Growth of sub-10 nm fluorescent nanodiamonds

Small and rounded-shape fluorescent nanodiamonds (FNDs) are of special interest for many promising applications, especially in biology. It was recently shown multiple times that rounded and small nanodiamonds (NDs) with a size less than 10 nm can easily be grown using hydrothermal growth experiments. As the growth of diamond nanocrystals at mild growth conditions is still controversial, it was important to prove the real diamond growth by creation of color centers that are unique to diamond. In this work, we report a hydrothermal growth of small NDs at low temperatures (220 o C ) and the saturated vapor pressure of water using a simple and available hydrocarbon (glucose). Small and rounded NDs with a size less than 10 nm were grown and then made fluorescent by appropriate ion implantation and post-annealing. In particular nitrogen-vacancy (NV) and silicon-vacancy (SiV) color centers were created in the grown small NDs to validate that the grown crystals are in fact cubic diamond. Because of its simplicity, and ability to grow high-quality diamond, this novel growth technique holds promise for the most demanding applications to biology.