This study deals with a hybrid system consisting in quaterthiophene derivative encapsulated inside single-walled and multi-walled carbon nanotubes. Investigations of the encapsulation step are performed by transmission electron microscopy. Raman spectroscopy data point out different behaviors depending on the laser excitation energy with respect to the optical absorption of quaterthiophene. At low excitation energy (far from the oligomer resonance window) there is no significant modification of the Raman spectra before and after encapsulation. By contrast, at high excitation energy (close to the oligomer resonance window), Raman spectra exhibit a G-band shift together with an important RBM intensity loss, suggesting a significant charge transfer between the inserted molecule and the host nanotubes. Those results suggest a photo induced process leading to a significant charge transfer.

A hybrid system consisting of quaterthiophene derivative inserted into carbon nanotubes is studied. Encapsulation efficiency of the conjugated oligomers in the hollow core of nanotubes is investigated by transmission electron microscopy and spatial-resolved electron energy loss spectroscopy. Infrared spectroscopy showed evidence of a significant positive charge transfer on the inserted oligothiophene. Raman spectra display different behaviors depending on the excitation energy and correlated to the quaterthiophene optical absorption energy. At high excitation wavelength (far from the oligomer resonance), radial breathing modes exhibit a significant upshift consistent with an encapsulation effect. At low excitation wavelength (close to the oligomer resonance), both the G-band shift and the low-frequency modes vanishing suggest a significant charge transfer between the quaterthiophene and the nanotubes

In this article, we report the synthesis of ultra-long carbon nanotubes (CNTs) by thermal chemical vapour deposition method. Ultra-long, individual and aligned CNTs were directly grown on a flat silicon substrate. The orientation of the nanotubes was found parallel to the gas flow direction. The ultra-long CNTs were grown with different transition metallic salts, such as nickel chloride, iron (III) chloride, cobalt acetate and ruthenium acetate, as the catalysts. The influence of the growth conditions, such as growth temperature, reactive gas flow on the length and alignment of the CNTs was studied in detail. By using different catalysts, ultra-long single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) were successfully grown. These ultra-long CNTs were transferred to other substrates by two methods. (1) The first method is to use polydimethylsiloxane as a stamp. (2) The second method is to use KOH as an etching agent. The diameter and length of the CNTs were characterised by transmission electron microscope, scanning electron microscope, atomic force microscope and Raman spectroscopy. The results indicate that the length of the CNTs can reach up to 4 mm. The diameter of the SWCNTs is in the range of 0.7-2.1 nm and the diameter of the MWCNTs is approximately 150 nm.

The temperature dependence of the Raman spectrum of a gelatine-based composite material doped with single-walled carbon nanotubes (SWNT@gelatin) is reported [1]. A significant up-shift of the G-mode frequency is observed when the temperature is decreased from room temperature to 20 K. This frequency shift is significantly stronger than the one found for pure thermal effects. In contrast, the features of the radial breathing modes (frequencies and width) display no significant change in the same temperature range. These results are well understood by considering a uniaxial strain on the nanotube induced by the thermal expansitivity mismatch between the nanotube and the surrounding matrix [2,3]. These conclusions are in good agreement with photoluminescence experiments performed on the same samples [4]. References [1] D. Levshov, J. Phys. Chem. C 2010, 114, 16210-16214. [2] S. Cronin, Phys. Rev. Lett. 2004, 93, 167401. [3] G. Wu, Phys. Rev. B 2005, 72, 115411. [4] S. Berger, J. Appl. Phys. 2009, 105, 094323.

By combining resonant Raman spectroscopy and electron diffraction experiments on suspended (free-standing) individual carbon nanotubes, we have been able to determine unambiguously their in-air and room-temperature main features. In this communication we review the results obtained from these combined experiments on single-walled (SWNT) and double-walled (DWNT) carbon nanotubes. The dependence of the Raman features of these nanotubes as a function of their structure is discussed and compared with theoretical predictions.

By combining resonant Raman spectroscopy and electron diffraction experiments on suspended (free-standing) individual single-walled carbon nanotubes, we have been able to determine unambiguously their in-air and room-temperature main features. In this communication we review the results obtained from these combined experiments. The Raman features are discussed with regards to theoretical predictions. On the base of these results, Raman criteria were defined allowing the identification of SWNTs from their Raman features only. We show their efficiency to assign the structure of individual carbon nanotubes . Extrinsic factors that can confuse the assignment of the tubes are discussed. Recently, by using a new-experimental set-up which combines imaging and Raman spectroscopy on individual nanotubes, a lot of new Raman data were measured on suspended nanotubes such as individual double-walled carbon nanotubes (DWNT) and individual DWNT bundles. The dependence of the Raman features of these nanotubes as a function of their structure is discussed.

In the past, by combining resonant Raman spectroscopy and electron diffraction experiments on suspended (free-standing) individual chiral and achiral single-walled carbon nanotubes (SWNTs) we have been able to determine unambiguously the in-air and room-temperature main features of their Raman spectrum. On the base of these results, Raman criteria were defined allowing the identification of SWNTs from their Raman features only [1]. In this communication we present these criteria and we show their efficiency to assign the structure of individual carbon nanotubes [2]. Extrinsic factors that can confuse the assignment of the tubes from their Raman spectra are discussed. The Raman features are discussed with regards to theoretical predictions. Recently, by using a new-experimental set-up which combines imaging and Raman spectroscopy, a lot of Raman data were measured on free-standing nanotubes: individual SWNTs, individual SWNT bundles, individual MWNTs and individual MWNT bundles. The dependence of the Raman features of these nanotubes as a function of their structure is discussed.