Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Plasmonics and nanooptics: Light-matter interaction, spectroscopy I

O 13.5: Vortrag

Montag, 12. März 2018, 16:00–16:15, MA 041

Nanoscale hydrogenography on individual magnesium nanoparticles — •Florian Sterl, Heiko Linnenbank, Tobias Steinle, Florian Mörz, Nikolai Strohfeldt, and Harald Giessen — 4th Physics Institute and Research Center SCoPE, University of Stuttgart, Germany

MgH₂ is considered a promising candidate for solid-state hydrogen storage, owing to its high hydrogen content. It can also be considered a model system for other energy storage materials, such as magnesium-based alloys. While the hydrogen diffusion mechanism in Mg at the 100 µm length scale has been investigated extensively using hydrogenography, in which the optical contrast between a metal and its hydride is exploited, an observation of this process at sub-diffraction limit length scales in single Mg nanoparticles has not been carried out so far.

In order to characterize this process at the nanoscale, we employ scattering type scanning near-field optical microscopy (s-SNOM). In this method, the local scattering ability of a nanoparticle is recorded along with its topography, enabling us to record the local material composition as well as topographical changes during hydrogen absorption and desorption. By combining s-SNOM imaging with dark-field scattering spectroscopy, we observe the distribution of metallic Mg and dielectric MgH₂ during both hydrogen absorption and desorption of Mg nanodisks. Our measurement results indicate a strong influence of the crystallinity, as individual Mg crystallites appear to hydrogenate independently from one another. In the future, this method can also be applied to other hydrogen-storage materials.