Nitrogen-doped carbon spheres: an X-ray absorption near-edge structure spectroscopy study |
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Authors: | Sekhar C Ray Zikhona N Tetana Rudolph Erasmus Way-Faung Pong Neil J Coville |
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Institution: | 1. School of Physics, DST/NRF Centre of Excellence in Strong Materials and Material Physics Research Institute, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa 2. DST/NRF Centre of Excellence in Strong Materials and the Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa 3. Department of Physics, Tamkang University, Tamsui, 251, Taiwan
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Abstract: | Carbon spheres (CSs) and low content nitrogen (2.5 and 3.5 at%) doped carbon spheres (NCSs) were synthesized by a pyrolysis process at 900 °C using $\mathrm{C}_{2}\mathrm{H}_{2}$ and CH3CN. The electronic structure and chemical bonding of CSs and NCSs were studied using Raman spectroscopy, valence-band photoemission spectroscopy (VBPES) and X-ray absorption near-edge structure spectroscopy (XANES). XANES spectroscopy showed the effect of carbon and nitrogen bonds and graphitic as well as pyridinic structures on the NCS structure. For the spheres VBPES showed the effect of nitrogen on the spectral shape of the density of states and confirmed the role played by the $\pi$ bonds in controlling the electronic and structural properties of the NCSs. VBPES also showed that both $\pi$ and $\sigma$ bands shift towards higher binding energies after N-doping which is consistent with the XANES data. The consistency of the spherical geometry, chemical purity, suitable electronic/bonding structure and the availability of macroscopic quantities of the N–CSs makes these spheres promising new materials for different applications. |
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