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Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Authors/others:Mowbray, Duncan J. (University of the Basque Country) Perez Paz, Alejandro (University of the Basque Country) Ruiz Soria, Rosa GeorginaSauer, MarkusLacovig, Paolo (Elettra Sincrotrone Trieste) Dalmiglio, Matteo (Elettra Sincrotrone Trieste) Lizzit, Silvano (Elettra Sincrotrone Trieste) Yanagi, Kazuhiro (Tokyo Metropolitan University) Goldoni, Andrea (Elettra Sincrotrone Trieste) Pichler, ThomasAyala, Paola (Yachay Tech University) Rubio, Angel (University of the Basque Country)
Abstract:Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O-2 and N-2, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O-2 doses (80 L), the X-ray photoelectron;spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all of the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first-principles density functional theory calculated Kohn-Sham O is binding energies may be used to assign the XPS O is spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O is signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C-2>O), carbonyl (C-2>C=O), and ketene (C=C=O), as ordered by abundance. Upon oxidation of nearly all of the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60% greater than that for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O-2 does not contribute to the measured XPS O is spectra.
Number of pages:7
Date of publication:18.8.2016
Journal title:The Journal of Physical Chemistry Part C (Nanomaterials and Interfaces)
Digital Object Identifier (DOI):http://dx.doi.org/10.1021/acs.jpcc.6b06163
Publication Type:Article
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