Η παρούσα Διδακτορική Διατριβή ασχολείται με τη σύνθεση καθώς και τον δομικό και φυσικοχημικό χαρακτηρισμό των έξης υαλωδών συστημάτων: (α) του δυαδικού συστήματος xMgO – (1 – x)SiO2, με 0.50 ≤ x ≤ 0.667, (β) του ψευδοδυαδικού συστήματος (1 – x)[CaO:MgO] – xSiO2, με 0.333 ≤ x ≤ 0.27 και (γ) του δυαδικού συστήματος xY2O3 – (1 – x)Al2O3, με 0.24 ≤ x ≤ 0.41 και x σε mol %. Τα συστήματα αυτά παρουσιάζουν σημαντικές δυσκολίες στο να σχηματίσουν υάλους με κλασικές μεθόδους υαλοποίησης και ως εκ' τούτου τα διαθέσιμα δεδομένα αναφορικά με τα δομικά και φυσικοχημικά τους χαρακτηριστικά είναι περιορισμένα. Η σύνθεση των υάλων αυτών κατέστη δυνατή με τη μέθοδο της αεροδυναμικής ανύψωσης και της τήξης των οξειδίων με Laser CO2 (Aerodynamic levitation/CO2 laser melting techniques). Αυτή η σχετικά νέα και μη συμβατική τεχνική υαλοποίησης είναι και η μόνη διαθέσιμη έως σήμερα μέθοδος με την οποία μπορούν να συντεθούν οι περισσότεροι από τους ανωτέρω υάλους. Για το δομικό και φυσικοχημικό χαρακτηρισμό των ανωτέρω συστημάτων, χρησιμοποιήθηκαν οι φασματοσκοπικές τεχνικές Raman και NMR, ενώ ταυτόχρονα πραγματοποιήθηκαν μετρήσεις Διαφορικής Θερμιδομετρίας Σάρωσης, Ηλεκτρονικής Μικροσκοπίας Σάρωσης, Ηλεκτρονικής Μικροσκοπίας Φαινομένου Σήραγγας και πυκνομετρίας, καθώς και Μοριακών Προσομοιώσεων. Τα δύο πρώτα συστήματα (α-β) ανήκουν στην ευρεία οικογένεια των ανόργανων υάλων του Πυριτίου με Οξείδια των Αλκαλικών Γαιών σε συστάσεις εξαιρετικά φτωχές σε οξείδιο του Πυριτίου. Το τελευταίο αυτό χαρακτηριστικό είναι και το πιο ενδιαφέρον από πλευράς δομής και Φυσικοχημικών διεργασιών, καθώς οι ύαλοι αυτοί χαρακτηρίζονται ως «φτωχοί σχηματιστές υάλων» με αποτέλεσμα η δομή τους να χαρακτηρίζεται από ακραίο αποπολυμερισμό. Στα πλαίσια της παρούσας Διατριβής κατέστη δυνατή η σύνθεση των υάλων αυτών σε συστάσεις οι οποίες για πρώτη φορά συντίθενται σε εργαστήριο και τα αποτελέσματα που προέκυψαν από τον δομικό και φυσικοχημικό τους χαρακτηρισμό, παρουσιάζονται επίσης για πρώτη φορά. Οι εξαιρετικά αποπολυμερισμένες δομές των υάλων αυτών - τους οποίους ονομάζουμε «υπο-ορθο-πυριτικούς» εξαιτίας της σύστασης τους η οποία περιέχει ποσοστό Πυριτίας λιγότερο από την Ορθο-Πυριτική σύσταση (33.3 mol % SiO2) - βρέθηκε ότι χαρακτηρίζονται από τετράεδρα πυριτίας με διαφορετικό αριθμό γεφυρωτικών οξυγόνων, με τα ελεύθερα τετράεδρα πυριτίας να κυριαρχούν στις δομές καθώς μειώνεται σταδιακά το ποσοστό του SiO2. Τα συμπεράσματα που προέκυψαν αναφορικά με τα δύο πρώτα συστήματα, δίνουν για πρώτη φορά, μια εικόνα αναφορικά με την δομική και φυσικοχημική συμπεριφορά Πυριτικών υάλων με οξείδια των Αλκαλικών Γαιών, όταν το ποσοστό του κλασικού υαλοσχηματιστή φτάνει στα όρια της δυνατότητας σχηματισμού υάλων. Το τελευταίο σύστημα (γ) το οποίο μελετήθηκε στα πλαίσια της παρούσας Διατριβής, αφορά στην σύνθεση και τον δομικό-Φυσικοχημικό χαρακτηρισμό υάλων Υττρίου-Αλουμίνας σε σχέση με το εξαιρετικά ιδιαίτερο χαρακτηριστικό που παρουσιάζει το σύστημα αυτό, το οποίο αναφέρεται ευρέως ως «πολυαμορφισμός». Στο σύστημα αυτό, μελετήθηκε και παρουσιάζεται για πρώτη φορά το περιβάλλον συναρμογής των ατόμων του Υττρίου, ενώ παρέχονται επιχειρήματα ότι το φαινόμενο του πολυαμορφισμού είναι παρόν σε όλους τους υάλους που σχηματίζονται εντός του δυαδικού συστήματος αυτού. Επίσης συσχετίζονται τα δομικά χαρακτηριστικά των υάλων αυτών με την εμφάνιση του πολυαμορφισμού ενώ για πρώτη επίσης φορά μελετώνται συστηματικά οι διεγέρσεις χαμηλών συχνοτήτων, σε σχέση με την μεταβολή της σύστασης και της θερμοκρασίας. Τα αποτελέσματα της ανάλυσης των διεγέρσεων χαμηλών συχνοτήτων για τα φάσματα Raman των υάλων αυτών, δείχνουν για πρώτη φορά σημαντικές εντάσεις για την κορυφή που παρατηρείται στις χαμηλές συχνότητες, ενώ αυτή παραμένει ανεπηρέαστη της σύστασης και της θερμοκρασίας. Τέλος, θα πρέπει να επισημανθεί ότι τα οξείδια τα οποία συναποτελούν το συγκεκριμένο σύστημα, δεν έχουν την δυνατότητα να σχηματίσουν υάλους αυτόνομα. / We present results from glass synthesis and the structural/physicochemical characterization from a series of glass forming systems and more specifically: (a) xMgO – (1 – x)SiO2 with 0.50 ≤ x ≤ 0.667, (b) the pseudobinary system (1 – x)[CaO:MgO] – xSiO2 with 0.333 ≤ x ≤ 0.27 and (c) the binary system xY2O3 – (1 – x)Al2O3 with 0.24 ≤ x ≤ 0.41, and x being the mol fraction. These systems exhibit significant difficulties regarding their ability to form glasses and hence the available data describing their structural and physicochemical characteristics are limited. Nevertheless, by using non-conventional glass forming techniques such as “Aerodynamic levitation/CO2 laser melting” we were able to synthesize these glasses and it is worth pointing out that this technique is the only available technique so far that glasses that belong to the above mentioned systems can be formed. For the structural and physicochemical characterization of the above mentioned systems, we used two spectroscopic techniques Raman and NMR whilst experiments using DSC, SEM, TEM, Densitometry and Molecular Dynamics simulations were also performed. The first two systems (a-b) belong in the greater family of silicate inorganic glasses mixed with Alkaline Earth oxides, in compositions significantly depleted in Silicon oxide. This last feature is the most interesting one structurally and physic-chemically wise, as these glasses are widely termed as “poor glass formers” having as a consequence their structure to be described by extreme depolymerization. In this work we were able to synthesize these glasses in a compositional range that is achieved for the very first time and the results derived from their structural and physicochemical characterization also presented for the very first time. These extensively depolymerized glass structures-whom we have termed as “Sub-Ortho-Silicates” due to their Silicate compound which is less than the Ortho-Silicate composition (33.3 mol % SiO2)-were found to be characterized by Silicate tetrahedral, having a varying number of bridging oxygens, with the “free” tetrahedral dominating the structures as the SiO2 content gradually diminishes. The conclusions derived from the first two systems, give for the first time an insight in relation with the structural and physicochemical behavior of Alkaline Earth oxide Silicate glasses when the percentage of the “classic” glassformer reaches the limits of glass formation. The last system we investigated (c) has to do with glass synthesis and structural/physicochemical characterization of Yttrium-Aluminate glasses in relation with an extremely interesting characteristic that this system exhibits, which is widely known as “polyamorphism”. In this system we investigated and present results for the very first time that reveal the coordination environment of Yttrium atoms, while we are also providing evidence that the phenomenon of polyamorphism is present in all glasses, formed within this binary system. Additionally we correlate the structural characteristics of these glasses with the appearance of polyamorphism while also for the very first time we have systematically investigated the low frequency vibrations, in relation with the variation of composition and temperature. The results derived from the analysis of the low frequency excitations exhibited in the Raman spectra of these glasses, show for the first time that the peak that makes its appearance in the low frequency region is characterized by significantly great intensity, while it also remains uninfluenced from the variation of composition and temperature. Finally, we must stress out that the oxides that constitute this specific system cannot form glasses independently.

Depuis plusieurs décennies la production mondiale de plastiques ne cesse d’augmenter, menant à une contamination des écosystèmes aquatiques à l’échelle de la planète qui a été récemment estimée à plus de cinq mille milliards de débris de plastiques flottants à la surface des océans. Les microplastiques (particules de plastique < 5 mm), introduits dans l’environnement aquatique directement en tant que microparticules (granulés plastiques industriels, cosmétiques, fibres textiles) ou lors de la fragmentation de plus gros débris plastiques, représentent une préoccupation scientifique et sociétale grandissante. Ces travaux de thèse se sont focalisés sur la contamination par les microplastiques de la rade de Brest (Bretagne, France), un système côtier macrotidal où l’activité anthropique est importante. Les objectifs de ces travaux sont (1) d’évaluer la contamination des matrices environnementales (eau de surface, sédiment subtidal et biote) par les microplastiques, et (2) d’identifier leur rôle potentiel en tant que vecteurs de contaminants chimiques et de bactéries dans la rade de Brest.Pour cela, des développements analytiques ont été nécessaires afin d’améliorer leur extraction des matrices environnementales ainsi que leur caractérisation morphologique et chimique via la microspectrométrie Raman. Les observations in situ ont montré que l’ensemble de l’écosystème de la rade de Brest est contaminé par les microplastiques, avec des concentrations de 0,24 ± 0,35, et 0,97 ± 2,08 (moyenne ± écart-type). L’eau de surface et le sédiment sont contaminés par le polyéthylène, le polypropylène et le polystyrène. Leur distribution à la surface de l’eau semble être liée à l’urbanisation très présente au nord de la rade, mais également à l’hydrodynamisme de cette région marine. Les premiers résultats concernant les bivalves marins ont montré un niveau relativement faible de contamination par les microplastiques (0,01 ± 0,04 et 0,08 ± 0,34 pour les moules et les coques, respectivement), cependant cela est probablement dû aux choix méthodologiques appliqués ici (exclusion des fibres). Les observations in situ ont montré que certains polluants organiques (HAP, PCB et pesticides) étaient détectés sur les microplastiques flottants à des valeurs (non détecté – 49763 ng.g-1, moyenne ± écart-type) similaires de celles retrouvées dans les sédiments et les bivalves locaux, ce qui suggère un risque faible dans le transfert des contaminants chimiques vers les organismes marins en cas d’ingestion. Enfin, les résultats concernant la colonisation bactérienne des microplastiques flottants ont montré des communautés distinctes de celles retrouvées dans l’eau de mer environnante, et l’identification du genre Vibrio en tant que biomarqueur discriminant de cette matrice. Dans l’ensemble, ces travaux fournissent une première évaluation approfondie de l’état de contamination de la rade de Brest par les microplastiques ainsi que de solides recommandations méthodologiques pour des travaux futurs. / World production of plastics has increased steadily for the past decades leading to a major contamination of the worldwide aquatic ecosystems recently estimated at more than five trillion plastic pieces floating the surface of the oceans. Microplastics (plastic particles < 5 mm) are introduced into aquatic environments directly as industrial raw material (plastic pellets, cosmetics, clothing) or indirectly via the fragmentation of larger plastics. This emerging contaminant represents an increasing ecological concern for science and society. The present study focused on the microplastic contamination of the Bay of Brest (Brittany, France), a macrotidal coastal ecosystem characterized by intense anthropogenic activity. The main objectives were: (1) to evaluate the contamination of environmental matrices (surface water, subtidal sediment and biota) by microplastics, and (2) to identify their potential role as vector of chemicals and bacteria in the bay of Brest.Methodological developments were first conducted to improve microplastic extraction from environmental matrices as well as their rapid morphological and chemical identification by Raman micro-spectrometry. The field investigations showed that the ecosystem of the bay of Brest is contaminated by microplastics with mean concentrations of 0.24 ± 0.35, and 0.97 ± 2.08 (mean ± standard deviation) in surface water and sediment, respectively. Microplastic contamination in surface water and sediment was dominated by polyethylene, polypropylene and polystyrene microparticles.Spatial microplastic distribution appeared to be related to proximity to urbanized areas and to hydrodynamic in the bay. Preliminarily results of microplastic contamination in marine bivalves demonstrated relatively low contamination (0.01 ± 0.04, and 0.08 ± 0.34 for mussels and cockles, respectively) by microplastics (mainly polyethylene and polypropylene fragments), however this could be partly related to the methodological limitation identified here (e.g. exclusion of fibers). Organic pollutant (PAH, PCB and pesticides) were detected on floating microplastics at levels (not detected – 49,763 ng g-1, mean ± SD) similar to those measured in sediment and bivalves suggesting low risks in transferring hazardous chemicals in local marine organisms upon microplastic ingestion. Finally, distinct bacterial community assemblages were demonstrated on microplastics as compared with surrounding surface water; the Vibrio genus was identified as a discriminant biomarker of the plastic matrix. Overall, this work provides a first and thorough assessment of the microplastic contamination in the bay of Brest and solid methodological recommendations for further work.

The polymeric gel-forming mucins provide the structural framework of saliva and the mucus barriers that cover the mucosal surfaces of the alimentary canal. Dietary compounds may influence the barrier properties of these protective layers. The effects of green tea polyphenols, which have many health benefits but have low bioavailability and contribute to the astringency of green tea, on the structural properties of the mucins in the alimentary canal are investigated here. Using well characterised, highly purified salivary mucins MUC5B and MUC7, and porcine gastric mucins, the effects of the green tea polyphenol epigallocatechin-3-gallate (EGCG) on mucins were studied here. Using rate-zonal centrifugation coupled to agarose gel electrophoresis, atomic force microscopy and particle tracking microrheology, EGCG, at concentrations found in a cup of green tea, caused increased aggregation of MUC5B in human whole saliva, and increased aggregation and viscosity of purified MUC5B. It was revealed using recombinant proteins of the N- and C-terminal regions of MUC5B that EGCG had these effects by aggregating the terminal globular protein domains of MUC5B. In contrast, MUC5B trypsin-resistant high molecular weight glycopeptides were not aggregated by EGCG, demonstrating that the oligosaccharide-rich, highly-glycosylated regions of mucins are not involved in the EGCG-induced aggregation of mucins. EGCG also caused the majority of MUC7 in human whole saliva to aggregate, and purified MUC7 also showed substantial aggregation in the presence of EGCG.Porcine gastric mucins were also used in order to model human gastric mucins. First, the identity of the porcine gastric mucins was explored using tandem mass spectrometry and immunohistochemistry. This revealed that Muc5ac was expressed by the surface epithelium and was the prominent mucin in porcine gastric mucus. Muc6 was expressed by gastric submucosal glands, but was not a major component of the secreted mucus barrier. Porcine Muc5ac and Muc6 were shown to be aggregated by EGCG. These data demonstrate that mucins from both saliva and the stomach are substantially altered by EGCG. This may contribute to the astringency and low bioavailability of EGCG. In contrast, the green tea polyphenol epicatechin (EC) did not cause aggregation of salivary mucins or porcine gastric mucins, suggesting that the galloyl ring of EGCG (which is absent in EC) is important for its aggregation of mucins, and that EC has different mechanisms of astringency. The structure of the mucins in the alimentary canal was studied using Raman spectroscopy, Raman optical activity (ROA) and Tip-enhanced Raman spectroscopy (TERS). The secondary structure of the oligosaccharide-rich regions of mucins was shown to be largely disordered, with some contribution of poly-proline II helix. The N- and C-terminal regions of MUC5B were largely β-sheet in structure, with some disordered structure also present in the C-terminal region. Raman spectroscopy could reliably distinguish between MUC5B glycoforms, demonstrating the sensitivity of this technique to mucin glycosylation and secondary structure. The first TERS spectra along the length of a MUC5B chain are reported, and suggest that patterns may exist in the glycosylation of MUC5B. Therefore, Raman spectroscopies are novel tools that shed new light on mucin structure and in future may be useful for studying the changes to mucin structure during interactions, such as those with polyphenols.

<p>U ovom radu prikazani su rezultati ispitivanja termičkih, mehaničkih, električnih i optičkih karakteristika kvazibinarnih halkogenida iz sistema Bi-As2S3. Na osnovu termičkih merenja analizirana je kinetika kristalizacionih i predkristalizacionih procesa i utvrđen je mehanizam dekompozicije za različite sastave dobijenih stakala. Primenom impedansne spektroskopije kvantitativno su ocenjeni doprinosi relaksacionih procesa na pojedinim temperaturama u ukupnoj polaraziciji za stakla sa 5 i 7 at.% Bi. Na osnovu merenja Raman spektroskopije identifikovane su nastale strukturne jedinice i konstatovana pojava nanofazne separacije u staklima sa 1.5 i 3 at.% Bi. Mehanička merenja ispitivanih halkogenida različitog sastava ukazala su na povećanje Vickers-ove tvrdoće sa povećanjem udela primesnih atoma. Na osnovu procenjene vrednosti modula elastičnosti ustanovljeno je da uzorak sa 5 at.% Bi odlikuje najgu&scaron;će atomsko pakovanje. Merenja električnih karakteristika u jednosmernom režimu (DC) pokazala su da je udeo lokalizovanih stanja u ukupnom mehanizmu provođenja značajan samo za manje koncentracije primesnih atoma, a da za veće koncentracije dominantan faktor postaju preskoci između delokalizovanih stanja. Skok u provodljivosti za nekoliko redova veličine kod sastava sa složenijom strukturom protumačen je kao posledica fazne separacije. Rezultati&nbsp; ACmerenja dobijeni za sastav sa 5 at.% Bi ukazali su da je u mernom frekventnom intervalu i dalje dominantan mehanizam termičke aktivacije nosilaca naelektrisanja. Kod sastava sa maksimalnim sadržajem Bi uočena je promena provodljivosti u funkciji frekvencije na svim temperaturama, a dobijeni rezultati su u skladu sa postavkama modela korelisanih preskoka barijere (CHB model).</p> / <p>This paper presents the results of investigation ofthermal, mechanical, electrical and optical propertiesof quasibinar chalcogenides from the system Bi-As2S3.&nbsp;Kinetics analysis of softening and crystallizationprocesses was done on the basis of thermalmeasurements, as well the analysis of decompositionmechanism for different compositions of obtainedglasses. The application of impedance spectroscopy enabled quantitative description of relaxation process contributions at selected temperatures in the overallpolarization for the samples with 5 and 7 at.% Bi.&nbsp;Based on measurements of Raman spectroscopy identification of structural units in the investigated chalcogenides was made, as well as the appearance of&nbsp;nano-scale phase separation in the glasses with 1.5 and 3 at.% Bi. Mechanical measurements pointed to the increase of the Vickers hardness with increase of&nbsp;doping atoms content. &nbsp;Based on the estimated value of the modulus of elasticity it was found that the sample &nbsp;with 5 at.% Bi is characterized by the densest atomic&nbsp;arrangement. Measurements of the electrical properties in dc regime (DC) pointed out that the share of localized states in the whole mechanism of conduction&nbsp;is significant only for the smaller concentrations of doping atoms. For the samples with higher concentrations dominant &nbsp;factor in conductivity are transitions between delocalized states. The jump in conductivity by few orders of magnitude, noticed for&nbsp;the compound with heterogeneous structure was interpreted as a consequence of micro-scale phase&nbsp; separation. Results of&nbsp; ACmeasurements for the&nbsp; composition with 5 at.% Bi showed that the mechanism of thermal activation of charge carriers is&nbsp;still dominant in the measured frequency range. For&nbsp;&nbsp; the composition with the maximum content of Bi changes in conductivity versus frequency were observed at all temperatures, and the results were interpreted in accordance with the model of correlated hopping over the barrier (CHB).</p>

Recently developed two-dimensional colloidal semiconductor nanocrystals, or nanoplatelets (NPLs), extend the palette of solution-processable free-standing 2D nanomaterials of high performance. Growing CdSe and CdS parts subsequently in either side-by-side or stacked manner results in core–crown or core/shell structures, respectively. Both kinds of heterogeneous NPLs find efficient applications and represent interesting materials to study the electronic and lattice excitations and interaction between them under strong one-directional confinement. Here, we investigated by Raman and infrared spectroscopy the phonon spectra and electron–phonon coupling in CdSe/CdS core/shell and core–crown NPLs. A number of distinct spectral features of the two NPL morphologies are observed, which are further modified by tuning the laser excitation energy Eexc between in- and off-resonant conditions. The general difference is the larger number of phonon modes in core/shell NPLs and their spectral shifts with increasing shell thickness, as well as with Eexc. This behaviour is explained by strong mutual influence of the core and shell and formation of combined phonon modes. In the core–crown structure, the CdSe and CdS modes preserve more independent behaviour with only interface modes forming the phonon overtones with phonons of the core. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Le sujet général de cette thèse est l’étude de la fonctionnalisation covalente des nanotubes de carbone (CNT) et son application en électronique. Premièrement, une introduction au sujet est présentée. Elle discute des propriétés des CNT, des différentes sortes de fonctionnalisation covalente ainsi que des principales techniques de caractérisation utilisées au cours de la thèse. Deuxièmement, les répercussions de la fonctionnalisation covalente sur les propriétés des nanotubes de carbone monoparoi (SWNT) sont étudiées. Deux types de fonctionnalisation sont regardés, soit le greffage de groupements phényles et le greffage de groupements dichlorométhylènes. Une diminution de l’absorption optique des SWNT dans le domaine du visible-proche infrarouge est observée ainsi qu’une modification de leur spectre Raman. De plus, pour les dérivés phényles, une importante diminution de la conductance des nanotubes est enregistrée. Troisièmement, la réversibilité de ces deux fonctionnalisations est examinée. Il est montré qu’un recuit permet de résorber les modifications structurales et retrouver, en majorité, les propriétés originales des SWNT. La température de défonctionnalisation varie selon le type de greffons, mais ne semble pas affectée par le diamètre des nanotubes (diamètre examinés : dérivés phényles, Ømoyen= 0,81 nm, 0,93 nm et 1,3 nm; dérivés dichlorométhylènes, Ømoyen = 0,81 nm et 0,93 nm). Quatrièmement, la polyvalence et la réversibilité de la fonctionnalisation covalente par des unités phényles sont exploitées afin de développer une méthode d’assemblage de réseaux de SWNT. Celle-ci, basée sur l’établissement de forces électrostatiques entre les greffons des SWNT et le substrat, est à la fois efficace et sélective quant à l’emplacement des SWNT sur le substrat. Son application à la fabrication de dispositifs électroniques est réalisée. Finalement, la fonctionnalisation covalente par des groupements phényles est appliquée aux nanotubes de carbone à double paroi (DWNT). Une étude spectroscopique montre que cette dernière s’effectue exclusivement sur la paroi externe. De plus, il est démontré que la signature électrique des DWNT avant et après la fonctionnalisation par des groupements phényles est caractéristique de l’agencement nanotube interne@ nanotube externe. / The general subject of this thesis is the covalent functionalization of carbon nanotubes and its applications in electronics. First, the properties of the carbon nanotubes, their functionalization, and the principal techniques used to characterize them are presented. Second, the repercussions of the grafting of phenyl addends and dichloromethylene addends on the properties of single-wall carbon nanotubes (SWNT) are investigated. A decrease of light absorption and a modification of the Raman spectra of the nanotubes are observed as well as, for the phenyl derivatives, an important loss of their electrical conductivity. Third, the reversibility of the functionalization is examined. The study shows that the addends are detached from the sidewall upon annealing, leading to the reconstruction of the graphene structure. Most of the original properties of the SWNT are then recovered. In addition, it is observed that the temperature of defunctionalization depends on the nature of the addends, but it is not influenced by the diameter of the SWNT (Range studied: phenyl derivatives, Ømoyen= 0,81 nm, 0,93 nm et 1,3 nm; dichlorométhylènes derivatives, Ømoyen = 0,81 nm et 0,93 nm). Fourth, a new method to reliably self-assemble networks of dense SWNT onto patterned substrates is presented. The method is based on covalent functionalization and electrostatic interactions. Its suitability for making electronic devices is demonstrated. Last, this thesis investigated the covalent functionalization of double-wall carbon nanotubes (DWNT). A spectroscopic study revealed that the grafting of the phenyl addends occurs exclusively on the outer wall. Furthermore, the identification of the metallic or semiconductor character of each wall of the DWNT is realized using electrical measurements taken before and after the functionalization.

Die Suche nach neuen Materialien von technischem Interesse hat in den letzten Jahren neue Antriebe zu der Untersuchung organischer Verbindungen gegeben. Organische Substanzen haben viele Vorteile wie z.B. die Möglichkeit, ihre Eigenschaften durch verschiedene chemische und physikalische Techniken im Herstellung-Prozess für ein bestimmtes Ziel zu modifizieren. Oxadiazolverbindungen sind interessant aufgrund ihrer Nutzung als Material für Licht emittierende Dioden und Scintillatoren. <br /> <br /> Die physikalischen Eigenschaften eines Festkörpers hängen von seiner Struktur ab. Unterschiedliche Strukturen entwickeln unterschiedliche intra- und intermolekülare Wechselwirkungen. Eine ausgezeichnete Weise, um sowohl die intra- als auch die intermolekularen Wechselwirkungen eines bestimmtes Stoffes zu beeinflussen, ohne seine chemischen Charakteristiken zu ändern, ist die Verwendung von hohem Druck. <br /> <br /> Wir haben den Einfluss von hohem Druck und hoher Temperatur auf die super-molekulare Struktur einiger Oxadiazolverbindungen im kristallinem Zustand untersucht. Aus diesen Untersuchungsergebnissen wurde eine Zustandsgleichung für diese Kristalle bestimmt. Überdies wurden die spektroskopischen Eigenschaften dieser Materialien unter hohem Druck charakterisiert. / In recent years the search for new materials of technological interest has given new impulses to the study of organic compounds. Organic substances possess a great number of advantages such as the possibility to adjust their properties for a given purpose by different chemical and physical techniques in the preparation process. Oxadiazole derivatives are interesting due to their use as material for light emitting diodes (LED) as well as scintillators. <br /> <br /> The physical properties of a solid depend on its structure. Different structures induce different intra- and intermolecular interactions. An advantageous method to modify the intra- as well as the intermolecular interactions of a given substance is the application of high pressure. Furthermore, using this method the chemical features of the compound are not influenced.<br /> <br /> We have investigated the influence of high pressure and high temperature on the super-molecular structure of several oxadiazole derivatives in crystalline state. From the results of this investigation an equation of state for these crystals was determined. Furthermore, the spectroscopical features of these materials under high pressure were characterized.

Le sujet général de cette thèse est l’étude de la fonctionnalisation covalente des nanotubes de carbone (CNT) et son application en électronique. Premièrement, une introduction au sujet est présentée. Elle discute des propriétés des CNT, des différentes sortes de fonctionnalisation covalente ainsi que des principales techniques de caractérisation utilisées au cours de la thèse. Deuxièmement, les répercussions de la fonctionnalisation covalente sur les propriétés des nanotubes de carbone monoparoi (SWNT) sont étudiées. Deux types de fonctionnalisation sont regardés, soit le greffage de groupements phényles et le greffage de groupements dichlorométhylènes. Une diminution de l’absorption optique des SWNT dans le domaine du visible-proche infrarouge est observée ainsi qu’une modification de leur spectre Raman. De plus, pour les dérivés phényles, une importante diminution de la conductance des nanotubes est enregistrée. Troisièmement, la réversibilité de ces deux fonctionnalisations est examinée. Il est montré qu’un recuit permet de résorber les modifications structurales et retrouver, en majorité, les propriétés originales des SWNT. La température de défonctionnalisation varie selon le type de greffons, mais ne semble pas affectée par le diamètre des nanotubes (diamètre examinés : dérivés phényles, Ømoyen= 0,81 nm, 0,93 nm et 1,3 nm; dérivés dichlorométhylènes, Ømoyen = 0,81 nm et 0,93 nm). Quatrièmement, la polyvalence et la réversibilité de la fonctionnalisation covalente par des unités phényles sont exploitées afin de développer une méthode d’assemblage de réseaux de SWNT. Celle-ci, basée sur l’établissement de forces électrostatiques entre les greffons des SWNT et le substrat, est à la fois efficace et sélective quant à l’emplacement des SWNT sur le substrat. Son application à la fabrication de dispositifs électroniques est réalisée. Finalement, la fonctionnalisation covalente par des groupements phényles est appliquée aux nanotubes de carbone à double paroi (DWNT). Une étude spectroscopique montre que cette dernière s’effectue exclusivement sur la paroi externe. De plus, il est démontré que la signature électrique des DWNT avant et après la fonctionnalisation par des groupements phényles est caractéristique de l’agencement nanotube interne@ nanotube externe. / The general subject of this thesis is the covalent functionalization of carbon nanotubes and its applications in electronics. First, the properties of the carbon nanotubes, their functionalization, and the principal techniques used to characterize them are presented. Second, the repercussions of the grafting of phenyl addends and dichloromethylene addends on the properties of single-wall carbon nanotubes (SWNT) are investigated. A decrease of light absorption and a modification of the Raman spectra of the nanotubes are observed as well as, for the phenyl derivatives, an important loss of their electrical conductivity. Third, the reversibility of the functionalization is examined. The study shows that the addends are detached from the sidewall upon annealing, leading to the reconstruction of the graphene structure. Most of the original properties of the SWNT are then recovered. In addition, it is observed that the temperature of defunctionalization depends on the nature of the addends, but it is not influenced by the diameter of the SWNT (Range studied: phenyl derivatives, Ømoyen= 0,81 nm, 0,93 nm et 1,3 nm; dichlorométhylènes derivatives, Ømoyen = 0,81 nm et 0,93 nm). Fourth, a new method to reliably self-assemble networks of dense SWNT onto patterned substrates is presented. The method is based on covalent functionalization and electrostatic interactions. Its suitability for making electronic devices is demonstrated. Last, this thesis investigated the covalent functionalization of double-wall carbon nanotubes (DWNT). A spectroscopic study revealed that the grafting of the phenyl addends occurs exclusively on the outer wall. Furthermore, the identification of the metallic or semiconductor character of each wall of the DWNT is realized using electrical measurements taken before and after the functionalization.

It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

The transformation of the vibrational spectrum of Cu2Zn(Sn1−xGex)S4 single crystals over the entire composition range (0 ≤ x ≤ 1) is studied experimentally by low-temperature Raman scattering and photoluminescence spectroscopies, as well as theoretically in the framework of density functional theory (DFT). It is shown that unlike “classic” mixed binary II–VI and III–V compounds, which are characterized by either one- or two-mode behavior of spectra transformation upon composition variation, the vibrational modes of the quaternary semiconductor Cu2Zn(Sn1−xGex)S4 exhibit both types of behavior within the same alloy system. DFT calculations reveal that the two-mode transformation is in fact observed for the vibrational modes, which possess a very small dispersion across the Brillouin zone, that is typical for a molecular crystal. These modes are due to the “breathing” motion of sulfur within GeS4 and SnS4 tetrahedra. The effects of structural (positional) disorder of mixed crystals are analyzed based on Raman scattering as well as photoluminescence results. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.