title: Chemical Identification at the Solid-Liquid Interface.
abstract: Solid-liquid interfaces are decisive for a wide range of natural and technological processes, including fields as diverse as geochemistry and environmental science as well as catalysis and corrosion protection. Dynamic atomic force microscopy nowadays provides unparalleled structural insights into solid-liquid interfaces, including the solvation structure above the surface. In contrast, chemical identification of individual interfacial atoms still remains a considerable challenge. So far, an identification of chemically alike atoms in a surface alloy has only been demonstrated under well-controlled ultrahigh vacuum conditions. In liquids, the recent advent of three-dimensional force mapping has opened the potential to discriminate between anionic and cationic surface species. However, a full chemical identification will also include the far more challenging situation of alike interfacial atoms (i.e., with the same net charge). Here we demonstrate the chemical identification capabilities of dynamic atomic force microscopy at solid-liquid interfaces by identifying Ca and Mg cations at the dolomite-water interface. Analyzing site-specific vertical positions of hydration layers and comparing them with molecular dynamics simulations unambiguously unravels the minute but decisive difference in ion hydration and provides a clear means for telling calcium and magnesium ions apart. Our work, thus, demonstrates the chemical identification capabilities of dynamic AFM at the solid-liquid interface.
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.|Graduate School Materials Science in Mainz , Staudingerweg 9, 55128 Mainz, Germany.
authors.forename: Hagen
authors.initials: H
authors.lastname: Söngen
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Marutschke
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University , Helsinki FI-00076, Finland.
authors.forename: Peter
authors.initials: P
authors.lastname: Spijker
authors.affiliation: University of Rochester , Rochester, New York 14627, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Holmgren
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Hermes
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Bechstein
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Klassen
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University , Helsinki FI-00076, Finland.
authors.forename: John
authors.initials: J
authors.lastname: Tracey
authors.affiliation: COMP Centre of Excellence, Department of Applied Physics, Aalto University , Helsinki FI-00076, Finland.|Division of Electrical Engineering and Computer Science, Kanazawa University , Kanazawa 920-1192, Japan.
authors.forename: Adam S
authors.identifier: 0000-0001-5371-5905
authors.initials: AS
authors.lastname: Foster
authors.affiliation: Institute of Physical Chemistry, Johannes Gutenberg University Mainz , Duesbergweg 10-14, 55099 Mainz, Germany.
authors.forename: Angelika
authors.identifier: 0000-0003-1214-1006
authors.initials: A
authors.lastname: Kühnle