Generation of nitrogen-vacancy color center in nanodiamonds by high temperature annealing

We make use of inherent vacancies and nitrogen substitutions in nanodiamonds to generate nitrogen-vacancy (NV) centers by high temperature annealing. After 800 °C annealing, low temperature photoluminescence intensity of nanodiamonds shows more than eight times improvement compared with that of unannealed samples. Confocal microscope images of well dispersed nanodiamonds indicate a dramatically increased proportion of nanodiamonds containing NV centers after annealing. Optically detected magnetic resonance spectrum of single NV center demonstrates that the resultant nanodiamonds are suitable for further application as magnetic field sensor. The annealing-oxidation method could be an attractive option for NV center generation in nanodiamonds.