Fiber-reinforced ceramics for thermostructural applications, produced by polymer impregnation pyrolysis

Several CFCC (Continuous Fiber Composite Ceramics) production processes were tested, concluding that PIP (Polymer Impregnation, or Infiltration, Pyrolysis) and CBC (Chemically Bonded Ceramics) based procedures have interesting potential applications in the construction and transportation fields, thanks to low costs to get potentially useful thermomechanical performances. Among the different processes considered during the Doctorate (from the synthesis of new preceramic polymers, to the PIP production of SiC / SiC composites) the more promising results came from the PIP process with poly-siloxanes on basalt fabrics preforms. Low processing time and costs, together with fairly good thermomechanical properties were demonstrated, even after only one or two PIP steps in nitrogen flow. In alternative, pyrolysis in vacuum was also tested, a procedure still not discussed in literature, but which could originate an interesting reduction of production costs, with only a moderate detrimental effect on the mechanical properties. The resulting CFCC is a basalt / SiCO composite that can be applied for continuous operation up to 600°C, also in oxidant environment, as TG and XRD demonstrated. The failure upon loading is generally pseudo-plastic, being interlaminar delamination the most probable rupture mechanism. . The strength depends on several different factors (microstructure, polymer curing and subsequent ceramic phase evolution, fiber pull-out, fiber strength, fiber percentage) and can only be optimized empirically. In order to be open minded in selecting the best technology, also CBC (Chemically Bonded Ceramics) matrixes were considered during this Doctorate, making some preliminary investigations on fire-resistant phosphate cements. Our results on a commercial product evidenced some interesting thermomechanical capabilities, even after thermal treatments. However the experiments showed also phase change and possible cracking and deformations even on slow drying (at 130°C) and easy rehydration upon exposure to environmental humidity.

From amphiphilic block copolymers to ferrocenyl-functionalized polymers for biosensoric applications

The present thesis can be divided in three main parts. In all parts new polymer architecturesrnwere synthesized and characterized concerning their special features.rnThe first part will emphasize the advantage of a polystyrene-block-(hyperbranchedrnpolyglycerol) copolymer in comparison to an analogue polystyrene-block-(linear polyglycerol)rncopolymer. Therefore a synthethic route to prepare linear block copolymersrnhas been developed. Two strategies were examined. One strategy was based on thernclassic, sequential anionic polymerization; the second strategy was based on arn“Click-Chemistry” coupling reaction. In a following step glycidol was hypergraftedrnfrom these block copolymers by applying a hypergrafting reaction with glycidol. Thernbehavior of the amphiphilic block copolymers synthesized was studied in differentrnsolvents. Furthermore the polarity of the solvent was changed to form the correspondingrninverse micelles. DLS, SLS, SEC-MALLS-VISCO, AFM and Cyro TEMrnmeasurements were performed to obtain a visual image from the appearance of thernaggregates. It was found that a linear-hyperbranched architecture is necessary, ifrnwell defined, monodisperse aggregates are required, e.g. for the preparation of orderedrnnanoarrays. Linear-linear block copolymers formed only polydisperse aggregates.rnAdditionally it was found that size distribution could be improved dramaticallyrnby passing the aggregates through a SEC column with large pores. The SEC columnsrnacted like a template in which the aggregates adopt a more stable conformation.rnIn the second part anionic polymerization was employed to synthesize silaneendfunctionalizedrnmacromonomers with different molecular weights based on polybutadienernand polyisoprene. These were polymerized by a hydrosilylation reaction inrnbulk to obtain branched polymers, using Karstedt’s catalyst. Surprisingly the additionrnof monofunctional silanes during the polymerization had only a minimal effect concerningrnthe degree of polymerization. It was possible to introduce silanes without increasingrnthe overall number of reaction steps by a very convenient “pseudo-copolymerization”rnmethod. All branched polymers were analyzed by SEC, SEC-MALLS,rnSEC-viscometry, 1H-NMR-spectroscopy and DSC concerning their branching ratio.rnThe branching parameters for the branched polymers exhibited similar characteristicsrnas hyperbranched polymers based on AB2 monomers. Detailed kinetic study showedrnthat the polymerization occurred very rapidly in comparison to the hydrosilylation polymerizationrnof classical AB2 type carbosilanes monomers.rnThe last part will deal with ferrocenyl-functionalized polymers. On the one hand,rnferrocenyl-functionalized polyglycerols (PG) were studied. Esterification of PGs withrndifferent molecular weight using ferrocenemonocarboxylic acid gave the ferrocenylrnfuntionalized polymers in high yields. On the other hand three different block copolymersrnwere prepared with different ratios of styrene to butadiene units (10:1, 4:1, 2:1).rnThe double bonds of the 1,2-PB block were hydrosilylated using silanes bearing onern(HSiMe2Fc) or two (HSiMeFc2) ferrocene units. High degrees of functionalizationrnwere obtained (up to 83 %). In this manner, six different ferrocenyl-rich block copolymersrnwith different fractions of ferrocene were prepared and analyzed, employingrnNMR-spectroscopy, SEC, SEC/MALLS/viscometry, DLS and cyclic voltammetry. Thernredox properties of the studied polymers varied primarily with the nature of the silanernunit attached. Additionally, the redox properties in solution of the studied polymersrnwere influenced by the block length ratio of the block copolymers. Unexpectedly, withrnincreasing block length of the ferrocenyl block the fraction of active ferrocenes decreased.rnNevertheless, in case of thin monolayer films this behaviour was not observed.rnAll polymers (PG and PS-b-PB based) exhibited good electrochemical propertiesrnin a wide range of solvents, which rendered them very interesting for biosensoricrnapplications.

Synthesis and applications of N-Metallo ketene imines

N-metallo ketene imines are attractive for the preparation of a wide range of organic compounds. Our research group has been engaged in the preparation and application of the N-metallo imines (SKIs). In this frame we have studied the uncatalyzed reaction of SKIs with isocyanates to give the corresponding malonamides with good yields. It has been demonstrated that the use of SKIs, instead of simple lithium anion of nitriles, is essential for the success of the reaction. A possible explanation assumes that this new reaction proceeds via a silatropism. In the course of our studies, reported in this thesis, the synthesis and the reactivity of N-silyl ketene imines in the preparation of 2,2-diaryl-3,4- dihydroxy- alcanonitrile in an uncatalyzed adol-type reaction has been performed. Our conception has been to use a chiral aldehyde to introduce asymmetric induction at the β-position and at the α-quaternary stereogenic center in the new forming diols. To achieve this goal, we used diarylacetonitrile as the substrate to form the corresponding N-trimethylsylilketene-imines to be reacted with (S)–lactic aldehyde with different protecting groups on the hydroxyl functionality. A number of 2,2-diaryl-3,4-dihydroxy-pentanenitrile were prepared with good to excellent stereo-control and satisfactory yields. Extension of this protocol to other metallo-ketene imines was performed. Accordingly, the preparation of tin ketene imines was attempted in analogy of the corresponding silyl ketene imine. The reaction of tin ketene imines with aldehydes was tested as a new tool for the synthesis of beta-hydroxynitriles starting from carbonyl compounds (aldehydes and/or ketones). Dialkyl(aryl)silyl nitriles and dialkyl(aryl)tin nitriles presents different reactivity. Finally, N-aluminium-ketene imines, as nucleophilic partner in the opening reaction of epoxides were studied. Preliminary positive results foster us to continue our studies in enlightening the scope and the limitations of this new reaction.

Flow Field–Flow Fractionation for size analysis and characterization of nanoparticles for applications in Life Sciences

Nanotechnologies are rapidly expanding because of the opportunities that the new materials offer in many areas such as the manufacturing industry, food production, processing and preservation, and in the pharmaceutical and cosmetic industry. Size distribution of the nanoparticles determines their properties and is a fundamental parameter that needs to be monitored from the small-scale synthesis up to the bulk production and quality control of nanotech products on the market. A consequence of the increasing number of applications of nanomaterial is that the EU regulatory authorities are introducing the obligation for companies that make use of nanomaterials to acquire analytical platforms for the assessment of the size parameters of the nanomaterials. In this work, Asymmetrical Flow Field-Flow Fractionation (AF4) and Hollow Fiber F4 (HF5), hyphenated with Multiangle Light Scattering (MALS) are presented as tools for a deep functional characterization of nanoparticles. In particular, it is demonstrated the applicability of AF4-MALS for the characterization of liposomes in a wide series of mediums. Afterwards the technique is used to explore the functional features of a liposomal drug vector in terms of its biological and physical interaction with blood serum components: a comprehensive approach to understand the behavior of lipid vesicles in terms of drug release and fusion/interaction with other biological species is described, together with weaknesses and strength of the method. Afterwards the size characterization, size stability, and conjugation of azidothymidine drug molecules with a new generation of metastable drug vectors, the Metal Organic Frameworks, is discussed. Lastly, it is shown the applicability of HF5-ICP-MS for the rapid screening of samples of relevant nanorisk: rather than a deep and comprehensive characterization it this time shown a quick and smart methodology that within few steps provides qualitative information on the content of metallic nanoparticles in tattoo ink samples.

Design and development of the new composite-material mainplane of the Dallara T12 race car

Abstract (US) Composite material components design and production techniques are discussed in the present graduation paper. In particular, this paper covers the design process and the production process of a carbon-fiber composite material component for a high performance car, more specifically, the Dallara T12 race car. This graduation paper is split in two. After a brief introduction on existing composite materials (their origins and applications), the first part of the present paper covers the main theoretical concepts behind the design of composite material components: particular focus will be given to carbon-fiber composites. The second part of the present paper covers the whole design and production process that the candidate carried out to create the new front mainplane of the Dallara T12 race car. This graduation paper is the result of a six-months-long internship that the candidate conducted as Design Office Trainee inside Dallara Automobili S.p.A. Abstract (ITA) La presente tesi di laurea discute le metodologie progettuali e produttive legate alla realizzazione di un componente in materiale composito. Nello specifico, viene discussa la progettazione e la produzione di un componente in fibra di carbonio destinato ad una vettura da competizione. La vettura in esame è la Dallara T12. Il lavoro è diviso in due parti. Nella prima parte, dopo una breve introduzione sull’origine e le tipologie di materiali compositi esistenti, vengono trattati i concetti teorici fondamentali su cui si basa la progettazione di generici componenti in materiale composito, con particolare riguardo ai materiali in fibra di carbonio. Nella seconda parte viene discusso tutto il processo produttivo che il candidato ha portato a termine per realizzare il nuovo alettone anteriore della Dallara T12. La presente tesi di laurea è il risultato del lavoro di progettazione che il candidato ha svolto presso l’Ufficio Tecnico di Dallara Automobili S.p.A. nel corso di un tirocinio formativo di sei mesi.

Role of outgrowth endothelial cells for applications in tissue engineering

Co-culture systems, consisting of outgrowth endothelial cells (OEC) and primary osteoblasts (pOB), represent a prom¬ising instrument to mimick the natural conditions in bone repair processes and provide a new concept to develop constructs for bone replacement. Furthermore, co-culture of OEC and pOB could provide new insights into the molecular and cellular mechanisms that control essential processes during bone repair. The present study described several advantages of the co-culture of pOB and OEC for bone tissue engineering applications, including beneficial effects on the angiogenic activation of OEC, as well as on the assembly of basement membrane matrix molecules and factors involved in vessel maturation and stabilization. The ongoing angiogenic process in the co-culture system proceeded during the course of co-cultivation and correlated with the upregulation of essential angiogenic factors, such as VEGF, angiopoietins, basement membrane molecules and mural cell-specific markers. Furthermore the co-culture system appeared to maintain osteogenic differentiation capacity.rnrnAdditional treatment of co-cultures with growth factors or morphogens might accelerate and improve bone formation and furthermore could be useful for potential clinical applications. In this context, the present study highlights the central role of the morphogen, sonic hedgehog, which has been shown to affect angiogenic activation as well as osteogenic differentiation in the co-culture model of OEC and pOB. Treatment of co-cultures with sonic hedgehog resulted in an increased formation of microvessel-like structures as early as after 24 hours. This proangiogenic effect was induced by the upregulation of the proangiogenic factors, VEGF, angiopoietin1 and angiopoietin 2. In contrast to treatment with a commonly used proangiogenic agent, VEGF, Shh stimulation induced an increased expression of factors associated with vessel maturation and stabilization, mediated through the upregulation of growth factors that are strongly involved in pericyte differentiation and recruitment, including PDGF-BB and TGFbeta. In addition, Shh treatment of co-cultures also resulted in an upregulation of osteogenic differentiation markers like alkaline phosphatase, osteocalcin, osteonectin and osteopontin, as well as an increased matrix calcification. This was a result of upregulation of the osteogenic differentiation regulating factors, BMP2 and RUNX2 which could be assessed in response to Shh treatment. rn

Simulation Guided Navigation in cranio-maxillo-facial surgery: a new approach to improve intraoperative three-dimensional accuracy and reproducibility during surgery.

The aim of this PhD thesis " Simulation Guided Navigation in cranio- maxillo- facial surgery : a new approach to Improve intraoperative three-dimensional accuracy and reproducibility during surgery ." was at the center of its attention the various applications of a method introduced by our School in 2010 and has as its theme the increase of interest of reproducibility of surgical programs through methods that in whole or in part are using intraoperative navigation. It was introduced in Orthognathic Surgery Validation a new method for the interventions carried out according to the method Simulation Guided Navigation in facial deformities ; was then analyzed the method of three-dimensional control of the osteotomies through the use of templates and cutting of plates using the method precontoured CAD -CAM and laser sintering . It was finally proceeded to introduce the method of piezonavigated surgery in the various branches of maxillofacial surgery . These studies have been subjected to validation processes and the results are presented .

A new method for continuous quality control of nsm cfrp systems

In the last decade the near-surface mounted (NSM) strengthening technique using carbon fibre reinforced polymers (CFRP) has been increasingly used to improve the load carrying capacity of concrete members. Compared to externally bonded reinforcement (EBR), the NSM system presents considerable advantages. This technique consists in the insertion of carbon fibre reinforced polymer laminate strips into pre-cut slits opened in the concrete cover of the elements to be strengthened. CFRP reinforcement is bonded to concrete with an appropriate groove filler, typically epoxy adhesive or cement grout. Up to now, research efforts have been mainly focused on several structural aspects, such as: bond behaviour, flexural and/or shear strengthening effectiveness, and energy dissipation capacity of beam-column joints. In such research works, as well as in field applications, the most widespread adhesives that are used to bond reinforcements to concrete are epoxy resins. It is largely accepted that the performance of the whole application of NSM systems strongly depends on the mechanical properties of the epoxy resins, for which proper curing conditions must be assured. Therefore, the existence of non-destructive methods that allow monitoring the curing process of epoxy resins in the NSM CFRP system is desirable, in view of obtaining continuous information that can provide indication in regard to the effectiveness of curing and the expectable bond behaviour of CFRP/adhesive/concrete systems. The experimental research was developed at the Laboratory of the Structural Division of the Civil Engineering Department of the University of Minho in Guimar\~aes, Portugal (LEST). The main objective was to develop and propose a new method for continuous quality control of the curing of epoxy resins applied in NSM CFRP strengthening systems. This objective is pursued through the adaptation of an existing technique, termed EMM-ARM (Elasticity Modulus Monitoring through Ambient Response Method) that has been developed for monitoring the early stiffness evolution of cement-based materials. The experimental program was composed of two parts: (i) direct pull-out tests on concrete specimens strengthened with NSM CFRP laminate strips were conducted to assess the evolution of bond behaviour between CFRP and concrete since early ages; and, (ii) EMM-ARM tests were carried out for monitoring the progressive stiffness development of the structural adhesive used in CFRP applications. In order to verify the capability of the proposed method for evaluating the elastic modulus of the epoxy, static E-Modulus was determined through tension tests. The results of the two series of tests were then combined and compared to evaluate the possibility of implementation of a new method for the continuous monitoring and quality control of NSM CFRP applications.

Structure and properties of quaternary and tetragonal Heusler compounds for spintronics and spin transfer torque applications

Diese Dissertation ist in zwei Teile aufgeteilt: Teil 1 befasst sich mit der Vorhersage von Halb-Metallizität in quarternären Heuslerverbindungen und deren Potential für Spintronik-Anwendungen. Teil 2 befasst sich mit den strukturellen Eigenschaften der Mn2-basierenden Heuslerverbindungen und dem Tuning von ihrer magnetischen Eigenschaften bzgl. Koerzitivfeldstärke und Remanenz. Diese Verbindungen sind geeignet für Spin-Transfer Torque-Anwendungen.rnrnIn Teil 1 wurden die folgenden drei Probenserien quarternärer Heuslerverbindungen untersucht: XX´MnGa (X = Cu, Ni und X´ = Fe, Co), CoFeMnZ (Z = Al, Ga, Si, Ge) und Co2−xRhxMnZ (Z = Ga, Sn, Sb). Abgesehen von CuCoMnGa wurden alle diese Verbindungen mittels ab-initio Bandstrukturrechnungen als halbmetallische Ferromagnete prognostiziert. In der XX´MnGa-Verbindungsklasse besitzt NiFeMnGa zwar eine zu niedrige Curie-Temperatur für technologische Anwendungen, jedoch NiCoMnGa mit seiner hohen Spinpolarisation, einem hohen magnetischen Moment und einer hohen Curie-Temperatur stellt ein neues Material für Spintronik-Anwendungen dar. Alle CoFeMnZ-Verbindungen kristallisieren in der kubischen Heuslerstruktur und ihre magnetischen Momente folgen der Slater-Pauling-Regel, was Halbmetalizität und eine hohe Spinpolarisation impliziert. Die ebenfalls hohen Curie-Temperaturen ermöglichen einen Einsatz weit über Raumtemperatur hinaus. In der strukturellen Charakterisierung wurde festgestellt, dass sämtliche Co2−xRhxMnZ abgesehen von CoRhMnSn verschiedene Typen von Unordnung aufweisen; daher war die ermittelte Abweichung von der Slater-Pauling-Regel sowie von der 100%-igen Spinpolarisation dieser Verbindungen zu erwarten. Die Halbmetallizität der geordneten CoRhMnSn-Verbindung sollte nach den durchgeführten magnetischen Messungen vorhanden sein.rnrnIm zweiten Teil wurden Mn3−xCoxGa und Mn2−xRh1+xSn synthetisiert und charakterisiert. Es wurde gezeigt, dass Mn3−xCoxGa im Bereich x = 0.1 − 0.4 in einer tetragonal verzerrten inversen Heuslerstruktur kristallisiert und im Bereich x = 0.6−1 in einer kubisch inversen Heuslerstruktur. Während die tetragonalen Materialien hartmagnetisch sind und Charakeristika aufweisen, die typischerweise für Spin-Transfer Torque-Anwengungen attraktiv sind, repräsentieren die weichmagnetischen kubischen Vertreter die 100% spinpolarisierten Materialien, die der Slater-Pauling-Regel folgen. Mn2RhSn kristallisiert in der inversen tetragonal verzerrten Heuslerstruktur, weist einernhartmagnetische Hystereseschleife auf und folgt nicht der Slater-Pauling-Regel. Bei hohen Rh-Gehalt wird die kubische inverse Heuslerstruktur gebildet. Alle kubischen Proben sind weichmagnetisch und folgen der Slater-Pauling-Regel.

Hyperbranched polyglycerols as building blocks for complex amphiphilic structures: synthesis, characterization and applications

Among hyperbranched polymers, polyglycerol is one of the most promising and commonly used macromolecules due to its biocompatibility and versatility. However, the synthesis of high molecular weight polyglycerols still involves many intricacies and has only been understood to a limited extent. Furthermore, only few complex structures like star or block copolymers incorporating polyglycerol have been realized so far. Particularly biocompatible block copolymers are considered promising candidates for biomedical applications.rnThe scope of this thesis was the enhancement of the synthetic process leading to polyglycerol derivatives which implies improved molecular weight control for a broad molecular weight range as well as the assembly of more complex structures like amphiphilic block copolymers. Further insight into the relation between reaction solvent, degree of deprotonation during the ring-opening multibranching polymerization of glycidol and the characteristics of the obtained polymers were achieved within the scope of this work. Based on these results, a novel concept for the preparation of hyperbranched polyglycerols with molecular weights up to 20,000 g/mol was developed, applying a two step synthesis pathway. Starting from a partially deprotonated TMP core, low molecular weight hb-PGs were prepared using the known synthetic protocol that has been established since the late 1990ies. In a subsequent reaction sequence, these well defined polymers were used as hyperbranched macroinitiator cores in order to obtain high molecular weight hb-PGs with remarkably low polydispersity (Mw/Mn < 1.8). Molecular weight control was shown to be excellent and undesired low molecular weight side products were absent. Furthermore, the technique of continuous spin fractionation has been discovered as an efficient method for polyglycerol work-up to remove quantitatively residual monomer- and oligomer traces from hb-PG compositions to result in samples with significantly reduced polydispersities. Based on these results the synthesis of amphiphilic block copolymers containing hydrophilic hyperbranched polyglycerol blocks and linear, apolar poly(propylene oxide) blocks has been significantly improved and augmented to hb-PG-b-l-PPO-b-hb-PG ABA block copolymers. The influence of different polyglycerol-based amphiphiles on the fibril formation was studied by Thioflavin T Fluorescence showing remarkable increasing lag times which is promising in order to enhance the stability of this protein. In addition the first synthesis of poly(glyceryl glycerols) (PGG), introducing a new solketyl glycidyl ether monomer (IGG) was shown. It was furthermore demonstrated that core-functional carbosilane wedges allow application in block copolymer synthesis. Bisglycidolized amine functional polymers were successfully employed as macroinitiators for glycidol polymerization. This resulted in the first example of amphiphilic hyperbranched-hyperbranched polymer structures. Finally, it has been shown that the previously reported synthetic pathway to carboxylated hyperbranched polyglycerol polyelectrolytes can also be applied for the amphiphilic linear-hyperbranched block copolymers. These novel biocompatible and highly amphiphilic polyelectrolytes offer great potential for further investigations. rnrn

Electronic structure and physical properties of Heusler compounds for thermoelectric and spintronic applications

This thesis focuses on synthesis as well as investigations of the electronic structure and properties of Heusler compounds for spintronic and thermoelectric applications.rnThe first part reports on the electronic and crystal structure as well as the mechanical, magnetic, and transport properties of the polycrystalline Heusler compound Co2MnGe. The crystalline structure was examined in detail by extended X-ray absorption fine structure spectroscopy and anomalous X-ray diffraction. The low-temperature magnetic moment agrees well with the Slater-Pauling rule and indicates a half-metallic ferromagnetic state of the compound, as is predicted by ab-initio calculations. Transport measurements and hard X-ray photoelectron spectroscopy (HAXPES) were performed to explain the electronic structure of the compound.rnA major part of the thesis deals with a systematical investigation of Heusler compounds for thermoelectric applications. Few studies have been reported on thermoelectric properties of p-type Heusler compounds. Therefore, this thesis focuses on the search for new p-type Heusler compounds with high thermoelectric efficiency. The substitutional series NiTi1−xMxSn and CoTi1−xMxSb (where M = Sc, V and 0 ≤ x ≤ 0.2) were synthesized and investigated theoretically and experimentally with respect to electronic structure and transport properties. The results show the possibility to create n-type and p-type thermoelectrics within one Heusler compound. The pure compounds showed n-type behavior, while under Sc substitution the system switched to p-type behavior. A maximum Seebeck coefficient of +230 μV/K (at 350 K) was obtained for NiTi0.26Sc0.04Zr0.35Hf0.35Sn, which is one of the highest values for p-type thermoelectric compounds based on Heusler alloys up to now. HAXPES valence band measurement show massive in gap states for the parent compounds NiTiSn, CoTiSb and NiTi0.3Zr0.35Hf0.35Sn. This proves that the electronic states close to the Fermi energy play a key role for the behavior of the transport properties. Furthermore, the electronic structure of the gapless Heusler compounds PtYSb, PtLaBi and PtLuSb were investigated by bulk sensitive HAXPES. The linear behavior of the spectra close to εF proves the bulk origin of Dirac-cone type density of states. Furthermore, a systematic study on the optical and transport properties of PtYSb is presented. The compound exhibits promising thermoelectric properties with a high figure of merit (ZT = 0.2) and a Hall mobility μh of 300 cm2/Vs at 350 K.rnThe last part of this thesis describes the linear dichroism in angular-resolved photoemission from the valence band of NiTi0.9Sc0.1Sn and NiMnSb. High resolution photoelectron spectroscopy was performed with an excitation energy of hν = 7.938 keV. The linear polarization of the photons was changed using an in-vacuum diamond phase retarder. Noticeable linear dichroism is found in the valence bands and this allows for a symmetry analysis of the contributing states. The differences in the spectra are found to be caused by symmetry dependent angular asymmetry parameters, and these occur even in polycrystalline samples without preferential crystallographic orientation.rnIn summary, Heusler compounds with 1:1:1 and 2:1:1 stoichiometry were synthesized and examined by chemical and physical methods. Overall, this thesis shows that the combination of first-principle calculations, transport measurements and high resolution high energy photoelectron spectroscopy analysis is a very powerful tool for the design and development of new materials for a wide range of applications from spintronic applications to thermoelectric applications.rn

Laboratory study on the optical properties of absorbing atmospheric aerosols and field applications

The interaction between aerosols and sun light plays an important role in the radiative balance of Earth’s atmosphere. This interaction is obtained by measuring the removal (extinction), redistribution (scattering), and transformation into heat (absorption) of light by the aerosols; i.e. their optical properties. Knowledge of these properties is crucial for our understanding of the atmospheric system. rn Light absorption by aerosols is a major contributor to the direct and indirect effects on our climate system, and an accurate and sensitive measurement method is crucial to further our understanding. A homebuilt photoacoustic sensor (PAS), measuring at a 532nm wavelength, was fully characterized and its functionality validated for measurements of absorbing aerosols. The optical absorption cross-sections of absorbing polystyrene latex spheres, to be used as a standard for aerosol absorption measurements, were measured and compared to literature values. Additionally, a calibration method using absorbing aerosol of known complex refractive index was presented.rn A new approach to retrieve the effective broadband refractive indices (mbroad,eff) of aerosol particles by a white light aerosol spectrometer (WELAS) optical particle counter (OPC) was achieved. Using a tandem differential mobility analyzer (DMA)-OPC system, the nbroad,eff are obtained for both laboratory and field applications. This method was tested in the laboratory using substances with a wide range of optical properties and it was used in ambient measurements to retrieve the nbroad,eff of biomass burning aerosols in a nationwide burning event in Israel. The retrieved effective broadband refractive indices for laboratory generated scattering aerosols were: ammonium sulfate (AS), glutaric acid (GA), and sodium chloride, all within 4% of literature values. For absorbing substances, nigrosine and various mixtures of nigrosine with AS and GA were measured, as well as a lightly absorbing substance, Suwannee river fulvic acid (SRFA). For the ambient measurements, the calibration curves generated from this method were to follow the optical evolution of biomass burning (BB) aerosols. A decrease in the overall aerosol absorption and scattering for aged aerosols during the day after the fires compared to the smoldering phase of the fires was found. rn The connection between light extinction of aerosols, their chemical composition and hygroscopicity for particles with different degrees of absorption was studied. The extinction cross-section (σext) at 532nm for different mobility diameters was measured at 80% and 90% relative humidity (RH), and at an RH<10%. The ratio of the humidified aerosols to the dry ones, fRHext(%RH,Dry), is presented. For purely scattering aerosols, fRHext(%RH,Dry) is inversely proportional with size; this dependence was suppressed for lightly absorbing ones. In addition, the validity of the mixing rules for water soluble absorbing aerosols is explored. The difference between the derived and calculated real parts of the complex RIs were less than 5.3% for all substances, wavelengths, and RHs. The obtained imaginary parts for the retrieved and calculated RIs were in good agreement with each other, and well within the measurement errors of retrieval from pulsed CRD spectroscopy measurements. Finally, a core-shell structure model is also used to explore the differences between the models, for substances with low growth factors, under these hydration conditions. It was found that at 80% RH and for size parameters less than 2.5, there is less than a 5 % difference between the extinction efficiencies calculated with both models. This difference is within measurement errors; hence, there is no significant difference between the models in this case. However, for greater size parameters the difference can be up to 10%. For 90% RH the differences below a size parameter of 2.5 were up to 7%.rn Finally, the fully characterized PAS together with a cavity ring down spectrometer (CRD), were used to study the optical properties of soot and secondary organic aerosol (SOA) during the SOOT-11 project in the AIDA chamber in Karlsruhe, Germany. The fresh fractal-like soot particles were allowed to coagulate for 28 hours before stepwise coating them with SOA. The single scattering albedo for fresh fractal-like soot was measured to be 0.2 (±0.03), and after allowing the soot to coagulate for 28 hours and coating it with SOA, it increased to 0.71(±0.01). An absorption enhancement of the coated soot of up to 1.71 (±0.03) times from the non-coated coagulated soot was directly measured with the PAS. Monodisperse measurements of SOA and soot coated with SOA were performed to derive the complex refractive index (m) of both aerosols. A complex refractive index of m = 1.471(±0.008) + i0.0(±0.002) for the SOA-αO3 was retrieved. For the compact coagulated soot a preliminary complex refractive index of m = 2.04(+0.21/-0.14) + i0.34(+0.18/-0.06) with 10nm(+4/-6) coating thickness was retrieved.rn These detail properties can be use by modelers to decrease uncertainties in assessing climatic impacts of the different species and to improve weather forecasting.rn

Synthesis of new xanthene derivatives

Xanthene dyes, including fluorescein, are a well-known class of fluorescent dyes, which have widespread applications in natural sciences. The synthesis of xanthene derivatives via acid catalyzed condensation of substituted phenols with phthalic anhydride, to afford the asymmetric derivatives, is well established. The high temperature, harsh reaction conditions and often low yields make this method less convenient. The synthesis of xanthene dyes by direct modification of the fluorophore moiety is a great option to circumvent the above mentioned drawbacks. rnOur new synthetic strategy for the preparation of novel asymmetric xanthene dyes via direct conversion of hydroxyl groups on 3'- and 6'-positions into leaving groups by mesylation is reported. It was discovered that 3',6'-di-mesylated fluorescein underwent a nucleophilic aromatic substitution with sulfur nucleophiles and afforded new asymmetric xanthene sulfides. rnThe impact of substituents possessing an electron-withdrawing character such as chlorines and bromines was investigated with the aim to improve the aromatic substitution on the electron-rich fluorescein structure. It was observed that the incorporation of these groups did not considerably affect the substitution reaction and the yields were comparable with the unsubstituted fluorescein. rnThis strategy provided novel fluorescent probes with the linker suitable to further modifications. The modifications of the linker delivered fluorescein derivatives that could be used as fluorescent labels in peptides, oligonucleotides and for cell imaging. rnThe hydroxyl group on the linker was modified to achieve potent bioconjugate functionality such as azide. The new fluorescent azides were obtained in a 4-step synthesis, namely 2-(6-(2-azidoethylthio)-3-oxo-3H-xanthen-9-yl)benzoic acid with an overall yield of 13%, its 2',7'-dichloro derivative with an overall yield of 10% and its 2',4',5'-tribromo derivative with an overall yield of 1%, respectively. rnAn asymmetric xanthene sulfide with an amino functionality placed on the aliphatic linker, namely 2-(6-((2-aminoethyl)thio)-3-oxo-3H-xanthen-9-yl)benzoic acid, was obtained in a 3-step synthesis with an overall yield of 33%. rnThe impact of the substitution with sulfur nucleophiles on the 6'-position of the xanthene moiety on its fluorescent characteristics was investigated. In comparison with fluorescein new asymmetric xanthene sulfides afforded lower extinction coefficients and fluorescent quantum yields. On the other hand, the substitution with a sulfur nucleophile significantly improved the photostability of xanthene dyes. It was shown that after 10 hours of continuous excitation, the asymmetric sulfur-containing xanthene fluorophores exhibited 58-94% of their initial fluorescent intensities. This observation suggested that the novel dyes were 1-2 orders of magnitude more stable than fluorescein. rnThe azido-modified xanthenes were “clicked” via Cu(I)-catalyzed azide-alkyne cycloaddition with an oligonucleotide, which contained the terminal alkyne residue. rn

Diblock copolymer - nanocrystal hybrids for optoelectronic applications

Small, smaller, nano - it is a milestone in the development of new materials and technologies. Nanoscience is now present in our daily lives: in the car industry with self-cleaning surfaces, in medicine with cancer therapies, even our clothes and cosmetics utilize nanoparticles. The number and variety of applications has been growing fast in recent years, and the possibilities seem almost infinite. Nanoparticles made of inorganic materials have found applications in new electronic technologies, and organic nanomaterials have been added to resins to produce very strong but light weight materials.rnThis work deals with the combination of organic and inorganic materials for the fabrication of new, functional hybrid systems. For that purpose, block copolymers were made with a long, solubility-enhancing and semiconducting block, and a short anchor block. They were synthesized by either RAFT polymerization or Siegrist polycondensation. For the second block, an active ester was grafted on and subsequently reacted with the anchor molecules in a polymer analogue reaction. The resulting block copolymers had different properties; poly(para-phenylene vinylene) showed self-assembly in organic solvents, which resulted in gelling of the solution. The fibers from a diluted solution were visible through microscopy. When polymer chains were attached to TiO2 nanorods, the hybrids could be integrated into polymer fibers. A light-induced charge separation was demonstrated through KPFM. The polymer charged positively and the charge could travel along the fibers for several hundred nanometers. Polymers made via RAFT polymerization were based on poly(vinyltriphenylamine). Ruthenium chromophores which carried anchor groups were attached to the second block. These novel block copolymers were then attached to ZnO nanorods. A light-induced charge separation was also demonstrated in this system. The ability to disperse inorganic nanoparticles within the film is another advantage of these block copolymers. This was shown with the example of CdSe tetrapods. Poly(vinyltriphenylamine dimer) with disulfide anchor groups was attached to CdSe tetrapods. These four-armed nanoparticles are supposed to show very high charge transport. A polymer without anchor groups was also mixed with the tetrapods in order to investigate the influence of the anchor groups. It was shown that without them no good films were formed and the tetrapods aggregated heavily in the samples. Additionally, a large difference in the film qualities and the aggregation of the tetrapods was found in the sample of the polymer with anchor groups, dependent on the tetrapod arm length and the polymer loading. These systems are very interesting for hybrid solar cells. This work also illustrates similar systems with quantum dots. The influence of the energy level of the polymer on the hole transport from the polymer to the quantum dots, as well as on the efficiency of QLEDs was studied. For this purpose two different polymers were synthesized with different HOMO levels. It was clearly shown that the polymer with the adjusted lower HOMO level had a better hole injection to the quantum dots, which resulted in more efficient light emitting diodes.rnThese systems all have in common the fact that novel, and specially designed polymers, were attached to inorganic nanocrystals. All of these hybrid materials show fascinating properties, and are helpful in the research of new materials for optoelectronic applications.

Synthesis of constrained peptidomimetics for therapeutic, diagnostic and theranostic applications

This thesis work deals, principally, with the development of different chemical protocols ranging from environmental sustainability peptide synthesis to asymmetric synthesis of modified tryptophans to a series of straightforward procedures for constraining peptide backbones without the need for a pre-formed scaffold. Much efforts have been dedicated to the structural analysis in a biomimetic environment, fundamental for predicting the in vivo conformation of compounds, as well as for giving a rationale to the experimentally determined bioactivity. The conformational analyses in solution has been done mostly by NMR (2D gCosy, Roesy, VT, titration experiments, molecular dynamics, etc.), FT-IR and ECD spectroscopy. As a practical application, 3D rigid scaffolds have been employed for the synthesis of biological active compounds based on peptidomimetic and retro-mimetic structures. These mimics have been investigated for their potential as antiflammatory agents and actually the results obtained are very promising. Moreover, the synthesis of Amo ring permitted the development of an alternative high effective synthetic pathway for obtaining Linezolid antibiotic. The final section is, instead, dedicated to the construction of a new biosensor based on zeolite L SAMs functionalized with the integrin ligand c[RGDfK], that has showed high efficiency for the selective detection of tumor cells. Such kind of sensor could, in fact, enable the convenient, non-invasive detection and diagnosis of cancer in early stages, from a few drops of a patient's blood or other biological fluids. In conclusion, the researches described herein demonstrate that the peptidomimetic approach to 3D definite structures, allows unambiguous investigation of the structure-activity relationships, giving an access to a wide range bioactive compounds of pharmaceutical interest to use not only as potential drugs but also for diagnostic and theranostic applications.