Understanding delayed fluorescence and triplet decays of Protoporphyrin IX under hypoxic conditions

Photosensitizers of singlet oxygen exhibit three main types reverse intersystem-crossing (RISC): thermally activated, triplet-triplet annihilation, and feedback. RISC can be followed by delayed fluorescence (DF) emission, which provide important information about the excited state dynamics in studied system. An excellent model example is a widely used clinical photosensitizer Protoporphyrin IX, manifests all mentioned DF. Here, we estimated rate constants individual DF processes IX dimethylformamide, showed how these affect triplet decays signals under diverse experimental conditions, such as varying concentration or excitation intensity. This provided basis for general discussion on guidelines more precise analysis long-lived signals. Furthermore, it has been found that PpIX photoproducts potential transient complexes introduce new overlapping luminescence spectral band with distinct lifetime. These findings are design accurate biological sensors assays based