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1.
Enhancement of photocatalytic activity of sol-gel TiO[sub]2 thin films with P25
Jerneja Šauta Ogorevc, Peter Bukovec, Urška Lavrenčič Štangar, 2008, izvirni znanstveni članek

Opis: Enhancement of photocatalytic activity of sol-gel TiOsub2 thin films with P25
Najdeno v: ključnih besedah
Ključne besede: TiO[sub]2 thin films, TiCl[sub]4, precursor, sol-gel, peroxo-modified sol, Degussa P25, photodegradation
Objavljeno: 17.05.2016; Ogledov: 1972; Prenosov: 15
URL Polno besedilo (0,00 KB)

2.
Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2–SiO2 nanoparticle composites
Iztok Arčon, Urška Lavrenčič Štangar, T. Čižmar, 2016, izvirni znanstveni članek

Opis: 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.
Najdeno v: ključnih besedah
Ključne besede: Cu-modified TiO2–SiO2photocatalysts, Titanium dioxide, Metal doping, Cu K-edge XANES, EXAFS, Photocatalytic activitya
Objavljeno: 17.01.2017; Ogledov: 2444; Prenosov: 0
.pdf Polno besedilo (580,62 KB)

3.
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, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: Cu-modified TiO2-SiO2, sol-gel, XANES, EXAFS
Objavljeno: 06.02.2017; Ogledov: 1603; Prenosov: 0
.pdf Polno besedilo (378,67 KB)

4.
Correlations between photocatalytic activity and Cu structure in Cu-modified TiO2-SiO2
T. Čižmar, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: Titanium dioxide, Cu-modified, TiO2-SiO2, photocatalysts, photocatalytic activity, Cu K-edge XANES, EXAFS
Objavljeno: 26.06.2017; Ogledov: 1655; Prenosov: 0
.pdf Polno besedilo (641,42 KB)

5.
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, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: Cu-modified TiO2-SiO2 photocatalysts, titanium dioxide, metal doping, Cu K-edge XANES, EXAFS, photocatalytic activity
Objavljeno: 22.08.2017; Ogledov: 11299; Prenosov: 0
Gradivo ima več datotek! Več...

6.
Surface modified titanium dioxide using transition metals
Andraž Šuligoj, Iztok Arčon, Matjaž Mazaj, Goran Dražić, Denis Arčon, Pegie Cool, Urška Lavrenčič Štangar, Nataša Novak Tušar, 2018, izvirni znanstveni članek

Opis: Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me ¼ Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5 wt%. We have shown in situ that metal-oxo-nanoclusters with a redox potential close to that of O2/O2 were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2 (reduction, Rz ink test) while the other detecting OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.
Najdeno v: ključnih besedah
Ključne besede: surface modified TiO2, XANES, EXAFS, Nickel, solar light photocatalyst
Objavljeno: 01.06.2018; Ogledov: 920; Prenosov: 0
.pdf Polno besedilo (1,24 MB)

7.
Effects of Different Copper Loadings on the Photocatalytic Activity of TiO2-SiO2 Prepared at a Low Temperature for the Oxidation of Organic Pollutants in Water
T. Čižmar, Iztok Arčon, Mattia Fanetti, Urška Lavrenčič Štangar, 2018, izvirni znanstveni članek

Opis: The objective of this research is to examine how Cu modification can improve the photocatalytic activity of TiO2-SiO2, to explainthe correlation between the Cu concentration and the chemical state of Cu cations in the TiO2-SiO2 matrix, and the photocatalytic activity under UV/solar irradiation. The Cu-modified TiO2-SiO2 photocatalysts were prepared by a low-temperature sol–gel method from organic Cu, Si and Ti precursors with various Cu concentrations (0.05–3 mol %). The sol–gels were dried at 150 8C to obtain the photocatalysts in a powder form. The photocatalytic activity was determined by using a fluorescence- based method of terephthalic acid decomposition. An up to three times increase in photocatalytic activity is obtained if the TiO2-SiO2 matrix is modified with Cu in a narrow concentration range from 0.05 to 0.1 mol%. At higher Cu loadings, the photocatalytic activity of the Cu-modified photocatalysts is lower than that of the un-modified reference TiO2-SiO2 photocatalyst. XRD was used to show that all Cu-modified TiO2-SiO2 composites with different Cu concentrations have the same crystalline structure as un-modified TiO2-SiO2 composites. The addition of Cu does not change the relative ratio between the anatase and brookite phases or unit cell parameters of the two TiO2 crystalline structures. We used Cu K-edge X-ray absorption near edge structure and extended X-ray absorption fine structure analyses to determine the valence state and local structure of Cu cations in the Cu-modified TiO2-SiO2 photocatalysts. The results elucidate the mechanism responsible for the improved photocatalytic activity. In samples with a low Cu content, which exhibit the highest activity, Cu@O@Ti connections are formed, which suggests that the activity enhancement is caused by the attachment of CuII cations on the surface of the photocatalytically active TiO2 nanoparticles, so CuII cations may act as free-electron traps, which reduce the intensity of recombination between electrons and holes at the TiO2 photocatalyst surface. At higher Cu loadings no additional Cu@O@Ti connections are formed, instead only Cu@O@Cu connections are established. This indicates the formation of amorphous or nanocrystalline copper oxide, which hinders the photocatalytic activity of TiO2.
Najdeno v: ključnih besedah
Povzetek najdenega: ...the photocatalytic activity under UV/solar irradiation. The Cu-modified TiO2-SiO2 photocatalysts were prepared by a low-temperature...
Ključne besede: Cu modified TiO2-SiO2 photocatalyst Cu EXAFS, XANES, Organic pollutants
Objavljeno: 30.08.2018; Ogledov: 972; Prenosov: 0
.pdf Polno besedilo (1,53 MB)

8.
The effect of Zr loading on photocatalytic activity of Cu modified TiO [sub] 2
Urška Lavrenčič Štangar, Nataša Novak Tušar, Iztok Arčon, Mattia Fanetti, O. L. Pliekhov, Olena Pliekhova, 2018, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Ključne besede: Cu Zr modified TiO2, EXAFS, XANES
Objavljeno: 12.09.2018; Ogledov: 839; Prenosov: 0
.pdf Polno besedilo (990,75 KB)

9.
Correlations between photocatalytic activity and chemical structure of Cu-modified TiO2-SiO2 nanoparticle composites
T. Čižmar, doktorska disertacija

Opis: The objective of this dissertation was to examine how copper modification can improve the photocatalytic activity of TiO2-SiO2 and to explain the correlation between Cu concentration and chemical state of Cu cations in the TiO2-SiO2 matrix, as well as the photocatalytic activity under the UV/solar irradiation. The Cu-modified TiO2-SiO2 photocatalysts were prepared by a low temperature sol-gel method based on organic copper, silicon and titanium precursors with varied Cu concentrations (from 0.05 to 3 mol%). The sol-gels were dried at 150 °C to obtain the photocatalysts in the powder form. To test thermal stability, additional set of photocatalysts was obtained by calcinating dried samples in air at 500 °C for 1 h. The photocatalytic activity was determined by a fluorescence-based method of terephthalic acid decomposition. Up to three times increase in photocatalytic activity of air-dried samples is obtained when TiO2-SiO2 matrix is modified with Cu in a narrow concentration range from 0.05 to 0.1 mol%. At higher Cu loadings the photocatalytic activity of Cu-modified photocatalyst is smaller than in the unmodified reference TiO2-SiO2 photocatalyst. Calcined samples showed significantly reduced photocatalytic activity compared to air-dried samples. XRD analysis showed that all Cu-modified TiO2-SiO2 nanocomposites with different Cu concentrations have the same crystalline structure as unmodified TiO2-SiO2 nanocomposites (air-dried or calcined). The addition of Cu does not change the relative ratio between the anatase and brookite phase or unit cell parameters of the two TiO2 crystalline structures. TEM analysis showed that the addition of Cu does not change the morphology of TiO2-SiO2 catalyst dried at 150 °C. The Cu K-edge XANES and EXAFS analysis were used to determine valence state and local structure of Cu cations in Cu-modified TiO2-SiO2 photocatalyst. The results elucidate the mechanism responsible for the improved or hindered photocatalytic activity. In the air-dried samples with low Cu content, which exhibit largest activity, Cu-O-Ti connections are formed, suggesting that the activity enhancement is due to Cu(II) cations attachment on the surface of the photocatalytically active TiO2 nanoparticles, so Cu(II) cations may act as free electron traps, reducing the intensity of recombination between electrons and holes at the TiO2 photocatalyst’s surface. At higher Cu loadings no additional Cu-O-Ti connections are formed, instead only Cu-O-Cu connections are established, indicating the formation of amorphous or nanocrystalline Cu(II) oxide, which hinders the photocatalytic activity of TiO2. Calcination of Cu-modified TiO2-SiO2 photocatalysts at 500 °C induces significant structural changes: Cu-O-Ti connections are lost, Cu partially incorporates into the SiO2 matrix and amorphous copper oxides, which again reduce the photocatalytic activity of the material, are formed.
Najdeno v: ključnih besedah
Ključne besede: titanium dioxide, Cu-modified TiO2-SiO2 photocatalyst, photocatalytic activity, Cu K-edge XANES, EXAFS.
Objavljeno: 17.12.2018; Ogledov: 1282; Prenosov: 61
.pdf Polno besedilo (3,05 MB)

10.
A long-term study on female mice fed on a genetically modified soybean: effects on liver ageing.
Serafina Battistelli, Beatrice Baldelli, Giulia Annovi, Federica Boraldi, Manuela Malatesta, Marco Baggiogera, Daniela Quaglino, 2008, izvirni znanstveni članek

Opis: Liver represents a suitable model for monitoring the effects of a diet, due to its key role in controlling the whole metabolism. Although no direct evidence has been reported so far that genetically modified (GM) food may affect health, previous studies on hepatocytes from young female mice fed on GM soybean demonstrated nuclear modifications involving transcription and splicing pathways. In this study, the effects of this diet were studied on liver of old female mice in order to elucidate possible interference with ageing. The morpho-functional characteristics of the liver of 24-month-old mice, fed from weaning on control or GM soybean, were investigated by combining a proteomic approach with ultrastructural, morphometrical and immunoelectron microscopical analyses. Several proteins belonging to hepatocyte metabolism, stress response, calcium signalling and mitochondria were differentially expressed in GM-fed mice, indicating a more marked expression of senescence markers in comparison to controls. Moreover, hepatocytes of GM-fed mice showed mitochondrial and nuclear modifications indicative of reduced metabolic rate. This study demonstrates that GM soybean intake can influence some liver features during ageing and, although the mechanisms remain unknown, underlines the importance to investigate the long-term consequences of GM-diets and the potential synergistic effects with ageing, xenobiotics and/or stress conditions.
Najdeno v: ključnih besedah
Ključne besede: Genetically modified soybean, liver, mitochondria
Objavljeno: 23.08.2019; Ogledov: 592; Prenosov: 0
.pdf Polno besedilo (514,70 KB)

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