Hybrid materials based on graphene and related materials with metal nanoclusters for energy conversion applications (Doctoral thesis)

Κοκλιώτη, Μαλαματένια

The isolation of monolayered graphene brought 2D family into the limelight extending the scientific interest to include other materials such as transition metal dichalcogenides (TMDs) with MoS2 and WS2 as main flatlanders. This PhD Thesis deals with the preparation of graphene and TMDs combined with fluorescent metal nanoclusters focusing on the development of hybrid materials for energy conversion applications. Firstly, graphene sheets were covalently functionalized with organic moiety bearing ammonium units and supramolecularly tethered to negatively charged α-lipoic acid-stabilized metal nanoclusters (MNCs) of gold and silver. The corresponding ensemble was successfully employed as a proficient catalyst for the model reduction of 4-nitrophenol to the corresponding 4-aminophenol as proof for the photoinduced hydrogen production, while the mechanistic pathways took place upon photoillumination of the hybrid are discussed. Next, a facile way to prepare nitrogen doped TMDs (MoS2 and WS2) through plasma treatment, while they were simultaneously decorated with silver nanoparticles, is demonstrated. The TMD-based materials functioned as efficient surface-enhanced Raman scattering (SERS) platforms for the sensitive detection of aromatic molecules (polycyclic aromatic hydrocarbons, such as pyrene, anthracene and naphthalene). The signal enhancement is mainly due to the existence of “hot spots” and charge transfer processes between modified MoS2 and fluorophore analyte molecules. Moreover, MoS2 sheets were covalently functionalized with a 1,2-dithiolane derivative anchored to defected Mo atoms bearing sulfur vacancies at the edges of MoS2. Fluorescent core – shell Ag@AuNCs labeled with BSA were electrostatically interacted with modified MoS2 sheets and the obtained ensemble examined towards photodegradation of RhB. The main responsible reactive species derived from charge transfer phenomena between MoS2 and Ag@AuNCs and plausible mechanistic pathways of photocatalytic decomposition of RhB are discussed. Finally, a new organic stabilizer based on a bulky adamantane moiety bearing also an 1,2-dithiolane derivative is demonstrated and employed for the synthesis of AuNCs with NIR- fluorescence. Next, the C=C group of the newly synthesized ligand was exploited to covalently react with thiol-functionalized graphene and MoS2 sheets through thiol–ene “click” reaction. The current strategy employed constitutes a general tool that is wide in scope and can, in principle, be extended to the modification of other 2D materials and/or compounds for the fabrication of hybrid schemed with tailored characteristics that today is unattainable.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας
Subject classification: Γραφένιο
Keywords: Γραφένιο,Διχαλκογενίδια μετάλλων μετάπτωσης,Μεταλλικές νανοσυστάδες,Χημική τροποποίηση,Φθορισμός,Υβριδικά υλικά,Μετατροπή ενέργειας,Graphene,Transition metal dichalcogenides,Metal nanoclusters,Chemical functionalization,Fluorescence,Hybrid materials,Energy conversion
URI: https://olympias.lib.uoi.gr/jspui/handle/123456789/29725
Appears in Collections:Διδακτορικές Διατριβές

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