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Nr. 97, 26.01.2019  voriger  Übersicht  weiter

An ion spy

Even today, there is still a lot of old handicraft in chemistry: you mix some things together, and in the end, something emerges. But what happens in between can sometimes be more interesting than the actual result. The Kiel researcher Dr Huayna Terraschke has developed a method to have a closer look at those happenings.


Rare earths are true beauties under black light – and can also be very useful for science. Photo: Geist

Chemical reactions are processes that often happen so quickly that they can hardly be fully comprehended. “Before we have the end product, intermediate products often appear for a few seconds or minutes,” says Huayna Terraschke. In order to take advantage of these intermediate products scientifically, it is necessary to access them at the moment they occur, or in situ as it is technically called in Latin.

“This can be extremely interesting for science as well as for industry,” emphasises Terraschke. “The intermediate products can have interesting properties, but they are never discovered when the product is analysed only after the finished reaction,” she adds.

In situ analysis methods can make such discoveries possible by optimising synthesis conditions to stabilise the intermediate product.

Dr Huayna Terraschke observes chemical reactions with a new method. Photo: Geist

The transient and inaccessible bearers of secrets can be outwitted with a trick. An ion is snatched from the solid compounds that serve as the raw material and is replaced with an ion of a similar size that has a crucial difference: it glows. Thanks to this spy-ion, it is now possible to follow visually what happens during the reaction. If the particle becomes lighter or darker or changes its colour, it must logically be due to altered chemical properties. And these, in turn, can be influenced by factors such as temperature or pressure so that, conversely, the formation of the intermediate products can also be influenced.

Rare earths such as europium or terbium are indispensable for in situ luminescence analysis. These types of rare earths convert energy into light, making them ideal ambassadors. “The material is very expensive, but we only need very small quantities,” says Huayna Terraschke, emphasising that she is by no means conducting any kind of luxury research.

Besides, the precious granules are sometimes used twice, as an auxiliary tool and as research objects. Terraschke believes that the more we know about these processes, the more effectively things like LED lights can be produced. The chemical engineer also reckons that having a closer look can help to produce new materials for warmer light colours.

In situ, i.e. in the situation, science has been looking at chemical processes for quite some time. This is mainly done in particle accelerators such as the Deutsches Elektronen-Synchrotron (DESY) in Hamburg, which uses the X-ray diffraction method. According to Huayna Terraschke, this method has the huge advantage that it is excellently suited for the analysis of crystal structures. However, securing a time slot for experiments can mean months of waiting, while the luminescence method can be carried out on site in Kiel right away. In addition, it has the advantage that ions can be used in solutions and even extremely small nanoparticles can be analysed.

The 33-year-old Brazilian with German roots invented the in situ luminescence method four years ago while working on her doctorate with nanoparticles from rare earths. “We are still at the beginning,” emphasises the scientist, who is now developing the process, funded by the German Research Foundation (DFG) since 2016, and its application possibilities with a team of seven to eight people, most of whom are students.

Many German universities and research institutions have taken a keen interest in it and are putting the method to brilliant use. A cooperation with the Helmholtz Association, which is responsible for DESY, is also in the process of being established.

Martin Geist
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