| 1. |
- Ahmed, Mukhtiar, et al.
(författare)
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Aromatic Heterocyclic Anion Based Ionic Liquids and Electrolytes
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:4, s. 3502-3512
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Tidskriftsartikel (refereegranskat)abstract
- Five new ionic materials comprising fluorine-free aromatic heterocyclic anions based on pyridine and pyrazine combined with a common n-tetrabutylphosphonium cation, (P4444)+, result in two room temperature ionic liquids (RTILs), one semi-solid, and two organic ionic plastic crystals (OIPCs) with melting points >20 °C. The OIPCs showed a plastic crystalline phase, multiple solid–solid transitions, and plastic crystalline and melt phases. For both the neat RTILs and the Li+ conducting electrolytes, the nature and strength of the ion–ion interactions mainly depend on the position of the nitrogen atom with respect to the carboxylate group in the anions. Furthermore, for the RTILs the ionic conductivity is effected by the electronic structure and flexibility of the ions and the anions diffuse faster than the (P4444)+ cation, but are slowed down in the electrolytes due to the strong electrostatic interactions between the carboxylate group of the anions and the Li+, as shown both experimentally and computationally. Overall, this study describes the effect of structural tuning of aromatic anions on the ion–ion interactions and introduces new ionic materials with promising properties to be used as solid and liquid electrolytes in energy storage devices.
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| 2. |
- Ahmed, Mukhtiar, et al.
(författare)
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Ionic Liquids and Electrolytes with Flexible Aromatic Anions
- 2023
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Ingår i: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765. ; 29:41
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Tidskriftsartikel (refereegranskat)abstract
- Five new n-tetrabutylphosphonium (P4444)+ cation based ionic liquids (ILs) with oligoether substituted aromatic carboxylate anions have been synthesized. The nature and position of the oligoether chain affect thermal stability (up to 330 ºC), phase behaviour (Tg < -55 ºC) and ion transport. Furthermore, with the aim of application in lithium batteries, electrolytes were created for two of the ILs by 10 mol% doping using the corresponding Li-salts. This affects the ion diffusion negatively, from being higher and equal for cations and anions to lower for all ions and unequal. This is due to the stronger ionic interactions and formation of aggregates, primarily between the Li+ ions and the carboxylate group of the anions. Electrochemically, the electrolytes have electrochemical stability windows up to 3.5 V, giving some promise for battery application.
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| 3. |
- Ahmed, Mukhtiar, et al.
(författare)
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Pyrrolidium- and Imidazolium-Based Ionic Liquids and Electrolytes with Flexible Oligoether Anions
- 2024
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Ingår i: ChemPhysChem. - : John Wiley & Sons. - 1439-7641 .- 1439-4235. ; 25:9
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Tidskriftsartikel (refereegranskat)abstract
- A new class of fluorine-free ionic liquids (ILs) and electrolytes based on aliphatic flexible oligoether anions, 2-(2-methoxyethoxy)acetate (MEA) and 2-[2-(2-methoxyethoxy)ethoxy]acetate (MEEA), coupled with pyrrolidinium and imidazolium cations is introduced. For the ILs with MEEA anions, Li+ conducting electrolytes are created by doping the ILs with 30 mol % of LiMEEA. The structural flexibility of the oligoether functionality in the anion results in glass transition temperatures (Tg) as low as −60 °C for the neat ILs and the electrolytes. The imidazolium-based ILs and electrolytes reveal better thermal stabilities but higher Tg and lower electrochemical stabilities than the corresponding pyrrolidinium-based analogues. All neat ILs show comparable transport properties for the cations and these decrease by the addition of lithium salt – the pyrrolidinium-based electrolyte being affected the most.
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| 4. |
- Arkhipov, Victor P., et al.
(författare)
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Abnormal diffusion behavior and aggregation of oxyethylated alkylphenols in aqueous solutions near their cloud point
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 358
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated solutions of oxyethylated alkylphenols (neonols) in a mixture of ordinary and heavy water with equal densities of the neonols and the aqueous mixture. The equal densities allow exclusion of sedimentation effects and study of the evolution of micelles and neonol aggregates in the range from room temperature to above the cloud point. The self-diffusion coefficients of neonols were measured by NMR and the effective hydrodynamic radii of micelles and neonol aggregates were calculated using the Stokes-Einstein relation. An abnormal decrease in neonols diffusion coefficients occurred when the system approached the cloud point, while an abnormal increase in the diffusion coefficients occurred at temperatures above the cloud point. We explained the abnormal temperature behavior of the diffusion coefficients of neonols by changes in the size of the diffusing objects from the spherical and spherocylindrical micelles to dehydrated aggregates and the destruction of micelles by thermal motion and by formation of aggregates with sizes of the order 102 nm at temperatures above the cloud point. Conclusions about the increase in the hydrodynamic radii of the micelles with increasing temperature up to the cloud point and about the formation of dehydrated aggregates above the cloud point are confirmed by the results of DLS studies.
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| 5. |
- Arkhipov, Victor P., et al.
(författare)
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Aggregation Properties of Triton X-100 in a Mixture of Ordinary and Heavy Water
- 2023
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Ingår i: Applied Magnetic Resonance. - : Springer Nature. - 0937-9347 .- 1613-7507. ; 54:3, s. 415-425
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic and aggregation properties of Triton X-100 in a mixture of ordinary and heavy water in a wide temperature range from room temperature to the cloud point and above were studied. The ratio of ordinary and heavy water was calculated in such a way as to ensure equal densities of Triton X-100 and the water mixture. This made it possible to exclude the effects of sedimentation and study the evolution of Triton X-100 micelles and aggregates, without complication by the effects of spatial phase separation above the cloud point. Self-diffusion coefficients of Triton X-100 molecules were measured by NMR, and the effective hydrodynamic radii of micelles and aggregates were calculated using the Stokes-Einstein relation. The anomalous temperature behavior of the diffusion coefficient of Triton X-100 molecules is explained by changes in the sizes of diffusing objects during their evolution from micelles to dehydrated aggregates below the cloud point and by changes in the sizes of aggregates above the cloud point. The results of the NMR studies are confirmed by data obtained by dynamic light scattering.
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| 6. |
- Arkhipov, Victor P., et al.
(författare)
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Dynamic and molecular association in premicellar aqueous solutions of dicarboxylate amino acid-based surfactant as studied by 1H NMR
- 2022
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 60:3, s. 359-368
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Tidskriftsartikel (refereegranskat)abstract
- We examined a series of amino acid-based surfactants with two carboxylic groups separated by a spacer of one, two, or three carbon atoms with sodium and calcium counterions in the premicellar concentration region near the CMC. 1H NMR spectroscopy and NMR diffusometry techniques were used to study the local environment, association and translational dynamics of the surfactant’s molecules. We measured the self-diffusion coefficients of the micelles, calculated the effective hydrodynamic radii, and determined the temperature region in which the premicelles exist. With an increase in temperature from 295 to 335 K, the premicellar state of the surfactant is replaced by the monomeric state.
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| 7. |
- Arkhipov, Viktor P., et al.
(författare)
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Dynamic and structural properties, cloud point of mixed micelles of oxyethylated isononylphenols
- 2021
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Ingår i: Journal of Dispersion Science and Technology. - : Taylor & Francis. - 0193-2691 .- 1532-2351. ; 42:2, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- We measured the self-diffusion coefficients of mixed micelles formed in binary mixtures of oxyethylated isononylphenols (neonols) AF9-2,3,4,6,8,9,10,12 by NMR diffusometry in aqueous 1 wt% solutions. The effective hydrodynamic radii of the micelles were calculated using the Stokes-Einstein relation. Cloud points of these solutions were determined visually and the relation between the cloud point and the composition of the mixture was suggested. Extraction of phenol from the solutions at their cloud points was also studied.
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| 8. |
- Arkhipov, Victor P., et al.
(författare)
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Micellar and solubilizing properties of rhamnolipids
- 2023
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 61:6, s. 345-355
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Tidskriftsartikel (refereegranskat)abstract
- We studied the micellar and solubilizing properties of aqueous solutions of unfractionated rhamnolipids produced by Pseudomonas aeruginosa. We used nuclear magnetic resonance (NMR) diffusometry, dynamic light scattering, and conductometry to measure the critical micelle concentration (CMC) of rhamnolipid solutions and determined the effective hydrodynamic radii of rhamnolipid monomers and micelles. Based on selective measurements of the self-diffusion coefficients of molecules, performed by NMR diffusometry, the solubilizing properties of rhamnolipids were studied depending on their concentration in solution; aromatic hydrocarbons, benzene, toluene, ethylbenzene, and para-xylene were taken as solubilizates. On the basis of the measurement results, we estimated the distribution coefficient of the solubilizate between the micellar (solubilized) and free (in the aqueous phase) states and the solubilizing capacity of rhamnolipid micelles.
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| 9. |
- Arkhipov, Victor P., et al.
(författare)
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Micelles of Oxyethylated Isononylphenols in Aqueous Solutions and Hydrophilic–Lipophilic Balance
- 2020
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:43, s. 28224-28232
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the self-diffusion coefficients and calculated the effective hydrodynamic radii of micelles of ethoxylated isononylphenols in aqueous solutions in the presence of sodium chloride, as well as in their binary mutual mixtures, when approaching cloudy conditions. These cloudy conditions were created by an increase in temperature, a change in the concentration of an electrolyte in the solution, or a mutual ratio of neonols in their binary mixtures. The results are discussed within the concept of the hydrophilic–lipophilic balance.
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| 10. |
- Arkhipov, Victor P., et al.
(författare)
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Rhamnolipid Biosurfactant: Use for the Removal of Phenol from Aqueous Solutions by Micellar Solubilization
- 2023
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Ingår i: ACS Omega. - : American Chemical Society. - 2470-1343. ; 8:33, s. 30646-30654
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Tidskriftsartikel (refereegranskat)abstract
- Selective measurements of the self-diffusion coefficients of molecules of the biological surfactant rhamnolipid (RL) in individual aqueous solutions and in solutions with phenol as a solubilizate were carried out by nuclear magnetic resonance (NMR) diffusometry. Based on the obtained results, the solubilization characteristics of RLs were calculated. They are the fraction of solubilized phenol molecules, the phenol micelle-water distribution coefficient, the molar solubilization coefficient, the hydrodynamic radii of RL monomers and micelles, the aggregation numbers of micelles, and the solubilization capacity of micelles. Fraction of the solubilized phenol molecules increases and approaches 80-90% with increasing RL concentration. The solubilization capacity of the micelles increases from several units to 102 with an increase in both the concentration of RLs and the concentration of phenol in solution.
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| 11. |
- Arkhipov, Victor P., et al.
(författare)
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Self-Diffusion Coefficients, Aggregation Numbers and the Range of Existence of Spherical Micelles of Oxyethylated Alkylphenols
- 2021
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Ingår i: Applied Magnetic Resonance. - : Springer. - 0937-9347 .- 1613-7507. ; 52:5, s. 607-617
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation numbers were calculated based on measurements of the self-diffusion coefficients, the effective hydrodynamic radii of micelles and aggregates of oxyethylated alkylphenols in aqueous solutions. On the assumption that the radii of spherical micelles are equal to the lengths of fully extended neonol molecules, the limiting values of aggregation numbers corresponding to spherically shaped neonol micelles were calculated. The concentration and temperature ranges under which spherical micelles of neonols are formed were determined.
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| 12. |
- Arkhipov, Victor P., et al.
(författare)
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Study of the premicellar state in aqueous solutions of sodium dodecyl sulfate by nuclear magnetic resonance diffusion
- 2021
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 59:11, s. 1126-1133
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Tidskriftsartikel (refereegranskat)abstract
- Self‐diffusion coefficients of sodium dodecyl sulfate (SDS) were measured in aqueous solutions in the premicellar range of the SDS concentrations 7‐34.7 mM and temperatures 30‐900C. Average effective hydrodynamic radii and aggregation numbers of SDS in the premicellar region were determined. At C < CMC at all temperatures, the SDS solution is the solution of monomers. At C > CMC the increase of temperature leads to decrease in the effective hydrodynamic radii and the average aggregation numbers. At C >> CMC, it is impossible to reach the monomeric state by increasing the temperature.
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| 13. |
- Arkhipov, Victor P., et al.
(författare)
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The efficiency of micellar solubilization of naphthalene from aqueous solutions using rhamnolipid as a biological surfactant according to NMR diffusometry
- 2024
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Ingår i: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X.
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.The micellar solubilization of naphthalene from its saturated aqueous solutions using the biosurfactant rhamnolipid was studied. Using the NMR diffusion method, selective measurements of the self-diffusion coefficients of molecules of all components of the solution—naphthalene, rhamnolipid, and water—were carried out at various rhamnolipid concentrations from 0.06 to 100 g/L. Based on the results of diffusometry, the distribution of naphthalene molecules between the states free in solution and states bound by micelles was found. With an increase in the concentration of rhamnolipids, the proportion of bound naphthalene molecules increases from 50% at CRL = 2 g/L to 100% at CRL ≥ 50 g/L. The micelle-water partition coefficient Km and the molar solubilization ratio MSR were calculated.
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| 14. |
- Bhowmick, Sourav, et al.
(författare)
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Ambient temperature liquid salt electrolytes
- 2023
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 59:18, s. 2620-2623
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Tidskriftsartikel (refereegranskat)abstract
- Alkali metal salts usually have high melting points due to strong electrostatic interactions and solvents are needed to create ambient temperature liquid electrolytes. Here, we report on six phosphate-anion-based alkali metal salts, Li/Na/K, all of which are liquids at room temperature, with glass transition temperatures ranging from −61 to −29 °C, and are thermally stable up to at least 225 °C. While the focus herein is on various physico-chemical properties, these salts also exhibit high anodic stabilities, up to 6 V vs. M/M+ (M = Li/Na/K), and deliver some battery performance - at elevated temperatures as there are severe viscosity limitations at room-temperature. While the battery performance arguably is sub-par, solvent-free electrolytes based on alkali metal salts such as these should pave the way for conceptually different Li/Na/K-batteries, either by refined anion design or by using several salts to create eutectic mixtures.
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| 15. |
- Bhowmick, Sourav, et al.
(författare)
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Physical and electrochemical properties of new structurally flexible imidazolium phosphate ionic liquids
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:38, s. 23289-23300
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Tidskriftsartikel (refereegranskat)abstract
- New structurally flexible 1-methyl- and 1,2-dimethyl-imidazolium phosphate ionic liquids (ILs) bearing oligoethers have been synthesized and thoroughly characterized. These novel ILs revealed high thermal stabilities, low glass transitions, high conductivity and wide electrochemical stability windows up to 6 V. Both anions and cations of 1-methyl-imidazolium ILs diffuse faster than the ions of 1,2-dimethyl-imidazolium ILs, as determined by pulsed field gradient nuclear magnetic resonance (PFG-NMR). The 1-methyl-imidazolium phosphate ILs showed relatively higher ionic conductivities and ion diffusivity as compare with the 1,2-dimethyl-imidazolium phosphate ILs. As expected, the diffusivity of all the anions and cations increases with an increase in the temperature. The 1-methyl-imidazolium phosphate ILs formed hydrogen bonding with the phosphate anions, the strength of which is decreased with increasing temperature, as confirmed by variable temperature 1H and 31P NMR spectroscopy. One of the representative IL, [EmDMIm][DEEP], presented a promising performance at elevated temperatures as an electrolyte in a supercapacitor composed of multiwall carbon nanotubes and activated charcoal (MWCNTs/AC) composite electrodes.
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| 16. |
- Bhowmick, Sourav, et al.
(författare)
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Structurally Flexible Pyrrolidinium- and Morpholinium-based Ionic Liquid Electrolytes
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 25:29, s. 19815-19823
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Tidskriftsartikel (refereegranskat)abstract
- Ion transport measures and details as well as physico-chemical and electrochemical properties are presented for a small set of structurally flexible pyrrolidinium (Pyrr) and morpholinium (Morph) cation-based ionic liquids (ILs), all with oligoether phosphate-based anions. All have high thermal stabilities, low glass transition temperatures, and wide electrochemical stability windows, but rather moderate ionic conductivities, whereas both the anions and the cations of the Pyrr-based ILs diffuse faster than those of the Morph-based ILs. Overall the former ILs have significantly more promise as high-temperature supercapacitor electrolytes, rendering a specific capacitance of 164 F g−1 at 1 mV s−1, a power density of 241 W kg−1 and a specific energy density of 30 Wh kg−1 at 90 °C in a symmetric graphite supercapacitor.
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| 17. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Diffusion of Ions in Phosphonium Orthoborate Ionic Liquids Studied by 1H and 11B Pulsed Field Gradient NMR
- 2020
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Ingår i: Frontiers in Chemistry. - : Frontiers Media S.A.. - 2296-2646. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Non-halogenated boron-based ionic liquids (ILs) composed of phosphonium cations and chelated orthoborate anions have high hydrolytic stability, low melting point and exceptional properties for various applications. This study is focused on ILs with the same type of cation, trihexyltetradecylphosphonium ([P6,6,6,14]+), and two orthoborate anions, such as bis(salicylato)borate ([BScB]−) and bis(oxalato)borate ([BOB]−). We compare the results of this study with our previous studies on ILs with bis(mandelato)borate ([BMB]−) and a variety of different cations (tetraalkylphosphonium, dialkylpyrrolidinium and dialkylimidazolium). The ion dynamics and phase behavior of these ILs is studied using 1H and 11B pulsed-field-gradient (PFG) NMR. PFG NMR is demonstrated to be a useful tool to elucidate the dynamics of ions in this class of phosphonium orthoborate ILs. In particular, the applicability of 11B PFG NMR for studying anions without 1H, such as [BOB]−, and the limitations of this technique to measure self-diffusion of ions in ILs are demonstrated and discussed in detail for the first time.
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| 18. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Diffusivity of ethylammonium nitrate protic ionic liquid confined in porous glasses
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 356
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Tidskriftsartikel (refereegranskat)abstract
- We studied the diffusion of ionic liquid ethylammonium nitrate confined within pores of two types of porous glass, Vycor and Varapor, with average pore sizes of 4 nm and 9.8 nm, respectively, by 1H NMR in the temperature range of 295–325 K. The diffusional behavior of the ionic liquid corresponds to long-term diffusion in a system of interconnected pores. It was shown that the diffusivity of EAN confined in Varapor is controlled by the porous system’s tortuosity and does need to take into consideration the interaction with the surface of the discrete pore walls. In the case of Vycor, the long-term diffusivity is a factor 1.5 lower than that expected in the absence of interaction with the pore walls. Two possible mechanisms that may explain this discrepancy are the EAN-surface interaction and retardation of EAN diffusion compared to n-decane in smaller pores present in Vycor porous glass due to pore size distribution. Confinement of EAN in nanoporous glass does not leads to the EAN phase transformation observed earlier for alkylammonium nitrates enclosed in a micrometer-sized layer. Prolonged exposure of EAN to a strong static magnetic field does not leads to changes in the NMR and diffusivity of EAN over time.
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| 19. |
- Filippov, Andrei, et al.
(författare)
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Dynamics and Structure of a Bitumen Emulsion as Studied by 1H NMR Diffusometry
- 2023
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Ingår i: ACS Omega. - : Amer Chemical Soc. - 2470-1343. ; 8:39, s. 36534-36542
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion in a bitumen emulsion was studied by H-1 NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of similar to 0.11 mu m. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from H-1 NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional H-1 NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.
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| 20. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Dynamics of ethylammonium nitrate near PTFE surface
- 2022
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Ingår i: Magnetic Resonance Imaging. - : Elsevier. - 0730-725X .- 1873-5894. ; 85, s. 102-107
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Tidskriftsartikel (refereegranskat)abstract
- Self-diffusion of ions in the protic ionic liquid ethylammonium nitrate (EAN) was studied by 1H NMR pulsed field gradient techniques between 294 and 393 K in the presence of a PTFE insert in a 5-mm NMR tube. At all temperatures, the bulk diffusion of ions (measured by 1H and 15N NMR) can be described by a unique diffusion coefficient. The presence of solid hydrophobic surfaces of PTFE induces regions of EAN in their vicinity, where diffusion of ions, both cations and anions, is reduced compared to the bulk values. An additional line-shape analysis in 1H NMR spectra showed that local mobility of ethylammonium cations in the surface layers near PTFE is also reduced.
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| 21. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Effect of rotating magnetic field on the diffusivity of ethylammonium nitrate ionic liquid confined between micrometer-spaced glass plates
- 2021
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 323
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Tidskriftsartikel (refereegranskat)abstract
- We studied changes in the diffusion coefficients in layers of EAN confined between glass plates, placed in a strong magnetic field with a magnetic flux density B0, and rotated around the axis directed along and normal to B0. Under the rotational conditions along B0, the diffusion coefficient decreases with time after placement in the magnetic field at the same rate as for a static sample, observed previously (Filippov and Antzutkin, Phys. Chem. Chem. Phys. 2018. 20. 6316). However, when the EAN layers are rotating around the axis perpendicular to B0, the duration of exposure to the magnetic field does not affect the diffusion coefficient until the rotation stops. On the other hand, the diffusivity after extended exposure to a static magnetic field increases as the sample starts to rotate around the axis perpendicular to B0. The observed effects are due to either the periodic change in the orientation of the thin surface layers of EAN or inhomogeneity of B0 in the sample due to the B0 fluctuation.
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| 22. |
- Filippov, Andrei, et al.
(författare)
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NMR study of nitrate ionic liquids confined between micrometerspaced plates
- 2024
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Ingår i: Applied Chemical Engineering. - : Arts and Science Press Pte. Ltd.. - 2578-2010. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- This review paper presents the results of a study conducted using nuclear magnetic resonance (NMR) methods to investigate the dynamic behaviour of ionic liquid-based compositions in micrometre-spaced confinement. Ethylammonium nitrate (EAN) and other ionic liquid (IL) systems with nitrate anion in glass or quartz spaced confinement demonstrate anomalous cation dynamics that differ from those observed in bulk and in nano-confinement. It was demonstrated that the principal axis of the nitrate anion exhibits preferential orientation to the surface, akin to that in liquid crystals. It was shown that the cation translational mobility reversibly changes during exposure to a static magnetic field. This phenomenon was interpreted as a result of intermolecular structure transformations occurring in the confined ILs. The mechanisms of these transformations were discussed.
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| 23. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Self-diffusion in ionic liquids with nitrate anion : Effects of confinement between glass plates and static magnetic field
- 2020
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- Alkylammonium nitrate protic ionic liquids (ILs), when placed between flat polar borosilicate glass plates, have demonstrated enhanced diffusivity and the gradual decrease of diffusivity after exposure to an external static magnetic field (Filippov et al., 2018). This phenomenon has been explained by phase transformations taking place in the ILs. In this study, we observed similar processes occurring in systems prepared with ethylammonium nitrate confined between quartz plates. A higher content of silicon oxide in the plates does not significantly alter the phenomenon previously found in the system prepared with borosilicate glass plates. For the first time, we have observed similar effects of confinement and magnetic field on the aprotic IL, 1‑ethyl‑3‑methylimidazolium nitrate. Substitution of the ethylammonium cation with a 1‑ethyl‑3‑methylimidazolium cation slows down the kinetics and increases magnitude of the processes occurring in the IL exposed to a magnetic field. We suggested that the main factor determining these effects is the presence and modification of the hydrogen-bonding network in the studied protic and aprotic ILs. The process of inverse phase transformation for the confined ethylammonium nitrate after removing the sample from the magnetic field was observed and analysed.
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| 24. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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State of anion in ethylammonium nitrate enclosed between micrometer-spaced glass plates as studied by 17O and 15N NMR
- 2023
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : RSC Publishing. - 1463-9076 .- 1463-9084. ; 25:20, s. 14538-14545
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Tidskriftsartikel (refereegranskat)abstract
- Some aprotic and protic ionic liquids (ILs) containing nitrate anion demonstrate unusual dynamic behavior of cations when these ILs are enclosed in micrometer-spaced layers between glass plates. We applied 17O and 15N NMR spectroscopy to discover the state and transformations of 17O and 15N isotopically enriched nitrate anion of ethylammonium nitrate (EAN) enclosed between glass plates. 15N NMR spectra demonstrated preferential orientation of the principal axes of the nitrate anions perpendicular to the normal of the glass surface. Therefore, isotropic ionic liquid EAN, when placed within a micrometer-spaced enclosure, forms an ordered phase, which is similar to a liquid crystal. The peculiarity of this phase is that the cations do not have a predominant orientation. Other features of this phase that are typical for liquid crystal phases are the changed local and translational dynamics in comparison with the isotropic state and slow transformation occurring under the action of an external magnetic field.
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| 25. |
- Filippov, Andrei, PhD, 1957-, et al.
(författare)
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Understanding the Interaction of Boric Acid and CO2 with Ionic Liquids in Aqueous Medium by Multinuclear NMR Spectroscopy
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:1, s. 552-560
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Tidskriftsartikel (refereegranskat)abstract
- Boric acid is known to enhance the kinetics of CO2 absorption by some active aqueous solutions. However, the mechanism of interaction of boric acid with CO2 in the presence of active molecules is not yet fully understood. In this work, the interaction and dynamics of ions in aqueous solutions of functionalized choline-based ionic liquids [N1,1,5,2OH][Threo] and [N1,1,5,2OH][Tau] in the presence of boric acid and CO2 was thoroughly investigated using a multinuclear NMR approach: 13C and 11B NMR spectroscopy, 11B NMR transverse relaxation, and 1H and 11B NMR diffusometry. 13C and 11B NMR spectroscopy revealed the formation of borate-based complexes as a result of a reaction between boric acid and the anions of the ILs at ionic liquid/boric acid molar ratios larger than ca. 0.15. The formation of these complexes and their dynamics were further investigated using 11B relaxation and 1H and 11B pulse-field-gradient (PFG) NMR. Plausible reaction mechanisms of boric acid with the anions of the ILs, formation of the borate complexes, and dissociation of these complexes facilitated by CO2 molecules are suggested.
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