Highlight Publications 2019

Comparative Adsorption of Acetone on Water and Ice Surfaces
J.D. Cyran, E.H.G. Backus, M.J. van Zadel, and M. Bonn
Comparative Adsorption of Acetone on Water and Ice Surfaces
Interactions of trace gases with ice and water surfaces play a major role in atmospheric chemistry. The chemical and photochemical processes of trace gases absorbed on ice surfaces are relevant for ozone depletion and alter the chemical composition of the atmosphere. Specifically, small-oxygenated organic molecules, such as acetone, are a critical contributor to the formation of HOx radicals. Here, we combine surface-specific vibrational spectroscopy and a controllable flow cell apparatus to investigate the molecular adsorption of acetone onto the basal plane of single crystalline Ih ice with large surface area. By comparing the adsorption of acetone on the ice/air with the water/air interface, we find two different types of acetone adsorption, as apparent from the different responses of both the free O-H and the hydrogen-bonded network vibrations for ice and liquid water. Adsorption on ice occurs preferentially through interactions with the free OH group, while the interaction of acetone with the surface of liquid water appears less specific.
© MPI-P (2019)
Acetone adsorption on water and ice surfaces unraveled by interfacial spectroscopy
Well-defined metal-polymer nanocomposites: The interplay of structure, thermoplasmonics, and elastic mechanical properties
David Saleta Reig, Patrick Hummel, Zuyuan Wang, Sabine Rosenfeldt, Bartlomiej Graczykowski, Markus Retsch, and George Fytas
Well-defined metal-polymer nanocomposites: The interplay of structure, thermoplasmonics, and elastic mechanical properties
Brillouin light spectroscopy (BLS) is a reliable technique for probing sound velocities in materials. The sound velocity and its temperature and power dependencies further allow determination of thermomechanical properties like elastic moduli and the glass transition temperature. Whereas non-metallic particle-brush systems (e.g., SiO2-PS) typically show linearly dependent sound velocity on temperature and power, thus giving a segmental linear relation between the laser spot temperature and the laser power, their metallic counterparts could display strong non-linearity, as demonstrated here by using Ag-PS nanocomposite films. This non-linearity is due to the plasmonic heating in the Ag nanoparticles induced by the incident laser, and it increases as the PS chain length decreases due to the increasing Ag volume fraction. Additional annealing of the nanocomposite films also increases the non-linearity through the annealing-time-dependent aggregation of Ag nanoparticles. This work reveals the combined effects of composition and (reversible) aggregation on the mechanical and thermoplasmonic properties of metal-polymer nanocomposites. It not only deepens our understanding of the interplay of structure, thermoplasmonics, and elastic properties in metal-polymer nanocomposites but also provides a guide for customizing Ag-PS nanocomposites for potential applications.
© MPI-P (2019)
Schematic laser heating in a Ag-PS (particle-brush) film and the dependence of the laser spot temperature on the laser power.
 
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