Rare-earth doped up-conversion materials for photocatalysis and photonic applications

Résumé

During all the research time the main goal kept in mind was to enhance and apply the radiation coming from up-conversion (UC) materials to activate photocatalytic processes such as water-splitting or degradation of pollutants, to study the real effects and possibilities of the spectral conversion, harvesting some typically unused ranges of the light spectrum and adding useful radiation for the mentioned processes. In this context more applications were tested, in concrete the photo-polymerization of resins used in 3D-printing technology which have been also included in this work. The first steps were focused to find, synthesize and characterize materials with the higher up-conversion efficiency possible. From the beginning we decided to use lanthanide doped glasses and crystals, on one hand due to the previous extensive bibliography available and the large research experience with those materials in our laboratories, and on the other hand due to the advantage of being able to change the ratios or amounts of luminescent ions without losing structural properties, which are repeatedly reported as one of the most appropriated for UC processes. After that, different experimental setups were designed to isolate and apply the UC radiation to activate photocatalysts and measure the effects of this activity, comprising methylene blue photocatalytic degradation, hydrogen and oxygen evolution via UC-driven water-splitting, and quasi-instantaneous photopolymerization of UV photo-curable resins, using low power NIR laser radiation as unique source of photons in all cases. After that, different experimental setups were designed to isolate and apply the UC radiation to activate photocatalysts and measure the effects of this activity, comprising methylene blue photocatalytic degradation, hydrogen and oxygen evolution via UC-driven water-splitting, and quasi-instantaneous photopolymerization of UV photo-curable resins, using low power NIR laser radiation as unique source of photons in all cases. This thesis is presented in the “compendium of published articles” format, and contains five articles.