The relationship between the unique characteristics of nanodiamonds (NDs) and the fluorescence properties of nitrogen-vacancy (NV) centers has lead to a tool with quantum sensing capabilities and nanometric spatial resolution; this tool is able to operate in a wide range of temperatures and pressures and in harsh chemical conditions. For the development of devices based on NDs, a great effort has been invested in researching cheap and easily scalable synthesis techniques for NDs and NV-NDs. In this review, we discuss the common fluorescent NDs synthesis techniques as well as the laser-assisted production methods. Then, we report recent results regarding the applications of fluorescent NDs, focusing in particular on sensing of the environmental parameters as well as in catalysis. Finally, we underline that the highly non-equilibrium processes occurring in the interactions of laser-materials in controlled laboratory conditions for NDs synthesis present unique opportunities for investigation of the phenomena occurring under extreme thermodynamic conditions in planetary cores or under warm dense matter conditions.

Nanodiamonds (NDs) containing negatively charged Nitrogen-Vacancy (NV) centers are promising materials for applications in photonics, quantum computing, and sensing of environmental parameters like temperature, strain and magnetic fields. However, the production of fluorescent NDs remains a technological challenge, requiring a complex multi-step process involving controlled introduction of substitutional nitrogen into the diamond lattice, annealing and fragmentation from macrocrystals to nanocrystals. Here, we report on a single-step, all-optical process for the production of nanometric-sized fluorescent diamonds based on laser ablation of a carbon substrate at low temperature (100 °C) under a nitrogen atmosphere. We demonstrate that this synthesis route yields fluorescent NDs with a concentration of native NV centers controlled by adjusting the experimental ablation conditions. Spin-polarization dependent optical-transitions are observed by optically detected magnetic resonance spectroscopy, thus providing strong evidence of the presence of negatively charged NV centers in the as-grown NDs. Finally, we propose a thermodynamic model able to describe the nucleation of NDs and the formation of NV centers in the present single-step optical process.