Early stages of surface graphitization on nanodiamond probed by x-ray photoelectron spectroscopy

Abstract

International audienceReceived 15 September 2011; revised 14 November 2011; published 19 December 2011 We have investigated the early stages of graphitization on detonation nanodiamond during sequential annealing treatments under vacuum using x-ray photoelectron spectroscopy. Two different temperature-dependent regimes were observed. Below 900 °C, the nanodiamond surface reconstructs into graphitic domain but does not alter the diamond core. Above 900 °C, graphitization, i.e., carbon hybridization changes from sp3 to sp2, occurs from the nanodiamond surface toward the diamond core. Graphitization is observed at much lower temperatures on nanodiamonds than on bulk diamond due to the high concentration of structural defects on their surface. These results indicate that low-temperature annealing under vacuum is an efficient method to uncouple surface and bulk graphitization. Hybrid nanocarbons formed in these conditions, constituted of a diamond core with a thin graphitic outer shell, may have interesting catalytic and chemical properties

Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour

“…The C 1s signal of both samples consists of four chemically shifted components: peaks at B284.0 and 285.0 eV corresponding to sp 2 -and sp 3 -hybridized carbon, respectively, and peaks at 286.1 and 287.4-287.7 eV corresponding to various hydrogen and oxygen functionalities including C-H, C-OH, C-O-C and C ¼ O, in order of increasing binding energies. These peak shifts are in agreement with previous studies of nanodiamonds 34,37 . We focused our analysis on the sp 2 and sp 3 carbon peaks that arise from the presence of graphitic and diamond phases, respectively, in the samples.…”

“…Although XPS is generally known to probe the surface of materials, for carbon materials the inelastic mean-free path of C 1s photoelectrons is B3 nm. Thus, the whole volume of small nanoparticles, as in the case of our samples, was probed 34 . The C 1s signal of both samples consists of four chemically shifted components: peaks at B284.0 and 285.0 eV corresponding to sp 2 -and sp 3 -hybridized carbon, respectively, and peaks at 286.1 and 287.4-287.7 eV corresponding to various hydrogen and oxygen functionalities including C-H, C-OH, C-O-C and C ¼ O, in order of increasing binding energies.…”

“…Figure 2c,d shows high-resolution C 1s XPS spectra collected from carbon nanoparticles synthesized with only ethanol vapour and a mixture of ethanol vapour and H 2 gas, respectively. XPS has been previously used to characterize the carbon bonding in a-C 33,35 and nanodiamond powders using C 1s spectra 34,36,37 . Although XPS is generally known to probe the surface of materials, for carbon materials the inelastic mean-free path of C 1s photoelectrons is B3 nm.…”

“…The purity of the diamondphase in the as-synthesized carbon nanoparticles was assessed by X-ray photoelectron spectroscopy (XPS) 33,34 . From survey spectra, the metal content was found to be o0.1% in all samples (Supplementary Table S3 and Supplementary Fig.…”

Diamond-Like Carbon Nanofoam from Low-Temperature Hydrothermal Carbonization of a Sucrose/Naphthalene Precursor Solution

“…XPS has been successfully applied to many different carbon materials [121] such as activated carbon [122], carbon spheres [123], amorphous carbon, nanodiamonds [124], diamond-like carbon films [125], carbon nanotubes [126], or nanoporous carbons [127]. Also, it can be used to study processes such as heat and chemical treatment [128], amorphization [129], electrochemical oxidation [130], or structural deformation [131].…”