Chemists unlock new possibilities for rare-earth metal
Researchers report method to isolate and separate terbium under non-lab conditions, potentially expanding its use
image:
Chemists led by the University of Iowa have isolated the rare-earth metal terbium under normal environmental conditions, which could lead to greater uses. The illustration shows how the team devised a cagelike, molecular structure primarily composed of tungsten (gray) and oxygen atoms (red) that bound the terbium (brown), creating the conditions for the terbium atom to change its oxidation state and be separated.
view moreCredit: Korey Carter lab, University of Iowa
Chemists led by the University of Iowa in a new study report they have isolated and described in detail an atypical state of the rare-earth metal terbium, an advance that could expand its use, such as in quantum technologies that could include computing and advanced sensors.
Terbium, a silvery-gray metal mined primarily in China but also found in the United States and a few other countries, is central to a host of devices and technologies. The element underpins green phosphors, which are essential for televisions, fluorescent lamps and LED displays. It also plays a key role in solid-state devices, fuel cells, and has been used to improve the safety of medical X-rays by allowing the same quality image to be produced with a much shorter exposure time.
While useful, terbium comes with obstacles to its access and use. It is part of a group of elements called the lanthanides, a suite of metals that have nearly the same physical properties, which makes it challenging to separate them unless under rigid laboratory conditions.
The Iowa chemists, led by Korey Carter, assistant professor in the Department of Chemistry, and Pere Miro, associate professor in the Department of Chemistry, sought a way to separate terbium under normal environmental conditions, which would make the process cheaper and easier, thus enabling the metal’s full range of properties to be explored.
To do that, he and his team devised a cage-like, molecular structure consisting of metal and oxygen atoms that bound the terbium and caused it to change its oxidation state –essentially yielding a new version that could be isolated and studied in detail.
It's a proof of concept that shows how terbium, and potentially other lanthanides, can be more efficiently separated from each other, opening up new avenues for how each of these rare-earth metals could be used more widely.
“One of challenges with lanthanides is they prefer to be in the same oxidation state, and it’s tricky to change that state and thus separate one from another without it being performed in a tightly controlled environment, such as a lab,” says Carter, the study’s co-corresponding author. “But we devised a method to isolate, or separate terbium, by changing its oxidation state in an environment that doesn’t require specialized lab controls.”
That could open terbium, like other rare-earth metals, for wider use. One area is quantum technology, the unseen world where atoms and other smaller constituents act in strange, hard-to-predict ways.
Among the potential applications there could be computing and advanced sensors in navigation, medical imaging, and other fields.
Terbium, like the other lanthanides, prefers to be in a plus-3 oxidation state, terminology that refers to the number of floating, or “free,” electrons orbiting the nucleus. Terbium’s properties in the plus-3 oxidation state – where it’s most stable – have been well documented, but its characteristics in other states have been little explored.
One of those under-explored areas is the plus-4 oxidation state, in which terbium would have an electron removed, changing its charge and in essence turning it into a new species. But like a stubborn person, terbium resists being transformed and only succumbs when forced.
“You can compel it to give away or accept an electron,” Carter explains, “but it's generally energetically unfavorable.”
Researchers have turned terbium into the plus-4 oxidation state, but they did so in rigorous air-free environments, according to Carter.
His team sought to lower the barriers by creating a molecular assembly of tungsten and oxygen, or polyoxometalate, and adding binding agents known as ligands. With the terbium atom sandwiched in these cages, the Iowa chemists added a chemical oxidant called potassium persulfate. That initiated a reaction that caused the terbium atom to lose an electron, change its oxidation state, and thus be isolated. Moreover, Carter’s team isolated terbium in ambient conditions, meaning in an environment that didn’t require special controls, such as temperature, humidity, or pressure.
“If you were in your house and you were setting up a chemistry experiment, it would be analogous to what we were doing in the lab,” he says.
The benefit to changing terbium’s chemistry in a normal environment could make it easier to access and potentially broaden its applications, such as in quantum technologies or through knowledge gained to separate other metals, Carter says. His group now wants to take what they learned with separating terbium to investigating actinides, a group of highly radioactive elements used in cancer-fighting treatments and devices, such as powering cardiac pacemakers in the body and smoke detectors.
“Our findings highlight the ability to do transformative research at the University of Iowa, and they provide a platform to extend the chemistry to the actinide series in UI Radiochemistry laboratories,” Carter says.
The study is titled “Structural and spectroscopic characterization of a Tb(IV) polyoxometalate.” It was published on July 16 in the journal Nature Communications.
Miro is a co-corresponding author on the study. Other co-corresponding authors are Benjamin Stein and Stosh Kozimor, from Los Alamos National Laboratory; and Jennifer Wacker, from Lawrence Berkeley National Laboratory.
Contributing authors include Primadi Subintoro, Brett Lottes, S. Genevieve Duggan, Daniel Unruh, from Iowa; Felipe Pereiro, from Los Alamos and the Colorado School of Mines; Nolwenn Mahieu, Alexander Brown and Joshua Woods, from Lawrence Berkeley; Monica Mullis, Aldo Jordan, Cassandra Gates and Samuel Greer, from Los Alamos; Rebecca J. Abergel, from Lawrence Berkeley and the University of California-Berkeley; and Jenifer Shafer, from the Colorado School of Mines.
The research was funded by the U.S. Department of Energy.
Journal
Nature Communications
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Structural and spectroscopic characterization of a Tb(IV) polyoxometalate
No comments:
Post a Comment