Materiali Ceramici per Edilizia con Funzionalità Fotocatalitica

This thesis wad aimed at the study and application of titanium dioxide photocatalytic activity on ceramic materials. As a matter of fact, photocatalysis is a very promising method to face most of the problems connected with the increasing environmental pollution. Furthermore, titanium dioxide, in its anatase crystallographic phase, is one of the most investigated photocatalytic material and results to be perfectly compatible with silicate body mixes. That goal was pursued by two different strategies: 1. the addition to a body mix used for heavy clay products of several titania powders, with different mean crystallite size, surface area, morphology and anatase/rutile ratio and a titania nanosuspension as well. The titania addition followed two procedures: bulk and spray addition over the ceramic samples surface. Titania was added in two different percentages: 2.5 and 7.5 wt.% in both of the methods. The ceramic samples were then fired at three maximum temperatures: 900, 950 and 1000 °C. Afterwards, the photocatalytic activity of the prepared ceramic samples was evaluated by following the degradation of an organic compound in aqueous medium, under UV radiation. The influence of titania morphological characteristics on the photoactivity of the fired materials was studied by means of XRD and SEM observations. The ceramic samples, sprayed with a slip containing 7.5 wt.% of titania powder and fired at 900 °C, have the best photoactivity, with a complete photo-decomposition of the organic compound. At 1000 °C no sample acted as a photocatalyst due to the anatase-to-rutile phase transformation and to the reaction between titania and calcium and iron oxides in the raw materials. 2. The second one foresaw the synthesis of TiO2-SiO2 solid solutions, using the following stoichiometry: Ti1-xSixO2 where x = 0, 0.1, 0.3 and 0.5 atoms per formula unit (apfu). The mixtures were then fired following two thermal cycles, each with three maximum temperatures. The effect of SiO2 addition into the TiO2 crystal structure and, consequently, on its photocatalytic activity when fired at high temperature, was thoroughly investigated by means of XRD, XPS, FE-SEM, TEM and BET analysis. The photoactivity of the prepared powders was assessed both in gas and liquid phase. Subsequently, the TiO2-SiO2 solid solutions, previously fired at 900 °C, were sprayed over the ceramic samples surface in the percentage of 7.5 wt.%. The prepared ceramic samples were fired at 900 and 1000 °C. The photocatalytic activity of the ceramic samples was evaluated in liquid phase. Unfortunately, that samples did not show any appreciable photoactivity. In fact, samples fired at 900 °C showed a pretty low photoactivity, while the one fired at 1000 °C showed no photoactivity at all. This was explained by the excessive coarsening of titania particles. To summarise, titania particle size, more than its crystalline phase, seems to have a relevant role in the photocatalytic activity of the ceramic samples.

Multiscale fabrication of functional materials for life sciences

Regenerative medicine claims for a better understanding of the cause-effect relation between cell behaviour and environment signals. The latter encompasses topographical, chemical and mechanical stimuli, electromagnetic fields, gradients of chemo-attractants and haptotaxis. In this perspective, a spatial control of the structures composing the environment is required. In this thesis I describe a novel approach for the multiscale patterning of biocompatible functional materials in order to provide systems able to accurately control cell adhesion and proliferation. The behaviour of different neural cell lines in response to several stimuli, specifically chemical, topographical and electrical gradients is presented. For each of the three kind of signals, I chose properly tailored materials and fabrication and characterization techniques. After a brief introduction on the state of art of nanotechnology, nanofabrication techniques and regenerative medicine in Chapter 1 and a detailed description of the main fabrication and characterization techniques employed in this work in Chapter 2, in Chapter 3 an easy route to obtain accurate control over cell proliferation close to 100% is described (chemical control). In Chapter 4 (topographical control) it is shown how the multiscale patterning of a well-established biocompatible material as titanium dioxide provides a versatile and robust method to study the effect of local topography on cell adhesion and growth. The third signal, viz. electric field, is investigated in Chapter 5 (electrical control), where the very early stages of neural cell adhesion are studied in the presence of modest steady electric fields. In Chapter 6 (appendix) a new patterning technique, called Lithographically Controlled Etching (LCE), is proposed. It is shown how LCE can provide at the same time the micro/nanostructuring and functionalization of a surface with nanosized objects, thus being suitable for applications both in regenerative medicine in biosensing.

Design, synthesis and Chemical-physical characterization of photocatalytic inorganic nanocrystals for technological applications

This work was based on the synthesis and characterization of innovative crystals for biomedical and technological applications. Different types of syntheses were developed in order to obtain crystals with high photocatalytic properties. A hydrothermal synthesis was also processed to correlate the chemical-physical characteristics with synthesis parameters obtaining synthesis of nanoparticles of titanium dioxide with different morphology, size and crystalline phase depending on the variation of the synthesis parameters. Also a synthesis in water at 80 °C temperature and low pressure was developed from which anatase containing a small percentage of brookite nanoparticles were obtained, presenting a high photocatalytic activity. These particles have been used to obtain the microcrystals formed by an inorganic core of hydroxyapatite surface covered by TiO2 nanoparticles. Micrometer material with higher photocatalytic has been produced. The same nanoparticles have been functionalized with resorcinol oxidized in order to increase the photocatalytic efficiency. Photodegradation test results have confirmed this increase. Finally, synthetic nanoparticles with a waterless synthesis using formic acid and octanol, through esterification "in situ" were synthesized. Nanoparticles superficially covered by carboxylic residues able to bind a wide range of molecules to obtain further photocatalytic properties were obtained.

Photocatalytic production of chemicals and hydrogen from biomass

In this work, with the aim to tackle several approaches towards sustainable chemistry, two reactions were studied: aerobic photo-oxidation of biomass derived 5-hydroxymethyl-2-furfural (HMF), and anaerobic photo-reforming of glycerol known as a by-product in biodiesel industry, towards production of chemicals and hydrogen. Solar-assisted reactions were performed by means of heterogeneous photocatalysis, in mild conditions such as atmospheric pressure, room temperature and water as a benign solvent. Titanium dioxide (lab-synthesized and commercial) was used as a photo-active catalyst, which surface was modified by introducing different metal (e.g. Au, Au-Cu, Pt) and metal oxide (e.g. NiO) nanoparticles. The prepared materials were characterized by XRD, DRS, BET, TEM, SEM, RAMAN and other techniques. The influence of the support, the size and type of the deposited metal and metal oxide nanoparticles on the photo-catalytic transformation of HMF and glycerol was evaluated. In the case of HMF, the influence of the base addition and the oxygen content on the reaction selectivity was also studied. The effect of the crystalline phase composition and morphology of TiO2 in the glycerol photo-reforming reaction was assessed as well. The surface of the synthesized TiO2 nano-powders was investigated by means of Surface Organometallic Chemistry (SOMC) approach. In particular, the surface was characterized by chemical titration and DRIFT techniques. Furthermore, the SOMC concept allowed preparing of well-dispersed Pt nanoparticles on the TiO2 surface. The photo-catalytic activity of this sample in the glycerol photo-reforming process was tested and compared to that of other Pt-containing catalysts prepared by conventional technics. In view of avoiding the agglomeration and sedimentation of suspended titania powders in water media, thick films of synthesized and commercial TiO2 were deposited on a conductive substrate using screen-printing technique. The prepared electrodes were characterized by profilometry, SEM, XRD, optical, electrochemical and photo-electrochemical methods.

Design and evaluation of aerosol and liquid separation systems

Conventional chromatographic columns are packed with porous beads by the universally employed slurry-packing method. The lack of precise control of the particle size distribution, shape and position inside the column have dramatic effects on the separation efficiency. In the first part the thesis an ordered, three-dimensional, pillar-array structure was designed by a CAD software. Several columns, characterized by different fluid distributors and bed length, were produced by a stereolithographic 3D printer and compared in terms of pressure drop and height equivalent to a theroretical plate (HETP). To prevent the release of unwanted substances and to provide a surface for immobilizing a ligand, pillars were coated with one or more of the following materials: titanium dioxide, nanofibrillated cellulose (NFC) and polystyrene. The external NFC layer was functionalized with Cibacron Blue and the dynamic binding capacity of the column was measured by performing three chromatographic cycles, using bovine serum albumin (BSA) as target molecule. The second part of the thesis deals with Covid-19 pandemic related research activities. In early 2020, due to the pandemic outbreak, surgical face masks became an essential non-pharmaceutical intervention to limit the spread. To address the consequent shortage and to support the reconversion of the Italian industry, in late March 2020 a multidisciplinary group of the University of Bologna created the first Italian laboratory able to perform all the tests required for the evaluation and certification of surgical masks. More than 1200 tests were performed on about 350 prototypes, according to the standard EN 14683:2019. The results were analyzed to define the best material properties and masks composition for the production of masks with excellent efficiency. To optimize the usage of surgical masks and to reduce their environmental burden, the variation of their performance over time of usage were investigated as to determine the maximum lifetime.

Modelling the effects of nitrogen deposition and carbon dioxide enrichment on forest carbon balance

Atmospheric CO2 concentration ([CO2]) has increased over the last 250 years, mainly due to human activities. Of total anthropogenic emissions, almost 31% has been sequestered by the terrestrial biosphere. A considerable contribution to this sink comes from temperate and boreal forest ecosystems of the northern hemisphere, which contain a large amount of carbon (C) stored as biomass and soil organic matter. Several potential drivers for this forest C sequestration have been proposed, including increasing atmospheric [CO2], temperature, nitrogen (N) deposition and changes in management practices. However, it is not known which of these drivers are most important. The overall aim of this thesis project was to develop a simple ecosystem model which explicitly incorporates our best understanding of the mechanisms by which these drivers affect forest C storage, and to use this model to investigate the sensitivity of the forest ecosystem to these drivers. I firstly developed a version of the Generic Decomposition and Yield (G’DAY) model to explicitly investigate the mechanisms leading to forest C sequestration following N deposition. Specifically, I modified the G’DAY model to include advances in understanding of C allocation, canopy N uptake, and leaf trait relationships. I also incorporated a simple forest management practice subroutine. Secondly, I investigated the effect of CO2 fertilization on forest productivity with relation to the soil N availability feedback. I modified the model to allow it to simulate short-term responses of deciduous forests to environmental drivers, and applied it to data from a large-scale forest Free-Air CO2 Enrichment (FACE) experiment. Finally, I used the model to investigate the combined effects of recent observed changes in atmospheric [CO2], N deposition, and climate on a European forest stand. The model developed in my thesis project was an effective tool for analysis of effects of environmental drivers on forest ecosystem C storage. Key results from model simulations include: (i) N availability has a major role in forest ecosystem C sequestration; (ii) atmospheric N deposition is an important driver of N availability on short and long time-scales; (iii) rising temperature increases C storage by enhancing soil N availability and (iv) increasing [CO2] significantly affects forest growth and C storage only when N availability is not limiting.

Bone-implant interface. Evaluation of osteoblastic cells behavior on nanopatterned titanium surfaces: an in vitro analysis

Protein-adsorption occurs immediately following implantation of biomaterials. It is unknown at which extent protein-adsorption impacts the cellular events at bone-implant interface. To investigate this question, we compared the in-vitro outcome of osteoblastic cells grown onto titanium substrates and glass as control, by modulating the exposure to serum-derived proteins. Substrates consisted of 1) polished titanium disks; 2) polished disks nanotextured with H2SO4/H2O2; 3) glass. In the pre-adsorption phase, substrates were treated for 1h with αMEM alone (M-noFBS) or supplemented with 10%-foetal-bovine-serum (M-FBS). MC3T3-osteoblastic-cells were cultured on the pre-treated substrates for 3h and 24h, in M-noFBS and M-FBS. Subsequently, the culture medium was replaced with M-FBS and cultures maintained for 3 and 7days. Cell-number was evaluated by: Alamar-Blue and MTT assay. Mitotic- and osteogenic-activities were evaluated through fluorescence-optical-microscope by immunolabeling for Ki-67 nuclear-protein and Osteopontin. Cellular morphology was evaluated by SEM-imaging. Data were statistically analyzed using ANOVA-test, (p<0.05). At day3 and day7, the presence or absence of serum-derived proteins during the pre-adsorption phase had not significant effect on cell-number. Only the absence of FBS during 24h of culture significantly affected cell-number (p<0.0001). Titanium surfaces performed better than glass, (p<0.01). The growth rate of cells between day3 and 7 was not affected by the initial absence of FBS. Immunolabeling for Ki-67 and Osteopontin showed that the mitotic- and osteogenic- activity were ongoing at 72h. SEM-analysis revealed that the absence of FBS had no major influence on cell-shape. • Physico-chemical interactions without mediation by proteins are sufficient to sustain the initial phase of culture and guide osteogenic-cells toward differentiation. • The challenge is avoiding adsorption of ‘undesirables’ molecules that negatively impact on the cueing cells receive from surface. This may not be a problem in healthy patients, but may have an important role in medically-compromised-individuals in whom the composition of tissue-fluids is altered.