Speaker
Description
The Liquid-Vapor Interfaces group in the Department of Inorganic Chemistry aims at a deeper understanding of the physical and chemical processes during heterogeneous reactions between common trace gas species and constituents of aqueous solutions, in particular dissolved ions and surfactants. The goal of this research is a detailed understanding of reaction mechanisms and kinetics, including the detection of gaseous, interface-affine and dissolved reaction products, as well as reaction intermediates.
To this end the Liquid-Vapor Interfaces group develops new experimental tools, both laboratory- and synchrotron-based. A combined infrared reflection absorption spectroscopy (IRRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) setup that is based on a multi-energy laboratory X-ray source is currently been commissioned. This setup allows simultaneous APXPS and RAIRS investigations of solution-vapor interfaces, albeit not from the same sample location. Custom-designed sample holders enable measurements on solutions with freely adjustable pH and bulk solute and surfactant concentrations across a wide temperature range, from 295 to 220 K, i.e. also for frozen solutions. The capabilities of the lab instrument will be expanded at the ELISA beamline at BESSY-II (Poster 6.5), which is currently in the design stage. There, RAIRS and APXPS, combined with grazing incidence X-ray scattering and near edge X-ray absorption fine structure spectroscopy data will be possible to obtain from the same sample location, which is in particular important for samples with in-plane heterogeneity and for the investigation of X-ray induced changes to the sample.
Since the new lab-based instrument became available only in 2022, the Liquid-Vapor Interfaces group (founded in October of 2018) has so far focused on the investigation of the fundamental properties of aqueous solution-vapor interfaces in the absence of heterogeneous reactions. The emphasis is on the interaction of surfactant species with dissolved ions. The measurements are performed in close collaboration with the Winter group (MP department), which has long-standing experience in liquid microjet XPS, and the Theory department for the interpretation of the experimental data based on Molecular Dynamics simulations. Examples for these collaborations are the demonstration of Å depth resolution in measurements of surfactants using photoelectron angular distributions (Poster 5.1); the determination of the adsorption energy of phenol and phenolate to the solution-vapor interface (Poster 5.2); and the effect of solvated surfactant functional groups on the propensity of ions for the liquid-vapor interface of model seawater solutions, where a significant enhancement of some of the minority species in seawater for the interface in the presence of surfactants was demonstrated, which is important information for the modeling of heterogeneous chemical reactions of seawater (and) aerosols with atmospheric trace gases (Poster 5.3). With the final commissioning of the laboratory-based APXPS/IRRAS instrument these investigations will be expanded to heterogeneous chemical reactions of trace gases (e.g., O3) at realistic partial pressures.
| Abstract Number (department-wise) | AC 5.0 |
|---|---|
| Department | AC (Schlögl) |
