ANTIOXIDANT EXTRACTS FROM WASTE GRAPE SKINS: CONVENTIONAL SOLVENT EXTRACTION AND SURFACTANT APPLICATION FOR PROCESS INTENSIFICATION

La tesi di dottorato è stata sviluppata all'interno del progetto nazionale Valorvitis ed è suddivisa in due parti. La prima riguarda la caratterizzazione chimica di sei estratti di vinacce d’uva ottenute diverse varietà di uva: tre a bacca rossa( Pinot Noir, Barbera e Nebbiolo) e tre a bacca bianca (Moscato, Muller Thurgau e Chardonnay). Ogni estratto è stato caratterizzato per contenuto e composizione in composti fenolici. La seconda attività consiste nello studio di un metodo alternativo di estrazione-purificazione basato sull'impiego di Gas Aphron Colloidali (CGAs) con la finalità di ridurre i costi di processo, la quantità di solvente da utilizzare durante la fase di estrazione e, allo stesso tempo, aumentare il grado di purezza dell’estratto in termini di contenuto polifenolico.The present PhD thesis work was carried out under the framework of the Valorvitis.Extracts have been obtained from different red (Pinot Noir, Barbera and Nebbiolo) and white (Moscato, Muller Thurgau and Chardonnay) grape marcs and quantitatively analysed for the content of total phenolics, tannins, anthocyanins, cinnamic acids, flavonoids, flavonols, sugars (glucose and fructose) and for the anti-oxidant power (AOP). A new extraction-purification process based on CGAs application has been investigated. CGAs were first reported by Sebba (1987) as micro bubbles, with dimension among 10–100 μm, composed of a gaseous inner core surrounded by a thin surfactant film, which are created by intense stirring of a surfactant solution above its critical micellar concentration. Surfactants are able to catch phenolics thanks to both electrostatic and hydrophobic interactions depending on the surfactant (ionic or non-ionic) and on the phenolic compound. In this project the low-cost non-ionic food grade surfactant Tween 20 was used

Silicon Carbide in Microsystem Technology — Thin Film Versus Bulk Material

This chapter looks at the role of silicon carbide (SiC) in microsystem technology. It starts with an introduction into the wide bandgap (WBG) materials and the properties that make them potential candidates to enable the development of harsh environment microsystems. The future commercial success of WBG microsystems depends mainly on the availability of high-quality materials, well-established microfabrication processes, and economic viability. In such aspects SiC platform, in relation to other WBG materials, provides a clear and competitive advantage. The reasons for this will be detailed. Furthermore, the current status of the SiC thin film and bulk material technologies will also be discussed. Both SiC material forms have played important roles in different microsystem types

Crystal structure and ferroelectric properties of ϵ-Ga2O3 films grown on (0001)-sapphire

The crystal structure and ferroelectric properties of ϵ-Ga2O3 deposited by low-temperature MOCVD on (0001)-sapphire were investigated by single-crystal X-ray diffraction and the dynamic hysteresis measurement technique. A thorough investigation of this relatively unknown polymorph of Ga2O3 showed that it is composed of layers of both octahedrally and tetrahedrally coordinated Ga3+ sites, which appear to be occupied with a 66% probability. The refinement of the crystal structure in the noncentrosymmetric space group P63mc pointed out the presence of uncompensated electrical dipoles suggesting ferroelectric properties, which were finally demonstrated by independent measurements of the ferroelectric hysteresis. A clear epitaxial relation is observed with respect to the c-oriented sapphire substrate, with the Ga2O3 [10-10] direction being parallel to the Al2O3 direction [11-20], yielding a lattice mismatch of about 4.1%

3C-SiC nanowires and layers grown on Si: attractive material for biosensor applications

Nonotechnology is becoming an interesting field of research for biomolecular and medical diagnostics. The repeated screening is of crucial importance in the diagnosis of cancer and malignant tumours, since the pathologies at the early stages can be treated with the highest success probability. Many innovative approaches are emerging for the overcoming of this challenge, such as nanostructured surfaces for the enhancement of proteomic analysis, nanowires (NW) as biologically gated transistor, transductor for molecular binding events into real-time electrical signals and cantilevers for mechanical-based detection of biomolecules The interface of a biological system with tailored made detectors at the molecular scale opens the possibility to develop a entirely new class of devices and personal monitoring systems. The materials selected for these nanostructures must be biocompatible to ensure they are nontoxic and non-invasive for the organism, and must be capable to work in a very harsh environment. Silicon carbide (SiC) is mechanically robust, chemically inert, non toxic and biocompatible, so is a good material for biomedical purpose and for biosensor and bioelectronic applications. Several medical tools already uses SiC as bio-compatible coating, such as biomedical needles used in open heart surgery monitoring or temperature sensors based on bulk SiC. Nanosensors for ultrasensitive detection of proteins down to individual virus particles are also realised. Covalent bonding between specific molecules and stable interfaces are required for the realisation of biosensors based on molecular recognition, and since it was also demonstrated that SiC surfaces can be functionalized in order to react to specific biomolecules, this material is an optimal candidate for these kind of medical applications. Here we report a study on properties b-SiC-NWs and SiC layers deposited on silicon. Nanowires has been prepared with carbon oxide and nickel as catalytic element in nitrogen or argon atmosphere at the temperature between 1050 to 1100?C. Nanowires has been characterised by X-ray diffraction (XRD), by Scanning Electron Microscopy (SEM), Cathodoluminescence (CL) and by means Transmission Electron Microscopy (TEM). XRD patterns confirmed the characteristic peaks at 2q =35.6? (111), 41.4? (200), 59.9? (220), 75.5? (222) indexed as b-SiC. The room temperature CL spectrum revealed a broad peak centred at about 2.34 eV, related to the indirect band gap transition in b-SiC, and an intense blue band at about 2.68 eV. TEM images showed the crystalline core, having a <111> growth axis, sheathed by amorphous oxide. Typical SiC planar defects were present mainly on (111) planes, either stacking faults or rotational twins. Selected area electron diffraction from single NWs indicated the main phase as b-SiC. The SiC thin films were deposited on 2?? 001 Si wafers by means of VPE technique in a home made reactor with induction heating. A growth procedure at atmospheric pressure involving several steps (thermal etching, carburisation, epitaxial growth) was implemented. The precursor of choice were dilute SiH4 and C3H8 while H2 was used as carrier gas. The layers have been characterised by XRD, SEM, AFM. X-Ray diffraction evidences SiC(001) film is well oriented whit respect to the substrate having a narrow peak. SEM and AFM observations indicate a smooth film with good morphology

Epitaxial preparation of germanium cells for photovoltaic and thermophotovoltaic applications

Germanium is widely used in the advanced III-V photovoltaic technology based on arsenides and phosphides to realise triple junction (TJ) solar cells for space application and in thermophotovoltaic (TPV) devices. Nowadays, Ge cells are realised by diffusion and the cell conversion efficiency is partially limited by the broad doping profile thus obtained. Better performances could be achieved by means of homo-epitaxy of Ge on the Ge substrate, as improved thickness and doping profile control can be obtained with the epitaxial process. TJ cells, made of a InGaP/InGaAs/Ge monolithic array, have reached an efficiency value over 40% under concentration. The AM1.5 current density of the TJ cells are in the range of 15 mA/cm2 and the limiting subcell is the GaAs one: theoretical models suggest that the Ge subcell could produce a current density up to 40 mA/cm2, so that a large amount of the Ge potential is not fulfilled in the TJ cell. Epitaxial deposition of Ge would permit novel cell design (e.g. stacking 2 Ge cells) in order to obtain higher open circuit voltage. Ge cells are also employed in TPV devices to produce electricity from a heating source, thus fulfilling all the energetic content of a particular fuel and obtaining both heat and power from a single source. In this application, the advantages of Ge compared to the more common GaSb are a larger wafer size and a cheaper price. Ge epitaxial layers were deposited on both Ge and GaAs substrates by means of a home made Metal-Organic Vapor Phase (MOVPE) reactor using isobutylgermane (iBuGe). The samples were characterised by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Ohmic contacts were deposited on the samples in order to perform electrical characterization and to realise a simple p-n junction which showed photovoltaic effect. This work analyses the epitaxial growth of Germanium and the effect of the growth parameters (iBuGe partial pressure, temperature) on growth rate, surface morphology and material quality. In the temperature interval between 500 and 600?C a mass transport controlled regime was observed. Surface morphology showed a dependence on both the growth rate and on the substrate orientation: by using a low iBuGe partial pressure, a large density of holes were observed both by TEM and AFM. The holes almost disappeared by increasing the growth rate up to a limit of about 1mm/h, after which the surface roughness increases, degrading sample quality. XRD showed a nearly perfect crystallographic structure for the samples deposited on exaclty oriented (001) Ge substrates, while a larger diffraction peak was obtained for samples grown on (001) Ge substrated 6?off toward (110) direction. On the latter, a rougher and wave-like surface was observed by AFM while on exaclty oriented the surface was mirrorlike. n/p junctions were characterised by means of I-V and C-V techniques, and an optimal rectifying behaviour was obtained. The illuminated Ge n/p junctions reported a VOC of about 170 mV

Environmental and lifestyle risk factors for early-onset dementia: a systematic review

The term early-onset dementia (EOD) encompasses several forms of neurodegenerative diseases characterized by symptom onset before 65 years and leading to severe impact on subjects already in working activities, as well as on their family and caregivers. Despite the increasing incidence, the etiology is still unknown, with possible association of environmental factors, although the evidence is still scarce. In this review, we aimed to assess how several environmental and lifestyle factors may be associated with the onset of this disease

Curvature and stress analysis in 3C-SiC layers grown on (001) and (111) Si substrates

Silicon carbide is an attractive material for the realization of devices and Micro Electro Mechanical Systems working in harsh environment and for biocompatible applications. More than 100 polytypes of SiC exist but the SiC cubic phase (3C-SiC) has drawn particular attention because it can be deposited on Si, enabling the low cost and large area growth and the use of conventional microfabrication processes. Unfortunately, high lattice and thermal mismatch (20% and 8%, respectively) hinder SiC growth on Si, leading to high residual stress and creating a highly defective layer at the interface, which must be effectively controlled for many applications. The residual stress can potentially lead to macroscopic wafer bending, while variation of stress through the film thickness could generate undesired deformation for SiC microstructures. In the standard 3C-SiC growth, a thin carbonization layer can help to relieve the lattice mismatch and thus high quality 3C-SiC/Si layers are commonly realized. However, large bending and warping of the structures are still reported, with complex shape depending on the growth recipes. This hinders the following-on wafer level processes.. To assess these key stress and deformation issues, we tested several kinds of pre-growth (carbonization) procedures, adding various amount of SiH4 to C3H8. 3C-SiC layers were grown on (001) and (111) Si substrates by Vapor Phase Epitaxy (VPE) using SiH4 and C3H8, diluted in H2. The mechanical deformation of the samples was measured by an optical technique called Makyoh, through which 3D deformation maps of the entire wafers were obtained. Curvature radius and stress profiles, parallel and perpendicular to the gas flow direction, were extracted from these maps and compared with those for the different growth conditions. These were correlated to the results of X-Ray Diffraction (XRD) and Raman spectroscopy (RS). XRD was used to check the crystal quality of the layers and, in transmission geometry, to assess whether the observed deformation was plastic or elastic. The 2\u27\u27 wafers were mapped in several points with RS and the peak position was related to the residual internal stress. It was observed that, for the same pre-growth procedures, the substrate curvature (convex, concave) is dependant on the (001) or (111) Si substrate used. In particular, the addition of SiH4 during carbonization ramp induced increased deformation for SiC/Si(001), while decreased deformation for SiC/Si (111). These results agree with the stress analysis from RS and XRD

TEM and SEM-CL studies of SiC Nanowires

3C-SiC and 3C-SiC/SiO2 core-shell nanowires (NWs) grown on silicon substrates by three different processes, based on the use of i) carbon monoxide, ii) silane with propane and iii) carbon tetrachloride precursors, are analysed by structural and optical techniques. Spectroscopic cathodoluminescence studies show a luminescence enhancement in core-shell structures, ascribed to an effective role of the shell as both carrier injecting barrier and passivation layer. In NWs grown using CCl4 precursor, a peculiar luminescence with dominant red component at about 2 eV has been detected and ascribed to point defects related to an unintentional oxygen incorporation.vedi abstract ingles

Growth and characterization of 3C-SiC grown using CBr4 as a precursor

The growth of silicon carbide on silicon is being studied for many diverse applications and so the search for precursors that could be used to grow with improved or novel physical, structural and morphological properties is a relevant issue in this field. Here we present a study of the use of CBr4 as a precursor in the deposition of 3C-SiC in a cold walled MOVPE reactor. The growth has been studied in a range of temperatures between 1100 and 1250 ?C, on differently oriented substrates. Additionally, the effect of the C:Si ratio in the gas phase was examined by the addition of propane to the reaction mixture. At lower temperatures faceted crystals grew as islands on the substrate; faceting and 2D planar growth was obtained if higher growth temperatures were applied and at higher C:Si ratios. Atomic force and scanning microscopies revealed interesting growth habits of the island type crystals. Transmission electron microscopy in cross-section confirms that these islands are 3C-SiC and have a high crystal perfection. The crystal habit has been characterised and will be presented. Carbon tetrabromide has revealed itself to be a useful precursor for the growth of SiC and, with a judicious control of the growth conditions could be applied to the growth of thin films and nanocrystals