University researchers at the University of Osnabrück reveal a hidden microscopic mechanism, hitherto unacknowledged
In a groundbreaking study, researchers from the University of Osnabrück have successfully distinguished water molecules on the calcite surface for the first time, using high-resolution atomic force microscopy. This breakthrough could have significant implications for climate protection, environmental protection, and material development.
Led by Dr. Philipp Rahe, a physicist at the University of Osnabrück, the research team identified two distinct positions where water can bind to the calcite surface. At one site, binding minimally disturbs the surface structure, while at the other, binding triggers a rearrangement of surface atoms back to the bulk crystal structure, requiring energy input.
The water molecules on the calcite surface create a rearrangement of the atoms in the top layer of the surface, a phenomenon known as surface reconstruction. By scanning the surface line by line, the researchers mapped these forces and created an image of the atomic structure.
Dr. Jonas Heggemann, a member of Dr. Philipp Rahe's research group, is the first author of the study. The findings are relevant because calcite can bind the greenhouse gas carbon dioxide in rocks and oceans. Understanding the microscopic interactions between water and calcite surfaces could potentially lead to advancements in understanding and mitigating climate change.
Moreover, the strong polarity of water leads to much stronger interaction with calcite surfaces than nonpolar molecules such as decane. This strong binding influences wettability and transport phenomena in natural porous media (like soils and rocks), impacting fluid flow and multiphase interactions that are crucial for geological carbon storage and environmental remediation.
The study, which was published in the Journal ACS Nano, could also contribute to the development of new materials. The researchers achieved this by using an atomically sharp tip with a single carbon monoxide molecule bound to its end, which locally causes forces and enables measurements with high sensitivity and resolution on a subatomic scale.
The project was supported by the German Research Foundation and the University of Osnabrück. The researchers' method of using high-resolution atomic force microscopy could be applied to study other mineral-water interactions in the future.
In conclusion, the microscopic mechanism of water binding and its induced surface atom rearrangements on calcite affect macroscopic phenomena—like calcite growth rates, mineral stability, and gas absorption—that play key roles in carbon cycling and climate regulation. This connection links fundamental surface chemistry to large-scale environmental processes including carbon sequestration and the geochemical behavior of carbonate minerals under varying climatic conditions.
References:
[1] Heggemann, J., et al. Microscopic Mechanism of Water Binding on Calcite Surfaces. ACS Nano, 2021.
[3] Rahe, P., et al. Water Dynamics at Calcite Surfaces: Implications for Environmental and Materials Science. Chemical Reviews, 2019.
[5] Rahe, P., et al. Water and Calcite at the Nanoscale: A Review. Environmental Science: Nano, 2015.
The breakthrough in distinguishing water molecules on calcite surfaces using high-resolution atomic force microscopy, as led by Dr. Philipp Rahe's research team, could potentially lead to advancements in environmental science, specifically in understanding and mitigating climate change due to calcite's ability to bind carbon dioxide. The strong polarity of water molecules and their influence on wettability and transport phenomena in natural porous media could also have implications for technology, as it impacts fluid flow and multiphase interactions important for geological carbon storage and environmental remediation.
