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21.
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: 1956; Downloads: 0
.pdf Fulltext (426,28 KB)

22.
Design and evaluation of a compact photocatalytic reactor for water treatment
Urška Lavrenčič Štangar, Lev Matoh, Olena Pliekhova, Marko Kete, 2017, original scientific article

Found in: ključnih besedah
Summary of found: ... Photocatalysis, Photocatalytic ozonation, TiO2, Al2O3 monolith, LAS, PBIC,...
Keywords: Photocatalysis, Photocatalytic ozonation, TiO2, Al2O3 monolith, LAS, PBIC, Reactive blue 19, Phenol
Published: 24.08.2017; Views: 2108; Downloads: 0
.pdf Fulltext (6,74 MB)

23.
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: 1726; Downloads: 0
.pdf Fulltext (577,74 KB)

24.
Contribution of Cu and Zr to the Properties of TiO2 for Photocatalytic Water Treatment
Olena Pliekhova, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2017, published scientific conference contribution abstract

Found in: ključnih besedah
Summary of found: ... Photocatalysis, water treatment, surface modification, durability...
Keywords: Photocatalysis, water treatment, surface modification, durability
Published: 23.08.2017; Views: 1829; Downloads: 0
.pdf Fulltext (509,62 KB)

25.
CuO Quantum Dots Decorated TiO2 Nanocomposite Photocatalyst for Stable Hydrogen Generation
Valluri Durga Kumari, Saim Emin, Nagappagari Lakshmana Reddy, Shankar Muthukonda Venkatakrishnan, 2017, original scientific article

Found in: ključnih besedah
Summary of found: ... photocatalysis, nanocomposites, TiO2...
Keywords: photocatalysis, nanocomposites, TiO2
Published: 31.01.2018; Views: 1163; Downloads: 0
.pdf Fulltext (8,78 MB)

26.
Transparent Photocatalytic Thin Films on Flexible Polymer Substrates
Nives Vodišek, Andraž Šuligoj, Dorota Korte, Urška Lavrenčič Štangar, 2018, original scientific article

Found in: ključnih besedah
Summary of found: ... photocatalysis, self-cleaning surface, TiO2, ZrO2, SiO2, transparent films,...
Keywords: photocatalysis, self-cleaning surface, TiO2, ZrO2, SiO2, transparent films, thermosensitive substrates, PMMA, PVC, PES, PVDF
Published: 19.10.2018; Views: 1093; Downloads: 81
.pdf Fulltext (4,37 MB)

27.
28.
Self-cleaning and photoactive TiO2 – ZrO2 – SiO2 films on thermosensitive and glass substrates
Urška Lavrenčič Štangar, Nives Vodišek, 2017, published scientific conference contribution abstract

Abstract: Nanosized TiO2 is well-known for its photocatalytic property. From the combination of photocatalysis and photoinduced hydrophilicity properties, thin films of this material have also anti-fogging, self-cleaning and antimicrobial properties. There are numerous deposition techniques e.g. spin-coating, dip-coating, spraying, the most suitable one is chosen based on substrate or solution characteristics. Thin films are often required to be transparent for visible light, especially if we use them on transparent substrates, or they should not affect the color of the substrate. Radicals that are produced during photosensitizing process are able to destroy structure of a substrate and substrate can lose mechanical stability [1,2]. Some studies show that adding a SiO2 protective layer can prevent the damage of the substrate [3–5]. Ti-Zr containing sols were prepared with sol-gel process, where titanium(IV) isopropoxide, zirconium(IV) butoxide and ethanol were hydrolyzed with aqueous solution of perchloric acid. Solution was then refluxed for 48 hours. During that time crystallization and deaggregation took place and that resulted in a stable final solution [6]. To prepare suitable solution for production of durable films silica binder was added. On glass and plastic substrates, thin films were deposited with the dip-coating method and dried with a heat-gun. Thin films were characterized by measurements of photocatalytic activity with terephthalic acid as model organic pollutant subjected to oxidation via fluorescent degradation product, photoinduced superhydrophilicity phenomena, UV-Vis and ATR-FTIR spectroscopy, SEM images, as well as mechanical properties measurements. References [1] H. Schmidt, M. Naumann, T.S. Müller, M. Akarsu, Thin Solid Films (2006) 502, 132– 137. [2] W. A. Daoud, J.H. Xin, Y.H. Zhang, Surf. Sci. (2005) 599, 69–75. [3] Ž. Senić, S. Bauk, M. Vitorović-Todorović, N. Pajić, A. Samolov, D. Rajić, Sci. Tech. Rev. (2011) 61, 63–72. [4] T. Yuranova, R. Mosteo, J. Bandara, D. Laub, J. Kiwi, J. Mol. Catal. A: Chem. (2006) 244, 160–167. [5] T. Yuranova, D. Laub, J. Kiwi, Catal. Today (2007) 122, 109–117. [6] N. Vodišek, K. Ramanujachary, V. Brezová, U. Lavrenčič Štangar, Catal. Today (2017) 287, 142–147.
Found in: ključnih besedah
Summary of found: ...its photocatalytic property. From the combination of photocatalysis and photoinduced hydrophilicity properties, thin films of...
Keywords: Self-cleaning surface, photocatalysis, TiO2, ZrO2, SiO2, PVC, PMMA, thermosensitive substrates, glass
Published: 05.03.2019; Views: 1053; Downloads: 0
.pdf Fulltext (5,20 MB)

29.
Photoactive nanocomposite thin films on glass and thermosensitive substrates
Nives Vodišek, 2019, doctoral dissertation

Abstract: Photocatalysis is a well-known process for the last few decades; it is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterization; ii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful.
Found in: ključnih besedah
Summary of found: ... Photocatalysis is a well-known process for the last...
Keywords: glass substrate, immobilization, nanocomposite, nanomaterials, PES, photocatalysis, PMMA, PVC, self-cleaning surfaces, silica, plastic substrates, thin films, titania, zirconia
Published: 14.10.2019; Views: 947; Downloads: 70
.pdf Fulltext (6,23 MB)

30.
Zr/Cu-TiO2 CATALYSTS FOR PHOTOCATALYTIC WATER TREATMENT
Olena Pliekhova, doctoral dissertation

Abstract: This work entitled «Zr/Cu-TiO2 catalysts for photocatalytic water treatment» tackles a problem of tons of dyes discharged everyday mainly from textile industries. This is a huge concern because of dyes persistence, toxicity and potential to the bioaccumulation in living organisms. Here, a small contribution to overall problem is presented. The research work consists of three main parts: Theoretical background, Experimental and Results and discussion. In the Theoretical background chapter the overall problem is identified and discussed. The main water treatment techniques are presented briefly with their advantages and drawbacks. Photocatalysis assisted with TiO2 is shown as an alternative additional technique with its own pros and cons. Further, a cursory overview of TiO2 modification techniques is made and advantages in using copper and zirconium oxides for TiO2 modification are presented. The reason and possible positive effect of using of two oxides simultaneously for TiO2 modification is indicated. Additionally, a positive impact of solar light for overall rate of dyes degradation assisted with TiO2 is discussed. Within the framework of photosensitization effect, the problem of using dyes for assessment of photocatalytic properties of materials under the visible light is touched on. Photothermal methods as possible beneficial techniques for this purpose are proposed. In the Experimental chapter, all experimental techniques used in current research work with the technical details specific for the research work are presented. There are methods of materials preparation, photocatalytic tests under different conditions and varying model pollutants, and physico-chemical characterization techniques. The Results and discussion chapter is divided by three subchapters. Each chapter is dedicated to one hypothesis, which was checked and confirmed or disproved. The first hypothesis is about beneficial loading of copper and zirconium oxides to TiO2. After numerous experiments held, it was concluded that the pair of copper and zirconium oxides is beneficial for simultaneous application on TiO2 surface to promote its performance. The second subchapter is about zirconium distribution and its impact on the activity of studied materials towards the antraquinone dye Reactive Blue 19. Different techniques such as XRD, TEM, EXAFS and many others were used in order to characterize the materials and to understand the details of the processes taking place. The existence of upper limit of copper oxide loading for its beneficial effect on TiO2 performance was demonstrated. It was observed that zirconium species loading leads to improvement in performance of materials with higher copper loading, which otherwise lowers activity of TiO2 – this is in case when copper only above its optimal level is present. It was concluded that zirconium oxide containing species occupy rutile surface sites in mixed phase TiO2 and this way beneficially influence the material performance towards the dye removal. The third subchapter is about the visible light TiO2 assisted dye degradation. It is well known that photosensitization mechanism of dye degradation appears under the visible and as a consequence under the solar light irradiation. This leads to the overall enhancement of dyes degradation, which is positive and may be used as a benefit for faster pollutant destruction. However, this fact leads to mishmash in the determination of real photocatalytic activity of materials towards the dye. It was hypothesized that the impact of photosensitization mechanism on the overall material performance against Reactive blue 19 dye (RB19) descends with the dye concentration lowering. Thermal lens spectrometry (TLS) which is sensitive to chemicals at low concentrations was used for hypothesis evaluation. To summarize the research work achievements, the conclusions of the thesis are given at the end.
Found in: ključnih besedah
Summary of found: ...presented briefly with their advantages and drawbacks. Photocatalysis assisted with TiO2 is shown as an...
Keywords: titanium dioxide, photocatalysis, zirconium/copper, surface modification, water treatment, dyes
Published: 03.12.2019; Views: 988; Downloads: 33
.pdf Fulltext (3,18 MB)

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