First direct look at how light excites electrons to kick off a chemical reaction

Light-driven reactions are at the heart of human vision, photosynthesis and solar power generation. Seeing the very first step opens the door to observing chemical bonds forming and breaking.

The first step in many light-driven chemical reactions, like the ones that power photosynthesis and human vision, is a shift in the arrangement of a molecule’s electrons as they absorb the light’s energy. This subtle rearrangement paves the way for everything that follows and determines how the reaction proceeds.
Now scientists have seen this first step directly for the first time, observing how the molecule’s electron cloud balloons out before any of the atomic nuclei in the molecule respond.

While this response has been predicted theoretically and detected indirectly, this is the first time it’s been directly imaged with X-rays in a process known as molecular movie-making, whose ultimate goal is to observe how both electrons and nuclei act in real time when chemical bonds form or break.

>Read more on the LCLS at SLAC website

Image: extract, full image here

Researchers use CHESS to map protein motion

Cornell structural biologists took a new approach to using a classic method of X-ray analysis to capture something the conventional method had never accounted for: the collective motion of proteins.

And they did so by creating software to painstakingly stitch together the scraps of data that are usually disregarded in the process.
Cornell structural biologists took a new approach to using a classic method of X-ray analysis to capture something the conventional method had never accounted for: the collective motion of proteins. And they did so by creating software to painstakingly stitch together the scraps of data that are usually disregarded in the process.
Their paper, “Diffuse X-ray Scattering from Correlated Motions in a Protein Crystal,”published March 9 in Nature Communications.
As a structural biologist, Nozomi Ando, M.S. ’04, Ph.D. ’08, assistant professor of chemistry and chemical biology, is interested in charting the motion of proteins, and their internal parts, to better understand protein function. This type of movement is well known but has been difficult to document because the standard technique for imaging proteins is X-ray crystallography, which produces essentially static snapshots.

>Read more on the CHESS website
>Read also: Diffuse X-ray Scattering from Correlated Motions in a Protein Crystal

Image: This slice through the three-dimensional diffuse map shows intense peaks resulting from lattice vibration, as well as cloudy features caused by internal protein motions.

Shaping attosecond waveforms

Scientists show how to control attosecond light pulses at a free-electron laser.

Chemical reactions and complex phenomena in liquids and solids are determined by the movement and rearrangement of electrons. These movements, however, occur on an extremely short timescale, typically only a few hundred attoseconds (1 attosecond =10-18 s or one quintillionth of a second).  Only light pulses of a comparable duration can be used to take snapshots of the dynamics of electrons. An international team of researchers led by Guiseppe Sansone from the University of Freiburg and including scientists from European XFEL have now, for the first time, been able to reliably generate, control and characterize such attosecond light pulses from a free-electron laser.

“These pulses enable us to study the first moment of the electronic response in a molecule or crystal,” explains Sansone. “With the ability to shape the electric field enables us to control electronic movements – with the long-term goal of optimising basic processes such as photosynthesis or charge separation in materials.”

>Read more on the European XFEL website

Image: Scientists have been able to shape the electric field of an attosecond light pulse.
Credit: Jürgen Oschwald and Carlo Callegari

Inventing a way to see attosecond electron motions with an X-ray laser

Called XLEAP, the new method will provide sharp views of electrons in chemical processes that take place in billionths of a billionth of a second and drive crucial aspects of life.

Researchers at the Department of Energy’s SLAC National Accelerator Laboratory have invented a way to observe the movements of electrons with powerful X-ray laser bursts just 280 attoseconds, or billionths of a billionth of a second, long.

The technology, called X-ray laser-enhanced attosecond pulse generation (XLEAP), is a big advance that scientists have been working toward for years, and it paves the way for breakthrough studies of how electrons speeding around molecules initiate crucial processes in biology, chemistry, materials science and more.
The team presented their method today in an article in Nature Photonics.

“Until now, we could precisely observe the motions of atomic nuclei, but the much faster electron motions that actually drive chemical reactions were blurred out,” said SLAC scientist James Cryan, one of the paper’s lead authors and an investigator with the Stanford PULSE Institute, a joint institute of SLAC and Stanford University. “With this advance, we’ll be able to use an X-ray laser to see how electrons move around and how that sets the stage for the chemistry that follows. It pushes the frontiers of ultrafast science.”

Image: A SLAC-led team has invented a method, called XLEAP, that generates powerful low-energy X-ray laser pulses that are only 280 attoseconds, or billionths of a billionth of a second, long and that can reveal for the first time the fastest motions of electrons that drive chemistry. This illustration shows how the scientists use a series of magnets to transform an electron bunch (blue shape at left) at SLAC’s Linac Coherent Light Source into a narrow current spike (blue shape at right), which then produces a very intense attosecond X-ray flash (yellow).
Credit: Greg Stewart/SLAC National Accelerator Laboratory

>Read more on the Linear Coherent Light Source (SLAC) website

A new stable form of plutonium discovered

An international team of scientists, led by the Helmholtz Zentrum Dresden-Rossendorf (HZDR), have found a new compound of plutonium with an unexpected, pentavalent oxidation state.

This new phase of plutonium is solid and stable, and may be a transient phase in radioactive waste repositories. The results are published this week in Angewandte Chemie as a Very Important Paper (VIP). Countries across the globe are making efforts to improve the safety of the nuclear waste storage in order to prevent release of radioactive nuclides to the environment. Plutonium, has been shown to be transported by groundwaters from contaminated sites for kilometres in the form of colloids, which are formed by interaction with clay, iron oxides or natural organic matter. 
A team of scientists lead by  HZDR studies the chemistry of actinides under environmentally relevant conditions, by synthesizing such compounds, and then studying their electronic and structural behaviour both with advanced synchrotron X-ray methods experimentally as well as theoretically. The latest paper of the international team shows how an experiment seemingly gone wrong leads to a breakthrough: the discovery of a new stable form of plutonium.
It all started when Kristina Kvashnina, physicist from HZDR and based at the ROBL beamline at the ESRF, and her team were trying to create plutonium dioxide nanoparticles using different precursors to be studied at ROBL. When they used the Pu (VI) precursor, they realized that a strange reaction took place during the formation of the plutonium dioxide nanoparticles. “Every time we create nanoparticles from the other precursors Pu(III), (IV) or (V) the reaction is very quick, but here we observed a weird phenomenon half way”, explains Kvashnina. She figured that it must be Pu (V), pentavalent plutonium, a never-observed-before form of the element, after doing a high-energy resolution fluorescence detection (HERFD) experiment at the Pu L3 edge at ROBL.

>Read more about the research at ROBL on the ESRF website

Image: The team in front of the spectrometer of ROBL. Kristina Kvashnina is the second from the right.

Worldwide scientific collaboration develops catalysis breakthrough

A new article  just published in Nature Catalysis shows the simple ways of controlling the structure of platinum nanoparticles and tuning their catalytic properties. 

Research led by Cardiff Catalysis Institute (CCI) in collaboration with scientists from Lehigh University, Jazan University, Zhejiang University, Glasgow University, University of Bologna, Research Complex at Harwell (RCaH), and University College London have combined their unique skills to develop and understand using advanced characterisation methods (particularly TEM and B18 at Diamond Light Source), how it is possible to use a simple preparation method to control and manipulate the structures of metal nanoparticles. These metal nanoparticles are widely used by industry as innovative catalysts for the production of bulk chemicals like polymers, liquid fuels (e.g., diesel, petrol) and other speciality chemicals (pharmaceutical products).

>Read more on the Diamond Light Source website

Image: Andy Beale works at Diamond Light Source.

Analysis of fingermarks with synchrotron techniques provide new insights

A new study by researchers from Curtin University using the infrared (IR) and X-ray fluorescence microscopy (XFM) beamlines at the Australian Synchrotron has provided a better understanding of the chemical and elemental composition of latent fingermarks.

The findings by lead researchers Prof Simon Lewis and Dr Mark Hackett may provide opportunities to optimise current fingermark detection methods or identify new detection strategies for forensic purposes.
Latent fingermarks are generally described as those requiring some process to make them readily visible to the eye. These fingermarks are typically made up of natural skin secretions, along with contaminants (such as food or cosmetics) picked up from various surfaces.
The detection of latent fingermarks is often crucial in forensic investigations, but this is not always a straightforward task. “We know that there are issues in detecting fingermarks as they get older, and also under certain environmental conditions”, said Lewis, whose main research focus is forensic exchange evidence.

“In order to improve our ability to detect fingermarks, we need to understand the nature of fingermark residue, and this includes both the organic and inorganic components. Many chemical components in fingermark residue are present at very low levels, and we don’t know how they are distributed within the fingermark. This is what took us to the Australian Synchrotron.”

>Read more on the Australian Synchrotron at ANSTO website

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

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.

>Read more on the ALS at Berkeley Lab website

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.

Brookhaven Lab and University of Delaware begin joint initiative

Through this partnership, scientists from both institutions will conduct collaborative research on rice soil chemistry and quantum materials.

The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and the University of Delaware (UD) have begun a two-year joint initiative to promote collaborative research in new areas of complementary strength and strategic importance. Though Brookhaven Lab and UD already have a tradition of collaboration, especially in catalysis, this initiative encourages partnerships in strategic areas where that tradition does not yet exist. After considering several potential areas, a committee from Brookhaven and UD selected two projects—one on rice soil chemistry and the other on quantum materials—for the new initiative. For each project, one graduate student based at Brookhaven and one graduate student from UD will work with and be supervised by a principal investigator from each respective institution. The research, to start in October 2019, is funded separately by the two institutions. Brookhaven funding is provided through its Laboratory-Directed Research and Development program, which promotes highly innovative and exploratory research that supports the Lab’s mission and areas for growth.

>Read more on the NSLS-II at Brookhaven Lab website

Image: Principal investigators from Brookhaven Lab and the University of Delaware (UD) will collaborate on two different research projects through a new joint initiative. Brookhaven’s Peter Johnson (left) and UD’s Stephanie Law (second from left) will measure the energy level spectrum of a topological insulator, a new type of material that behaves as an insulator internally but as a conductor on the surface; Brookhaven’s Ryan Tappero (second from the right) and UD’s Angelia Seyfferth (right) will study how toxic and nutrient metals are distributed in rice grain.

Unravelling the growth mechanism of the coprecipitation of iron oxide nanoparticles

Applications involving iron oxide nanoparticles (IONPs) and nanomaterials in general, are expected to provide solutions to many problems in the fields of healthcare, energy and environment. Magnetic nanoparticles (such as IONPs) have been in the exploratory stage for cancer diagnostic (e.g.in the form of magnetic resonance imaging contrast agents) for more than three decades and treatment (e.g.via hypothermia) in the recent decade. However, success stories are rare, partly due to the limited performance of commercially available nanoparticles, related to the particle quality attributes such as size and shape, polydispersity, crystallinity and surface chemistry. Although today’s literature provides many reports on the synthesis of highly complex nanoparticles with superior properties respect the currently approved products, there seems to be a gap to the application of these materials to fully exploit their enhanced capabilities. This is due, at least partly, to obstacles such as low yield and, most importantly, the robustness and reproducibility of the synthesis method. Hence, detailed studies on nanoparticle formation mechanisms are essential to guarantee that successful syntheses are not a “one-off” but can be performed and reproduced at various research institutions at small to large scales. This work presents such a detailed study, unravelling the growth mechanism of the co-precipitation of IONPs in solution with the aid of synchrotron X-Ray diffraction.

>Read more on the Elettra website

Image: TEM images of the nanoparticles formed after 30 s, 1, 2, 3, 4, 5, 7 and 10 min of reaction.

Surface instability and chemical reactivity of ZrSiS and ZrSiSe nodal-line semimetals

Among topological semimetals, in nodal-line semimetals (NLSM) conduction and valence bands cross each other. In particular, in NLSM, topological constraints protect band crossings and, moreover, band touching forms nodal lines or rings. Recently, topological nodal lines have been observed in bulk ZrSiX compounds (X = S, Se, Te). In ZrSiX, a tetragonal structure is formed by the stacking of X-ZrSi-Zr-X slabs covalently bonded between each other, whose strength decreases by replacing S with Se or Te ions. This class of materials exhibits large and non-saturating magnetoresistance and ultrahigh mobility of charge carriers.
The control over surface phenomena, including oxidation, degradation, and surface reconstruction is a crucial step in order to evaluate the feasibility of the exploitation in technology of ZrSiX.
By means of X-ray photoelectron spectroscopy (XPS) carried out at the APE-HE beamline, high-resolution electron energy loss (HREELS) and density functional theory, an international team of researchers from Italy, China, Russia, Taiwan, and USA (coordinated by University of L’Aquila) has studied the evolution of ZrSiS and ZrSiSe surfaces in oxygen and ambient atmosphere.
The chemical activity of ZrSiX compounds is mainly determined by the interactions of Si layer with ZrX sublayer. Any adsorption provides distortion of the Si layer (flat in bulk). In the case of ZrSiS, the ZrS sublayer is almost the same as in bulk and therefore adsorption is unfavorable because it provides distortions of Si layer. In the case of ZrSiSe, the ZrSe sublayer is already strongly distorted (structure different from bulk), and, therefore, further distortion of Si layer by adsorption is favorable (see figure).

>Read more on the Elettra website

Image: Atomic structure of different steps of the process of the oxidation of ZrSiSe from (a-d) Zr-sites and (e-h) Si-sites. Red, light blue, black and yellow balls represent O, Zr, Se, and Si atoms, respectively. On panels (a) and (e) physical adsorption of single oxygen molecule is depicted. Panels (b) and (f) represent the situation of uniform coverage of the surfaces by molecular oxygen. In panels (c) and (g), decomposition of single oxygen molecule on the surfaces is represented. Panels (d) and (h) show total oxidation of the surfaces.

Keeping nuclear power safe

Nuclear energy is clean, powerful, affordable, and zero-emission. A new study uses the Canadian Light Source (CLS) at the University of Saskatchewan to help ensure that waste from nuclear power plants remains safe and secure for thousands of years to come.
The project, led by Dan Kaplan and Dien Li, researchers at the Savannah River National Laboratory in South Carolina, looks at storing iodine, which is generated during uranium use, including in nuclear power generation.
Among the challenges of iodine management is its slow rate of decay—it has a half-life of 16 million years. Iodine is volatile and highly mobile in the environment, making containment critically important in nuclear waste management.
Currently, nuclear waste disposal sites use Ag-zeolite to sequester iodine from nuclear waste streams, which is then encased in concrete to prevent leaching.

>Read more on the Canadian Light Source website

Image: Samples of different formulations of cement that were tested for their ability to immobilize radioiodine.

Watching molecules in a light-triggered catalyst ring ‘like an ensemble of bells’

A better understanding of these systems will aid in developing next-generation energy technologies.

Photocatalysts ­– materials that trigger chemical reactions when hit by light – are important in a number of natural and industrial processes, from producing hydrogen for fuel to enabling photosynthesis.
Now an international team has used an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory to get an incredibly detailed look at what happens to the structure of a model photocatalyst when it absorbs light.
The researchers used extremely fast laser pulses to watch the structure change and see the molecules vibrating, ringing “like an ensemble of bells,” says lead author Kristoffer Haldrup, a senior scientist at Technical University of Denmark (DTU). This study paves the way for deeper investigation into these processes, which could help in the design of better catalysts for splitting water into hydrogen and oxygen for next-generation energy technologies.
“If we can understand such processes, then we can apply that understanding to developing molecular systems that do tricks like that with very high efficiency,” Haldrup says.

>Read more on the Linac Coherent Light Source at SLAC website

Image: When photocatalyst molecules absorb light, they start vibrating in a coordinated way, like an ensemble of bells. Capturing this response is a critical step towards understanding how to design molecules for the efficient transformation of light energy to high-value chemicals.
Credit: Gregory Stewart/SLAC National Accelerator Laboratory

A series of stories celebrating the periodic table’s 150th anniversary

The ESRF is celebrating the International Year of the Periodic Table, because its elements are omnipresent in the research done at the facility. We will publish a series of stories on different elements during the coming weeks. The first series is about the fascinating elements at the bottom of the periodic table.

See the series start here on the ESRF website

Image: Kristina Kvashnina in front of the periodic table. She is from the Helmoltz-Zentrum Dresden-Rossendorf (HZDR) but based at the Rossendorf Beamline (BM20) of ESRF in Grenoble.
Credits: Moulyneux

Single atoms can make more efficient catalysts

Detailed observations of iridium atoms at work could help make catalysts that drive chemical reactions smaller, cheaper and more efficient.

Catalysts are chemical matchmakers: They bring other chemicals close together, increasing the chance that they’ll react with each other and produce something people want, like fuel or fertilizer.

Since some of the best catalyst materials are also quite expensive, like the platinum in a car’s catalytic converter, scientists have been looking for ways to shrink the amount they have to use.

Now scientists have their first direct, detailed look at how a single atom catalyzes a chemical reaction. The reaction is the same one that strips poisonous carbon monoxide out of car exhaust, and individual atoms of iridium did the job up to 25 times more efficiently than the iridium nanoparticles containing 50 to 100 atoms that are used today.

>Read more on the SSRL at SLAC website

Image: Scientists used a combination of four techniques, represented here by four incoming beams, to reveal in unprecedented detail how a single atom of iridium catalyzes a chemical reaction.
Credit: Greg Stewart/SLAC National Accelerator Laboratory

Improving lithium-ion battery capacity

Toward cost-effective solutions for next-generation consumer electronics, electric vehicles and power grids.

The search for a better lithium-ion battery—one that could keep a cell phone working for days, increase the range of electric cars and maximize energy storage on a grid—is an ongoing quest, but a recent study done by Canadian Light Source (CLS) scientists with the National Research Council of Canada (NRC) showed that the answer can be found in chemistry.
“People have tried everything at an engineering level to improve batteries,” said Dr. Yaser Abu-Lebdeh, a senior research officer at the NRC, “but to improve their capacity, you have to play with the chemistry of the materials.”

>Read more on the Canadian Light Source website

Image: The decomposition of a polyvinylidene fluoride (PVDF) binder in a high energy battery.
Credit: Jigang Zhou