Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Author(s)
Duncan J. Mowbray, Alejandro Perez Paz, Rosa Georgina Ruiz Soria, Markus Sauer, Paolo Lacovig, Matteo Dalmiglio, Silvano Lizzit, Kazuhiro Yanagi, Andrea Goldoni, Thomas Pichler, Paola Ayala, Angel Rubio
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 1s binding energies may be used to assign the XPS O 1s 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 1s 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 1s spectra.

Organisation(s)
Electronic Properties of Materials
External organisation(s)
University of the Basque Country, Elettra─Sincrotrone Trieste, Tokyo Metropolitan University, Yachay Tech University, Max Planck Institute for the Structure and Dynamics of Matter, Universität Hamburg
Journal
The Journal of Physical Chemistry Part C (Nanomaterials and Interfaces)
Volume
120
Pages
18316-18322
No. of pages
7
ISSN
1932-7447
DOI
https://doi.org/10.1021/acs.jpcc.6b06163
Publication date
08-2016
Peer reviewed
Yes
Austrian Fields of Science 2012
103018 Materials physics
Keywords
ASJC Scopus subject areas
Electronic, Optical and Magnetic Materials, General Energy, Surfaces, Coatings and Films, Physical and Theoretical Chemistry
Portal url
https://ucrisportal.univie.ac.at/en/publications/77be3d5c-41f4-4dc6-9408-013ede2067d0