Regensburg 2022 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 18: Poster Session 2

MM 18.35: Poster

Tuesday, September 6, 2022, 17:30–20:00, P2

In situ X-ray spectroscopic and scattering studies on the emergence of CoO nano-assemblies in solution — •Cecilia Zito¹, Lukas Grote^1,2, Kilian Frank³, Ann-Christin Dippel², Patrick Reisbeck³, Krzysztof Pitala⁴, Kristina Kvashnina⁵, Stephen Bauters⁵, Blanka Detlefs⁵, Oleh Ivashko², Pallavi Pandit², Matthias Rebber¹, Sani Harouna-Mayer¹, Bert Nickel³, and Dorota Koziej¹ — ¹University of Hamburg, Germany — ²Deutsches Elektronen-Synchrotron, Hamburg, Germany — ³Ludwig-Maximilians-Universität München, Germany — ⁴AGH, University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, Poland — ⁵European Synchrotron Radiation Facility ESRF, Grenoble, France

The key to fabricating complex, hierarchical materials is the control of chemical reactions at various length scales. The classical crystallization theory is insufficient to properly describe the chemical reaction leading to monomer formation, the evolution of small primary particles, and how they assemble into superstructures. Here, we illustrate how the combination of advanced X-ray spectroscopic and scattering in situ studies probe length scales all the way from atomic to macroscopic, and shed light on the formation mechanism of CoO nanocrystal assemblies in solution. Utilizing HERFD-XANES, we directly access the molecular level of the nanomaterial synthesis. We reveal that initially Co(acac)3 rapidly reduces to square-planar Co(acac)2 and coordinates to two solvent molecules. Furthermore, we track subsequent structural changes with in situ total X-ray scattering and atomic pair distribution function analysis, pinning down the transition from the dissolved Co complex to crystalline CoO. Ultimately, SAXS uncovers the assembly process of the crystallites into distinct spherical superstructures. The concomitant growth and assembly of crystallites into a superstructure differentiates the investigated pathway from a classical mechanism. The combination of X-ray spectroscopy and scattering can elucidate the emergence of assemblies in solution with a broad perspective.