Structural variations and evidence of segmental motion in the aliphatic region in coals observed with dipolar-dephasing NMR

Soderquist, Arlen; Burton, David J.; Pugmire, Ronald J.; Beeler, Alvin J.; Grant, David M.; Durand, Bernard; Huk, A. Y.

doi:10.1021/ef00001a009

Cited by 27 publications

(19 citation statements)

References 5 publications

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“…Dipolar dephasing rates differing by up to an order of magnitude were observed for the signal at 30 ppm in the nonmobile and mobile components [55]. A similar study on another coal also provided evidence for segmental motion associated with the moieties giving rise to the signal at 30 ppm [56].…”

Section: Nano Researchmentioning

confidence: 60%

“…Similarly, dipolar dephasing experiments on some low-rank coals have provided evidence for segmental motion thought to arise from methylene groups associated with hydroaromatic and/or polymethylene structural units [55]. Dipolar dephasing rates differing by up to an order of magnitude were observed for the signal at 30 ppm in the nonmobile and mobile components [55].…”

Section: Nano Researchmentioning

confidence: 94%

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Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

et al. 2008

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Carboxylic acid-functionalized single walled carbon nanotubes (SWNTs) prepared via the reaction of an amino acid, NH 2 (CH 2 ) n CO 2 H where n = 1 (glycine, GLY), 5 (6-aminohexanoic acid, AHA), 10 (11-aminoundecanoic acid, AUDA), with fl uorinated single walled carbon nanotubes (F-SWNTs) have been characterized by MAS 13 C NMR spectroscopy. The ease of observing the aliphatic CH 2 groups and the resolution of the signal are dependent on the length of the amino acid's aliphatic chain. We have proposed that where substituent chains are short (making NMR data collection difficult) chemical modification to extend the chain length should alleviate analysis problems. In this regard, we have investigated the esterifi cation of the carboxylic acid termini. The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length, i.e., GLY-SWNT (C 1 ) + 1-dodecanol (C 12 ) = DOD-GLY-SWNT (1), AHA-SWNT (C 5 ) + 1-octanol (C 8 ) = OCT-AHA-SWNT (2), and AUDA-SWNT (C 10 ) + 1-propanol (C 3 ) = PRO-AUDA-SWNT (3). The 13 C NMR shift for the sp 3 nitrogen-substituted carbon atoms of the SWNT sidewall is observed at ≈ 75 ppm. Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp 3 carbon. The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives, suggesting more motional freedom of the side chain in the solid state. The confi rmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol: PPD-AUDA-SWNT (4).

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Section: Nano Researchmentioning

confidence: 60%

Section: Nano Researchmentioning

confidence: 94%

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

et al. 2008

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“…34 Unfortunately, we do not have any suitable solid hydroaromatic model compounds to study for comparison. In this context, we note that dipolar dephasing experiments on some low-rank coals have provided evidence for segmental motion thought to arise from CH 2 groups associated with hydroaromatic and/or polymethylene structural units.…”

Section: T-buohmentioning

confidence: 99%

Birch Reduction of Graphite. Edge and Interior Functionalization by Hydrogen

et al. 2012

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The Birch reduction (lithium in liquid ammonia) of graphite gives a highly reduced, exfoliated product that is free of lithium. Edge and interior hydrogenation were demonstrated by solid-state (13)C NMR spectroscopy. Elemental analysis of a carefully purified sample allows the chemical composition to be expressed as (C(1.3)H)(n). Atomic force microscopy images showed that the reduced graphene was highly exfoliated. Hydrogen mapping by electron energy loss spectroscopy showed that the entire surface of the reduced sample was covered by hydrogen, consistent with the NMR studies also indicating that hydrogen was added in interior positions of the graphene lattice as well as along the edge. A large band gap (4 eV) further establishes the high level of hydrogenation.

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“…The remainingpapersinthisarea (4,(17)(18)(19)(20)(21)(22)(23)(24)(25) were concerned with solubilization an,_ liquefaction ofcoaland lignite. Two ofthese (18,19) utilized fungiisolated from lignite outcroppings.…”

Section: Thermogravimetry(tg) and Insituelectron Spinresonance (Esr) mentioning

confidence: 99%

Cooperative research in coal liquefaction

Huffman¹,

Sendlein²

1991

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Structural variations and evidence of segmental motion in the aliphatic region in coals observed with dipolar-dephasing NMR

Cited by 27 publications

References 5 publications

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Birch Reduction of Graphite. Edge and Interior Functionalization by Hydrogen

Cooperative research in coal liquefaction

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