Browsing by Author "Danuta Kruk"

Now showing 1 - 7 of 7

Cation-Cation, Cation-Anion, and Anion-Anion Translation Diffusion in Ionic Liquids─Insight from NMR Relaxometry
(American Chemical Society, 2025) Elzbieta Masiewicz; Roksana Markiewicz; Rajendra K. Singh; Sujeet Kumar Chaurasia; Danuta Kruk
1H and 19F spin-lattice relaxation experiments have been performed for a series of ionic liquids: [HMIM][TFSI], [OMIM][TFSI], and [DMIM][TFSI] including the same anion and cations with progressively longer alkyl chains. The experiments were performed in a wide frequency range from 10 kHz to 10 MHz (referring to the 1H resonance frequency) versus temperature. This extensive data set has been analyzed in terms of a theoretical model including all relevant homonuclear (1H-1H and 19F-19F) and heteronuclear (1H-19F) relaxation pathways and linking the relaxation features to the relative translational diffusion between the ion pairs (cation-cation, cation-anion, and anion-anion). In addition to the comprehensive theoretical approach, closed-form expressions have been provided and applied to determine the diffusion coefficients from the slopes of the linear dependences of the relaxation rates on the square root of the resonance frequency. The combined experimental and theoretical studies have led to the determination of the complete set of diffusion coefficients, forming a consistent picture of the dynamical scenario. In addition to revealing the dynamical properties of the liquids and the influence of the subtle changes in the cation structure on the movement of both cations and anions, the theoretical means for exploiting Nuclear Magnetic Resonance relaxometry for ionic liquids have been provided. © 2024 American Chemical Society.
Dynamical properties of EMIM-SCN confined in a SiO2 matrix by means of 1H NMR relaxometry
(Royal Society of Chemistry, 2017) Danuta Kruk; Milosz Wojciechowski; Yogendra Lal Verma; Sujeet Kumar Chaurasia; Rajendra Kumar Singh
1H nuclear magnetic resonance relaxometry is applied to investigate the translational and rotational dynamics of ionogels composed of an ionic liquid (IL): 1-ethyl-3-methyl-imidazolium-thiocyanate (EMIM-SCN) confined in a nanoporous SiO2 matrix. The relaxation studies were performed in the frequency range of 4 kHz-40 MHz and the temperature range of 223-248 K for different concentrations of the IL; the ratio (no. of moles of IL/no. of moles of SiO2) yields: 1/2, 3/5 and 7/10. A thorough analysis of this large set of experimental data was performed assuming the existence of two fractions of the liquid: a core fraction (near the pore center) and a surface fraction (near the confining walls). It was shown for all concentrations that the confinement does not significantly affect the translational motion near the pore center compared to the dynamics in bulk. The diffusion coefficients in the surface fraction are considerably smaller compared to the core fraction (from one to two orders of magnitude) and the difference becomes larger with increasing temperature. The diffusion coefficients become smaller for higher concentrations-this effect is not large, but visible. Very importantly, it was shown that, despite the interactions with the surface, the diffusion in the surface fraction remains of 3D character. As far as rotational dynamics in the surface fraction is concerned, it slows down compared to the bulk (and the core fraction), but this effect is of the order of factor 2-3. © the Owner Societies 2017.
Dynamics of ionic liquid-polymer gel membranes—Insight from NMR relaxometry for [BMIM][BF4]-PVDF-HFP systems
(American Institute of Physics, 2024) Shitanshu Pratap Singh; Elżbieta Masiewicz; Rajendra Kumar Singh; Sujeet Kumar Chaurasia; Danuta Kruk
1H spin-lattice relaxation experiments have been performed for ionic liquid-polymer gel membranes, including 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) with different proportions. The experiments have been performed in a broad range of resonance frequencies (from about 5 Hz to 40 MHz) vs temperature and complemented with analogous studies for [BMIM][BF4] in bulk as a reference. A model of the relaxation processes in the membranes has been proposed. The model includes two relaxation contributions. One of them corresponds to the concept of restricted, two-dimensional translation diffusion with a residence lifetime, while the second one has the form characteristic of polymers (mathematically similar to the limiting behavior of two-dimensional translation diffusion with a very long residence lifetime). The extensive dataset has been consistently interpreted in terms of the model, revealing two dynamical processes on the time scales of 10−7 s (for the second relaxation contribution) and 10−9 s (for the first one). The relationship of these relaxation contributions to the motion of the polymer or ionic liquid-polymer complexes and to the translation diffusion of BMIM cations in the matrix has been discussed. © 2024 Author(s).
Dynamics of ionic liquids by means of nuclear magnetic resonance relaxation - overview of theoretical approaches
(Royal Society of Chemistry, 2024) Danuta Kruk; Elzbieta Masiewicz; Roksana Markiewicz; Rajendra Kumar Singh
This paper presents a comprehensive overview of the spin relaxation theory needed for exploring nuclear magnetic resonance (NMR) relaxometry to study the dynamical properties of ionic liquids. The term NMR relaxometry refers to relaxation experiments performed over a wide range of magnetic fields (resonance frequencies). In this way, dynamical processes occurring on timescales from milliseconds to nanoseconds can be studied, including translational and rotational dynamics of both types of ions (cations and anions). In order to take advantage of the remarkable experimental possibilities, appropriate theoretical models linking relaxation properties with ionic motion are needed. With the aim of providing such theoretical tools, 1H and 19F relaxation models for ionic liquids have been reviewed and their applications have been illustrated by several examples. The presented models are valid for an arbitrary magnetic field, include all relevant relaxation pathways and allow to extract detailed information about the translational and rotational dynamics of the ions. On the basis of the theoretical models, formulas allowing a straightforward determination of the translational diffusion coefficients of cations and anions from combined 1H and 19F relaxation studies have been derived and discussed in detail. © 2024 The Royal Society of Chemistry.
Dynamics of ionic liquids in bulk and in confinement by means of 1H NMR relaxometry-BMIM-OcSO4 in an SiO2 matrix as an example
(Royal Society of Chemistry, 2016) Danuta Kruk; Milosz Wojciechowski; Szczepan Brym; Rajendra Kumar Singh
1H nuclear magnetic resonance relaxometry is applied to reveal information on the translational and rotational dynamics of the ionic liquid: 1-butyl-3-methyl imidazoliumoctyl sulfate (BMIM-OcSO4) in bulk and in a confinement formed by a nanoporous SiO2 matrix. The experimental studies were performed in a very broad frequency range, from 8 kHz to 40 MHz (referring to the 1H resonance frequency), in order to probe motional processes at very different time scales using a single experiment, and in the temperature range of 243-303 K. The relaxation results for BMIM-OcSO4 in bulk are interpreted in terms of three relaxation contributions: a term associated with the translational dynamics of the ions (it has been assumed that the translational dynamics of cations and anions can be described by one diffusion coefficient) and two terms associated with the rotational motion of the anion and the cation, respectively. The relationships between the obtained dynamic parameters (rotational correlation times and translational diffusion coefficients) are thoroughly discussed and used as a "reference" for the dynamics of BMIM-OcSO4 confined in an SiO2 matrix. Analysis of the corresponding relaxation data for the confined liquid shows that the confinement does not significantly affect the rotational dynamics, but it has a considerable impact on the translational motion. It is demonstrated that the relaxation term associated with the translational dynamics stems from two contributions: a contribution from a core (bulk-like) fraction of the liquid and from a fraction moving near the pore surface and therefore being for some time adsorbed on the pore walls. The translational diffusion coefficient for the last fraction is determined and several conclusions regarding the residence lifetime of the ions on the surface are drawn. Moreover, an additional motional process on the timescale of ns or shorter is revealed in the confinement. © the Owner Societies 2016.
Dynamics of ionic liquids in confinement by means of nmr relaxometry—emim-fsi in a silica matrix as an example
(MDPI AG, 2020) Danuta Kruk; Milosz Wojciechowski; Malgorzata Florek-Wojciechowska; Rajendra Kumar Singh
1 H and19 F spin–lattice relaxation studies for 1-ethyl-3-methylimidazolium bis(fluorosulfonyl) imide in bulk and mesoporous MCM-41 silica matrix confinement were performed under varying temperatures in a broad range of magnetic fields, corresponding to1 H resonance frequency from 5Hz to 30MHz.A thorough analysis of the relaxation data revealed a three-dimensional translation diffusion of the ions in the bulk liquid and two-dimensional diffusion in the vicinity of the confining walls in the confinement. Parameters describing the translation dynamics were determined and compared. The rotational motion of both kinds of ions in the confinement was described by two correlation times that might be attributed to anisotropic reorientation of these species. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Sponge-like porous sustainable hard carbon as an efficient anode for sodium-ion batteries
(Elsevier Ltd, 2025) Anupam Patel; Anurag Tiwari; Samriddhi; Shitanshu Pratap Singh; Vikas G. Yadav; Tanya Jaiswal; Danuta Kruk; Ranjith Krishna Pai; Rajendra K. Singh
Renewable, cost-effective, eco-friendly, and abundant biodegradable waste has emerged as a promising resource for developing hard carbon (HC) anode materials for rechargeable sodium-ion batteries (SIBs). This study focuses on synthesizing HC anode materials from mango leaves using hydrothermal carbonization process, and thereafter pyrolysis at 900 °C and 1000 °C. The synthesized HC shows the spongelike morphology along with large specific surface area (88.3 m² g−1). The resulting materials pyrolyzed at 900 °C and 1000 °C, designated as Mango (Mangifera indica) Leaves Hard Carbon (MLHC-900) and (MLHC-1000) respectively, deliver impressive discharge capacities per unit mass of approximately 241 mAh g−1 and 215 mAh g−1 at a current density of 10 mA g−1, respectively. After 1200 cycles at a current density 1000 mA g−1, the MLHC-900 demonstrated superior capacity retention compared to MLHC-1000. These results signify the potential of using biodegradable waste utilizing hydrothermal carbonization to fabricate efficient HC anodes for SIBs. © 2025 Elsevier Ltd