Hideyuki Funasaka

ELECTROCHEMICAL PROPERTIES OF FULLERENOLANTHANIDES

Abstract The cyclic voltammogram (CV) of Y@C 82 shows one reversible oxidation and four reversible reductions in 1,2-dichlorobenzene. The first redox potentials of Y@C 82 are anodically shifted by 30 and 50 mV, respectively, relative to those of La@C 82 . As observed for La@C 82 and Y@C 82 , the first redox processes of Ce@C 82 and Gd@C 82 are reversible by CV, and their potentials are also very close to those of La@C 82 and Y@C 82 . It was found that the ionic radii of Ln 3+ show good linear relationships with the first redox potentials of La@C 82 , Ce@C 82 , Gd@C 82 , and Y@C 82 .

Magnetic properties of Gd@C82 metallofullerene

Abstract A macroscopic quantity of the metallofullerene Gd@C 82 has been isolated in pure form from various hollow fullerenes on pyrenylethyl silica with toluene as an eluent. Magnetization data for a powder sample of the isolated Gd@C 82 have been obtained employing a SQUID magnetometer between +-5.5 T at temperatures ranging 3 to 200 K. These magnetization data, when scaled as a function of H / T , fall on a universal curve which is fitted to a Brillouin function consistent with J = 3.38 and g = 2. This is a signature of paramagnetic behavior.

Chemical derivatization of endohedral metallofullerene La@C82 with digermirane

Abstract Addition reaction of an endohedral metallofullerene La@C 82 with digermirane has been investigated by means of the mass and EPR measurements. It is found that photochemical and thermal reactions of La@C 82 with digermirane afford an exohedral adduct of the endohedral metallofullerene. This is in sharp contrast with the fact that empty fullerenes react only photochemically. The remarkable thermal reactivity of La@C 82 is ascribed to the unique electronic properties due to endohedral metal doping.

Epitaxial growth of C60 and C70 films on GaSe (0001) and MoS2 (0001) surfaces

Abstract Molecular arrangements in C 60 and C 70 films grown epitaxially on GaSe and MoS 2 have been studied by reflection high-energy electron diffraction. C 60 and C 70 molecules were found to form close-packed hexagonal lattices on these substrates with lattice constants of 1.00 − 0.02 and 1.08 − 0.02 nm, respectively. The crystal axes of the C 60 and C 70 films grown on GaSe (0001) and the C 60 films on MoS 2 (0001) were parallel to the [11 2 0] axis of the substrates. On the other hand, the C 70 molecules were arranged along the [10 1 0] axis of the MoS 2 (0001) substrate. The lattice matching condition between a grown film and a substrate is thought to be a determining factor for the growth of the C 70 film on MoS 2 .

Exohedral derivatization of an endohedral metallofullerene Gd@C82

Photochemical and thermal reactions of an endohedral metallofullerene Gd@C82 with disilirane afford an exohedral adduct.

SYNTHESIS OF ACTINIDE CARBIDES ENCAPSULATED WITHIN CARBON NANOPARTICLES

Actinide carbides encapsulated with multilayered graphitic capsules have been produced by the arc burning of a composite carbon rod containing thoriated tungsten or uranium ore. The morphology of these filled nanoparticles was observed by transmission electron microscopy. The preferential encapsulation in the constituent elements of the core materials surrounded by the graphite cage was demonstrated. Furthermore, it was found that these carbon nanoparticles filled with radioactive materials have been quite stable for 1 year or more.

Electrochemical properties of fullerenolanthanides

Abstract Cyclic-(CV), differential pulse (DPV), and Osteryoung square wave voltammograms (OSWV) have been performed on the pure fullerenolanthanides, two La@C 82 isomers and Y@C 82 , for the first time. Five reversible reduction and one reversible oxidation processes were observed for La@C 82 -A (major isomer). The first oxidation potential is approximately equal to that of ferrocene, indicating that La@C 82 -A is a good electron donor. The CV of La@C 82 -B (minor isomer) is similar to that of the major isomer, but the first oxidation potential is cathodically shifted by 0.14 V. The electrochemistry of Y@C 82 resembles those of the La@C 82 isomers. The first oxidation and reduction potentials of Y@C 82 are anodically shifted by 0.03 and 0.08 V, respectively, relative to those of the major isomer of La@C 82 . These small anodic shifts could be attributed to the difference of the ionic radii of Y 3+ and La 3+ . Fullerenolanthanides studied in the present work are stronger electron acceptors than empty fullerenes such as C 60 , C 70 , C 76 , C 82 , C 84 , and C 86 .

ESR study on the reactivity of two isomers of LaC82 with disilirane

We observed photochemical and thermal addition of disilirane to the LaC82-A isomer, which give new ESR active species. Both ESR spectra of the adducts in photo- and thermal reactions are well simulated by at least six octet components, and the isotropic La coupling constants and g-factors of the six octet components are determined. On the other hand, the reaction of the LaC82-B isomer with disilirane gives no ESR active species. This fact is also verified by mass spectroscopic measurements. The different reactivities with disilirane of the two isomers are not interpreted by a popular view that the two isomers have a different C82 cage structure, but we rather suggest that the origin of the isomers of metallofullerenes should be re-examined.

Synthesis of lanthanum compound encapsulated within carbon nanoparticles

Abstract Encapsulated forms in multilayered graphitic capsules have been studied by varying the lanthanum compounds filled in the positive graphite electrode. The morphology of these filled nanoparticles was observed by transmission electron microscopy. It was found that the encapsulated forms in nanoparticles varied with the compounds filled in the anode: in the case of a La2O3/graphite, a LaN/graphite, and a LaB6/graphite composite anode, the corresponding encapsulated forms are LaC2, La, and LaB6, respectively.

SUPERCONDUCTING TRANSITION AT 12.5 K IN RBXC60

Abstract The effect of heat treatment of RbxC60 (x = 3, 4, 5, and 6) on the superconducting transition has been studied with shielding diamagnetism measurements. For RbxC60 (x = 4, 5, and 6), a superconducting transition at 12.5 K appeared in the course of annealing treatment at 400°C and disappeared on further prolonged annealing, while a clear superconducting transition at 30 K due to the Rb3C60 phase still remained. We speculate that this superconducting transition at 12.5 K is due to a certain phase which appears in the course of the annealing treatment.