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Mastering the growth of antimonene on ▫$Bi_2Se_3$▫ : strategies and insights
Roberto Flammini, Conor Hogan, Stefano Colonna, Fabio Ronci, Mauro Satta, Marco Papagno, Ziya S. Aliev, Sergey V. Eremeev, Zipporah Rini Benher, Sandra Gardonio, 2025, original scientific article

Abstract: Antimonene, the two-dimensional phase of antimony, appears in two distinct allotropes when epitaxially grown on Bi2Se3: the puckered asymmetric washboard (α) and buckled honeycomb (β) bilayer structures. As-deposited antimony films exhibit varying proportions of single α and β structures. We identify the conditions necessary for ordered, pure-phase growth of single to triple β-antimonene bilayers. Additionally, we determine their electronic structure, work function, and characteristic core-level binding energies, offering an explanation for the relatively large chemical shifts observed among the different phases. This study not only establishes a protocol for achieving a single β phase of antimonene but also provides key signatures for distinguishing between the different allotropes using standard spectroscopic and microscopic techniques.
Keywords: density functional theory, electronic band structure, topological insulators, work functions, scanning tunneling microscopy, atomic structure, antimony, angle-resolved photoemission spectroscopy, core level shifts
Published in RUNG: 20.03.2025; Views: 390; Downloads: 7
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3.
Beyond surface area : enhanced pseudocapacitive properties of cobalt layered double hydroxide through structural modifications
Anja Siher, Ksenija Maver, Uroš Luin, Albin Pintar, Iztok Arčon, Andraž Mavrič, 2025, original scientific article

Abstract: Cobalt hydroxide and other first-row transition metal hydroxides have gained significant attention as pseudocapacitor materials due to their rapid and reversible redox processes. Their layered structures facilitate interactions between electrolyte anions and cobalt cation sites within the bulk of the material, enabling higher charge density and extending redox activity beyond the particle surface. By controlled precipitation under hydrothermal conditions, the structure and morphology of cobalt hydroxides can be optimized to enhance electrochemical performance. Challenging conventional assumptions, surface area alone is not the primary factor driving increased pseudocapacitive performance. The hexagonal hydrotalcite-like structure, characterized by lower skeletal density and larger basal plane spacing, outperforms the monoclinic cobalt carbonate hydroxide structure, achieving an order of magnitude higher capacitance. In situ X-ray absorption spectroscopy provides critical insights into the pseudocapacitive behavior, revealing enhanced accessibility of Co2+ sites for electrochemical oxidation. While monoclinic cobalt carbonate hydroxide exhibits minimal changes in the Co2+ oxidation state, indicative of surface-limited redox activity, the hydrotalcite-like cobalt hydroxides show substantial shifts in the Co K-edge position, highlighting oxidation of Co2+ sites throughout the bulk.
Keywords: pseudocapacitors, layered-double hydroxides, cobalt hydroxide, redox processes, in situ x-ray absorption spectroscopy
Published in RUNG: 14.03.2025; Views: 510; Downloads: 7
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4.
Iodine K- and L-edge X-ray absorption spectra of HI : the effect of molecular orbitals and core subshells
Robert Hauko, Jana Padežnik Gomilšek, Alojz Kodre, Iztok Arčon, Uroš Luin, 2024, original scientific article

Abstract: Analysis of the recently measured absorption spectra of molecular HI at K and L edges of iodine, in parallel with previously measured spectra of noble gas Xe and the K edge spectrum of atomic I, is presented. A strong dependence of some valence multielectron photoexcitation features on the orbital momentum of the core vacancy is found, attributed to the change of the symmetry of the HI molecule: the shake-up coexcitation of a valence electron to a free molecular orbital is much stronger at L3 than L1 edge. The effect of angular momentum of the core hole on the shake processes of deeper multielectron photoexcitations is found negligible. Both HI and Xe exhibit a much weaker one-electron transition [1s]6p than monatomic I. At the K edge, the strength of coexcitations of 4d, 4p and 3d subshells in atomic I is close to the HI and Xe. The same is found for HI and Xe at the L edges, due to a weak contribution of the additional free molecular orbital in HI.
Keywords: X-ray absorption spectroscopy, K edge spectrum of atomic I, multielectron photoexcitations (MEPE), core vacancy angular momentum
Published in RUNG: 09.01.2025; Views: 651; Downloads: 6
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5.
Light-Assisted Catalysis and the Dynamic Nature of Surface Species in the Reverse Water Gas Shift Reaction over Cu/γ-Al2O3
Kristijan Lorber, Iztok Arčon, Matej Huš, Janez Zavašnik, Jordi Sancho-Parramon, Anže Prašnikar, Blaž Likozar, Nataša Novak Tušar, Petar Djinović, original scientific article

Abstract: The reverse water gas shift (RWGS) reaction converts CO2 and H2 into CO and water. We investigated Cu/γ-Al2O3 catalysts in both thermally driven and light-assisted RWGS reactions using visible light. When driven by combined visible light and thermal energy, the CO2 conversion rates were lower than in the dark. Light-assisted reactions showed an increase in the apparent activation energy from 68 to 87 kJ/mol, indicating that light disrupts the energetically favorable pathway active in the dark. A linear correlation between irradiance and decreasing reaction rate suggests a photon-driven phenomenon. In situ diffuse reflectance infrared Fourier transform spectroscopy and TD-DFT analyses revealed that catalyst illumination causes significant, partly irreversible surface dehydroxylation, highlighting the importance of OH groups in the most favorable RWGS pathway. This study offers a novel approach to manipulate surface species and control activity in the RWGS reaction.
Keywords: light-assisted catalysis, reaction mechanism, in situ spectroscopy, hydroxyl, copper, RWGS
Published in RUNG: 07.01.2025; Views: 649; Downloads: 6
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Gases
Alojz Kodre, Iztok Arčon, Jana Padežnik Gomilšek, 2024, scientific entry in dictionary, encyclopaedia or lexicon

Abstract: X-ray absorption spectroscopy of gases is seldom used for structural analysis, except in as much as the extended X-ray absorption fine-structure (EXAFS) signal is used to monitor some specific molecular process. Gas spectroscopy, however, has been the main tool in the systematic study of higher-order photoabsorption processes, multielectron photoexcitations (MEEs), which were introduced with an experiment at the K edge of argon. Along with noble gases, where MEEs are studied in the pure form, free of the structural signal, measurements have been extended to monatomic metal vapours, although at the cost of considerable experimental difficulties. Several types of absorption cells have been devised, among them the ceramic double cell and the heat-pipe cell for experiments in the low-energy region. In a high-temperature oven with considerable technical refinement, edge profiles of nonvolatile metals were measured up to 2500 K. Edge profiles and MEEs, which are strongly dependent on electron correlation, provide sensitive tests of the theory of atomic and molecular structure.
Keywords: X-ray absorption spectroscopy, absorption cells, gas and vapour samples, multielectron photoexcitation, effects of electron correlation
Published in RUNG: 05.09.2024; Views: 1218; Downloads: 4
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Contributed talk at the European Astronomical Society Annual Meeting 2023 : The rise and fall of the iron-rich nuclear transient PS16dtm
Tanja Petrushevska, published scientific conference contribution abstract

Keywords: nuclear transients, photometry, spectroscopy, EAS
Published in RUNG: 19.07.2023; Views: 2314; Downloads: 4
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