Fabrication of blue-fluorescent nanodiamonds modified with alkyl isocyanate for cellular bioimaging.

•Conjugation of alkyl isocyanate onto nanodiamonds gives their blue fluorescence.•A longer alkyl isocyanate leads to a higher fluorescence intensity.•Conjugation of monomethoxy polyethylene glycol gives water dispersity.•Nontoxic fluorescent nanodiamonds are imaged after cellular uptake.