Dipartimento di Chimica e Tecnologie Chimiche - Tesi di Dottorato
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Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Chimica e Tecnologie Chimiche dell'Università della Calabria.
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Item New hybrid solar cell (СNT – RUTHENIUM DYE)(2012-12-06) Siprova, Svetlana; Versace, Carlo; De Filpo, Giovanni; Bartolino, RobertoNegli ultimi anni le applicazioni dei nanotubi di carbonio nel settore microelettronico sono notevolmente aumentate date le proprieta’ uniche. In particolare la conducibilita’ dei nanotubi fa si che essi trovino interessanti utilizzi nel settore fotovoltaico. Questo lavoro si concentra sulla progettazione di una cella solare ibrida a base di nanotubi di carbonio e dye di Rutenio. Nella prima parte sono stati studiati diversi metodi di realizzazione dello starto omogeneo di nanotubi come starto conduttivo della cella. E’ stata proposta la molecola 1-Pyrenemethanol che contiene i gruppi pirenico e ossidrilico, per creare il contatto tra i nanotubi ed il dye. Nella seconda parte del lavoro lo starto di nanotubi e’ stato formato mediante elettroforesi per single-walled nanotubes (SWNTs) e metal-organic chemical vapor deposition (CVD) per multi-walled nanotubes (MWNTs). Entrambi i metodi hanno dato la possibilita’ di creare campioni con ampia area superficiale, dai quali sono state fabbricate le celle solari. Sono state studiate determinate le dipendenze tra i fattori dei metodi e le proprieta’ delle celle prodotte.Item Novel organic optoelectronic materials(2012-11-28) Cospito, Sante; Versace, Carlo; De Simone, Bruna Carla; Bartolino, RobertoIl presente lavoro di Tesi di Dottorato di Ricerca (Scuola di Dottorato in Scienza e Tecnica "Bernardino Telesio") dal titolo "Novel Organic Optoelectronic Materials" è stato svolto all'interno dei laboratori di "Organic Optoelectronic Materials" e "New Syntheses via Organometallic Catalysis" del Dipartimento di Chimica dell'Università della Calabria. Nuovi semiconduttori organici potenzialmente impiegabili in dispositivi optoelettronici quali OLEDs, celle solari, transitors ed elettrocromici sono state progettate, sintetizzate e caratterizzate. La prima parte del lavoro ha riguardato la sintesi e la caratterizzazione di derivati di triarilammine, molecole elettron-donatrici (anodiche), da impiegare in dispositivi elettrocromici ("smart windows") per l'attenuazione della radiazione solare nel vicino infrarosso (NIR). L'intensa ed estesa banda di assorbimento nel NIR prodotta delle specie mono-ossidate ha suggerito l'impiego di queste triarilammine in dispositivi "complementari" in cui vengono utilizzate insieme a molecole elettron-accetrici (catodiche) elettrocromiche nel visibile, per un'ampia modulazione dello spettro solare. Tali sistemi sono stati dispersi all'interno di matrici polimeriche al fine di realizzare dei gel elettrocromici le cui prestazioni sono state ampiamente studiate. La risposta elettrocromica del gel è stata inoltre provata in un dispositivo plastico, dimostrandone le potenziali applicazioni campo dell'elettronica flessibile. La seconda parte del lavoro invece, ha riguardato la sintesi e lo studio delle proprietà di cristalli liquidi semiconduttori di tipo "n" (elettron-accetori) da impiegare in celle solari organiche "bulk heterojunction". Tali molecole, appartenenti alla famiglia dei viologeni estesi, hanno mostrato interessantissime proprietà mesomorfiche fortemente influenzate dalla lunghezza delle catene alchiliche ( a 9, 10 e 11 atomi di carbonio) e dell'anione utilizzato, la bis(triflimmide). Le proprietà elettrochimiche di questi composti sono state investigate sia in soluzione che nelle mesofasi. Un'efficace elettrocromismo dovuta (i) al doppio strato elettrico creato all'elettrodo degli anioni presenti e (ii) all'elevata sovrapposizione degli orbitali di frontiera dell'esteso sistema π- coniugato è stato osservato nelle fasi colonnari e smettiche in cui le molecole si sono auto-assemblate. Infine, le proprietà elettrocromiche di questi composti sono state studiate all'interno di film plastici utilizzabili in dispositivi quali i displays.Item Hybrid nanostructured fillers for polymer electrolytes in the PEM Fuel Cells(2012-11-30) Angjeli, Kristina; Versace, Carlo; Nicotera, Isabella; Bartolino, RobertoThe present thesis is focused on the development of novel nancomposite membranes, prepared by the incorporation of two-dimensional inorganic layered structures such as (i) smectite clays (synthetic and natural), (ii) graphene oxide (GO), and (iii) layered double hydroxides (LDHs) with different compositions into the polymer matrix of Nafion, for use as electrolytes in Proton Exchange Membrane fuel cells. The characteristics of the membranes were studied mainly, in terms of transport properties by NMR spectroscopy, in order to study the water dynamics inside the electrolyte membranes. For this purpose the Pulse-Field-Gradient Spin-Echo NMR (PFGSENMR) method was employed to obtain a direct measurement of water self-diffusion coefficients on the water-swelled membranes in a wide temperature range (25-140 °C). This technique together with the 1H-NMR spectral analysis and NMR spin-lattice relaxation times (T1) conducted under variable temperature. Furthermore, both pristine materials (fillers and Nafion) as well as the resulted nanocomposite membranes were characterized by a combination of X-ray diffraction, FTIR spectroscopy, thermal analysis (DTA/TGA), Raman spectroscopies and scanning electronic microscopy (SEM).Item Hydrophilic Ir(III) complexes suitable for the construction of functional mesoporous materials(2012-11-27) Yadav, Yogesh Jivajirao; Versace, Carlo; Ghedini, Mauro; Bartolino, RobertoNowadays, intensive efforts have been carried out on the design of novel advanced molecular materials, which can self-assemble in a strong, directional and reversible way to construct supramolecular materials with specific properties. The rational design and preparation of supramolecular assemblies through the coordination of metal ions with organic ligands has attracted attention for developing novel crystalline materials with interesting structural topologies and promising applications, and has evolved as an interesting research. The metals used in these complexes can serve as structural components and/or as a source of properties (e.g., magnetic, catalytic, optoelectronic, etc). Cyclometallated Ir(III) octahedral complexes possess fascinating properties used in various applications such as luminescent and electrochemiluminescent labeling reagents for biological substrates1, sensors2, or electronic devices3,4. Recently, the interest in ionic Ir(III) complexes is growing rapidly because not only high internal quantum efficiency (~100%) can be achieved in principle, but also tunable emission wavelengths over the entire visible spectrum can be successfully obtained through ingenious modification of ligands. In particular, Ir(III) complexes based on the chelating ligand 2,2’-bipyridine (bpy) have been successfully applied in light-emitting electrochemical cells (LECs) and sensors.5 The theoretically calculated phosphorescence yield (Fp) of the Ir(III) complexes are close to unity in solution.6 The solution investigations have made great contributions to the fundamental understanding of luminescence processes at molecular level. The conclusions drawn from the dilute solution data, however, cannot commonly be extended to the concentrated solutions. Indeed, many Ir(III) complexes show very different light-emitting behaviors in dilute and concentrated solutions and respectively in the solid state. The luminescence is often weakened or quenched at high concentrations, a phenomenon widely known as “concentration quenching”. A main cause for the quenching process is mechanistically associated with the “formation of aggregates”, which is probably why the concentration quenching effect has frequently been referred to as “aggregationcaused quenching” (ACQ). On the other hand “aggregation-induced phosphorescent emission” (AIPE) is an unusual phenomenon existing also in transition metal complexes, which have no emission in solution but enhanced emission in the solid state.7 There are some examples of AIPE, most of them in neutral Ir(III) complexes.8, 9, 10, 11, 12 The main strategies to avoid unpleasant quenching phenomena are based on the dispersion of the chromophore. Mainly, two strategies are employed: engineering at molecular level by introducing functionalities able to electronically disconnect the chromophores (bulky groups or functionalities capable to construct hard crystalline or soft dynamic supramolecular assemblies) or isolating the active molecules in different host matrices (host-guest systems).13 In particular, the dispersion of a chromophore into mesoporous materials not only prevents the aggregation phenomena but also provides increased thermal, chemical and mechanical stability to the final materials. Mesoporous materials are ordered porous materials with periodic distribution of pores, high surface area, controllable large pore sizes in the range of 2 – 50 nm and variable topology of the pores. The inorganic matrixes may be made up of SiO2, TIO2, ZrO2, Al2O3, Nb2O5 etc. Basically, the synthesis of ordered functional mesoporous materials is based on the condensation of an inorganic scaffold on the organised structure formed in water by surfactant molecules. Two different strategies may be employed, the cooperative self-assembly mechanism (CSA) and the true liquid crystal templating’ (TLCT) mechanism.14 The functionalization of the mesoporous material may be done in both cases by inserting the chromophore into the primarily water solution. Therefore, water soluble chromophores may guarantee a better compatibility with the surfactant/water system, whereas a proper functionalization on the molecular structure of the chromophore that permit the self-assembly into supramolecular ordered water assemblies, will allow to use the chromophores directly as structure directing agents (SDAs). Since the photophysical properties of the ionic complexes are influenced profoundly by the surroundings of the molecule both in solution and in condensed states, it is fundamental to study the behavior of such complexes in these different states, in order to achieve a fine tuning of the properties as a function of their structure and order in the final material. The knowledge gained in the assembling of supramolecular materials using non-covalent bonds may be used for the construction of ordered systems in water. This strategy will permit the one-step synthesis of functional mesoporous materials, and to control the order of the final material controlling the order in water of the functional Ir(III) complexes. In particular, the molecular fragments that one can change to achieve the desired properties in the final ionic Ir(III) complexes are the cyclometallating or coordinating ligands, and respectively the counterion. My research therefore is focused on the design and synthesis of hydrophilic ionic Ir(III) complexes with flexible or rigid ancillary ligands and use of different counterions, all suitable for controlling the supramolecular assembly in the solid state, and to transfer the knowledge gained into obtaining ordered structures in water, or water-surfactant systems, necessary for the synthesis of mesoporous materials with defined properties. The ionic octahedral Ir(III) complexes synthesised during this thesis and their classification in different classes are presented in the figure S1Item Behavior and effects of additives in liquid crystal compounds(2011-11-03) Vivacqua, Marco; Bartolino, Roberto; Versace, Carlo; Nicoletta, Fiore P.Item Dense Hyflon® AD membranes for gas separation: influence of the solvent and determination of local free volume(2007-11-30) Macchione, Marialuigia; Longeri, Marcello; Versace, Carlo; Yampolskii, YuriItem Study of composite systems of polymers and liquid crystals with homeotropic orientation(2014-06-24) Gallucci, Maria Caterina; Versace, Carlo; De Filpo, GiovanniItem Synthesis and characterization of new hybrid organic/inorganic materials for electro-optic applications(2014-03-28) Teocoli, Francesca; Ghedini, Mauro; Versace, CarloItem Sintesi e studio di nuovi complessi contenenti Zn(II) e Pd(II) con potenziali proprietà elettroottiche(2014-03-26) Spataro, Tania; Versace, Carlo; Aiello, Iolinda