An electron paramagnetic resonance, 13C nuclear magnetic resonance and transmission electron microscopic study of ultra-disperse diamond samples was reported. The compounds contained a high concentration of paramagnetic centers (up to 1020spin/g), which were due to structural defects (dangling C–C bonds) on the diamond cluster surface. An anomalous reduction in the spin–lattice relaxation time of 13C (from several hours in natural diamond to about 150ms in ultra-disperse diamond clusters) was attributed to interactions between the unpaired electrons of the paramagnetic centers and nuclear spins. The 13C nuclear magnetic resonance linewidth reflected the fact that the structure of the ultra-disperse diamond surface was distorted in comparison to that of the bulk diamond structure.

Defects and Impurities in Nanodiamonds - EPR, NMR and TEM Study. A.I.Shames, A.M.Panich, W.Kempiński, A.E.Alexenskii, M.V.Baidakova, A.T.Dideikin, V.Y.Osipov, V.I.Siklitski, E.Osawa, M.Ozawa, A.Y.Vul: Journal of Physics and Chemistry of Solids, 2002, 63[11], 1993-2001