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11.
X-ray absorption spectroscopy studies of the room-temperature ferromagnetic Fe-doped 6H-BaTiO[sub]3
I. Mikulska, Matjaž Valant, Iztok Arčon, Darja Lisjak, 2015, original scientific article

Found in: ključnih besedah
Summary of found: ...magnetni polprevodniki, barijev titan, EXAFS, ...
Keywords: magnetni polprevodniki, barijev titan, EXAFS
Published: 16.06.2016; Views: 2225; Downloads: 70
URL Fulltext (0,00 KB)

12.
XAS and micro-XRF analysis of mono and bi-metallic exopolysaccharide (FePd-EPS) bio-generated by K. oxytoca
Franco Baldi, Katarina Vogel-Mikuš, Michele Gallo, Oreste Piccolo, Stefano Paganelli, Iztok Arčon, 2016, published scientific conference contribution abstract

Abstract: Bacteria Klebsiella oxytoca (DSM 29614) secret a specific exopolysaccharide (EPS) in the presence of Fe(III)-citrate, as sole carbon and energy source, and produces after 7 days an iron gel precipitate (Fe-EPS) [1]. In the presence of palladium or other metal species, the culture of K. oxytoca can produce other mono or bimetal species (Pd-EPS, FePd-EPS) [2]. These bio-materials may be used as green biogenerated catalysts or for other biotechnological purposes. In this work we present the analysis of the morphology and the chemical state of the metals in mono and bi-metallic (Fe-EPS, Pd-EPS, FePd-EPS) complexes, by a combination of micro X-ray fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show that iron in monometallic Fe-EPS and bimetalic FePd-EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, as a mixture of different nano-crystalline iron oxides and hydroxides. Palladium on the other hand is found as Pd(0) in the form of metallic nanoparticles with fcc structure in both, bi-metallic (FePd-EPS) and mono-metallic (Pd-EPS) species. In bi-metallic species Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. Access to the SR facilities at ESRF (beamline ID21, project LS-2225), DESY (beamline C) Hamburg (project I-20110511 EC) and ELETTRA (beamline XAFS, project 20115112) is acknowledged.
Found in: ključnih besedah
Summary of found: ...fluorescence, X-ray absorption spectroscopy methods (XANES and EXAFS), and transmission electron microscopy. The results show...
Keywords: Klebsiella oxytoca, Fe, Pd, XANES, EXAFS, exopolysaccharide, FePd-EPS
Published: 28.06.2016; Views: 2874; Downloads: 0
.pdf Fulltext (388,27 KB)

13.
Arbuscular mycorrhizal fungi alter Hg root uptake and ligand environment as studied by X-ray absorption fine structure
Alojz Kodre, Iztok Arčon, Marta Debeljak, Mateja Potisek, Matevž Likar, Katarina Vogel-Mikuš, 2017, original scientific article

Abstract: Mercury (Hg) – plant – fungal interactions are only poorly studied. Hg speciation and ligand environment in maize roots inoculated with arbuscular mycorrhizal (AM) fungi were investigated in order to better understand the role of AM in Hg soil to root transfer. The maize plants were grown in Hg polluted substrate (50 mg g1 as dissolved HgCl2) and inoculated with AM fungi originating from: a) highly Hg polluted environment of a former Hg smelting site in Idrija, Slovenia, (Glomus sp. – sample AmI), and b) non-polluted environment (commercial AM inoculum Symbivit1 – sample AmC). Hg speciation and ligand environment in maize roots was studied by Hg-L3 XANES and EXAFS with emphasis on XAS methodology – modelling and fitting the XAFS spectra to extract in a reliable way as much information on Hg coordination as possible. The AmI plants developed more arbuscules and less vesicles than the AmC plants, and also accumulated more Hg in the roots. A clear difference in Hg coordination between the AM (AmC & AmI) and the control (ConC & ConI) plants is recognized in Hg L3-edge EXAFS analysis: in the ConC & ConI maize roots 73–80% of Hg is attached between two sulphur atoms at the distance of 2.34 Å. The remaining ligand is nitrogen at 2.04 Å. In AmI & AmC roots another Hg-S attachment encompassing four thiol groups at the S-distance of 2.50 Å are identified, accounting for 21–26%. AM fungi can modify Hg ligand environment in plant roots, thus playing an important role in biogeochemical cycling of Hg in terrestrial ecosystems.
Found in: ključnih besedah
Summary of found: ...maize roots was studied by Hg-L3 XANES and EXAFS with emphasis on XAS methodology – modelling...
Keywords: EXAFS XANES Arbuscular mycorrhiza Phytoremediation Toxicity Hg coordination Ligand environment
Published: 27.09.2016; Views: 2801; Downloads: 0
.pdf Fulltext (1,82 MB)

14.
Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2–SiO2 nanoparticle composites
Iztok Arčon, Urška Lavrenčič Štangar, T. Čižmar, 2016, original scientific article

Abstract: Copper-modified TiO2–SiO2photocatalysts were prepared by sol–gel method based on organic copper,silicon and titanium precursors. Copper concentration varied from 0.1 to 3.0 mol%. A widely appliedmodel reaction of photocatalytic oxidation of terephtalic acid (TPA) in water solution was used in order toevaluate the catalytic activities of elaborated samples. The crystal structures of the titania components ofall tested titania–silica species were studied using XRD analysis. The influence of Cu2+cation incorporationon the crystal structure of titania, as well as the chemical states and the neighbouring structures of coppercations, have been examined by means of Cu K-edge EXAFS and XANES analysis. The experimental datashow that there is a ten times increase in photocatalytic activity when TiO2–SiO2matrix is modified with0.1 mol% of Cu. It can be supposed that an enhancement of photocatalytic activity of low-concentratedcopper-modified titania–silica nanocomposites is probably due to a close attachment of Cu2+cationsto the surfaces of photocatalytically active TiO2nanoparticles. In this case, Cu2+cations may possiblyact as free electron traps reducing the intensity of recombination between opposite free charge carriers(electrons, holes) available at the photocatalyst’s surface.
Found in: ključnih besedah
Summary of found: ...been examined by means of Cu K-edge EXAFS and XANES analysis. The experimental datashow that...
Keywords: Cu-modified TiO2–SiO2photocatalysts, Titanium dioxide, Metal doping, Cu K-edge XANES, EXAFS, Photocatalytic activitya
Published: 17.01.2017; Views: 2459; Downloads: 0
.pdf Fulltext (580,62 KB)

15.
Correlations between photocatalytic activity and chemical structure of Cu-modified TiO [sub] 2-SiO [sub] 2 nanoparticle composites
T. Čižmar, Iztok Arčon, Urška Lavrenčič Štangar, 2016, published scientific conference contribution abstract

Found in: ključnih besedah
Keywords: Cu-modified TiO2-SiO2, sol-gel, XANES, EXAFS
Published: 06.02.2017; Views: 1604; Downloads: 0
.pdf Fulltext (378,67 KB)

16.
An extracellular polymeric substance quickly chelates mercury(II) with N-heterocyclic groups
Claudia Faleri, Dario Battistel, Salvatore Daniale, Michele Gallo, Franco Baldi, Alojz Kodre, Iztok Arčon, 2017, original scientific article

Abstract: A strain of Klebsiella oxytoca DSM 29614 is grown on sodium citrate in the presence of 50 mg l−1 of Hg as Hg(NO3)2. During growth, the strain produces an extracellular polymeric substance (EPS), constituted by a mixture of proteins and a specific exopolysaccharide. The protein components, derived from the outer membrane of cells, are co-extracted with the extracellular exopolysaccharide using ethanol. The extracted EPS contains 7.5% of Hg (total amount). This indicates that EPS is an excellent material for the biosorption of Hg2+, through chemical complexation with the EPS components. The binding capacity of these species towards Hg2+ is studied by cyclic voltammetry, and Hg L3-edge XANES and EXAFS spectroscopy. The results found indicate that Hg2+ is mainly bound to the nitrogen of the imidazole ring or other N-heterocycle compounds. The hydroxyl moities of sugars and/or the carboxyl groups of two glucuronic acids in the polysaccharide can also play an important role in sequestring Hg2+ ions. However, N-heterocyclic groups of proteins bind Hg2+ faster than hydroxyl and carboxyl groups of the polysaccharide.
Found in: ključnih besedah
Summary of found: ...cyclic voltammetry, and Hg L3-edge XANES and EXAFS spectroscopy. The results found indicate that Hg2+...
Keywords: Klebsiella oxytoca, Biosorption, Proteins, Polysaccharide, Cyclic voltammetry, EXAFS analysis
Published: 03.03.2017; Views: 1969; Downloads: 0
.pdf Fulltext (1,66 MB)

17.
Correlations between photocatalytic activity and Cu structure in Cu-modified TiO2-SiO2
T. Čižmar, published scientific conference contribution abstract

Found in: ključnih besedah
Keywords: Titanium dioxide, Cu-modified, TiO2-SiO2, photocatalysts, photocatalytic activity, Cu K-edge XANES, EXAFS
Published: 26.06.2017; Views: 1663; Downloads: 0
.pdf Fulltext (641,42 KB)

18.
Chemical structure in Cu-modified TiO2-SiO2 nanocomposites calcined at 500 °C for 1 h in air
T. Čižmar, Iztok Arčon, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...titanium dioxide, metal doping, Cu K-edge XANES, EXAFS, photocatalytic activity...
Keywords: Cu-modified TiO2-SiO2 photocatalysts, titanium dioxide, metal doping, Cu K-edge XANES, EXAFS, photocatalytic activity
Published: 22.08.2017; Views: 11303; Downloads: 0
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19.
Role of Surface Cu-O-Zr Sites in the Photocatalytic Activity of TiO2 Nanoscale Particles
Nataša Novak Tušar, Iztok Arčon, Urška Lavrenčič Štangar, Olena Pliekhova, 2016, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...Photocatalysis, Titanium dioxide, Copper, Zirconia, co-doping, EXAFS, XANES...
Keywords: Photocatalysis, Titanium dioxide, Copper, Zirconia, co-doping, EXAFS, XANES
Published: 23.08.2017; Views: 1814; Downloads: 0
.pdf Fulltext (426,28 KB)

20.
Structural analysis of sunlight efficient Cu and Zr modified TiO2 photocatalyst
Olena Pliekhova, Iztok Arčon, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ...TiO2, photocatalysis, EXAFS, surface modification...
Keywords: TiO2, photocatalysis, EXAFS, surface modification
Published: 23.08.2017; Views: 1611; Downloads: 0
.pdf Fulltext (577,74 KB)

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