Volume 42, Issue 3 p. 303-312
Research Article

Electrochemical functionalisation of SWNTs with poly(3,4-ethylenedioxythiophene) evidenced by anti-Stokes/Stokes Raman spectroscopy

Ioan Baltog

Corresponding Author

Ioan Baltog

Laboratory of Optics and Spectroscopy, National Institute of Materials Physics, P.O. Box MEG-7, Bucharest R-77125, Romania

Laboratory of Optics and Spectroscopy, National Institute of Materials Physics, P.O. Box MEG-7, R-77125 Bucharest, Romania.Search for more papers by this author
Mihaela Baibarac

Mihaela Baibarac

Laboratory of Optics and Spectroscopy, National Institute of Materials Physics, P.O. Box MEG-7, Bucharest R-77125, Romania

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Serge Lefrant

Serge Lefrant

Institut des Materiaux ‘Jean Rouxel’, 2 rue de la Houssinière, B.P. 32229, F-44322 Nantes, France

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Jean Yves Mevellec

Jean Yves Mevellec

Institut des Materiaux ‘Jean Rouxel’, 2 rue de la Houssinière, B.P. 32229, F-44322 Nantes, France

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First published: 21 March 2011
Citations: 16

Abstract

The capability of anti-Stokes/Stokes Raman spectroscopy to evaluate chemical interactions at the interface of a conducting polymer/carbon nanotubes is demonstrated. Electrochemical polymerisation of the monomer 3,4-ethylenedioxythiophene (EDOT) on a Au support covered with a single-walled carbon nanotube (SWNT) film immersed in a LiClO4/CH3CN solution was carried out. At the resonant optical excitation, which occurs when the energy of the exciting light coincides with the energy of an electronic transition, poly(3,4-ethylenedioxythiophene) (PEDOT) deposited electrochemically as a thin film of nanometric thickness on a rough Au support presents an abnormally intense anti-Stokes Raman spectrum. The additional increase in Raman intensity in the anti-Stokes branch observed when PEDOT is deposited on SWNTs is interpreted as resulting from the excitation of plasmons in the metallic nanotubes. A covalent functionalisation of SWNTs with PEDOT both in un-doped and doped states takes place when the electropolymerisation of EDOT, with stopping at +1.6 V versus Ag/Ag+, is performed on a SWNT film deposited on a Au plate. The presence of PEDOT covalently functionalised SWNTs is rationalised by (1) a downshift by a few wavenumbers of the polymer Raman line associated with the symmetric CC stretching mode and (2) an upshift of the radial breathing modes of SWNTs, both variations revealing an interaction between SWNTs and the conjugated polymer. Raman studies performed at different excitation wavelengths indicate that the resonant optical excitation is the key condition to observe the abnormal anti-Stokes Raman effect. Copyright © 2010 John Wiley & Sons, Ltd.