Identification, quantification and modification of detonation nanodiamond functional groups

Abstract

The chemical composition of the detonation nanodiamond (DND) surface has to be unambiguously known in order to use them for specific applications and to develop strategies of functionalization. To this end, the Boehm titration method was here applied to DNDs of different origins subjected to different purification procedures. This method allows the determination of the oxygenated functional groups present on the surface of carbonaceous materials according to their acidity. The DNDs synthesized at the Institut franco-allemand de recherches de Saint-Louis (ISL) and purified through a two-step method were compared to commercial nanodiamonds. This work proves that the nature of the DND functional groups is very dependent on the history of the post-treatment applied to the nanodiamonds during the purification process of the detonation soot. The nanodiamonds synthesized at ISL and commercial nanodiamonds possess 0.81 COOH sites/nm2 and 0.15 COOH sites/nm2, respectively. However, an oxidation treatment, similar to the one performed on the ISL nanodiamonds, applied to the commercial sample, increases the COOH ratio to 0.80 function/nm2. In addition, the existence of lactone sites was pointed out on oxidized samples, indicating the presence of hydroxyl groups on the surface of untreated nanodiamonds. From experimental values and modelling, it was suggested that these functions are located on the edges of the nanodiamond particles.