151 research outputs found
Nuclear Magnetic Resonance Study of Ultrananocrystalline Diamonds
We report on a nuclear magnetic resonance (NMR) study of ultrananocrystalline
diamond (UNCD) materials produced by detonation technique. Analysis of the 13C
and 1H NMR spectra, spin-spin and spin-lattice relaxation times in purified
UNCD samples is presented. Our measurements show that UNCD particles consist of
a diamond core that is partially covered by a sp2-carbon fullerene-like shell.
The uncovered part of outer diamond surface comprises a number of hydrocarbon
groups that saturate the dangling bonds. Our findings are discussed along with
recent calculations of the UNCD structure. Significant increase in the
spin-lattice relaxation rate (in comparison with that of natural diamond), as
well as stretched exponential character of the magnetization recovery, are
attributed to the interaction of nuclear spins with paramagnetic centers which
are likely fabrication-driven dangling bonds with unpaired electrons. We show
that these centers are located mainly at the interface between the diamond core
and shell.Comment: 25 pages, 7 figure
Caracterização de adubos orgânicos por espectroscopia de ressonância paramagnética eletrônica
Interpretation of the13C NMR spectra of thirteen methoxycarbonylpyridines and some of their derivatives
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United States Bureau of Mines Bulletin 649
From Introduction: "The present study was undertaken as the initial phase of the investigation of substituent effects on the carbon shieldings in 6-membered- and 5-membered-ring heterocyclic modules.
Study of Paramagnetic Centers in Natural and Solvent Refined Coal by Multifrequency ESR, Endor and ESE Modulation Spectroscopy
EPR Study of Excited Triplet States and Interactions between the Molecular Phases in Coal
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