Nanoscience and Advanced Materials

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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NSF STCc

STROBE STC

IMOD STC

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.

The ability to observe and better understand the cation exchange process in these semiconductor nanocrystals has significant implications for the development of next-generation materials. It has been suggested that graded compositions, like those observed here, could help suppress certain energy-loss processes in semiconductor devices, potentially enabling more efficient lighting and lower-power electronics. Whether these specific nanocrystals deliver on that promise remains an open and exciting research question, but this work provides the observational foundation needed to begin answering it. Additionally, the molten-salt synthesis approach that underpins this research is an active area of development as a potentially more versatile route to III–V semiconductor nanocrystals, materials that have historically been among the most challenging to synthesize with fine compositional control.

By developing new tools to better observe the game of "atomic musical chairs," the researchers are providing the field with insights into how to engineer materials at the atomic scale and revealing that the path from one material to another is more nuanced, and more interesting, than previously understood.

March 2026

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Upward band gap bowing and negative mixing enthalpy in multi-component cubic halide perovskite alloys

Daniel Morton — Wed, 25 Feb 2026 18:14:59 +0000

Upward band gap bowing and negative mixing enthalpy in multi-component cubic halide perovskite alloys Daniel Morton Wed, 02/25/2026 - 11:14

PHYSICAL REVIEW MATERIALS, 2026, 10, 025405

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2026 Three Minute Thesis Finalists

Daniel Morton — Tue, 24 Feb 2026 20:57:33 +0000

2026 Three Minute Thesis Finalists Daniel Morton Tue, 02/24/2026 - 13:57

Daniel Morton

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91��ý 3MT Competition

2026 3MT Announcement

Recording of 2026 3MT Final

Meet 3MT Finalist Ben Hammel

Ben Hammel, a graduate student in the Dukovic Group, was a finalist in the 2026 91��ý Three Minute Thesis Competition. We caught up with Ben to find out more about the whole 3MT process.

What is 3MT?

3MT stands for Three-Minute Thesis, which was a competition started at the University of Queensland. I think the history behind it is that they were going through droughts in Australia and everyone had these three-minute egg timers in their showers to limit water usage. Someone had this idea of maybe this was a good challenge for condensing/communicating your research: how well can you present your thesis in three minutes?

What did you have to do?

I came into this wanting to learn how to clearly describe my research. The rubric is really about explaining your science. They look at clarity, your enthusiasm, and about the slide and presentation. But they also look at can you describe the motivation of your research? Can you describe the design of your research? Can you describe the conclusions and societal impact of your work? So it is about science communication, with a strong grounding in the scientific aspects. Going through this process and thinking through these things has given me a better understanding of my own science.

Can you describe your research in five words?

Using microscope to look at nanocrystals. Six, that is ok, right?

What drew you to do the 3MT?

I wanted to improve my scientific communication skills, and I felt like there was something really cool about my research that I wanted to share. It is this simple idea that we need to look at nanocrystals to understand how they work. I get to use this amazing microscope to do just that!

What was the best part of the 3MT program?

The best part was definitely the cohort of talks. In the final competition folks got to see eleven presentations from across the graduate school, and that was awesome, but in the preliminary round there were more than 25. There were so many great talks from so many parts of the school that I got to see. It was really fun. You get to see in an hour so much condensed scientific knowledge. That was definitely the best part.

What was the worst/hardest part of the 3MT program?

The hardest part was talking about the science. It is so easy for me to say “we study these nanocrystals, and they’re cool, and I use this microscope”, but when people really ask me about what are the scientific questions you have and what are the experiments you run to answer them? And how are you going to engineer nanocrystals? It’s difficult to answer these kinds of technical questions in an accessible way.

How do you think your experience in 3MT will help you in the future?

Oh, it’s already helping me! Just in the way I talk to people and explain things. I feel like it has made me intellectually stronger and I am already noticing that it helps me communicate more clearly and think about my research in different ways.

Daniel Morton — Tue, 27 Jan 2026 17:02:14 +0000

The case of the vanishing seeds: How curiosity-driven research is future-proofing “Smart Windows” Daniel Morton Tue, 01/27/2026 - 10:02

Daniel Morton

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Have you ever walked into a room on a glorious Colorado summer day and felt the heat radiating through the glass?

We usually solve this by cranking up the air conditioning or closing the blinds, losing our mountain view in the process. But what if the window itself could think? A team led by Mike McGehee, a Fellow at RASEI, describes research that improves the robustness of such a device.

For years researchers have been working on “smart windows”, devices that could “sense” the conditions outside and “react” to them. This investigation centers around a promising technology called Reversible Metal Electrodeposition (RME). The technical details of this process are complex, but you can understand the concept by thinking of it as a reversible coat of paint. At the flip of a switch, a thin layer of metal, in this case silver, spreads across the glass to form a layer that tints it, blocking out the heat and the glare. Flip the switch again and the silver dissolves back into a clear liquid, making the window transparent.

Buildings are responsible for consuming around 40% of all generated energy globally, much of which is expended in regulating the temperature, heating and cooling the building interior. Installing smart windows that can react to the environmental conditions could provide a very effective mechanism to reduce energy use and slash energy bills by automatically managing how much heat enters a room. It has been estimated that just by controlling the amount of sunlight that is let into a building through a window, we could cut energy bills by up to as much as 20%.

However, there have been a number of challenges to overcome in order to take this initial discovery from the lab to a product that can be deployed for use in buildings. One challenge is that early versions of these windows started out fast but grew “lazy” over time. After a few thousand uses the tinting / de-tinting process slowed, taking almost four times longer than it did on day one.

This is where the researchers undertook some detailed investigations to identify what was going on, and what could be done to fix it. A collaboration between the McGehee group (at the University of Colorado Boulder) and the Barile Group (at the University of Nevada) set out to find out exactly what was happening. The team decided to look closer, using a combination of high-powered x-rays and electrochemical tests. The windows were using tiny “seeds” of platinum to help the silver grow on the glass. Platinum is recognized for being tough and non-reactive, and so should be perfect as a nucleation point for the silver. Using these advanced techniques the team explored exactly what was happening to the platinum seeds during the clearing phase, when the silver “paint” is stripped away.

To their surprise, the platinum was not as tough as they initially thought. In the special liquid environment needed for the windows, the platinum seeds were actually dissolving and washing away when the window was switched to clear. As the number of seeds dropped, the silver had fewer locations to grow from, which was the cause behind the window tinting slowing.

This led the team to ask the question “What can we do to make the seeds more resilient?”, which led them to use gold in place of platinum. While gold and platinum are both precious metals, in water, which is the solvent used inside the window panels, gold is more stable and less susceptible to decomposition and dissolving. When they swapped the platinum seeds for gold ones, the results were immediate. Even after 7,500 cycles, the equivalent of years of daily use, the windows transitioned just as fast as the first time they were used.

These gold-based windows provide an exciting range of opportunities. Not only because of their improved stability over many thousands of cycles, but also because they can express multiple colors by varying the voltage, a feature of the size of the gold particles. This presents opportunities for their use in displays and communications devices. This technology offers a better, smarter window that could passively save significant amounts of energy if deployed in commercial and residential buildings. This work shows how the impact of making fundamental chemical changes can unlock the potential of new technologies.

January 2026

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Influence of Ligand Exchange on Single Particle Properties of Cesium Lead Bromide Quantum Dots

Daniel Morton — Tue, 20 Jan 2026 21:16:48 +0000

Influence of Ligand Exchange on Single Particle Properties of Cesium Lead Bromide Quantum Dots Daniel Morton Tue, 01/20/2026 - 14:16

CHEMISTRY OF MATERIALS, 2026, 38, 3, 1074-1083

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