Matthias Karg: Soft microgels for smart surface nanostructuring: Structural diversity and optical properties
Place: Kemicentrum, Lecture hall B
Contact: peter [dot] schurtenberger [at] fkem1 [dot] lu [dot] se
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A seminar by Professor Matthias Karg, Heinrich-Heine-University Düsseldorf, Germany.
The encapsulation of inorganic nanoparticles by cross-linked polymers yields core-shell microgels that spontaneously self-assemble at air/liquid interfaces forming highly ordered monolayers. Transfer of these monolayers from the interface to macroscopic solid supports allows the fabrication of hexagonally ordered superstructures with large single crystalline domains. Depending on the thickness of the polymer shell such structures possess inter-core distances from a few up to several hundred nm. Multiple depositions on one substrate or deposition to substrates with different contact angles gives access to a broad range of complex superstructures including non-hexagonal 2D Bravais lattices.
In this contribution we will demonstrate the structural diversity that is accessible by interface- mediated self-assembly of hard-soft core-shell microgels. Furthermore, we will show how assembly of particles with plasmonic cores can lead to superstructures that show collective optical responses that differ strongly from the single particle behavior. The observed diffractive/plasmonic coupling can be reversibly tuned by addressing the refractive index environment through changing the swelling state of a responsive hydrogel matrix. This way fully reversible resonance tuning becomes possible by either solvent exchange or temperature.
 K. Volk et al., Adv. Mater. 24 (2015), 7332.
 T. Honold et al., Colloids and Surfaces A 510 (2016), 198.
 K. Volk et al., Adv. Optical Mater. 5 (2017), 1600971.
Matthias Karg studied chemistry at the TU Berlin (Germany) and received his PhD in physical chemistry from the same university in 2009. Afterwards he joined the group of Prof. Paul Mulvaney at the University of Melbourne (Australia) as a research fellow of the Alexander von Humboldt foundation (Feodor Lynen program). In 2012 he was appointed as Juniorprofessor in physical chemistry at the University of Bayreuth (Germany). Since 2016 he is full professor in the physical chemistry department of the Heinrich-Heine-University Duesseldorf (Germany). The current research interests of the Karg group cover fields such as soft and responsive hydrogel particles, colloidal self-assembly, plasmon resonance coupling in periodic nanoparticle arrays and the development and application of multifunctional colloids. We use a broad range of techniques including spectroscopy, electron and atomic force microscopy, light, neutron and X-ray scattering.