Yazdi

Atomic Musical Chairs: How Tiny Nanocrystals Are Informing the Future of Energy-Efficient Electronics

Daniel Morton — Tue, 17 Mar 2026 19:43:33 +0000

Atomic Musical Chairs: How Tiny Nanocrystals Are Informing the Future of Energy-Efficient Electronics Daniel Morton Tue, 03/17/2026 - 13:43

Daniel Morton

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While most people, when asked about energy innovation, think about some of the "large" technologies, such as wind turbines, long transmission lines, or massive power plants, some of the most important advances in how we use energy are happening at a scale so small that millions of the "machines" involved could fit on the head of a pin.

New research from a team led by RASEI Fellow Gordana Dukovic, working in collaboration with RASEI Fellow Sadegh Yazdi and Prof. Dmitri Talapin from the University of Chicago, reveals new insights on a high-speed game of "atomic musical chairs." This collaboration involved two large teams working together. Researchers from two United States National Science Foundation Science and Technology Centers (STCs) including IMOD and STROBE, employed cutting-edge microscopy techniques to directly visualize, for the first time at this scale, how atoms swap places inside tiny semiconductor nanocrystals, which is a crucial step toward understanding the composition, and ultimately the properties, of these materials.

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Science and Technology Centers are hubs for collaboration, bringing together multidisciplinary researchers from across the United States to solve large, challenging and complex problems. This article describes a space where two of these large networks worked together. STROBE, or Science and Technology Center on Real-Time Functional Imaging pushes the boundaries of microscopy to observe and understand materials at the atomic and nano-scales. IMOD, or The Center for Integration of Modern Optoelectronic Materials on Demand, focuses on making atomically precise semiconductors and integrating them into applications in VR displays, and devices for quantum communication and computing. This team leverages the expertise from both Centers to create new semiconductors and using cutting-edge microscopes to observe and understand them.

Almost all of our electronic devices are built from semiconductors. Whether it is the screen on your smartphone, the components in your car, or the microchips in your computer, these electronics rely on semiconductors. Traditionally, these materials are "grown" through rigid and often expensive processes. Tuning the properties of a semiconductor using this approach is not straightforward. If you want a specific color of light for a display, or a specific energy absorption profile for a solar panel, you often have to start from scratch with an entirely different material.

This is where semiconductor nanocrystals offer remarkable opportunities. The specific size, shape, and composition of these tiny nanocrystals determine the physical and electronic properties of the overall material. A particularly powerful process with such nanocrystals is called cation exchange. Instead of building a new crystal from scratch, you can take an existing one and swap out its internal atomic components to change its properties.

“This is a project that we have been working on for a long time” explains Ben Hammel, a graduate student in the Dukovic Group, and lead author on this research. “We have been looking at these materials from the Talapin Group for a long time”.

This work, just published in ACS Nano, focuses on what are called III–V nanocrystals, which are tiny, four-sided pyramids, or tetrahedrons, named for the groups of the periodic table their constituent elements come from (Group III includes elements like Indium, Gallium, and Aluminum; Group V includes Phosphorus, Arsenic, and Antimony). In this research, the nanocrystals are made of a mixture of Indium, Phosphorus, and Arsenic. To exert more control over the properties of these nanocrystals, the researchers introduced Gallium. Adding Gallium is like tuning a guitar string: it changes the energy of the crystal, influencing how it interacts with light.

“A lot of people have developed ways to make III-V bulk semiconductors, but the real challenge is making them into nanocrystals, where you have more control over their properties, and the Talapin Group have developed a really neat molten salt process to do this” explains Hammel. The molten salt work was published in Science in 2024.

Imagine the inside of one of these tiny crystals as a perfectly ordered lattice of "seats." There are two types of players: Anions (the Phosphorus and Arsenic atoms) and Cations (the Indium atoms). A key observation from the team was that the "house" never moves. The Anions are like the floor and the chairs, they stay perfectly still, maintaining the overall crystal framework. The Cations, on the other hand, are the players sitting in those chairs.

In this work, the nanocrystals were placed into a "hot bath" of molten Gallium salts, essentially starting the music on the game of atomic musical chairs. Previous work had shown that the atoms exchange, but there was not a lot of evidence for how this process worked. “Understanding how this works is very important, and finding out more about the local elemental composition, and how the Gallium atoms move can inform how we design these systems in the future” explains Hammel.

These nanocrystals are only 5 to 10 nanometers wide. A typical human hair is between 80,000 and 100,000 nanometers wide. These crystals are called "nano" for a reason! To observe this game of atomic musical chairs in action, the team used Scanning Transmission Electron Microscopy (STEM), an instrument that uses a focused beam of electrons to probe and image matter at the atomic scale. “Early on there were some signs that there was heterogeneity within the particles, but it was unclear, a big technical challenge we had to overcome was how we can actually measure the Gallium moving through the nanocrystal” said Hammel.

A key challenge they had to figure out was the sensitivity of the nanocrystals to the very tool being used to study them. The electron beam of the STEM, if used at high intensity, can damage the nanocrystals before a useful image can even be collected. To solve this, the team developed an innovative "statistical" imaging approach. Rather than blasting a single crystal with a high dose of electrons to get a sharp image, the researchers instead took many low-dose, and individually blurry, snapshots of hundreds of different crystals at different stages of the molten salt reaction. “We essentially stacked the data on top of each other” describes Hammel, “If I can add together 10 nanocrystals, I can get 10 times the signal”. Adding these kinds of signals together hadn’t been done before with semiconductor nanocrystals. “A lot of this came together from teamwork, I got a lot of really great suggestions from collaborators on how to collect and analyze this information. I used a suite of open source Python tools, which I was a little lost with until I met the researcher who developed them at a conference (Josh Taillon from NIST), who gave me some great suggestions and ideas” said Hammel. Using these advanced computer algorithms, they aligned and stacked hundreds of images on top of each other. Much like a long-exposure photograph of the night sky reveals stars the naked eye cannot see, this averaged stacked image revealed a detailed map of where the Gallium atoms were moving inside the nanocrystals. To the team’s knowledge, this signal-averaging approach for elemental mapping has not previously been applied to semiconductor nanocrystals.

The Gallium atoms rush in to claim “seats”, but not randomly. Gallium grabs the seats near the surface first. Because of the high surface-to-volume ratio of these tiny particles, this surface exchange causes a dramatic and rapid change in overall composition: within the first 15 minutes in the molten salt bath, the outside of the nanocrystals is substantially transformed. However, as the game goes on, it gets progressively harder. The Indium atoms sitting in the seats at the center of the nanocrystal are crowded in, and for a Gallium atom to reach the core, an Indium atom must fight its way out through an increasingly Gallium-rich lattice. This sets up a compositional gradient, essentially a smooth transition from a Gallium-rich exterior to an Indium-rich core, that persists even after 16 hours of reaction.

This new methodology, combining STEM with advanced computational image processing, is sensitive enough to detect and map the movement of atoms through individual nanocrystals. Applying it here directly revealed that the cation exchange process (Indium being replaced by Gallium) creates a graded composition rather than a simple sharp boundary between materials. The team also used computer simulations (finite element analysis in COMSOL) to model this exchange as a diffusion-limited process, finding that the rate of exchange slows dramatically as more Gallium enters the lattice, likely because the smaller Gallium atoms cause the lattice to contract, making it progressively harder for further exchange to occur.

Importantly, the methods developed in this work are broadly applicable and could be used to determine the elemental composition of many other types of nanocrystals that have previously been difficult to study due to their sensitivity to electron beams.

Daniel Morton — Thu, 24 Oct 2024 19:50:17 +0000

RASEI Researchers unlock a 'new synthetic frontier' for quantum dots Daniel Morton Thu, 10/24/2024 - 13:50

Lauren Scholz

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University of Chicago Press Release

In a breakthrough for nanotechnology, researchers have discovered a new way to synthesize quantum dot nanocrystals using molten salt as a medium. Traditional methods to create these materials required organic solvents, which cannot withstand the high temperatures needed for certain semiconductor materials, particularly those combining elements from groups III and V on the periodic table. By using superheated molten sodium chloride, scientists were able to synthesize these semiconductor nanocrystals, paving the way for improved applications in fields like quantum computing, LED lighting, and solar technology.

Led by a team from the University of Chicago and collaborating institutions, including RASEI Fellows Sadegh Yazdi and Gordana Dukovic, this novel method also opens new avenues for materials science by enabling the synthesis of previously inaccessible nanocrystal compositions. The technique addresses long-standing challenges by providing a high-temperature environment without degrading the materials. Researchers hope this advance will contribute to new types of devices and materials, marking a significant expansion in the range of accessible quantum dot technologies.

For a more information, please see the press release from The University of Chicago.

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Profile: Benjamin Hammel

Anonymous — Mon, 09 Sep 2024 06:00:00 +0000

Profile: Benjamin Hammel Anonymous (not verified) Mon, 09/09/2024 - 00:00

Daniel Morton

Ben Hammel is a graduate student in the Dukovic group at CU ��ý��, who is using advanced microscopic techniques with Sadegh Yazdi to provide insights into the relationships between materials structures and properties, specifically materials associated with renewable energy research. We caught up with Ben to find out more about what led him to this research area, what excites him about this field of study, and what he gets up to outside the lab.

Where did you grow up?

I am from Albuquerque, New Mexico. I grew up outside the city limits, on the southwest mesa. There are a lot of alfalfa farms and other agricultural industries around there. One of the really cool things about that part of New Mexico is the rich cultural heritage, there is a lot of cultures coming together, with such a long history. Some of the earliest settlements in the United States are in New Mexico!

What did you get up to as a kid?

I enjoyed exploring outside and hiking. Lots of great mountains near Albuquerque and good camping in northern New Mexico.

What drew you into science and research?

New Mexico is kind of this secret hub for scientific research. There is such a rich community of scientists and researchers there and a long history of amazing work. The Manhattan Project, Los Alamos and Sandia National Labs – they set up these huge institutions for research. These all have a trickle-down effect that has impacted a huge number of people and was definitely something that played a big part in my early thinking.

I started doing research at a really young age. As a freshman in high school, I wrote on my resume that my goal was to become a particle physicist! This got passed along to a retired Sandia National Labs scientist, Pace VanDevender, who then took me under his wing. I worked with him as a summer research assistant that year, and it made me think that my path would lead to working at Sandia.

When I was 16, I had the opportunity to work in a chemistry lab at Sandia National Labs – prior to that I had been all about physics and electrical engineering. I was very much interested in energy research and I was really into building projects and devices, such as a regenerative bicycle braking system. I didn’t really like chemistry and I started from basically nothing. On my first day, the researchers in the lab (LaRico Treadwell and Daniel Yonemoto) took me through my first reaction, how to calculate the amount of reagents and how to mix them – I didn’t even know how to do a mass balance! The support I got from that lab (Tim, Rico, Daniel, Jeremiah, Francesca, Diana, and Fernando to name a few) was fantastic and very rapidly chemistry became my main interest. My mentor, the venerable Timothy J. Boyle, said “Ben, learning chemistry in this lab is like learning how to drive in a Lamborghini!” I had a very flexible school schedule that enabled me to work at Sandia a lot. And I fell in love with chemistry.

So, you were hooked on research at a young age, how did this inform your decisions about university?

I really wanted to find a way to combine my early interest in building things and engineering with my passion for chemistry. The University of Pennsylvania has this program called the Vagelos Integrated Program in Energy Research, or VIPER, that gives you the chance to do 2 degrees and that really drew me in. I did chemistry plus materials science and engineering and I stuck with those all the way through.

I was looking for ways to combine making molecules with applications in nanoscience, and that led me to working in the lab of Christopher Murray. I was looking for paid work and my Mom said “You can either work as a dishwasher, or you can work in a chemistry lab”, so I was glad that I persuaded Chris to let me join his lab.

Later during my undergraduate degree, in 2019, I did an internship at NREL, and I ended up working on something completely different, microbubble insulation. This was much more a materials engineering project working with researchers Lin Simpson and Chaiwat Engtrakul. We were gluing bubbles together to form foam bricks for use in insulation. The aim was to try and make something that was cheap, had high performance, and robust to damage and defects.

Coming out of that internship I realized that what really fascinated me was the fundamental chemistry I was doing more than the engineering aspects. I became very interested in the fundamentals of what was happening at the surfaces of these microbubbles, much more than the engineering challenges, and that is what steered me more toward chemistry and materials science.

I really enjoyed my time at NREL, both the research and the opportunities to spend time outdoors, it was one of the big draws when I was looking into graduate school.

Describe the research that you are involved in now

I work on the fundamental end of materials and energy research. We aim to learn how we can make nanomaterials that are better catalysts, which involves fabricating these nanomaterials in an extremely precise fashion, so that we have clear understanding about the materials structure and properties. Of specific interest is the electronic structure, since this impacts how it absorbs light. Armed with this fundamental understanding we can better guide the design of the next generation of materials for energy harvesting, storage, and transport. Working out how the structure of a material influences its properties is what really interests me at the moment.

Your research involves a great deal of collaboration, how has that impacted your work?

I think my experience of working in both engineering and chemistry has helped me connect with folks from different disciplines. I have learned that there are many ways in which teams are forming in the energy sciences, and it’s these teams that are doing the really cool science. It’s also interesting to consider some of the social and economic impacts of doing research and thinking about cost and other factors that are going to dictate which technologies get commercialized.

Early on I wanted to be involved in every part of the research spectrum, from discovery to application. But you can’t do it all. And as I have specialized, I have really enjoyed working as an integral part of bigger research teams, where I can be aware of the big picture, make meaningful contributions through my specialty, and engage and learn from others.

What do you enjoy doing outside of the lab?

I do really enjoy spending time outdoors, but my main hobby is gaming. I play a game called League of Legends, and at one point I was in the top 0.1% of players online. It got pretty competitive and required a ton of work. I entertained the idea of playing professionally. But when I ended up playing against some professional players, I quickly realized there was no chance I could ever go pro! I play a lot more casually now.

What would you say to someone considering a research path?

For me I found that scientists and engineers operate in quite different ways, and when you start taking both sets of classes you rapidly pick up on this. If someone is trying to do the same kind of dual pathway, it is hard at first, but it really is worth persevering. Having expertise in one area is important but having a more general perspective can come in very useful and gives you a broad skillset. You can think at a bunch of different scales, and from different perspectives, which I found challenging at first but have found to be very useful.

What are the future impacts of your research that you are excited about?

I think virtual reality displays are going to bring huge benefits. The most expensive part of these at the moment is the display. Engineering new materials that are super small and super bright will make these really high-resolution. We are going to get this amazing technology that is going to have a lot of great practical applications, I think VR will be a game changer.

Microscopy is also blowing up right now. It is now almost routine to look at atoms, which really changes how you think about and make materials. We are reaching higher and higher levels of precision, which I think is going to open the door to new applications. I don’t know what those are going to be!

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Colossal Core/Shell CdSe/CdS Quantum Dot Emitters

Anonymous — Fri, 26 Jul 2024 06:00:00 +0000

Colossal Core/Shell CdSe/CdS Quantum Dot Emitters Anonymous (not verified) Fri, 07/26/2024 - 00:00

ACS NANO, 2024, 18, 31, 20726-20739

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Ligand Equilibrium Influences Photoluminescence Blinking in CsPbBr3: A Change Point Analysis of Widefield Imaging Data

Anonymous — Tue, 09 Jul 2024 06:00:00 +0000

Ligand Equilibrium Influences Photoluminescence Blinking in CsPbBr3: A Change Point Analysis of Widefield Imaging Data Anonymous (not verified) Tue, 07/09/2024 - 00:00

ACS NANO, 2024, 18, 29, 19208-19219

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