UCI graduate student Cory Windorff could have studied abroad for a year in Bangkok, Barcelona or Buenos Aires. Instead, he chose an austere outpost at the Los Alamos National Laboratory near Santa Fe, New Mexico. What the location lacked in culture and amenities, it more than made up for in historical significance, and it allowed the young researcher to play a central role in a groundbreaking scientific discovery.
In 2015, Windorff went to Los Alamos with the support of UCI and a Science Graduate Student Research Fellowship from the U.S. Department of Energy. While there, he served as a key member of a team of chemists that uncovered a previously unknown oxidation state of plutonium, the highly radioactive, synthetic element used in nuclear power plants and weaponry.
“Chemists are generally aware of the applications of plutonium and have known the available oxidation states since it was first made decades ago,” says Windorff, who was awarded a Ph.D. in chemistry this summer. “But we still don’t fundamentally understand everything we would like to know about plutonium and some of its closely related elements, including all of their oxidation states, apparently. This is important information because oxidation states dictate how elements will react in chemical compounds.”
Derived by either adding electrons to the outer shells of atoms or taking them away, oxidation states are fundamental aspects of elements on the periodic table. In nomenclature perplexing to nonchemists, removing electrons results in a “plus” oxidation state, and adding them produces a “minus” state. (This has to do with the fact that electrons have a negative charge.) A well-known example is rust, which is iron 3 plus (with three missing electrons) in chemistry terminology. Windorff and his colleagues had a breakthrough when they added an electron to plutonium 3 plus to make plutonium 2 plus.
“The charge on a metallic element is a basic quantity in chemistry,” says William Evans, UCI professor of chemistry and Windorff’s Ph.D. adviser. “Oxidation states have been studied extensively by scientists for over 100 years, and many thought that all were well-established.”
But Evans and his students have made a habit of toppling these assumptions.
Their focus has largely been on the metals called lanthanides and actinides in the two rows usually shown at the bottom of the periodic table, separate from the main body of elements. In a lab in UCI’s Frederick Reines Hall, Evans’ team developed innovative techniques to tease out new oxidation states for six lanthanide elements and three actinide metals.
Their approach involves combining reagents at low temperatures and working quickly before the materials decompose. Evans’ students log a lot of hours with their hands inside glove boxes (transparent sealed containers that allow manipulation of substances inside), mixing compounds, and moving samples in and out of cold baths and freezers to keep things chilly and stable.
When a perfect crystal is formed, it’s loaded onto a diffractometer and X-rayed to tell the researchers exactly where the atoms are in the molecules. “You can see your target metal ion surrounded by a group of atoms we call ligands that protect the ion we’re studying,” Evans says.
With the help of Los Alamos actinide chemist Stosh Kozimor, a veteran of the Evans lab, Windorff was able to bring these techniques to the national lab to be used on plutonium; he worked closely with Los Alamos senior scientist Andrew Gaunt.
“Cory was a fourth-year graduate student, so he was at his peak in terms of his ability to make these molecules,” Evans says. “We can’t handle plutonium here – it’s too dangerous – but they can at Los Alamos, and they wanted to work with us on this project, so what better way than to drop your student into the lab that has the capacity to do this.”
He notes that the young chemist not only got to participate in cutting-edge research, but benefited from exposure to the national lab environment.
Windorff agrees: “It was an unbelievable experience, being able to rub elbows and shake hands with so many well-known scientists from a field that I’m interested in. It was really exciting. When I came back to UCI after a year in Los Alamos, I began to think differently about my research because of what I learned there.”
The sojourn also opened his eyes to possible new career paths. “I had always thought about a position in academia after I got my Ph.D.,” Windorff says. “Los Alamos made me think about doing research at a national lab, so I’ve included a few in my application process.”
For Evans, the driving factor is the ongoing quest for fundamental knowledge about the world around us.
“What’s special to me is the idea that we’re finding out things about the elements that we never knew were possible – and this after looking closely at them for years and years,” he says. “As a scientist, you might think, ‘Okay, we’ve gone about as far as we can go,’ then somebody finds something completely different that opens up a whole new world. That, to me, is what makes this plutonium oxidation state research a very big deal.”