Category: Chemistry

Plasma engineers and chemists at the University of Illinois have demonstrated a sustainable way of forming carbon-carbon bonds—the bedrock of all organic compounds—without expensive, rare metals that are typically required as catalysts in bond-forming organic reactions.

Through an interdisciplinary collaboration, Illinois researchers in Nuclear, Plasma, and Radiological Engineering, Bioengineering and Chemistry combined their expertise to develop this novel metal-catalyst-free approach that could lead organic chemistry in a new direction, according to the researchers.

In the study, “Plasma Electrochemistry for Carbon−Carbon Bond Formation via Pinacol Coupling,” published in the Journal of the American Chemical Society, the team explains how they used electricity and a plasma-liquid process to generate solvated electrons to form carbon-carbon bonds in a pinacol coupling reaction. C-C bond formation is widely used in the production of many man-made chemicals like pharmaceuticals and plastics.

According to researchers, this is the first example of plasma-generated solvated electrons for an organic redox coupling reaction and offers a sustainable solution for similar reductive organic reactions. Typically, such reactions require metal reagents or catalysts that are not only scarce and costly, but also present safety or environmental issues and sometimes require heat in the reactive process.

“Our process only really requires electricity—other than the reactor cell and equipment—and in the future hopefully this can come from renewable sources like wind or solar or nuclear, so the whole process is sustainable,” said study co-author R. Mohan Sankaran, Donald Biggar Willett Professor in Engineering in the Department of Nuclear, Plasma, and Radiological Engineering.

Sankaran said their process produces electrons from argon gas and then injects these electrons into solution to generate solvated electrons, a powerful chemical species typically generated by radiolysis, which requires complex equipment.

“In our case, the solvated electrons are generated with just a DC power supply and a relatively simple electrolysis reactor that houses our electrodes and the solution where we have the organic substrates,” said Sankaran, whose group has been developing atmospheric pressure plasmas for over a decade, and in previous work, has applied this type of plasma-liquid process to other applications—nanoparticle synthesis and nitrogen fixation. “We were curious about organic chemistry, but we had no expertise in either the methods or the characterization.”

Sankaran, who reached out to Jeffrey S. Moore, research professor in chemistry, for expertise, said this project would not have been possible without the collaboration.

“Most of this is chemistry—something that my group doesn’t do—and there is no way we would have succeeded without having someone with the requisite chemistry background,” Sankaran said.

Jian Wang, lead author of the study and a postdoctoral associate in the Moore group, brought his expertise in chemistry and materials science to the project and worked with plasma expert Scott Dubowsky, study co-author and research scientist in the Sankaran group, to learn the plasma-liquid process and then identify an organic reaction to study.

Wang experimented with different organic substrates, characterizing reactions using various analytical techniques, and ultimately chose pinacol coupling, because it is a well-established reaction for carbon-carbon bond formation and a reaction they believed could work with the plasma liquid process. Matthew Confer, another co-author and a postdoctoral researcher in the group of Rohit Bhargava, professor of bioengineering and faculty affiliate in chemistry, used his computational chemistry expertise to model how the pinacol product was formed from the solvated electron chemistry and radical reactions.

“This is an excellent illustration of the golden rule for a successful collaboration: the best collaborators share a common goal but bring different expertise,” said Moore, Stanley O. Ikenberry Research Professor, Professor Emeritus of Chemistry, and Howard Hughes Medical Institute Professor.

There have been a few studies where a plasma was used for an organic reaction, Sankaran explained, but the reactions and the mechanism were different.

“The plasma was typically used to oxidize a chemical and the chemical that was produced by the plasma was a reactive oxygen species. In our case, the reaction we studied was reduction which required electrons (or solvated electrons), and the reduction led to the formation of new carbon-carbon bonds,” Sankaran said.

Their next step will be applying their process to another organic chemistry reaction and showing that this approach is general and can be applied to different reactions.

“We also hope to find a reaction that is difficult to carry out, because it has a low yield, requires harsh conditions, or there is no active metal,” said Sankaran, who also explained that they hope to address one issue their study revealed—that yields can be limited by mass transfer limitations. “Our reaction occurs at the interface of a plasma and the solution, and for the substrate to reach the interface, it must diffuse. We can address this issue by incorporating liquid flow which will enhance mass transport by convection. Liquid flow will also potentially help us scale up the process whereby we can make a product continuously.”

Wang said one particular challenge for plasma electrochemistry as an alternative to more traditional organic synthesis is that the plasma is so energetic.

“Although we are able to achieve relatively good yield and selectivity, the control is still not as good as for example traditional chemistries with metal catalysts, or electro- or photocatalytic chemistries,” Wang said. “We are working on improving the controllability and selectivity right now.”

More information: Jian Wang et al, Plasma Electrochemistry for Carbon–Carbon Bond Formation via Pinacol Coupling, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c01779

Journal information: Journal of the American Chemical Society 

Provided by University of Illinois at Urbana-Champaign, College of Liberal Arts and Sciences

Scientists from the Radboud University have developed synthetic molecules that resemble real organic molecules. A collaboration of researchers, led by Alex Khajetoorians and Daniel Wegner, can now simulate the behavior of real molecules by using artificial molecules. In this way, they can tweak properties of molecules in ways that are normally difficult or unrealistic, and they can understand much better how molecules change.

Their paper is published in the journal Science.

Emil Sierda, who was in charge of conducting the experiments at Radboud University said, “A few years ago we had this crazy idea to build a quantum simulator. We wanted to create artificial molecules that resembled real molecules. So we developed a system in which we can trap electrons. Electrons surround a molecule like a cloud, and we used those trapped electrons to build an artificial molecule.” The results the team found were astonishing. Sierda says, “The resemblance between what we built and real molecules was uncanny.”

Changing molecules

Alex Khajetoorians, head of the Scanning Probe Microscopy (SPM) department at the Institute for Molecules and Materials of Radboud University said, “Making molecules is difficult enough. What is often harder, is to understand how certain molecules react, for example how they change when they are twisted or altered.”

How molecules change and react is the basis of chemistry, and leads to chemical reactions, like the formation of water from hydrogen and oxygen. “We wanted to simulate molecules, so we could have the ultimate toolkit to bend them and tune them in ways that are nearly impossible with real molecules. In that way we can say something about real molecules, without making them, or without having to deal with the challenges they present, like their constantly changing shape.”

Using this simulator, the researchers created an artificial version of one of the basic organic molecules in chemistry, benzene. Benzene is the first component for a number of chemicals, like styrene, which is used to make polystyrene. Khajetoorians says, “By making benzene, we simulated a textbook organic molecule, and built a molecule that is made up of elements that are not organic.” In addition, the molecules are 10 times bigger than their real counterparts, which makes them easier to work with.

Practical uses

The uses of this new technique are endless. Daniel Wegner, assistant professor within the SPM department says, “We have only begun to imagine what we can use this for. We have so many ideas that it is hard to decide where to start.” By using the simulator, scientists can understand molecules and their reactions much better, which will help in every scientific field imaginable.

Wegner adds, “New materials for future computer hardware are really hard to make, for instance. By making a simulated version, we can look for the novel properties and functionalities of certain molecules and evaluate whether it will be worth making the real material.”

In the far future, all kinds of things may be possible: understanding chemical reactions step by step like in a slow-motion video, or making artificial single-molecule electronic devices, like shrinking the size of a transistor on a computer chip. Quantum simulators are even suggested to perform as quantum computers. Sierda says, “But that’s a long way to go, for now we can start by beginning to understand molecules in a way we never understood before.”

More information: E. Sierda et al, Quantum simulator to emulate lower-dimensional molecular structure, Science (2023). DOI: 10.1126/science.adf2685. www.science.org/doi/10.1126/science.adf2685

Journal information: Science 

Provided by Radboud University Nijmegen 

by Leibniz-Institut für Polymerforschung Dresden e. V.

Living organisms use powerful physical principles to control interactions at their surfaces. Researchers at the Leibniz Institute of Polymer Research Dresden, Leipzig University and TU Dresden have now discovered why cholesterol-containing surfaces can exhibit greatly reduced attachment of proteins and bacteria.

The interdisciplinary team led by Carsten Werner had previously identified cholesterol as a component of the skin of widespread invertebrates (collembolae), which breathe through their skin and therefore need to protect it from contamination. In their paper published in Nature on June 22, 2023, the scientists have now elucidated a repulsive mechanism of cholesterol-containing surfaces.

Using experiments, simulations and thermodynamic analyses, they were able to show how the spontaneous change in the orientation of interfacial cholesterol molecules creates an “entropic barrier” that makes cholesterol-containing surfaces repellent.

The development of synthetic materials using the discovered principle is promising, as it is important for many products and technologies to effectively minimize the attachment of biomolecules and bacteria. However, such “translation” of the effect to scalable, robust surface functionalization requires further research.

More information: Jens Friedrichs et al, Entropic repulsion of cholesterol-containing layers counteracts bioadhesion, Nature (2023). DOI: 10.1038/s41586-023-06033-4

Journal information: Nature 

Provided by Leibniz-Institut für Polymerforschung Dresden e. V.

by Leibniz-Institut für Zoo- und Wildtierforschung (IZW) im Forschungsverbund Berlin e.V.

Mammalian seminal fluid contains a variety of proteins secreted by the accessory sex glands that are important for the processes involved in fertilization. One of these proteins, which is found in ungulates—and in particularly large quantities in boars—is the spermadhesin AQN-3.

A science team from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), the Humboldt University of Berlin (HUB) and the Leibniz Institute for Molecular Pharmacology has studied the protein and discovered unexpected properties that could help sperm remain functional until they reach the egg. The findings are published in the scientific journal Chemistry and Physics of Lipids.

The proteins in seminal fluid are important for the survival of male germ cells and their species-specific interactions with the components of the female genital tract. There are five different spermadhesins in the seminal fluid of ungulates. Spermadhesins are found in particularly large quantities in porcine semen. In order to understand the function of these proteins, which—as the name suggests—attach themselves to the sperm surface, the spermadhesins AWN and AQN-3, named after the letter code of the first three amino acids of the protein sequence, have so far been artificially produced in bacteria.

In a previous study, the scientific team led by Karin Mueller and Beate Braun from the Leibniz-IZW showed that AWN binds specifically to negatively charged lipids. However, these are primarily found on the half of the cell membrane facing the inside of the sperm cell. This raises the question of how the spermadhesins attach to the surface of the sperm? Since it is known from work of other scientific groups that AWN forms aggregates with AQN-3, it was now investigated whether AQN-3 binds to typical lipids on the outside of the sperm membrane, such as phosphatidylcholine and sphingomyelin.

“Surprisingly, the applied model systems with lipid strips and vesicles showed that AQN-3 also binds selectively with negatively charged lipids, such as phosphatidic acid and various phosphatidylinositol phosphates,” explains Mueller. In addition, AQN-3 has a strong tendency to form aggregates with itself and other proteins.

Studies by other scientific groups describe yet another protein in the aggregates of native AWN and AQN-3 in seminal fluid, the protein pB1. “The pB1 protein belongs to a group of proteins that are known to bind to the phosphatidylcholine on the outside of the cell membrane in bovine sperm and thus have a stabilizing effect,” says Peter Müller from the Humboldt University in Berlin.

It is therefore assumed that pB1 anchors the protective protein envelope of AWN and AQN-3 in the cell membrane of sperm through aggregate formation. Negatively charged lipids such as phosphatidylinositol phosphates serve, among other things, as signaling molecules during fertilization. If they are formed and released prematurely, they could be “intercepted” by spermadhesins until the sperm have reached the egg at the site of fertilization.

Interestingly, the composition of the protein coat around the sperm is species-specific, so spermadhesins are the main component in seminal fluid only in porcine species. This raises the question of how their role is fulfilled in other species and whether their protective properties could be exploited in the application of assisted reproduction techniques in the context of species conservation.

More information: Karin Müller et al, Porcine spermadhesin AQN-3 binds to negatively charged phospholipids, Chemistry and Physics of Lipids (2023). DOI: 10.1016/j.chemphyslip.2023.105306

Provided by Leibniz-Institut für Zoo- und Wildtierforschung (IZW) im Forschungsverbund Berlin e.V.

by University of Vienna

To unveil the previously elusive behavior and stability of complex metal compounds found in aqueous solutions, researchers at the University of Vienna have created a speciation atlas now published in Science Advances. This achievement has the potential to drive new discoveries and advancements in fields like catalysis, medicine, and beyond.

Metal atoms can form tiny 3D structures with oxygen, intricate frameworks that look not unlike wire mandalas and that are called “polyoxometalates,” or “POMs.” These POMs are useful for controlling chemical reactions in chemistry, biology, or material science, but also are relevant for understanding natural processes in these fields.

However, like wire mandalas, their structure is highly variable and depends on minute changes in their environment, making it very difficult for researchers to predict their structure and thus their function for various applications, from medicine to environmental remediation.

Nadiia Gumerova and Annette Rompel from the Faculty of Chemistry at the University of Vienna have now developed a so-called speciation atlas, a cheat sheet that allows researchers to accurately ascertain the expected structure and behavior of 10 commonly used POMs for any given chemical condition.

More specifically, this atlas is a database including a predictive model that can be extended to other than the 10 selected POMs, that will yield POM species distributions, stability and catalytic activity considering the factors pH, temperature, incubation time, buffer solutions, reducing or chelating agents, and ionic strength.

To further support future research, Gumerova and Rompel have also developed a “roadmap” for other scientists conducting experiments with their own POMs: By selecting stable POM variants, listing the application system parameters and then conducting so-called “POM speciation studies”—experiments that reveal the change of POM structure under a change of conditions—researchers can ensure that they are getting the most accurate results and make the best use of POMs in their work.

“The speciation atlas for POMs represents a significant advancement in our understanding of these complex metal compounds. Its insights have the potential to drive new discoveries and advancements in catalysis, biology, medicine, and beyond,” says Annette Rompel.

More information: Nadiia I. Gumerova et al, Speciation atlas of polyoxometalates in aqueous solutions, Science Advances (2023). DOI: 10.1126/sciadv.adi0814

Journal information: Science Advances 

Provided by University of Vienna 

by University of Science and Technology of China

Recently, flexible and foldable devices have developed at a dramatic rate. More and more foldable devices appear in people’s lives. Long-term service requires the folded parts to endure repeated deformation which might cause fatigue damage to the devices. Consequently, the damage will affect the normal function of the devices.

Inspired by the hinge of bivalve Cristaria plicata, which experiences hundreds of thousands of repeating opening-and-closing valve motions throughout the bivalve’s lifetime, a research team led by Prof. Yu Shuhong collaborating with Prof. Wu Hengan from the University of Science and Technology of China (USTC) proposed their tactics to improve the fatigue resistance of structural materials. The work titled “Deformable hard tissue with high fatigue resistance in the hinge of bivalve Cristaria plicata” was published in Science on 23 June 2023.

The researchers illuminated the mechanism of fatigue resistance of deformable biomineral tissue in the hinge of bivalve C. plicata, a species of mollusk, and proposed a novel design strategy of fatigue-resistant structural materials by exploiting the inherent properties of each component through the multiscale structure.

They found that the folding fan-shaped region (FFR) in the hinge can sustain large deformation during repetitive opening-and-closing valve motions and maintain its structure and function for a long period. The tissue still functions well and shows no signs of fatigue behaviors even after 1,500,000 cycles.

The hinge is composed of two regions, the outer ligament (OL) and the folding fan-shaped region. Through observation and finite element analysis, the researchers uncovered the roles of each hinge region during the valves’ motion. When closing, the stretched OL undertakes the circumferential stress dominantly and stores most of the elastic strain energy, while the FFR is deformed circumferentially and provides strong radial support to fix the OL under the limited radial deformation.

They revealed that the hierarchical structures which span from the macroscale level down to the lattice level endow the FFR with notable deformability and load translation capability.

This work provides a novel biomimetic model for designing artificial materials with brittle components and brings a new perspective for elongating materials’ longevity. The multi-level design strategy sheds light on development of the future fatigue-resistant materials.

More information: Xiang-Sen Meng et al, Deformable hard tissue with high fatigue resistance in the hinge of bivalve Cristaria plicata, Science (2023). DOI: 10.1126/science.ade2038. www.science.org/doi/10.1126/science.ade2038

Journal information: Science 

Provided by University of Science and Technology of China

by Massachusetts Institute of Technology

A team of chemists from MIT and Duke University has discovered a counterintuitive way to make polymers stronger: introduce a few weaker bonds into the material.

Working with a type of polymer known as polyacrylate elastomers, the researchers found that they could increase the materials’ resistance to tearing up to tenfold, simply by using a weaker type of crosslinker to join some of the polymer building blocks.

These rubber-like polymers are commonly used in car parts, and they are also often used as the “ink” for 3D-printed objects. The researchers are now exploring the possible expansion of this approach to other types of materials, such as rubber tires.

“If you could make a rubber tire 10 times more resistant to tearing, that could have a dramatic impact on the lifetime of the tire and on the amount of microplastic waste that breaks off,” says Jeremiah Johnson, a professor of chemistry at MIT and one of the senior authors of the study, which appears in Science.

A significant advantage of this approach is that it doesn’t appear to alter any of the other physical properties of the polymers.

“Polymer engineers know how to make materials tougher, but it invariably involves changing some other property of the material that you don’t want to change. Here, the toughness enhancement comes without any other significant change in physical properties—at least that we can measure—and it is brought about through the replacement of only a small fraction of the overall material,” says Stephen Craig, a professor of chemistry at Duke University who is also a senior author of the paper.

This project grew out of a longstanding collaboration between Johnson, Craig, and Duke University Professor Michael Rubinstein, who is also a senior author of the paper. The paper’s lead author is Shu Wang, an MIT postdoc who earned his Ph.D. at Duke.

The weakest link

Polyacrylate elastomers are polymer networks made from strands of acrylate held together by linking molecules. These building blocks can be joined together in different ways to create materials with different properties.

One architecture often used for these polymers is a star polymer network. These polymers are made from two types of building blocks: one, a star with four identical arms, and the other a chain that acts as a linker. These linkers bind to the end of each arm of the stars, creating a network that resembles a volleyball net.

In a 2021 study, Craig, Rubinstein, and MIT Professor Bradley Olsen teamed up to measure the strength of these polymers. As they expected, they found that when weaker end-linkers were used to hold the polymer strands together, the material became weaker. Those weaker linkers, which contain cyclic molecules known as cyclobutane, can be broken with much less force than the linkers that are usually used to join these building blocks.

As a follow-up to that study, the researchers decided to investigate a different type of polymer network in which polymer strands are cross-linked to other strands in random locations, instead of being joined at the ends.

This time, when the researchers used weaker linkers to join the acrylate building blocks together, they found that the material became much more resistant to tearing.

This occurs, the researchers believe, because the weaker bonds are randomly distributed as junctions between otherwise strong strands throughout the material, instead of being part of the ultimate strands themselves. When this material is stretched to the breaking point, any cracks propagating through the material try to avoid the stronger bonds and go through the weaker bonds instead. This means the crack has to break more bonds than it would if all of the bonds were the same strength.

“Even though those bonds are weaker, more of them end up needing to be broken, because the crack takes a path through the weakest bonds, which ends up being a longer path,” Johnson says.

Tough materials

Using this approach, the researchers showed that polyacrylates that incorporated some weaker linkers were nine to 10 times harder to tear than polyacrylates made with stronger crosslinking molecules. This effect was achieved even when the weak crosslinkers made up only about 2% of the overall composition of the material.

The researchers also showed that this altered composition did not alter any of the other properties of the material, such as resistance to breaking down when heated.

“For two materials to have the same structure and same properties at the network level, but have an almost order of magnitude difference in tearing, is quite rare,” Johnson says.

The researchers are now investigating whether this approach could be used to improve the toughness of other materials, including rubber.

More information: Shu Wang et al, Facile mechanochemical cycloreversion of polymer cross-linkers enhances tear resistance, Science (2023). DOI: 10.1126/science.adg3229. www.science.org/doi/10.1126/science.adg3229

Journal information: Science 

Provided by Massachusetts Institute of Technology 

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

by University of Tsukuba

Research and development of organic electronics such as organic solar cells and organic light-emitting diodes is rapidly advancing. The “shape” of the electron orbitals of organic molecules (molecular orbitals) is crucial to the development of organic electronics; however, methods for visualizing molecular orbitals are extremely limited.

Dynamic imaging of molecular orbitals in real space and real time has been particularly difficult yet is essential for studying structural changes and reactions of molecules.

In a new study published in the journal Carbon, researchers demonstrated that the particular molecular orbitals of single molecules can be imaged by projecting the electrons emitted from organic semiconductor molecules adsorbed on a needle tip. This imaging technique is called “field emission microscopy.”

The field emission from a molecule and its spatial distribution were analyzed in detail, revealing that the visualized orbitals might spatially extend beyond the molecule. Such orbitals, called superatom molecular orbitals (SAMOs), are suitable for electron transport in organic electronics.

These detailed measurements of SAMOs are the results of ongoing efforts by the research group. This achievement will not only facilitate future SAMO research but also promises a new dynamic method for imaging the diffusion and reactions of single molecules on surfaces.

More information: Yoichi Yamada et al, Field emission angular distribution from single molecules, Carbon (2023). DOI: 10.1016/j.carbon.2023.118215

Journal information: Carbon 

Provided by University of Tsukuba 

by Tokyo Institute of Technology

Phenanthridines are heterocyclic compounds consisting of two six-membered benzene rings fused to a six-membered ring containing nitrogen. They are found in many naturally occurring organic compounds known for their anticancer and antitumor properties. Due to their potential medicinal applications, there is a significant interest in synthesizing phenanthridine derivatives in laboratories.

A promising synthesis approach involves radical isonitrile insertion to produce imidoyl radical intermediates, which then cyclize to form phenanthridine. However, the exact mechanism of isonitrile insertion is not well understood.

Recently, a team of researchers, led by Associate Professor Shigekazu Ito from Tokyo Institute of Technology (Tokyo Tech), has investigated the use of aryl-substituted difluoromethylborates for synthesizing difluoromethylated phenanthridines. Their study, published in The Journal of Organic Chemistry, assesses the scope of producing pharmaceutically relevant fluorinated phenanthridines from aryl-substituted difluoromethylborates and elucidates the reaction mechanism underlying isonitrile radical addition.

“Taking into account the significance of difluoromethylated phenanthridines in drug discovery, it is desirable to develop novel and complementary synthetic methods for producing 6-(difluoromethyl)phenanthridines, especially via radical isonitrile insertion,” points out Dr. Ito.

The researchers synthesized 6-(difluoromethyl)phenanthridines by first generating a highly reactive difluoromethyl radical (^•CF₂H) through the oxidation of aryl-substituted difluoromethylborates. This radical served as the starting point for the isonitrile insertion and cyclization processes within the isonitrile group.

After screening various oxidizing conditions, the researchers identified a combination of silver oxide (Ag₂O) and potassium peroxodisulfate (K₂S₂O₈) as ideal initiators for radical isonitrile insertion in 2-isocyano-1,1′-biphenyls. They observed that K₂S₂O₈ oxidizes Ag₂O, which, in turn, oxidizes the aryl-substituted difluoromethylborates, leading to the generation of the ^•CF₂H radical. It attaches to the isonitrile group, producing the imidoyl radical, which then undergoes intramolecular cyclization, ultimately leading to the formation of 6-(difluoromethyl)phenanthridine.

The researchers explored various aryl groups in aryl-substituted difluoromethylborates to maximize the yield of 6-(difluoromethyl)phenanthridine. Among the tested aryl groups, p-diethylamino-phenyl-substituted borate was stable and produced the corresponding phenanthridine with a reasonable yield of 53%.

Furthermore, the researchers employed a technique called “transverse-field muon spin rotation” to confirm the reaction mechanism and the presence of the short-lived imidoyl radical. They directed a beam of positive muons (subatomic particles similar to protons but nine times lighter) towards the isonitrile group and carefully observed the changes in their spins.

Muons accompanying electrons, called muoniums, preferentially added to the carbon atom of the isonitrile unit, forming an intermediate that subsequently underwent a cyclization process. This observation provided compelling evidence for the existence of the elusive imidoyl radical.

In the future, the team hopes to explore different approaches to generate the difluoromethyl radical for facilitating the production of difluoromethylated phenanthridines. “Besides chemical oxidation, it might be possible to use photocatalytic and electrochemical methods to synthetically generate the difluoromethyl radical from difluoromethylborates,” says Dr. Ito.

In conclusion, this study presents a highly promising pathway for synthesizing 6-(difluoromethyl)phenanthridines, a breakthrough that holds tremendous potential for drug development.

More information: Kakeru Konagaya et al, Difluoromethylborates and Muonium for the Study of Isonitrile Insertion Affording Phenanthridines via Imidoyl Radicals, The Journal of Organic Chemistry (2023). DOI: 10.1021/acs.joc.3c00056

Provided by Tokyo Institute of Technology 

by Abigail Gruskin, The Baltimore Sun

At summertime backyard feasts, crab shells are just a barrier between hunger and satisfaction. Marylanders smash the crustaceans’ protective casings with wooden mallets, pick out the tasty meat and toss the remnants aside.

But what if crab shells could have a bigger impact, playing a vital role in harnessing renewable energy and reducing planet-warming emissions?

University of Maryland researchers are changing the way people look at those thin exoskeletons—investigating the feasibility of putting them to work in an innovative battery.

“People never thought of that before,” said Lin Xu, 31, a postdoctoral researcher in the Department of Materials Science and Engineering at College Park.

Xu and a team of researchers have been exploring the use of a chemical that comes from crustacean shells in a zinc-ion battery designed to store renewable energy.

Last fall, working under the direction of Liangbing Hu, a Maryland professor who said he conceived the idea, the team published their findings on chitosan, a substance found in a variety of seafood shells, including crab and lobster.

Since appearing in a scientific journal, their work has turned heads.

“The paper has been cited already more than 20 times,” said Xu, who grew up in China and received his doctorate at Massachusetts Institute of Technology. “That’s very fast.”

He and his colleagues are attempting to solve the problem of how renewable energy—like that generated from solar or wind power—can be stored.

“It’s just like a reservoir,” Xu said of the way batteries function, essentially holding onto energy until it is needed.

At night, for example, a home’s appliances still could be powered by energy from the sun if a battery hooked up to solar panels on the roof stored energy generated during the day. On a larger scale, a battery plant placed next to a solar panel farm could stockpile energy to power a nearby city.

“We still need to find the material to store that energy, to act as a reservoir,” Xu said.

While lithium-ion batteries like those that power cellphones and electric vehicles might seem suited to the task, Xu said they are expensive, and the price tag may rise as demand grows for lithium, a finite resource.

There are also safety concerns surrounding lithium-ion batteries, which can explode and cause fires, said Xueying Zheng, a researcher who has worked alongside Xu.

“If we use a very large scale of lithium-ion batteries packed together … if one pack explodes, that will cause all of the batteries to explode,” Zheng said.

The zinc-ion battery has a different drawback: It doesn’t have a long lifespan, operating at full capacity for only a few days or a week, Xu said.

That’s where crab shells provide a solution perhaps.

With a gel membrane containing chitosan, the chemical found in seafood shells and pronounced CHI-tuh-sn, a zinc-ion battery can last a year and still function at 70% of its initial capacity. They’re also much safer, Zheng said.

The battery created and studied by UMD researchers is coin-sized, Xu said, but could be scaled up—with the goal of a more reasonable cost compared to alternatives since chitosan abounds in nature. The substance has an array of applications from biopesticides in agriculture to bandages that aid wound healing in medicine, according to Hu.

In the lab, chitosan arrives as a light yellow powder that is transformed into a translucent gel when dissolved into a solution, according to Hu, who is the director of UMD’s Center for Materials Innovation and teaches materials science and engineering.

Chitosan, a carbohydrate, “is most abundantly found in the hard outer skeletons of shellfish, including crabs, lobsters, and shrimps,” Hu wrote in an email to The Baltimore Sun. After the shells are washed and dried, they’re “pulverized into fine powders,” he explained, then treated with chemicals.

Hu’s lab has purchased chitosan from Sigma-Aldrich, a chemical and life sciences company. On its website, chitosan sells for around $300 for 250 grams, the equivalent of a little over half a pound.

A spokesperson for Merck, which owns Sigma-Aldrich, said the company could not provide details about how or where it sources chitosan since it is “proprietary information.”

“Many researchers are using our products and solutions in very interesting and unique ways,” the spokesperson told The Sun via email. “Scientific breakthroughs, both big and small, are exciting to us—especially as they positively impact life and health to create a more sustainable future.”

In Maryland, a state known for its blue crabs, some in the crab processing industry have taken notice of the potential new use for their scraps.

“I was blown away when I first saw it, thinking ‘Isn’t that crazy?'” said Jack Brooks, who read about the battery research in a seafood trade newsletter.

Brooks, 71, is president of the Chesapeake Bay Seafood Industries Association and also co-runs J.M. Clayton Co., a family-owned crab and oyster processing plant that has been operating in Cambridge since 1921.

In a single day, J.M. Clayton processes 80 to 350 bushels of crabs with each bushel containing roughly 100 crabs. The crabs are sorted and steamed before being stripped of meat in a “picking room,” Brooks explained.

From there, the discarded shells have faced different fates over the decades.

Starting in the 1920s, when J.M. Clayton operated a dehydrating plant in Cambridge, the exoskeletons were turned into a heavy powder called “crab meal,” Brooks said.

The product was used as fertilizer and chicken feed, but the equipment was “old and primitive,” he said, and his family closed the plant in the 1970s.

For about a decade after that, the shells went straight to the landfill, “which was unfortunate,” Brooks said.

Today, J.M. Clayton has a contract to provide crab shells daily—via dumpster truck—to a Dorchester County farm, where they’re used as part of a fertilizer program, he said.

“It’s a very good source of nutrients for the ground,” Brooks said.

Other area processing plants have similar arrangements, he said.

A.E. Phillips & Son, a crab processor that sells to Phillips Seafood Restaurants and other local restaurants and seafood distributors, operates a plant in Fishing Creek that has offloaded its crab shells to a farmer for use as fertilizer since 2018.

It’s the most cost-effective option for the plant, which doesn’t make any profit from the shells but likely spends less money than it would hiring a private waste removal company, said Brice Phillips, whose great-grandfather started A.E. Phillips & Son over a century ago.

“This is not just normal waste; this is waste that if you don’t get rid of it quickly, it starts to rot—and it really stinks,” said Phillips, 47, who serves as vice president of sustainability for the separate Phillips Foods.

But A.E. Phillips & Son’s processing of 60,000 pounds of crab meat per year in Maryland is dwarfed by Phillips Foods’ production in Asia. There, Phillips said, four factories in Indonesia, one in Vietnam and another in India process a combined 100,000 pounds of crab meat each week.

Phillips said he’s not sure what happens to the crab shells after they’re picked at those plants. But he suggested Asia is an ideal place for innovation.

“Whoever’s running this battery research, if they’re ever going to do anything with this, they’re basically going to be setting up a plant in Asia to get the crab shells,” Phillips said.

In Asia, each pound of crab meat comes with four pounds of “guts and shells,” he noted.

Both Brooks and Phillips said they’d be open to embracing a new use for shells.

“We’ve seen ideas come and go, but in this day and time, with all the research and technology and creative minds out there, I mean, hey, anything’s possible,” Brooks said.

Phillips views it as a potentially fruitful business venture, especially since “it seems there is no demand” for crab shells currently.

“My entrepreneurial spirit’s already just grinding the gears, trying to figure out what’s the best way to collect this stuff in mass,” he mused. “How would it be processed, where would it be processed? Where would the battery production be?”

There’s still a long way to go to make chitosan-based batteries a reality outside of the lab. A startup to commercialize the new technology is in its infancy, according to Xu.

If chitosan proves to be part of the solution—and if locally processed crab shells can be put to use—it’s likely something people in the state would get behind.

“Marylanders certainly love their crabs, and I think most people like renewable energy,” Phillips said.

More information: Liangbing Hu, A sustainable chitosan-zinc electrolyte for high-rate zinc metal batteries, Matter (2022). DOI: 10.1016/j.matt.2022.07.015. www.cell.com/matter/fulltext/S2590-2385(22)00414-3

Journal information: Matter 

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