Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Journal Of Physical Chemistry C 120 (32), pp 18316–18322 (2016)

Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Duncan J. Mowbray,Alejandro Pérez Paz, Georgina Ruiz-Soria, Markus Sauer, Paolo Lacovig, Matteo Dalmiglio, Silvano Lizzit, Kazuhiro Yanagi, Andrea Goldoni, Thomas Pichler, Paola Ayala, Angel Rubio

Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O2 and N2, 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 O2 doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all 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 (C2>O), carbonyl (C2>C=O),and ketene (C=C=O), as ordered by abundance. Upon oxidation of nearly all the SWCNT’s vacancies, the central peak’s intensity for the metallic SWCNT sample is 60% greater than 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 O2 does not contribute to the measured XPS O 1s spectra.

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D.J.M. acknowledges funding through the Spanish “Juan de la Cierva” program (JCI-2010-08156). A.P.P. acknowledges funding through the Proyecto Diputación Foral de Gipuzkoa (Q4818001B), “Ayuda para la Especialización de Personal Investigador del Vicerrectorado de Investigación de la UPV/EHU–2013”, and the Spanish “Juan de la Cierva-incorporación” program (IJCI-2014-20147).P.A. was supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme. A.G. thanks the COST ACTION EuNetAir (n. TD1105). We acknowledge funding by European Projects DYNamo (ERC-2015-AdG-694097), POCAONTAS (FP7-PEOPLE-2012-ITN-316633),MOSTOPHOS (GA no. 646259), and EUSpec (COST Action MP1306); Spanish Grants (FIS2013-46159-C3-1-P) and “Grupos Consolidados UPV/EHU del Gobierno” (IT-578-13); and the Air Force Office of Scientific Research (AFOSR) (FA2386-15-1-0006 AOARD 144088). This work was supported by the Austrian Science Fund through project FWF P21333-N20, FWF P27769-N20, and FWF NanoBlends I 943-N19 and by the EU Proposal No 20105285 for ELETTRA.

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