Artemii Nikolaevich Beltiukov

An array of highly oriented anatase nanoparticles was successfully prepared from NH₄TiOF₃ with the assistance of polyetheleneglycol-400 at 450 °C. The study showed the stability of obtained layered TiO₂-anatase close to 1200 °C. This research confirmed for the first time that the transition of mesocrystalline anatase to the rutile phase occurs between 1000 °C and 1200 °C, which is more than 400 °C higher than the transition of bulk TiO₂ due to the used precursor. A small quantity of K-phase nanowhiskers, which issued after 800 °C in the composite based on TiO₂, stimulated a fourfold increase in photocatalytic performance. This study offers a new approach to the construction and preparation of effective nanocrystalline photocatalyst.

In this work, we studied the efficiency of introducing nanoporous silicon as a buffer layer in the growth of AlxGa1–xN/AlN/Si(111) on a single-crystal silicon by molecular beam growth technology. We also considered its influence on the morphological characteristics and atomic composition of the surface layers of heterostructures. As determined by X-ray diffraction, microscopic, and X-ray photoelectron methods, the heterostructure grown on Si(111) n-type monocrystalline silicon wafer with nanoporous por-Si buffer layer has a more homogeneous epitaxial layer, and the surface morphology of the layer is also more homogeneous.

Here we report a successful one-step synthesis of vanadium-doped anatase mesocrystals by reactive annealing of NH ₄ TiOF ₃ /PEG2000 mesocrystal precursors with NH ₄ VO ₃ . The formation solid solution Ti _{1− x} V _x O ₂ with vanadium content up to x = 25 at% inheriting the structure of mesocrystals is observed for the first time. The doping mechanism via vapor phase transport of vanadium is proposed. The Ti _{1− x} V _x O ₂ mesocrystals exhibit improved specific capacity of 175 mAh g ⁻¹ (compared to 150 mAh g ⁻¹ for pure anatase phase) and decreased potential gap between charge and discharge processes.

― The crystallization of thin germanium films during vacuum thermal deposition on an aluminum surface has been investigated. Significant changes in the morphology and crystal structure of...

We report synthesis of periodic Ge/Al₂O₃ composites containing interstitial Ge nanocrystals in the walls of porous anodic aluminum oxide by anodic oxidation of Al/Ge multi-layers. The structure and luminescent characteristics of composites were investigated by transmission and scanning electron microscopy, as well as Raman and photoluminescence spectroscopy. The photoluminescence of Ge nanocrystallites was detected at ~2.0 eV after annealing of samples in the temperature range of 500 – 700 °С.

Improvement of sensitivity, lower detection limits, stability and reproducibility of semiconductor metal oxide gas sensor characteristics are required for their application in the fields of ecological monitoring, industrial safety, public security, express medical diagnostics, etc. Facile and scalable single step flame spray pyrolysis (FSP) synthesis of bimetal AuPd sensitized nanocrystalline SnO₂ is reported. The materials chemical composition, structure and morphology has been studied by XRD, XPS, HAADFSTEM, BET, ICP-MS techniques. Thermo-programmed reduction with hydrogen (TPR-H₂) has been used for materials chemical reactivity characterization. Superior gas sensor response of bimetallic modified SnO₂ towards wide concentration range of reducing (CO, CH₄, C₃H₈, H₂S, NH₃) and oxidizing (NO₂) gases compared to pure and monometallic modified SnO₂ is reported for dry and humid gas detection conditions. The combination of facilitated oxygen molecule spillover on gold particles and electronic effect of Fermi level control by reoxidizing Pd-PdO clusters on SnO₂ surface is proposed to give rise to the observed enhanced gas sensor performance.

The reaction between (NH₄)₂TiF₆ and H₃BO₃ in the presence of varying quantities of PEG-6000 was used to form NH₄TiOF₃ mesocrystals (MCs). The amount of PEG-6000, employed as a template, is crucial to the formation of defect free, non-agglomerated NH₄TiOF₃ MCs; high concentrations lead to MC agglomeration, lower ones result in centralized defects. This polymer-mediated formation process may be understood using an analogy with known polymerization reactions. The oxofluorotitanate MCs readily undergo a thermal topotactic transformation to give anatase MCs with photocatalytic activity. The TiO₂ MCs are porous, with highly orientated lamellar crystallites that form part of the larger mesocrystal structure.

We present EXAFS, XANES, and X-ray diffraction data on nanoscale ZnS:Cu (5 at %) structures fabricated by the thermal deposition of a ZnS and Cu powder mixture in porous anodic alumina matrices with a pore diameter of 80 nm and thicknesses of 1, 3, and 5 μm. The results obtained are compared with data on ZnS:Cu films deposited onto a polycor surface. According to X-ray diffraction data, the samples contain copper and zinc compounds with sulfur (Cu₂S and ZnS, respectively); the ZnS compound is in the cubic (sphalerite) and hexagonal (wurtzite) modifications. EXAFS and XANES studies at the K absorption edges of zinc and copper showed that, in samples deposited onto polycor and alumina with thicknesses of 3 and 5 μm, most copper atoms form the Cu₂S compound, while, in the sample deposited onto a 1-μm-thick alumina layer, copper atoms form metallic particles on the sample surface. Copper crystals affect the Zn–S interatomic distance in the sample with a 1-μm-thick porous Al₂O₃ layer; this distance is smaller than in the other samples.

This paper describes a method for forming an array of Ge/ZnSe nanoheterostructures by vacuum thermal evaporation. ZnSe and Ge layers were deposited on an anodic aluminum oxide surface with a pore diameter of 24 nm. Scanning electron microscopy showed that nanoheterostructures are formed in the pore channels. The features of the electron structure of the samples obtained were investigated by x-ray photoelectron spectroscopy and optic absorption spectroscopy. These investigations showed that the band gap of germanium increases. Also, there is a significant increase in valence band discontinuity (to 3.6 eV). Thus, we obtained Ge/ZnSe heterostructures with non-overlapping band gaps or broken-gap heterostructures.

The effect of structural properties and the morphology of Ge@PAA nanocomposites synthesized by thermal deposition of Ge on porous anodic alumina matrices with different porosity on the band gap value and PL properties is investigated. PL in the range of 330–520 nm may be due to F and F₂ luminescent centers in the surface of nanopores of PAA matrices. The density of electronic states in this interface depends on the temperature of matrices during deposition and on the surface morphology. The role of radiative recombination centers is played by the broken bonds in a thin intermediate Ge _x –Al _y –O _z layer in the Ge/oxide matrix interface. No obvious effect of the crystalline structure of germanium nanoparticles on the PL maximum position is observed, but the spatial localization of electron–hole pairs of small-sized Ge crystallites of which nanoparticles consist leads to an increase in the optical band gap.