M. V. Kharlamova

New method of the directional modification of the electronic structure of single-walled carbon nanotubes by filling channels with metallic copper from a liquid phase

A method has been proposed and successfully implemented for filling the channels of single-walled carbon nanotubes with metallic copper by permeating with an aqueous solution of copper nitrate with subsequent thermal treatment. It has been demonstrated that the introduction of metallic copper into the channels of nanotubes leads to donor doping accompanied both by an increase in the Fermi energy of nanotubes and by the transfer of the electron density from introduced metal nanoparticles to the walls of nanotubes.

Charge transfer in single-walled carbon nanotubes filled with cadmium halogenides

In this work the internal channels of the single-walled carbon nanotubes (SWCNTs) were filled with cadmium chloride, cadmium bromide, and cadmium iodide by a capillary method using melts of these salts. The influence of incorporated chemical compounds on the electronic properties of the carbon nanotubes was investigated by optical absorption spectroscopy, Raman spectroscopy, near edge X-ray absorption fine structure spectroscopy, and X-ray photoelectron spectroscopy. It was found that there is the chemical bonding between carbon atoms of nanotube walls and metal atoms of encapsulated CdX2 nanocrystals. The obtained data testify acceptor doping effect of cadmium halogenides incorporated into the SWCNT channels, which is accompanied by the charge transfer from nanotube walls to introduced substances.

Optical properties of γ-ferric oxide nanoparticles in a mesoporous silica matrix

Magnetic γ-Fe2O3/SiO2 nanocomposites have been synthesized by impregnating a mesoporous silica matrix with a hexane solution of γ-ferric oxide nanoparticles. The subsequent heat treatment of samples in the course of synthesis influences the optical properties of the final nanostructural material. It is established that an increase in the temperature of annealing (crystallization) leads to a decrease in the energies of both direct and indirect allowed electron transitions to the conduction band.

Novel approach to tailoring the electronic properties of single-walled carbon nanotubes by the encapsulation of high-melting gallium selenide using a single-step process

A single-step method of filling the channels of single-walled carbon nanotubes with the melt of refractory GaSe is proposed and successfully implemented. The filled nanotubes are investigated by optical absorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It is found that charge transfer from the nanotube walls to embedded GaSe accompanied by lowering of the Fermi level in nanotubes occurs in the obtained nanocomposite; i.e., acceptor doping of nanotubes takes place.

Comparative analysis of electronic properties of tin, gallium, and bismuth chalcogenide-filled single-walled carbon nanotubes

In the present work, the channels of single-walled carbon nanotubes (SWCNTs) were filled with tin sulfide (SnS), gallium telluride (GaTe), and bismuth selenide (Bi2Se3). The successful encapsulation of the compounds was proven by high-resolution transmission electron microscopy. The electronic properties of the filled SWCNTs were studied by optical absorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that the embedded metal chalcogenides have different influence on the electronic properties of the nanotubes. The incorporation of tin sulfide into the SWCNTs does not result in sufficient changes in the electronic structure of SWCNTs, except for a minor influence on metallic nanotubes. The filling of SWCNTs with gallium telluride causes the charge transfer from the SWCNT walls to the encapsulated compound due to acceptor doping of the nanotubes. The insertion of bismuth selenide inside the SWCNT channels does not lead to the modification of the electronic properties of nanotubes.

Phase transition in nanostructured LaMnO3

Nanocrystalline LaMnO3 samples have been synthesized by the coprecipitation of lanthanum and manganese salt solutions followed by annealing at 800°C in air and then in an argon flow. With the use of X-ray and neutron diffraction analysis, it has been found that the resulting samples had an orthorhombic crystal structure (space group Pbnm). In the nanocrystalline LaMnO3 samples, an order-disorder phase transition from the low-temperature phase to the high-temperature phase occurs at (220 ± 10)°C, which is much lower than the value of 477°C for bulk LaMnO3. The phase transition is due to the removal of the Jahn-Teller distortion of the Mn3+O6 oxygen octahedrons and is accompanied by a decrease in the unit cell volume of lanthanum manganite over a narrow temperature range.

Synthesis of nanocomposites on basis of single-walled carbon nanotubes intercalated by manganese halogenides

In this work MnCl2@SWNT and MnBr2@SWNT nanocomposites were prepared via capillary filling of single-walled carbon nanotube channels by melts of manganese halogenides with slow cooling to room temperature for better crystallization. Electronic properties of MnHal2@SWNT nanocomposites have been investigated by X-ray photoelectron spectroscopy, optical absorption spectroscopy and Raman spectroscopy. It was found that the manganese halogenides show acceptor behavior and there is the charge transfer from the carbon nanotube walls to intercalated nanocrystals.

Magnetic properties of γ-iron oxide nanoparticles in a mesoporous silica matrix

Magnetic γ-Fe2O3/SiO2 nanocomposites are synthesized by impregnating mesoporous silica with a hexane solution of γ-iron oxide nanoparticles. Materials with various structural and magnetic properties can be obtained using a subsequent thermal treatment of the synthesized samples (annealing for three hours in an air flow).

Study of the atomically clean InSe(0001) surface by X-ray photoelectron spectroscopy

The (0001) surface of layered InSe semiconductor crystals is studied experimentally using X-ray photoelectron spectroscopy and theoretically within the context of the method of the electron density functional with periodic boundary conditions. It was found that the structure of the surface layer of atoms and their state has much in common with the corresponding structure and state in the volume. The InSe(0001) surface is resistant to long exposure to air, which makes this material promising for applications as a standard for composition analysis when using electron spectroscopy.