Limitations of the Fluorination of Graphene on a Substrate

The experimentally observed incomplete fluorination of graphene (CF _x , x ≤ 0.2?0.3) on a smooth substrate has been explained. It has been shown that fluorine atoms are covalently attached primarily to scanty folds or to defects of graphene on one of its free sides.     

Hybrids of carbyne and fullerene

A new class of quasi-linear carbon molecules [C₆₀] _n [C _m ]_n?1 consisting of n fullerenes C₆₀ linked by n?1 carbyne-type C _m fragments with a system of conjugated bonds is described. The possible geometric configurations of such molecules and crystals on their base are discussed. The structure optimization by the empirical (MM+), semiempirical (PM3), and ab initio (HF/6-21) methods showed that these molecules are energetically stable.     

C<Subscript>60</Subscript> fullerene decoration of carbon nanotubes

A new fully carbon nanocomposite material is synthesized by the immersion of carbon nanotubes in a fullerene solution in carbon disulfide. The presence of a dense layer of fullerene molecules on the outer nanotube surface is demonstrated by TEM and XPS. Fullerenes are redistributed on the nanotube surface during a long-term action of an electron beam, which points to the existence of a molecular bond between a nanotube and fullerenes. Theoretical calculations show that the formation of a fullerene shell begins with the attachment of one C₆₀ molecule to a defect on the nanotube surface.     

Electronic and transport properties of heterophase compounds based on MoS<Subscript>2</Subscript>

New heterophase superlattices based on MoS₂ are studied in detail by the electron density functional theory. It is shown that the incorporation of the 1Т phase in the 2H-MoS₂ monolayer is responsible for the formation of electronic levels near the Fermi level and quantum wells in the transverse direction of superlattices. The proposed lateral heterophase structures of transition metal dichalcogenides are promising for the construction of new elements of nanoelectronics.     

Transition Mechanism from Semimetallic to Semiconductor Behavior in a Graphene Film at the Formation of a Multiply Connected Structure

JETP Letters - Recently, it has been found that “closed” nanopores with connected edges lying in neighboring layers can be formed in films consisting of one-to-five-layer graphene...     

A calculation model for X-ray diffraction by curved-graphene nanoparticles

An approximation of the positions of carbon atoms in a curved graphene sheet is suggested for calculation of X-ray diffraction (XRD) patterns of curved-graphene nanoparticles. The model is tested for carbon nanotubes and newly calculated carbon nanotoroids consisting of several hundreds of atoms. It is shown that the random distribution of carbon atoms with graphene surface-averaged density and the local graphene-like rearrangement of atoms in a curved lattice are sufficient for describing the XRD patterns of an ensemble of respective exact carbon nanoparticles of random isotropic orientation in the range of scattering wave vector's modulus q from several units to several tens of inverse nanometers. The model is of interest to a fast-routine identification of curved-graphene nanoparticles in carbonaceous materials.     

Formation,structure, and properties of “welded” <Emphasis Type="Italic">h</Emphasis>-BN/graphene compounds

Structures of h-BN/graphene with holes where atoms at the edges are bonded to each other by sp² hybridized C–B and C–N bonds and form continuous junctions from layer to layer with topological defects inside holes have been considered. Their formation, as well as the moiré-type stable atomic structure of such compounds (with different rotation angles of graphene with respect to the hexagonal boron nitride monolayer) with closed hexagonal holes in the AA centers of packing of the moiré superlattice, has been studied. The stability, as well as the electronic and mechanical properties, of such bilayer BN/graphene nanomeshes has been analyzed within electron density functional theory. It has been shown that they have semiconducting properties. Their electronic band structures and mechanical characteristics differ from the respective properties of separate monolayer nanomeshes with the same geometry and arrangement of holes.     

A model of single-electron transport. Calculation of the thermodynamic parameters for electron capture by the bound proton of oxyacids

Electron transfer is an elementary chemical event involved in many biochemical reactions. Experiments have shown that some oxyacids participating in electron transport are capable of dissociative capture of low-energy electrons, a process indicative of the formation of a metastable anion. The present work reports the results of quantum-chemical simulations of the dissociative electron attachment to a number of oxyacids (H₃PO₄, H₂SO₄⁻, HPO₄²⁻, H₂SO₄, HSO₄⁻, B(OH)₄⁻, HCOOH) with formation of a hydrogen atom in vacuum and in the aqueous medium. Phosphate is one of the most important building units of biological molecules, whereas formic acid can serve as a model of the −COOH group in amino acids, carboxylic acids, functional sites of enzymes, etc. The electron affinity of these oxyacids in the aquatic environment is positive and exceeds the energy of hydrogen atom abstraction. The proton of the OH group captures the electron, while the aquatic environment stabilizes it in the trapped state due to its polarizability. The data obtained provide a fresh look at the phenomenon of proton-assisted electron transfer and at the use of oxyacid buffers.     

Effect of high-pressure high-temperature treatment on the structure of a hexagonal modification of fullerite C<Subscript>60</Subscript>

Powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular dynamics have been employed to investigate structural transformations in hexagonal and cubic modifications of fullerite C₆₀ after the action of high pressure (4 GPa) within the temperature range 20–1450°C. It has been found that fullerene molecules polymerize to afford polymer structures only in the case of face-centered cubic samples. Under the effect of high pressure and temperature, fullerite C₆₀ with a hexagonal close-packed structure is initially transformed into the cubic modification and, then, forms polymerized structures, which, during an increase in the treatment temperature, become less stable and ordered than the same polymerized structures obtained directly from cubic fullerite C₆₀. X-ray photoelectron spectroscopy measurements suggest deformation of the cages of fullerene molecules in the polymerized structures.