Artificial photosynthesis (AP) is one of the scientific challenges that could help us achieving a global “carbon neutral” society. Photocatalytic water splitting is considered as the first... Show moreArtificial photosynthesis (AP) is one of the scientific challenges that could help us achieving a global “carbon neutral” society. Photocatalytic water splitting is considered as the first challenge of AP, which contains two half reactions: water oxidation and hydrogen evolution. It is widely accepted that a photocatalytic system needs a minimum of three components: a photosensitizer (PS), a catalyst (Cat) and a sacrificial electron donor or acceptor (SE). In such a photocatalytic system, at least three electron-transfer steps can be identified: one between the SE and the excited PS (PS*), one between the photo-reduced or photo-oxidized PS and the Cat, and one between the Cat and its substrate. This thesis on the one hand focused on developing improved molecular components for the two half reactions of water splitting in purely homogeneous systems. On the other hand optimized photocatalytic systems with balances between the driving force of electron transfer from the SE to the PS*, and that of electron transfer between the catalyst and the oxidized or reduced photosensitizer (PS+ or PS–). Show less
The safety of blood transfusion can be increased by introducing methods that eliminate blood-borne pathogens such as viruses and bacteria. In this thesis, the use of photodynamic treatment (PDT) to... Show moreThe safety of blood transfusion can be increased by introducing methods that eliminate blood-borne pathogens such as viruses and bacteria. In this thesis, the use of photodynamic treatment (PDT) to inactivate pathogens in cellular blood products is described. Various photosensitizers, from phenothiazines to porphyrins, were tested for their efficacy to inactivate a wide range of pathogens with minimal induction of blood cell damage. From this series of photosensitizers, meso-substituted mono-phenyl-tri (N-methyl-4-pyridyl) porphyrin [Tri-P(4)] stood out as the most efficacious. Besides the virucidal and bactericidal efficacy of PDT, we also studied the effect of the treatment on the quality and functionality of red blood cells and of haematopoietic stem cells from cord blood stem cell products. In addition, we evaluated the potential of Tri-P(4)-mediated PDT to induce immunomodulation Show less
Porphyrins are essential in living organisms. E.g. in the red oxygen carrying blood protein hemoglobin oxygen binds to the Fe2+-containing heme and in plants the green pigment chlorophyll is... Show morePorphyrins are essential in living organisms. E.g. in the red oxygen carrying blood protein hemoglobin oxygen binds to the Fe2+-containing heme and in plants the green pigment chlorophyll is responsible for the initial steps in photosynthesis. The absorption of light by a porphyrin, followed by energy transfer to oxygen can lead to the formation of highly toxic but short living singlet oxygen. When such a porphyrin localizes in a tumor it is possible to destroy the tumor locally by the irradiating it with light. This treatment is known as photodynamic therapy and the pigment is called a photosensitizer. However a major drawback of current photosensitizers is that they do not show strong absorption in the far-red part of the spectrum where light penetrates tissue optimal. Besides patients treated with these photosensitizers remain light sensitive for 3-8 weeks. This thesis describes the preparation of new photosensitizers with strong absorption of light at 680-690 nm. The preparation of these porphyrin derivatives takes place via unprecedented chemical reactions and an explanation for the chemistry involved is given. Tests on mice showed that the lifetime of these new porphyrin derivatives in their body is reduced to less then 3 days, which makes them very interesting candidates as new generation photosensitizers for photodynamic therapy Show less
