Application of EPR spectroscopy to the characterization of magnetic interactions in thermally decomposed coal

Pilawa, Barbara; Wiȩckowski, Andrzej; Lewandowski, Marek

doi:10.1002/(sici)1097-458x(199912)37:12<871::aid-mrc566>3.0.co;2-8

Cited by 18 publications

(12 citation statements)

References 24 publications

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“…The analysis of the lineshape of electron paramagnetic resonance (EPR) spectra points out a complex character of paramagnetic centers in coal samples [1][2][3][4][5][6][7][8][9][10][11][12][13]. EPR spectra of coals and their petrographic constituents are a superposition of several lines resulting from paramagnetic centers of different molecular units.…”

Section: Introductionmentioning

confidence: 99%

“…The broad and narrow components of the EPR spectra of coal samples saturate at low and high microwave power, respectively [1,2,4,5,[11][12][13]. The differences in microwave saturation of these EPR lines were helpful for the separatien of components of EPR spectra of coal and macerals.…”

Section: Introductionmentioning

confidence: 99%

“…There are many works [1][2][3][10][11][12][13][14][15][16][17][18][19][20][21] about the application of EPR spectroscopy to study different chemical processes in coal. The difficult separation of component lines in complex EPR spectra of coal is probably responsible for the narrow range of these studies.…”

Section: Introductionmentioning

confidence: 99%

“…We applied EPR spectroscopy to study the evolution of different paramagnetic centers in thermally decomposed coal and macerals [1][2][3], in oxidized anthracite [21], in pyridine-extracted coal and macerals [10][11]. We used a microwave saturation technique in all these works.…”

Section: Introductionmentioning

confidence: 99%

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Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

et al. 2003

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Changes in individual groups of paramagnetic centers after reduction and reductive butylation of Polish flame coal (70.8 wt.% C) were studied by electron paramagnetic resonance (EPR) spectroscopy. The modero method of reductive butylation of coal in a potassium-liquid ammonia system was used. This process increases the solubility of coal in organic solvents. Microwave saturation of EPR spectra was applied to test the spin-lattice relaxation in coal. The measured EPR spectra were a superposition of broad (ABpp, 0.424).49 mT) and narrow (ABpp, 0.09-0.13 toT) Lorentz lines. Paramagnetic centers located in simple and multiring aromatic structures were responsible for the broad and narrow lines, respectively. Microwave saturation indicates that slow and fast spin-lattice relaxation processes are characteristic for these two types of structures in the original coal. A decrease of the microwave power saturation of the broad Lorentz line after a single reduction of coal was observed. It inereased for both 4 times reduced coal and reductively butylated coal. As the result of multiple reduction and butylation, spin-lattice relaxation processes in simple coal aromatic units were fastened. The narrow Lorentz lines of both 4 times reduced and reductively butylated coal were saturated and the spin-lattiee relaxation time increased.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

et al. 2003

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“…The values of g-factor are nearly the same for each component and they are related with the value of the spin-orbit coupling constant λ and with the localization of unpaired electrons responsible for the EPR signal [20]. The temperature and the chemical treatments used affect more the linewidth and the concentration of paramagnetic centers [21,22]. Table I presents the values of the EPR parameters of recorded spectra (g-factor, peak-to-peak linewidth ∆B pp compared to the g-value of the pristine activated carbon (g = 2.0037).…”

Section: Resultsmentioning

confidence: 99%

EPR Characteristics of Activated Carbon for Hydrogen Production by the Thermo-Catalytic Decomposition of Methane

et al. 2016

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The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750 . The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ∆Bpp, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.

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Quantitative Decoupling of Strong Mn─Mn Coupling on Photoluminescence of Zero‐Dimensional Hybrid Manganese Chlorides Single Crystals

Luo,

Li,

Zhang

et al. 2024

Advanced Optical Materials

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Strong Mn─Mn coupling interactions, including dipolar and exchange interactions, significantly affect the photoluminescence quantum yields (PLQYs) in Mn2+‐based luminescent materials. However, clarifying the individual effects of dipole–dipole and exchange interactions on photoluminescence (PL) is challenging because these interactions may have similar effects on PL properties, and there is a lack of materials with precisely tunable Mn─Mn distances over a wide range. In this study, the influence of dipolar and exchange coupling on PLQY is quantitatively decoupled by designing a series of hybrid manganese chlorides single crystals with a wide tuning range of Mn─Mn distances, from 6.0 to 9.5 Å. It is found that the PLQY can be enhanced from 2.1% to 57.1%, and the PL lifetime increased from 0.21 to 3.81 ms as the Mn─Mn distance increased. This enhancement is solely attributed to the decreased energy transfer dominated by dipole–dipole interactions. At the shortest Mn─Mn distance of 6 Å, exchange coupling becomes dominant, resulting in an additional red‐side PL band with negligible effects on PLQY and lifetime. This work provides valuable insights into the mechanisms underlying the regulation of PLQY in Mn2⁺‐based luminescent materials.

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Application of EPR spectroscopy to the characterization of magnetic interactions in thermally decomposed coal

Cited by 18 publications

References 24 publications

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

EPR Characteristics of Activated Carbon for Hydrogen Production by the Thermo-Catalytic Decomposition of Methane

Quantitative Decoupling of Strong Mn─Mn Coupling on Photoluminescence of Zero‐Dimensional Hybrid Manganese Chlorides Single Crystals

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