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350 results on '"Vul’, A. Ya."'

3. Modification of Detonation Nanodiamonds with Endofullerenols to Obtain Magnetic Photosensitive Structures for Theranostics

Author

Lebedev, Vasily T., Kulvelis, Yuri V., Vul, Alexander Ya., Peters, Georgy S., Vovk, Mikhail A., Orlova, Vera A., Tropin, Timur V., Popova, Maria V., Bolshakova, Olga I., Fomin, Eduard V., He, Liang-Nian, Series Editor, Tundo, Pietro, Series Editor, Zhang, Z. Conrad, Series Editor, Garg, Seema, editor, and Chandra, Amrish, editor

Published
2023
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5. Size Effect in Electron Paramagnetic Resonance Spectra of Impurity Centers in Diamond Nanoparticles

Author

Zegrya, G. G., Samosvat, D. M., Osipov, V. Yu., Vul', A. Ya., and Shames, A. I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The evolution of the polycrystalline pattern of electron paramagnetic resonance (EPR) spectra of intrinsic and induced paramagnetic centers in an ensemble of submicrometer diamond particles on diminishing average particle size is considered. Recent experimental data unambiguously demonstrate consistent reduction and then zeroing of typical hyperfine pattern from P1 centers on approaching a certain particle size and below it. These changes are accompanied by appearance and strengthening of new structureless signals. In small particles the electron wave function of a surface paramagnetic center is delocalized over the whole nanoparticle. In result the electron spin "experiences" the average field of all surrounding nuclei, which is zero. At the same time, the paramagnetic centers localized in the bulk of a nanoparticle are also cut off the hyperfine interaction due to the electron spin diffusion. Thus, upon the nanodiamond particle size decreases the hyperfine related features of the polycrystalline EPR spectrum become weaker and the spectrum appear to be structureless.

Published
2019

16. Nuclear Magnetic Resonance Study of Ultrananocrystalline Diamonds

Author

Panich, A. M., Shames, A. I., Vieth, H. -M., Osawa, E., Takahashi, M., and Vul, A. Ya.

Subjects
Condensed Matter - Materials Science
Abstract

We report on a nuclear magnetic resonance (NMR) study of ultrananocrystalline diamond (UNCD) materials produced by detonation technique. Analysis of the 13C and 1H NMR spectra, spin-spin and spin-lattice relaxation times in purified UNCD samples is presented. Our measurements show that UNCD particles consist of a diamond core that is partially covered by a sp2-carbon fullerene-like shell. The uncovered part of outer diamond surface comprises a number of hydrocarbon groups that saturate the dangling bonds. Our findings are discussed along with recent calculations of the UNCD structure. Significant increase in the spin-lattice relaxation rate (in comparison with that of natural diamond), as well as stretched exponential character of the magnetization recovery, are attributed to the interaction of nuclear spins with paramagnetic centers which are likely fabrication-driven dangling bonds with unpaired electrons. We show that these centers are located mainly at the interface between the diamond core and shell., Comment: 25 pages, 7 figures

Published
2007
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30. Non-thermal and low-destructive X-ray induced graphene oxide reduction.

Author

Mikoushkin, V. M., Kriukov, A. S., Nikonov, S. Yu., Dideikin, A. T., Vul, A. Ya., and Vilkov, O. Yu.

Subjects
GRAPHENE oxide, CHEMICAL reduction, ELECTRONIC excitation, CHALCOGENS, SYNCHROTRON radiation
Abstract

Large-scale graphene fabrication by thermal and chemical reductions of graphene oxide has faced the problem of defect formation. To solve the problem, we have considered a physically alternative reduction process including electronic excitation followed by the oxygen group detachment from the carbon sheet without capturing a sheet of carbon atoms. Single-layer graphene oxide films were studied by photoemission spectroscopy in the course of monochromatic synchrotron X-ray radiation with in situ control of the layer thickness, chemical composition, atomic ordering, and defect concentration exactly in the modified area. The radiation flux was too low to heat the film. A non-thermal and low-destructive effect of X-ray induced graphene oxide reduction has been revealed. Transformation of the sp3 σ bonds into sp2 π ordered bonds, bandgap closing, and significant diminishing of the oxygen content (below 5 at. %) have been observed without any signs of defects in the photoemission spectra. The effective cross section of the oxygen group detachment induced by a soft X-ray photon (hν = 130 eV) was estimated to be σ* ∼ 3 × 10−18 cm2. A reduced single-layer graphene oxide with a narrow bandgap (0.4 – 0.8 eV) attractive for many applications was obtained, as well as almost pure graphene. [ABSTRACT FROM AUTHOR]

Published
2018
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33. Diamond-based nanostructures with metal-organic molecules

Author

Lebedev, Vasily T., primary, Török, Gyula, additional, Kulvelis, Yury V., additional, Bolshkova, Olga I., additional, Yevlampieva, Natalia P., additional, Soroka, Marina A., additional, Fomin, Eduard V., additional, Vul, Alexander Ya, additional, and Garg, Seema, additional

Published
2021
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34. Diamond-based nanostructures with metal-organic molecules.

Author

Lebedev, Vasily T., Török, Gyula, Kulvelis, Yury V., Bolshkova, Olga I., Yevlampieva, Natalia P., Soroka, Marina A., Fomin, Eduard V., Vul, Alexander Ya, and Garg, Seema

Subjects
NANODIAMONDS, SINGLE molecule magnets, MAGNETIC resonance imaging, NEUTRON scattering, NANOSTRUCTURES, SURFACE potential, INELASTIC neutron scattering
Abstract

Recent results on synthesis, structural, and physicochemical studies of complexes based on detonation nanodiamonds modified with metal-organic molecules with functional magnetic and fluorescent properties have been presented. Neutron scattering experiments have discovered subtle features of the assembly of electro-negative molecules of Eu diphthalocyanines and nanodiamonds with positive surface potential in aqueous media. Nanoscale ordering of diamonds reinforced by their linking via diphthalocyanines was confirmed by TEM. The stable complexes possess X-ray luminescent and magnetic properties. Such nanostructures with low toxicity are prospective as contrasting and photoactive agents for magnetic resonance imaging and photodynamic therapy. [ABSTRACT FROM AUTHOR]

Published
2022
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47. Investigation of the effect of hydrogen content on the conductivity of nanocrystalline diamond films

Author

null Vul` A. Ya., null Yakovlev Y. A., null Loginov V. P., null Ovechkin N. M., null Bogdanov S. A., null Vikharev A. L., and null Ivanov O. A.

Abstract

The results are presented for investigation of electrical conductivity of nanocrystalline diamond (NCD) films with thickness of 0.5-0.6 microns grown on silicon Si(100) substrates by the CVD method using methane-hydrogen and methane-hydrogen-oxygen mixtures. By the method of heating in vacuum with using hydrogen analyzer AB-1, the concentration of hydrogen in the studied films was determined and the relationship between the content of hydrogen in the NCD film and its conductivity was estimated. It has been shown that high-temperature processing in vacuum at the temperature of 600oC leads to desorption of hydrogen from the films and to a significant increase in their resistance. Keywords: nanocrystalline diamond, thin diamond films, electrical properties of films, hydrogen content.

Published
2022

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