Nanocomposites

(version française)

Nanostructures, Nanocomposites

Carbon Nanotubes

Leaders :

Serge Lefrant (PR) , Jean-Pierre. Buisson (CR)

Participants:

Jean-Yves Mevellec (IR)
Han Athalin (CDD)

Summary:

Context
a) Developing the SERS technique (Surface Enhanced Raman Scattering)
b) The discovery of a CARS effect (Coherent Anti-Stokes Raman Scattering)
c) Covalent functionalization of nanotubes
d) Boron Nitride (BN) nanotubes
Main collaborations
Publications
Recent Publications

Context

Since the first observation of carbon nanotubes in 1991 by Iijima, carbon nanotubes have been extensively studied, by means of transmission electronic microscopy on one hand, and by Raman spectroscopy on the other hand. In our Institute, this latter characterization technique has been developed by using several excitation wavelengths, putting in evidence the semi-conducting or the metallic character of single-walled nanotubes (SWNTs). As a matter of fact, if one refers to the so-called “Kataura diagram”, the laser excitation selectively fulfils resonance conditions with allowed optical transitions. On figure 1 for example, we show the absorption spectrum of single-walled nanotubes prepared by the “electric arc” method. This spectrum exhibits absorption bands of semi-conducting nanotubes E₁₁^s and E₂₂^s, as well as the band E₁₁^m of metallic nanotubes. The three arrows indicate the three laser lines currently used as excitation (514.5 nm, 676.4 nm et 1064 nm) allowing to evidence the selectivity of this spectroscopy with respect to the metallic or semi-conducting character of the nanotubes.

Figure 1

Figure 1 : Absorption spectrum of single-walled nanotubes prepared by the ”electric arc” synthesis. The three arrows indicate the three laser lines currently used as excitation for Raman scattering (514.5 nm, 676.4 nm and 1064 nm).

On figure 2, the main features of Raman spectra are presented. On one hand, « G » modes or tangential modes around 1580 cm^-1 exhibit different profiles according to the electronic nature of the tubes : sharp and splitted in the case of semi-conducting nanotubes, broader and asymmetric, (Breit-Wigner-Fano profile) in the case of metallic tubes. This result is a consequence of the resonance conditions mentioned above.

Figure 2 : Raman spectra of carbon single-walled nanotubes prepared by the “electric arc” synthesis. Top curve, for an excitation wavelength of 514.5 nm ;

Bottom curve, for an excitation wavelength of 676.4 nm.

Figure 2 top

Figure 2 bottom

The energy of the allowed optical transitions is inversely proportional to the nanotubes diameters and the absorption bands are in fact an envelope of the individual bands weighted by their number in the diameter distribution. This is the reason why in HiPco nanotubes for example, for which diameters are shifted towards smaller values, the metallic character of the tubes will be put in evidence by using an excitation wavelength different from the one used for “electric arc” tubes. In order to do so, we have used a 561 nm wavelength issued from a solid diode laser.

Another important frequency range is that of the radial breathing modes (RBM) at lower frequencies. They allow in principle to determine the diameter distributions since their frequency is inversely proportional to the inverse of the tube diameter, provided we can evaluate correctly the impact of the environment. To achieve this goal, we have carried out theoretical calculations in order to evaluate Van der Waals interactions between single-walled nanotubes and therefore their influence on the low frequency modes whenever they are in bundles. A similar analysis has allowed us also to interpret low frequency modes in multi-walled nanotubes.

These two particular features are of primary importance whenever the behaviour of nanotubes is concerned in specific conditions such as the incorporation in composites, or whenever tubes are submitted to chemical treatments (functionalization), dispersed in liquids, or simply when they originate from different syntheses.

Beyond the objectives of characterizing SWNTs, Raman spectroscopy has been extensively developed in our group in order to determine the Raman signature of individual tubes. This is what is illustrated in the following sections:

a) Developing the SERS technique (Surface Enhanced Raman Scattering)

The search for the Raman features of individual nanotubes needs adapted tools, especially in optics, such as Near-Field Raman Spectroscopy called SNOM-Raman (SNOM for Scanning Near-Field Optical Microscopy) or selective confocal Raman scattering. Furthermore in order to amplify the scattered signal, the SERS technique has been extensively used. It consists in depositing a thin layer of material on a rough surface made of gold or silver and therefore, one can benefit from a huge amplification of the electromagnetic field by a coupling with surface plasmons. We could therefore in this way put in evidence :

interactions between nanotubes and the SERS surface leading to the breaking of nanotubes and the formation of particles of fullerene type;
solid-solid interactions in the case of nanotubes imbedded in different host matrices;
the transformation of single-walled nanotubes submitted to a sulfuric acid treatment;
the functionalization of nanotubes in composites nanotubes/ conjugated polymers.

b) The discovery of a CARS effect (Coherent Anti-Stokes Raman Scattering)

The SERS mechanism can also induce a phenomenon of wave mixing known as CARS. It occurs via a coupling between the exciting light and the Stokes emission. It provides an explanation for the abnormal intensity observed in anti-Stokes Raman scattering which does not follow the usual rules of intensity calculated from the level population described by the Maxwell-Boltzman law. Although the phenomenon is not specific to carbon nanotubes, it allows a correct interpretation of the quadratic behaviour of the anti-Stokes emission as a function of the laser excitation power.

This interpretation is not in agreement with previously proposed mechanisms implying an overpopulation of the vibrational excited states induced by the high photon density received by the nanotubes, combined with an increase of the Raman scattering cross section. Also, double resonance mechanisms have been invoked to explain the abnormal intensity of the anti-Stokes emission. Our experiments fulfil all the criteria encountered for a CARS mechanism.

More recently, by using two laser lines at 676.4 nm et 1064 nm, we have been able to put in evidence a different behaviour for the RBM bands associated to individual nanotubes one one hand and to bundles on the other hand. This effect only occurs for semi-conducting tubes. It can be seen as an apparent “cooling” and “heating” effect of isolated tubes and bundled tubes respectively, by comparison to the thermodynamic equilibrium described by the Maxwell-Boltzman law. This effect is not seen for metallic tubes.

c) Covalent functionalization of nanotubes

In collaboration with the CIMMA in Angers, we have started Raman studies of single-walled nanotubes covalently functionalized with carbon chains of different lengths. The goal is to prepare soluble samples with specific properties, in particular in the photovoltaic domain. Raman studies, coupled to XPS and TGA measurements and performed on both HiPco and “electric arc” samples have first confirmed the efficiency of the different chemical steps leading to the functionalization of nanotubes. Secondly, they have led to the determination without ambiguity of the modifications of the Raman spectra, evidenced by frequency shifts and the lost of the metallic character of the metallic tubes.

d) Boron Nitride (BN) nanotubes

Finally, we have actively participated to the experimental Raman studies on BN nanotubes synthesized at LEM of ONERA (Chatillon, France). This project is part of an INTAS programme (coordinated by A. Loiseau at ONERA) with russian teams in Moscow and Novossibirsk.

Main collaborations :

Baltog, M. Baibarac, L. Mihut , National Institute of Materials Physics, Lab. Optics & Spectroscopy, Bucarest - Magurele, MG-7, R-77125, Roumanie
E. Mulazzi, R. Perego, Dipartimento di Fisica, Universitá degli Studi di Milano
Via Celoria, 16, 20133 Milano, Italie
A. Loiseau, R. Arenal de la Conche, LEM, ONERA, Viry Chatillon, France
J. Cousseau et C. Bergeret, laboratoire CIMMA, Angers, France

Publications:

Book Chapters

1. Raman and SERS study of carbon nanotubes, dans « Spectroscopy of Emerging Materials »
S. Lefrant, J.P. Buisson, J. Schreiber, J. Wéry, E. Faulques, O. Chauvet, M. Baibarac, I. Baltog
Eds. E. Faulques, D.L. Perry, A.V. Yeremenko, Kluwer Academic Publishers, NATO Science Series II Mathematics, Physics and Chemistry- vol.165 (Dordrecht), pp. 127-138 (2004).

2. Surface Enhanced Raman Scattering of Carbon-based nanomaterials
BALTOG I., BAIBARAC M. and LEFRANT S.
Second Edition of the "Encyclopedia of Nanoscience and Nanotechlogy, J. of Nanoscience and nanotechnoly, Ed. Nalwa in press (2007)

Invited Review Article

1. Surface-enhanced Raman scattering studies on chemically transformed carbon nanotube thin films
LEFRANT S., BALTOG I., BAIBARAC M.
J. Raman Spectrosc., 36, 676-698, 2005

Recent Publications

1. Covalent functionalization of single-walled carbon nanotubes by aniline electrochemical polymerization
Baibarac M., Baltog I., Godon C., Lefrant S., Chauvet O.
Carbon 42, 3143-3152, 2004

2. SERS spectroscopy studies on the electrochemical oxidation of single-walled carbon nanotubes in sulfuric acid solutions
LEFRANT S., BAIBARAC M., BALTOG I., MEVELLEC J.Y., MIHUT L., CHAUVET O.
Synth. Met., 144, 133-142, 2004

3. SERS spectra of polyaniline/carbon nanotubes and polyaniline/fullerene composites
BAIBARAC M., BALTOG I., LEFRANT S., MEVELLEC J.Y., CHAUVET O.
Mol. Cryst. Liquid Cryst., 415, 229, 2004

4. Raman studies of carbon nanotubes ans polymer nanotube composites
LEFRANTS., BUISSON J.P., SCHREIBER J., CHAUVET O., BAIBARAC M., BALTOG I.
Mol. Cryst. Liquid Cryst., 415, 125, 2004

5. Analysing one isolated single walled carbon nanotube in the near-field domain with selective nanovolume Raman spectroscopy
ATALAY H., LEFRANT S.
J. of Nanoscience and Nanotechnology, Vol. 4, N0 7, 2004
SERS, FTIR, and photoluminescence studies on single-walled carbon nanotubes/conducting polymers composites,
LEFRANT S., BAIBARAC M., BALTOG I., GODON C., MEVELLEC J.Y., WERY J., FAULQUES E., MIHUT L., AARAB H., CHAUVET O.
Proc. International Conference on Science and Technology of Synthetic Metals, 2004, CD Rom ISBN .1 741280613

6. Electrochemical functionalisation of single walled carbon nanotubes with polyaniline evidenced by Raman and FTIR spectroscopy
LEFRANT S., BAIBARAC M., BALTOG I., GODON C., MEVELLEC J.Y., CHAUVET O.
in Electronic Properties of Synthetic Nanostructures,
Eds H. Kuzmany, J. Fink, M. Mehring, S. Roth, AIP Conf. Proc. 2004, 723, 201

7. Raman and SERS studies of carbon nanotubes
LEFRANT S., BUISSON J.P., SCRREIBER J., WERY J., FAULQUES E., CHAUVET O., BAIBARAC M.and BALTOG I.
in "Frontiers in Spectroscopy of Emergent Materials", Kluwer Ac. Publ., NATO Science Series, 127-138, 2004

8. A correlated method for quantifying mixed and dispersed carbon nanotubes : analysis of the Raman band intensities and evidence of wavenumber shift
ATHALIN H., LEFRANT S.,
J. Raman Spectrosc., 36, 400-408, 2005

9. Imaging and mapping of individual nanoparticles and nanotubes by selective nanovolume Raman spectroscopy
ATHALIN H., LEFRANT S.,
International Journal of Nanosciences, 4, 31-44, 2005

10. Optically addressable selective nanovolume Raman spectroscopy of nanoparticles
ATHALIN H., LEFRANT S.,
Journal of Nanoparticles Research, 7, 89-93, 2005

11. Electrochemical and vibrationnal properties of single-walled carbon nanotubes in hydrochloric acid solutions
LEFRANT S., BAIBARAC M., BALTOG I. , VELULA T., MEVELLEC J.Y., CHAUVET O.
Diam. Relat. Mat, 14, 873-880, 2005

12. Functionalization of single-walled carbon nanotubes with conducting polymers evidenced by Raman and FTIR spectroscopy
LEFRANT S., BAIBARAC M., BALTOG I., MEVELLEC J.Y., GODON C.,CHAUVET O.
Diam. Relat. Mat., 14, 867-872, 2005

13. Mechanico-chemical interaction of single-walled carbon nanotubes with different host matrices evidenced by SERS spectroscopy
BAIBARAC M., BALTOG I., LEFRANT S., GODON C, MEVELLEC J.Y.
Chem. Phys. Lett., 406, 222-227, 2005

14. Coherent anti-Stokes Raman scattering on single-walled carbon nanotubes and copper phthalocyanine thin films excited through surface plasmons
BALTOG I., BAIBARAC M., LEFRANT S.
J. Opt. A-Pure Appl. Opt., 7, 632-639, 2005

15. SERS, FT-IR and photoluminescence studies on single-walled carbon nanotubes/conducting polymers composites
LEFRANT S., BAIBARAC M., BALTOG I., GODON C., MEVELLEC J.Y., WERY J., FAULQUES E., MIHUT L., AARAB H., CHAUVET O.
Synth. Met., 155, 666-669, 2005

16. Mechanico-chemical interaction of single-walled carbon nanotubes with different host matrices evidenced by SERS spectroscopy
LEFRANT S., BAIBARAC M., BALTOG I., GODON C., MEVELLEC J.Y., MIHUT L.
Proc. SPIE Int. Soc. Opt. Eng. 5838, p105-113 in Nanotechnology II, 2005

17. Coherent anti-Stokes Raman scattering on single-walled carbon nanotube thin films excited through surface plasmons
BALTOG, I., BAIBARAC, M., LEFRANT, S.
Phys. Rev. B, 72(24), pp. 1-11, 2005

18. Spectroscopic studies on nanocomposites obtained by functionalization of carbon nanotubes with conducting polymers
LEFRANT, S., BAIBARAC, M., BALTOG, I.
Mol. Cryst. Liquid Cryst, 447, 75/[393]-85/[403], 2006

19. Mechanico-chemical interaction of SWNTs with different host matrices evidenced by SERS spectroscopy
LEFRANT, S., BAIBARAC, M., MIHUT L., BALTOG, I.
Phys. Status Solidi B-Basic Solid State Phys., 1-5, 2006

20. Evidence of temperature dependent charge migration on conjugated segments in poly_p-phenylene vinylene and single-walled carbon nanotubes composite films
MULAZZI, E., PEREGO, R., WERY, J., MIHUT, L., LEFRANT, S., FAULQUES, E.
J. Chem. Phys. 125, 014703, 2006

21. Raman Spectroscopy of Single-Wall Boron Nitride Nanotubes
Arenal, R., Ferrari, A. C. , Reich, S., Wirtz, L., Mevellec, J.-Y., Lefrant, S., Rubio, A., Loiseau,
Nano Lett.; 6(8) pp 1812 – 1816, 2006

22. Abnormal anti-Stokes Raman spectra of single-walled carbon nanotubes raised from coherent anti-Stokes Raman scattering and optical cooling processes

BALTOG, I., BAIBARAC, M., MIHUT, L. and LEFRANT, S.

Digest Journal of nanomaterials and Biostructures, 2, n°1, 185, 2007

23. Single-pumped coherent Raman scattering on carbon nanotubes thin films through surface plasmons

BALTOG, I., BAIBARAC, M., and LEFRANT, S.

Physica E, sous presse, 2007

24. Mecanico-chemical interaction of single-walled carbon nanotubes with ZnO evidenced by photoluminescence and SERS spectroscopy

BAIBARAC, M., BALTOG, I., FRUNZA, S., LEFRANT, S.? MEVELLEC, J.Y., and GODON,C.

J. of Optoelectronics and Advanced Materials 9 (5): 1422, 2007