Microscopy advances could allow unprecedented look at chemical reactions

At the atomic level, chemistry is a whirlwind of activity. But our view of this fascinating world is mostly static. Scientists have to infer the details of chemical reactions from still images, experimental results and simulations that fill in the gaps.

Now, scientists from the University of Illinois Chicago and other institutions are collaborating on new electron microscopy techniques to create a movie studio for chemical reactions. The Center for Multimodal Observations for Single Atom Imaging of Chemistry, or MOSAIC, was funded this fall through a $1.8 million grant from the National Science Foundation. UIC will receive $270,000 from the award.

The collaboration, part of the NSF Centers for Chemical Innovation program, will create "liquid cells" that allow scientists to set up, control and measure chemical reactions under a microscope like never before. The researchers will use powerful, state-of-the-art electron microscopes at UIC to capture these reactions in motion, providing fresh insight into atomic and molecular dynamics.

"We are trying to develop electron microscopy sample environments that will allow us to observe chemistry at the very earliest stages of matter formation," said Robert Klie, professor and head of the department of physics at UIC and associate director of the center. "We could potentially understand how organic molecules form and interact with different environments, which is the ultimate holy grail for chemistry and materials science."

With electron microscopes, scientists can see matter at the level of individual atoms. They do so by shooting a high-energy beam of electrons through the sample, but that can alter or even destroy the sample. This means scientists can capture only one image at a time. Often, they have to freeze samples at critical points in the chemical reaction to catch key steps.

The discovery in the early 2000s of graphene - a material made from a single layer of carbon atoms - offered a solution. By placing a layer of graphene above and a layer below a liquid sample, scientists can protect the sample from the beam and other interference. In 2014, Klie was one of the first to use this system when he studied ferritin, a protein important for storing iron.

"The goal of this method is we want to observe chemistry in a microscope and not cause it," Klie said. "We want to know that what you actually observe is the chemistry that would naturally occur, and not what you cause by shining such a highly reactive electron beam onto it."

The center will advance this graphene liquid cell method to allow for additional measurements and expanded control of the sample. Scientists at the University of Chicago will engineer cells that contain the ingredients for a chemical reaction, which then can be triggered and manipulated under the microscope.

The researchers will start small. They'll observe the behavior of single-atom particles that catalyze chemical reactions. Then they'll move to larger molecule clusters and nanocrystal structures. But Klie hopes they'll also reach the point where they can view more complex molecules and see unprecedented views of processes that are critical in chemistry, biology and materials science.

The NSF grant will fund upgrades of electron microscopy equipment at UIC to enable the use of the new graphene liquid cells. The university's new magnetic-field-free electron microscope - the first of its kind in the United States - will also play a role in the center's research once it's installed in early 2025.

By collaborating on the design and use of these cutting-edge imaging approaches, UIC will remain a leader in electron microscopy advances, Klie said.

"Our electron microscopy center will be key to MOSAIC and demonstrating the potential of these liquid cells," Klie said. "We hope to become the destination for the wider chemistry community to do this kind of analysis."

In addition to UIC and University of Chicago, the center includes researchers from the University of Illinois Urbana-Champaign and Argonne National Laboratory.