carbon – Lightsources.org

An X-ray view of carbon

2021/10/052021/10/07

New measurement method promises spectacular insights into the interior of planets

At the heart of planets, extreme states are to be found: temperatures of thousands of degrees, pressures a million times greater than atmospheric pressure. They can therefore only be explored directly to a limited extent – which is why the expert community is trying to use sophisticated experiments to recreate equivalent extreme conditions. An international research team including the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has adapted an established measurement method to these extreme conditions and tested it successfully: Using the light flashes of the world’s strongest X-ray laser the team managed to take a closer look at the important element, carbon, along with its chemical properties. As reported in the journal Physics of Plasmas (DOI: 10.1063/5.0048150), the method now has the potential to deliver new insights into the interior of planets both within and outside of our solar system.

The heat is unimaginable, the pressure huge: The conditions in the interior of Jupiter or Saturn ensure that the matter found there exhibits an unusual state: It is as dense as a metal but, at the same time, electrically charged like a plasma. “We refer to this state as warm dense matter,” explains Dominik Kraus, physicist at HZDR and professor at the University of Rostock. “It is a transitional state between solid state and plasma that is found in the interior of planets, although it can occur briefly on Earth, too, for example during meteor impacts.” Examining this state of matter in any detail in the lab is a complicated process involving, for example, firing strong laser flashes at a sample, and, for the blink of an eye, heating and condensing it.

Read more on the HZDR website

Image: High-resolution spectroscopy will enable unique insights into chemistry happening deep inside planets

Credit: HZDR / U. Lehmann

Observation of flat bands in twisted bilayer graphene

2020/10/142020/10/28

Magic-angle materials represent a surprising recent physics discovery in double layers of graphene, the two-dimensional material made of carbon atoms in a hexagonal pattern.

When the upper layer of two stacked layers of graphene is rotated by about 1 degree, the material suddenly turns into a superconductor. At a temperature of 3 Kelvin, this so-called twisted bilayer graphene (tbg) conducts electricity without resistance.

Now, an international team of scientists from Geneva, Barcelona, and Leiden have finally confirmed the mechanism behind this new type of superconductors. In Nature Physics, they show that the slight twist causes the electrons in the material to slow down enough to sense each other. This enables them to form the electron pairs which are necessary for superconductivity.

How can such a small twist make such a big difference? This is connected with moiré patterns, a phenomenon also seen in the everyday world. When two patterned fences are in front of another, one observes additional dark and bright spots, caused by the varying overlap between the patterns. Such moiré patterns (derived from the the French name of textile patterns made in a similar way) generally appear where periodical structures overlap imperfectly.

Liquid carbon can be disclosed if one is ultrafast enough

2020/10/012020/10/07

At the FERMI FEL, beamline EIS-TIMEX, a novel approach combining FEL and fs-laser radiation has been developed for generating liquid carbon under controlled conditions and monitoring its properties of at the atomic scale. The method has been put to the test depositing a huge amount (5 eV/atom, 40 MJ/kg) of optical energy delivered by an ultrashort laser pulse (less than 100 fs, 10^-13 s) into a self-standing amorphous carbon foil (a-C, thickness about 80 nm) and subsequently probing the excited sample volume with the FEL pulse varying both the FEL photon energy across the C K-edge (~ 283 eV) and delay between FEL and laser. A time-resolved x-ray absorption spectroscopy (tr-XAS, Fig. 2a) has been obtained of l-C with a record time resolution of less than 100 fs.

This method allowed researchers to monitor the formation of the liquid carbon phase at a temperature of 14200 K and pressure of 0.5 Mbar occurring in about 300 fs after absorption of the laser pump pulse as an effect of the constant volume (isochoric) heating of the carbon sample.

Read more on the ELETTRA website

Image: Artistic image illustrating the ultrafast laser-heating process used to generate liquid carbon in the laboratory. Illustration: Emiliano Principi.

Helping to neutralise greenhouse gases

2020/07/082020/07/09

Researchers used the Canadian Light Source (CLS) at the University of Saskatchewan to create an affordable and efficient electrocatalyst that can transform CO2 into valuable chemicals. The result could help businesses as well as the environment.

Electrocatalysts help to collect CO₂ pollution and efficiently convert it into more valuable carbon monoxide gas, which is an important product used in industrial applications. Carbon monoxide gas could also help the environment by allowing renewable fuels and chemicals to be manufactured more readily.

The end goal would be to try to neutralize the greenhouse gases that worsen climate change.

Precious metals are often used in electrocatalysts, but a team of scientists from Canada and China set out to find a less expensive alternative that would not compromise performance. In a new paper, the stability and energy efficiency of the team’s novel electrocatalyst offered promising results.

Read more on the Canadian Light Source website

Image : Schematic of an electrochemistry CO₂-to-CO reduction reaction.

Helping to protect California farms from drought

2020/04/152020/04/29

Researchers used the Canadian Light Source (CLS) at the University of Saskatchewan to look at where carbon ends up in soil and are contributing to an effort to mitigate the effects of drought for California farmers.

Samantha Ying and Michael Schaefer, both from the Department of Environmental Sciences at University of California (UC) Riverside, are part of a team set on untangling the mystery of a practice upon which farmers have relied for centuries to reduce water use—cover crops. Cover crops are an ancient practice whereby a crop is planted for the sole purpose of fertilizing the soil, not for consumption. It is known that increased organic carbon in soil resulting from the use of cover crops “turns the soil into a sponge that holds water,” explained Ying. “But how does this work? We really don’t know what’s happening to the carbon and soil.”

Image: Researcher Samantha Ying loading samples at our SGM beamline.

Canadian researchers extend the life of rechargeable batteries

2019/11/182019/11/18

Carbon coating that extends lithium ion battery capacity by 50% could pave the way for next-generation batteries in electric vehicles.

Researchers from Western University, using the Canadian Light Source (CLS) at the University of Saskatchewan, found that adding a carbon-based layer to lithium-ion rechargeable batteries extends their life up to 50%.
The finding, recently published in the journal ACS Applied Materials and Interfaces, tackles a problem many Canadians will be familiar with: rechargeable batteries gradually hold less charge over time.
“We added a thin layer of carbon coating to the aluminum foil that conducts electric current in rechargeable batteries,” said lead researcher Dr. Xia Li of Western University. “It was a small change, but we found the carbon coating protected the aluminum foil from corrosion of electrolyte in both high voltage and high energy environments – boosting the battery capacities up to 50% more than batteries without the carbon coating.”

Image: Dr. Li in the lab.

Study reveals ‘radical’ wrinkle in forming complex carbon molecules in space

2019/09/032019/09/05

Unique experiments at Berkeley Lab’s Advanced Light Source shine a light on a new pathway for carbon chemistry to evolve in space.

A team of scientists has discovered a new possible pathway toward forming carbon structures in space using a specialized chemical exploration technique at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). The team’s research has now identified several avenues by which ringed molecules known as polycyclic aromatic hydrocarbons, or PAHs, can form in space. The latest study is a part of an ongoing effort to retrace the chemical steps leading to the formation of complex carbon-containing molecules in deep space. PAHs – which also occur on Earth in emissions and soot from the combustion of fossil fuels – could provide clues to the formation of life’s chemistry in space as precursors to interstellar nanoparticles. They are estimated to account for about 20 percent of all carbon in our galaxy, and they have the chemical building blocks needed to form 2D and 3D carbon structures.

Image: This composite image shows an illustration of a carbon-rich red giant star (middle) warming an exoplanet (bottom left) and an overlay of a newly found chemical pathway that could enable complex carbons to form near these stars.
Credits: ESO/L. Calçada; Berkeley Lab, Florida International University, and University of Hawaii at Manoa.

Beryllium configuration with neighbouring oxygen atoms revealed

2019/06/252019/06/26

High-pressure experiments prove 50-year-old theoretical prediction.

In high-pressure experiments at DESY’s X-ray light source PETRA III, scientists have observed a unique configuration of beryllium for the first time: At pressures nearly a million times the average atmospheric pressure, beryllium in a phosphate crystal acquires six neighbouring atoms instead of the usual four. This six-fold coordination had been predicted by theory more than 50 ago, but could not be observed until now in inorganic compounds. DESY scientist Anna Pakhomova and her collaborators report their results in the journal Nature Communications.
“Originally, chemistry textbooks stated that elements like beryllium from the second period of the periodic table could never have more than four neighbours, due to their electron configuration”, explains Pakhomova. “Then around 50 years ago theorists discovered that higher coordinations could actually be possible, but these have adamantly evaded experimental proof in inorganic compounds.” Inorganic compounds are typically those without carbon – apart from a few exceptions like carbon dioxide and carbon monoxide.

Image: Transformation of the usual fourfold coordination of beryllium to five- and sixfold with increasing pressure. (Credit: DESY, Anna Pakhomova)

Meteorites suggest galvanic origins for martian organic carbon

2019/02/252019/02/26

The nature of carbon on Mars has been the subject of intense research since NASA’s Viking-era missions in the 1970s, due to the link between organic (carbon-containing) molecules and the detection of extraterrestrial life. Analyses of Martian meteorites marked the first confirmation that macromolecular carbon (MMC)—large chains of carbon and hydrogen—are a common occurrence in Mars rocks. More recently, researchers have applied the lessons taken from studies of meteorites to the data being gathered by the Curiosity rover, finding similar MMC signatures on Mars itself. Now, the central question is “what is the synthesis mechanism of this abiotic organic carbon?”

>Read more about on the Advanced Light Source website

Image: A high-resolution transmission electron micrograph (scale bar = 50 nm) of a grain from a Martian meteorite. Reminiscent of a long dinner fork, organic carbon layers were found between the intact “tines.” This texture was created when the volcanic minerals of the Martian rock interacted with a salty brine and became the anode and cathode of a naturally occurring battery in a corrosion reaction. This reaction would then have enough energy—under certain conditions—to synthesize organic carbon.
Credit: Andrew Steele

Light-activated, single- ion catalyst breaks down carbon dioxide

2018/11/262018/11/28

X-ray studies reveal structural details that may point the way to designing better catalysts for converting pollutant gas into useful products

A team of scientists has discovered a single-site, visible-light-activated catalyst that converts carbon dioxide (CO₂) into “building block” molecules that could be used for creating useful chemicals. The discovery opens the possibility of using sunlight to turn a greenhouse gas into hydrocarbon fuels.

The scientists used the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science user facility at Brookhaven National Laboratory, to uncover details of the efficient reaction, which used a single ion of cobalt to help lower the energy barrier for breaking down CO₂. The team describes this single-site catalyst in a paper just published in the Journal of the American Chemical Society.

Converting CO₂into simpler parts—carbon monoxide (CO) and oxygen—has valuable real-world applications. “By breaking CO₂, we can kill two birds with one stone—remove CO₂ from the atmosphere and make building blocks for making fuel,” said Anatoly Frenkel, a chemist with a joint appointment at Brookhaven Lab and Stony Brook University. Frenkel led the effort to understand the activity of the catalyst, which was made by Gonghu Li, a physical chemist at the University of New Hampshire.

Image: National Synchrotron Light Source II (NSLS-II) QAS beamline scientist Steven Ehrlich, Stony Brook University (SBU) graduate student Jiahao Huang, and Brookhaven Lab-SBU joint appointee Anatoly Frenkel at the QAS beamline at NSLS-II.

Graphene on the way to superconductivity

2018/11/102018/11/15

Scientists at HZB have found evidence that double layers of graphene have a property that may let them conduct current completely without resistance. They probed the bandstructure at BESSY II with extremely high resolution ARPES and could identify a flat area at a surprising location.

Carbon atoms have diverse possibilities to form bonds. Pure carbon can therefore occur in many forms, as diamond, graphite, as nanotubes, football molecules or as a honeycomb-net with hexagonal meshes, graphene. This exotic, strictly two-dimensional material conducts electricity excellently, but is not a superconductor. But perhaps this can be changed.

A complicated option for superconductivity
In April 2018, a group at MIT, USA, showed that it is possible to generate a form of superconductivity in a system of two layers of graphene under very specific conditions: To do this, the two hexagonal nets must be twisted against each other by exactly the magic angle of 1.1°. Under this condition a flat band forms in the electronic structure. The preparation of samples from two layers of graphene with such an exactly adjusted twist is complex, and not suitable for mass production. Nevertheless, the study has attracted a lot of attention among experts.

Image: The data show that In the case of the two-layer graphene, a flat part of bandstructure only 200 milli-electron volts below the Fermi energy. Credit: HZB

The search for clean hydrogen fuel

2018/10/192018/10/22

The world is transitioning away from fossil fuels and hydrogen is poised to be the replacement.

Two things are needed if we are to make the transition to a low carbon, “hydrogen economy” they are clean and high yielding sources of hydrogen, as well as efficient means of producing and storing energy using hydrogen.

Hydrogen powered cars are the perfect case study for how a hydrogen-fuelled future would look. While they work and show a great deal of promise, the best examples of hydrogen being used in fuel require very clean sources of hydrogen. If the source of hydrogen is mixed with contaminants like carbon monoxide, the efficiency of the fuel goes down and causes downstream problems in the fuel cell.

A team from KTH led by Jonas Weissenrieder is visiting MAX IV this week to try and solve this exact problem, how can we generate clean hydrogen for fuel cells? The team is working on a process to catalyse the oxidation of carbon monoxide, which adversely affects fuel cell performance, to harmless carbon dioxide. The catalysis reaction must be selective, and not affect the hydrogen gas that could be oxidised to water which is not great for running car engines.

Research gives clues to CO2 trapping underground

2018/08/082018/08/09

CO2 is an environmentally important gas that plays a crucial role in climate change.

It is a compound that is also present in the depth of the Earth but very little information about it is available. What happens to CO2 in the Earth’s mantle? Could it be eventually hosted underground? A new publication in Nature Communications unveils some key findings.

Carbon dioxide is a widespread simple molecule in the Universe. In spite of its simplicity, it has a very complex phase diagram, forming both amorphous and crystalline phases above the pressure of 40 GPa. In the depths of the Earth, CO₂ does not appear as we know it in everyday life. Instead of being a gas consisting of molecules, it has a polymeric solid form that structurally resembles quartz (a main mineral of sand) due to the pressure it sustains, which is a million times bigger than that at the surface of the Earth.

Researchers have been long studying what happens to carbonates at high temperature and high pressure, the same conditions as deep inside the Earth. Until now, the majority of experiments had shown that CO₂ decomposes, with the formation of diamond and oxygen. These studies were all focused on CO₂ at the upper mantle, with a 70 GPa of pressure and 1800-2800 Kelvin of temperature.

Picture: Mohamed Mezouar, scientist in charge of ID27, on the beamline.
Credit: S. Candé.

One size does not fit all when exploring how carbon in soil affects the climate

2018/05/032018/05/18

Scientists from Stanford University are opening a window into soil organic carbon, a critical component of the global carbon cycle and climate change.

“We have to know what kind of carbon is in soil in order to understand where the carbon comes from and where it will go,” said Hsiao-Tieh Hsu, a PhD student in chemistry at Stanford University and a member of a Kate Maher’s research group.

The natural fluxes of soil organic carbon, the exchange of carbon moving from vegetation to the soil and recycled by microorganisms before being stabilized in the soil or returned to the atmosphere, is 10 to 20 times higher than human emissions. Even the smallest change in the flux of soil organic carbon would have a huge impact on the climate.

Soil organic carbon occurs naturally and is part of the carbon cycle. Through photosynthesis, plants absorb carbon dioxide from the atmosphere. As plants and their roots decompose, they deposit organic carbon in the soil. Microorganisms, decomposing animals, animal feces and minerals also contribute to the organic carbon in the soil. In turn, plants and microorganisms “eat” that carbon, which is an essential nutrient.

All of this results in different “flavours” or compounds within the soil, say Hsu and Maher, who is also a faculty member of the Stanford Center for Carbon Storage.

Image: Members of the research team at the East River, Colorado, field site (left to right): Hsiao-Tieh Hsu; Grace Rainaldi, Stanford undergraduate; Corey Lawrence, research geologist at United States Geological Survey; Kate Maher; Matthew Winnick, Stanford postdoctoral fellow.
Credit: Kate Maher.