21. Preparation of porous [alpha]-Fe[sub]2O[sub]3 thin films for efficient photoelectrocatalytic degradation of basic blue 41 dyeManel Machreki, Takwa Chouki, Mitja Martelanc, Lorena Butinar, Branka Mozetič Vodopivec, Saim Emin, 2021, original scientific article Abstract: A novel method was developed for the preparation of porous hematite (α-Fe2O3) thin films. First, a solution containing iron precursor was spin-coated on fluorine-doped tin oxide substrate and later short heat-treated at 750 °C. The prepared α-Fe2O3 thin films were applied as dual-function catalyst in photoelectrochemical (PEC) water oxidation and textile dye degradation studies. For the first time, α-Fe2O3 thin films were used in efficient PEC degradation of a textile dye (Basic Blue 41 – B41) using in-situ generated reactive chlorine species. In comparison with photocatalytic and electrocatalytic approaches, the PEC technique allows faster degradation of B41 dye at an applied bias potential of 1.5 V versus reversible hydrogen electrode and under visible light illumination. In the presence of Cl− using the PEC approach the degradation of B41 reaches 99.8%. High-performance liquid chromatography coupled with UV–VIS system confirmed the degradation of B41 dye using PEC. Gas-chromatography coupled to mass spectrometry was used to study the by-products obtained during PEC degradation. Chemical oxygen demand analyses confirmed that the mineralization level of B41 is in the order of 68%. The α-Fe2O3 films developed in this study give a higher level of PEC degradation efficiency compared to other iron oxide-based systems.
Keywords: thin films, photoelectrocatalysis, kinetics, visible light, degradation, textile dye
Published in RUNG: 10.05.2021; Views: 2396; Downloads: 12
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24. New air fluorescence detectors employed in the Telescope Array experimentH. Tokuno, Jon Paul Lundquist, 2012, original scientific article Abstract: Since 2007, the Telescope Array (TA) experiment, based in Utah, USA, has been observing ultra high energy cosmic rays to understand their origins. The experiment includes a surface detector (SD) array and three fluorescence detector (FD) stations. The FD stations, installed surrounding the SD array, measure the air fluorescence light emitted from extensive air showers (EASs) for precise determination of their energies and species. The detectors employed at one of the three FD stations were relocated from the High Resolution Fly's Eye (HiRes) experiment. At the other two stations, newly designed detectors were constructed for the TA experiment. An FD consists of a primary mirror and a camera equipped with photomultiplier tube pixels. To obtain the EAS parameters with high accuracy, understanding the FD optical characteristics is important. In this paper, we report the characteristics and installation of the new FDs and the performances of the FD components. The results of the monitored mirror reflectance during the observation time are also described in this report.
Keywords: Ultra high energy cosmic rays, Extensive air showers, Air fluorescence light detectors
Published in RUNG: 19.05.2020; Views: 2536; Downloads: 0
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25. SnO2-Containing Clinoptilolite as a Composite Photocatalyst for Dyes Removal fromWastewater under Solar LightAndraž Šuligoj, Jelena Pavlovič, Iztok Arčon, Nevenka Rajić, Nataša Novak Tušar, 2020, original scientific article Abstract: Due to their adsorbent, ion exchange and catalytic properties zeolites are suitable for a variety of applications. We report on the photocatalytic activity of a readily available and inexpensive natural zeolite clinoptilolite (Z) containing SnO2 (Sn-Z). The Sn-Z samples with 3–15 wt. % of Sn were prepared by using a precipitation–deposition method. Powder X-ray diffraction analysis showed that the zeolite structure was unaffected by the introduction of the Sn-phase. Diffuse reflectance UV/VIS spectra of the Sn-Z samples confirmed the presence of SnO2 and X-Ray absorption spectroscopy analyses suggested that the SnO2 particles mainly resided on the surface of the clinoptilolite, while ATR-FTIR analysis gave some clues that part of the SnO2 phase was incorporated in the pores of the zeolite. The presence of SnO2 in Sn-Z increased both adsorption capacity and photocatalytic performance which could be partially explained by higher surface area and partially with an increased negative potential of the surface. Adsorption and total degradation of methylene blue (MB) for the Sn-Z with the highest amount of Sn (15 wt.%) was about 30% and 45%, respectively, suggesting a synergetic effect between SnO2 and the clinoptilolite lattice. Reusability tests showed that these catalysts present a promising material for water purification.
Keywords: SnO2, zeolite, SnO2-clinoptilolite composite, photocatalysis, solar light, methylene blue
removal, wastewater treatment
Published in RUNG: 25.02.2020; Views: 3052; Downloads: 132
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26. Recent advances in 2D imaging of element distribution in Plants by focused beam techniquesKatarina Vogel-Mikuš, Johannes Teun van Elteren, Marjana Regvar, Jitrin Chaiprapa, Boštjan Jenčič, Iztok Arčon, Alojz Kodre, Peter Kump, Anja Kavčič, Mitja Kelemen, Dino Metarapi, Marijan Nečemer, Primož Vavpetič, Primož Pelicon, Paula Pongrac, 2019, independent scientific component part or a chapter in a monograph Keywords: 2D Imiging, XRF, XANES, synchrotron light
Published in RUNG: 05.09.2019; Views: 3275; Downloads: 0
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29. FIRST EFFORT TO FIGHT LIGHT POLLUTION IN MACEDONIATanja Petrushevska, 2018, professional article Abstract: Light pollution is a serious problem in majority of European countries, with negative effects on the environment, animal life and human health. Not only light pollution is causing unnecessary electricity consumption, it also prevents the citizens to enjoy the dark night sky. Following the experience in Slovenia and Friuli Venezia Giulia, Italy with approaching this problem, we proposed a joined effort to perform field measurements of the light pollution, increase the awareness of this issue to the public and the policy makers in Macedonia. Light pollution is a very interdisciplinary field that necessitates the collaboration of policy makers, environmentalist, amateur and professional astronomers.
The proposal was submitted to proESOF initiative in Trieste, Italy. This initiative consists of the organisation of collaborative events in North East Italy and the Balkan countries where the objective is to spread science for the benefit to the citizens. ProESOF events will happen before 2020, after which the main event “Trieste – European City of Science” will follow. Our proposal has been positively judged by the proESOF evaluators, and currently we are waiting for their decision regarding the financial support they will provide. The first step will to train a group of people to perform field measurements of light pollution. The second step is to share these results, so the target is the general public in Macedonia. To successfully fight light pollution, anti-light pollution laws have to be made and enforced, so relevant politicians and law makers in Macedonia will be included. We will use the local team who has experience and contacts with the media, so that this event gets covered well. This will be a first meeting of this kind in Skopje, Macedonia which will join experts of the region and offer new ideas to fight light pollution in Macedonia and the Balkans. Macedonia is one of the few countries that is lacking any initiative when it comes to light pollution. It is very important to act timely, also because in Macedonia there are still some regions with dark sky that can be saved. Italy and Slovenia have collaborated previously on several occasion regarding light pollution: the purpose of the project Public Lighting of the Future that was running from 2011 to 2014 was to create a common methodology and database. After our proposed workshop and measurement, the aim will be to include Macedonia in this common effort to fight light light pollution.
Keywords: light pollution
Published in RUNG: 11.09.2018; Views: 3032; Downloads: 0
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30. Amorphous nanocomposite of polycarbosilanes and aluminum oxideAndraž Mavrič, 2018, doctoral dissertation Abstract: This work presents a paradigm for high temperature stabilization of bulk amorphous aluminium oxide. The thermodynamic stabilization is achieved by preparing a nanocomposite, where polymethylsilane dendritic molecules are dispersed in an aluminium hydroxide gel. Upon heat-treatment the gel transforms to the amorphous aluminium oxide that is stable up to 900°C. The dispersion of the macromolecules and their covalent bonding to the alumina matrix induce homogeneously distributed strain fields that keep the alumina amorphous.
The first part of the thesis focuses on the synthesis, characterization and solubility properties of the dendritic polymethylsilane. The polymethylsilane is synthetized by electrochemical polymerization from trichloromethylsilane monomer. The polymerization mechanism, involving a single polymerization pathway, is identified. The polymer growth proceeds through reduction of the monomers to the silyl anions and their addition to the growing polymer.
The solubility of three chemically related but topologically different polysilanes (linear, dendritic and network) were studied by dynamic light scattering. At room temperature the agglomerates in a range from 500 to 1300 nm are present. They undergo de-agglomeration at slightly elevated temperatures of around 40°C. The de-agglomeration results in formation of stable solutions, where a hydrodynamic diameter of the individual polymer molecules was measured to be in a range from 20 to 40 nm.
The obtained diameters of two dendritic polymethylsilane macromolecules, synthesized under different electrolysis conditions, are much larger than the theoretical size estimated for an ideal dendrimer. We determined by 29Si NMR that the reason for this is in a large number of branching irregularities (defects) contained in the molecular structure. Combining the experimental values obtained by DLS and density measurements with a structural model that considers the branching irregularities, it is shown that the inclusion of the defects allows the dendritic polymer to exceed the sterical limitations and form the hyperbranched dendritic structure. The final size depends on a relative amount of the branching defects.
In the second part, the synthetized polymethylsilane molecules were successfully used for the nanocomposite formation. The aluminium hydroxide gel with the dispersed polymethylsilane molecules was prepared as a precursor. Upon heat-treatment it gives the amorphous aluminium oxide stable up to 900°C. The dispersed macromolecules induce homogeneously distributed strain fields that keep the aluminium oxide amorphous during the thermal treatment the dispersed macromolecules covalently bind to the matrix, inducing the interface strain. The amorphous state was confirmed by the presence of penta-coordinated aluminium detected by 27Al NMR and a low bandgap measured by UV-vis absorption spectroscopy.
Keywords: amorphous aluminium oxide, polymethylsilane, nanocomposite, electropolymerization, solubility, agglomeration, de-agglomeration, dendrimer, hyperbranched dendritic structure, dynamic light scattering, thermal analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, infrared spectroscopy, UV-Vis spectroscopy
Published in RUNG: 19.07.2018; Views: 6186; Downloads: 211
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