Detection and identification of nitrogen defects in nanodiamond as studied by EPR

Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band and at high-frequency W-band (95 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of similar to 4.5 nm and detonation ND after high-temperature, high-pressure sintering with a size of similar to 8.5 nm. Atomic nitrogen centers N-0 and nitrogen pairs N-2(+) have been detected and identified and their structure has been unambiguously determined by means of the high frequency EPR and ESE in natural diamond nanocrystals. In detonation ND and detonation ND after sintering atomic nitrogen centers N-0 have been discovered in nanodiamond core. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND. (C) 2009 Elsevier B.V. All rights reserved.