Defects and impurities in nanodiamonds: EPR, NMR and TEM study

EPR, C-13 NMR and TEM study of ultradisperse diamond (UDD) samples is reported. The compounds show a high concentration of paramagnetic centers (up to 10(20) spin/g), which are due to structural defects (dangling C-C bonds) on the diamond cluster surface. The anomalous reduction in the spin-lattice relaxation time of C-13 (from several hours in natural diamond to similar to 150 ms in UDD clusters) is attributed to the interaction between the unpaired electrons of the paramagnetic centers and nuclear spins. C-13 NMR line-width reflects the fact that the structure of the UDD surface is distorted in comparison to the 'bulk' diamond structure. (C) 2002 Elsevier Science Ltd. All rights reserved.