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Journal Articles

A New method for separating the $$D$$$$_{3}$$ and $$C$$$$_{2v}$$ isomers of C$$_{78}$$

Han, A. H.*; Wakahara, Takatsugu*; Maeda, Yutaka*; Akasaka, Takeshi*; Fujitsuka, Mamoru*; Ito, Osamu*; Yamamoto, Kazunori; Kako, Masahiro*; Kobayashi, Kaoru*; Nagase, Shigeru*

New Journal of Chemistry, 33(3), p.497 - 500, 2009/03

https://doi.org/10.1039/B808119K
 Times Cited Count：7 Percentile：32.52(Chemistry, Multidisciplinary)

A new chemical method can be applied to isolate the isomers of C$$_{78}$$. The photochemical cycloaddition of a mixture of C$$_{78}$$($$D$$$$_{3}$$) and C$$_{78}$$($$C$$$$_{2v}$$) with disilirane affords only the mono-adduct of the $$C$$$$_{2v}$$ isomer of C$$_{78}$$. The counter part (C$$_{78}$$($$D$$$$_{3}$$)) does not give the mono-adduct with disilirane. The $$D$$$$_{3}$$ isomer itself and the adduct of the $$C$$$$_{2v}$$ isomer of C$$_{78}$$ with disilirane was easily separated by a HPLC procedure. A facile oxidative desilylation of the adduct took place, resulting in the formation of pristine C$$_{78}$$($$C$$$$_{2v}$$). In this context, the separation and the isolation of two isomers of C$$_{78}$$($$C$$$$_{2v}$$) and C$$_{78}$$($$D$$$$_{3}$$) were successfully accomplished by using a silylation-oxidative desilylation process.

Journal Articles

Does Gd@C$$_{82}$$ have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

Akasaka, Takeshi*; Kono, Takayoshi*; Takematsu, Yuji*; Nikawa, Hidefumi*; Nakahodo, Tsukasa*; Wakahara, Takatsugu*; Ishitsuka, Midori*; Tsuchiya, Takahiro*; Maeda, Yutaka*; Liu, M. T. H.*; et al.

Journal of the American Chemical Society, 130(39), p.12840 - 12841, 2008/10

https://doi.org/10.1021/ja802156n
 Times Cited Count：76 Percentile：84.42(Chemistry, Multidisciplinary)

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C$$_{82}$$ carbene adduct (Gd@C$$_{82}$$(ad), Ad=adamantylidene). The Gd atom in Gd@C$$_{82}$$(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C$$_{82}$$ cage, as found for M@C$$_{82}$$ (M = Sc and La) and La@C$$_{82}$$(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.

Journal Articles

Bulk Synthesis and Characterization of Carbon Nanocapsules Containing Lanthanum Carbide

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

MA2004-01 (CD-ROM), 0 Pages, 2003/00

Carbon nanocapsules stuffed with lanthanum carbide did not degrade after exposure to air for considerable length of time, suggesting the carbide particle was completely enclosed within the carbon shell, although the carbide readily hydrolyze in moist air. In this study we present our optimization study that attempted to determine the effect of variations of the processing conditions on the morphorogy of the carbon nanocapsules.

Oral presentation

Protective nature of the outer graphitic cages against oxidation of the inner LaC$$_{2}$$ crystallites in nanocapsules

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

There has been great interest in the incorporation of foreign materials into fullerene-like carbon structures (C$$_{60}$$, nanotubes, nanocapsules). Nanocapsules filled with LaC$$_{2}$$ crystallites were discovered in carbonaceous cathode deposits grown by arc discharge under an inert gas atmosphere in 1993. Although rare-earth carbides are hygroscopic and readily hydrolyze in moist air, the carbides in the capsules did not degrade even after a decade of exposure. Moreover, empty nanocapsules and nanotubes are more resistant to oxidation than other forms of carbon (such as diamond, soot, graphite, and C$$_{60}$$). Therefore higher oxidation resistance is also expected for the filled nanocapsules. In this study protective nature of the outer graphitic cages of stuffed nanocapsules was demonstrated.

Oral presentation

Oxidative properties of carbon nanocapsules encapsulated with lanthanum carbide

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

There has been great interest in the incorporation of foreign materials into fullerene-like carbon structures. Nanocapsules filled with LaC$$_{2}$$ crystallites were discovered in carbonaceous cathode deposits grown by arc discharge. Although rare-earth carbides are hygroscopic and readily hydrolyze in moist air, the carbides in the capsules did not degrade even after a decade of exposure. Moreover, empty nanocapsules are more resistant to oxidation than other forms of carbon (such as diamond, soot, graphite, and C$$_{60}$$). Therefore higher oxidation resistance is also expected for the filled nanocapsules. In this study protective nature of the outer graphitic cages of stuffed nanocapsules was demonstrated. Nanocapsules stuffed with LaC$$_{2}$$ were heated in thermogravimetric analyser in excess air. The observation showed that all carbon nanocapsules including filled and empty nanocapsules seen in the sample were completely changed, suggesting degradation of nanocapsules at 580$$^{circ}$$C.

Oral presentation

Encapsulation of La in spherical graphitic shells by Arc discharge

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

There has been great interest in the incorporation of foreign materials into fullerene-like multi-shell carbon cage structures such as polyhedral nanocapsules and spherical onions. Polyhedral nanocapsules filled with LaC$$_{2}$$ crystals were discovered in carbonaceous cathode deposits formed by arc-discharge evaporation and following deposition of La with carbon under an inert gas atmosphere. The transmission electron microscopy (TEM) characterization of the deposits shows that polyhedral graphitic particles generally show a hollow in the center whose shape is given by the outer faceting of the particle. On the other hand, spherical multi-shell onions filled with metals were formed by irradiation of a composite of graphitic carbon and nano-sized metal crystals at higher temperature alone. In this study spherical multi-shell onions filled with La have been found in the conventional fullerene arc soot of La synthesized at 35 Torr He.

Oral presentation

High temperature treatment of carbon fullerene soot and formation of multi-shell carbon nano-capsules filled with La carbide

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

There has been great interest in the incorporation of foreign materials into fullerenes, nanotubes, and fullerene-like multi-shell cage structures such as polyhedral nanocapsules. Polyhedral nanocapsules containing La element were not found in the fullerene soot, which were discovered in carbonaceous cathode deposits in 1993 formed by arc-discharge evaporation and following deposition of La with carbon on the cathode surface. In this study, multi-shell single-digit nanoparticles filled with La have been found in La fullerene arc soot synthesized at 35 Torr He. Furthermore, the soot materials have been treated at temperatures between 1000 and 2200$$^{circ}$$C in vacuum. The single-digit nanoparticles have been transformed into larger multi-shell nanocapsules filled with LaC$$_{2}$$.

Oral presentation

Influence of high temperature treatments on fullerene soot and formation of multi-shell carbon nanoparticles filled with LaC$$_{2}$$

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

There has been great interest in the incorporation of foreign materials into fullerenes, nanotubes, and fullerene-like multi-shell cage structures such as polyhedral nanocapsules. Polyhedral nanocapsules containing La element were not found in the fullerene soot, which were discovered in carbonaceous cathode deposits in 1993 formed by arc-discharge evaporation and following deposition of La with carbon on the cathode surface. In this study, multi-shell single-digit nanoparticles filled with La have been found in La fullerene arc soot synthesized at 35 Torr He. Furthermore, the soot materials have been treated at temperatures between 1000 and 2200$$^{circ}$$C in vacuum. The single-digit nanoparticles have been transformed into larger multi-shell nanocapsules filled with LaC$$_{2}$$.

Oral presentation

High temperature treatment of some specially synthesized fullerene soot and formation of lanthanum-carbide encapsulated carbon nanocapsules

Yamamoto, Kazunori; Wakahara, Takatsugu*; Akasaka, Takeshi*

no journal, , 

no abstracts in English

Oral presentation

Raman and TEM studies of heat-treated La fullerene soot

Yamamoto, Kazunori; Shamoto, Shinichi; Akasaka, Takeshi*; Wakahara, Takatsugu*; Miyazawa, Kunichi*

no journal, , 

no abstracts in English

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