Production of carbon soot with a high content of C60 and C70 fullerenes by electric arc

The effect of the parameters of the electric arc (helium pressure, current and voltage, clearance between electrodes) and of the peculiarities of the setup design (arrangement of electrodes, distance between the arc and the cooling surface, temperature of the soot condensation surface) on the yield of fullerenes has been studied. Conditions for producing soot with a C₆₀ and C₇₀ content up to 43% (toluene extract) have been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 805–809, May, 1994.The authors are grateful to N. G. Spitsyna and A. V. Dubovitskii for the determination of the content of C₆₀ and C₇₀ fullerenes in the extract.The work was financially supported by the Russian Foundation for Basic Research (Project 93-03-18705).     

Influence of conditions for preparation of fullerene-containing carbon black on its microwave properties and yield of fullerenes

Conditions for preparation of the fullerene-containing carbon black with the maximum yield of fullerenes were determined. A correlation between the dielectric constant of the carbon black in the microwave range and the yield of fullerenes was found. The relation of the fullerene-containing carbon black structure to the conditions of its preparation and dielectric constant are discussed.     

Microwave-assisted extraction of C60 and C70 from fullerene soot

Microwave-assisted extraction (MAE) was examined as an alternative to the traditional Soxhlet method of extracting C₆₀ and C₇₀ from fullerene soot. MAE of 0.20 g of fullerene soot with 95:5 toluene–acetonitrile yielded greater than 7.8 mg of C₆₀ and greater than 0.54 mg of C₇₀ in 4 min with no further increase in yield after 30 min of irradiation. By comparison, exhaustive Soxhlet extraction of the same size sample with the same solvent yielded 7.1 mg of C₆₀ and 0.58 mg of C₇₀ in 340 min. Reextraction by MAE of soot initially extracted by Soxhlet increased the yield of Soxhlet alone. Although MAE was limited to less than 0.5-g sample per extraction vessel, multiple samples were extracted with minimal increased extraction time and no reduction in the amount of material recovered.     

Concerning the existence of linear carbon molecules in soot obtained in an electric arc

The presence of soluble linear carbon molecules in fullerene-containing soot obtained by arc spraying of graphite was confirmed by Fourier IR spectroscopy, electron diffraction, mass spectrometry, and NMR spectrometry data. Carbon chains are oriented in the layer perpendicular to the support surface and are packed in a hexagonal crystal lattice with d₁₁₀ = 4.35 Å.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1387–1390, July, 1995.The present work was supported by the Russian Foundation for Basic Research (Project Nos. 93-03-4492 and 93-03-18705).     

Extraction equilibria in the fullerene-containing system C60-C70-1,2,4-trichlorobenzene-ethanol-H2O

The liquid (I)-liquid (II) extraction equilibria in the five-component system fullerene C₆₀-fullerene C₇₀-1,2,4-C₆H₃Cl₃-C₂H₅OH-H₂O were studied at 25°C. Isothermal diagrams of distribution of the fullerene components among stratifying liquid phases at a constant content of H₂O were obtained.     

Supramolecular hybrids of [60]fullerene and single-wall carbon nanotubes

Noncovalent interactions between purified HiPCO single-wall carbon nanotubes (SWNT) and a [60]fullerene-pyrene dyad, synthesized through a regioselective double-cyclopropanation process, produce stable suspensions in which the tubes are very well dispersed, as evidenced by microscopy characterization. Cyclic voltammetry experiments and photophysical characterization of the suspensions in organic solvents are all indicative of sizeable interactions of the pyrene moiety with the SWNT and, therefore, of the prevalence in solution of [60]fullerene-pyreneSWNT hybrids.     

Do Carbon Nano-onions Behave as Nanoscopic Faraday Cages? A Comparison of the Reactivity of C60, C240, C60@C240, Li+@C60, Li+@C240, and Li+@C60@C240

From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C₂₄₀ cage should be the same in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀. In this work, the Diels–Alder reaction of cyclopentadiene to the free C₂₄₀ cage and the C₆₀@C₂₄₀ CNO together with their Li⁺-doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C₂₄₀. Encapsulation of Li⁺ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C₂₄₀ cage. When the Li⁺ is placed inside the CNO C₆₀@C₂₄₀, the decrease in enthalpy barrier is similar to that of Li⁺@C₂₄₀. However, the location of Li⁺ in Li⁺@C₂₄₀ (off-centered) and Li⁺@C₆₀@C₂₄₀ (centered) is quite different. When Li⁺ was placed in the center of the C₂₄₀ cage in Li⁺@C₂₄₀, the barriers increased significantly. Taking into account this effect, the barriers in Li⁺@C₂₄₀ and Li⁺@C₆₀@C₂₄₀ differ by about 4 kcal mol⁻¹. This result can be attributed to the shielding effect of C₆₀ in Li⁺@C₆₀@C₂₄₀. As a result, we conclude that this CNO does not act as a perfect Faraday cage.     

Electrochemical polymerization of fullerene C60

Cyclic voltammetry data show that fullerene C₆₀ films on the Pt electrode surface in MeCN are electropolymerized to form polymeric C₆₀. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 863–865, April, 1997.     

Extraction of atabron residues from cabbage with supercritical carbon dioxide

Summary In this work we present a new procedure for extraction of Atabron residues from cabbage samples using supercritical carbon dioxide. The results obtained with this procedure were compared with those obtained using traditional extraction methods for Atabron residues. The extraction yields found by both procedures are similar but SFE has several advantages, especially higher speed, greater economy, better selectivity and greater reproducibility.     

Contrasting photodynamics between C60-dithiapyrene and C60-pyrene dyads

The photodynamics of a C60-dithiapyrene donor-acceptor conjugate were compared with the corresponding C60-pyrene conjugate. The photoinduced charge separation and subsequent charge recombination processes were examined by time-resolved fluorescence measurements on the picosecond timescale and transient absorption measurements on the picosecond and microsecond timescales with detection in the visible and near-infrared regions. We have observed quite long lifetimes (i.e., up to 1.01 ns) for the photogenerated charge-separated state in a C60-dithiapyrene dyad without the need for i) a long spacer between the two moieties, or ii) a gain in aromaticity in the radical ion pair.     

Interaction of fullerene C60 with iodine in organic solvents

The interaction of fullerene C₆₀ with molecular iodine in organic solvents was studied. The stoichiometry of the complex formed, C₆₀I₂=13, was determined spectrophotometrically and by the interphase distribution technique. The constant of the formation of the adduct in toluene was calculated to be logK=8.9±0.3.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 481–483, March, 1995.     

超临界CO_2萃取甾醇的研究(1)

本文用超临界ＣＯ＿２对高酸价麦胚油进行选择住萃取，结果表明，萃取温度和压力不同时，萃取物中甾醇的含量不同．且甾醇混合物主要为β－谷甾醇和菜籽甾醇。萃取物的酸价也明显高于高酸价麦胚油。     

Bond orders and atomic properties of the highly deformed halogenated fullerenes C60F18 and C60Cl30 derived from their charge densities

The experimental charge densities of the halogenated C(60) fullerenes C(60)F(18) and C(60)Cl(30) were determined from high-resolution X-ray data sets measured with conventional Mo(Kalpha) radiation at 20 K for C(60)Cl(30) and with synchrotron radiation at 92 K for the fluorine compound. Bond topological and atomic properties were analyzed by using Bader's AIM theory. For the different C--C bonds, which vary in lengths between 1.35 and 1.70 A bond orders n between n=2 and significantly below n=1 were calculated from the bond topological properties at the bond critical points (BCP's). The low bond orders are seen for 5/6 bonds with each contributing carbon carrying a halogen atom. By integration over Bader's zero flux basins in the electron density gradient vector field atomic properties were also obtained. In contrast to free C(60), in which all carbon atoms have a uniform volume of 11 A(3) and zero charge, atomic volumes vary roughly between 5 and 10 A(3) in the halogenated compounds. Almost zero atomic charges are also found in the Cl derivative but a charge separation up to +/-0.8 e exists between C and F in C(60)F(18) due to the higher fluorine electronegativity, which is also seen in the electrostatic potential for which the electronegativity difference between carbon and fluorine, and the addition to one hemisphere of the fullerene cage leads to a strong potential gradient along the C(60)F(18) molecule. From the summation over all atomic volumes it follows that the halogen addition does not only lead to a dramatic distortion of the C(60) cage but also to a significant shrinkage of its volume.