Whats the melting point of steel? A conversation with a chemist about the Brent Spence Bridge crash – The Cincinnati Enquirer

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Stefanie Ferguson has a Ph.D. in chemistry.(Photo: Provided)

Stefanie Ferguson is a chemistry teacher at GIO International High School in Bowling Green, Kentucky. She has a bachelors degree in chemistry from Western Kentucky University and a Ph.D. in chemistry from the University of Tennessee-Knoxville.

Below are excerpts from a conversation with Ferguson about the crash and subsequent fire that closed Cincinnatis Brent Spence Bridge. The conversationhas been edited for length and clarity.

What happens to a bridge like the Brent Spence when it catches on fire?

The melting point of steel, fortunately, is a lot hotter than what the fire got up to, 1,500 degrees Fahrenheit. Thats very hot.There are different degrees and grades of steel, butfortunately, steel melts at1,500 degrees Celsius. Thats just a little less than double the temperature of the fire. So, it's not going to be one of those things where the bridgewould just collapse.

Steel is made of iron and carbon, and the good thing is theyre very stable. You would just want to get it checked out, and thats something an engineering team would be able to do.

One of the trucks involved in the crash was carrying potassium hydroxide.

That can do quite a bit of damage to anything that would be a carbon base, or that petroleum texture. All the petroleum-based compounds that we use for asphalts that potassium hydroxide probably did a number on that.

Potassium hydroxide is very caustic. It is a base. The cool thing about that is, in the chemistry lab, if you want to clean stuff, thats what you use. You can clean a lot of nasty things with a solution with that inside it. But in a massive amount on a highway, that could really do some damage.

I always go back to the kitchen. If people buy oven cleaner, that stuff is really nasty, you should wear gloves and such. That is sodium hydroxide, and its nasty for sure. Potassium hydroxide is a degree worse and harder to deal with. And so, depending on how much time the potassium hydroxide was on the highway, it could start that deterioration process.

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Officials said the potassium hydroxide probably contributed to the heat and duration of the fire. Would it have caused any other problems?

It would be very hard to get rid of it, too. If you say, OK, well just pour water on it, well just dilute it down, well, wheres it going? It can go into the environment, and thats not a great thing to do. So its a tough, tough situation.

I made the joke with a friend, its hard to find an engineers worth supply of baking soda to cover up chemical spills like that.

In the 911 call, the truck driver can be heard saying he couldnt get his hazmat paperwork before he jumped out of the truck.

I was told this for years as a chemist, its so important that we give the proper information so everyone knows what we have in our lab, or in this situation, what was on board. We call them material safety data sheets. First of all, it tells what the concentration was, what it was, how much is there, and what we need to do in terms of fire or emergencies, poison control, things like that.

Those data sheets are uniform nationwide, so that part is good. OK, the sheets were destroyed, but do you know what was in here? Chemists and chemical engineers have that information and share that out so law enforcement and the fire department can do their job properly.

This is causing major traffic headaches and taxpayers could be facing hefty repair bills. Is there any good news here?

The good news is, at least you didnt have an issue where this happened in the middle of January or February, where its very cold outside and you have thishigh, high temperature from the fire.

Think of it like when you cook, youre not supposed to put certain pots and pans into a hot oven if theyre cold. It shouldnt go from your refrigerator straight into the oven because you have a chance of damaging the container.

The same holds true with the bridge. If this were to happen in January, February, say it was sub-zero degrees, that could give more cause for concern. Its a good thing that didnt happen.

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Whats the melting point of steel? A conversation with a chemist about the Brent Spence Bridge crash - The Cincinnati Enquirer

Surface chemistry discovery points way to cheaper water splitting – Chemistry World

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Surface chemistry and electric potential are the two driving forces of electrocatalysis. Until now, researchers assumed the latter drove water oxidation the bottleneck of water splitting but new work shows otherwise. It has now been discovered that in electrocatalysed water splitting the breaking and forming of bonds at the catalysts surface is what actually controls the reaction, an unexpected finding that could accelerate the development of renewable hydrogen generation.1

We show that electrocatalytic oxygen evolution really behaves like traditional catalysis, explains Travis Jones from the Fritz Haber Institute in Germany, who co-led the study. Surprisingly, electric potential does not play an important role in the reaction coordinate. The secret of electrocatalytic water oxidation rests on fundamental chemistry. We can apply the same concepts we use in classic thermally catalysed reactions, Jones adds.

Taking voltage out of the equation could mean huge energy savings. Usually, electrochemical reactions need additional energy to overcome the activation barrier the overpotential. However, if surface chemistry regulates the limiting step, overpotential could be drastically reduced. Chemists could focus on designing more efficient water splitting catalysts, says Jones.

To show that oxygen evolution is like any other catalytic reaction, the researchers first had to disentangle the effects of potential and surface chemistry, which are intimately connected. They did this by modifying the surface of iridium oxide, one of the best electrocatalysts for water oxidation, by gradually poisoning it with chlorine atoms. When the surface is completely covered in chlorine, any catalytic effects we observe would come from voltage alone, explains Javier Prez-Ramrez at ETH Zurich in Switzerland. The experimental results they observed matched computational predictions electric potential merely oxidises the surface and doesnt influences the reactions progress.

This is a really interesting way to show the importance of surface chemistry, explains Annabella Selloni, an expert in theoretical chemistry and new materials at Princeton University, US. The roles of voltage and surface chemistry are very interconnected, separating [them] is far from trivial.

Further experiments confirmed the initial observations. Using x-ray spectroscopy, we could see iridium going to higher oxidation states, until it reached a point where it could not oxidise further, explains Jones. As oxygen starts accumulating charge, it reaches an unusual oxyl (-1) oxidation state . At this point, the reaction starts going, adds Jones. Oxygen becomes active, water molecules can attack it and start making the new oxygenoxygen bond. Forging that bond is the limiting step.

The team also performed theoretical studies, which were key to identifying the unusual oxygen species. DFT computational experiments show that oxidised surface species reduce the energy barrier of the oxygenoxygen bond formation, says Selloni.

This combination of theory and experiments gives a really holistic picture, says Ifan Stevens, an electrochemist at Imperial College London, UK. These results provide a lot of precise information on the active catalytic species in the oxygen evolution reaction. This is essential to design better catalysts, and potentially reduce the amount of iridium oxide needed, he adds. Although iridium is a precious metal, it has some advantages over nickel and iron-based electrocatalysts it can withstand the highly acidic and oxidising conditions of proton exchange membrane electrolysers. These devices are particularly useful, because they can operate efficiently at high rates and fluctuating power inputs, which makes them ideal for storing intermittent sources of power such as solar or wind, explains Stephens.

People have been applying a kinetic theory from the 1930s [to electrocatalysis], but we show it doesnt work for this type of reaction, says Jones. Stephens agrees that traditional textbook analyses may be insufficient to explain these phenomena. Previous studies carried out by James Durrant and other colleagues at Imperial2 already showed the rate of water oxidation is often controlled by the population of reactive intermediates, he says. This settles it voltage is important, but does not control the rate determining step.

With this new book of instructions, researchers could create more efficient catalysts for other electrocatalysed processes, such as ammonia fixation or carbon dioxide reduction, Jones says. Their preliminary results indicate their concept is transferrable to other systems, he adds.

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Surface chemistry discovery points way to cheaper water splitting - Chemistry World

Jeff Teague takes a crash course in chemistry – Boston Herald

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Jeff Teague was attracted to the Celtics, in part, because of the opportunity to play with one of the NBAs great young twosomes.

But the veteran point guard doesnt have a lot of time to mesh with Jayson Tatum and Jaylen Brown or, for that matter, Marcus Smart and Daniel Theis.

With the first exhibition game three days away in Philadelphia, all are scrambling for a groove. Tristan Thompson, according to Brad Stevens, may not even be available by the regular season opener on Dec. 23 due to lingering hamstring trouble.

And none of it is helped by this cram session of a training camp. The process admittedly hasnt been smooth for Teague.

Its a little difficult, because we cant spend as much time together because of certain rules, Teague said during a Saturday Zoom session. Its going fast, and we dont have as much time to jell as we would in a normal offseason. Usually guys come in, play pickup and things like that, and you get to know someone on and off the court. Right now its a crash course. The good thing about this team is they have a really good nucleus, and Im just trying to fit in and figure it all out.

Another orientation is set for January, when Kemba Walker is expected to return from a knee rehab project. Until then, much will fall on Walkers backup.

Weve got a lot of great guys, a lot of talented players, and its going to be a wholeteam effort not having a guy like that right now, a dynamic point guard like that, so I guess well figure it out, said Teague, who has found a particularly receptive audience in Tatum and Brown.

They do a great job of listening, he said. They take advice and its a back-and-forth thing. I know how talented they are and how much they mean to the team, so I just try to give my pointers where I can. If I see something, I try to let them know what I see, and vice versa if they see something, they let me know.

But youve got to find your role, and for them, theyre going to be here for years to come. I just got to find ways to help them be better, and obviously theyre going to help me be better. But thats one thing just trying to help them be the players that they can be and this team to be the team that they can be. And it should be a great year.

Teague also has a varied group of big men to learn and blend with.

Ive played with a lot of talented bigs. Youve just got to figure out the person, he said. Figuring out that you throw the ball up to Rob (Wiliams) because hes an athletic big, he goes and gets it. Theis, you can play different ways on him. And obviously with Tacko (Fall), you want to make sure you throw the ball up. But you learn each other. You figure it out where guys are comfortable catching the ball. Its going to be a work in progress. Were still a team thats trying to figure it out right now. Weve got some time to try to get it right before our first game, but were still working.

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Jeff Teague takes a crash course in chemistry - Boston Herald

‘The Writing On The Wall’ Finds Poetry Behind Bars, Projects It Onto Buildings – NPR

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"The Writing On The Wall" art installation projects writings by incarcerated people onto the sides of buildings, such as The New York State Supreme Court Building, above. Chemistry Creative hide caption

"The Writing On The Wall" art installation projects writings by incarcerated people onto the sides of buildings, such as The New York State Supreme Court Building, above.

With millions of people behind bars in the U.S., artist Hank Willis Thomas thinks about all of the ideas that are locked away with them. "Look at all the wisdom, look at all the heart that is imprisoned in our society," he says.

He and professor Baz Dreisinger are the co-founders of The Writing on the Wall, a project that takes the words of incarcerated people beyond prison and jail walls. "There was so much poetry in there, just so much beauty, drawings, thoughts, so much reflection of humanity," says Dreisinger.

Dreisinger also founded the Incarceration Nations Network, a coalition of prison reformers, and she teaches English at John Jay College of Criminal Justice. "Technically I was teaching English classes, but really I was teaching criminal justice through the lens of the humanities and that to me is what The Writing on the Wall is," she says.

The project began small and grew to institutional proportions through projections of those words on the sides of buildings in the U.S. and Mexico.

Initially, Dreisinger and Thomas enlisted architects to design a mobile installation booth that resembled a prison cell with the words of the incarcerated on the walls, floor and ceiling. The idea was to take the booth to cities around the U.S. and Canada, but after its New York debut, the pandemic hit.

With the tour canceled, the organizers got the idea of projecting those words on public buildings, often ones that are part of the criminal justice system. A company called Chemistry Creative came up with a projection system. The Writing on the Wall has been seen in Detroit, New Orleans, Philadelphia, Washington, D.C., Columbus, Ohio and Mexico City. Their last installation was at Brooklyn Public Library.

A poem projected onto the Brooklyn Public Library. Chemistry Creative hide caption

"There is nothing that I as an artist or anyone can really do or say that is more extraordinary than the things these artists were doing ..." says Thomas. "Some of them had not thought of themselves as artists but it was clear that they were."

One of those artists, Devon Simmons, served 15 years in New York prisons, graduated from the Prison-to-College Pipeline program, and is now working as a paid curator and tour guide for the project.

"People who are incarcerated are not only talking about issues that they're enduring in prison, but talking about issues which impact everybody ..." Simmons says. "It's really powerful for the Writing on the Wall to be in these public spaces to create the dialogue in pursuant to create the change that we need to see."

In the coming weeks, The Writing on the Wall will be projected on buildings in East Harlem, Boise, Idaho and the San Francisco Bay Area.

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'The Writing On The Wall' Finds Poetry Behind Bars, Projects It Onto Buildings - NPR

$5,000 Reward Offered In Chemical Attack That Left Germantown Grandmother Blind – CBS Philly

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PHILADELPHIA (CBS) The Philadelphia Fraternal Order of Police Lodge 5 is offering a $5,000 reward for any information leading to the arrest of a suspect that attacked a Germantown grandmother earlier this month. Investigators say the suspect threw a mixture of dangerous chemicals in the womans face as she left her Germantown home on the 5100 block of Newhall Street.

The attack on Oct. 6 left 61-year-old Helen Jones with burns to her lips, tongue and eyes. Family members told Eyewitness News the potent mixture included Draino and it burned through Jones skin, leaving her blind.

Shes a phlebotomist, so she was leaving her home like she does every day. And he [the suspect] asked her, was she good, as if he was asking her about her safety, stepdaughter Aneesha Summerville said. When she looked up to him to respond to him to say yes, he threw a chemical in her face and ran off.

Police dont have a good description of the suspect. They say he was wearing a mask.

Summerville believes the suspect likely has a mental illness since the attack was random and unprovoked.

This random acid attack is a disturbing crime, FOP Lodge 5 President John McNesby said. We need to find this male suspect immediately to prevent another attack.

Anyone with information is being asked to call Northwest detectives at 215-686-3353, 9-1-1 or 686-TIPS.

Meanwhile, the family has created a GoFundMe to help with medical bills and the trauma therapy Jones will need.

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$5,000 Reward Offered In Chemical Attack That Left Germantown Grandmother Blind - CBS Philly

Chemistry Call: The Meeting That Helped Turned the Panthers Around – Sports Illustrated

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Shortly after the Carolina Panthers dropped their second straight game to open the season, cornerback Rasul Douglas reached out to head coach Matt Rhule and talked about what change needed to be made for this team to be successful.

Chemistry was almost non-existent, effort at times was questionable, and the will to win just didn't seem to be there. Being one of the most experienced players on the defense, Douglas saw the signs early on and knew that this trend could not continue if they wanted to win and win now.

The team held a meeting and just let everyone speak about who they are, what they like, their lifestyle, hobbies, family, where they come from and a variety of other things. This was to help eliminate chemistry being an issue on the field and so far, it has worked as the Panthers have rattled off three straight wins since this meeting took place.

"It was more about explaining whatever you felt on your heart to tell the guys about yourself," Douglas said. "Teddy [Bridgewater] got up there and talked about how his mom had cancer and just watching her go through that and her smiling and her being happy and her caring about him was bigger than anything. We also talked to one of the linemen where he said he had COVID and he couldn't be with his wife and his wife was pregnant and he couldn't be around her and the whole time he wasn't, he was thinking about the team. It was basically just expressing how we need to do it together and we need to know each other. If we are going to call each other a family, we've got to feel like family. From 7 a.m. to 7 p.m. I'm here. I go home, I get two hours and then I'm going back to sleep to get ready for here, so it's like if I'm going to be here with you all day, I need to know you. I need to know who you are, I need to know how you think, so when I'm on the field I want to play for you."

While the meeting may not be the one single turning point of the season, it has certainly paid off and you can see it firsthand on the field every Sunday. Defensive coordinator Phil Snow talked about the growth he has seen in the last month.

"I think this team is growing together right now. You've got to have some success too to have that happen and we're fortunate we've won three games in a row, but you can really see this group coming together on both sides of the football and special teams. It's fun to watch. When you get a little confidence, the confidence grows and so does everything else. It's just been fun to watch over the last month."

A lack of chemistry in football or any sport for that matter usually boils down to the players' negligence of wanting to form relationships with their teammates and understanding who they are as a person, not just a football player. These guys spend more time together than they do with their family, so if you have rock solid chemistry, you're going to get rock solid results. Unfortunately, the players were not afforded the opportunity to bond and get to know one another this offseason due to the pandemic. And even once players did make it to camp, it didn't just click right away as rookie defensive lineman Derrick Brown noted during Thursday's press conference.

"We weren't together for long and everybody kind of knew each other behind the IPad's. This year has been crazy, so we never got a chance to really get in here in the spring and early summer. Even my time coming in I really only got to meet a handful of guys at one time. We had to figure out us, we had to figure out the trust. The d-line and linebackers have to trust one another and the backend's got to trust us to be able to do our part and once we figured that out, now it seems like we're starting to play for one another more."

Head coach Matt Rhule has said time and time again about how this team doesn't have any egos and is a bunch that loves playing together. The more football they play, the better the chemistry will be and the better this team will be. The good thing is, the Panthers are 3-2 and are on a three-game winning streak while learning how to play alongside each other.

You can follow us for future coverage by clicking "Follow" on the top righthand corner of the page. Also, be sure to like us on Facebook & Twitter:

Facebook - @PanthersOnSI

Twitter - @SI_Panthers and Schuyler Callihan at @Callihan_.

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Chemistry Call: The Meeting That Helped Turned the Panthers Around - Sports Illustrated

Chemical Grinding Fluid Market Industry Outline, Global and United States Executive Manufacturers, Interpretation and Benefit Growth 2026 by Fujimi…

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NBA Finals: Heat have chemistry and blueprint to beat Lakers – Los Angeles Times

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One night earlier, staffers with plastic face shields covering their masked mouths scampered on both baselines, waiting for the cue to fire off the confetti cans that rained down onto the Western Conference champion Lakers.

Sunday, that same cue the final buzzer came but the shredded paper didnt fall. It could have if the winning team wanted.

Meet the Miami Heat the team that said No.

After beating the Boston Celtics 125-113 in Game 6 of the Eastern Conference finals, the Heat are ready to be introduced to Lakers fans. But you might already know them (and not just the guy with the slicked-back hair, Pat Riley, who put them together).

A Lakers team built on the backs of two of the NBAs most dominant stars will face an underdog group that was stronger as a collective than as individuals, and whose culture and identity are as valuable as jumpers and slam dunks just like the Lakers did in 2004 against the Detroit Pistons.

That season, Ben Wallace, Chauncey Billups and Richard Hamilton were good enough together to beat a Lakers team with four future Hall of Famers, to stare down Kobe Bryant, Shaquille ONeal, Karl Malone and Gary Payton.

On Wednesday, the Lakers will meet the Heat, a team thats beaten higher-seeded teams in each of the playoffs three rounds because of a not-so-secret weapon.

Together, Heat star Jimmy Butler said. Thats how we were able to do it.

The Heat earned the right to be underdogs in the NBA Finals against the Lakers by going through Indiana, Milwaukee and Boston.

They did by betting on Butler, a star who left three previous franchises worse off than when he got there. His leadership style was controversial and not universally embraced. And to teams with salary-cap room last summer like the Lakers and Clippers Butler wasnt a top priority.

Celtics guard Marcus Smart, left, defends against Heat guard Jimmy Butler during Miamis series-clinching victory in Game 6 of the Eastern Conference finals on Sunday.

(Kevin C. Cox / Getty Images)

Thats what this whole thing comes down to is being wanted, being appreciated for what you bring to the table, Butler said. And as Ive said time and time again, as [coach Erik Spoelstra] constantly says, Were not for everybody. Im not for everybody, but here, I am.

The guys we have, were for one another. Were going to constantly compete for one another, and this is home for me.

Hes surrounded by a younger star in Bam Adebayo, who turned in a Game 6 performance that more than made up for his Game 5 clunker, his 10 points and seven rebounds in the fourth quarter the result of an unrelenting force too much for Boston to handle. Goran Dragic is on the backside of his peak, but hes proved all postseason that he still can be a difference maker, a former All-Star guard who can dial back and look like one again for stretches.

And theres the rest of the cast Andre Iguodalas sage championship experience, Tyler Herros confident scoring, Duncan Robinsons shot-making and Jae Crowders all-around game.

Highlights from the Miami Heats victory over the Boston Celtics in Game 6 of the Eastern Conference finals on Sunday.

Those seven players did all of Miamis scoring Sunday, led by Adebayos 32 points and 22 from Butler.

Defensively, though, is where the Heat can give teams problems. Theyll use a bunch of different looks, including plenty of zone. And while theyre not as tall as the Lakers, theyre probably big enough to not be bullied.

Theyre super physical, super tough, very, very savvy, Boston coach Brad Stevens said.

Stevens called the Heat a handful, just like those 2004 Pistons were a team that could dominate pace and find ways to negate its gaps in talent with commitment to one another and selflessness. Led by Billups, the Pistons were the kind of team that would go flying over the front row at Staples Center to chase a loose ball because it might help them win. Tayshaun Princes length, Rasheed Wallaces swagger, Hamiltons smooth style, Ben Wallaces fury and Billups savvy pushed the Pistons past the Lakers talent.

The Heat are built from the same DNA and Butler is the perfect leader.

Everybody in the league has always known that he impacts winning. Its not about stats. Its not about anything else. He cares, Spoelstra said. And for us, thats our language.

And the 2004 Pistons spoke it fluently.

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NBA Finals: Heat have chemistry and blueprint to beat Lakers - Los Angeles Times

Rowan-led research identifies chemical tool for finding proteins in fossil bones – Rowan Today

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Rowan University paleontologist Dr. Paul Ullmann is the lead author on new research into the preservation of ancient biomolecules, such as dinosaur proteins.

The molecules include preserved blood vessels and blood material, pigment cells and proteins that have been observed in recent years by a number of researchers working in the emerging field of molecular paleontology.

Published in the journal Scientific Reports Sept. 23, the research is reminiscent of that in the mega movie franchise Jurassic Park, in which scientists extract a bit of DNA from a mosquito lodged in a piece of solidified amber and, from it, recreate a world of dinosaurs.

Though Ullmann and his team do not seek to reanimate extinct dinosaurs, they used an array of molecular biology techniques to identify preservation of the protein collagen in a 67 million year old bone of the duck-billed dinosaur Edmontosaurus.

When you perform molecular biology tests on certain fossils, you can recover original, ancient molecules, said Ullmann, an assistant professor in Rowans Department of Geology. We havent succeeded with DNA, like in Jurassic Park, but my colleagues and I have recovered ancient proteins.

Ullmann said big questions remain, including how its even possible that genetic material can be viable for millions of years in fossilized dinosaur bones.

Thats part of what were trying to figure out, he said.

Researchers for the article, Molecular tests support the viability of rare earth elements as proxies for fossil biomolecule preservation, included Dr. Ken Lacovara, dean of Rowans School of Earth and Environment and Rowan Assistant Professor Dr. Kristyn Voegele.

Scientists are just beginning to understand the processes that lead to the preservation of minute bits of ancient flesh trapped inside fossils, Lacovara said. This work sheds light on the conditions that make these amazing discoveries possible.

Groundbreaking research

Ullmann said the project began eight years ago when he and Voegele were doctoral students under Lacovara at Drexel University. To investigate how groundwater chemistry influences the decay of molecules in bones, Ullmann began studying a vast dinosaur bonebed in South Dakota. Part of his work involved firing a laser at slices of the bones to determine their elemental chemistry, which hinted that the bones had been little altered over the millennia, and that led his team to predict they might contain ancient molecules.

Ullmann said he and other paleontologists have not only identified ancient proteins in fossilized bones but demonstrated that they derive from the animals themselves and not environmental contamination.

For the first time, weve identified a chemical signature, or indicator, for molecular preservation in fossil bones, Ullmann said. In the end, the real benefit of our work is that scientists can use this tool to make more ancient molecule discoveries, which then have numerous and diverse applications, everything from learning about the physiology and biology of dinosaurs to pathways of molecular evolution.

Like bar codes on fossils

While Ullmanns research never sought to reanimate long-extinct species, he said comparisons to the Jurassic Park storyline are easy to make.

Molecular recovery is an idea that is gaining real traction in paleontology, the most famous of which is the notion that we can use ancient DNA to resurrect animals like dinosaurs and the wooly mammoth, he said.

Which isnt very likely.

The real promise of molecular paleontology, Lacovara said, is that its like having bar codes on fossils. As this technology develops, paleontologists will be able to test hypotheses about ancient creatures in the same way that biologists use molecular fingerprints to study living animals today.

These discoveries are advancing scientific knowledge of how molecules evolve over time and how extinct animals responded to past climate change, Ullmann said. The technological advancements required to recognize molecular fragments in fossils may one day see applications in everything from medicine to materials engineering.

To learn more, take a deeper dive into the research in a fascinating Q&A with Ullmann.

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Rowan-led research identifies chemical tool for finding proteins in fossil bones - Rowan Today

US chemical industry overreaches by invoking USMCA | TheHill – The Hill

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The world is drowning in plastic. The sheer volume and variety of plastics on the market, and its persistence in nature, create significant risks for human and animal health and the survival of sensitive ecosystems.

To its credit, the Canadian government wants to start addressing the problem. Last week it released a scientific assessment of plastic pollution alongside a plan to manage it. Canada proposes regulating plastics as a toxic substance under the Canadian Environmental Protection Act, and to ban outright the manufacture and import of many single-use plastics by 2021.

But the U.S.-based plastics industry is saying not so fast and invoking provisions of the U.S.-Mexico-Canada Agreement (USMCA). In late September, a coalition of U.S. industry associations representing chemicals, fossil fuels, food packaging and transportation wrote to Canadian Trade Minister Mary Ng, asserting Canadas plan to ban certain single-use plastics, set recycled-content requirements for plastic products and packaging, and develop standards for extended producer responsibility violates international trade obligations and the USMCA.

Threatening a trade dispute is a common scare tactic to discourage regulation. Still, the ink was barely dry on the USMCA before the plastics lobby seized on it to raise doubts about Canadas plastic pollution plan. Claiming the scientific assessment isnt based on sound science, and that regulators didnt use a risk-based approach or engage in regulatory cooperation discussions beforehand, the industry says Canadas plan is an unlawful trade barrier and must be stopped.

The devastating consequences of global plastic pollution are so well-established and significant that the United Nations urged action under the Basel Convention on hazardous waste. As the U.N. observes, Plastic accounts for around 10 percent of the total waste generated and constitutes approximately 90 percent of all trash floating on the ocean's surface, with 46,000 pieces of plastic per square mile. It is nearly impossible to clean the seas from plastic waste and microplastics. The USMCA itself requires Canada, Mexico and the U.S. to each take measures to prevent and reduce marine litter.

Yet the chemical lobby makes the claim not only that Canadas proposed measures limiting plastic waste and pollution are unsupported by science, but that they would undermine partnerships and progress against marine litter pursuant to international commitments. Apparently, the industry is using the promise of its future voluntary cooperation to postpone or bar more effective regulatory measures now relying on language in the USMCA to make its case.

Before the USMCA was approved by Canada, Mexico and the U.S., we warned the agreements regulatory cooperation provisions could provide opportunities for enhanced corporate meddling and an excuse to evade and delay regulations. A Canadian Centre for Policy Alternatives report authored by Stuart Trew found even voluntary regulatory cooperation has helped multinational business interests weaken standards for rail safety, workplace hazard labeling and chemicals risk assessment. We worried that incorporating these provisions into an enforceable trade agreement would further undermine public protections.

Our fears were well-founded. Business interests have already cited these provisions to question Mexicos law requiring junk food warning labels. The salvo against Canadas plastics regulation is part of an international campaign to use trade agreements to limit controls on plastic exports and regulation. The New York Times documented that many of the lobby groups behind the letter to Canadas trade minister want to use a proposed U.S. trade agreement with Kenya to roll back the African nations 2017 ban on plastic bags and force Kenya to continue importing waste plastics. The story prompted a bipartisan group of 62 U.S. lawmakers to urge U.S. trade negotiators not to undermine Kenyas policies to regulate plastic products and wastes. This trade-based corporate strategy is crucial for the fossil fuel industry, which has pivoted hard into plastics in anticipation of a sharp drop in oil demand as countries try to lower greenhouse gas emissions.

All countries need the regulatory freedom to take the plastics crisis seriously. Expansive new language in the USMCA chips away at that freedom. Regardless of whether the oil, chemicals and plastics firms would have a winnable case against Canada, the USMCA offers new tools to strip public protections. Canada and Mexico are already facing the consequences of agreeing to corporate-written deregulatory text in the USMCA. The Trump administration is using the USMCA as a template for new trade deals. Other countries, including Kenya and the United Kingdom, should steer clear of U.S. demands for new regulatory restrictions in any trade deals resulting from current negotiations.

Ultimately, these measures will blow back on the U.S. as well. Future U.S. governments looking to rein in the fossil fuel sector and strengthen environmental protections may find themselves tangled in a trade dispute of their own making.

Sharon Treat is senior attorney at the Institute for Agriculture and Trade Policy, focused on international trade agreements and their intersection with environmental, food and public health policy.

Stuart Trew is senior researcher at the Canadian Centre for Policy Alternatives, based in Ottawa, ON.

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US chemical industry overreaches by invoking USMCA | TheHill - The Hill

Explore the science of chemical reactions by baking some tasty apple muffins – WWLP.com

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(Mass Appeal) Are you looking to sneak in a little extra education in your childrens day? Have them join you in the kitchen for a lesson in chemical reactions while you make dinner or some tasty muffins. Ashley Tresoline, Owner of Bella Foodie explains how she keeps children engaged in cooking lessons by explaining the chemistry involved with recipes. She also shares her recipe for apple crunch muffins.

Apple Crunch MuffinsBy: Ashley Tresoline

Ingredients:

cup non diary milk plus tbs apple cider vinegar (I use almond milk)1/3 cup applesauce unsweetened cup maple syrup plus 2 tbs. cup melted coconut oil1 egg2 tsp. vanilla extract cup almond flour or almond meal1 cup all purpose flour (can sub 1 to 1 gfree flour)1 tsp. baking powder tsp. baking soda tsp. salt1 tbs. cinnamon tsp. nutmeg1 cup granny smith apples, peeled and diced

Crumble topping1/3 to cup almond meal flour2 tbs. maple syrup2 tbs. coconut sugar almonds, coarsely chopped or your favorite nut2 tbs. coconut oil, meltedPinch of cinnamon

Directions:Preheat the oven to 425and line a muffin tin with paper liners about 9 muffins. Measure out the non-diary milk and add the cider vinegar and set aside. In a small bowl combine all the crumble ingredients and set aside. In a large bowl add the almond flour, all purpose flour, baking powder, baking soda, salt, cinnamon and nutmeg. Whisk the dry ingredients together until well combined. Peel and chop your apple and set aside. In a small bowl combine the wet ingredients milk vinegar mixture, egg, unsweetened applesauce, cup maple syrup, the rest of the coconut oil and the vanilla extract. Whisk together until combined and then add to the dry ingredients and mix together. Once well combined fold in the apples. Fill the muffin tins way. Bake at 425for 5 minutes then lower the oven to 350for 10-15 minutes.

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Explore the science of chemical reactions by baking some tasty apple muffins - WWLP.com

Tri-Town gets grant to remove ‘forever chemical’ – The Patriot Ledger

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The money will be used to design ways to remove a group of chemicals from the drinking water of Braintree, Randolph and Holbrook.

BRAINTREE The Tri-Town Water District has received a $200,000 grant from the state to reduce the levels of a "forever chemical" in the water system.

The state has also announced new regulations that will require regular testing of drinking water for a group of chemicals known as PFAS starting next year, and also sets a state limit for the levels of those chemicals. There is no federal standard.

Gov. Charlie Baker said the state is committed to making sure all residents have access to safe and clean drinking water.

"By setting stringent standards for PFAS in drinking water, we can ensure that all public water systems across the commonwealth are testing for these emerging contaminants, while providing them the tools and resources they need to address any contamination," Baker said in a statement.

PFAS is an acronym for per- and polyfluoroalkyl substances, a group of man-made chemicals which have been used in a variety of applications since the 1950s, from nonstick cookware and water-resistant clothing to food packaging materials and firefighting foam. They are considered a "forever chemical" because they don't break down and can accumulate in the body. They have been linked to a number of negative health impacts, from weakening the immune system of children, increasing cholesterol levels and causing tumors. They have also been shown to be a health risk for pregnant and nursing mothers.

Braintree Mayor Charles Kokoros, who is chairman of the Tri-Town Water Board, said the money will be used for the engineering and design work needed for PFAS removal at the proposed regional water plant at Great Pond. The plant will serve the town as well as Randolph and Holbrook, the other tri-town members. The regional plant will replace two outdated treatment plants, one for Braintree and one which serves Randolph and Holbrook.

PFAS were discovered in Braintree's drinking water last year as part of the design process for the new water treatment plant. Braintree officials made changes that brought down the PFAS level in the town's drinking water from 24.5 parts per trillion last fall to 21 parts per trillion in January. In April, the town council approved spending $693,020 to install granular activated carbon in the treatment plant's filter system to further reduce the levels.

The new state limit will be 20 parts per trillion and water systems will be required to take corrective action when the limit is exceeded. Testing for PFAS will be required starting in January for large water systems and public notices will be required when the limit is exceeded.

A total of $1.9 million in grants were awarded to 10 water systems by the state.

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Tri-Town gets grant to remove 'forever chemical' - The Patriot Ledger

USCCB warns against rising chemical abortions, calls for support for Save Moms and Babies Act | News Headlines – Catholic Culture

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Catholic World News

September 22, 2020

Continue to this story on USCCB

CWN Editor's Note: A rising threat to the lives of unborn babies is the chemical abortion pill, the US Conference of Catholic Bishops said in an action alert. The number of chemical abortions in the US has gone up dramatically, while the overall number of abortions has decreased. COVID-19 is expected to only make the problem worse, with more women (and teen girls) seeking chemical abortions at homeeven illegally, by mail and without a doctors prescription.

For all current news, visit our News home page.

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Five arrested after chemical tanks struck by gunfire – WKBW-TV

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RIDGEWAY, N.Y. (WKBW) 3 adults and 2 juveniles are facing charges after chemical tanks were found punctured by bullets and leaking chemicals.

Monday afternoon, the Ridgeway Fire Department was called to the Helena Agri-Enterprises LLC facility on Allis Road due to a chemical leak issue. Once on the scene, first responders determined that the leak was due to bullet holes in the chemical tank itself. It appeared that bullets had ricocheted of nearby buildings and the tank.

The Orleans County Sheriffs Office, NYS DEC, NYS Police and Medina Police all responded to the scene and searched the nearby area. Police found 5 people, 2 adults and 3 juveniles, south of the chemical facility who admitted to target hooting in the area, according to the Orleans County Sheriff's Office.

Investigators believe the chemical facility was directly in line with the target shooting. Jared S. Silva, Stephen J. Jackson, Joe W. Jackson and the 3 juveniles were arrested and charged with reckless endangerment and criminal mischief.

It's estimated that $65,000 in damage was done to the chemical storage tanks.

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Five arrested after chemical tanks struck by gunfire - WKBW-TV

There’s an Actual Scientific Way to Perfectly Melt Cheese on Toast – ourcommunitynow.com

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Courtesy of D. Sharon Pruitt

Chemists from the Royal Society of Chemistry and cheese experts from the British Cheese Board teamed up to conduct scientific research onthe best way to melt cheese on toast. (No, we arent making this up.)

Like any other scientific experiment, the chemists carried out several tests changing one variable at a time in order to come up with the perfect formula.According tothe Science Executive, Ruth Neale, they testedthree different components: consistency of the temperature of the melted cheese across the slice, the texture of the cheese, and the taste. The chemists focused on the temperature and scientific documentation working alongside the Secretary of the British Cheese Board, Nigel White, who judged the texture of the cheese and the taste.

Courtesy of the Royal Society of Chemistry

Okay, after reading that formula, you probably had one of two reactionseither younerded-outabout the scientific method, or your eyes glazed over and your brain shut down. If you didnt ace your high school chemistry class, dont worry! Well explain what the formula actually means without the scientific jargon:

"We found that the perfect slice can be made by melting 50 grams of sliced hard cheese, such as cheddar, on a slice of white bread, 10mm thick, under the grill. The cheese on toast should sit at a distance of 18cm from the heat sourcewhich in our grill was at a temperature of 115 degrees Celsiusand needs to cook for four minutes to achieve the perfect consistency and taste." Ruth Neale

For those of us who aren't chemists using the metric system, that means use about 1.75 ounces of sliced hard cheese on white bread that's about .4 inches thick. Make sure the heat source is heated to 239 degrees Fahrenheit and is keptabout 7 inches away from the cheese toast.

We're almost certain this might be a publicity stunt to get us interested in studying science, but who cares! It got us talking about a few of our favorite thingscarbs and cheese! What's your favorite type of cheese to melt on toast? Let us know in the comments below.

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How ‘green chemistry’ could have a big part to play in the future – CNBC

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Used in everything from the detergent that washes our clothes to the toothpaste that keeps our mouths clean, chemicals play an integral role in society.

While it's hard to imagine life without them, if not used in a responsible way their effect on the natural world and us can be harmful.

The European Commission has stated that some chemicals "can severely damage our health or the environment," while the World Health Organization has previously estimated that exposure to selected chemicals resulted in the loss of 1.6 million lives in 2016.

It's against this backdrop that the notion of "green chemistry" comes into play. In relatively simple terms, the United States Environmental Protection Agency has defined it as "the design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances."

The EPA goes on to explain that the idea of green chemistry relates to a product's entire life cycle, which includes everything from its design and production to utilization and disposal.

Paul Anastas is the director of Yale University's Center for Green Chemistry and Green Engineering. Speaking on the latest episode of CNBC's Sustainable Energy, he explained how he became interested in the subject.

"When I was a young chemist, I looked around at all of the technological miracles that chemistry produced," he said. "And then I looked at the other side of the equation all of the unintended consequences of pollution and its effect on the environment and on human health," he added.

"So green chemistry is really a way of keeping all of those technological miracles, those innovations, without all of those unintended consequences."

Anastas, together with John Warner a chemist who is now president and chief technology officer of the Warner Babcock Institute for Green Chemistry co-authored the book "Green Chemistry: Theory and Practice," a key body of work in the field.

First published in 1998, the book lists 12 principles of green chemistry, one of which focuses on the prevention of waste, a subject that Anastas expanded upon when speaking to CNBC.

"Waste, we need to recognize, is a man-made concept," he said. "In nature, there is no waste: every time a waste is generated, an organism evolves to use that waste as a feedstock."

He added: "And so, we think about how to do the same thing in industry, how you either prevent or avoid waste, or utilize whatever waste in a valuable way."

With attitudes regarding pollution and the environment shifting in recent years, many governments and businesses are emphasizing their commitments to sustainable practices.

But while actions need to match words and there is clearly a long way to go, Anastas sought to emphasize the changes that were being made.

"I simply cannot name an industry sector that isn't using green chemistry," he said. "Everything from pharmaceuticals, to plastics, everything from cosmetics to the way that we generate, store and transport our energy," he added. "Now, I'm not going to say that companies are doing it systematically or in all of their products, but great strides are being made."

When it comes to the production of chemicals, there is some serious work to be done, however. According to the International Energy Agency (IEA), in 2018 direct carbon dioxide emissions from primary chemical production hit 880 million tonnes, a jump of almost 4% compared to 2017. The IEA goes on to describe the chemical sector as being "the largest industrial consumer of both oil and gas."

Anastas was asked how easy it would be to lower the use of energy in chemical production by applying the principles of green chemistry.

"We've forced chemicals to do things they didn't naturally want to do," he said. "So we've heated them up, we've put them under pressure and we've tortured them to obey and become the things we want them to become," he added.

"But it's not just the quantities of energy that's important, it's the character and the nature of energy that we use: it needs to be renewable and non-depleting, and nontoxic, and not polluting."

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How 'green chemistry' could have a big part to play in the future - CNBC

Exclusive – Kundali Bhagya’s Dheeraj Dhoopar on his offscreen chemistry with Shraddha Arya, pay cut, family planning, and more – Times of India

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It was a very good thing. When lockdown started, we were at home. My wife is a great cook. So, we were enjoying all the great food. So, I was very happy spending time with Vinnie and Oreo (his pet dog). Later, there was a time when I wanted to step out to work. It wasn't like I wasn't enjoying being home but there was this urge within to face the camera, perform. But knowing the fact that pandemic and all, the counts are increasing, I was just hoping for the vaccine to come out as soon as possible, and everything gets sorted. But we started shooting, and hopefully, it's going out quite well. Kundali Bhagya again picked up, and we are at the top. (Photo: Instagram)

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Exclusive - Kundali Bhagya's Dheeraj Dhoopar on his offscreen chemistry with Shraddha Arya, pay cut, family planning, and more - Times of India

UN Official: Impunity in Use of Chemical Weapons Must Not Be Tolerated – Global Biodefense

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The senior United Nations disarmament official urged the Security Council to unite and ensure that the use of chemical weapons shall never be tolerated, as she briefed the 15-member body on Feb. 3 on efforts by the Organisation for the Prohibition of Chemical Weapons (OPCW) to verify the destruction of Syrias chemical weapons stockpiles and production facilities.

Izumi Nakamitsu, Under-Secretary-General and High Representative for Disarmament Affairs, said that the COVID-19 pandemic continues to hamper the ability of OPCWs Investigation and Identification Team tasked with identifying the perpetrators of the use of chemical weapons in Syria to deploy in that country.

I say this every month because it bears consistent repeating: There is an urgent need to not only identify but hold accountable all those who have used chemical weapons in violation of international law

She also urged Syria to fully cooperate with the OPCW Technical Secretariat to address 19 issues still outstanding from its initial declaration on its chemical weapons programme, submitted to OPCW in The Hague in 2013. One of those issues is at the heart of a request by the OPCW Technical Secretariat for details about chemical agents produced or weaponized at a facility which, according to Damascus, has never been used for chemical weapons.

Without such action, we are allowing the use of chemical weapons to take place with impunity. It is imperative that this Council show leadership in demonstrating that impunity in the use of these weapons will not be tolerated, she said, adding that the Secretary-General, in his address to Member States on 28January, had underscored the need for Council unity to address todays roiling threats to peace and security.

She urged Damascus to cooperate fully with the OPCW Technical Secretariat, which stands by its assessment that due to unresolved gaps, inconsistencies and discrepancies Syrias initial declaration cannot be considered accurate and complete, as it is required to be under the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and of Their Destruction.

She added, as she has said in the past, that international confidence in the full elimination of Syrias weapons programme hinges upon OPCW being able to resolve the outstanding issues. I hope that during the next round of consultations between the [OPCW] Declaration Assessment Team and the Syrian National Authority, to be held later this month, further progress will be made to resolve these issues, she added.

The representative of theUnited Statessaid any use of chemical weapons is a clear thereat to international peace and security, and his country is committed to holding perpetrators to account. The Assad regime has repeatedly used chemical weapons against Syrias people, seeking to avoid accountability by obstructing independent investigations and undermining the work of OPCW. Its allies, including the Russian Federation, have sought to block all efforts to promote accountability, shielding it from responsibility, notably by spreading disinformation, attacking OPCW and seeking to undermine efforts by responsible nations to hold the Assad regime accountable. He hailed OPCW leadership, its Technical Secretariat and its professionalism in carrying out its mandate, and said the United States looks forward to the future reports of the Investigation and Identification Team.

Noting that the Teams first report, in April2020, concluded that the Assad regime had used chemical weapons, he said the decision by OPCW in July 2020requested that Syria take steps to redress the situation. But Damascus has failed to complete any measures outlined in that decision, as communicated by the OPCW Director General in October 2020. Recalling that the United States, along with 45 co-sponsors, submitted a draft decision to the OPCW Conference of the States Parties in response, he called on the Conference to take appropriate action when it reconvenes this spring so as to send a strong message to the Syrian regime.

The Security Council likewise must ensure there are serious consequences for Syrias use of chemical weapons, he said, recalling it had decided that the regime must cooperate fully with OPCW and the United Nations, efforts which the United States supports. Accountability is needed to bring long-overdue justice to the victims, he stressed, as is a broader political process, as called for in resolution2254(2015). The Assad regime must uphold its Convention obligations, while the Council must call out atrocities and hold those who use chemical weapons accountable.

The representative of theUnited Kingdom, Council president for February, underlined in her national capacity that, despite decisions by OCPW and the Security Council, Syrias declaration of its chemical weapons programme cannot be considered complete. She called the 19 unresolved issues substantive and serious in nature, among them, issues pertaining to a production facility which Syria claims has never been used. However, a review of all information and materials collected by the Declaration Assessment Team indicates the production of chemical nerve agents did take place there. That four outstanding issues have been closed demonstrates that such questions can be concluded if Damascus chooses to engage. She pressed Syria to provide complete access to documents and witnesses, stressing that the cat-and-mouse game of explanations and excuses cannot continue. Noting the Declaration Assessment Teams intention to deploy for consultations in February, she outlined the United Kingdoms expectation that Syria provide full responses during those meetings.

The representative ofSyria said that his country no longer has any chemical weapons, as the Head of the Joint Investigative Mission told the Council in June 2014. However, some Western countries, denying that reality, continue to use the chemical weapons issue as a weapon of war and blackmail. For its part, OPCW is forced to produce reports based on conjecture and information from terrorist groups such as the White Helmets which fail to meet even the basic criteria for objectivity. He added that OPCW and the High Representative for Disarmament are trying to serve the Western agenda by denying information provided by the Governments of Syria and the Russian Federation. Despite the hostile Western approach, Damascus is continuing to cooperate with OPCW and its Technical Secretariat, he said, adding that discussions on an OPCW visit took place last week, although no agreement was finalized.

He emphasized that Damascus rejects any attempt to undermine its initial declaration to OPCW or its efforts to cooperate with that organization. A draft resolution before the Conference of the Parties to the Chemical Weapons Convention, if adopted, would represent a hostile act par excellence by levelling false accusations against the Government of Syria while exonerating terrorists and their co-sponsors for the use of chemical weapons, he said. Such a text would also lay the groundwork for hostile unilateral or trilateral acts not unlike the United States attack on the Shayrat airfield in April 2017. He went on to say that Western Governments have seized upon the chemical weapons issues to provide cover for Israels development of nuclear, chemical and biological weapons.

The representative ofTurkeysaid that of the 19 outstanding issues, one requires urgent attention, and that the Syrian regime must be forced to declare the types and quantities of chemical weapons produced at a facility which Syria says was never used for such a purpose. Underscoring the importance of Council unity, he said that his country is a co-sponsor of a draft resolution before the Conference of the Parties to the Chemical Weapons Convention on the Syrian chemical weapons dossier. Going forward, investigations by the fact-finding mission and the Investigation and Identification Team must continue, he said, adding that the Syrian regimes denial of visas to members of the latter is
a violation of the Chemical Weapons Convention. He concluded by saying that ending impunity is indispensable for peace in Syria and that those with influence on the regime bear a special responsibility.

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UN Official: Impunity in Use of Chemical Weapons Must Not Be Tolerated - Global Biodefense

Physics – Selective Bond Breaking with Splat Chemistry – Physics

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February 1, 2021• Physics 14, 13

Colliding a large organic molecule with a surface can break a specific chemical bond in the molecule with surprising precision.

The ability to selectively excite and break specific bonds in molecules would open new vistas in synthetic chemistry, allowing the creation of compounds that are difficult to synthesize via conventional chemical techniques. However, decades of research have shown that, with a few exceptions [1], when energy is put into a specific molecular bondwith a laser, for exampleit is quickly redistributed among many vibrations in the molecule long before a reaction may occur. In other words, attempting to selectively put energy into a bond usually leads to the same chemical reaction as heating the reactants on a hot plate. Surprisingly, Lukas Krumbein, at the Max Planck Institute for Solid State Research in Germany, and colleagues have now observed that a bond in a large molecule can be selectively broken by adding energy to the system in the simplest way possibleby colliding the molecule with a surface [2]. The result improves our understanding of the dynamics of large molecules and could offer novel ways to control their reaction products.

The idea that energy imparted during a collision can promote chemical reactionsa process sometimes called splat chemistryhas been around for decades. Researchers have shown, for instance, that the collision of argon atoms onto methane (CH4) molecules adsorbed on a surface can lead to the molecules dissociation [3]. In that experiment, the equivalence of the four CH bonds means that the collision process is not bond specific. What is significant about the work by Krumbein and colleagues is that they demonstrate the cleavage of a particular bond.

The researchers use electrospray ionization and ion-beam deposition to accelerate a 73-atom molecule called Reichardts dye toward a copper surface. Using scanning tunneling microscopy to inspect the scene of the collision, they find that when the molecule collides with the surface at translational energies of 250 eVlarger than the energy associated with thermal excitationit selectively cracks at a specific carbonnitrogen (CN) bond. Breaking this bond results in the molecule opening into a more spread-out configuration. In contrast, when the molecule is simply heated, a different CN bond is broken, which splits the original molecule into two pieces. Krumbein and colleagues also observe this lower-energy splitting reaction in some collisions, but this reaction has a lower probability than the cracking reaction.

Key to the success of their experiment is the sheer size of the molecule involved. Previous studies of surface dynamics have focused on the reactions of small molecules, such as nitric oxide (NO) or CH4. The collision-induced excitation of single bonds in such small molecules is relatively ineffective. For example, when a molecule of NO collides with a surface, the efficient compression of the NO bond would require a perfectly aligned, head-on collision geometry. With any other alignment, the molecule would behave much like an American football, hitting with its long axis at an angle to the surface [4, 5]. This off-axis geometry causes most of the translational energy to be converted into rotational energy, sending the molecule spinning away from the surface but without inducing any chemical change.

The situation is very different for Reichardts dye, named after the doctoral student who developed the molecule while searching for a compound that would change its color depending on the solvent. This large organic molecule consists of seven rings surrounding a central nitrogen atom. When a Reichardts dye molecule hits the surface, the collision doesnt compress a single bond. Instead, the collision causes the entire molecule to undergo a large-scale distortion in a very short period of timemore like a prop-comedy rubber chicken hitting a wall than like a football.

Based on simulations of their experiment, Krumbein and colleagues explain that the fate of the molecule depends on its orientation when hitting the surface. The key difference between the collision geometries is how the large-scale distortion strains the three carbon atoms surrounding the central nitrogen atom (Fig. 1). Collisions that focus the molecules distortion on one particular carbon atom lead to splitting, with the molecule breaking apart into two fragments. Distortions focused on one of the other two (symmetry equivalent) carbon atoms lead to cracking, in which the molecule hinges open but remains in one piece. Other impact configurations produce no reaction, leaving all three bonds unbroken and the molecule intact (Fig. 2).

The experiments demonstrate that, as expected, the probability of a reaction is dependent on the initial translational energy of the molecule. Faster molecules split or crack with higher probability than slower molecules. Using simulations that account for the collision process, the researchers explain the experimental observation that the more common outcome is a cracking reaction, even though splitting is the thermally favored pathway. This is not contradictory, as the reaction rate is controlled both by the activation barrier and by the probability of attaining a suitable molecular configuration for the reaction. The simulations reveal that the collisions selectively strain the central nitrogen atom in a way that promotes CN bond cleavage. In contrast, heating the molecule distributes energy randomly.

The results obtained by Krumbein and colleagues provide important new insight into the localization of energy in molecules: The large-scale distortion of the molecule focuses the energy on a single bond while simultaneously preventing the energy from rapidly delocalizingat least for the picosecond or so that it takes for the molecules geometry to stabilize after the collision. These types of large-scale deformations are common in macromolecules under strain, such as polymers, proteins, and DNA. Accounting for the way that energy is concentrated on specific bonds within these molecules will help predict how they respond to such strain. Insights such as those provided by this work are also important for understanding mechanochemistry, the coupling between macroscopic strain and chemical reactivity. Mechanochemistry underlies important phenomena, such as stress-corrosion cracking and polymer degradation under shear. An atomistic understanding of mechanochemistry is still in its infancy, but Krumbein and colleagues experiment represents a considerable advance.

Melissa A. Hines is a professor of chemistry at Cornell University. Her research focuses on understanding and controlling the chemical reactivity of surfaces to enable advances in areas ranging from photocatalysis and self-cleaning surfaces to the development of stable, high-brightness photocathodes.

Lukas Krumbein, Kelvin Anggara, Martina Stella, Tomasz Michnowicz, Hannah Ochner, Sabine Abb, Gordon Rinke, Andr Portz, Michael Drr, Uta Schlickum, Andrew Baldwin, Andrea Floris, Klaus Kern, and Stephan Rauschenbach

Phys. Rev. Lett. 126, 056001 (2021)

Published February 1, 2021

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Physics - Selective Bond Breaking with Splat Chemistry - Physics

Regulating the reactivity of black phosphorus via protective chemistry – Science Advances

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INTRODUCTION

Precisely tuning the properties of nanomaterials to obtain desired characteristics is one of the most important goals of nanoscience. Within this scope, rationally regulating the reactivity of nanomaterials is critical for future multistep programmable processing and applications. Some nanomaterials (or some certain parts) need to be protected to reduce their reactivity under certain specific conditions and to restore their activity after successful deprotection (13).

Scientists have, in the past few decades, proposed plenty of efficient and selective protection-deprotection strategies toward regulating the reactivity of various functional groups in organic chemistry (4, 5). Usually, the functional group (or organic molecule) is linked with the protective group via various chemical/physical interactions (typically covalent bond) to reduce its reactivity, so that the protected functional group (or molecule) can survive in the subsequent steps. Subsequently (after the steps involving the attack of other functional groups), the protective group is removed, restoring the original functional group or molecule. This protective strategy is pervasive in multistep organic syntheses, such as natural product synthesis, solid-phase peptide synthesis, and polymer synthesis (4, 6, 7). Unfortunately, these well-established organic protective-deprotective processes are hardly applicable in inorganic nanomaterials owing to the lack of functional groups in inorganic nanomaterial surfaces, their irreversible agglomeration, surface reconstruction, and particle etching during the complex protective-deprotective process (8, 9). An efficient and facile approach to regulate the reactivity of inorganic nanomaterials remains elusive.

Black phosphorus (BP), a rising star in postgraphene two-dimensional (2D) nanomaterials, is known for its tunable bandgap (from ~0.3 to ~2.0 eV), its good compromise between charge carrier mobility and current on/off ratios, its broadband absorption from the visible to the mid-infrared range (1012), and its excellent biocompatibility (13). These attractive properties position BP to be suitable for application in optoelectronics and biomedical areas (10, 13). However, the high chemical reactivity of BP and oxygen/water leads to BP degradation under ambient conditions, causing functional failure of BP (14, 15). Recent research reveals that the reactivity of BP is directly related to the lone pair electrons of the P atom (internal factor) and the surrounding oxygen/water (external factor) (14). The lone pair electrons of each P atom contribute to the high electron density on the BP surface (16, 17), which gives BP strong reducibility. The surrounding oxygen/water can easily attach to the highly reactive surface of BP and react to form PxOy. To protect BP, a conceivable strategy could be to decrease its surface electron density and prevent oxygen/water from accessing the BP surface. On the basis of this idea, considerable efforts have been made to protect BP from ambient degradation. However, despite the rapid progress in the effective protection of BP, a practical method to deprotect passivated BP has not been developed. It is even more difficult to develop a method that combines protection and deprotection processes to switch BP from a passivated state to a reactive state in response to environmental changes (i.e., passivation by storing under ambient condition, and reactivity resuming to facilitate further functionalization or degradation when necessary) (13, 1720).

Here, we develop a protective chemistrybased strategy (Fig. 1) for rationally regulating the reactivity of BP. We begin by binding the BP with Al3+ ions to decrease its surface electron density, effectively decreasing its reducibility. Then, the hydrophobic 1,2-benzenedithiol (BDT) molecule assembles into a dense array on the surface of BP/Al3+ via the AlS bond, which effectively isolates the nanocomposite from oxygen/water. This protective process offers an ultrastable BP complex (BP/Al3+/BDT), which can be stable under ambient conditions even for 2 months without its key physical/chemical characteristics being altered. Contrary to previous reports, this ultrastable BP/Al3+/BDT can be deprotected by chelator treatment [typically EDTA-tetrasodium (EDTA-4Na)]. This is possible because of the stronger binding affinity between Al3+ and EDTA-4Na in BP that enables the removal of Al3+ and BDT layers from the BP surface. The removal of the Al3+ and BDT layers restores the high surface electron density of BP, resuming its reactivity. To prove this concept, we used the deprotected BP in a degradation study. Expectedly, it exhibited the same behavior as original BP.

Protective step 1: Binding Al3+ ions with lone pair electrons on the surface of P atoms decreases surface electron density of BP, leading to a reduced chemical reactivity of BP. Protective step 2: Self-assembly of the hydrophobic dense array on the BP surface isolates BP from surrounding oxygen/water. Deprotective step: Removal of Al3+ ions and hydrophobic dense array on the BP surface by a chelating agent. The treatment recovers the electron density of BP, restoring the original reactivity of the deprotected BP. BDT, 1,2-benzenedithiol; EDTA-4Na, EDTA-tetrasodium.

Bulk BP was prepared and characterized following a methodology highlighted in a previous report (fig. S1, A to C) (21). BP nanosheets were obtained via the sonication of powdered bulk BP in N,N-dimethylformamide. Scanning electron microscopy and transmission electron microscopy (TEM) images show that the size of the BP is 858.6 89.1 nm (fig. S1, D and E). High-resolution TEM images show a single-crystal BP nanosheet with a lattice spacing of 2.56 , which assigns to the (111) plane of BP (fig. S1F). Atomic force microscopy (AFM) analysis reveals that the thickness of BP is 2.65 0.27 nm, which implies that there are four to six individual phosphorene layers (fig. S1G) (21). X-ray diffraction (XRD) and Raman spectra demonstrate the same crystal characteristic of BP as its bulk form (fig. S1, H and I).

The protective step starts by binding Al3+ to the BP surface. BP/Al3+ is obtained by the simple mixing of BP and AlCl3 in an ethanol solution at room temperature. In our case, besides Al3+, a wide range of metal ions were systematically screened (see note S1). Noble metal ions (such as Au3+, Ag+, and Pd2+) can form a redox pair with BP and quickly react with BP to form noble metal nanoparticles on the BP surface (fig. S2, A to I). Heavy metal ions (such as Cu2+, Zn2+, Ni+, Co2+, Mn2+, Fe2+, and Sn4+) and light metal ions (such as Na+, K+, Mg2+, Ca2+, Al3+, and Ti4+) can form similar BP/metal ion complexes. However, compared to Al3+, most of them show the weaker ability for passivating BP (fig. S2K). A more detailed discussion about the effect of charge and radius on interaction strength can be found in fig. S3 and note S1. Some metal ions (typically Ti4+ and Sn4+) undergo fast hydrolysis, which is not conducive for regulating the reactivity of BP (fig. S3, A to G). Therefore, Al3+ ions are selected to form BP/Al3+ coordination complexes because they have a strong electron-withdrawing ability, relatively high stability, and low reactivity over other metal ions (2224). The changes in zeta potential suggest the successful binding of Al3+ ions on BP (fig. S3D). X-ray photoelectron spectroscopy (XPS) characterization provides further evidence for the successful attachment of Al3+ ions to the BP surface (fig. S3I).

Subsequently, a layer of BDT attaches to the surface of BP/Al3+ via self-assembly to further strengthen the protection of BP. BDT was chosen as the protective layer for the following reasons. (i) It can form an orderly molecular array on the selected substrate owing to its rich electron density and hydrophobic nature (25, 26); (ii) the thiol group, in this case, is more suitable than other functional groups such as carboxyl, oxhydryl, and amino groups for the assembly of a hydrophobic layer on the surface of BP/Al3+ (note S2 and fig. S4); (iii) BDT exhibits less
conformational freedom over the linear n-alkane thiol ligands and thus can assemble into a denser monolayer on the substrate (fig. S4E) (27, 28); and (iv) theoretically, the BDT monolayer is sufficiently thin (~0.50 nm, based on AFM images in fig. S1G and Fig. 2), and as such, it will have little influence on the physical/chemical properties of the coated BP.

(A) TEM image. (B) AFM (height profile along the white line) image. (C) STEMenergy-dispersive x-ray spectroscopy (EDX) elemental mapping images. (D) High-angle annular dark-field (HAADF) image. (E) Magnified HAADF image taken from the selected area in (D). a.u.: arbitrary units. (F) Selected-area electron diffraction (SAED) pattern of BP and BP/Al3+/BDT. (G) FTIR spectra of BP, BP/Al3+, BP/Al3+/BDT, and BDT. (H) 1H NMR spectra of BP, BP/Al3+/BDT, and BDT. (I) Thermogravimetric curves of BP and BP/Al3+/BDT. ppm, parts per million.

The morphology of the obtained BP/Al3+/BDT was investigated. TEM (Fig. 2A) images show that the morphology of BP/Al3+/BDT has a 2D nanostructure without observable defects on its surface. AFM images show that the thickness of BP/Al3+/BDT is 3.75 0.22 nm (Fig. 2B). These suggest that the obtained BP/Al3+/BDT does not show a notable morphological difference from the original BP nanosheets (fig. S1, E and G). The XRD pattern of BP/Al3+/BDT gives the same feature peaks like that of the original BP, indicating that the crystal structure was unaltered (fig. S4H). The conductivity of BP is also preserved after the protective treatment (fig. S4I).

The surface configuration of BP/Al3+/BDT was studied by scanning TEM (STEM). High-angle annular dark-field (HAADF)STEM images and energy-dispersive x-ray spectroscopy (EDX) analysis of BP/Al3+/BDT reveal the uniformity of the distribution of P, Al, and S over the whole nanosheet (Fig. 2C). The HAADF image of BP/Al3+/BDT in Fig. 2D indicates a lattice constant of 0.256 nm, which is consistent with the original BP nanosheets. Figure 2E shows the HAADF image of the enlarged area in Fig. 2D (dashed yellow rectangle). The spots with relatively high contrast (labeled with dashed white circle) located at the central area of the P atom (with low contrast) hexagons can be assigned to the Al3+ ions. The Z-contrast intensity distribution (Fig. 2E, inset, corresponding to the selected area labeled with dashed green rectangle) discloses a P-Al periodic pattern, which further suggests that the Al3+ ions favor a central location in P hexagons. Figure 2F shows the selected area electron diffraction (SAED) pattern of BP and BP/Al3+/BDT. In comparison to BP, the diffraction spots associated with the (001) and (021) lattice planes of BP/Al3+/BDT are almost extinct (labeled with dashed red circle), while the (111) lattice plane of BP/Al3+/BDT gets enhanced (labeled with dashed green circle). The difference in diffraction spots between BP and BP/Al3+/BDT is attributed to the difference in electron beam scattering and interference, further confirming the binding of Al3+ to BP.

The formation of BP/Al3+/BDT was further verified by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (1H NMR) (Fig. 2, G and H). In comparison with BP, the FTIR spectra of BP/Al3+/BDT show six substantial characteristic bands at 3400, 1637, 1563, 1430, 1024, and 770 cm1, respectively (Fig. 2G). The characteristic bands at 3400 and 1637 cm1 are assigned to the OH stretching vibration (29). A similar characteristic band is also observed in the FTIR spectrum of BP/Al3+, suggesting that a few OH groups were attached to Al3+ in the synthesis of BP/Al3+ (30). The other characteristic bands at 1563, 1430, 1024, and 770 cm1 are attributed to the BDT molecule, suggesting the presence of BDT molecule in the complex. The SH stretching vibration in the spectrum of BDT is found at 2653 cm1, where the FTIR spectrum of BP/Al3+/BDT shows a flat curve (Fig. 2G, red line) (31). The disappearance of the SH stretching vibration in the FTIR spectrum of BP/Al3+/BDT is evidence of bond formation between Al and S. Figure 2H shows 1H NMR spectra of BP, BP/Al3+/BDT, and BDT. A single peak assigned to hydrogen in the SH group is observed in the BDT at 3.6 parts per million (ppm). Contrastingly, no such peaks are observed at 3.6 ppm for BP/Al3+/BDT (Fig. 2H, red line) (32). This further confirms the formation of the AlS bond. In addition, two chemical shifts of the H in the benzene ring of BDT are observed after the self-assembly slightly shifts to 7.16 ppm (7.07 for original BDT) and 7.48 ppm (7.36 for original BDT) (Fig. 2H, inset). This can be attributed to the covalent interaction of BDT and Al3+ ions (33). FTIR and 1H NMR characterization provide robust evidence for the formation of the BP/Al3+/BDT complex. The Raman spectrum of BP/Al3+/BDT further supports the existence of BDT on the BP surface (fig. S4J). Thermogravimetric analysis reveals that the mass ratio of BP:Al:BDT is approximately 11:1:3 (Fig. 2I). BP is fully covered by Al3+/BDT according to the theoretical calculation (theoretical ratio of BP:Al:BDT is 10:1:3, and the mass ratio of BP:Al:BDT is directly affected by the layer number of BP; see fig. S5, A to C, and note S3 for calculation details).

The reactivity (to oxygen/water) of BP/Al3+/BDT was investigated via a polarizing microscope, TEM, XPS, and ultraviolet-visible (UV-vis) spectroscopy. At the initial stage, the polarizing optical microscope images of both as-prepared BP and as-prepared BP/Al3+/BDT showed a perfectly clean and flat surface (Fig. 3, A1 and B1). TEM images of these two samples showed the same 2D nanosheet structures without observable defects (Fig. 3, A1 and B1, insets). The surface of BP exhibited rough and small topographic protrusions (hereafter termed bubbles) after 1 day of ambient exposure (Fig. 3A2). The surface became rougher, and the bubble size increased when the exposure time was extended to 7 days (Fig. 3A3). The corresponding TEM images show the evolution process of structural destruction and surface bubble growth (Fig. 3, A1 to A3, insets). These results suggest that BP is oxidized after ambient exposure for 1 day and heavily oxidized after 7 days. Contrary to BP, the surface of BP/Al3+/BDT remains almost unaltered after 60 days of ambient exposure (Fig. 3B). Furthermore, a crystal structure is observed for BP/Al3+/BDT with a lattice spacing of 2.56 , which is indexed to the (111) plane of BP even after 1 year of ambient exposure. This result is further supported by XRD, Raman spectra, water contact angle, and zeta potential characterizations, demonstrating the long-term ambient stability of BP/Al3+/BDT (see fig. S5D and note S3 for details).

Polarizing microscope images of (A) bulk BP (0, 1, and 7 days) and (B) bulk BP/Al3+/BDT (0, 30, and 60 days). Insets: Corresponding TEM images. Scale bars, 200 nm. (C and D) HR-XPS spectra of P 2p peaks for BP and BP/Al3+/BDT with ambient exposure for various durations. (E and F) UV-vis spectra of BP and BP/Al3+/BDT dispersed in water for various durations. Insets: variation of the UV-vis absorption ratios at 470 nm (A/A0) of BP (A0: original value).

Degradation of BP yields a product of PxOy and, lastly, produces phosphate anions (BPPxOyPO43) (15). With degradation, the content of PxOy on the BP surface or the content of PO43 in the BP aqueous dispersion are conceivably increased. High-resolution XPS (HR-XPS) spectra of P 2p were used to determine the evolution of the content on the PxOy surface during the degradation process of both BP and BP/Al3+/BDT under ambient conditions. As shown in Fig. 3 (C and D), both BP and BP/Al3+/BDT show two peaks. One peak is visible at 128.5 to 131.5 eV and is assigned to P, while the other is visible at 132.5 to 135.2 eV and is assigned to PxOy. At the initial stage, both as-prepared BP and BP/Al3+/BDT display a high-intensity P peak and low-intensity PxOy peak, respectively. After ambient exposure for 7 days, the peak intensity of BP decreases (P: from 87.3 to 10.7%), while the peak intensity of PxOy increases (PxOy: from 12.7 to 89.3%) simultaneously (Fig. 3C). In contrast, for BP/Al3+/BD
T, the peak intensity of P exhibited no significant changes (P: from 89.9 to 76.3%) even after ambient exposure for 60 days (Fig. 3D), while the peak intensity of PxOy slightly increased (PxOy: from 10.1 to 23.7%). In addition, the intensity of PP/PO for BP/Al3+/BDT is very close to that of the original BP, indicating that the BP/Al3+/BDT offers reliable protection to improve the stability. XPS analysis results were consistent with those of polarizing microscopy. This indicates that the stability of BP/Al3+/BDT is superior to that of BP.

To further address the degradation of both BP and BP/Al3+/BDT, we detected the amount of PO43 in BP dispersion and BP/Al3+/BDT dispersion by UV-vis [see experimental procedures in the Supplementary Materials and fig. S5 (E and F) for details] (21). For the initial dispersion, the absorbance intensity of both BP and BP/Al3+/BDT at 470 nm is roughly the same (Fig. 3, E and F), indicating the same concentration of BP in these two solutions. With increasing dispersion time, this absorbance intensity of BP gradually dwindles, and the absorbance intensity of PO43 at 710 nm increases simultaneously (Fig. 3E and fig. S5G). After incubating in aqueous solution for 7 days, the absorbance intensity of BP at 470 nm (A) decreased by 95.5% compared to the original value (A0) (Fig. 3E, inset), while the absorbance intensity of PO43 at 710 nm increased by 93.7% compared to the original value (fig. S5G). These results reveal the fast degradation of BP in aqueous solution. The final concentration of PO43 (6.6 g/ml) in the degraded solution is close to the initial concentration of BP (6.8 g/ml), which is consistent with the UV-vis observation. Contrarily, for BP/Al3+/BDT aqueous dispersion, the UV-vis absorbance intensity of BP/Al3+/BDT and PO43 shows no significant changes after incubating for 60 days (Fig. 3F and fig. S5H). UV-vis spectra prove that the stability of BP/Al3+/BDT is superior to BP.

The above results indicate that our protective strategy through BP/Al3+/BDT successfully embeds BP with an ultrastability and reduces its reactivity. Our strategy relies on the coordinated interaction between Al3+ and BP, which is expected to be stronger than that induced by noncovalent functionalization (34, 35). Furthermore, the BDT hydrophobic layer provides a dense barrier to oxygen/water. Therefore, both internal and external influencers for BP degradation are minimized, rendering an ultrastable BP in comparison to the BP passivated by other methods (table S1). The BP/Al3+/BDT can even survive some harsh oxidation conditions. As shown in fig. S5 (I and J), BP/Al3+/BDT can remain stable in solutions containing strong oxidants (such as noble metal salt water solution HAuCl4, H2PdCl4, and AgNO3) for 8 days, while the as-prepared BP reacts with noble metal salts immediately.

The reducing reactivity of BP/Al3+/BDT can be attributed to two factors: first, the binding of Al3+ to the BP surface, which results in an electron density shift from the BP surface to Al3+, rendering a lower chemical reactivity of BP/Al3+/BDT; second, the self-assembled hydrophobic dense array on the BP surface effectively isolates BP from oxygen and water, preventing further degradation. Decreasing electron density on the BP surface is revealed by XPS spectra and further supported by density functional theory (DFT) simulation. Full-scan XPS spectra (Fig. 4A) reveals the presence of the relevant elements (the signal of Si derives from the substrate). In the BP sample, the P 2p core-level XPS spectrum shows P 2p3/2 and P 2p1/2 doublet at 129.6 and 130.7 eV, respectively, corresponding to the characteristic of crystalline BP (Fig. 4B) (13, 21). In the BP/Al3+ sample, owing to Al-P interaction, P 2p3/2 and P 2p1/2 doublet appears at higher binding energy (shift from 129.6 to 130.2 eV and from 130.7 to 131.2 eV, respectively). The lone pair electrons from the P atom donate to Al3+, which reduces the electron density on the surface of BP (3s and 3p orbitals) (17, 20). The decreased electron density of the BP surface layer causes strong attractive interactions in the inner layer of the P atom (2p orbitals); therefore, the appearance of XPS signals goes to higher binding energy. After BDT functionalization, owing to the formation of AlS bonds, electrons of S enter the empty orbitals of Al3+ (36). In comparison to BP/Al3+ (~74.6 eV), the XPS peak of Al 2p for BP/Al3+/BDT (~75.0 eV) appears at the higher binding energy (Fig. 4C). Meanwhile, partial electrons retrace from Al3+ to P, which leads to the P 2p3/2 and P 2p1/2 doublet of BP/Al3+/BDT shifting to the lower binding energy (Fig. 4B, red line).

(A) Full XPS spectra of BP, BP/Al3+, and BP/Al3+/BDT. (B and C) HR-XPS spectra of P 2p and Al 2p. (D to F) Calculated NBO charge of P atom, Al3+ ion, and S atom. Structure model of (G1) BP/Al3+ and (G2) BP/Al3+/BDT. Computational mapping of electron density difference in (G3) BP/Al3+ and (G4) BP/Al3+/BDT. Green regions indicate increased electron density, and blue regions indicate decreased electron density. Contours are shown at the 0.0001 a.u. level. (H) Water contact angles of BP, BP/Al3+, and BP/Al3+/BDT.

DFT calculations were carried out to investigate the electron transfer during the binding of Al3+ to the BP surface. After geometry optimization, a BP/Al3+ and BP/Al3+/BDT complex combined by coordination interaction was generated without showing the H atom (Fig. 4, G1 and G2). To quantitatively analyze the charge transfer, we calculated natural bond orbital (NBO) charges of BP, BP/Al3+, and BP/Al3+/BDT (Fig. 4, D to F). After the binding of Al3+ to the BP surface, NBO charges for P atoms increased (Fig. 4D), while NBO charges for Al3+ ions decreased (Fig. 4E). These results verify that electron density shifting occurs from BP to Al3+. Theoretically, the electron density of the BP surface should experience a decrease owing to the electron transfer from P to Al3+. This hypothesis is confirmed by mapping the electron density of BP/Al3+ (Fig. 4G3). As expected, a decrease in electron density (blue area) is observed for BP, whereas an increase in electron density (green region) is observed for Al3+ (Fig. 4G3). After BDT functionalization, compared to BP/Al3+, NBO charges for the P atoms decrease slightly, while NBO charges for Al3+ ions remain almost unchanged. Meanwhile, in comparison to BDT, NBO charges for S atoms of BDT increase slightly in the presence of Al3+ ions (Fig. 4F). The variation of NBO charges strongly confirms the electron transfer from Al3+/BDT to BP. These results are also consistent with the electron density mapping of BP/Al3+/BDT. As shown in Fig. 4G4, the electron density of BP increases slightly (green region in Fig. 4G4), while the electron density of Al3+/BDT decreases slightly (blue area in Fig. 4G4).

Self-assembly of a hydrophobic dense array on the BP surface is another crucial factor that contributes to the enhancement of BP stability. Previous reports demonstrated that water and oxygen are key factors in the process of ambient degradation of BP (14). In our case, the BP surface was fully covered by Al3+. However, the Al3+ layer was not hydrophobic enough to prevent water diffusion (contact angle of 12.3 for BP and 24.8 for BP/Al3+, as shown in Fig. 4H), and the monolayer of Al3+ was too thin to block the penetration of oxygen/water. Assembly of the hydrophobic dense array increases the contact angle of the BP surface from 24.8 to 130.5, which, in turn, strongly increases the hydrophobicity of the obtained BP/Al3+/BDT complex. As shown in Fig. 3 and fig. S3L, although the BP/Al3+ shows improved stability (see note S1), further functionalization with the BDT layer promotes the stability of the material over the BP/Al3+ complex even further. The hydrophobic surface of BP can effectively prevent contact between water and BP, decreasing water-induced BP degradation (27, 28).

Beyond the hydrophobic surface, a closed-packed array-like dense molecular film was formed, which effectively isolated BP from oxygen and water. Owing to the interactions among aromatic rings, the BDT could form a highly ordered c
losed-packed array on the surface of BP. The interspace between the BDT molecules was around 3.40 (37), which is slightly smaller than the size of O2 (~3.46 ) and water (~3.50 ) molecules (3840). Thus, oxygen and water were blocked from the molecular layer, preventing BP from being easily degraded by the environment. When BDT was replaced by 2-naphthalenethiol (NAT; a similar aromatic thiol with BDT) for self-assembly on the BP surface (fig. S6), the obtained BP/Al3+/NAT complex demonstrated a stability similar to that of BP/Al3+/BDT (fig. S6E). The enhanced stability of BP/Al3+/NAT can be attributed to the hydrophobic surface (the measured water contact angle was 122.8) and the dense-packed NAT (fig. S6E, inset). However, when a mixture of hydrophobic molecules was used (BDT/NAT = 1/1; fig. S6C), the obtained BP complex was less stable than BP/Al3+/BDT or BP/Al3+/NAT (fig. S6, D to F). Mixed hydrophobic molecule coassembling on the BP surface can induce defects within the closed-packed array (fig. S6, G to I). Thus, although BP/Al3+/BDT-NAT achieved a similar hydrophobicity, water and oxygen invasion would take place at this defect site, inducing degradation of BP (fig. S6F, inset). Therefore, the dense-packed hydrophobic array on the BP surface is also an important factor in isolating oxygen/water for improving the stability of BP.

The ultrastable BP/Al3+/BDT can be deprotected by removal of Al3+ from the BP/Al3+/BDT surface, as shown in Fig. 5A. Here, the removal of Al3+ is realized when EDTA-4Na is added, which is a conventional metal ion chelator (41). The full methodology is described as follows: First, we assess the removal ability of Al3+ in EDTA-4Na aqueous solution. The BP/Al3+/BDT complex is immersed in EDTA-4Na aqueous solution with different concentrations. Then, the residue Al3+ ions on the BP/Al3+/BDT surface are detected via fluorescence photometry using 8-hydroxyquinoline (see the Supplementary Materials for details and fig. S7, A and B) (42). The emission peak at 510 nm, which is a characteristic emission of 8-hydroxyquinoline aluminum salt, disappeared gradually, indicating that Al3+ ions had been successfully removed from the BP/Al3+/BDT surface. The removed amount of Al3+ ions by EDTA-4Na is directly correlated to the concentration of EDTA-4Na. The concentration of EDTA-4Na was 5 mM (fig. S7C). Figure 5B shows that photoluminescence (PL) intensity at 510 nm (Al3+ residue in BP/Al3+/BDT) decreases as incubation time increases in the presence of EDTA-4Na. The relationship between ln (Ct/C0) and time (t) reveals a linear correlation [ln (Ct/C0) = 0.139t + 0.063, R2 = 0.995] (Fig. 5C), where C0 and Ct refer to the loading concentration of Al3+ in BP/Al3+/BDT at an immersion time of 0 and t, respectively. The above analysis indicates that EDTA-4Na is a suitable chelator for the removal of Al3+ from the BP/Al3+/BDT surface. Al3+ ions on the BP/Al3+/BDT surface can also be removed by other chelating agents, such as sodium citrate (SC) and glutathione (GSH) (fig. S7, D to F), thus indicating its great potential for the application in biomedical-related fields.

(A) Schematic illustration of Al3+ ion and BDT removal by EDTA-4Na. (B) Photoluminescence (PL) emission spectra of Al3+ residue on BP/Al3+/BDT after EDTA-4Na treatment. (C) Plot of ln (Ct/C0) as a function of EDTA-4Na treatment time. (D and E) HR-XPS spectra of P 2p, Al 2p, and S 2p for BP, BP/Al3+/BDT, and deprotected BP/Al3+/BDT. (F) Plots of water contact angles and zeta potentials of BP as measured at each protective-deprotective cycle. (G) Polarizing microscope images of bulk BP (0 and 7 days) and bulk deprotected BP/Al3+/BDT (0 and 7 days). (H) Variation of PO43 concentration in solutions of BP and deprotected BP/Al3+/BDT with varying ambient exposure durations. (I) Stability of deprotected BP/Al3+/BDT with a varying residual amount of Al3+ ion on the BP surface. (J) TEM images of BP, BP/Al3+/BDT, and deprotected BP/Al3+/BDT after HAuCl4 (aqueous solution) treatment.

The hydrophobic molecules (BDT) were also removed together with Al3+. The deprotected BP/Al3+/BDT produces a hydrophilic surface with a negative zeta potential (fig. S7G), which is similar to the original BP. The P 2p binding energy of deprotected BP/Al3+/BDT (129.7 and 130.8 eV) is same as that of the original BP (129.6 and 130.7 eV) (Fig. 5D), indicating a resumed electron density on the BP surface. Furthermore, no Al and S signals were found in Al 2p and S 2p. XPS spectra of deprotected BP/Al3+/BDT (Fig. 5E) show the complete removal of Al3+ and BDT from BP/Al3+/BDT. The deprotective process does not affect the BP lattice structure (fig. S7H), Raman spectra (fig. S7I), conductivity (fig. S7J), and inherent photothermal conversion efficiency (fig. S7K).

Our protective-deprotective process achieves the reversible regulation of the BP reactivity. Figure 5F illustrates the plots of water contact angles and zeta potentials of BP measured at each interval of the protective-deprotective process cycles. In the five-cycled protective-deprotective process, the surface properties of BP fluctuate between hydrophilicity and hydrophobicity, and the corresponding zeta potentials of BP exhibit excellent reversibility.

The recovery of surface electron density and surface properties of deprotected BP/Al3+/BDT is supposed to have the same reactivity (such as degradation upon ambient exposure) as the as-prepared BP. As expected, the deprotected BP/Al3+/BDT displays the same degradation behavior as the original BP (Fig. 5G), which completely converts to PO43 after 7 days (Fig. 5H). In addition, the residue amount of Al3+ ions on deprotected BP/Al3+/BDT surface can be rationally tuned via different immersing times of BP/Al3+/BDT in EDTA-4Na aqueous solution. The reactivity of deprotected BP/Al3+/BDT highly depends on the residue amount of surface Al3+ ions (Fig. 5I and fig. S8), demonstrating the efficient approach for regulating the reactivity of BP. Beyond the degradability, the deprotected BP can also be used for further functionalization. As shown in Fig. 5J, the deprotected BP can react with HAuCl4 aqueous solution, and Au nanoparticle-functionalized BP is achieved. We also prove that Al3+-based BP reactivity regulation can be extended to other metal ions such as Fe3+, Zn2+, and lanthanide metal ions (fig. S9). Notably, some metal ions, typically Fe3+ with relatively high oxidizability, enable the oxidation of BP when the normal protective process is applied. For these cases, Fe3+ is linked to the BDT molecule to form the Fe3+-BDT complex before functionalization on the BP surface to yield BP/Fe3+/BDT (see note S4 for details). The slight modification for the protection process can reduce the induced oxidation by metal ions in high valance state, further extending the scope of the developed protective strategy.

To verify this concept, we used the established protective strategy for tuning the reactivity of BP in practical application (e.g., solar vapor generation). BP, BP/Al3+/BDT, and deprotected BP were deposited on hydrophilic poly(vinylidene fluoride) (PVDF) to fabricate BP/PVDF, BP/Al3+/BDT/PVDF, and the deprotected BP film, respectively (fig. S10, A and B; see also experimental details in the Supplementary Materials). BP/PVDF, BP/Al3+/BDT/PVDF, and deprotected BP show similar H2O evaporation rates (fig. S10, C and D), suggesting the same photothermal conversion property of these samples. However, after five cycles, the evaporation rates for the BP/PVDF film gradually decreased (fig. S10E). Further characterization revealed the significant degradation of the BP/PVDF film (fig. S10F), and the BP content in the BP/PVDF film dropped significantly (fig. S10G). In contrast, for the BP/Al3+/BDT/PVDF film, after five cycles, the evaporation rates did not change. No such degradation of BP/Al3+/BDT/PVDF film was observed (fig. S10F), and the BP content in the sample exhibited almost no changes (fig. S10G) after five cycles. The result demonstrates the low reactivity (to oxygen/water) of the protected BP during the solar vapor generation. For the deprotected BP film, its structure
(fig. S10F) and BP content changed significantly, and therefore, similar degradation behavior to that of BP/PVDF film was observed, as expected. Analyzed together, these results suggest the feasibility of using the developed protective strategy for efficient regulation of the reactivity of BP for practical application.

Acknowledgments: We are grateful for the technical support from H. Wang, R. Yu, Y. Yang, and L. Yang from the Department of Physics and College of Materials, Xiamen University. Funding: This study was financially supported by the National Natural Science Foundation of China (21771154), the Shenzhen Fundamental Research Programs (JCYJ20190809161013453), the Natural Science Foundation of Fujian Province of China (2018J01019 and 2018J05025), and the Fundamental Research Funds for the Central Universities (20720180019 and 20720180016). This research was also supported by the Singapore National Research Foundation Investigatorship (NRF-NRFI2018-03). Author contributions: J.X., J.W., and Y.Z. conceived the idea and supervised the project. X.L. performed the experiments and collected the data. L.X. performed the TEM and analyzed the results. W.L. performed the Raman measurements. X.L., J.X., J.W., and Y.Z. analyzed the data and cowrote the paper. C.Z. and Q.X. discussed the results and commented on the paper. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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