Nanodiamond graphitization: a magnetic resonance study

• Published in: Journal of physics. Condensed matter 2013-06, Vol.25 (24), p.245303-245303
• Main Authors: Panich, A M, Shames, A I, Sergeev, N A, Olszewski, M, McDonough, J K, Mochalin, V N, Gogotsi, Y
• Format: Article
• Language: English
• Subjects: Annealing; Carbon; Condensed matter; Condensed matter: structure, mechanical and thermal properties; Diamonds; Exact sciences and technology; Graphitization; Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals; Nanostructure; Nuclear magnetic resonance; Physics; Spectra; Structure of solids and liquids; crystallography
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/25/24/245303

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. 1H, 13C 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 sp2 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.