|Tipo di tesi||Tesi di dottorato di ricerca|
|Autore||SPADARO, MARIA CHIARA|
|Titolo||Nanoparticelle metalliche/di ossido: dalla sintesi e fine analisi strutturale alle proprietà magnetiche, catalitiche e plasmoniche|
|Titolo in inglese||Metal/Oxide Nanoparticles: from assembly and fine structural analysis to magnetic, catalytic and plasmonic properties|
|Settore scientifico disciplinare||FIS/03 - FISICA DELLA MATERIA|
|Corso di studi||Scuola di D.R. in PHYSICS AND NANO SCIENCES|
|Data inizio appello||2016-02-19|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
Lo sviluppo delle tecniche di crescita di nanoparticelle con forma e dimensione controllabili rappresenta uno dei principali aspetti della ricerca scientifica nel campo delle nanotecnologie.
The development of nanoparticles growth techniques with desired nanoparticle shape and size is an aspect of major interest in the scientific research on nanotechnology. Among the nanoparticles physical synthesis techniques, the magnetron sputtering technique implemented in a gas aggregation source proves to be very promising in terms of tunability of shape and size of nanoparticles. Nanoparticles with a specific shape and size show particular properties that can be exploited in several fields, such as magnetism, catalysis and plasmonics. In order to control and study in detail the properties of the produced nanoparticles, it is important to characterize these systems, using techniques with a high resolution degree; the transmission electron microscopy is an optimal technique thanks to the possibility to obtain information on nanoparticles with a high spatial resolution degree. In the present thesis work three different systems have been studied, demonstrating in this way the high versatility of the used growth technique. Nickel nanoparticles, a ferromagnetic material, surrounded by an antiferromagnetic material, nickel oxide or cobalt oxide, have been synthetized in order to verify the possibility of stabilizing the nickel nanoparticles magnetization, even at low dimension, exploiting the exchange bias effect that arises at the metal-oxide interface. In particular, at constant nickel nanoparticle size, the exchange bias dependence on the oxide shell thickness and anisotropy has been investigated. From the high resolution transmission electron microscopy measurements it has been possible to study the metal-oxide interface characteristics. A detailed study on cerium dioxide nanoparticles was also carried out, because CeOx is a material that finds its application in catalysis processes thanks to its ability to store and release oxygen depending on the ambient conditions. For this aim it is important to understand how its properties are related to the growth process, to the size and to the exposed crystallographic planes. In the present thesis work it has been investigated the influence of these parameters, observing in particular that the synthesis procedure has a strong influence on the density and distribution of Ce3+ sites and of structural defects, which in turn determinate the mobility of the oxygen ions. Finally, the plasmonic properties of silver nanoparticles and silver nanoparticles embedded in magnesium oxide have been investigated. The nanoparticles aggregation and their interaction with the substrate influence the system plasmonic properties. Furthermore, in case of silver nanoparticles embedded in magnesium oxide, it has been demonstrated that the plasmonic properties of the system are preserved in time.