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Identifier 000422998
Title Functionalization of graphene and related two-dimensional materials with organic dyes
Alternative Title Τροποποίηση γραφενίου και σχετικών δι-διάστατων υλικών με οργανικά χρωμοφόρα μόρια
Author Canton-Vitoria, Ruben
Thesis advisor Κατερινόπουλος, Χαράλαμπος
Reviewer Ταγματάρχης, Νικόλαος
Σμόνου, Ιουλία
Βασιλοκογιαννάκης, Γεώργιος
Στρατάκης, Εμμανουήλ
Κουτσολέλος, Αθανάσιος
Φρουδάκης, Γεώργιος
Abstract This PhD thesis deals with the chemical functionalization of graphene sheets and related two-dimensional analogues based on transition metals dichalcogenides, e.g. MoS2 and WS2, focusing on the development of hybrid materials for energy conversion applications. More specifically, both covalent and supramolecular functionalization methodologies were employed for interaction of organic chromophores with graphene, MoS2 and WS2 sheets. The first part focuses on the covalent attachment of (a) 4,4-difluoro-4-boron-3a,4a,8-triazo-s-indacene (boron azadipyrromethenes – azaBDP) on exfoliated graphene, which it was prior chemically functionalized with in situ aryl-diazonium salts carrying alkyne groups that subsequently reacted by "click" chemistry with azaBDP derivatives bearing azide groups; and (b) cyanines following the chemical functionalization methodology with in situ formed aryl-diazonium salts which either brought already the cyanines as part of their structure or used for further coupling with cyanines via condensation reactions onto the already modified graphene sheets. The second part of this thesis provides a methodology for the chemical functionalization of the two-dimensional transition metal dichalcogenides, e.g. MoS2 and WS2, which it was then applied for the preparation of hybrid materials. In particular, it has been found that 1,2-dithiolane units possess high affinity to Mo and W atoms due to sulfur vacancy sites that are located at the edges of the MoS2 and WS2 sheets. These defects are introduced during the exfoliation process of MoS2 and WS2 from their respective bulk materials, highlighting the versatility and wide utility of the proposed procedure. In parallel, the stability of the N-methyl pyrrolidone (NMP) solvent, which is widely used in graphene as well as MoS2 and WS2 liquid exfoliation processes, was investigated and its effects and limitations on the developed materials were examined. Next, MoS2 and WS2-based hybrid materials bearing covalently bonded chromophore groups of (a) pyrene, (b) porphyrin, (c) zinc phthalocyanine, and, (d) carbon dots were prepared. Additionally, hybrid materials were developed in which the transition metal dichalcogenides were suitably modified to carry ammonium salts. The positive charges of the ammonium salts were then used to electrostatically interact with negatively charged chromophore groups of (a) porphyrin, (b) polythiophene, and (c) carbon dots to construct new supramolecular hybrid materials. Moreover, supramolecular interactions of exfoliated MoS2 and WS2 sheets with pyrene were developed attributable to multiple S-π forces between the two components of the hybrid material. All hybrid materials were structurally characterized by complementary spectroscopic and thermal techniques, while their morphology was studied by electron microscopy, confirming their successful preparation. In addition, the photophysical, electrochemical and electrocatalytic properties of newly prepared graphene, MoS2 and WS2-based hybrid materials have been thoroughly investigated, revealing their applicability in energy conversion systems.
Language English
Subject Chemical functionalization
Chromophore molecules
Eelectron transfer
Hybrid materials
Μεταφορά ηλεκτρονίων
Υβριδικά υλικά
Χημική τροποποίηση
Issue date 2019-07-10
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Chemistry--Doctoral theses
  Type of Work--Doctoral theses
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