Static magnetic field alters properties of confined alkylammonium nitrate ionic liquids (original) (raw)
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Magnetic field effects dynamics of ethylammonium nitrate ionic liquid confined between glass plates
Physical chemistry chemical physics : PCCP, 2018
Self-diffusion and NMR relaxation of the ethylammonium (EA) cation were studied in the protic ionic liquid, ethylammonium nitrate (EAN), confined between polar glass plates separated by a few μm distance and exposed to an external magnetic field of 9.4 T. The diffusion coefficient of EA (D) and the transverse NMR relaxation rate (1/T) of -NH protons were increased immediately after placing the sample in the magnetic field by factors of ∼2 and ∼22, respectively, in comparison with those of bulk EAN. Further exposure of the sample to the magnetic field led to gradual changes in D, T and T towards their bulk values with a time constant of ∼70 min. Complete "recovery" of the sample to the "accelerated" D and "shortened" T values occurred at longer than 24 hours after the removal of the EAN sample from the magnet. Because the observed characteristic times of the change far exceed the times of molecular processes in EAN, we suggested that this phenomenon is r...
2017
Self-diffusion and NMR relaxation of ethylammonium (EA) cations were studied in the protic ionic liquid ethylammonium nitrate (EAN) confined between parallel polar glass plates separated by a few um as a function of time after placement in a magnetic field of 9.40 T. Immediately after sample placement, the diffusion coefficient of EA (D) increased by a factor of 2, while the transverse NMR relaxation of NH3 protons decreased by factors of up to 22 in comparison with bulk EAN, according to previously published data. Further exposure to the magnetic field leads to gradual changes of D, T1 and T2 with a time constant of 70 min and a total equilibration time of longer than 4 hours. This process does not depend on the orientation of the glass plates relative to the magnetic field. Removing the sample from the magnetic field and repeating the experiment demonstrated that complete recovery of the sample to the accelerated D and shortened T2 occurs in approximately 24 hours. Thus, EA cation...
Properties of Confined Ammonium Nitrate Ionic Liquids
arXiv: Chemical Physics, 2018
Ethylammonium nitrate (EAN) and propylammonium nitrate ionic liquids confined between polar glass plates and exposed to a strong magnetic field 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 a change in the state of residual water. Generally, our findings confirm our previous suggestion that alteration of the dynamic properties of confined ammonium nitrate ionic liquids exposed to a magnetic field is related to the alteration of real physical-chemical phases.
Journal of Molecular Liquids, 2019
We used 1 H NMR diffusometry to study mixtures of ethylammonium nitrate (EAN) with water (3.1-12.4 mol% of added H 2 O) confined between polar glass plates and exposed to a static magnetic field of 9.4 T. The presence of such restrictions reverses the concentration dependence of the diffusivities of the EA (ethylammonium) cation and water typical for the bulk system. The presence of water weakens the effects of a static magnetic field on diffusion of the EA cation as well as on proton exchange of-NH 3 groups. Surprisingly, the amplitude of the echo signal of water protons decreases during exposure to the magnetic field and finally disappears, a phenomenon that depends on the concentration of water in the system. Based on experimental data, we suggest that water in the system is present in two states with different dynamic properties. One type of water formed in confinement possesses NMR relaxation time typical for liquids; its diffusivity can be measured by 1 H NMR. The second type of water is formed upon exposure of the sample of the first type to the magnetic field and eventually includes all the water in the system. This type of water possesses "solid-like" NMR relaxation features that makes it "invisible" to the NMR diffusometry technique. We suggest that this second type of water is adsorbed onto the glass plates. Correspondingly, EAN exists in two liquid phases: the first one contains an EAN-water mixture, while the second one contains neat EAN, and forms on the microscopic scale range under the influence of a static magnetic field.
Journal of Molecular Liquids, 2021
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 B 0 , and rotated around the axis directed along and normal to B 0. Under the rotational conditions along B 0 , 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 B 0 , 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 B 0. The observed effects are due to either the periodic change in the orientation of the thin surface layers of EAN or inhomogeneity of B 0 in the sample due to the B 0 fluctuation.
Journal of Molecular Liquids
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Physical Chemistry Chemical Physics, 2023
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 17 O and 15 N NMR spectroscopy to discover the state and transformations of 17 O and 15 N isotopically enriched nitrate anion of ethylammonium nitrate (EAN) enclosed between glass plates. 15 N 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.
Water dynamics in ionic magnetic colloids studied by 1H nuclear magnetic resonance
Physica B: Condensed Matter, 2002
In a previous nuclear magnetic resonance (NMR) study we observed that the NMR spectra of water in both surfacted and ionic ferrofluids are asymmetric and several orders of magnitude wider than the one of pure water. It has been proposed that this effect is produced by extremely strong magnetic field gradients in the intergrain volume and/or by surface interactions between the carrier liquid molecules and the grains surface. In the case of aqueous ionic ferrofluids the latter possibility should be interpreted as electric interactions between water (polar) molecules and the charges in the grain surface.
The effects of external magnetic field upon the stability of ionic magnetic fluids
Journal of Magnetism and Magnetic Materials, 2004
Effects of an external magnetic field on the energy spectrum and surface charge density of semiconductor nanoparticles (SNPs) in ionic colloids were investigated in the frame of finite element method. The maximum probability for carriers increases with the increasing of the applied magnetic field for both spherical and nonspherical nanoparticles. The effect of an applied external magnetic field on the surface charge density of SNPs is dramatically modified by the nanoparticle shape. Our observations can be well explained through the competition of the quantum confinement effects introduced by both particle geometry and magnetic field. r
A New Class of Magnetic Fluids: bmim[FeCl ]and nbmim[FeCl ] Ionic Liquids
The responses to a magnet of two room-temperature ionic liquids containing tetrachloroferrate(III) ions, 1-butyl-3-methylimidazolium tetrachloroferrate (bmim[FeCl 4 ]) and 1-butyronitrile-3-methylimidazolium tetrachloroferrate (nbmim[FeCl 4 ]) are compared. Although their magnetic susceptibilities are similar, the observed responses are distinct from each other, suggesting that the response is determined not only by the magnetic susceptibility but also by the other factors including density, viscosity, and surface tension. The two magnetic ionic liquids constitute a new class of magnetic fluids that hold many attractive physical properties for practical applications.