Main Attraction: Scientists Create World’s Thinnest Magnet

The development of an ultrathin magnet that operates at room temperature could lead to new applications in computing and electronics – such as high-density, compact spintronic memory devices – and new tools for the study of quantum physics.

The ultrathin magnet, which was recently reported in the journal Nature Communications, could make big advances in next-gen memory devices, computing, spintronics, and quantum physics. It was discovered by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley.

“We’re the first to make a room-temperature 2D magnet that is chemically stable under ambient conditions,” said senior author Jie Yao, a faculty scientist in Berkeley Lab’s Materials Sciences Division and associate professor of materials science and engineering at UC Berkeley.

“This discovery is exciting because it not only makes 2D magnetism possible at room temperature, but it also uncovers a new mechanism to realize 2D magnetic materials,” added Rui Chen, a UC Berkeley graduate student in the Yao Research Group and lead author on the study.

Read more on the ALS website

Image: Illustration of magnetic coupling in a cobalt-doped zinc-oxide monolayer. Red, blue, and yellow spheres represent cobalt, oxygen, and zinc atoms, respectively.

Credit: Berkeley Lab

Scientists uncover a different facet of fuel-cell chemistry

Solid oxide fuel cells (SOFCs) are a promising technology for cleanly converting chemical energy to electrical energy. But their efficiency depends on the rate at which solids and gases interact at the devices’ electrode surfaces. Thus, to explore ways to improve SOFC efficiency, an international team led by researchers from Berkeley Lab studied a model electrode material in a new way—by exposing a different facet of its crystal structure to oxygen gas at operating pressures and temperatures.

“We began by asking questions like, could different reaction rates be achieved from the same material, just by changing which surface the oxygen reacts with?” said Lane Martin, a faculty scientist in Berkeley Lab’s Materials Sciences Division. “We wanted to examine how the atomic configuration at specific surfaces of these materials makes a difference when it comes to reacting with the oxygen gas.”

Thin films of a common SOFC cathode material, La0.8Sr0.2Co0.2Fe0.8O3 (LSCF), were epitaxially grown to expose a surface that was oriented along a diagonal crystallographic plane. Electrochemical measurements on this atypical surface yielded oxygen reaction rates up to three times faster than those measured on the usual horizontal plane.

To better understand the mechanisms underlying this improvement, the researchers used Advanced Light Source (ALS) Beamline 9.3.2 to perform ambient-pressure spectroscopy experiments at high temperatures and in varying pressures of oxygen. The results, combined with first-principles calculations, revealed that different crystallographic planes stabilize different surface chemistries, even though the bulk chemistry of the films is identical.

Read more on the ALS website

Image: A model SOFC cathode material adsorbs oxygen molecules (purple spheres) at vacancy sites, an important step in the electrochemical reaction taking place in fuel cells. Ambient-pressure experiments at the ALS allowed measurement of the surface chemical and electronic interactions at high temperature so that researchers could “see” the adsorption of oxygen at it happens. Light blue = La, dark blue = Sr, red = lattice O or O2 molecules, purple = adsorbed O2 molecules.

Credit: Abel Fernandez/UC Berkeley

Artificial spin ice toggles twist in X-ray beams on demand

SCIENTIFIC ACHIEVEMENT

Advanced Light Source (ALS) studies helped scientists understand how a nanoscale magnetic lattice (an artifical spin ice) acts as a toggle switch for x-ray beams with spiral character.

SIGNIFICANCE AND IMPACT

The findings represent an important step toward the development of a versatile new tool for probing or controlling exotic phenomena in electronic and magnetic systems.

A curious singularity

Artificial spin ices (ASIs) are engineered arrays of nanomagnets that are often “frustrated,” meaning that the magnets, constrained by geometry, cannot align themselves to minimize their interaction energy. Water ice exhibits a similar property with regard to the positioning of hydrogen atoms.

While studying ASIs, a collaboration between scientists from the University of Kentucky and the ALS (see related feature article) made an interesting observation: light scattered from certain ASIs produced diffraction patterns in which spots of constructive interference were shaped like donuts instead of dots. The donuts were indicative of a phase singularity—a hallmark of light with a property known as orbital angular momentum (OAM).

Read more on the ALS website

Image: When x-rays are scattered from a patterned array of nanoscale magnets with a lattice defect, the beams acquire a spiral character (orbital angular momentum, or OAM) that produces diffraction patterns with donut-shaped spots. Researchers have found that these OAM beams can be switched on and off by adjusting the temperature or applying an external magnetic field.

Target selection for COVID-19 antibody therapeutics

SCIENTIFIC ACHIEVEMENT

Protein-structure studies at the Advanced Light Source (ALS) helped demonstrate that the primary target of antibody-based COVID-19 immunity is the part of the virus’s spike protein that can most easily mutate.

SIGNIFICANCE AND IMPACT

This work anticipated the rise of SARS-CoV-2 variants and guides the selection of antibody therapeutics that are likely to be more resistant to immune escape.

A better understanding of immunity

To better predict the course of the COVID-19 pandemic and to develop the best new therapeutics, researchers need to understand what regions of the SARS-CoV-2 virus are most critical to the immune response and how likely these regions are to mutate and evade immunity.

Two recent papers, relying in part on protein-structure studies at the ALS, have provided detailed information about the SARS-CoV-2 virus that causes COVID-19 and the human immune response to it. The results reveal where the virus surface protein is most likely to mutate, what the consequences of those mutations may be, and which types of antibodies may be the most effective therapeutics.

Read more on the ALS website

Image: Left: Composite model of the SARS-CoV-2 spike protein trimer with six mAbs shown bound to one RBD (Piccoli et al.). Right: The first RBD–ACE2 complex structure where the RBD is a variant, in this case N439K; the figure highlights a new interaction between the N439K residue and ACE2 (Thomson et al.).

How X-rays could make reliable, rapid COVID-19 tests a reality

Vaccines are turning the tide in the pandemic, but the risk of infection is still present in some situations. If you want to visit a friend, get on a plane, or go see a movie, there is no highly accurate, instant test that can tell you right then and there whether or not you have a SARS-CoV-2 infection. But new research from Lawrence Berkeley National Laboratory (Berkeley Lab) could help get reliable instant tests on the market.

A study led by Michal Hammel and Curtis D. Hodge suggests that a highly sensitive lateral flow assay – the same type of device used in home pregnancy tests – could be developed using pairs of rigid antibodies that bind to the SARS-CoV-2 nucleocapsid protein. Such a test would only require a small drop of mucus or saliva, could give results in 15 minutes, and could detect a COVID-19 infection one day before the onset of symptoms. Their work was published in the journal mABs.

The current gold standard tests for COVID-19 use a form of polymerase chain reaction (PCR) to identify the presence of SARS-CoV-2 nucleic acid (RNA) rather than a viral protein. They are quite accurate, with false negative rates ranging less then 5%  (depending primarily on the sampling site, sample type, and stage of infection). However, PCR tests must be sent away for analysis at an accredited lab.

Read more on the Berkeley Lab website

Image: Molecular models constructed from the X-ray data show different antibodies bound to the SARS-CoV-2 nucleocapsid protein (pink). The scientists determined that the linear arrangement (right) has higher detection sensitivity than the sandwich arrangement (left).

Credit: Berkeley Lab

A properly tailored tail boosts solar-cell efficiency

With the help of structural insights from the Advanced Light Source (ALS), researchers optimized the fit between organic and inorganic ions in a perovskite solar-cell material.

The work increased the material’s power-conversion efficiency and stability and opens up a new avenue for improving the current-carrier dynamics of a promising class of materials.

A photovoltaic rising star

To address the effects of global climate change, it’s essential that we capitalize on energy from the sun. However, although solar energy is freely available, it needs to be converted into usable electricity in a way that’s efficient, cost-effective, and commercially scalable.

Perovskites are high-performance inorganic semiconductors recognized as some of the most promising photovoltaic materials of the future. Perovskite films—thin, lightweight, and flexible—can be produced using low-cost solution-processing techniques, and their power-conversion efficiencies (PCEs) have rapidly risen to the brink of 30% in just 15 years, surpassing conventional silicon panels.

A structure with room to tinker

The most intriguing perovskite materials today are organic–inorganic hybrids. They have the general formula ABX3, in which the inorganic B and X ions form a framework of octahedral cages, and the organic A ions are located in the spaces between the cages.

Previously, it was thought that perovskite electronic performance mainly depended on the B and X electronic orbitals, and that A merely served a structural function. In this work, researchers showed that A-site organic ions with specially designed characteristics can increase charge-carrier mobility and power conversion efficiency while also improving device stability.

Read more on the ALS website

Image: Left: The basic structure of perovskite, a promising solar-cell material, has three types of sites, A (blue), B (gray), and X (purple). Right: By attaching organic tails to the interstitial “A” sites (and testing different linker lengths), researchers improved the material’s photovoltaic response.

A 1-Atom-Deep Look at a Water-Splitting Catalyst

X-ray experiments at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) revealed an unexpected transformation in a single atomic layer of a material that contributed to a doubling in the speed of a chemical reaction – the splitting of water into hydrogen and oxygen gases. This process is a first step in producing hydrogen fuel for applications such as electric vehicles powered by hydrogen fuel cells.

The research team, led by scientists at SLAC National Accelerator Laboratory, performed a unique X-ray technique and related analyses, pioneered at Berkeley Lab’s Advanced Light Source (ALS), to home in on the changes at the surface layer of the material. The ALS produces X-rays and other forms of intense light to carry out simultaneous experiments at dozens of beamlines.

Read more on the LBL website

Image: This illustration shows two possible types of surface layers for a catalyst that performs the water-splitting reaction, the first step in making hydrogen fuel: The gray surface is lanthanum oxide and the colorful surface is nickel oxide. A rearrangement of nickel oxide’s atoms while carrying out the reaction made it twice as efficient. Researchers hope to harness this phenomenon to make better catalysts. Lanthanum atoms are depicted in green, nickel atoms in blue, and oxygen atoms in red.

Credit: CUBE3D

Newly discovered photosynthesis enzyme yields evolutionary clues

Rubisco is one of the oldest carbon-fixing enzymes on the planet, taking CO2 from the atmosphere and fixing it into sugar for plants and other photosynthetic organisms. Form I (“form one”) rubisco goes back nearly 2.4 billion years and is a key focus of scientists studying the evolution of life as well as those seeking to develop bio-based fuels and renewable-energy technologies. A newly discovered form of rubisco—dubbed form I′ (“one prime”)—is thought to represent a missing link in the evolution of photosynthetic organisms, potentially providing clues as to how this enzyme changed the planet.

To learn how form I′ rubisco compares to other rubisco enzymes, researchers performed x-ray crystallography at Advanced Light Source (ALS) Beamline 8.2.2. Then, to capture how the enzyme’s structure changes during different states of activity, they applied small-angle x-ray scattering (SAXS) using Beamline 12.3.1 (SIBYLS). This combination of approaches enables scientists to construct unprecedented models of complex molecules as they appear in nature.

Read more on the ALS website

Image: A ribbon diagram (left) and molecular surface representation (right) of carbon-fixing form I′ rubisco, showing eight molecular subunits without the small subunits found in other forms of rubisco. An x-ray diffraction pattern of the enzyme, also generated by the research team, is in the background.

Credit: Henrique Pereira/Berkeley Lab

Experimental drug targets HIV in a novel way

SCIENTIFIC ACHIEVEMENT

Using the Advanced Light Source (ALS), researchers from Gilead Sciences Inc. solved the structure of an experimental HIV drug bound to a novel target: the capsid protein that forms a shield around the viral RNA.

SIGNIFICANCE AND IMPACT

The work could lead to a long-lasting treatment for HIV that overcomes the problem of drug resistance and avoids the need for burdensome daily pill-taking.

Progress in HIV treatment still needed

Over the past couple of decades, safe and effective treatment for HIV infection has turned what was once a death sentence into a chronic disease. Today, people on the latest HIV drugs have near-normal life expectancy.

However, many people are still living with multidrug-resistant HIV, unable to control their virus loads with currently available HIV drugs. The virus develops resistance when people take their pills inconsistently due to forgetfulness, side effects, or a complex schedule. To some, taking a pill every day is a burden: they schedule their lives around it for fear of missing a dose. To others, it is a stigma, as it makes it difficult to hide one’s HIV status from close friends and family.

Read more on the Advanced Light Source website

Image: An experimental small-molecule drug (GS-6207) targets the protein building blocks of the HIV capsid—a conical shell (colored red in this artistic rendering) that encloses and protects the viral RNA—making the virus unable to replicate in cells. Credit Advanced Light Source

A probe of light-harvesting efficiency at the nanoscale

SCIENTIFIC ACHIEVEMENT

Using time-resolved experiments at the Advanced Light Source (ALS), researchers found a way to count electrons moving back and forth across a model interface for photoelectrochemical cells.

SIGNIFICANCE AND IMPACT

The findings provide real-time, nanoscale insight into the efficiency of nanomaterial catalysts that help turn sunlight and water into fuel through artificial photosynthesis.

Solar-fuel tech goes for gold

In the search for clean-energy alternatives to fossil fuels, one promising solution relies on photoelectrochemical (PEC) cells: water-splitting, artificial-photosynthesis devices that turn sunlight and water into solar fuels such as hydrogen. In just a decade, researchers have achieved great progress in the development of PEC systems made of light-absorbing gold nanoparticles (NPs) attached to a semiconductor film of titanium dioxide (TiO2).

Read more on the Advanced Light Source website

Image: Laser pulses were used to excite electrons in gold nanoparticles (AuNPs) on a titanium dioxide (TiO2) substrate. X-ray pulses were used to count the electrons moving between the nanoparticles and the substrate. (Credit: Oliver Gessner/Berkeley Lab)

Unexpected rise in ferroelectricity as material thins

SCIENTIFIC ACHIEVEMENT

Researchers working at the Advanced Light Source (ALS) showed that hafnium oxide surprisingly exhibits enhanced ferroelectricity (reversible electric polarization) as it gets thinner.

SIGNIFICANCE AND IMPACT

The work shifts the focus of ferroelectric studies from more complex, problematic compounds to a simpler class of materials and opens the door to novel ultrasmall, energy-efficient electronics.

Ferroelectric lower limit?

Distortions in the atomic geometries of certain materials can lead to ferroelectricity—the presence of electric dipoles (charge separations) with switchable polarizations. The ability to control this polarization with an external voltage offers great promise for ultralow-power microprocessors and nonvolatile memory.

As electronic devices become smaller, however, the materials used to store and manipulate electronic data are being pushed to low-dimensional extremes. Properties that function reliably in bulk materials often diminish in ultrathin films just a few atomic units thick. Therefore, exploring the critical thickness limit in “polar” materials (i.e., materials having spontaneous electric polarization) is not only a fundamental issue for nanoscale ferroelectric research, it also has extensive implications for the future of high-density ferroelectric-based electronics.

Read more on Advanced Light Source (ALS) website

Image : A thin layer of hafnium oxide (two unit-cell thicknesses, or about 1 nm) has an electric polarization that’s reversible by an external electric field, making it attractive for use in next-generation low-power microelectronics.

Credit: Ella Maru Studio

A scalable platform for two-dimensional metals

SCIENTIFIC ACHIEVEMENT

Using a new method for stabilizing a two-dimensional (2D) metal on a large-area platform, researchers probed the origins of the material’s superconductivity at the Advanced Light Source (ALS).

SIGNIFICANCE AND IMPACT

The work represents a notable milestone in advancing 2D materials toward broad applications in topological computing, advanced optics, and molecular sensing.

Expanding the scientific palette

If you confine everyday metals to layers only a few atoms thick, they acquire new properties that are different from those exhibited by their more common bulk forms. The ability to synthesize such two-dimensional (2D) metals means that the range of materials available for novel uses can be expanded to different areas of the periodic table—providing a much richer “scientific palette” of properties for applications in topological computing, advanced optics, and molecular sensing.

Read more on the ALS website

Image: A confined layer of metal atoms (silver spheres) on a silicon carbide (SiC) substrate is capped by a layer of graphene, allowing for new forms of low-dimensional metals with unique properties. Gold spheres represent Cooper pairs, responsible for conventional superconductivity. 

Credit: Yihuang Xiong/Penn State

Assembly lines for designer bioactive compounds

Researchers successfully bioengineered changes to a molecular “assembly line” for bioactive compounds, based in part on insights gained from small-angle x-ray scattering at the Advanced Light Source (ALS).

The ability to re-engineer these assembly lines could improve their performance and facilitate the synthesis of new medically useful compounds.

Microbes are known to possess molecular “assembly lines” that produce an important class of compounds, many of which have uses as antibiotics, antifungals, and immunosuppressants. The compounds are peptides—chains of amino acids like RNA, but shorter and produced, not by ribosomes, but by cellular machines known as nonribosomal peptide synthetases (NRPSs).

>Read more on the Advanced Light Source website

Image: Top: Comparison of experimental SAXS scattering data (black) with theoretical curves (green) obtained using an ensemble optimization method (EOM) shows excellent agreement. Bottom: LgrA structural models corresponding to the EOM analyses show large differences in conformation, similar to the differences observed using crystallography.

Seeing “under the hood” in batteries

From next-gen smartphones to longer-range electric cars and an improved power grid, better batteries are driving tech innovation. And to push batteries beyond their present-day performance, researchers want to see “under the hood” to learn how the individual ingredients of battery materials behave beneath the surface.

This could ultimately lead to battery improvements such as increased capacity and voltage.

But many of the techniques scientists use can only scratch the surface of what’s at work inside batteries, and a high-sensitivity X-ray technique at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is attracting a growing group of scientists because it provides a deeper, more precise dive into battery chemistry.

>Read more on the Advaced Light Source at LBNL website

Image: The high-efficiency RIXS system at the Advanced Light Source’s Beamline 8.0.1
Credit: Marilyn Sargent/Berkeley Lab

How a new electrocatalyst enables ultrafast reactions

The work provides rational guidance for the development of better electrocatalysts for applications such as hydrogen-fuel production and long-range batteries for electric vehicles.

The oxygen evolution reaction (OER) is the electrochemical mechanism at the heart of many processes relevant to energy storage and conversion, including the splitting of water to generate hydrogen fuel and the operation of proposed long-range batteries for electric vehicles. Because the OER rate is a limiting factor in such processes, highly active OER electrocatalysts with long-term stability are being sought to increase reaction rates, reduce energy losses, and improve cycling stability. Catalysts incorporating rare and expensive materials such as iridium and ruthenium exhibit good performance, but an easily prepared, efficient, and durable OER catalyst based on earth-abundant elements is still needed for large-scale applications.

Key insight: shorter O-O bonds
In an earlier study, a group led by John Goodenough (2019 Nobel laureate in chemistry) measured the OER activities of two compounds with similar structures: CaCoO3 and SrCoO3. They found that the CaCoO3 exhibited higher OER activity, which they attributed to its shorter oxygen–oxygen (O-O) bonds. Inspired by this, members of the Goodenough group have now analyzed a metallic layered oxide, Na0.67CoO2, which has an even more compact structure than CaCoO3. X-ray diffraction (XRD) experiments performed at the Advanced Photon Source (APS) confirmed that the shortest O-O separation in Na0.67CoO2 is 2.30 Å, compared to 2.64 Å for CaCoO3. The researchers then compared the OER performance of Na0.67CoO2 with IrO2, Co3O4, and Co(OH)2. They found that Na0.67CoO2 exhibited the highest current density, the lowest overpotential (a measure of thermodynamic energy loss), and the most favorable Tafel slope (sensitivity of the electric current to applied potential). The Na0.67CoO2 also showed excellent stability under typical operating conditions.

>Read more on the Advanced Light Source website

Image: (extract, full image here) A new electrocatalyst prepared for this study, Na0.67CoO2, consists of two-dimensional CoO2 layers separated by Na layers (not shown). The Co ions (blue spheres) have four different positions (Co1-Co4), and the distorted Co–O octahedra have varying oxygen–oxygen (O-O) separations (thick red lines connecting red spheres). All of the O-O bonds are shorter than 2.64 Å (the length of the corresponding bonds in a comparable material), and the shortest bonds are less than 2.40 Å. It turns out that O-O separation has a strong effect on the oxygen evolution reaction (OER) in this material.

Water improves material’s ability to capture CO2

With the help of the Advanced Light Source (ALS), researchers from UC Berkeley and ExxonMobil fine-tuned a material to capture CO2 in the presence of water.

About 65% of anthropogenic greenhouse gas emissions comes from the combustion of fossil fuels in power plants. So far, efforts to capture CO2 from power-plant flue gases and sequester it underground have mainly focused on coal-fired power plants. However, in the United States, natural gas has surpassed coal in the amount CO2 released, despite the fact that natural gas emits approximately half as much CO2 per unit of electricity. Therefore, new materials are urgently needed to address this situation.

Not all combustion is alike

Compared to coal-fired power plants, natural gas combined cycle (NGCC) plants produce flue gases with low CO2 concentrations. This reduces the carbon footprint, but increases the technical difficulty of CO2 capture. Also, materials capable of adsorbing such low concentrations of CO2 often require high temperatures to release it for sequestration, an important part of the cycle that offsets initial low-carbon benefits. NGCC emissions also have a higher concentration of O2, which has a corrosive effect on adsorbent materials, and both NGCC and coal flue streams are saturated in water, which can both degrade materials and reduce efficiency. Thus, an effective NGCC CO2-capture material must selectively bind low-concentration CO2 under humid conditions while being thermally and oxidatively stable.

>Read more on the Advanced Light Source website

Image: Single-crystal x-ray diffraction enables the precise determination of the positions of the atoms in metal–organic frameworks (MOFs), highly porous materials capable of soaking up vast quantities of a specific gas molecule, such as CO2. This structure represents 2-ampd–Zn2(dobpdc), a MOF with the same structure as 2-ampd–Mg2(dobpdc), the subject of this study. Light blue, blue, red, gray, and white spheres represent Zn, N, O, C, and H atoms, respectively.