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3933. Operando XAS analysis of CuO/SiO2 and CuO/CeO2 catalystsIztok Arčon, Janvit Teržan, Petar Djinović, Maxim Zabilsky, Albin Pintar, 2018, published scientific conference contribution abstract Abstract: The possibilities of the operando XAS analysis of catalysts will be presented on two case
studies of promising new catalytic materials: alkali doped nano-dispersed copper oxide
clusters on ordered mesoporous SiO2, which is highly active and selective towards propylene
epoxidation [1], and nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction [2].
Operando Cu K-edge and Ce L3-edge XANES and EXAFS analysis was performed during
catalytic reactions under controlled reaction conditions in a tubular reactor filled with
protective He atmosphere at 1 bar. The spectra were measured before the reaction at RT, then
during heating, and during catalytic reaction at 400 °C under controlled atmosphere.
Operando XANES analysis is used to monitor the changes in valence states and local
symmetries of Cu and Ce cations in the catalysts. A partial reduction of Cu2+ to Cu+ and Cu0
and Ce4+ to Ce3+ species was detected during catalyst activation, and re-oxidation during
catalytic reaction. Different dynamics of reaching a quasi-steady oxidation state were revealed
as the tested catalysts approached the quasi-steady state after 300 min of reaction.
Operando EXAFS spectra are used to precisely determine local structure of Cu and Ce
cations, to identify structural characteristics and changes of Cu and Ce species during the
catalytic reactions. In this way, the active site in the catalytic reactions can be identified and
the mechanism of the reaction clarified.
The results of operando XAS analyses are crucial to guide further material modification, to
obtain more effective catalyst, and material which is more resistant to inhibiting effects that
cause catalyst deactivation during catalytic reaction.
Keywords: katalizatorji, Cu XANES, EXAFS
Published in RUNG: 12.09.2018; Views: 3480; Downloads: 0
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3936. X-ray spectrometry in plant biologyKatarina Vogel-Mikuš, Iztok Arčon, Alojz Kodre, Anja Kavčič, Peter Kump, Primož Pelicon, 2018, published scientific conference contribution abstract (invited lecture) Abstract: Trace elements are essential components of living systems, but at the same time they can be toxic at concentrations beyond those necessary for their biological functions. In addition, the toxicity can be extended to other non-essential elements of very similar atomic characteristics that can mimic the properties of a trace element.
Trace element malnutrition affects more than half of the world’s population, while on the other hand industrialization, traffic and extensive use of fertilizers have resulted in exceedingly high concentrations of non-essential elements in food crops, posing risks to human health.
In order to be able to develop and improve phyto-technologies that enable production of safe and quality food, knowledge on the basic mechanisms involved in trace and non-essential element uptake, transport, accumulation and ligand environment in plants is needed.
Such studies are nowadays supported by highly sophisticated X-ray based techniques, such as synchrotron based X-ray fluorescence spectrometry, proton induced X-ray emission and X-ray absorption spectroscopy, enabling imaging of element distribution and determination of speciation and ligand environment of trace elements in biological tissues and cells with high spatial resolution and sensitivity.
Selected case studies of metal distribution and speciation in selected model and crop plants, achieved by interdisciplinary work, will be presented.
Keywords: X-ray spectrometry, plants, XANES, EXAFS
Published in RUNG: 12.09.2018; Views: 3539; Downloads: 0
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3937. 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: 3009; Downloads: 0
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3939. The effect of Zr loading on photocatalytic activity of Cu modified TiO2Olena Pliekhova, O. L. Pliekhov, Mattia Fanetti, Iztok Arčon, Nataša Novak Tušar, Urška Lavrenčič Štangar, 2018, published scientific conference contribution Keywords: Titanium diokside, acidic sites, surface titration, copper, zirconium
Published in RUNG: 10.09.2018; Views: 3919; Downloads: 0
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