Surface graphitization of ozone-treated detonation nanodiamonds

Abstract

International audienceBifunctional detonation nanodiamonds (NDs) were obtained by vacuum annealing at 750 °C of NDs previously oxidized in ozone (ND-ozone). Raman investigations demonstrate a significantly higher amount of sp2 carbon compared to ND with polyfunctional surface (ND-NRI) annealed in vacuum under the same conditions. In addition to sp2 carbon caps, thermal desorption mass spectroscopy analysis revealed a higher oxygen concentration at the ND-ozone surface with abundant carbonyl and carboxylic acid anhydride groups. The supernatant of ND-ozone annealed in vacuum exhibits a positive zeta potential (+50 mV at pH 6.5), while the starting sample has a high negative zeta potential (−60 mV). This supports the oxygen hole-doping model previously proposed to explain the positive zeta potential of NDs after vacuum annealing

New Insights into the Reactivity of Detonation Nanodiamonds during the First Stages of Graphitization

“…The exodiffusion of hydrogen from the DND core was strengthened by a previous TDMS study performed on annealed DND. Hydrogen release was detected starting at 800 • C and raising up to 1000 • C [57]. To resume, we suggest here that the annealing of DND (at least from 800 • C) is accompanied by a thermodesorption of hydrogen initially trapped in the core, which induces the creation of CH x functions through a catalytic pathway already described elsewhere [58].…”

Hydroxyl radical production induced by plasma hydrogenated nanodiamonds under X-ray irradiation

“…. Mass treatments (air or vacuum annealing, wet chemistry and plasma activation) leading to oxidised 11 , hydrogenated 3 and graphitised 12 NDs have been mostly explored as well as NDs corresponding properties and behaviours 10,13 . Focusing only on the hydrogen-terminated surface, homogenisation of the NDs introduced via annealing or plasma treatment leads to a modification of their colloidal properties 3,14 resulting in positive zeta potential (ZP) in aqueous solution 5 providing colloidal stability 5,15,16 .…”

Nanodiamonds: From Synthesis and Purification to Deposition Techniques, Hybrids Fabrication and Applications

“…The proposed model corresponds to a surface mechanism of charge transfer occurring between adsorbed oxygen molecules and electron-enriched FLRs via an electron transfer from the diamond core. This model was supported by a recent study combining ozone treatment and graphitization of detonation NDs [90]. Moreover, X-ray absorption and emission spectroscopies directly performed in a microjet demonstrate the presence of valence holes for NDs dispersed in water (Fig.…”

“…A second challenge concerns the combination of surface treatments to reach hybrid surface chemistries. This was recently reported for detonation NDs combining ozone treatment and surface graphitization [90]. Seeding techniques may be applied to 3D substrates to synthetize diamond foam or porous materials [105,228,229].…”