Кафедра фізико-математичних наук
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Item Cu-Related Paramagnetic Centers in Cu- and (Cu,Y)-Doped ZrO2 Nanopowders(2025) Nosenko, Valentyna; Vorona, Igor; Trachevskyi, Viacheslav; Zagorodniy, Yuriy; Okulov, Sergey; Isaieva, Oksana; Yukhymchuk, Volodymyr; Kulinich, Sergei; Borkovska, Lyudmyla; Khomenkova, LarysaIn this work, we studied Cu-doped and (Cu,Y)-codoped ZrO2 nanopowders produced through a coprecipitation approach to identify the nature of Cu-related bulk and surface paramagnetic centers. We conducted EPR, NMR, and Raman scattering studies on Cu- and (Cu,Y)-doped ZrO2 powders calcined at different temperatures. At low calcination temperatures (400 ◦C) and low Cu loading (0.1–1.0 mol.% of CuO), the EPR signal was found to be attributed to surface-related Cu-H2O complexes. For powders with higher Cu content (up to 8.0 mol.% of CuO), the superparamagnetic signal associated with the formation of copper clusters was observed. At higher calcination temperatures, the destruction of Cu-related surface complexes promotes the incorporation of Cu2+ ions into the bulk of ZrO2 nanocrystals at Zr positions. Co-doping ZrO2 with Cu and Y was observed to facilitate the incorporation of Cu2+ ions into cation sites at lower calcination temperatures when compared with Cu-doped ZrO2.Item Luminophores for luminescent solar concentrators(2024) Rudko, GalynaThe war in Ukraine demonstrated the vulnerability of the energy supply system with centralized power supply. Moreover, it showed that the country must not rely on imported gas and oil, and also highlighted the danger of using nuclear plants. Under these circumstances solar energy gains the acute attention especially because of possibility to decentralize energy production. However, using of traditional solar cells in Ukraine encounters a problem of rather low amount of sunny days thus there is a demand for the devices capable of operating under diffuse illumination.Item Mn2+ як ЕПР зонд для вивчення структури мікро- та нанорозмірних порошків ZnS(2024) Ворона, Ігор; Іщенко, С.; Баран, Н.; Носенко, Валентина; Грачов, В.Матеріали доповіді учасників міжнародного наукового семінару "ЕПР-орієнтири еволюції методології пізнання"Item Радіаційні дефекти в термічно відпаленому карбонатвмісному гідроксилапатиті(2024) Носенко, Валентина; Ворона, Ігор; Іщенко, С.; Окулов, СергійМатеріали доповіді учасників міжнародного наукового семінару "ЕПР-орієнтири еволюції методології пізнання".Item DNA condensation induced by Li+ counterions(2024) Bubon, Tetiana; Piatnytskyi, Dmytro; Perepelytsya, SergiyMaterials of the participants' report of Bogolyubov Kyiv Conference "Problems of Theoretical and Mathematical Physics", dedicated to the 115-th anniversary of the outstanding theoretician in physics and mathematics Mykola BogolyubovItem Effects of metallic and molecular counterions in structural dynamics of the DNA double helix(2024) Perepelytsya, SergiyThe aim of this paper is to derive the hydrodynamics for a cold Bose gas from the microscopic platform based on the many-body Schr¨odinger equation and general assumptions of the hydrodynamic approach (HA) applicable to any dimension.Item To the 115th anniversary of the birth of Mykola Bogolyubov(2024) Zagorodny, A.; Zasenko, V.; Perepelytsya, SergiyMaterials of the participants' report of Bogolyubov Kyiv Conference "Problems of Theoretical and Mathematical Physics", dedicated to the 115-th anniversary of the outstanding theoretician in physics and mathematics Mykola BogolyubovItem Primordial black holes and their gravitational-wave signatures(2023) Bagui, Eleni; Clesse, Sébastien; De Luca, Valerio; Ezquiaga, Jose María; Franciolini, Gabriele; García-Bellido, Juan; Joana, Cristian; Jain, Rajeev Kumar; Kuroyanagi, Sachiko; Musco, Ilia; Papanikolaou, Theodoros; Raccanelli, Alvise; Renaux-Petel, Sébastien; Riotto, Antonio; Morales, Ester Ruiz; Scalisi, Marco; Sergijenko, Olga; Unal, Caner; Vennin, Vincent; Wands, DavidIn the recent years, primordial black holes (PBHs) have emerged as one of the most interesting and hotly debated topics in cosmology. Among other possibilities, PBHs could explain both some of the signals from binary black hole mergers observed in gravitational wave detectors and an important component of the dark matter in the Universe. Significant progress has been achieved both on the theory side and from the point of view of observations, including new models and more accurate calculations of PBH formation, evolution, clustering, merger rates, as well as new astrophysical and cosmological probes. In this work, we review, analyse and combine the latest developments in order to perform end-to-end calculations of the various gravitational wave signatures of PBHs. Different ways to distinguish PBHs from stellar black holes are emphasized. Finally, we discuss their detectability with LISA, the first planned gravitational-wave observatory in space.Item High-Performance Multiwavelength GaNAs Single Nanowire Lasers(2024) Jansson, Mattias; Nosenko, Valentyna; Torigo, Yuto; Nakama, Kaito; Yukimune, Mitsuki; Higo, Akio; Ishikawa, Fumitaro; Chen, Weimin; Buyanova, IrinaIn this study, we report a significant enhancement in the performance of GaNAs-based single nanowire lasersthrough optimization of growth conditions, leading to a lowerlasing threshold and higher operation temperatures. Ouranalysis reveals that these improvements in the laser performance can be attributed to a decrease in the density of localizedstates within the material. Furthermore, we demonstrate thatowing to their excellent nonlinear optical properties, thesenanowires support selffrequency conversion of the stimulatedemission through second harmonic generation (SHG) and sumfrequency generation (SFG), providing coherent light emissionin the cyan-green range. Mode-specific differences in the self-conversion efficiency are revealed and explained by differencesin the light extraction efficiency of the converted light caused by the electric field distribution of the fundamental modes. Ourwork, therefore, facilitates the design and development of multiwavelength coherent light generation and higher-temperatureoperation of GaNAs nanowire lasers, which will be useful in the fields of optical communications, sensing, and nanophotonicsItem Dual-channel SPR biosensor for enhanced glioma relapse diagnostics: Blood cell aggregation as a biomarker for tumor malignancy(2024) Samoylov, Anton; Khristosenko, Roman; Gridina, N.; Dorozinsky, Glib; Romanchuk, V.; Khomenkova, LarysaAbstract. A biosensor based on the surface plasmon resonance (SPR) phenomenon has been developed for the express diagnosis of brain gliomas relapse by assessing blood cell aggregation indicators. The device features two optical channels, allowing for two studies to be performed simultaneously or enabling one channel to be used as a reference. This approach significantly increases biosensor sensitivity by reducing the impact of external factors. The optical excitation source is a p-polarized semiconductor laser with a 650 nm wavelength. The sensing elements were F1 optical glass plates with a refractive index of 1.61, with sputtered layers of chromium (5 nm) and gold (45…50 nm). As a result of the studies, a correlation was ascertained between the level of peripheral blood cell aggregation in patients and the degree of malignancy of gliomas. A statistically significant difference (p ≤ 0.05) was found between the groups of conditionally healthy individuals and those with grade II-IV gliomas. A decrease in the shift of the SPR curve during blood testing indicates an increase in cell aggregation levels and a decrease in their electric charge on membranes. This trend gradually intensifies with the increasing degree of glioma malig-nancy, reaching minimal values in patients with grade IV gliomas, indicating changes in the physicochemical properties of cell membranes and a reduction in their electric charge.Item The 2nd Scientific workshop for students "Computational Physics of DNA"(2024) Perepelytsya, Sergiy; Tetiana, BubonThe article is devoted to the 2nd Scientific workshop for students “Computational physics of DNA”.Item Про можливість створення науково-технічного центру з використання радіаційних технологій у медицині(2024) Поворозник, Орест; Горпинич, ОльгаРозглянуто можливість створення в Інституті ядерних досліджень НАН України науково-технічного підприємства з виробництва широкого спектра радіаційних ізотопів та радіонуклідних фармацевтичних препаратів на їх основі. Наразі в Україні потреба в таких препаратах забезпечується виключно завдяки імпорту. В Інституті є всі передумови для створення такого підприємства: приміщення, пристосовані для проведення радіаційно небезпечних робіт, персонал, який має відповідний досвід з виготовлення експериментальних зразків радіофармпрепаратів, і наявність осіб, які можуть організувати і налагодити виробництво. Наведено огляд прискорювачів і технологій з метою визначення оптимальних для України рішень. Обговорено можливість проведення робіт з пучкової онкотерапії та створення підрозділу бор-нейтрон-захоплювальної терапії на базі низькоенергетичного прискорювача ЕГП-10К.Item Reality conditions for the KdV equation and exact quasi-periodic solutions in finite phase spaces(2024) Bernatska, JuliaIn the present paper reality conditions for quasi-periodic solutions of the KdV equation are determined completely. As a result, solutions in the form of non-linear waves can be plotted and investigated. The full scope of obtaining finite-gap solutions of the KdV equation is presented. It is proven that the multiply periodic }1, 1-function on the Jacobian variety of a hyperelliptic curve of arbitrary genus serves as the finite-gap solution, the genus coincides with the number of gaps. The subspace of the Jacobian variety where }1, 1, as well as other }-functions, are bounded and real-valued is found in any genus. This result covers every finite phase space of the KdV hierarchy, and can be extended to other completely integrable equations. A method of effective computation of this type of solutions is suggested, and illustrated in genera 2 and 3.Item Electronic Spectrum and Conductivity in Graphene with Impurities(2023) Kruchinin, Sergei; Repetsky, Stanislav; Vyshyvana, Iryna; Polishchuk, ArkadiyIn the tight-binding one-electron model, the influence of substitutional impurity atoms on the energy spectrum and electrical conductance of graphene is studied. It is established that the ordering of substitutional impurity atoms on nodes of the crystal lattice causes the appearance of a gap in the energy spectrum of graphene 𝜂|𝛿| in width centered at the point 𝑦𝛿, where 𝜂 is the parameter of ordering, 𝛿 is the difference of the scattering potentials of impurity atoms and carbon atoms, and 𝑦 is the impurity concentration. If the Fermi level is located outside the gap, then the electrical conductance increases with the parameter of order 𝜂. It is shown that an increase in the electrical conductance with the order parameter is a result of both the growth of the density of states at the Fermi level and the time of relaxation of electron states. We have demonstrated the presence of a domain of localized states on the edges of the energy gap arising at the ordering of atoms of the admixture.Item Effect of MgO/ZnO ratio on the formation process of MgxZn1-xO ceramics(2024) Korsunska, Nadiia; Polishchuk, Yuliya; Ponomaryov, Semyon; Kozoriz, K.; Chusnutdinow, S.; Melnichuk, Olexandr; Melnichuk, Lyudmyla; Khomenkova, LarysaThe structural characteristics, chemical composition, and element spatial distribution in MgxZn1-xO ceramics were investigated using X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, energy-dispersive X-ray spectroscopy, and cathodoluminescence techniques. The study revealed that the morphology of the ceramic samples, as well as the mechanism of solid solution formation, depend on the relative contribution of both oxides in the charge. It was discovered that hexagonal and cubic phases of the solid solution were found to form simultaneously. An increase in the MgO content in the charge results in the magnesium content rise in the hexagonal grains continuously, reaching approximately 13 at.%. It was discovered an enrichment of grain boundaries with zinc and magnesium playing a significant role in doping ZnO and MgO grains. Obtained results allowed to propose two mechanisms involved in the formation of solid solution ceramics: i) diffusion of Mg and Zn along grain boundaries, followed by their incorporation into ZnO or MgO grains, respectively, and ii) interdiffusion of Mg into ZnO and Zn into MgO due to direct contact of ZnO and MgO grains. The second mechanism appears to dominate when both ZnO and MgO contribute comparably, increasing the probability of their direct contact. This study significantly advances the understanding of the process of the formation of MgxZn1-xO ceramics under thermodynamic conditions. These insights are crucial for optimizing the doping process and improving the material properties, thereby promoting innovations in the ceramics industry.Item Effect of dopant loading and calcination conditions on structural and optical properties of ZrO2 nanopowders doped with copper and yttrium(2024) Khomenkova, Larysa; Marchylo, Oleg; Polishchuk, Yulia; Ponomaryov, Semyon; Isaieva, Oksana; Vorona, Igor; Melnichuk, Liudmyla; Portier, Xavier; Melnichuk, Olexandr; Korsunska, NadiiaUndoped, Cu and/or Y doped ZrO2 nanopowders were synthesized with Zr, Y, and Cu nitrates using a co-precipitation approach. Their structural and optical properties were examined regarding dopant content (0.1–8.0 mol.% of CuO and 3–15 mol.% of Y2O3) and calcination conditions (400 °C– 1000 °Cand, 1,2 or 5 h) through Raman scattering, XRD, TEM, EDS, AES, EPR,UV–vis and FTIR diffused reflectance methods. The results showed that both Cu and Y dopants promoted the appearance of additional oxygen vacancies in ZrO2 host, while the formation of tetragonal and cubic ZrO2 phases was primarily influenced by the Y content, regardless of Cu loading. The bandgap of most of the powders was observed within the 5.45–5.65 eV spectral range, while for those with high Y content it exceeded 5.8 eV. The (Cu,Y)-ZrO2 powders with 0.2 mol.% CuO and 3 mol.% Y2O3 calcined at 600 °Cfor 2 h demonstrated nanoscaled tetragonal grains (8–12 nm) and a significant surface area covered with dispersed CuxOspecies. For higher calcination temperatures, the formation of CuZr 2+ EPR centers, accompanied by tetragonal-to-monoclinic phase transformation, was found. For fitting of experimental FTIR reflection spectra, theoretical models with one, five, and seven oscillators were constructed for cubic, tetragonal, and monoclinic ZrO2 phases, respectively. Comparing experimental and theoretical spectra, the parameters of various phonons were determined. It was found that the distinct position of the high-frequency FTIR reflection minimum is a unique feature for each crystalline phase. It was centered at 700–720 cm−1, 790–800 cm−1, and 820–840 cm−1 for cubic, tetragonal, and monoclinic phases, respectively, showing minimal dependence on phonon damping coefficients. Based on the complementary nature of results obtained from structural and optical methods, an approach for monitoring powder properties and predicting catalytic activity can be proposed for ZrO2–based nanopowders.Item Influence of compacting pressure on the electrical properties of ZnO and ZnO:Mn ceramics(2024) Korsunska, N.; Markevich, Iryna; Stara, T.; Polishchuk, Yu.; Ponomaryov, S.; Kozoriz, K.; Tsybrii, Zinoviia; Melnichuk, O.; Melnichuk, L.; Venger, E.; Khomenkova, LarysaUndoped and Mn-doped ZnO ceramics were prepared from the powders compacted at different pressures and sintered in air at high temperature. Their structural, optical, light emitting and electrical characteristics as well as the distribution of chemical elements were studied. It was found that an increase in compacting pressure stimulates an increase in direct current conductivity in both undoped and doped samples. In the case of doped samples, this effect was accompanied by a decrease in the height of potential barriers at the grain boundaries. It is found that electron concentration in ceramic grains, estimated from the modelling of infrared reflection spectra, remained relatively constant. The analysis of luminescence spectra and spatial zinc distribution revealed that the increase in compacting pressure results in the accumulation of interstitial zinc at the grain boundaries forming channels with enhanced conductivity. These findings provide an explanation for the evolution of electrical properties of ceramic samples with compacting pressure.Item Вплив термічно та радіаційно стимульованих процесів дифузії на властивості матеріалів мікроелектроніки та приладів на їх основі : монографія(Вид-во НДУ ім. М. Гоголя, 2019) Корсунська, Надія; Маркевич, Ірина; Борковська, Людмила; Хоменкова, Лариса; Савкіна, Рада; Смірнов, Олексій; Венгер, Євген; Мельничук, Людмила; Мельничук, ОлександрНаведено результати досліджень трансформації структурних, оптичних, електричних та люмінесцентних властивостей напівпровідникових та діелектричних матеріалів внаслідок термічної, ультразвукової та радіаційної обробки. Описані методи виготовлення матеріалів. Приділяється увага процесам термічної дифузії домішок та власних дефектів, їх дифузії під дією світла, а також дрейфу дефектів в електричному полі; взаємодії об’ємних дефектів; утворенню різного типу радіаційних дефектів, а також процесам фазово-структурних перетворень в різних сполуках та їх твердих розчинах. Розглянуто вплив цих процесів на стабільність роботи приладів на основі таких матеріалів та визначено чинники, що відповідають за процеси деградації приладів. Для студентів, аспірантів фізичних факультетів, а також для науковців, які працюють у галузі фізики твердого тіла.Item Photoluminescence quantum yield of carbon dots: emission due to multiple centers versus excitonic emission(2024) Dimitriev, Oleg; Kysil, Dmytro; Zaderko, Alexander; Isaieva, Oksana; Vasin, Andrii; Piryatinski, Yuri; Fahlman, Mats; Nazarov, AlexeiCarbon dots (CDs) are recognized as promising fluorescent nanomaterials with bright emission and large variations of photoluminescence quantum yield (PLQY). However, there is still no unique approach for explanation of mechanisms and recipes for synthetic procedures/chemical composition of CDs responsible for the enhancement of PLQY. Here, we compare photophysical behavior and PLQY of two types of CDs synthesized by different routes, leading to the different extent of oxidation and composition. The first type of CDs represents a conjugated carbon system oxidized by F, N and O heteroatoms, whereas the second type represents a non-conjugated carbon system oxidized by oxygen. Photophysical data, photoemission spectroscopy and microscopy data yield the suggestion that in the first case, a structure with a distinct carbon core and highly oxidized electron-accepting shell is formed. This leads to the excitonic type non-tunable emission with single-exponent decay and high PLQY with a strong dependence on the solvent polarity, being as high as 93% in dioxane and as low as 30% in aqueous medium, but which is vulnerable to photobleaching. In the second case, the oxidized CDs do not indicate a clear core–shell structure and show poor solvatochromism, negligible photobleaching, low PLQY varying in the range of 0.7–2.3% depending on the solvent used, and tunable emission with multi-exponent decay, which can be described by the model of multiple emission centers acting through a clustering-triggered emission mechanism. The obtained results lead to a strategy that allows one to design carbon nanomaterials with principally different PLQYs that differ by orders of magnitude.Item From the personal history of teaching philosophy of physics(Талком, 2022) Kuznetsov, VolodymyrThe experience of teaching philosophy o f physics to Ukrainian physics masters is described. The goal of the course is to promote their conscious and clear understanding of i’ physical theories as complex and necessary tools for gaining new knowledge about their domains of application. Theoretical physics is viewed as a network of developing and t interrelated theories. They are practical because, on the one hand, they are learned by ft students as future physicists. On the other hand, professional physicists are constantly t improving practical theories to produce new knowledge. Thus, it is needed to analyze r theories both as changeable systems and as complex polysystems under more detailed hscrutiny. That is why the course is based on a modified structure-nominative reconstruction a of practical physical theories as polysystems consisting of interconnected and flexible I homogeneous subsystems.