Scientists always want to know exactly what is at the heart of a matter - not so with the new XPS spectrometer at the Institute of Chemistry, where only the surface counts.
Prof Dr Gunther Wittstock will not soon forget the first few weeks with the XPS spectrometer. Not only was it pouring with rain when the special transport with the long-awaited large device finally arrived at the Institute of Chemistry: No sooner had everything been installed and operational in the specially converted laboratory than an employee of an external company accidentally drilled into a water pipe - and the brand new device, worth 1.2 million euros, sprung a leak. A few doormats, hastily brought in and stretched upwards to form a kind of water pipe, prevent worse from happening.
However, the XPS spectrometer survived these adventures unscathed. "It left me with a few grey hairs, but now everything is working again," says Gunther Wittstock. The device, which he acquired in the course of his stay negotiations, has now been in operation for six months. It already offers around 30 scientists from the fields of chemistry and physics completely new analysis possibilities - especially in materials research.
XPS stands for X-ray photoelectron spectroscopy. The method precisely analyses the surface of solids - an advantage that is particularly useful in electrochemistry, as this deals with extremely thin layers. The fact that the device is limited to the surface is important because otherwise the signals from the inside of the material would mask the actually important information about the surface. The thickness of the investigated layer is only around five nanometres, which is one ten-thousandth of the diameter of a hair.
Five working groups at the Wechloy campus use the XPS spectrometer for different research questions. For example, the aim is to optimise layer structures in batteries and solar cells in order to make them more efficient. The device helps to recognise the small but often crucial chemical changes on the surfaces. It also plays a central role for the DFG research group "Nanoporous Gold", in which scientists from Bremen, Oldenburg, Hamburg and Berlin are jointly researching new catalysts. A catalyst helps to produce chemical products in the most energy-efficient way possible. The new spectrometer can be used to determine how the active centres of the catalyst located on the surface work. The findings will be used to customise better catalysts in the future.
Other projects are focussing on the development of sensor materials that can specifically bind nanoparticles of a certain size and composition to a surface and thus enrich them. Only then can they be analysed in more detail. The chemistry between the particles and the outermost layer of the sensor is also crucial for these materials.
The spectrometer was financed in equal parts by the federal and state governments. It has a predicted lifespan of 25 years and will also be used in future as part of co-operation projects with scientists from other research institutions.