Synthetic Metals 155 (2005) 666–669 SERS, FT-IR and photoluminescence studies on single-walled carbon nanotubes/conducting polymers composites  S. Lefrant a,∗ , M. Baibarac a,b , I. Baltog b , C. Godon a , J.Y. Mevellec a , J. W´ ery a , E. Faulques a , L. Mihut b , H. Aarab a , O. Chauvet a a Institut des Mat´ eriaux Jean Rouxel, Lab. de Physique Cristalline, 2 rue de la Houssini` ere, B.P. 32229, 44322 Nantes, C´ edex 03, France b National Institute of Materials Physics, Laboratory of Optics and Spectroscopy, Bucharest, P.O. Box MG-7, R-77125, Romania Received 28 June 2004; received in revised form 17 January 2005; accepted 15 August 2005 Available online 7 November 2005 Abstract Surface-enhanced Raman scattering (SERS), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopies were used to investigate composites based on single-walled carbon nanotubes (SWNTs) and different conducting polymers like polyaniline (PANI), poly- paraphenylene vinylene (PPV) and poly 3-hexylthiophene (3-PHT). In the case of SWNTs/PANI, different composites are obtained by adding dispersed SWNTs powder to the polymer solutions and by chemical polymerization of aniline in presence of SWNTs. The difference originates in the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs in fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FT-IR spectra of the composites PANI/SWNTs and PANI/C 60 , chemically synthesized. Electrochemical polymerization of aniline in an HCl solution on a SWNT film leads to a covalent functionalization of SWNTs with PANI. In this case, Raman scattering data suggest an additional nanotubes roping with PANI as a binding agent. A post treatment with the NH 4 OH solution of polymer-functionalized SWNTs involves an internal redox reaction between PANI and carbon nanotubes. As a result, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. In the case of PPV and 3-PHT, the effect of the concentration of SWNTs on the photoluminescence properties will be described and compared, as probes of interaction. © 2005 Elsevier B.V. All rights reserved. Keywords: Infrared and Raman spectroscopy; Photoluminescence; Polyaniline and derivatives; Polythiophene and derivatives; Poly(phenyene vinylene) and deriva- tives; Graphite and related compounds 1. Introduction Detailed investigation of the physical and chemical properties of conducting polymers/carbon nanotubes (CPs/CNT) compos- ites are of interest nowadays, because these materials have a great potential in technological applications such as: plastic transitors and logic gates, organic light emitting diodes, photovoltaic cells, antistatic coatings, field-effect transistors, etc. In this paper, we show by SERS and FT-IR spectroscopy that depending on the synthesis way used, i.e. (i) adding CNT powder to the polymer solution (M samples), (ii) chemical poly-  Based on presentation at the International Conference on Synthetic Metals, Wollongong, Australia, June 28–July 2, 2004 (ICSM 2004). ∗ Corresponding author. Tel.: +33 240 373 910; fax: +33 240 373 991. E-mail address: Serge.Lefrant@cnrs-imn.fr (S. Lefrant). merization of monomer in the presence of CNT (S samples) and (iii) electropolymerization of aromatic compounds on the CNT films (EC samples), different composites are obtained. The modification of PL spectra of composites PPV/SWNTs and 3-PHT/SWNTs, induced by the filling of the polymer with SWNTs, was investigated too. 2. Experimental PANI/SWNT, 3-PHT/SWNT and PPV/SWNT composites were prepared in accordance with procedures previously reported [1–3]. SERS spectra were recorded in a backscatter- ing geometry with the 676 and 1064 nm excitation wavelengths using a Jobin Yvon T64000 Raman-spectrophotometer and a FT Raman Bruker RFS 100 spectrophotometer, respectively. FT-IR and PL spectra were acquired with a Bruker IFS 28 0379-6779/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2005.08.026