Haruhito Kato

Smallest limit of tube diameters for encasing of particular fullerenes determined by radial breathing mode Raman scattering

Abstract Lineshapes of radial breathing mode (RBM) Raman scattering from single-wall carbon nanotubes (SWNTs) encasing the fullerenes vary depending on the sizes of fullerenes. The lineshape fit using Lorentzian lines to the spectrum indicates downshift of ωr (RBM frequency) for most lines as compared with those observed in empty-SWNTs, except for one upshifted line associating with the stress to the tube-wall from the inside fullerenes. The smallest limit of tube diameters (d) is determined from this upshifted line, and they are resulting to be ∼1.37 nm for C60, ∼1.45 nm for both C76 and C78, and ∼1.54 nm for C84 when using ω r ( cm −1 )=246/d ( nm ) .

Syntheses and Biological Evaluations of α-d-Mannosyl [60]fullerenols

[60]Fullerenols carrying mono- and bis-alpha-D-mannosyl linkages on the surface were prepared via a [3+2]-cycloaddition reaction between 2-azidoethyl alpha-D-mannoside and C(60) followed by polyhydroxylation with aqueous NaOH. Their biological activity was evaluated in terms of binding affinity to lectins by hemagglutination assay and surface plasmon resonance. [60]Fullerenols without the mannosyl linkage caused aggregation of erythrocytes and binding to a beta-D-galactopyranoside specific lectin (RCA(120)). In contrast, mono- and bis-mannosyl fullerenols were found to decrease the activity for both aggregating erythrocytes and binding to RCA(120), and mono-mannosyl fullerenols turned to binding to alpha-D-mannose specific lectin (Con A).

Syntheses and EELS characterization of water-soluble multi-hydroxyl Gd@C82 fullerenols

Abstract Various water-soluble multi-hydroxyl fullerenes (fullerenols), C60(OH)n, C70(OH)n and C84(OH)n, and a Gd metallo-fullerenols, Gd@C82(OH)n have been synthesized by the Kitazawa method. Elementary chemical analyses indicate that all of these fullerenols have 30–40 hydroxyl groups and 11–15 coordinated water molecules via hydrogen bonds. Electron energy loss spectroscopy (EELS) on Gd@C82 fullerenols shows that the π ∗ peak area in the C K-edge spectra decreases on going from intact Gd@C82 metallofullerene to Gd@C82 fullerenols, indicating an increase in sp3 character of the fullerenols. Furthermore, Gd M4,5-edge EELS spectra show that the encapsulated Gd atom has a trivalent Gd3+ state.

Ab initio MO calculations on the electronics structures of H2S+ and H2O+

Abstract Ab initio MO calculations for the potential curves of H2S+ and H2O+ are carried out in order to obtain a theoretical description of the electronic structure and geometry of these systems. The results are in satisfactory agreement with experiment and show that both radicals are very similar both in geometry and in electronic structure.

Evaluation of water-soluble metallofullerenes as MRI contrast agents.

The conventional MRI contrast agents consisting of a chelate complex with a Gadolinium (Gd) ion, such as Magnevist® (Schering AG, Germany), enhance MRI signal by shorting the longitudinal relaxation time of protons of surrounding water molecules (1). These agents have been used as a routine clinical tool to reveal anatomical details in vivo and to detect lesions for diagnosis. For the future imaging of molecular/cellular diagnosis (2), innovative agents having much stronger proton relaxivity should be required. Since their discovery in 1985 (3), potential applications for fullerene and metallofullerene materials have been proposed because of their unique structural and electronic properties. Biomedical application, especially as MRI contrast, X-ray or radiopharmaceutical agents, should be a prominent field because fullerene cage can encage various metal ions, such as Ca, Sc, Sr, Y, La, Ce, Sm, Gd, Dy, Er, Yb, Ho, etc. (4). Here, we have investigated the possibility of application of water-soluble Gd metallofullerene for MRI contrast agents, and have evaluated them in vivo as well as in vitro.

Tunable Field-Effect Transistor Device with Metallofullerene Nanopeapods

A fine tuning of the band gap of single-wall carbon nanotubes (SWNTs) has been achieved by filling various types of endohedral metallofullerenes into the SWNTs, the so-called nanopeapods. We report various electronic transport properties of fullerene peapods used as the channels of field-effect transistors (FETs) and demonstrate that the metallofullerene peapods can provide the tunable band gaps of the FET channels depending on the type of metallofullerene inserted in the SWNTs. All of the metallofullerene peapods FETs exhibit p- and n-type, the so-called ambipolar carrier transportation by variable gate bias. The ranges of the off state regions of the FET fabricated highly sensitivity with respect to the amount of charge transfer in metallofullerenes, which results in band-gap engineering. Metallofullerene peapods can be used to manipulate the electronic structure of SWNTs in nanometer scale. In such a highly functionalized SWNT, metallofullerene peapods, might be a key material for fabricating and developing sophisticated electronic devices in the future.

Azafullerene (C59N)2 thin-film field-effect transistors

Thin-film field-effect transistors (FETs) of azafullerene (C59N)2 are fabricated, and their properties are investigated. The (C59N)2 FET exhibits n-channel characteristics with the field-effect electron mobility of 3.8×10−4 cm2 V−1 s−1 and the on–off current ratio of 103 at room temperature. The observed differences are ascribed to the much smaller grain size and the worse crystallinity of (C59N)2 thin films, on a basis of low angle x-ray diffraction structural data. The anticipated dimer to monomer conversion with electron carrier injection is not observed. The FET characteristics are discussed from the temperature evolution of the mobilities between (C59N)2 and C60 FETs.

On the interchain interaction in the (SN)x polymer

Abstract The interchain interactions in the (SN)x polymer are discussed on the basis of one-dimensional tight-binding SCF MO calculations of two chains of (SN)x. We conclude that the interchain interaction in the (100) crystallographic plane is more significant than that in the ( 1 02) plane in accordance with the previous result by Messmer and Salahub and that, from more quantitative analysis, these interactions are mainly caused by the shortest interchain SS coupling in both planes.

Cluster expansion of the wavefunction. Ionization potentilals of benzene

Abstract The vertical and adiabatic ionization potentiais of benzene are studied by the cluster expansion of the wavefunction theory. The calculation confirms the assignment of the photoelectron spectrum experimentally proposed by Jonsson and Lindholm. The nature of the Jahn-Teller effect in states arising from ionization of doubly degenerate π and σ orbitals is also discussed.

Semi-empirical UHF treatment for the solvated electron

Abstract Solvated electrons in water, ammonia and hydrogen fluoride are investigated by applying the activity model which consists of four or six solvent molecules and using the UHF method with the INDO approximation. Various conclusions concerning several properties of solvated electrons, solvent molecules and the structure of the cavity, particularly, the proton spin densities of water and ammonia, are obtained.