Category: Chemistry

A new type of catalyst breaks down polyolefin plastics into new, useful products. This project is part of a new strategy to reduce the amount of plastic waste and its impact on our environment, as well as recover value that is lost when plastics are thrown away. The catalyst was developed by a team from the Institute for Cooperative Upcycling of Plastic (iCOUP), a U.S. Department of Energy, Energy Frontier Research Center. The effort was led by Aaron Sadow, the director of iCOUP, scientist at Ames National Laboratory, and professor at Iowa State University; Andreas Heyden, professor at the University of South Carolina; and Wenyu Huang, scientist at Ames Lab and professor at Iowa State. The new catalyst is made only of earth-abundant materials, which they demonstrated can break carbon-carbon (CC) bonds in aliphatic hydrocarbons.

Aliphatic hydrocarbons are organic compounds made up of only hydrogen and carbon. Polyolefin plastics are aliphatic hydrocarbon materials composed of long chains of carbon atoms linked together to form strong materials. These materials are a big part of the plastic waste crisis. Wenyu Huang said, “More than half of produced plastics so far are polyolefin based.”

Polyolefin plastics are used everywhere in the modern world, including in shrink wrap and other packaging products, containers for liquids such as detergents or milk, fibers in waterproof clothing, dental floss, and electronics. Yet, as Andreas Heyden explained, polyolefins are some of the most difficult plastics to recycle and new approaches are needed. One such promising alternative to recycling is known as upcycling. This approach involves chemical transformation of the materials into higher value products.

One way to upcycle polyolefins is a chemical process called hydrogenolysis. During this process, a catalyst splits chains of molecules by cutting CC bonds and adding hydrogen. According to Aaron Sadow, catalysts that are used for hydrogenolysis are typically based on precious metals, such as platinum. Platinum is expensive because of its low abundance in the earth’s crust, and due to its effectiveness, it is used in many types of catalytic transformations.

To address both challenges of sustainability and economy, Heyden said, “We thought we’d be able to use earth-abundant elements to create much cheaper catalytic materials, and by assembling these elements in a certain way we might achieve a high selectivity and still very good activity.”

The team discovered that zirconia, an earth-abundant metal oxide, can cut CC bonds in aliphatic hydrocarbon polymers at about the same speed of precious metal catalysts. “We were surprised that we could do hydrogenolysis of CC bonds, using zirconium oxide as the catalyst. The conventional paradigm is that zirconia is not very reactive on its own,” said Sadow.

The key to its success is the structure of the catalyst, which was designed by Wenyu Huang and his group. “In this architecture, ultrasmall zirconia nanoparticles are embedded between two plates of mesoporous silica. The two silica plates are fused, with the zirconia embedded in the middle, like a sandwich,” Huang said. “The pores in the silica provide access to the zirconia, while the sandwich-like structure protects the zirconia nanoparticles from sintering or crystallization, which would make them less effective.”

Heyden’s team was in charge of modeling the reaction and understanding where and how the active site works under reaction conditions. “And so for that we do both quantum chemical modeling of the catalyst and the chemical reactions together with some classical chemical reactor modeling,” he explained. “And here we really saw the importance of that amorphous zirconia structure.”

According to Sadow, the idea to study zirconia in hydrogenolysis was based on previous pioneering research of polymer depolymerization using zirconium hydrides studied in the late 1990s. “Harnessing zirconium hydrides for hydrogenolysis is really nice chemistry,” he said. “The problem is those zirconium organometallic species are really air and water sensitive. So they have to be handled under the cleanest of conditions. Typically polymer waste is not pure and isn’t supplied as a clean and perfectly dry starting material. Using a zirconium hydride catalyst, you’d have to really worry about impurities that inhibit the chemistry.”

The new zirconia material the team developed is simply heated under vacuum before the reactions, and it stays active during the hydrogenolysis process. “Zirconium oxide is easily handled in air and then activated. It doesn’t require any kind of really specialized conditions, which was also exciting,” Sadow said. “Being able to take an air-exposed metal oxide, heat it with an alkane, and generate an organometallic is a really powerful reaction that enables this kind of hydrogenolysis process. It potentially could enable lots of interesting catalytic transformations of hydrocarbons that were previously not considered.”

This research is further discussed in the paper “Ultrasmall amorphous zirconia nanoparticles catalyse polyolefin hydrogenolysis,” written by Shaojiang Chen, Akalanka Tennakoon, Kyung-Eun You, Alexander L. Paterson, Ryan Yappert, Selim Alayoglu, Lingzhe Fang, Xun Wu, Tommy Yunpu Zhao, Michelle P. Lapak, Mukunth Saravanan, Ryan A. Hackler, Yi-Yu Wang, Long Qi, Massimiliano Delferro, Tao Li, Byeongdu Lee, Baron Peters, Kenneth R. Poeppelmeier, Salai C. Ammal, Clifford R. Bowers, Frédéric A. Perras, Andreas Heyden, Aaron D. Sadow, and Wenyu Huang, and published in the Nature Catalysis.

More information: Shaojiang Chen et al, Ultrasmall amorphous zirconia nanoparticles catalyse polyolefin hydrogenolysis, Nature Catalysis (2023). DOI: 10.1038/s41929-023-00910-x

Journal information: Nature Catalysis 

Provided by Ames Laboratory 

Snakes bite 5.4 million people each year—and roughly half are injected with venom, according to the WHO. Between 81,000 and 138,000 people die, while around three times as many suffer amputations and other permanent disabilities. Due to their size, children often suffer the most severe effects.

For 128 years, our primary treatment against snakebite has been using mixtures of polyclonal antibodies derived from immunized animal blood. Although they are proven effective, these medicines may cause adverse reactions that can sometimes be severe. So, the search for novel ways to treat severe snakebite envenoming is ongoing.

Recently, an international team of scientists led by DTU reached remarkable results and developed a new modernized prototype treatment that proves effective against the venom of African and Asian elapid snakes, such as some cobra, mamba, and krait species—many of which are among the world’s deadliest.

“We have previously developed antibodies against the venom toxins from single snake species; however, our new results demonstrate that our technology has great potential in neutralizing toxins from multiple species, even from different continents. This broadened cross-neutralization capacity is very promising. It could provide the basis for more effective treatments for snakebite victims in the future,” says Andreas Hougaard Laustsen-Kiel, a professor at DTU Bioengineering.

He conducted the research with colleagues at DTU, ETH Zurich, Universidad de Costa Rica, and industrial partners Sophion Bioscience and IONTAS. Their work is published in Nature Communications.

New antibody works against several neurotoxins

In essence, their approach is to develop antibodies of fully human origin, which offer fewer adverse reactions, competitive costs, and, when fine-tuned, superior efficacy. They use phage display technology, a popular in vitro methodology within drug discovery, to select antibodies that bind well to the toxins in the venom, enabling broad neutralization.

“There has been a revolution in recombinant antibody technology over the last three decades. I am delighted to be involved in these efforts to direct phage display technology to the blight of snakebite envenomation,” says John McCafferty, the inventor of antibody phage display. He founded IONTAS and has recently established a new anti-venom group at the University of Cambridge.

Deliberately selecting hundreds of antibody candidates and testing the most promising against toxins in different snake venoms, the researchers found that one in particular (2554_01_D11) was especially potent and broadly neutralizing. It bound to various neurotoxins present in the venoms of the monocled cobra, the forest cobra, the spectacled cobra, the king cobra, the black mamba, and the many-banded krait.

Subsequent in vivo studies showed that the antibody prevented or delayed death from venom. For the monocled cobra specifically, the antibody completely prevented lethality in envenomed mice.

“In light of the positive results regarding the neutralization of venom from the monocled cobra, we mimicked a true rescue situation, injecting mice with cobra venom and then administering the antibody. And sure enough, we were able to prevent death when the antibody was injected rapidly after envenoming,” says José María Gutiérrez, emeritus professor of Instituto Clodomiro Picado, University of Costa Rica.

While the antibody could not prevent death from black mamba venom, survival was prolonged by several hours, suggesting that the antibody provided a partial neutralization of the venom.

“These are remarkable results,” says Andreas Hougaard Laustsen-Kiel:

“The antibody we used worked against different neurotoxins derived from different snake species from different parts of the world. These toxins are far from identical but share some crucial similarities in their structure. And apparently, these are just enough for our antibody to display extensive cross-reactivity. We have yet to establish the boundaries of what this antibody can neutralize. Still, we would like to see if it shows the same promise concerning neurotoxins from, for example, the blue krait, the banded krait, and the Egyptian cobra.”

The researchers expect antibodies, such as 2554_01_D11, will be helpful when designing future envenoming therapies. At the same time, however, they stress that their pipeline for discovery could be useful in developing other broadly neutralizing antibodies against toxins from other animals, bacteria, viruses, and parasites or even in developing cancer therapies.

More information: Line Ledsgaard et al, Discovery and optimization of a broadly-neutralizing human monoclonal antibody against long-chain α-neurotoxins from snakes, Nature Communications (2023). DOI: 10.1038/s41467-023-36393-4

Journal information: Nature Communications 

Provided by Technical University of Denmark 

An air filter made out of corn protein instead of petroleum products can concurrently capture small particulates as well as toxic chemicals like formaldehyde that current air filters can’t.

The research could lead to better air purifiers, particularly in regions of the world that suffer from very poor air quality. Washington State University engineers report on the design and tests of materials for this bio-based filter in the journal Separation and Purification Technology.

“Particulate matter is not that challenging to filter but to simultaneously capture various kinds of chemical gas molecules, that’s more significant,” said Katie Zhong, professor in WSU’s School of Mechanical and Materials Engineering and a corresponding author on the paper. “These protein-based air filtering materials should be very promising to capture multiple species of air pollutants.”

Poor air quality is a factor in diseases such as asthma, heart disease and lung cancer. Commercial air purifiers remove tiny particles in soot, smoke or car exhaust, which could be inhaled directly into the lungs, but air pollution also often contains other hazardous gaseous molecules, such as carbon monoxide, formaldehyde and other volatile organic compounds.

With micron-sized pores, typical high efficiency particulate air filters, also known as HEPA filters, can capture the small particles but aren’t able to capture gaseous molecules. They are most often made of petroleum products and glass, which leads to secondary pollution when old filters are thrown away, Zhong said.

The WSU researchers developed a more environmentally friendly air filter made from corn protein fibers that was able to simultaneously capture 99.5% of small particulate matter, similar to commercial HEPA filters, and 87% of formaldehyde, which is higher than specially designed air filters for those types of toxics.

The researchers chose corn to study because of its abundance as an agricultural product in the U.S. The corn protein is also hydrophobic, which means that the protein repels water and could work well in a moist environment such as in a mask.

The amino acids in the corn protein are known as functional groups. When exposed at the protein’s surface, these functional groups act like multiple hands, grabbing the toxic chemical molecules. The researchers demonstrated this by exposing a functional group at the protein surface, where it grabbed formaldehyde. They theorize that further rearrangement of the proteins could develop a tentacle-like set of functional groups that could grab a variety of chemicals from the air.

“From the mechanism, it’s very reasonable to expect that this protein-based air filter could capture more species of toxic chemical molecules,” Zhong said.

The three-dimensional structure that they developed also offers more promise for a simple manufacturing method than thin films of proteins that the research team developed previously. They used a small amount of a chemical, polyvinyl alcohol, to glue the nanofibers together into a lightweight foam-like material.

“This work provides a new route to fabricating environmentally friendly and multi-functional air filters made from abundant natural biomass,” Zhong said. “I believe this technology is very important for people’s health and our environment, and it should be commercialized.”

The researchers would like to do more testing, including using a variety of functional group structures and other toxic chemical molecules. In addition to Zhong, the work was conducted by graduate student Shengnan Lin, Ming Luo, Flaherty assistant professor in the WSU School of Mechanical and Materials Engineering, and post-doctoral fellow Xuewei Fu.

More information: Shengnan Lin et al, A protein aerogel with distinctive filtration capabilities for formaldehyde and particulate pollutants, Separation and Purification Technology (2023). DOI: 10.1016/j.seppur.2023.123179

Provided by Washington State University 

Huge amounts of technical or Kraft lignin are formed during pulp production. This lignin is difficult to process and so is usually just incinerated for heat production. A team of researchers, reporting in the journal Angewandte Chemie, have now succeeded in developing a green method for recovering the flavoring agent vanillin from this raw material. The materials used in this method are all recycled from papermaking processes, and only power and heat need to be added.

Lignin and cellulose are essential components of wood. The molecular structure of lignin contains the structure of vanillin, the main flavoring substance from the vanilla plant, meaning that vanillin can be produced from lignin, although the process is laborious. At present, lignosulfonate, a substance also formed in some papermaking methods, is used for the industrial production of vanillin.

In order to make paper from wood fibers, all lignin has to be removed, otherwise the paper will take on the brown color of the lignin. However, the waste product in the most commonly used pulping method for industrial papermaking, the Kraft method, is not lignosulfonate but rather a technical lignin referred to as Kraft lignin. Kraft lignin is much harder to oxidize and depolymerize than other lignins and so at present cannot be used as a raw material. Instead, it is simply burnt as fuel for papermaking processes.

Siegfried Waldvogel and a team of researchers at the University of Mainz, Germany, have now discovered a method for producing vanillin from Kraft lignin. They say the method is environmentally friendly as it does not use any harmful chemicals, and it is convenient as it uses the raw materials present in pulp production. A key step in this new method is the production of the oxidizer by electrolysis of sodium carbonate.

“The idea started many years ago when playing around with innovative electrode materials that make it possible to take simple carbonates and make an oxidizer from them,” explains Waldvogel. One of these electrode materials was boron-doped diamond, and the researchers observed that, when carrying out electrolysis using this electrode material, the sodium carbonate was readily oxidized to peroxodicarbonate. The team then found out that this oxidizer was strong enough to degrade stubborn Kraft lignin.

The team report that, when freshly produced, the peroxodicarbonate depolymerizes and oxidizes Kraft lignin with similar effectiveness to traditional methods. However, in a departure from these conventional methods, no environmentally harmful chemicals are used or produced in the process.

The need for vanillin is high: “Most people only know of it from vanilla flavoring, but it is present in most chocolates and perfumes as well,” explains Waldvogel. Vanillin is also a precursor material for pharmaceuticals. All these uses mean that around twenty thousand tons of vanillin are needed every year, and the vanilla plant alone cannot keep up with this demand.

Until now it wasn’t possible to utilize Kraft lignin to meet demand, but the first steps are being made. Waldvogel and the team are already working on a pilot plant to test scaling up.

More information: Michael Zirbes et al, Peroxodicarbonate as a Green Oxidizer for the Selective Degradation of Kraft Lignin into Vanillin, Angewandte Chemie International Edition (2023). DOI: 10.1002/anie.202219217

Journal information: Angewandte Chemie International Edition  , Angewandte Chemie 

Provided by Wiley 

Many owners of electric cars have wished for a battery pack that could power their vehicle for more than a thousand miles on a single charge. Researchers at the Illinois Institute of Technology (IIT) and U.S. Department of Energy’s (DOE) Argonne National Laboratory have developed a lithium-air battery that could make that dream a reality. The team’s new battery design could also one day power domestic airplanes and long-haul trucks.

The main new component in this lithium-air battery is a solid electrolyte instead of the usual liquid variety. Batteries with solid electrolytes are not subject to the safety issue with the liquid electrolytes used in lithium-ion and other battery types, which can overheat and catch fire.

More importantly, the team’s battery chemistry with the solid electrolyte can potentially boost the energy density by as much as four times above batteries”>lithium-ion batteries, which translates into longer driving range.

“For over a decade, scientists at Argonne and elsewhere have been working overtime to develop a lithium battery that makes use of the oxygen in air,” said Larry Curtiss, an Argonne Distinguished Fellow. “The lithium-air battery has the highest projected energy density of any battery technology being considered for the next generation of batteries beyond lithium-ion.”

In past lithium-air designs, the lithium in a lithium metal anode moves through a liquid electrolyte to combine with oxygen during the discharge, yielding lithium peroxide (Li₂O₂) or superoxide (LiO₂) at the cathode. The lithium peroxide or superoxide is then broken back down into its lithium and oxygen components during the charge. This chemical sequence stores and releases energy on demand.

The team’s new solid electrolyte is composed of a ceramic polymer material made from relatively inexpensive elements in nanoparticle form. This new solid enables chemical reactions that produce lithium oxide (Li₂O) on discharge.

“The chemical reaction for lithium superoxide or peroxide only involves one or two electrons stored per oxygen molecule, whereas that for lithium oxide involves four electrons,” said Argonne chemist Rachid Amine. More electrons stored means higher energy density.

The team’s lithium-air design is the first lithium-air battery that has achieved a four-electron reaction at room temperature. It also operates with oxygen supplied by air from the surrounding environment. The capability to run with air avoids the need for oxygen tanks to operate, a problem with earlier designs.

The team employed many different techniques to establish that a four-electron reaction was actually taking place. One key technique was transmission electron microscopy (TEM) of the discharge products on the cathode surface, which was carried out at Argonne’s Center for Nanoscale Materials, a DOE Office of Science user facility. The TEM images provided valuable insight into the four-electron discharge mechanism.

Past lithium-air test cells suffered from very short cycle lives. The team established that this shortcoming is not the case for their new battery design by building and operating a test cell for 1000 cycles, demonstrating its stability over repeated charge and discharge.

“With further development, we expect our new design for the lithium-air battery to also reach a record energy density of 1200 watt-hours per kilogram,” said Curtiss. “That is nearly four times better than lithium-ion batteries.”

This research was published in a recent issue of Science. Argonne authors include Larry Curtiss, Rachid Amine, Lei Yu, Jianguo Wen, Tongchao Liu, Hsien-Hau Wang, Paul C. Redfern, Christopher Johnson and Khalil Amine. Authors from IIT include Mohammad Asadi, Mohammadreza Esmaeilirad and Ahmad Mosen Harzandi. And Authors from the University of Illinois Chicago include Reza Shahbazian-Yassar, Mahmoud Tamadoni Saray, Nannan Shan and Anh Ngo.

More information: Alireza Kondori et al, A room temperature rechargeable Li 2 O-based lithium-air battery enabled by a solid electrolyte, Science (2023). DOI: 10.1126/science.abq1347

Journal information: Science 

Provided by Argonne National Laboratory

A research group from VTT Technical Research Center of Finland has unlocked the secret behind the extraordinary mechanical properties and ultra-light weight of certain fungi. The complex architectural design of mushrooms could be mimicked and used to create new materials to replace plastics. The research results were published on February 22, 2023, in Science Advances.

VTT’s research shows for the first time the complex structural, chemical, and mechanical features adapted throughout the course of evolution by Hoof mushroom (Fomes fomentarius). These features interplay synergistically to create a completely new class of high-performance materials.

Research findings can be used as a source of inspiration to grow from the bottom up the next generation of mechanically robust and lightweight sustainable materials for a variety of applications under laboratory conditions. These include impact-resistant implants, sports equipment, body armor, exoskeletons for aircraft, electronics, or surface coatings for windshields.

Unraveling the unique microstructure of Fomes fungus

Nature provides insights into design strategies evolved by living organisms to construct robust materials. The tinder fungus Fomes is a particularly interesting species for advanced material applications. It is a common inhabitant of the birch tree, with the important function of releasing carbon and other nutrients from the dead trees. The Fomes fruiting bodies are ingeniously lightweight biological designs, simple in composition but efficient in performance. They fulfill a variety of mechanical and functional needs, for example, protection against insects or fallen branches, propagation, survival (unpreferred texture and taste for animals), and a thriving multi-year fruiting body through changing seasons.

VTT’s new research reveals that the Fomes fruiting body is a functionally graded material with three distinct layers that undergo multiscale hierarchical self-assembly.

“The mycelium network is the primary component in all layers. However, in each layer, mycelium exhibits a very distinct microstructure with unique preferential orientation, aspect ratio, density, and branch length. An extracellular matrix acts as a reinforcing adhesive that differs in each layer in terms of quantity, polymeric content, and interconnectivity,” said Pezhman Mohammadi, Senior scientist at VTT.

Alterable structure enables different features

The structure of Fomes is extraordinary because it can be modified to create diverse materials with distinct performances. Minimal changes in the cell morphology and extracellular polymeric composition result in diverse materials with different physico-chemical features that surpass most natural and man-made materials. While traditional materials are usually confronted by property tradeoffs (e.g., increasing weight or density to increase strength or stiffness), Fomes achieves high performance without this tradeoff.

“Architectural design and biochemical principles of the Fomes fungus open new possibilities for material engineering, such as manufacturing ultra-lightweight technical structures, fabricating nanocomposites with enhanced mechanical properties, or exploring new fabrication routes for the next generation of programmable materials with high-performance functionalities.

“Furthermore, growing the material using simple ingredients could help to overcome the cost, time, mass production, and sustainability of how we make and consume materials in the future,” explains Pezhman.

More information: Robert Pylkkänen et al, The complex structure of Fomes fomentarius represents an architectural design for high-performance ultralightweight materials, Science Advances (2023). DOI: 10.1126/sciadv.ade5417

Journal information: Science Advances 

Provided by VTT Technical Research Centre of Finland 

A recent study published in the journal Science China Life Sciences was led by Dr. Nan Qiao (Laboratory of Health Intelligence, Huawei Cloud Computing Technologies), Dr. Hualiang Jiang (Shanghai Institute of Materia Medica, Chinese Academy of Sciences) and Dr. Mingyue Zheng (Shanghai Institute of Materia Medica, Chinese Academy of Sciences).

“Over the past year, the parameter size of the language model has continued to grow, exceeding 175 billion GPT3s. Recently, ChatGPT, a new-generation language model, interacts with users in a more real-life way, such as answering questions, admitting mistakes, questioning incorrect questions or rejecting inappropriate requests, and is even thought to subvert search engines,” Dr. Qiao says.

In addition to language models, areas such as image, video and multimodality were refreshed by transformer architectures these years at the same time. These large models usually use self-supervised learning, which can greatly reduce the workload and achieve better performance in long tail tasks. However, in the AI for drug discovery field, there has been no really big model to accelerate drug research and development and improve the efficiency.

Xinyuan Lin and Zhaoping Xiong, together with lab director Nan Qiao, sought to build a big model for drug discovery that can be used for drug discovery tasks such as molecular property prediction, molecular generation and optimization. The team proposes a novel graph-to-sequence (graph2seq) asymmetric structure, which is different from the classical sequence-to-sequence (seq2seq) and graph-to-graph (graph2graph) variational auto-encoding processes.

The model is pre-trained for 1.7 billion druglike molecules (currently the largest), the input is a two-dimensional undirected cyclic graph of drug-like molecules, and the output is the corresponding chemical formula or SMILES string. Humans read images of chemical structures and write down the text of the corresponding formulas, so after billions of repetitions, Pangu can learn the relationship between chemical structures and formula strings, similar to human cognitive transformations.

After pre-training with 1.7 billion druglike small molecules, the model achieved state-of-the-art results in 20 drug discovery tasks, including molecular property prediction. (predicting ADMET properties, compound-protein interactions, drug-drug interactions, and chemical reaction yields) , molecular generation and molecular optimization.

The Pangu Molecular Generator has also generated a new drug screening library of 100 million drug-like small molecules with a novelty of 99.68%, which can also effectively generate new compounds with similar physicochemical properties to a given distribution. This library can be used to supplement the existing compound database. In addition, the Pangu Molecular Optimizer can optimize the chemical structure of the starting molecule and improve the characteristics of the molecule of interest.

More information: Xinyuan Lin et al, PanGu Drug Model: learn a molecule like a human, Science China Life Sciences (2022). DOI: 10.1007/s11427-022-2239-y

Provided by Science China Press 

A team from Florida State University and Lawrence Berkeley National Laboratory has developed a new strategy to build solid-state batteries that are less dependent on specific chemical elements, particularly pricey metals with supply chain issues.

Their work was published in the journal Science.

Bin Ouyang, an associate professor in the Department of Chemistry and Biochemistry, first developed the idea for this work while finishing his postdoctoral research at the University of California, Berkeley, along with his co-first author Yan Zeng, and their postdoctoral adviser Gerbrand Ceder. In their study, they demonstrated that a mix of various solid-state molecules could result in a more conductive battery that was less dependent on a large quantity of an individual element.

“There’s no hero element here,” Ouyang said. “It’s a collective of diverse elements that make things work. What we found is that we can get this highly conductive material as long as different elements can assemble in a way that atoms can move around quickly. And there are many situations that can lead to these so-called atom diffusion highways, regardless of which elements it may contain.”

Solid-state batteries operate almost the same way as other batteries—they store energy and then release it to power devices. But rather than liquid or polymer gel electrolytes found in lithium-ion batteries, they use solid electrodes and a solid electrolyte. This means that a higher energy density can occur in the battery because lithium metal can be used as the anode. Additionally, they have lower fire risk and potentially increase the mileage of electric vehicles.

However, many of the batteries constructed thus far are based on critical metals that are not available in large quantities. Some aren’t found at all in the United States. Given that the U.S. and many other countries plan to replace all vehicles with electric vehicles by 2050, there is an enormous strain being put on the supply chain for critical metals.

The research team considered the straightforward path of using one element to replace commonly used ones, but that approach raised its own supply chain issues. Instead, the team approached the problem by designing materials that weren’t beholden to one specific element. For example, instead of creating a battery made with germanium, which rarely appears naturally in high concentrations, the team created a mixture of titanium, zirconium, tin, and hafnium.

“With such a feature, we need to assemble those elements in a way so that we have many ‘good’ local configurations which can form a network for the fast transport of atoms or energy,” Ouyang said. “Think of it as a highway. As long as there is a connected highway for atom diffusion, the atoms can move quickly.”

This study opened a new area of research for Ouyang and his colleagues as they work to build more efficient solid-state batteries.

Government, research and academia have heavily invested in the development of solid-state batteries because batteries that contain liquids are more prone to overheating, fire and loss of charge. Smaller solid-state batteries already power devices like smartwatches and pacemakers. Still, many manufacturers believe that breakthroughs in this area could mean solid-state batteries could one day be helping electric vehicles or aircraft.

More information: Yan Zeng et al, High-entropy mechanism to boost ionic conductivity, Science (2022). DOI: 10.1126/science.abq1346

Journal information: Science 

Provided by Florida State University 

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Researchers at Kanazawa University report in Angewandte Chemie International Edition how the formation and deformation speed of interlocked molecular structures called rotaxanes can be tuned—a discovery that may lead to an enhanced functionality of rotaxanes as building blocks for molecular machines.

Rotaxanes are molecules with a two-component structure: a dumbbell-shaped part (the “axle”) threaded through a ring-like part (the “wheel”). The two components are normally not chemically bound but mechanically interlocked. Rotaxanes are of particular interest because of their potential as building blocks for molecular machines, exploiting the rotation of the wheel or its motion along the axle.

An extra level of rotaxane functionality is achieved if the wheel can be removed from the axle (dissociation) and put back (formation) in a controlled way. Shigehisa Akine, Yoko Sakata, and colleagues from Kanazawa University have now developed a new approach for controlled rotaxane dissociation and formation.

Earlier methods for the formation and dissociation of rotaxanes involved chemical modifications. One approach is to chemically replace one end (also called stopper) of the axle by a less bulky one so that the wheel can slide over it more easily. Another is to enlarge the wheel size. These two modifications result in “pseudorotaxanes,” however: rotaxanes for which the wheel can easily slide off the structure since at least one stopper doesn’t block the wheel anymore.

Akine, Sakata, and colleagues performed experiments with a proper rotaxane. At the center of the dumbbell is a palladium atom. At opposite sides to it, two identical organic groups (called 2,3-diaminotriptycene) are bound. For the wheel, they used a so-called crown ether, consisting of 9 oxygen atoms and 18 carbon atoms arranged in a symmetric, cyclic way.

The palladium rotaxanes did not form immediately when mixing axle and wheel parts. Nuclear magnetic resonance measurements showed that only after 10 hours, conversion to the rotaxane structure—confirmed by X-ray analysis—was complete. The researchers found that the rotaxane formation involves a temporary cleavage of the axle part: one 2,3-diaminotriptycene group disconnects from the palladium atom, the crown ether wheel then slides onto the part with the palladium atom, after which the “loose” 2,3-diaminotriptycene group connects back. A similar cleavage process, with the wheel leaving the structure, results in dissociation.

Akine, Sakata, and colleagues then looked for a way to speed up the processes. They discovered that halide ions, and in particular bromine ions, had an accelerating effect on both formation and dissociation. The former was accelerated 27 times with the right amount of bromine ions added, and the latter 52 times. To achieve dissociation, though, the scientists had to add cesium ions to the mixture. A cesium ion easily forms a complex with a crown ether wheel; the cesium ion sits in the center of the wheel and prevents it from sliding back onto an axle molecule.

The use of accelerators as shown for this particular palladium-containing rotaxane is expected to be applicable to other molecules too. The scientists conclude that this strategy can be applied to the speed tuning of the formation/dissociation of various types of interlocked molecules based on metal coordination bonds.

Rotaxanes background

A rotaxane is a mechanically interlocked molecular structure consisting of a dumbbell-shaped molecule (axle) threaded through a circular molecule (wheel). The two components are locked because the ends of the dumbbell (called stoppers) are bigger than the internal diameter of the wheel, which prevents unthreading (dissociation) of the components. (A significant amount of distortion would be required to achieve unthreading.)

Most of the interest in rotaxanes and other mechanically interlocked molecular architectures lies in their potential as building blocks for molecular machines—nanoscale components that produce mechanical motion in response to particular external stimuli. Rotaxanes can act as molecular shuttles, for example: the wheel can be made to slide between the stoppers, from one side to the other, by stimuli such as light, solvents or ions.

Shigehisa Akine, Yoko Sakata, and colleagues from Kanazawa University have now studied the formation and dissociation process of a palladium-containing rotaxane. They discovered an intermediate cleavage phase in the formation/dissociation process and found that both the formation and the dissociation process can be significantly sped up by introducing accelerators, such as bromine ions.

More information: Yoko Sakata et al, Speed Tuning of the Formation/Dissociation of a Metallorotaxane, Angewandte Chemie International Edition (2023). DOI: 10.1002/anie.202217048

Journal information: Angewandte Chemie International Edition 

Provided by Kanazawa University