Advanced Light Source (ALS) – Page 5

A new twist in soft x-ray beams

2019/03/262019/04/03

Light waves, when generated a certain way, can exert twisting forces on matter. In the visible-light regime, such beams have been used as “optical tweezers” to trap and manipulate tiny particles (like a tractor beam) or to detect rotational motion in targets. Now, the ability to generate beams with a specific type of rotational character, known as orbital angular momentum (OAM), has been extended to the soft x-ray regime. The work lays the foundation for a new type of soft x-ray contrast mechanism that could provide access to previously hidden material properties.
In a recently published Nature Photonics paper, researchers from the Advanced Light Source (ALS) and the University of Oregon reported on the fabrication and testing of specialized diffraction gratings that, when placed in the coherent light of ALS Beamline 12.0.2, produce OAM soft x-ray beams of exceptionally high quality.

Image: A flower-like interference pattern generated by a special diffraction grating that superposes two different orbital angular momentum (OAM) modes on a soft x-ray beam.

Absorber captures excess chemotherapy drugs

2019/03/222019/04/10

The work opens up a new route to fighting cancer that minimizes drug toxicity and enables personalized, targeted, high-dose chemotherapy.

Most anticancer drugs are poisonous, so doctors walk a delicate line when administering chemotherapy. A dose must be sufficient to kill or stop the growth of cancer cells in the target organ, but not high enough to irreparably damage a patient’s other organs. To avoid this, doctors can thread catheters through the bloodstream to deliver chemotherapy drugs directly to the site of the tumor—a method known as intra-arterial chemotherapy. Still, typically more than half of the dose injected into the body escapes the target organ. Several years ago, researchers began working on a major improvement: placing a device “downstream” of the targeted organ to filter out excess chemo so that much less of the drug reaches the body as a whole.

>Read more on the Advanced Light Source

Image: (extract, see here the full image)
(a) Diagram of the proposed approach for drug capture using a 3D-printed cylindrical absorber. (b) Chemical structure of doxorubicin, the chemotherapy drug used in this study. (c) Schematic of the endovascular treatment of liver cancer. Excess drug molecules are captured by the absorber in the vein draining the organ. An introducer sheath guides the absorber to the desired location via a guide wire.

The best topological conductor yet: spiraling crystal is the key to exotic discovery

2019/03/202019/03/22

X-ray research at Berkeley Lab reveals samples are a new state of matter

The realization of so-called topological materials – which exhibit exotic, defect-resistant properties and are expected to have applications in electronics, optics, quantum computing, and other fields – has opened up a new realm in materials discovery.
Several of the hotly studied topological materials to date are known as topological insulators. Their surfaces are expected to conduct electricity with very little resistance, somewhat akin to superconductors but without the need for incredibly chilly temperatures, while their interiors – the so-called “bulk” of the material – do not conduct current.
Now, a team of researchers working at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered the strongest topological conductor yet, in the form of thin crystal samples that have a spiral-staircase structure. The team’s study of crystals, dubbed topological chiral crystals, is reported in the March 20 edition of the journal Nature.

Image: This illustration shows a repeated 2D patterning of a property related to electrical conductivity, known as the surface Fermi arc, in rhodium-silicon crystal samples.
Credit: Hasan Lab/Princeton University

Reversible lattice-oxygen reactions in batteries

2019/03/152019/03/25

The results open up new ways to explore how to pack more energy into batteries with electrodes made out of low-cost, common materials.

For a wide range of applications, from mobile phones to electric vehicles, the reversibility and cyclability of the chemical reactions occurring inside a rechargeable battery are key to commercial viability. Conventional wisdom had held that involving oxygen in a battery’s electrochemical operation spontaneously triggers irreversible oxygen losses and parasitic surface reactions, reducing reversibility and safety. Recently however, the idea emerged that reactions involving lattice oxygen (i.e., oxygen that’s part of the crystal-lattice structure vs oxygen on the surface) could be useful for improving battery capacity. Here, researchers report the first direct quantification of a strong, beneficial, and highly reversible chemical reaction involving lattice oxygen in electrodes made with low-cost elements.

>Read more on the Advanced Light Source

Image: Advanced spectroscopy at the ALS clearly resolves the activities of cations and anions (known in Chinese as “yin” and “yang” ions) in battery electrodes.

A deep dive into the imperfect world of 2D materials

2019/03/082019/03/12

Berkeley Lab-led team combines several nanoscale techniques to gain new insights on the effects of defects in a well-studied monolayer material

Nothing is perfect, or so the saying goes, and that’s not always a bad thing. In a study at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), scientists learned how nanoscale defects can enhance the properties of an ultrathin, so-called 2D material. They combined a toolbox of techniques to home in on natural, nanoscale defects formed in the manufacture of tiny flakes of a monolayer material known as tungsten disulfide (WS₂) and measured their electronic effects in detail not possible before. “Usually we say that defects are bad for a material,” said Christoph Kastl, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry and the lead author of the study, published in the journal ACS Nano. “Here they provide functionality.”

Tungsten disulfide is a well-studied 2D material that, like other 2D materials of its kind, exhibits special properties because of its atomic thinness. It is particularly well-known for its efficiency in absorbing and emitting light, and it is a semiconductor.

Image: This image shows an illustration of the atomic structure of a 2D material called tungsten disulfide. Tungsten atoms are shown in blue and sulfur atoms are shown in yellow. The background image, taken by an electron microscope at Berkeley Lab’s Molecular Foundry, shows groupings of flakes of the material (dark gray) grown by a process called chemical vapor deposition on a titanium dioxide layer (light gray).
Credit: Katherine Cochrane/Berkeley Lab

How to catch a magnetic monopole in the act

2019/03/042019/03/08

Berkeley Lab-led study could lead to smaller memory devices, microelectronics, and spintronics

A research team led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created a nanoscale “playground” on a chip that simulates the formation of exotic magnetic particles called monopoles. The study – published recently in Science Advances – could unlock the secrets to ever-smaller, more powerful memory devices, microelectronics, and next-generation hard drives that employ the power of magnetic spin to store data.

Follow the ‘ice rules’
For years, other researchers have been trying to create a real-world model of a magnetic monopole – a theoretical magnetic, subatomic particle that has a single north or south pole. These elusive particles can be simulated and observed by manufacturing artificial spin ice materials – large arrays of nanomagnets that have structures analogous to water ice – wherein the arrangement of atoms isn’t perfectly symmetrical, leading to residual north or south poles.

Image: Full image here. This nanoscale “playground” on a chip uses nanomagnets to simulate the formation of exotic magnetic particles called “monopoles.” Credit: Farhan/Berkeley Lab

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

Spin-momentum locking in cuprate high-temperature superconductors

2019/02/192019/02/26

The results open a new chapter in the mystery of high-temperature superconductors, suggesting that new, unexplored interactions and mechanisms might be at play.

In the world of superconductors, “high temperature” means that the material can conduct electricity without resistance at temperatures higher than expected, but still far below room temperature. Within this special class of high-temperature superconductors (HTSCs), cuprates—consisting of superconducting CuO₂ layers separated by spacer layers—are some of the best performers, generating interest in these materials for potential use in super-efficient electrical wires that can carry power without any loss of electron momentum.

A new spin on cuprate HTSCs

Two kinds of electron interactions have been known to give rise to novel properties in new materials, including superconductors. Scientists who study cuprate superconductors have focused on just one of those interactions: electron correlation—electrons interacting with each other. The other kind of electron interaction found in exotic materials is spin-orbit coupling—the way in which an electron’s magnetic moment interacts with atoms in the material.

Image: Chris Jozwiak, Alessandra Lanzara, Kenneth Gotlieb, and Chiu-Yun Lin.
Credit: Peter DaSilva/Berkeley Lab

Project Director Dave Robin announces ALS-U project beamlines

2019/01/292019/02/13

Over the past year, a process involving ALS and ALS-U staff, the ALS user community, and external advisory committees has been ongoing to select the insertion-device beamlines that will be built and upgraded within the scope of the ALS-U Project. These beamlines will join existing ALS beamlines to form the full complement of capabilities that will be available at the upgraded ALS in several years. I am delighted to inform you that the selection process is now complete and to announce the result.

The ALS-U Project will build two new beamlines

a soft x-ray beamline in Sector 10, dubbed “FLEXON,” whose high-brightness coherent flux and multiple complementary techniques will probe the roles of multiscale heterogeneity in quantum materials; and
a tender x-ray beamline in Sector 8, whose coherent scattering and scanning spectromicroscopy capabilities will address challenges at the frontiers of diverse scientific areas, ranging from soft condensed matter and biomaterials to energy science and Earth and environmental sciences.

Image: ALS-U Project Director Dave Robin.

Award for a pioneer in synchrotron techniques and tools

2019/01/222019/01/23

Zahid Hussain is honored with the Secretary’s Distinguished Service Award during a surprise ceremony.

Zahid Hussain, a longtime scientist at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), has always been more focused on achievements than accolades, though his lists run long in both categories.

His fingerprints are on many of the instruments and scientific milestones at Berkeley Lab’s Advanced Light Source (ALS), which produces many types of light, from infrared to X-rays, for a range of experiments carried out by visiting scientists from around the world. He has pioneered soft X-ray techniques and instrumentation at the ALS that have been widely adopted by the global scientific community.

A two-pronged defense against bacterial self-intoxication

2019/01/182019/01/23

Researchers solved the structure of a bacterial toxin bound to a neutralizing protein, revealing two distinct mechanisms for how the toxin-producing bacteria avoid poisoning themselves.

Microbial communities are of fundamental importance to virtually all natural ecosystems, from the ocean floor to the gastrointestinal tract. Although the term “communities” implies cooperation, scientists now realize that bacterial colonies compete with each other for life-sustaining resources, availing themselves of a variety of strategies to reduce overcrowding. In some cases, they secrete toxins in their fight for survival. Here, researchers studied one such toxin from the bacterium Serratia proteamaculans, various strains of which live inside tree roots or inhabit the digestive tracts of insects and other animals.

Toxin targets cell division

The researchers showed that the toxin, Tre1, targets a bacterial protein, FtsZ, which is analogous to tubulin in human cells. Tubulin molecules are the building blocks of microtubules—long polymers that provide structure and shape to our cells and play an important role in cell division. In bacteria, FtsZ loses the ability to polymerize when attacked by the Tre1 toxin. Instead of dividing, the intoxicated cells grow longer and longer until they eventually split open and die (cellular elongation and lysis).

Image: Healthy bacteria (left) and bacteria (right) whose cell-division machinery has been disrupted by a toxin newly discovered in some bacterial arsenals.
Credit: Mougous Lab

Topological matters: toward a new kind of transistor

2018/12/102018/12/11

X-ray experiments at Berkeley Lab provide first demonstration of room temperature switching in ultrathin material that could serve as a ‘topological transistor’

Billions of tiny transistors supply the processing power in modern smartphones, controlling the flow of electrons with rapid on-and-off switching. But continual progress in packing more transistors into smaller devices is pushing toward the physical limits of conventional materials. Common inefficiencies in transistor materials cause energy loss that results in heat buildup and shorter battery life, so researchers are in hot pursuit of alternative materials that allow devices to operate more efficiently at lower power.
Now, an experiment conducted at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has demonstrated, for the first time, electronic switching in an exotic, ultrathin material that can carry a charge with nearly zero loss at room temperature. Researchers demonstrated this switching when subjecting the material to a low-current electric field.

Image: James Collins, a researcher at Monash University in Australia, works on an experiment at Beamline 10.0.1, part of Berkeley Lab’s Advanced Light Source.
Credit: Marilyn Chung/Berkeley Lab

Toward a blueprint for anti-influenza drugs

2018/12/072019/01/08

The structures provide an atomic-level blueprint from which to design more effective anti-influenza drugs that can overcome growing drug resistance.

Influenza virus infection is a perennial problem. According to the Centers for Disease Control and Prevention, the 2017-18 flu season saw high levels of emergency-department visits for influenza-like illness, high influenza-related hospitalization rates, and elevated and geographically widespread influenza activity for an extended period.

Although yearly vaccinations can reduce the number of flu infections, these vaccines are able to target only a subset of viral strains—there is, as yet, no “universal vaccine.” As a result, there is still a need for antiviral drugs to treat the illness after infection has occurred. This is especially important for groups of people who can experience serious complications from the flu, such as those with respiratory diseases or immune disorders. In recent years, however, resistance to certain classes of antiviral drugs has become a problem.

Image: Molecular dynamics simulation of a drug molecule, amantadine (cyan sticks), in the M2 proton channel. The drug’s ammonium group (blue tip) mimics hydronium, stabilizing the drug molecule in a position to block the channel.

Tunable ferromagnetism in a 2D material at room temperature

2018/12/052018/12/06

Breakthroughs in next-generation spintronic logic and memory devices could hinge on our ability to control spin behavior in two-dimensional materials—stacks of ultrathin layers held together by relatively weak electrostatic (van der Waals) forces. The reduced dimensionality of these so-called “van der Waals materials” often leads to tunable electronic and magnetic properties, including intrinsic ferromagnetism. However, it remains a challenge to tune this ferromagnetism (e.g. spin orientation, magnetic domain phase, and magnetic long-range order) at ambient temperatures.

In this work, researchers performed a study of Fe₃GeTe₂, a van der Waals material that consists of Fe₃Ge layers alternating with two Te layers. The material’s magnetic properties were characterized using a variety of techniques, including x-ray absorption spectroscopy (XAS) with x-ray magnetic circular dichroism (XMCD) contrast at Beamline 6.3.1 and photoemission electron microscopy (PEEM) at Beamline 11.0.1.

Image: PEEM images for unpatterned and patterned Fe₃GeTe₂ samples at 110 K and 300 K. The unpatterned samples formed stripe domains at 110 K, which disappeared at 300 K. The patterned samples formed out-of-plane stripe domains at 110 K and transitioned to in-plane vortex states at 300 K, demonstrating control over magnetism at room temperature and beyond.

Researchers create most complete high-res atomic movie of photosynthesis to date

2018/11/082018/11/08

In a major step forward, SLAC’s X-ray laser captures all four stable states of the process that produces the oxygen we breathe, as well as fleeting steps in between. The work opens doors to understanding the past and creating a greener future.

Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international collaboration between scientists at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and several other institutions is working to change that. The researchers used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser to capture the most complete and highest-resolution picture to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. The results were published in Nature today.

Explosion of life

When Earth formed about 4.5 billion years ago, the planet’s landscape was almost nothing like what it is today. Junko Yano, one of the authors of the study and a senior scientist at Berkeley Lab, describes it as “hellish.” Meteors sizzled through a carbon dioxide-rich atmosphere and volcanoes flooded the surface with magmatic seas.
Over the next 2.5 billion years, water vapor accumulating in the air started to rain down and form oceans where the very first life appeared in the form of single-celled organisms. But it wasn’t until one of those specks of life mutated and developed the ability to harness light from the sun and turn it into energy, releasing oxygen molecules from water in the process, that Earth started to evolve into the planet it is today. This process, oxygenic photosynthesis, is considered one of nature’s crown jewels and has remained relatively unchanged in the more than 2 billion years since it emerged.

Image: Using SLAC’s X-ray laser, researchers have captured the most complete high-res atomic movie to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe.
Credit: Gregory Stewart, SLAC National Accelerator Laboratory)

Expanding the infrared nanospectroscopy window

2018/10/262018/11/04

The ability to investigate heterogeneous materials at nanometer scales and far-infrared energies will benefit a wide range of fields, from condensed matter physics to biology.

Scientific studies require tools that match the natural length and energy scales of the phenomena under investigation. For many questions in biology, quantum materials, and electronics, this means nanometer spatial resolution combined with far-infrared energies. For example, scientists might want to study collective electron oscillations in quantum materials for optoelectronic circuits, or the characteristic vibration modes of protein molecules in biological systems.

A recently developed infrared technique—synchrotron infrared nanospectroscopy (SINS)—combines broadband synchrotron light with atomic-force microscopes to enable infrared imaging and spectroscopy at the nanoscale. However, the technique could only be used in a narrow range of the electromagnetic spectrum that excluded far-infrared wavelengths, due to a scarcity of suitable light sources and detectors for that range. In this work, researchers extended SINS to far-infrared wavelengths, opening up a whole new experimental regime.

Image: Left: Nanoscale images of SiO₂ hole array, obtained using atomic-force microscopy (AFM, top) and synchrotron infrared nanospectroscopy (SINS, bottom), demonstrating SINS contrast between patterned SiO₂ and underlying Si substrate with ~30 nm spatial resolution (inset). Scale bar = 200 nm. Right: SINS broadband spectroscopic data for SiO₂, taken along dotted line in images at left, showing amplitude (top) and phase (bottom) information from asymmetric Si–O stretching (1200 cm^–1) and bending (460 cm^–1) modes. The lower-energy bending mode had previously been inaccessible with this technique.