Tesi di Dottorato
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Item Laser action in liquid crystals: from random to periodic syatems(2007) Ferjani, Sameh; Strangi, Giuseppe; Versace, CarloItem TiO2 nanotubes in nanotechnologies(2017-10-10) Jimenez, Leticia; Versace, CarloItem TiO2 nanotubes in nanotechnologies(2010-12-14) Jimenez, Leticia; Versace, CarloItem TiO2 nanotubes in nanotechnologies(2010-12-14) Jimenez, Leticia; Versace, CarloItem Advanced Materials (Ceramics in particular) for Structural Applications(2015-12-15) Koduru, Hari Krishna; Bartolino, Roberto; Versace, Carlo; Scaramuzza, NicolaThe study of ‘Intrinsic and Metal nano particles doped polymer thin films for soft matter applications and nanostructured Hyperbolic metamaterials’ is an challenging and dynamic field of research with significant implications in the development of novel technologies, like gas sensors, bio-medical application and engineering of spontaneous emission of florescent molecules. In the present investigation, we presented research work in two directions. We prepared Polymer thin films by homemade Cold Plasma Polymerization technique and studied their Microstructural, Optical and dielectric responses as a function of thin film growth parameters, in view of gas sensor applications. In other direction, we fabricated lamellar structured Hyperbolic Metamaterials by employing physical and chemical vapour thin film deposition techniques and employed them as effective substrates to engineer the life time of florescent dye molecules. The first part of this thesis is devoted to preparing Polypyrrole (PPy) thin films of nano sized thickness, by Cold plasma polymerization technique and analyzing the influence of Plasma power on Microstructural, Optical, wetting and dielectric properties of grown PPy films. Fabricating layered structures of “PVA/AgNPs/PVA” thin films to investigate the influence of rate of distribution of AgNPs on dielectric responses of PVA matrix to employ them as a gas sensor applications, whose study is still open and is getting substantial interest in industrial and academic environments. Enhancement of spontaneous emission is a dynamic and challenging fundamental quantum phenomenon in optics and in nutshell it opens new avenues for spectrum of futuristic applications. Metamaterials are artificially designed nanocomposite materials, in which bulk electromagnetic properties arise due to underlying structural resonances and near field coupling between the designed sub-wavelength building blocks. Metamaterials promise to alleviate the classical limitations of optics and led to exotic applications such as negative refraction, sub-wavelength resolution imaging, invisibility devices and perfect absorbers. In the second part of this thesis, we fabricated Hyperbolic metamaterials and proposed new grating coupled hyperbolic metamaterial (GCHMM) configuration for the enhancement of spontaneous emission rate of dye molecules by exploiting the unique property of a hypergrating to outcouple and extract the non-radiative plasmonic modes.Item Transport Properties in Polymer Nanocomposite Membranes Cataldo Simari(2015-12-15) Simari, Cataldo; Versace, Carlo; Nicotera, IsabellaThe aim of this thesis has been to prepare and characterize innovative composite membranes for polymer electrolyte fuel cells (PEMFCs) applications. Among the different energy conversion devices based on polymer electrolytes, PEMFCs, both hydrogen (DHFC) and direct methanol (DMFC), seems to be one of the most promising clean energy technologies. As electrochemical devices able to directly convert the chemical energy of a fuel into electrical energy, PEMFCs offer interesting advantages in vehicular or portable applications , as the quick start, the high energy conversion efficiency (~ 50%), the reduced environmental impact for the low CO2 emissions (zero in the case where the primary fuel is hydrogen) and the flexibility respect to the fuel, in fact, besides hydrogen (DHFC), they can be fed for example with methanol (DMFC). However, considerable efforts are still needed to be able to achieve satisfactory performance in terms of efficiency, durability and cost for mass deployment of such technology. It is necessary to deal with some problems that concern the electrolyte membrane, such as the degradation of the materials, the low proton conductivity at low relative humidity (RH) and poor mechanical properties at temperature higher than 130 °C. Therefore, the development of high-performance proton conducting polymer electrolyte membranes is critical for the optimal power density and efficiency a PEMFC can achieve because membrane ohmic loss is the major cause of overpotential in the operational current range of the fuel cell. In recent years, increasing interest has been devoted to the development of high temperature proton conducting polymer electrolyte fuel cell systems. In fact, most of the shortcomings associated with the lowtemperature PEMFC technology based on perfluorosulfonic acid (PFSA) membranes can be solved or avoided by developing alternative membranes with suitable ionic conductivity and stability up to 150 °C. The increasing the operational temperature would result in increased performance of the cell because of easier and more efficient water management, higher reaction rates to the electrodes, improved CO tolerance by the anode electro-catalysts, faster heat rejection rates and better systems integration. It has been mentioned the possibility to feed PEMFCs systems with other fuel respect to hydrogen. In particular, direct methanol fuel cells (DMFCs) combine the merits of polymer electrolyte fuel cells fueled by H2 with the advantages of a liquid fuel, such as easy handling and high energy density. However, despite these advantages, also regard this devices there are still technical barriers to overcome for their widespread commercialization such as methanol crossover from anode to cathode through the proton exchange membrane. From the above, it is thus highly important to enhance the proton conductivity of the electrolyte membrane under low RH in order to accomplish higher PEMFCs performance. On the other hand, is essential to develop polymer electrolytes with reduced methanol cross-over for DMFC. The work presented in this thesis is the result of a Ph.D. project carried out during a period of about three years from 2012 – 2015, in the Physical Chemistry Soft Matter Laboratory “Mario Terenzi” (PC_SM Mario Terenzi) at the Department of Chemistry and Chemical Technologies in the University of Calabria. The thesis was written as part of the requirements for obtaining the doctor of philosophy degree. The overall objective of this doctoral thesis was to design, synthesize and evaluate innovative composite electrolytes with specific properties suitable for PEM fuel cells that operate at high temperatures (above 100 ° C ) and low RH and/or with low methanol permeability. To this purpose, three main classes of materials have been explored as nanoadditives to create nanocomposite membranes: (i) organo-modified TiO2 nanoparticles, (ii) layered materials based on clays (anionic and cationic) and graphene oxide and (iii) hybrids clays-carbon nanotubes. While, as concern the ionomers, perfluorosulfonic acid (Nafion®) and polyaromatic polymers (sulfonated Polyether Ether Ketone and Polybenzimidazole) have been evaluated. In my doctoral porject an attempt was made to conjugate an intense basic research in order to understand the molecular mechanisms at the basis of ionic conduction in such complex systems, and the design, synthesis and more comprehensive characterization of new nanocomposites with opportune requisites. For this purpose an deep study of the transport properties of the water confined within the electrolyte membranes has been performed by NMR spectrocopy (diffusometry, relaxometry and 1H spectral analysis) together to a wide physico-chemical, mechanical and electrochemical characterization in order to achieve a systematic understanding at a fundamental level of the effects of dimensionality, architecture and organization of these nanofillers on the properties of the ionomers and to exploit this knowledge for the preparation of high performance electrolytes. Some of the electrolytes membranes investigated during my PhD thesis were prepared and studied in the framework of the PRIN Project: NAMED-PEM “Advanced nanocomposite membranes and innovative electrocatalysts for durable polymer electrolyte membrane fuel cells”. The last part of this thesis concerns a research work arisen from a collaboration with ITM-CNR of the University of Calabria, on the Ion Exchange Membranes for Reverse Electrodialysis (RED) process. Here, the NMR techniques were used to study the water dynamics in anion- and cation- exchange membranes (AEMs and CEMs) in order to achieved additional important insights about the effect of the electrolyte solution, on membrane microstructure and its transport and electrical properties. The results of this research have been published in scientific international Journals and reported in appendix to the end of the thesis. During these years I have spent two stages periods abroad: 1) in the “Department of Materials Science and Engineering of the University of Ioannina, Ioannina (Greece)”, where I worked under the supervision of Prof. D. Gournis, my research has been focused on the synthesis of novel carbon-based materials as additives for nanocomposite membranes; 2) in Department of Physics & Astronomy of the Hunter College, New York (USA), where I worked under the supervision of Prof. S. Greenbaumn, I performed the High Pressure NMR investigation of water and methanol transport properties in sPEEK-based nanocomposite electrolytes. Two scientific papers, based on the results obtained during these stages, have been recently submitted and also reported in appendixItem Across Scales Approach Based on Exciton-Plasmon Coupling for Low Loss Optical Metamaterials(2015-12-15) Dhama, Rakesh; Bartolino, Roberto; Versace, Carlo; De Luca, AntonioItem Atomic forcemicroscopy of corneal biomechanics(2014-11-28) Labate, Cristina; Bartolino, Roberto; Versace, Carlo; Barberi, Riccardo; De Santo, Maria P.Item New methods for characterization and dating in material of cultural heritage(2014-11-03) Bosco, Stefania; Versace, Carlo; Chidichimo, GiuseppeItem Optical systems for diagnostics: Near-Infrared Imaging technique for detection of dental demineralisation(2012-11-30) Salsone, Silvia; Versace, Carlo; Lombardo, Giuseppe; Zakian, Christian; Bartolino, RobertoIn dentistry, a correct detection of caries severity is still a challenging descision-making task that crucially a ects the choice for the best treatment plan. The challenge is to nd both the most objective parameters to detect caries at di erent stages (from an early reversibile stage to a severe one) and the most reliable method(s) that should be used to distinguish these stages. Currently, methods used in clinics are visual inspection, aided with light probe and pick inspection tools, and radiography. The main issue rising by the use of these methods is that both of them are subjective, with possibility for intra- and inter-examiner variability. For this reason, radiography needs an extreme care of interpretation especially when assessing occlusal caries. Visual methods, instead, are a ected by confounding factors, such as stain or uorosis, a ecting the accurate assessment of early caries lesions. Radiography, moreover, should be performed with care considering that the emission of ionising radiation may cause malignant change in tissues, especially for young age patients and are counter-indicated during pregnancy. They are also inadequate for the detection of initial caries and to locate the lesions looking at the superimposition of the tooth along its buccal-lingual axis. The aim of this study was to overcome the limits of the current detection techniques, o ering a non-invasive, objective method for the detection of caries at any stage of the demineralisation process. The proposed method measures the near-infrared (NIR) re ectance response of the tooth at three speci c wavelengths. It is then possible to investigate properties of the sample at the surface and in depth and get an image that maps the lesions on the occlusal view of the sample when combining these wavelengths. Due to the properties of the NIR light, this method is non-invasive, non-contact and allows for detection both at the enamel and at the dentine level. The NIR method o ers objective supporting information to quantify and detect dental caries and is especially suitable for areas a ected by confounding factors, such as stain. The objective of the study was to design and implement a NIR multispetral imaging system, developing e cient image analysis algorithms. In order to prove this objective, an in vitro validation of the technique against gold standard histology was performed together with a comparison to other detection methods - International Caries Detection and Assessment System (ICDAS - clinical visual inspection), bre optic transillumination method (FOTI - visual inspection with light probe), radiography and Quantitative Light-induced Fluorescence method (QLF), used in clinics or in research. A total of 112 teeh, molars and premolars, with di erent lesion severities were used for this study. Histologcal sections were obtained to con rm the lesion severities and used as a gold standard to compare the sensitivity and speci cty among techniques. Visual inspection methods recorded the highest values of sensitivity (ICDAS: >99%, FOTI: 93%) and speci city to dental caries (FOTI: >99%, ICDAS: 90%). However, these methods could have been highly facilitated by the in-vitro viewing of the samples. Sensitivity to dental caries was higher for NIR (91%) than for QLF (88%) and radiography (63%) while speci city was higher for radiography (81%) than for NIR (73%) and QLF (63%). The results from this study suggest that the NIR method has the ability to detect dental caries when other methods fail, providing an alternative to assist in the decision-making process with the further advantage of removing the confounding e ect of stain. This method can enhance patient communication and o ers an objective and safe alternative to ionising radiation methods.