Tag Archives: Argonne National Laboratory (ANL)

Alloy nanoparticles make better catalysts

A Jan. 4, 2021 news item on Nanowerk describes new insights into nanoscale catalysts derived from work at the US Argonne National Laboratory,

Catalysts are integral to countless aspects of modern society. By speeding up important chemical reactions, catalysts support industrial manufacturing and reduce harmful emissions. They also increase efficiency in chemical processes for applications ranging from batteries and transportation to beer and laundry detergent.

As significant as catalysts are, the way they work is often a mystery to scientists. Understanding catalytic processes can help scientists develop more efficient and cost-effective catalysts. In a recent study, scientists from University of Illinois Chicago (UIC) and the U.S. Department of Energy’s (DOE) Argonne National Laboratory discovered that, during a chemical reaction that often quickly degrades catalytic materials, a certain type of catalyst displays exceptionally high stability and durability.

The catalysts in this study are alloy nanoparticles, or nanosized particles made up of multiple metallic elements, such as cobalt, nickel, copper and platinum. These nanoparticles could have multiple practical applications, including water-splitting to generate hydrogen in fuel cells; reduction of carbon dioxide by capturing and converting it into useful materials like methanol; more efficient reactions in biosensors to detect substances in the body; and solar cells that produce heat, electricity and fuel more effectively.

A January 4, 2021 Argonne National Laboratory news release (also on EurekAlert) by Savannah Mitchem fills in some details,

In this study, the scientists investigated “high-entropy” (highly stable) alloy nanoparticles. The team of researchers, led by Reza Shahbazian-Yassar at UIC, used Argonne’s Center for Nanoscale Materials (CNM), a DOE Office of Science user facility, to characterize the particles’ compositions during oxidation, a process that degrades the material and reduces its usefulness in catalytic reactions.

“Using gas flow transmission electron microscopy (TEM) at CNM, we can capture the whole oxidation process in real time and at very high resolution,” said scientist Bob Song from UIC, a lead scientist on the study. “We found that the high-entropy alloy nanoparticles are able to resist oxidation much better than general metal particles.”

To perform the TEM, the scientists embedded the nanoparticles into a silicon nitride membrane and flowed different types of gas through a channel over the particles. A beam of electrons probed the reactions between the particles and the gas, revealing the low rate of oxidation and the migration of certain metals — iron, cobalt, nickel and copper — to the particles’ surfaces during the process.

“Our objective was to understand how fast high-entropy materials react with oxygen and how the chemistry of nanoparticles evolves during such a reaction,” said Shahbazian-Yassar, UIC professor of mechanical and industrial engineering at the College of Engineering.

According to Shahbazian-Yassar, the discoveries made in this research could benefit many energy storage and conversion technologies, such as fuel cells, lithium-air batteries, supercapacitors and catalyst materials. The nanoparticles could also be used to develop corrosion-resistant and high-temperature materials.

“This was a successful showcase of how CNM’s capabilities and services can meet the needs of our collaborators,” said Argonne’s Yuzi Liu, a scientist at CNM. “We have state-of-the-art facilities, and we want to deliver state-of-the-art science as well.”

Here’s a link to and a citation for the paper,

In Situ Oxidation Studies of High-Entropy Alloy Nanoparticles by Boao Song, Yong Yang, Muztoba Rabbani, Timothy T. Yang, Kun He, Xiaobing Hu, Yifei Yuan, Pankaj Ghildiyal, Vinayak P. Dravid, Michael R. Zachariah, Wissam A. Saidi, Yuzi Liu, and Reza Shahbazian-Yassar. ACS Nano 2020, 14, 11, 15131–15143 DOI: https://doi.org/10.1021/acsnano.0c05250 Publication Date:October 20, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Below is one of my favourite types of video work, a ‘blob video’ from the University of Illinois showing the alloy nanoparticles as they oxidate,

Video of transmission electron microscopy, performed at Argonne’s CNM, showing the oxidation of high-entropy nanoparticles in air at 400 °C, sped up by a factor of four. The oxidation process is depicted by the dissolution of the edges of the nanoparticles in the video. (Image by University of Illinois.)

Ferroelectric roadmap to neuromorphic computing

Having written about memristors and neuromorphic engineering a number of times here, I’m  quite intrigued to see some research into another nanoscale device for mimicking the functions of a human brain.

The announcement about the latest research from the team at the US Department of Energy’s Argonne National Laboratory is in a Feb. 14, 2017 news item on Nanowerk (Note: A link has been removed),

Research published in Nature Scientific Reports (“Ferroelectric symmetry-protected multibit memory cell”) lays out a theoretical map to use ferroelectric material to process information using multivalued logic – a leap beyond the simple ones and zeroes that make up our current computing systems that could let us process information much more efficiently.

A Feb. 10, 2017 Argonne National Laboratory news release by Louise Lerner, which originated the news item, expands on the theme,

The language of computers is written in just two symbols – ones and zeroes, meaning yes or no. But a world of richer possibilities awaits us if we could expand to three or more values, so that the same physical switch could encode much more information.

“Most importantly, this novel logic unit will enable information processing using not only “yes” and “no”, but also “either yes or no” or “maybe” operations,” said Valerii Vinokur, a materials scientist and Distinguished Fellow at the U.S. Department of Energy’s Argonne National Laboratory and the corresponding author on the paper, along with Laurent Baudry with the Lille University of Science and Technology and Igor Lukyanchuk with the University of Picardie Jules Verne.

This is the way our brains operate, and they’re something on the order of a million times more efficient than the best computers we’ve ever managed to build – while consuming orders of magnitude less energy.

“Our brains process so much more information, but if our synapses were built like our current computers are, the brain would not just boil but evaporate from the energy they use,” Vinokur said.

While the advantages of this type of computing, called multivalued logic, have long been known, the problem is that we haven’t discovered a material system that could implement it. Right now, transistors can only operate as “on” or “off,” so this new system would have to find a new way to consistently maintain more states – as well as be easy to read and write and, ideally, to work at room temperature.

Hence Vinokur and the team’s interest in ferroelectrics, a class of materials whose polarization can be controlled with electric fields. As ferroelectrics physically change shape when the polarization changes, they’re very useful in sensors and other devices, such as medical ultrasound machines. Scientists are very interested in tapping these properties for computer memory and other applications; but the theory behind their behavior is very much still emerging.

The new paper lays out a recipe by which we could tap the properties of very thin films of a particular class of ferroelectric material called perovskites.

According to the calculations, perovskite films could hold two, three, or even four polarization positions that are energetically stable – “so they could ‘click’ into place, and thus provide a stable platform for encoding information,” Vinokur said.

The team calculated these stable configurations and how to manipulate the polarization to move it between stable positions using electric fields, Vinokur said.

“When we realize this in a device, it will enormously increase the efficiency of memory units and processors,” Vinokur said. “This offers a significant step towards realization of so-called neuromorphic computing, which strives to model the human brain.”

Vinokur said the team is working with experimentalists to apply the principles to create a working system

Here’s a link to and a citation for the paper,

Ferroelectric symmetry-protected multibit memory cell by Laurent Baudry, Igor Lukyanchuk, & Valerii M. Vinokur. Scientific Reports 7, Article number: 42196 (2017) doi:10.1038/srep42196 Published online: 08 February 2017

This paper is open access.

X-ray of a butterfly’s wing reveals structural colour secrets

Over millions of years, butterflies evolved sophisticated cellular mechanisms to produce brightly colored wings for mating and camouflage. iStock photo by Borut Trdina

Over millions of years, butterflies evolved sophisticated cellular mechanisms to produce brightly colored wings for mating and camouflage. iStock photo by Borut Trdina

A June 13, 2016 news item on Nanowerk announced a discovery about the physics of colour,

A team of physicists that visualized the internal nanostructure of an intact butterfly wing has discovered two physical attributes that make those structures so bright and colorful.

“Over millions of years, butterflies have evolved sophisticated cellular mechanisms to grow brightly colored structures, normally for the purpose of camouflage as well as mating,” says Oleg Shpyrko, an associate professor of physics at UC San Diego, who headed the research effort. “It’s been known for a century that the wings of these beautiful creatures contain what are called photonic crystals, which can reflect light of only a particular color.”

But exactly how these complex optical structures are assembled in a way that make them so bright and colorful remained a mystery.

A June 10, 2016 University of California at San Diego news release (also on EurekAlert), which originated the news item, describes how the mystery was solved,

In an effort to answer that question, Shpyrko and Andrej Singer, a postdoctoral researcher in his laboratory, went to the Advanced Photon Source at the Argonne National Laboratory in Illinois, which produces coherent x-rays very much like an optical laser

By combining these laser-like x-rays with an advanced imaging technique called “ptychography,” the UC San Diego physicists, in collaboration with physicists at Yale University and the Argonne National Laboratory, developed a new microscopy method to visualize the internal nanostructure of the tiny “scales” that make up the butterfly wing without the need to cut them apart.

The researchers report in the current issue of the journal Science Advances that their examination of the scales of the Emperor of India butterfly, Teinopalpus imperialis, revealed that these tiny wing structures consist of “highly oriented” photonic crystals.

“This explains why the scales appear to have a single color,” says Singer, the first author of the paper. “We also found through careful study of the high-resolution micrographs tiny crystal irregularities that may enhance light-scattering properties, making the butterfly wings appear brighter.”

These crystal dislocations or defects occur, the researchers say, when an otherwise perfectly periodic crystal lattice slips by one row of atoms. “Defects may have a negative connotation, but they are actually very useful in improving materials,” explains Singer. “For example, blacksmiths have learned over centuries how to purposefully induce defects into metals to make them stronger. ‘Defect engineering’ is also a focus for many research teams and companies working in the semiconductor field. In photonic crystals, defects can enhance light-scattering properties through an effect called light localization.”

“In the evolution of butterfly wings,” he adds, “it appears nature learned how to engineer these defects on purpose.”

The researchers have made this image illustrating their work available,

Scales from the wings of the Emperor of India butterfly consist of “highly oriented” photonic crystals. Photos by Andrej Singer, UC San Diego

Scales from the wings of the Emperor of India butterfly consist of “highly oriented” photonic crystals. Photos by Andrej Singer, UC San Diego

Here’s a link to and a citation for the paper,

Domain morphology, boundaries, and topological defects in biophotonic gyroid nanostructures of butterfly wing scales by Andrej Singer, Leandra Boucheron, Sebastian H. Dietze, Katharine E. Jensen, David Vine, Ian McNulty, Eric R. Dufresne, Richard O. Prum, Simon G. J. Mochrie, and Oleg G. Shpyrko. Science Advances  10 Jun 2016: Vol. 2, no. 6, e1600149 DOI: 10.1126/sciadv.1600149

This paper is open access.