  Nano-crystalline diamond is a new carbon phase with numerous intriguing
physical and chemical properties and applications. Small doped nanodiamonds for
example do find increased use as novel quantum markers in biomedical
applications. However, growing doped nanodiamonds below sizes of 5 nm with
controlled composition has been elusive so far. Here we grow nanodiamonds under
conditions where diamond-like organic seed molecules do not decompose. This is
a key first step toward engineered growth of fluorescent nanodiamonds wherein a
custom designed seed molecule can be incorporated at the center of a
nanodiamond. By substituting atoms at particular locations in the seed molecule
it will be possible to achieve complex multi-atom diamond color centers or even
to engineer complete nitrogen-vacancy (NV) quantum registers. Other benefits
include the potential to grow ultrasmall nanodiamonds, wherein each diamond no
matter how small can have at least one bright and photostable fluorescent
emitter.
