Forschung - Prof. Fuhrmann-Lieker
Our research is focused on self-organization and photonics of soft matter. We apply the physicochemical principles of pattern formation on a mesoscopic scale in order to provide optical functions to soft materials. At the moment we are treating two distinct material classes:
Organic optoelectronic materials
We develop molecular glasses that can be easily prepared in optical layer systems by vacuum vapour deposition. A long history in our group has the development of spiro-type molecular glasses for organic lasing and other applications.
At the moment, random lasers in which resonating modes form spontaneously a disordered mesoscopic structure are an important topic of interest. We generate random structures from mechanically stressed films that relax to surface corrugations with a dominant spatial wavelength, so-called wrinkles. We were able to show that within the spectral range of amplified spontaneous emission (3 nm width) numerous laser modes can be excited. In a related project, we also achieved stimulated emission in daily-life materials such as copy paper as scattering medium. Results were published recently in two papers in the journal Scientific Reports and constitute the PhD thesis of Nicolai Hoinka. Further research on wrinkling in molecular glasses for various applications is performed by Lukas Wolfram in his PhD project.
Mixtures of molecular glasses give rise to interesting morphologies based on nanophases that may be useful as interpenetrating networks for bulks heterojunction organic solar cells. In a work by Michael Grimann, who obtained his PhD in 2018, we succeeded in generating phase separation in molecular glasses in the solid state and were able to stabilize the interface using surfactant-like spiro molecules in ternary mixtures.
3D-nanofabrication with azo materials is the topic of projects by Sekvan Bagatur (PhD)and Marcel Schlesag (Bachelor thesis) that explore the possibility of producing three-dimensional structures from flat layer systems with the help of light. Key materials are molecular glasses and high-performance polymers that bear the photosensitive azo group allowing optical and mechanical deformation in response to polarized light. Self-organized surface patterns, birefringent helices in the bulk, holographic patterns and micro-origami structures belong to the realizable structures with these materials.
Hybrid Biological Materials
In diatoms, single-celled algae that bear an ornamental silica cell wall, structures that inspire nanoscientists are built by biological morphogenesis. In a highly cited paper from 2004, we introduced the diatom cell wall as a photonic crystal slab waveguide. Since then we are working on the interplay between structure and function in algae nanostructures. In order to reveal the formation process of the cell wall, we investigate the role of highly phosphorylated proteins in interaction with polycations and silica, also in biomimetic approaches done by Benedikt Mohr as member of the PhosMOrg consortium. The influence of the unique reproduction mechanism of diatoms on the pattern formation and population dynamics is addressed within the graduate programme "Biological clocks", with PhD students Bahar Khonsari and now Jonas Ziebarth.
Our postdoctoral researcher Dr. Marilia Horn from Brazil has established new activities in the field of biopolymers and nanopharmacy. Related projects aiming at the utilisation of renewable resources are conducted by our visiting PhD student Eduardo Milan and Master student Jan Livingsan.
T. Fuhrmann-Lieker, et al. “Optical amplification and stability of spiroquaterphenyl compounds and blends”, J. Europ. Opt. Soc. Rap. Public. 10, 15007 (2015)
N. Hoinka, T. Fuhrmann-Lieker, “Amplified Spontaneous Emission in Paper”, Scientific Reports 9, 1862 (2019)
N. Hoinka, C. Ostwald, T. Fuhrmann-Lieker, “Two-dimensional Wrinkle Resonators for Random lasing in Organic Glasses”, Scientific Reports 10, 2434 (2020)
M. Grimann, R. Ueberschaer, E. Tatarov, T. Fuhrmann-Lieker, “Phase Separation and Nanostructure Formation in Binary and Ternary Blends of Spiro-Linked Molecular Glasses“, J. Phys. Chem B 124, 5507 (2020)
T. Fuhrmann, T. Tsutsui, “Synthesis and Properties of a Hole-Conducting, Photopatternable Molecular Glass”, Chem. Mater. 11, 2226 (1999)
A. Perschke, T. Fuhrmann, “Molecular Azo Glasses as Grating Couplers and Resonators for Optical Devices”, Adv. Mater. 14, 841 (2002)
P. Gruner, M. Arlt, T. Fuhrmann-Lieker, “Surface wrinkling induced by photofluidization of low molecular glasses”, ChemPhysChem 14, 259 (2013)
T. Fuhrmann, S. Landwehr, M. El Rharbi-Kucki, M. Sumper, “Diatoms as living photonic crystals”, Appl. Phys. B. 78, 257 (2004)
M. Kucki, T. Fuhrmann-Lieker, “Staining diatoms with rhodamine dyes: control of emission colour in photonic biocomposites”, J. R. Soc. Interface 9, 727 (2012)
T.P.I. Saragi, R. Pudzich, T. Fuhrmann, J. Salbeck, “Organic phototransistor based on intramolecular charge transfer in a bifunctional spiro compound”, Appl. Phys. Lett. 84, 2334 (2004)