Redox and Organic Post-Annealing Chemical Processes Impacting the Fluorescence of N V (-) Centers into Nanodiamonds

Among the several aspects involved into the synthesis of monocharged nitrogene-vacancy N V (-) colored centers produced into nanodiamonds ND, the post-annealing cleaning process, such as sulfo-nitric acid cleaning or thermal oxidation under acid conditions, can be seen as a factor impacting the optical response of these N V (-) colored centers. A significative difference of optical response is in fact noticed modifying the post-annealing treatment conditions, between a pure oxidative treatment at room temperature and a mixed-process including oxidation and thermal activation. Specific chemical processes and surface chemical aspects are proposed to explain the optical signals obtained by fluorescence. Some chemical pathways are then found more efficient than others to limit the fluorescence quenching of these colored N V (-) emitters.