| 1. |
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| 2. |
- Arkhipov, Victor P., et al.
(author)
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Molecular self-diffusion and micellar structure in the aqueous solutions of AF9-10 ethoxylated isononylphenol near a cloud point
- 2014
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In: Mendeleev communications (Print). - : Elsevier BV. - 0959-9436 .- 1364-551X. ; 24:5, s. 266-268
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Journal article (peer-reviewed)abstract
- Sizes of micelles and compositions of aggregates in the aqueous solutions of the nonionic surfactant oxyethylated monoalkyl phenol (neonol AF9-10) were determined by NMR spectroscopy, NMR diffusometry and dynamic light scattering in a wide range of tem- peratures near the cloud point. The cloud point extraction of phenol from aqueous solutions by the surfactant AF9-10 was performed.
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| 3. |
- Filippov, Andrei, PhD, 1957-, et al.
(author)
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Diffusivity of ethylammonium nitrate protic ionic liquid confined in porous glasses
- 2022
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In: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 356
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Journal article (peer-reviewed)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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| 4. |
- Filippov, Andrei, PhD, 1957-, et al.
(author)
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Dynamics of ethylammonium nitrate near PTFE surface
- 2022
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In: Magnetic Resonance Imaging. - : Elsevier. - 0730-725X .- 1873-5894. ; 85, s. 102-107
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Journal article (peer-reviewed)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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| 5. |
- Filippov, Andrei, et al.
(author)
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Effect of curcumin on lateral diffusion in lipid bilayers
- 2016
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In: Mendeleev communications (Print). - : Elsevier BV. - 0959-9436 .- 1364-551X. ; 26:2, s. 109-110
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Journal article (peer-reviewed)abstract
- Lateral diffusion in dimyristoylphosphatidylcholine lipid bilayers decreases in the presence of cholesterol and curcumin, as measured by 1H NMR spectroscopy, but the mechanisms of action of these two compounds are different.
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| 6. |
- Filippov, Andrei, PhD, 1957-, et al.
(author)
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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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In: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 323
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Journal article (peer-reviewed)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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| 7. |
- Filippov, Andrei, PhD, 1957-, et al.
(author)
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Self-diffusion of ethylammonium nitrate ionic liquid confined between modified polar glasses
- 2019
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In: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 284, s. 366-371
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Journal article (peer-reviewed)abstract
- Ethylammonium nitrate (EAN) ionic liquid confined between flat polar glass platesdemonstrates variable diffusivity that is sensitive to an external static magnetic field. Outside the magnetic field, diffusivity between the plates is higher than that in the bulk. However, after placing the system in a strong static magnetic field, the diffusivity gradually decreased. These processes occur during transformations between phases formed in EAN subjected to micrometer-size restrictions outside and within the magnetic field (Filippov et al., J. Mol. Liq. [2018] 268, 49). In this study, we used samples of two types: (i) with roughened surface formed by treatment of the glass plates with aqueous solutions of hydrofluoric acid and (ii) with vacuum deposited TiO2 layers with a thickness of ca. 1 μm at glass-plate edges. Neither the surface modification of the glass plates, nor the TiO2 layers controlled thickness of EAN confined between glass-plates significantly changed the above-described effects, which have been observed in studies using untreated glass plates. Therefore, the range of systems with detected phase transformations in EAN and accompanying effects, such as accelerated diffusivity and change in diffusivity under the influence of a static magnetic field, was expanded to the systems with roughened surfaces and the systems with TiO2 layers controlled inter-plates distances. Results of experiments with roughened surfaces additionally suggested that the phase transformation of confined EAN in the external magnetic field is isotropic in nature rather than a phase transition from “layered to bulk” structures.
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| 8. |
- Filippov, Andrei, et al.
(author)
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Static magnetic field alters properties of confined alkylammonium nitrate ionic liquids
- 2018
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In: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 268, s. 49-54
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Journal article (peer-reviewed)abstract
- Ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) ionic liquids confined between polar glass plates and exposed to a strong magnetic field of 9.4 T demonstrate gradually slowing diffusivity, a process that can be reversed by removing the sample from the magnetic field. The process can be described well by the Avrami equation, which is typical for autocatalytic (particularly, nucleation controlled) processes. The transition can be stopped by freezing the sample. Cooling and heating investigations showed differences in the freezing and melting behavior of the sample depending on whether it had been exposed to the magnetic field. After exposure to the magnetic field, the sample demonstrated decrease in the 1H NMR signal of residual water. 1H NMR spectroscopy with presaturation demonstrates that the most probable mechanism of the decrease of the bulk water signal is adsorption of water on polar surfaces of glass plates. Generally, our findings confirm our previous suggestion that alteration of the dynamic properties of confined alkylammonium nitrate ionic liquids exposed to a magnetic field is related to the alteration of real physical-chemical phases
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| 9. |
- Gnezdilov, Oleg I., et al.
(author)
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Temperature dependence of 1H NMR chemical shifts and diffusivity of confined ethylammonium nitrate ionic liquid
- 2020
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In: Magnetic Resonance Imaging. - : Elsevier. - 0730-725X .- 1873-5894. ; 74, s. 84-89
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Journal article (peer-reviewed)abstract
- Some ionic liquids (ILs) change their dynamic properties when placed in a confinement between polar surfaces (Filippov et al., Phys. Chem. Chem. Phys. 2018, 20, 6316). The diffusivities of ions and NMR relaxation times in these ILs also reversibly change under a strong static magnetic field. The mechanisms of these phenomena are not clear, but it has been suggested that they involve modified hydrogen-bonding networks formed in these ILs in the presence of polar surfaces. To obtain a better understanding of these effects, we performed temperature-dependent measurements of chemical shifts and diffusion coefficients for ethylammonium nitrate (EAN) IL in the bulk phase (IB) and confined in layers with a thickness of ~4 μm between quartz plates unexposed (I phase) and exposed (IMF phase) to a static magnetic field of 9.4 T. It was shown that the NMR chemical shift of NH3 protons of EAN in the I phase is strongly shifted upfield, ~0.0145 ppm/K, which is due to weakening of the hydrogen-bonding network of the confined EAN. Exposure to the magnetic field leads to restitution of the hydrogen-bonding (H-bonding network). The temperature dependences of diffusion coefficients follow the order D(I) > D(IB) > D(IMF) and can be described by a Vogel-Fulcher-Tammann approach with variation of the pre-exponential factor, which is determined by the strength of the H-bonding network. Confinement of EAN between plates (IB → I) is an endothermic process, while processes occurring in a magnetic field, I → IMF and IMF → I, are exothermic and endothermic, respectively.
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| 10. |
- Kotenkov, Sergey A., et al.
(author)
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Effect of Cholesterol and Curcumin on Ordering of DMPC Bilayers
- 2019
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In: Applied Magnetic Resonance. - : Springer. - 0937-9347 .- 1613-7507. ; 50:1-3, s. 511-520
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Journal article (peer-reviewed)abstract
- In this work, we compared the effects of curcumin and cholesterol directly competing to insert into the DMPC lipid bilayer during bilayer formation from an initially non-ordered state. 2H and 14N nuclear magnetic resonance spectroscopy showed that curcumin is not embedded deep in the lipid bilayer and interacts mainly with the head group of the lipid. In a more complex system of DMPC/CHOL/CUR, curcumin amplifies the effect of cholesterol on the ordering of lipid acyl chains.
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