National Lab, Others May Benefit from USC Aiken Prof's Research

Aiken, SC (07/08/2019) — After sticking with an idea conceived while in grad school, one chemistry professor's research now appears in Inorganic Chemistry, a flagship publication of the American Chemical Society.

Dr. Nicholas Marshall says his project is a marriage of two modern super-materials which come together to make something entirely new. The two materials are metal-organic frameworks and conducting polymers.

Metal-organic frameworks are crystalline materials with huge pores that are mostly empty space. Many of them are used for gas storage. Marshall says that at the Savannah River National Laboratory, they are studied for storing hydrogen and as catalysts for hydrogen fuel cells and environmental waste remediation.

Conducting polymers are plastics that conduct electricity. They are used in one kind of solar cell and in state-of-the-art flat screen displays.

He says the idea to bring the two materials together came to him almost 10 years ago when he was a graduate student.

"I was working on making conducting polymer layers that had just the right small-scale structure to work in solar cells," Marshall says.

"You want the polymer to be in little blobs or ridges that are only a few nanometers across in order to get the most electric current for a given amount of light. The trouble is that it's hard to make the polymer stay in that shape."

The assistant professor of organic chemistry explains that as the polymer gets hot during use, it tends to melt and form bigger regions, like chocolate chips melting together in a pan. Marshall wanted something that would hold the polymer in its shape and remembered reading about metal-organic frameworks that had holes in them of about the right size.

"Wouldn't it be cool, I thought, if we could make conducting polymers inside a metal-organic framework, so that it held it in the structure that we wanted?"

But then he had to put his research on hold temporarily - but only until he landed on campus.

"When I took the USC Aiken job, I had the resources to try this idea out."

He joined forces with Will James, student on active duty with the National Guard, who conducted a few "why the heck not" experiments. Additionally, Marshall discovered that a few people had explored a similar idea during his hiatus. They had made composites of metal-organic frameworks and conjugated polymers by filling the pores with monomer and exposing the mixture to some kind of chemical treatment.

"That was disappointing, but that was right when Will stumbled on a really cool discovery. One of the frameworks we were studying reacted directly to make a 'polymers inside a framework' structure, with no additional treatment required," Marshall said.

The reaction was caused by the framework itself, which was not something that anyone had figured out how to do before.

"Will tried so many different combinations to find something that worked, I owe a lot to his determination."

After that, the researching duo had to get a team together to get enough data to prove this reaction worked the way they thought it did. James and Marshall made the composites, and another USC Aiken student -- Jeremy Fulmer -- helped take microscope images and spectra of them. The research team grew when they we brought another USC Aiken chemist, Gerard Rowe, and scientists from the Savannah River National Lab and USC Columbia.

Ultimately, the paper on the research was accepted by Inorganic Chemistry, which published it this spring.

The team isn't done, though. Now, they are focusing on further developing their technique to try to understand it better and working to find collaborators who can try building these materials they're making into pixels or solar cells. Since the work was published, they've been awarded more funding to keep working on it.

"I'm very happy that my students and I were able to take a blue-sky idea from so long ago and turn it into a cool and potentially useful discovery," Marshall said.

Editor's note: For more information on Dr. Nicholas Marshall's research, go to: https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.8b03465 .

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