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Eric Stach

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From left, BNL Staff Scientist Lihua Zhang, former postdoctoral researcher Vitor Manfrinato and BNL Senior Scientist Aaron Stein. Photo courtesy of BNL

By Daniel Dunaief

It took a village to build this particular village or, more precisely, a pattern so small it could fit thousands of times over on the head of a pin.

Working at Brookhaven National Laboratory’s Center for Functional Nanomaterials, a team of researchers wanted to exceed the boundaries of creating small patterns with finely honed features. The group included Aaron Stein, a senior scientist at CFN, Charles Black, the head of CFN, Vitor Manfrinato, a former postdoctoral researcher at BNL and several other key members of the BNL team. The team added a pattern generator that allowed them to control a microscope to create a pattern that set a record for drawing at the 1-nanometer scale.

Just for reference, the width of a human hair is about 80,000 to 100,000 nanometers. The size of the pattern is a breakthrough as standard tools and processes generally produce patterns on a scale of 10 nanometers. “We were able to push that by a factor of five or 10 below,” Stein said. “When you get to those small size scales, that’s pretty significant.”

In this case, the novelty that enabled this resolution originated with the idea of employing the scanning transmission electron microscope, which isn’t typically used for patterning to create these images. The scanning transmission electron microscope has an extraordinarily high resolution, while the pattern generator allowed them to control the patterns they drew and other aspects of the exposure.

Researchers at CFN are focusing on this spectacularly small world to manipulate properties such as chemical reactivity, electrical conductivity and light interactions. “This new development is exciting because it will allow other researchers to create nanomaterials at previously impossible size scales,” Kevin Yager, a group leader at CFN explained in an email. “There are numerous predictions about how materials should behave differently at a size scale at 1 to 3 nanometers. With this patterning capability, we can finally test some of those hypotheses,” he said.

Stein and the research team were able to create this pattern on a simple polymer, polymethyl methacrylate, or PMMA for short. “It’s surprising to us that you don’t need fancy materials to create these kinds of features,” said Stein. “PMMA is a common polymer. It’s Plexiglas. It’s kind of exciting to do something that is beyond what people have done” up until now.

One of the many possible next steps, now that the researchers have developed this proof of principle, is to apply this technique to a substance that might have commercial use. Taking the same approach with silicon, for example, could lead to innovations in electronics. “We can make them with a high clarity of patterns and sharp corners, which we can’t do with other techniques,” Stein said.

The BNL research team would “like to apply this to real world research,” which could include electronics and transistors, as well as photonics and plasmonics, he added. This project arose out of a doctoral thesis that Manfrinato was conducting. He is one of the many scientists who came to BNL, which isa Department of Energy funded user facility that provides tools to conduct research for scientists from around the world.

Manfrinato was a doctoral student in Professor Karl Berggren’s group at the Massachusetts Institute of Technology. In an email, Manfrinato explained that he was interested in pushing the resolution limits of e-beam lithography. “BNL has state of the art facilities and expert staff, so our collaboration was a great fit, starting in 2011,” he explained.

Other scientists thought it was worthwhile to continue to pursue this effort, encouraging him to “come here and work on this. It’s a home grown project,” Stein said. Manfrinato worked on his doctorate from 2011 to 2015, at which point he became a postdoctoral researcher at BNL. His efforts involved several groups, all within the Center for Functional Nanomaterials at BNL. Stein, Manfrinato and Black worked on the lithography part of the project, while Lihua Zhang and Eric Stach developed the microscopy. Yager helped the team to understand the processes by which they could pattern PMMA at such small scale lengths.

“No one or two of us could have made this happen,” Stein said. “That’s really the joy of working in a place like this: There are [so many] permutations for collaborating.” Indeed, the other scientists involved in this study were Yager; Zhang, a staff scientist in electron microscopy; Stach, the electron microscopy group leader at CFN; and Chang-Yong Nam, who assisted with the pattern transfer.

Manfrinato, who is now a research and development engineer at a startup company in the San Francisco Bay area, explained that this lithographic technique has numerous possible applications. Other researchers could create prototypes of their devices at a level below the 10-nanometer scale at CFN. Manfrinato interacts with the BNL team a few times a month and he has “exciting results to be further analyzed, explored and published,” he wrote in an email.

Stein said BNL would like to offer this patterning device for other users who come to BNL. Ultimately, researchers use materials at this scale to find properties that may vary when the materials are larger. Sometimes, the properties such as color, chemical reactivity, electrical conductivity and light interactions change enough to create opportunities for new products, innovations or more efficient designs.

A resident of Huntington, Stein and his wife Sasha Abraham, who works in the planning department for the Town of Huntington, have a 15-year-old daughter Lily and a 13-year-old son Henry.

As for his work, Stein said he’s interested in continuing to push the limits of understanding various properties of nanomaterials. “My career has been using the e-beam lithography to make all sorts of structures,” he said. “We’re in a regime where people have not been there before. Finding the bottom is very interesting. Figuring out the limits of this technique is, in and of itself” an incredible opportunity.

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By Daniel Dunaief

First responders, soldiers or those exposed to any kind of chemical weapons attack need a way to remove the gas from the air. While masks with activated carbon have been effective, the latest technological breakthrough involving a metal organic framework may not only remove the gas, but it could also disarm and decompose it.

That’s the recent finding from research led by Anatoly Frenkel in a study on a substance that simulates the action of sarin nerve gas.

Frenkel, who is a senior chemist at Brookhaven National Laboratory and a professor in the Department of Materials Science and Chemical Engineering at Stony Brook University, worked with metal organic frameworks, which contain zirconium cluster nodes that are connected through a lattice of organic linkages.

Anatoly Frenkel with his son, Yoni, at Lake Hopatcong in New Jersey. Photo by Mikhail Loutsenko.

These structures would “do the job even without any catalytic activity,” Frenkel said, because they are porous and capture gases as they pass through them. “It’s like a sponge that can take in moisture. Its high porosity was already an asset.”

Frenkel and his colleagues, which include John Morris and Diego Troya from Virginia Tech, Wesley Gordon from Edgewood Chemical Biological Center and Craig Hill from Emory University, among other contributors, suspected that these frameworks might also decompose the gas.

Theoretically, researchers had predicted this might be the case, although they had no proof. Frenkel and his team used a differential method to see what was left in the structure after the gas passed through. Their studies demonstrated a high density of electrons near the zirconium atoms. “These were like bread crumbs congregated around a place where the zirconium nodes with the connecting linkers were,” Frenkel said.

While this work, which the scientists published in the Journal of the American Chemical Society, has implications for protecting soldiers or civilians in the event of a chemical weapons attack, Frenkel and his colleagues, who received funding from the Defense Threat Reduction Agency, can share their results with the public and scientific community because they are not working on classified materials and they used a substance that’s similar to a nerve gas and not sarin or any other potentially lethal gas.

“This knowledge can be transferred to classified research,” Frenkel said. “This is a stepping stone.” Indeed, Frenkel can envision the creation of a mask that includes a metal organic framework that removes deadly nerve gases from the air and, at the same time, disarms the gas, providing a defense for first responders or the military after a chemical weapons attack. Even though he doesn’t work in this arena, Frenkel also described how manufacturers might use these frameworks in treating the fabric that is used to make clothing that can prevent gases that can be harmful to the skin from making contact.

A physicist by training, Frenkel’s work, which includes collaborations on five other grants, has a common theme: He explores the relationship between structure and function, particularly in the world of nanomaterials, where smaller materials with large surface areas have applications in a range of industries, from storing and transmitting energy to delivering drugs or pharmaceuticals to a targeted site.

Eric Stach, a group leader in electron microscopy at BNL, has collaborated with Frenkel and suggested that his colleague has helped “develop all these approaches for characterizing these materials.” Stach said that Frenkel has “an outstanding reputation internationally” as an expert in X-ray absorption spectroscopy, and, in particular, a subarea that allows scientists to learn about extremely subtle changes in the distance between atoms when they are subjected to reactive environments.

Frenkel said some of the next steps in the work with metal organic frameworks include understanding how these materials might become saturated with decomposed gas after they perform their catalytic function. “It’s not clear what can affect saturation,” he said, and that is something that “needs to be systematically investigated.” After the catalyst reaches saturation, it would also be helpful to know whether it’s possible to remove the remaining compound and reuse the catalyst.

“The next question is whether to discard” the framework after it’s trapped and deactivated the chemicals or regenerate it, Frenkel said. He is also exploring how temperature ranges might affect the performance of the framework. Ideally, it would function as well in an arctic environment as it would in a desert under extreme heat. A commercial application might require the synthesis of a material with different physical characteristics for a range of temperature conditions.

Frenkel has been working on this project for about one and a half years. A colleague approached him to become a part of this new collaboration. “My role was to bring this work to a national lab setting,” where the scientists could use the advanced tools at BNL to study the material as it was working, he said.

A resident of Great Neck, Frenkel, who grew up in St. Petersburg, Russia, lives with his wife Hope Chafiian, a teacher at the Spence School in Manhattan for almost 30 years. He has three children: Yoni lives in Manhattan and works at JP Morgan Chase, Ariela is a student at Binghampton and Sophie is in middle school in Great Neck.

Frenkel appreciates the opportunity to explore the broader world of nanomaterials, which, he said, are not constrained by crystal structures and can be synthesized by design. “They show a lot of mysteries that are not understood fully,” he said. Indeed, Frenkel explained that there are numerous commercial processes that might benefit from design studies conducted by scientists. As for his work with metal organic frameworks, he said “there’s no way to overestimate how important [it is] to do work that has a practical application that improves technology, saves costs, protects the environment” and/or has the potential to save lives.

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Eric Stach, group leader of Electron Microscopy at BNL and Special Assistant for Operando Experimentation for the Energy Sciences Directorate. Photo from BNL

In a carpool, one child might be the slowest to get ready, hunting for his second sneaker, putting the finishing touches on the previous night’s homework, or taming a gravity-defying patch of hair. For that group, the slowest child is the rate-limiting step, dictating when everyone arrives at school.

Similarly, chemical reactions have a rate-limiting step, in which the slower speed of one or more reactions dictates the speed and energy needed for a reaction. Scientists use catalysts to speed up those slower steps.

In the world of energy conversion, where experts turn biomass into alcohol, knowing exactly what happens with these catalysts at the atomic level, can be critical to improving the efficiency of the process. A better and more efficient catalyst can make a reaction more efficient and profitable.

That’s where Brookhaven National Laboratory’s Eric Stach enters the picture. The group leader of Electron Microscopy, Stach said there are several steps that are rate-limiting in converting biomass to ethanol.

By using the electron microscope at Center for Functional Nanomaterials, Stach can get a better structural understanding of how the catalysts work and find ways to make them even more efficient.

“If you could lower the energy cost” of some of the higher-energy steps, “the overall system becomes more efficient,” Stach said.

Studying catalysts as they are reacting, rather than in a static way, provides “tremendous progress that puts BNL and the Center for Functional Nanomaterials at the center” of an important emerging ability, said Emilio Mendez, the director of CFN. Looking at individual atoms that might provide insight into ways to improve reactions in energy conversion and energy storage is an example of a real impact Stach has had, Mendez said.

Stach works in a variety of areas, including Earth-abundant solar materials, and battery electrodes, all in an effort to see the structure of materials at an atomic scale.

“I literally take pictures of other people’s materials,” Stach said, although the pictures are of electrons rather than of light.

Stach, who has been working with electron microscopes for 23 years, gathers information from the 10-foot tall microscope, which has 25 primary lenses and numerous smaller lenses that help align the material under exploration.

His work enables him to see how electrons, which are tiny, negatively charged particles, bounce or scatter as they interact with atoms. These interactions reveal the structure of the test materials. When these electrons collide with a gold atom, they bounce strongly, but when they run into a lighter hydrogen or oxygen atom, the effect is smaller.

Since Stach arrived at BNL in 2010, he and his staff have enabled the number of users of the electron microscope facility to triple, estimated Mendez.

“The program has grown because of his leadership,” Mendez said. “He was instrumental in putting the group together and in enlarging the group. Thanks to him, directly or indirectly, the program has thrived.”

Lately, working with experts at the newly-opened National Synchrotron Light Source II, Stach, among other researchers, is looking in real time at changes in the atomic structure of materials like batteries.

In February, Stach was named Special Assistant for Operando Experimentation for the Energy Sciences Directorate.

“The idea is to look at materials while they are performing,” he said. Colleagues at the NSLS-II will shoot a beam of x-rays through the battery to “see where the failure points are,” he said. At the same time, Stach and his team will confirm and explore the atomic-scale structure of materials at Electron Microscopy.

Working with batteries, solar cells, and other materials suits Stach, who said he “likes to learn new things frequently.”

Residents of Setauket, Stach and his wife Dana Adamson, who works at North Shore Montessori School, have an 11-year old daughter, Gwyneth, and a nine year-old son, Augustus. The family routinely perambulates around Melville Park with their black lab, Lola.

In his work, Stach said he often has an idea of the structure of a material when he learns about its properties or composition, even before he uses the electron microscope. “The more interesting [moments] are when you get it wrong,” he said. “That’s what indicates something fundamentally new is going on, and that’s what’s exciting.”

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