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001     449
005     20180208225227.0
024 7 _ |2 DOI
|a 10.2116/analsci.24.1183
024 7 _ |2 WOS
|a WOS:000259584800019
037 _ _ |a PreJuSER-449
041 _ _ |a eng
082 _ _ |a 540
084 _ _ |2 WoS
|a Chemistry, Analytical
100 1 _ |a Conte, P.
|b 0
|0 P:(DE-HGF)0
245 _ _ |a Dynamics of Cross Polarization in Solid State Nuclear Magnetic Resonance Experiments of Amorphous and Heterogeneous Natural Organic Substances
260 _ _ |a Tokyo
|b Japan Society for Analytical Chemistry
|c 2008
300 _ _ |a 1183 - 1188
336 7 _ |a Journal Article
|0 PUB:(DE-HGF)16
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336 7 _ |a Journal Article
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336 7 _ |a ARTICLE
|2 BibTeX
336 7 _ |a JOURNAL_ARTICLE
|2 ORCID
336 7 _ |a article
|2 DRIVER
440 _ 0 |a Analytical Sciences
|x 0910-6340
|0 19241
|v 24
500 _ _ |a P.C. acknowledges Forschungszentrum Julich GmbH (Germany) for enabling him to perform experimental work as visiting scientist at the NMR center of the Institute of Chemistry and Dynamics of the Geosphere, Institute 4: Agrosphere. The authors are grateful to Dipl.-Ing. H. Philipp (FZJ) for his assistance in sample preparation. This paper was partially funded by University of Palermo within a project titled "Nuovi processi sostenibili per la bonifica di suoli contaminati".
520 _ _ |a Nuclear magnetic resonance (NMR) experiments on carbon-13 in the solid state were done with cross polarization (CP) and magic angle spinning (MAS) in order to overcome the low NMR sensitivity of C-13 and the chemical shift anisotropy, respectively. In the present research, CPMAS C-13-NMR spectra were collected by modulating the contact time needed for cross polarization (variable contact times experiments, VCT) on two different humic acids (a soil-HA and a coal-HA). VCT data were fitted by a model containing either a monotonic or a non-monotonic cross polarization term. The non-monotonic model, which fitted the experimental results better than the monotonic one, provided two cross-polarization rates, thereby suggesting that two different mechanisms for the energy transfer from protons to carbons arise in amorphous and heterogeneous humic substances. The first mechanism was a fast proton-to-carbon energy transfer due to protons directly bound to carbons. The second mechanism was related to a slow transfer mediated by local segmental motions. Different domains in the humic acids were identified. Soil-HA was made of rigid domains, containing mainly aromatic and carboxylic moieties, and fast moving domains, containing alkyl, C-O and C-N groups. Coal-HA showed a rigid aromatic domain that was differentiated from a very mobile domain made of alkyl and COOH groups.
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588 _ _ |a Dataset connected to Web of Science
650 _ 7 |a J
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700 1 _ |a Berns, A. E.
|b 1
|u FZJ
|0 P:(DE-Juel1)129438
773 _ _ |a 10.2116/analsci.24.1183
|g Vol. 24, p. 1183 - 1188
|p 1183 - 1188
|q 24<1183 - 1188
|0 PERI:(DE-600)1483376-1
|t Analytical sciences
|v 24
|y 2008
|x 0910-6340
909 C O |o oai:juser.fz-juelich.de:449
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914 1 _ |y 2008
915 _ _ |0 StatID:(DE-HGF)0010
|a JCR/ISI refereed
920 1 _ |k ICG-4
|l Agrosphäre
|d 31.10.2010
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|0 I:(DE-Juel1)VDB793
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