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Elena F. Sheka

Bio: Elena F. Sheka is an academic researcher from Peoples' Friendship University of Russia. The author has contributed to research in topics: Graphene & Fullerene. The author has an hindex of 23, co-authored 158 publications receiving 1740 citations. Previous affiliations of Elena F. Sheka include National Academy of Sciences of Ukraine.


Papers
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Book
01 Nov 1985
TL;DR: Molecular excitons may or may not play an important role in the newly discovered high-temperature superconductors They also may or might not play important roles in the nervous system as mentioned in this paper, but they certainly do play a role in organic conductors, in the characterization of polymers, and in the primary process of photosynthesis.
Abstract: Molecular excitons may or may not play an important role in the newly discovered high-temperature superconductors They also may or may not play an important role in the nervous system They certainly do play an important role in organic conductors, in the characterization of polymers, and in the primary process of photosynthesis The discovery of molecular excitons, as well as their basic characterization, comes from work on molecular crystals, mainly from spectroscopic work Based on an earlier Russian version, this book is a beautiful exposition of more than two decades of work based, to an important extent, in the Soviet Union and in which the three authors played a major role

98 citations

Journal ArticleDOI
TL;DR: Shungite is presented as a natural carbon allotrope of a multilevel fractal structure that is formed by a successive aggregation of reduced graphene oxide nanosheets.
Abstract: Shungite is presented as a natural carbon allotrope of a multilevel fractal structure that is formed by a successive aggregation of ~1 nm reduced graphene oxide nanosheets. Turbostratic stacks of the sheets of ~1.5 nm in thickness and globular composition of the stacks of ~6 nm in size determine the secondary and tertiary levels of the structure. Aggregates of globules of tens of nanometers complete the structure. Molecular theory of graphene oxide, supported by large experience gained by the modern graphene science, has led to the foundation of the suggested presentation. The microscopic view has found a definite confirmation when analyzing the available empirical appearance of shungite. To our knowledge, this is the first time a geological process is described at quantum level.

66 citations

Journal ArticleDOI
TL;DR: In this article, the phonon dispersion curves for the 12 external and the four lowest internal modes in d8-naphthalene (C10D8) have been determined at 6K for the ( xi, 0,0), (0, xi, 0), ( 0, 0, xi ), (1/2, xI, 0) and ( x i, xa, 0) directions by coherent inelastic neutron scattering.
Abstract: The phonon dispersion curves for the 12 external and the four lowest internal modes in d8-naphthalene (C10D8) have been determined at 6K for the ( xi ,0,0), (0, xi ,0), (0,0, xi ), (1/2, xi ,0) and ( xi , xi ,0) directions by coherent inelastic neutron scattering. The results agree very well with optical data. Calculations performed in the harmonic approximation for the rigid-molecule model based on the atom '6-exp' potential were carried out beforehand to produce inelastic structure factors, which turned out to be very useful in the experimental work. This model predicts the qualitative behaviour of the dispersion curves surprisingly well, although some frequencies do differ by 20%. The experimental results show many mode-mixing and anticrossing effects. The present results should serve as a basis for improvements on the model.

63 citations

Book
16 Feb 2011
TL;DR: In this paper, the Hartree-Fock approach was used as a basis for a quantitative description of odd electrons in the fullerene community, including odd electron structure of fullerenes C60 and C70.
Abstract: Single-determinant Hartree-Fock approach as basis for a quantitative description of odd electrons Odd electron structure of fullerenes C60 and C70 Computational synthesis of the fullerene C60 derivatives Intermolecular interaction in the fullerene community Oligomerization of fullerenes C60 and C70 Magnetism of fullerenes C60 and C70 Medicinal chemistry of fullerenes Nanophotonics of fullerenes Fullerenes, carbon nanotubes, and graphene - similarity and difference

46 citations

Journal ArticleDOI
TL;DR: In this paper, the molecular theory of graphene oxide is applied to graphene oxide, which considers its oxide as a final product in a succession of polyderivatives related to a series of oxidation reactions involving different oxidants.
Abstract: Applied to graphene oxide, the molecular theory of graphene considers its oxide as a final product in the succession of polyderivatives related to a series of oxidation reactions involving different oxidants. The graphene oxide structure is created in the course of a stepwise computational synthesis of polyoxides of the (5,5) nanographene molecule governed by an algorithm that takes into account the molecule’s natural radicalization due to the correlation of its odd electrons, the extremely strong influence of the structure on properties, and a sharp response of the molecule behavior on small actions of external factors. Taking these together, the theory has allowed for a clear, transparent and understandable explanation of the hot points of graphene oxide chemistry and suggesting reliable models of both chemically produced and chemically reduced graphene oxides.

46 citations


Cited by
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Journal ArticleDOI
TL;DR: This paper presents a probabilistic procedure for estimating the polymethine content of carbon dioxide using a straightforward two-step procedure, and shows good results in both the stationary and the liquid phase.
Abstract: Liming Dai,*,†,‡ Yuhua Xue,†,‡ Liangti Qu,* Hyun-Jung Choi, and Jong-Beom Baek* †Center of Advanced Science and Engineering for Carbon (Case4Carbon), Department of Macromolecular Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States Key Laboratory of Cluster Science, Ministry of Education of China, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, Department of Chemistry, School of Science, Beijing Institute of Technology, Beijing 100081, People’s Republic of China School of Energy and Chemical Engineering/Center for Dimension-Controllable Covalent Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon, Ulsan, 689-798, South Korea

1,967 citations

Journal ArticleDOI
01 Oct 1971-Nature
TL;DR: Lipson and Steeple as mentioned in this paper interpreted X-ray powder diffraction patterns and found that powder-diffraction patterns can be represented by a set of 3-dimensional planes.
Abstract: Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

1,867 citations

Journal ArticleDOI
TL;DR: This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods and describes the most important work which has been published in this field since the emergence of OMBD in the mid-1980s.
Abstract: During the past decade, enormous progress has been made in growing ultrathin organic films and multilayer structures with a wide range of exciting optoelectronic properties. This progress has been made possible by several important advances in our understanding of organic films and their modes of growth. Perhaps the single most important advance has been the use of ultrahigh vacuum (UHV) as a means to achieve, for the first time, monolayer control over the growth of organic thin films with extremely high chemical purity and structural precision.1-3 Such monolayer control has been possible for many years using well-known techniques such as Langmuir-Blodgett film deposition,4 and more recently, self-assembled monolayers from solution have also been achieved.5 However, ultrahighvacuum growth, sometimes referred to as organic molecular beam deposition (OMBD) or organic molecular beam epitaxy (OMBE), has the advantage of providing both layer thickness control and an atomically clean environment and substrate. When combined with the ability to perform in situ highresolution structural diagnostics of the films as they are being deposited, techniques such as OMBD have provided an entirely new prospect for understanding many of the fundamental structural and optoelectronic properties of ultrathin organic film systems. Since such systems are both of intrinsic as well as practical interest, substantial effort worldwide has been invested in attempting to grow and investigate the properties of such thin-film systems. This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods. We will describe the most important work which has been published in this field since the emergence of OMBD in the mid-1980s. Both the nature of thin-film growth and structural ordering will be discussed, as well as some of the more interesting consequences to the physical properties of such organic thin-film systems will be considered both from a theoretical as well as an experimental viewpoint. Indeed, it will 1793 Chem. Rev. 1997, 97, 1793−1896

1,809 citations

Journal ArticleDOI
23 Apr 2012-Small
TL;DR: Progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage is reviewed, along with some discussions on challenges and perspectives in this exciting field.
Abstract: It is estimated that the world will need to double its energy supply by 2050. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. Comparing to conventional energy materials, carbon nanomaterials possess unique size-/surface-dependent (e.g., morphological, electrical, optical, and mechanical) properties useful for enhancing the energy-conversion and storage performances. During the past 25 years or so, therefore, considerable efforts have been made to utilize the unique properties of carbon nanomaterials, including fullerenes, carbon nanotubes, and graphene, as energy materials, and tremendous progress has been achieved in developing high-performance energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) devices. This article reviews progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage, along with some discussions on challenges and perspectives in this exciting field.

1,287 citations

01 Jan 1958
TL;DR: In this article, it was shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions).
Abstract: It is shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions). A more complete theory is developed. It is shown that excitons are approximate bosons, and, in interaction with the electromagnetic field, the exciton field plays the role of the classical polarization field. The eigenstates of the system of crystal and radiation field are mixtures of photons and excitons. The ordinary one-quantum optical lifetime of an excitation is infinite. Absorption occurs only when "three-body" processes are introduced. The theory includes "local field" effects, leading to the Lorentz local field correction when it is applicable. A Smakula equation for the oscillator strength in terms of the integrated absorption constant is derived.

1,238 citations