Mass production and dynamic imaging of fluorescent nanodiamonds

Fluorescent nanodiamond is a new nanomaterial that possesses several useful properties, including good biocompatibility 1 , excellent photostability 1 , 2 and facile surface functionalizability 2 , 3 . Moreover, when excited by a laser, defect centres within the nanodiamond emit photons that are capable of penetrating tissue, making them well suited for biological imaging applications 1 , 2 , 4 . Here, we show that bright fluorescent nanodiamonds can be produced in large quantities by irradiating synthetic diamond nanocrystallites with helium ions. The fluorescence is sufficiently bright and stable to allow three-dimensional tracking of a single particle within the cell by means of either one- or two-photon-excited fluorescence microscopy. The excellent photophysical characteristics are maintained for particles as small as 25 nm, suggesting that fluorescent nanodiamond is an ideal probe for long-term tracking and imaging in vivo , with good temporal and spatial resolution.