In this project, the research field of electrochemistry is combined with that of ultrafast spectroscopy to investigate the dynamics of molecules with different oxidation states on the femtosecond time scale. By applying a voltage to an electrochemical cell, charges are transferred between the molecules, or between the molecules and the external electrodes. This charging of molecules leads to a change in the electronic configuration and thus also to a change in the excitation and emission properties as well as the molecular dynamics upon light excitation. The charged molecules can act as radical anions with a non-zero electronic spin. Investigating these electrochemically generated species with ultrafast spectroscopy opens up the possibility of monitoring the dynamics of reduction processes, or processes that exhibit intersystem crossing and spin-orbit coupling. Since charged molecules are particularly involved in charge transfer processes, the time-resolved investigation of their light-induced molecular dynamics is also of great technological importance when it comes to manufacturing low-cost, sustainable and large-area producible optoelectronic components, such as light-emitting diodes, transistors or photovoltaic cells, from organic molecules.
The spectroscopic methods used in this project are transient absorption spectroscopy and coherent 2D spectroscopy. Participating in this project therefore primarily involves the planning and implementation of time-resolved experiments with the methods mentioned. This requires, in particular, the handling of lasers and optical components, or also the control of components with software, some of which is written by the students themselves. Another important part of the project is dealing with electrochemical flow cells, which are specially made for combination with ultrafast spectroscopy.
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Rebecca Fröhlich, firstname.lastname@example.org
Literature for overview:
The topic of your thesis in our working group is always assigned based on the current research work in the laboratory. Therefore, it does not make sense to constantly post new open topics here. Just contact us! In order to get an impression of possible theses in this project, a selection of already completed theses is presented below.
In this work, the second reduced species of a perylene bisimide cyclophane was generated with a spectroelectrochemical cell and investigated with transient absorption spectroscopy. The tasks included the adjustment of the setup, laser pulse characterization, preparation of the solution, handling of an electrochemical cell and performing and evaluating time-resolved experiments.
In this project, the radical anion of a perylene bisimide was generated with a spectroelectrochemical cell and studied with transient absorption spectroscopy. For this experiment, a new beam path had to be set up to excite the molecules with laser pulses at a wavelength of 800 nm. In addition, the neutral form of a perylene bisimide cyclophane was studied with transient absorption and 2D spectroscopy. Comparison of the measurements of the radical anion with the cyclophane shows that after excitation, the cyclophane enters a charge-separated state and an ion pair is formed.