On the route towards a facile fluorescent nanodiamonds laser-synthesis

Research activity on effective production methods of nanodiamonds (NDs) containing controlled number, in specific lattice sites, of negatively charged nitrogen-vacancy (NV−) centers, plays an important role in materials science because of the large number of application fields. Indeed, because of their unique properties, NV-doped NDs have been proposed for applications in bio-imaging, quantum computing, and as nano-sensors for surroundings physical parameters (temperature, electric and magnetic fields, etc.). Here, we demonstrate the production of nanometric-sized fluorescent NDs through pulsed laser ablation (PLA) of a graphite target immersed in liquid nitrogen without the need of any post-process activation. This achievement represents a relevant development compared to the standard synthesis of NV-embedded NDs. Evidence of the NDs formation is given by selected area electron diffraction, while the presence of NV− centers in NDs is proved by optically detected magnetic resonance spectroscopy. Furthermore, a thermodynamic model is reported that explains diamond phase formation in strong undercooling conditions as well as nitrogen doping. Finally, a comparison between present results and our recent findings on pulsed laser deposition of NDs in N2 atmosphere is performed to confirm that a post-process for fluorescence activation is not necessary