HZB Freigeist Fellow Dr. Annika Bande
HZB Freigeist Fellow: Dr. Annika Bande
Foto: Mirko Krenzel for VolkswagenStiftung
As of early October, the HZB is home to one of the Volkswagen Foundation's Freigeist Fellows: Dr. Annika Bande recently joined Prof. Dr. Emad Aziz' institute "Methods for Material Development". There she will build up her own junior research group with initially three PhD students.
The theoretical chemist's research focus is on ultrafast energy transfer processes. Central to her research is what's known as interatomic Coulombic decay (ICD) where an electronically excited state is produced within an atom. Upon returning to its ground state, the atom transfers its excess energy to a neighboring atom or molecule through electronic Coulomb interactions. During this process, the electrons interact with each other even over long distances.
These ultrafast energy transfer processes have already been studied both theoretically and experimentally, including at the HZB, in a number of variations in atomic and molecular systems. As part of her theoretical work, Annika Bande was able to demonstrate that ICD must also be taking place in semiconductor nanocrystals called quantum dots. Furnishing experimental evidence is what Bande and her team is hoping to accomplish as part of her work with Emad Aziz' institute. In a unique approach the scientists observe the electrons' motion in calculations and with various types of spectroscopy. From this they expect numerous direction-giving contributions to the investigation of chemical processes and to materials' research.
"Here at the HZB, I encountered optimal conditions for experiments being done that support my theory," Annika Bande says. The Aziz group has already conducted ICD investigations on atomic systems in aqueous solution. Adds Bande: "I'll be able to build on this experience while also broadening the instutute's spectrum as I'll be focusing my own work mostly on quantum dots." The scientist, who is currently working on earning the title of 'professor' at Heidelberg University, expects this will help her glean insights that will prove relevant to future solar cells, among other things.
The 790,000 Euro Volkswagen Foundation's Freigeist Fellowship provides funding for a five-year period during this initial phase. According to the Foundation, funding is granted to "exceptional researchers who have already earned their doctoral degrees and whose goal it is to move between established research areas while conducting cutting-edge, 'risky' science."
- Ultrafast dissociation of molecules studied at BESSY IIFor the first time, an international team has tracked at BESSY II how heavy molecules – in this case bromochloromethane – disintegrate into smaller fragments when they absorb X-ray light. Using a newly developed analytical method, they were able to visualise the ultrafast dynamics of this process. In this process, the X-ray photons trigger a "molecular catapult effect": light atomic groups are ejected first, similar to projectiles fired from a catapult, while the heavier atoms - bromine and chlorine - separate more slowly.
- Battery research with the HZB X-ray microscopeNew cathode materials are being developed to further increase the capacity of lithium batteries. Multilayer lithium-rich transition metal oxides (LRTMOs) offer particularly high energy density. However, their capacity decreases with each charging cycle due to structural and chemical changes. Using X-ray methods at BESSY II, teams from several Chinese research institutions have now investigated these changes for the first time with highest precision: at the unique X-ray microscope, they were able to observe morphological and structural developments on the nanometre scale and also clarify chemical changes.
- BESSY II: New procedure for better thermoplasticsBio-based thermoplastics are produced from renewable organic materials and can be recycled after use. Their resilience can be improved by blending bio-based thermoplastics with other thermoplastics. However, the interface between the materials in these blends sometimes requires enhancement to achieve optimal properties. A team from the Eindhoven University of Technology in the Netherlands has now investigated at BESSY II how a new process enables thermoplastic blends with a high interfacial strength to be made from two base materials: Images taken at the new nano station of the IRIS beamline showed that nanocrystalline layers form during the process, which increase material performance.