Light induced processes - from supramolecular systems to photoanodes

This thesis investigates light induced process occurring in different kind of materials, spacing from complex supramolecular systems to solid state catalysts and photoanodes. The interest towards those materials is related to light-stimulated applications such as smart photoresponsive molecular systems or photoinduced water splitting. Through a combination of photophysical methods, such as steady-state and time-resolved absorption and emission spectroscopy and time-correlated single photon counting, this work seeks to advance understanding of photoinduced processes and contribute to general knowledge in this field. A detailed study of the femtosecond transient absorption of a-Fe2O3 and BiVO4/WO3 photoanodes for oxygen evolution has been performed. With these techniques it was possible to elucidate charge carriers dynamics occurring in WO3/BiVO4 photoanodes coated with Co/Fe-based overlayers and -Fe2O3 photoanodes with or without CoPi catalyst. Acridinium-porphyrin conjugates stand out for their peculiar photophysical behavior, related to the photoswitching properties of acridinium ions, coupled with the rich photophysics of porphyrins. When such components are combined, photoinduced electron or energy transfer processes are activated. Such processes were investigated in novel acridinium-porphyrin conjugates. The inclusion of a photoactive guest in some of these conjugates shows that they can act as supramolecular receptors. Interestingly, it was observed that polarity effects can substantially affect the photophysical behavior. Covalent triazine frameworks (CTFs) polymeric materials are of particular interest as photosensitizers to be coupled with water oxidation catalysts for photoinduced water splitting. CTF containing covalently-linked Ru water oxidation catalysts for light induced catalytic water oxidation have been previously developed. A low molecular weight model of CTF has been synthesized and photophysically characterized, in order to unravel the photoinduced processes occurring in a CTF upon light excitation.