Enhanced Raman signal of CH 3 on carbon nanotubes
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Enhanced Raman signal of CH3 on carbon nanotubes A. Bassil1, P. Puech1*, G. Landa1, W. Bacsa1, H. Hubel2, D. J. Dunstan2, S. Barrau3, Ph. Demont3, C. Lacabanne3, E. Perez4, E. Flahaut5, R. Bacsa5, A. Peigney5, Ch. Laurent5 1 LPST, IRSAMC, UMR5477, Université Paul Sabatier, 31062 Toulouse Cedex 4, France 2 Department of Physics, Queen Mary, University of London, London E1 4NS, United Kingdom 3 LPP, CIRIMAT, UMR5085, Université Paul Sabatier, 31062 Toulouse Cedex 4, France 4 IMRCP, UMR5623, Université Paul Sabatier, 31062 Toulouse Cedex 4, France 5 LCMIE, CIRIMAT, UMR5085, Université Paul Sabatier, 31062 Toulouse Cedex 4, France * [email protected]
ABSTRACT We find that functionalized SWCNT and DWCNT’s (mainly double wall carbon nanotubes) in composites, DWCNTs under hydrostatic pressure and blue illuminated DWCNTs in methanol show the same up shift of the Raman G band and the appearance of a new band at 1455cm-1. This is attributed to the interaction of the CH3 group of the amphiphilic molecule in composites or the CH3 group of alcohol with the outer tube of DWCNT’s and indicates that laser heating of DWCNT’s in methanol can induce the chemical adsorption of CH3 onto the CNT (carbon nanotube) surface.
INTRODUCTION The remarkable physical properties of carbon nanotubes (CNTs), which combine high strength and low weight, have lead to their applications in polymer-CNT composites. It is expected that both electrical and mechanical characteristics can be improved by adding CNTs [1-6] into suitable polymer matrices. Wood et al. [7-8] have shown that CNTs can be considered as molecular sensors due to their high sensitivity to their immediate chemical environment. The phonon frequencies of the Raman D* band at 2700 cm-1 is up shifted by 20 cm-1 for CNTs in water. The first order G-band shows similar sensitivity to its environment [9]. It is also found that the fluorescence of SWCNTs depends on the surrounding medium and the surfactant molecule [10]. Many adsorbed species on CNT have been studied. Williams et al, [11] using hydrogen and deuterium, have shown the signature of the adsorbed gas can be seen by Raman spectroscopy. Coherent neutron scattering has shown that Argon can be found on interstitial channel sites, grooves and the outer surface of CNT [12]. Infrared spectroscopy shows that CO2 frequencies are modified by interacting with CNTs [13]. Recently, ab-inito model calculation on the adsorption of CHn on nanotubes have been carried out [14]. In the case where the absorbed species is affected by the CNT, it is found that the CNT Raman signal is also influenced by the absorption and hence can be used to probe the interaction between the two. The aim of this paper is to analyse the signal originating from both CH3 and CNTs in various experimental conditions and to find the correlation between the observations. We describing our results obtained with the CNT polymer composite, CNT immersed in alcohol and strong irradiation and finally, CNTs under hydrostatic pressure (methanol-ethanol pressure me
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