Tag: XANES

X-ray Excited Optical Luminescence (XEOL)

X-ray Excited Optical Luminescence (XEOL)

XEOL is an X-ray photon in/optical photon out technique that is related to the conversion of the X-ray energy absorbed by the materials to optical photons, involving multi-step energy transfer cascade processes. XEOL is often used together with XANES to reveal the electronic structure and optical properties of the system of interest, such as rare earth down conversion phosphors, quantum confined semiconductors, heterogeneous materials etc., and is applied in display/lighting technologies (TV, smartphone and LED lamps), scintillators, rechargeable batteries and energy conversion devices (photovoltaic cells). XEOL is now available at the end station of BM-08 XAFS/XRF beamline with emission spectra measurement capability under irradiation with X-ray beam.

Read more in SESAME website

Image: General view of the XEOL experimental setup at BM-08 XAFS/XRF beamline.  Sample environment with optical fiber for collecting the luminescence signals

Serpentinization Offers Clues to the Early History of Mars

Serpentinization Offers Clues to the Early History of Mars

Studying how water changes iron-rich rocks on Earth can help us understand Mars, habitability, and even the origins of life

Olivines are silicate minerals containing varying proportions of magnesium and iron. Magnesium-rich olivines are common on Earth, being the primary component of the upper mantle. 

Ferromagnesian minerals such as olivines react with water, releasing hydrogen, in a process known as serpentinization. Serpentinites are rocks composed predominantly of one or more serpentine group minerals, and serpentinization has played a significant role in the development of Earth’s surface environments over time. Our current understanding of Mars, pieced together from our examination of meteorites, satellite images and data collected by NASA’s rovers, is that the planet was once warm and wet. However, our understanding of serpentinization on Earth doesn’t directly translate to a Martian context. The olivine minerals found on Mars are much richer in iron; the least iron-rich olivine ever observed in Martian rocks contains more than double the iron of common Earth olivines. As iron-rich olivines are rare on Earth, they have not been the focus of scientific research. In work recently published in Science Advances, researchers from the University of Calgary and the University of Cambridge undertook a detailed study of iron-rich olivines from Minnesota. Their results show that serpentinization reactions could have provided the vital boost needed to stabilise liquid water and promote habitability on early Mars. 

Studying Mars on Earth

The 1.1-billion-year-old Duluth Complex is a large igneous intrusion under much of north-eastern Minnesota, USA. It is part of a large structure known as the Midcontinent Rift, which formed when North America began, but ultimately failed, to split apart. Molten rock from the mantle rose through the rift and cooled to form a complex and heterogeneous body of rock. The olivines found there are iron-rich and similar in composition to Martian olivines, offering a close compositional analog we can study here on Earth. 

Dr Benjamin Tutolo from the University of Calgary said;

There are two fundamental reasons we’re interested in studying serpentinization reactions on early Earth and early Mars. One is that they generate lots of hydrogen, and perhaps through other reactions, hydrocarbons that could then be strung together to make the first cells and biomolecules. Serpentinization might be one of the key reactions for the origins of life on planetary surfaces. A second is that 4.5 billion years ago, the Sun was only about 70% as bright as it is today. That means that more greenhouse gases would have been needed to trap the Sun’s heat and keep a planet warm, and climate simulations of early Mars tell us that carbon dioxide on its own isn’t enough. It needs an extra kick from something, and hydrogen has been proposed as being that extra kick.

Hydrogen can combine with other atmospheric gases to generate a strong greenhouse effect. However, on Earth, serpentinization reactions in magnesium-rich olivines don’t generate the quantities of hydrogen that would be needed. In this work, the researchers investigated whether serpentinization in the iron-rich olivines found on Mars would make a more significant contribution.

Determining the Oxidation State of Iron

At Diamond’s I18 beamline, Dr Tutolo used X-ray Absorption Near Edge Structure (XANES) to analyse the Duluth Complex rock samples. He explained;

XANES is useful for iron for two reasons. One is that it gives you redox (oxidation) states, at a scale that’s impossible using any other technique. So we could map the redox state in our samples and get individual spot analyses of the redox state of iron in the rocks. And in so doing, you can also say something about the coordination state of the iron – whether it’s in serpentine, and what kind of serpentine it is. So we could see how iron was partitioning during serpentinization reactions into the oxidized versus reduced state and how it was generating hydrogen.

Microfocus Spectroscopy beamline I18 allowed not only measuring redox state of iron which was important for this study, but also made it possible to measure it in individual mineral grains which could be as small as several micron in size. 

Read more on the Diamond website

Vestiges of the Early Solar System in Ryugu Asteroid

Vestiges of the Early Solar System in Ryugu Asteroid

Samples returned to Earth from the asteroid Ryugu, analyzed in part at the Advanced Light Source (ALS), revealed that the building blocks of life formed 4.6 billions years ago in the extreme cold of space, followed by reaction with water.

The dark, coal-like organic matter in the carbonaceous asteroid could have contributed to the formation of habitable planetary environments.

In 2014, the Japan Aerospace Exploration Agency (JAXA) launched the Hayabusa2 spacecraft. Its mission: to collect and return samples from the near-Earth asteroid, Ryugu. Asteroids are excellent time capsules, preserving material sourced from the early solar system in pristine condition. With such samples, scientists aim to learn more about how extraterrestrial organic compounds were formed and modified, and whether this material could have eventually seeded life on Earth. Although meteorites can provide valuable information along these lines, they are subject to terrestrial weathering and other contamination from a planet teeming with life.

Hayabusa2 returned to Earth in 2020 to drop off a capsule containing about 5 grams of extraterrestrial material. The spacecraft then left Earth orbit for an extended mission to a smaller asteroid, called 1998 KY26. The samples it left behind were carefully curated and distributed to teams around the world for study.

In the portion of the sample analysis described here, an international team of 130 researchers, led by Hikaru Yabuta at Hiroshima University, received a share of the irreplaceable Ryugu particles for studies of their organic (carbon-based) content. They examined intact Ryugu grains and insoluble carbonaceous residues isolated by acid treatment.

At ALS Beamline 5.3.2.2, the researchers used scanning transmission x-ray microscopy (STXM) to identify discrete grains of organic material (about 200 nm in size) for further examination by x-ray absorption near-edge structure (XANES) spectroscopy. The beamline enables the acquisition of elemental maps and functional group compositions in submicron-sized sample areas with a spatial resolution below 30 nm.

Read more on the ALS website

Image: Artwork showing the Hayabusa2 spacecraft retrieving a sample from the surface of asteroid Ryugu

Credit: Akihiro Ikeshita

Ancient asteroid grains provide insight into the evolution of our solar system

Ancient asteroid grains provide insight into the evolution of our solar system

The UK’s national synchrotron facility, Diamond Light Source, was used by a large, international collaboration to study grains collected from a near-Earth asteroid to further our understanding of the evolution of our solar system.

Researchers from the University of Leicester brought a fragment of the Ryugu asteroid to Diamond’s Nanoprobe beamline I14 where a special technique called X-ray Absorption Near Edge Spectroscopy (XANES) was used to map out the chemical states of the elements within the asteroid material, to examine its composition in fine detail. The team also studied the asteroid grains using an electron microscope at Diamond’s electron Physical Science Imaging Centre (ePSIC).

Julia Parker is the Principal Beamline Scientist for I14 at Diamond. She said:

The X-ray Nanoprobe allows scientists to examine the chemical structure of their samples at micron to nano lengthscales, which is complemented by the nano to atomic resolution of the imaging at ePSIC. It’s very exciting to be able to contribute to the understanding of these unique samples, and to work with the team at Leicester to demonstrate how the techniques at the beamline, and correlatively at ePSIC, can benefit future sample return missions.

The data collected at Diamond contributed to a wider study of the space weathering signatures on the asteroid. The pristine asteroid samples enabled the collaborators to explore how space weathering can alter the physical and chemical composition of the surface of carbonaceous asteroids like Ryugu.

The researchers discovered that the surface of Ryugu is dehydrated and that it is likely that space weathering is responsible. The findings of the study, published today in Nature Astronomy, have led the authors to conclude that asteroids that appear dry on the surface may be water-rich, potentially requiring revision of our understanding of the abundances of asteroid types and the formation history of the asteroid belt.

Read more on the Diamond website

Image: Image taken at E01 ePSIC of Ryugu serpentine and Fe oxide minerals.

Credit: ePSIC/University of Leicester.

Riverine iron survives salty exit to sea

Riverine iron survives salty exit to sea

Iron organic complexes in Sweden’s boreal rivers significantly contribute to increased iron concentration in open marine waters, X-ray spectroscopy data shows. A Lund University study in Biogeosciences characterizes the role of salinity for iron-loading in estuarine zones, a factor which underpins intensifying seasonal algal blooms in the Baltic Sea.

The study ties in with a reported trend of increased riverine iron concentrations over the last decade in North America, northern Europe and in particular, Swedish and Finnish rivers. This, in conjunction with a predicted rise in extreme weather events in Scandinavia due to climate change, provides momentum for more bioavailable iron to enter marine environments such as the Baltic Sea.

“The consequences of increasing riverine iron for the receiving [marine] system depend first and foremost on the fate of iron in the estuarine salinity gradient. We had questions on what factors determine the movement and transport capacity of iron in these boreal rivers,” said Simon Herzog, postdoctoral researcher at Lund University.

The research group investigated the iron discharge in eight boreal rivers in Sweden which drain into the Baltic Sea, a brackish marine system. Water samples were taken upstream and at the river mouths, the latter just before estuarine mixing and stronger saline conditions occur. Spring and autumn specimens enabled the comparative analysis of flow conditions. To determine the type and amounts of iron species, measurements with X-ray absorbance spectroscopy (XAS) were taken at beamline I811 at Max-lab in Lund, Sweden and X-ray Absorption Near-Edge Structure (XANES) spectra at beamline ID26 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

Read more on the MAX IV website

Image: A view of the Ore River in northern Sweden

Credit: Simon Herzog

Building knowledge of changes in uranium chemistry

Building knowledge of changes in uranium chemistry

ANSTO’s considerable expertise in characterising uranium-containing compounds has contributed to a new systematic investigation of the origins of atomic structural distortions in a family of actinide compounds.

These compounds are known as rutile-related mixed metal ternary (three-part) uranium oxides. Rutile refers to mineral compounds composed primarily of titanium dioxide.

In research published in Inorganic Chemistry, a large team of researchers used both neutron and synchrotron radiation and theoretical calculations to establish systematically precise and accurate crystal structures and uranium oxidation states in the rutile-related mixed metal ternary uranium oxide systems.

Read more on the ANSTO website

Image:  Dr Zhaoming Zhang, Principal Research Scientist, Nuclear Fuel Cycle, ANSTO

Credit: ANSTO

Out of the blue: X-rays shed light on on ultramarine blue in masterpieces

Out of the blue: X-rays shed light on on ultramarine blue in masterpieces

According to a survey led by Nature in 2016, 70% of scientists admitted they could not reproduce another scientist’s experiments and more than half could not reproduce their own. In order to improve sharing and, in turn, enhancing innovation, the European Union is working on implementing the European Open Science Cloud (EOSC), a kind of “library” of all experimental raw data and methods, available to everyone.

The ESRF is doing its bit by leading the PaNOSC (Photon and Neutron Open Science Cloud) project: “We are in the process of implementing the ESRF Data Policy to organise the data from experiments in an archive, which ultimately everyone will be able to access. The scientific teams will have three years to keep their data closed to the public, and after that any other scientist can try to repeat or do new data analysis of the very same experiment if he or she wishes to”, explains Andy Götz, coordinator of the project. The final goal of PaNOSC and the EOSC is to make data from publicly funded research in Europe Findable, Accessible, Interoperable and Reusable (FAIR).

>Read more on the ESRF website

Image: Alessa Gambardella at a stereomicroscope looking at ultramarine blue in Hendrick per Brugghen’s The Adoration of the Kings (1619)

Credit: Courtesy of Department of Conservation & Science, Rijksmuseum.

Plant roots police toxic pollutants

Plant roots police toxic pollutants

X-ray studies reveal details of how P. juliflora shrub roots scavenge and immobilize arsenic from toxic mine tailings.

Working in collaboration with scientists at the U.S. Department of Energy’s Brookhaven National Laboratory and SLAC National Accelerator Laboratory, researchers at the University of Arizona have identified details of how certain plants scavenge and accumulate pollutants in contaminated soil. Their work revealed that plant roots effectively “lock up” toxic arsenic found loose in mine tailings—piles of crushed rock, fluid, and soil left behind after the extraction of minerals and metals. The research shows that this strategy of using plants to stabilize pollutants, called phytostabilization, could even be used in arid areas where plants require more watering, because the plant root activity alters the pollutants to forms that are unlikely to leach into groundwater.

The Arizona based researchers were particularly concerned with exploring phytostabilization strategies for mining regions in the southwestern U.S., where tailings can contain high levels of arsenic, a contaminant that has toxic effects on humans and animals. In the arid environment with low levels of vegetation, wind and water erosion can carry arsenic and other metal pollutants to neighboring communities.

>Read more on the National Synchrotron Light Source II (NSLS-II) website

Image: Scientists from the University of Arizona collect plant samples from the mine tailings at the Iron King Mine and Humboldt Smelter Superfund site in central Arizona. X-ray studies at Brookhaven Lab helped reveal how these plants’ roots lock up toxic forms of arsenic in the soil.
Credit: Jon Chorover