Scientific Highlights
How is sulfur incorporated in biogenic carbonates and how is it affected by hydrothermal alteration?
Sulfate in biogenic carbonates is an important proxy for reconstructing the marine sulfur cycle. To investigate the exact location of carbonate associated sulfate (CAS) in biogenic carbonates and the effects of diagenetic alteration on sulfur in carbonates, shells of the marine bivalve Arctica islandica were artificially altered in modified seawater. Sulfur XANES analyses showed that CAS in A. islandica is indeed incorporated into the mineral part of the pristine shell, most likely as a hydrated or partly hydrated sulfate phase. The multi-analytical approach of XANES and µ-XRF analyses, sulfur isotope measurements, NanoSIMS analyses, and microstructural analysis on thin-sections of the shell samples further revealed that the different sulfur in a bivalve shell sensitively reacts to artificially induced hydrothermal alteration.
Tracking the Chemical Transformations at a Zeolite Brønsted Acid Site with Al K-edge XANES
Al T-sites are of crucial importance for the function of zeolite catalysts. These T-sites, which serve as Brønsted acid reaction centers, interact strongly with water. The location of these T-sites and their chemical state in the presence of water were elucidated using x-ray absorption spectroscopy (XAS) at the PHOENIX beamline at the Swiss Light Source of the PSI.
Biophysical effects of UV radiation on biological samples
The biological influence of radiation on living matter has been studied for years; however, several questions about the detailed mechanism of radiation damage formation remain largely unanswered. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death.
Aluminium X-ray absorption near-edge spectroscopy analysis of discoloured ultramarine blue in 20th century oil paintings
A specific case of synthetic ultramarine degradation was observed in three oil paintings from the early 20th century. Pigment particleswere found to have been discoloured, resulting in intricate patterns ofwhite lines, approximately 10 to 30 microns wide, criss-crossing the paint surface. Colour in ultramarine pigments comes from the encapsulated sulphur radical anions, chromophores, inside the cage framework built from SiO4 4 − and AlO4 5 −
Single- (K) and Double-Electron Excitation (KLII&III) XANES Spectra of α-Alumina and Aqueous Al3+•(H2O)6
X-ray absorption spectroscopy (XAS) probes the local environment around an atom by study of the local photoelectron’s scattering. Multielectron excitations become more important at higher x-ray dose, which are used for examples in x-FEL experiments. Here we demonstrate that multielectron excitations, observed in the Al K-edges EXAFS spectra can be used to derive structural information.
Operando Characterization of a LiS Battery
One of the technological barriers to electrification of transport is the insufficient storage capacity of the Li-ion batteries on which the current electric cars are based. The lithium-sulfur (Li-S) battery is an advanced technology whose successful commercialization can lead to significant gains in the storage capacity of batteries and promote wide-spread adoption of electric vehicles.
Quantitatively Probing the Al Distribution in Zeolites
The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts.