Formation of small-diameter carbon nanotubes from PTCDA arranged inside the single-wall carbon nanotubes
Introduction
It was shown that C60 encapsulated single-wall carbon nanotubes (C60 peapods) were turned into double-wall carbon nanotubes (DWNTs) after high-temperature annealing [1]. The turning process of encased C60 molecules to a tubular structure has been studied in detail by using high-resolution transmission electron microscopy (HRTEM) and by analyzing the time trace of high-resolution Raman spectra [2]. Encapsulation of non-fullerene molecules to single-wall carbon nanotubes (SWNTs) was achieved by doping tetracyanoquinodimethane (TCNQ) in the interior of SWNT [3]. The results of measurements on conductivities, UV–vis spectra and X-ray diffraction indicate the existence of electron charge transfer from TCNQ to SWNTs. Ice tube was also formed in the interior of SWNT [4]. These experimental facts suggest that various molecular materials can be easily incorporated in the nano-space spread widely over the SWNT, so that this space is usable for a reaction cell with a molecular size.
We have taken in the present study an aromatic molecule for filling the nano-space of SWNT and recorded the time trace of polymerizing process for encased molecules by Raman spectroscopy. We have selected a perylene-derivative, PTCDA (perylene-3,4,9,10-tetracarboxylic dianhydride), since this compound is known to form a two-dimensional graphene sheet at ≈2800 °C [5].
Section snippets
Experimental
SWNTs were prepared by high-temperature laser ablation of a composite carbon rod containing both 0.6 at.% of Co and Ni metals in a 500 Torr of argon, and purified by refluxing in concentrated HNO3 at 160 °C. SWNTs thus purified were heated at 480 °C in dry air for 1 h to make entrance holes for the dopant [1], [6]. PTCDA (Lancaster Synthesis Ltd., 98%) was used as a doping material to the interior of SWNT to study the polymerization in the confined nano-space. PTCDA was incorporated by a vapor-phase
Raman scattering study
Fig. 1 is the Raman spectra taken for empty-SWNTs (before doping of PTCDA), PTCDA-doped SWNTs and heat-treated of PTCDA-doped SWNTs at various temperatures with several reaction times. An obvious change on the Raman spectral feature is observable in the range of 300–400 cm−1, which shows two clear peaks newly appearing at 337 and 358 cm−1 (see arrowhead positions) by heating the sample over 1050 °C. These spectral features indicate the formation of inner tubes as a result of polymerization
Summary
We have prepared one-dimensionally arranged PTCDA molecular chains inside the SWNTs. The structure of this molecular chain is categorized into the double-barreled state. Regarding the relation between the tube diameter and the size of PTCDA molecule, tubes with large diameters (≈1.54 nm) can include a greater amount of dopants than those with smaller diameters (≈1.38 nm). Such encased PTCDA molecules are polymerized without dedoping and turn into the inner tube by heat treatment above 1050 °C in
Acknowledgements
This work was supported by a Grant-in-Aid for 21st Century COE Program by the Ministry of Education, Culture, Sports, Science and Technology of Japan. Y.F. is grateful to Meijo University for financial support.
References (12)
- et al.
Chem. Phys. Lett.
(2001) - et al.
Chem. Phys. Lett.
(2004) - et al.
Chem. Phys. Lett.
(2005) - et al.
J. Cryst. Growth.
(1992) - et al.
Nat. Mater.
(2003) - et al.
Appl. Phys. Lett.
(1986)
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