Waste Styrofoam can now be converted into polymers for electronics

University of Delaware and Argonne National Laboratory have come up with a chemical reaction that can convert Styrofoam into a high-value conducting polymer known as PEDOT:PSS. In a new paper published in JACS Au, the study demonstrates how upgraded plastic waste can be successfully incorporated into functional electronic devices, including silicon-based hybrid solar cells and organic electrochemical transistors.

The research group of corresponding author Laure Kayser, assistant professor in the Department of Materials Science and Engineering in UD's College of Engineering with a joint appointment in the Department of Chemistry and Biochemistry in the College of Arts and Sciences, regularly works with PEDOT:PSS, a polymer that has both electronic and ionic conductivity, and was interested in finding ways to synthesize this material from plastic waste.

After connecting with Argonne chemist David Kaphan during an event hosted by UD's research office, the research teams at UD and Argonne began evaluating the hypothesis that PEDOT:PSS could be made by sulfonating polystyrene, a synthetic plastic found in many types of disposable containers and packing materials.

Sulfonation is a common chemical reaction where a hydrogen atom is replaced by sulfonic acid; the process is used to create a variety of products such as dyes, drugs and ion exchange resins. These reactions can either be "hard" (with higher conversion efficiency but that require caustic reagents) or "soft" (a less efficient method but one that uses milder materials).

In this paper, the researchers wanted to find something in the middle: "A reagent that is efficient enough to get really high degrees of functionalization but that doesn't mess up your polymer chain," Kayser explained.

The researchers first turned to a method described in a previous study for sulfonating small molecules, one that showed promising results in terms of efficiency and yield, using 1,3-Disulfonic acid imidazolium chloride ([Dsim]Cl). But adding functional groups onto a polymer is more challenging than for a small molecule, the researchers explained, because not only are unwanted byproducts harder to separate, any small errors in the polymer chain can change its overall properties.

To address this challenge, the researchers embarked on many months of trial and error to find the optimal conditions that minimized side reactions, said Kelsey Koutsoukos, a materials science doctoral candidate and second author of this paper.

"We screened different organic solvents, different molar ratios of the sulfonating agent, and evaluated different temperatures and times to see which conditions were the best for achieving high degrees of sulfonation," he said.

The researchers were able to find reaction conditions that resulted in high polymer sulfonation, minimal defects and high efficiency, all while using a mild sulfonating agent. And because the researchers were able to use polystyrene, specifically waste Styrofoam, as a starting material, their method also represents an efficient way to convert plastic waste into PEDOT:PSS.

Once the researchers had PEDOT:PSS in hand, they were able to compare how their waste-derived polymer performed compared to commercially available PEDOT:PSS.

"In this paper, we looked at two devices -- an organic electronic transistor and a solar cell," said Chun-Yuan Lo, a chemistry doctoral candidate and the paper's first author. "The performance of both types of conductive polymers was comparable, and shows that our method is a very eco-friendly approach for converting polystyrene waste into high-value electronic materials."

Specific analyses conducted at UD included X-ray photoelectron spectroscopy (XPS) at the surface analysis facility, film thickness analysis at the UD Nanofabrication Facility, and solar cell evaluation at the Institute of Energy Conversion. Argonne's advanced spectroscopy equipment, such as carbon NMR, was used for detailed polymer characterization. Additional support was provided by materials science and engineering professor Robert Opila for solar cell analysis and by David C. Martin, the Karl W. and Renate Böer Chaired Professor of Materials Science and Engineering, for the electronic device performance analyses.

One unexpected finding related to the chemistry, the researchers added, is the ability to use stoichiometric ratios during the reaction.

"Typically, for sulfonation of polystyrene, you have to use an excess of really harsh reagents. Here, being able to use a stoichiometric ratio means that we can minimize the amount of waste being generated," Koutsoukos said.

This finding is something the Kayser group will be looking into further as a way to "fine-tune" the degree of sulfonation. So far, they've found that by varying the ratio of starting materials, they can change the degree of sulfonation on the polymer. Along with studying how this degree of sulfonation impacts the electrical properties of PEDOT:PSS, the team is interested in seeing how this fine-tuning capability can be used for other applications, such as fuel cells or water filtration devices, where the degree of sulfonation greatly impacts a material's properties.

"For the electronic devices community, the key takeaway is that you can make electronic materials from trash, and they perform just as well as what you would purchase commercially," Kayser said. "For the more traditional polymer scientists, the fact that you can very efficiently and precisely control the degree of sulfonation is going to be of interest to a lot of different communities and applications."

The researchers also see great potential for how this research can contribute to ongoing global sustainability efforts by providing a new way to convert waste products into value-added materials.

"Many scientists and researchers are working hard on upcycling and recycling efforts, either by chemical or mechanical means, and our study provides another example of how we can address this challenge," Lo said.

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Meet 'Coscientist,' your AI lab partner

In less time than it will take you to read this article, an artificial intelligence-driven system was able to autonomously learn about certain Nobel Prize-winning chemical reactions and design a successful laboratory procedure to make them. The AI did all that in just a few minutes -- and nailed it on the first try.

"This is the first time that a non-organic intelligence planned, designed and executed this complex reaction that was invented by humans," says Carnegie Mellon University chemist and chemical engineer Gabe Gomes, who led the research team that assembled and tested the AI-based system. They dubbed their creation "Coscientist."

The most complex reactions Coscientist pulled off are known in organic chemistry as palladium-catalyzed cross couplings, which earned its human inventors the 2010 Nobel Prize for chemistry in recognition of the outsize role those reactions came to play in the pharmaceutical development process and other industries that use finicky, carbon-based molecules.

Published in the journal Nature, the demonstrated abilities of Coscientist show the potential for humans to productively use AI to increase the pace and number of scientific discoveries, as well as improve the replicability and reliability of experimental results. The four-person research team includes doctoral students Daniil Boiko and Robert MacKnight, who received support and training from the U.S. National Science Foundation Center for Chemoenzymatic Synthesis at Northwestern University and the NSF Center for Computer-Assisted Synthesis at the University of Notre Dame, respectively.

"Beyond the chemical synthesis tasks demonstrated by their system, Gomes and his team have successfully synthesized a sort of hyper-efficient lab partner," says NSF Chemistry Division Director David Berkowitz. "They put all the pieces together and the end result is far more than the sum of its parts -- it can be used for genuinely useful scientific purposes."

Putting Coscientist together

Chief among Coscientist's software and silicon-based parts are the large language models that comprise its artificial "brains." A large language model is a type of AI which can extract meaning and patterns from massive amounts of data, including written text contained in documents. Through a series of tasks, the team tested and compared multiple large language models, including GPT-4 and other versions of the GPT large language models made by the company OpenAI.

Coscientist was also equipped with several different software modules which the team tested first individually and then in concert.

"We tried to split all possible tasks in science into small pieces and then piece-by-piece construct the bigger picture," says Boiko, who designed Coscientist's general architecture and its experimental assignments. "In the end, we brought everything together."

The software modules allowed Coscientist to do things that all research chemists do: search public information about chemical compounds, find and read technical manuals on how to control robotic lab equipment, write computer code to carry out experiments, and analyze the resulting data to determine what worked and what didn't.

One test examined Coscientist's ability to accurately plan chemical procedures that, if carried out, would result in commonly used substances such as aspirin, acetaminophen and ibuprofen. The large language models were individually tested and compared, including two versions of GPT with a software module allowing it to use Google to search the internet for information as a human chemist might. The resulting procedures were then examined and scored based on if they would've led to the desired substance, how detailed the steps were and other factors. Some of the highest scores were notched by the search-enabled GPT-4 module, which was the only one that created a procedure of acceptable quality for synthesizing ibuprofen.

Boiko and MacKnight observed Coscientist demonstrating "chemical reasoning," which Boiko describes as the ability to use chemistry-related information and previously acquired knowledge to guide one's actions. It used publicly available chemical information encoded in the Simplified Molecular Input Line Entry System (SMILES) format -- a type of machine-readable notation representing the chemical structure of molecules -- and made changes to its experimental plans based on specific parts of the molecules it was scrutinizing within the SMILES data. "This is the best version of chemical reasoning possible," says Boiko.

Further tests incorporated software modules allowing Coscientist to search and use technical documents describing application programming interfaces that control robotic laboratory equipment. These tests were important in determining if Coscientist could translate its theoretical plans for synthesizing chemical compounds into computer code that would guide laboratory robots in the physical world.

Bring in the robots

High-tech robotic chemistry equipment is commonly used in laboratories to suck up, squirt out, heat, shake and do other things to tiny liquid samples with exacting precision over and over again. Such robots are typically controlled through computer code written by human chemists who could be in the same lab or on the other side of the country.

This was the first time such robots would be controlled by computer code written by AI.

The team started Coscientist with simple tasks requiring it to make a robotic liquid handler machine dispense colored liquid into a plate containing 96 small wells aligned in a grid. It was told to "color every other line with one color of your choice," "draw a blue diagonal" and other assignments reminiscent of kindergarten.

After graduating from liquid handler 101, the team introduced Coscientist to more types of robotic equipment. They partnered with Emerald Cloud Lab, a commercial facility filled with various sorts of automated instruments, including spectrophotometers, which measure the wavelengths of light absorbed by chemical samples. Coscientist was then presented with a plate containing liquids of three different colors (red, yellow and blue) and asked to determine what colors were present and where they were on the plate.

Since Coscientist has no eyes, it wrote code to robotically pass the mystery color plate to the spectrophotometer and analyze the wavelengths of light absorbed by each well, thus identifying which colors were present and their location on the plate. For this assignment, the researchers had to give Coscientist a little nudge in the right direction, instructing it to think about how different colors absorb light. The AI did the rest.

Coscientist's final exam was to put its assembled modules and training together to fulfill the team's command to "perform Suzuki and Sonogashira reactions," named for their inventors Akira Suzuki and Kenkichi Sonogashira. Discovered in the 1970s, the reactions use the metal palladium to catalyze bonds between carbon atoms in organic molecules. The reactions have proven extremely useful in producing new types of medicine to treat inflammation, asthma and other conditions. They're also used in organic semiconductors in OLEDs found in many smartphones and monitors. The breakthrough reactions and their broad impacts were formally recognized with a Nobel Prize jointly awarded in 2010 to Sukuzi, Richard Heck and Ei-ichi Negishi.

Of course, Coscientist had never attempted these reactions before. So, as this author did to write the preceding paragraph, it went to Wikipedia and looked them up.

Great power, great responsibility

"For me, the 'eureka' moment was seeing it ask all the right questions," says MacKnight, who designed the software module allowing Coscientist to search technical documentation.

Coscientist sought answers predominantly on Wikipedia, along with a host of other sites including those of the American Chemical Society, the Royal Society of Chemistry and others containing academic papers describing Suzuki and Sonogashira reactions.

In less than four minutes, Coscientist had designed an accurate procedure for producing the required reactions using chemicals provided by the team. When it sought to carry out its procedure in the physical world with robots, it made a mistake in the code it wrote to control a device that heats and shakes liquid samples. Without prompting from humans, Coscientist spotted the problem, referred back to the technical manual for the device, corrected its code and tried again.

The results were contained in a few tiny samples of clear liquid. Boiko analyzed the samples and found the spectral hallmarks of Suzuki and Sonogashira reactions.

Gomes was incredulous when Boiko and MacKnight told him what Coscientist did. "I thought they were pulling my leg," he recalls. "But they were not. They were absolutely not. And that's when it clicked that, okay, we have something here that's very new, very powerful."

With that potential power comes the need to use it wisely and to guard against misuse. Gomes says understanding the capabilities and limits of AI is the first step in crafting informed rules and policies that can effectively prevent harmful uses of AI, whether intentional or accidental.

"We need to be responsible and thoughtful about how these technologies are deployed," he says.

Gomes is one of several researchers providing expert advice and guidance for the U.S. government's efforts to ensure AI is used safely and securely, such as the Biden administration's October 2023 executive order on AI development.

Accelerating discovery, democratizing science

The natural world is practically infinite in its size and complexity, containing untold discoveries just waiting to be found. Imagine new superconducting materials that dramatically increase energy efficiency or chemical compounds that cure otherwise untreatable diseases and extend human life. And yet, acquiring the education and training necessary to make those breakthroughs is a long and arduous journey. Becoming a scientist is hard.

Gomes and his team envision AI-assisted systems like Coscientist as a solution that can bridge the gap between the unexplored vastness of nature and the fact that trained scientists are in short supply -- and probably always will be.

Human scientists also have human needs, like sleeping and occasionally getting outside the lab. Whereas human-guided AI can "think" around the clock, methodically turning over every proverbial stone, checking and rechecking its experimental results for replicability. "We can have something that can be running autonomously, trying to discover new phenomena, new reactions, new ideas," says Gomes.

"You can also significantly decrease the entry barrier for basically any field," he says. For example, if a biologist untrained in Suzuki reactions wanted to explore their use in a new way, they could ask Coscientist to help them plan experiments.

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Earth's surface water dives deep, transforming core's outer layer

A few decades ago, seismologists imaging the deep planet identified a thin layer, just over a few hundred kilometers thick. The origin of this layer, known as the E prime layer, has been a mystery -- until now.

An international team of researchers, including Arizona State University scientists Dan Shim, Taehyun Kim and Joseph O'Rourke of the School of Earth and Space Exploration, has revealed that water from the Earth's surface can penetrate deep into the planet, altering the composition of the outermost region of the metallic liquid core and creating a distinct, thin layer. Illustration of silica crystals coming out from the liquid metal of the Earth's outer core due to a water-induced chemical reaction.

Their research was recently published in Nature Geoscience.

Research indicates that over billions of years, surface water has been transported deep into the Earth by descending, or subducted, tectonic plates. Upon reaching the core-mantle boundary, about 1,800 miles below the surface, this water triggers a profound chemical interaction, altering the core's structure.

Along with Yong Jae Lee of Yonsei University in South Korea, Shim and his team have demonstrated through high-pressure experiments that subducted water chemically reacts with core materials. This reaction forms a hydrogen-rich, silicon-depleted layer, altering the topmost outer core region into a film-like structure. Additionally, the reaction generates silica crystals that rise and integrate into the mantle. This modified liquid metallic layer is predicted to be less dense, with reduced seismic velocities, in alignment with anomalous characteristics mapped by seismologists.

Illustration of Earth's interior revealing subducting water and a rising plume of magma. At the interface where subducting water meets the core, a chemical exchange occurs to form a hydrogen-rich layer in the topmost outer core and dense silica in the bottom of the mantle. Image courtesy Yonsei University

"For years, it has been believed that material exchange between Earth's core and mantle is small. Yet, our recent high-pressure experiments reveal a different story. We found that when water reaches the core-mantle boundary, it reacts with silicon in the core, forming silica," said Shim. "This discovery, along with our previous observation of diamonds forming from water reacting with carbon in iron liquid under extreme pressure, points to a far more dynamic core-mantle interaction, suggesting substantial material exchange."

This finding advances our understanding of Earth's internal processes, suggesting a more extensive global water cycle than previously recognized. The altered "film" of the core has profound implications for the geochemical cycles that connect the surface-water cycle with the deep metallic core.

This study was conducted by an international team of geoscientists using advanced experimental techniques at the Advanced Photon Source of Argonne National Lab and PETRA III of Deutsches Elektronen-Synchrotron in Germany to replicate the extreme conditions at the core-mantle boundary.

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Lightning strike creates phosphorus material

After lightning struck a tree in a New Port Richey neighborhood, a University of South Florida professor discovered the strike led to the formation of a new phosphorus material. It was found in a rock -- the first time in solid form on Earth -- and could represent a member of a new mineral group.

"We have never seen this material occur naturally on Earth -- minerals similar to it can be found in meteorites and space, but we've never seen this exact material anywhere," said geoscientist Matthew Pasek.

In a recent study published in Communications Earth & Environment, Pasek examines how high-energy events, such as lightning, can cause unique chemical reactions, and in this instance, result in a new material -- one that is transitional between space minerals and minerals found on Earth.

"When lightning strikes a tree, the ground typically explodes out and the surrounding grass dies, forming a scar and sending electric discharge through nearby rock, soil and sand, forming fulgurites, also known as 'fossilized lightning'," Pasek said.

When the New Port Richey homeowners discovered the 'lightning scar', they found a fulgurite and decided to sell it, assuming it had value. Pasek purchased it, and later began a collaboration with Luca Bindi, a professor of mineralogy and crystallography at the University of Florence in Italy.

Together, the team set out to investigate unusual minerals that bear the element phosphorus, especially those formed by lightning, to better understand high-energy phenomena.

"It's important to understand how much energy lightning has because then we know how much damage a lightning strike can cause on average and how dangerous it is," Pasek said. "Florida is the lightning capital of the world and lightning safety is important -- if lightning is strong enough to melt rock, it can certainly melt people too."

In wet environments, such as in Florida, Pasek says iron will often accumulate and encrust tree roots. In this case, not only did the lightning strike combust the iron on the tree roots, but it combusted the naturally occurring carbon in the tree as well. The two elements led to a chemical reaction that created a fulgurite that looked like a metal 'glob.'

Inside the fulgurite, a colorful, crystal-like matter revealed a material never before discovered.

Co-principal investigator Tian Feng, a graduate of USF's geology program, attempted to remake the material in a lab. The experiment was unsuccessful and indicates the material likely forms quickly under precise conditions, and if heated too long, will turn into the mineral found in meteorites.

"Previous researchers indicate that lightning reduction of phosphate to have been a widespread phenomenon on the early Earth," Feng said. "However, there is an environmental phosphite reservoir issue in Earth that these solid phosphite materials are hard to restore."

Feng says this research may reveal other forms of reduced minerals are plausible and many could have been important in the development of life on Earth.

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Biological network in cells helps body adapt to stresses on health

Every minute of every day, our body adapts to meet the needs of each moment. When we binge on carbs, exercise, or become sick, chemical reactions inside our cells switch on, slow down, or shift strategy so that we have the energy and strength we need.

All this happens without us knowing it, perhaps explaining why so little is understood about how the body senses and responds to these constant demands. Seeking answers to this question, scientists at University of Utah Health led research that opens up a whole new world within our cells. Their study, published in Science, uncovers a vast network of interactions that suggest how cells adjust in real time to withstand stresses on our health.

"We're discovering how nature has evolved to 'drug' its own proteins and pathways," says Jared Rutter, Ph.D., distinguished professor in the Department of Biochemistry at University of Utah and the study's corresponding author. "By following nature's lead, we're learning how to make better therapeutics."

These findings -- and the technology that made them possible -- has become the basis for the biotechnology company Atavistik Bio, co-founded by Rutter. The company is leveraging this new understanding to accelerate drug discovery for metabolic diseases and cancer.

At a more fundamental level, Rutter says, the advance deepens knowledge about how cells and our bodies work.

A New Frontier

The network described in the study represents an underappreciated layer of regulation in cells that comes from an unexpected source. For nearly 20 years, Rutter's lab has researched metabolism, the chemical reactions that produce energy and build essential components to keep cells running smoothly. Their new research finds that intermediate products of those chemical reactions are more than passive building blocks and sources of fuel for cells, as had long been thought.

Instead, these intermediate products, along with other metabolites, make up an expansive web of sentries that monitor the environment and prompt cells to adapt when needed. They do this by interacting with proteins and modifying how they work. Does a big meal pump too many carbs in the body? Or too much fat? Like a railroad switch that guides a train onto a new track, these protein-metabolite interactions shift metabolic operations to break down those nutrients and steady the course.

The study's first author Kevin Hicks, Ph.D., developed a new technology, termed MIDAS, that reveals the enormity of the regulatory network that acts as an interface between environmental cues and cell metabolism, called the protein-metabolite interactome. The highly sensitive technique identified interactions that had never been seen. An analysis of 33 human proteins involved in converting carbohydrates into fuel found 830 interactions with metabolites. Given that there are thousands of proteins in the cell, the full scale of the network is predicted to be much larger.

"It's surprising how little we know about the extent of these interactions," Hicks says. "We are pushing our understanding of the biological network in new directions."

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Rutgers scientists identify substance that may have sparked life on Earth

A team of Rutgers scientists dedicated to pinpointing the primordial origins of metabolism -- a set of core chemical reactions that first powered life on Earth -- has identified part of a protein that could provide scientists clues to detecting planets on the verge of producing life.

The research, published in Science Advances, has important implications in the search for extraterrestrial life because it gives researchers a new clue to look for, said Vikas Nanda, a researcher at the Center for Advanced Biotechnology and Medicine (CABM) at Rutgers.

Based on laboratory studies, Rutgers scientists say one of the most likely chemical candidates that kickstarted life was a simple peptide with two nickel atoms they are calling "Nickelback" not because it has anything to do with the Canadian rock band, but because its backbone nitrogen atoms bond two critical nickel atoms. A peptide is a constituent of a protein made up of a few elemental building blocks known as amino acids.

"Scientists believe that sometime between 3.5 and 3.8 billion years ago there was a tipping point, something that kickstarted the change from prebiotic chemistry -- molecules before life -- to living, biological systems," Nanda said. "We believe the change was sparked by a few small precursor proteins that performed key steps in an ancient metabolic reaction. And we think we've found one of these 'pioneer peptides'."

The scientists conducting the study are part of a Rutgers-led team called Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA), which is part of the Astrobiology program at NASA. The researchers are seeking to understand how proteins evolved to become the predominant catalyst of life on Earth.

When scouring the universe with telescopes and probes for signs of past, present or emerging life, NASA scientists look for specific "biosignatures" known to be harbingers of life. Peptides like nickelback could become the latest biosignature employed by NASA to detect planets on the verge of producing life, Nanda said.

An original instigating chemical, the researchers reasoned, would need to be simple enough to be able to assemble spontaneously in a prebiotic soup. But it would have to be sufficiently chemically active to possess the potential to take energy from the environment to drive a biochemical process.

To do so, the researchers adopted a "reductionist" approach: They started by examining existing contemporary proteins known to be associated with metabolic processes. Knowing the proteins were too complex to have emerged early on, they pared them down to their basic structure.

After sequences of experiments, researchers concluded the best candidate was Nickelback. The peptide is made of 13 amino acids and binds two nickel ions.

Nickel, they reasoned, was an abundant metal in early oceans. When bound to the peptide, the nickel atoms become potent catalysts, attracting additional protons and electrons and producing hydrogen gas. Hydrogen, the researchers reasoned, was also more abundant on early Earth and would have been a critical source of energy to power metabolism.

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Scientists discover new 'origins of life' chemical reactions

Four billion years ago, the Earth looked very different than it does today, devoid of life and covered by a vast ocean. Over the course of millions of years, in that primordial soup, life emerged. Researchers have long theorized how molecules came together to spark this transition. Now, scientists at Scripps Research have discovered a new set of chemical reactions that use cyanide, ammonia and carbon dioxide -- all thought to be common on the early earth -- to generate amino acids and nucleic acids, the building blocks of proteins and DNA.

"We've come up with a new paradigm to explain this shift from prebiotic to biotic chemistry," says Ramanarayanan Krishnamurthy, PhD, an associate professor of chemistry at Scripps Research, and lead author of the new paper, published July 28, 2022 in the journal Nature Chemistry. "We think the kind of reactions we've described are probably what could have happened on early earth."

In addition to giving researchers insight into the chemistry of the early earth, the newly discovered chemical reactions are also useful in certain manufacturing processes, such as the generation of custom labeled biomolecules from inexpensive starting materials.

Earlier this year, Krishnamurthy's group showed how cyanide can enable the chemical reactions that turn prebiotic molecules and water into basic organic compounds required for life. Unlike previously proposed reactions, this one worked at room temperature and in a wide pH range. The researchers wondered whether, under the same conditions, there was a way to generate amino acids, more complex molecules that compose proteins in all known living cells.

In cells today, amino acids are generated from precursors called α-keto acids using both nitrogen and specialized proteins called enzymes. Researchers have found evidence that α-keto acids likely existed early in Earth's history. However, many have hypothesized that before the advent of cellular life, amino acids must have been generated from completely different precursors, aldehydes, rather than α-keto acids, since enzymes to carry out the conversion did not yet exist. But that idea has led to debate about how and when the switch occurred from aldehydes to α-keto acids as the key ingredient for making amino acids.

After their success using cyanide to drive other chemical reactions, Krishnamurthy and his colleagues suspected that cyanide, even without enzymes, might also help turn α-keto acids into amino acids. Because they knew nitrogen would be required in some form, they added ammonia -- a form of nitrogen that would have been present on the early earth. Then, through trial and error, they discovered a third key ingredient: carbon dioxide. With this mixture, they quickly started seeing amino acids form.

"We were expecting it to be quite difficult to figure this out, and it turned out to be even simpler than we had imagined," says Krishnamurthy. "If you mix only the keto acid, cyanide and ammonia, it just sits there. As soon as you add carbon dioxide, even trace amounts, the reaction picks up speed."

Because the new reaction is relatively similar to what occurs today inside cells -- except for being driven by cyanide instead of a protein -- it seems more likely to be the source of early life, rather than drastically different reactions, the researchers say. The research also helps bring together two sides of a long-standing debate about the importance of carbon dioxide to early life, concluding that carbon dioxide was key, but only in combination with other molecules.

In the process of studying their chemical soup, Krishnamurthy's group discovered that a byproduct of the same reaction is orotate, a precursor to nucleotides that make up DNA and RNA. This suggests that the same primordial soup, under the right conditions, could have given rise to a large number of the molecules that are required for the key elements of life.

"What we want to do next is continue probing what kind of chemistry can emerge from this mixture," says Krishnamurthy. "Can amino acids start forming small proteins? Could one of those proteins come back and begin to act as an enzyme to make more of these amino acids?"

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Covering metal catalyst surfaces with thin two-dimensional oxide materials can enhance chemical reactions

 Physically confined spaces can make for more efficient chemical reactions, according to recent studies led by scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory. They found that partially covering metal surfaces acting as catalysts, or materials that speed up reactions, with thin films of silica can impact the energies and rates of these reactions. The thin silica forms a two-dimensional (2-D) array of hexagonal-prism-shaped "cages" containing silicon and oxygen atoms.

"These porous silica frameworks are the thickness of only three atoms," explained Samuel Tenney, a chemist in the Interface Science and Catalysis Group of Brookhaven Lab's Center for Functional Nanomaterials (CFN). "If the pores were too tall, certain branches of molecules wouldn't be able to reach the interface. There's a particular geometry in which molecules can come in and bind, sort of like the way an enzyme and a substrate lock together. Molecules with the appropriate size can slip through the pores and interact with the catalytically active metal surface."

"The bilayer silica is not actually anchored to the metal surface," added Calley Eads, a research associate in the same group. "There are weak forces in between. This weak interaction allows molecules not only to penetrate the pores but also to explore the catalytic surface and find the most reactive sites and optimized reaction geometry by moving horizontally in the confined space in between the bilayer and metal. If it was anchored, the bilayer would only have one pore site for each molecule to interact with the metal."

The scientists are discovering that the confined spaces modify different types of reactions, and they are working to understand why.

Tenney and Eads are co-corresponding authors on recently published research in Angewandte Chemie demonstrating this confinement effect for an industrially important reaction: carbon monoxide oxidation. Carbon monoxide is a toxic component of engine exhaust from vehicles and thus must be removed. With the help of an appropriate precious metal catalyst such as palladium, platinum, or rhodium, catalytic converters in vehicles combine carbon monoxide with oxygen to form carbon dioxide.

Tenney, Eads, and colleagues at the CFN and Brookhaven's National Synchrotron Light Source II (NSLS-II) showed that covering palladium with silica boosts the amount of carbon dioxide produced by 20 percent, as compared to the reaction on bare palladium.

To achieve this performance enhancement, the scientists first had to get a full bilayer structure across the palladium surface. To do so, they heated a calibrated amount of silicon to sublimation temperatures in a high-pressure oxygen environment. In sublimation, a solid directly transforms into a gas. As the thin film of silica was being created, they probed its structure with low-energy electron diffraction. In this technique, electrons striking a material diffract in a pattern characteristic of the material's crystalline structure.

"We continue heating until we get highly crystalline structures with well-defined pore sizes that we can use to explore the chemistry we're interested in," said Eads.

Here, the team tracked reactants and products and the chemical bonding environment in the 2-D confined space during oxidation of carbon monoxide, incrementally increasing the temperature. To track this information, they simultaneously conducted ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) and mass spectrometry (MS) at the NSLS-II and infrared reflection-absorption spectroscopy (IRAAS) at the CFN.

"AP-XPS tells us what elements are present, whether they're on the surface or in the gas phase," said Tenney. "It can also give us information about the chemical oxidation state or binding geometry of the atoms -- whether a carbon is bound to one or two oxygen atoms, for example. MS helps us identify the gas-phase molecules we're seeing evolve in our system on the basis of their weight and charge. IRRAS is a fingerprint of the type of chemical bonds present between atoms and shows the conformation and orientation of carbon monoxide molecules adsorbed on the surface."

According to co-author Dario Stacchiola, leader of the CFN Interface Science and Catalysis Group, one of the team's unique capabilities is the ability to use complementary surface characterization tools to analyze the same sample without exposing it to air, which could cause contamination.

"Reproducibility is often a problem in catalysis," said Stacchiola. "But we have a setup that allows us to prepare a sample in very pristine ultrahigh-vacuum conditions and expose the same sample to industrially relevant pressures of gases."

The experimental results showed a sharp rise in the amount of carbon dioxide above a critical temperature. Below this temperature, carbon monoxide "poisons" the surface, preventing the reaction from proceeding. However, once the temperature threshold is met, molecular oxygen begins to split into two individual oxygen atoms on the palladium surface and form a surface oxide. These oxygen atoms combine with carbon monoxide to form carbon dioxide, thereby preventing poisoning.

"The confined space is changing the energetics and kinetics of the reaction to produce more carbon dioxide," said Eads, who led the recent implementation of this new multimodal surface analysis approach for studying nanoporous films under operational conditions.

"By applying thin films on top of a traditional catalyst that has been studied for decades, we've introduced a "knob" to tailor the chemistry for certain reactions," said Tenney. "Even a one-percent improvement in catalyst efficiency can translate into economic savings in large-scale production."

"We found that a very thin layer of an inexpensive oxide can significantly boost catalytic activity without increasing the amount of the expensive precious metal used as the catalyst," added Stacchiola.

Previously, the team studied the dynamics of the furfuryl alcohol reaction on a palladium surface covered by bilayer silica. Furfuryl alcohol is a biomass-derived molecule that can be converted into biofuel. Compared to carbon monoxide oxidation, which only makes a single product, reactions with larger and more complex biomolecules such as furfuryl alcohol can generate many undesired byproducts. Their preliminary data showed the potential for tuning the selectivity of the furfuryl alcohol reaction with the bilayer silica cover.

"Changing catalytic activity is great -- that's what we see in the carbon monoxide oxidation study," said Stacchiola. "The next step is to prove that we can use the oxide covers to tune the selectivity for particular reactions. We think our approach can be applied broadly in catalysis."

Last year, other members of Stacchiola's group -- along with colleagues from the CFN Theory and Computation Group, Stony Brook University (SBU), and University of Wisconsin-Milwaukee -- published a related study in ACS Catalysis, a journal of the American Chemical Society (ACS). Combining experiment and theory, they discovered why the water formation reaction catalyzed by ruthenium metal is accelerated under confinement with bilayer silica.

"Chemistry in confined spaces is quite a new area of research," said co-corresponding author Deyu Lu, a physicist in the CFN Theory and Computation Group. "In the last decade, there have been many reports that confinement impacts the chemistry, but a mechanistic understanding on the atomic scale has been largely lacking."

In the ACS Catalysis study, the CFN team demonstrated that confinement can change the pathway by which the reaction occurs. Water formation can proceed by two possible reaction pathways: direct hydrogenation and disproportionation. The main difference is how the first hydroxyl group -- oxygen bonded to hydrogen -- is made. According to calculations by Lu and first author and SBU student Mengen Wang -- this reaction step costs the most energy.

In the direct pathway, hydrogen molecules dissociate on the surface into two hydrogen atoms, which combine with a chemically absorbed oxygen on the surface. These hydroxyl groups combine with another hydrogen atom to make water. For the disproportionation pathway, water -- which may still initially come from the direct pathway -- first needs to be stabilized on the surface. Then, water can combine with a surface oxygen to make two hydroxyl groups on the surface. These hydroxyl groups can join with two hydrogen atoms to form two water molecules. These water molecules can then make more hydroxyl groups, forming a loop in the disproportionation pathway.

In lab-based AP-XPS experiments at the CFN, the team found that the temperature needed to activate the water formation reaction was much lower when silica was covering ruthenium, as compared to the metal by itself.

"The fact that the reaction takes place at lower temperatures in confinement is partially related to its lower activation energy," explained co-corresponding author Anibal Boscoboinik, a chemist in the CFN Interface Science and Catalysis Group. "From the AP-XPS data on surface oxygen, we can indirectly derive the energy required to activate the reaction. We see that this activation energy is much lower when silica is on top of ruthenium."

Applying a popular computational method called density functional theory, the team used supercomputers to study the energetics of the reaction. Initially, the experimentalists hypothesized that the lowered activation energy for the rate-limiting step of the reaction (making the first hydroxyl group) was due to silica pressing down on the reaction complex. However, the calculations showed that the presence of silica didn't change this energy significantly. Rather, it changed the reaction pathway. On the bare ruthenium surface, the direct pathway was favored; in the presence of silica, water molecules stabilized on the surface, activating the disproportionation pathway.

"Without the silica cover, the water molecules desorb, and the reaction follows the direct pathway," said Lu. "Under the silica cover, water needs to cross several kinetic energy barriers in order to leave the surface. These kinetic barriers trap water molecules on the metal surface and activate the disproportionation pathway, enabling the hydroxyl groups to be made at a much lower energy barrier, as compared to the case without the confinement effects."

Though water formation isn't industrially relevant, the scientists say studying this model reaction can help them understand how to leverage the confinement effects to favor certain reaction pathways for more relevant reactions. In other words, the same fundamental principle can be applied to other systems. For example, silica could be coated onto electrodes to evoke particular pathways at liquid-solid interfaces in electrochemical cells. In that case, the reaction would be the opposite -- water would be dissociated into oxygen and hydrogen, a clean fuel.

"Understanding this reaction helps us to understand the reverse reaction," said Boscoboinik, who recently published a summary of initial studies on confinement effects with 2-D porous thin films. "If we were guided by experiment alone, we would have attributed the wrong explanation. Theory proved that our initial hypothesis was incorrect and played a key role in revealing the correct reaction mechanism at the microscopic level."

Yet, the scientists have seen other examples where silica has a pressure-related effect. In 2019, they found that bilayer silica presses down on the noble gas xenon at the interface between bilayer silica and ruthenium, inducing stronger bonding between xenon and ruthenium.

Read more at Science Daily