Das Entwicklungsstadium bestimmter Krankheiten ist eng mit der Konzentration diverser Proteine in biologischen Proben verknüpft. Eine sensitive Detektion dieser sogenannten Biomarker kann somit maßgeblich zu einer frühzeitigen Diagnose beitragen. In der vorliegenden Arbeit wurden strukturierte, fluorogene Sonden entwickelt, die die Möglichkeit bieten in einem homogenen Verfahren Zielproteine sensitiv, direkt und in Echtzeit nachzuweisen. Die peptidische Erkennungssequenz für das Zielprotein wurde dabei von zwei zueinander komplementären PNA-Segmenten flankiert. Die Sonden besaßen dadurch eine haarnadelförmige Anordnung, die kontrolliert eingebaute Reporter in eine enge Proximität zwang und ein minimales Hintergrundsignal im ungebundenen Zustand gewährleistete. Durch die Wechselwirkung mit dem Zielprotein erfolgte eine Reorganisation der Sondenstruktur, die fluoreszenzspektroskopisch verfolgt werden konnte. Für den Einbau der fluorogenen Einheiten wurden verschiedene Strategien entwickelt und die resultierenden Architekturen bzgl. ihres Einsatzes als sensitives Detektionssystem validiert. Als Zielproteine wurden die intrazellulären SH2-Domänen der Src- und Lck-Kinase sowie die extrazelluläre Matrix-Metalloprotease MMP-7, ein proteolytischer Biomarker für Krebs, untersucht. Besonders die neuartigen In-Stem Hairpin Peptide Beacons (IS-HPBs), bei denen fluorogene Pseudonukleobasen in die PNA-Stammregion eingebaut wurden, zeichneten sich als sensitive Proteasereporter mit einer bis zu 50-fachen Signalverstärkung aus. Mit einem excimerbasierten IS-HPB und einer zeitaufgelösten Fluoreszenzmethode konnte die direkte Detektion von MMP-7 bei einer kritischen Konzentration von 1 nM im humanen Blutserum erreicht werden. Eine mögliche Anwendbarkeit in der medizinischen Diagnostik wurde somit bekräftigt. Weiterhin wurden erste Hinweise mithilfe thermodynamischer Untersuchungen erhalten, dass die Strukturierung einer peptidischen Sonde zu einer erhöhten Selektivität beiträgt. / The developmental stage of certain diseases is closely linked to the concentration of various proteins in biological samples. A sensitive detection of these so-called biomarkers can thus significantly contribute to an early diagnosis. In the present work, structured, fluorogenic probes were developed that offer the possibility of a sensitive, direct and in real-time detection of target proteins in a homogeneous process. The peptidic recognition sequence for the target protein was thereby flanked by two self-complementary PNA segments. As a result, the probes possessed a hairpin-type arrangement, in which suitable appended labels are forced into close proximity and guaranteed a minimal background signal in the unbound state. By interacting with the target protein a reorganization of the probe structure occured, which could be followed by fluorescence spectroscopy. To embed the fluorogenic units different approaches were developed and the resulting architectures were validated relating to their use as a sensitive detection system. As target proteins the intracellular SH2-domains of the Src and Lck kinase and the extracellular matrix metalloprotease MMP-7, a proteolytic biomarker for cancer, were investigated. In particular, the new In-Stem Hairpin Peptide Beacons (IS-HPBs), in which fluorogenic pseudo nucleic acids were incorporated into the PNA-stem region, proved as sensitive protease reporters with an up to 50-fold signal amplification. By using an excimer-signaling IS-HPB and a time-resolved fluorescence method the direct detection of MMP-7 with a critical concentration of 1 nM within complex human blood serum was achieved. A possible application in medical diagnostics was thus confirmed. Furthermore, initial indications were obtained using thermodynamic studies that the structure of a peptide-based probe contributes to increased selectivity.

Hintergrund: Die Excimer Laser PRK zur Korrektur der geringen bis moderaten Myopie wird als präzises Verfahren der refraktiven Chirurgie angesehen und weltweit angewandt. Die Genauigkeit der PRK nimmt jedoch mit steigender Korrektur ab. Das Ziel dieser Untersuchung bestand darin, den Einfluß unterschiedlicher Laserstrahlapplikations- und -formungssysteme auf die korneale Oberflächenstruktur, das Hornhautprofil und die Zielrefraktion zu untersuchen. Materialien und Methoden: Es wurden mit dem Meditec Mel 60 und dem Schwind Keratom, zwei Excimer Laser der Wellenlänge 193 nm, an jeweils 10 enukleierten Schweinehornhäuten eine PRK mit einer Zielkorrektur von -3, -6, -9 D mit einem Ablationsdurchmesser von 6 mm (5 mm - 9D) durchgeführt, ein Silikonabdruck von der Hornhautoberfläche angefertigt und mit einem dynamisch fokussierenden Topometrie System UBM Microfocus vermessen. Hornhautradius, Brechkraft der stromalen Oberfläche, Profilabweichungen von der idealen sphärischen Form sowie Rauheitsparameter der verschiedenen Zonen wurden ermittelt. Ergebnisse: Epithelfreie Hornhäute besitzen ein sphärisches Profil. Der Meditec Mel60 Laser erzielte nach PRK von -3, -6 und -9 D sphärische Profile mit einer durchschnittlichen Refraktionsänderung von -3.4, -6.7 und -8.7 D. Das Schwind Keratom erzeugte eine mittlere Refraktionsänderung von -3.5, -5.8 und 8.4 D, wobei das korneale Ablationsprofil in allen Korrekturgruppen erhebliche Profilabweichungen in Form von zentralen Profilkuppen aufwies. Die durchschnittliche Höhe der zentralen Profilkuppen betrug nach der -3 D PRK 7.39 (±0.34) µm und stieg auf 16.31 (±1.06) µm bzw. 15.06 (±0.96) µm in der -6 und in der -9 D Serie. Die Relation zwischen der Profilkuppenhöhe und der Abtragtiefe lag zwischen 21 - 25% und konnte durch eine Anti-Central-Island Programm (ACI 100%) nur um 4% auf 18-20 % der Abtragtiefe reduziert werden. Die stromale Oberfläche der unbehandelten, epithelfreien Kontrollgruppe hat eine glatte, homogene Struktur. Die Rauheit der stromalen Oberfläche nach Ablation mit dem Meditec Laser war um 50 % stärker ausgeprägt als beim Schwind Keratom. Diskussion: Die Beschaffenheit der stromalen Oberfläche nach der Excimer Laser PRK zur Korrektur der Myopie, wird durch die Rauheitsparameter quantitativ beschrieben und ermöglicht den direkten Vergleich zwischen den Lasersystemen. Die Rauheit ist positiv mit der Ablationstiefe und dem Ablationsdurchmesser korreliert. Je höher eine myope Korrektur angestrebt wird, desto rauher ist die stromale Oberfläche und damit das Risiko, dass sich eine epitheliale Hyperplasie und subepitheliale Trübungen entwickeln, die ursächlich mit den klinisch beobachteten Phänomenen der myopen Regression, der Abnahme der Kontrastsehschärfe, dem Verlust der bestkorrigierten Sehschärfe und monokularer Doppelbilder in Zusammenhang stehen. Ob der Unterschied der Rauheit von durchschnittlich 50% sich in der Inzidenz der klinischen Komplikationen widerspiegelt, können nur vergleichende Studien belegen. Sicher ist, das die Vorhersagbarkeit des refraktiven Ergebnisses durch die Ablation mit dem Aesculap Meditec MEL 60 Laser besser einzuschätzen ist, als das mit zentralen Profilkuppen komplizierte Ablationsprofil des Schwind Keratoms. / Purpose: To evaluate the predictability of refractive outcome, sphericitiy of corneal profiles and surface roughness parameters after myopic PRK with different, commercially available excimer laser beam delivery and beam shaping systems. Materials and Methods: Myopic Excimer Laser PRK of -3, -6 and -9 D in 6mm ablation zone (5 mm in -9 D) on performed on porcine eyes was performed with the Aesculap Meditec Mel 60, a slit scanning Laser and the Schwind Keratom I, a broad area laser with band mask beam shaping. A silicone replica was obtained to conserve the corneal profile and measured with a dynamic focusing topometry system (UBM Microfocus) to obtain radius, corrected corneal refraction and corneal surface roughness parameters. Results: Untreated corneas of the control group displayed spherical profiles. PRK of intended -3, -6 and -9 D correction with the slit scanning Aesculap Meditec Mel60 excimer laser achieved a refractive change of an average -3.4, -6.7 and -8.7 D respectively without major profile deviations. PRK with the Schwind Keratom, a broad area beam excimer laser resulted a refractive change of -3.5, -5.8 and -8.4 D respectively. The Ablation created considerable central profile deviations representing central islands of 7.39 (±0.34) µm after -3 D, 16.31 (±1.06) µm and 15.06 (±0.96) µm height after - 6 and -9 D PRK, respectively. Mean central island height was 21 - 25% of ablation depth and was reduced by anti-central-island-program to 18-20 % of ablation depth. Stromal surface roughness increased with ablation depth and was significantly rougher after scanning beam ablation compared to broad area ablation. Conclusions: Profile deviations increase with higher corrections and lessen the predictability of the refractive results. The Aesculap Meditec MEL60 Slit scanning system creates predictable spherical corneal profiles. The Schwind Keratom broad area laser create with band mask beam shaping central islands increasing with higher corrections. The application of an Anti-Central-Island Program does not eliminate the central profile elevations sufficiently. Stromal surface was rougher after scanning beam compared to broad area beam ablation.

Résumé : Les circuits photoniques intégrés qui combinent des dispositifs photoniques pour la génération, la détection, la modulation, l'amplification, la commutation et le transport de la lumière dans une puce, ont été rapportés comme étant une innovation technologique importante qui simplifie la conception du système optique et qui réduit l'espace et la consommation de l'énergie en améliorant ainsi la fiabilité. La capacité de modifier la bande interdite des zones sélectives des différents dispositifs photoniques à travers la puce est la clé majeure pour le développement de circuits photoniques intégrés. Comparé à d'autres méthodes d’épitaxie, l’interdiffusion de puits quantiques a attiré beaucoup d'intérêt en raison de sa simplicité et son efficacité en accordant la bande interdite durant le processus de post-épitaxie. Cependant, l’interdiffusion de puits quantiques a subi des problèmes reliés au manque de précision pour modifier convenablement la bande interdite ciblée et à l’incontrôlabilité de l’absorption des impuretés au cours du processus qui peut dégrader la qualité du matériel interdiffusé. Dans cette thèse, nous avons utilisé les lasers excimer pour créer des défauts à proximité de la surface (~ 10 nm) des microstructures à base de puits quantiques III-V (par exemple InP et GaAs) et pour induire l’interdiffusion après le recuit thermique. L'irradiation par les lasers excimer (ArF et KrF) des microstructures à puits quantiques a été réalisée dans différents environnements, y compris l'air, l'eau déionisée, les couches diélectriques (SiO2 et Si3N4) et les couches d’InOx. Pour proposer un bon contrôle de la technique d’interdiffusion de puits quantiques par laser excimer, nous avons étudié la génération et la diffusion de défauts de surface en utilisant différentes méthodes de caractérisation de surface/interface, comme l'AFM, SEM, XPS et SIMS qui ont été utilisées pour analyser la modification de la morphologie de surface/interface et la modification chimique de la microstructure de ces puits quantiques. La qualité des microstructures à puits quantiques étudiées a été représentée par des mesures de photoluminescence et de luminescence des diodes lasers ainsi fabriqués. Les résultats montrent que le laser excimer induit des quantités d'oxydes de surface dans les surfaces des microstructure à puits quantiques InP/InGaAs/InGaAsP dans l'air et des impuretés d'oxygène des couches d'oxydes diffusées dans la région active de la microstructure lors du recuit, ce qui améliore l’interdiffusion, mais réduit l'intensité de la photoluminescence. Par contre, l’irradiation dans un environnement d'eau déionisée n’a pas démontré de diffusion des impuretés évidentes d'un excès d'oxygène vers les régions actives, mais la stœchiométrie de surface a été restaurée après l’interdiffusion. L’InOx a été trouvé avec un grand coefficient de dilatation thermique dans la microstructure interdiffusée qui était supposée d’augmenter la contrainte de compression dans la région active et ainsi d’augmenter l'intensité de photoluminescence de 10 fois dans l’échantillon irradié dans l'eau déionisée. Concernant les microstructures avec une couche diélectrique, la modification de la bande interdite a été toujours réalisée sur des échantillons dont les couches diélectriques ont été irradiées et la surface de InP a été modifiée par le laser excimer. Pour l'échantillon avec une couche de 243 nm de SiO2, les variations de la photoluminescence ont été mesurées sans l’ablation de cette couche de SiO2 lors de l'irradiation par le laser KrF. Cependant, la morphologie de l'interface d’InP a été modifiée, les oxydes d'interface ont été générés et les impuretés d'oxygène se sont diffusées à l'intérieur des surfaces irradiées. Les améliorations de l’interdiffusion dans les deux surfaces non irradiées et irradiés de l'échantillon couvert de couche d’InOx ont démontré l'importance des oxydes dans l’interdiffusion des puits quantiques. Les diodes laser fabriquées à partir d’un matériau interdiffusé par un laser KrF ont montré un seuil de courant comparable à celui des matériaux non interdiffusés avec un décalage de photoluminescence de 100 nm. En combinant un masque d'aluminium, nous avons créé un déplacement uniforme de photoluminescence de 70 nm sur une matrice rectangulaire de 40 μm x 200 μm ce qui présente un potentiel d’application de l’interdiffusion des puits quantiques par les lasers excimer dans les circuits photoniques intégrés. En outre, les lasers excimer ont été utilisés pour créer des structures de nano-cônes auto-organisées sur des surfaces de microstructure de InP/InGaAs/InGaAsP en augmentant l'intensité de PL par ~ 1.4 fois. Les lasers excimer ont été aussi utilisés pour modifier la mouillabilité sélective des zones d’une surface de silicium par une modification chimique de surface induite par laser dans différents milieux liquides. Ainsi, la fluorescence des nanosphères a été réussie pour des fonctions de configuration spécifique avec une surface de silicium. // Abstract : Photonic integrated circuits (PICs) which combine photonic devices for generation, detection, modulation, amplification, switching and transport of light on a chip have been reported as a significant technology innovation that simplifies optical system design, reduces space and power consumption, improves reliability. The ability of selective area modifying the bandgap for different photonic devices across the chip is the important key for PICs development. Compared with other growth methods, quantum well intermixing (QWI) has attracted amounts of interest due to its simplicity and effectiveness in tuning the bandgap in post-growth process. However, QWI has suffered problems of lack of precision in achieving targeted bandgap modification and uncontrollable up-taking of impurities during process which possibly degrade the quality of intermixed material. In this thesis, we have employed excimer laser to create surface defects in the near surface region (~ 10 nm) of III-V e.g. InP and GaAs, based QW microstructure and then annealing to induce intermixing. The irradiation by ArF and KrF excimer lasers on the QW microstructure was carried out surrounded by different environments, including air, DI water, dielectric layers (SiO2 and Si3N4) and InOx coatings. To propose a more controllable UV laser QWI technique, we have studied surface defects generation and diffusion with various surface/interface characterization methods, like AFM, SEM, XPS and SIMS, which were used to analyse the QW surface/interface morphology and chemical modification during QWI. The quality of processed QW microstructure was represented by photoluminescence measurements and luminescence measurements of fabricated laser diodes. The results shows that excimer laser induced amounts of surface oxides on the InP/InGaAs/InGaAsP microstructure surface in air and the oxygen impurities from oxides layer diffused to the active region of the QW microstructure during annealing, which enhance intermixing but also reduce the PL intensity. When irradiated in DI water environment, no obvious excessive oxygen impurities were found to diffuse to the active regions and the surface stoichiometry has been restored after intermixing. InOx with large coefficient of thermal expansion was found inside the intermixed QW microstructure, which was supposed to increase the compressive strain in active region and enhance the PL intensity to maximum 10 times on sample irradiated in DI water. On microstructure coated with dielectric layers, bandgap modifications were always found on samples whose dielectric layers were ablated and InP surface was modified by excimer laser. On sample coated with 243 nm SiO2 layer, the PL shifts were found on sample without ablation of the SiO2 layer when irradiated by KrF laser. However, the InP interface morphology was modified, interface oxides were generated and oxygen impurities have diffused inside on the irradiated sites. The enhancements of interdiffusion on both non irradiated and irradiated sites of sample coated with InOx layer have verified the importance of oxides in QWI. The laser diodes fabricated from KrF laser intermixed material have shown comparable threshold current density with as grown material with PL shifted by 133 nm. Combined aluminum mask, we have created uniform 70 nm PL shifts on 40 μm x 200 μm rectangle arrays which presents UV laser QWI potential application in PICs. In addition, excimer lasers have been used to create self organized nano-cone structures on the surface of InP/InGaAs/InGaAsP microstructure and enhance the PL intensity by ~1.4x. Excimer lasers have selective area modified wettability of silicon surface based on laser induced surface chemical modification in different liquid environments. Then the fluorescence nanospheres succeeded to specific pattern functions with silicon surface.

Abstract : Photonic Integrated Circuits (PIC) are of tremendous interest for photonics system in order to reduce their power consumption, size, fabrication cost and improve their reliability of fiber optics linked discrete component architecture. However, unlike for microelectronics, in photonics different heterostructures are required depending on the type of device (laser sources, detectors, modulators, passive waveguides…). Therefore photonics integration needs a technology able to produce multiple bandgap energy wafers with a suitable final material quality in a reproducible manner and at a competitive cost: a technological challenge that has not been completely solved yet. Quantum Well Intermixing (QWI) is a post growth bandgap tuning process based on the localized and controlled modification of quantum well composition profile that aims to address these matters. UV laser induced QWI (UV-Laser-QWI) relies on high power excimer laser to introduce point defects near the heterostructure surface. By adjusting the laser beam shape, position, fluence and the number of pulse delivered, the different regions to be intermixed can be defined prior to a rapid thermal annealing step that will activate the point defects diffusion across the heterostructure and generate quantum well intermixing. UV-LaserQWI presents the consequent advantage of allowing the patterning of multiple bandgap regions without relying on photolithographic means, thus offering potentially larger versatility and time efficiency than other QWI processes. UV-Laser-QWI reproducibility was studied by processing samples from an InGaAs/InGaAsP/InP 5 quantum well heterostructure emitting at 1.55 µm. 217 different sites on 12 samples were processed with various laser doses. The quantum well intermixing generated was then characterized by room temperature photoluminescence (PL) mapping. Under those experimental conditions, UV-Laser-QWI was able to deliver heterostructures with a PL peak wavelength blue shift controlled within a +/- 15 % range up to 101.5nm. The annealing temperature proved to be the most critical parameter as the PL peak wavelength in the laser irradiated areas varied at the rate of 1.8 nm per degree Celsius. When processing a single wafer, thus limiting the annealing temperature variations, the bandgap tuned regions proved to be deliverable within ± 7.9%, hence establishing the potential of UV-Laser-QWI as a reproducible bandgap tuning solution. The UV-Laser-QWI was used to produce multiple bandgap wafers for the fabrication of broad spectrum superluminescent diodes (SLD). Multiple bandgap energy profiles were tested and their influence on the SLDs’ performances was measured. The most favorable bandgap modifications for the delivery of a very broadband emitting SLD were analyzed, as well as the ones to be considered for producing devices with a flat top shaped spectrum. The intermixed SLDs spectra reached full width at half maximum values of 100 nm for a relatively flattop spectrum which compare favorably with the ≈ 40nm of reference devices at equal power. The light-intensity characteristics of intermixed material made devices were very close to the ones of reference SLD made from as-grown material which let us think that the alteration of material quality by the intermixing process was extremely limited. These results demonstrated that the suitability of UV-Laser-QWI for concrete application to photonic devices fabrication. Finally, an alternative laser QWI technique was evaluated for SLD fabrication and compared to the UV laser based one. IR-RTA relies on the simultaneous use of two IR laser to anneal local region of a wafer: a 980 nm laser diode coupled to a pigtailed fiber for the wafer background heating and a 500 µm large beam TEM 00 Nd:YAG laser emitting at 1064 nm to anneal up to intermixing temperature a localized region of the wafer. The processed samples exhibited a 33 % spectral width increase of the spectrum compare to reference device at equal power of 1.5 mW. However, the PL intensity was decreased by up to 60 % in the intermixed regions and the experiments proved the difficulty to avoid these material degradations of material quality with IR-RTA. / Résumé : L’intégration de circuit photonique vise à réduire la consommation énergétique, la taille, le coût et les risques de panne des systèmes photoniques traditionnels faits de composants distincts connectés par fibre optique. Cependant, contrairement à la microélectronique, des hétérostructures spécifiques sont requises pour chaque composant : lasers, détecteurs, modulateurs, guides d’ondes… De cette constatation découle le besoin d’une technologie capable de produire des gaufres d’hétérostructures III/V de qualité à plusieurs énergies de gap, et ce de façon reproductible pour un coût compétitif. Aucune des techniques actuelles ne répond pour l’instant pleinement à tous ces impératifs. L’interdiffusion de puits quantique (IPQ) est un procédé post épitaxie basé sur la modification locale de la composition des puits quantiques. L’IPQ induite par laser UV (IPQ-UV) est basée sur l’utilisation de laser excimer (Argon-Fluor émettant à 193 nm ou Krypton-Fluor à 248 nm) pour introduire des défauts ponctuels à la surface de l’hétérostructure. En ajustant la taille du faisceau, sa position, son énergie ainsi que le nombre d’impulsions laser délivrées à la surface du matériau, on peut définir les régions à interdiffuser ainsi que leur futur degré d’interdiffusion. Un recuit de la gaufre active ensuite la diffusion des défauts et par conséquent l’interdiffusion du puits. L’IPQ-UV présente l’avantage considérable de se passer de photolithographie pour définir les zones de différentes énergies de gap, diminuant ainsi la durée et potentiellement le coût du procédé. La reproductibilité de l’IPQ-UV a été étudiée pour l’interdiffusion d’une structure à 5 puits quantiques d’InGaAs/InGaAsP/InP émettant à 1.55 µm. 217 régions sur 12 échantillons ont été irradiés par un laser KrF avec des nombres d’impulsion variables selon les sites et avec une densité d’énergie constante de 155 mJ/cm². Les modifications de la structure générée par ce traitement furent ensuite mesurées par cartographie en photoluminescence (PL) à température ambiante. L’analyse des données montra que l’IPQ-UV permet un contrôle du décalage vers le bleu du pic de PL à +/- 15 % jusqu’à 101.5nm. La température du recuit est apparue comme le paramètre crucial du procédé, puisque la longueur d’onde du pic de PL des zones interdiffusées varie de 1.8 nm par degré Celsius. En considérant les sites irradiés sur une seule gaufre, c’est à dire en s’affranchissant des variations de température entre deux recuits de notre système, la variation du pic de PL est contrôlable dans une plage de ± 7.9%. Ces résultats démontrent le potentiel de l’IPQ-UV en tant que procédé reproductible de production de gaufre à plusieurs énergies de gap. L’IPQ-UV a été utilisé pour la fabrication de diodes superluminescentes (DSLs). Différents type de structure à énergie de gap multiple ont été testés et leurs influences sur les performances spectrales des diodes évalués. Les spectres des DSLs faites de matériau interdiffusé ont atteint des largeurs à mi-hauteur dépassant les 100 nm (jusqu’à 132 nm), ce qui est une amélioration conséquente des ≈ 40nm des DSLs de référence à puissance égale. Les caractéristiques intensité–courant des DSLs interdiffusés furent mesurées comme étant très proches de celle des dispositifs de référence faits de matériau brut, ce qui suggère que l’IPQ-UV n’a pas ou très peu altéré la qualité du matériau initial. Ces résultats prouvent la capacité de l’IPQ-UV à être utilisé pour la fabrication de dispositifs photoniques. Une technique alternative d’IPQ par laser a été évaluée et comparée à l’IPQ-UV pour la fabrication de DSL. Le recuit rapide par laser IR est basé sur l’utilisation simultanée de deux lasers IR pour chauffer localement l’hétérostructure jusqu’à une température suffisante pour provoquer l’interdiffusion: une diode laser haute puissante émettant à 980 nanomètre couplée dans une fibre chauffe la face arrière de la gaufre sur une large surface à une température restant inférieure à celle requise pour provoquer l’interdiffusion et un laser Nd:YAG TEM 00 émettant à 1064 nm un faisceau de 500 µm de large provoque une élévation de température additionnelle localisée à la surface de l’échantillon, permettant ainsi l’interdiffusion de l’hétérostructure. Les dispositifs fabriqués ont montré une augmentation de 33 % de la largeur à mi-hauteur du spectre émis à puissance égale de 1.5 mW. Cependant, l’intensité du pic de PL dans les zones interdiffusées est diminuée de 60 %, suggérant une dégradation du matériau et la difficulté à produire un matériau de qualité satisfaisante.

The control of cell adhesion to synthetic polymers is a key factor in tissue engineering, resting on the ability to direct specific cell types to adhere and proliferate in order to stimulate tissue reconstruction. But often the surface properties are compromised for the sake of the bulk properties, leading to surfaces that do not support sufficiently the level of bioactivity required and accordingly the polymeric biomaterial will fail clinically. Laser treatment offers a unique means of enhancing the osteoblast cell response of the surface of a polymeric biomaterial, whilst keeping the already sufficient bulk properties intact. To this end, infra-red (IR) and ultraviolet (UV) lasers have been employed to modify the wettability characteristics of nylon 6,6, as wetting is often the primary factor dictating the adhesion and bonding potential of materials, as a route to enhancing the surface in terms of osteoblast cell response. What is more, modifying wettability characteristics in this way is a highly attractive means of estimating the biofunctionality of a polymer. IR (CO2) and UV (F2 and KrF excimer) lasers were employed to carry out two different processes: laser whole area irradiative processing and laser-induced patterning. With both CO2 and the excimer lasers changes in the wettability characteristics could be effected with subsequent enhancement of osteoblast cell response. This was also the case with both laser-induced patterning and laser whole area irradiative processing. Essentially, an approach has been established whereby the osteoblast cell response on the surfaces of laser treated nylon 6,6 can be predicted through the laser-induced wettability characteristics modification, particularly for the laser whole area irradiative processed nylon 6,6. This ultimately allows one to determine the osteoblast cell response of the laser surface treated nylon 6,6 surfaces directly from the laser operating parameters. In concurrence with established wetting theory the laser whole area irradiative processing of the nylon 6,6 surfaces caused increased surface roughness, increased surface oxygen content, increased polar component, γP , and increased total surface energy, γT ; thereby generating surfaces displaying reduced contact angle, θ, making the nylon 6,6 surfaces more hydrophilic. The laser-induced patterned samples differed from current theory insofar as the nylon 6,6 surfaces became less hydrophilic due to an increase in θ despite an increase in surface roughness, an increase in surface oxygen content, an increase in γP and an increase in γT . This phenomena can be explained by the transition in wetting regimes from a Wenzel regime to a mixed-state wetting regime. Nevertheless, collation of the wettability characteristics results revealed that θ was a strong correlative decreasing function of both γP and γT , indicating that surface energy played a large role in determining the wetting nature of the nylon 6,6. It was found that for all laser whole area irradiative processed nylon 6,6 surfaces the osteoblast cell response was an increasing correlative and therefore predictive function of θ and was a decreasing function of γP . To an extent, the surface oxygen content and surface roughness could be used indirectly to foretell the osteoblast cell response of the nylon 6,6 surfaces. This is on account of the CO2 and KrF excimer laser whole area irradiative processing bringing about increased surface toxicity, which above a certain level hindered the osteoblast cell response. For the laser-induced patterned nylon 6,6 samples there did not appear to be any particular correlative trend between the modified surface parameters and osteoblast cell response. This can be accounted for by the transition in wetting regimes. Another important factor is that cell morphologies were modulated over all samples which suggests that varying surface parameters on account of laser surface treatment gave rise to variations in cell signaling. It was determined that θ, γP and γT all had very strong correlative relationships with the cytotoxicity. The cytotoxicity reduced upon an increase in θ until a minimum constant was achieved, whereas the cytotoxicity remained constant at low γP and γT until a point at which the cytotoxicity began to increase. These results are noteworthy as they allow one to deduce that, with constant cytotoxicity levels, the osteoblast cell response appeared to be modulated by the wettability characteristics. But once the cytotoxicity increased, the toxicity began to dominate and so negated the identified positive wettability characteristic correlations with osteoblast cell response. Practically, the surface roughness and surface oxygen content could be implemented indirectly to estimate the cytotoxicity. Increase in cytotoxicity was the result of the laser processing with higher fluences generating excessive melting. As a result of this, it is possible to deduce that there was a maximum threshold fluence, beyond which the toxicity of the nylon 6,6 began to dominate, giving rise to a less enhanced osteoblast cell response. On account of the correlative trends which have been identified between the laser surface treatment, wettability characteristics and osteoblast cell response of nylon 6,6 it is likely for one to have the ability to estimate the osteoblast cell response in vitro. This is significant as it indicates that laser surface modification of polymeric materials could have tremendous potential for application within the field of regenerative medicine.

Biobased materials made from renewable resources, such as wood, play an important role in the sustainable development of society. One main challenge of biobased building materials is their inherent moisture sensitivity, a major cause for fungal decay, mold growth and dimensional instability, resulting in decreased service life as well as costly maintenance. A new building material known as wood-plastic composites (WPCs) has emerged. WPCs are a combination of a thermoplastic matrix and a wood component, the former is usually recycled polyethylene or polypropylene, and the latter a wood processing residual, e.g. sawdust and wood shavings. The objective of this thesis was to gain more insight about characteristics of WPCs containing a modified wood component. The hypothesis was that a modified wood component in WPCs would increase the moisture resistance and durability in outdoor applications. The study comprises both injection molded and extruded WPC samples made with an unmodified, acetylated, thermally modified or furfurylated wood component in a polypropylene (PP), high density polyethylene (HDPE), cellulose ester (CAP, a cellulose ester containing both acetate and propionate substituents) or polylactate (PLA) matrix. The WPCs were prepared with 50-70 weight-% wood. The emphasis was on studying the moisture sorption, fungal resistance and micromorphological features of these new types of composites. Water sorption in both liquid and vapor phases was studied, and the biological performance was studied both in laboratory and in long term outdoor field tests. Micromorphological features were assessed by analyzing of the wood component prior to and after processing, and by studying the composite microstructure by means of a new sample preparation technique based on UV excimer laser ablation combined with scanning electron microscopy (SEM). Results showed that the WPCs with a modified wood component had a distinctly lower hygroscopicity than the WPCs with unmodified wood, which resulted in less wood-plastic interfacial cracks when subjected to a moisture soaking-drying cycle. Durability assessments in field and marine tests showed that WPCs with PP or CAP as a matrix and 70 weight-% unmodified wood degraded severely within a few years, whereas the corresponding WPCs with a modified wood component were sound after 7 years in field tests and 6 years in marine tests. Accelerated durability tests of WPCs with PLA as a matrix showed only low mass losses due to decay. However, strength losses due to moisture sorption suggest that the compatibility between the PLA and the different wood components must be improved. The micromorphological studies showed that WPC processing distinctly reduces the size and changes the shape of the wood component. The change was most pronounced in the thermally modified wood component which became significantly reduced in size. The disintegration of the modified wood components during processing also creates a more homogeneous micromorphology of the WPCs, which may be beneficial from a mechanical performance perspective. Future studies are suggested to include analyses of the surface composition, the surface energy and the surface energy heterogeneity of both wood and polymer components in order to tailor new compatible wood-polymer combinations in WPCs and biocomposites. / <p>QC 20121119</p>

This Thesis presents the synthesis, characterization and mechanistic explorations into a series of diphenylacetylene-containing oligoester ion channels. Eighteen final compounds were synthesized and tested for ion transport activity utilizing both vesicle and planar bilayer assays. The oligomers varied in length, hydrophobicity and the nature of the aromatic moiety. Compounds incorporating a modified diphenylacetylene (‘Dip’), or a novel phenyl-extended fluorophore (‘Trip’) were made using a reliable, modular synthesis. The final compounds were prepared in a total of 5 to 11 steps from commercial materials in yields ranging from 10 to 40%. The compounds’ activity varied considerably; both highly active and completely inactive compounds were discovered. The differences in activity are controlled by structure via the influence of structural variables on the aqueous phase aggregation and the ability of the compound to insert into the bilayer membrane. These structure-activity studies uncovered two highly-active ion transporters, HO2C-Hex-Dip-Hex-Hex-OH and –OPO32- (Hex = 6-hydroxyhexanoyl) which exhibited activity almost 10-fold higher than the fully-saturated oligoesters developed in previous work. In some cases, the transport activity is initially high but declines over a period of 20-30 minutes following compound addition. This suggests that the compound slowly transitions to an environment where it cannot form active channels. In the bilayer clamp, a variety of behaviours including highly-conducting openings were observed. An apparent voltage-gated response was exhibited by one of the Trip compounds (HO2C-Trip-G(E3)-OH), a property rarely seen for synthetic ion channels. The Dip and Trip molecules exhibited environment-sensitive fluorescence. The observed Dip excimer-like emission is the second reported instance of this in solution. The Trip compounds are solvatochromic; this property was used to infer their location in the membrane. Partitioning into the membrane was followed by a blue-shifting and increased intensity of the fluorescence emission for both series of compounds. For the Trip isomers, which are significantly more emissive than the Dip molecules, this enhancement in intensity could be visualized by eye. For the Dip oligomers, the excimer emission is a broad band with variable shape and intensity; it is time-dependent under some conditions. The excimer emission has a sub-nanosecond lifetime in homogenous solution that is significantly prolonged in the presence of vesicle bilayers, in which a number of lifetimes could be detected. Both monomer and excimer emissions can be quenched by aqueous copper, the excimer emission is more efficiently quenched than is the monomer. The photophysical characteristics of these molecules allowed for a variety of experiments designed to probe their membrane partitioning and localization behaviours. The results indicate the formation of a complex mixture of interconverting monomeric and aggregate species as the compounds move from water to the bilayer. The slow evolution of the mixture is consistent with the times noted for loss of membrane activity in transport assays. From these data a new model that describes the transport process is proposed. The key feature of this model is that transport must occur via a species that forms quickly upon the mixing of the components. Possible structures of the intermediates formed are discussed. / Graduate

Η εξέλιξη που γνώρισε το laser κατά τα χρόνια που πέρασαν μέχρι σήμερα είναι ραγδαία και θεαματική. Οι καταπληκτικές ιδιότητες του γοήτεψαν τόσο τους ερευνητές όσο και τους εκπροσώπους της βιομηχανίας και της τεχνολογίας. Τα laser αερίου ενεργού μέσου αποτελούν την πλειοψηφία των βιομηχανικών laser. Ένας τύπος αυτών είναι τα excimer laser τα οποία αποτελούν τα πιο ισχυρά laser στην υπεριώδη UV φασματική περιοχή. Το excimer (ή ακριβεστερα exciplex) laser XeCl αποτελεί αντικείμενο της παρούσας διπλωματικής εργασίας και περιλαμβάνει τα εξής μέρη: a. Συνοπτική παρουσίαση των βασικών αρχών λειτουργίας ενός laser b. Γενική παρουσίαση των Excimer laser αλλά και του laser XeCl c. Γενικές παρατηρήσεις στη μοντελοποίηση ενός excimer d. Παρουσίαση ενός απλού θεωρητικού μοντέλου για το laser XeCl e. Παρουσίαση και αξιολόγηση της υπολογιστικής μεθόδου και των αποτελεσμάτων της. Για τη μηδενικής διάστασης αριθμητική προσέγγιση αναπτύσσεται μία υπολογιστική μέθοδος επίλυσης. Η ίδια η μέθοδος στηρίζεται σε εξομοίωση που πραγματοποιήθηκε με χρήση του πακέτου λογισμικού Matlab 7.0. Τέλος, γίνεται έλεγχος της εξάρτησης της ισχύος και σύγκριση των αποτελεσμάτων, όπου αυτό είναι δυνατό. / -

In the present research, a novel method, namely sol-gel/laser-induced technique (SGLIT), has been developed to generate nano-structured TiO2-based films. The TiO2 films based on unloaded (pure) TiO2, Ce-TiO2, W-TiO2 and Ag-TiO2, have been investigated in attempt to stabilise the formation of anatase and consequently of enhancing photo-catalytic and anti-bacterial activities. The TiO2 precursor loaded with Ce2+, W6+ and Ag2+ ions (Ce-TiO2, W-TiO2 and Ag-TiO2) were separately prepared by sol-gel method and spin-coated on microscopic glass slides. A pulsed KrF excimer laser with a wavelength of 248 nm and pulse width of 13-20 ns was employed to irradiate on the sol-gel prepared films at various operating parameters, in terms of laser fluence, number of laser pulses and repetition rate. The work has been focussed on microstructural characterisation of various films prepared by both SGLIT and furnace, in the consideration of crystallographic structure, phase transformation, crystallite sizes, surface morphology, film thickness and optical properties, by means of Raman spectroscopy, XRD, FEG-SEM/EDX, TEM/HR-TEM/EDX, AFM and UV-Vis spectroscopy etc. The results showed that nano-crystallisation of the films after laser irradiation has been achieved, with controllable amount of anatase formation. These coatings presented a unique feature of surface morphology with meso-porosity and much enlarged surface areas, compared with the films prepared by furnace sintering technique. The addition of Ce and Ag, stabilized the anatase structure during the laser irradiations, whereas the addition of W destabilized the anatase structure. The Ce-TiO2 films prepared by SGLIT exhibited anatase structure which was stable up to 500 laser pulses at 35 mJ cm-2 fluence. The anatase was formed after 10 laser pulses only at 65-75 mJ cm-2 fluence in the W-TiO2 films. When a higher number of laser pulses, fluence or higher W6+ loading were chosen, rutile structure started to form. On the other hand, the Ag-TiO2 nano-composite films prepared by SGLIT presented the anatase up to 200 laser pulses at 85 mJ cm-2 fluence. On average, anatase crystallite size of about 38 nm was achieved from both the W-TiO2 and Ag-TiO2 films prepared by SGLIT. In contrast, the furnace-sintered W-TiO2 and Ag-TiO2 films produced anatase crystallite size of 49.4 nm and 29.8 nm respectively. Another achievement of the present research is the development of a single-step laser irradiation technique to generate an Ag-TiO2 nano-composite film on the glass substrate. A pulsed laser beam produced hexagonal Ag nanoparticles along with the crystallization of anatase-based nano-structured TiO2 film which was accomplished in 1 µs only. The films prepared by SGLIT displayed a higher photo-absorption compared to their furnace-sintered counterparts due to the unique surface features with a higher surface roughness. Overall, an enhanced bactericidal activity against E. coli cells was demonstrated under UV light by each of the W-TiO2 films compared to furnace-sintered films except the 1W-TiO2. The E. coli cells did not survive on the W-TiO2 films prepared by SGLIT, after 80 minutes under UV (365 nm) light. In contrast, E. coli cells still survived on the surface of furnace-sintered W-TiO2 films under the same conditions. Ag-TiO2 nano-composite films prepared by SGLIT, demonstrated an enhanced anti-bacterial activity against E. coli compared to the conventionally- made Ag-TiO2 films. No bacteria survived on the Ag-TiO2 films prepared by 50 laser pulses at 85 mJ cm-2 fluence, whereas E. coli colonies always survived on the furnace-sintered Ag-TiO2 films under the UV, natural light and the dark room conditions.

High strength 7xxx aluminium alloys are used extensively in the aerospace industry because the alloys offer excellent mechanical properties. Unfortunately, the alloys can suffer localised corrosion due to the presence of large intermetallic particles at the alloy surface that are aligned in the rolling direction. Laser surface melting (LSM) techniques offer the potential to reduce and/or to eliminate the intermetallic phases from the surface of the alloy without affecting the alloy matrix.The present study concerns the application of LSM using an excimer laser to enhance the corrosion resistance of AA 7075-T6 aluminium alloy. The initial stage of the project was aimed at optimising the laser conditions for production of a uniform microstructure, with the increase in the corrosion resistance of the alloy being determined by potentiodynamic polarization measurements in sodium chloride solution. Low and high laser energy densities were used with a different number of pulses per unit area to treat the alloy surface, which were achieved by changing both the laser fluence and the pulse repetition frequency. A laser fluence of 3.3 J/cm2 with 80 pulses was subsequently selected as the optimum condition to treat the surface of the alloy. The composition and microstructure of the alloy before and after LSM treatment, and following corrosion tests, were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).After the laser treatment, the surface and the cross-sections of the alloy showed a significant reduction in the number of large intermetallic particles and a relatively homogenous melted layer was generated that provided significant improvement in the resistance of the alloy against corrosion, as assessed by several corrosion test methods, including exfoliation corrosion (EXCO) tests. However, delamination of the melted layer was observed after extended testing in the EXCO solution which is possibly related to the formation of bands of fine magnesium and zinc-rich precipitates within the melted layer. Therefore, anodising in sulphuric acid was applied to the LSM alloy, in order to further increase the corrosion resistance and to protect the laser treated layer from delamination by generating a thin oxide film over the LSM layer. The results revealed that the anodic treatment increased the resistance of the alloy to exfoliation attack.