polymer nanoparticles as photosensitizers

The main subject of the planned project are novel nanoparticles (NP) made of π-conjugated polymers (polythiophene), which do not contain a separate photosensitizer and are only able to generate singlet oxygen (a highly reactive, first excited state of oxygen, which is hardly excitable in a direct way) very efficiently due to their molecular structure, shape and material composition as an organic semiconductor. It will be investigated where and how the energy transfer to the molecular oxygen takes place, in particular the location (within the NP or at its surface), the speed of 1O2 generation and subsequent processes (diffusion and quenching until leaving the NP). A numerical model to describe all these processes under consideration of the material parameters (especially O2 solubility and radiative rate constants) shall be developed to allow a reliable determination of the 1O2 quantum yield of such NPs. Furthermore, the question up to which value the 1O2 quantum yield for water soluble NPs from polythiophene and PEG can be optimized and how much of the generated 1O2 is actually usable (reaches and leaves the surface of the NP) is to be answered. This is made possible by highly sensitive, temporally and spectrally resolved 1O2 luminescence measurements (partly also in real time during on-site synthesis) and comparison with existing and the numerical model to be newly developed. The stability and biocompatibility of the NPs will be tested, as well as the phototoxic effect on different cell types (eukaryotic cells and bacteria). Possible optimization possibilities will be investigated in order to determine possible areas of application for this new class of photosensitizers, which can be easily produced on an industrial scale.