Fluorescent nanodiamonds
(FNDs) containing nitrogen-vacancy (NV)
centers as built-in fluorophores exhibit a nearly constant emission
profile over 550–750 nm upon excitation by vacuum-ultraviolet
(VUV), extreme ultraviolet (EUV), and X-radiations from a synchrotron
source over the energy (wavelength) range of 6.2–1450 eV (0.86–200
nm). The photoluminescence (PL) quantum yield of FNDs increases steadily
with the increasing excitation energy, attaining a value as great
as 1700% at 700 eV (1.77 nm). Notably, the yield curve is continuous,
having no gap in the VUV to X-ray region. In addition, no significant
PL intensity decreases were observed for hours. Applying the FND sensor
to measure the absorption cross-sections of gaseous O2 over
110–200 nm and comparing the measurements with the sodium-salicylate
scintillator, we obtained results in agreement with each other within
5%. The superb photostability and broad applicability of FNDs offer
a promising solution for the long-standing problem of lacking a robust
and reliable detector for VUV, EUV, and X-radiations.