This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Chemists in a new study led by the University of Iowa report they have isolated and described in detail an atypical state of the rare-earth metal terbium, an advance that could expand its use in quantum technologies, including computing and advanced sensors. The study, "Structural and spectroscopic characterization of a Tb(IV) polyoxometalate," is published in the journal Nature Communications.
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 and 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, making them challenging to separate except under tightly controlled 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, enabling the metal's full range of properties to be explored.
To do that, they 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 new avenues for how each of these rare-earth metals could be used more widely. "One of the 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," Carter says, 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, up to wider use. One area is quantum technology, the unseen world where atoms and other smaller constituents act in strange, hard-to-predict ways. Potential applications include 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 underexplored 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.
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