Wolfgang Krätschmer

The infrared and ultraviolet absorption spectra of laboratory-produced carbon dust: evidence for the presence of the C60 molecule

Abstract In carbon smoke samples prepared from vaporized graphite at elevated quenching gas pressures (e.g. > 100 Torr He) new absorption features have been observed in the infrared (the strongest at 1429, 1183, 577, and 528 cm −1 ). Broader features also have been observed in the ultraviolet (the strongest at 340, 270, and 220 nm). By studying 13 C-enriched samples we have shown that the infrared absorptions are produced by large, pure carbon molecules. The evidence supports the idea that the features are produced by the icosahedral C 60 molecule.

High-yield fullerene encapsulation in single-wall carbon nanotubes

We have successfully synthesized single-wall carbon nanotubes encapsulating specified fullerenes (peapods) in high yield using a sublimation method. Side and section images by HRTEM indicate that almost all nanotubes are filled with high-density fullerene chains. We measured Raman spectra to estimate macroscopic yield. The observed Raman intensity of C 70 molecules in the C 70 -peapods is 1/10 of that in C 70 film, which indicates a filling rate of C 70 to be higher than 26 %. In the case of C 60 -peapods, Raman spectrum has changed rapidly by laser irradiation. Since the final spectrum at room temperature is similar to that of the orthorhombic polymer phase, a formation of one-dimensional photopolymers inside SWNTs is suggested.

Preparation and characterisation of C119

Abstract Thermolysis of C 120 O at 550–600°C yielded a soluble product fraction containing C 60 , C 119 and higher-mass species. Using a two-step HPLC procedure two species, both with molecular weight corresponding to C 119 , were isolated in 3.5% and 2% yield. The 125.76 MHz 13 C-NMR spectrum of the latter more stable product obtained from 13 C enriched samples proved that this species consists of two C 58 cages bridged by three sp 3 carbons, two of which are equivalent. NMR-consistent C 119 structures have been investigated by molecular modeling and turned out to exhibit C 2 symmetry.

Electron energy-loss spectroscopy studies on C60 and C70 fullerite

The electronic structure of the crystalline fullerites C60 and C70 has been investigated by high-energy electron energy-loss spectroscopy in transmission. From valence band excitations and from core-level excitations of the C 1s level information on occupied and unoccupied π and ϖ bands has been obtained.

Synthesis of C120O: A new dimeric [60]fullerene derivative

Abstract C 120 O, prepared in preparative amounts by the reaction of C 60 and C 60 O in the solid state, has been characterized by UV-VIS, FT-IR, and MALDI-TOF MS. We propose that the structure is a C 60 dimer in which the 6,6 bonds of each cage form part of a furan-like bridge.

Hydrogenation of buckminsterfullerene C60 via hydrozirconation : a new way to organofullerenes

Hydrogenation of buckminsterfullerene C60 has been achieved via reaction with (η5-C5H5)2Zr(H)Cl (hydrozirconation). Hydrolysis of the intermediate C60 zirconium(IV) complex, [(η5-C5H5)2ZrCl]nC60Hn with n=1,2,3, yielded a mixture of C60H2n and unreacted C60, from which C60H2 has been isolated through preparative high performance liquid chromatography (HPLC).

An EELS study of fullerite — C60/C70

Abstract Electron-energy-loss spectroscopy (EELS) with a new parallel detection system is used to study the electronic structure of the solid form of C 60 — fullerite. A band gap of 1.8 eV is found and transition energies of single-electron excitations are in qualitative agreement with published electronic-structure calculations for a truncated icosahedral shape of the C 60 molecule. The absorption coefficient calculated from a Kramers-Kronig analysis agrees qualitatively with UV optical absorption data. The plasmon energy is found to be 25.5 eV — indicating that the electron density in fullerite is similar to that of graphite.

Superconductivity and NMR investigations of KTl1.5-doped C60

Doping of C60 fullerene with KTl1.5 results in superconductivity withTconset=17.6 K as shown by a dc magnetization measurement. Preliminary13C NMR studies on a doped and undoped sample are reported. Compared to original C60 the linewidth increases by a factor of 3, the resonance frequency is shifted by 42 ppm, and the relaxation rateT1−1 is an order of magnitude larger in the intercalated material at room temperature. Both observations support the picture of a metallic sample.

Raman scattering study of C120, a C60 dimer

Abstract A modified preparation method and results of a Raman scattering study for C 120 , a dimer of C 60 , are reported. The Raman features of C 120 are compared with those of the dimer-like oxides C 120 O and C 120 O 2 , phototransformed C 60 and with calculations.

Optical properties of SiC for crystalline/amorphous pattern fabrication

The optical contrast between crystalline and ion beam amorphized regions in SiC has been studied by transmission spectrometry for photon energies ranging up to the ultraviolet. The working range of such an optical device with crystalline/amorphous patterns, e.g., for use as a photolithographic mask, is extended to considerably higher photon energies than with Si as a recording material. Thus, SiC, in the form of thin crystalline layers on a transparent substrate, is a promising candidate for submicron structuring in various fields of application.