41. Stimulation of acidic reduction of nitrite to nitric oxide by soybean phenolics: possible relevance to gastrointestinal host defensePablo Ferreira, Maria Souza, Robert Alvin Bernedo Navarro, Rogério Conceição, Edlaine Linhares, Tomomasa Yano, Ione Salgado, 2011, izvirni znanstveni članek Ključne besede: Soybean, nitric oxide, host defense Objavljeno v RUNG: 27.05.2019; Ogledov: 3075; Prenosov: 0 Gradivo ima več datotek! Več... |
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44. Peptides derived from phage display libraries as potential neutralizers of Shiga toxin-induced cytotoxicity in vitro and in vivoRobert Alvin Bernedo Navarro, Mayara Miyachiro, Márcio da Silva, Rogério Conceição, Silvia Gatti, Tomomasa Yano, 2014, izvirni znanstveni članek Ključne besede: Shiga toxins, phage display, Stx1, Stx2, neutralizers Objavljeno v RUNG: 27.05.2019; Ogledov: 3689; Prenosov: 0 Gradivo ima več datotek! Več... |
45. Structural basis for the specific neutralization of Stx2a with a camelid single domain antibody fragmentRobert Alvin Bernedo Navarro, Ema Romao, Tomomasa Yano, Joar Pinto, Henri de Greve, Yann Sterckx, Serge Muyldermans, 2018, izvirni znanstveni članek Ključne besede: Shiga toxins, nanobodies, Stx2, neutralizers Objavljeno v RUNG: 27.05.2019; Ogledov: 3181; Prenosov: 120 Celotno besedilo (8,26 MB) |
46. Sulfur based batteries studied by in-operando S K-edge RIXS and XAS spectroscopyMatjaž Kavčič, Ana Robba, Janez Bitenc, Alen Vižintin, Iztok Arčon, Matjaž Žitnik, Klemen Bučar, Robert Dominko, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Opis: Sulfur based batteries are considered as very attractive energy storage devices. Sulfur is one of the most abundant elements in the earth, it is electrochemically active material which can accept up to two electrons per atom. In combination with alkali metals, sulfur forms electrochemical couples with much higher theoretical energy density compared to Li-ion batteries commonly available today. At the moment, the electrochemical couple with Li is most extensively studied. While the main principle of operation is known the relevant operation mechanism(s) is not completely clear. Even more promising is the electrochemical couple with Mg providing almost twofold higher volumetric energy density due to its ability to provide two electrons during oxidation. However, Mg-S batteries are still in the very early stage of research and development and the complex mechanism of sulfur conversion has been less extensively studied.
In order to improve the understanding of sulfur electrochemical conversion and its interactions within electrode, we need to apply new experimental approaches capable to provide precise information about local environment of S in the cathode during battery operation. In our work, resonant inelastic X-ray scattering (RIXS) and XAS measurements at the sulfur K-edge performed in operando mode were used to study the lithium-polysulfide formation during the discharge process. Measurements were performed at ID26 beamline of the ESRF synchrotron using tender X-ray emission spectrometer [1]. Resonant excitation condition enhanced the sensitivity for the lithium−polysulfide detection. On the other hand, the sulfate signal from the electrolyte was heavily suppressed and the self-absorption effects minimized due to fixed excitation energy.
This experimental methodology was used to provide quantitative analysis of sulfur compounds in the cathode of a Li−S battery cell during the discharge process [2]. The high-voltage plateau in the discharge curve was characterized by a rapid conversion of solid sulfur into liquid phase Li polysulfides reaching its maximum at the end of this plateau. At this point the starting point for the precipitation of the Li2S from the liquid polysulfide phase was observed. The same approach has been used also for the Mg-S battery revealing similar mechanism as in case of Li-S battery [3]. The electrochemical conversion of sulfur with magnesium proceeds through two well-defined plateaus, which correspond to the equilibrium between sulfur and Mg polysulfides (high-voltage plateau) and polysulfides and MgS (low-voltage plateau). Ključne besede: Mg-Sulphur batteries, XANES, RIXS Objavljeno v RUNG: 13.09.2018; Ogledov: 4554; Prenosov: 0 Gradivo ima več datotek! Več... |
47. K-edge absorption spectra of isoelectronic gaseous hydrides: a combination of atomic and molecular channelsRobert Hauko, Jana Padežnik Gomilšek, Alojz Kodre, Iztok Arčon, Giuliana Aquilanti, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The fine detail in the x-ray absorption spectra in the energy region of absorption edges
provides the insight into the mechanism of inner-shell photoexcitation: in particular in spectra of
free atoms or simple molecules, the simplest being gaseous hydrides [1-2].
Measured K edge absorption spectra of hydrides of 3p (PH3, H2S in HCl) and 4p (GeH4,
AsH3, H2Se, HBr) elements, and published data of 2p hydrides (CH4, NH3, H2O, HF) as well as
SiH4 [3-6] and the noble gases at the end of the isoelectronic series (Ne, Ar, Kr) are compared to
the respective calculated spectra, obtained by atomic HF86, GRASP codes [7] and molecular
DFT (Density functional theory) ORCA code [8]. For a clearer view of intraatomic processes,
the weak and simple structural (XAFS) signal of the molecule is removed from the spectra.
Among the spectral features below the continuum limit, those with the lowest energy
belong to the transition of the core electron to the lowermost free orbitals with the molecular
character. They are, as a rule, wider than the transitions to the higher orbitals with prevailing
atomic character. The theoretical description with DFT code without specific adaptations is
sufficient for a qualitative picture of the pre-edge structure. The fine structure immediately above
the K edge stems from the coexcitation of valence electrons. We have proved that the
coexcitations can be explained as a two-step process: the inner-shell photoeffect followed by the
shake-up of a valence electron predominantly to a free atomic orbital. This process is markedly
different from coexcitations of more tightly bound electrons [9].
In the collection of consecutive and homologous data, analyzed by a common procedure,
the reaction channels can be identified with better precision and reliability than in analysis of
individual spectra. Our analysis showed that the energies and probabilities of single-electron
transitions into the molecular orbitals are strongly affected by the symmetry of the molecule,
essentially in the same way in 3p and 4p homologues, but not in 2p homologues with a stronger
influence of the core charge. In transitions to atomic orbitals the influence of the molecular field
is negligible. Ključne besede: hidridi, rentgenska spektroskopija, XAFS Objavljeno v RUNG: 12.09.2018; Ogledov: 3931; Prenosov: 0 Gradivo ima več datotek! Več... |
48. K-edge absorption spectra of gaseous hydridesAlojz Kodre, Robert Hauko, Jana Padežnik Gomilšek, Iztok Arčon, Giuliana Aquilanti, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Opis: X-ray absorption spectra in the energy region of absorption edges reveal fine details of the
mechanism of inner-shell photoexcitation: in particular in spectra of free atoms or simple
molecules, the simplest being gaseous hydrides [1-2]. In a collection of data from consecutive
and homologous elements, analyzed by a common procedure, the reaction channels can be
identified with better precision and reliability than in analysis of individual spectra.
Absorption spectra of the hydrides of 3p elements (PH3, H2S in HCl) were measured at the
XAFS beamline of the Elettra synchrotron in Trieste: a new type of adjustable absorption cell
for measurement of noxious gases at room temperature and at low photon energies was
developed for the purpose. For the analysis, data from an earlier experiment on 4p hydrides
(GeH4, AsH3, H2Se, HBr), and published data of 2p hydrides (CH4, NH3, H2O, HF) [3-4] as
well as SiH4 and the noble gases concluding the isoelectronic series (Ne, Ar, Kr) were
adopted. The spectra are compared to respective calculated spectra, obtained by atomic HF86,
GRASP codes and molecular DFT (Density functional theory) ORCA code [5].
Our analysis of the pre-edge structures showed that the energies and probabilities of singleelectron
transitions into the lowermost orbitals with the molecular character were strongly
affected by the symmetry of the molecule, essentially in the same way in 3p and 4p
homologues, but not in 2p homologues with a stronger influence of the core charge. In
transitions to higher orbitals with prevailing atomic character the influence of the molecular
field is negligible.
The fine structure immediately above the K edge stems from the coexcitation of valence
electrons. These coexcitations can be explained as a two-step process: the inner-shell
photoeffect followed by the shake-up of a valence electron predominantly to a free atomic
orbital. The process is markedly different from coexcitations of more tightly bound electrons
[3]. The results of relative shake-up probabilities can be compared to results of emission
spectroscopies, the probabilities of double excitation to bound states show a correlation with
the dissociation probability of the molecule. Ključne besede: večelektronske vzbuditve, hidridi, rentgenska absorpcijska spektroskopija Objavljeno v RUNG: 12.09.2018; Ogledov: 4216; Prenosov: 0 Gradivo ima več datotek! Več... |
49. Fluorinated ether based electrolyte for high-energy lithium-sulfur batteries : Li [sup] + solvation role behind reduced polysulfide solubilitySara Drvarič Talian, Steffen Jeschke, Alen Vižintin, Klemen Pirnat, Iztok Arčon, Giuliana Aquilanti, Patrik Johansson, Robert Dominko, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: Li-žveplive baterije, XANES, polisulfidi Objavljeno v RUNG: 12.09.2018; Ogledov: 3264; Prenosov: 0 Gradivo ima več datotek! Več... |
50. Polysulfides formation in different electrolytes from the perspective of X-ray absorption spectroscopyRobert Dominko, Alen Vižintin, Giuliana Aquilanti, Lorenzo Stievano, Maria Joseph Helen, Anji Reddy Munnangi, Maximilian Fichtner, Iztok Arčon, 2018, izvirni znanstveni članek Opis: Li-S batteries are promising energy storage technology for the future, however there two major problems remained which need to be
solved before successful commercialization. Capacity fading due to polysulfide shuttle and corrosion of lithium metal are directly
connected with the type and quantity of electrolyte used in the cells. Several recent works show dependence of the electrochemical
behavior of Li-S batteries on type of the electrolyte. In this work we compare and discuss a discharge mechanism of sulfur conversion
in three different electrolytes based on measurements with sulfur K-edge XAS. The sulfur conversion mechanism in the ether based
electrolytes, the most studied type of solvents in the Li-S batteries, which are enabling high solubility of polysulfides are compared
with the fluorinated ether based electrolytes with a reduced polysulfide solubility and in carbonate based electrolytes with the sulfur
confined into a ultramicroporous carbon. In all three cases the sulfur reduction proceeds through polysulfide intermediate phases
with a difference on the type polysulfides detected at different steps of discharge. Ključne besede: Li-S batteries, operando sulphur K-edge XANES, EXAFS, Li-polysulphides Objavljeno v RUNG: 01.06.2018; Ogledov: 3656; Prenosov: 0 Gradivo ima več datotek! Več... |