Then, we report for each structure its associated calculated Raman responses. We show that the structure of the C 60 and C 70 molecules encapsulated inside SWCNTs adopt different configurations according to the nanotube diameter. In this chapter, the structure and vibrational properties of C 60 and C 70 peapods are reviewed. Raman spectroscopy is a useful tool to characterize carbon nanotubes and related nanomaterials and widely used by experimentalists as a fast and nondestructive method to identify the type of nanoparticle and to study their electronic and vibrational properties. Peapods are typically characterized by one or more of the conventional techniques such as transmission electron microscopy (TEM), Raman spectroscopy, electron diffraction, electron energy loss spectroscopy (EELS), and X-ray diffraction. But what happened when these same molecules are confined inside a carbon nanotube? Furthermore, changes in the electronic and mechanical properties of carbon nanotubes induced by the insertion of these molecules have been demonstrated. The physicochemical properties of the fullerene molecules inserted inside carbon nanotubes are generally well known in their stable phase. (b) Schematic representation of the molecular structure of an individual C 60 peapod. (a) Electron microscopy image of C 60 peapod (from reference ). Using high-resolution transmission electron microscopy (HR-TEM) experiments, the peapods are clearly observed, as seen in Figure 1, and organized into bundles. However, these materials represent a new class of a hybrid system between fullerenes and SWCNTs where the encapsulated molecules peas and the SWCNT pod are bonded through van der Waals interactions. in 1998, many experimental studies clearly evidenced the existence of various fullerenes like C 70, C 76, and C 80 inside SWCNTs. After the discovery of C 60 peapods by Smith et al. This class of hybrid materials has been dubbed as “peapods” (C and C reflecting structural similarities to real peapods. These fillings are highly dependent on the nanotube diameter and the inserted molecule size, so that even small changes in SWCNT diameter can alter the geometry of fullerene arrays. A remarkable property of SWCNT is its ability to have been filled with various fullerenes and metallofullerenes, fullerenes adducts, metal complexes, and other small molecules. Since the discovery of multiwalled carbon nanotubes and single-walled carbon nanotube (SWCNT) in 1991, fullerenes and carbon nanotube systems have attracted significant attention from the scientific community. Other fullerenes were discovered shortly afterward with more and fewer carbon atoms. discovered C 60 by laser vaporizing graphite into a helium stream in September 1985, fullerenes are at the heart of nanotechnology. Finally, the variation of the average intensity ratio between C60 and C70 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. The experimental Raman spectra of fullerenes and fullerenes peapods are discussed in the light of theoretical calculation results. 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. We also briefly review the concept of Raman spectroscopy technique that provides information on phonon modes in carbon nanopeapods. Therefore, the following changes of properties of the empty nanotubes, such as phonon modes, induced by the C60 and C70 filling inside nanotube are presented. First, the different possible configurations of C60 and C70 molecules inside CNTs are reviewed. For that purpose, note every conventional characterization technique is suitable, but Raman spectroscopy has already proven to be. 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. Carbon nanotubes (CNTs) can encapsulate small and large molecules, including C60 and C70 fullerenes (so-called carbon peapods).
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