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21.
22.
Določanje atomske strukture snovi z rentgensko absorpcijsko spektrometrijo s sinhrotronsko svetlobo
Iztok Arčon, invited lecture at foreign university

Abstract: Zakaj so velike evropske države pripravljene investirati ogromna sredstva v izgradnjo in delovanje sinhrotronov? Gre za izjemno svetle vire ultravijolične in rentgenske svetlobe, ki so v zadnjih dveh ali treh desetletjih postali nepogrešljivo orodje pri analizi snovi na atomskem oziroma molekularnem nivoju. Razvoja in sinteze novih materialov z želenimi lastnostmi si ne moremo predstavljati brez sodobnih preiskovalnih metod, ki temeljijo na sinhrotronski svetlobi. V predavanju bo predstavljen princip delovanja in primeri uporabe ene od rentgenskih metod s sinhrotronsko svetlobo – rentgensko absorpcijsko spektroskopijo, s katero lahko določamo atomsko oz. molekularno strukturo snovi v vseh agregatnih stanjih. Za take raziskave so danes zanimivi predvsem različni nanostrukturni materiali, kot so katalizatorji, katodni materiali za Li-ionske in Li-žveplove baterije, tanke zaščitne plasti, in drugi, pri katerih atomska struktura določa njihove funkcionalne lastnosti. Na predavanju bodo izpostavljeni v prvi vrsti primeri in-operando karakterizacije z metodama XANES in EXAFS ki omogoča zelo natančno in neposredno spremljanje postopnih sprememb valence kovinskih kationov in njihove lokalne atomske strukture v nanozrnih v katodnem materialu med polnjenjem in praznjenjem baterije, ali kovinskih kationov na površini nanostrukturnega (foto)katalitskega materiala med samo katalitsko reakcijo. Sodobni sinhrotronski viri rentgenske svetlobe pa omogočajo tudi uporabo kombinacije rentgenske absorpcijske spektroskopije z rentgenskimi mikroskopskimi metodami, z ločljivostjo do nekaj deset nanometrov. Na predavanju bodo predstavljeni primeri mikro-XANES in EXAFS analize lokalizacije in vezave toksičnih kovinskih kationov na sub-celičnem nivoju v različnih tkivih rastlin, s čimer lahko ključno prispevamo k razumevanju mehanizmov zajemanja, transporta, akumulacije in kompleksacije kovinskih kationov na sub-celičnem nivoju v različnih tkivih rastlin, ki te polutante (hiper)akumulirajo, in jih s tem prenašajo v prehranjevalno verigo, s čimer je ogroženo zdravje ljudi.
Found in: osebi
Keywords: rentgenska absorpcijska spektroskopija, XANES, EXAFS, strukturna analiza, sinhrotronska svetloba
Published: 01.06.2018; Views: 2076; Downloads: 0
.pdf Fulltext (151,01 KB)

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Spremljanje, ugotavljanje in zagotavljanje kakovosti
Sabina Zelinšček, Matjaž Valant, MAJA TERČON, Nivec Štefančič, Tea Stibilj Nemec, MARINA ARTICO, Iztok Arčon, Blaž Belec, treatise, preliminary study, study

Found in: osebi
Keywords: Samoevalvacijsko poročilo
Published: 06.01.2020; Views: 1292; Downloads: 0
.pdf Fulltext (3,52 MB)

26.
Spremljanje, ugotavljanje in zagotavljanje kakovosti Univerza v Novi Gorici
Iztok Arčon, Martina Bergant Marušič, Blaž Belec, treatise, preliminary study, study

Found in: osebi
Keywords: samoevalvacija
Published: 23.01.2020; Views: 1171; Downloads: 0
.pdf Fulltext (4,79 MB)

27.
28.
Spremljanje, ugotavljanje in zagotavljanje kakovosti:
Aljaž Rener, JANA BLEGUŠ, MAJA TERČON, Matjaž Valant, Iztok Arčon, Blaž Belec, MARINA ARTICO, Tea Stibilj Nemec, treatise, preliminary study, study

Found in: osebi
Keywords: samoevalvacijsko poročilo
Published: 23.12.2020; Views: 791; Downloads: 21
.pdf Fulltext (3,81 MB)

29.
Photo-Chemically-Deposited and Industrial Cu/ZnO/Al2O3 Catalyst Material Surface Structures During CO2 Hydrogenation to Methanol: EXAFS, XANES and XPS Analyses of Phases After Oxidation, Reduction, and Reaction
Blaž Likozar, Iztok Arčon, Venkata Dasireddy, Maja Pori, 2021, original scientific article

Abstract: Industrial Cu/ZnO/Al2O3 or novel rate catalysts, prepared with a photochemical deposition method, were studied under functional CH3OH synthesis conditions at the set temperature (T) range of 240–350 °C, 20 bar pressure, and stoichiometric carbon dioxide/hydrogen composition. Analytical scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray adsorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) methods were systematically utilized to investigate the interfaces, measured local geometry, and chemical state electronics around the structured active sites of commercially available Cu/ZnO/Al2O3 material or synthesized Cu/ZnO. Processed Cu K-edge EXAFS analysis suggested that various Cu atom species, clusters, metallic fcc Cu, Cu oxides (Cu2O or CuO) and the Cu0.7Zn2 alloy with hexagonal crystalline particles are contained after testing. It was proposed that in addition to the model’s Cu surface area, the amount, ratio and dispersion of the mentioned bonded Cu compounds significantly influenced activity. Additionally, XPS revealed that carbon may be deposited on the commercial Cu/ZnO/Al2O3, forming the inactive carbide coating with Cu or/and Zn, which may be the cause of basicity’s severe deactivation during reactions. The selectivity to methanol decreased with increasing T, whereas more Cu0.7Zn2 inhibited the CO formation through reverse water–gas shift (RWGS) CO2 reduction.
Found in: osebi
Keywords: CH3OH synthesis, Cu/ZnO-based catalyst, XPS, XANES, EXAFS analyses, Catalyst selectivity and activity
Published: 03.06.2021; Views: 351; Downloads: 0
.pdf Fulltext (3,98 MB)

30.
X-ray absorption spectroscopy analysis: in situ, operando, in vivo
Iztok Arčon, 2020, published scientific conference contribution abstract (invited lecture)

Abstract: X-ray absorption spectroscopy (XAS) is a powerful tool for characterisation of local structure and chemical state of selected elements in different new functional materials and biological or environmental samples. The XAS spectroscopy is based on extremely bright synchrotron radiation X-rays sources, which allow precise characterisation of bulk, nanostructured or highly diluted samples. With its two methods (XANES and EXAFS) it enables monitoring changes in valence states and local structures of constituent elements during chemical reactions under controlled reaction conditions, and it offers a possibility of a combination of X-ray spectroscopy and microscopy with sub-micron lateral resolution, crucial for analysis of biological samples on sub-cellular level. In this talk some typical examples of advanced XAS analysis will be presented.
Found in: osebi
Keywords: X-ray absorption spectroscopy, EXAFS, XANES, in-situ, operando
Published: 17.10.2020; Views: 934; Downloads: 0
.pdf Fulltext (68,21 KB)

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