Fig. 3

Spectral characterization of irradiated 35-nm and 150-nm nanodiamonds (NDs). a–c reveals how increased radiation damage a, b lowers relative fluorescence intensities c with increasing irradiation time in a nuclear reactor: a Content of sp³ carbon, b Raman spectra (for complete set of Raman spectra for all irradiation times, see Supplementary Figure 6), c Relative fluorescence intensity. d The average Gaussian NV^– ZPL linewidths⁵⁷ measured at temperature of 4 K and the zero-magnetic-field splitting of the optically detected magnetic resonance (ODMR) dip for 150 nm ND [n-α], electron-irradiated NDs (150 nm ND [e^–]), and electron-irradiated commercially available NDs (100 nm ND [e^–]). The error bars indicate the standard deviation between values obtained for individual particles or particle aggregates (for spectra see Supplementary Figure 13). e Comparison of photoluminescence spectra of samples irradiated in a nuclear reactor [n-α] with samples irradiated in a cyclotron with protons [p⁺] or α particles [α]. For spectral measurements, the NDs were drop casted on a silicon wafer. The values of the x-axes in (a, c) are expressed as either irradiation time or the overall radiation damage expressed as dpa, which corresponds to the number of vacancies formed in NDs in our sample obtained from SRIM simulation (see Methods). The intensities in (c) are normalized to the diamond Raman band (the values are quantitatively comparable). The spectra in (e) are normalized at their maxima. Vertical dash lines labeled ZPL denotes the zero phonon line of the NV⁻ (wavelength 637 nm) and NV⁰ (wavelength 575 nm) color center.