Figure 1.

(A) DRIFT spectra of the OX- and H-NDs. (B) OX- and H-ND PL spectra. The spectra labelled as “18 H2” and “18 H1”, which are referred to the 18 nm NDs (see Table 1), were multiplied by 10 to render them visible on the same scale as the other ones. NV⁰ and NV⁻ zero-phonon lines are marked with black dashed lines. The Raman first-order peak of diamond, appearing in PL spectra at ~572.5 nm, is instead evidenced by a black star.