We studied SWCNTs and derivatives separated according to their metallicity using X‐ray diffractometry, optical absorption, and Raman spectroscopy. The X‐ray study evidences a complete absence of ...graphite and metal catalysts. Optical absorption shows that the metallic sample is of high purity, however, a small amount of metallic tubes are present in the semiconducting sample. We synthesized double‐wall carbon nanotubes from the separated SWCNTs by filling‐in C60's and heating these samples. The Raman spectra of the inner tubes are markedly distinct in the two types of samples and also allows to characterize the efficiency of the separation.
The low frequency excitations of C60 chains inserted inside single-walled carbon nanotubes (SWNTs) have been studied by inelastic neutron scattering (INS) on a high quality sample of peapods. The ...comparison of the neutron-derived generalized phonon density of states (GDOS) of the peapods sample with that of a raw SWNTs allows the vibrational properties of the C60 chains encapsulated in the hollow core of the SWNTs to be probed. Lattice dynamical models are used to calculate the GDOS of chains of monomers, dimers and polymers inserted into SWNTs, which are compared to the experimental data. The presence of strong interactions between C60 cages inside the nanotube is clearly demonstrated by an excess of mode density in the frequency range around 10 meV. However, the presence of a quasi-elastic signal indicates that some of the C60\'s undergo rotational motion. This suggests that peapods are made from a mixture of C60 monomers and C60 n-mer (dimer, trimer ... polymer) structures.
Highly graphitized multiwalled carbon nanotubes (MWNTs) with very thin inner diameter of ∼1
nm, which were prepared by hydrogen arc discharge, were studied by using micro, polarized, resonance and ...surface-enhanced Raman scattering techniques. The radial breathing modes originating from very thin core nanotubes in MWNTs were observed. The multiple splitting of graphite-like G mode of MWNTs as also found in the surface-enhanced Raman spectra of isolated MWNTs. Thus, MWNTs prepared by hydrogen arc discharge possess characteristic Raman spectral features.
Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni–Co-graphite composite targets at 1200°C under argon gas. The effects of the temperature gradient near the target and the ...gas flow rate on the diameter distribution of SWNTs were studied in order to understand their growth dynamics. Raman spectroscopy was used to analyze the diameter distribution of SWNTs. The flow rate was found to affect the relative yields of SWNTs having different diameters when the temperature gradient around the target was large. Scattering images from the ablated species at different flow rates, recorded by a high-speed video camera, indicated that 10 ms after the ablation the velocities of backward moving species increased with increasing flow rate. These findings are used to estimate the time required for determining the diameter distribution and the growth of SWNTs.
Single wall carbon nanotubes filled with C60 were analyzed using resonance Raman scattering and electron energy loss spectroscopy. In order to obtain concentrations of the fullerene molecules inside ...the tubes, the scattering intensity from the fullerenes relative to that from the tubes was used. Since the scattering intensity from the tubes is subject to strong fluctuations, the determination of the concentrations is shown to require averaging of results from different lasers and from all observable Raman lines. The fluctuations are shown to be intrinsic and a consequence of photoselective resonance scattering. Calibration of absolute concentrations can be obtained from electron energy loss spectroscopy performed on the same samples. Samples with three different diameters were analyzed and good agreement between the fullerene concentrations measured by the two methods was obtained.
Supramolecular assemblages made of single wall carbon nanotubes (SWNT) filled with fullerenes or metal doped fullerenes exhibit promising electronic structure variations at a nanometer scale. ...Nevertheless, the knowledge about the structural defects of these systems is still very limited. Here, we report structural evolutions under high-resolution electron microscopic observation at the sensitivity of a single atom detection for Ca@C
82 molecules encapsulated within SWNT.
Physisorption of linear-chain alkane and fatty acid molecules on the outer surface of single-wall carbon nanotubes (SWNTs) has been studied by scanning tunneling microscopy (STM) measurements. These ...molecules are known to organize and form a self-assembled monolayer on a basal plane of graphite, showing a lamellar pattern. We have found that stearic acid molecules (C
17H
35COOH) also show a lamellar pattern on the SWNT surface. This suggests that stearic acid forms a self-assembled monolayer and modulates the surface charge density of SWNT. Formation of the self-assembled monolayer has been observed on the SWNTs surface less frequently than on the graphite surface. This can be explained in terms of an inhomogeneous chirality distribution of the SWNTs and weak van der Waals interaction between the molecules and SWNTs.
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