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23. Vpliv notranjih in zunanjih okoljskih dejavnikov na nastanek virusov HPVJana Sitar, 2017, undergraduate thesis Abstract: Humani virusi papiloma so eden najpogostejših vzrokov spolno prenosljivih bolezni in nastanka nekaterih vrst raka, kot so rak materničnega vratu, rakava obolenja na spolovilih ter rak glave in vratu. V diplomskem delu smo ugotavljali vpliv notranjih in zunanjih dejavnikov na nastanek in infektivnost virusov HPV-16, določali pa smo tudi strukturne lastnosti virusnega plašča. Kot notranji dejavnik smo uporabili gostiteljski protein SNX17, ki je ključen za okužbo HPV, kot zunanji dejavnik pa nanodelce titanovega dioksida, ki so pogosta sestavina kozmetičnih izdelkov. Pri pridobivanju virusnih delcev HPV-16 v celični liniji 293TT smo ugotovili, da protein SNX17 in nanodelci TiO2 ne vplivajo na količino virusnih delcev, vplivajo pa na njihovo infektivnost. Potrdili smo, da je protein SNX17 ključnega pomena za okužbo HPV, saj so imeli mutirani virusni delci AA2 bistveno zmanjšano stopnjo okužbe. Podobno smo ugotovili pri uporabi nanodelcev TiO2, kjer je bil upad infektivnosti sorazmeren koncentraciji uporabljenih nanodelcev med fazo nastanka virusnih delcev. Pri strukturnih lastnostih virusnega plašča smo analizirali količino in vrsto vključene reporterske DNA, stabilnost plašča in razmerje proteinov L1 : L2 v plašču. Ugotovili smo, da vezava plaščnega proteina L2 s SNX17 in prisotnost nanodelcev TiO2 na te lastnosti ne vplivata. Zaključili smo, da izbrani okoljski dejavniki, protein SNX17 in nanodelci TiO2 ne vplivajo na osnovne značilnosti nastanka virusnih delcev HPV-16, vplivajo pa na njihovo učinkovitost okužbe gostiteljskih celic.
Found in: ključnih besedah
Keywords: HPV, plaščni proteini, okužba, TiO2, SNX17
Published: 17.11.2017; Views: 5251; Downloads: 230
 Fulltext (1,73 MB) |
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25. Surface modified titanium dioxide using transition metalsAndraž Šuligoj, Iztok Arčon, Matjaž Mazaj, Goran Dražić, Denis Arčon, Pegie Cool, Urška Lavrenčič Štangar, Nataša Novak Tušar, 2018, original scientific article Abstract: 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.
Found in: ključnih besedah
Keywords: surface modified TiO2, XANES, EXAFS, Nickel, solar light photocatalyst
Published: 01.06.2018; Views: 2681; Downloads: 0
Fulltext (1,24 MB) |
26. Effects of Different Copper Loadings on the Photocatalytic Activity of TiO2-SiO2 Prepared at a Low Temperature for the Oxidation of Organic Pollutants in WaterT. Čižmar, Iztok Arčon, Mattia Fanetti, Urška Lavrenčič Štangar, 2018, original scientific article Abstract: 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.
Found in: ključnih besedah
Keywords: Cu modified TiO2-SiO2 photocatalyst
Cu EXAFS, XANES, Organic pollutants
Published: 30.08.2018; Views: 2745; Downloads: 0
Fulltext (1,53 MB) |
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28. XAS studies of Sn modified TiO2 coatingsUrška Lavrenčič Štangar, Iztok Arčon, Ksenija Maver, 2018, published scientific conference contribution abstract Abstract: Coatings based on TiO2 are extensively investigated material for the preparation of surfaces which are referred as self-cleaning. Under solar illumination these coatings catalyze pollutants degradation and enhance their removal from the surface due to photoinduced superhydrophilicity [1]. There are two main drawbacks of using pure TiO2 (anatase) as a photocatalyst; i) its band gap lies in the UVA region so it can exploit only a part of the sunlight spectrum, and ii) it has a high degree of recombination between photo generated electrons and holes on the surface. There are various strategies to improve the photocatalytic efficiency of TiO2, one of them is the modification with transition metals.
Based on our previous experiences with sol-gel synthesis of low-temperature TiO2 thin films [2], we prepared a series of Sn modified TiO2 photocatalysts. As a starting material only organic (Ti and Sn alkoxide) precursors were used. The loadings of Sn cations were varied in the range of 0.05 to 20 mol.%. The coatings, deposited on glass substrates by dip-coating technique, were dried at 150 oC. In addition, another set of photocatalyst coatings was prepared by further calcination at 500 °C in air. The comparison of photocatalytic activities of Sn modified TiO2 to unmodified TiO2 showed that Sn loadings in the range of 1-10 mol.% improved photocatalytic activity up to 8 times. At lower loadings of Sn, the photocatalytic activity was improved only by 30 %. After the coatings are calcined, their photocatalytic activity was significantly reduced.
The objective of the research was to examine the mechanism responsible for photocatalytic properties of Sn modified TiO2 and to to clarify the role of Sn cations in the TiO2 photocatalytic process. For this purpose, Sn and Ti K-edge XANES and EXAFS analysis was used to precisely determine the local structure and the site of incorporation of Sn cations on titania nanoparticles in the coatings. We examined the hypothesis that the solid-solid interface was a crucial structural feature that facilitates charge separation and enhances photocatalytic efficiency of titania.
Found in: ključnih besedah
Keywords: Sn, EXAFS, TiO2 fotokatalizator
Published: 12.09.2018; Views: 2631; Downloads: 0
Fulltext (97,78 KB) |
29. The effect of Zr loading on photocatalytic activity of Cu modified TiO [sub] 2Urška Lavrenčič Štangar, Nataša Novak Tušar, Iztok Arčon, Mattia Fanetti, O. L. Pliekhov, Olena Pliekhova, 2018, published scientific conference contribution abstract Found in: ključnih besedah
Keywords: Cu Zr modified TiO2, EXAFS, XANES
Published: 12.09.2018; Views: 2609; Downloads: 0
Fulltext (990,75 KB) |
30. Photocatalytic properties of metal modified TiO2 by photothermal techniquesMladen Franko, Dorota Korte, Urška Lavrenčič Štangar, Olena Pliekhova, Humberto Cabrera, Zeinab Ebrahimpour, 2018, published scientific conference contribution abstract Found in: ključnih besedah
Keywords: Thermal lens spectrometry, Photothermal beam deflection spectroscopy, Dye remediation, Photothermal technique, Photocatalytic degradation, Reactive Blue 19, TiO2 modification
Published: 09.11.2018; Views: 2805; Downloads: 0
Fulltext (208,76 KB) |
