1. Atmospheric concentrations and emission ratios of black carbon and nitrogen oxides in the Arabian/Persian Gulf regionBálint Alföldy, Mohamed M. Mahfouz, Asta Gregorič, Matic Ivančič, Irena Ježek, Martin Rigler, 2021, original scientific article Keywords: black carbon, nitrogen oxides, emission ratio, Arabian Gulf region
Published in RUNG: 08.07.2021; Views: 2210; Downloads: 0
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4. Uranium isotope fractionation during adsorption, (co) precipitation, and biotic reductionDuc Huy Dang, Breda Novotnik, Wei Wang, Bastian R. Georg, Douglas R. Evans, 2016, original scientific article Abstract: Uranium contamination of surface environments is a problem associated with both U-ore extraction/processing and situations in which groundwater comes into contact with geological formations high in uranium. Apart from the environmental concerns about U contamination, its accumulation and isotope composition have been used in marine sediments as a paleoproxy of the Earth’s oxygenation history. Understanding U isotope geochemistry is then essential either to develop sustainable remediation procedures as well as for use in paleotracer applications. We report on parameters controlling U immobilization and U isotope fractionation by adsorption onto Mn/Fe oxides, precipitation with phosphate, and biotic reduction. The light U isotope (235U) is preferentially adsorbed on Mn/Fe oxides in an oxic system. When adsorbed onto Mn/Fe oxides, dissolved organic carbon and carbonate are the most efficient ligands limiting U binding resulting in slight differences in U isotope composition (δ238U = 0.22 ± 0.06‰) compared to the DOC/DIC-free configuration (δ238U = 0.39 ± 0.04‰). Uranium precipitation with phosphate does not induce isotope fractionation. In contrast, during U biotic reduction, the heavy U isotope (238U) is accumulated in reduced species (δ238U up to −1‰). The different trends of U isotope fractionation in oxic and anoxic environments makes its isotope composition a useful tracer for both environmental and paleogeochemical applications.
Keywords: Uranium, fractionation, biotic, abiotic, oxides
Published in RUNG: 04.10.2019; Views: 2896; Downloads: 0
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5. Metal oxide and metal carbides thin films for photo/electrochemical water splitting studiesSaim Emin, 2017, published scientific conference contribution abstract Abstract: We used wet-chemistry techniques to prepare colloidal tungsten (W) nanoparticles (NPs). The synthesis of W NPs was conducted using the so called hot-matrix method in 1-octadecene [1]. The sizes of obtained W NPs are in the order of 2 - 5 nm. These W NPs are coated with hydrophobic molecules which allow their dispersion in organic solvents like choloroform (CHCl3). It was found that the colloidal stability of the dispersions is exceptionally high exceeding several years. The stability of W NPs which prevents coagulation allows the preparation of thin films with uniform thicknesses by spin-coating, inkjet-printing and spray coating.
We have prepared both tungsten trioxide (WO3) and tungsten carbide (W2C, WC) thin films. The preparation of WO3 thin films was achieved by spin-coating of W NPs on fluorine doped tin oxide (FTO) glass substrates and following thermal treatment in air at 500°C. The preparation of W2C and WC were done after spin-coating of W NPs on graphite substrate and following heat treatment under Ar atmosphere at 1000 and 1450°C.
The obtained WO3 and W2C (e.g WC) films were used both in photo/electrochemical water splitting studies. In conclusion, we have developed a procedure for the synthesis of W NPs which can be used for the preparation of different class of materials for water splitting studies.
Keywords: metal oxides, metal carbides, tungsten nanoparticles
Published in RUNG: 09.10.2017; Views: 5243; Downloads: 0
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6. ORR stability of Mn–Co/polypyrrole nanocomposite electrocatalysts studied by quasi in-situ identical-location photoelectron microspectroscopyPatrizia Bocchetta, Belen Aleman, Matteo Amati, Mattia Fanetti, Andrea Goldoni, Luca Gregoratti, Maya Kiskinova, Claudio Mele, Hikmet Sezen, Benedetto Bozzini, 2016, original scientific article Abstract: The stability of pyrolyzed Mn–Co/polypyrrole (PPy) nanocomposites towards the Oxygen Reduction Reaction (ORR)
in alkaline solution, was studied with a close-knit group of complementary microscopic and space-resolved spectroscopic
approaches: Atomic Force Microscopy (AFM), Scanning and High-Resolution Transmission Electron
Microscopy (SEM, HRTEM) and identical-location Scanning PhotoElectron Microscopy (SPEM). Tracking quasi-in
situ the morphochemical evolution of the Mn–Co/PPy catalyst upon electrochemical aging under ORR conditions
by this multi-technique approach, has allowed to clarify the key physico-chemical processes underlying
the dramatic impact of Co additions to stability improvement.
Keywords: Mixed manganese oxides, Polypyrrole, Oxygen reduction, Electrocatalysis, Nanocomposites, X-ray photoelectron microspectroscopy
Published in RUNG: 25.07.2016; Views: 5218; Downloads: 0
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