27.08.2021 - 15:15
On 27 August at 15:15 Ekaterina Vagapova will defend her doctoral thesis “Fluorescence quenching in inorganic cristalline solids activated by neodymium ions; from bulk to micro- and nanocrystals” for obtaining the degree of Doctor of Philosophy (in Materials Science).
Associate Professor Yury Orlovskiy, University of Tartu
Associate Professor Valter Kiisk, University of Tartu
Associate Professor Viktor Peet, University of Tartu
Senior Research Fellow Sergey Sekatskii, École Polytechnique Fédérale de Lausanne (Switzerland)
Professor Toomas Rõõm, National Institute of Chemical Physics and Biophysics
Complex phosphate and fluoride compounds are widely used in biomedicine due to their compatibility with biological tissues. Compounds of complex phosphates are currently used mainly as bone implants, but also as thin coatings for large implants for better engraftment. Doping of these materials with ions of rare earth (RE) ions, neodymium in particular, makes it possible to expand the area of their application. For example, fluoride compounds in the form of aqueous colloidal solutions of nanoparticles doped with RE ions can be used to visualize biological tissues at a depth of 1 cm, for local thermal heating, drug delivery, etc.
In this context, from the point of view of both fundamental and applied science, the study of light radiation (fluorescence) and its quenching is of great interest. Fluorescence quenching processes ultimately determine the possibility of using a fluorescent material, for example, to visualize biological tissue, including non-invasive visualization at great depths. On the one hand, these processes are negative, and minimizing their contribution leads to an increase in the fluorescence intensity. On the other hand, by analyzing the fluorescence quenching processes, one can obtain additional information on the local crystal structure of the studied material. In the thesis, both aspects are discussed in detail. To minimize the quenching processes and, as a consequence, increase the fluorescence brightness, simple criteria are proposed for choosing a crystal matrix for doping with RE ions. In addition, the analysis of the fluorescence impurity quenching kinetics was used to determine the local structure of neodymium ions optical centers in an artificial analogue of bone tissue - tri-calcium phosphate microceramics.
The results of the thesis can be used to expand the functions and improve fluorescence materials, doped with RE ions, in particular, for various biomedical applications.
W. Ostwaldi 1, aud B103