Vortrag im Rahmen der Chemisch Physikalischen Gesellschaft
Mineral-water interfaces are central to many environmental processes. For example, the weathering of silicates and their reprecipitation as carbonate minerals are important parts of the geological carbonate-silicate cycle, which regulates atmospheric carbon dioxide levels on geological timescales. Moreover, airborne mineral dust particles can act as ice nucleating particles catalyzing the glaciation of mixed-phase clouds, thereby significantly affecting our weather and climate. To understand these kinds of processes, detailed molecular-level insights into mineral-water interfaces are vital.
In this talk, the examples of two mineral surfaces with considerable environmental significance, calcite (10.4) and K-feldspar (001), and their interaction with water will be discussed. On calcite, the most stable polymorph of calcium carbonate, we apply vibrational sum frequency generation spectroscopy to directly assess the water species present at the calcite-water interface. As reported previously, we observe an opposite orientation of the first two water layers at neutral pH [1], while at very high pH spectral features that suggest surface charging and the presence of interfacial hydroxyl groups emerge.
Furthermore, we investigated K-feldspar microcline (001) as relevant for atmospheric ice nucleation. Atomic-resolution atomic force microscopy reveals that cleaved microcline (001) forms a hydroxyl-terminated surface with residual water even in vacuo [2]. Based on this surface model, temperature programmed desorption provides insights into the adsorption energy and structure of water on microcline, confirming previous theoretical predictions [4].
[1] Söngen et al., J. Phys. Chem. Lett. 12 (2021), 7605.
[2] Dickbreder and Sabath et al., Nanoscale 16 (2024), 3462.
[3] Dickbreder et al., Phys. Chem. Chem. Phys. 27 (2025), 18317.
[4] Pedevilla et al., J. Phys. Chem. C 120 (2016), 6704.
