How the structure of a halide perovskite is distorted when it interacts with chiral molecules. Credit: National Renewable Energy Laboratory
A research team has discovered a new process to induce chirality in halide perovskite semiconductors, which could open the door to cutting-edge electronic applications.
The development is the latest in a series of advancements made by the team involving the introduction and control of chirality. Chirality refers to a structure that cannot be superimposed on its mirror image, such as a hand, and allows greater control of electrons by directing their “spin.” Most traditional optoelectronic devices in use today exploit control of charge and light but not the spin of the electron.
The researchers have been able to create a spin-polarized LED using chiral perovskite semiconductor in the absence of extremely low temperatures and a magnetic field, as was previously reported. The newest advance accelerates the materials development process for spin control.
The details are spelled out in a new paper, “Remote Chirality Transfer in Low-Dimensional Hybrid Metal Halide Semiconductors,” which is published in the journal Nature Chemistry. The key was in introducing a chiral molecule with a different headgroup into the perovskite.
The chiral molecule intentionally does not fit into the perovskite lattice but “twists” the structure from the surface. The chiral molecule transfers its properties several unit cells or layers deep into the perovskite structure. This twist can be controlled by employing left- or right-handed chiral molecules into the grain boundaries and surfaces of a perovskite film, which control the spin properties accordingly.
Remote chirality transfer in hybrid metal halides. Credit: Nature Chemistry (2024). DOI: 10.1038/s41557-024-01662-2
Such twisted structures enable unique functionalities for energy applications where spin-control adds additional potential by acting as electronic spin filters.
Md Azimul Haque, the first author of the paper, said introducing chirality to the low-dimensional perovskite semiconductors generally includes a chiral molecule being present in the perovskite lattice, which needs extensive analysis every time one changes the composition of the chiral molecule.
The ability of a proximal chiral molecule to transfer its properties without changing the perovskite composition makes the process simple, faster, and less limiting on the composition, he said.
“We can create materials with known properties now with added chirality very easily compared to traditional methods,” said Haque, a postdoctoral researcher. “The next step is to experiment with the materials and incorporate them into new applications.”
Hybrid perovskites refer to a crystalline structure, containing both inorganic and organic components. In other semiconductors, such as those made from silicon, the material is purely inorganic and rigid. Hybrid perovskites are soft and more flexible, “so a twisting molecule on the surface, will extend the effect deeper into this semiconductor than it can in most rigid, inorganic semiconductors,” said Joey Luther, a National Renewable Energy Laboratory (NREL) senior research fellow and corresponding author.
“This is a new way to induce chirality in halide perovskites,” Luther said, “and it could lead to technologies that we can’t really envision but might be somewhere along the lines of polarized cameras, 3D displays, spin information transfer, optical computation, or better optical communication—things of that nature.”
More information: Md Azimul Haque et al, Remote chirality transfer in low-dimensional hybrid metal halide semiconductors, Nature Chemistry (2024). DOI: 10.1038/s41557-024-01662-2
Graphical Abstract. Credit: Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202415124
Increasing amounts of data require storage, often for long periods. Synthetic polymers are an alternative to conventional storage media because they maintain stored information while using less space and energy. However, data retrieval by mass spectrometry limits the length and thus the storage capacity of individual polymer chains.
In the journal Angewandte Chemie International Edition, researchers have introduced a method that overcomes this limitation and allows direct access to specific bits without reading the entire chain.
Data accumulates constantly, resulting from business transactions, process monitoring, quality assurance, or tracking product batches. Archiving this data for decades requires much space and energy. For long-term archival of large amounts of data that requires infrequent access, macromolecules with a defined sequence, like DNA and synthetic polymers, are an attractive alternative.
Synthetic polymers have advantages over DNA: simple synthesis, higher storage density, and stability under harsh conditions. Their disadvantage is that the information encoded in polymers is decoded by mass spectrometry (MS) or tandem-mass sequencing (MS2). For these methods, the size of the molecules must be limited, which severely limits the storage capacity of each polymer chain.
In addition, the complete chain must be decoded in sequence, building block by building block—the bits of interest cannot be accessed directly. It is like having to read through an entire book instead of just opening it to the relevant page. In contrast, long chains of DNA can be cut into fragments of random length, sequenced individually, and then computationally reconstructed into the original sequence.
Kyoung Taek Kim and his team at the Department of Chemistry at Seoul National University have developed a new method by which very long synthetic polymer chains whose molecular weights greatly exceed the analytical limits of MS and MS2 can be efficiently decoded.
As a demonstration, the team encoded their university address into ASCII and translated this—together with an error detection code (CRC, an established method used to ensure data integrity)—into a binary code, a sequence of ones and zeroes.
This 512-bit sequence was stored in a polymer chain made of two different monomers: lactic acid to represent a 1 and phenyllactic acid to represent a 0. At irregular intervals, they also included fragmentation codes containing mandelic acid. When chemically activated, the chains break at those locations.
In their demonstration, they obtained 18 fragments of various sizes that could be individually decoded by MS2 sequencing.
Specially developed software initially identified the fragments based on their mass and their end groups, as shown by the MS spectra. During the MS2 process, previously measured molecular ions break down further, and these pieces were then also analyzed.
The fragments could be sequenced based on the mass difference of the pieces. With the aid of the CRC error detection code, the software reconstructed the sequence of the entire chain, overcoming the length limit for the polymer chains.
The team was also able to decode interesting bits without sequencing the entire polymer chain (random access), such as the word “chemistry” in the code for their address.
By taking into account that the parts of their address are all in a specific order (department, institution, city, postal code, country) and separated by commas, they were able to isolate the location where the desired information was stored within the chain and only sequenced the relevant fragments.
More information: Heejeong Jang et al, Shotgun Sequencing of 512‐mer Copolyester Allows Random Access to Stored Information, Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202415124
Cross-section of the food vacuole, the Plasmodium’s stomach-like sac, in which it digests hemoglobin. The image, obtained by cryogenic scanning transmission electron tomography (CSTET), reveals several large kitchen cleaver-shaped crystals of the malaria pigment in the center, and numerous smaller ones on the periphery. Credit: ACS Central Science (2024). DOI: 10.1021/acscentsci.4c00162
Prof. Leslie Leiserowitz first became intrigued by malaria when he was a young boy in South Africa. His father, who scouted the continent in search of wood for the family business, brought back not only tales of elephants and gorillas but also skin rashes and ringing in his ears, side effects of the quinine he took to prevent malaria.
Decades later, while studying crystals at the Weizmann Institute of Science, Leiserowitz realized that malaria was in fact surprisingly pertinent to his research. He learned that the malaria parasite thrives inside red blood cells thanks to its knack for crafting crystals, and he set out to study these crystals, later joining forces with a chemistry faculty colleague, Prof. Michael Elbaum.
A new study—headed by Elbaum and Leiserowitz and conducted in collaboration with prominent research teams around the world—has culminated in a paper that might help outwit the malaria parasite. It reveals in unprecedented detail the structure of crystals that the parasite builds in order to survive.
Since most antimalarial drugs are thought to work by interfering with the formation and growth of these crystals, the new findings might lead to improved antimalarial medications.
The research is published in the journal ACS Central Science.
“There had been enormous advances in imaging technologies such as electron and X-ray microscopy, and we realized that we could apply them to do something good for humanity,” says Elbaum, explaining how this research came about. “It was an opportunity we simply couldn’t pass up.”
Watch how an image of the food vacuole – the Plasmodium’s stomach-like sac, in which the parasite digests hemoglobin – is being constructed using CSTET. A cross-section of the vacuole reveals several large crystals of the malaria pigment in the center, and numerous smaller ones on the periphery
Seeing malaria pigment in a whole new way
Even though the incidence of malaria was drastically slashed in the first two decades of the 21st century, the disease remains an immense global health problem, killing more than half a million people each year, most of them young children. Much of the eradication effort is aimed at controlling the mosquitoes that, through their bites, transmit the malaria parasite—a single-celled organism belonging to the genus Plasmodium.
Antimalarial drugs are also essential to this effort, but many of the existing medications have lost their effectiveness because the parasites have become resistant to them. Improved drugs could help break the cycle of the parasite’s passage from mosquitoes to humans and back.
The production of crystals is a survival trick the parasite uses in its takeover of blood cells. This maneuver enables it to feast on hemoglobin, the oxygen-carrying protein in the blood.
Digesting the hemoglobin releases heme, an iron-containing molecular complex needed for binding oxygen. Freed from the surrounding protein, however, heme is so reactive that it can kill the parasite. That’s precisely why Plasmodium pulls a survival stunt, in which it renders the heme harmless by packaging it into dark-colored crystals known as the malaria pigment, or more technically, as hemozoin.
When it was discovered in the 19th century, hemozoin was initially thought to be made by the patient’s body in response to the infection, but its true origin—through the doings of the parasite—was eventually understood.
In his early studies on hemozoin crystals, Leiserowitz was fascinated by their symmetries, a topic he had worked on for many years with his Weizmann colleague Prof. Meir Lahav. When applied to malaria, this topic becomes a life-and-death matter: The different ways in which heme molecules fit into the crystals not only create different symmetries but can also affect crystal growth, which, in turn, can seal the parasite’s fate. However, such structural nuances were too subtle to be resolved by the methods of the day.
In the meantime, Elbaum had been independently working on Plasmodium from an entirely different angle. Together with colleagues at the Hebrew University of Jerusalem, he was studying Plasmodium cells as they go through their peculiar process of replication.
Whereas most cells divide by splitting in two, the malaria parasite first makes numerous copies of its components within a red blood cell, then instantly divides into multiple daughter parasites that go on to infect new blood cells.
When the scientists explored cellular nuclei during this process using newly available 3D electron microscopy methods, the hemozoin crystals also came into full view. So when Leiserowitz presented his work on these crystals at a faculty meeting, the collaboration with Elbaum was a natural outcome.
The collaboration proved fruitful from the start, thanks in large part to emerging new technologies for probing matter on the nanoscale. In their very first joint study, the scientists shed new light on crystal formation using soft X-ray tomography, a method that Elbaum had helped develop during a sabbatical in Berlin.
Then, a new approach to cryo-electron tomography that Elbaum developed with Weizmann and colleagues enabled the study of intact cells in which the malaria pigment is manufactured.
As luck would have it, a new lab working on the biology of the malaria parasite opened at Weizmann. It supplied Elbaum and Leiserowitz with infected red blood cells from which the hemozoin could be extracted.
Revealing the structure of these natural crystals was crucial for medical applications, particularly because existing structural knowledge had been largely based on the more readily available synthetic crystals, used in most previous hemozoin studies.
But the crystals did not divulge their secrets easily. Searching for pieces of the structure puzzle that were still missing after a detailed three-dimensional analysis at Weizmann, Elbaum and Leiserowitz sent their pigment samples to colleagues at the University of Oxford and the Diamond Light Source (the UK’s national synchrotron) who had installed a new method of electron crystallography that produced astounding images of the pigment.
Having finished their initial analysis, the British scientists suggested securing the collaboration of researchers elsewhere.
“From then on, the research turned into a relay race of sorts, with each lab suggesting involving colleagues with top expertise in additional fields,” Elbaum recalls. “The group finally expanded to a kind of all-star team for increasingly sophisticated analysis.”
Ultimately, the list of study authors came to comprise 17 researchers from Israel, the UK, Austria, the Czech Republic and the United States. That is, it took a coalition of some of the world’s most advanced labs and a battery of the latest technologies to unravel the survival savvy honed over the course of evolution by a bunch of single-celled blood parasites.
Answering the question of the ugly crystals
The result of this international collaboration—a definitive, atom-by-atom three-dimensional structure of the malaria pigment—supplied a host of valuable insights. For starters, it solved a puzzle generated by previous studies, in which the Weizmann scientists had observed crystals of a peculiar trapezoid shape that resembled a kitchen cleaver: The “blade” end was always smooth and sharp, like a chisel, while the “handle” end was variable and often jagged.
“We were wondering how nature could produce something so ugly—these crystals looked as if they’d been bitten on one side,” Leiserowitz recalls.
The detailed structure resolved the kitchen cleaver quandary. Heme molecules fit into the malaria pigment crystals in pairs, but because the “front” and “back” faces of these molecules differ chemically, they can pair up vis-à-vis one another in four distinct ways. In other words, there are four distinct heme building blocks, or basic units, of hemozoin crystals.
Two of these are symmetric, but the other two are chiral, which means that they are mirror images of one another and cannot be superimposed, like the left and the right hand.
When they grow together in a single crystal, the result can be an atomically disordered surface, including a jagged end. Such clear understanding of the crystal surfaces is essential to designing or evaluating drugs that must bind to the crystal to inhibit its growth.
Drugs can attain their goal in ways that are more complex than stopping crystal growth, but the stoppage is vital for those other effects too.
Leiserowitz explains the complexity using a car factory analogy: “Imagine that you are churning out cars, say, 500 a day, but at the end of the line, the drivers who have to take these cars away stop working, so all those cars pile up. That’s exactly what happens when a drug prevents heme molecules from moving on to join a crystal. They pile up and jam the membranes, so nothing can get in or out, which helps to kill the parasite.”
The study can facilitate the design of new drugs by making it much easier to, for example, calculate the interactions between crystals and the medication. In addition, the findings clarified which facets of the crystals grow more rapidly than others and identified facets whose growth is most likely to be inhibited by drug binding.
Finally, the study revealed subtle but essential differences between natural and synthetic malaria crystals, which underscores the importance of designing future drugs on the basis of structural information about real-life crystals made by the parasite.
Elbaum presented the study’s findings at the symposium “Leslie at 90: A Scientific Odyssey,” held at Weizmann to mark Leiserowitz’s 90th birthday. Of course, the publication of the paper coincided with this milestone birthday merely by chance, but it surely served as a grand reward for some two decades of Leiserowitz’s research on the malaria pigment and for his life-long interest in malaria.
More information: Paul Benjamin Klar et al, Cryo-tomography and 3D Electron Diffraction Reveal the Polar Habit and Chiral Structure of the Malaria Pigment Crystal Hemozoin, ACS Central Science (2024). DOI: 10.1021/acscentsci.4c00162
Helical wheel diagrams of; (A) K47; and (B) K311. Helical wheels generated using HeliQuest (https://heliquest.ipmc.cnrs.fr/). (C) Sequences of K47 and K311 aligned with the heptad abcdefg and hendecad abcdefghijk registers. Credit: Biomacromolecules (2024). DOI: 10.1021/acs.biomac.4c00661
Peptides come and peptides go, sometimes too fast. These strings of amino acids—the building blocks of life—are of intense interest to researchers for their potential to treat everything from stroke to infection, either as the drug or the drug delivery vehicle. That is, when they last long enough to do their work.
“Peptides are potentially powerful components of medicines, because they’re just fragments of our natural proteins that our bodies can recognize,” said University of Virginia assistant professor of chemical engineering Rachel Letteri. “But one limitation is that they tend to break down quickly, so we need to figure out how to make them more stable.”
Letteri’s lab, led by her Ph.D. advisee Vincent Gray, has demonstrated an approach for overcoming the longevity problem by designing mirror images of natural peptides called coiled coils.
Coiled coils, helix-shaped peptides resembling curly ribbons twisted together, are found in nearly 10% of the proteins in many organisms. They play critical roles in preparing proteins to properly carry out their jobs, in part by pulling together multiple copies of proteins.
“This happens when individual helices in a protein recognize their match and bind in a specific way, forming the coiled coil,” Letteri said. “It’s like puzzle pieces fitting together. This binding is crucial for proteins to work as they should.”
Proteins help build and repair the body, oxygenate the blood, regulate digestion and perform a host of other functions.
The binding and connecting features of coiled coils make them especially tantalizing as components for medicines, including biomaterials for tissue regeneration. Yet, like other natural peptides, they degrade quickly.
Coiled coil mirrors extend peptide life
Previous research has shown that blending natural peptides with their mirror images results in excellent binding and stability. Gray and Letteri wondered if the strategy would also work with coiled coils. Could the team design mirrored coiled coils, with all their medicinal promise, to improve both their specific binding ability and longevity for medicinal use?
Gray and Letteri found that compared to natural coiled coil combinations in which the two strands spiral in same direction, their engineered coils—with the two strands spiraling in opposite directions—indeed showed stronger binding and greater longevity in biological environments.
Why does it work? Mirror-image peptides improve stability because they are not affected by enzymes that accelerate chemical breakdown of natural peptides. Moreover, the mirror images can be designed to target natural peptides and bind tightly in specific ways due to their opposite but complimentary shape—much like intertwining the fingers of your left and right hands.
While the team successfully demonstrated the concept, the research has a long way to go, Letteri said.
“Researchers are just beginning to understand how to engineer peptides to leverage specific interactions between peptides and their mirror images,” she said. “We hope that these specific, long-lasting interactions between mirror-image peptides will unlock new design tools for next-generation therapeutics and biomaterials.”
More information: Vincent P. Gray et al, Designing Coiled Coils for Heterochiral Complexation to Enhance Binding and Enzymatic Stability, Biomacromolecules (2024). DOI: 10.1021/acs.biomac.4c00661
At left is a molecule that is a known carcinogen, and at right a chemical cousin. The green dashes surround an extra space that might connect to DNA; that space is obscured inside the orange dashes. Credit: Derek Urwin/UCLA
Derek Urwin has a special stake in his work as a cancer control researcher. After undergraduate studies in applied mathematics at UCLA, he became a firefighter. His inspiration to launch a second career as a scientist was the loss of his brother, Isaac, who died of leukemia at only 33 despite no history of cancer in their family. Working with Anastassia Alexandrova, a professor of chemistry and biochemistry at UCLA College, he earned his doctorate.
Urwin is now a UCLA adjunct professor of chemistry—and still a full-time firefighter with the Los Angeles County Fire Department. In a recent publication, his science shed new light on the chemical underpinnings of exposures that may lead to cancer.
When organic substances burn, the smoke carries compounds known as polycyclic aromatic hydrocarbons, or PAHs. PAHs can enter the body through breathing, eating, drinking and skin contact. Because emissions from industry and automobiles are one source, nearly everyone encounters these chemicals in day-to-day life. Certain jobs such as firefighting and coal-tar production expose workers to concentrated doses of PAHs—the same jobs that tend to be associated with increased risk for cancer.
In fact, the International Agency for Research on Cancer has listed many PAHs as probable or possible carcinogens. Only one among these thousands of chemicals, benzo[a]pyrene (B[a]P), is classified as a known carcinogen in humans.
A study by Urwin, Alexandrova and UCLA undergraduate Elise Tran, published in the Proceedings of the National Academy of Sciences, shows that some of B[a]P’s chemical cousins may present more serious risk for cancer. The scientists used computer simulations of molecular interactions to profile what happens when each of 15 PAHs settles onto a spot in the DNA helix commonly linked to cancer-causing mutations. Compared to the known carcinogen, six of the PAHs showed a greater affinity for binding to the mutational hotspot. Those six chemicals also had a higher likelihood of avoiding detection by a crucial mechanism for repairing DNA lesions.
In addition to the new insight into the relative toxicity of PAHs, the research may offer a faster way to filter potentially dangerous chemicals and identify which ones are riskiest to human health. Such findings could inform not only laboratory and population studies but also public policy.
“We hope that our strategy can speed up the process of studying these chemicals,” said Urwin, the study’s first author. “Instead of casting a wide net, this could show exactly where we ought to start the process. Efficient, effective, accurate computational studies can even enhance or accelerate the process of developing policy that improves public and occupational health.”
Urwin also serves as chief science advisor for the International Association of Fire Fighters and was recently appointed to the California Occupational Safety and Health Standards Board.
“Derek’s work as a firefighter made this research possible,” said corresponding author Alexandrova, who is a member of the California NanoSystems Institute at UCLA. “He knows what’s going on in the field very intimately, and that enables us to make the connection to chemistry and the tools that we have. Real-life experience educated us about what to do.”
Credit is also due to Urwin’s intuition. The germ of the investigation was his observation that based on their structure, several PAHs simply looked as though they ought to fit more snugly within the DNA double helix than others, where they insert themselves like a key into a keyhole.
The investigators built on previous research in which they applied an advanced algebraic technique to accurately model PAHs’ atomic interactions. They compared how strongly B[a]P and 14 other PAHs bind to a DNA sequence that is mutated in one-third of all human cancers.
The team plans to apply their computational method to other genetic hot spots related to cancer, as well as to more PAHs and other compounds, including the “forever chemicals” known as PFAS.
With connections to the world of firefighting and science, Urwin also relishes the opportunity for community-based participatory research. In that model, the people being studied help shape the questions being asked, the design and execution of the research, and the dissemination of resulting information to those affected in a way that they understand.
“My fellow firefighters have historically been underserved by the scientific community, not out of disdain, but rather because it’s complicated to conduct research in the midst of emergency service operations,” Urwin said. “Having my feet in both arenas, I want to bring access to scientists, so their research can create a positive impact on health in the fire service community. Science is supposed to make the world better for people, whether it’s firefighters or anyone else.”
More information: Derek J. Urwin et al, Relative genotoxicity of polycyclic aromatic hydrocarbons inferred from free energy perturbation approaches, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2322155121
Credit: The Journal of Physical Chemistry B (2024). DOI: 10.1021/acs.jpcb.4c05317
Conducting polymers exhibit a variety of properties in addition to their conductivity. Research has explored their use in light-emitting devices, electromagnetic wave shielding, and anticorrosion materials. One notable characteristic is paramagnetism.
Researchers at University of Tsukuba have synthesized a conducting polymer, polyaniline, exhibiting perfect diamagnetic properties, which eliminate external magnetic fields within the material. These properties are typically associated with superconductors.
While conducting polymers generally display paramagnetism—where they are weakly attracted to magnetic fields—this breakthrough marks the first step towards developing a conducting material that demonstrates diamagnetism, the opposite of paramagnetic behavior. The results are published in The Journal of Physical Chemistry B.
The research team has previously developed methods for synthesizing various conducting polymers. In this study, they successfully synthesized polyaniline, one of the most commonly studied conductive polymers, in the presence of iron sulfate, imparting perfect diamagnetism—a property that excludes external magnetic fields from the material. This behavior is analogous to that of superconductors and contrasts with the paramagnetism typically found in conducting polymers.
Superconducting Quantum Interference Device measurements of the synthesized polyaniline confirmed that its magnetic susceptibility exhibits a gradual negative shift from approximately 100 K (−173°C), and it demonstrates perfect antiferromagnetism below 24 K (−249°C).
However, the polyaniline synthesized in this study showed minimal variation in electrical resistance with temperature. A significant reduction in electrical conductivity was only observed at extremely low temperatures.
The discovery of perfect diamagnetism in polyaniline represents a unique phenomenon not observed in conventional organic or inorganic conductive materials. It is plausible that an unconventional mechanism of perfect diamagnetism is at play, potentially leading to novel advancements in the field of conductive polymers.
More information: Hiromasa Goto et al, Perfect Diamagnetism of Polyaniline, The Journal of Physical Chemistry B (2024). DOI: 10.1021/acs.jpcb.4c05317
The AEM water electrolyser cell works with a newly developed membrane electrode (MEA) that is directly coated with a nickel-based anode catalyst. Its molecular mode of action has been elucidated, and the AEM cell has proven to be almost as powerful as a conventional PEM cell with iridium catalyst. Credit: Flo Force Fotografie, Hahn-Schickard & IMTEK Universität Freiburg
A team from the Technical University of Berlin, HZB, IMTEK (University of Freiburg) and Siemens Energy has developed a highly efficient alkaline membrane electrolyzer that approaches the performance of established proton-exchange membrane(PEM) electrolyzers. What makes this achievement remarkable is the use of inexpensive nickel compounds for the anode catalyst, replacing costly and rare iridium.
At BESSY II, the team was able to elucidate the catalytic processes in detail using operando measurements, and a theory team (U.S., Singapore) provided a consistent molecular description. In Freiburg, prototype cells were built using a new coating process and tested in operation. The results have been published in the journal Nature Catalysis.
Hydrogen will play a major role in the energy system of the future, as an energy storage medium, a fuel and valuable raw material for the chemical industry. Hydrogen can be produced by electrolysis of water in a virtually climate-neutral way, provided this is done with electricity from solar or wind power.
Scale-up efforts for a green hydrogen economy are currently largely dominated by two systems: proton-conducting membrane electrolysis (PEM) and classic liquid alkaline electrolysis. AEM electrolyzers combine the advantages of both systems and, for example, do not require rare precious metals such as iridium.
Now, research teams from TU Berlin and HZB, together with the Department of Microsystems Engineering (IMTEK) at the University of Freiburg and Siemens Energy, have presented the first AEM electrolyzer that produces hydrogen almost as efficiently as a PEM electrolyzer. Instead of iridium, they used nickel double hydroxide compounds with iron, cobalt or manganese and developed a process to coat them directly onto an alkaline ion exchange membrane.
Insight into molecular processes during electrolysis at BESSY II
During the electrolysis in the cell, they were able to carry out operando measurements at the Berlin X-ray source BESSY II at the LiXEdrom end station. A theory team from Singapore and the U.S. helped to interpret the experimental data.
“This enabled us to elucidate the relevant catalytic-chemical processes at the catalyst-coated membrane, in particular the phase transition from a catalytically inactive alpha phase to a highly active gamma phase and the role of the various O ligands and Ni4+ centers in the catalysis,” explains Prof. Peter Strasser, TU Berlin.
“It is this gamma phase that makes our catalyst competitive with the current state-of-the-art iridium catalysts. Our work shows important similarities to iridium in the catalytic mechanism, but also some surprising molecular differences.”
The study has thus significantly advanced our understanding of the fundamental catalysis mechanisms of the new nickel-based electrode materials. In addition, the newly developed coating method for the membrane electrode promises excellent scalability. A first fully functional laboratory cell has already been tested at IMTEK. The work lays the foundation for further industrial evaluation and demonstrates that an AEM water electrolyzer can also be highly efficient.
More information: M. Klingenhof et al, High-performance anion-exchange membrane water electrolysers using NiX (X = Fe,Co,Mn) catalyst-coated membranes with redox-active Ni–O ligands, Nature Catalysis (2024). DOI: 10.1038/s41929-024-01238-w
A toy boat printed with the new solvent-free resin through digital light processing, demonstrating the details made possible through the new material. Credit: Duke University
Additive manufacturing (AM) has revolutionized many industries and holds the promise to affect many more in the not too distant future. While people are most familiar with the 3D printers that function much like inkjet printers, another type of AM offers advantages using a different approach: building objects with light one layer at a time.
One such technology is digital light processing (DLP). Widely used in both industrial and dental applications, DLP works by converting a liquid resin into a solid part using light, essentially pulling solid objects out of a shallow pool of resin one layer at a time.
A major challenge to using this 3D printing method, however, is that the resins need to have a low viscosity, almost like water, to function properly at high resolution. Plenty of polymers that would otherwise be useful in DLP printing are solids or too viscous, requiring solvents to dilute them to an appropriate consistency.
But adding these solvents also causes significant drawbacks, like poor dimensional accuracy after printing due to part shrinkage (up to 30%) coupled with residual stress that occurs as the solvent evaporates.
In a paper published in Angewandte Chemie International Edition, researchers at Duke University have invented a new solvent free polymer for DLP printing. Besides eliminating the shrinkage problem, the lack of solvent also results in improved mechanical properties of the part while maintaining the ability to degrade in the body.
“I wanted to create an inherently thin, low-viscosity material for DLP to use for degradable medical devices,” said Maddiy Segal, a MEMS Ph.D. candidate working in the laboratory of Matthew Becker, the Hugo L. Blomquist Distinguished Professor of Chemistry at Duke. “It took a lot of attempts, but eventually I was able to identify optimal monomers and a synthetic technique to create a solvent free polymer that can be used in a DLP printer without any dilution.”
Since the new material is one of the first solvent free resins that can be used in DLP printing, Segal was interested in testing the properties of parts made with it. She was excited to discover that the test parts did not shrink or distort at all, and in general, they were also stronger and more durable than those made with solvents. According to her findings, this is one of the first empirical demonstrations of increased mechanical properties from eliminating solvent use in DLP 3D printing of degradable polymers.
To create her new polymer, Segal analyzed the structure and properties of existing resins developed by the Becker Lab and others and modified the monomers and chain length in a step-by-step empirical approach to achieve the desired low-viscosity polymers. She essentially used a “guess and check” approach, adjusting the polymer’s monomers or “recipes” until she found a combination that worked.
The process isn’t entirely dissimilar from cooking a meal. It involves mixing specific combinations of ingredients, heating them, and then testing the results until achieving the desired outcome. In total, Segal experimented with about 60 different combinations before finally making the product she had been hoping for.
“Besides making a material that didn’t shrink and was stronger, I also wanted it to be useful for medical applications,” Segal said. “I’m trying to make prototype devices that are both biocompatible and degradable. Eliminating toxic solvents from the process will help me do that.”
Segal’s ultimate goal with this work is to apply this technique to biodegradable medical implants. Some materials used to make temporary medical implants today are not degradable and require multiple surgeries to not only implant them, but also remove them. Through her research, Segal aims to develop implants that can be degraded through the body’s natural processes.
Devices fabricated from this material could be implanted and designed to degrade naturally over time, eliminating the need for additional surgeries to remove the device. It could also potentially be used as a bone adhesive to hold fractures together temporarily or in soft robotics applications, where a soft, degradable material is needed.
“This kind of material is what makes this particular application the primary goal of my work,” Segal said. “And in reality, this technique could be used for any sort of implant that you would want to degrade after some time and not stay there forever.”
More information: Maddison I. Segal et al, Synthesis and Solvent Free DLP 3D Printing of Degradable Poly(Allyl Glycidyl Ether Succinate), Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202414016
Penn State professor of chemistry Joseph Cotruvo, Jr. and graduate student Wonseok Choi have been researching ways to separate rare earth elements using reengineered bacterial proteins that are found in nature. Credit: Michelle Bixby/Penn State
A newly discovered protein naturally houses an unusual binding site that can differentiate between rare earth elements, and researchers at Penn State have made it even better. Rare earth elements are key components used in everything from modern tech to gasoline production. The protein, called LanD, enriches neodymium and praseodymium over other similar rare earth elements (REEs) and has the potential to revolutionize industrial mining, researchers said.
Scientists at Penn State, led by professor of chemistry Joseph Cotruvo, Jr., recently published their LanD discovery in the Proceedings of the National Academy of Sciences.
“Each rare earth element has specific properties that make it useful for different applications, yet they are notoriously difficult to separate from each other,” said Cotruvo, who has filed a patent application related to the work. “Current industrial methods are inefficient and require heavy use of toxic chemicals, so a protein-based method for rare earth mining could make this process more efficient, greener, and less expensive.”
Close to 80% of the United States’ REE supply is imported, according to the United States International Trade Commission. Cotruvo explained that there is plenty of domestic raw material—including recycling old tech and industrial byproducts—to source REEs, but not all REEs are of equal value and application.
A more effective separation approach could help secure a national supply of REEs. The 17 REEs, including 15 metals called “lanthanides,” are commonly divided into “light” and “heavy” groups, with the light REEs being far more abundant. Unfortunately, however, the most common light REEs, lanthanum and cerium, have little value, whereas the other light REEs, praseodymium and (in particular) neodymium, are much more valuable.
Neodymium is a critical component of permanent magnets used in smartphones and renewable energy machinery like wind turbines, and praseodymium is often combined with neodymium for these applications.
Cotruvo’s lab previously identified another protein, LanM, that binds to all REEs with high specificity over any other metal. It does this in a fashion similar to a lock and key mechanism, with the protein being the lock and the REE a key. When the protein binds a REE, it undergoes a change in shape analogous to the key turning in the lock. The LanM proteins studied to date are very good at differentiating between heavy REEs, but they do not do well separating the light REEs, akin to a keyhole that fits a few different keys.
The newly discovered LanD protein, however, has improved separation abilities among the light REEs that are as good as, if not better than, current industry practices, Cotruvo said. With a unique, never-before-seen binding site—where the metal “key” can lock into the protein—LanD’s natural REE separation abilities can be engineered to be even more efficient, offering new hope for a greener rare earth element mining industry, he said.
“Current efforts are concentrated towards optimizing REE separation to make it less labor and material intensive,” Cotruvo said. “But this organism, Methylobacterium extorquens, a bacterium found abundantly in nature, makes proteins that seem to have already solved the problem.”
Methylobacterium extorquens is a species of bacteria known for its ability to grow on one-carbon compounds like methanol, and prefers to use specific REEs, mostly lanthanum and cerium, to support that growth.
When Cotruvo discovered LanM as the first high-affinity, high-specificity REE-binding protein six years ago, it was not clear why LanM needed to bind REEs so tightly in the cell. The discovery of LanD suggested an answer to that question: the two proteins work in tandem, with LanD binding to the lanthanides that the bacterium takes up but doesn’t need and delivering them to LanM, where they are sequestered. Those lanthanides, while not important to the bacteria, are the ones that are most important to tech production, Cotruvo said.
“The bacterium can take up a broader group of lanthanides than the small subset that it prefers to use, so it needs a way to prevent those undesirable lanthanides from interfering with the functions of the desirable lanthanides in the cell,” Cotruvo said. “LanD and LanM appear to work together to do this sorting, which explains why the previously identified LanM protein is good at lanthanide separations in general.”
He added that LanD, with its unique binding site, is much better for the light REEs specifically.
“LanD conveniently binds best to neodymium, which is by far the most valuable of the light REEs,” Cotruvo said. “While the naturally occurring LanD protein exhibits a preference for neodymium, we re-engineered it to more effectively be able to extract neodymium from a mixed solution of light REEs, disfavoring the other REEs that are of lesser value.”
The researchers found that engineering the LanD binding site allows separations yielding the desired neodymium and praseodymium to become much more effective. In future applications, the researchers said they hope to be able to whittle down the protein size and increase the preference of this binding site even more—and implement it in a larger-scale separation. The site can serve as the starting point for chemists and engineers to develop highly specific proteins to perfect sorting of other tricky-to-separate elements, Cotruvo said.
Furthermore, because LanD and LanM specialize in separation of different REEs, they could be used together in a process to separate complex REE sources like ores.
“The LanD protein is a promising way to improve REE separation practices,” he said. “And we’re working on making it even better, to pave a path toward more effective, greener rare earth mining.”
Paper co-authors include Wyatt Larrinaga and Jonathan Jung, graduate students in chemistry; Chi-Yun Lin, postdoctoral researcher in chemistry; and Amie Boal, professor of chemistry and of biochemistry and molecular biology.
More information: Wyatt B. Larrinaga et al, Modulating metal-centered dimerization of a lanthanide chaperone protein for separation of light lanthanides, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2410926121
Graphical abstract portraying the development of the LitChemPlast database. Credit: Wiesinger et al. 2024; DOI: 10.1021/acs.estlett.4c00355
Plastics contain a vast number of chemicals, some of which greatly impact the environment and human health. However, information on the presence of individual substances in plastic products is oftentimes not publicly available.
In a study, published on 29 October 2024, in Environmental Science and Technology Letters, a new publicly accessible database on chemicals measured in plastics is presented—LitChemPlast. The database contains over 3,500 substances measured in over 47,000 samples of plastic products across 372 studies.
The database shows that, due to inadequate control measures, mechanical recycling of plastics often leads to contamination with hazardous substances. For example, brominated flame retardants have frequently been detected in toys.
LitChemPlast is a significant step forward for better understanding of chemicals’ movement through different life stages of plastics. The database provides real-world chemical data, including on concentrations in products, that is useful for improving models estimating human and environmental exposure to plastic chemicals.
Moreover, LitChemPlast enables researchers, regulators and practitioners to identify chemicals that are of interest for regulation, to find safer materials for recycling, and to trace plastic pollution back to its source. It may also assist in identifying hazardous chemicals that are non-intentionally added to plastics (so called NIAS).
LitChemPlast also highlights research gaps, such as limited regional coverage in low- and middle-income countries, a lack of nontargeted measurements for non-food packaging categories, and a narrow focus on well-known hazardous chemicals.
Future concerted efforts in these understudied areas are essential to support the transition toward a safe and sustainable circular plastics economy, including achieving full transparency of chemicals in plastics.
The open database can serve as a starting point for guiding future research on identifying and quantifying chemicals in plastics, develop policy measures for ensuring safer material cycles, and support researchers, regulators and practitioners in better understanding the flow of chemicals throughout plastic products’ life cycles.
Finally, the authors encourage the scientific and regulatory communities to continue developing and using the database which is part of the larger PlastChem database that was published earlier in 2024.
Helene Wiesinger, Ph.D., currently scientific officer at the Food Packaging Forum and corresponding author of the study said, “Many scientific efforts focus only on whether plastics comply with current regulations, rather than whether they are actually safe. This is worrying because there are many chemicals in plastics that are not yet adequately regulated, meaning that potential risks could slip through the cracks.”
Zhanyun Wang, Ph.D., Scientist at Empa—Swiss Federal Laboratories for Materials Science and Technology and corresponding author of the study said, “Transparency of chemicals in plastics is crucial for ensuring safer material cycles, protecting human and environmental health, and fostering a sustainable circular economy.
“LitChemPlast marks a significant step in this direction, and we encourage widespread collaboration to further expand and refine this valuable resource.”
More information: LitChemPlast: An open database of chemicals measured in plastics, Environmental Science & Technology Letters (2024). DOI: 10.1021/acs.estlett.4c00355
