA Astrophysics Data System (ADS)

Politova, E. D.; Stefanovich, S. Yu.; Aleksandrovskii, V. V.; Kaleva, G. M.; Mosunov, A. V.; Avetisov, A. K.; Sung, J. S.; Choo, K. Y.; Kim, T. H.

2005-01-01

The structure, microstructure, dielectric, and transport properties of the anion deficient perovskite solid solutions (La,Sr)(Ga,Mg,M)O3- with M=Fe, Ni have been studied. Substitution of iron and nickel for gallium up to about 20 and 40 at.% respectively, leads to the perovskite lattice contraction due to the cation substitutions by the transition elements. The transition from pure ionic to mixed ionic-electronic conductivity was observed for both the systems studied. Both the enhancement of total conductivity and increasing in the thermal expansion coefficient values has been proved to correlate with the increasing amount of weakly bounded oxygen species in the Fe or Ni-doped ceramics. The oxygen ionic conductivity has been estimated from the kinetic experiments using the dc-conductivity and dilatometry methods under the condition of the stepwise change of the atmosphere from nitrogen to oxygen.

Polymer electrolyte based on crosslinked poly(glycidyl methacrylate) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fei, Beatrice Wong Chui; Hanifah, Sharina Abu; Ahmad, Azizan

2015-09-25

Polymer electrolytes based on crosslinked poly(glycidyl methacrylate) as polymer host and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) as incorporated salt were prepared by in-situ photopolymerization technique. The complexes with different mass ratio of glycidyl methacrylate (GMA) monomer to BmimTFSI were investigated. The ionic conductivity of the polymer electrolyte was increased and reach the highest value of 7.50 × 10{sup −4} S cm{sup −1} at the ratio of 3:7 (GMA: BmimTFSI). The interaction between the polymer host and ionic liquid was proved by Attenuated Total Reflectance-Fourier Transformation Infra-Red Spectroscopy (ATR-FTIR). Meanwhile, the X-ray diffraction analysis shows the amorphousity of the polymer electrolyte film increasemore » with the ionic liquid ratio.« less

Optimization and development of a SPE-HPLC-UV method to determine astaxanthin in Saccharina japonica.

PubMed

Zhou, Jun; Bi, Wentao; Row, Kyung Ho

2011-04-01

An effective and accurate method including extraction, saponification, and separation was developed to determine astaxanthin (AX) in Saccharina japonica. The optimal extraction conditions with different solvents were investigated. 29.30 μg/g of AX was extracted from dry Saccharina japonica powder by solvent. After subsequent saponification, the extracted amount of AX was increased to 37.26 μg/g. Furthermore, 3 different ionic liquid-based silicas were prepared as sorbents for the solid phase extraction of AX from the extract. By comparing the adsorption isotherms of AX on different ionic liquid-based silicas, suitable sorbent was successfully selected and applied for separation of AX from extract. Astaxanthin, in 3 main forms (free, monoesters, and diesters), can be obtained from marine plants and animals. By extraction with subsequent saponification, the astaxanthin was extracted from Saccharina japonica. And then, ionic liquid-based silicas were used to separate the astaxanthin from the extract solution. This method can be widely applied for determination, or even industrial separation and purification of astaxanthin from many other algae.

Matrix solid-phase dispersion coupled with homogeneous ionic liquid microextraction for the determination of sulfonamides in animal tissues using high-performance liquid chromatography.

PubMed

Wang, Zhibing; He, Mengyu; Jiang, Chunzhu; Zhang, Fengqing; Du, Shanshan; Feng, Wennan; Zhang, Hanqi

2015-12-01

Matrix solid-phase dispersion coupled with homogeneous ionic liquid microextraction was developed and applied to the extraction of some sulfonamides, including sulfamerazine, sulfamethazine, sulfathiazole, sulfachloropyridazine, sulfadoxine, sulfisoxazole, and sulfaphenazole, in animal tissues. High-performance liquid chromatography was applied to the separation and determination of the target analytes. The solid sample was directly treated by matrix solid-phase dispersion and the eluate obtained was treated by homogeneous ionic liquid microextraction. The ionic liquid was used as the extraction solvent in this method, which may result in the improvement of the recoveries of the target analytes. To avoid using organic solvent and reduce environmental pollution, water was used as the elution solvent of matrix solid-phase dispersion. The effects of the experimental parameters on recoveries, including the type and volume of ionic liquid, type of dispersant, ratio of sample to dispersant, pH value of elution solvent, volume of elution solvent, amount of salt in eluate, amount of ion-pairing agent (NH4 PF6 ), and centrifuging time, were evaluated. When the present method was applied to the analysis of animal tissues, the recoveries of the analytes ranged from 85.4 to 118.0%, and the relative standard deviations were lower than 9.30%. The detection limits for the analytes were 4.3-13.4 μg/kg. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sodium influxes in internally perfused squid giant axon during voltage clamp.

PubMed

Atwater, I; Bezanilla, F; Rojas, E

1969-05-01

1. An experimental method for measuring ionic influxes during voltage clamp in the giant axon of Dosidicus is described; the technique combines intracellular perfusion with a method for controlling membrane potential.2. Sodium influx determinations were carried out while applying rectangular pulses of membrane depolarization. The ratio ;measured sodium influx/computed ionic flux during the early current' is 0.92 +/- 0.12.3. Plots of measured sodium influx and computed ionic flux during the early current against membrane potential are very similar. There was evidence that the membrane potential at which the sodium influx vanishes is the potential at which the early current reverses.

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

NASA Astrophysics Data System (ADS)

Rudakov, A. M.; Sergievskii, V. V.; Zhukova, T. V.

2014-06-01

A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Hückel equation are developed.

Properties of small Ar sub N-1 K/+/ ionic clusters

NASA Technical Reports Server (NTRS)

Etters, R. D.; Danilowicz, R.; Dugan, J.

1977-01-01

A self-consistent formalism is developed that, based upon a many-body potential, dynamically determines the thermodynamic properties of ionic clusters without an a priori designation of the equilibrium structures. Aggregates consisting of a single closed shell K(+) ion and N-1 isoelectronic argon atoms were studied. The clusters form crystallites at low temperatures, and melting transitions and spontaneous dissociations are indicated. The results confirm experimental evidence that shows that ionic clusters become less stable with increasing N. The crystallite structures formed by four different clusters are isosceles triangle, skewed form, octahedron with ion in the middle, and icosahedron with the ion in the middle.

Diffuse-charge dynamics of ionic liquids in electrochemical systems.

PubMed

Zhao, Hui

2011-11-01

We employ a continuum theory of solvent-free ionic liquids accounting for both short-range electrostatic correlations and steric effects (finite ion size) [Bazant et al., Phys. Rev. Lett. 106, 046102 (2011)] to study the response of a model microelectrochemical cell to a step voltage. The model problem consists of a 1-1 symmetric ionic liquid between two parallel blocking electrodes, neglecting any transverse transport phenomena. Matched asymptotic expansions in the limit of thin double layers are applied to analyze the resulting one-dimensional equations and study the overall charge-time relation in the weakly nonlinear regime. One important conclusion is that our simple scaling analysis suggests that the length scale √(λ*(D)l*(c)) accurately characterizes the double-layer structure of ionic liquids with strong electrostatic correlations where l*(c) is the electrostatic correlation length (in contrast, the Debye screening length λ*(D) is the primary double-layer length for electrolytes) and the response time of λ(D)(*3/2)L*/(D*l(c)(1/2)) (not λ*(D)L*/D* that is the primary charging time of electrolytes) is the correct charging time scale of ionic liquids with strong electrostatic correlations where D* is the diffusivity and L* is the separation length of the cell. With these two new scales, data of both electric potential versus distance from the electrode and the total diffuse charge versus time collapse onto each individual master curve in the presence of strong electrostatic correlations. In addition, the dependance of the total diffuse charge on steric effects, short-range correlations, and driving voltages is thoroughly examined. The results from the asymptotic analysis are compared favorably with those from full numerical simulations. Finally, the absorption of excess salt by the double layer creates a depletion region outside the double layer. Such salt depletion may bring a correction to the leading order terms and break down the weakly nonlinear analysis. A criterion which justifies the weakly nonlinear analysis is verified with numerical simulations.

Non-ionic iodinated contrast media related immediate reactions: A mechanism study of 27 patients.

PubMed

Zhai, Liqin; Guo, Xiangjie; Zhang, Haoyue; Jin, Qianqian; Zeng, Qiang; Tang, Xiaoxian; Gao, Cairong

2017-01-01

The underlying mechanism of non-ionic iodinated contrast media-related immediate reactions was evaluated in this study. Patients presenting at least grade II immediate reactions after non-ionic iodinated contrast media injection were enrolled. Basophil activation was evaluated by flow cytometry. The plasma concentration of human terminal complement complex SC5b-9, as well as concentrations of serum chymase, tryptase, human mast cell carboxypeptidase A3, human prostaglandin D2, and total IgE were measured by enzyme-linked immunosorbent assay. The basophil activation percentage was significantly higher in the study group than in the control group (17.94±21.06% vs 3.45±1.49%). The plasma concentration of human terminal complement complex SC5b-9 and concentrations of serum chymase, human mast cell carboxypeptidase A3, prostaglandin D2, tryptase, and total IgE were also significantly increased (236.99±318.21 vs 49.70±30.41ng/mL, 0.41±0.49 vs 0.09±0.06ng/mL, 1.17±0.67 vs 0.30±0.17ng/mL, 203.52±137.27 vs 102.28±48.72pg/mL, 3.81±0.22 vs 2.70±0.16ng/mL, 102.00±51.84 vs 19.97±2.75ng/mL, respectively). Both mast cells and basophils were activated in non-ionic iodinated contrast media to mediate immediate hypersensitivity, and mast cells may be involved. Different mechanisms, including IgE-dependent, complement-dependent, and direct membrane effects, contributed to mast cell and basophil activation. Individual patients may use a single or combined mechanism involving single or combined mast cells and basophils. Immediate reactions following non-ionic iodinated contrast media injection may be a mechanically heterogenous disease. Copyright © 2016. Published by Elsevier B.V.

Water dynamics at neutral and ionic interfaces

PubMed Central

Fenn, Emily E.; Wong, Daryl B.; Fayer, M. D.

2009-01-01

The orientational dynamics of water at a neutral surfactant reverse micelle interface are measured with ultrafast infrared spectroscopy of the hydroxyl stretch, and the results are compared to orientational relaxation of water interacting with an ionic interface. The comparison provides insights into the influence of a neutral vs. ionic interface on hydrogen bond dynamics. Measurements are made and analyzed for large nonionic surfactant Igepal CO-520reverse micelles (water nanopool with a 9-nm diameter). The results are compared with those from a previous study of reverse micelles of the same size formed with the ionic surfactant Aerosol-OT (AOT). The results demonstrate that the orientational relaxation times for interfacial water molecules in the two types of reverse micelles are very similar (13 ps for Igepal and 18 ps for AOT) and are significantly slower than that of bulk water (2.6 ps). The comparison of water orientational relaxation at neutral and ionic interfaces shows that the presence of an interface plays the dominant role in determining the hydrogen bond dynamics, whereas the chemical nature of the interface plays a secondary role. PMID:19706895

Some blood chemistry values for five Chesapeake Bay area fishes

USGS Publications Warehouse

Hunn, J.B.; Robinson, P.F.

1966-01-01

Blood samples from gizzard shad,largemouth bass, white perch, pumpkinseed, and toadfish were analyzed for hemoglobin, total plasma protein, total plasma cholesterol, and ion concentrations of plasma sodium, potassium, and chloride. The hemoglobin concentration and total plasma cholesterol found in a given species seem to have positive correlation with the customary activity level of that species. The plasma ionic concentrations in general agree with those found by other authors.

Nanoscale structure and morphology of sulfonated polyphenylenes via atomistic simulations

DOE PAGES

Abbott, Lauren J.; Frischknecht, Amalie L.

2017-01-23

We performed atomistic simulations on a series of sulfonated polyphenylenes systematically varying the degree of sulfonation and water content to determine their effect on the nanoscale structure, particularly for the hydrophilic domains formed by the ionic groups and water molecules. We found that the local structure around the ionic groups depended on the sulfonation and hydration levels, with the sulfonate groups and hydronium ions less strongly coupled at higher water contents. In addition, we characterized the morphology of the ionic domains employing two complementary clustering algorithms. At low sulfonation and hydration levels, clusters were more elongated in shape and poorlymore » connected throughout the system. As the degree of sulfonation and water content were increased, the clusters became more spherical, and a fully percolated ionic domain was formed. As a result, these structural details have important implications for ion transport.« less

Density and refractive index data of binary and ternary mixtures of imidazolium-based ionic liquids, n-hexane and organic compounds involved in the kinetic resolution of rac-2-pentanol.

PubMed

Montalbán, Mercedes G; Collado-González, Mar; Lozano-Pérez, A Abel; Baños, F Guillermo Díaz; Víllora, Gloria

2018-08-01

This data article is related to the subject of the research article "Extraction of Organic Compounds Involved in the Kinetic Resolution of rac-2-Pentanol from n-Hexane by Imidazolium-based Ionic Liquids: Liquid-Liquid Equilibrium" (Montalbán et al., 2018) [1]. It contains experimental data of density and refractive index of binary and ternary mixtures of imidazolium-based ionic liquids, n -hexane and organic compounds involved in the kinetic resolution of rac -2-pentanol ( rac -2-pentanol, vinyl butyrate, rac -2-pentyl butyrate or butyric acid) measured at 303.15 K and 1 atm. These data are presented as calibration curves which help to determine the composition of the ionic liquid-rich phase knowing its density or refractive index.

A rapid and simple pretreatment method for benzoylurea insecticides in honey samples using in-syringe dispersive liquid-liquid microextraction based on the direct solidification of ionic liquids.

PubMed

Wang, Huazi; Hu, Lu; Li, Wanzhen; Lu, Runhua; Zhang, Sanbing; Zhou, Wenfeng; Gao, Haixiang

2016-11-04

A pretreatment method using in-syringe dispersive liquid-liquid microextraction based on the direct solidification of ionic liquids before high performance liquid chromatography analysis was developed for the determination of benzoylurea insecticides (BUs) in honey samples. The hydrophobic ionic liquid [N 4444 ][PF 6 ], formed in situ by the hydrophilic ionic liquid [N 4444 ]Cl and the ion exchange reagent KPF 6 , was used to extract the target analytes. The entire extraction procedure was performed in a syringe. The extractant was solidified at room temperature and collected using a nylon membrane filter. This technique did not require a dispersive solvent, vortex mixer, ultrasound bath, or centrifugation. The parameters affecting the extraction efficiency were investigated through an experimental design. Under the optimal conditions, the limits of detection for the four BUs varied from 0.21 to 0.42μgL -1 in solution (2.1-4.2μgkg -1 in honey). Good linearities were obtained in the range of 2-300μgL -1 , with coefficients of determination greater than 0.999. The recoveries of the four BUs ranged from 80.94% to 84.59%. The intra-day (n=3) and inter-day (n=3) relative standard deviations were less than 5.08%. Finally, the proposed method was applied to the determination of BUs in commercial honey samples with satisfactory results. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of gold nanoparticles with different hydrophilic coatings via capillary electrophoresis and Taylor dispersion analysis. Part I: determination of the zeta potential employing a modified analytic approximation.

PubMed

Pyell, Ute; Jalil, Alaa H; Pfeiffer, Christian; Pelaz, Beatriz; Parak, Wolfgang J

2015-07-15

Taking gold nanoparticles with different hydrophilic coatings as an example, it is investigated whether capillary electrophoresis in combination with Taylor dispersion analysis allows for the precise determination of mean electrophoretic mobilities, electrophoretic mobility distributions, and zeta potentials in a matrix of exactly known composition and the calibration-free determination of number-weighted mean hydrodynamic radii. Our experimental data confirm that the calculation of the zeta potential for colloidal nanoparticles with ζ>25 mV requires to take the relaxation effect into account. Because of the requirement to avoid particle-wall interactions, a solution of disodiumtetraborate decahydrate (borax) in deionized water had been selected as suitable electrolyte. Measurements of the electrophoretic mobility at different ionic strength and application of the analytic approximation developed by Ohshima show that in the present case of a buffered solution with a weak electrolyte co-ion and a strong electrolyte counterion, the effective ionic drag coefficient should be approximated with the ionic drag coefficient of the counterion. The obtained results are in good agreement with theoretical expectations regarding the dependence of the zeta potential and the electrokinetic surface charge density on the ionic strength. We also show that Taylor dispersion analysis (besides estimation of the number-weighted mean hydrodynamic radius) provides additional information on the type and width of the number-weighted particle distribution. Copyright © 2015 Elsevier Inc. All rights reserved.

Protic ammonium carboxylate ionic liquids: insight into structure, dynamics and thermophysical properties by alkyl group functionalization.

PubMed

Reddy, Th Dhileep N; Mallik, Bhabani S

2017-04-19

This study is aimed at characterising the structure, dynamics and thermophysical properties of five alkylammonium carboxylate ionic liquids (ILs) from classical molecular dynamics simulations. The structural features of these ILs were characterised by calculating the site-site radial distribution functions, g(r), spatial distribution functions and structure factors. The structural properties demonstrate that ILs show greater interaction between cations and anions when alkyl chain length increases on the cation or anion. In all ILs, spatial distribution functions show that the anion is close to the acidic hydrogen atoms of the ammonium cation. We determined the role of alkyl group functionalization of the charged entities, cations and anions, in the dynamical behavior and the transport coefficients of this family of ionic liquids. The dynamics of ILs are described by studying the mean square displacement (MSD) of the centres of mass of the ions, diffusion coefficients, ionic conductivities and hydrogen bonds as well as residence dynamics. The diffusion coefficients and ionic conductivity decrease with an increase in the size of the cation or anion. The effect of alkyl chain length on ionic conductivity calculated in this article is consistent with the findings of other experimental studies. Hydrogen bond lifetimes and residence times along with structure factors were also calculated, and are related to alkyl chain length.

Isopiestic Determination of the Osmotic Coefficients of NaNO3 + Eu(NO3)3 + H2O at 298.15 K and Representation with an Extended Ion-Interaction (Pitzer) Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peter R. Zalupski; Rocklan McDowell; Simon L. Clegg

Isopiestic vapor pressures were measured at 298.15 K for aqueous NaNO3 + Eu(NO3)3 solutions, using NaCl(aq) as the reference standard. Measurements were made for both binary (single salt) solutions and for ternary solutions of the following NaNO3 ionic strength fractions: 0.05995, 0.08749, 0.16084, 0.27709, and 0.36313 over the water activity range 0.8951 = aw = 0.9832. (These ionic strength fractions correspond to NaNO3 molality fractions 0.27675, 0.36519, 0.53489, 0.69695, and 0.77381, respectively.) The results, and those of other studies for the two pure aqueous solutions, were used to determine the Pitzer model parameters for aqueous Eu(NO3)3 for molalities up tomore » 3 mol kg–1 and the two ternary (mixture) parameters ?Eu,Na = 0.367 ± 0.0035 and ?Eu,Na,NO3 = -0.0743 ± 0.0014. Some deviations of the measurements from the fitted model, of the order of +0.0075 in the osmotic coefficient, were noted for mixtures containing less than about 1 mol kg–1 total NO3–. The use of the mixture parameters in the Pitzer model yields predicted trace activity coefficients of Eu3+ in 1 mol kg–1 aqueous NaNO3 almost a factor of 2 greater than if they are omitted.« less

Ionic Vapor Composition in Critical and Supercritical States of Strongly Interacting Ionic Compounds.

PubMed

Chaban, Vitaly V; Prezhdo, Oleg V

2016-05-12

The critical point, CP (T, P), of the phase diagram quantifies the minimum amount of kinetic energy needed to prevent a substance from existing in a condensed phase. Therefore, the CP is closely related to the properties of the fluid far below the critical temperature. Approaches designed to predict thermophysical properties of a system necessarily aim to provide reliable estimates of the CP. Vice versa, CP estimation is impossible without knowledge of the vapor phase behavior. We report ab initio Born-Oppenheimer molecular dynamics (BOMD) simulations of sodium and potassium chlorides, NaCl and KCl, at and above their expected CPs. We advance the present knowledge regarding the existence of ionic species in the vapor phase by establishing significant percentages of atomic clusters: 29-30% in NaCl and 34-38% in KCl. A neutral pair of counterions is the most abundant cluster in the ionic vapors (ca. 35% of all vaporized ions exist in this form). Unexpectedly, an appreciable fraction of clusters is charged. The ionic vapor composition is determined by the vapor density, rather than the nature of the alkali ion. The previously suggested CPs of NaCl and KCl appear overestimated, based on the present simulations. The reported results offer essential insights into the ionic fluid properties and assist in development of thermodynamic theories. The ab initio BOMD method has been applied to investigate the vapor phase composition of an ionic fluid for the first time.

Determination of metal ions in tea samples using task-specific ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography with ultraviolet detection.

PubMed

Werner, Justyna

2016-04-01

Task-specific ionic liquid-based ultrasound-assisted dispersive liquid-liquid microextraction was used for the preconcentration of cadmium(II), cobalt(II), and lead(II) ions in tea samples, which were subsequently analyzed by liquid chromatography with UV detection. The proposed method of preconcentration is free of volatile organic compounds, which are often used as extractants and dispersing solvents in classic techniques of microextraction. A task-specific ionic liquid trioctylmethylammonium thiosalicylate was used as an extractant and a chelating agent. Ultrasound was used to disperse the ionic liquid. After microextraction, the phases were separated by centrifugation, and the ionic liquid phase was solubilized in methanol and directly injected into the liquid chromatograph. Selected microextraction parameters, such as the volume of ionic liquid, the pH of the sample, the duration of ultrasound treatment, the speed and time of centrifugation, and the effect of ionic strength, were optimized. Under optimal conditions an enrichment factor of 200 was obtained for each analyte. The limits of detection were 0.002 mg/kg for Cd(II), 0.009 mg/kg for Co(II), and 0.013 mg/kg for Pb(II). The accuracy of the proposed method was evaluated by an analysis of the Certified Reference Materials (INCT-TL-1, INCT-MPH-2) with the recovery values in the range of 90-104%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermoelectric Generators Based on Ionic Liquids

NASA Astrophysics Data System (ADS)

Laux, Edith; Uhl, Stefanie; Jeandupeux, Laure; López, Pilar Pérez; Sanglard, Pauline; Vanoli, Ennio; Marti, Roger; Keppner, Herbert

2018-03-01

Looking at energy harvesting using body or waste heat for portable electronic or on-board devices, Ionic liquids are interesting candidates as thermoactive materials in thermoelectric generators (TEGs) because of their outstanding properties. Two different kinds of ionic liquid, with alkylammonium and choline as cations, were studied, whereby different anions and redox couples were combined. This study focussed on the intention to find non-hazardous and environmentally friendly ionic liquids for TEGs to be selected among the thousands that can potentially be used. Seebeck coefficients (SEs) as high as - 15 mV/K were measured, in a particular case for an electrode temperature difference of 20 K. The bottleneck of our TEG device is still the abundance of negative SE liquids matching the internal resistance with the existing positive SE-liquids at series connections. In this paper, we show further progress in finding increased negative SE liquids. For current extraction from the TEG, the ionic liquid must be blended with a redox couple, allowing carrier exchange in a cyclic process under a voltage which is incuced by the asymmetry of the generator in terms of hot and cold electrodes. In our study, two types of redox pairs were tested. It was observed that a high SE of an ionic liquid/redox blend is not a sufficient condition for high power output. It appears that more complex effects between the ionic liquid and the electrode determine the magnitude of the final current/power output. The physico-chemical understanding of such a TEG cell is not yet available.

Thermoelectric Generators Based on Ionic Liquids

NASA Astrophysics Data System (ADS)

Laux, Edith; Uhl, Stefanie; Jeandupeux, Laure; López, Pilar Pérez; Sanglard, Pauline; Vanoli, Ennio; Marti, Roger; Keppner, Herbert

2018-06-01

Looking at energy harvesting using body or waste heat for portable electronic or on-board devices, Ionic liquids are interesting candidates as thermoactive materials in thermoelectric generators (TEGs) because of their outstanding properties. Two different kinds of ionic liquid, with alkylammonium and choline as cations, were studied, whereby different anions and redox couples were combined. This study focussed on the intention to find non-hazardous and environmentally friendly ionic liquids for TEGs to be selected among the thousands that can potentially be used. Seebeck coefficients (SEs) as high as - 15 mV/K were measured, in a particular case for an electrode temperature difference of 20 K. The bottleneck of our TEG device is still the abundance of negative SE liquids matching the internal resistance with the existing positive SE-liquids at series connections. In this paper, we show further progress in finding increased negative SE liquids. For current extraction from the TEG, the ionic liquid must be blended with a redox couple, allowing carrier exchange in a cyclic process under a voltage which is incuced by the asymmetry of the generator in terms of hot and cold electrodes. In our study, two types of redox pairs were tested. It was observed that a high SE of an ionic liquid/redox blend is not a sufficient condition for high power output. It appears that more complex effects between the ionic liquid and the electrode determine the magnitude of the final current/power output. The physico-chemical understanding of such a TEG cell is not yet available.

Elucidation of the effect of ionic liquid pretreatment on rice husk via structural analyses

PubMed Central

2012-01-01

Background In the present study, three ionic liquids, namely 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), and 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM]DEP), were used to partially dissolve rice husk, after which the cellulose were regenerated by the addition of water. The aim of the investigation is to examine the implications of the ionic liquid pretreatments on rice husk composition and structure. Results From the attenuated total reflectance Fourier transform-infrared (ATR FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, the regenerated cellulose were more amorphous, less crystalline, and possessed higher structural disruption compared with untreated rice husk. The major component of regenerated cellulose from [BMIM]Cl and [EMIM]DEP pretreatments was cellulose-rich material, while cellulose regenerated from [EMIM]OAc was a matrix of cellulose and lignin. Cellulose regenerated from ionic pretreatments could be saccharified via enzymatic hydrolysis, and resulted in relatively high reducing sugars yields, whereas enzymatic hydrolysis of untreated rice husk did not yield reducing sugars. Rice husk residues generated from the ionic liquid pretreatments had similar chemical composition and amorphousity to that of untreated rice husk, but with varying extent of surface disruption and swelling. Conclusions The structural architecture of the regenerated cellulose and rice husk residues showed that they could be used for subsequent fermentation or derivation of cellulosic compounds. Therefore, ionic liquid pretreatment is an alternative in the pretreatment of lignocellulosic biomass in addition to the conventional chemical pretreatments. PMID:22958710

Potential of Zero Charge and Its Temperature Derivative for Au(111) Electrode|Alkanethiol SAM|1.0 M Aqueous Electrolyte Solution Interfaces: Impact of Electrolyte Solution Ionic Strength and Its Effect on the Structure of the Modified Electrode|Electrolyte Solution Interface

DOE PAGES

Smalley, John F.

2017-04-06

In this study, we demonstrate how small and rapid temperature perturbations (produced by the indirect laser-induced temperature jump (ILIT) technique) of solid metal electrode|electrolyte solution interfaces may be used to determine the potential of zero (total) charge (E pzc) and its temperature derivativemore » $$\\left(\\frac{dEpzc}{dT}\\right)$$ of Au(111) electrode surfaces modified by alkanethiol self-assembled monolayers in contact with high ionic strength (i.e., 1.0 M) aqueous electrolyte solutions. The E pzc’s measured for two different types of SAMs (made from either HS(CH 2) n-1CH 3 (5 ≤ n ≤ 12, E pzc = -(0.99 ± 0.12) V vs SSCE) or HS(CH 2) nOH (3 ≤ n ≤ 16, E pzc = (0.46 ± 0.22) V vs SSCE)) are considerably different than those measured previously at much lower electrolyte solution ionic strengths. For mixed monolayers made from both HS(CH 2) n-1CH 3 and HS(CH 2) nFc (where Fc refers to ferrocene), the difference in Epzc decreases as a function of the surface concentration of the Fc moiety (i.e., [Fc]), and it completely disappears at a surprisingly small [Fc] (~4.0 × 10 –11 mol cm –2). These observations for the Au(111)|hydrophobic (neat and mixed) SAM|aqueous electrolyte solution interfaces, along with the surface potentials (g Sml(dip)) evaluated for the contacting electrolyte solution surfaces of these interfaces, are consistent with a structure for the water molecule components of these surfaces where there is a net orientation of the dipoles of these molecules. Accordingly, the negative (oxygen) ends of these molecules point toward the SAM surface. The positive values of g Sml(dip) evaluated for hydrophilic SAM (e.g., made from HS(CH 2) nOH)|aqueous electrolyte solution interfaces) also indicate that the structure of these interfaces is similar to that of the hydrophobic interfaces. However, g Sml(dip) decreases with increasing ionic strength for the hydrophilic interfaces, while it increases with increasing ionic strength for the hydrophobic interfaces. The data (and calculations) reported in the present work and other studies of hydrophobic (and hydrophilic)|aqueous solution interfaces are as yet insufficient to support a complete explanation for the effects of ionic strength observed in the present study. Nevertheless, an analysis based upon the value of $$\\left(\\frac{dEpzc}{dT}\\right)$$ (= (0.51 ± 0.12) mV/K, essentially the same for SAMs made from both HS(CH 2) n-1CH 3 and HS(CH 2) nOH), determined in the present study provides a further indication that upon formation of the SAM there is a partial charge transfer of electrons from the relevant gold atoms on the Au(111) surface to the sulfur atoms of the alkanethiols.« less

In situ metathesis reaction combined with liquid-phase microextraction based on the solidification of sedimentary ionic liquids for the determination of pyrethroid insecticides in water samples.

PubMed

Hu, Lu; Zhang, Panjie; Shan, Wanyu; Wang, Xuan; Li, Songqing; Zhou, Wenfeng; Gao, Haixiang

2015-11-01

A novel dispersion liquid-liquid microextraction method based on the solidification of sedimentary ionic liquids (SSIL-DLLME), in which an in situ metathesis reaction forms an ionic liquid (IL) extraction phase, was developed to determine four pyrethroid insecticides (i.e., permethrin, cyhalothrin, fenpropathrin, and transfluthrin) in water followed by separation using high-performance liquid chromatography. In the developed method, in situ DLLME was used to enhance the extraction efficiency and yield. After centrifugation, the extraction solvent, tributyldodecylphosphonium hexafluorophosphate ([P44412][PF6]), was easily collected by solidification in the bottom of the tube. The effects of various experimental parameters, the quantity of tributyldodecylphosphonium bromide ([P44412]Br), the molar ratio of [P44412]Br to potassium hexafluorophosphate (KPF6), the ionic strength, the temperature of the sample solution, and the centrifugation time, were optimized using a Plackett-Burman design to identify the significant factors that affected the extraction efficiency. These significant factors were then optimized using a central composite design. Under the optimized conditions, the recoveries of the four pyrethroid insecticides at four spiked levels ranged from 87.1% to 101.7%, with relative standard deviations (RSDs) ranging from 0.1% to 5.5%. At concentration levels between 1 and 500 µg/L, good linearity was obtained, with coefficients of determination greater than 0.9995. The limits of detection (LODs) for the four pyrethroid insecticides were in the range of 0.71-1.54 µg/L. The developed method was then successfully used for the determination of pyrethroid insecticides in environmental samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Product control by halide ions of ionic liquids in the ionothermal syntheses of Ni-(H)BTC metal-organic frameworks.

PubMed

Xu, Ling; Yan, Shihai; Choi, Eun-Young; Lee, Jin Yong; Kwon, Young-Uk

2009-06-21

Ni(OAc)(2)-H(3)BTC system in various ionic liquids, [RMI]X (R = ethyl, n-propyl, n-butyl; X = Cl, Br, I), produced five MOFs in two structure types; their relative thermodynamic stability varies with the size of RMI(+), and the X(-) ions govern the kinetic factors so that their combination effects determine the final product.

Application of the compensated Arrhenius formalism to self-diffusion: implications for ionic conductivity and dielectric relaxation.

PubMed

Petrowsky, Matt; Frech, Roger

2010-07-08

Self-diffusion coefficients are measured from -5 to 80 degrees C in a series of linear alcohols using pulsed field gradient NMR. The temperature dependence of these data is studied using a compensated Arrhenius formalism that assumes an Arrhenius-like expression for the diffusion coefficient; however, this expression includes a dielectric constant dependence in the exponential prefactor. Scaling temperature-dependent diffusion coefficients to isothermal diffusion coefficients so that the exponential prefactors cancel results in calculated energies of activation E(a). The exponential prefactor is determined by dividing the temperature-dependent diffusion coefficients by the Boltzmann term exp(-E(a)/RT). Plotting the prefactors versus the dielectric constant places the data on a single master curve. This procedure is identical to that previously used to study the temperature dependence of ionic conductivities and dielectric relaxation rate constants. The energies of activation determined from self-diffusion coefficients in the series of alcohols are strikingly similar to those calculated for the same series of alcohols from both dielectric relaxation rate constants and ionic conductivities of dilute electrolytes. The experimental results are described in terms of an activated transport mechanism that is mediated by relaxation of the solution molecules. This microscopic picture of transport is postulated to be common to diffusion, dielectric relaxation, and ionic transport.

Contact lens material characteristics associated with hydrogel lens dehydration.

PubMed

Ramamoorthy, Padmapriya; Sinnott, Loraine T; Nichols, Jason J

2010-03-01

To determine the association between material dehydration and hydrogel contact lens material characteristics, including water content and ionicity. Water content and refractive index data were derived from automated refractometry measurements of worn hydrogel contact lenses of 318 participants in the Contact Lens and Dry Eye Study (CLADES). Dehydration was determined in two ways; as the difference between nominal and measured (1) water content and (2) refractive index. Multiple regression models were used to examine the relation between dehydration and material characteristics, controlling for tear osmolality. The overall measured and nominal water content values were 52.58 +/- 7.49% and 56.88 +/- 7.81% respectively, while the measured and nominal refractive indices were 1.429 +/- 0.015 and 1.410 +/- 0.017. High water content and ionic hydrogel lens materials were associated with greater dehydration (p < 0.0001 for both) than low water content and non-ionic materials. When dehydration was assessed as the difference in refractive index, only high water content was associated with dehydration (p < 0.0001). High water content and ionic characteristics of hydrogel lens materials are associated with hydrogel lens dehydration, with the former being more strongly associated. Such dehydration changes could in turn lead to important clinical ramifications such as reduced oxygen transmissibility, greater lens adherence and reduced tear exchange.

Structure-activity relationship of the ionic cocrystal: 5-amino-2-naphthalene sulfonate·ammonium ions for pharmaceutical applications

NASA Astrophysics Data System (ADS)

Sangeetha, M.; Mathammal, R.

2018-02-01

The ionic cocrystals of 5-amino-2-naphthalene sulfonate · ammonium ions (ANSA-ṡNH4+) were grown under slow evaporation method and examined in detail for pharmaceutical applications. The crystal structure and intermolecular interactions were studied from the single X-ray diffraction analysis and the Hirshfeld surfaces. The 2D fingerprint plots displayed the inter-contacts possible in the ionic crystal. Computational DFT method was established to determine the structural, physical and chemical properties. The molecular geometries obtained from the X-ray studies were compared with the optimized geometrical parameters calculated using DFT/6-31 + G(d,p) method. The band gap energy calculated from the UV-Visible spectral analysis and the HOMO-LUMO energy gap are compared. The theoretical UV-Visible calculations helped in determining the type of electronic transition taking place in the title molecule. The maximum absorption bands and transitions involved in the molecule represented the drug reaction possible. Non-linear optical properties were characterized from SHG efficiency measurements experimentally and the NLO parameters are also calculated from the optimized structure. The reactive sites within the molecule are detailed from the MEP surface maps. The molecular docking studies evident the structure-activity of the ionic cocrystal for anti-cancer drug property.

Ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction and derivatization of sulfonamides in river water, honey, milk, and animal plasma.

PubMed

Xu, Xu; Su, Rui; Zhao, Xin; Liu, Zhuang; Zhang, Yupu; Li, Dan; Li, Xueyuan; Zhang, Hanqi; Wang, Ziming

2011-11-30

The ionic liquid-based microwave-assisted dispersive liquid-liquid microextraction (IL-based MADLLME) and derivatization was applied for the pretreatment of six sulfonamides (SAs) prior to the determination by high-performance liquid chromatography (HPLC). By adding methanol (disperser), fluorescamine solution (derivatization reagent) and ionic liquid (extraction solvent) into sample, extraction, derivatization, and preconcentration were continuously performed. Several experimental parameters, such as the type and volume of extraction solvent, the type and volume of disperser, amount of derivatization reagent, microwave power, microwave irradiation time, pH of sample solution, and ionic strength were investigated and optimized. When the microwave power was 240 W, the analytes could be derivatized and extracted simultaneously within 90 s. The proposed method was applied to the analysis of river water, honey, milk, and pig plasma samples, and the recoveries of analytes obtained were in the range of 95.0-110.8, 95.4-106.3, 95.0-108.3, and 95.7-107.7, respectively. The relative standard deviations varied between 1.5% and 7.3% (n=5). The results showed that the proposed method was a rapid, convenient and feasible method for the determination of SAs in liquid samples. Copyright © 2011 Elsevier B.V. All rights reserved.

Frontiers in poly(ionic liquid)s: syntheses and applications.

PubMed

Qian, Wenjing; Texter, John; Yan, Feng

2017-02-20

We review recent works on the synthesis and application of poly(ionic liquid)s (PILs). Novel chemical structures, different synthetic strategies and controllable morphologies are introduced as a supplement to PIL systems already reported. The primary properties determining applications, such as ionic conductivity, aqueous solubility, thermodynamic stability and electrochemical/chemical durability, are discussed. Furthermore, the near-term applications of PILs in multiple fields, such as their use in electrochemical energy materials, stimuli-responsive materials, carbon materials, and antimicrobial materials, in catalysis, in sensors, in absorption and in separation materials, as well as several special-interest applications, are described in detail. We also discuss the limitations of PIL applications, efforts to improve PIL physics, and likely future developments.

Sodium influxes in internally perfused squid giant axon during voltage clamp

PubMed Central

Atwater, I.; Bezanilla, F.; Rojas, E.

1969-01-01

1. An experimental method for measuring ionic influxes during voltage clamp in the giant axon of Dosidicus is described; the technique combines intracellular perfusion with a method for controlling membrane potential. 2. Sodium influx determinations were carried out while applying rectangular pulses of membrane depolarization. The ratio `measured sodium influx/computed ionic flux during the early current' is 0·92 ± 0·12. 3. Plots of measured sodium influx and computed ionic flux during the early current against membrane potential are very similar. There was evidence that the membrane potential at which the sodium influx vanishes is the potential at which the early current reverses. PMID:5767887

Structure and dynamics of biomembranes in room-temperature ionic liquid water solutions studied by neutron scattering and by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Benedetto, Antonio; Ballone, Pietro

2018-05-01

Increasing attention is being devoted to the interaction of a new class of organic ionic liquids known as room-temperature ionic liquids (RTILs) with biomolecules, partly because of health and environment concerns, and, even more, for the prospect of exciting new applications in biomedicine, sensing and energy technologies. Here we focus on the interaction between RTILs and phospholipid bilayers that are well-accepted models for bio-membranes. We discuss how neutron scattering has been used to probe both the structure and the dynamics of these systems, and how its integration with molecular dynamics simulation has allowed the determination of the microscopic details of their interaction.

Development of an ionic liquid-based ultrasonic-assisted liquid-liquid microextraction method for sensitive determination of biogenic amines: application to the analysis of octopamine, tyramine and phenethylamine in beer samples.

PubMed

Huang, Ke-Jing; Jin, Chun-Xue; Song, Shi-Lin; Wei, Cai-Yun; Liu, Yan-Ming; Li, Jing

2011-03-15

A simple and efficient method, ionic liquid-based ultrasound-assisted liquid-liquid microextraction, has been developed for the determination of three biogenic amines including octopamine (OCT), tyramine (TYR) and phenethylamine (PHE). Fluorescence probe 2,6-dimethyl-4-quinolinecarboxylic acid N-hydroxysuccinimide ester was applied for derivatization of biogenic amines and high-performance liquid chromatography coupled with fluorescence detection was used for the determination of the derivatives. The factors affecting the extraction efficiency, such as the type and volume of ionic liquid, ultrasonication time and centrifugation time have been investigated in detail. Under the optimum conditions, linearity of the method was observed in the range of 0.5-50 μgmL(-1) for OCT and TYR, and 0.025-2.5 μgmL(-1) for PHE, respectively, with correlation coefficients (γ)>0.996. The limits of detection ranged from 0.25-50 ngmL(-1) (S/N=3). The spiked recoveries of three target compounds in beer samples were in the range of 90.2-114%. As a result, this method has been successfully applied for the sensitive determination of OCT, TYR and PHE in beer samples. Copyright © 2011 Elsevier B.V. All rights reserved.

Calorimetric determination of the enthalpy of 1-butyl-3-methylimidazolium bromide synthesis: a key quantity in thermodynamics of ionic liquids.

PubMed

Paulechka, Yauheni U; Kabo, Andrey G; Blokhin, Andrey V

2009-11-05

The enthalpy of the 1-butyl-3-methylimidazolium bromide [C(4)mim]Br ionic liquid synthesis reaction 1-methylimidazole (liq) + 1-bromobutane (liq) --> [C(4)mim]Br (liq) was determined in a homemade small-volume isoperibol calorimeter to be Delta(r)H degrees (298) = -87.7 +/- 1.6 kJ x mol(-1). The activation energy for this reaction in a homogeneous system E(A) = 73 +/- 4 kJ x mol(-1) was found from the results of calorimetric measurements. The formation enthalpies for the crystalline and liquid [C(4)mim]Br were determined from the calorimetric data: Delta(f)H degrees (298)(cr) = -178 +/- 5 kJ x mol(-1) and Delta(f)H degrees (298)(liq) = -158 +/- 5 kJ x mol(-1). The ideal-gas formation enthalpy of this compound Delta(f)H degrees (298)(g) = 16 +/- 7 kJ x mol(-1) was calculated using the methods of quantum chemistry and statistical thermodynamics. The vaporization enthalpy of [C(4)mim]Br, Delta(vap)H degrees (298) = 174 +/- 9 kJ x mol(-1), was estimated from the experimental and calculated formation enthalpies. It was demonstrated that vapor pressure of this ionic liquid cannot be experimentally determined.

Improved thermodynamic model for interaction of EDTA with trivalent actinides and lanthanide to ionic strength of 6.60 m

NASA Astrophysics Data System (ADS)

Thakur, Punam; Xiong, Yongliang; Borkowski, Marian; Choppin, Gregory R.

2014-05-01

The dissociation constants of ethylenediaminetetraacetic acid (H4EDTA), and the stability constants of Am3+, Cm3+and Eu3+ with EDTA4- have been determined at 25 °C, over a range of concentration varying from 0.1 to 6.60 m NaClO4 using potentiometric titration and an extraction technique, respectively. The formation of only 1:1 complex, M(EDTA)-, where (M = Am3+, Cm3+ and Eu3+), was observed under the experimental conditions. The observed ionic strength dependencies of the dissociation constants and the stability constants have been described successfully over the entire ionic strength range using the Pitzer model. The thermodynamic stability constant: logβ1010=20.55±0.18 for Am3+, logβ1010=20.43±0.20 for Cm3+ and logβ1010=20.65±0.19 for Eu3+ were calculated by extrapolation of data to zero ionic strength in an NaClO4 medium. In addition, logβ1010 of 20.05 ± 0.40 for Am3+ was obtained by simultaneously modeling data both in NaCl and NaClO4 media. For all stability constants, the Pitzer model gives an excellent representation of the data using interaction parameters β(0), β(1), and Cϕ determined in this work. The improved model presented in this work would enable researchers to model accurately the potential mobility of actinides (III) and light rare earth elements to ionic strength of 6.60 m in low temperature environments in the presence of EDTA.

Solubility of alkali metal halides in the ionic liquid [C4C1im][OTf].

PubMed

Kuzmina, O; Bordes, E; Schmauck, J; Hunt, P A; Hallett, J P; Welton, T

2016-06-28

The solubilities of the metal halides LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbCl, CsCl, CsI, were measured at temperatures ranging from 298.15 to 378.15 K in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4C1im][OTf]). Li(+), Na(+) and K(+) salts with anions matching the ionic liquid have also been investigated to determine how well these cations dissolve in [C4C1im][OTf]. This study compares the influence of metal cation and halide anion on the solubility of salts within this ionic liquid. The highest solubility found was for iodide salts, and the lowest solubility for the three fluoride salts. There is no outstanding difference in the solubility of salts with matching anions in comparison to halide salts. The experimental data were correlated employing several phase equilibria models, including ideal mixtures, van't Hoff, the λh (Buchowski) equation, the modified Apelblat equation, and the non-random two-liquid model (NRTL). It was found that the van't Hoff model gave the best correlation results. On the basis of the experimental data the thermodynamic dissolution parameters (ΔH, ΔS, and ΔG) were determined for the studied systems together with computed gas phase metathesis parameters. Dissolution depends on the energy difference between enthalpies of fusion and dissolution of the solute salt. This demonstrates that overcoming the lattice energy of the solid matrix is the key to the solubility of inorganic salts in ionic liquids.

Determination of heat capacity of ionic liquid based nanofluids using group method of data handling technique

NASA Astrophysics Data System (ADS)

Sadi, Maryam

2018-01-01

In this study a group method of data handling model has been successfully developed to predict heat capacity of ionic liquid based nanofluids by considering reduced temperature, acentric factor and molecular weight of ionic liquids, and nanoparticle concentration as input parameters. In order to accomplish modeling, 528 experimental data points extracted from the literature have been divided into training and testing subsets. The training set has been used to predict model coefficients and the testing set has been applied for model validation. The ability and accuracy of developed model, has been evaluated by comparison of model predictions with experimental values using different statistical parameters such as coefficient of determination, mean square error and mean absolute percentage error. The mean absolute percentage error of developed model for training and testing sets are 1.38% and 1.66%, respectively, which indicate excellent agreement between model predictions and experimental data. Also, the results estimated by the developed GMDH model exhibit a higher accuracy when compared to the available theoretical correlations.

Quantitative Determination on Ionic-Liquid-Gating Control of Interfacial Magnetism

DOE PAGES

Zhao, Shishun; Zhou, Ziyao; Peng, Bin; ...

2017-03-03

Ionic-liquid gating on a functional thin film with a low voltage has drawn a lot of attention due to rich chemical, electronic, and magnetic phenomena at the interface. A key challenge in quantitative determination of voltage-controlled magnetic anisotropy (VCMA) in Au/[DEME] +[TFSI] -/Co field-effect transistor heterostructures is addressed. The magnetic anisotropy change as response to the gating voltage is precisely detected by in situ electron spin resonance measurements. Furthermore, a reversible change of magnetic anisotropy up to 219 Oe is achieved with a low gating voltage of 1.5 V at room temperature, corresponding to a record high VCMA coefficient ofmore » ≈146 Oe V -1. Two gating effects, the electrostatic doping and electrochemical reaction, are distinguished at various gating voltage regions, as confirmed by X-ray photoelectron spectroscopy and atomic force microscopy experiments. Our work shows a unique ionic-liquid-gating system for strong interfacial magnetoelectric coupling with many practical advantages, paving the way toward ion-liquid-gating spintronic/electronic devices.« less

Quantitative Determination on Ionic-Liquid-Gating Control of Interfacial Magnetism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shishun; Zhou, Ziyao; Peng, Bin

Ionic-liquid gating on a functional thin film with a low voltage has drawn a lot of attention due to rich chemical, electronic, and magnetic phenomena at the interface. A key challenge in quantitative determination of voltage-controlled magnetic anisotropy (VCMA) in Au/[DEME] +[TFSI] -/Co field-effect transistor heterostructures is addressed. The magnetic anisotropy change as response to the gating voltage is precisely detected by in situ electron spin resonance measurements. Furthermore, a reversible change of magnetic anisotropy up to 219 Oe is achieved with a low gating voltage of 1.5 V at room temperature, corresponding to a record high VCMA coefficient ofmore » ≈146 Oe V -1. Two gating effects, the electrostatic doping and electrochemical reaction, are distinguished at various gating voltage regions, as confirmed by X-ray photoelectron spectroscopy and atomic force microscopy experiments. Our work shows a unique ionic-liquid-gating system for strong interfacial magnetoelectric coupling with many practical advantages, paving the way toward ion-liquid-gating spintronic/electronic devices.« less

Can the scaling behavior of electric conductivity be used to probe the self-organizational changes in solution with respect to the ionic liquid structure? The case of [C8MIM][NTf2].

PubMed

Paluch, Marian; Wojnarowska, Zaneta; Goodrich, Peter; Jacquemin, Johan; Pionteck, Jürgen; Hensel-Bielowka, Stella

2015-08-28

Electrical conductivity of the supercooled ionic liquid [C8MIM][NTf2], determined as a function of temperature and pressure, highlights strong differences in its ionic transport behavior between low and high temperature regions. To date, the crossover effect which is very well known for low molecular van der Waals liquids has been rarely described for classical ionic liquids. This finding highlights that the thermal fluctuations could be dominant mechanisms driving the dramatic slowing down of ion motions near Tg. An alternative way to analyze separately low and high temperature dc-conductivity data using a density scaling approach was then proposed. Based on which a common value of the scaling exponent γ = 2.4 was obtained, indicating that the applied density scaling is insensitive to the crossover effect. By comparing the scaling exponent γ reported herein along with literature data for other ionic liquids, it appears that γ decreases by increasing the alkyl chain length on the 1-alkyl-3-methylimidazolium-based ionic liquids. This observation may be related to changes in the interaction between ions in solution driven by an increase in the van der Waals type interaction by increasing the alkyl chain length on the cation. This effect may be related to changes in the ionic liquid nanostructural organization with the alkyl chain length on the cation as previously reported in the literature based on molecular dynamic simulations. In other words, the calculated scaling exponent γ may be then used as a key parameter to probe the interaction and/or self-organizational changes in solution with respect to the ionic liquid structure.

Toxicity prediction of ionic liquids based on Daphnia magna by using density functional theory

NASA Astrophysics Data System (ADS)

Nu’aim, M. N.; Bustam, M. A.

2018-04-01

By using a model called density functional theory, the toxicity of ionic liquids can be predicted and forecast. It is a theory that allowing the researcher to have a substantial tool for computation of the quantum state of atoms, molecules and solids, and molecular dynamics which also known as computer simulation method. It can be done by using structural feature based quantum chemical reactivity descriptor. The identification of ionic liquids and its Log[EC50] data are from literature data that available in Ismail Hossain thesis entitled “Synthesis, Characterization and Quantitative Structure Toxicity Relationship of Imidazolium, Pyridinium and Ammonium Based Ionic Liquids”. Each cation and anion of the ionic liquids were optimized and calculated. The geometry optimization and calculation from the software, produce the value of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). From the value of HOMO and LUMO, the value for other toxicity descriptors were obtained according to their formulas. The toxicity descriptor that involves are electrophilicity index, HOMO, LUMO, energy gap, chemical potential, hardness and electronegativity. The interrelation between the descriptors are being determined by using a multiple linear regression (MLR). From this MLR, all descriptors being analyzed and the descriptors that are significant were chosen. In order to develop the finest model equation for toxicity prediction of ionic liquids, the selected descriptors that are significant were used. The validation of model equation was performed with the Log[EC50] data from the literature and the final model equation was developed. A bigger range of ionic liquids which nearly 108 of ionic liquids can be predicted from this model equation.

Surface adsorption of oppositely charged C14TAB-PAMPS mixtures at the air/water interface and the impact on foam film stability.

PubMed

Fauser, Heiko; von Klitzing, Regine; Campbell, Richard A

2015-01-08

We have studied the oppositely charged polyelectrolyte/surfactant mixture of poly(acrylamidomethylpropanesulfonate) sodium salt (PAMPS) and tetradecyl trimethylammonium bromide (C14TAB) using a combination of neutron reflectivity and ellipsometry measurements. The interfacial composition was determined using three different analysis methods involving the two techniques for the first time. The bulk surfactant concentration was fixed at a modest value while the bulk polyelectrolyte concentration was varied over a wide range. We reveal complex changes in the surface adsorption behavior. Mixtures with low bulk PAMPS concentrations result in the components interacting synergistically in charge neutral layers at the air/water interface. At the bulk composition where PAMPS and C14TAB are mixed in an equimolar charge ratio in the bulk, we observe a dramatic drop in the surfactant surface excess to leave a large excess of polyelectrolyte at the interface, which we infer to have loops in its interfacial structure. Further increase of the bulk PAMPS concentration leads to a more pronounced depletion of material from the surface. Mixtures containing a large excess of PAMPS in the bulk showed enhanced adsorption, which is attributed to the large increase in total ionic strength of the system and screening of the surfactant headgroup charges. The data are compared to our former results on PAMPS/C14TAB mixtures [Kristen et al. J. Phys. Chem. B, 2009, 23, 7986]. A peak in the surface tension is rationalized in terms of the changing surface adsorption and, unlike in more concentrated systems, is unrelated to bulk precipitation. Also, a comparison between the determined interfacial composition with zeta potential and foam film stability data shows that the highest film stability occurs when there is enhanced synergistic adsorption of both components at the interface due to charge screening when the total ionic strength of the system is highest. The additional contribution to the foam stability of the negatively charged polyelectrolyte within the film bulk is also discussed.

Highly integrated autonomous lab-on-a-chip device for on-line and in situ determination of environmental chemical parameters.

PubMed

Martinez-Cisneros, Cynthia; da Rocha, Zaira; Seabra, Antonio; Valdés, Francisco; Alonso-Chamarro, Julián

2018-06-05

The successful integration of sample pretreatment stages, sensors, actuators and electronics in microfluidic devices enables the attainment of complete micro total analysis systems, also known as lab-on-a-chip devices. In this work, we present a novel monolithic autonomous microanalyzer that integrates microfluidics, electronics, a highly sensitive photometric detection system and a sample pretreatment stage consisting on an embedded microcolumn, all in the same device, for on-line determination of relevant environmental parameters. The microcolumn can be filled/emptied with any resin or powder substrate whenever required, paving the way for its application to several analytical processes: separation, pre-concentration or ionic-exchange. To promote its autonomous operation, avoiding issues caused by bubbles in photometric detection systems, an efficient monolithic bubble removal structure was also integrated. To demonstrate its feasibility, the microanalyzer was successfully used to determine nitrate and nitrite in continuous flow conditions, providing real time and continuous information.

Determination of ionic abundances in the Io torus using the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Moos, H. W.; Feldman, P. D.; Durrance, S. T.; Blair, W. P.; Bowers, C. W.; Davidsen, A. F.; Dixon, W. V.; Henry, R. C.; Ferguson, H. C.; Kimble, R. A.

1991-01-01

Attention is given to a 415-1864-A spectrum of the emissions from the Io torus with about 3-A resolution in first order (830-1864 A) obtained with HUT in December 1990. A list of the 31 strongest features shows that, apart from five features that are totally or partially terrestrial, all are due to O(+), S(+), S(2+), and S(3+). There is no evidence for elements other than oxygen and sulfur. The spectrum shows many additional weaker emission features so that the existence of minor species cannot be ruled out at this time. Because the HUT spectrum contains well-resolved lines for all four of the major species, the mixing ratio (Ni/ne) for each one can be determined without using models of the spectral emissions, or a detailed geometric model of the torus plasma. The relative concentration of O(+) determined from the HUT observation is 38 percent less than that obtained from the Voyager UVS data.

Constant fields and constant gradients in open ionic channels.

PubMed Central

Chen, D P; Barcilon, V; Eisenberg, R S

1992-01-01

Ions enter cells through pores in proteins that are holes in dielectrics. The energy of interaction between ion and charge induced on the dielectric is many kT, and so the dielectric properties of channel and pore are important. We describe ionic movement by (three-dimensional) Nemst-Planck equations (including flux and net charge). Potential is described by Poisson's equation in the pore and Laplace's equation in the channel wall, allowing induced but not permanent charge. Asymptotic expansions are constructed exploiting the long narrow shape of the pore and the relatively high dielectric constant of the pore's contents. The resulting one-dimensional equations can be integrated numerically; they can be analyzed when channels are short or long (compared with the Debye length). Traditional constant field equations are derived if the induced charge is small, e.g., if the channel is short or if the total concentration gradient is zero. A constant gradient of concentration is derived if the channel is long. Plots directly comparable to experiments are given of current vs voltage, reversal potential vs. concentration, and slope conductance vs. concentration. This dielectric theory can easily be tested: its parameters can be determined by traditional constant field measurements. The dielectric theory then predicts current-voltage relations quite different from constant field, usually more linear, when gradients of total concentration are imposed. Numerical analysis shows that the interaction of ion and channel can be described by a mean potential if, but only if, the induced charge is negligible, that is to say, the electric field is spatially constant. Images FIGURE 1 PMID:1376159

Electrochemical determination of hydroquinone using hydrophobic ionic liquid-type carbon paste electrodes

PubMed Central

2010-01-01

Three types of carbon paste electrodes (CPEs) with different liquid binders were fabricated, and their electrochemical behavior was characterized via a potassium hexacyanoferrate(II) probe. 1-Octyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) as a hydrophobic conductive pasting binder showed better electrochemical performance compared with the commonly employed binder. The IL-contained CPEs demonstrated excellent electroactivity for oxidation of hydroquinone. A diffusion control mechanism was confirmed and the diffusion coefficient (D) of 5.05 × 10-4 cm2 s-1 was obtained. The hydrophobic IL-CPE is promising for the determination of hydroquinone in terms of high sensitivity, easy operation, and good durability. PMID:20977733

Determination of trace mercury in water based on N-octylpyridinium ionic liquids preconcentration and stripping voltammetry.

PubMed

Li, Zhenhan; Xia, Shanhong; Wang, Jinfen; Bian, Chao; Tong, Jianhua

2016-01-15

A novel method for determination of trace mercury in water is developed. The method is performed by extracting mercury firstly with ionic liquids (ILs) and then detecting the concentration of mercury in organic media with anodic stripping voltammetry. Liquid-liquid extraction of mercury(II) ions by four ionic liquids with N-octylpyridinium cations ([OPy](+)) was studied. N-octylpyridinium tetrafluoroborate and N-octylpyridinium trifluoromethylsulfonate were found to be efficient and selective extractant for mercury. Temperature controlled dispersive liquid phase microextraction (TC-DLPME) technique was utilized to improve the performance of preconcentration. After extraction, precipitated IL was diluted by acetonitrile buffer and mercury was detected by differential pulse stripping voltammetry (DPSV) with gold disc electrode. Mercury was enriched by 17 times while interfering ions were reduced by two orders of magnitude in the organic media under optimum condition. Sensitivity and selectivity for electrochemical determination of mercury were improved by using the proposed method. Tap, pond and waste water samples were analyzed with recoveries ranging from 81% to 107% and detection limit of 0.05 μg/L. Copyright © 2015 Elsevier B.V. All rights reserved.

Binding in alkali and alkaline-earth tetrahydroborates: Special position of magnesium tetrahydroborate

NASA Astrophysics Data System (ADS)

Łodziana, Zbigniew; van Setten, Michiel J.

2010-01-01

Compounds of light elements and hydrogen are currently extensively studied due to their potential application in the field of hydrogen or energy storage. A number of new interesting tetrahydroborates that are especially promising due to their very high gravimetric hydrogen content were recently reported. However, the determination and understanding of their complex crystalline structures has created considerable debate. Metal tetrahydroborates, in general, form a large variety of structures ranging from simple for NaBH4 to very complex for Mg(BH4)2 . Despite the extensive discussion in the literature no clear explanation has been offered for this variety so far. In this paper we analyze the structural and electronic properties of a broad range of metal tetrahydroborates and reveal the factors that determine their structure: ionic bonding, the orientation of the BH4 groups, and the coordination number of the metal cation. We show, in a simple way, that the charge transfer in the metal tetrahydroborates rationally explains the structural diversity of these compounds. Being ionic systems, the metal tetrahydroborates fall into the classification of Linus Pauling. By using the ionic radius for the BH4 group as determined in this paper, this allows for structural predictions for new and mixed compounds.

Preparation of porous aromatic framework/ionic liquid hybrid composite coated solid-phase microextraction fibers and their application in the determination of organochlorine pesticides combined with GC-ECD detection.

PubMed

Wu, Mingxue; Chen, Gang; Liu, Ping; Zhou, Weihong; Jia, Qiong

2016-01-07

A novel hybrid material incorporating porous aromatic frameworks and an ionic liquid, 1-(triethoxy silyl)propyl-3-aminopropyl imidazole hexafluorophosphate, was prepared as solid-phase microextraction coating and employed for the extraction of organochlorine pesticides. Combining the advantages of porous aromatic frameworks and an ionic liquid, the fiber exhibited a high adsorption capacity for organochlorine pesticides. Under optimized experimental conditions, enhancement factors of 247-1696 were obtained with good linearity in the range of 1-500 μg L(-1). The detection limits and quantification limits were determined to be in the range of 0.11-0.29 μg L(-1) and 0.35-0.93 μg L(-1). The relative standard deviations for six replicates of organochlorine pesticides were in the range of 4.4%-7.2% and 5.7%-10.1% for one fiber and fiber-to-fiber, respectively. By coupling with a gas chromatography-electron capture detector, the novel fiber was successfully used for the determination of organochlorine pesticides in juice and milk samples with recoveries of 76.1%-121.3%.

Enhancement of force generated by individual myosin heads in skinned rabbit psoas muscle fibers at low ionic strength.

PubMed

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca(2+)-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca(2+)-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca(2+)-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca(2+) activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca(2+)-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca(2+)-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction.

The Relation between Vaporization Enthalpies and Viscosities: Eyring's Theory Applied to Selected Ionic Liquids.

PubMed

Bonsa, Anne-Marie; Paschek, Dietmar; Zaitsau, Dzmitry H; Emel'yanenko, Vladimir N; Verevkin, Sergey P; Ludwig, Ralf

2017-05-19

Key properties for the use of ionic liquids as electrolytes in batteries are low viscosities, low vapor pressure and high vaporization enthalpies. Whereas the measurement of transport properties is well established, the determination of vaporization enthalpies of these extremely low volatile compounds is still a challenge. At a first glance both properties seem to describe different thermophysical phenomena. However, eighty years ago Eyring suggested a theory which related viscosities and vaporization enthalpies to each other. The model is based on Eyring's theory of absolute reaction rates. Recent attempts to apply Eyring's theory to ionic liquids failed. The motivation of our study is to show that Eyring's theory works, if the assumptions specific for ionic liquids are fulfilled. For that purpose we measured the viscosities of three well selected protic ionic liquids (PILs) at different temperatures. The temperature dependences of viscosities were approximated by the Vogel-Fulcher-Tamann (VFT) relation and extrapolated to the high-temperature regime up to 600 K. Then the VFT-data could be fitted to the Eyring-model. The values of vaporization enthalpies for the three selected PILs predicted by the Eyring model have been very close to the experimental values measured by well-established techniques. We conclude that the Eyring theory can be successfully applied to the chosen set of PILs, if the assumption that ionic pairs of the viscous flow in the liquid and the ionic pairs in the gas phase are similar is fulfilled. It was also noticed that proper transfer of energies can be only derived if the viscosities and the vaporization energies are known for temperatures close to the liquid-gas transition temperature. The idea to correlate easy measurable viscosities of ionic liquids with their vaporization enthalpies opens a new way for a reliable assessment of these thermodynamic properties for a broad range of ionic liquids. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Molten Bis(trifluoromethylsulfonyl)amide Salts: Effects of Cation Species.

PubMed

Kakinuma, Shohei; Shirota, Hideaki

2018-05-25

In this study, we have investigated the effects of cation structures on the temperature dependence of the intermolecular vibrational dynamics of ionic liquids using femtosecond Raman-induced Kerr effect spectroscopy. The ionic liquids used in this study are bis(trifluoromethylsulfonyl)amide [NTf 2 ] - salts of the cations 1-butyl-3-methylimidazolium [C 4 MIm] + , 1-butyl-1-methylpyrrolidinium [Pyrr 14 ] + , 1-butylpyridinium [C 4 Py] + , butyldiethylmethylammonium [N 1224 ] + , triethyloctylammonium [N 2228 ] + , and triethyloctylphosphonium [P 2228 ] + . All of the ionic liquids show temperature-dependent low-frequency spectra. A difference in the temperature dependence between the spectra of the aromatic and nonaromatic cation based ionic liquids is especially significant. In the case of the aromatic cation based ionic liquids [C 4 MIm][NTf 2 ] and [C 4 Py][NTf 2 ], the spectral intensities in the low-frequency region below ca. 50 cm -1 increase and the high-frequency components at ca. 80 cm -1 shift to lower frequencies with rising temperature. In contrast, the ionic liquids based on nonaromatic cations only exhibit an increase in the low-frequency region below ca. 50 cm -1 with increasing temperature, while the high-frequency region of the spectra above ca. 50 cm -1 shows little change with variation of the temperature. These results suggest that the presence or absence of aromatic rings is the main factor in determining the temperature-dependent spectral features, particularly in the high-frequency region. We also found that the alkyl chain length and central atoms of the nonaromatic quaternary cations do not have much influence on the temperature-dependent spectral features. The first moments of the aromatic cation based ionic liquids are a little more sensitive to temperature than those of the nonaromatic cation based ionic liquids. The temperature-dependent viscosities and fragilities of the ionic liquids have also been examined.

Mobilization of natural colloids from an iron oxide-coated sand aquifer--Effect of pH and ionic strength

USGS Publications Warehouse

Bunn, Rebecca A.; Magelky, Robin D.; Ryan, Joseph N.; Elimelech, Menachem

2002-01-01

Field and laboratory column experiments were performed to assess the effect of elevated pH and reduced ionic strength on the mobilization of natural colloids in a ferric oxyhydroxide-coated aquifer sediment. The field experiments were conducted as natural gradient injections of groundwater amended by sodium hydroxide additions. The laboratory experiments were conducted in columns of undisturbed, oriented sediments and disturbed, disoriented sediments. In the field, the breakthrough of released colloids coincided with the pH pulse breakthrough and lagged the bromide tracer breakthrough. The breakthrough behavior suggested that the progress of the elevated pH front controlled the transport of the mobilized colloids. In the laboratory, about twice as much colloid release occurred in the disturbed sediments as in the undisturbed sediments. The field and laboratory experiments both showed that the total mass of colloid release increased with increasing pH until the concurrent increase in ionic strength limited release. A decrease in ionic strength did not mobilize significant amounts of colloids in the field. The amount of colloids released normalized to the mass of the sediments was similar for the field and the undisturbed laboratory experiments.

Isothermal transport properties and majority-type defects of BaCo(0.70)Fe(0.22)Nb(0.08)O(3-δ).

PubMed

Lee, Taewon; Cho, Deok-Yong; Kwon, Hyung-Soon; Yoo, Han-Ill

2015-01-28

(Ba,Sr)(Co,Fe)O3-δ based mixed conducting oxides, e.g. (Ba0.5Sr0.5)(Co1-xFex)O3-δ and Ba(Co0.7Fe0.3-xNbx)O3-δ, are promising candidates for oxygen permeable membranes and SOFC cathodes due to their excellent ambipolar conductivities. Despite these excellent properties, however, their mass/charge transport properties have not been fully characterized and hence, their defect structure has not been clearly elucidated. Until now, the majority types of ionic and electronic defects have been regarded as oxygen vacancies and localized holes. Holes, whether localized or not, are acceptable as majority electronic carriers on the basis of the as-measured total conductivity, which is essentially electronic, and electronic thermopower. On the other hand, the proposal of oxygen vacancies as majority ionic carriers lacks solid evidence. In this work, we document all the isothermal transport properties of Ba(Co0.70Fe0.22Nb0.08)O3-δ in terms of a 2 × 2 Onsager transport coefficient matrix and its steady-state electronic thermopower against oxygen activity at elevated temperatures, and determine the valences of Co and Fe via soft X-ray absorption spectroscopy. It turns out that the ionic and electronic defects in majority should be oxygen interstitials and at least two kinds of holes, one free and the other trapped. Furthermore, the lattice molecule should be Ba(Co0.7Fe0.3-xNbx)O2+δ, not Ba(Co0.7Fe0.3-xNbx)O3-δ, to be consistent with all the results observed.

Rotational and translational dynamics and their relation to hydrogen bond lifetimes in an ionic liquid by means of NMR relaxation time experiments and molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Strate, Anne; Neumann, Jan; Overbeck, Viviane; Bonsa, Anne-Marie; Michalik, Dirk; Paschek, Dietmar; Ludwig, Ralf

2018-05-01

We report a concerted theoretical and experimental effort to determine the reorientational dynamics as well as hydrogen bond lifetimes for the doubly ionic hydrogen bond +OH⋯O- in the ionic liquid (2-hydroxyethyl)trimethylammonium bis(trifluoromethylsulfonyl)imide [Ch][NTf2] by using a combination of NMR relaxation time experiments, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. Due to fast proton exchange, the determination of rotational correlation times is challenging. For molecular liquids, 17O-enhanced proton relaxation time experiments have been used to determine the rotational correlation times for the OH vectors in water or alcohols. As an alternative to those expensive isotopic substitution experiments, we employed a recently introduced approach which is providing access to the rotational dynamics from a single NMR deuteron quadrupolar relaxation time experiment. Here, the deuteron quadrupole coupling constants (DQCCs) are obtained from a relation between the DQCC and the δ1H proton chemical shifts determined from a set of DFT calculated clusters in combination with experimentally determined proton chemical shifts. The NMR-obtained rotational correlation times were compared to those obtained from MD simulations and then related to viscosities for testing the applicability of popular hydrodynamic models. In addition, hydrogen bond lifetimes were derived, using hydrogen bond population correlation functions computed from MD simulations. Here, two different time domains were observed: The short-time contributions to the hydrogen lifetimes and the reorientational correlation times have roughly the same size and are located in the picosecond range, whereas the long-time contributions decay with relaxation times in the nanosecond regime and are related to rather slow diffusion processes. The computed average hydrogen bond lifetime is dominated by the long-time process, highlighting the importance and longevity of hydrogen-bonded ion pairs in these ionic liquids.

Microwave-assisted ionic liquid homogeneous liquid-liquid microextraction coupled with high performance liquid chromatography for the determination of anthraquinones in Rheum palmatum L.

PubMed

Wang, Zhibing; Hu, Jianxue; Du, Hongxia; He, Shuang; Li, Qing; Zhang, Hanqi

2016-06-05

The microwave-assisted ionic liquid homogeneous liquid-liquid microextraction (MA-IL-HLLME) coupled with high performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of anthraquinones, including aloe-emodin, emodin, chrysophanol and physcion in root of Rheum palmatum L. Several experimental parameters influencing the extraction efficiency, including amount of sample, type and volume of ionic liquid, volume and pH value of extraction medium, microwave power and extraction time, concentration of NH4PF6 as well as centrifugal condition were optimized. When 140μL of ionic liquid ([C8MIM][BF4]) was used as an extraction solvent, target analytes can be extracted from sample matrix in one minute with the help of microwave irradiation. The MA-IL-HLLME is simple and quick. The calibration curves exhibited good linear relationship (r>0.9984). The limits of detection and quantification were in the range of 0.015-0.026 and 0.051-0.088μgmL(-1), respectively. The spiked recovery for each analyte was in the range of 81.13-93.07% with relative standard deviations lower than 6.89%. The present method is free of volatile organic solvents, and represents lower expenditures of sample, extraction time and solvent, compared with ultrasonic and heat reflux extraction. The results indicated that the present method can be successfully applied to the determination of anthraquinones in medicinal plant. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantum dots and ionic liquid-sensitized effect as an efficient and green catalyst for the sensitive determination of glucose.

PubMed

Azizi, Seyed Naser; Chaichi, Mohammad Javad; Shakeri, Parmis; Bekhradnia, Ahmadreza

2015-07-05

A novel fluorescence (FL) method using water-soluble CdSe quantum dots (QDs) is proposed for the fluorometric determination of hydrogen peroxide and glucose. Water-soluble CdSe QDs were synthesized by using thioglycolic acid as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy and transmission electron microscope (TEM). Ionic liquid-sensitized effect in aqueous solution was then investigated. In the presence of ionic liquid as catalyst, H2O2 was decomposed into radical that could quench the fluorescence of CdSe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdSe QDs by H2O2 producer with ionic liquid catalyst, which can be used to detect glucose. Therefore, a new FL analysis system was developed for the determination of glucose. Under the optimum conditions, there is a good linear relationship between the relative PL emission intensity and the concentration of glucose in the range of 5.0×10(-7)-1.0×10(-4) M of glucose with a correlation coefficient (R(2)) of 0.9973. The limit of detection of this system was found to be 1.0×10(-7) M. This method is not only simple, sensitive and low cost, but also reliable for practical applications. Copyright © 2015. Published by Elsevier B.V.

Microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid for the determination of sulfonamides in environmental water samples.

PubMed

Song, Ying; Wu, Lijie; Lu, Chunmei; Li, Na; Hu, Mingzhu; Wang, Ziming

2014-12-01

An easy, quick, and green method, microwave-assisted liquid-liquid microextraction based on solidification of ionic liquid, was first developed and applied to the extraction of sulfonamides in environmental water samples. 1-Ethy-3-methylimidazolium hexafluorophosphate, which is a solid-state ionic liquid at room temperature, was used as extraction solvent in the present method. After microwave irradiation for 90 s, the solid-state ionic liquid was melted into liquid phase and used to finish the extraction of the analytes. The ionic liquid and sample matrix can be separated by freezing and centrifuging. Several experimental parameters, including amount of extraction solvent, microwave power and irradiation time, pH of sample solution, and ionic strength, were investigated and optimized. Under the optimum experimental conditions, good linearity was observed in the range of 2.00-400.00 μg/L with the correlation coefficients ranging from 0.9995 to 0.9999. The limits of detection for sulfathiazole, sulfachlorpyridazine, sulfamethoxazole, and sulfaphenazole were 0.39, 0.33, 0.62, and 0.85 μg/L, respectively. When the present method was applied to the analysis of environmental water samples, the recoveries of the analytes ranged from 75.09 to 115.78% and relative standard deviations were lower than 11.89%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Counterion-induced swelling of ionic microgels

NASA Astrophysics Data System (ADS)

Denton, Alan R.; Tang, Qiyun

2016-10-01

Ionic microgel particles, when dispersed in a solvent, swell to equilibrium sizes that are governed by a balance between electrostatic and elastic forces. Tuning of particle size by varying external stimuli, such as pH, salt concentration, and temperature, has relevance for drug delivery, microfluidics, and filtration. To model swelling of ionic microgels, we derive a statistical mechanical theorem, which proves exact within the cell model, for the electrostatic contribution to the osmotic pressure inside a permeable colloidal macroion. Applying the theorem, we demonstrate how the distribution of counterions within an ionic microgel determines the internal osmotic pressure. By combining the electrostatic pressure, which we compute via both Poisson-Boltzmann theory and molecular dynamics simulation, with the elastic pressure, modeled via the Flory-Rehner theory of swollen polymer networks, we show how deswelling of ionic microgels with increasing concentration of particles can result from a redistribution of counterions that reduces electrostatic pressure. A linearized approximation for the electrostatic pressure, which proves remarkably accurate, provides physical insight and greatly eases numerical calculations for practical applications. Comparing with experiments, we explain why soft particles in deionized suspensions deswell upon increasing concentration and why this effect may be suppressed at higher ionic strength. The failure of the uniform ideal-gas approximation to adequately account for counterion-induced deswelling below close packing of microgels is attributed to neglect of spatial variation of the counterion density profile and the electrostatic pressure of incompletely neutralized macroions.

Surface Adsorption in Nonpolarizable Atomic Models.

PubMed

Whitmer, Jonathan K; Joshi, Abhijeet A; Carlton, Rebecca J; Abbott, Nicholas L; de Pablo, Juan J

2014-12-09

Many ionic solutions exhibit species-dependent properties, including surface tension and the salting-out of proteins. These effects may be loosely quantified in terms of the Hofmeister series, first identified in the context of protein solubility. Here, our interest is to develop atomistic models capable of capturing Hofmeister effects rigorously. Importantly, we aim to capture this dependence in computationally cheap "hard" ionic models, which do not exhibit dynamic polarization. To do this, we have performed an investigation detailing the effects of the water model on these properties. Though incredibly important, the role of water models in simulation of ionic solutions and biological systems is essentially unexplored. We quantify this via the ion-dependent surface attraction of the halide series (Cl, Br, I) and, in so doing, determine the relative importance of various hypothesized contributions to ionic surface free energies. Importantly, we demonstrate surface adsorption can result in hard ionic models combined with a thermodynamically accurate representation of the water molecule (TIP4Q). The effect observed in simulations of iodide is commensurate with previous calculations of the surface potential of mean force in rigid molecular dynamics and polarizable density-functional models. Our calculations are direct simulation evidence of the subtle but sensitive role of water thermodynamics in atomistic simulations.

Electrophoretic mobilities of erythrocytes in various buffers

NASA Technical Reports Server (NTRS)

Plank, L. D.; Kunze, M. E.; Todd, P. W.

1985-01-01

The calibration of space flight equipment depends on a source of standard test particles, this test particle of choice is the fixed erythrocyte. Erythrocytes from different species have different electrophoretic mobilities. Electrophoretic mobility depends upon zeta potential, which, in turn depends upon ionic strength. Zeta potential decreases with increasing ionic strength, so cells have high electrophoretic mobility in space electrophoresis buffers than in typical physiological buffers. The electrophoretic mobilities of fixed human, rat, and rabbit erythrocytes in 0.145 M salt and buffers of varying ionic strength, temperature, and composition, to assess the effects of some of the unique combinations used in space buffers were characterized. Several effects were assessed: glycerol or DMSO (dimethylsulfoxide) were considered for use as cryoprotectants. The effect of these substances on erythrocyte electrophoretic mobility was examined. The choice of buffer depended upon cell mobility. Primary experiments with kidney cells established the choice of buffer and cryoprotectant. A nonstandard temperature of EPM in the suitable buffer was determined. A loss of ionic strength control occurs in the course of preparing columns for flight, the effects of small increases in ionic strength over the expected low values need to be evaluated.

New Insights into the Compositional Dependence of Li-Ion Transport in Polymer-Ceramic Composite Electrolytes.

PubMed

Zheng, Jin; Hu, Yan-Yan

2018-01-31

Composite electrolytes are widely studied for their potential in realizing improved ionic conductivity and electrochemical stability. Understanding the complex mechanisms of ion transport within composites is critical for effectively designing high-performance solid electrolytes. This study examines the compositional dependence of the three determining factors for ionic conductivity, including ion mobility, ion transport pathways, and active ion concentration. The results show that with increase in the fraction of ceramic Li 7 La 3 Zr 2 O 12 (LLZO) phase in the LLZO-poly(ethylene oxide) composites, ion mobility decreases, ion transport pathways transit from polymer to ceramic routes, and the active ion concentration increases. These changes in ion mobility, transport pathways, and concentration collectively explain the observed trend of ionic conductivity in composite electrolytes. Liquid additives alter ion transport pathways and increase ion mobility, thus enhancing ionic conductivity significantly. It is also found that a higher content of LLZO leads to improved electrochemical stability of composite electrolytes. This study provides insight into the recurring observations of compositional dependence of ionic conductivity in current composite electrolytes and pinpoints the intrinsic limitations of composite electrolytes in achieving fast ion conduction.

Synthesis and properties of alkoxy- and alkenyl-substituted peralkylated imidazolium ionic liquids.

PubMed

Maton, Cedric; Brooks, Neil R; Van Meervelt, Luc; Binnemans, Koen; Schaltin, Stijn; Fransaer, Jan; Stevens, Christian V

2013-10-21

Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2](-)), and dicyanamide {[N(CN)2](-)} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2](-) and [N(CN)2](-). For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamics of aggregate formation between a non-ionic polymer and ionic surfactants: An isothermal titration calorimetric study.

PubMed

Patel, Salin Gupta; Bummer, Paul M

2017-01-10

This report examines the energetics of aggregate formation between hydroxypropyl methylcellulose (HPMC) and model ionic surfactants including sodium dodecyl sulfate (SDS) at pharmaceutically relevant concentrations using the isothermal titration calorimetry (ITC) technique and a novel treatment of calorimetric data that accounts for the various species formed. The influence of molecular weight of HPMC, temperature and ionic strength of solution on the aggregate formation process was explored. The interaction between SDS and HPMC was determined to be an endothermic process and initiated at a critical aggregation concentration (CAC). The SDS-HPMC interactions were observed to be cooperative in nature and dependent on temperature and ionic strength of the solution. Molecular weight of HPMC significantly shifted the interaction parameters between HPMC and SDS such that at the highest molecular weight (HPMC K-100M;>240kDa), although the general shape of the titration curve (enthalpogram) was observed to remain similar, the critical concentration parameters (CAC, polymer saturation concentration (C sat ) and critical micelle concentration (CMC)) were significantly altered and shifted to lower concentrations of SDS. Ionic strength was also observed to influence the critical concentration parameters for the SDS-HPMC aggregation and decreased to lower SDS concentrations with increasing ionic strength for both anionic and cationic surfactant-HPMC systems. From these data, other thermodynamic parameters of aggregation such as ΔH agg ° , ΔG agg ° , H agg ° , ΔS agg ° , and ΔC p were calculated and utilized to postulate the hydrophobic nature of SDS-HPMC aggregate formation. The type of ionic surfactant head group (anionic vs. cationic i.e., dodecyltrimethylammonium bromide (DTAB)) was found to influence the strength of HPMC-surfactant interactions wherein a distinct CAC signifying the strength of HPMC-DTAB interactions was not observed. The interpretation of the microcalorimetric data at different temperatures and ionic strengths while varying properties of polymer and surfactant was a very effective tool in investigating the nature and energetics of HPMC and ionic surfactant interactions. Copyright © 2016 Elsevier B.V. All rights reserved.

An empirical equation with tables of smoothed solubilities of methane in water and aqueous sodium chloride solutions up to 25 weight percent, 360 degrees C, and 138 MPa

USGS Publications Warehouse

Haas, John L.

1978-01-01

The total pressure for the system H2O-CH 4 is given by p(total) = P(H2O,t) + exp10[log x(CH 4) - a - b x(CH4)], where P(H2O,t) is the vapor pressure of H2O liquid at the temperature t (?C) and x(CH 4) is the molal concentration of methane in the solution. The terms a and b are functions of temperature only. Where the total pressure and temperature are known, the concentration of methane, x(CH4), is found by iteration. The concentration of methane in a sodium chloride brine, y(CH4), is estimated using the function log y(CH4) = log x(CH4) - A I, where A is the salting out constant and I is the ionic strength. For sodium chloride solutions, the ionic strength is equal to the molality of the salt. The equations are valid to 360?C, 138 MPa, and 25 weight percent sodium chloride.

Surfactant Behavior of Sodium Dodecylsulfate in Deep Eutectic Solvent Choline Chloride/Urea.

PubMed

Arnold, T; Jackson, A J; Sanchez-Fernandez, A; Magnone, D; Terry, A E; Edler, K J

2015-12-01

Deep eutectic solvents (DES) resemble ionic liquids but are formed from an ionic mixture instead of being a single ionic compound. Here we present some results that demonstrate that surfactant sodium dodecyl sulfate (SDS) remains surface-active and shows self-assembly phenomena in the most commonly studied DES, choline chloride/urea. X-ray reflectivity (XRR) and small angle neutron scattering (SANS) suggest that the behavior is significantly different from that in water. Our SANS data supports our determination of the critical micelle concentration using surface-tension measurements and suggests that the micelles formed in DES do not have the same shape and size as those seen in water. Reflectivity measurements have also demonstrated that the surfactants remain surface-active below this concentration.

Computational analysis of the solvation of coffee ingredients in aqueous ionic liquid mixtures.

PubMed

Zeindlhofer, Veronika; Khlan, Diana; Bica, Katharina; Schröder, Christian

2017-01-13

In this paper, we investigate the solvation of coffee ingredients including caffeine, gallic acid as representative for phenolic compounds and quercetin as representative for flavonoids in aqueous mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate [C 2 mim][OAc] at various concentrations. Due to the anisotropy of the solutes we show that classical Kirkwood-Buff theory is not appropriate to study solvation effects with increasing ionic liquid content. However, excess coordination numbers as well as the mean residence time of solvent molecules at the surface of the solutes can be determined by Voronoi tessellation. Since the volume of the hydration shells is also available by this method, solvation free energies will be discussed as a function of the ionic liquid concentration to yield a physical meaningful picture of solvation for the anisotropic solutes. Hydrogen bonding capabilities of the solutes and their relevance for experimental extraction yields from spent coffee grounds are also discussed.

Exceptionally High Electric Double Layer Capacitances of Oligomeric Ionic Liquids.

PubMed

Matsumoto, Michio; Shimizu, Sunao; Sotoike, Rina; Watanabe, Masayoshi; Iwasa, Yoshihiro; Itoh, Yoshimitsu; Aida, Takuzo

2017-11-15

Electric double layer (EDL) capacitors are promising as next-generation energy accumulators if their capacitances and operation voltages are both high. However, only few electrolytes can simultaneously fulfill these two requisites. Here we report that an oligomeric ionic liquid such as IL4 TFSI with four imidazolium ion units in its structure provides a wide electrochemical window of ∼5.0 V, similar to monomeric ionic liquids. Furthermore, electrochemical impedance measurements using Au working electrodes demonstrated that IL4 TFSI exhibits an exceptionally high EDL capacitance of ∼66 μF/cm 2 , which is ∼6 times as high as those of monomeric ionic liquids so far reported. We also found that an EDL-based field effect transistor (FET) using IL4 TFSI as a gate dielectric material and SrTiO 3 as a channel material displays a very sharp transfer curve with an enhanced carrier accumulation capability of ∼64 μF/cm 2 , as determined by Hall-effect measurements.

Determination of chlorophenols in honey samples using in-situ ionic liquid-dispersive liquid-liquid microextraction as a pretreatment method followed by high-performance liquid chromatography.

PubMed

Fan, Chen; Li, Nai; Cao, Xueli

2015-05-01

In-situ ionic liquid-dispersive liquid-liquid microextraction (IL-DLLME) method was developed as a pretreatment method for the detection of six chlorophenols (CPs) in honey samples. The hydrophobic ionic liquid [C4MIM][NTf2], formed in-situ by the hydrophilic ionic liquid [C4MIM][BF4] and the ion exchange reagent LiNTf2 was used as the microextractant solvent of CPs from honey sample. Then the enriched analytes were back-extracted into 40 μL of 0.14 M NaOH solution and finally subjected to analysis by high-performance liquid chromatography. The method showed low limit of detection of CPs, 0.8-3.2 μg/L and high enrichment factor, 34-65 with the recoveries range from 91.60% to 114.33%. The method is simple, rapid, environmentally friendly and with high extraction efficiency. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Ionic liquids as lubricants or lubrication additives: an ecotoxicity and biodegradability assessment.

PubMed

Stolte, Stefan; Steudte, Stephanie; Areitioaurtena, Olatz; Pagano, Francesco; Thöming, Jorg; Stepnowski, Piotr; Igartua, Amaya

2012-11-01

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF(3)SO(2))(2)N(-) anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes. Copyright © 2012 Elsevier Ltd. All rights reserved.

Fabrication of core-shell structured magnetic nanocellulose base polymeric ionic liquid for effective biosorption of Congo red dye.

PubMed

Beyki, Mostafa Hossein; Bayat, Mehrnoosh; Shemirani, Farzaneh

2016-10-01

Ionic liquids are considered to be a class of environmentally friendly compounds as combination of them with bioresource polymeric substances such as; cellulose, constitute emerging coating materials. Biosorption by polymeric ionic liquids exhibits an attractive green way that involves low cost and irrespective of toxicity. As a result, a novel polymeric ionic liquid has been developed by the reaction of one step synthesized Fe3O4-cellulose nanohybrid, epichlorohydrin and 1-methylimidazole and employed as a green sorbent for efficient biosorption of Congo red dye. Effective parameters on dye removing as well as their interactions were determined with response surface methodology (RSM). Congo red adsorption showed fast equilibrium time (11min) with maximum uptake of 131mgg(-1). Isotherm study revealed that Langmuir adsorption model can better describe dye adsorption behavior. Regeneration of the sorbent was performed with a mixture of methanol-acetone-NaOH (3.0molL(-1)) solution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaporation Study of an Ionic Liquid with a Double-Charged Cation.

PubMed

Chilingarov, Norbert S; Zhirov, Maksim S; Shmykova, Anna M; Martynova, Ekaterina A; Glukhov, Lev M; Chernikova, Elena A; Kustov, Leonid M; Markov, Vitaliy Yu; Ioutsi, Vitaliy A; Sidorov, Lev N

2018-05-07

The evaporation of a dicationic ionic liquid, 1,3-bis(3-methylimidazolium-1-yl)propane bis(trifluoromethanesulfonyl)amide ([C 3 (MIm) 2 2+ ][Tf 2 N - ] 2 ), was studied by Knudsen effusion mass spectrometry. Its evaporation is accompanied by a partial thermal decomposition producing monocationic ionic liquids, 1,3-dimethylimidazolium and 1-(2-propenyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)amides, as volatile products. This decomposition does not affect the vaporization characteristics of [C 3 (MIm) 2 2+ ][Tf 2 N - ] 2 , which were established to be as follows. The vaporization enthalpy (550 K) is equal to (155.5 ± 3.2) kJ·mol -1 ; the saturated vapor pressure is described by the equation ln( p/Pa) = -(18699 ± 381)/( T/K) + (30.21 ± 0.82) in the range of 508-583 K. 1,3-Bis(3-methylimidazolium-1-yl)propane bis(trifluoromethanesulfonyl)amide is the first dicationic ionic liquid, the vaporization characteristics of which were determined with an acceptable accuracy.

Radiochemical determination of 237NP in soil samples contaminated with weapon grade plutonium

NASA Astrophysics Data System (ADS)

Antón, M. P.; Espinosa, A.; Aragón, A.

2006-01-01

The Palomares terrestrial ecosystem (Spain) constitutes a natural laboratory to study transuranics. This scenario is partially contaminated with weapon-grade plutonium since the burnout and fragmentation of two thermonuclear bombs accidentally dropped in 1966. While performing radiometric measurements in the field, the possible presence of 237Np was observed through its 29 keV gamma emission. To accomplish a detailed characterization of the source term in the contaminated area using the isotopic ratios Pu-Am-Np, the radiochemical isolation and quantification by alpha spectrometry of 237Np was initiated. The selected radiochemical procedure involves separation of Np from Am, U and Pu with ionic resins, given that in soil samples from Palomares 239+240Pu levels are several orders of magnitude higher than 237Np. Then neptunium is isolated using TEVA organic resins. After electrodeposition, quantification is performed by alpha spectrometry. Different tests were done with blank solutions spiked with 236Pu and 237Np, solutions resulting from the total dissolution of radioactive particles and soil samples. Results indicate that the optimal sequential radionuclide separation order is Pu-Np, with decontamination percentages obtained with the ionic resins ranging from 98% to 100%. Also, the addition of NaNO2 has proved to be necessary, acting as a stabilizer of Pu-Np valences.

Ionic association and solvation of the ionic liquid 1-hexyl-3-methylimidazolium chloride in molecular solvents revealed by vapor pressure osmometry, conductometry, volumetry, and acoustic measurements.

PubMed

Sadeghi, Rahmat; Ebrahimi, Nosaibah

2011-11-17

A systematic study of osmotic coefficient, conductivity, volumetric and acoustic properties of solutions of ionic liquid 1-hexyl-3-methylimidazolium chloride ([C(6)mim][Cl]) in various molecular solvents has been made at different temperatures in order to study of ionic association and solvation behavior of [C(6)mim][Cl] in different solutions. Precise measurements on electrical conductances of solutions of [C(6)mim][Cl] in water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and acetonitrile at 293.15, 298.15, and 303.15 K are reported and analyzed with Barthel's low-concentration chemical model (lcCM) to obtain the limiting molar conductivities and association constants of this ionic liquid in the investigated solvents. Strong ion pairing was found for the ionic liquid in 2-propanol, 1-butanol, and 1-propanol, whereas ion association in acetonitrile, methanol and ethanol is rather weak and in water the ionic liquid is fully dissociated. In the second part of this work, the apparent molar volumes and isentropic compressibilities of [C(6)mim][Cl] in water, methanol, ethanol, acetonitrile, 1-propanol, 2-propanol, and 1-butanol are obtained at the 288.15-313.15 K temperature range at 5 K intervals at atmospheric pressure from the precise measurements of density and sound velocity. The infinite dilution apparent molar volume and isentropic compressibility values of the free ions and ion pairs of [C(6)mim][Cl] in the investigated solvents as well as the excess molar volume of the investigated solutions are determined and their variations with temperature and type of solvents are also studied. Finally, the experimental measurements of osmotic coefficient at 318.15 K for binary solutions of [C(6)mim][Cl] in water, methanol, ethanol, 2-propanol, and acetonitrile are taken using the vapor pressure osmometry (VPO) method and from which the values of the solvent activity, vapor pressure, activity coefficients, and Gibbs free energies are calculated. The results are interpreted in terms of ion association, ion-dipole interactions, and structural factors of the ionic liquid and investigated organic solvents. The ionic liquid is solvated to a different extent by the molecular solvents, and ionic association is affected significantly by ionic solvation.

The road not taken: Applications of fluorescence spectroscopy and electronic structure theory to systems of materials and biological relevance

NASA Astrophysics Data System (ADS)

Carlson, Philip Joseph

Applications of Fluorescence Spectroscopy and Electronic Structure Theory to Systems of Materials and Biological Relevance. The photophysics of curcumin was studied in micelles and the solvation dynamics were probed. The high-energy ionic liquid HEATN was also studied using the fragment molecular orbital method. The solvation dynamics of the HEATN system were determined. This marks the first study of the solvation dynamics in a triazolium ionic liquid system.

Ionic Ckonductivity and Glass Transition of Phosphoric Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yangyang; Lane, Nathan A; Sun, Che-Nan

2013-01-01

Here we report the low-temperature dielectric and viscoelastic properties of phosphoric acids in the range of H2O:P2O5 1.5 5. Both dielectric and viscosity measurements allow us to determine the glass-transition temperatures of phosphoric acids. The obtained glass-transition temperatures are in good agreement with previous differential scanning calorimetric measurements. Moreover, our analysis reveals moderate decoupling of ionic conductivity from structural relaxation in the vicinity of the glass transition.

Ionic conductivity and glass transition of phosphoric acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yangyang; Lane, Nathan A; Sun, Che-Nan

2013-01-01

Here we report the low-temperature dielectric and viscoelastic properties of phosphoric acids in the range of H2O:P2O5 1.5 5. Both dielectric and viscosity measurements allow us to determine the glass-transition temperatures of phosphoric acids. The obtained glass-transition temperatures are in good agreement with previous differential scanning calorimetric measurements. Moreover, our analysis reveals moderate decoupling of ionic conductivity from structural relaxation in the vicinity of the glass transition.

Expression of Aspergillus niger CAZymes is determined by compositional changes in wheat straw generated by hydrothermal or ionic liquid pretreatments.

PubMed

Daly, Paul; van Munster, Jolanda M; Blythe, Martin J; Ibbett, Roger; Kokolski, Matt; Gaddipati, Sanyasi; Lindquist, Erika; Singan, Vasanth R; Barry, Kerrie W; Lipzen, Anna; Ngan, Chew Yee; Petzold, Christopher J; Chan, Leanne Jade G; Pullan, Steven T; Delmas, Stéphane; Waldron, Paul R; Grigoriev, Igor V; Tucker, Gregory A; Simmons, Blake A; Archer, David B

2017-01-01

The capacity of fungi, such as Aspergillus niger, to degrade lignocellulose is harnessed in biotechnology to generate biofuels and high-value compounds from renewable feedstocks. Most feedstocks are currently pretreated to increase enzymatic digestibility: improving our understanding of the transcriptomic responses of fungi to pretreated lignocellulosic substrates could help to improve the mix of activities and reduce the production costs of commercial lignocellulose saccharifying cocktails. We investigated the responses of A. niger to untreated, ionic liquid and hydrothermally pretreated wheat straw over a 5-day time course using RNA-seq and targeted proteomics. The ionic liquid pretreatment altered the cellulose crystallinity while retaining more of the hemicellulosic sugars than the hydrothermal pretreatment. Ionic liquid pretreatment of straw led to a dynamic induction and repression of genes, which was correlated with the higher levels of pentose sugars saccharified from the ionic liquid-pretreated straw. Hydrothermal pretreatment of straw led to reduced levels of transcripts of genes encoding carbohydrate-active enzymes as well as the derived proteins and enzyme activities. Both pretreatments abolished the expression of a large set of genes encoding pectinolytic enzymes. These reduced levels could be explained by the removal of parts of the lignocellulose by the hydrothermal pretreatment. The time course also facilitated identification of temporally limited gene induction patterns. The presented transcriptomic and biochemical datasets demonstrate that pretreatments caused modifications of the lignocellulose, to both specific structural features as well as the organisation of the overall lignocellulosic structure, that determined A. niger transcript levels. The experimental setup allowed reliable detection of substrate-specific gene expression patterns as well as hitherto non-expressed genes. Our data suggest beneficial effects of using untreated and IL-pretreated straw, but not HT-pretreated straw, as feedstock for CAZyme production.

Interaction of copper with dinitrogen tetroxide in 1-butyl-3-methylimidazolium-based ionic liquids.

PubMed

Morozov, I V; Deeva, E B; Glazunova, T Yu; Troyanov, S I; Guseinov, F I; Kustov, L M

2017-03-27

Ionic liquids that are stable toward oxidation and nitration and are based on the 1-n-butyl-3-methylimidazolium cation (BMIm + ) can be used as solvents and reaction media for copper dissolution in liquid dinitrogen tetraoxide N 2 O 4 . The ionic liquid not only favors the dissociation of N 2 O 4 into NO + and NO 3 - , but also takes part in the formation of different crystalline products. Thus, NO[BF 4 ], NO[Cu(NO 3 ) 3 ] and (BMIm) 2 [Cu 2 (CF 3 COO) 6 ] were prepared using (BMIm)A, A - = [BF 4 ] - , (CF 3 SO 2 ) 2 N - , CF 3 COO - , respectively. The formation of a certain product is determined by the nature of the anion A - and the relative solubility of the reaction products in the ionic liquid. Crystals of NO[BF 4 ] were also prepared directly from a mixture of N 2 O 4 and BMImBF 4 . According to XRD single-crystal structure analysis, the structure of NO[BF 4 ] consists of tetrahedral [BF 4 ] - anions and nitrosonium NO + cations; the formation of these ions prove the heterolytic dissociation of N 2 O 4 dissolved in the ionic liquid. The crystal structure of the earlier unknown binuclear copper trifluoroacetate (BMIm) 2 [Cu 2 (CF 3 COO) 6 ] were determined by X-ray diffraction. The peculiarity of this dimer compared to the majority of known dimeric copper(ii) carboxylates is the unusually long CuCu distance (3.15 Å), with Cu(ii) ions demonstrating an atypical coordination of a distorted trigonal bipyramid formed by five O atoms of five trifluoroacetate groups.

Ecotoxicological characterization of polyoxyethylene glycerol ester non-ionic surfactants and their mixtures with anionic and non-ionic surfactants.

PubMed

Ríos, Francisco; Fernández-Arteaga, Alejandro; Lechuga, Manuela; Fernández-Serrano, Mercedes

2017-04-01

This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants derived from renewable raw materials, polyoxyethylene glycerol ester (PGE), and their binary mixtures with anionic and non-ionic surfactants. Toxicity of pure PGEs was determined using representative organisms from different trophic levels: luminescent bacteria (Vibrio fischeri), microalgae (Pseudokirchneriella subcapitata), and freshwater crustaceans (Daphnia magna). Relationships between toxicity and the structural parameters such as unit of ethylene oxide (EO) and hydrophilic-lipophilic balance (HLB) were evaluated. Critical micellar concentration (CMC) in the conditions of the toxicity test was also determined. It was found that the toxicity of the aqueous solutions of PGE decreased when the number of EO units in the molecule, HLB, and CMC increased. PGEs showed lower CMC in marine medium, and the toxicity to V. ficheri is lower when the CMC was higher. Given their non-polar nature, narcosis was expected to be the primary mode of toxic action of PGEs. For the mixture of surfactants, we observed that the mixtures with PGE that had the higher numbers of EO units were more toxic than the aqueous solutions of pure surfactants. Moreover, we found that concentration addition was the type of action more likely to occur for mixtures of PGE with lower numbers of EO units with non-ionic surfactants (alkylpolyglucoside and fatty alcohol ethoxylate), whereas for the mixture of PGE with lower EO units and anionic surfactant (ether carboxylic derivative), the most common response type was response addition. In case of mixtures involving amphoteric surfactants and PGEs with the higher numbers of EO units, no clear pattern with regard to the mixture toxicity response type could be observed.

Mass spectrometric studies of 1-ethyl-3-methylimidazolium and 1-propyl-2,3-dimethylimidazolium bis(trifluoromethyl)-sulfonylimides.

PubMed

Chilingarov, Norbert S; Medvedev, Artem A; Deyko, Grigoriy S; Kustov, Leonid M; Chernikova, Elena A; Glukhov, Lev M; Markov, Vitaliy Yu; Ioffe, Il'ya N; Senyavin, Vladimir M; Polyakova, Marina V; Sidorov, Lev N

2015-07-15

Ionic liquids ([Cat(+)][An(-)]) were believed to decompose before reaching vaporization temperatures, but recently some of them have been shown to vaporize congruently. Low-temperature vaporization of ionic substances is an intriguing phenomenon, so the vapor-phase composition and reactions of ionic liquids deserve more extensive study. Evaporation of two ionic liquids, [C2MIM(+)][Tf2 N(-)] and [C3MMIM(+)][Tf2N(-)], was studied by means of Knudsen effusion mass spectrometry. These liquids were also characterized using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, UV/Vis, IR, NMR spectroscopy, and elemental analysis. The vaporization enthalpies of (118 ± 3) and (124 ± 2) kJ·mol(-1) were determined for [C2MIM(+)][Tf2N(-)] and [C3MMIM(+)][Tf2N(-)], respectively. The corresponding equations for their saturated vapor pressures are: ln(p{[C2MIM(+)][Tf2N(-)]}/Pa) = -(14213 ± 325)/(T/K) + (26.57 ± 1.04), ln(p{[C2MMIM(+)][Tf2N(-)]}/Pa) = -(14868 ± 221)/(T/K) + (27.19 ± 0.60). The MALDI studies (positive and negative ion modes) enabled detection of monomeric [Cat(+)] and [An(-)] ions, the cluster ions {[Cat(+)]2 [An(-)]}(+) and {[Cat(+)][An(-)]2}(-), and some complex anions {2[An(-)] + Na(+)}(-), {2[An(-)] + K(+)}(-), {2[An(-)] + Cu(+)}(-) and {3[An(-)] + Ca(2+)}(-). Knudsen effusion mass spectrometry proved to be a valuable method to study the thermodynamics of ionic liquids. The saturated vapor pressure and vaporization enthalpy of [C3MMIM(+)][Tf2N(-)] were accurately determined for the first time. MALDI is also capable of providing indirect information on hydrogen bonding. Copyright © 2015 John Wiley & Sons, Ltd.

Ionic liquid and aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of seven rare ginsenosides in Xue-Sai-Tong injection.

PubMed

Li, Lan-Jie; Jin, Yong-Ri; Wang, Xiao-Zhong; Liu, Ying; Wu, Qian; Shi, Xiao-Lei; Li, Xu-Wen

2015-09-01

A method of ionic liquid salt aqueous two-phase extraction coupled with high-performance liquid chromatography has been developed for the analysis of seven rare ginsenosides including Rg6 , F4 , 20(S)-Rg3 , 20(R)-Rg3 , Rk3 , Rk1 , and Rg5 in Xue-Sai-Tong injection. The injection was mixed with ionic liquid 1-butyl-3-methylimidazolium bromide aqueous solution, and a mixture was obtained. With the addition of sodium dodecyl sulfate and dipotassium phosphate into the mixture, the aqueous two-phase mixture was formed after ultrasonic treatment and centrifuged. Rare ginsenosides were extracted into the upper phase. To obtain a high extraction factors, various influences were considered systematically, such as the volume of ionic liquid, the category and amount of salts, the amount of sodium dodecyl sulfate, the pH value of system, and the time of ultrasonic treatment. Under the optimal condition, rare ginsenosides in Xue-Sai-Tong injection were enriched and detected, the recoveries of seven rare ginsenosides ranged from 90.05 to 112.55%, while relative standard deviations were lower than 2.50%. The developed method was reliable, rapid and sensitive for the determination of seven rare ginsenosides in the injections. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Empirical Modeling of ICMEs Using ACE/SWICS Ionic Distributions

NASA Astrophysics Data System (ADS)

Rivera, Y.; Landi, E.; Lepri, S. T.; Gilbert, J. A.

2017-12-01

Coronal Mass Ejections (CMEs) are some of the largest, most energetic events in the solar system releasing an immense amount of plasma and magnetic field into the Heliosphere. The Earth-bound plasma plays a large role in space weather, causing geomagnetic storms that can damage space and ground based instrumentation. As a CME is released, the plasma experiences heating, expansion and acceleration; however, the physical mechanism supplying the heating as it lifts out of the corona still remains uncertain. From previous work we know the ionic composition of solar ejecta undergoes a gradual transition to a state where ionization and recombination processes become ineffective rendering the ionic composition static along its trajectory. This property makes them a good indicator of thermal conditions in the corona, where the CME plasma likely receives most of its heating. We model this so-called `freeze-in' process in Earth-directed CMEs using an ionization code to empirically determine the electron temperature, density and bulk velocity. `Frozen-in' ions from an ensemble of independently modeled plasmas within the CME are added together to fit the full range of observational ionic abundances collected by ACE/SWICS during ICME events. The models derived using this method are used to estimate the CME energy budget to determine a heating rate used to compare with a variety of heating mechanisms that can sustain the required heating with a compatible timescale.

Optimization of oligomeric enzyme activity in ionic liquids using Rhodotorula glutinis yeast phenylalanine ammonia lyase.

PubMed

Barron, Christiaan C; Sponagle, Brandon J D; Arivalagan, Pugazhendhi; D'Cunha, Godwin B

2017-01-01

Phenylalanine ammonia lyase (E.C.4.3.1.24, PAL) activity of Rhodotorula glutinis yeast has been demonstrated in four commonly used ionic liquids. PAL forward reaction was carried out in 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO 4 ]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6 ]) and 1-butyl-3-methylimidazolium lactate ([BMIM][lactate]). Our experiments have revealed that PAL is catalytically active in ionic liquids and the enzyme activity in ([BMIM][PF 6 ]) is comparable to that obtained in aqueous buffer medium. Different conditions were optimized for maximal PAL forward activity including time of incubation (30.0min) L -phenylalanine substrate concentration (30.0mM), nature of buffer (50.0mM Tris-HCl), pH (9.0), temperature (37°C), and speed of agitation (100 rev min -1 ). Under these optimized conditions, about 83% conversion of substrate to product was obtained for the PAL forward reaction that was determined using UV spectroscopy at 290nm. PAL reverse reaction in ([BMIM][PF 6 ]) was determined spectrophotometrically at 520nm; and about 59% substrate conversion was obtained. This data provides further knowledge in enzyme biocatalysis in non-aqueous media, and may be of importance when studying the function of other oligomeric/multimeric proteins and enzymes in ionic liquids. Copyright © 2016 Elsevier Inc. All rights reserved.

Simultaneous extraction and HPLC determination of 3-indole butyric acid and 3-indole acetic acid in pea plant by using ionic liquid-modified silica as sorbent.

PubMed

Sheikhian, Leila; Bina, Sedigheh

2016-01-15

In this study, ionic liquid-modified silica was used as sorbent for simultaneous extraction and preconcentration of 3-indole butyric acid and 3-indole acetic acid in pea plants. The effect of some parameters such as pH and ionic strength of sample solution, amount of sorbent, flow rate of aqueous sample solution and eluent solution, concentration of eluent solution, and temperature were studied for each hormone solution. Percent extraction of 3-indole butyric acid and 3-indole acetic acid was strongly affected by pH of aqueous sample solution. Ionic strength of aqueous phase and temperature showed no serious effects on extraction efficiency of studied plant hormones. Obtained breakthrough volume was 200mL for each of studied hormones. Preconcentration factor for spectroscopic and chromatographic determination of studied hormones was 100 and 4.0×10(3) respectively. Each solid sorbent phase was reusable for almost 10 times of extraction/stripping procedure. Relative standard deviations of extraction/stripping processes of 3-indole butyric acid and 3-indole acetic acid were 2.79% and 3.66% respectively. The calculated limit of detections for IBA and IAA were 9.1×10(-2)mgL(-1) and 1.6×10(-1)mgL(-1) respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smalley, John F.

In this study, we demonstrate how small and rapid temperature perturbations (produced by the indirect laser-induced temperature jump (ILIT) technique) of solid metal electrode|electrolyte solution interfaces may be used to determine the potential of zero (total) charge (E pzc) and its temperature derivativemore » $$\\left(\\frac{dEpzc}{dT}\\right)$$ of Au(111) electrode surfaces modified by alkanethiol self-assembled monolayers in contact with high ionic strength (i.e., 1.0 M) aqueous electrolyte solutions. The E pzc’s measured for two different types of SAMs (made from either HS(CH 2) n-1CH 3 (5 ≤ n ≤ 12, E pzc = -(0.99 ± 0.12) V vs SSCE) or HS(CH 2) nOH (3 ≤ n ≤ 16, E pzc = (0.46 ± 0.22) V vs SSCE)) are considerably different than those measured previously at much lower electrolyte solution ionic strengths. For mixed monolayers made from both HS(CH 2) n-1CH 3 and HS(CH 2) nFc (where Fc refers to ferrocene), the difference in Epzc decreases as a function of the surface concentration of the Fc moiety (i.e., [Fc]), and it completely disappears at a surprisingly small [Fc] (~4.0 × 10 –11 mol cm –2). These observations for the Au(111)|hydrophobic (neat and mixed) SAM|aqueous electrolyte solution interfaces, along with the surface potentials (g Sml(dip)) evaluated for the contacting electrolyte solution surfaces of these interfaces, are consistent with a structure for the water molecule components of these surfaces where there is a net orientation of the dipoles of these molecules. Accordingly, the negative (oxygen) ends of these molecules point toward the SAM surface. The positive values of g Sml(dip) evaluated for hydrophilic SAM (e.g., made from HS(CH 2) nOH)|aqueous electrolyte solution interfaces) also indicate that the structure of these interfaces is similar to that of the hydrophobic interfaces. However, g Sml(dip) decreases with increasing ionic strength for the hydrophilic interfaces, while it increases with increasing ionic strength for the hydrophobic interfaces. The data (and calculations) reported in the present work and other studies of hydrophobic (and hydrophilic)|aqueous solution interfaces are as yet insufficient to support a complete explanation for the effects of ionic strength observed in the present study. Nevertheless, an analysis based upon the value of $$\\left(\\frac{dEpzc}{dT}\\right)$$ (= (0.51 ± 0.12) mV/K, essentially the same for SAMs made from both HS(CH 2) n-1CH 3 and HS(CH 2) nOH), determined in the present study provides a further indication that upon formation of the SAM there is a partial charge transfer of electrons from the relevant gold atoms on the Au(111) surface to the sulfur atoms of the alkanethiols.« less

Theory of space-charge polarization for determining ionic constants of electrolytic solutions

NASA Astrophysics Data System (ADS)

Sawada, Atsushi

2007-06-01

A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA +(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.

Enhancing oxygen transport through Mixed-Ionic-and-Electronic-Conducting ceramic membranes

NASA Astrophysics Data System (ADS)

Yu, Anthony S.

Ceramic membranes based on Mixed-Ionic-and-Electronic-Conducting (MIEC) oxides are capable of separating oxygen from air in the presence of an oxygen partial-pressure gradient. These MIEC membranes show great promise for oxygen consuming industrial processes, such as the production of syngas from steam reforming of natural gas (SRM), as well as for electricity generation in Solid Oxide Fuel Cells (SOFC). For both applications, the overall performance is dictated by the rate of oxygen transport across the membrane. Oxygen transport across MIEC membranes is composed of a bulk oxygen-ion diffusion process and surface processes, such as surface reactions and adsorption/desorption of gaseous reactants/products. The main goal of this thesis was to determine which process is rate-limiting in order to significantly enhance the overall rate of oxygen transport in MIEC membrane systems. The rate-limiting step was determined by evaluating the total resistance to oxygen transfer, Rtot. Rtot is the sum of a bulk diffusion resistance in the membrane itself, Rb, and interfacial loss components, Rs. Rb is a function of the membrane's ionic conductivity and thickness, while Rs arises primarily from slow surface-exchange kinetics that cause the P(O2) at the surfaces of the membrane to differ from the P(O 2) in the adjacent gas phases. Rtot can be calculated from the Nernst potential across the membrane and the measured oxygen flux. The rate-limiting process can be determined by evaluating the relative contributions of the various losses, Rs and Rb, to Rtot. Using this method, this thesis demonstrates that for most membrane systems, Rs is the dominating factor. In the development of membrane systems with high oxygen transport rates, thin membranes with high ionic conductivities are required to achieve fast bulk oxygen-ion diffusion. However, as membrane thickness is decreased, surface reaction kinetics become more important in determining the overall transport rate. The two approaches to increase surface reaction kinetics and decrease Rs that were examined in this thesis involved modifying the surface microstructure, as well as adding both metallic (e.g. Pt) and oxide (e.g. CeO2, La0.8Sr0.2FeO3) catalysts to both membrane surfaces. These two approaches were investigated for single-phase MIEC membrane reactors (La0.9Ca0.1FeO3-delta ), as well as composite membrane reactors composed of an electronic conductor (La0.8Sr-0.2CrO3-delta) and an ionic conductor (YSZ). The use of catalysts and microstructure modifications to decrease interfacial losses is equally important for SOFCs. In this thesis, the electrochemical activity and microstructure of metallic catalysts formed by "ex-solving" metals from an oxide lattice, and oxide catalysts deposited by Atomic Layer Deposition (ALD) were investigated. It is shown that these methods for depositing catalysts resulted in very different effects on electrode performance when compared to the same catalysts deposited by wet impregnation. For example, when transition metals, such as Ni and Co, were "ex-solved" from a La0.8Sr0.2CrO3-delta anode lattice, these "ex-solved" metal particles not only exhibited great catalytic activity, they were also less prone to coking compared to their wet impregnated counterparts. On the cathode side, thin layers of various oxides (e.g. Al 2O3, CeOx, SrO) that were deposited using ALD also exhibited drastically different electrochemical activity compared to their wet impregnated counterparts. It was determined that differences in electrochemical activity could be attributed to a difference in the oxide morphology, showing that a catalyst's microstructure and morphology are very important in dictating its overall activity in SOFC electrodes.

Recommendations for terminology and databases for biochemical thermodynamics.

PubMed

Alberty, Robert A; Cornish-Bowden, Athel; Goldberg, Robert N; Hammes, Gordon G; Tipton, Keith; Westerhoff, Hans V

2011-05-01

Chemical equations are normally written in terms of specific ionic and elemental species and balance atoms of elements and electric charge. However, in a biochemical context it is usually better to write them with ionic reactants expressed as totals of species in equilibrium with each other. This implies that atoms of elements assumed to be at fixed concentrations, such as hydrogen at a specified pH, should not be balanced in a biochemical equation used for thermodynamic analysis. However, both kinds of equations are needed in biochemistry. The apparent equilibrium constant K' for a biochemical reaction is written in terms of such sums of species and can be used to calculate standard transformed Gibbs energies of reaction Δ(r)G'°. This property for a biochemical reaction can be calculated from the standard transformed Gibbs energies of formation Δ(f)G(i)'° of reactants, which can be calculated from the standard Gibbs energies of formation of species Δ(f)G(j)° and measured apparent equilibrium constants of enzyme-catalyzed reactions. Tables of Δ(r)G'° of reactions and Δ(f)G(i)'° of reactants as functions of pH and temperature are available on the web, as are functions for calculating these properties. Biochemical thermodynamics is also important in enzyme kinetics because apparent equilibrium constant K' can be calculated from experimentally determined kinetic parameters when initial velocities have been determined for both forward and reverse reactions. Specific recommendations are made for reporting experimental results in the literature. Copyright © 2011 Elsevier B.V. All rights reserved.

The effect of pH and ionic strength of dissolution media on in-vitro release of two model drugs of different solubilities from HPMC matrices.

PubMed

Asare-Addo, Kofi; Conway, Barbara R; Larhrib, Hassan; Levina, Marina; Rajabi-Siahboomi, Ali R; Tetteh, John; Boateng, Joshua; Nokhodchi, Ali

2013-11-01

The evaluation of the effects of different media ionic strengths and pH on the release of hydrochlorothiazide, a poorly soluble drug, and diltiazem hydrochloride, a cationic and soluble drug, from a gel forming hydrophilic polymeric matrix was the objective of this study. The drug to polymer ratio of formulated tablets was 4:1. Hydrochlorothiazide or diltiazem HCl extended release (ER) matrices containing hypromellose (hydroxypropyl methylcellulose (HPMC)) were evaluated in media with a pH range of 1.2-7.5, using an automated USP type III, Bio-Dis dissolution apparatus. The ionic strength of the media was varied over a range of 0-0.4M to simulate the gastrointestinal fed and fasted states and various physiological pH conditions. Sodium chloride was used for ionic regulation due to its ability to salt out polymers in the midrange of the lyotropic series. The results showed that the ionic strength had a profound effect on the drug release from the diltiazem HCl K100LV matrices. The K4M, K15M and K100M tablets however withstood the effects of media ionic strength and showed a decrease in drug release to occur with an increase in ionic strength. For example, drug release after the 1h mark for the K100M matrices in water was 36%. Drug release in pH 1.2 after 1h was 30%. An increase of the pH 1.2 ionic strength to 0.4M saw a reduction of drug release to 26%. This was the general trend for the K4M and K15M matrices as well. The similarity factor f2 was calculated using drug release in water as a reference. Despite similarity occurring for all the diltiazem HCl matrices in the pH 1.2 media (f2=64-72), increases of ionic strength at 0.2M and 0.4M brought about dissimilarity. The hydrochlorothiazide tablet matrices showed similarity at all the ionic strength tested for all polymers (f2=56-81). The values of f2 however reduced with increasing ionic strengths. DSC hydration results explained the hydrochlorothiazide release from their HPMC matrices. There was an increase in bound water as ionic strengths increased. Texture analysis was employed to determine the gel strength and also to explain the drug release for the diltiazem hydrochloride. This methodology can be used as a valuable tool for predicting potential ionic effects related to in vivo fed and fasted states on drug release from hydrophilic ER matrices. Copyright © 2013 Elsevier B.V. All rights reserved.

Speciation analysis and bioaccessibility evaluation of trace elements in goji berries (Lycium Barbarum, L.).

PubMed

Wojcieszek, Justyna; Kwiatkowski, Piotr; Ruzik, Lena

2017-04-07

Goji berries (Lycium Barbarum, L.) are known for their nutritional potential as a great source of trace metals (e.g., copper, zinc and manganese) which are present in the form of highly bioaccessible compounds. In order to assess the bioaccessibility of trace elements and to identify compounds responsible for better bioaccessibility of copper and zinc, an in vitro simulation of gastrointestinal digestion was used in this study. The total content of trace metals was evaluated using sample digestion followed by inductively coupled plasma mass spectrometry. Bioaccessibility of trace elements was estimated by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry. These analytical methods were used to analyse samples of goji berries to determine the highest amount of elements. For total trace metal content in goji berries, Zn had the highest level of the three studied (10.6μgg -1 ), while the total content of manganese and copper was 9.9μgg -1 and 6.1μgg -1 , respectively. Additionally, the analysed metals were found to be highly bioaccessible to the human body (about 56% for Mn, 72% for Cu and 64% for Zn in the gastric extract and approximately 35% for Mn, 23% for Cu and 31% for Zn in the case of gastrointestinal extract). To obtain information about metal complexes present in goji berries, extraction treatment using different solutions (ionic liquid, HEPES, SDS, Tris-HCl, ammonium acetate, water) was performed. Enzymatic treatment using pectinase and hemicellulase was also checked. Extracts of berries were analysed by SEC-ICP-MS and μHPLC-ESI-MS/MS techniques. The ionic liquid and pectinase extraction helped efficiently extract copper (seven compounds) and zinc (four compounds) complexes. Compounds identified in goji berries are most likely to be responsible for better bioaccessibility of those elements to the human organism. Copyright © 2017 Elsevier B.V. All rights reserved.

In situ XANES and EXAFS Analysis of Redox Active Fe Center Ionic Liquids

DOE PAGES

Apblett, Christopher A.; Stewart, David M.; Fryer, Robert T.; ...

2015-10-23

We apply in situ X-Ray Absorption Near Edge Spectroscopy (XANES) and Extended X-Ray Absorption Fine Structure (EXAFS) techniques to a metal center ionic liquid undergoing oxidation and reduction in a three electrode spectroscopic cell. Furthermore, the determination of the extent of reduction under negative bias on the working electrode and the extent of oxidation are determined after pulse voltammetry to quiescence. While the ionic liquid undergoes full oxidation, it undergoes only partial reduction, likely due to transport issues on the timescale of the experiment. Nearest neighbor Fe-O distances in the fully oxidized state match well to expected values for similarlymore » coordinated solids, but reduction does not result in an extension of the Fe-O bond length, as would be expected from comparisons to the solid phase. Instead, little change in bond length is observed. Finally, we suggest that this may be due to a more complex interaction between the monodentate ligands of the metal center anion and the surrounding charge cloud, rather than straightforward electrostatics between the metal center and the nearest neighbor grouping.« less

Ionic liquid-based air-assisted liquid-liquid microextraction followed by high performance liquid chromatography for the determination of five fungicides in juice samples.

PubMed

You, Xiangwei; Chen, Xiaochu; Liu, Fengmao; Hou, Fan; Li, Yiqiang

2018-01-15

A novel and simple ionic liquid-based air-assisted liquid-liquid microextraction technique combined with high performance liquid chromatography was developed to analyze five fungicides in juice samples. In this method, ionic liquid was used instead of a volatile organic solvent as the extraction solvent. The emulsion was formed by pulling in and pushing out the mixture of aqueous sample solution and extraction solvent repeatedly using a 10mL glass syringe. No organic dispersive solvent was required. Under the optimized conditions, the limits of detection (LODs) were 0.4-1.8μgL -1 at a signal-to-noise ratio of 3. The limits of quantification (LOQs) set as the lowest spiking levels with acceptable recovery in juices were 10μgL -1 , except for fludioxonil whose LOQ was 20μgL -1 . The proposed method was applied to determine the target fungicides in juice samples, and acceptable recoveries ranging from 74.9% to 115.4% were achieved. Copyright © 2017. Published by Elsevier Ltd.

Influence of the DNA structure on the free radical induction due to proflavine and light treatment.

PubMed

Piette, J; Calberg-Bacq, C M; Van de Vorst, A

1979-04-30

Induction of peroxide free radicals (detected by Electron Paramagnetic Resonance at 77 K) due to the photodynamic activity of proflavine was measured on bacteriophage phi X174 DNA either single-stranded (ss) as isolated from the virion, or double-stranded supercoiled (RFI) as isolated from the infected bacteria. Comparison was made with calf thymus DNA photosensitization. In order to use equivalent DNA-proflavine complexes, binding of the dye to the three DNA's was first determined under those conditions of high ionic strength favourable to the photodynamic reaction. Free radical induction was maximal for definite amounts of bound proflavine (which varied depending upon the DNA substrate) and at an ionic strength value of 0.5. The level of the maximal reaction increased in the following order: from phi Xss DNA to calf thymus DNA and finally to phi XRFI DNA. The conformation of the proflavine-DNA complex was thus a determinant for the efficiency of the photodynamic process. The ionic strength effect could not be explained by the evolution of the proflavine triplet state in irradiated proflavine-calf thymus DNA complexes.

Determination of the content of alkyl ketene dimer in its latex by an ionic-liquid assisted headspace gas chromatography.

PubMed

Yan, Ning; Wan, Xiao-Fang; Chai, Xin-Sheng; Chen, Run-Quan; Chen, Chun-Xia

2017-12-29

This paper reports on an ionic-liquid assisted headspace gas chromatographic (HS-GC) for the determination of the content of alkyl ketene dimer (AKD) in its latex samples, in which the GC system was equipped with a thermal conductivity detector (TCD). The method was based on the AKD hydrolysis conducted in 1-butyl-3-methylimidazolium chloride (ionic-liquid) added medium at 100°C for 10min in a closed headspace sample vial, and the measured CO 2 (the resulting product of the hydrolysis) by HS-GC. The results showed that the present method has a good measurement precision (RSD <2.3%) and accuracy (recoveries from 96 - 105%), and the limit of quantitation (LOQ) is 0.9%. The present method is very suitable to be used for the routine check of AKD content in its latex sample in mill applications. The study also showed that the content of AKD in the tested commercial latex samples were in the range of 3.5-12%. Copyright © 2017 Elsevier B.V. All rights reserved.

Monitoring sodium removal and delivered dialysis by conductivity.

PubMed

Locatelli, F; Di Filippo, S; Manzoni, C; Corti, M; Andrulli, S; Pontoriero, G

1995-11-01

As cardiovascular stability and the delivery of the prescribed dialysis "dose" seem to be the main factors in determining the morbidity and mortality of hemodialyzer patients today, it is of paramount importance to match hydro-sodium removal with interdialytic load and to verify the delivered dialysis at each session. A specially designed Biofeedback Module (BM--COT Hospal) allows the automatic determination of plasma water conductivity and effective ionic dialysance with no need for blood samples. Using BM, we evaluated the validity of "conductivity kinetic modelling" (CKM) and the possibility that this may substitute "sodium kinetic modelling". Moreover, we evaluated the "in vivo" relationship between ionic dialysance and effective urea clearance. Our results demonstrate that: 1) CKM makes it possible to obtain programmed end-dialysis plasma water conductivity with an error of less than +/- 0.14 mS/cm, roughly equivalent to a sodium concentration of +/- 1.4 mEq/L. 2). Ionic dialysance and effective urea clearance are not equivalent but, as the interrelationship between these is known, the BM allows the routine monitoring of delivered dialysis.

In situ ionic liquid dispersive liquid-liquid microextraction and direct microvial insert thermal desorption for gas chromatographic determination of bisphenol compounds.

PubMed

Cacho, Juan Ignacio; Campillo, Natalia; Viñas, Pilar; Hernández-Córdoba, Manuel

2016-01-01

A new procedure based on direct insert microvial thermal desorption injection allows the direct analysis of ionic liquid extracts by gas chromatography and mass spectrometry (GC-MS). For this purpose, an in situ ionic liquid dispersive liquid-liquid microextraction (in situ IL DLLME) has been developed for the quantification of bisphenol A (BPA), bisphenol Z (BPZ) and bisphenol F (BPF). Different parameters affecting the extraction efficiency of the microextraction technique and the thermal desorption step were studied. The optimized procedure, determining the analytes as acetyl derivatives, provided detection limits of 26, 18 and 19 ng L(-1) for BPA, BPZ and BPF, respectively. The release of the three analytes from plastic containers was monitored using this newly developed analytical method. Analysis of the migration test solutions for 15 different plastic containers in daily use identified the presence of the analytes at concentrations ranging between 0.07 and 37 μg L(-1) in six of the samples studied, BPA being the most commonly found and at higher concentrations than the other analytes.

A new method for the determination of vaporization enthalpies of ionic liquids at low temperatures.

PubMed

Verevkin, Sergey P; Zaitsau, Dzmitry H; Emelyanenko, Vladimir N; Heintz, Andreas

2011-11-10

A new method for the determination of vaporization enthalpies of extremely low volatile ILs has been developed using a newly constructed quartz crystal microbalance (QCM) vacuum setup. Because of the very high sensitivity of the QCM it has been possible to reduce the average temperature of the vaporization studies by approximately 100 K in comparison to other conventional techniques. The physical basis of the evaluation procedure has been developed and test measurements have been performed with the common ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C(2)mim][NTf(2)] extending the range of measuring vaporization enthalpies down to 363 K. The results obtained for [C(2)mim][NTf(2)] have been tested for thermodynamic consistency by comparison with data already available at higher temperatures. Comparison of the temperature-dependent vaporization enthalpy data taken from the literature show only acceptable agreement with the heat capacity difference of -40 J K(-1) mol(-1). The method developed in this work opens also a new way to obtain reliable values of vaporization enthalpies of thermally unstable ionic liquids.

Biocompatible ionic liquid-biopolymer electrolyte-enabled thin and compact magnesium-air batteries.

PubMed

Jia, Xiaoteng; Yang, Yang; Wang, Caiyun; Zhao, Chen; Vijayaraghavan, R; MacFarlane, Douglas R; Forsyth, Maria; Wallace, Gordon G

2014-12-10

With the surge of interest in miniaturized implanted medical devices (IMDs), implantable power sources with small dimensions and biocompatibility are in high demand. Implanted battery/supercapacitor devices are commonly packaged within a case that occupies a large volume, making miniaturization difficult. In this study, we demonstrate a polymer electrolyte-enabled biocompatible magnesium-air battery device with a total thickness of approximately 300 μm. It consists of a biocompatible polypyrrole-para(toluene sulfonic acid) cathode and a bioresorbable magnesium alloy anode. The biocompatible electrolyte used is made of choline nitrate (ionic liquid) embedded in a biopolymer, chitosan. This polymer electrolyte is mechanically robust and offers a high ionic conductivity of 8.9 × 10(-3) S cm(-1). The assembled battery delivers a maximum volumetric power density of 3.9 W L(-1), which is sufficient to drive some types of IMDs, such as cardiac pacemakers or biomonitoring systems. This miniaturized, biocompatible magnesium-air battery may pave the way to a future generation of implantable power sources.

New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics.

PubMed

Drüschler, Marcel; Borisenko, Natalia; Wallauer, Jens; Winter, Christian; Huber, Benedikt; Endres, Frank; Roling, Bernhard

2012-04-21

Ionic liquids are of high interest for the development of safe electrolytes in modern electrochemical cells, such as batteries, supercapacitors and dye-sensitised solar cells. However, electrochemical applications of ionic liquids are still hindered by the limited understanding of the interface between electrode materials and ionic liquids. In this article, we first review the state of the art in both experiment and theory. Then we illustrate some general trends by taking the interface between the extremely pure ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and an Au(111) electrode as an example. For the study of this interface, electrochemical impedance spectroscopy was combined with in situ STM and in situ AFM techniques. In addition, we present new results for the temperature dependence of the interfacial capacitance and dynamics. Since the interfacial dynamics are characterised by different processes taking place on different time scales, the temperature dependence of the dynamics can only be reliably studied by recording and carefully analysing broadband capacitance spectra. Single-frequency experiments may lead to artefacts in the temperature dependence of the interfacial capacitance. We demonstrate that the fast capacitive process exhibits a Vogel-Fulcher-Tamman temperature dependence, since its time scale is governed by the ionic conductivity of the ionic liquid. In contrast, the slower capacitive process appears to be Arrhenius activated. This suggests that the time scale of this process is determined by a temperature-independent barrier, which may be related to structural reorganisations of the Au surface and/or to charge redistributions in the strongly bound innermost ion layer. This journal is © the Owner Societies 2012

The mean ionic charge of silicon in 3HE-rich solar flares

NASA Technical Reports Server (NTRS)

Luhn, A.; Klecker, B.; Hovestadt, E.; Moebius, E.

1985-01-01

Mean ionic charge of iron in 3He-rich solar flares and the average mean charge of Silicon for 23 #He-rich periods during the time interval from September 1978 to October 1979 were determined. It is indicated that the value of the mean charge state of Silicon is higher than the normal flare average by approximately 3 units and in perticular it is higher then the value predicted by resonant heating models for 3He-rich solar flares.

Comparison of micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction and modified quick, easy, cheap, effective, rugged, and safe method for the determination of difenoconazole in cowpea.

PubMed

Chen, Xiaochu; Bian, Yanli; Liu, Fengmao; Teng, Peipei; Sun, Pan

2017-10-06

Two simple sample pretreatment for the determination of difenoconazole in cowpea was developed including micellar extraction combined with ionic liquid based vortex-assisted liquid-liquid microextraction (ME-IL-VALLME) prior to high performance liquid chromatography (HPLC), and modified quick, easy, cheap, effective, rugged, and safe method (QuEChERS) coupled with HPLC-MS/MS. In ME-IL-VALLME method, the target analyte was extracted by surfactant Tween 20 micellar solution, then the supernatant was diluted with 3mL water to decrease the solubility of micellar solution. Subsequently, the vortex-assisted liquid-liquid microextraction (VALLME) procedure was performed in the diluted extraction solution by using the ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF 6 ) as the extraction solvent and Tween 20 as an emulsifier to enhance the dispersion of the water-immiscible ionic liquid into the aqueous phase. Parameters that affect the extraction have been investigated in both methods Under the optimum conditions, the limits of quantitation were 0.10 and 0.05mgkg -1 , respectively. And good linearity was achieved with the correlation coefficient higher than 0.9941. The relative recoveries ranged from 78.6 to 94.8% and 92.0 to 118.0% with the relative standard deviations (RSD) of 7.9-9.6% and 1.2-3.2%, respectively. Both methods were quick, simple and inexpensive. However, the ME-IL-VALLME method provides higher enrichment factor compared with conventional QuEChERS method. The ME-IL-VALLME method has a strong potential for the determination of difenoconazole in complex vegetable matrices with HPLC. Copyright © 2017 Elsevier B.V. All rights reserved.

[Determination of Chloride Salt Solution by NIR Spectroscopy].

PubMed

Zhang, Bin; Chen, Jian-hong; Jiao, Ming-xing

2015-07-01

Determination of chloride salt solution by near infrared spectrum plays a very important role in Biomedicine. The near infrared spectrum analysis of Sodium chloride, potassium chloride, calcium chloride aqueous solution shows that the concentration change of chloride salt can affect hydrogen bond, resulting in the variation of near infrared spectrum of water. The temperature influence on NIR spectrum has been decreased by choosing reasonable wavelength range and the wavelength where the temperature effects are zero (isosbestic point). Chlorine salt prediction model was established based on partial least squares method and used for predicting the concentration of the chlorine ion. The impact on near infrared spectrum of the cation ionic radius, the number of ionic charge, the complex effect of ionic in water has also discussed in this article and the reason of every factor are analysed. Experimental results show that the temperature and concentration will affect the near-infrared spectrum of the solution, It is found that the effect of temperature plays the dominant role at low concentrations of chlorine salt; rather, the ionic dominates at high concentration. Chloride complexes are formed in aqueous solution, It has an effect on hydrogen bond of water combining with the cations in chlorine salt solution, Comparing different chloride solutions at the same concentration, the destruction effects of chloride complexes and catnions on the hydrogen bond of water increases in the sequences: CaCl2 >NaCl>KC. The modeling result shows that the determination coefficients (R2) = 99.97%, the root mean square error of cross validation (RM- SECV) = 4.51, and the residual prediction deviation (RPD) = 62.7, it meets the daily requirements of biochemical detection accuracy.

Ionic Interactions in Actinide Tetrahalides

NASA Astrophysics Data System (ADS)

Akdeniz, Z.; Karaman, A.; Tosi, M. P.

2001-05-01

We determine a model of the ionic interactions in AX 4 compounds (where A is an atom in the actinide series from Th to Am and X = F, Cl, Br or I) by an analysis of data on the static and dynamic structure of their molecular monomers. The potential energy function that we adopt is taken from earlier work on rare-earth trihalides [Z. Akdeniz, Z. Q q e k and M. P. Tosi, Z. Naturforsch. 55a, 861 (2000)] and in particular allows for the electronic polarizability of the actinide ion. This polarizability quantitatively determines the antisymmetric-bending vibrational mode, but its magnitude remains compatible with a symmetric tetrahedral shape of the molecule at equilibrium. The fluorides have an especially high degree of ionic character, and the interionic-force parameters for each halide of the U, Np, Pu and Am series show regular trends, suggesting that extrapolations to the other transuranic-element halides may usefully be made. The Th compounds show some deviations from these trends, and the interionic-force model that we determine for ThCl4 differs somewhat from that obtained in a previous study. We therefore return on the evaluation of the relative stability of charged oligomers of ThCl4 and ZrCl4 and find confirmation of our earlier results on this problem.

Determination of diflubenzuron and chlorbenzuron in fruits by combining acetonitrile-based extraction with dispersive liquid-liquid microextraction followed by high-performance liquid chromatography.

PubMed

Ruan, Chunqiang; Zhao, Xiang; Liu, Chenglan

2015-09-01

In this study, a simple and low-organic-solvent-consuming method combining an acetonitrile-partitioning extraction procedure followed by "quick, easy, cheap, effective, rugged and safe" cleanup with ionic-liquid-based dispersive liquid-liquid microextraction and high-performance liquid chromatography with diode array detection was developed for the determination of diflubenzuron and chlorbenzuron in grapes and pears. Ionic-liquid-based dispersive liquid-liquid microextraction was performed using the ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate as the extractive solvent and acetonitrile extract as the dispersive solvent. The main factors influencing the efficiency of the dispersive liquid-liquid microextraction were evaluated, including the extractive solvent type and volume and the dispersive solvent volume. The validation parameters indicated the suitability of the method for routine analyses of benzoylurea insecticides in a large number of samples. The relative recoveries at three spiked levels ranged between 98.6 and 109.3% with relative standard deviations of less than 5.2%. The limit of detection was 0.005 mg/kg for the two insecticides. The proposed method was successfully used for the rapid determination of diflubenzuron and chlorbenzuron residues in real fruit samples. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Label-free biosensing with functionalized nanopipette probes.

PubMed

Umehara, Senkei; Karhanek, Miloslav; Davis, Ronald W; Pourmand, Nader

2009-03-24

Nanopipette technology can uniquely identify biomolecules such as proteins based on differences in size, shape, and electrical charge. These differences are determined by the detection of changes in ionic current as the proteins interact with the nanopipette tip coated with probe molecules. Here we show that electrostatic, biotin-streptavidin, and antibody-antigen interactions on the nanopipette tip surface affect ionic current flowing through a 50-nm pore. Highly charged polymers interacting with the glass surface modulated the rectification property of the nanopipette electrode. Affinity-based binding between the probes tethered to the surface and their target proteins caused a change in the ionic current due to a partial blockade or an altered surface charge. These findings suggest that nanopipettes functionalized with appropriate molecular recognition elements can be used as nanosensors in biomedical and biological research.

The potential of incorporation of binary salts and ionic liquid in P(VP-co-VAc) gel polymer electrolyte in electrochemical and photovoltaic performances

PubMed Central

Ming, Ng Hon; Ramesh, S.; Ramesh, K.

2016-01-01

In this study, dye-sensitized solar cells (DSSCs) has been assembled with poly(1-vinylpyrrolidone-co-vinyl acetate) (P(VP-co-VAc)) gel polymer electrolytes (GPEs) which have been incorporated with binary salt and an ionic liquid. The potential of this combination was studied and reported. The binary salt system GPEs was having ionic conductivity and power conversion efficiency (PCE) that could reach up to 1.90 × 10−3 S cm−1 and 5.53%, respectively. Interestingly, upon the addition of the ionic liquid, MPII into the binary salt system the ionic conductivity and PCE had risen steadily up to 4.09 × 10−3 S cm−1 and 5.94%, respectively. In order to know more about this phenomenon, the electrochemical impedance studies (EIS) of the GPE samples have been done and reported. Fourier transform infrared studies (FTIR) and thermogravimetric analysis (TGA) have also been studied to understand more on the structural and thermal properties of the GPEs. The Nyquist plot and Bodes plot studies have been done in order to understand the electrochemical properties of the GPE based DSSCs and Tafel polarization studies were done to determine the electrocatalytic activity of the GPE samples. PMID:27273020

Theoretical derivation of anodizing current and comparison between fitted curves and measured curves under different conditions.

PubMed

Chong, Bin; Yu, Dongliang; Jin, Rong; Wang, Yang; Li, Dongdong; Song, Ye; Gao, Mingqi; Zhu, Xufei

2015-04-10

Anodic TiO2 nanotubes have been studied extensively for many years. However, the growth kinetics still remains unclear. The systematic study of the current transient under constant anodizing voltage has not been mentioned in the original literature. Here, a derivation and its corresponding theoretical formula are proposed to overcome this challenge. In this paper, the theoretical expressions for the time dependent ionic current and electronic current are derived to explore the anodizing process of Ti. The anodizing current-time curves under different anodizing voltages and different temperatures are experimentally investigated in the anodization of Ti. Furthermore, the quantitative relationship between the thickness of the barrier layer and anodizing time, and the relationships between the ionic/electronic current and temperatures are proposed in this paper. All of the current-transient plots can be fitted consistently by the proposed theoretical expressions. Additionally, it is the first time that the coefficient A of the exponential relationship (ionic current j(ion) = A exp(BE)) has been determined under various temperatures and voltages. And the results indicate that as temperature and voltage increase, ionic current and electronic current both increase. The temperature has a larger effect on electronic current than ionic current. These results can promote the research of kinetics from a qualitative to quantitative level.

Mesoscopic Framework Enables Facile Ionic Transport in Solid Electrolytes for Li Batteries

DOE PAGES

Ma, Cheng; Cheng, Yongqiang; Chen, Kai; ...

2016-03-29

In Li-ion-conducting solid electrolytes can simultaneously overcome two grand challenges for Li-ion batteries: the severe safety concerns that limit the large-scale application and the poor electrolyte stability that forbids the use of high-voltage cathodes. Nevertheless, the ionic conductivity of solid electrolytes is typically low, compromising the battery performances. Precisely determining the ionic transport mechanism(s) is a prerequisite for the rational design of highly conductive solid electrolytes. For decades, the research on this subject has primarily focused on the atomic and microscopic scales, where the main features of interest are unit cells and microstructures, respectively. We show that the largely overlookedmore » mesoscopic scale lying between these extremes could be the key to fast ionic conduction. In a prototype system, (Li 0.33La 0.56)TiO 3, a mesoscopic framework is revealed for the first time by state-of-the-art scanning transmission electron microscopy. Corroborated by theoretical calculations and impedance measurements, it is demonstrated that such a unique configuration maximizes the number of percolation directions and thus most effectively improves the ionic conductivity. Finally, this discovery reconciles the long-standing structure–property inconsistency in (Li 0.33La 0.56)TiO 3 and also identifies mesoscopic ordering as a promising general strategy for optimizing Li+ conduction.« less

Self-consistent field theory of polymer-ionic molecule complexation.

PubMed

Nakamura, Issei; Shi, An-Chang

2010-05-21

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C(i) ((a))(kDelta)(=0 or 1), whose average determines the number of adsorbed molecules, n(BI). Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for n(BI) are obtained, depending on the equilibrium constant of single-ion binding. Spinodal lines calculated from the mean-field free energy exhibit closed-loop regions where the homogeneous phase becomes unstable. This phase instability is driven by the excluded-volume interaction due to the single occupancy of ion-binding sites on the polymers. Moreover, sol-gel transitions are examined using a critical degree of conversion. A gel phase is induced when the concentration of adsorbates is increased. At a higher concentration of the adsorbates, however, a re-entrance from a gel phase into a sol phase arises from the correlation between unoccupied and occupied ion-binding sites. The theory is applied to a model system, poly(vinyl alcohol) and borate ion in aqueous solution with sodium chloride. Good agreement between theory and experiment is obtained.

Theoretical derivation of anodizing current and comparison between fitted curves and measured curves under different conditions

NASA Astrophysics Data System (ADS)

Chong, Bin; Yu, Dongliang; Jin, Rong; Wang, Yang; Li, Dongdong; Song, Ye; Gao, Mingqi; Zhu, Xufei

2015-04-01

Anodic TiO2 nanotubes have been studied extensively for many years. However, the growth kinetics still remains unclear. The systematic study of the current transient under constant anodizing voltage has not been mentioned in the original literature. Here, a derivation and its corresponding theoretical formula are proposed to overcome this challenge. In this paper, the theoretical expressions for the time dependent ionic current and electronic current are derived to explore the anodizing process of Ti. The anodizing current-time curves under different anodizing voltages and different temperatures are experimentally investigated in the anodization of Ti. Furthermore, the quantitative relationship between the thickness of the barrier layer and anodizing time, and the relationships between the ionic/electronic current and temperatures are proposed in this paper. All of the current-transient plots can be fitted consistently by the proposed theoretical expressions. Additionally, it is the first time that the coefficient A of the exponential relationship (ionic current jion = A exp(BE)) has been determined under various temperatures and voltages. And the results indicate that as temperature and voltage increase, ionic current and electronic current both increase. The temperature has a larger effect on electronic current than ionic current. These results can promote the research of kinetics from a qualitative to quantitative level.

Mutual solubility of water and structural/positional isomers of N-alkylpyridinium-based ionic liquids.

PubMed

Freire, Mara G; Neves, Catarina M S S; Shimizu, Karina; Bernardes, Carlos E S; Marrucho, Isabel M; Coutinho, João A P; Canongia Lopes, José N; Rebelo, Luís Paulo N

2010-12-09

Despite many previous important contributions to the characterization of the liquid-liquid phase behavior of ionic liquids (ILs) plus water systems, a gap still exists as far as the effect of isomers (of ILs) is concerned. Therefore, in this work, a comprehensive study of the liquid-liquid equilibria between water and isomeric pyridinium-based ionic liquids has been performed. Atmospheric pressure mutual solubilities between water and pyridinium-based ionic liquids combined with the common anion bis[(trifluoromethyl)sulfonyl]imide were experimentally determined between (288.15 and 318.15) K. The main goal of this work is to study the isomeric effects on the pyridinium-based cation, namely, the structural and positional isomerism, as well as the alkyl side chain length. To the best of our knowledge, the influence of both structural and positional isomerism on the liquid-liquid behavior in ionic-liquid-water-containing systems is an unexplored field and is here assessed for the first time. Moreover, from the experimental solubility data, several infinite dilution molar thermodynamic functions of solution, namely, the Gibbs energy, the enthalpy, and the entropy, were estimated and discussed. In addition, aiming at gathering a broader picture of the underlying thermodynamic solvation phenomenon, molecular dynamics simulations were also carried out for the same experimental systems.

Interaction of Cellulose Chains with Ionic Liquids and Water via MD simulations

NASA Astrophysics Data System (ADS)

Ismail, Ahmed; Rabideau, Brooks

2012-02-01

One promising route for combustible fuel sources which are both renewable and have a low environmental impact is the conversion of waste biomass into tailor-made fuels. An important aspect of this process is the low-energy separation of cellulose from the biomass. Ionic liquids (ILs) have proven to be very good in dissolving cellulose with the added benefit of being essentially non-volatile making them ideal for ``green'' processing. IL research, however, remains relatively new, with many parts of this dissolution process remaining uncertain. We examine the behavior of cellulose with the ionic liquids [BMIM]Cl, [EMIM]Ac and [DMIM]DMP as well as water via MD simulation. All three ionic liquids have been observed to dissolve cellulose quite well yet have differently sized anions. We explore these differences and the impacts they have on their interactions with cellulose. First we examine the dynamics of a single cellulose strand in these ionic liquids. We determine the radius of gyration and the hydrogen bonds that are formed between the anions and cellulose. Next, we probe the dissolution mechanism of multiple, bound cellulose strands examining of multiple, bound cellulose strands examining interactions at the IL/cellulose interface and the breakup of inter-cellulose hydrogen bonds.

A Rayleighian approach for modeling kinetics of ionic transport in polymeric media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Rajeev

2017-02-14

Here, we report a theoretical approach for analyzing impedance of ionic liquids (ILs) and charged polymers such as polymerized ionic liquids (PolyILs) within linear response. The approach is based on the Rayleigh dissipation function formalism, which provides a computational framework for a systematic study of various factors, including polymer dynamics, in affecting the impedance. We present an analytical expression for the impedance within linear response by constructing a one-dimensional model for ionic transport in ILs/PolyILs. This expression is used to extract mutual diffusion constants, the length scale of mutual diffusion, and thicknesses of a low-dielectric layer on the electrodes frommore » the broadband dielectric spectroscopy (BDS) measurements done for an IL and three PolyILs. Also, static dielectric permittivities of the IL and the PolyILs are determined. The extracted mutual diffusion constants are compared with the self diffusion constants of ions measured using pulse field gradient (PFG) fluorine nuclear magnetic resonance (NMR). For the first time, excellent agreements between the diffusivities extracted from the Electrode Polarization spectra (EPS) of IL/PolyILs and those measured using the PFG-NMR are found, which allows the use of the EPS and the PFG-NMR techniques in a complimentary manner for a general understanding of the ionic transport.« less

Enhancement of Force Generated by Individual Myosin Heads in Skinned Rabbit Psoas Muscle Fibers at Low Ionic Strength

PubMed Central

Sugi, Haruo; Abe, Takahiro; Kobayashi, Takakazu; Chaen, Shigeru; Ohnuki, Yoshiki; Saeki, Yasutake; Sugiura, Seiryo

2013-01-01

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca2+-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca2+-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca2+-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca2+ activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca2+-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca2+-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction. PMID:23691080

A new approach combining different MRI methods to provide detailed view on swelling dynamics of xanthan tablets influencing drug release at different pH and ionic strength.

PubMed

Mikac, Ursa; Sepe, Ana; Kristl, Julijana; Baumgartner, Sasa

2010-08-03

The key element in drug release from hydrophilic matrix tablets is the gel layer that regulates the penetration of water and controls drug dissolution and diffusion. We have selected magnetic resonance imaging (MRI) as the method of choice for visualizing the dynamic processes occurring during the swelling of xanthan tablets in a variety of media. The aims were (i) to develop a new method using MRI for accurate determination of penetration, swelling and erosion fronts, (ii) to investigate the effects of pH and ionic strength on swelling, and (iii) to study the influence of structural changes in xanthan gel on drug release. Two dimensional (2D) MRI and one dimensional single point imaging (SPI) of swollen xanthan tablets were recorded, together with T(2) mapping. The border between dry and hydrated glassy xanthan-the penetration front-was determined from 1D SPI signal intensity profiles. The erosion front was obtained from signal intensity profiles of 2D MR images. The swelling front, where xanthan is transformed from a glassy to a rubbery state (gel formation), was determined from T(2) profiles. Further, the new combination of MRI methods for swelling front determination enables to explain the appearance of the unusual "bright front" observed on 2D MR images in tablets swollen in HCl pH 1.2 media, which represents the position of swelling front. All six media studied, differing in pH and ionic strength, penetrate through the whole tablet in 4h+/-0.3h, but formation of the gel layer is significantly delayed. Unexpectedly, the position of the swelling front was the same, independently of the different xanthan gel structures formed under different conditions of pH and ionic strength. The position of the erosion front, on the other hand, is strongly dependent on pH and ionic strength, as reflected in different thicknesses of the gel layers. The latter are seen to be the consequence of the different hydrodynamic radii of the xanthan molecules, which affect the drug release kinetics. The slowest release of pentoxifylline was observed in water where the thickest gel was formed, whereas the fastest release was observed in HCl pH 1.2, in which the gel layer was thinnest. Moreover, experiments simulating physiological conditions showed that changes of pH and ionic strength influence the xanthan gel structure relatively quickly, and consequently the drug release kinetics. It is therefore concluded that drug release is greatly influenced by changes in the xanthan molecular conformation, as reflected in changed thickness of the gel layer. A new method utilizing combination of SPI, multi-echo MRI and T(2) mapping eliminates the limitations of standard methods used in previous studies for determining moving fronts and improves current understanding of the dynamic processes involved in polymer swelling. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Macrophage Solubilization and Cytotoxicity of Indium-Containing Particles as in vitro Correlates to Pulmonary Toxicity in vivo

PubMed Central

Gwinn, William M.; Qu, Wei; Bousquet, Ronald W.; Price, Herman; Shines, Cassandra J.; Taylor, Genie J.; Waalkes, Michael P.; Morgan, Daniel L.

2015-01-01

Macrophage-solubilized indium-containing particles (ICPs) were previously shown in vitro to be cytotoxic. In this study, we compared macrophage solubilization and cytotoxicity of indium phosphide (InP) and indium-tin oxide (ITO) with similar particle diameters (∼1.5 µm) and then determined if relative differences in these in vitro parameters correlated with pulmonary toxicity in vivo. RAW 264.7 macrophages were treated with InP or ITO particles and cytotoxicity was assayed at 24 h. Ionic indium was measured in 24 h culture supernatants. Macrophage cytotoxicity and particle solubilization in vitro were much greater for InP compared with ITO. To correlate changes in vivo, B6C3F1 mice were treated with InP or ITO by oropharyngeal aspiration. On Days 14 and 28, bronchoalveolar lavage (BAL) and pleural lavage (PL) fluids were collected and assayed for total leukocytes. Cell differentials, lactate dehydrogenase activity, and protein levels were also measured in BAL. All lavage parameters were greatly increased in mice treated with InP compared with ITO. These data suggest that macrophage solubilization and cytotoxicity of some ICPs in vitro are capable of predicting pulmonary toxicity in vivo. In addition, these differences in toxicity were observed despite the two particulate compounds containing similar amounts of indium suggesting that solubilization, not total indium content, better reflects the toxic potential of some ICPs. Soluble InCl3 was shown to be more cytotoxic than InP to macrophages and lung epithelial cells in vitro further suggesting that ionic indium is the primary cytotoxic component of InP. PMID:25527823

Studies of Ionic Photoionization Using Relativistic Random Phase Approximation and Relativistic Multichannel Quantum Defect Theory

NASA Astrophysics Data System (ADS)

Haque, Ghousia Nasreen

The absorption of electromagnetic radiation by positive ions is one of the fundamental processes of nature which occurs in every intensely hot environment. Due to the difficulties in producing sufficient densities of ions in a laboratory, there are very few measurements of ionic photoabsorption parameters. On the theoretical side, some calculations have been made of a few major photoionization parameters, but generally speaking, most of the work done so far has employed rather simple single particle models and any theoretical work which has adequately taken into account intricate atomic many-body and relativistic effects is only scanty. In the present work, several complex aspects of atomic/ionic photoabsorption parameters have been studied. Non -resonant photoionization in neon and argon isonuclear as well as isoelectronic sequences has been studied using a very sophisticated technique, namely the relativistic random phase approximation (RRPA). This technique takes into account relativistic effects as well as an important class of major many-body effects on the same footing. The present calculations confirmed that gross features of photoionization parameters calculated using simpler models were not an artifact of the simple model. Also, the present RRPA calculations on K^+ ion and neutral Ar brought out the relative importance of various many-body effects such the inter-channel coupling. Inter-channel coupling between discrete bound state photoexcitation channels from an inner atomic/ionic level and photoionization continuum channels from an outer atomic/ionic level leads to the phenomena of autoionization resonances in the photoionization process. These resonances lead to very complex effects in the atomic/ionic photoabsorption spectra. These resonances have been calculated and studied in the present work in the neon and magnesium isoelectronic sequences using the relativistic multi-channel quantum defect theory (RMQDT) within the framework of the RRPA. The character of the autoionization resonances studied was determined in the present work and the effect of series perturbations in the Rydberg series due to interference between various multichannel processes was quantitatively determined. Furthermore, results of the present calculations also serve as important pointer to measure the relative strengths of radiative (fluorescence) decay modes and non -radiative (autoionization/auger) decay modes in an isoelectronic sequence.

Extraction of triazole fungicides in environmental waters utilizing poly (ionic liquid)-functionalized magnetic adsorbent.

PubMed

Liu, Cheng; Liao, Yingmin; Huang, Xiaojia

2017-11-17

This work prepared a new poly (ionic liquid)-functionalized magnetic adsorbent (PFMA) for the extraction of triazole fungicides (TFs) in environmental waters prior to determination by high performance liquid chromatography/diode array detection (HPLC-DAD). A polymerizable ionic liquid, 1-methyl-3-allylimidazolium bis(trifluoromethylsulfonyl)imide was employed to copolymerize with divinylbenzene on the surface of modified magnetite to fabricate the PFMA. The morphology, spectroscopic and magnetic properties of the new adsorbent were investigated by different techniques. A series of key parameters that influence the extraction performance including the amount of PFMA, desorption solvent, adsorption and desorption time, sample pH value and ionic strength were optimized in detail. Under the optimum conditions, the prepared PFMA could extract targeted TFs effectively and quickly under the format of magnetic solid-phase extraction (MSPE). Satisfactory linearities were achieved in the range of 0.1-200.0μg/L for triadimenol and 0.05-200.0μg/L for other TFs with good coefficients of determination above 0.99 for all analytes. The limits of detection (S/N=3) and limits of quantification (S/N=10) for TFs were in the range of 0.0050-0.0078μg/L and 0.017-0.026μg/L, respectively. Environmental waters including lake, river and well waters were used to demonstrate the applicability of developed MSPE-HPLC-DAD method, and satisfactory recoveries and repeatability were obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

Developing a polymeric sensor to monitor intracellular conditions

NASA Astrophysics Data System (ADS)

Mudarri, Timothy C.; Leo, Donald J.; Wood, Brett C.; Shires, Peter K.

2004-07-01

Ionic electroactive polymers have been developed as mechanical sensors or actuators, taking advantage of the electromechanical coupling of the materials. This research attempts to take advantage of the chemomechanical and chemoelectrical coupling by characterizing the transient response as the polymer undergoes an ion exchange, thus using the polymer for ionic sensing. Nafion is a biocompatible material, and an implantable polymeric ion sensor which has applications in the biomedical field for bone healing research. An ion sensor and a strain gauge could determine the effects of motion allowed at the fracture site, thus improving rehabilitation procedures for bone fractures. The charge sensitivity of the material and the capacitance of the material were analyzed to determine the transient response. Both measures indicate a change when immersed in ionic salt solutions. It is demonstrated that measuring the capacitance is the best indicator of an ion exchange. Relative to a flat response in deionized water (+/-2%), the capacitance of the polymer exhibits an exponential decay of ~25% of its peak when placed in a salt solution. A linear correlation between the time constant of the decay and the ionic size of the exchanging ion was developed that could reasonably predict a diffusing ion. Tests using an energy dispersive spectrometer (EDS) indicate that 90% of the exchange occurs in the first 20 minutes, shown by both capacitance decay and an atomic level scan. The diffusion rate time constant was found to within 0.3% of the capacitance time constant, confirming the ability of capacitance to measure ion exchange.

The Na+/K+ pump is an important modulator of refractoriness and rotor dynamics in human atrial tissue.

PubMed

Sánchez, Carlos; Corrias, Alberto; Bueno-Orovio, Alfonso; Davies, Mark; Swinton, Jonathan; Jacobson, Ingemar; Laguna, Pablo; Pueyo, Esther; Rodríguez, Blanca

2012-03-01

Pharmacological treatment of atrial fibrillation (AF) exhibits limited efficacy. Further developments require a comprehensive characterization of ionic modulators of electrophysiology in human atria. Our aim is to systematically investigate the relative importance of ionic properties in modulating excitability, refractoriness, and rotor dynamics in human atria before and after AF-related electrical remodeling (AFER). Computer simulations of single cell and tissue atrial electrophysiology were conducted using two human atrial action potential (AP) models. Changes in AP, refractory period (RP), conduction velocity (CV), and rotor dynamics caused by alterations in key properties of all atrial ionic currents were characterized before and after AFER. Results show that the investigated human atrial electrophysiological properties are primarily modulated by maximal value of Na(+)/K(+) pump current (G(NaK)) as well as conductances of inward rectifier potassium current (G(K1)) and fast inward sodium current (G(Na)). G(NaK) plays a fundamental role through both electrogenic and homeostatic modulation of AP duration (APD), APD restitution, RP, and reentrant dominant frequency (DF). G(K1) controls DF through modulation of AP, APD restitution, RP, and CV. G(Na) is key in determining DF through alteration of CV and RP, particularly in AFER. Changes in ionic currents have qualitatively similar effects in control and AFER, but effects are smaller in AFER. The systematic analysis conducted in this study unravels the important role of the Na(+)/K(+) pump current in determining human atrial electrophysiology.

Determination of volatile polycyclic aromatic hydrocarbons in waters using headspace solid-phase microextraction with a benzyl-functionalized crosslinked polymeric ionic liquid coating.

PubMed

Merdivan, Melek; Pino, Verónica; Anderson, Jared L

2017-08-01

A benzyl-functionalized crosslinked polymeric ionic liquid (PIL), produced through the co-polymerization of the 1-vinylbenzyl-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (VBHDIM-NTf 2 ) ionic liquid (IL) monomer and 1,12-di(3-vinylbenzylimidazolium)dodecane bis[(trifluoromethyl)sulfonyl]imide ((DVBIM) 2 C 12- 2NTf 2 ) IL crosslinker, was successfully used as a sorbent coating in headspace solid-phase microextraction (SPME) coupled to gas chromatography (GC) with flame-ionization detection (FID) to determine seven volatile polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Optimum extraction conditions for the PAHs when using the novel sorbent include an extraction temperature of 50°C, an ionic strength content adjusted with 30% (w/v) NaCl in the aqueous sample, and an extraction time of 60 min. The extraction performance of the crosslinked PIL fiber was compared to the SPME commercial coating polydimethylsiloxane fiber. The calibration ranges of the studied PAHs were linear in the range of 0.02-20 µg L -1 for the crosslinked PIL fiber. The accuracy of the proposed method was demonstrated by examining the spiked recoveries of seven PAHs which produced values ranging from 67.2% to 130% (for river- and seawater samples), and precision values lower than 9.4% for a spiked level of 1 µg L -1 , and detection limits between 0.01 and 0.04 µg L -1 , which supports the sensitivity of the method using GC-FID.

Prediction of Osmotic Pressure of Ionic Liquids Inside a Nanoslit by MD Simulation and Continuum Approach

NASA Astrophysics Data System (ADS)

Moon, Gi Jong; Yang, Yu Dong; Oh, Jung Min; Kang, In Seok

2017-11-01

Osmotic pressure plays an important role in the processes of charging and discharging of lithium batteries. In this work, osmotic pressure of the ionic liquids confined inside a nanoslit is calculated by using both MD simulation and continuum approach. In the case of MD simulation, an ionic liquid is modeled as singly charged spheres with a short-ranged repulsive Lennard-Jones potential. The radii of the spheres are 0.5nm, reflecting the symmetry of ion sizes for simplicity. The simulation box size is 11nm×11nm×7.5nm with 1050 ion pairs. The concentration of ionic liquid is about 1.922mol/L, and the total charge on an individual wall varies from +/-60e(7.944 μm/cm2) to +/-600e(79.44 μm/cm2) . In the case of continuum approach, we classify the problems according to the correlation length and steric factor, and considered the four separate cases: 1) zero correlation length and zero steric factor, 2) zero correlation length and non-zero steric factor, 3) non-zero correlation length and zero steric factor, and 4) non-zero correlation and non-zero steric factor. Better understanding of the osmotic pressure of ionic liquids confined inside a nanoslit can be achieved by comparing the results of MD simulation and continuum approach. This research was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP: Ministry of Science, ICT & Future Planning) (No. 2017R1D1A1B05035211).

Effects of Dopant Ionic Radius on Cerium Reduction in Epitaxial Cerium Oxide Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Nan; Orgiani, Pasquale; Di Bartolomeo, Elisabetta

The role of trivalent rare-earth dopants in ceria epitaxial films on surface ion exchange reactivity and ion conductivity has been systematically studied. Single-crystal epitaxial films with unique crystal orientation and micro-structure nature have allowed us to rule out the influence of structural defects on both transport and surface ion exchange properties. The films conductivities were larger than those reported in literature for both polycrystalline ceramic pellets and crystalline films. An increase in oxygen vacancies and Ce 3+ concentration while decreasing the dopant ionic radius from La 3+ to Yb 3+ was observed, thus explaining the measured increased activation energy andmore » enhanced surface reactivity. The more significant ability of smaller dopant ionic radius in releasing the stress strength induced by the larger Ce 3+ ionic radius allows promoting the formation of oxygen vacancies and Ce 3+, which are two precious species in determining the efficiency of ion transport and surface ion exchange processes. This can open new perspectives in designing ceria-based materials in tailoring functional properties, either ion migration or surface reactivity, by rational cation substitutions.« less

Ionic liquid-anionic surfactant based aqueous two-phase extraction for determination of antibiotics in honey by high-performance liquid chromatography.

PubMed

Yang, Xiao; Zhang, Shaohua; Yu, Wei; Liu, Zhongling; Lei, Lei; Li, Na; Zhang, Hanqi; Yu, Yong

2014-06-01

An ionic liquid-anionic surfactant based aqueous two-phase extraction was developed and applied for the extraction of tetracycline, oxytetracycline and chloramphenicol in honey. The honey sample was mixed with Na2EDTA aqueous solution. The sodium dodecyl sulfate, ionic liquid 1-octyl-3-methylimidazolium bromide and sodium chloride were added in the mixture. After the resulting mixture was ultrasonically shaken and centrifuged, the aqueous two phase system was formed and analytes were extracted into the upper phase. The parameters affecting the extraction efficiency, such as the volume of ionic liquid, the category and amount of salts, sample pH value, extraction time and temperature were investigated. The limits of detection of tetracycline, oxytetracycline and chloramphenicol were 5.8, 8.2 and 4.2 μg kg(-1), respectively. When the present method was applied to the analysis of real honey samples, the recoveries of analytes ranged from 85.5 to 110.9% and relative standard deviations were lower than 6.9%. Copyright © 2014 Elsevier B.V. All rights reserved.

Computational analysis of the solvation of coffee ingredients in aqueous ionic liquid mixtures† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra24736a Click here for additional data file.

PubMed Central

Zeindlhofer, Veronika; Khlan, Diana; Bica, Katharina

2017-01-01

In this paper, we investigate the solvation of coffee ingredients including caffeine, gallic acid as representative for phenolic compounds and quercetin as representative for flavonoids in aqueous mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate [C2mim][OAc] at various concentrations. Due to the anisotropy of the solutes we show that classical Kirkwood–Buff theory is not appropriate to study solvation effects with increasing ionic liquid content. However, excess coordination numbers as well as the mean residence time of solvent molecules at the surface of the solutes can be determined by Voronoi tessellation. Since the volume of the hydration shells is also available by this method, solvation free energies will be discussed as a function of the ionic liquid concentration to yield a physical meaningful picture of solvation for the anisotropic solutes. Hydrogen bonding capabilities of the solutes and their relevance for experimental extraction yields from spent coffee grounds are also discussed. PMID:28496974

Absorption Refrigeration Cycles with Ammonia-Ionic Liquid Working Pairs Studied by Molecular Simulation.

PubMed

Becker, Tim M; Wang, Meng; Kabra, Abhishek; Jamali, Seyed Hossein; Ramdin, Mahinder; Dubbeldam, David; Infante Ferreira, Carlos A; Vlugt, Thijs J H

2018-04-18

For absorption refrigeration, it has been shown that ionic liquids have the potential to replace conventional working pairs. Due to the huge number of possibilities, conducting lab experiments to find the optimal ionic liquid is infeasible. Here, we provide a proof-of-principle study of an alternative computational approach. The required thermodynamic properties, i.e., solubility, heat capacity, and heat of absorption, are determined via molecular simulations. These properties are used in a model of the absorption refrigeration cycle to estimate the circulation ratio and the coefficient of performance. We selected two ionic liquids as absorbents: [emim][Tf 2 N], and [emim][SCN]. As refrigerant NH 3 was chosen due to its favorable operating range. The results are compared to the traditional approach in which parameters of a thermodynamic model are fitted to reproduce experimental data. The work shows that simulations can be used to predict the required thermodynamic properties to estimate the performance of absorption refrigeration cycles. However, high-quality force fields are required to accurately predict the cycle performance.

Ionic association and solvation in solutions of magnesium and nickel perchlorates in acetonitrile

NASA Astrophysics Data System (ADS)

Kalugin, O. N.; Agieienko, V. N.; Otroshko, N. A.; Moroz, V. V.

2009-02-01

The paper presents the conductometric data on solutions of Mg(ClO4)2 and Ni(ClO4)2 in acetonitrile over the temperature ranges 5-55°C for Mg(ClO4)2 and 25-75°C for Ni(ClO4)2. The extended Lee-Wheaton equation for unsymmetrical electrolytes was used to determine the limiting equivalent conductivities of the Mg2+, Ni2+, and ClO{4/-} ions and first-step ionic association constants with the formation of [KtClO4]+ ion pairs. Lower ionic association constants for Ni(ClO4)2 compared with Mg(ClO4)2 were a consequence of stronger non-Coulomb repulsion in the formation of [KtClO4]+ ion pairs because of the formation of a firmer solvation shell by the nickel compared with magnesium cation. The structure-dynamic parameter of ionic solvation was estimated. It was found that spatial-time correlations in the nearest environment of ions increased in the series ClO{4/-} > Mg2+ > Ni2+.

Absorption Refrigeration Cycles with Ammonia–Ionic Liquid Working Pairs Studied by Molecular Simulation

PubMed Central

2018-01-01

For absorption refrigeration, it has been shown that ionic liquids have the potential to replace conventional working pairs. Due to the huge number of possibilities, conducting lab experiments to find the optimal ionic liquid is infeasible. Here, we provide a proof-of-principle study of an alternative computational approach. The required thermodynamic properties, i.e., solubility, heat capacity, and heat of absorption, are determined via molecular simulations. These properties are used in a model of the absorption refrigeration cycle to estimate the circulation ratio and the coefficient of performance. We selected two ionic liquids as absorbents: [emim][Tf2N], and [emim][SCN]. As refrigerant NH3 was chosen due to its favorable operating range. The results are compared to the traditional approach in which parameters of a thermodynamic model are fitted to reproduce experimental data. The work shows that simulations can be used to predict the required thermodynamic properties to estimate the performance of absorption refrigeration cycles. However, high-quality force fields are required to accurately predict the cycle performance. PMID:29749996

A microextraction procedure based on a task-specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves.

PubMed

Saljooqi, Asma; Shamspur, Tayebeh; Mohamadi, Maryam; Afzali, Daryoush; Mostafavi, Ali

2015-05-01

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Dopant Ionic Radius on Cerium Reduction in Epitaxial Cerium Oxide Thin Films

DOE PAGES

Yang, Nan; Orgiani, Pasquale; Di Bartolomeo, Elisabetta; ...

2017-04-17

The role of trivalent rare-earth dopants in ceria epitaxial films on surface ion exchange reactivity and ion conductivity has been systematically studied. Single-crystal epitaxial films with unique crystal orientation and micro-structure nature have allowed us to rule out the influence of structural defects on both transport and surface ion exchange properties. The films conductivities were larger than those reported in literature for both polycrystalline ceramic pellets and crystalline films. An increase in oxygen vacancies and Ce 3+ concentration while decreasing the dopant ionic radius from La 3+ to Yb 3+ was observed, thus explaining the measured increased activation energy andmore » enhanced surface reactivity. The more significant ability of smaller dopant ionic radius in releasing the stress strength induced by the larger Ce 3+ ionic radius allows promoting the formation of oxygen vacancies and Ce 3+, which are two precious species in determining the efficiency of ion transport and surface ion exchange processes. This can open new perspectives in designing ceria-based materials in tailoring functional properties, either ion migration or surface reactivity, by rational cation substitutions.« less

Vaporization behavior of tetraoctylphosphonium bis(2-ethylhexyl)phosphate ionic liquid

DOE PAGES

McMurray, J. W.; Zhou, Y.; Luo, H. M.; ...

2016-11-18

We determined the equilibrium vapor pressures, p e, of the ionic liquid tetraoctylphosphonium bis(2-ethylhexyl)phosphate ([P 8888][DEHP]) over the temperature range 409–495 K using mass loss Knudsen effusion. The p e versus temperature relationship compares well to 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C 8mim][NTf 2]) but is lower than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C 2mim][NTf 2]) when measured using the same technique. Here, we determined the discrepancies between the p e for [C 8mim][NTf 2] and [C 2mim][NTf 2] with previous studies is discussed. Finally, the enthalpy and entropy of vaporization for all three fluids are estimated from the Clasius-Clapeyron relation.

Vaporization behavior of tetraoctylphosphonium bis(2-ethylhexyl)phosphate ionic liquid

NASA Astrophysics Data System (ADS)

McMurray, J. W.; Zhou, Y.; Luo, H. M.; Qu, J.

2017-01-01

The equilibrium vapor pressures, pe, of the ionic liquid tetraoctylphosphonium bis(2-ethylhexyl)phosphate ([P8888][DEHP]) over the temperature range 409-495 K were determined for the first time using mass loss Knudsen effusion. The pe versus temperature relationship compares well to 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C8mim][NTf2]) but is lower than that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) when measured using the same technique. The discrepancies between the pe determined in this work for [C8mim][NTf2] and [C2mim][NTf2] with previous studies is discussed. The enthalpy and entropy of vaporization for all three fluids are estimated from the Clasius-Clapeyron relation.

Brillouin-scattering study of liquid-glass transitions in ternary mixtures of water, trehalose, and an ionic liquid

NASA Astrophysics Data System (ADS)

Takayama, Haruki; Shibata, Tomohiko; Ishii, Takahiro; Kojima, Seiji

2013-04-01

Ternary mixtures of water, sugar, and ionic liquid have been studied as new candidates for bioprotectants. To clarify the elastic properties and relaxation dynamics of the supercooled liquid and glassy states at low temperatures, the liquid-glass transitions were investigated by using a micro-Brillouin-scattering technique. The refractive index was measured accurately as a function of content and temperature to determine the sound velocity and the attenuation from Brillouin frequency shift and peak width. The relaxation times of structural relaxations related to liquidglass transitions were determined as functions of temperature. The Meyer-Neldel rule was found to hold for the activation energy and the prefactor of the Arrhenius law for the relaxation time.

Assessment of the Density Functional Tight Binding Method for Protic Ionic Liquids

PubMed Central

2015-01-01

Density functional tight binding (DFTB), which is ∼100–1000 times faster than full density functional theory (DFT), has been used to simulate the structure and properties of protic ionic liquid (IL) ions, clusters of ions and the bulk liquid. Proton affinities for a wide range of IL cations and anions determined using DFTB generally reproduce G3B3 values to within 5–10 kcal/mol. The structures and thermodynamic stabilities of n-alkyl ammonium nitrate clusters (up to 450 quantum chemical atoms) predicted with DFTB are in excellent agreement with those determined using DFT. The IL bulk structure simulated using DFTB with periodic boundary conditions is in excellent agreement with published neutron diffraction data. PMID:25328497

Charged Particles on Surfaces: Coexistence of Dilute Phases and Periodic Structures at Interfaces

NASA Astrophysics Data System (ADS)

Loverde, Sharon M.; Solis, Francisco J.; Olvera de La Cruz, Monica

2007-06-01

We consider a mixture of two immiscible oppositely charged molecules strongly adsorbed to an interface, with a neutral nonselective molecular background. We determine the coexistence between a high density ionic periodic phase and a dilute isotropic ionic phase. We use a strong segregation approach for the periodic phase and determine the one-loop free energy for the dilute phase. Lamellar and hexagonal patterns are calculated for different charge stoichiometries of the mixture. Molecular dynamics simulations exhibit the predicted phase behavior. The periodic length scale of the solid phase is found to scale as ɛ/(lBψ3/2), where ψ is the effective charge density, lB is the Bjerrum length, and ɛ is the cohesive energy.

In situ ionic liquid dispersive liquid-liquid microextraction coupled to gas chromatography-mass spectrometry for the determination of organophosphorus pesticides.

PubMed

Cacho, J I; Campillo, N; Viñas, P; Hernández-Córdoba, M

2018-07-20

Nine organophosphorus pesticides (OPPs) were determined in environmental waters from different origins using in situ ionic liquid dispersive liquid microextraction (IL-DLLME). This preconcentration technique was coupled to gas chromatography-mass spectrometry (GC-MS) using microvial insert thermal desorption, an approach that uses a thermal desorption injector as sample introduction system. The parameters affecting both the microextraction and sample injection steps were optimized. The proposed method showed good precision, with RSD values ranging from 4.1 to 9.7%, accuracy with recoveries in the 85-118% range, and sensitivity with DLs ranging from 5 to 16 ng L -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of the aqueous phase for preconcentration of heavy metals ions prior to determination by LC-UV.

PubMed

Werner, Justyna

2018-05-15

Ionic liquid ultrasound-assisted dispersive liquid-liquid microextraction based on solidification of the aqueous phase was used for preconcentration of Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ , Pb 2+ in natural water samples prior to liquid chromatography with UV detection. In the proposed method, the ammonium pyrrolidinedithiocarbamate was used as a complexing agent and the phosphonium ionic liquid trihexyl(tetradecyl)phosphonium bis[(2,4,4-trimethyl)pentyl]phosphinate (Cyphos IL 104) was used as an extractant. Ultrasound energy was used to disperse the extractant in the aqueous phase. After microextraction, the ionic liquid and aqueous phases were separated by centrifugation. Then the aqueous phase was frozen and the lighter than water ionic liquid phase containing metal ions complexes with pyrrolidinedithiocarbamate was separated and dissolved in a small volume of methanol prior to injection into the liquid chromatograph. Several parameters including the volume of extractant, the pH of the sample, the concentration of complexing agent, the time of ultrasound energy treatment, the time and speed of centrifugation and the effect of ionic strength were optimized. Under the optimized conditions (10 µL of Cyphos IL 104, pH = 5, 0.3% w/v ammonium pyrrolidinedithiocarbamate, 60 s of ultrasound use, 5 min/5000 rpm (2516×g) of centrifugation, 2.0 mg of NaCl), preconcentration factors were 211, 210, 209, 207 and 211 for Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ and Pb 2+ respectively. Linearity was observed in the ranges 0.2-75.0 µg L -1 for Pb 2+ , Cd 2+ , Co 2+ and 0.5-100.0 µg L -1 for Cu 2+ , Ni 2+ . The limits of detection were 0.03 µg L -1 for Ni 2+ , 0.03 µg L -1 for Co 2+ , 0.03 µg L -1 for Cd 2+ , 0.02 µg L -1 for Cu 2+ , 0.02 µg L -1 for Pb 2+ , respectively. The accuracy of this method was evaluated by preconcentration and determination of Ni 2+ , Co 2+ , Cd 2+ , Cu 2+ , Pb 2+ in certified reference materials (TMRAIN-04 and NIST 1643e) with the recovery values in the range of 97-102%. The presented method has been successfully applied for the determination of analytes in natural water samples (river and lake waters). Copyright © 2018 Elsevier B.V. All rights reserved.

Ionic liquid-salt aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of sulfonamides in water and food.

PubMed

Han, Juan; Wang, Yun; Liu, Yan; Li, Yanfang; Lu, Yang; Yan, Yongsheng; Ni, Liang

2013-02-01

Ionic liquid-salt aqueous two-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection was developed for the determination of sulfonamides in water and food samples. In the procedure, the analytes were extracted from the aqueous samples into the ionic liquid top phase in one step. Three sulfonamides, sulfamerazine, sulfamethoxazole, and sulfamethizole were selected here as model compounds for developing and evaluating the method. The effects of various experimental parameters in extraction step were studied using two optimization methods, one variable at a time and Box-Behnken design. The results showed that the amount of sulfonamides did not have effect on the extraction efficiency. Therefore, a three-level Box-Behnken experimental design with three factors, which combined the response surface modeling, was used to optimize sulfonamides extraction. Under the most favorable extraction parameters, the detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.15-0.3 ng/mL and 0.5-1.0 ng/mL from spiked samples, respectively, which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Finally, the proposed method was successfully applied to the determination of sulfonamide compounds in different water and food samples and satisfactory recoveries of spiked target compounds in real samples were obtained.

A general ionic liquid pH-zone-refining countercurrent chromatography method for separation of alkaloids from Nelumbo nucifera Gaertn.

PubMed

Fang, Yingtong; Li, Quan; Shao, Qian; Wang, Binghai; Wei, Yun

2017-07-21

The alkaloids from lotus (Nelumbo nucifera Gaertn) are effective in lowering hyperlipemia and level of cholesterol. However, there is not a general method for their separation. In this work, a general ionic liquid pH-zone-refining countercurrent chromatography method for isolation and purification of six alkaloids from the whole lotus plant was successfully established by using ionic liquids as the modifier of the two-phase solvent system. The conditions of ionic liquid pH-zone-refining countercurrent chromatography, involving solvent systems, concentration of retainer and eluter, types of ionic liquids, the content of ionic liquids as well as ionic liquids posttreatment, were optimized to improve extraction efficiency. Finally, the separation of these six alkaloids was performed with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water-[C 4 mim][PF 6 ] at a volume ratio of 5:2:2:8:0.1, where 10mM TEA was added to the organic stationary phase as a retainer and 3mM HCl was added to the aqueous mobile phase as an eluter. As a result, six alkaloids including N-nornuciferine, liensinine, nuciferine, isoliensinine, roemerine and neferine were successfully separated with the purities of 97.0%, 90.2%, 94.7%, 92.8%, 90.4% and 95.9%, respectively. The established general method has been respectively applied to the crude samples of lotus leaves and lotus plumules. A total of 37.3mg of liensinine, 57.7mg of isoliensinine and 179.9mg of neferine were successfully purified in one run from 1.00g crude extract of lotus plumule with the purities of 93.2%, 96.5% and 98.8%, respectively. Amount of 45.6mg N-nornuciferine, 21.6mg nuciferine and 11.7mg roemerine was obtained in one step separation from 1.05g crude extract of lotus leaves with the purity of 96.9%, 95.6% and 91.33%, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Composite fabrication and polymer modification using neoteric solvents

NASA Astrophysics Data System (ADS)

Eastman, Scott A.

This thesis is divided into two research initiatives: The fabrication and study of bulk, co-continuous, cellulosic-polymer composites with the aid of supercritical CO2 (SC CO2); and the study of poly(vinyl alcohol) (PVOH) modification and surface activity in ionic liquids. The first part of this thesis utilizes the tunable solubility, gas-like diffusivity, and omniphilic wettability of SC CO2 to incorporate and subsequently polymerize silicone and poly(enemer) prepolymer mixtures throughout various cellulosic substrates. Chapters two and three investigate the mechanical properties of these composites and demonstrate that nearly every resulting composite demonstrates an improved flexural modulus and energy release rate upon splitting. Fire resistance of these composites was also investigated and indicates that the heat release rate, total heat released, and char yield were significantly improved upon for all silicone composites compared to the untreated cellulosic material. Chapter four looks specifically at aspen-silicone composites for thermo-oxidative studies under applied loads in order to study the effect of silicone incorporation on the failure kinetics of aspen. The aspen-silicone composites tested under these conditions demonstrated significantly longer lifetimes under the same loading and heating conditions compared with untreated aspen. The second part of this thesis focuses on studying ionic liquids as potentially useful solvents and reaction media for poly(vinyl alcohol). Two ionic liquids (1-Butyl-3-methylimidizolium chloride and tributylethylphosphonium diethylphosphate) were found to readily dissolve PVOH. More importantly, we have demonstrated that these solvents can be used as inert reaction media for PVOH modification. Both ionic liquids were found to facilitate the quantitative esterification of PVOH, while only the phosphonium ionic liquid supports the quantitative urethanation of the polymer. In an attempt to tune the surface properties of ionic liquid/polymer solutions, PVOH was also partially esterified with low surface energy substituents. Both surface tension and surface composition of the ionic liquid/polymer solutions can be manipulated by the stoichiometric addition of low surface energy acid chlorides. This work on the modification of PVOH can be directly applied to the modification of polysaccharides such as cellulose which could have important implications from a sustainability and energy standpoint.

Development of chitosan-nanoparticle film based materials for controlled quality of minced beef during refrigerated storage

NASA Astrophysics Data System (ADS)

Erdawati

2010-10-01

Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. The physicochemical properties of the chitosan nanoparticles were determined by FTIR analysis, XRD pattern and TEM. The effects of chitosan nanoparticles treatment on the shelf-life extension of minced beef stored at 20±1° C were studied, including chemical and microbiological,. Results indicated that chitosan nanoparticle treatment reduced the total microbial load of fresh minced beef about 10-fold (from 3.2×104 CFU/g to 5.4×102 CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from minced beef was confirmed, and chitosan concentration of 400 ppm was eventually determined for application in minced beef. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 2-3 days for control, 4-5 days for nanoparticle chitosan treatment samples, were observed, indicating that chitosan nanoparticle have a great potential for minced beef preservation.

Ionic liquid-based ultrasonic/microwave-assisted extraction combined with UPLC-MS-MS for the determination of tannins in Galla chinensis.

PubMed

Lu, Chunxia; Wang, Hongxin; Lv, Wenping; Ma, Chaoyang; Lou, Zaixiang; Xie, Jun; Liu, Bo

2012-01-01

Ionic liquid was used as extraction solvents and applied to the extraction of tannins from Galla chinensis in the simultaneous ultrasonic- and microwave-assisted extraction (UMAE) technique. Several parameters of UMAE were optimised, and the results were compared with of the conventional extraction techniques. Under optimal conditions, the content of tannins was 630.2 ± 12.1 mg g⁻¹. Compared with the conventional heat-reflux extraction, maceration extraction, regular ultrasound- and microwave-assisted extraction, the proposed approach exhibited higher efficiency (11.7-22.0% enhanced) and shorter extraction time (from 6 h to 1 min). The tannins were then identified by ultraperformance liquid chromatography tandem mass spectrometry. This study suggests that ionic liquid-based UMAE is an efficient, rapid, simple and green sample preparation technique.

Label-free biosensing with functionalized nanopipette probes

PubMed Central

Umehara, Senkei; Karhanek, Miloslav; Davis, Ronald W.; Pourmand, Nader

2009-01-01

Nanopipette technology can uniquely identify biomolecules such as proteins based on differences in size, shape, and electrical charge. These differences are determined by the detection of changes in ionic current as the proteins interact with the nanopipette tip coated with probe molecules. Here we show that electrostatic, biotin-streptavidin, and antibody-antigen interactions on the nanopipette tip surface affect ionic current flowing through a 50-nm pore. Highly charged polymers interacting with the glass surface modulated the rectification property of the nanopipette electrode. Affinity-based binding between the probes tethered to the surface and their target proteins caused a change in the ionic current due to a partial blockade or an altered surface charge. These findings suggest that nanopipettes functionalized with appropriate molecular recognition elements can be used as nanosensors in biomedical and biological research. PMID:19264962

Sequencing proteins with transverse ionic transport in nanochannels.

PubMed

Boynton, Paul; Di Ventra, Massimiliano

2016-05-03

De novo protein sequencing is essential for understanding cellular processes that govern the function of living organisms and all sequence modifications that occur after a protein has been constructed from its corresponding DNA code. By obtaining the order of the amino acids that compose a given protein one can then determine both its secondary and tertiary structures through structure prediction, which is used to create models for protein aggregation diseases such as Alzheimer's Disease. Here, we propose a new technique for de novo protein sequencing that involves translocating a polypeptide through a synthetic nanochannel and measuring the ionic current of each amino acid through an intersecting perpendicular nanochannel. We find that the distribution of ionic currents for each of the 20 proteinogenic amino acids encoded by eukaryotic genes is statistically distinct, showing this technique's potential for de novo protein sequencing.

Electrochemical characterisation of a lithium-ion battery electrolyte based on mixtures of carbonates with a ferrocene-functionalised imidazolium electroactive ionic liquid.

PubMed

Forgie, John C; El Khakani, Soumia; MacNeil, Dean D; Rochefort, Dominic

2013-05-28

Electrolytic solutions of lithium-ion batteries can be modified with additives to improve their stability and safety. Electroactive molecules can be used as such additives to act as an electron (redox) shuttle between the two electrodes to prevent overcharging. The electroactive ionic liquid, 1-ferrocenylmethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (TFSI), was synthesised and its electrochemical properties were investigated when diluted with ethylene carbonate-diethyl carbonate solvent at various concentrations. Cyclic voltammetry data were gathered to determine the redox potential, diffusion coefficient and heterogeneous rate constants of the electroactive imidazolium TFSI ionic liquid in the carbonate solution. The properties of this molecule as an additive in lithium battery electrolytes were studied in standard coin cells with a metallic Li anode and a Li4Ti5O12 cathode.

Long-Term Experimental Determination of Solubilities of Micro-Crystalline Nd(III) Hydroxide in High Ionic Strength Solutions: Applications to Nuclear Waste Management [A Pitzer Model for Am(III)/Nd(III) hydroxide solubility in NaCl-H 2O at 298.15 K to high ionic strengths: Experimental validation and model applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, Yongliang; Kirkes, Leslie Dawn; Marrs, Cassandra

In this paper, the experimental results from long-term solubility experiments on micro crystalline neodymium hydroxide, Nd(OH) 3(micro cr), in high ionic strength solutions at 298.15 K under well-constrained conditions are presented. The starting material was synthesized according to a well-established method in the literature. In contrast with the previous studies in which hydrogen ion concentrations in experiments were adjusted with addition of either an acid or a base, the hydrogen ion concentrations in our experiments are controlled by the dissolution of Nd(OH) 3(micro cr), avoiding the possibility of phase change.

Direct Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol at Room Temperature Using Imidazolium Hydrogen Carbonate Ionic Liquid as a Recyclable Catalyst and Dehydrant.

PubMed

Zhao, Tianxiang; Hu, Xingbang; Wu, Dongsheng; Li, Rui; Yang, Guoqiang; Wu, Youting

2017-05-09

The direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH was achieved at room temperature with 74 % CH 3 OH conversion in the presence of an imidazolium hydrogen carbonate ionic liquid ([C n C m Im][HCO 3 ]). Experimental and theoretical results reveal that [C n C m Im][HCO 3 ] can transform quickly into a CO 2 adduct, which serves as an effective catalyst and dehydrant. Its dehydration ability is reversible. The energy barrier of the rate-determining step for the DMC synthesis is only 21.7 kcal mol -1 . The ionic liquid can be reused easily without a significant loss of its catalytic and dehydrating ability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-Term Experimental Determination of Solubilities of Micro-Crystalline Nd(III) Hydroxide in High Ionic Strength Solutions: Applications to Nuclear Waste Management [A Pitzer Model for Am(III)/Nd(III) hydroxide solubility in NaCl-H 2O at 298.15 K to high ionic strengths: Experimental validation and model applications

DOE PAGES

Xiong, Yongliang; Kirkes, Leslie Dawn; Marrs, Cassandra

2017-12-01

In this paper, the experimental results from long-term solubility experiments on micro crystalline neodymium hydroxide, Nd(OH) 3(micro cr), in high ionic strength solutions at 298.15 K under well-constrained conditions are presented. The starting material was synthesized according to a well-established method in the literature. In contrast with the previous studies in which hydrogen ion concentrations in experiments were adjusted with addition of either an acid or a base, the hydrogen ion concentrations in our experiments are controlled by the dissolution of Nd(OH) 3(micro cr), avoiding the possibility of phase change.

Anesthetic biotransformation and renal function in obese patients during and after methoxyflurane or halothane anesthesia.

PubMed

Young, S R; Stoelting, R K; Peterson, C; Madura, J A

1975-04-01

Anesthetic biotransformation and renal function were studied in obese adult patients (148 plus or minus 8 kg; mean plus or minus SE) anesthetized for three hours with 60 per cent nitrous oxide plus either methoxyflurane or halothane for elective jejunoileal small-bowel-bypass operations. There was no evidence of persistent renal dysfunction in any patient postoperatively, but serum osmolality was elevated 72 hours after methoxyflurane anesthesia. Urine concentrating ability was not determined. Peak serum ionic fluoride concentration was 55.8 plus or minus 5.8 muM/1 two hours after discontinuation of methoxyflurane. Urinary ionic fluoride and oxalate excretions increased postoperatively. Compared with previously reported data from nonobese patients, serum ionic fluoride concentrations in obese patients increased more rapidly during methoxyflurane anesthesia and peaked higher and sooner after discontinuation of methoxyflurane. The peak serum ionic fluoride concentration was 10.4 plus or minus 1.5 muM/1 at the conclusion of halothane anesthesia, significantly more than the corresponding value in nonobese patients. Intraoperative liver biopsies from 23 of 27 patients showed moderate to severe fatty metamorphosis. Fatty liver infiltration may have increased hepatic anesthetic uptake and exposed more methoxyflurane or halothane to hepatic microsomal enzymes. The more rapid elevation and higher peak levels of serum ionic fluoride following methoxyflurane, and to a lesser extent following halothane, may reflect increased anesthetic biotransformation in obese compared with nonobese patients. To avoid excessive serum ionic fluoride elevations the authors recommended limiting low-dose methoxyflurane anesthesia delivered to obese patients with potential fatty liver infiltration to no more than three hours.

Simultaneous determination of Magnolol and Honokiol by amino acid ionic liquid synchronous fluorescence spectrometry

NASA Astrophysics Data System (ADS)

Liu, Wei; Zhu, Xiashi

2018-05-01

A novel method based on amino acid ionic liquids (AAILs) as an additive synchronous fluorescence spectrometry is proposed for simultaneous determination of magnolol (MN) and honokiol (HN) in traditional Chinese medicine Houpu. The overlapping fluorescence spectrum of MN and HN could be completely separated in the AAILs medium. Experiment parameters (the type and concentration of AAILs, pH values and temperature) were discussed. The detection limits of MN and HN reached 1.46 ng/mL, 0.92 ng/mL and the recovery rates ranged from 98.6%-100.7%, 99.7%-100.6%, respectively. This methods was successfully employed for simultaneously determination of MN and HN in real samples. No significant differences could be found in the results of this method and the pharmacopoeia of People's Republic of China 2015 (Ch.P.2015). The experiment mechanisms were discussed by the Gaussian simulation and fluorescence quantum yield.

Ionization correction factors for H II regions in blue compact dwarf galaxies

NASA Astrophysics Data System (ADS)

Holovatyi, V. V.; Melekh, B. Ya.

2002-08-01

Energy distributions in the spectra of the ionizing nuclei of H II regions beyond λ <= 91.2 nm were calculated. A grid of photoionization models of 270 H II regions was constructed. The free parameters of the model grid are the hydrogen density nH in the nebular gas, filling factor, energy Lc-spectrum of ionizing nuclei, and metallicity. The chemical composition from the studies of Izotov et al. were used for model grid initialization. The integral linear spectra calculated for the photoionization models were used to determine the concentration ne, temperatures Te of electrons, and ionic concentrations n(A+i)/n(H+) by the nebular gas diagnostic method. The averaged relative ionic abundances n(A+i)/n(H+) thus calculated were used to determine new expressions for ionization correction factors which we recommend for the determination of abundances in the H II regions of blue compact dwarf galaxies.

Eu3+ as a dual probe for the determination of IL anion donor power: A combined luminescence spectroscopic and electrochemical approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babai, Arash; Kopiec, Gabriel; Lackmann, Anastasia

2014-04-01

This work is aimed at giving proof that Eu(Tf2N)(3) (Tf2N = bis(trifluoromethanesulfonyl)amide) can act as both an optical and electrochemical probe for the determination of the Lewis acidity of an ionic liquid anion. For that reason the luminescence spectra and cyclic voltammograms of dilute solutions of Eu(Tf2N)(3) in various ionic liquids were investigated. The Eu2+/3+ redox potential in the investigated ILs can be related to the Lewis basicity of the IL anion. The IL cation had little influence. The lower the determined halfwave potential, the higher the IL anion basicity. The obtained ranking can be confirmed by luminescence spectroscopy wheremore » a bathochromic shift of the D-5(0) -> F-7(4) transition indicates a stronger Lewis basicity of the IL anion. (C) 2014 Published by Elsevier B.V.« less

Time-resolved determination of the potential of zero charge at polycrystalline Au/ionic liquid interfaces

NASA Astrophysics Data System (ADS)

Vargas-Barbosa, Nella M.; Roling, Bernhard

2018-05-01

The potential of zero charge (PZC) is a fundamental property that describes the electrode/electrolyte interface. The determination of the PZC at electrode/ionic liquid interfaces has been challenging due to the lack of models that fully describe these complex interfaces as well as the non-standardized approaches used to characterize them. In this work, we present a method that combines electrode immersion transient and impedance measurements for the determination of the PZC. This combined approach allows the distinction of the potential of zero free charge (pzfc), related to fast double layer charging on a millisecond timescale, from a potential of zero charge on a timescale of tens of seconds related to slower ion transport processes at the interface. Our method highlights the complementarity of these electrochemical techniques and the importance of selecting the correct timescale to execute experiments and interpret the results.

HIEN-LO: An experiment for charge determination of cosmic rays of interplanetary and solar origin

NASA Technical Reports Server (NTRS)

Klecker, B.; Hovestadt, D.; Mason, G. M.; Blake, J. B.; Nicholas, J.

1988-01-01

The experiment is designed to measure the heavy ion environment at low altitude (HIEN-LO) in the energy range 0.3 to 100 MeV/nucleon. In order to cover this wide energy range a complement of three sensors is used. A large area ion drift chamber and a time-of-flight telescope are used to determine the mass and energy of the incoming cosmic rays. A third omnidirectional counter serves as a proton monitor. The analysis of mass, energy and incoming direction in combination with the directional geomagnetic cut-off allows the determination of the ionic charge of the cosmic rays. The ionic charge in this energy range is of particular interest because it provides clues to the origin of these particles and to the plasma conditions at the acceleration site. The experiment is expected to be flown in 1988/1989.

Isothermogravimetric determination of the enthalpies of vaporization of 1-alkyl-3-methylimidazolium ionic liquids.

PubMed

Luo, Huimin; Baker, Gary A; Dai, Sheng

2008-08-21

Vaporization enthalpies for two series of ionic liquids (ILs) composed of 1- n-alkyl-3-methylimidazolium cations, [Imm1+] (m=2, 3, 4, 6, 8, or 10), paired with either the bis(trifluoromethanesulfonyl)amide, [Tf2N-], or the bis(perfluoroethylsulfonyl)amide anion, [beti-], were determined using a simple, convenient, and highly reproducible thermogravimetric approach, and from these values, Hildebrand solubility parameters were estimated. Our results reveal two interesting and unanticipated outcomes: (i) methylation at the C2 position of [Imm1+] affords a significantly higher vaporization enthalpy; (ii) in all cases, the [beti-] anion served to lower the enthalpy of vaporization relative to [Tf2N-]. The widespread availability of the apparatus required for these measurements coupled with the ease of automation suggests the broad potential of this methodology for determining this critical parameter in a multitude of ILs.

THE ROLE OF INORGANIC ION IMBALANCE IN AQUATIC TOXICITY TESTING

EPA Science Inventory

Effluent toxicity testing methods have been well defined, but to a large part have not attempted to segregate the effects of active ionic concentrations and ion imbalances upon test and species performances. The role that various total dissolved solids in effluents have on regula...

Photoionization and ionic dissociation of the C3 H3 NS molecule induced by soft X-ray near the C1s edge.

PubMed

Lago, A F; Januário, R D; Cavasso Filho, R L; Simon, M; Dávalos, J Z

2017-10-01

Time of flight mass spectrometry, electron-ion coincidence, and ion yield spectroscopy were employed to investigate for the first time the thiazole (C 3 H 3 NS) molecule in the gas phase excited by synchrotron radiation in the soft X-ray domain. Total ion yield (TIY) and photoelectron-photoion coincidence (PEPICO) spectra were recorded as a function of the photon energy in the vicinity of the carbon K edge (C1s). The C1s resonant transitions as well as the core ionization thresholds have been determined from the profile of TIY spectrum, and the features were discussed. The corresponding partial ion yields were determined from the PEPICO spectra for the cation species produced upon the molecular photodissociation. Additional ab initio calculations have also been performed from where relevant structural and electronic configuration parameters were obtained for this molecule. Copyright © 2017 John Wiley & Sons, Ltd.

Determination of sub-ng g-1 levels of total inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry after pre-concentration.

PubMed

Altunay, Nail; Gürkan, Ramazan

2017-03-01

A new and simple ultrasonic-assisted extraction (UAE) procedure was developed for the determination of inorganic arsenic and selenium in foods by hydride-generation atomic absorption spectrometry (HG-AAS). The various analytical variables affecting complex formation and extraction efficiency were investigated and optimised. The method is based on selective complex formation of As(III) and Se(IV) in the presence of excess As(V) and Se(VI) with toluidine red in the presence of tartaric acid at pH 4.5, and then extraction of the resulting condensation products into the micellar phase of non-ionic surfactant, polyethylene glycol dodecyl ether, Brij 35. Under optimised conditions, good linear relationships were obtained in the ranges of 4-225 and 12-400 ng l - 1 with limits of detection of 1.1 and 3.5 ng l - 1 for As(III) and Se(IV), respectively. The repeatability was better than 3.9% for both analytes (n = 10, 25 ng l - 1 ) while reproducibility ranged from 4.2% to 4.8%. The recoveries of As(III) and Se(IV) spiked at 25-100 ng l - 1 were in the range of 94.2-104.8%. After pre-concentration of a 5.0 ml sample, the sensitivity enhancement factors for As(III) and Se(IV) were 185 and 140, respectively. Accuracy was assessed by analysis of two standard reference materials (SRMs) and spiked recovery experiments. The method was successfully applied to the accurate and reliable determination of total As and total Se by HG-AAS after pre-reduction with a mixture of L-cysteine and tartaric acid. Finally, the method was shown to be rapid and sensitive, with good results for extraction, pre-concentration and determination of total As and Se contents (as As(III) and Se(IV)) from food samples.

The physicochemical properties of the low-temperature ionic liquid silver bromide-1-butyl-3-methylimidazolium bromide

NASA Astrophysics Data System (ADS)

Grishina, E. P.; Ramenskaya, L. M.; Pimenova, A. M.

2009-11-01

The physicochemical properties of the low-temperature ionic liquid based on 1-butyl-3-methylimidazolium bromide (BMImBr) and silver bromide were studied. Differential scanning calorimetry, Fourier transform IR spectroscopy, densimetry, viscometry, and conductometry measurements were performed to determine the dependences of the parameters under study on the concentration of AgBr. It was shown that the temperature and concentration behavior of the physicochemical properties of BMImBr-AgBr melts characterized the interaction between the system components with the formation of complex particles.

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids.

PubMed

Ismail Hossain, M; El-Harbawi, Mohanad; Noaman, Yousr Abdulhadi; Bustam, Mohd Azmi B; Alitheen, Noorjahan Banu Mohamed; Affandi, Nor Azrin; Hefter, Glenn; Yin, Chun-Yang

2011-06-01

Eight hydroxylammonium-based room temperature ionic liquids (ILs) have been synthesized by acid-base neutralization of ethanolamines with organic acids. The ILs were characterized by infrared and nuclear magnetic resonance spectroscopies and elemental analysis. Their anti-microbial activities were determined using the well-diffusion method. All eight ILs were toxic to Staphylococcus aureus, while 2-hydroxyethylammonium lactate and 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate showed high anti-microbial activity against a wide range of human pathogens. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Formation of hybrid ABX3 perovskite compounds for solar cell application: first-principles calculations of effective ionic radii and determination of tolerance factors.

PubMed

Becker, Markus; Klüner, Thorsten; Wark, Michael

2017-03-14

The development of hybrid organic-inorganic perovskite solar cells is one of the most rapidly growing fields in the photovoltaic community and is on its way to challenge polycrystalline silicon and thin film technologies. High power conversion efficiencies can be achieved by simple processing with low cost. However, due to the limited long-term stability and environmental toxicity of lead in the prototypic CH 3 NH 3 PbI 3 , there is a need to find alternative ABX 3 constitutional combinations in order to promote commercialization. The Goldschmidt tolerance factor and the octahedral factor were found to be necessary geometrical concepts to evaluate which perovskite compounds can be formed. It was figured out that the main challenge lies in estimating an effective ionic radius for the molecular cation. We calculated tolerance factors and octahedral factors for 486 ABX 3 monoammonium-metal-halide combinations, where the steric size of the molecular cation in the A-position was estimated concerning the total charge density. A thorough inquiry about existing mixed organic-inorganic perovskites was undertaken. Our results are in excellent agreement with the reported hybrid compounds and indicate the potential existence of 106 ABX 3 combinations hitherto not discussed in the literature, giving hints for more intense research on prospective individual candidates.

Cu(II) binding by a pH-fractionated fulvic acid

USGS Publications Warehouse

Brown, G.K.; Cabaniss, S.E.; MacCarthy, P.; Leenheer, J.A.

1999-01-01

The relationship between acidity, Cu(II) binding and sorption to XAD resin was examined using Suwannee River fulvic acid (SRFA). The work was based on the hypothesis that fractions of SRFA eluted from an XAD column at various pH's from 1.0 to 12.0 would show systematic variations in acidity and possibly aromaticity which in turn would lead to different Cu(II) binding properties. We measured equilibrium Cu(II) binding to these fractions using Cu2+ ion-selective electrode (ISE) potentiometry at pH 6.0. Several model ligands were also examined, including cyclopentane-1,2,3,4-tetracarboxylic acid (CP-TCA) and tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THF-TCA), the latter binding Cu(II) much more strongly as a consequence of the ether linkage. The SRFA Cu(II) binding properties agreed with previous work at high ionic strength, and binding was enhanced substantially at lower ionic strength, in agreement with Poisson-Boltzmann predictions for small spheres. Determining Cu binding constants (K(i)) by non-linear regression with total ligand concentrations (L(Ti)) taken from previous work, the fractions eluted at varying pH had K(i) similar to the unfractionated SRFA, with a maximum enhancement of 0.50 log units. We conclude that variable-pH elution from XAD does not isolate significantly strong (or weak) Cu(II)-binding components from the SRFA mixture. Copyright (C) 1999 Elsevier Science B.V.

Estimating Dermal Transfer of Copper Particles from the ...

EPA Pesticide Factsheets

Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper based formulations. Micronized copper (nano to micron sized particles) has become the preferred treatment formulation. There is a lack of information on the release of copper, the fate of the particles during dermal contact, and the copper exposure level to children from hand-to-mouth transfer. For the current study, three treated lumber products, two micronized copper and one ionic copper, were purchased from commercial retailers. The boards were left to weather outdoors for approximately 1 year. Over the year time period, hand wipe samples were collected periodically to determine copper transfer from the wood surfaces. The two micronized formulations and the ionic formulation released similar levels of total copper. The amount of copper released was high initially, but decreased to a constant level (~1.5 mg m-2) after the first month of outdoor exposure. Copper particles were identified on the sampling cloths during the first two months of the experiment, after which the levels of copper were insufficient to collect interpretable data. After 1 month, the particles exhibited minimal changes in shape and size. At the end of 2-months, significant deterioration of the particles was

Microwave Crystallization of Lithium Aluminum Germanium Phosphate Solid-State Electrolyte.

PubMed

Mahmoud, Morsi M; Cui, Yuantao; Rohde, Magnus; Ziebert, Carlos; Link, Guido; Seifert, Hans Juergen

2016-06-23

Lithium aluminum germanium phosphate (LAGP) glass-ceramics are considered as promising solid-state electrolytes for Li-ion batteries. LAGP glass was prepared via the regular conventional melt-quenching method. Thermal, chemical analyses and X-ray diffraction (XRD) were performed to characterize the prepared glass. The crystallization of the prepared LAGP glass was done using conventional heating and high frequency microwave (MW) processing. Thirty GHz microwave (MW) processing setup were used to convert the prepared LAGP glass into glass-ceramics and compared with the conventionally crystallized LAGP glass-ceramics that were heat-treated in an electric conventional furnace. The ionic conductivities of the LAGP samples obtained from the two different routes were measured using impedance spectroscopy. These samples were also characterized using XRD and scanning electron microscopy (SEM). Microwave processing was successfully used to crystallize LAGP glass into glass-ceramic without the aid of susceptors. The MW treated sample showed higher total, grains and grain boundary ionic conductivities values, lower activation energy and relatively larger-grained microstructure with less porosity compared to the corresponding conventionally treated sample at the same optimized heat-treatment conditions. The enhanced total, grains and grain boundary ionic conductivities values along with the reduced activation energy that were observed in the MW treated sample was considered as an experimental evidence for the existence of the microwave effect in LAGP crystallization process. MW processing is a promising candidate technology for the production of solid-state electrolytes for Li-ion battery.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Soumya; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

Electron transfer and proton coupled electron transfer (PCET) reactions at electrochemical interfaces play an essential role in a broad range of energy conversion processes. The reorganization energy, which is a measure of the free energy change associated with solute and solvent rearrangements, is a key quantity for calculating rate constants for these reactions. We present a computational method for including the effects of the double layer and ionic environment of the diffuse layer in calculations of electrochemical solvent reorganization energies. This approach incorporates an accurate electronic charge distribution of the solute within a molecular-shaped cavity in conjunction with a dielectricmore » continuum treatment of the solvent, ions, and electrode using the integral equations formalism polarizable continuum model. The molecule-solvent boundary is treated explicitly, but the effects of the electrode-double layer and double layer-diffuse layer boundaries, as well as the effects of the ionic strength of the solvent, are included through an external Green’s function. The calculated total reorganization energies agree well with experimentally measured values for a series of electrochemical systems, and the effects of including both the double layer and ionic environment are found to be very small. This general approach was also extended to electrochemical PCET and produced total reorganization energies in close agreement with experimental values for two experimentally studied PCET systems. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.« less

Osmotic Pressure of Aqueous Chondroitin Sulfate Solution: A Molecular Modeling Investigation

PubMed Central

Bathe, Mark; Rutledge, Gregory C.; Grodzinsky, Alan J.; Tidor, Bruce

2005-01-01

The osmotic pressure of chondroitin sulfate (CS) solution in contact with an aqueous 1:1 salt reservoir of fixed ionic strength is studied using a recently developed coarse-grained molecular model. The effects of sulfation type (4- vs. 6-sulfation), sulfation pattern (statistical distribution of sulfate groups along a chain), ionic strength, CS intrinsic stiffness, and steric interactions on CS osmotic pressure are investigated. At physiological ionic strength (0.15 M NaCl), the sulfation type and pattern, as measured by a standard statistical description of copolymerization, are found to have a negligible influence on CS osmotic pressure, which depends principally on the mean volumetric fixed charge density. The intrinsic backbone stiffness characteristic of polysaccharides such as CS, however, is demonstrated to contribute significantly to its osmotic pressure behavior, which is similar to that of a solution of charged rods for the 20-disaccharide chains considered. Steric excluded volume is found to play a negligible role in determining CS osmotic pressure at physiological ionic strength due to the dominance of repulsive intermolecular electrostatic interactions that maintain chains maximally spaced in that regime, whereas at high ionic-strength steric interactions become dominant due to electrostatic screening. Osmotic pressure predictions are compared to experimental data and to well-established theoretical models including the Donnan theory and the Poisson-Boltzmann cylindrical cell model. PMID:16055525

Biodegradation of diesel fuel by a microbial consortium in the presence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues.

PubMed

Chrzanowski, Lukasz; Stasiewicz, Monika; Owsianiak, Mikołaj; Szulc, Alicja; Piotrowska-Cyplik, Agnieszka; Olejnik-Schmidt, Agnieszka K; Wyrwas, Bogdan

2009-09-01

Fast development of ionic liquids as gaining more and more attention valuable chemicals will undoubtedly lead to environmental pollution. New formulations and application of ionic liquids may result in contamination in the presence of hydrophobic compounds, such as petroleum mixtures. We hypothesize that in the presence of diesel fuel low-water-soluble ionic liquids may become more toxic to hydrocarbon-degrading microorganisms. In this study the influence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues (side-chain length from C(3) to C(18)) on biodegradation of diesel fuel by a bacterial consortium was investigated. Whereas test performed for the consortium cultivated on disodium succinate showed that toxicity of the investigated ionic liquids decreased with increase in side-chain length, only higher homologues (C(8)-C(18)) caused a decrease in diesel fuel biodegradation. As a result of exposure to toxic compounds also modification in cell surface hydrophobicity was observed (MATH). Disulphine blue active substances method was employed to determine partitioning index of ionic liquids between water and diesel fuel phase, which varied from 1.1 to 51% for C(3) and C(18) homologues, respectively. We conclude that in the presence of hydrocarbons acting as a solvent, the increased bioavailability of hydrophobic homologues is responsible for the decrease in biodegradation efficiency of diesel fuel.

Influence of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Moudane, M., E-mail: m.elmoudane@gmail.com; El Maniani, M.; Sabbar, A.

2015-12-15

Highlights: • Results of ionic conductivities of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. • Determination of glass transition temperature using DSC method. • Study of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. - Abstract: Lithium–Lead–Bismuth phosphates glasses having, a composition 30Li{sub 3}PO{sub 4}–(70 − x)Pb{sub 3}(PO{sub 4}){sub 2}–xBiPO{sub 4} (45 ≤ x ≤ 60 mol%) were prepared by using the melt quenching method 1000 °C. The thermal stability of theses glasses increases with the substitution of Bi{sub 2}O{sub 3} with PbO. The ionic conductivity of all compositions havemore » been measured over a wide temperature (200–500 °C) and frequency range (1–106 Hz). The ionic conductivity data below and above T{sub g} follows Arrhenius and Vogel–Tamman–Fulcher (VTF) relationship, respectively. The activation energies are estimated and discussed. The dependence in frequency of AC conductivity is found to obey Jonscher’s relation.« less

Hydrodynamic model of temperature change in open ionic channels.

PubMed Central

Chen, D P; Eisenberg, R S; Jerome, J W; Shu, C W

1995-01-01

Most theories of open ionic channels ignore heat generated by current flow, but that heat is known to be significant when analogous currents flow in semiconductors, so a generalization of the Poisson-Nernst-Planck theory of channels, called the hydrodynamic model, is needed. The hydrodynamic theory is a combination of the Poisson and Euler field equations of electrostatics and fluid dynamics, conservation laws that describe diffusive and convective flow of mass, heat, and charge (i.e., current), and their coupling. That is to say, it is a kinetic theory of solute and solvent flow, allowing heat and current flow as well, taking into account density changes, temperature changes, and electrical potential gradients. We integrate the equations with an essentially nonoscillatory shock-capturing numerical scheme previously shown to be stable and accurate. Our calculations show that 1) a significant amount of electrical energy is exchanged with the permeating ions; 2) the local temperature of the ions rises some tens of degrees, and this temperature rise significantly alters for ionic flux in a channel 25 A long, such as gramicidin-A; and 3) a critical parameter, called the saturation velocity, determines whether ionic motion is overdamped (Poisson-Nernst-Planck theory), is an intermediate regime (called the adiabatic approximation in semiconductor theory), or is altogether unrestricted (requiring the full hydrodynamic model). It seems that significant temperature changes are likely to accompany current flow in the open ionic channel. PMID:8599638

Surfactant-based ionic liquids for extraction of phenolic compounds combined with rapid quantification using capillary electrophoresis.

PubMed

Huang, Fangzhi; Berton, Paula; Lu, Chengfei; Siraj, Noureen; Wang, Chun; Magut, Paul K S; Warner, Isiah M

2014-09-01

A rapid liquid phase extraction employing a novel hydrophobic surfactant-based room temperature ionic liquid (RTIL), tetrabutylphosphonium dioctyl sulfosuccinate ([4C4 P][AOT]), coupled with capillary electrophoretic-UV (CE-UV) detection is developed for removal and determination of phenolic compounds. The long-carbon-chain RTIL used is sparingly soluble in most solvents and can be used to replace volatile organic solvents. This fact, in combination with functional-surfactant-anions, is proposed to reduce the interfacial energy of the two immiscible liquid phases, resulting in highly efficient extraction of analytes. Several parameters that influence the extraction efficiencies, such as extraction time, RTIL type, pH value, and ionic strength of aqueous solutions, were investigated. It was found that, under acidic conditions, most of the investigated phenols were extracted from aqueous solution into the RTIL phase within 12 min. Good linearity was observed over the concentration range of 0.1-80.0 μg/mL for all phenols investigated. The precision of this method, expressed as RSD, was determined to be within 3.4-5.3% range. The LODs (S/N = 3) of the method were in the range of 0.047-0.257 μg/mL. The proposed methodology was successfully applied to determination of phenols in real water samples. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gas-assisted dispersive liquid-phase microextraction using ionic liquid as extracting solvent for spectrophotometric speciation of copper.

PubMed

Akhond, Morteza; Absalan, Ghodratollah; Pourshamsi, Tayebe; Ramezani, Amir M

2016-07-01

Gas-assisted dispersive liquid-phase microextraction (GA-DLPME) has been developed for preconcentration and spectrophotometric determination of copper ion in different water samples. The ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate and argon gas, respectively, were used as the extracting solvent and disperser. The procedure was based on direct reduction of Cu(II) to Cu(I) by hydroxylamine hydrochloride, followed by extracting Cu(I) into ionic liquid phase by using neocuproine as the chelating agent. Several experimental variables that affected the GA-DLPME efficiency were investigated and optimized. Under the optimum experimental conditions (IL volume, 50µL; pH, 6.0; acetate buffer, 1.5molL(-1); reducing agent concentration, 0.2molL(-1); NC concentration, 120µgmL(-1); Ar gas bubbling time, 6min; argon flow rate, 1Lmin(-1); NaCl concentration, 6% w/w; and centrifugation time, 3min), the calibration graph was linear over the concentration range of 0.30-2.00µgmL(-1) copper ion with a limit of detection of 0.07µgmL(-1). Relative standard deviation for five replicate determinations of 1.0µgmL(-1) copper ion was found to be 3.9%. The developed method was successfully applied to determination of both Cu(I) and Cu(II) species in water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

The Nature of the Interactions in Triethanolammonium-Based Ionic Liquids. A Quantum Chemical Study.

PubMed

Fedorova, Irina V; Safonova, Lyubov P

2018-05-10

Structural features and interionic interactions play a crucial role in determining the overall stability of ionic liquids and their physicochemical properties. Therefore, we performed high-level quantum-chemical study of different cation-anion pairs representing the building units of protic ionic liquids based on triethanolammonium cation and anions of sulfuric, nitric, phosphoric, and phosphorus acids to provide essential insight into these phenomena at the molecular level. It was shown that every structure is stabilized through multiple H bonds between the protons in the N-H and O-H groups of the cation and different oxygen atoms of the anion acid. Using atoms in molecules topological parameters and natural bond orbital analysis, we determined the nature and strength of these interactions. Our calculations suggest that the N-H group of the cation has more proton donor-like character than the O-H group that makes the N-H···O hydrogen bonds stronger. A close relation between the binding energies of these ion pairs and experimental melting points was established: the smaller the absolute value of the binding energy between ions, the lower is the melting point.

Sequential injection ionic liquid dispersive liquid-liquid microextraction for thallium preconcentration and determination with flame atomic absorption spectrometry.

PubMed

Anthemidis, Aristidis N; Ioannou, Kallirroy-Ioanna G

2012-08-01

A novel, automatic on-line sequential injection dispersive liquid-liquid microextraction (SI-DLLME) method, based on 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF(6)]) ionic liquid as an extractant solvent was developed and demonstrated for trace thallium determination by flame atomic absorption spectrometry. The ionic liquid was on-line fully dispersed into the aqueous solution in a continuous flow format while the TlBr(4)(-) complex was easily migrated into the fine droplets of the extractant due to the huge contact area of them with the aqueous phase. Furthermore, the extractant was simply retained onto the surface of polyurethane foam packed into a microcolumn. No specific conditions like low temperature are required for extractant isolation. All analytical parameters of the proposed method were investigated and optimized. For 15 mL of sample solution, an enhancement factor of 290, a detection limit of 0.86 μg L(-1) and a precision (RSD) of 2.7% at 20.0 μg L(-1) Tl(I) concentration level, was obtained. The developed method was evaluated by analyzing certified reference materials while good recoveries from environmental and biological samples proved that present method was competitive in practical applications.

Determination of antimony and tin in beverages using inductively coupled plasma-optical emission spectrometry after ultrasound-assisted ionic liquid dispersive liquid-liquid phase microextraction.

PubMed

Biata, N Raphael; Nyaba, Luthando; Ramontja, James; Mketo, Nomvano; Nomngongo, Philiswa N

2017-12-15

The aim of this study was to develop a simple and fast ultrasound-assisted ionic liquid dispersive liquid-liquid phase microextraction (UA-IL-DLLME) method for preconcetration of trace antimony and tin in beverage samples. The novelty of this study was based on the application of ligandless UA-IL-DLLME using low-density ionic liquid and organic solvents for preconcentration of Sb and Sn. The concentration of Sb and Sn were quantified using ICP-OES. Under the optimum conditions, the calibration graph was found to be LOQ-250µgL -1 (r 2 =0.9987) for Sb and LOQ-350µgL -1 for Sn. The LOD and LOQ of Sb and Sn ranged from 1.2to 2.5ngL -1 and 4.0 to 8.3ngL -1 , respectively, with high preconcentration factors. The precisions (%RSD) of the proposed method ranged from 2.1% to 2.5% and 3.9% to 4.7% for Sb and Sn, respectively. The proposed method was successfully applied for determination of Sb and Sn in beverages. Copyright © 2017 Elsevier Ltd. All rights reserved.

Oxygen ion transference number of doped lanthanum gallate

NASA Astrophysics Data System (ADS)

Wang, Shizhong; Wu, Lingli; Gao, Jie; He, Qiong; Liu, Meilin

The transference numbers for oxygen ion (t O) in several LaGaO 3-based materials are determined from oxygen concentration cells using the materials as the electrolyte, including La 0.8Sr 0.2Ga 0.8Mg 0.2O 3- δ (LSGM8282), La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3- δ (LSGMC5) and La 0.8Sr 0.2Ga 0.8Mg 0.115Co 0.085O 3- δ (LSGMC8.5). Analysis indicates that the accuracy in determination of oxygen ion transference number depends on the electrode polarization resistances of the concentration cell as well as the transport properties of the materials studied. For example, the ratio of open cell voltage to Nernst potential is a good approximation to the ionic transference number for LSGM8282. However, this approximation is no longer adequate for LSGMC5 and LSGMC8.5; the effect of electrode polarization resistances must be taken into consideration in estimation of the ionic transference numbers. In particular, the ionic transference number for LSGMC5 is as high as 0.99, suggesting that it is a promising electrolyte material for low-temperature solid-state electrochemical applications.

Curvature effects on activation speed and repolarization in an ionic model of cardiac myocytes

NASA Astrophysics Data System (ADS)

Comtois, P.; Vinet, A.

1999-10-01

Reentry is a major mechanism underlying the initiation and perpetuation of many cardiac arrhythmias 12345. Stimulated ventricular myocytes give action potential characterized by a fast upstroke, a long-lasting plateau, and a late repolarization phase. The plateau phase determines the action potential duration (APD) during which the system remains refractory, a property essential to the synchronization of the heart cycle. The APD varies much with prematurity and this change has been shown to be the main determinant of the dynamics in models of paced cells and cable, and during reentry in the one-dimensional loop. Curvature has also been shown to be an important factor for propagation in experimental and theoretical cardiac extended tissue. The objective of this paper is to combine both curvature and prematurity effects in a kinematical model of propagation in cardiac tissue. First, an approximation of the ionic model is used to obtain the effects of curvature and prematurity on the speed of propagation, the APD, and the absolute refractory period. Two versions of the ionic model are studied that differ in their rate of excitability recovery. The functions are used in a kinematical model describing the propagation of period-1 solutions around an annulus.

Ionic liquid supported on an electrodeposited polycarbazole film for the headspace solid-phase microextraction and gas chromatography determination of aromatic esters.

PubMed

Feng, Yuanyuan; Zhao, Faqiong; Zeng, Baizhao

2015-05-01

A polycarbazole film was electrodeposited on a stainless-steel wire from a solution of N,N-dimethylformamide/propylene carbonate (1:9 v/v) containing 0.10 M carbazole and 0.10 M tetrabutylammonium perchlorate. The obtained polycarbazole fiber was immersed into an ionic liquid (1-hydroxyethyl-3-methyl imidazolium bis[(trifluoromethyl)sulfonyl]imide) solution (in dimethylsulfoxide) for 30 min, followed by drying under an infrared lamp. The resulting polycarbazole/ionic liquid fiber was applied to the headspace solid-phase microextraction and determination of aromatic esters by coupling with gas chromatography and flame ionization detection. Under the optimized conditions, the limits of detection were below 61 ng/L (S/N = 3) and the linear ranges were 0.061-500 μg/L with correlation coefficients above 0.9876. The relative standard deviations were below 4.8% (n = 5) for a single fiber, and below 9.9% for multi-fiber (n = 4). This fiber also exhibited good stability. It could be used for more than 160 times of headspace solid-phase microextraction and could withstand a high temperature up to 350°C. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Halloysite clay nanotubes and platinum nanoparticles dispersed in ionic liquid applied in the development of a catecholamine biosensor.

PubMed

Brondani, Daniela; Scheeren, Carla Weber; Dupont, Jairton; Vieira, Iolanda Cruz

2012-08-21

Halloysite clay nanotubes were used as a support for the immobilization of the enzyme peroxidase from clover sprouts (Trifolium), and employed together with platinum nanoparticles in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (Pt-BMI·PF(6)) in the development of a new biosensor for the determination of catecholamines by square-wave voltammetry. Under optimized conditions, the analytical curves showed detection limits of 0.05, 0.06, 0.07, 0.12 μM for dopamine, isoproterenol, dobutamine and epinephrine, respectively. The biosensor demonstrated high sensitivity, good repeatability and reproducibility, and long-term stability (18% decrease in response over 150 days). A recovery study of dopamine in pharmaceutical samples gave values from 97.5 to 101.4%. The proposed biosensor was successfully applied to the determination of dopamine in pharmaceutical samples, with a maximum relative error of ±1.0% in relation to the standard (spectrophotometric) method. The good analytical performance of the proposed method can be attributed to the efficient immobilization of the peroxidase in the nanoclay, and the facilitation of electron transfer between the protein and the electrode surface due to the presence of the Pt nanoparticles and ionic liquid.

Expression of Aspergillus niger CAZymes is determined by compositional changes in wheat straw generated by hydrothermal or ionic liquid pretreatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daly, Paul; van Munster, Jolanda M.; Blythe, Martin J.

The capacity of fungi, such as Aspergillus niger, to degrade lignocellulose is harnessed in biotechnology to generate biofuels and high-value compounds from renewable feedstocks. Most feedstocks are currently pretreated to increase enzymatic digestibility: improving our understanding of the transcriptomic responses of fungi to pretreated lignocellulosic substrates could help to improve the mix of activities and reduce the production costs of commercial lignocellulose saccharifying cocktails. We investigated the responses of A. niger to untreated, ionic liquid and hydrothermally pretreated wheat straw over a 5-day time course using RNA-seq and targeted proteomics. The ionic liquid pretreatment altered the cellulose crystallinity while retainingmore » more of the hemicellulosic sugars than the hydrothermal pretreatment. Ionic liquid pretreatment of straw led to a dynamic induction and repression of genes, which was correlated with the higher levels of pentose sugars saccharified from the ionic liquid-pretreated straw. Hydrothermal pretreatment of straw led to reduced levels of transcripts of genes encoding carbohydrate-active enzymes as well as the derived proteins and enzyme activities. Both pretreatments abolished the expression of a large set of genes encoding pectinolytic enzymes. These reduced levels could be explained by the removal of parts of the lignocellulose by the hydrothermal pretreatment. The time course also facilitated identification of temporally limited gene induction patterns. The presented transcriptomic and biochemical datasets demonstrate that pretreatments caused modifications of the lignocellulose, to both specific structural features as well as the organisation of the overall lignocellulosic structure, that determined A. niger transcript levels. The experimental setup allowed reliable detection of substrate-specific gene expression patterns as well as hitherto non-expressed genes. Our data suggest beneficial effects of using untreated and IL-pretreated straw, but not HT-pretreated straw, as feedstock for CAZyme production.« less

Expression of Aspergillus niger CAZymes is determined by compositional changes in wheat straw generated by hydrothermal or ionic liquid pretreatments

DOE PAGES

Daly, Paul; van Munster, Jolanda M.; Blythe, Martin J.; ...

2017-02-07

The capacity of fungi, such as Aspergillus niger, to degrade lignocellulose is harnessed in biotechnology to generate biofuels and high-value compounds from renewable feedstocks. Most feedstocks are currently pretreated to increase enzymatic digestibility: improving our understanding of the transcriptomic responses of fungi to pretreated lignocellulosic substrates could help to improve the mix of activities and reduce the production costs of commercial lignocellulose saccharifying cocktails. We investigated the responses of A. niger to untreated, ionic liquid and hydrothermally pretreated wheat straw over a 5-day time course using RNA-seq and targeted proteomics. The ionic liquid pretreatment altered the cellulose crystallinity while retainingmore » more of the hemicellulosic sugars than the hydrothermal pretreatment. Ionic liquid pretreatment of straw led to a dynamic induction and repression of genes, which was correlated with the higher levels of pentose sugars saccharified from the ionic liquid-pretreated straw. Hydrothermal pretreatment of straw led to reduced levels of transcripts of genes encoding carbohydrate-active enzymes as well as the derived proteins and enzyme activities. Both pretreatments abolished the expression of a large set of genes encoding pectinolytic enzymes. These reduced levels could be explained by the removal of parts of the lignocellulose by the hydrothermal pretreatment. The time course also facilitated identification of temporally limited gene induction patterns. The presented transcriptomic and biochemical datasets demonstrate that pretreatments caused modifications of the lignocellulose, to both specific structural features as well as the organisation of the overall lignocellulosic structure, that determined A. niger transcript levels. The experimental setup allowed reliable detection of substrate-specific gene expression patterns as well as hitherto non-expressed genes. Our data suggest beneficial effects of using untreated and IL-pretreated straw, but not HT-pretreated straw, as feedstock for CAZyme production.« less

Human fibrinogen adsorption on positively charged latex particles.

PubMed

Zeliszewska, Paulina; Bratek-Skicki, Anna; Adamczyk, Zbigniew; Cieśla, Michał

2014-09-23

Fibrinogen (Fb) adsorption on positively charged latex particles (average diameter of 800 nm) was studied using the microelectrophoretic and the concentration depletion methods based on AFM imaging. Monolayers on latex were adsorbed from diluted bulk solutions at pH 7.4 and an ionic strength in the range of 10(-3) to 0.15 M where fibrinogen molecules exhibited an average negative charge. The electrophoretic mobility of the latex after controlled fibrinogen adsorption was systematically measured. A monotonic decrease in the electrophoretic mobility of fibrinogen-covered latex was observed for all ionic strengths. The results of these experiments were interpreted according to the three-dimensional electrokinetic model. It was also determined using the concentration depletion method that fibrinogen adsorption was irreversible and the maximum coverage was equal to 0.6 mg m(-2) for ionic strength 10(-3) M and 1.3 mg m(-2) for ionic strength 0.15 M. The increase of the maximum coverage was confirmed by theoretical modeling based on the random sequential adsorption approach. Paradoxically, the maximum coverage of fibrinogen on positively charged latex particles was more than two times lower than the maximum coverage obtained for negative latex particles (3.2 mg m(-2)) at pH 7.4 and ionic strength of 0.15 M. This was interpreted as a result of the side-on adsorption of fibrinogen molecules with their negatively charged core attached to the positively charged latex surface. The stability and acid base properties of fibrinogen monolayers on latex were also determined in pH cycling experiments where it was observed that there were no irreversible conformational changes in the fibrinogen monolayers. Additionally, the zeta potential of monolayers was more positive than the zeta potential of fibrinogen in the bulk, which proves a heterogeneous charge distribution. These experimental data reveal a new, side-on adsorption mechanism of fibrinogen on positively charged surfaces and confirmed the decisive role of electrostatic interactions in this process.

Application of non-ionic surfactant as a developed method for the enhancement of two-phase solvent bar microextraction for the simultaneous determination of three phthalate esters from water samples.

PubMed

Bandforuzi, Samereh Ranjbar; Hadjmohammadi, Mohammad Reza

2018-08-03

The extraction of phthalate esters (PEs) from aqueous matrices using two-phase solvent bar microextraction by organic micellar phase was investigated. A short hollow fiber immobilized with reverse micelles of Brij 35 surfactant in 1-octanol was served as the solvent bar for microextraction. Experimental results show that the extraction efficiency were much higher using two-phase solvent bar microextraction based on non-ionic surfactant than conventional two-phase solvent bar microextraction because of a positive effect of surfactant-containing extraction phase in promoting the partition process by non-ionic intermolecular forces such as polar and hydrophobicity interactions. The nature of the extraction solvent, type and concentration of non-ionic surfactant, extraction time, sample pH, temperature, stirring rate and ionic strength were the effecting parameters which optimized to obtain the highest extraction recovery. Analysis of recovered analytes was carried out with high performance liquid chromatography coupled with ultraviolet detection (HPLC-UV). Under the optimum conditions, linearity was observed in the range of 1-800 ng mL -1 for dimethylphthalate (DMP) and 0.5-800 ng mL -1 for diethylphthalate (DEP) and di-n-butyl phthalate (DBP) with correlation determination values above 0.99 for them. The limits of detection and quantification were ranged from 0.012 to 0.03 ng mL -1 and 0.04-0.1 ng mL -1 , respectively. The ranges of intra-day and inter-day RSD (n = 3) at 20 ng mL -1 of PEs were 1.8-2.1% and 2.1-2.6%, respectively. Results showed that developed method can be a very powerful, innovative and promising sample preparation technique in PEs analysis from environmental and drinking water samples. Copyright © 2018. Published by Elsevier B.V.

Whole house particle removal and clean air delivery rates for in-duct and portable ventilation systems.

PubMed

Macintosh, David L; Myatt, Theodore A; Ludwig, Jerry F; Baker, Brian J; Suh, Helen H; Spengler, John D

2008-11-01

A novel method for determining whole house particle removal and clean air delivery rates attributable to central and portable ventilation/air cleaning systems is described. The method is used to characterize total and air-cleaner-specific particle removal rates during operation of four in-duct air cleaners and two portable air-cleaning devices in a fully instrumented test home. Operation of in-duct and portable air cleaners typically increased particle removal rates over the baseline rates determined in the absence of operating a central fan or an indoor air cleaner. Removal rates of 0.3- to 0.5-microm particles ranged from 1.5 hr(-1) during operation of an in-duct, 5-in. pleated media filter to 7.2 hr(-1) for an in-duct electrostatic air cleaner in comparison to a baseline rate of 0 hr(-1) when the air handler was operating without a filter. Removal rates for total particulate matter less than 2.5 microm in aerodynamic diameter (PM2.5) mass concentrations were 0.5 hr(-1) under baseline conditions, 0.5 hr(-1) during operation of three portable ionic air cleaners, 1 hr(-1) for an in-duct 1-in. media filter, 2.4 hr(-1) for a single high-efficiency particle arrestance (HEPA) portable air cleaner, 4.6 hr(-1) for an in-duct 5-in. media filter, 4.7 hr(-1) during operation of five portable HEPA filters, 6.1 hr(-1) for a conventional in-duct electronic air cleaner, and 7.5 hr(-1) for a high efficiency in-duct electrostatic air cleaner. Corresponding whole house clean air delivery rates for PM2.5 attributable to the air cleaner independent of losses within the central ventilation system ranged from 2 m3/min for the conventional media filter to 32 m3/min for the high efficiency in-duct electrostatic device. Except for the portable ionic air cleaner, the devices considered here increased particle removal indoors over baseline deposition rates.

Sr- and Nb-co-doped Li7La3Zr2O12 solid electrolyte with Al2O3 addition towards high ionic conductivity

NASA Astrophysics Data System (ADS)

Lin, Changwei; Tang, Yu; Song, Jun; Han, Lei; Yu, Jingbo; Lu, Anxian

2018-06-01

In the present study, series of garnet-type Li6.75+ x La3- x Sr x Zr1.75Nb0.25O12 solid electrolytes [LLSZN with various Sr contents ( x = 0.05-0.25)] have been prepared via conventional solid-state method. The effects of Sr contents on their phase structure and ionic conductivity have been systematically investigated on the combined measurements of X-ray diffraction and scanning electron microscopy and alter current impedance spectroscopy. Our results reveal that a phase transition from tetragonal to cubic structure occurs when both Sr and Nb elements is introduced, and such a cubic structure can be stable over the whole Sr contents variation, which is suggested to provide a beneficial impact on the performance of LLSZN. Accordingly, both relative density and total ionic conductivity exhibit a favorable tendency of increasing first and then decreasing with increased Sr contents, wherein a peak value at 93.46% and 5.09 × 10-4 S cm-1, respectively, can be well achieved. Particularly, the maximum ionic conductivity is almost twice that of the compared sample (2.93 × 10-4 S cm-1), and possess the minimum activation energy 0.30 eV. Such a modification method, featured with higher efficiency and lower cost, is expected to be helpful for the development of solid electrolyte.

Catalysis of Rice Straw Hydrolysis by the Combination of Immobilized Cellulase from Aspergillus niger on β-Cyclodextrin-Fe3O4 Nanoparticles and Ionic Liquid

PubMed Central

Huang, Po-Jung; Chang, Ken-Lin; Chen, Shui-Tein

2015-01-01

Cellulase from Aspergillus niger was immobilized onto β-cyclodextrin-conjugated magnetic particles by silanization and reductive amidation. The immobilized cellulase gained supermagnetism due to the magnetic nanoparticles. Ninety percent of cellulase was immobilized, but the activity of immobilized cellulase decreased by 10%. In this study, ionic liquid (1-butyl-3-methylimidazolium chloride) was introduced into the hydrolytic process because the original reaction was a solid-solid reaction. The activity of immobilized cellulase was improved from 54.87 to 59.11 U g immobilized cellulase−1 at an ionic liquid concentration of 200 mM. Using immobilized cellulase and ionic liquid in the hydrolysis of rice straw, the initial reaction rate was increased from 1.629 to 2.739 g h−1 L−1. One of the advantages of immobilized cellulase is high reusability—it was usable for a total of 16 times in this study. Compared with free cellulase, magnetized cellulase can be recycled by magnetic field and the activity of immobilized cellulase was shown to remain at 85% of free cellulase without denaturation under a high concentration of glucose (15 g L−1). Therefore, immobilized cellulase can hydrolyze rice straw continuously compared with free cellulase. The amount of harvested glucose can be up to twentyfold higher than that from the hydrolysis by free cellulase. PMID:25874210

Cluster approach to the prediction of thermodynamic and transport properties of ionic liquids

NASA Astrophysics Data System (ADS)

Seeger, Zoe L.; Kobayashi, Rika; Izgorodina, Ekaterina I.

2018-05-01

The prediction of physicochemical properties of ionic liquids such as conductivity and melting point would substantially aid the targeted design of ionic liquids for specific applications ranging from solvents for extraction of valuable chemicals to biowaste to electrolytes in alternative energy devices. The previously published study connecting the interaction energies of single ion pairs (1 IP) of ionic liquids to their thermodynamic and transport properties has been extended to larger systems consisting of two ion pairs (2 IPs), in which many-body and same-ion interactions are included. Routinely used cations, of the imidazolium and pyrrolidinium families, were selected in the study coupled with chloride, tetrafluoroborate, and dicyanamide. Their two ion pair clusters were subjected to extensive configuration screening to establish most stable structures. Interaction energies of these clusters were calculated at the spin-ratio scaled MP2 (SRS-MP2) level for the correlation interaction energy, and a newly developed scaled Hartree-Fock method for the rest of energetic contributions to interaction energy. A full geometry screening for each cation-anion combination resulted in 192 unique structures, whose stability was assessed using two criteria—widely used interaction energy and total electronic energy. Furthermore, the ratio of interaction energy to its dispersion component was correlated with experimentally observed melting points in 64 energetically favourable structures. These systems were also used to test the correlation of the dispersion contribution to interaction energy with measured conductivity.

Monitoring and Analyzing Process Streams Towards Understanding Ionic Liquid Pretreatment of Switchgrass (Panicum virgatum L.)

USDA-ARS?s Scientific Manuscript database

Fundamental understanding of biomass pretreatment and its influence on sacchrification kinetics, total sugar yield, and inhibitor formation is essential to develop efficient next-generation biofuels strategies, capable of displacing fossil fuels at a commercial level. In this study we investigate t...

Implications of effluent organic matter and its hydrophilic fraction on zinc(II) complexation in rivers under strong urban pressure: aromaticity as an inaccurate indicator of DOM-metal binding.

PubMed

Louis, Yoann; Pernet-Coudrier, Benoît; Varrault, Gilles

2014-08-15

The zinc binding characteristics of dissolved organic matter (DOM) fractions from the Seine River Basin were studied after being separated and extracted according to their polarity: hydrophobic, transphilic, and hydrophilic. The applied experimental methodology was based on a determination of labile zinc species by means of differential pulse anodic stripping voltammetry (DPASV) at increasing concentrations of total zinc on a logarithmic scale and at fixed levels of: pH, ionic strength, and temperature. Fitting the DOM fractions with two discrete classes of ligands successfully allowed determining the conditional zinc binding constants (Ki) as well as total ligand density (LiT). The binding constants obtained for each DOM fraction were then compared and discussed with respect to the hydrophobic/hydrophilic nature and sample origin. Results highlighted a strong complexation of zinc to the effluent organic matter and especially the most hydrophilic fraction, which also displayed a very low specific UV absorbance. Although the biotic ligand model takes into account the quality of DOM through UV absorbance in the predictions of metal bioavailability and toxicity, this correction is not efficient for urban waters. Copyright © 2014 Elsevier B.V. All rights reserved.

Neptunium(V) Adsorption to Bacteria at Low and High Ionic Strength

NASA Astrophysics Data System (ADS)

Ams, D.; Swanson, J. S.; Reed, D. T.

2010-12-01

Np(V) is expected to be the predominant oxidation state of neptunium in aerobic natural waters. Np(V), as the NpO2+ aquo and associated complexed species, is readily soluble, interacts weakly with geologic media, and has a high redox stability under a relatively wide range of subsurface conditions. These chemical properties, along with a long half-life make it a primary element of concern regarding long-term nuclear waste storage and subsurface containment. The fate and transport of neptunium in the environment may be influenced by adsorption onto bacterial surfaces. The adsorption of neptunium to bacterial surfaces ties the mobility of the contaminant to the mobility of the bacterium. In this study, the adsorption of the neptunyl (NpO2+) ion was evaluated at low ionic strength on a common soil bacterium and at high ionic strength on a halophilic bacterium isolated from a briny groundwater near the Waste Isolation Pilot Plant (WIPP) in southeast New Mexico. Adsorption experiments were performed in batch reactors as a function of pH, ionic strength, and bacteria/Np mass ratio. Np(V) adsorption was modeled using a surface complexation approach with the mathematical program FITEQL to determine functional group specific binding constants. The data from acid and base titrations of the bacteria used were also modeled to estimate the concentrations and deprotonation constants of discrete bacterial surface functional groups. Bacterial functional group characteristics and Np(V) adsorption behavior between the soil bacterium and the halophilic bacterium were compared. These results highlight key similarities and differences in actinide adsorption behavior in environments of significantly different ionic strength. The observed adsorption behavior may be linked to similarities and differences in the characteristics of the moieties between the cell walls of common gram-negative soil and halophilic bacteria. Moreover, differences in adsorption behavior may also reflect ionic strength effects as the electronic double layer is compressed with increasing ionic strength. These results further highlight the importance of electrostatic interactions in the adsorption process between dissolved metals and bacterial surfaces. This work expands the understanding of actinide-bacteria adsorption phenomena to high ionic strength environmental conditions that are relevant as an aid to predicting Np(V) fate and transport behavior in areas such as the vicinity of salt-based nuclear waste repositories and high ionic-strength groundwaters at DOE sites.

Modulation of the aggregation properties of sodium deoxycholate in presence of hydrophilic imidazolium based ionic liquid: water dynamics study to probe the structural alteration of the aggregates.

PubMed

Kundu, Niloy; Banik, Debasis; Roy, Arpita; Kuchlyan, Jagannath; Sarkar, Nilmoni

2015-10-14

In this article, we have investigated the effect of a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]-BF4), on the aggregation properties of a biological surfactant, sodium deoxycholate (NaDC), in water. In solution, unlike conventional surfactants it shows stepwise aggregation and the effect of the conventional ionic liquid on the aggregation properties is rather interesting. We have observed concentration dependent dual role of the ionic liquid; at their low concentration, the aggregated structure of NaDC reorganizes itself into an elongated rod like structure. However, the aggregated network is disintegrated into small aggregates upon further addition of ionic liquid. TEM (Transmission Electron Microscopy), SEM (Scanning Electron Microscopy) and FLIM (Fluorescence Lifetime Imaging Microscopy) images also confirmed the structural alteration of NaDC upon varying the concentration of the ionic liquid. The proton NMR data indicate that hydrophobic as well as electrostatic interaction is solely responsible for such structural adaptation of NaDC in the presence of an ionic liquid. The host-guest interaction inside the aggregates is monitored using Coumarin-153 (C-153) and the location of C-153 is probed by varying the excitation wavelength from 375 nm to 440 nm and the two binding sites of the aggregates are affected in a different fashion in the presence of ionic liquid. Excitation in the blue region selects the fluorophores which preferably bind to the buried region of the aggregates, whereas 440 nm excitation corresponds to the guest molecules which are exposed to the solvent molecules. The average solvation time of C-153 is increased in the presence of 1.68 wt% [bmim]-BF4 at λexc = 440 nm i.e. the probe molecules relocate themselves to a more restricted region. However, the average solvation time became 2.6 times faster in the presence of 11.2 wt% [bmim]-BF4, which corresponds to a more polar and exposed region. The time resolved anisotropy measurements and polarity determined by pyrene also supported our results in addition to solvation dynamics measurements. In summary, ionic liquids can modulate the host-guest interaction of bile salt aggregates, which can be used as nanocarriers for drug delivery.

Understanding the effect models of ionic liquids in the synthesis of NH4-Dw and γ-AlOOH nanostructures and their conversion into porous γ-Al2O3.

PubMed

Duan, Xiaochuan; Kim, Tongil; Li, Di; Ma, Jianmin; Zheng, Wenjun

2013-05-03

Well-dispersed ammonium aluminum carbonate hydroxide (NH4-Dw) and γ-AlOOH nanostructures with controlled morphologies have been synthesized by employing an ionic-liquid-assisted hydrothermal process. The basic strategies that were used in this work were: 1) A controllable phase transition from NH4-Dw to γ-AlOOH could be realized by increasing the reaction temperature and 2) the morphological evolution of NH4-Dw and γ-AlOOH nanostructures could be influenced by the concentration of the ionic liquid. Based on these experimental results, the main objective of this work was to clarify the effect models of the ionic liquids on the synthesis of NH4-Dw and γ-AlOOH nanostructures, which could be divided into cationic- or anionic-dominant effect models, as determined by the different surface structures of the targets. Specifically, under the cationic-dominant regime, the ionic liquids mainly showed dispersion effects for the NH4-Dw nanostructures, whereas the anionic-dominant model could induce the self-assembly of the γ-AlOOH particles to form hierarchical structures. Under the guidance of the proposed models, the effect of the ionic liquids would be optimized by an appropriate choice of cations or anions, as well as by considering the different effect models with the substrate surface. We expect that such effect models between ionic liquids and the target products will be helpful for understanding and designing rational ionic liquids that contain specific functional groups, thus open up new opportunities for the synthesis of inorganic nanomaterials with new morphologies and improved properties. In addition, these as-prepared NH4-Dw and γ-AlOOH nanostructures were converted into porous γ-Al2O3 nanostructures by thermal decomposition, whilst preserving the same morphology. By using HRTEM and nitrogen-adsorption analysis, the obtained γ-Al2O3 samples were found to have excellent porous properties and, hence, may have applications in catalysis and adsorption. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acid-Base Chemistry of White Wine: Analytical Characterisation and Chemical Modelling

PubMed Central

Prenesti, Enrico; Berto, Silvia; Toso, Simona; Daniele, Pier Giuseppe

2012-01-01

A chemical model of the acid-base properties is optimized for each white wine under study, together with the calculation of their ionic strength, taking into account the contributions of all significant ionic species (strong electrolytes and weak one sensitive to the chemical equilibria). Coupling the HPLC-IEC and HPLC-RP methods, we are able to quantify up to 12 carboxylic acids, the most relevant substances responsible of the acid-base equilibria of wine. The analytical concentration of carboxylic acids and of other acid-base active substances was used as input, with the total acidity, for the chemical modelling step of the study based on the contemporary treatment of overlapped protonation equilibria. New protonation constants were refined (L-lactic and succinic acids) with respect to our previous investigation on red wines. Attention was paid for mixed solvent (ethanol-water mixture), ionic strength, and temperature to ensure a thermodynamic level to the study. Validation of the chemical model optimized is achieved by way of conductometric measurements and using a synthetic “wine” especially adapted for testing. PMID:22566762

In Situ Characterization of the Initial Effect of Water on Molecular Interactions at the Interface of Organic/Inorganic Hybrid Systems

PubMed Central

Pletincx, Sven; Trotochaud, Lena; Fockaert, Laura-Lynn; Mol, Johannes M. C.; Head, Ashley R.; Karslıoğlu, Osman; Bluhm, Hendrik; Terryn, Herman; Hauffman, Tom

2017-01-01

Probing initial interactions at the interface of hybrid systems under humid conditions has the potential to reveal the local chemical environment at solid/solid interfaces under real-world, technologically relevant conditions. Here, we show that ambient pressure X-ray photoelectron spectroscopy (APXPS) with a conventional X-ray source can be used to study the effects of water exposure on the interaction of a nanometer-thin polyacrylic acid (PAA) layer with a native aluminum oxide surface. The formation of a carboxylate ionic bond at the interface is characterized both with APXPS and in situ attenuated total reflectance Fourier transform infrared spectroscopy in the Kretschmann geometry (ATR-FTIR Kretschmann). When water is dosed in the APXPS chamber up to 5 Torr (~28% relative humidity), an increase in the amount of ionic bonds at the interface is observed. To confirm our APXPS interpretation, complementary ATR-FTIR Kretschmann experiments on a similar model system, which is exposed to an aqueous electrolyte, are conducted. These spectra demonstrate that water leads to an increased wet adhesion through increased ionic bond formation. PMID:28327587

Acid-base chemistry of white wine: analytical characterisation and chemical modelling.

PubMed

Prenesti, Enrico; Berto, Silvia; Toso, Simona; Daniele, Pier Giuseppe

2012-01-01

A chemical model of the acid-base properties is optimized for each white wine under study, together with the calculation of their ionic strength, taking into account the contributions of all significant ionic species (strong electrolytes and weak one sensitive to the chemical equilibria). Coupling the HPLC-IEC and HPLC-RP methods, we are able to quantify up to 12 carboxylic acids, the most relevant substances responsible of the acid-base equilibria of wine. The analytical concentration of carboxylic acids and of other acid-base active substances was used as input, with the total acidity, for the chemical modelling step of the study based on the contemporary treatment of overlapped protonation equilibria. New protonation constants were refined (L-lactic and succinic acids) with respect to our previous investigation on red wines. Attention was paid for mixed solvent (ethanol-water mixture), ionic strength, and temperature to ensure a thermodynamic level to the study. Validation of the chemical model optimized is achieved by way of conductometric measurements and using a synthetic "wine" especially adapted for testing.

Synthesis, spectroscopic, and molecular structure characterizations of some azo derivatives of 2-hydroxyacetophenone

NASA Astrophysics Data System (ADS)

Albayrak, Çiğdem; Gümrükçüoğlu, İsmail E.; Odabaşoğlu, Mustafa; İskeleli, Nazan Ocak; Ağar, Erbil

2009-08-01

Some novel azo compounds were prepared by the reaction of 2-hydroxyacetophenone with aniline and its substituted derivatives. The structures of synthesized azo compounds were determined by IR, UV-Vis, 1H NMR and 13C NMR spectroscopic techniques and the structures of some of these compounds were also determined by X-ray diffraction studies. Structural analysis using IR in solid state shows that the azo form is favoured in the azo compounds whereas UV-Vis analysis of the azo compounds in solution has shown that there is a azo and ionic form. The azo compounds in the basic solvents dimethylformamide (DMF) and dimethylsulfoxide (DMSO) are both azo and ionic form while these compounds in ethyl alcohol (EtOH) and chloroform (CHCl 3) are only azo form.

Non-ionic surfactant vesicles in pulmonary glucocorticoid delivery: characterization and interaction with human lung fibroblasts.

PubMed

Marianecci, Carlotta; Paolino, Donatella; Celia, Christian; Fresta, Massimo; Carafa, Maria; Alhaique, Franco

2010-10-01

Non-ionic surfactant vesicles (NSVs) were proposed for the pulmonary delivery of glucocorticoids such as beclomethasone dipropionate (BDP) for the treatment of inflammatory lung diseases, e.g. asthma, chronic obstructive pulmonary disease and various type of pulmonary fibrosis. The thin layer evaporation method followed by sonication was used to prepare small non-ionic surfactant vesicles containing beclomethasone dipropionate. Light scattering experiments showed that beclomethasone dipropionate-loaded non-ionic surfactant vesicles were larger than unloaded ones and showed a significant (P<0.001) decrease of the zeta potential. The morphological analysis, by freeze-fracture transmission electron microscopy, showed the maintenance of a vesicular structure in the presence of the drug. The colloidal and storage stability were evaluated by Turbiscan Lab Expert, which evidenced the good stability of BDP-loaded non-ionic surfactant vesicles, thus showing no significant variations of mean size and no colloidal phase segregation. Primary human lung fibroblast (HLF) cells were used for in vitro investigation of vesicle tolerability, carrier-cell interaction, intracellular drug uptake and drug-loaded vesicle anti-inflammatory activity. The investigated NSVs did not show a significant cytotoxic activity at all incubation times for concentrations ranging from 0.01 to 1 μM. Confocal laser scanning microscopy showed vesicular carrier localization at the level of the cytoplasm compartment, where the glucocorticoid receptor (target site) is localized. BDP-loaded non-ionic surfactant vesicles elicited a significant improvement of the HLF intracellular uptake of the drug with respect to the free drug solution, drug/surfactant mixtures and empty vesicles used as references. The treatment of HLF cells with BDP-loaded non-ionic surfactant vesicles determined a noticeable increase of the drug anti-inflammatory activity by reducing the secretion of both constitutive and interleukin-1β-stimulated nerve growth factor (as inflammatory index) of 68% and 85%, respectively. Obtained data indicate that the investigated NSVs represent a promising tool as a pulmonary drug delivery system. Copyright © 2010 Elsevier B.V. All rights reserved.

Ions in water: Free energies, surface effects, and geometrical constraints

NASA Astrophysics Data System (ADS)

Herce, Henry David

In this work, we present our results for ion solvation in finite and infinite water clusters. Molecular Dynamic simulations are used to connect the fundamental macroscopic quantities such as free energy, internal energy and entropy with the underlying microscopic description. Molecular dynamics studies complement experimental results and lead to a deeper insight into the solvation and diffusion of ionic species. Beyond its intrinsic interest, the ion solvation problem has practical relevance because of its role as ideal model system with which to construct and test ion-water interaction potentials. The ionic charging free energy is a very sensitive probe for the treatment of electrostatics in any given simulation setting. In this work, we present methods to compute the ionic charging free energy in systems characterized by atomic charges, and higher-order multipoles, mainly dipoles and quadrupoles. The results of these methods under periodic boundary conditions and spherical boundary conditions are then compared. For the treatment of spherical boundary conditions, we introduce a generalization of Gauss' law that links the microscopic variables to the relevant thermodynamic quantities. Ionic solvation in finite clusters is a problem relevant for many areas of chemistry and biology, such as the gas-liquid interface of tropospheric aerosol particles, or the interphase between water and proteins, membranes, etc. Careful evaluations of the free energy, internal energy and entropy are used to address controversial or unresolved issues, related to the underlying physical cause of surface solvation, and the basic assumptions that go with it. Our main conclusions are the following: (i) The main cause of surface solvation of a single ion in a water cluster is both water and ion polarization, coupled to the charge and size of the ion. Interestingly, the total energy of the ion increases near the cluster surface, while the total energy of water decreases. Also, our analysis clearly shows that the cause of surface solvation is not the size of the total water dipole (unless this is too small). (ii) The entropic contribution is the same order of magnitude as the energetic contribution, and therefore cannot be neglected for quantitative results. (iii) A pure energetic analysis can give a qualitative description of the ion position at room temperature. (iv) We have observed surface solvation of a large positive iodine-like ion in a polarizable water cluster, but not in a non-polarizable water cluster.

Efficient production of free fatty acids from ionic liquid-based acid- or enzyme-catalyzed bamboo hydrolysate.

PubMed

Mi, Le; Qin, Dandan; Cheng, Jie; Wang, Dan; Li, Sha; Wei, Xuetuan

2017-03-01

Two engineered Escherichia coli strains, DQ101 (MG1655 fadD - )/pDQTES and DQ101 (MG1655 fadD - )/pDQTESZ were constructed to investigate the free fatty acid production using ionic liquid-based acid- or enzyme-catalyzed bamboo hydrolysate as carbon source in this study. The plasmid, pDQTES, carrying an acyl-ACP thioesterase 'TesA of E. coli in pTrc99A was constructed firstly, and then (3R)-hydroxyacyl-ACP dehydratase was ligated after the TesA to give the plasmid pDQTESZ. These two strains exhibited efficient fatty acid production when glucose was used as the sole carbon source, with a final concentration of 2.45 and 3.32 g/L, respectively. The free fatty acid production of the two strains on xylose is not as efficient as that on glucose, which was 2.32 and 2.96 g/L, respectively. For mixed sugars, DQ101 (MG1655 fadD - )-based strains utilized glucose and pentose sequentially under the carbon catabolite repression (CCR) regulation. The highest total FFAs concentration from the mixed sugar culture reached 2.81 g/L by DQ101 (MG1655 fadD - )/pDQTESZ. Furthermore, when ionic liquid-based enzyme-catalyzed bamboo hydrolysate was used as the carbon source, the strain DQ101 (MG1655 fadD - )/pDQTESZ could produce 1.23 g/L FFAs with a yield of 0.13 g/g, and while it just produced 0.65 g/L free fatty acid with the ionic liquid-based acid-catalyzed bamboo hydrolysate as the feedstock. The results suggested that enzymatic catalyzed bamboo hydrolysate with ionic liquid pretreatment could serve as an efficient feedstock for free fatty acid production.

Simulation study of the lithium ion transport mechanism in ternary polymer electrolytes: the critical role of the segmental mobility.

PubMed

Diddens, Diddo; Heuer, Andreas

2014-01-30

We present an extensive molecular dynamics (MD) simulation study of the lithium ion transport in ternary polymer electrolytes consisting of poly(ethylene oxide) (PEO), lithium-bis(trifluoromethane)sulfonimide (LiTFSI), and the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethane)sulfonimide (PYR13TFSI). In particular, we focus on two different strategies by which the ternary electrolytes can be devised, namely by (a) adding the ionic liquid to PEO20LiTFSI and (b) substituting the PEO chains in PEO20LiTFSI by the ionic liquid. To grasp the changes of the overall lithium transport mechanism, we employ an analytical, Rouse-based cation transport model (Maitra et al. Phys. Rev. Lett. 2007, 98, 227802), which has originally been devised for binary PEO-based electrolytes. This model distinguishes three different microscopic transport mechanisms, each quantified by an individual time scale. In the course of our analysis, we extend this mathematical description to account for an entirely new transport mechanism, namely, the TFSI-supported diffusion of lithium ions decoupled from the PEO chains, which emerges for certain stoichiometries. We find that the segmental mobility plays a decisive role in PEO-based polymer electrolytes. That is, whereas the addition of the ionic liquid to PEO20LiTFSI plasticizes the polymer network and thus also increases the lithium diffusion, the amount of free, mobile ether oxygens reduces when substituting the PEO chains by the ionic liquid, which compensates the plasticizing effect. In total, our observations allow us to formulate some general principles about the lithium ion transport mechanism in ternary polymer electrolytes. Moreover, our insights also shed light on recent experimental observations (Joost et al. Electrochim. Acta 2012, 86, 330).

Addition of ammonia and/or oxygen to an ionic liquid for delignification of miscanthus.

PubMed

Rodríguez, Héctor; Padmanabhan, Sasisanker; Poon, Geoffrey; Prausnitz, John M

2011-09-01

Ammonia and/or oxygen were used to enhance the delignification of miscanthus dissolved in 1-ethyl-3-methylimidazolium acetate at 140°C. After dissolution of the gas at 9 bar, water was added as antisolvent to regenerate the dissolved biomass. In a next step, an acetone/water mixture was used to remove carbohydrate-free lignin from the regenerated biomass. The lignin content in the final product was around 10%, much lower than the ca. 23% lignin content of the raw dry miscanthus. This lignin reduction is achieved without diminution of cellulose or of total carbohydrates recovered, relative to the recovery achieved with the ionic liquid pretreatment in contact with air or nitrogen. Copyright © 2011 Elsevier Ltd. All rights reserved.

Steric and electrostatic surface forces on sulfonated PEG graft surfaces with selective albumin adsorption.

PubMed

Bremmell, Kristen E; Britcher, Leanne; Griesser, Hans J

2013-06-01

Addition of ionized terminal groups to PEG graft layers may cause additional interfacial forces to modulate the net interfacial interactions between PEG graft layers and proteins. In this study we investigated the effect of terminal sulfonate groups, characterizing PEG-aldehyde (PEG-CHO) and sulfonated PEG (PEG-SO3) graft layers by XPS and colloid probe AFM interaction force measurements as a function of ionic strength, in order to determine surface forces relevant to protein resistance and models of bio-interfacial interaction of such graft coatings. On the PEG-CHO surface the measured interaction force does not alter with ionic strength, typical of a repulsive steric barrier coating. An analogous repulsive interaction force of steric origin was also observed on the PEG-SO3 graft coating; however, the net interaction force changed with ionic strength. Interaction forces were modelled by steric and electrical double layer interaction theories, with fitting to a scaling theory model enabling determination of the spacing and stretching of the grafted chains. Albumin, fibrinogen, and lysozyme did not adsorb on the PEG-CHO coating, whereas the PEG graft with terminal sulfonate groups showed substantial adsorption of albumin but not fibrinogen or lysozyme from 0.15 M salt solutions. Under lower ionic strength conditions albumin adsorption was again minimized as a result of the increased electrical double-layer interaction observed with the PEG-SO3 modified surface. This unique and unexpected adsorption behaviour of albumin provides an alternative explanation to the "negative cilia" model used by others to rationalize observed thromboresistance on PEG-sulfonate coatings. Copyright © 2013 Elsevier B.V. All rights reserved.

Ionic Conductivity, Structural Deformation and Programmable Anisotropy of DNA Origami in Electric Field

PubMed Central

Li, Chen-Yu; Hemmig, Elisa A.; Kong, Jinglin; Yoo, Jejoong; Hernández-Ainsa, Silvia

2015-01-01

The DNA origami technique can enable functionalization of inorganic structures for single-molecule electric current recordings. Experiments have shown that several layers of DNA molecules—a DNA origami plate— placed on top of a solid-state nanopore is permeable to ions. Here, we report a comprehensive characterization of the ionic conductivity of DNA origami plates by means of all-atom molecular dynamics (MD) simulations and nanocapillary electric current recordings. Using the MD method, we characterize the ionic conductivity of several origami constructs, revealing the local distribution of ions, the distribution of the electrostatic potential and contribution of different molecular species to the current. The simulations determine the dependence of the ionic conductivity on the applied voltage, the number of DNA layers, the nucleotide content and the lattice type of the plates. We demonstrate that increasing the concentration of Mg2+ ions makes the origami plates more compact, reducing their conductivity. The conductance of a DNA origami plate on top of a solid-state nanopore is determined by the two competing effects: bending of the DNA origami plate that reduces the current and separation of the DNA origami layers that increases the current. The latter is produced by the electro-osmotic flow and is reversible at the time scale of a hundred nanoseconds. The conductance of a DNA origami object is found to depend on its orientation, reaching maximum when the electric field aligns with the direction of the DNA helices. Our work demonstrates feasibility of programming the electrical properties of a self-assembled nanoscale object using DNA. PMID:25623807

Ionic conductivity, structural deformation, and programmable anisotropy of DNA origami in electric field.

PubMed

Li, Chen-Yu; Hemmig, Elisa A; Kong, Jinglin; Yoo, Jejoong; Hernández-Ainsa, Silvia; Keyser, Ulrich F; Aksimentiev, Aleksei

2015-02-24

The DNA origami technique can enable functionalization of inorganic structures for single-molecule electric current recordings. Experiments have shown that several layers of DNA molecules, a DNA origami plate, placed on top of a solid-state nanopore is permeable to ions. Here, we report a comprehensive characterization of the ionic conductivity of DNA origami plates by means of all-atom molecular dynamics (MD) simulations and nanocapillary electric current recordings. Using the MD method, we characterize the ionic conductivity of several origami constructs, revealing the local distribution of ions, the distribution of the electrostatic potential and contribution of different molecular species to the current. The simulations determine the dependence of the ionic conductivity on the applied voltage, the number of DNA layers, the nucleotide content and the lattice type of the plates. We demonstrate that increasing the concentration of Mg(2+) ions makes the origami plates more compact, reducing their conductivity. The conductance of a DNA origami plate on top of a solid-state nanopore is determined by the two competing effects: bending of the DNA origami plate that reduces the current and separation of the DNA origami layers that increases the current. The latter is produced by the electro-osmotic flow and is reversible at the time scale of a hundred nanoseconds. The conductance of a DNA origami object is found to depend on its orientation, reaching maximum when the electric field aligns with the direction of the DNA helices. Our work demonstrates feasibility of programming the electrical properties of a self-assembled nanoscale object using DNA.

Comparison in the analytical performance between krypton and argon glow discharge plasmas as the excitation source for atomic emission spectrometry.

PubMed

Wagatsuma, Kazuaki

2009-04-01

The emission characteristics of ionic lines of nickel, cobalt, and vanadium were investigated when argon or krypton was employed as the plasma gas in glow discharge optical emission spectrometry. A dc Grimm-style lamp was employed as the excitation source. Detection limits of the ionic lines in each iron-matrix alloy sample were compared between the krypton and the argon plasmas. Particular intense ionic lines were observed in the emission spectra as a function of the discharge gas (krypton or argon), such as the Co II 258.033 nm for krypton and the Co II 231.707 nm for argon. The explanation for this is that collisions with the plasma gases dominantly populate particular excited levels of cobalt ion, which can receive the internal energy from each gas ion selectively, for example, the 3d(7)4p (3)G(5) (6.0201 eV) for krypton and the 3d(7)4p (3)G(4) (8.0779 eV) for argon. In the determination of nickel as well as cobalt in iron-matrix samples, more sensitive ionic lines could be found in the krypton plasma rather than the argon plasma. Detection limits in the krypton plasma were 0.0039 mass% Ni for the Ni II 230.299-nm line and 0.002 mass% Co for the Co II 258.033-nm line. However, in the determination of vanadium, the argon plasma had better analytical performance, giving a detection limit of 0.0023 mass% V for the V II 309.310-nm line.

Peroxyoxalate chemiluminescence enhanced by oligophenylenevinylene fluorophores in the presence of various surfactants.

PubMed

Motoyoshiya, Jiro; Takigawa, Setsuko

2014-11-01

The effect of several surfactants on peroxyoxalate chemiluminescence (PO-CL) using oligophenylenevinylene fluorophores was investigated. Among several oligophenylenevinylenes consisting of stilbene units, linearly conjugated ones, such as distyrylbenzene and distyrylstilbene, effectively enhanced PO-CL efficiency. Various effects of anionic, cationic, amphoteric and non-ionic surfactants on the CL efficiency of PO-CL were determined using three oxalates and the distyrylbenzene fluorophore. Anionic and non-ionic surfactants effectively enhanced CL efficiency, in contrast to the negative effect of cationic and amphoteric surfactants. Non-ionic surfactants were also effective in CL reactions of oxalates bearing dodecyl ester groups by the hydrophobic interaction between their alkyl chains. Considering these results, the surfactants not only increase the concentrations of water-insoluble interacting species in the hydrophobic micelle cores, but also control rapid degradation of the oxalates by alkaline hydrolysis. Copyright © 2014 John Wiley & Sons, Ltd.

Solvent screening for a hard-to-dissolve molecular crystal.

PubMed

Maiti, A; Pagoria, P F; Gash, A E; Han, T Y; Orme, C A; Gee, R H; Fried, L E

2008-09-01

Materials with a high-degree of inter- and intra-molecular hydrogen bonding generally have limited solubility in conventional organic solvents. This presents a problem for the dissolution, manipulation and purification of these materials. Using a state-of-the-art density-functional-theory based quantum chemical solvation model we systematically evaluated solvents for a known hydrogen-bonded molecular crystal. This, coupled with direct solubility measurements, uncovered a class of ionic liquids involving fluoride anions that possess more than two orders of magnitude higher solvation power as compared with the best conventional solvents. The crystal structure of one such ionic liquid, determined by X-ray diffraction spectroscopy, indicates that F- ions are stabilized through H-bonded chains with water. The presence of coordinating water in such ionic liquids seems to facilitate the dissolution process by keeping the chemical activity of the F- ions in check.

Ionic charge state measurements during He(+)-rich solar particle events

NASA Technical Reports Server (NTRS)

Hovestadt, D.; Klecker, B.; Scholer, M.; Gloeckler, G.

1984-01-01

Ionic charge state measurements of carbon, oxygen, and iron in He(+)-rich energetic particle events are presented. The data have been obtained with the Max-Planck-Institut/University of Maryland sensor system on the ISEE 3 spacecraft. The ionic charge states cannot be explained in terms of a model in which the coronal temperature determines a charge equilibrium which is subsequently frozen-in nor in terms of charge exchange during transition through coronal matter after acceleration. It is concluded that the acceleration and probably also the injection process is biased against particles with high mass-to-charge ratios. The plasma injected into the acceleration process must consist of material of cold (not greater than 8.5 x 10 to the 4th K) as well as hot (2.5 x 10 to the 6th K) origin. The cold material must be more abundant than the hot material.

Alkali Metal-Glucose Interaction Probed with Infrared Pre-Dissociation Spectroscopy

NASA Astrophysics Data System (ADS)

Kregel, Steven J.; Marsh, Brett; Zhou, Jia; Garand, Etienne

2015-06-01

The efficient extraction of cellulose from biomass and its subsequent conversion to glucose derivatives is an attractive goal in the field of energy science. However, current industrial methods require high ionic strength and harsh conditions. Ionic liquids (IL's) are a class of "green" compounds that have been shown to dissolve cellulose in concentrations of up to 25 wt%. In order to understand IL's extraordinary cellulose dissolving power, a molecular level understanding of the IL-cellulose interaction is needed. Toward that end, we have acquired infrared pre-dissociation spectra of M+-glucose, where M+=Li+, Na+, or K+. Through comparisons with density functional theory calculations, we have determined the relative abundances of various M+-glucose binding motifs in both the thermodynamic and kinetic limits. These results provide insight on the hydrogen bonding dynamics of glucose and are a step towards a fuller understanding of cellulose interactions with ionic liquids.

Development of flame retardant cotton fabric based on ionic liquids via sol-gel technique.

NASA Astrophysics Data System (ADS)

Bentis, A.; Boukhriss, A.; Boyer, D.; Gmouh, S.

2017-10-01

In this study, flame retardant cotton fabrics were developed by the sol-gel method, in order to enhance their flame retardant proprieties. For this aim, seven sols were prepared using tetraethylorthosilicate (TEOS) and different ionic liquids (ILs) consist on pyridinium and Methylimidazolium cations with different anions such as: PF6-, CH3COO-, and Br-. Those sols were applied separately to the cotton fabrics by a pad-dry-cure process. The flame retardant properties of functionalized cotton fabrics before and after washing were determined by the vertical flame tests according to ISO6940:2004(F) standard. The effects of anions have been thoroughly investigated, aiming at the optimization of the targeted properties. Thermogravimetric and mechanical according to NF EN ISO 13934-1:2013standard, analyses have been also investigated. The results showed that flame retardancy, thermal stability and mechanical properties of treated fabrics were enhanced by using ionic liquids.

Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales

PubMed Central

Zhang, Yonghe

2010-01-01

Ionocovalency (IC), a quantitative dual nature of the atom, is defined and correlated with quantum-mechanical potential to describe quantitatively the dual properties of the bond. Orbiotal hybrid IC model scale, IC, and IC electronegativity scale, XIC, are proposed, wherein the ionicity and the covalent radius are determined by spectroscopy. Being composed of the ionic function I and the covalent function C, the model describes quantitatively the dual properties of bond strengths, charge density and ionic potential. Based on the atomic electron configuration and the various quantum-mechanical built-up dual parameters, the model formed a Dual Method of the multiple-functional prediction, which has much more versatile and exceptional applications than traditional electronegativity scales and molecular properties. Hydrogen has unconventional values of IC and XIC, lower than that of boron. The IC model can agree fairly well with the data of bond properties and satisfactorily explain chemical observations of elements throughout the Periodic Table. PMID:21151444

Intrinsic electronic defects and multiple-atom processes in the oxidic semiconductor Ga2O3

NASA Astrophysics Data System (ADS)

Schmeißer, Dieter; Henkel, Karsten

2018-04-01

We report on the electronic structure of gallium oxide (Ga2O3) single crystals as studied by resonant photoelectron spectroscopy (resPES). We identify intrinsic electronic defects that are formed by mixed-atomic valence states. We differentiate three coexisting defect states that differ in their electronic correlation energy and their spatial localization lengths. Their relative abundance is described by a fractional ionicity with covalent and ionic bonding contributions. For Ga2O3, our analyses of the resPES data enable us to derive two main aspects: first, experimental access is given to determine the ionicity based on the original concepts of Pauling and Phillips. Second, we report on multi-atomic energy loss processes in the Ga2p core level and X-ray absorption data. The two experimental findings can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects.

The interactions between ionic surfactants and phosphatidylcholine vesicles: Conductometry

NASA Astrophysics Data System (ADS)

Tsao, Heng-Kwong; Tseng, Wen Liang

2001-11-01

The interaction between ionic surfactants and phosphatidylcholine vesicles, which are prepared without addition of buffer and salt, is investigated by conductivity measurements. On the basis of the vesicle acting as a trap of charge carriers, the bilayer/aqueous phase partition coefficient K and the surfactant/lipid molar ratio Re of nine surfactants are determined. The thermodynamic consistency is satisfied by the measured parameters. The effects of the alkyl chain length (C10-C16) and ionic head group are then studied. The inverse partition coefficient K-1 is linearly related to the critical micelle concentration. The solubilizing ability Reb is a consequence of the competition between the surfactant incorporation into the bilayer and the formation of micelles. Consequently, the K parameter rises whereas the Reb parameter declines as the chain length is increased. The influence due to addition of salt is also discussed.

Structure and diffusion of furans and other cellulose-derived compounds in solvents via MD simulation

NASA Astrophysics Data System (ADS)

Rabideau, Brooks; Ismail, Ahmed

2011-03-01

There is now a large push towards the development of energy sources that are both environmentally friendly and sustainable; with the conversion of cellulose derived from biomass into biofuels being one promising route. In this conversion, a variety of intermediary compounds have been identified, which appear critical to successful expansion of the process to an industrial scale. Here we examine the structure and diffusion of these furans and acids derived from cellulose within ionic liquids via molecular dynamic simulation. Ionic liquids have shown the ability to dissolve cellulose with certain `green' benefits over existing, conventional solvents. Specifically, we study the solvation properties of these chemicals by examining the pair correlation functions of solute with solvent, and by exploring the agglomeration and separation of these chemicals from the solvent as well as the hydrogen bonding between species. Additionally, we determine the diffusion constant of these compounds in ionic liquid and aqueous solvents.

Water uptake, ionic conductivity and swelling properties of anion-exchange membrane

NASA Astrophysics Data System (ADS)

Duan, Qiongjuan; Ge, Shanhai; Wang, Chao-Yang

2013-12-01

Water uptake, ionic conductivity and dimensional change of the anion-exchange membrane made by Tokuyama Corporation (A201 membrane) are investigated at different temperatures and water activities. Specifically, the amount of water taken up by membranes exposed to water vapor and membranes soaked in liquid water is determined. The water uptake of the A201 membrane increases with water content as well as temperature. In addition, water sorption data shows Schroeder's paradox for the AEMs investigated. The swelling properties of the A201 membrane exhibit improved dimensional stability compared with Nafion membrane. Water sorption of the A201 membrane occurs with a substantial negative excess volume of mixing. The threshold value of hydrophilic fraction in the A201 membrane for ionic conductivity is around 0.34, above which, the conductivity begins to rise quickly. This indicates that a change in the connectivity of the hydrophilic domains occurs when hydrophilic fraction approaches 0.34.

Extraction of acetanilides in rice using ionic liquid-based matrix solid phase dispersion-solvent flotation.

PubMed

Zhang, Liyuan; Wang, Changyuan; Li, Zuotong; Zhao, Changjiang; Zhang, Hanqi; Zhang, Dongjie

2018-04-15

Ionic liquid-based matrix solid phase dispersion-solvent flotation coupled with high performance liquid chromatography was developed for the determination of the acetanilide herbicides, including metazachlor, propanil, alachlor, propisochlor, pretilachlor, and butachlor in rice samples. Some experimental parameters, including the type of dispersant, the mass ratio of dispersant to sample, pH of sample solution, the type of extraction solvent, the type of ionic liquid, flotation time, and flow rate of N 2 were optimized. The average recoveries of the acetanilide herbicides at spiked concentrations of 50, 125, and 250 µg/kg ranged from 89.4% to 108.7%, and relative standard deviations were equal to or lower than 7.1%, the limits of quantification were in the range of 38.0 to 84.7 µg/kg. Copyright © 2017 Elsevier Ltd. All rights reserved.

Per- and polyfluorinated compounds (PFCs) in house dust and indoor air in Catalonia, Spain: implications for human exposure.

PubMed

Ericson Jogsten, I; Nadal, M; van Bavel, B; Lindström, G; Domingo, J L

2012-02-01

A total of 27 per- and polyfluorinated compounds (PFCs) were determined in both house dust (n=10) and indoor air (n=10) from selected homes in Catalonia, Spain. Concentrations were found to be similar or lower than those previously reported for household microenvironments in other countries. Ten PFCs were detected in all house dust samples. The highest mean concentrations corresponded to perfluorodecanoic acid (PFDA) and perfluorononanoic acid (PFNA), 10.7 ng/g (median: 1.5 ng/g) and 10.4 ng/g (median: 5.4 ng/g), respectively, while the 8:2 fluorotelomer alcohol (FTOH) was the dominating neutral PFC at a concentration of 0.41 ng/g (median: 0.35 ng/g). The indoor air was dominated by the FTOHs, especially the 8:2 FTOH at a mean (median) concentration of 51 pg/m(3) (median: 42 pg/m(3)). A limited number of ionic PFCs were also detected in the indoor air samples. Daily intakes of PFCs were estimated for average and worst case scenarios of human exposure from indoor sources. For toddlers, this resulted in average intakes of ∑ionic PFCs of 4.9ng/day (0.33 ng/kg(bw)/day for a 15 kg toddlers) and ∑neutral PFCs of 0.072 ng/day (0.005 ng/kg(bw)/day) from house dust. For adults, the average daily intakes of dust were 3.6 and 0.053 ng/day (0.05 and 0.001 ng/kg(bw)/day for a 70 kg adult) for ∑ionic and ∑neutral PFCs, respectively. The average daily inhalation of ∑neutral PFCs was estimated to be 0.9 and 1.3 ng/day (0.06 and 0.02 ng/kg(bw)/day) for toddlers and adults, respectively. For PFOS, the main ionic PFC detected in indoor air samples, the median intakes (based on those samples where PFOS was detected), resulted in indoor exposures of 0.06 and 0.11 ng/day (0.004 and 0.002 ng/kg(bw)/day) for toddlers and adults, respectively. Based on previous studies on dietary intake and drinking water consumption, both house dust and indoor air contribute significantly less to PFC exposure within this population. Copyright © 2011 Elsevier Ltd. All rights reserved.

Red-Shifting versus Blue-Shifting Hydrogen Bonds: Perspective from Ab Initio Valence Bond Theory.

PubMed

Chang, Xin; Zhang, Yang; Weng, Xinzhen; Su, Peifeng; Wu, Wei; Mo, Yirong

2016-05-05

Both proper, red-shifting and improper, blue-shifting hydrogen bonds have been well-recognized with enormous experimental and computational studies. The current consensus is that there is no difference in nature between these two kinds of hydrogen bonds, where the electrostatic interaction dominates. Since most if not all the computational studies are based on molecular orbital theory, it would be interesting to gain insight into the hydrogen bonds with modern valence bond (VB) theory. In this work, we performed ab initio VBSCF computations on a series of hydrogen-bonding systems, where the sole hydrogen bond donor CF3H interacts with ten hydrogen bond acceptors Y (═NH2CH3, NH3, NH2Cl, OH(-), H2O, CH3OH, (CH3)2O, F(-), HF, or CH3F). This series includes four red-shifting and six blue-shifting hydrogen bonds. Consistent with existing findings in literature, VB-based energy decomposition analyses show that electrostatic interaction plays the dominating role and polarization plays the secondary role in all these hydrogen-bonding systems, and the charge transfer interaction, which denotes the hyperconjugation effect, contributes only slightly to the total interaction energy. As VB theory describes any real chemical bond in terms of pure covalent and ionic structures, our fragment interaction analysis reveals that with the approaching of a hydrogen bond acceptor Y, the covalent state of the F3C-H bond tends to blue-shift, due to the strong repulsion between the hydrogen atom and Y. In contrast, the ionic state F3C(-) H(+) leads to the red-shifting of the C-H vibrational frequency, owing to the attraction between the proton and Y. Thus, the relative weights of the covalent and ionic structures essentially determine the direction of frequency change. Indeed, we find the correlation between the structural weights and vibrational frequency changes.

Effect of ionic strength and presence of serum on lipoplexes structure monitorized by FRET

PubMed Central

Madeira, Catarina; Loura, Luís MS; Prieto, Manuel; Fedorov, Aleksander; Aires-Barros, M Raquel

2008-01-01

Background Serum and high ionic strength solutions constitute important barriers to cationic lipid-mediated intravenous gene transfer. Preparation or incubation of lipoplexes in these media results in alteration of their biophysical properties, generally leading to a decrease in transfection efficiency. Accurate quantification of these changes is of paramount importance for the success of lipoplex-mediated gene transfer in vivo. Results In this work, a novel time-resolved fluorescence resonance energy transfer (FRET) methodology was used to monitor lipoplex structural changes in the presence of phosphate-buffered saline solution (PBS) and fetal bovine serum. 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/pDNA lipoplexes, prepared in high and low ionic strength solutions, are compared in terms of complexation efficiency. Lipoplexes prepared in PBS show lower complexation efficiencies when compared to lipoplexes prepared in low ionic strength buffer followed by addition of PBS. Moreover, when serum is added to the referred formulation no significant effect on the complexation efficiency was observed. In physiological saline solutions and serum, a multilamellar arrangement of the lipoplexes is maintained, with reduced spacing distances between the FRET probes, relative to those in low ionic strength medium. Conclusion The time-resolved FRET methodology described in this work allowed us to monitor stability and characterize quantitatively the structural changes (variations in interchromophore spacing distances and complexation efficiencies) undergone by DOTAP/DNA complexes in high ionic strength solutions and in presence of serum, as well as to determine the minimum amount of potentially cytotoxic cationic lipid necessary for complete coverage of DNA. This constitutes essential information regarding thoughtful design of future in vivo applications. PMID:18302788

Importance of elastic finite-size effects: Neutral defects in ionic compounds

DOE PAGES

Burr, P. A.; Cooper, M. W. D.

2017-09-15

Small system sizes are a well known source of error in DFT calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite size effects have been well characterised, but self-interaction of charge neutral defects is often discounted or assumed to follow an asymptotic behaviour and thus easily corrected with linear elastic theory. Here we show that elastic effect are also important in the description of defects in ionic compounds and can lead to qualitatively incorrect conclusions if inadequatly small supercells are used; moreover,more » the spurious self-interaction does not follow the behaviour predicted by linear elastic theory. Considering the exemplar cases of metal oxides with fluorite structure, we show that numerous previous studies, employing 96-atom supercells, misidentify the ground state structure of (charge neutral) Schottky defects. We show that the error is eliminated by employing larger cells (324, 768 and 1500 atoms), and careful analysis determines that elastic effects, not electrostatic, are responsible. The spurious self-interaction was also observed in non-oxide ionic compounds and irrespective of the computational method used, thereby resolving long standing discrepancies between DFT and force-field methods, previously attributed to the level of theory. The surprising magnitude of the elastic effects are a cautionary tale for defect calculations in ionic materials, particularly when employing computationally expensive methods (e.g. hybrid functionals) or when modelling large defect clusters. We propose two computationally practicable methods to test the magnitude of the elastic self-interaction in any ionic system. In commonly studies oxides, where electrostatic effects would be expected to be dominant, it is the elastic effects that dictate the need for larger supercells | greater than 96 atoms.« less

Importance of elastic finite-size effects: Neutral defects in ionic compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burr, P. A.; Cooper, M. W. D.

Small system sizes are a well known source of error in DFT calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite size effects have been well characterised, but self-interaction of charge neutral defects is often discounted or assumed to follow an asymptotic behaviour and thus easily corrected with linear elastic theory. Here we show that elastic effect are also important in the description of defects in ionic compounds and can lead to qualitatively incorrect conclusions if inadequatly small supercells are used; moreover,more » the spurious self-interaction does not follow the behaviour predicted by linear elastic theory. Considering the exemplar cases of metal oxides with fluorite structure, we show that numerous previous studies, employing 96-atom supercells, misidentify the ground state structure of (charge neutral) Schottky defects. We show that the error is eliminated by employing larger cells (324, 768 and 1500 atoms), and careful analysis determines that elastic effects, not electrostatic, are responsible. The spurious self-interaction was also observed in non-oxide ionic compounds and irrespective of the computational method used, thereby resolving long standing discrepancies between DFT and force-field methods, previously attributed to the level of theory. The surprising magnitude of the elastic effects are a cautionary tale for defect calculations in ionic materials, particularly when employing computationally expensive methods (e.g. hybrid functionals) or when modelling large defect clusters. We propose two computationally practicable methods to test the magnitude of the elastic self-interaction in any ionic system. In commonly studies oxides, where electrostatic effects would be expected to be dominant, it is the elastic effects that dictate the need for larger supercells | greater than 96 atoms.« less

Importance of elastic finite-size effects: Neutral defects in ionic compounds

NASA Astrophysics Data System (ADS)

Burr, P. A.; Cooper, M. W. D.

2017-09-01

Small system sizes are a well-known source of error in density functional theory (DFT) calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite-size effects have been well characterized, but self-interaction of charge-neutral defects is often discounted or assumed to follow an asymptotic behavior and thus easily corrected with linear elastic theory. Here we show that elastic effects are also important in the description of defects in ionic compounds and can lead to qualitatively incorrect conclusions if inadequately small supercells are used; moreover, the spurious self-interaction does not follow the behavior predicted by linear elastic theory. Considering the exemplar cases of metal oxides with fluorite structure, we show that numerous previous studies, employing 96-atom supercells, misidentify the ground-state structure of (charge-neutral) Schottky defects. We show that the error is eliminated by employing larger cells (324, 768, and 1500 atoms), and careful analysis determines that elastic, not electrostatic, effects are responsible. The spurious self-interaction was also observed in nonoxide ionic compounds irrespective of the computational method used, thereby resolving long-standing discrepancies between DFT and force-field methods, previously attributed to the level of theory. The surprising magnitude of the elastic effects is a cautionary tale for defect calculations in ionic materials, particularly when employing computationally expensive methods (e.g., hybrid functionals) or when modeling large defect clusters. We propose two computationally practicable methods to test the magnitude of the elastic self-interaction in any ionic system. In commonly studied oxides, where electrostatic effects would be expected to be dominant, it is the elastic effects that dictate the need for larger supercells: greater than 96 atoms.

Fluorescence recognition of chiral amino alcohols by using a novel ionic liquid sensor.

PubMed

Cai, Pengfei; Wu, Datong; Zhao, Xiaoyong; Pan, Yuanjiang

2017-08-07

A novel task-specific ionic liquid derived from l-phenylalaninol was prepared as an enantioselective fluorescent sensor for the first time. Fluorescent chiral ionic liquid 1 (FCIL1) is found to exhibit highly enantioselective fluorescence enhancements toward both aromatic and non-aromatic chiral amino alcohols. When (S)-FCIL1 was treated with the enantiomers of phenylalaninol, a great fluorescence enhancement at 349 nm could be observed and the value of the enantiomeric fluorescence difference (ef) is 5.92. This demonstrated that the chiral sensor (S)-FCIL1 exhibited an excellent enantioselective response behaviour to d-phenylalaninol. Besides that, both the fluorescence intensity at 349 nm (I 349 ) and the ratio of I 349 to I 282 depend linearly on the concentration of amino alcohols. Both the concentration and the enantiomeric composition could be determined by using the chiral ionic liquid. Differently, the sensor treated with the enantiomers of 2-amino-1-butanol showed an opposite result: the fluorescence intensity of the S-enantiomer is higher than that of the R-enantiomer. Furthermore, the size of the substituents on the chiral carbon might be important for the enantioselective fluorescent response.

Synthesis, structure, and ionic conductivity of solid solution, Li10+δM1+δP2-δS12 (M = Si, Sn).

PubMed

Hori, Satoshi; Suzuki, Kota; Hirayama, Masaaki; Kato, Yuki; Saito, Toshiya; Yonemura, Masao; Kanno, Ryoji

2014-01-01

Solid solutions of the silicon and tin analogous phases of the superionic conductor Li(10)MP(2)S(12) (M = Si, Sn) were synthesized by a conventional solid-state reaction in an evacuated silica tube at 823 K. The ranges of the solid solutions were determined to be 0.20 < δ < 0.43 and -0.25 < δ < -0.01 in Li(10+δ)M(1+δ)P(2-δ)S(12) (0.525 ≤k≤ 0.60 and 0.67 ≤k≤ 0.75 in Li(4-k)M(1-k)PkS(4)) for the Si and Sn systems, respectively. The ionic conductivity of these systems varied as a function of the changing M ions: the Si and Sn systems showed lower conductivity than the Ge system, Li(10+δ)Ge(1+δ)P(2-δ)S(12). The conductivity change for different elements might be due to the lattice size and lithium content affecting the ionic conduction. The relationship between ionic conduction, structure, and lithium concentration is discussed based on the structural and electrochemical information for the silicon, germanium, and tin systems.

Spatial inhomogeneities in ionic liquids, charged proteins, and charge stabilized colloids from collective variables theory.

PubMed

Patsahan, O; Ciach, A

2012-09-01

Effects of size and charge asymmetry between oppositely charged ions or particles on spatial inhomogeneities are studied for a large range of charge and size ratios. We perform a stability analysis of the primitive model of ionic systems with respect to periodic ordering using the collective variables-based theory. We extend previous studies [Ciach et al., Phys. Rev. E 75, 051505 (2007)] in several ways. First, we employ a nonlocal approximation for the reference hard-sphere fluid which leads to the Percus-Yevick pair direct correlation functions for the uniform case. Second, we use the Weeks-Chandler-Anderson regularization scheme for the Coulomb potential inside the hard core. We determine the relevant order parameter connected with the periodic ordering and analyze the character of the dominant fluctuations along the λ lines. We show that the above-mentioned modifications produce large quantitative and partly qualitative changes in the phase diagrams obtained previously. We discuss possible scenarios of the periodic ordering for the whole range of size and charge ratios of the two ionic species, covering electrolytes, ionic liquids, charged globular proteins or nanoparticles in aqueous solutions, and charge-stabilized colloids.

Transport and deposition of Suwannee River Humic Acid/Natural Organic Matter formed silver nanoparticles on silica matrices: the influence of solution pH and ionic strength.

PubMed

Akaighe, Nelson; Depner, Sean W; Banerjee, Sarbajit; Sohn, Mary

2013-07-01

The transport and deposition of silver nanoparticles (AgNPs) formed from Ag(+) reduction by Suwannee River Humic Acid (SRHA) and Suwannee River Natural Organic Matter (SRNOM) utilizing a silica matrix is reported. The morphology and stability of the AgNPs was analyzed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements. The percentage conversion of the initial [Ag(+)] to [AgNPs] was determined from a combination of atomic absorption (AAS) and UV-Vis spectroscopy, and centrifugation techniques. The results indicate higher AgNP transport and consequently low deposition in the porous media at basic pH conditions and low ionic strength. However, at low acidic pH and high ionic strength, especially with the divalent metallic cations, the mobility of the AgNPs in the porous media was very low, most likely due to NP aggregation. Overall, the results suggest the potential for AgNP contamination of subsurface soils and groundwater aquifers is mostly dependent on their aggregation state, controlled by the soil water and sediment ionic strength and pH. Copyright © 2013 Elsevier Ltd. All rights reserved.

Criticality in charge-asymmetric hard-sphere ionic fluids.

PubMed

Aqua, Jean-Noël; Banerjee, Shubho; Fisher, Michael E

2005-10-01

Phase separation and criticality are analyzed in z:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-Hückel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, Tc* (normalized by z), decrease with charge asymmetry, while the critical densities increase rapidly with . The results compare favorably with simulations and represent a distinct improvement over all current theories such as the mean spherical approximation, symmetric Poisson-Boltzmann theory, etc. For z not equal to 1, the interphase Galvani (or absolute electrostatic) potential difference, Deltaphi(T), between coexisting liquid and vapor phases is calculated and found to vanish as absolute value (T-Tc) beta when T-->Tc-with, since our approximations are classical, beta = (1/2). Above Tc, the compressibility maxima and so-called k-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong z dependence.

Two-Stage Conversion of High Free Fatty Acid Jatropha curcas Oil to Biodiesel Using Brønsted Acidic Ionic Liquid and KOH as Catalysts

PubMed Central

Das, Subrata; Thakur, Ashim Jyoti; Deka, Dhanapati

2014-01-01

Biodiesel was produced from high free fatty acid (FFA) Jatropha curcas oil (JCO) by two-stage process in which esterification was performed by Brønsted acidic ionic liquid 1-(1-butylsulfonic)-3-methylimidazolium chloride ([BSMIM]Cl) followed by KOH catalyzed transesterification. Maximum FFA conversion of 93.9% was achieved and it reduced from 8.15 wt% to 0.49 wt% under the optimum reaction conditions of methanol oil molar ratio 12 : 1 and 10 wt% of ionic liquid catalyst at 70°C in 6 h. The ionic liquid catalyst was reusable up to four times of consecutive runs under the optimum reaction conditions. At the second stage, the esterified JCO was transesterified by using 1.3 wt% KOH and methanol oil molar ratio of 6 : 1 in 20 min at 64°C. The yield of the final biodiesel was found to be 98.6% as analyzed by NMR spectroscopy. Chemical composition of the final biodiesel was also determined by GC-MS analysis. PMID:24987726

Reactive solid surface morphology variation via ionic diffusion.

PubMed

Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

2012-08-14

In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

Assimilation of NH₄Br in Polyvinyl Alcohol/Poly(N-vinyl pyrrolidone) Polymer Blend-Based Electrolyte and Its Effect on Ionic Conductivity.

PubMed

Parameswaran, V; Nallamuthu, N; Devendran, P; Manikandan, A; Nagarajan, E R

2018-06-01

Biodegradable polymer blend electrolyte based on ammonium based salt in variation composition consisting of PVA:PVP were prepared by using solution casting technique. The obtained films have been analyzed by various technical methods like as XRD, FT-IR, TG-DSC, SEM analysis and impedance spectroscopy. The XRD and FT-IR analysis exposed the amorphous nature and structural properties of the complex formation between PVA/PVP/NH4Br. Impedance spectroscopy analysis revealed the ionic conductivity and the dielectric properties of PVA/PVP/NH4Br polymer blend electrolyte films. The maximum ionic conductivity was determined to be 6.14 × 10-5 Scm-1 for the composition of 50%PVA: 50%PVP: 10% NH4Br with low activation energy 0.3457 eV at room temperature. Solid state battery is fabricated using highest ionic conducting polymer blend as electrolyte with the configuration Zn/ZnSO4 · 7H2O (anode) ∥ 50%PVA: 50%PVP: 10% NH4Br ∥ Mn2O3 (cathode). The observed open circuit voltage is 1.2 V and its performance has been studied.

Chiral separation of phenylalanine and tryptophan by capillary electrophoresis using a mixture of β-CD and chiral ionic liquid ([TBA] [L-ASP]) as selectors.

PubMed

Yujiao, Wu; Guoyan, Wang; Wenyan, Zhao; Hongfen, Zhang; Huanwang, Jing; Anjia, Chen

2014-05-01

In this paper, a simple, effective and green capillary electrophoresis separation and detection method was developed for the quantification of underivatized amino acids (dl-phenylalanine; dl-tryptophan) using β-Cyclodextrin and chiral ionic liquid ([TBA] [l-ASP]) as selectors. Separation parameters such as buffer concentrations, pH, β-CD and chiral ionic liquid concentrations and separation voltage were investigated for the enantioseparation in order to achieve the maximum possible resolution. A good separation was achieved in a background electrolyte composed of 15 mm sodium tetraborate, 5 mm β-CD and 4 mm chiral ionic liquid at pH 9.5, and an applied voltage of 10 kV. Under optimum conditions, linearity was achieved within concentration ranges from 0.08 to 10 µg/mL for the analytes with correlation coefficients from 0.9956 to 0.9998, and the analytes were separated in less than 6 min with efficiencies up to 970,000 plates/m. The proposed method was successfully applied to the determination of amino acid enantiomers in compound amino acids injections, such as 18AA-I, 18AA-II and 3AA.

The effect of humidity on ionic wind velocity in ambient air

NASA Astrophysics Data System (ADS)

Chen, She; Nobelen, J. C. P. Y.; Nijdam, S.

2016-09-01

Due to the evolution of portable electronics and LED lightning system, advances in air cooling technologies must also keep pace. Active cooling by ionic wind, which is usually generated by corona discharge, can greatly reduce the noise and lifetime issues compared to the mechanical fans. The wind is induced when a gas discharge is formed, and neutral molecules gain their energy by the momentum transfer of ion-neutral collisions. However, there is few discussion about the effect of gas composition such as humidity on the wind generation and the physical mechanism is not clear. In the experiment, a positive 5-20 kV DC voltage is applied to the needle-cylinder electrodes with separation of 20 mm. The ionic wind velocity is measured by hot wire anemometry. As the relative humidity (RH) in the ambient air increases, the velocity is found to be severely inhibited. The current is also measured between the cylinder electrode and earth. The results show that the DC component of corona current decreases when RH increases. Since both the discharge current and the ion mobility are reduced when RH increases, their combined effects determine the ionic wind velocity. This work is supported by STW project 13651.

[Application of simultaneous determination of inorganic ionic species by advanced ion chromatography for water quality monitoring of river water and wastewater].

PubMed

Nakatani, Nobutake; Kozaki, Daisuke; Tanaka, Kazuhiko

2012-04-01

In this study, our recent work on advanced ion chromatographic methods for the simultaneous determination of inorganic ionic species such as common anions (SO4(2-), Cl(-) and NO3(-)) and cations (Na+, NH4+, K+, Mg2+, and Ca2+), nutrients (phosphate and silicate) and hydrogen ion/alkalinity are summarized first. Then, the applications using these methods for monitoring environmental water quality are also presented. For the determination of common anions and cations with nutrients, the separation was successfully performed by a polymethacrylate-based weakly acidic cation-exchange column of TSKgel Super IC-A/C (Tosoh, 150 mm x 6.0 mm i. d.) and a mixture solution of 100 mmol/L ascorbic acid and 4 mmol/L 18-crown-6 as acidic eluent with dual detection of conductivity and spectrophotometry. For the determination of hydrogen ion/alkalinity, the separation was conducted by TSKgel ODS-100Z column (Tosoh, 150 mm x 4.5 mm i. d.) modified with lithium dodecylsulfate and an eluent of 40 mmol/L LiCl/0.1 mmol/L lithium dodecylsulfate/0.05 mmol/L H2SO4 with conductivity detector. The differences of ion concentration between untreated and treated wastewater showed the variation of ionic species during biological treatment process in a sewage treatment plant. Occurrence and distribution of water-quality conditions were related to the bioavailability and human activity in watershed. From these results, our advanced ion chromatographic methods have contributed significantly for water quality monitoring of environmental waters.

Source apportionment of heavy metals and ionic contaminants in rainwater tanks in a subtropical urban area in Australia.

PubMed

Huston, R; Chan, Y C; Chapman, H; Gardner, T; Shaw, G

2012-03-15

Due to prolonged droughts in recent years, the use of rainwater tanks in urban areas has increased in Australia. In order to apportion sources of contribution to heavy metal and ionic contaminants in rainwater tanks in Brisbane, a subtropical urban area in Australia, monthly tank water samples (24 sites, 31 tanks) and concurrent bulk deposition samples (18 sites) were collected during mainly April 2007-March 2008. The samples were analysed for acid-soluble metals, soluble anions, total inorganic carbon and total organic carbon, and characteristics such as total solid and pH. The Positive Matrix Factorisation model, EPA PMF 3.0, was used to apportion sources of contribution to the contaminants. Four source factors were identified for the bulk deposition samples, including 'crustal matter/sea salt', 'car exhausts/road side dust', 'industrial dust' and 'aged sea salt/secondary aerosols'. For the tank water samples, apart from these atmospheric deposition related factors which contributed in total to 65% of the total contaminant concentration on average, another six rainwater collection system related factors were identified, including 'plumbing', 'building material', 'galvanizing', 'roofing', 'steel' and 'lead flashing/paint' (contributing in total to 35% of the total concentration on average). The Australian Drinking Water Guideline for lead was exceeded in 15% of the tank water samples. The collection system related factors, in particular the 'lead flashing/paint' factor, contributed to 79% of the lead in the tank water samples on average. The concentration of lead in tank water was found to vary with various environmental and collection system factors, in particular the presence of lead flashing on the roof. The results also indicated the important role of sludge dynamics inside the tank on the quality of tank water. Copyright © 2011 Elsevier Ltd. All rights reserved.

Formation of positively charged gold nanoparticle monolayers on silica sensors.

PubMed

Oćwieja, Magdalena; Maciejewska-Prończuk, Julia; Adamczyk, Zbigniew; Roman, Maciej

2017-09-01

Formation of positively charged gold nanoparticle monolayers on the Si/SiO 2 was studied under in situ conditions using quartz microbalance (QCM). The gold nanoparticles were synthesized in a chemical reduction method using sodium borohydride as reducing agent. Cysteamine hydrochloride was applied to generate a positive surface charge of nanoparticles. The micrographs obtained from transmission electron microscopy (TEM) revealed that the average size of nanoparticles was equal to 12±3nm. The stability of nanoparticle suspensions under controlled pH and ionic strength was determined by dynamic light scattering (DLS). The electrophoretic mobility measurements showed that the zeta potential of nanoparticles was positive, decreasing with ionic strength and pH from 56mV at pH 4.2 and I=10 -4 M to 22mV at pH 8.3 and I=3×10 -3 M. The surface enhanced Raman spectroscopy (SERS) confirmed chemisorption of cysteamine on nanoparticles and the contribution of amine moieties in the generation of nanoparticle charge. The influence of suspension concentration, ionic strength and flow rate on the kinetics of nanoparticle deposition on the sensors was quantitatively determined. It was confirmed that the deposition for the low coverage regime is governed by the bulk mass transfer that results in a linear increase of the coverage with time. The significant increase in the maximum coverage of gold monolayers with ionic strength was interpreted as due to the decreasing range of the electrostatic interactions among deposited particles. Moreover, the hydratation of formed monolayers, their structure and the stability were determined by the comparison of the QCM results with those obtained by AFM and SEM. The experimental data were adequately interpreted in terms of the extended random sequential adsorption (eRSA) model that considers the bulk and surface transfer steps in a rigorous way. The obtained results are useful for a facile fabrication of gold nanoparticle-based biosensors capable to bind target molecules via available amine moieties. Copyright © 2017 Elsevier Inc. All rights reserved.

Combination of counterpropagation artificial neural networks and antioxidant activities for comprehensive evaluation of associated-extraction efficiency of various cyclodextrins in the traditional Chinese formula Xue-Zhi-Ning.

PubMed

Sun, Lili; Yang, Jianwen; Wang, Meng; Zhang, Huijie; Liu, Yanan; Ren, Xiaoliang; Qi, Aidi

2015-11-10

Xue-Zhi-Ning (XZN) is a widely used traditional Chinese medicine formula to treat hyperlipidemia. Recently, cyclodextrins (CDs) have been extensively used to minimize problems relative to medicine bioavailability, such as low solubility and poor stability. The objective of this study was to determine the associated-extraction efficiency of various CDs in XZN. Three various type CDs were evaluated, including native CDs (α-CD, β-CD), hydrophilic CD derivatives (HP-β-CD and Me-β-CD), and ionic CD derivatives (SBE-β-CD and CM-β-CD). An ultra high-performance liquid chromatography (UHPLC) fingerprint was applied to determine the components in CD extracts and original aqueous extract (OAE). A counterpropagation artificial neural network (CP-ANN) was used to analyze the components in different extracts and compare the selective extraction of various CDs. Extraction efficiencies of the various CDs in terms of extracted components follow the ranking, ionic CD derivatives>hydrophilic CD derivatives>native CDs>OAE. Besides, different types of CDs have their own selective extraction and ionic CD derivatives present the strongest associated-extraction efficiency. Antioxidant potentials of various extracts were evaluated by determining the inhibition of spontaneous, H2O2-induced, CCl4-induced and Fe(2+)/ascorbic acid-induced lipid peroxidation (LPO) and analyzing the scavenging capacity for DPPH and hydroxyl radicals. The order of extraction efficiencies of the various CDs relative to antioxidant activities is as follows: SBE-β-CD>CM-β-CD>HP-β-CD>Me-β-CD>β-CD>α-CD. It can be demonstrated that all of the CDs studied increase the extraction efficiency and that ionic CD derivatives (SBE-β-CD and CM-β-CD) present the highest extraction capability in terms of amount extracted and antioxidant activities of extracts. Copyright © 2015 Elsevier B.V. All rights reserved.

Ionospheric tomography using ADS-B signals

NASA Astrophysics Data System (ADS)

Cushley, A. C.; Noël, J.-M.

2014-07-01

Numerical modeling has demonstrated that Automatic Dependent Surveillance Broadcast (ADS-B) signals can be used to reconstruct two-dimensional (2-D) electron density maps of the ionosphere using techniques for computerized tomography. Ray tracing techniques were used to determine the characteristics of individual waves, including the wave path and the state of polarization at the satellite receiver. The modeled Faraday rotation was computed and converted to total electron content (TEC) along the raypaths. The resulting TEC was used as input for computerized ionospheric tomography (CIT) using algebraic reconstruction technique. This study concentrated on reconstructing mesoscale structures 25-100 km in horizontal extent. The primary scientific interest of this study was to show that ADS-B signals can be used as a new source of data for CIT to image the ionosphere and to obtain a better understanding of magneto-ionic wave propagation.

Molecular simulations and experimental studies of solubility and diffusivity for pure and mixed gases of H2, CO2, and Ar absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]).

PubMed

Shi, Wei; Sorescu, Dan C; Luebke, David R; Keller, Murphy J; Wickramanayake, Shan

2010-05-20

Classical molecular dynamics and Monte Carlo simulations are used to calculate the self-diffusivity and solubility of pure and mixed CO(2), H(2), and Ar gases absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf(2)N]). Overall, the computed absorption isotherms, Henry's law constants, and partial molar enthalpies for pure H(2) agree well with the experimental data obtained by Maurer et al. [J. Chem. Eng. Data 2006, 51, 1364] and the experimental values determined in this work. However, the agreement is poor between the simulations and the experimental data by Noble et al. [Ind. Eng. Chem. Res. 2008, 47, 3453] and Costa Gomes [J. Chem. Eng. Data 2007, 52, 472] at high temperatures. The computed H(2) permeability values are in good agreement with the experimental data at 313 K obtained by Luebke et al. [J. Membr. Sci. 2007, 298, 41; ibid, 2008, 322, 28], but about three times larger than the experimental value at 573 K from the same group. Our computed H(2) solubilities using different H(2) potential models have similar values and solute polarizations were found to have a negligible effect on the predicted gas solubilities for both the H(2) and Ar. The interaction between H(2) and the ionic liquid is weak, about three times smaller than between the ionic liquid and Ar and six times smaller than that of CO(2) with the ionic liquid, results that are consistent with a decreasing solubility from CO(2) to Ar and to H(2). The molar volume of the ionic liquid was found to be the determining factor for the H(2) solubility. For mixed H(2) and Ar gases, the solubilities for both solutes decrease compared to the respective pure gas solubilities. For mixed gases of CO(2) and H(2), the solubility selectivity of CO(2) over H(2) decreases from about 30 at 313 K to about 3 at 573 K. For the permeability, the simulated values for CO(2) in [hmim][Tf(2)N] are about 20-60% different than the experimental data by Luebke et al. [J. Membr. Sci. 2008, 322, 28].

Field measurement of alkalinity and pH

USGS Publications Warehouse

Barnes, Ivan

1964-01-01

The behavior of electrometric pH equipment under field conditions departs from the behavior predicted from Nernst's law. The response is a linear function of pH, and hence measured pH values may be corrected to true pH if the instrument is calibrated with two reference solutions for each measurement. Alkalinity titrations may also be made in terms of true pH. Standard methods, such as colorimetric titrations, were rejected as unreliable or too cumbersome for rapid field use. The true pH of the end point of the alkalinity titration as a function of temperature, ionic strength, and total alkalinity has been calculated. Total alkalinity in potable waters is the most important factor influencing the end point pH, which varies from 5.38 (0 ? C, 5 ppm (parts per million) HC0a-) to 4.32 (300 ppm HC0a-,35 ? C), for the ranges of variables considered. With proper precautions, the pH may be determined to =i:0.02 pH and the alkalinity to =i:0.6 ppm HCO3- for many naturally occurring bodies of fresh water.

Ion mobility and transport properties of bismuth fluoride-containing solid solutions with tysonite-type structure

NASA Astrophysics Data System (ADS)

Kavun, V. Ya.; Uvarov, N. F.; Slobodyuk, A. B.; Merkulov, E. B.; Polyantsev, M. M.

2018-07-01

The ion mobility and conductivity of solid solutions with tysonite-type structure obtained by doping bismuth trifluoride with lead (II) fluoride, and zirconium and bismuth oxides have been studied using 19F NMR, X-ray diffraction analysis, and impedance spectroscopy. The types of ionic motions in the fluoride sublattice of the synthesized solid solutions in the temperature range 150-450 K have been determined and the energy of their activation has been estimated. Due to high ionic conductivity, above 10-2 S/cm at 570 K, these solid solutions can be considered as superionic conductors.

Ionic Diffusion in Cu6PS5Br Studied by 63Cu NMR

NASA Astrophysics Data System (ADS)

Ohki, H.; Harazono, K.; Erata, T.; Tasaki, A.; Ikeda, R.

1993-10-01

Applying 63Cu NMR technique, we observed exchange between the nonequivalent copper sites in crystalline Cu6PS5Br, known as a member of the mineral "argyrodite". Below 200 K, where the motion of the copper (I) ion is slow, we could distinguish several nonequivalent copper sites. On increasing the temperature, the chemical exchange between the nonequivalent cation sites was seen on the 63Cu NMR spectra. We could determine the activation energy for this motion to be 35 kJ mol-1 , in good agreement with the published ionic conductivity.

Simultaneous determination of brazilin and protosappanin B in Caesalpinia sappan by ionic-liquid dispersive liquid-phase microextraction method combined with HPLC.

PubMed

Xia, Zhaoyang; Li, Dongdong; Li, Qing; Zhang, Yan; Kang, Wenyi

2017-11-13

The conditions of heating, ionic liquid-based ultrasonic-assisted extraction combined with reverse-phase high performance liquid chromatography were optimized to simultaneously isolate and determinate brazilin and protosappanin B in Caesalpinia sappan. Ionic liquids, including [BMIM]Br, [BMIM]BF 4 , [BMIM]PF 6 and [HMIM]PF 6 , were selected as extraction solvents while methanol, acetone, acetonitrile, ethanol and water were selected as dispersants. The chromatographic column was Purospher star RP-C 18 (250 mm × 4.6 mm, 5 μm), a mixture of methanol and 0.2% phosphoric acid-water was used as mobile phase at a flow rate 0.65 mL/min. The result displayed that the extraction yields of brazilin and protosappanin B were highest when the concentration of [BMIM]Br methanol solution as extraction solvent was 0.5 mol/L and the solid-liquid ratio was 1:50 (g/mL). Under the optimal extraction conditions, the contents of brazilin showed a good linearity (r = 1.0000) within the range of 1.25-7.50 μg with the average recovery of 99.33%, the contents of protosappanin B also showed a good linearity (r = 0.9999) within the range of 0.50-3.00 μg with the average recovery of 98.31%. This experiment, which adopted environmentally friendly reagent as extraction solvent, not only improved the extraction efficiency, but also avoided the environmental pollution caused by organic solvent. Moreover, it was simple and reliable, and can be of important significance in the study of Traditional Chinese Medicine active ingredient extraction methods. The antibacterial activities of the ionic liquids and methanol extracts were determined using the paper disc diffusion method. The ionic liquid extract was found to possess antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MIC value of 37.5 mg crude drug/mL), β-Lactamase producing S. aureus (MIC values of 18.8 mg crude drug/mL), but not against E. coli, Extended spectrum β-Lactamases E. coli and P. aeruginosa. Compared with the ionic liquid extract, the methanol extract was found to have antibacterial activity against S. aureus and methicillin-resistant S. aureus (MIC value of 75.0 mg crude drug/mL), β-Lactamase producing S. aureus (MIC values of 150.0 mg crude drug/mL). However, the same, the methanol extract did not have antibacterial activity against E. coli, Extended spectrum β-Lactamases E. coli and P. aeruginosa.

Development of an ionic-liquid-based dispersive liquid-liquid microextraction method for the determination of antichagasic drugs in human breast milk: Optimization by central composite design.

PubMed

Padró, Juan M; Pellegrino Vidal, Rocío B; Echevarria, Romina N; Califano, Alicia N; Reta, Mario R

2015-05-01

Chagas disease constitutes a major public health problem in Latin America. Human breast milk is a biological sample of great importance for the analysis of therapeutic drugs, as unwanted exposure through breast milk could result in pharmacological effects in the nursing infant. Thus, the goal of breast milk drug analysis is to inquire to which extent a neonate may be exposed to a drug during lactation. In this work, we developed an analytical technique to quantify benznidazole and nifurtimox (the two antichagasic drugs currently available for medical treatment) in human breast milk, with a simple sample pretreatment followed by an ionic-liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography and UV detection. For this technique, the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate has been used as the "extraction solvent." A central composite design was used to find the optimum values for the significant variables affecting the extraction process: volume of ionic liquid, volume of dispersant solvent, ionic strength, and pH. At the optimum working conditions, the average recoveries were 77.5 and 89.7%, the limits of detection were 0.06 and 0.09 μg/mL and the interday reproducibilities were 6.25 and 5.77% for benznidazole and nifurtimox, respectively. The proposed methodology can be considered sensitive, simple, robust, accurate, and green. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-situ functionalization of mesoporous hexagonal ZnO synthesized in task specific ionic liquid as a photocatalyst for elimination of SO2, NOx, and CO

NASA Astrophysics Data System (ADS)

Kowsari, Elaheh; Abdpour, Soheil

2017-12-01

A novel mesoporous structure of zinc oxide was synthesized in hydrothermal autocalve in the presence of a functional ionic liquid (FIL) {[CH2CH2] O2 (mm)2}. This FIL with ether groups was used simultaneously as a designer templating agent and a source of the hydroxyl radical. The presence of this ionic liquid led to producing ethylene glycol in the reaction media, which adsorb on the surface of mesoporous hexagonal ZnO plates. These mesoporous structures can adsorb pollutant gases and increase photocatalytic oxidation of pollutant gases in compare with commercial ZnO nanoparticles and agglomerated nanoparticles synthesized in this work. XPS data confirmed ethylene glycol production by the ionic liquid, which could prove a role for ionic liquids as designers. The estimated BET surface area values of ZnO hexagonal mesoporous plates and agglomerated particles were 84 m2/g and 12 m2/g respectively. Optical properties of the mesoporous structures were analyzed by photoluminescence spectroscopy and diffuse reflectance UV-visible spectroscopy. The performance of these structures as efficient photocatalysts was further demonstrated by their removal of NOx, SO2, and CO under UV irradiation. The removal of NOx, SO2, and CO under UV irradiation was 56%, 81%, and 35% respectively, after 40 min of irradiation time. Reusability of the photocatalyst was determined; the results show no significant decrease of activity of photocatalyst. after five cycles.

Ionic liquid as a mobile phase additive in high-performance liquid chromatography for the simultaneous determination of eleven fluorescent whitening agents in paper materials.

PubMed

Wang, Qing; Chen, Xianbo; Qiu, Bin; Zhou, Liang; Zhang, Hui; Xie, Juan; Luo, Yan; Wang, Bin

2016-04-01

In the present study, 11 4,4'-diaminostilbene-2,2'-disulfonic acid based fluorescent whitening agents with different numbers of sulfonic acid groups were separated by using an ionic liquid as a mobile phase additive in high-performance liquid chromatography with fluorescence detection. The effects of ionic liquid concentration, pH of mobile phase B, and composition of mobile phase A on the separation of fluorescent whitening agents were systematically investigated. The ionic liquid tetrabutylammonium tetrafluoroborate is superior to tetrabutylammomnium bromide for the separation of the fluorescent whitening agents. The optimal separation conditions were an ionic liquid concentration at 8 mM and the pH of mobile phase B at 8.5 with methanol as mobile phase A. The established method exhibited low limits of detection (0.04-0.07 ng/mL) and wide linearity ranges (0.30-20 ng/mL) with high linear correlation coefficients from 0.9994 to 0.9998. The optimized procedure was applied to analyze target analytes in paper samples with satisfactory results. Eleven target analytes were quantified, and the recoveries of spiked paper samples were in the range of 85-105% with the relative standard deviations from 2.1 to 5.1%. The obtained results indicated that the method was efficient for detection of 11 fluorescent whitening agents. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrical and electrochemical studies on sodium ion-based gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Isa, K. B. Md; Othman, L.; Hambali, D.; Osman, Z.

2017-09-01

Gel polymer electrolytes (GPEs) have captured great attention because of their unique properties such as good mechanical stability, high flexibility and high conductivity approachable to that of the liquid electrolytes. In this work, we have prepared sodium ion conducting gel polymer electrolyte (GPE) films consisting of polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) as a polymer host using the solution casting technique. Sodium trifluoromethane- sulfonate (NaCF3SO3) was used as an ionic salt and the mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizing solvent. Impedance spectroscopy measurements were carried out to determine the ionic conductivity of the GPE films. The sample containing 20 wt.% of NaCF3SO3 salt exhibits the highest room temperature ionic conductivity of 2.50 × 10-3 S cm-1. The conductivity of the GPE films was found to depend on the salt concentration that added to the films. The ionic and cationic transference numbers of GPE films were estimated by DC polarization and the combination of AC and DC polarization method, respectively. The results had shown that both ionic and cationic transference numbers are consistent with the conductivity studies. The electrochemical stability of the GPE films was tested using linear sweep voltammetry (LSV) and the value of working voltage range appears to be high enough to be used as an electrolyte in sodium batteries. The cyclic voltammetry (CV) studies confirmed the sodium ion conduction in the GPE films.

The influence of the mould cooling temperature on the surface appearance and the internal quality of ESR ingots

NASA Astrophysics Data System (ADS)

Kubin, M.; Ofner, B.; Holzgruber, H.; Schneider, R.; Enzenhofer, D.; Filzwieser, A.; Konetschnik, S.

2016-07-01

One of the main benefits of the ESR process is to obtain an ingot surface which is smooth and allows a subsequent forging operation without any surface dressing. The main influencing factor on surface quality is the precise controlling of the process such as melt rate and electrode immersion depth. However, the relatively strong cooling effect of water as a cooling medium can result in the solidification of the meniscus of the liquid steel on the boundary liquid steel and slag which is most likely the origin of surface defects. The usage of different cooling media like ionic liquids, a salt solution which can be heated up to 250°C operating temperature might diminish the meniscus solidification phenomenon. This paper shows the first results of the usage of an ionic liquid as a mould cooling medium. In doing so, 210mm diameter ESR ingots were produced with the laboratory scale ESR furnace at the university of applied science using an ionic liquid cooling device developed by the company METTOP. For each trial melt different inlet and outlet temperatures of the ionic liquid were chosen and the impact on the surface appearance and internal quality were analyzed. Furthermore the influence on the energy balance is also briefly highlighted. Ultimately, an effect of the usage of ionic liquids as a cooling medium could be determined and these results will be described in detail within the scope of this paper.

The gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide from combustion calorimetry, vapor pressure measurements, and ab initio calculations.

PubMed

Emel'yanenko, Vladimir N; Verevkin, Sergey P; Heintz, Andreas

2007-04-04

Ionic liquids are attracting growing interest as alternatives to conventional molecular solvents. Experimental values of vapor pressure, enthalpy of vaporization, and enthalpy of formation of ionic liquids are the key thermodynamic quantities, which are required for the validation and development of the molecular modeling and ab initio methods toward this new class of solvents. In this work, the molar enthalpy of formation of the liquid 1-butyl-3-methylimidazolium dicyanamide, 206.2 +/- 2.5 kJ.mol-1, was measured by means of combustion calorimetry. The molar enthalpy of vaporization of 1-butyl-3-methylimidazolium dicyanamide, 157.2 +/- 1.1 kJ.mol-1, was obtained from the temperature dependence of the vapor pressure measured using the transpiration method. The latter method has been checked with measurements of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, where data are available from the effusion technique. The first experimental determination of the gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide, 363.4 +/- 2.7 kJ.mol-1, from thermochemical measurements (combustion and transpiration) is presented. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for 1-butyl-3-methylimidazolium dicyanamide using the G3MP2 theory. Excellent agreement with experimental results has been observed. The method developed opens a new way to obtain thermodynamic properties of ionic liquids which have not been available so far.

Individual and community responses in stream mesocosms with different ionic compositions of conductivity and compared to a field-based benchmark

EPA Science Inventory

Several anthropogenic activities cause excess total dissolved solids (TDS) content and its correlate, specific conductivity, in surface waters due to increases in the major geochemical ions (e.g., Na, Ca, Cl, SO4). However, the relative concentrations of major ions varies with t...

Determination of colloidal and dissolved silver in water samples using colorimetric solid-phase extraction.

PubMed

Hill, April A; Lipert, Robert J; Porter, Marc D

2010-03-15

The increase in bacterial resistance to antibiotics has led to resurgence in the use of silver as a biocidal agent in applications ranging from washing machine additives to the drinking water treatment system on the International Space Station (ISS). However, growing concerns about the possible toxicity of colloidal silver to bacteria, aquatic organisms and humans have led to recently issued regulations by the US EPA and FDA regarding the usage of silver. As part of an ongoing project, we have developed a rapid, simple method for determining total silver, both ionic (silver(I)) and colloidal, in 0.1-1mg/L aqueous samples, which spans the ISS potable water target of 0.3-0.5mg/L (total silver) and meets the US EPA limit of 0.1mg/L in drinking water. The method is based on colorimetric solid-phase extraction (C-SPE) and involves the extraction of silver(I) from water samples by passage through a solid-phase membrane impregnated with the colorimetric reagent DMABR (5-[4-(dimethylamino)benzylidene]rhodanine). Silver(I) exhaustively reacts with impregnated DMABR to form a colored compound, which is quantified using a handheld diffuse reflectance spectrophotometer. Total silver is determined by first passing the sample through a cartridge containing Oxone, which exhaustively oxidizes colloidal silver to dissolved silver(I). The method, which takes less than 2 min to complete and requires only approximately 1 mL of sample, has been validated through a series of tests, including a comparison with the ICP-MS analysis of a water sample from ISS that contained both silver(I) and colloidal silver. Potential earth-bound applications are also briefly discussed. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Investigation of Physically and Chemically Ionic Liquid Confinement in Nanoporous Materials by a Combination of SANS, Contrast-Matching SANS, XRD and Nitrogen Adsorption

NASA Astrophysics Data System (ADS)

Romanos, G. E.; Stefanopoulos, K. L.; Vangeli, O. C.; Mergia, K.; Beltsios, K. G.; Kanellopoulos, N. K.; Lairez, D.

2012-02-01

In the present study, [bmim][PF6] ionic liquid (IL) was introduced into the pores of two ordered mesoporous silicas (MCM-41 and SBA-15) having different pore sizes by means of two different processes: a) with physical imbibition from a methanol solution under high vacuum and b) by chemically immobilising the IL with silanisation of the pore surface followed by reaction with butyl-methyl imidazolium chloride and anion exchange with PF6, the process termed as the "grafting to" method. Both the extent of IL entrapment and the structural properties of the IL phase under confinement were investigated by SANS, contrast-matching SANS, XRD and nitrogen adsorption measurements. The results show that the pores of chemically prepared samples are not totally filled by IL and also suggest for ordering of the silylated IL phase. On the other hand, the physically prepared samples are almost or totally filled with IL whereas no evidence for ordering of the confined IL phase was observed.

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds and Ionic Liquids. Sublimation, Vaporization, and Fusion Enthalpies from 1880 to 2015. Part 2. C11-C192

NASA Astrophysics Data System (ADS)

Acree, William; Chickos, James S.

2017-03-01

The second part of this compendium concludes with a collection of phase change enthalpies of organic molecules inclusive of C11-C192 reported over the period 1880-2015. Also included are phase change enthalpies including fusion, vaporization, and sublimation enthalpies for organometallic, ionic liquids, and a few inorganic compounds. Paper I of this compendium, published separately, includes organic compounds from C1 to C10 and describes a group additivity method for evaluating solid, liquid, and gas phase heat capacities as well as temperature adjustments of phase changes. Paper II of this compendium also includes an updated version of a group additivity method for evaluating total phase change entropies which together with the fusion temperature can be useful in estimating total phase change enthalpies. Other uses include application in identifying potential substances that either form liquid or plastic crystals or exhibit additional phase changes such as undetected solid-solid transitions or behave anisotropically in the liquid state.

CADDIS Volume 2. Sources, Stressors and Responses: Ionic Strength

EPA Pesticide Factsheets

Introduction to the ionic strength module, when to list ionic strength as a candidate cause, ways to measure ionic strength, simple and detailed conceptual diagrams for ionic strength, ionic strength module references and literature reviews.

Precipitation and Solubility of Calcium Hydrogenurate Hexahydrate

PubMed Central

Babić-Ivančić, V.; Füredi-Milhofer, H.; Brničević, N.; Marković, M.

1992-01-01

Solid phases formed in the quaternary system: uric acid—calcium hydroxide —hydrochloric acid—water aged for 2 months at 310 K were studied to determine conditions for calcium hydrogenurate hexahydrate, Ca(C5H3N4O)2 · 6H2O precipitation. The precipitates were identified by chemical and thermogravimetric analyses, x-ray powder diffraction, infrared spectroscopy, light microscopy, and scanning electron microscopy. In the precipitation diagram the concentration region in which calcium hydrogenurate hexahydrate precipitated as a single solid phase was established. The solubility of calcium hydrogenurate hexahydrate was investigated in the pH range from 6.2 to 10.1 at different temperatures. The total soluble and ionic concentration of calcium (atomic absorption spectroscopy and Ca-selective electrode), total urate concentration (spectrophotometry), and pH were determined in equilibrated solutions. The data are presented in the form of tables and chemical potential diagrams. By using these data the thermodynamic solubility products of calcium hydrogenurate hexahydrate, Ks = a(Ca2+) · a2(C5H3N4O3−), were determined: pKs=10.12±0.07at288K,pKs=9.81±0.09at298K,pKs=9.28±0.04at310K,andpKs=9.01±0.03at318K.The formation of calcium hydrogenurate hexahydrate crystals in urinary tract of patients with pathologically high concentrations of calcium and urates (hypercalciuria and hyperuricosiuria) is possible. PMID:28053438

Potentiometric chip-based multipumping flow system for the simultaneous determination of fluoride, chloride, pH, and redox potential in water samples.

PubMed

Chango, Gabriela; Palacio, Edwin; Cerdà, Víctor

2018-08-15

A simple potentiometric chip-based multipumping flow system (MPFS) has been developed for the simultaneous determination of fluoride, chloride, pH, and redox potential in water samples. The proposed system was developed by using a poly(methyl methacrylate) chip microfluidic-conductor using the advantages of flow techniques with potentiometric detection. For this purpose, an automatic system has been designed and built by optimizing the variables involved in the process, such as: pH, ionic strength, stirring and sample volume. This system was applied successfully to water samples getting a versatile system with an analysis frequency of 12 samples per hour. Good correlation between chloride and fluoride concentration measured with ISE and ionic chromatography technique suggests satisfactory reliability of the system. Copyright © 2018 Elsevier B.V. All rights reserved.