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Exploiting the properties of mesoporous thin films
Full text linkQuesta tesi di dottorato si pone l’obbiettivo di esplorare le potenzialità offerte dai film
sottili mesoporosi. Questi sistemi, infatti, offrono la possibilità di modulare molte delle
loro caratteristiche più peculiari come la composizione chimica delle pareti dei pori, la
struttura dei pori e la loro organizzazione e sono inoltre eccellenti matrici per strutture
host-guest. Inizialmente, sono stati svolti diversi esperimenti in-situ durante l’autoorganizzazione
dei film per indagare alcuni aspetti fondamentali di tale processo e per
studiare le proprietà chimico-fisiche delle pareti dei pori. In seguito, sono state sfruttate
le proprietà di questi materiali attraverso la funzionalizzazione delle loro strutture
porose con coloranti, molecole organiche fotoattive e complessi inorganici. E’ stata
anche testata la possibilità di utilizzare i pori come stampi monodispersi per la sintesi di
nanoparticelle metalliche. Grazie all’elevata area superficiale e ad una particolare
composizione chimica delle pareti dei pori, sono stati realizzati film mesoporosi a base
di ossidi misti con proprietà ottiche modulabili. Infine, si è cercato di indurre più di un
grado di auto-organizzazione all’interno dello stesso materiale per realizzare film a
porosità gerarchica. Tre diverse strategie sono state impiegate per ottenere simultaneamente
una macro- e una meso-porosità: stampaggio diretto con nanoparticelle
fluorurate, separazione di fase controllata mediante l’aggiunta di un agente costampante
e cristallizzazione controllata di un sale inorganico. I risultati presentati in
questa tesi di dottorato dimostrano la versatilità dei sistemi mesoporosi per la
realizzazione di materiali avanzati funzionali con un’ampia varietà di proprietà
chimiche e morfologiche.Mesoporous materials show the possibility to tailor several of their characteristic
features such as pore structure and arrangement, chemical composition of the pore walls,
and, in addition, are excellent matrixes for host-guest systems. This doctoral work
explores many of the potentialities offered by mesoporous thin films to produce
advanced functional materials with a wide range of tunability in terms of properties and
morphology. The first aim was to promote a basic study of self-assembly by in-situ
experiments to reveal some fundamental aspects of the process and some chemicalphysical
properties of the pore walls. Then, a full set of experiments was dedicated to
exploit the mesoporous materials by functionalizing their porous structures with dyes,
organic photoactive molecules and inorganic complexes. The pores were also used as a
nanoreactor for controlled growth of metallic nanoparticles. Mesoporous mixed oxides
films with tunable optical properties were obtained by using the high surface area and
controlling the chemical composition of the pore walls. Finally, the possibility of
inducing more than one degree of self-organization in the same material, to design
hierarchical porous films, was also explored. Three different strategies were used to
obtain macro- and meso-porosity, which include direct templating with fluorinated
nanoparticles, controlled phase separation using a co-templating agent and controlled
crystallization of an inorganic salt
Water Droplets to Nanotechnology. A journey through self-assembly
No full textThe ability of nanostructures to organize into complex arrangements leads to unique materials with valuable applications. Self-assembly is therefore a key concept for
nanotechnology, but it can be quite a complex and difficult
subject to approach. Water Droplets to Nanotechnology gives a simple and general overview of the different self-assembly processes which are at the basis of recent developments in nanotechnology.
The book shows how simple phenomenon from everyday
examples can become sophisticated tools for self-assembly and the fabrication of nanomaterials. By exploring the coffee stain and tears of wine phenomena, the first part looks at how
the evaporation of a droplet of colloidal solution can be used in designing organized structures. This leads onto more complex systems such as templated porous materials, photonic crystals, colloidal nanocrystals and quasi-crystals through to bottom-up
systems for designing hierarchal materials.
By taking the reader on a journey from everyday life to the secrets of nanotechnology, the book is suitable for a nonspecialist
audience interested in self-assembly as well as the wider perspectives and latest developments of nanoscience
Thermal Induced Polymerization of l-Lysine forms Branched Particles with Blue Fluorescence
No full textThe polycondensation of amino acids can originate complex polymers that display fascinating structural and optical properties. Thermally induced amidation of l-lysine allows forming a branched polymer without the support of any catalyst. The polycondensation is completed at 240–250 °C; at higher temperatures, the amino acid degrades. The obtained polylysine particles have been studied by transmission electron microscopy (TEM), nuclear magnetic resonance, and infrared spectroscopy that allow for investigating the different steps of the synthesis. The resulting structure is characterized by peculiar optical properties, e.g., excitation-dependent blue fluorescence and good quantum efficiency. Hydrogen bonds and the interactions of the amino acids are considered responsible for the optical properties of both l-lysine monomer solutions at high concentrations and the branched nanopolymers
Controlling shape and dimensions of pores in organic-inorganic films: nanocubes and nanospheres
No full textPorous organic-inorganic hybrid films with well defined pore shape and dimension have been obtained via a salt-template route. Sodium chloride precipitates during film deposition as templating for cubic shape pores; combining this salt-template route with controlled phase separation, pores of spherical shape in the same film have been also obtained. The dimensions of the nanocubes and nanospheres are in the 20-200 nm range and can be modulated through the film processing conditions. We have systematically investigated the effect of precursor solution aging and surfactant concentration on the porous film structure using infrared spectroscopy, spectroscopic ellipsometry, X-ray diffraction, Raman imaging, atomic force microscopy and transmission electron microscopy. Only a very specific combination of different synthesis parameters, such as surfactant concentration and aging of the precursor solution, allows the formation of the pore templates
Controlling the processing of mesoporous titania films by in-situ FTIR spectroscopy: getting Crystalline Micelles into the Mesopores
No full textApplication of IR and UV–VIS spectroscopies and multivariate analysis for the classification of waste vegetable oils
No full textDue to the ever-increasing worldwide interest in the exploitation of waste vegetable oils, the development of analytical tools able to detect their adulteration with edible oils, is considered a priority for the scientific and industrial community. In this work, edible and waste vegetable oils have been analysed by Fourier Transform-InfraRed (FT-IR) and Ultraviolet-Visible (UV–VIS) spectroscopies and the corresponding spectral data subjected to statistical multivariate analysis for classification purposes. In particular, Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis (PLS-DA) were performed in order to develop an analytical tool which is able to distinguish between edible and waste vegetable oil. Qualitative analysis of the spectra suggested FT-IR and UV–VIS as the more suitable techniques to distinguish between wastes and edible samples. Also, statistical multivariate analysis revealed that FT-IR-based methodology is more adequate for the target, even if the elevated sensibility of the method produces an undesired distinction between edible oils of the same type. Finally, further attempts on UV–VIS data obtained in reflection mode allowed to produce a good dataset which after statistical treatment gave a clear differentiation between edible and waste oil samples
Time resolved IR and X-ray simultaneous spectroscopy: new opportunities for the analysis of fast chemical-physical phenomena in materials science
No full text
Pore-confined synthesis of mesoporous nanocrystalline La–Ce phosphate films for sensing applications
No full textA new method for the preparation of fluorescent mesoporous La–Ce phosphate films by spin coating is
reported here. The structure is obtained by a pore-confined synthesis involving an in situ growth of
La0.5Ce0.5PO4 nanoparticles inside the pores of a mesoporous silica thin film and the subsequent partial
sintering. The removal of the sacrificial mesoporous silica matrix is achieved by chemical etching, which
leaves on the substrate a La0.5Ce0.5PO4 mesoporous film exhibiting good adhesion properties and high
fluorescence intensity that can be quenched by a water solution containing organo-phosphate bearing
nitrophenyl groups. The sensing capabilities of these materials have been tested for the detection of
pesticides in water
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