Preparation and characterization of carbon nano-onions by nanodiamond annealing and functionalization by radio-frequency Ar/O2 plasma

Identifier:  imarina:5131050

Handle: https://hdl.handle.net/20.500.11797/imarina5131050

Authors:  Bartolome, JP; Fragoso, A

Abstract:
Carbon nanomaterials can be prepared by several methods having in common that need a carbon source and often require high energies. In this study, we report the synthesis and characterization of carbon nano-onions by annealing of commercially available nanodiamonds and explore for the first time their functionalization with a radio frequency Ar/O2 plasma. Heat treatment of nanodiamonds at 1200°C for 6 hours under argon atmosphere afforded small spherical carbon nano-onion particles of 3-4 nm diameter and 5-6 graphitic shells. The prepared CNOs were visualized by HRTEM and showed the characteristic XRD and Raman features. The results have been compared with a sample prepared by annealing at 1600°C. Plasma functionalization in Ar/O2 atmosphere was used to introduce oxygen moieties into the surface of synthesized CNOs. X-ray photoemission spectroscopy showed that oxygen-containing groups like C─O, C═O and O─C═O were introduced on the surface of CNOs, a process that is accompanied by a surface reorganization as evidenced by the change of ID/IG ratios in the Raman spectra, indicating a conversion of sp2 to sp3 as a result of functionalization in the surface of CNO.