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Identifier 000447626
Title Light harvesting applications of self-assembled and surface-anchored porphyrin chromophores
Alternative Title Εφαρμογές αξιοποίησης ηλιακής ακτινοβολίας με τη χρήση αυτο-οργανωμένων και προσροφημένων σε επιφάνεια πορφυρινικών χρωμοφόρων
Author Νικολουδάκης, Εμμανουήλ Ν
Thesis advisor Κουτσολέλος, Αθανάσιος
Reviewer Βασιλικογιαννάκης, Γεώργιος
Κιτσόπουλος, Θεοφάνης
Μητράκη, Άννα
Odobel, Fabrice
Ταβερναράκης, Νεκτάριος
Ταγματάρχης, Νίκος
Abstract The present PhD dissertation describes the synthesis of new porphyrin-based hybrid molecules and their utilization in light harvesting applications. The synthesized porphyrin conjugates were modified with functional groups or connected with other entities depending on their target application. The first aim of this work was the development of well-organized assemblies by covalently connecting a molecular self-assembly inducer to a porphyrinoid chromophore. This approach aims to construct materials with enhanced properties in the self-assembly state. The resulting hybrids possessed both light harvesting and self-assembling properties and were further investigated in applications such as photocatalytic H2 production and photodynamic therapy. Regarding the self-assembly part, we synthesized and investigated hybrid chromophore conjugates connected with peptide-based molecules. In detail, we utilized aromatic and aliphatic dipeptides as well as peptide nucleic acids (PNAs), bearing various protecting groups, and linked them with porphyrin and boron-dipyrromethene chromophores. From the synthesized hybrids, those coupled with a peptide nucleic acid, were applied in photodynamic therapy in vitro after their self-assembly in spherical nanoparticles. Concerning the photocatalytic hydrogen (H2) evolution using self-assembled nanostructures, we covalently attached the diphenylalanine dipeptide to a tripyridyl porphyrin macrocycle, and the resulting hybrid was able to form selfassembling nanostructures. This hybrid was metallated with non-noble metals, Zn and Sn, and investigated towards photo-induced H2 production. The Sn derivative was able to produce hydrogen photocatalytically in the presence of a cobaloxime catalyst and TEOA as sacrificial electron donor. When the selfassembling nanostructures of the Sn metallated hybrid were employed in the catalysis, the hydrogen production was improved. The second target investigated herein concerns the development of artificial photosynthetic systems based on porphyrin dyads for light driven oxidation transformations. To that end, several photosensitizer-catalyst dyads were synthesized, characterized and investigated in dye-sensitized photoelectrochemical (DSPEC) devices for water and alcohol oxidation. For the photocatalytic water oxidation we synthesized a dyad (NiP-Ru) consisting of a ruthenium tris(bipyridyl), [Ru(bpy)3]2+2+ as photosensitizer, and a nickel porphyrin, as water oxidation catalyst. Photocatalytic experiments in organic solutions demonstrated that the covalently connected dyad exhibited enhanced catalytic activity compared to the non-covalent two-component system. Moreover, a dye sensitized photoelectrochemical cell (PEC) was prepared using the NiP-Ru dyad (bearing appropriate anchoring moiety on the photosensitizer) anchored on TiO2 as photoanode and demonstrated its ability to perform water oxidation in aqueous media at neutral pH. Finally, a series of dyads consisted of a zinc porphyrin (ZnP) sensitizer and a TEMPO organo-catalyst, bearing different anchoring groups on the ZnP, were synthesized. TiO2 based dye-sensitized photo-electrochemical (DSPEC) systems were fabricated with these dyads and their catalytic activity in light driven oxidation of methoxybenzyl alcohol into aldehyde was explored. The chemisorbed dyads were proved photocatalytically active towards alcohol oxidation both in aqueous and in organic solutions. The comparison between the intra-molecular dyad system and the intermolecular two-component system revealed that both strategies lead to similar performances. However, the employment dyad is preferable since the recovery of the catalyst is much easier and the quantity of the catalyst involved is much lower.
Language English
Subject Alcohol oxidation
Hydrogen production
Photo-electrochemical cells
Water oxidation
Οξείδωση αλκοολών
Οξείδωση του νερού
Παραγωγή υδρογόνου
Φωτοηλεκτροχημικά κελιά
Issue date 2022-05-09
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
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