Commercial quantities of ultrasmall fluorescent nanodiamonds containing color centers

Optically active nanodiamond particles remain one of the most popular research topics due to the photoluminescent properties of crystallographic defects in the diamond lattice, referred to as color centers. A number of groups are currently undertaking efforts to commercialize this material. Recently, our group succeeded in large-scale production of fluorescent diamond particles containing nitrogen-vacancy (NV) color centers in hundred-gram per batch scales using irradiation with 2-3 MeV electrons. Production of ND-NV fractions with median sizes ranging between 10 nm and 100 nm was achieved. While 100 nm fluorescent nanodiamonds (FNDs) are ∼10x brighter than a conventional dye (Atto 532), the brightness of FNDs drops with decreasing particle size. Because of this, significant efforts must be undertaken to elucidate the size/brightness compromise and identify relevant application niches for FND in bioimaging and biolabeling. In order for a new material to be considered for applications in the overcrowded optical reagent market, the reagent must be convenient to use by an end user from the biomedical community, be validated both in vitro and in vivo, and offer measurable and significant (rather than incremental) benefit to end users in specific applications. This paper reports on the characteristics of the ultrasmall (10-40nm) and larger fluorescent nanodiamonds as well as our efforts toward their adaptation for use in the biological science community.