Nanodiamond graphitization: a magnetic resonance study

Abstract

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. (1)H, (13)C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp(2) carbon content with increased annealing temperature. Such quantitative experimental data were recorded for the first time. These findings correlate with EPR data on the sensitivity of the dangling bond EPR line width to air content, progressing with rising annealing temperature, that evidences consequent graphitization of the external layers of the diamond core. The sample annealed at 1800 ° C shows complete conversion of nanodiamond particles into carbon onions.

Surface Modifications of Nanodiamonds and Current Issues for Their Biomedical Applications

“…These results were recently confirmed by a Raman study of the sp 3 to sp 2 conversion for detonation NDs [160]. NMR and EPR investigations detect the early stages of graphitization for annealing temperatures included between 600 and 800°C [161].…”

“…Recently, several groups focused on the early stages of surface graphitization of detonation NDs using XPS, HRTEM, Raman or NMR characterizations [55,75,99,160,161]. The aim is to control the formation of hybrid nanoparticles with a sp 2 organized surface covering a sp 3 core, thus avoiding the graphitization of the diamond core.…”

Carbon Nano‐Onions: A Review of Recent Progress in Synthesis and Applications

“…The formation of spherical CNOs was investigated by several experimental methods, such as Raman spectroscopy,, solid state 13 C nuclear magnetic resonance spectroscopy,, and X‐ray emission and X‐ray diffraction (XRD) studies ,. Raman spectroscopic study of spherical CNOs and comparisons of their spectroscopic properties to diamond and graphite were performed ,.…”

Solid‐phase synthesis, characterization, and cellular activities of collagen‐model Nanodiamond‐peptide conjugates

“…ND bearing free carboxylic acid groups was produced by air oxidation as described 29 followed by boiling in aqueous HCl and HNO 3 to remove metal impurities. 30 Synthesis of a1(I)fTHP [(Gly-Pro-Hyp) 4 -Gly-Ala-Arg-Gly-Glu-Arg-Gly-Phe-Hyp-Gly-Glu-Arg-(Gly-Pro-Hyp) 4 -Gly-Pro-Lys(5-Fam)-NH 2 , where Hyp5 4-hydroxyproline and 5-Fam 5 5-carboxyfluorescein] and a control peptide a1(V)THP [(Gly-Pro-Hyp) 4 -Gly-Pro-Pro-Gly-Val-Val-Gly-Glu-Gln-Gly-Glu-Gln-(Gly-Pro-Hyp) 4 ] followed N a -(9-fluorenylmethoxycarbonyl) (Fmoc) chemistry procedures well established in our laboratory. 31,32 Peptides were assembled using NovaPEG Rink amide resin (substitution level 5 0.48 mmol g 21 ) on the Liberty automated microwave assisted peptide synthesizer (CEM, Matthews, NC) equipped with a Discover microwave module.…”