[show abstract][hide abstract] ABSTRACT: Oxidized fullerite was obtained by heating a fullerite sample intercalated with oxygen, (O2)0.44C60, up to 300 degrees C. Orientational phase transitions in the oxidized fullerite are studied using differential scanning calorimetry (DSC) and have been found to possess a specific enthalpy whose value is lower by 25% than in the initial (O2)0.44C60 sample. In order to find possible reasons for hindrance to the buckyball rotations, we performed optimizations of defect buckyball fullerenes C60-n with different distributions of vacancies along with the dimers C60-n-C60-n and C60-C60-n for n = 1-4 using density functional theory with generalized gradient approximation. We found that the dimerization energy ranges from 1.07 eV (C58-C58) to 6.56 eV (C56-C56) and from 1.81 eV (C60-C58) to 4.29 eV (C60-C56), respectively. The formation of such dimers, which could in addition interact with defect buckyball cages and form larger aggregates, is to be related to the lowering of the orientational transition enthalpy.
Journal of Nanoscience and Nanotechnology 03/2011; 11(3):1887-96. · 1.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Nonpyrophoric tungsten powders with an average particle size of about 30 nm were obtained by pyrolysis of tungsten hexacarbonyl
in a flow of microwave discharge nitrogen plasma. It is found that these powders are stable in air up to 300°C. The reason
for such stability is that the structure of powder particles is of the core-double shell type, in which the metal core is
covered with an oxide film approximately 1 nm in thickness, coated in turn with roentgenoamorphous layer consisting of carbon,
oxygen, and nitrogen atoms. It is also established that the powders under investigation mainly release carbon oxides (CO and
CO2) and water into the gas phase upon heating in vacuum. Among the molecules present in the gas phase in small concentrations,
nitrogen monoxide (NO) and formaldehyde (H2CO) are worth mentioning apart from C1–C3 hydrocarbons.
[show abstract][hide abstract] ABSTRACT: Mass-spectrometric investigation of gases produced by heating in vacuum fluorinated single-wall nanotubes (with fluorine content of 25 mass %) which have been kept in air was carried out. It has been shown that nanotubes, which are preliminary, treated in vacuum at 23 °C, being heated in the temperature range from 23 to 100 °C produce generally H2O, CO and CO2. The gases containing fluorine appear in the range from 100 to 150 °C. In the range of 150–300 °C the mixture of disintegration products contain molecules COF2, and in the range of 300–400 °C mostly CF4 and C4F6 appear.
International Journal of Hydrogen Energy. 01/2011;
[show abstract][hide abstract] ABSTRACT: The photoreduction of graphite oxide (GO) films and solutions by UV light was studied. The electrical resistance of a GO film decreases upon irradiation by more than an order of magnitude. The threshold of photoreduction was determined to be 3.2 eV. The photoreduction is accompanied by an increase in absorption in the visible spectral region, and the CO, CO2, O2, and H2O molecules were found in the gas phase above the irradiated GO film.
High Energy Chemistry 01/2011; 45(1):57-61. · 0.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: The composition of gases over a graphite oxide is found to depend on the temperature with CO2 being the main component with a range of 23–460 °C. In the temperature range of 150–230 °C, where the most intense yield of gases was observed, CO forms in small amounts. CH4 and CH2O were produced at temperatures below 230 °C, O2 was observed at 150–300 °C, while the complex H2OH·COOH was produced at temperatures above 150 °C. When films composed of graphite oxide nano-sheets were exposed to UV radiation, CO2, CO, H2O, and O2 were produced.
Chemical Physics Letters 08/2010; 498(4-6):287-291. · 2.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: The mass spectra of the dissociative electron-impact ionization products of telomers formed upon the radiation-chemical telomerization
of tetrafluoroethylene in acetone were measured over the range of m/z from 1 to 204. The most intense bands at m/z = 43, 51, and 57 were attributed to the CH3CO+, CF2H+ and CH3COCH2+ cations—the main dissociation products of the H(C2F4)
CH2COCH3 telomers. The telomer composition was consistent with a radical telomerization mechanism, in which chain growth and chain
transfer are due to the formation of the CH3COCH2· radical. Based on published data supplemented with quantum-chemical calculations, the enthalpies of formation of the radicals
(n = 2–8; R = H, CH3, CH3CO, and CH3COCH2) were tabulated. The formation of telomers with the same terminal groups is consistent with thermodynamic data and a polymerization
mechanism in which the chain growth reaction is diffusion-limited and the chain transfer reaction is activated hydrogen-atom
High Energy Chemistry 01/2010; 44(6):449-454. · 0.64 Impact Factor
[show abstract][hide abstract] ABSTRACT: We have obtained fullerite intercalated with CH2F2 by precipitation of C60 from the solution in 1,2-dichlorobenzene saturated by CH2F2. The chemical composition was identified as (CH2F2)xC60 (x = 1.03 ± 0.21). The fcc lattice parameter (14.28 Å) was found to increase significantly for (CH2F2)C60 in comparison with that for pristine C60 (14.16 Å). The IR absorption peak attributed to the stretching vibration of the C–F bond in (CH2F2)C60 was 30 cm–1 shifted to lower wave numbers in comparison with the gas phase CH2F2 spectrum.
physica status solidi (RRL) - Rapid Research Letters 12/2009; 3(2):43-45. · 2.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: Fullerite with the bulk formula ArxC60, where 0.60 < x < 0.75, was synthesized by precipitation from a mixture of argon-saturated solutions. The fcc unit cell parameter in the
sample was 1.422 nm; the orientational phase transition (OPT) temperature was 247 K. These values noticeably differ from the relevant parameters of undoped fullerite (1.416 nm and 260 K, respectively). Heating accompanied by argon evolution restores
the fullerite C60 structure.
[show abstract][hide abstract] ABSTRACT: The optimum conditions for the fluorination of single-walled carbon nanotubes (SWCNT) in the atmosphere of gaseous fluorine
with the nanotube structure remaining intact up to a stoichiometry of CF
, x ∼ 0.5 were determined. The kinetics of fluorination was examined. The fluorinated SWCNTs were characterized by various methods,
including transmission electron microscopy, measurements of specific surface area and accessible internal volume, NMR spectroscopy,
IR spectroscopy, X-ray absorption and photoelectron spectroscopies, thermal stability, and analysis of gaseous products by
mass-spectrometry. The structure of fluorinated SWCNT was preserved up to brutto-composition CF0.5 but degree of fluorination of SWCNT bundles was decreased with distance from the SWCNT surface to its core. Such a decrease
becomes evident at ∼1.5 nm distance. It means that the degree of fluorination depends on the degree of its dispersion.
[show abstract][hide abstract] ABSTRACT: C60 fullerite intercalated by acetylene was synthesized for the first time and studied by a number of experimental methods. It is found that the intercalate obtained corresponds to (C2H2)0.23C60 and possesses an fcc lattice. We also performed optimizations of the C60+C2H2 complex using density functional theory with the generalized gradient approximation. Two complexes were studied corresponding to acetylene chemisorbed by or inserted inside C60. Both complexes do correspond to local minima that are lower than the dissociation limit to C60 and C2H2. However, these complexes were not observed in experiment most likely because of their high energy barriers.
Chemical Physics Letters 01/2009; 483:115-119. · 2.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: Processes induced by the heating of C60 fullerite intercalated by oxygen are analyzed using mass-spectrometry, thermogravimetry, differential scanning calorimetry, and electronic spin resonance (ESR) techniques. It was found that the primary gas produced at the heating temperatures below 100 °C is molecular oxygen while at higher temperatures up to 200 °C carbon mono- and dioxides were also observed. The heating was accompanied by an appreciable increase in the ESR signal intensity. In order to gain insight into the oxidation products that are capable to contribute to the ESR signal, we performed all-electron density functional theory computations for C58On (n = 0−4), C59On (n = 0−2), and endohedral complexes O2@C58, O2@C59, and O2@C60. It is found that the triplet states of C58, C58O3, O2@C58O2, O2@C58, and O2@C60 are lower in total energy than the corresponding triplet states. The singlet and triplet states of C59, O2@C59, and C602− are nearly degenerate in total energy. Thus, there are a number of species that can be responsible for the paramagnetic behavior observed in the oxidized fullerene.
Journal of Physical Chemistry C - J PHYS CHEM C. 07/2008; 112(32).
[show abstract][hide abstract] ABSTRACT: Fullerite C60 with intercalated CH2F2 (Freon-32) was prepared for the first time. The sample was studied by elemental analysis, X-ray powder diffraction, mass
spectrometry, and IR spectroscopy. The composition of the sample was found to be (CH2F2)C60. The sample had a face-centered cubic lattice with the lattice parameter (1.4284 nm) much larger than that of pure fullerite
(1.416 nm). The gas released from the sample during heating in a vacuum to 450°C largely consisted of initial Freon (mass
spectrometry data); no Freon destruction products were observed at this temperature. The C-F stretching vibration frequency
(1058 cm−1) was shifted in (CH2F2)C60 by 30 cm−1 toward lower wave numbers compared with the gas phase. The absorption bands at 1182 and 1428 cm−1 (IR active modes (F
) of high-symmetry (I
) C60 molecules) did not change their positions in the intercalate.
[show abstract][hide abstract] ABSTRACT: For fullerite C60 with intercalated oxygen, a sharp (by three orders of magnitude) increase in the intensity of the EPR signal with a g-factor of 2.0024 was observed at ∼200°C. Studies of gases formed in heating of the sample in a vacuum showed that molecular
oxygen was largely released at temperatures below 100°C, whereas the gas phase formed as the temperature increased to 200°C
contained carbon oxides CO and CO2 in addition to oxygen. The conclusion was drawn that the intensity of the EPR signal was determined by the products of oxygen
interaction with fullerene rather than the concentration of oxygen in the sample.
[show abstract][hide abstract] ABSTRACT: Gas interstitial fullerenes was produced by precipitation of C60 from the solution in 1,2 dichlorobenzene saturated by O2, N2, or Ar. The structure and chemical composition of the fullerenes was characterized by X-ray powder diffraction analysis,
FTIR spectroscopy, thermal desorption mass spectrometry, differential scanning calorimetric and chemical analysis.The images of fullerene microcrystals were analysed by SEM equipped with energy dispersive X-ray spectroscopy (EDS) attachment. Thermal desorption mass spectroscopy and EDS analysis confirmed the presence of Ar, N and O in C60 specimens.
[show abstract][hide abstract] ABSTRACT: Two methods are described for doping of fullerite C60 with molecular oxygen at a pressure of ∼104 Pa and at temperature 20–30 °C. It was found by mass spectrometry using oxygen
18O as dopant that a portion of molecular oxygen absorbed by the pre-decontaminated fullerite (first method) is removed as CO
and CO2 at the heating temperature ≤200 °C. Doping during fullerite precipitation from the liquid phase (second method) makes it
possible to prepare samples with the oxygen content ≥1.2 at.%. The fullerite doped with oxygen to this level is diamagnetic.
The paramagnetic properties of an O2 molecule disappear when O2 is incorporated into the fullerene lattice. This is interpreted on the basis of quantum chemical calculations as a sequence
of equilibrium formation of the adduct C60O2. Calculations showed that the subsequent chemical transformation of C60O2 resulting in the O-O bond cleavage is energetically favorable, enabling prerequisites for the formation of products of incomplete
(CO) and deep (CO2) oxidation of fullerene under mild conditions.
Russian Chemical Bulletin 03/2006; 55(4):687-696. · 0.42 Impact Factor
[show abstract][hide abstract] ABSTRACT: The mass‐spectrometric investigation of the gases evolved from fluorinated multi‐walled carbon nanotubes under heating was carried out. It was shown that in temperature interval from 20°C to 120°C the gases are composed predominantly of CO2, CO and H2O. Molecules of COF2 can be finding in gas phase of products of decomposition at 120–300°C. Molecules of CF4 and C2F6 realized from fluorinated nanotubes at 300–450°C.
[show abstract][hide abstract] ABSTRACT: Bi-nuclear neutral sulfur–nitrosyl iron complex [Fe2(SR)2(NO)4] (I) has been obtained by replacement of thiosulfate ligands in dianion [Fe2(S2O3)2(NO)4]2− by 1-methyl-imidazole-2-yl. From X-ray analysis data, the complex has centrosymmetrical dimeric structure, with the iron atoms being linked via μ-N–C–S bridge. From Mossbauer spectroscopy, isomeric shift δFe is 0.180(1) mm/s and quadrupole splitting ΔEQ is 0.928(2) mm/s at T = 290 K. By comparative studying the mass-spectra in the gaseous phase of solid samples decomposition and kinetics of NO release in 1% aqueous solutions of dimethylsulfoxide, using of the ligand with CH3 substituent in position 1 of imidazole-2-thiol was shown to yield a more stable donor of nitrogen monoxide than earlier obtained analog with imidazole-2-thiol, [Fe2(C3H3N2S)2(NO)4].