Henrik Rausch

Endohedral incorporation of argon atoms into C60 by neutron irradiation

Abstract It is demonstrated that by neutron irradiation of polycrystalline C60 in an argon atmosphere or of C60 crystals containing absorbed or adsorbed argon, a stable endohedral argon compound is formed. The concentration of argon has been determined by instrumental neutron activation analysis via the short-lived 41Ar isotope. It is supposed that the endohedral compound is formed by penetration of the argon atom into the C60 cages; a mechanism due to the high kinetic energy recoiling 41Ar atoms according to the 40Ar(n, γ)41Ar nuclear reaction seems the most plausible.

Radioactive endohedral metallofullerenes formed by prompt gamma-generated nuclear recoil implosion

Abstract Previous investigations by instrumental neutron activation analysis of a variety of C60, C70 fullerenes and fullerene precursors have shown that these compounds contain non-negligible amounts of about 35 elemental trace impurities. These impurities may be distributed on the surface of the C60 and C70 samples and/or at some interstitial positions of the crystal lattice. Some of these impurity atoms can penetrate the fullerene cages by nuclear recoil during neutron irradiation. The recoiled atoms move with a large kinetic energy which they successively lose upon excitation and ionization on the atoms of the fullerene crystals. After reduction of the kinetic energy below ∼100 eV, this energy is enough for the atom to implode into the fullerene cages. Results are reported on the formation of some endohedral radioactive metal fullerenes.

Dose effect in neutron-irradiated C60: a positron lifetime spectroscopy and DSC study

Abstract Polycrystalline C 60 samples irradiated with five doses of nuclear reactor neutrons stretching from 2.44 × 10 14 to 1.03 × 10 18 n/cm 2 were investigated by positron annihilation spectroscopy and DSC. The measurements indicated that the crystal structure of buckminsterfullerene is unaffected up to a dose of about 7.56 × 10 16 n/cm 2 . Above that dose the crystal lattice begins to collapse and at a dose of 1.03 × 10 18 n/cm 2 the structure becomes totally disordered.

Distribution of toxic elements in fly-ash particulates

Abstract The physical properties and the chemical compositions of various lignite and coal fly-ash particulate matters sampled in the four main power plants in Hungary are investigated. The morphology of the particles is studied by optical microscopy and SEM, while for chemical analysis SEM micro-X-ray analysis, INAA and ICP-AES/AAS techniques are used. Analytical results are given for about 30 minor- and micro-components. Distribution coefficients for 16 selected toxic elements are calculated among the various species of fly-ash fractions investigated.

Determination of traces of elemental impurities in single walled (SWNT) and multi walled (MWNT) pristine and purified carbon nanotubes by instrumental neutron activation analysis

By using instrumental neutron activation analysis (INAA) it has been shown that some pristine carbon SWNTs and MWNTs of different makes, contain a multitude of trace element impurities at various concentration levels including also amounts which can be considered as nanoelectronically dopant quantities. The same holds for the above mentioned carbon nanotubes also after their inadequately so-called purification.

The survivability of polycrystalline C60 to high speed vibration milling

Abstract For the solvent free mechanochemical synthesis of fullerene compounds as initiated by us in 1994, it became necessary to know how the polycrystalline C 60 structures resist to high speed vibration milling (HSVM). We have shown that there is no mechanical damage in the C 60 molecule up to a HSVM time of 30 min.

Multielemental Characterization of Several Brands of Fullerenes and Fullerene Precursors by Instrumental Neutron Activation Analysis

The characterization of the purity of fullerenes is based on the concept of defining the percentage amount of the main component (e.g., C(60), C(70), etc.) versus the minor fractions or microfractions of the homologue species and/or other polycyclic organic compounds. It has also to be considered that fullerene products may be contaminated in some degree by element impurities as well, both from the production processes and from the various precursor materials themselves. We report here for the first time detailed data on trace element impurities in various fullerene precursors as well as in the main C(60) and C(70) fullerene products of different producers, measured by instrumental neutron activation analysis. The concentration distributions of about 35 trace elements have been studied, including the determination of the relevant limits of detection. It could be established that all fullerene materials investigated contain a broad scale of trace elements distributed within a fairly wide concentration range, from ppb (ng/g) up to ppm (μg/g) levels. For some impurity elements, extremely high concentration levels were found, indicating that elemental impurities have to be considered when studying the electrical, magnetic, and other features of the fullerenes.

Antiretroviral effects of nonderivatized C60 in vitro

Abstract We have observed thai nonderivatized C60 (buckminsterfullerene) could inhibit the replication of simian immunodeficiency virus (SIV) in vitro and the activity of Moloney murine leukemia virus (M-MuLV) reverse transcriptase (RT) (IC50 ≈3 μM). This means that biological effects are exerted via a direct and active interaction of the C6o skeleton with other macromolecules.

Sublimation behaviour of C60 and of the endohedral radiofullerenes formed by nuclear recoil implosion via neutron irradiation

Abstract A sublimation procedure has been developed to detect radioactive nuclides which have formed an endohedral radiofullerene by nuclear implosion via neutron irradiation. The detection of the endohedralized nuclide has been demonstrated on the example of the sublimable 140 La @ C 60 . The procedure can be also used in the case of other endohedral radionuclides formed by nuclear recoil implosion.

Analysis of toxic and radioactive components in sedimental type air particulates by INAA and XRF

The chemical composition of brown coal fuels and several sedimental type atmospheric particulate pollutants of industrial origin (e.g. fly-ash, bottom-ash, dust particulates from foundry-halls and casting-halls) was studied in relation to their toxic and their natural radioactive contents. In addition, some agricultural crops (e.g. soya bean, sunflower, rape, barley and luceme) sampled, in the near vicinity within a radius of about 10 km of the industrial centre were also analysed for significant distributions of any toxic components. Because of the high uranium and thorium concentrations in Hungarian coal fuels and, consequently, in various fly-ash particulate pollutants, the natural gamma activities of the samples were also measured and the relevant equilibriu states of the232Th and238U natural decay series were studied.