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2. XAS analysis of bifunctional Ni/ZSM-5 catalystsIztok Arčon, Hue-Tong Vu, Goran Dražić, Janez Volavšek, Gregor Mali, Nataša Zabukovec Logar, Nataša Novak Tušar, 2024, published scientific conference contribution abstract Abstract: In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al
and Ni contents [1]. Here we present a systematic structural study of the Ni/ZSM-5 materials by Ni
K-edge XANES and EXAFS analyses, to monitor the changes of local structure and chemical state
of Ni species in the catalysts as a function of Al and Ni content. A series of Ni/ZSM-5 type zeolites
with different Al to Si and Ni to Si molar ratios were synthesized by a “green”, template free technique
[2]. With a combination of XAS, XRD and TEM we resolved the changes in the local environment
of Ni species induced by the different Al contents in the
Ni/ZSM-5 catalysts.
Ni species in Ni/ZSM-5 exist as NiO nanocrystals and as
charge compensating Ni2+ cations. The Ni K-edge
XANES and EXAFS results enabled the quantification
of Ni-containing species. At a low Al to Si ratio (nAl/nSi
< 0.04), the NiO nanoparticles predominate in the
samples and account for over 65% of Ni phases.
However, NiO is outnumbered by Ni2+ cations attached
to the zeolite framework in ZSM-5 with a high Al to Si
ratio (nAl/nSi = 0.05) due to a higher number of
framework negative charges imparted by Al. The
obtained results show that the number of highly reducible
and active NiO nanocrystals is strongly correlated with
the framework Al sites present in Ni/ZSM-5 zeolites.
Keywords: Ni EXAFS, XANES Ni/ZSM-5 catalyst
Published in RUNG: 05.07.2024; Views: 10; Downloads: 0
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3. Non-oxidative calcination enhances the methane dry reforming performance of ▫$Ni/CeO_{2−x}$▫ catalysts under thermal and photo-thermal conditionsKristijan Lorber, Vasyl Shvalya, Janez Zavašnik, Damjan Vengust, Iztok Arčon, Matej Huš, Andraž Pavlišič, Janvit Teržan, Uroš Cvelbar, Blaž Likozar, Petar Djinović, 2024, original scientific article Abstract: We analyzed the effect of the calcination atmosphere and visible-light contribution to an accelerated
reaction rate and improved H2 selectivity over 2 wt% Ni/CeO2−x nanorod catalysts. Spectroscopic and
structural characterization was performed by operando DRIFTS, in situ Raman, UV-vis and XAS
techniques, which were complemented by DFT calculations. Calcination in an argon or H2 atmosphere
yields 15% more active catalysts in the thermally driven reaction, which are also more susceptible to
light-induced rate acceleration compared to the catalyst calcined in air. The most active 2Ni/CeO2
catalyst calcined in hydrogen converts methane with a rate of 7.5 mmol (gcat min)−1 and produces a H2/
CO ratio of 0.6 at 460 °C when stimulated by a combination of visible light and thermal energy. In the
absence of visible light illumination and at an identical catalyst temperature, the achieved methane rate
was 4.2 mmol (gcat min)−1 and the H2/CO ratio was 0.49. The non-oxidative calcination improves nickel
dispersion and the formation of subnanometer sized Ni clusters, together with a higher abundance of
surface and bulk oxygen vacancies in ceria nanorods. The Ni–Ov–Ce3+components constitute the
catalytically active sites under visible light illumination, which enable the DRM reaction to proceed with
an Ea value of 20 kJ mol−1. Visible light also induces the following changes in the 2Ni/CeO2−x catalyst
during the DRM reaction: (1) decomposition and desorption of carbonates from the nickel–ceria
interface sites, (2) reduced population of nickel surface with carbonyl species and (3) promoted
adsorption and dissociation of methane.
Keywords: methane dry reforming performance, calcination
Published in RUNG: 05.07.2024; Views: 10; Downloads: 0
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4. A porous organic polymer for synergistic light-triggered NO release and anticancer drug delivery : lecture at the iCeMS Retreat 2024, Kobe, Japan, 4. 7. 2024Tina Škorjanc, 2024, unpublished conference contribution Abstract: Treatment of biologically complex diseases, such as cancer, can significantly benefit from combination therapies. These powerful therapies are able to simultaneously target different biological targets, thereby overcoming or reducing drug resistance, decreasing dose-related toxicity, and potentially exhibiting synergistic effects. Herein, we combine the effects of nitric oxide (NO) gas therapy and an anticancer drug Doxorubicin (Dox) using a porous organic polymer (POP) as a delivery vehicle for both. SH-POP, synthesized by a facile, room-temperature method, is rich in both thiol (-SH) and secondary amine (R-NH-R’) functional groups, which can be post-synthetically nitrosylated in a room-temperature reaction that uses water as a solvent, yielding SNO-POP. Fourier-transform infrared (FT-IR) and Raman spectroscopy confirm that both types of functional groups are nitrosylated. Upon white light irradiation, SNO-POP releases up to ~60 µmol of NO per g, and exhibits reversible switch on – switch off NO release behavior triggered by simple light irradiation for at least 20 cycles. Unlike many conventional systems, where a known small-molecule NO donor is incorporated into the pores, here, the porous polymer itself serves as a NO donor, so the pores remain available for the encapsulation of another therapeutic, i.e. Dox. The release of Dox from the Dox@SNO-POP system is pH-sensitive and occurs preferentially in a slightly acidic environment (pH = 5.4). HeLa cancer cell viability studies confirm an enhancement in toxicity that can be ascribed to the synergistic effects of light-triggered NO release and pH-triggered Dox release. Confocal microscopy imaging reveals the presence of both species inside cells. This study is expected to stimulate the development of porous polymers as potent vehicles for combination therapies in cancer treatment and beyond.
Keywords: porous organic polymer, nitric oxide, combination therapy, synergistic therapy, chemotherapy
Published in RUNG: 05.07.2024; Views: 11; Downloads: 0
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5. Drought and temperature interaction on leaf hydraulic traits in grapevineElena Farolfi, Jan Reščič, Jacobs Spencer Harrison, Astrid Forneck, Jose Carlos Herrera, 2022, published scientific conference contribution abstract Abstract: Global warming and increased frequency and/or severity of drought events are among the most
threatening consequences of climate change for agricultural crops. Understanding the mechanisms of
plant responses to both stressors is pivotal to successfully implement management strategies. Here
we explored the effect of temperature on the development of grapevine leaves with particular focus
on hydraulic traits under well-watered and water deficit conditions. We grew grafted grapevine (Vitis
vinifera L. cv. Pinot noir) in two different greenhouse chambers (20/15°C vs 25/20°C day/night) and
monitored their gas exchange, leaf size, stomatal density, chlorophyll fluorescence, pressure-volume
(PV) curves, osmotic potential and petiole xylem anatomy. PV curves provided clear evidence that
both, temperature and water availability, strongly affected the turgor loss point (TLP) as well as the
connected physiological traits. Leaves developing at higher temperature exhibited a more conservative
behaviour characterised by a lower gs max and a tighter stomatal closure in response to drought. The
study further discusses the results considering the coordination of traits changing in tandem and
implications in the face of climate change.
Key message: The ambient temperature at which leaves develop impacts on its hydraulic traits and
therefore on their successive response to drought
Keywords: drought, temperature, grapevine, xylem
Published in RUNG: 05.07.2024; Views: 15; Downloads: 0
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