Spectral properties of single-walled carbon nanotubes encapsulating fullerenes (original) (raw)
Related papers
Structural and Vibrational Properties of C60 and C70 Fullerenes Encapsulating Carbon Nanotubes
Fullerenes and Relative Materials - Properties and Applications, 2018
Carbon nanotubes (CNTs) can encapsulate small and large molecules, including C 60 and C 70 fullerenes (so-called carbon peapods). The challenge for nanotechnology is to achieve perfect control of nanoscale-related properties, which requires correlating the parameters of synthesis process with the resulting nanostructure. For that purpose, note every conventional characterization technique is suitable, but Raman spectroscopy has already proven to be. First, the different possible configurations of C 60 and C 70 molecules inside CNTs are reviewed. Therefore, the following changes of properties of the empty nanotubes, such as phonon modes, induced by the C 60 and C 70 filling inside nanotube are presented. We also briefly review the concept of Raman spectroscopy technique that provides information on phonon modes in carbon nanopeapods. The dependencies of the Raman spectrum as a function of nanotube diameter and chirality, fullerene molecules configuration and the filling level are identified and discussed. The experimental Raman spectra of fullerenes and fullerenes peapods are discussed in the light of theoretical calculation results. Finally, the variation of the average intensity ratio between C 60 and C 70 Raman-active modes and the nanotube ones, as a function of the concentration molecules, are analyzed, and a general good agreement is found between calculations and measurements.
Fullerene derivatives encapsulated in carbon nanotubes
physica status solidi (b), 2007
We report on the preparation and subsequent Raman analysis of carbon nanotube peapods, using the fullerene C 60 and its heterofullerene derivative (C 59 N) 2 as filling materials. The filling with (C 59 N) 2 was done from liquid solution at room temperature and from the gas phase at elevated temperatures. The success of the encapsulation procedure is confirmed through the identification of fingerprint Raman modes and the conversion to double wall nanotubes through heating to 1250°C. The 2D mode of double wall nanotubes made from (C 59 N) 2 peapods is observed to be downshifted compared to the same mode in double wall nanotubes made from C 60 peapods. We interpret this downshift as an evidence for the integration of the nitrogen into the lattice of the inner tube.
Optical Band Gap Modification of Single-Walled Carbon Nanotubes by Encapsulated Fullerenes
Journal of the American Chemical Society, 2008
We report optical band gap modifications of single-walled carbon nanotubes upon C60 insertions by using photoluminescence and the corresponding excitation spectroscopy. The shifts in optical transition energies strongly depend on the tube diameter (dt) and the "2n + m" family type, which can be explained by the local strain and the hybridization between the nanotube states and the C60 molecular orbitals. The present results provide possible design rules for nanotube-based heterostructures having a specific type of electronic functionality.
Optical microspectroscopy study on enriched (11,10) SWCNTs encapsulating C 60 fullerene molecules
The interaction between C 60 fullerene molecules and single-chirality (11,10) single-walled carbon nanotubes (SWCNTs) is demonstrated by probing the optical transitions in (11,10) peapods by optical microspectroscopy. The results of the (11,10) SWCNTs and (11,10) peapods are compared to multi-chirality SWCNTs and peapods. The absence of the fine structure of the absorption bands in the case of (11,10) SWCNTs in comparison to multi-chirality SWCNTs demonstrates that the (11,10) SWCNTs provide a well-defined environment for studying the interaction between the encapsulated C 60 molecules and the nanotubes. As compared to (11,10) SWCNTs, the absorption bands in (11,10) peapods show a large red shift and a reduction of the spectral weight. These findings suggest that the filling of the (11,10) SWCNTs with C 60 molecules increases the internal dielectric constant and induces a charge transfer between the SWCNTs and the encapsulated C 60 molecules. For testing the effect of the internal dielectric constant and charge transfer on the optical properties of the (11,10) SWCNTs, the (11,10) peapods were transformed to double-walled carbon nanotubes (DWCNTs) using the laser irradiation method. The transformation of the encapsulated fullerene molecules into inner wall reduces the environmental dielectric constant as well as the charge transfer from the outer tube.
Fullerene-peapods: Synthesis, structure, and Raman spectroscopy
AIP Conference Proceedings, 2001
Single-wall carbon nanotubes (SWNTs) encapsulating fullerenes, so-called fullerenepeapods, were synthesized in high yield by using diameter-selected nanotubes as pods. Highresolution transmission electron microscopy revealed high-density fullerene chains inside nanotubes. X-ray diffraction measurements indicate 60% filling of C 60 molecules in a macroscopic average. Room temperature Raman spectra show one-dimensional photopolymerization of C 60 inside nanotubes by blue laser irradiation, indicating molecular rotation inside. In C 70-peapod case, Raman active modes peculiar to C 70 were strongly suppressed by encapsulation. The suppression is probably caused by deformation of molecule due to the unisotropic interaction between C 70 and SWNT. Anomalous resonance effects in C 70peas suggest hybridization of electronic states of C 70 and nanotubes. High-symmetry mode Raman intensity suggests the filling factor to be higher than 50%, which is consistent with the X ray diffraction analysis.
Chemical Physics Letters, 2001
Double-wall carbon nanotubes (DWNTs) were prepared in quantitative amount from the chains of C 60 molecules generated inside single-wall carbon nanotubes (SWNTs). The C 60 molecules inside the SWNT unchange up to 800°Cwithoutdedoping.Furtherheatingat800°C without dedoping. Further heating at 800°Cwithoutdedoping.Furtherheatingat1200°C induces the coalescence between C 60 and eventually the C 60 molecules transform into a tubular structure. The DWNTs thus prepared show radial breathing mode (RBM) Raman scattering associated with inner tubes as well as those from parent outer tubes, which are all explained by a model of diameter pairing in DWNT with an inner tube diameter smaller by 0:71 AE 0:05 nm than an outer one. Ó
Physical Review B, 2002
We report recent measurements of the electronic and structural properties of bulk samples of C 60 molecules encapsulated in single-wall carbon nanotubes ͑so-called peapods͒ using electron-energy-loss spectroscopy in transmission. We demonstrate that C 60 peapods with a single-wall carbon nanotube ͑SWNT͒ diameter distribution of 1.37Ϯ0.08 nm have an average fullerene filling of 60%. Regarding the electronic and optical properties, the overall shape of the response of the SWNT and the peapods is very similar, but with distinct differences in the fine structure. The interband transitions of the SWNT are slightly downshifted in the peapods, which can be explained by either a small increase of the SWNT diameter or by a change of the intertube interaction. The electronic and optical properties of the encapsulated C 60 peas closely resemble those of solid fcc C 60 showing small changes in the relative intensities, peak positions, and peak width, which point to a weak van der Waals interaction between the tubes and the encapsulated fullerenes.
The Journal of Physical Chemistry C, 2009
Band gap photoluminescence (PL) of single-walled carbon nanotubes (SWCNTs) encapsulating C 60 fullerenes (nanopeapods) is examined over a wide range of diameters (∼1.25-1.55 nm). The encapsulated fullerenes induce characteristic PL peak shifts that strongly depend on the tube diameter (d t ) and the "2n + m" family type {type I [mod(2n + m, 3) ) 1] and type II [mod(2n + m, 3) ) 2]}. This behavior can be explained by the strain-induced band gap shifts due to the C 60 insertion and the hybridization between the electronic states of SWCNTs and C 60 . The present results provide significant insights into band gap engineering of SWCNTs in future nanodevices.
Chemical physics …, 2007
Double-wall carbon nanotubes (DWNTs) encapsulating C 60 and C 70 fullerenes have been synthesized by the vapor reaction method. Arrangements of C 60 and C 70 molecules in phases of single chain and multi-layers are observed in DWNTs of different sizes by TEM observation. Distinct signals of XRD patterns and Raman spectra can distinguish C 60 and C 70 fullerenes inside from those attached outside DWNTs. TGA of the as-prepared DWNT-peapods clearly show that they have a higher thermal stability in comparison with pristine DWNTs. This supplies a simple method to evaluate the filling ratio of peapods, which is 74.7 wt% for the current DWNT-peapods.