The role of oxygen in a carbon source (castor oil versus paraffin oil) in the synthesis of carbon nano-onions

Annah Makhongoana; Boitumelo J Matsoso; Thomas H Mongwe; Neil J Coville; Daniel Wamwangi; Manoko S Maubane-Nkadimeng

doi:10.1088/1361-6528/abd0b1

The role of oxygen in a carbon source (castor oil versus paraffin oil) in the synthesis of carbon nano-onions

Nanotechnology. 2021 Mar 26;32(13):135603. doi: 10.1088/1361-6528/abd0b1.

Authors

Annah Makhongoana^{1

2}, Boitumelo J Matsoso^{1

2

3}, Thomas H Mongwe^{1

2}, Neil J Coville^{1

2}, Daniel Wamwangi^{1

4}, Manoko S Maubane-Nkadimeng^{1

2

5}

Affiliations

¹ DSI-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, 2050, Johannesburg, South Africa.
² Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, 2050, Johannesburg, South Africa.
³ Laboratoires des Multimatériaux et Interfaces, UMR 5615 CNRS, Université Claude Bernard Lyon 1, F-69622 Villeurbanne Cedex, France.
⁴ Material Physics Research Institute (MPRI) and the School of Physics, University of the Witwatersrand, Johannesburg, 2050, South Africa.
⁵ Microscopy and Microanalysis Unit, University of the Witwatersrand, Johannesburg, South Africa.

PMID: 33276354
DOI: 10.1088/1361-6528/abd0b1

Abstract

The role of a carbon source containing oxygen groups on the physicochemical properties of carbon nano-onions (CNOs) was investigated. Two oils, castor oil (with O groups) and paraffin oil (without O groups) were converted to CNOs in gram-scale yields using an open flame pyrolysis procedure. The products were heated under argon at 900 °C for varying times (1 h, 2 h, 3 h), to investigate the temperature dependence on their structural properties. TGA studies indicated different decomposition behaviour for the different samples with the annealed paraffinic CNOs (CNO_P) having a higher decomposition temperature (>600 °C) than the castor oil derived CNOs (CNO_C) (<600 °C). TEM images revealed formation of typical chain-like quasi-spherical nanostructures with particles size distributions for the CNO_P (22-32 ± 7.8 nm) and the CNO_C (44-51 ± 9.9 nm) materials. A detailed Raman analysis of the CNOs revealed that the graphicity of the CNOs varied with both the carbon oil source and the annealing time. Deconvolution of the first order Raman spectra revealed changes in the parameters of the major Raman bands that were then correlated with defect density ratios. Finally, bandwidth analysis depicted the dependence of the graphicity of the CNOs with heat treatment. The data thus indicate that the presence of oxygen in the carbon source provides a method for producing different CNOs and that simple procedures can be used to produce these different CNOs.