2026-01-31
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Researchers at the University of Hamburg, the University of Toulouse, and the DESY and ESRF research institutes have observed for the first time in real time how iron-sulfur nanostructures form in solution. Using time-resolved X-ray methods, the researchers were able to visualize the entire reaction pathway – from the initial molecular precursors to complete ultra-thin nanolayers.
Iron-sulfur compounds play a significant role in both geological processes and technological applications, such as energy material research. Of particular interest is the mineral greigite (Fe₃S₄), which is characterized by exceptional magnetic and electronic properties. Despite intensive research, however, it has remained unclear how such nanostructures form in chemical synthesis.
An international team led by Prof. Dr. Dorota Koziej from the University of Hamburg and the Cluster of Excellence “CUI: Advanced Imaging of Matter” has succeeded in deciphering the previously hidden formation process as part of the ERC Consolidator Project LINCHPIN. To do this, the researchers combined several X-ray methods at the high-energy X-ray sources of the European Synchrotron Radiation Facility (ESRF) and DESY, applying in particular the so-called vtc XES method under real reaction conditions in solution and at higher temperatures. Without the highly brilliant X-ray sources at the ESRF, the otherwise very weak signal would not have been measurable. While the reaction was underway, the team simultaneously observed the structure, the oxidation state of the iron, and the chemical bonding environment.
An unexpected intermediate step leads to the formation of a crumpled nanosheet
The measurements show that the desired material does not form directly. Instead, a short-lived, layer-like intermediate iron sulfide is first formed. This grows preferentially in two dimensions and then passes on its crumpled nanosheet shape to the final material. In a so-called topotactic transformation step, the atoms in the solid rearrange themselves, but particles preserve their characteristic crumpled nanosheet shape.
“We were able to gain a very good overview of the individual steps of the reaction – from the initial reduction of the iron compound to the formation of the final iron-sulfide nanostructure,” says Dr. Cecilia Zito. “Such detailed insights are only possible by combining several analytical methods at a synchrotron using specially developed measuring cells,” adds Dr. Lars Klemeyer.
Significance for material design and natural processes
The research results are significant far beyond the specific material system investigated. They demonstrate the extent to which intermediate steps and growth dynamics determine the final form of nanomaterials. These insights are crucial for the targeted design of nanostructures in the future, for example for more efficient energy storage devices, catalysts, or functional materials.
At the same time, the experiments provide new clues as to how similar minerals may have formed in nature, for example in the oxygen-poor environments of the early Earth.
The work also highlights the potential of modern multimodal in situ X-ray analysis methods to decipher chemical processes at the molecular and nanoscale level over time – an approach that can be applied to many other material systems in the future.
Read the original article on University of Hamburg.