Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Covalent Functionalization of HiPco Single-Walled Carbon Nanotubes: Differences in the Oxidizing Action of H2SO4 and HNO3 during a Soft Oxidation Process
Institut Jean Lamour, Department P2M, UMR 7198 CNRS–Université de Lorraine, Ecole des Mines, 54042 Nancy.
Institut Jean Lamour, CNRS – Nancy Université, Laboratoire de Chimie du Solide Minéral, Nancy Université.
Institut Jean Lamour, CNRS – Nancy Université, Laboratoire de Chimie du Solide Minéral, Nancy Université.
Institut Jean Lamour, Nancy Universite.
Show others and affiliations
2015 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 16, no 12, p. 2692-2701Article in journal (Refereed) Published
Abstract [en]

The results of a study on the evolution of HiPco single-walled carbon nanotubes during the oxidizing action of H2SO4 and HNO3 are presented. The process conditions used have been chosen so as to avoid any significant damage to the nanotube structure. The type and level of functionalization, the location of the grafted functions on the surface of the nanotube and the changes in morphological characteristics of the samples were examined by using a wide and complementary range of analytical techniques. We propose an explanation for the differences in the oxidizing action of sulfuric and nitric acids. The combined results allow us to suggest possible reaction mechanisms that occur on the surface of the nanotube.

Place, publisher, year, edition, pages
2015. Vol. 16, no 12, p. 2692-2701
National Category
Other Physics Topics
Research subject
Experimental physics
Identifiers
URN: urn:nbn:se:ltu:diva-7362DOI: 10.1002/cphc.201500248ISI: 000359906900026PubMedID: 26136373Scopus ID: 2-s2.0-84939252266Local ID: 5bc47731-9547-4a86-99ba-8d3283d0a889OAI: oai:DiVA.org:ltu-7362DiVA, id: diva2:980251
Note
Validerad; 2015; Nivå 2; 20150703 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2019-04-11Bibliographically approved
In thesis
1. Covalent functionalization of carbon nanomaterials for bioelectrochemical applications
Open this publication in new window or tab >>Covalent functionalization of carbon nanomaterials for bioelectrochemical applications
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Kovalent funktionalisering av kolnanomaterial för bioelektrokemiska tillämpningar
Abstract [en]

Carbon nanotubes (CTNs) are renowned for their exceptional electronic and mechanical properties. Their structure can be considered as rolling up a graphene sheet along a specific crystallographic direction, leading to a 1D confinement of the electronic wavefunction of the delocalized electrons along the perimeter of the cylindrical structure thus obtained. This confinement produces the existence of defined spikes of high intensity in the electronic density of states, called van Hove singularities. These singularities are primordial to understand both the optical and electronic properties of CNTs through electronphonon coupling processes. If the electronic density of states (DoS) is non zero at the Fermi level the nanotube is metallic, otherwise the nanotube is semiconducting. The synthesis of CNTs always produces a mixture of both metallic and semiconducting nanotubes, and this material can be useful to be incorporated at the surface of electrodes for electrochemical devices. The high specific surface area, the high mechanical and thermal stability of CNTs and the low percolation threshold for electron transport in a mat of CNTs render them very attractive for such kind of applications. There is yet a drawback of using raw CNTs: they are not compatible with solvents and modification of their surfaces by chemistry is required to make good suspensions for easy deposition at the electrode surface and to introduce specific functional groups for promoting electron transfer, called electron shuttles.

The final aim of this thesis is therefore the covalent functionalization of CNTs by electron shuttles and their incorporation at the surface of glassy carbon electrodes for electrochemical devices application. A strategy of chemical grafting in three steps has been chosen: i) a controlled oxidation step in acidic media assisted by microwave irradiation in order to keep the structural integrity of CNTs, so as to save their useful electronic properties; ii) a chloration step to produce acid chloride groups and iii) reaction of these groups with electron shuttles modified by specific linkers. The study was first conducted on very clean HiPCO single-walled CNTs (SWCNTs). This enabled to avoid any disturbing effects of carbonaceous impurities or residual catalytic particles, since their possible effects are extremely controversial in the literature. Once validated, this approach was then conducted with cheaper material including few-walls carbon nanotubes (FWCNTs). The use of FWCNTs compared to SWCNTs was not only beneficial for the production of costeffective electrochemical devices but also for a better durability ofthe final device, the inner nanotubes being not functionalized.

The challenge was to obtain a functionalization process with enough grafted electron shuttles to obtain a good electrocatalytic activity but maintaining CNTs integrity. The first step is predominant to reach this goal, and requires a very accurate understanding of the nature and the number of defects created in the CNTs structure versus the physico-chemical conditions used. The introduction of defects in the crystallographic structure of CNTs has strong consequences both for the electronic DoS and for the phononic properties of the material. Spectroscopic methods are essential in probing these consequences. UV-visible-near IR absorption spectroscopy is the method of choice to directly probe the existence of van Hove singularities and the oscillator strength associated with the authorized electronic transitions between theses ingularities. Covalent grafting of chemical groups at the surface of CNTs changes both the energy and the intensity of these transitions. However, this spectroscopic method requires solubilizing CNTs in non-absorbing solvents using adequate surfactants. Interactions between surfactant molecules and CNT sidewalls may also alter the position and intensity of electronic transitions between van Hove singularities unrelated to the chemical groups covalently grafted.

Raman spectroscopy of CNTs involves the electronphonon coupling processes through the resonant electronic enhancement of Raman modes. Double resonance processes are also observed in Raman spectrum of CNTs, for instance with the D-band mode that is actually related to the existence of defects in the graphene structure of CNTs. Therefore, Raman spectroscopy is a widespread analytical method to characterize the structural defects created by covalent functionalization processes. Indeed, the intensity ratio of the D and G bands in the Raman spectrum is correlated to the number of defects. However, CNTs are used as bundles when chemical functionalization is performed, which produces a heterogeneous distribution of chemical species grafted on CNTs. Therefore, we have developed a new protocol to obtain statistically significant data for most of the samples made in this thesis. Nevertheless, this statistical approach is still limited for samples slightly functionalized, whence the idea to use spectroscopic ellipsometry as an alternative method to characterize these samples.

More specifically, ellipsometric data were collected from UV to the IR part of the electromagnetic spectrum for CNTs functionalized in different conditions. The complex dielectric function was retrieved from the experimental data. A Drude model was used to model the infrared part of the data for raw and acid oxidized CNTs. The optical conductivity of the samples was obtained. These results, combined with other information collected using a set of complementary analytical techniques (Raman scattering, UV-visible-NIR absorption, X-ray photoelectron spectroscopy, thermogravimetric analysis coupled to mass spectrometry, transmission electron microscopy and rare gas volumetric adsorption), show that the microwave-assisted oxidation process actually consists in removing amorphous carbon deposits away from the surface of CNTs and transforming the already existing defects in the CNT structure to oxygen-containing groups such as carboxylic acids.

Rare gas volumetric adsorption was also used to compare the distribution of chemical groups at the surface of CNT bundles when two different acids are used (HNO3 and H2SO4). The chloration step was also studied by these methods, as well as the final grafting of electron shuttles. Finally, these functionalized CNTs were deposited at the surface of glassy carbon electrodes and used as electron mediators for diaphorase-catalysed oxidation of nicotinamide adenine dinucleotide (NADH). This was a good example of mediated electron transfer for development of electrochemical devices based on NADH recycling and it validated the good electrocatalytic properties of functionalized CNTs for making electrochemical sensors and actuators, opening new perspectives with potential market applications.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-73331 (URN)978-91-7790-342-0 (ISBN)978-91-7790-343-7 (ISBN)
Public defence
E231, Luleå (English)
Opponent
Supervisors
Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2019-04-30Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMedScopus

Authority records BETA

Allali, NaoualSoldatov, Alexander

Search in DiVA

By author/editor
Allali, NaoualSoldatov, Alexander
By organisation
Material Science
In the same journal
ChemPhysChem
Other Physics Topics

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 65 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf