Category: Chemistry

For decades, the fields of physics and chemistry have maintained that the atoms and molecules that make up the natural world define the character of solid matter. Salt crystals get their crystalline quality from the ionic bond between sodium and chloride ions, metals like iron or copper get their strength from the metallic bonds between iron or copper atoms, and rubbers get their stretchiness from the flexible bonds within polymers that constitute the rubber. The same principle applies for materials like fungi, bacteria, and wood.

Or so the story goes.

A new paper published in Nature upends that paradigm, and argues that the character of many biological materials is actually created by the water that permeates these materials. Water gives rise to a solid and goes on to define the properties of that solid, all the while maintaining its liquid characteristics. In their paper, the authors group these and other materials into a new class of matter that they call “hydration solids,” which they say “acquire their structural rigidity, the defining characteristic of the solid state, from the fluid permeating their pores.” The new understanding of biological matter can help answer questions that have dogged scientists for years.

“I think this is a really special moment in science,” Ozgur Sahin, a professor of Biological Sciences and Physics and one of the paper’s authors, said. “It’s unifying something incredibly diverse and complex with a simple explanation. It’s a big surprise, an intellectual delight.”

Steven G. Harrellson, who recently completed doctoral studies in Columbia’s physics department, and is an author on the study, used the metaphor of a building to describe the team’s finding: “If you think of biological materials like a skyscraper, the molecular building blocks are the steel frames that hold them up, and water in between the molecular building blocks is the air inside the steel frames. We discovered that some skyscrapers aren’t supported by their steel frames, but by the air within those frames.”

“This idea may seem hard to believe, but it resolves mysteries and helps predict the existence of exciting phenomena in materials,” Sahin added.

When water is in its liquid form, its molecules strike a fine balance between order and disorder. But when the molecules that form biological materials combine with water, they tip the balance toward order: Water wants to return to its original state. As a result, the water molecules push the biological matter’s molecules away. That pushing force, called the hydration force, was identified in the 1970s, but its impact on biological matter was thought to be limited. This new paper’s argument that the hydration force is what defines the character of biological matter almost entirely, including how soft or hard it is, thus comes as a surprise.

We have long known that biological materials absorb ambient moisture. Think, for example, of a wooden door, that expands during a humid spell. This research, however, shows that that ambient water is much more central to wood, fungi, plants, and other natural materials’ character than we had ever known.

The team found that bringing water to the front and center allowed them to describe the characteristics that familiar organic materials display with very simple math. Previous models of how water interacts with organic matter have required advanced computer simulations to predict the properties of the material. The simplicity of the formulas that the team found can predict these properties suggests that they’re onto something.

To take one example, the team found that the simple equation E=Al/λ neatly describes how a material’s elasticity changes based on factors including humidity, temperature, and molecule size. (E in this equation refers to the elasticity of a material; A is a factor that depends on the temperature and humidity of the environment; l is the approximate size of biological molecules and λ is the distance over which hydration forces lose their strength).

“The more we worked on this project, the simpler the answers became,” Harrellson said, adding that the experience “is very rare in science.”

The new findings emerged from Professor Sahin’s ongoing research into the strange behavior of spores, dormant bacterial cells. For years, Sahin and his students have studied spores to understand why they expand forcefully when water is added to them and contract when water is removed. Several years ago, Sahin and colleagues garnered media coverage for harnessing that capability to create small engine-like contraptions powered by spores.

Around 2012, Sahin decided to take a step back to ask why the spores behave the way they do. He was joined by researchers Michael S. DeLay and Xi Chen, authors on the new paper, who were then members of his lab. Their experiments did not provide a resolution to the mysterious behavior of spores. “We ended up with more mysteries than when we started,” Sahin remembers. They were stuck, but the mysteries they encountered were hinting that there was something worth pursuing.

After years of pondering potential explanations, it occurred to Sahin that the mysteries the team continually encountered could be explained if the hydration force governed the way that water moved in spores.

“When we initially tackled the project, it seemed impossibly complicated. We were trying to explain several different effects, each with their own unsatisfying formula. Once we started using hydration forces, every one of the old formulas could be stripped away. When only hydration forces were left, it felt like our feet finally hit the ground. It was amazing, and a huge relief; things made sense,” he said.

The paper’s findings apply to huge amounts of the world around us: Hygroscopic biological materials—that is, biological materials that allow water in and out of them–potentially make up anywhere from 50% to 90% of the living world around us, including all of the world’s wood, but also other familiar materials like bamboo, cotton, pine cones, wool, hair, fingernails, pollen grains in plants, the outer skin of animals, and bacterial and fungal spores that help these organisms survive and reproduce.

The term coined in the paper, “hydration solids,” applies to any natural material that’s responsive to the ambient humidity around it. With the equations that the team identified, they and other researchers can now predict materials’ mechanical properties from basic physics principles. So far that was true mainly of gases, thanks to the well-known general gas equation, which has been known to scientists since the 19th century.

“When we take a walk in the woods, we think of the trees and plants around us as typical solids. This research shows that we should really think of those trees and plants as towers of water holding sugars and proteins in place,” Sahin said, “It’s really water’s world.”

More information: Ozgur Sahin, Hydration solids, Nature (2023). DOI: 10.1038/s41586-023-06144-y. www.nature.com/articles/s41586-023-06144-y

Journal information: Nature 

Provided by Columbia University 

In a study published in the journal Science China Chemistry, fluorinated cyclic carbonate (DFEC) was introduced into ether electrolyte as a SEI-forming additive. The modified electrolyte could improve the interface of Li metal anode and achieve high efficiency and long cycling stability of LMBs.

LMBs are regarded as the most promising next-generation battery system due to the high specific capacity (3860 mAh g⁻¹) and low electrode potential (-3.04 V vs. SHE) of the Li metal anode.

However, there are many limiting factors which limit the development of LMBs—such as a side reaction between Li anode and electrolyte, Li dendrite growth and a serious volume effect of Li anode, etc.—which lead to low coulombic efficiency (CE) and poor cycle life. Stable solid electrolyte interphase (SEI) is the key to achieve high efficiency and long cycling stability of LMBs.

Adjusting SEI through electrolyte optimization is regard as a low-cost and efficient way to improve Li metal anode interface. So, it is critical to design an electrolyte formulation which can form a stable SEI, the key is the choice of solvents and film-forming additive.

Recently, Prof. Renjie Chen and Prof. Ji Qian proposed an ether-ester mixed electrolyte in which trans-difluoroethylene carbonate (DFEC) was introduced into the ether electrolyte as a film-forming additive. Firstly, ether electrolyte has good anti-reduction stability with Li metal. Secondly, due to the lower LUMO level of DFEC, it can be preferentially reduced during the initial cycle, forming LiF-rich SEI on the Li metal anode.

LiF-rich SEI can inhibit the growth of lithium dendrite, alleviate side reactions, and induce dense lithium deposition. Thanks to the above advantages, the LMBs using modified electrolyte show high efficiency and stable cycling performance. The first author of this paper is Tianyang Xue, a graduate student at Beijing Institute of Technology, and the corresponding authors are Prof. Renjie Chen, Prof. Ji Qian, and Prof. Xingming Guo.

A few implications thus emerge for designing an electrolyte to boost high efficiency and long cycling stability of LMBs. This work explores the interphase chemistry of LMBs, and provides important insights for further study on the novel electrolyte system for LMBs.

More information: Tianyang Xue et al, Tailoring fluorine-rich solid electrolyte interphase to boost high efficiency and long cycling stability of lithium metal batteries, Science China Chemistry (2023). DOI: 10.1007/s11426-022-1623-2

Provided by Science China Press 

A screening technique commonly used in drug discovery can yield important details about the actions of molecular ‘glues’ in protein interactions.

Molecular glues are emerging as powerful therapeutic tools that can stick proteins together in the body. The interactions between proteins underpin all biological cell functions, including those of disease, and so interventions that can control protein-protein interactions have significant potential for disrupting the progress of various diseases.

While in many cases, drugs are required to interrupt the processes that connect proteins together, there are also occasions when the intervention is needed to restore an interaction, or to make it function correctly.

Researchers at the University of Birmingham, together with partners at the University of Leicester and the Eindhoven University of Technology, have devised a way of using mass spectrometry to analyze candidate glues for these processes and assess their relative strengths.

Dr. Aneika Leney, of the School of Biosciences at the University of Birmingham, explained, “Often when we are designing new drugs, it is to stop harmful protein interactions in the body, such as those that lead to tumor cell growth in cancers. Sometimes, however, the disease is caused by protein interactions falling apart and in these cases finding the right glue to hold them together could be extremely beneficial.”

In a new study, published in Chemical Science, the research team focused on one particular molecular glue, called MG1. Using the mass spectrometry method, they were able to disentangle the different mechanisms through which the glue bound to the proteins and stabilized the protein interaction. The MS method also allowed the researchers to elucidate the relative time taken by the different processes involved.

Dr. Peter Cossar, from the Department of Biomedical Engineering at Eindhoven University of Technology further explained, “Understanding how molecular glues stick proteins together enables scientist to better design and build the next generation of molecular glue drugs. Mass Spectrometry provides a tool to do so, by providing high fidelity information on how these unique molecules behave in real time.”

The team expect that the research will provide a robust framework for testing a wide range of molecular glues, offering a significant advance in drug discovery understanding in this area.

More information: Carlo J. A. Verhoef et al, Tracking the mechanism of covalent molecular glue stabilization using native mass spectrometry, Chemical Science (2023). DOI: 10.1039/D3SC01732J

Journal information: Chemical Science 

Provided by University of Birmingham 

by Virginia Tech

Adhesive tape fulfills many purposes, from quickly fixing household appliances to ensuring a reliable seal on a mailed package. When using tape with a strong bond, removing it may only be possible by scraping and prying at the tape’s corners, hoping desperately that surface pieces don’t tear away with the tape.

But what if you could make adhesives both strong and easily removable? This seemingly paradoxical combination of properties could dramatically change applications in robotic grasping, wearables for health monitoring, and manufacturing for assembly and recycling.

Developing such adhesives may not by that far off through the latest research conducted by the team of Michael Bartlett, assistant professor in the Department of Mechanical Engineering at Virginia Tech, and published in Nature Materials on June 22.

The physics of stickiness

Adhesive tapes were first developed in the 1920s to meet a need for automobile painters who wanted better options for painting two colors on car bodies. Since the first masking tape was put into use, many other variations have been created. Factories have rolled out invisible tape for wrapping presents, electrical tape for covering wires, and duct tape for more uses than it was ever intended to fill.

Normally, when tapes are peeled off, they separate in a straight line along the length of the strip until the tape is completely removed. Strong adhesives are made more difficult to peel, while reusable adhesives promote the strength-limiting separation.

Bartlett’s team theorized that if the separation path were controlled, then perhaps adhesives could be made both strong and removable. They tapped into the methods of a 2,000-year-old Japanese art form to determine how to do it.

More information: Dohgyu Hwang et al, Metamaterial adhesives for programmable adhesion through reverse crack propagation, Nature Materials (2023). DOI: 10.1038/s41563-023-01577-2 , dx.doi.org/10.1038/s41563-023-01577-2

Journal information: Nature Materials 

Provided by Virginia Tech 

Billions of years ago, Earth was an extremely hostile planet with active volcanoes, a harsh atmosphere, and no life. This prebiotic Earth, however, was filled with a wide array of abiotic organic molecules derived from its early environment, which underwent chemical reactions that eventually led to the origin of life.

A class of such abiotic molecules abundant during the prebiotic era was the ?-hydroxy acid (?HA)–monomers with structures somewhat similar to those of the ?-amino acids essential to modern life. However, their present abundance in biology is low.

Polyester microdroplets generated from dehydration and rehydration of ?HA monomers were proposed as protocell models and could have been a type of primitive compartment that interacted with and took up various primitive analytes, such as salts within primitive aqueous environments. However, salt–polyester interactions and salt-uptake within polyester microdroplets remains poorly studied due to a lack of appropriate analytical techniques.

To bridge this gap in understanding, a team of researchers led by Special Postdoctoral Researcher Chen Chen from RIKEN (formerly of Tokyo Institute of Technology) and Specially Appointed Associate Professor Tony Z. Jia from the Earth-Life Science Institute at Tokyo Institute of Technology have recently come up with a new strategy for investigating the effect of salt uptake on polyester microdroplets.

Their breakthrough, published in Small Methods, proposed a novel way of using existing spectroscopic and biophysical methods to characterize salt uptake by polyester microdroplets and understand their salt-mediated behavior.

“Primitive molecules such as ?HAs and polyesters, though not as commonly used by current living systems as amino acids, may have laid the ground for the evolution of primitive chemical systems that led to the origin of life on Earth. Examining the interaction of polyesters with different prebiotic analytes such as salts and determining whether polyester droplets can uptake salts can provide insights into the relevant functions exhibited by primitive compartments,” explains Prof. Jia.

?HAs such as ᴅʟ-3-phenyllactic acid (PA) can undergo dehydration under early Earth mimicking conditions to form gel-like polyesters; further rehydration results in assembly of membraneless microdroplets. These membraneless droplets have previously been found to segregate primitive analytes such as nucleic acids, small organic molecules, and proteins.

Studies have hypothesized that life originated and evolved in ancient aqueous environments. If polyester microdroplets existed in primitive aqueous environments, then they might have also uptaken salts, a major analyte found in primitive aqueous environments, which could have subsequently changed the microdroplets’ structure as well.

Thus, the team subjected various ?HAs, such as PA (a neutral monomer), malic acid (a monomer with an acidic side chain), and 4-amino-2-hydroxybutyric acid (a monomer with a basic side chain) to dehydration synthesis, followed by rehydration in aqueous medium to generate neutral, acidic residue-containing, and basic residue-containing polyester microdroplets.

In fact, this study was the first to show the plausibility of acidic residue-containing polyester microdroplets! They then incubated the polyester microdroplets in aqueous solutions consisting of different concentrations of different chloride salts (NaCl, KCl, MgCl_2, and CaCl₂) that may have been abundant in early oceans.

Post salt uptake, the polyester microdroplets were subjected to a novel analytical technique utilizing inductively coupled plasma mass spectrometry (ICP–MS) to analyze the salt cation concentration within the microdroplets. The analyses were performed in collaboration with researchers from the Pheasant Memorial Lab at the Institute of Planetary Materials at Okayama University, where the ICP–MS was located, as part of a joint use collaborative grant.

Furthermore, in collaboration with other members, each with unique specialties, the team then coupled ICP–MS with other spectroscopic and biophysical analytical methods, such as zeta potential analysis, optical density, dynamic light scattering, and micro-Raman imaging to study in detail how salt uptake affects the surface potential, droplet turbidity, size, and internal water distribution, respectively, of the microdroplets.

The results indicated that microdroplets possessed the ability to selectively partition salt cations, leading to differential coalescence of microdroplets, likely due to reduced electrostatic repulsions between the microdroplets as a result of surface charge neutralization by the uptaken salts, which preferentially localized to the droplet surface.

The present study highlights that even slight changes in salt-uptake could significantly affect protocell structure, which could potentially account for diversity in chemistries of primitive systems that emerged in different aqueous systems—ranging from freshwater to oceanic to hypersaline under-ocean brines.

“The adoption of a novel and highly sensitive strategy for analyzing salt uptake by polyester microdroplets widened the range of known primitive chemicals that could have had an effect on primitive protocell structure and function. This opens new avenues for future investigations regarding the relevance of polyester microdroplets during the origins of life both on and off Earth,” concludes Dr. Chen.

More information: Chen Chen et al, Spectroscopic and Biophysical Methods to Determine Differential Salt‐Uptake by Primitive Membraneless Polyester Microdroplets, Small Methods (2023). DOI: 10.1002/smtd.202300119

Journal information: Small Methods 

Provided by Tokyo Institute of Technology 

Everyday materials such as paper and plastic could be transformed into electronic “smart devices” by using a simple new method to apply liquid metal to surfaces, according to scientists in Beijing, China. The study, published June 9 in the journal Cell Reports Physical Science, demonstrates a technique for applying a liquid metal coating to surfaces that do not easily bond with liquid metal. The approach is designed to work at a large scale and may have applications in wearable testing platforms, flexible devices, and soft robotics.

“Before, we thought that it was impossible for liquid metal to adhere to non-wetting surfaces so easily, but here it can adhere to various surfaces only by adjusting the pressure, which is very interesting,” said Bo Yuan, a scientist at Tsinghua University and the first author of the study.

Scientists seeking to combine liquid metal with traditional materials have been impeded by liquid metal’s extremely high surface tension, which prevents it from binding with most materials, including paper. To overcome this issue, previous research has mainly focused on a technique called “transfer printing,” which involves using a third material to bind the liquid metal to the surface. But this strategy comes with drawbacks—adding more materials can complicate the process and may weaken the end product’s electrical, thermal, or mechanical performance.

To explore an alternative approach that would allow them to directly print liquid metal on substrates without sacrificing the metal’s properties, Yuan and colleagues applied two different liquid metals (eGaln and BilnSn) to various silicone and silicone polymer stamps, then applied different forces as they rubbed the stamps onto paper surfaces.

“At first, it was hard to realize stable adhesion of the liquid metal coating on the substrate,” said Yuan. “However, after a lot of trial and error, we finally had the right parameters to achieve stable, repeatable adhesion.”

The researchers found that rubbing the liquid metal-covered stamp against the paper with a small amount of force enabled the metal droplets to bind effectively to the surface, while applying larger amounts of force prevented the droplets from staying in place.

Next, the team folded the metal-coated paper into a paper crane, demonstrating that the surface can still be folded as usual after the process is completed. And after doing so, the modified paper still maintains its usual properties.

While the technique appears promising, Yuan noted that the researchers are still figuring out how to guarantee that the liquid metal coating stays in place after it has been applied. For now, a packaging material can be added to the paper’s surface, but the team hopes to figure out a solution that won’t require it.

“Just like wet ink on paper can be wiped off by hand, the liquid metal coating without packaging here also can be wiped off by the object it touches as it is applied,” said Yuan. “The properties of the coating itself will not be greatly affected, but objects in contact may be soiled.”

In the future, the team also plans to build on the method so that it can be used to apply liquid metal to a greater variety of surfaces, including metal and ceramic.

“We also plan to construct smart devices using materials treated by this method,” said Yuan.

More information: Hongzhang Wang, Direct Fabrication of Liquid Metal Multifunctional Paper Based on Force responsive Adhesion, Cell Reports Physical Science (2023). DOI: 10.1016/j.xcrp.2023.101419. www.cell.com/cell-reports-phys … 2666-3864(23)00193-5

Journal information: Cell Reports Physical Science 

Provided by Cell Press 

Do an image search for “electronic implants,” and you’ll draw up a wide assortment of devices, from traditional pacemakers and cochlear implants to more futuristic brain and retinal microchips aimed at augmenting vision, treating depression, and restoring mobility.

Some implants are hard and bulky, while others are flexible and thin. But no matter their form and function, nearly all implants incorporate electrodes—small conductive elements that attach directly to target tissues to electrically stimulate muscles and nerves.

Implantable electrodes are predominantly made from rigid metals that are electrically conductive by nature. But over time, metals can aggravate tissues, causing scarring and inflammation that in turn can degrade an implant’s performance.

Now, MIT engineers have developed a metal-free, Jell-O-like material that is as soft and tough as biological tissue and can conduct electricity similarly to conventional metals. The material can be made into a printable ink, which the researchers patterned into flexible, rubbery electrodes. The new material, which is a type of high-performance conducting polymer hydrogel, may one day replace metals as functional, gel-based electrodes, with the look and feel of biological tissue.

“This material operates the same as metal electrodes but is made from gels that are similar to our bodies, and with similar water content,” says Hyunwoo Yuk Ph.D., co-founder of SanaHeal, a medical device startup. “It’s like an artificial tissue or nerve.”

“We believe that for the first time, we have a tough, robust, Jell-O-like electrode that can potentially replace metal to stimulate nerves and interface with the heart, brain, and other organs in the body,” adds Xuanhe Zhao, professor of mechanical engineering and of civil and environmental engineering at MIT.

Zhao, Yuk, and others at MIT and elsewhere report their results in Nature Materials. The study’s co-authors include first author and former MIT postdoc Tao Zhou, who is now an assistant professor at Penn State University, and colleagues at Jiangxi Science and Technology Normal University and Shanghai Jiao Tong University.

A true challenge

The vast majority of polymers are insulating by nature, meaning that electricity does not pass easily through them. But there exists a small and special class of polymers that can in fact pass electrons through their bulk. Some conductive polymers were first shown to exhibit high electrical conductivity in the 1970s—work that was later awarded a Nobel Prize in Chemistry.

Recently, researchers including those in Zhao’s lab have tried using conductive polymers to fabricate soft, metal-free electrodes for use in bioelectronic implants and other medical devices. These efforts have aimed to make soft yet tough, electrically conductive films and patches, primarily by mixing particles of conductive polymers, with hydrogel—a type of soft and spongy water-rich polymer.

Researchers hoped the combination of conductive polymer and hydrogel would yield a flexible, biocompatible, and electrically conductive gel. But the materials made to date were either too weak and brittle, or they exhibited poor electrical performance.

“In gel materials, the electrical and mechanical properties always fight each other,” Yuk says. “If you improve a gel’s electrical properties, you have to sacrifice mechanical properties, and vice versa. But in reality, we need both: A material should be conductive, and also stretchy and robust. That was the true challenge and the reason why people could not make conductive polymers into reliable devices entirely made out of gel.”

Electric spaghetti

In their new study, Yuk and his colleagues found they needed a new recipe to mix conductive polymers with hydrogels in a way that enhanced both the electrical and mechanical properties of the respective ingredients.

“People previously relied on homogenous, random mixing of the two materials,” Yuk says.

Such mixtures produced gels made of randomly dispersed polymer particles. The group realized that to preserve the electrical and mechanical strengths of the conductive polymer and the hydrogel respectively, both ingredients should be mixed in a way that they slightly repel—a state known as phase separation. In this slightly separated state, each ingredient could then link its respective polymers to form long, microscopic strands, while also mixing as a whole.

“Imagine we are making electrical and mechanical spaghetti,” Zhao offers. “The electrical spaghetti is the conductive polymer, which can now transmit electricity across the material because it is continuous. And the mechanical spaghetti is the hydrogel, which can transmit mechanical forces and be tough and stretchy because it is also continuous.”

The researchers then tweaked the recipe to cook the spaghettified gel into an ink, which they fed through a 3D printer, and printed onto films of pure hydrogel, in patterns similar to conventional metal electrodes.

“Because this gel is 3D-printable, we can customize geometries and shapes, which makes it easy to fabricate electrical interfaces for all kinds of organs,” says first-author Zhou.

The researchers then implanted the printed, Jell-O-like electrodes onto the heart, sciatic nerve, and spinal cord of rats. The team tested the electrodes’ electrical and mechanical performance in the animals for up to two months and found the devices remained stable throughout, with little inflammation or scarring to the surrounding tissues. The electrodes also were able to relay electrical pulses from the heart to an external monitor, as well as deliver small pulses to the sciatic nerve and spinal cord, which in turn stimulated motor activity in the associated muscles and limbs.

Going forward, Yuk envisions that an immediate application for the new material may be for people recovering from heart surgery. “These patients need a few weeks of electrical support to avoid heart attack as a side effect of surgery,” Yuk says. “So, doctors stitch a metallic electrode on the surface of the heart and stimulate it over weeks. We may replace those metal electrodes with our gel to minimize complications and side effects that people currently just accept.”

The team is working to extend the material’s lifetime and performance. Then, the gel could be used as a soft electrical interface between organs and longer-term implants, including pacemakers and deep-brain stimulators.

“The goal of our group is to replace glass, ceramic, and metal inside the body, with something like Jell-O so it’s more benign but better performance, and can last a long time,” Zhao says. “That’s our hope.”

More information: “3D Printable High Performance Conducting Polymer Hydrogel for All-Hydrogel Bioelectronic Interfaces”, Nature Materials (2023). DOI: 10.1038/s41563-023-01569-2

Journal information: Nature Materials 

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.

A study by a team of University of Oklahoma researchers has been featured in Cell Reports Physical Science, an open-access journal highlighting cutting-edge research in the physical sciences.

The study, “Cooperative roles of water and metal-support interfaces in the selective hydrogenation of cinnamaldehyde over cobalt boride catalysts,” explores the role of water in the selective hydrogenation of carbonyl over alkene bonds. Utilizing cobalt and cobalt boride catalysts, OU researchers analyzed the hydrogenation of an organic compound called cinnamaldehyde. They discovered that the chemical element boron species plays a crucial role in enhancing catalytic activity and selectivity.

“We want to mimic nature’s enzymes and learn more about what we can create synthetically. Our findings could have far-reaching implications in the production of industrial chemicals,” said the project’s co-investigator, Daniel Resasco, Ph.D., a professor in the School of Chemical, Biological and Materials Engineering, Gallogly College of Engineering.

During thermal treatments, the boron species undergo a process called exsolution, where they separate from the bulk phase and accumulate on the catalyst’s surface. This enrichment leads to the formation of acidic species, which boost the activity and selectivity of carbonyl bond hydrogenation by three and two times, respectively.

Resasco explains the significance of the team’s findings. “The role of water in selective hydrogenation has long been a subject of interest. Our study provides new insights into the underlying mechanisms and uncovers a synergistic effect between boron species and water, ultimately leading to enhanced stability and selectivity of the catalysts,” he said.

Associate professor Bin Wang, Ph.D., is a co-investigator on the project and says the study highlights the importance of finding the right balance between catalyst support and desired chemical outcomes. “This research opens new possibilities for developing more efficient and selective catalytic processes in the production of industrial chemicals,” Wang said.

Resasco credits Li Gengnan, Ph.D., for the project’s scientific thinking. Gengnan served as a post-doctorate fellow at OU before joining the Center for Functional Nanomaterials at Brookhaven National Laboratory, one of five Nanoscale Science Research Centers created by the Department of Energy.

“As the search for sustainable and efficient chemical processes continues, we hope to pave the way for transformative advancements in catalysis, driving us closer to a greener and more resourceful future,” Resasco said.

More information: Gengnan Li et al, Cooperative roles of water and metal-support interfaces in the selective hydrogenation of cinnamaldehyde over cobalt boride catalysts, Cell Reports Physical Science (2023). DOI: 10.1016/j.xcrp.2023.101367

Journal information: Cell Reports Physical Science 

Provided by University of Oklahoma 

At least 2 billion people worldwide routinely drink water contaminated with disease-causing microbes.

Now Stanford University scientists have invented a low-cost, recyclable powder that kills thousands of waterborne bacteria per second when exposed to ordinary sunlight. The discovery of this ultrafast disinfectant could be a significant advance for nearly 30% of the world’s population with no access to safe drinking water, according to the Stanford team. Their results are published in Nature Wateron May 18.

“Waterborne diseases are responsible for 2 million deaths annually, the majority in children under the age of 5,” said study co-lead author Tong Wu, a former postdoctoral scholar of materials science and engineering (MSE) in the Stanford School of Engineering. “We believe that our novel technology will facilitate revolutionary changes in water disinfection and inspire more innovations in this exciting interdisciplinary field.”

Conventional water-treatment technologies include chemicals, which can produce toxic byproducts, and ultraviolet light, which takes a relatively long time to disinfect and requires a source of electricity.

The new disinfectant developed at Stanford is a harmless metallic powder that works by absorbing both UV and high-energy visible light from the sun. The powder consists of nano-sized flakes of aluminum oxide, molybdenum sulfide, copper, and iron oxide.

“We only used a tiny amount of these materials,” said senior author Yi Cui, the Fortinet Founders Professor of MSE and of Energy Science & Engineering in the Stanford Doerr School of Sustainability. “The materials are low cost and fairly abundant. The key innovation is that, when immersed in water, they all function together.”

Fast, nontoxic, and recyclable

After absorbing photons from the sun, the molybdenum sulfide/copper catalyst performs like a semiconductor/metal junction, enabling the photons to dislodge electrons. The freed electrons then react with the surrounding water, generating hydrogen peroxide and hydroxyl radicals—one of the most biologically destructive forms of oxygen. The newly formed chemicals quickly kill the bacteria by seriously damaging their cell membranes.

For the study, the Stanford team used a 200 milliliter [6.8 ounce] beaker of room-temperature water contaminated with about 1 million E. coli bacteria per mL [.03 oz.].

“We stirred the powder into the contaminated water,” said co-lead author Bofei Liu, a former MSE postdoc. “Then we carried out the disinfection test on the Stanford campus in real sunlight, and within 60 seconds, no live bacteria were detected.”

The powdery nanoflakes can move around quickly, make physical contact with a lot of bacteria and kill them fast, he added.

The chemical byproducts generated by sunlight also dissipate quickly.

“The lifetime of hydrogen peroxide and hydroxy radicals is very short,” Cui said. “If they don’t immediately find bacteria to oxidize, the chemicals break down into water and oxygen and are discarded within seconds. So you can drink the water right away.”

The nontoxic powder is also recyclable. Iron oxide enables the nanoflakes to be removed from water with an ordinary magnet. In the study, the researchers used magnetism to collect the same powder 30 times to treat 30 different samples of contaminated water.

“For hikers and backpackers, I could envision carrying a tiny amount of powder and a small magnet,” Cui said. “During the day you put the powder in water, shake it up a little bit under sunlight and within a minute you have drinkable water. You use the magnet to take out the particles for later use.”

The powder might also be useful in wastewater treatment plants that currently use UV lamps to disinfect treated water, he added.

“During the day the plant can use visible sunlight, which would work much faster than UV and would probably save energy,” Cui said. “The nanoflakes are fairly easy to make and can be rapidly scaled up by the ton.”

The study focused on E. coli, which can cause severe gastrointestinal illness and can even be life-threatening. The U.S. Environmental Protection Agency has set the maximum contaminant-level goal for E. coli in drinking water at zero. The Stanford team plans to test the new powder on other waterborne pathogens, including viruses, protozoa, and parasites that also cause serious diseases and death.

More information: Yi Cui, Solar-driven efficient heterogeneous subminute water disinfection nanosystem assembled with fingerprint MoS2, Nature Water (2023). DOI: 10.1038/s44221-023-00079-4. www.nature.com/articles/s44221-023-00079-4

Journal information: Nature Water 

Provided by Stanford University