Nanodiamonds (NDs) containing NV color centers exhibit fluorescence in red/near infra-red (NIR) region. The fluorescence in NDs originates from nitrogen vacancies and, unlike quantum dots and organic dyes, NDs do not photobleach. Fluorescent NDs find applications in background-free imaging, flow cytometry, super-resolution imaging etc. Our PEG coated aminated fluorescent nanodiamonds are well suited for conjugation with activated biomolecules where steric hindrance is of concern.