bluuebunny/crossref_metadata_2025 huggingface dataset:
On the theory of the binding energy of exciton quasimolecules in germanium/silicon double quantum dots
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Pokutnyi S. I. , Shkoda N. G. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Usik J. ,   Wrocław University of Science and Technology Poland
Published: December 2022

A theory of exciton quasimolecules (formed from spatially separated electrons and holes) in a nanosystem consisting of double quantum dots (QDs) of germanium synthesized in a silicon matrix is presented. It is shown that the binding energy of the singlet ground state of the quasimolecule of an exciton is considerably larger than the binding energy of biexciton in a silicon single crystal by almost two orders of magnitude. It is shown that the exciton quasimolecule formation is of the threshold character and possible in a nanosystem, where D is the distance between the surfaces of QD that satisfies the following condition: (where and are some critical distances). Using the variational method, we obtain the binding energy of the exciton quasimolecule singlet ground state of the system as a function of the distance between the surfaces of QD D, and the QD radius a. It is shown that the convergence of two QDs up to a certain critical value of the distance between the surfaces of QD DC leads to the effective overlapping of the electron wave functions and the appearance of exchange interactions. As a result, the exciton quasimolecules can be formed from the QDs. It is shown that the existence of such a critical distance DC arises from the quantum size effects. Dimensional quantization of electrons and holes motion leads to the following fact: as the distance between the surfaces of the QD DC decreases, the decrease in the energies of interaction of the electrons and holes entering into the Hamiltonian of the exciton quasimolecule cannot compensate for the increase in the kinetic energy of the electrons and holes. At larger values of the distance between the surfaces of the QD D, , the exciton quasimolecule breaks down into two excitons (consisting of spatially separated electrons and holes), localized over the QD surfaces. The fact that the energy of the ground state of singlet excitonic quasimolecule is in the infrared range of the spectrum, presumably, allows us to use a quasimolecule for the development of new elements of silicon infrared nanooptoelectronics.
A theoretical study on the effect of heteroatoms (N, B, Si) on the interaction of aluminum clusters with a carbon graphene-like plane
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Demianenko E. M. , Terets M. I. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Ushakova L. M. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Zhuravskyi S. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Sementsov Yu. I. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Lobanov V. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Filonenko O. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Kuts V. S. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Grebenyuk A. G. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Kartel M. T. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

It is known that the addition of a small amount of carbon nanomaterials significantly improves the mechanical properties of composites with a metal matrix. One of the most important, promising and available metals as a matrix for such modification is aluminum. However, at the interface between the carbon material and Al, aluminum carbides of different composition are formed, which are brittle and have the main disadvantage - solubility in water. Therefore, the appearance of aluminum carbide is a serious problem, since it contributes to the formation of defects, which, when the composite is deformed, leads to cracking of the composite due to the presence of microneedles. In this regard, in order to predict the features of the interaction of aluminum itself with the surface of carbon nanomaterials, it is advisable to model such processes using quantum chemistry methods. The aim of the work was to reveal the effect of temperature on the chemical interaction of aluminum clusters with native, boron-, silicon-, and nitrogen-containing graphene-like planes (GLP). All the calculated by three methods (B3LYP/6-31G(d,p), MP2/6-31G(d,p) and PВЕ0/6-31G(d,p)) values of the dependence of the Gibbs free energy on temperature for different cluster sizes of aluminum and graphene-like clusters are the highest for native graphene-like planes. In all cases, the values of the Gibbs free energy increase with temperature. The lowest values of the temperature dependence of the Gibbs free energy vary as dependent on the size of the reactant models and research methods, this is especially characteristic of the presence of boron and silicon atoms in the graphene-like clusters. Therefore, the absence of heteroatoms in the composition of the nanocarbon matrix contributes to the fact that aluminum carbide islands should not be formed in the carbon-containing nanocomposite with aluminum, which negatively affects the physical and chemical characteristics of the resulting nanocomposite.
Water in a hydrophobic environment and the effect of some organic substances on it
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Turov V. V. , Krupska T. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

The structure of water in the interparticle gaps of methyl silica was investigated using the method of low-temperature 1H NMR spectroscopy. It is shown that the main part of the interfacial water is in the form of large clusters, or nanodroplets, which freeze at a temperature of about 273 K. After freezing of this water, signals of strongly and weakly associated water are observed in the spectra, which melts at temperatures of 215–368 K. It is likely that the freezing of weakly associated of water occurs through the formation of clusters in which closely spaced water molecules interact not through hydrogen bonds, but through dipole-dipole interactions. In the presence of chloroform, the amount of weakly associated water increases several times. This is explained by the possibility of formation of chloroform hydrates, in which the mobility of water molecules is approximately the same as in strongly associated water clusters. If joint adsorption of chloroform and methane occurs on the hydrated surface of methyl silica, under the influence of CH4, weakly mobile weakly associated water is transformed into methane hydrates in quasi-liquid and solid states, while only mobile forms of hydrates are recorded in the spectra. DMSO reduces the possibility of formation of weakly associated water, but a certain amount of it is fixed even in the medium of liquid DMSO. At the same time, the freezing of water in systems containing DMSO occurs at much lower temperatures due to solvation of water and DMSO molecules. The difference in interphase energy in air and in organic media determines the solvation energy.
Influence of f-d exchange interaction on the properties of nanoscale structures based on Fe, Co, Ni metals and rem oxides. A review
Authors:   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine, Kasumov A. M. , Dmitriev A. I. ,   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine, Korotko K. A. ,   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine, Karavaeva V. M. ,   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine, Vyshnevska K. O. ,   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine, Ievtushenko A. I. ,   Institute for Problems of Material Sciences of National Academy of Sciences of Ukraine
Published: December 2022

A review of the works of the authors published in the period 2009–2022 and devoted to the study of the properties of nanosized structures containing contacting layers of Fe, Co, Ni, Fe2O3 / REM (Rare Earth Metal) oxide is carried out. The technology for the creation and structural features of these nanostructures are also considered. Physicochemical phenomena in the interface of contacting layers are very multidisciplinary. This is a consequence of their dependence on various conditions, primarily on the modes of technologies for their production and the properties of the initial components. The problem becomes much more complicated when studying magnetic nanostructures. To study effectively the properties of layered nanostructures containing ferromagnetic films, we used magnetic research methods. Using the EPR method, it has been found that between atoms with unfilled f- and d-electron sub-shells, which are part of the contacting layers, an f-d exchange interaction occurs, which orders the magnetic structure of the ferromagnetic layers. Using the method of the anomalous Hall effect, it is shown that the ordering of the magnetic structure leads to an increase in their magnetization. The enhancement of the galvanomagnetic properties in the Fe3O4/REМ оxide/Fe3O4 structures shows that the exchange interaction can have both f-d and d-d character. And this, in turn, leads to an increase in magnetization-dependent properties, such as galvanomagnetic, magneto-optical, and current-voltage properties. This can be used in nanotechnologies to enhance the above properties without energy consumption and the use of amplifying equipment.
Formation of β-SiC on por-Si/mono-Si surface according to stranski - krastanow mechanism
Authors:   Berdyansk State Pedagogical University Ukraine, Suchikova Y. O. , Kovachov S. S. ,   Berdyansk State Pedagogical University Ukraine, Bardus I. O. ,   Berdyansk State Pedagogical University Ukraine, Lazarenko A. S. ,   Berdyansk State Pedagogical University Ukraine, Bohdanov I. T. ,   Berdyansk State Pedagogical University Ukraine
Published: December 2022

We report the synthesis of β-SiC/por-Si/mono-Si heterostructure by a hybrid method, consisting of the electrochemical etching of the single-crystal silicon surface with a subsequent carbidization by a thermal annealing in a methane atmosphere. This method has a number of advantages over the known ones, because it is cheap enough and allows one to form the silicon carbide layers of high- quality. The formed structure was studied by means of SEM, EDX and XRD methods. As a result, the dense β-SiC layer, consisting of an array of the spherical islands with diameters of 2–6 μm, coated with the small pores, was formed on the por-Si/mono-Si surface. The geometric dimensions of the islands were studied by calibrating the sample image in the ImageJ software package. The maximum value of the linear size (diameter) of the island dmax = 5.95 μm and the minimum value dmin = 2.11 μm were found in the studied area. In general, the average diameter of the islands is d = 3.72 μm. The distribution has the left-sided asymmetry, that is, the smaller islets predominate. Roundness (the ratio of the area to the square of the larger axis) R = 0.86. According to the results of EDX analysis, it was found that the synthesized structure surface consists exclusively of the carbon and silicon atoms, indicating the high quality of the formed structures. It was found that the SiC film crystallizes in the cubic phase. The formation of the islands is explained by means of the layer-plus-island growth model according to Stranski-Krastanow mechanism, which is characterized by the formation of the dense wetting layer with the massive island complex on the surface. It should be also noted that the porous SiC layers of island type can, in turn, show the perspective as the buffers with the heteroepitaxy of the silicon substrate materials.
Dielectric function and the absorption cross-section of the metal-graphene nanocylinders of the finite length
Authors:   National University Zaporizhzhia Polytechnic Ukraine, Karandas Ya. V. , Korotun A. V. ,   National University Zaporizhzhia Polytechnic Ukraine
Published: December 2022

The behavior of the diagonal components of the dielectric tensor and the behavior of the absorption cross-section in the different frequency ranges for the composite cylindrical nanostructures “metallic core – graphene shell” have been studied. In order to obtain the calculation formulas one uses the relations for the longitudinal and transverse components of the dielectric tensors for metallic core and graphene shell, which are determined by Drude model and Cubo model correspondingly. The consideration is carried out in the frameworks of “equivalent” elongated spheroid approach, according to which the defining dimensional parameter is effective aspect ratio, calculated from the condition of the equality of the corresponding axial inertia moments for two-layer cylinder and the “equivalent” elongated spheroid. The numerical results have been obtained for the nanocylinders with the cores of different metals, different radius and with the different number of graphene layers. The variation of amplitude and the variation of the location of extremes of the real and imaginary parts of the transverse component of the dielectric tensor under the increase in radius of the metallic core and the thickness of the graphene shell have been analyzed. It has been shown that the variation of the radius of the core has the significantly greater influence on the properties of the polarizability resonances and absorption cross-section than the variation of the number of graphene layers. The reasons of the presence of two maxima of the absorption cross-section for the metal-graphene cylinders which differ in both amplitude and width and located in infrared, violet and near ultraviolet parts of the spectrum and their relation with the surface plasmonic resonances in the metallic core and with the terahertz plasmons of graphene have been found. The factors which have an effect on amplitude and on the shift of the maxima of the absorption cross-section have been found. The reasons of the different width of maxima, which are located in the different spectral intervals, have been determined.
An influence of the adsorbed molecules layer on the localized surface plasmons in the spherical metallic nanoparticles
Authors:   National University Zaporizhzhia Polytechnic Ukraine, Smirnova N. A. , Korotun A. V. ,   National University Zaporizhzhia Polytechnic Ukraine, Titov L. M. ,   UAD Systems Ukraine
Published: December 2022

An influence of the adsorbed molecules layer on the optical characteristics of the spherical metallic nanoparticles has been studied in the work. In order to do this one considers the additional term which takes into account the scattering of electrons at the interface between metal and adsorbate. The analytical expressions for the frequency dependences for the parameter of coherence loss due to the scattering at the interface “metal – adsorbed layer” have been obtained. It has been found that the presence of the adsorbed molecules results in the electron scattering anisotropy, and, hence, in the anisotropy of the optic response of such systems. The result of the indicated anisotropy is the appearance of the additional maximum in the infrared part of the spectrum in the frequency dependences for the optical characteristics. An evolution of the frequency dependences for the components of the polarizability tensor and the absorption cross-section and scattering cross-section for the two-layer spherical nanoparticles of the type “metal – adsorbate” under the variation of their geometrical parameters has been analyzed. It has been shown that the weak maximum of the real, imaginary parts and the module of the transverse component of the polarizability tensor and the absorption and scattering cross-sections in the infrared part of the spectrum appears due to inducing of the local density of the states by adsorbate. The reason of the shift of the maxima of the absorption cross-section and scattering cross-section for the nanoparticles of the constant sizes with the cores of different metals has been found. It has been demonstrated the existence of the small-scale oscillations at the frequency dependences for the components of the polarizability tensor and at the absorption and scattering cross-sections, caused by an oscillating contribution of the surface electron scattering. The dependence of the location and the value of the maximum of the absorption cross-section for the particle “metal – adsorbate” with the constant geometrical parameters and content on the dielectric permittivity of the medium, in which the nanoparticle is situated, has been proved.
Bactericidal metal-containing zeolites
Authors:   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Tsitsishvili V. G. , Dolaberidze N. M. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Mirdzveli N. A. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Nijaradze M. O. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Amiridze Z. S. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Khutsishvili B. T. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia
Published: December 2022

The coronavirus pandemic has increased interest in antibacterial agents containing bioactive metals, for which zeolites are promising carriers. On the other hand, zeolite adsorbents and ion exchangers containing bioactive metals and endowed with bactericidal properties are promising for water treatment and other environmental and medical applications.Silver-, copper-, and zinc-containing microporous materials have been prepared on the base of natural analcime,phillipsite and heulandite from Georgian manifestations using ion-exchange reactions between zeolite microcrystals and a salt of a corresponding transition metal in the solid phase followed by washing with distilled water. Synthesized in such way adsorbent-ion-exchangers are characterized by chemical composition based on the X-ray energy dispersion spectra, powder X-ray diffraction patterns, Fourier transform infra-red spectra and low-temperature adsorption-desorption isotherms of N2. Obtained materials remain the zeolite crystal structure and contain 130–230 mg/g of silver, 65–72 mg/g of copper, and 58–86 mg/g of zinc, as compared with modified samples of synthetic type A zeolite containing up to 380 mg/g of silver, 150 mg/g of copper, and 150 mg/g of zinc. Prepared metal-containing materials show bacteriostatic activity against Gram negative bacterium Escherichia coli, Gram positive bacteria Staphylococcus aureus and Bacillus subtilis, fungal pathogenic yeastCandida albicans, and a fungus Aspergilusniger, and natural zeolites enriched with biometals exhibit a synergistic effect – their mixtures have a higher bacteriostatic activity. It is shown that mixtures of copper and zinc forms have a higher activity than the silver-containing form, which is very important from a practical point of view for replacing expensive silver with cheaper copper and zinc. It has been found that the bacteriostatic activity of metal-containing zeolites is determined not only and not so much by the ions of bioactive metals released into the liquid medium, but an important role ininhibiting the growth of microorganisms plays a type of zeolite matrix. Despite the relatively low ion-exchange capacity, heulandite turned out to be a fairly effective matrix for bioactive metals.
Effect of acid modification of natural zeolites on the adsorption of some pharmacopollutants
Authors:   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Eprikashvili L. G. , Tsintskaladze G. P. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Kordzakhia T. N. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Zautashvili M. G. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Pirtskhalava N. V. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Dzagania M. A. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Sharashenidze T. M. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia
Published: December 2022

Wastewater and natural waters contain various pollutants of both natural and artificial origin. Treatment of these waters is carried out comprehensively by various methods, which significantly increases costs. Currently, the problem of a large amount of drugs entering the wastewater is very relevant. Drugs, unchanged or in the form of metabolites, enter the wastewater together with the waste products of a living organism. To solve urgent practical problems of water purification, a possibility of using natural zeolite materials as sorbents has been recently considered. Being a natural aluminosilicates of frame-type structure, these minerals have a number of unique adsorption properties that can be used in water treatment processes. Treatment with acid solutions (alkalis, salt solutions and some organic compounds) allows to improve significantly their sorption characteristics for decision of a particular problem. Zeolites, being chemically stable minerals, are capable to withstand the effects of chemically active medium without destruction of the crystal lattice. The effect of boiling acid (HC1) on natural zeolites from Georgian deposits (mordenite and clinoptilolite) and the possibility of their use for adsorption treatment of wastewater were studied in this work. Identification of modified zeolites was carried out on the basis of X-ray diffractograms and IR-spectra. It has been shown that natural clinoptilolites (mordenite and zeolite) are characterized by high thermostability and acid resistance even after acid-modification, and the resulting hydrogen forms are distinguished by high concentration of active centers; the efficiency of adsorption method for wastewater treatment from some pharmacopolutants when using acid-modified natural zeolites has been also shown. This method will solve the problem of entering the environment of drugs with lower costs
Study on the structure of phosphorus-containing zeolite anionic nanoporous materials
Authors:   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Tsintskaladze G. P. , Sharashenidze T. M. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Eprikashvili L. G. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Zautashvili M. G. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Kordzakhia T. N. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia, Dzagania M. A. ,   Petre Melikishvili Institute of Physical and Organic Chemistry of the Iv. Javakhishvili Tbilisi State University Georgia
Published: December 2022

Phosphates are specific compounds of the composition of living organisms, that play a special role in plant and animal life. The skeleton of most living organisms consists mainly of calcium, sodium, magnesium and other phosphates. Because phosphorus plays an important role in supplying nutrients to the environment, it is central to all forms of life. Therefore, interest in this type of material is great, and the scope of application is enormous, from agriculture to medicine. On the basis of clinoptilolite, a natural zeolite located in Georgia, zeolitic nanomaterials containing phosphates were obtained by two different methods. The first method is the introduction of mono-, di-, and tri-substituted sodium phosphates into the zeolite structure under conditions of boiling on a sand bath, where the introduction of phosphate ions is difficult. In the second method, phosphate ions almost completely occupy the inner structural area of the zeolite. The zeolitic nanoporous materials of mono-substituted, di-substituted and tri-substituted phosphates obtained by these methods and subsequently studied by Fourier spectroscopic method. The obtained materials have preserved the zeolitic structure, although their IR spectra are sharply different from each other, which can be explained by different anions occupying different positions in the zeolitic structure. It should be noted that after washing the obtained material with water, phosphate ions are almost completely washed out of the zeolite structure. The importance of the received materials and the perspective of their use are given.
Theoretical simulation of the interaction of Fe2 cluster with A N, B, Si-containing carbon graphene-like plane
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Demianenko E. M. , Terets M. I. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Zhuravskyi S. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Sementsov Yu. I. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Lobanov V. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Kuts V. S. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Grebenyuk A. G. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Kartel M. T. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

Metal composites modified with various heteroatoms, such as N, B, Si, are used to obtain matrix composites with specified parameters with the strongest adhesive-cohesive bonds between metal atoms and a carbon nanoparticle. Such carbon nanoparticles functionalized with heteroatoms are promising for many metal composites. One of the interesting and promising metals as a matrix for such research work is iron. To predict the specifics of the interaction of iron with the surface of carbon nanomaterials supplemented with heteroatoms of different chemical structure, it is advisable to model such processes using quantum chemistry methods. The aim of the work was to find out the effect of temperature on the chemical interaction of iron clusters with native, boron-, silicon-, and nitrogen-containing graphene-like planes (GLP). The results of the calculations show that the highest value of the energy effect of the chemical interaction for the native graphene-like plane is +204.3 kJ/mol, in the case of calculations both by the B3LYP/6-31G(d,p) method and by the MP2/6-31G(d, p) (+370.7 kJ/mol). The lower value of the energy effect is found in the presence of nitrogen atoms in the composition of the graphene-like plane. This value is even lower for the interaction of iron dimers with a silicon-containing carbon nanocluster. The lowest values of the energy effect, calculated by both methods, are characteristic of the boron-containing graphene-like plane. In particular, for the B3LYP/6-31G(d,p) method, the value of the energy effect of the reaction is ‑210.5 kJ/mol, and for the MP2/6-31G(d,p) method this value is +16.6 kJ/mol. The presence of boron atoms in the composition of the nanocarbon matrix best contributes to the interaction with the iron nanocluster, regardless of the chosen research method. The dependence curves of the Gibbs free energy of the interaction of iron dimers with a graphene-like plane and its derivatives in all cases qualitatively correlate with similar energy effects. In addition, in all cases, the values of the Gibbs free energy increase with increasing temperature.
Exciton quasimolecules in nanosystems with semiconductor and dielectric colloidal quantum dots: a review
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Pokytnyi S. I. , Terets A. D. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

In review, deals with the theory of exciton quasimolecules (formed of spatially separated electrons and holes) in a nanosystems that consists of semiconductor and dielectric colloidal quantum dots (QDs) synthesized in a dielectric and semiconductor matrixs. It has been shown that the exciton quasimolecule formation is of the threshold character and possible in a nanosystem, where the distance D between the surfaces of QD is given by the condition (where and are some critical distance). We have shown that in such a nanoheterostructures acting as “exciton molecules” are the QDs with excitons localizing over their surfaces. The position of the quasimolecule state energy band depends both on the mean radius of the QDs, and the distance between their surfaces, which enables one to purposefully control it by varying these parameters of the nanostructure. It was found that the binding energy of singlet ground state of exciton quasimolecules, consisting of two semiconductor and dielectric QDs is a significant large values, larger than the binding energy of the biexciton in a semiconductor and dielectric single crystals almost two orders of magnitude. It is shown that the major contribution to tue binding energy of singlet ground state of exciton quasimolecule is made by the energy of the exchange interaction of electrons with holes and this contribution is much more substantial than the contribution of the energy of the Coulomb interaction between the electrons and holes. It is established that the position of the exciton quasimolecule energy band depends both on the mean radius of the QDs and the distance between their surfaces. It is shown that with increase in temperature above the threshold (), a transition can occur from the exciton quasimolecule to exciton state. It has been found that at a constant concentration of excitons (i.e. constant concentration of QD) and temperatures Т below , one can expect a new luminescence band shifted from the exciton band by the value of the exciton quasimolecule binding energy. This new band disappears at higher temperatures (). At a constant temperature below , an increase in exciton concentration (i.e. in QD concentration) brings about weakening of the exciton luminescence band and strengthening of the exciton quasimolecule. These exciton quasimolecules are of fundamental interest as new quasi-atomic colloidal nanostructures; they may also have practical value as new nanomaterials for nanooptoelectronics. The fact that the energy of the ground state singlet exciton quasimolecule is in the infrared range of the spectrum, presumably, allow the use of a quasimolecule to create new infrared sensors in biomedical research.
Carbon based hybrid nanomaterials: overview and challenges ahead
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Semchuk O. Yu. , Gatti T. ,   Politecnico di Torino, Osella S. ,   Centre of New Technologies University of Warsaw
Published: December 2022

In recent years, many new materials have been developed and prepared to improve the performance of light-harvesting technologies and to develop new and attractive applications. The problem of stability of long-term operation of various optoelectronic devices based on organic materials, both conjugated polymers and small molecules of organic semiconductors (SMOSs), is becoming relevant now. One way to solve this problem is to use carbon nanostructures, such as carbon nanotubes and a large family of graphene-based materials, which have enhanced stability, in carefully designed nanohybrid or nanocomposite architectures that can be integrated into photosensitive layers and where their potential is not yet know fully disclosed. Recently, a new trend has been seen in this direction - the use of nanoscale materials for, first of all, the conversion of light into electricity. The main goal of this approach is to rationally design stable and highly efficient carbon-based hybrid nanomaterials for optoelectrical applications, namely light harvesting/electricity conversion, which can be implemented in real optoelectrical devices. In this review, we will discuss the theoretical and experimental foundations of the hybridization of carbon nanostructures (CNSs) with other materials to reveal new optoelectronic properties and provide an overview of existing examples in the literature that will predict interesting future perspectives for use in future devices.
Pyrolysis regeneration of activated carbon used for glycerin purification
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Borysenko M. V. , Borysenko L. I. ,   Institute of Renewable Energy of NAS of Ukraine, Klius V. P. ,   Institute of Renewable Energy of NAS of Ukraine, Klius S. V. ,   Institute of Renewable Energy of NAS of Ukraine, Shynkarenko V. I. ,   Institute of Renewable Energy of NAS of Ukraine
Published: December 2022

In this work, we investigated granular activated carbons Norit 1240 (AC) – initial and spent (SAC) with adsorbed impurities after purification of technical glycerin and subsequent washing with water. The aim of the work was to establish the optimal conditions for the thermal regeneration of AC at the pyrolysis unit and to quantify the adsorbed impurities in the SAC using thermogravimetric analysis (TGA). For all AC samples, the specific surface area (S), adsorption activity on iodine and mass fraction of moisture were measured. It was established by the TGA method that water is released in the temperature range of 20 – 180 °C, and glycerin – 180 – 400 °C. Spent AC contains up to 31.3 wt. % H2O and up to 37.3 wt. % C3H5(OH)3. The pyrolysis reactor was used for the regeneration of SAC samples. It was shown that after the reactivation of SACs, their specific surface area is restored to 45-94% of the initial one. There is a weak correlation between S and iodine number, R=0.64. Adsorption activity for iodine and S increase in the same row ACspent > ACregenerated > ACinitial. As a result of regeneration, activated carbons suitable for reuse were obtained.
On the use of model diffraction profiles in the microstructure analysis of nanocrystalline metal oxides based on powder x-ray diffraction data
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Oranska O. I. , Gornikov Yu. I. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Gun’ko V. M. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Brichka A. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

The study of the microstructure of nanocrystalline substances by the method of powder diffractometry based on the physical broadening of diffraction lines involves the use of diffraction data of standard polycrystalline samples, preferably, one nature with the test samples with the size of crystallites exceeding 100 nm. In the absence of such standards, researchers resort to the existing dependence of the width of diffraction peaks on the angle of diffraction for the standard sample or the construction of theoretical instrumental profiles due to the collimation parameters of x -rays used. In this paper a comparative study of the microstructure of nanocrystalline titanium oxide (anatase), tin oxide iron oxide (magnetite), synthesized in various ways, using several methods of analysis of powder diffractograms, was carried out. To evaluate the average crystallite sizes of the studied oxides, the Sherer equation with a graphical method of determining the width of instrumental profile and the influence of dublet radiation was chosen. Methods of profile analysis of diffraction spectra, such as a method of whole profile modeling of powder diffractograms (WPPM) and the chord method, were used to construct crystallite size distribution functions and determine the average size of crystallites of the oxides. Modeling of instrumental diffraction profiles of titanium, tin and iron oxides was performed using X -rays collimation parameters determinated using a polycrystalline silicon as standard and pseudo -Voigt function, which best describes the form of diffraction peak. The crystallite size distribution functions were constructed by means of WPPM and chords methods based on the instrumental profiles. It has been found that the values of average size of the crystallites, obtained by the methods of Sherer, WPPM and chords, differ within the one order of magnitude for each oxide. Thus, for titanium oxide this value is within 12-18 nm, for tin oxide within 7-10 nm, the iron oxide of iron within 9-12 nm. Analysis of size crystallite distribution functions and average sizes of the crystallites of the studied oxides showed the advisability of using different methods of studying microstructure to clarify the true type of the size crystallites distribution and establish its connection with the conditions and the synthesis method.
Properties of composite systems based on suspensions of lactobacillus and silica
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Krupska T. V. , Turov V. V. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Tsapko M. D. ,   Taras Shevchenko National University of Kyiv, Skubyshevskaya-Ziemba J. ,   Maria Curie-Skłodowska University, Charmas B. ,   Maria Curie-Skłodowska University
Published: December 2022

Low-temperature 1H NMR spectroscopy and DSC methods were used to study the hydration process of Lactobacillus, the influence of a weakly polar organic environment on it, and the encapsulation of cells with silica and the possibility of penetration of such an active substance as trifluoroacetic acid (TFAA) into them. It is shown that the spectral parameters of water in concentrated cell suspensions of Lactobacillus significantly depend on the concentration of the suspensions, which is probably related to the possibility of forming a stable cell gel, which can be encapsulated by silica particles both in the air environment and in the environment without its destruction chloroform with the addition of trifluoroacetic acid. There are two maxima corresponding to R = 2 and 20-100 nm on the distribution curves of the radii of clusters of unfreezing water. The contribution to the distribution of the second maximum increases with increasing water concentration. On the DSC-thermograms of lactobacilli, the value of the thermal effect related to the amount of bound water is much smaller than the thermal effect of ice melting, which is due to the presence of a significant amount of non-freezing water.
Modern methods of obtaining iron endofullerenes
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Zolotarenko Ol. D. , Akhanova N. Y. ,   Al-Farabi Kazakh National University, Zolotarenko An. D. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Shchur D. V. ,   Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Gabdullin M. T. ,   Kazakhstan-British Technical University, Ualkhanova M. ,   Al-Farabi Kazakh National University, Gavrylyuk N. A. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Zolotarenko A. D. ,   Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Chymbai M. V. ,   Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Rudakova E. P. ,   Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Myronenko T. V. ,   Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Zagorulko I. V. ,   G.V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine, Havryliuk O. O. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Tarasenko Yu. O. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

The review examines experimental and theoretical works devoted to the description of modern methods for the preparation of iron endometal-fullerenes(EMF), as well as works that dispute such results due to the extremely low efficiency of the used methods. The paper also considers the advantages and disadvantages of synthesis, as well as the areas of possible application of synthesis products. It is shown that EMF is obtained mainly by two methods - arc discharge (plasma) and synthesis using ablation and implantation methods. Despite a very small number of works on iron-endometal-fullerenes, the group of authors managed to achieve some progress in their analysis. Thus, the fact of obtaining Fe-endometal-fullerenes with their isolation from a mixture of synthesis products was proved. In addition, the influence of the magnetic state of metal atoms on the stability of endohedral fullerenes was predicted, a relationship between the EMF output and the plasma temperature, as well as the chemical nature of the precursor of iron atoms, was established. In particular, it was established that with an increase in the atomic mass of the elements, the EMF output decreases exponentially. It was concluded that the magnetic properties of EMF make them perspective materials in the field of clinical diagnostics (for example, as contrast agents in MRI) and medicine (for magnetically controlled delivery of drugs directly to a diseased organ).
The polyethylene-based composite films, containing carbon nanofibers and magnetic nanoparticles
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Dzubenko L. S. , Gorbyk P. P. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Sapyanenko O. O. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Makhno S. M. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

There are influence of Fe/C as polymer composition component studied, for use as PCM of special purposes, on structure, mechanical, and electrophysical properties, when regarding to goal for usage possibilty establishing for carbon and iron-containing material of Fe/C, and last was synthesized with CVD technique on iron-containing catalyst. There were PEHD- and nano-disperse addition of Fe/C - based composite films prepared, with hot pressing method, of mass equation in 42/58 for Fe/C, and addition content in PCM of 1 – 15 % mass. Then, there were films oriented with thermogradient hot stretching.. It is established, that Fe/C presence is decreasing for maximal stretching value λmax, for pure HDPE, to 5 for highly-loaded compositions. There are addition’s influence on PE phase transitions in composite films: when at low addition’s contents, then, there are forming more perfect crystallic structure of more larger and uniform crystallites by dimensions, but, at those higher - less uniform one. It is established, that specific saturation magntetization values (σs ), for composite and non-oriented films, are increasing, from 1.1 Gs∙cm3/g for film of 5 %mass. of Fe/C, to 5.6 Gs∙cm3/g (film of 15 % mass. Fe/C). There are cohertzitive power values, changing dependently from Fe/C comtent, from 97 to 99 E. It is founded, that electrical conductivity values (s), at frequency of 1 kHz , is absent, for non-oriented film of 1 %mass. Fe/C (σ=9,4∙10-11 Om-1cm-1), but, for those non-oriented ones of 5- 15 %mass. are 2,4∙10-5 ‒ 1∙10 Om-1cm-1. Where are orientational stretching actions, there are decreasing in electrical conductivity values - σ=1,4∙10-12‒2,7∙10‑1 Om-1cm-1 for films of λ=5‒6. Those films, when at own intrinsic structure-mechanical, electrical and magnetic properties, depending of Fe/C content, are perspective ones as magnetic, anti-static and electrical conductive materials.
Spectral and quantum-chemical investigation of interactions in supra-molecular systems: cucumin - decametoxin - silica in aqueous solutions
Authors:   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Kazakova O. O. , Lipkovska N. O. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, Barvinchenko V. M. ,   Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
Published: December 2022

The peculiarities of the interaction in the supramolecular system: the natural hydrophobic polyphenol curcumin - the antiseptic cationic surface-active substance decamethoxin - highly dispersed silica was revealed by the spectrophotometric method. It was established that significant changes in the spectral characteristics of curcumin in aqueous solutions and on the surface of the sorbent depend on the concentration of this cationic surfactant, which can exist in the solution in the form of monomers, associates, and micelles. The PM7 method and the COSMO solvation model, implemented in the MOPAC2016 software package were used to determine the mechanism of adsorption of the supramolecular complex of curcumin (in ketone or enol form) with decamethoxine on the silica surface. The distribution of electrostatic and hydrophobic potentials of the studied molecules, calculated by the FieldView 2.0.2 method (Flare software package), indicates a significant contribution of hydrophobic interactions in the formation of supramolecular complexes of curcumin with decamethoxin in solution and on the surface of silica. The obtained results are of practical importance and can be used in the development of new more effective drugs containing bioactive curcumin, antiseptic decamethoxine and enterosorbent silicon dioxide.
Most Recent Trials and Advances in Hypertension
Authors: Martínez Rey-Rañal Elías , Cordero Alberto
Published: December 2022

Hypertension is one of the most prevalent cardiovascular risk factors and blood pressure control remains a clinical challenge, especially for patients with established cardiovascular disease. Late-breaking clinical trials and other evidence in hypertension have evolved to assess the most accurate ways to measure blood pressure, the use of combination therapies, considerations in special populations and evaluation of new techniques. Recent evidence supports the superiority of ambulatory or 24-hour blood pressure measurements, rather than office blood pressure measurements, for the assessment of cardiovascular risk. The use of fixed-dose combinations and polypills has been demonstrated to be valid and to provide clinical benefits beyond blood pressure control. There have also been advances in new approaches such as telemedicine, devices and the use of algorithms. Clinical trials have provided valuable data on blood pressure control in primary prevention, during pregnancy and in the elderly. The role of renal denervation remains unsolved but innovative techniques using ultrasound or alcohol injections are being explored. Current evidence and results of latest trials are summarised in this review.