Karlsruhe School of Optics and Photonics
Optics & Photonics are key enabling technologies for many high-end industrial applications and furthermore drive research in physics, chemistry, biology, and engineering. The mission of the Karlsruhe School of Optics & Photonics (KSOP) is to provide a multidisciplinary environment for first-class research and education as well as for the generation of knowledge and innovation in Optics & Photonics. KSOP research activities cover a wide range of topics in Optics & Photonics and excel in particular in the four Research Areas: Photonic Materials & Devices, Advanced Spectroscopy, Biomedical Photonics, and Optical Systems.
Comprising both M.Sc. and Ph.D. programs, KSOP presently encompasses professors from four different faculties at KIT, i.e., Physics, Electrical and Mechanical engineering, as well as Chemistry and Biosciences. Currently, 14 Professors, some 70 doctoral researchers, more than 35 Ph.D. alumni as well as 72 M.Sc. students have positioned KSOP as a premium research and education institution. Next to this the KSOP holds strong cooperation support by the European Erasmus Mundus program, the German O&P industry, the Federal Ministry of Research and Education, and, sustainably, by the State of Baden-Württemberg.
The mission of the Karlsruhe School of Optics & Photonics (KSOP) is to provide a multidisciplinary environment for first-class research and education as well as for the generation of knowledge and innovation in Optics & Photonics.
The KSOP educational concept is designed to qualify our graduates for accelerated careers at world leading academic institutions and in high-technology industries. We actively promote the thesis work of our doctoral researchers by dedicated supervision, mentoring, networking as well as scientific and technical training. Concomitantly, we augment the professional skills of our graduates by tailored personal- and management training. A strong pillar of the KSOP concept is the individual coaching of doctoral researchers by one mentor for each Research Area.
Building on this excellent basis, the KSOP aims on becoming a world-leading institution for education, research and innovation in Optics & Photonics.
In 2011, the Bräse group joined KSOP. (Research Area I). On the one hand, we work on peptoids marked with fluorescence dyes to gain new insights in biological systems. Another focus is the designing and synthesis of new efficient materials for organic light-emitting diodes (OLEDs) and for organic solar cells (OSC)..
Find out more about KSOP under www.ksop.de
Synthesis of peptoid-based molecular transporters
Figure 1: Transport through cell membranes: The exact mechanism is still unclear.
For many biological and medicinal applications the direct uptake of bioactive molecules is of great importance e. g. for bringing drugs directly to their intracellular target. Nature provides the so-called cell penetrating peptides (CPPs), which are able to transport other molecules through the cell membrane. Unfortunately, these peptide transporters are often unstable against enzymatic degradation and therefore not feasible/usable as carrier for drugs.
Figure 2: Solid phase synthesis of peptoids.
Peptoids (N-substituted oligoglycines) show greater stability against enzymatic degradation. Those oligoglycines, or in other words, peptides whose side chains are formally shifted from the α carbon atom to the adjacent nitrogen atom show also good transport properties. Peptoids can be synthesized with solid-phase-protocols with nearly any composition. With simple reactions, fluorescent groups (cargo) can be attached to the peptoids. With this model systems, the transport mechanism can be directly monitored via fluorescence microscopy.
Figure 3: Rhodamine B as a cargo.
Hence, our approach is to synthesize different peptoid transporters to target certain cells or organs. Since we want to track our peptoids by fluorescence microscopy, they are often labeled with a fluorophore. By observing single molecules upon their way into the cell, we want to gain information about the exact uptake mechanism across the cellular membrane.
Figure 4: Some peptoid transporters, taken from .
Organic light-emitting diodes and organic solar cells
„Metals do conduct electrical current, organic molecules don’t“ is what is taught in our schools until now. However, this is not true: In the 1960’s, it was found out that organic mater shows electroluminescence just as gallium arsenide and other inorganic semiconductors. One of the first examples was the luminescence found in single crystals of anthracene in 1963.
Today, suitable organic materials are used just like other semiconductors for sensors, organic solar cells, laser resonators and even conductors in organic field-effect-transistors.
Figure 5: Organic semiconductors combine the useful properties of conventional semiconductors with the benefits of organic mater.
The big advantage of organic molecules for semiconductor applications is their good processability and the big variance: With modular systems, nearly every color can be generated for LEDs. Also, organic mater can be processed via vacuum deposition as well as with solution protocols (e.g. knife coating, inkjet-printing). OLEDs can be processed on large-area-substrates, while classic LEDs contain small single-crystals.
Figure 6: Complexes with one or more d-block-metals are suitable emitting materials for OLEDs.
The Bräse group is working on metalorganic materials of d-block-metals, that are suitable for OLEDs. The molecules containing one or more metal centers substitute the often-used, but expensive and rare metal iridium, basing on much cheaper and well-available metals like zinc or copper. With proper ligands, those systems can be used as efficient emitting layers for OLEDs.
Figure 7: With simple, modular systems, every color of the visible spectrum can be generated with metal complexes.
Also, the group is working on material systems for organic solar cells (OSC). While the first commercial applications for OLEDs are on the market, for OSC only demonstrators have been made. The potential of OSC of being a serious alternative fort he generation of energy has yet to be shown. People are lacking the ability of controlling the morphology in the devices resulting in efficiencies far smaller than the performance found in Si-devices. With self-organisation on a molecular level basing on fullerene-chemistry, better performances can be achieved. Even today, organic solar cells are more advanced than classic systems in terms of processability. They can be made on transparent plastic substrates.
Figure 8: Organic mater can solved in common solvents and processed on any given substrate: glass, aluminum foil and even flexible polymer substrates are possible.
 Birgit Rudat, Esther Birtalan, Isabelle Thomé, Dominik K. Kölmel, Viviana L. Horhoiu, Matthias D. Wissert, Uli Lemmer, Hans-Jürgen Eisler, Teodor Silviu Balaban, Stefan Bräse Philippe Pierrat, Céline Réthoré, Thierry Muller, Stefan Bräse. “Novel Pyridinium Dyes That Enable Investigations of Peptoids at the Single-Molecule Level”, J. Phys. Chem. B 2010, 114, 13473–13480.
 Birgit Rudat, Esther Birtalan, Sidonie B. L. Vollrath, Daniel Fritz, Dominik K. Kölmel, Martin Nieger, Ute Schepers, Klaus Müllen, Hans-Jürgen Eisler, Uli Lemmer, Stefan Bräse “Photophysical properties of ﬂuorescently-labeled peptoids”, Eur. J. Med. Chem. 2011, 46, 4457-4465.
 Esther Birtalan, Birgit Rudat, Dominik K. Kölmel, Daniel Fritz, Sidonie B. L. Vollrath, Ute Schepers, Stefan Bräse, “Investigating Rhodamine B-Labeled Peptoids: Scopes and Limitations of Its Applications” Biopolymers (Pept. Sci.) 2011, 96, 694-701.