Nitrogen impurities and fluorescent nitrogen-vacancy centers in detonation nanodiamonds: identification and distinct features

Abstract

We show that nitrogen is the main impurity contained in detonation nanodiamonds at a concentration of 16,000 ppm. The content of nitrogen-vacancy NV− centers in these nanodiamonds is about 2.7 ppm, which is the largest of all known types of nanodiamonds of size less than 10 nm with artificially created NV− centers. The removal of graphite-like fragments from the nanodiamond surface allowed us to detect the characteristic photoluminescence of the NV− color centers in individual nanodiamond aggregates of sizes from 50–100 to 500–700 nm. We have further confirmed the detection of the negatively charged NV− through the observation of a strong decrease in the photoluminescence intensity when an external magnetic field is applied. Such an effect results from the optically detectable magnetic resonance of the electronic spin triplet ground state of NV− that cannot be observed in other emitting defects in a similar spectral range, including the neutral NV0 centers.