Diagnostic studies of species concentrations in a capacitively coupled RF plasma containing CH4-H2-Ar

Three plasma diagnostic methods, tunable infrared diode laser absorption spectroscopy, optical emission spectroscopy and microwave interferometry have been used to monitor concentrations of transient and stable molecules, CH3, CH4, C2H2, C2H6, and of electrons in capacitively coupled CH4-H-2-Ar radiofrequency (RF) plasmas (f(RF) = 13.56 MHz, p = 100 Pa, phi (total)= 66 sccm) for various discharge power values (P = 10-100 W) and gas mixtures. The degree of dissociation of the methane precursor varied between 3% and 60%. The methyl radical concentration was found to be in the order of 10(12) molecules cm(-3) and the electron concentration in the order of loll cm(-3). The methyl radical concentration and the concentrations of the stable C-2 hydrocarbons, C2H2 and C2H6, produced in the plasma, increased with discharge power. The fragmentation rates of the methane precursor and conversion rates to the measured C-2 hydrocarbons were estimated in dependence on discharge power. Radial distributions of the electron and methyl radical concentrations, and of the gas temperature were measured for the first time simultaneously in the plasma region between the discharge electrodes. The measurements allow us to draw qualitative conclusions on the main chemical processes and the plasma chemical reaction paths.

Visualization of water vapour flow in a packed bed adsorber by near-infrared diffused transmittance tomography

This work presents a procedure based on spatially-resolved near-infrared imaging, in order to observe temperature and composition maps in gas-solid packed beds subjected to effects of aspect ratio and non-isothermal conditions. The technique was applied to the water vapour flow in a packed bed adsorber of low aspect ratio, filled with silica gel, using a tuneable diode laser, focal planar array detector and tomographic reconstruction. The 2D projected images from parallel scanning permitted data to be retrieved from the packing and above the packing sections of 12.0×12.0×18.2mm at a volume-resolution of 0.15×0.15×0.026mm and a time-resolution of less than 3min. The technique revealed uneven temperature and composition maps in the core packed bed and in the vicinity of the wall due to flow maldistribution. In addition, the heat uptake from the packed bed and local cross-mixing were experimentally ascertained by local profiles of the water vapour composition and temperature under various aspect ratios and feed flow rates. The relative deviations in temperature and compositions were 11.1% and 9.3%, respectively. The deviation in composition, which covers the packing and above the packing sections, was slightly higher than the deviation of 8% obtained up-to-date but was limited to the exit of a packed bed adsorber. © 2011.

Analyse quantitative des cyanotoxines d'eau douce par LDTD-APCI-MS/MS

Avec la hausse mondiale de la fréquence des floraisons de cyanobactéries (CB), dont certaines produisent des cyanotoxines (CT), le développement d’une méthode de détection/quantification rapide d’un maximum de CT s’impose. Cette méthode permettrait de faire un suivi quotidien de la toxicité de plans d’eau contaminés par des CB et ainsi d’émettre rapidement des avis d’alerte appropriés afin de protéger la santé publique. Une nouvelle technologie utilisant la désorption thermique induite par diode laser (LDTD) couplée à l’ionisation chimique sous pression atmosphérique (APCI) et reliée à la spectrométrie de masse en tandem (MS/MS) a déjà fait ses preuves avec des temps d'analyse de l’ordre de quelques secondes. Les analytes sont désorbés par la LDTD, ionisés en phase gazeuse par APCI et détectés par la MS/MS. Il n’y a donc pas de séparation chromatographique, et la préparation de l’échantillon avant l’analyse est minimale selon la complexité de la matrice contenant les analytes. Parmi les quatre CT testées (microcystine-LR, cylindrospermopsine, saxitoxine et anatoxine-a (ANA-a)), seule l’ANA-a a généré une désorption significative nécessaire au développement d’une méthode analytique avec l’interface LDTD-APCI. La forte polarité ou le poids moléculaire élevé des autres CT empêche probablement leur désorption. L’optimisation des paramètres instrumentaux, tout en tenant compte de l’interférence isobarique de l’acide aminé phénylalanine (PHE) lors de la détection de l’ANA-a par MS/MS, a généré une limite de détection d’ANA-a de l’ordre de 1 ug/L. Celle-ci a été évaluée à partir d’une matrice apparentée à une matrice réelle, démontrant qu’il serait possible d’utiliser la LDTD pour effectuer le suivi de l’ANA-a dans les eaux naturelles selon les normes environnementales applicables (1 à 12 ug/L). Il a été possible d’éviter l’interférence isobarique de la PHE en raison de sa très faible désorption avec l’interface LDTD-APCI. En effet, il a été démontré qu’une concentration aussi élevée que 500 ug/L de PHE ne causait aucune interférence sur le signal de l’ANA-a.

Développement d’une nouvelle méthode d’analyse multi-résidus par LDTD/APCI-MS/MS pour la quantification de pesticides et de produits pharmaceutiques dans les eaux usées

Une nouvelle méthode d'extraction en phase solide (SPE) couplée à une technique d'analyse ultrarapide a été développée pour la détermination simultanée de neuf contaminants émergents (l'atrazine, le déséthylatrazine, le 17(béta)-estradiol, l'éthynylestradiol, la noréthindrone, la caféine, la carbamazépine, le diclofénac et le sulfaméthoxazole) provenant de différentes classes thérapeutiques et présents dans les eaux usées. La pré-concentration et la purification des échantillons a été réalisée avec une cartouche SPE en mode mixte (Strata ABW) ayant à la fois des propriétés échangeuses de cations et d'anions suivie d'une analyse par une désorption thermique par diode laser/ionisation chimique à pression atmosphérique couplée à la spectrométrie de masse en tandem (LDTD-APCI-MS/MS). La LDTD est une nouvelle méthode d'introduction d'échantillon qui réduit le temps total d'analyse à moins de 15 secondes par rapport à plusieurs minutes avec la chromatographie liquide couplée à la spectrométrie de masse en tandem traditionnelle (LC-MS/MS). Plusieurs paramètres SPE ont été évalués dans le but d'optimiser l'efficacité de récupération lors de l'extraction des analytes provenant des eaux usées, tels que la nature de la phase stationnaire, le débit de chargement, le pH d'extraction, le volume et la composition de la solution de lavage et le volume de l'échantillon initial. Cette nouvelle méthode a été appliquée avec succès à de vrais échantillons d'eaux usées provenant d'un réservoir de décantation primaire. Le recouvrement des composés ciblés provenant des eaux usées a été de 78 à 106%, la limite de détection a été de 30 à 122 ng L-1, alors que la limite de quantification a été de 88 à 370 ng L-1. Les courbes d'étalonnage dans les matrices d'eaux usées ont montré une bonne linéarité (R2 > 0,991) pour les analytes cibles ainsi qu’une précision avec un coefficient de variance inférieure à 15%.

Analyse par spectrométrie de masse d’hormones stéroïdiennes dans les eaux usées et abattement par oxydation chimique

Thèse réalisée en cotutelle avec Michèle Prévost (Ph.D), Professeure titulaire au département des génies civil, géologique et des mines de l'École Polytechnique de Montréal.

Nouvelles stratégies pour l’analyse des cyanotoxines par spectrométrie de masse

Les cyanobactéries ont une place très importante dans les écosystèmes aquatiques et un nombre important d’espèces considéré comme nuisible de par leur production de métabolites toxiques. Ces cyanotoxines possèdent des propriétés très variées et ont souvent été associées à des épisodes d’empoisonnement. L’augmentation des épisodes d’efflorescence d’origine cyanobactériennes et le potentiel qu’ils augmentent avec les changements climatiques a renchéri l’intérêt de l’étude des cyanobactéries et de leurs toxines. Considérant la complexité chimique des cyanotoxines, le développement de méthodes de détection simples, sensibles et rapides est toujours considéré comme étant un défi analytique. Considérant ces défis, le développement de nouvelles approches analytiques pour la détection de cyanotoxines dans l’eau et les poissons ayant été contaminés par des efflorescences cyanobactériennes nuisibles a été proposé. Une première approche consiste en l’utilisation d’une extraction sur phase solide en ligne couplée à une chromatographie liquide et à une détection en spectrométrie de masse en tandem (SPE-LC-MS/MS) permettant l’analyse de six analogues de microcystines (MC), de l’anatoxine (ANA-a) et de la cylindrospermopsine (CYN). La méthode permet une analyse simple et rapide et ainsi que la séparation chromatographique d’ANA-a et de son interférence isobare, la phénylalanine. Les limites de détection obtenues se trouvaient entre 0,01 et 0,02 μg L-1 et des concentrations retrouvées dans des eaux de lacs du Québec se trouvaient entre 0,024 et 36 μg L-1. Une deuxième méthode a permis l’analyse du b-N-méthylamino-L-alanine (BMAA), d’ANA-a, de CYN et de la saxitoxine (STX) dans les eaux de lac contaminés. L’analyse de deux isomères de conformation du BMAA a été effectuée afin d’améliorer la sélectivité de la détection. L’utilisation d’une SPE manuelle permet la purification et préconcentration des échantillons et une dérivatisation à base de chlorure de dansyle permet une chromatographie simplifiée. L’analyse effectuée par LC couplée à la spectrométrie de masse à haute résolution (HRMS) et des limites de détections ont été obtenues entre 0,007 et 0,01 µg L-1. Des échantillons réels ont été analysés avec des concentrations entre 0,01 et 0,3 µg L-1 permettant ainsi la confirmation de la présence du BMAA dans les efflorescences de cyanobactéries au Québec. Un deuxième volet du projet consiste en l’utilisation d’une technologie d’introduction d’échantillon permettant des analyses ultra-rapides (< 15 secondes/échantillons) sans étape chromatographique, la désorption thermique à diode laser (LDTD) couplée à l’ionisation chimique à pression atmosphérique (APCI) et à la spectrométrie de masse (MS). Un premier projet consiste en l’analyse des MC totales par l’intermédiaire d’une oxydation de Lemieux permettant un bris de la molécule et obtenant une fraction commune aux multiples congénères existants des MC. Cette fraction, le MMPB, est analysée, après une extraction liquide-liquide, par LDTD-APCI-MS/MS. Une limite de détection de 0,2 µg L-1 a été obtenue et des concentrations entre 1 et 425 µg L-1 ont été trouvées dans des échantillons d’eau de lac contaminés du Québec. De plus, une analyse en parallèle avec des étalons pour divers congénères des MC a permis de suggérer la possible présence de congénères ou d’isomères non détectés. Un deuxième projet consiste en l’analyse directe d’ANA-a par LDTD-APCI-HRMS pour résoudre son interférence isobare, la phénylalanine, grâce à la détection à haute résolution. La LDTD n’offre pas de séparation chromatographique et l’utilisation de la HRMS permet de distinguer les signaux d’ANA-a de ceux de la phénylalanine. Une limite de détection de 0,2 µg L-1 a été obtenue et la méthode a été appliquée sur des échantillons réels d’eau avec un échantillon positif en ANA-a avec une concentration de 0,21 µg L-1. Finalement, à l’aide de la LDTD-APCI-HRMS, l’analyse des MC totales a été adaptée pour la chair de poisson afin de déterminer la fraction libre et liée des MC et comparer les résultats avec des analyses conventionnelles. L’utilisation d’une digestion par hydroxyde de sodium précédant l’oxydation de Lemieux suivi d’une purification par SPE a permis d’obtenir une limite de détection de 2,7 µg kg-1. Des échantillons de poissons contaminés ont été analysés, on a retrouvé des concentrations en MC totales de 2,9 et 13,2 µg kg-1 comparativement aux analyses usuelles qui avaient démontré un seul échantillon positif à 2 µg kg-1, indiquant la possible présence de MC non détectés en utilisant les méthodes conventionnelles.

Analyse par spectrométrie de masse des antibiotiques vétérinaires liés à l’élevage porcin

L’élevage des porcs représente une source importante de déversement d’antibiotiques dans l’environnement par l’intermédiaire de l’épandage du lisier qui contient une grande quantité de ces molécules sur les champs agricoles. Il a été prouvé que ces molécules biologiquement actives peuvent avoir un impact toxique sur l’écosystème. Par ailleurs, elles sont aussi suspectées d’engendrer des problèmes sanitaires et de contribuer à la résistance bactérienne pouvant mener à des infections difficilement traitables chez les humains. Le contrôle de ces substances dans l’environnement est donc nécessaire. De nombreuses méthodes analytiques sont proposées dans la littérature scientifique pour recenser ces composés dans plusieurs types de matrice. Cependant, peu de ces méthodes permettent l’analyse de ces contaminants dans des matrices issues de l’élevage agricole intensif. Par ailleurs, les méthodes analytiques disponibles sont souvent sujettes à des faux positifs compte tenu de la complexité des matrices étudiées et du matériel utilisé et ne prennent souvent pas en compte les métabolites et produits de dégradation. Enfin, les niveaux d’analyse atteints avec ces méthodes ne sont parfois plus à jour étant donné l’évolution de la chimie analytique et de la spectrométrie de masse. Dans cette optique, de nouvelles méthodes d’analyses ont été développées pour rechercher et quantifier les antibiotiques dans des matrices dérivées de l’élevage intensif des porcs en essayant de proposer des approches alternatives sensibles, sélectives et robustes pour quantifier ces molécules. Une première méthode d’analyse basée sur une technique d’introduction d’échantillon alternative à l’aide d’une interface fonctionnant à l’aide d’une désorption thermique par diode laser munie d’une source à ionisation à pression atmosphérique, couplée à la spectrométrie de masse en tandem a été développée. L’objectif est de proposer une analyse plus rapide tout en atteignant des niveaux de concentration adaptés à la matrice étudiée. Cette technique d’analyse couplée à un traitement d’échantillon efficace a permis l’analyse de plusieurs antibiotiques vétérinaires de différentes classes dans des échantillons de lisier avec des temps d’analyse courts. Les limites de détection atteintes sont comprises entre 2,5 et 8,3 µg kg-1 et sont comparables avec celles pouvant être obtenues avec la chromatographie liquide dans une matrice similaire. En vue d’analyser simultanément une série de tétracyclines, une deuxième méthode d’analyse utilisant la chromatographie liquide couplée à la spectrométrie de masse à haute résolution (HRMS) a été proposée. L’utilisation de la HRMS a été motivée par le fait que cette technique d’analyse est moins sensible aux faux positifs que le triple quadripôle traditionnel. Des limites de détection comprises entre 1,5 et 3,6 µg kg-1 ont été atteintes dans des échantillons de lisier en utilisant un mode d’analyse par fragmentation. L’utilisation de méthodes de quantifications ciblées est une démarche intéressante lorsque la présence de contaminants est suspectée dans un échantillon. Toutefois, les contaminants non intégrés à cette méthode d’analyse ciblée ne peuvent être détectés même à de fortes concentrations. Dans ce contexte, une méthode d’analyse non ciblée a été développée pour la recherche de pharmaceutiques vétérinaires dans des effluents agricoles en utilisant la spectrométrie de masse à haute résolution et une cartouche SPE polymérique polyvalente. Cette méthode a permis l’identification d’antibiotiques et de pharmaceutiques couramment utilisés dans l’élevage porcin. La plupart des méthodes d’analyse disponibles dans la littérature se concentrent sur l’analyse des composés parents, mais pas sur les sous-produits de dégradation. L’approche utilisée dans la deuxième méthode d’analyse a donc été étendue et appliquée à d’autres classes d’antibiotiques pour mesurer les concentrations de plusieurs résidus d’antibiotiques dans les sols et les eaux de drainage d’un champ agricole expérimental. Les sols du champ renfermaient un mélange d’antibiotiques ainsi que leurs produits de dégradation relatifs à des concentrations mesurées jusqu’à 1020 µg kg-1. Une partie de ces composés ont voyagé par l’intermédiaire des eaux de drainage du champ ou des concentrations pouvant atteindre 3200 ng L-1 ont pu être relevées.

Spectroscopic Investigation of Tooth Caries and Demineralization

Dental caries persists to be the most predominant oral disease in spite of remarkable progress made during the past half- century to reduce its prevalence. Early diagnosis of carious lesions is an important factor in the prevention and management of dental caries. Conventional procedures for caries detection involve visual-tactile and radiographic examination, which is considered as “gold standard”. These techniques are subjective and are unable to detect the lesions until they are well advanced and involve about one-third of the thickness of enamel. Therefore, all these factors necessitate the need for the development of new techniques for early diagnosis of carious lesions. Researchers have been trying to develop various instruments based on optical spectroscopic techniques for detection of dental caries during the last two decades. These optical spectroscopic techniques facilitate noninvasive and real-time tissue characterization with reduced radiation exposure to patient, thereby improving the management of dental caries. Nonetheless, a costeffective optical system with adequate sensitivity and specificity for clinical use is still not realized and development of such a system is a challenging task.Two key techniques based on the optical properties of dental hard tissues are discussed in this current thesis, namely laser-induced fluorescence (LIF) and diffuse reflectance (DR) spectroscopy for detection of tooth caries and demineralization. The work described in this thesis is mainly of applied nature, focusing on the analysis of data from in vitro tooth samples and extending these results to diagnose dental caries in a clinical environment. The work mainly aims to improve and contribute to the contemporary research on fluorescence and diffuse reflectance for discriminating different stages of carious lesions. Towards this, a portable and compact laser-induced fluorescence and reflectance spectroscopic system (LIFRS) was developed for point monitoring of fluorescence and diffuse reflectance spectra from tooth samples. The LIFRS system uses either a 337 nm nitrogen laser or a 404 nm diode laser for the excitation of tooth autofluorescence and a white light source (tungsten halogen lamp) for measuring diffuse reflectance.Extensive in vitro studies were carried out on extracted tooth samples to test the applicability of LIFRS system for detecting dental caries, before being tested in a clinical environment. Both LIF and DR studies were performed for diagnosis of dental caries, but special emphasis was given for early detection and also to discriminate between different stages of carious lesions. Further the potential of LIFRS system in detecting demineralization and remineralization were also assessed.In the clinical trial on 105 patients, fluorescence reference standard (FRS) criteria was developed based on LIF spectral ratios (F500/F635 and F500/F680) to discriminate different stages of caries and for early detection of dental caries. The FRS ratio scatter plots developed showed better sensitivity and specificity as compared to clinical and radiographic examination, and the results were validated with the blindtests. Moreover, the LIF spectra were analyzed by curve-fitting using Gaussian spectral functions and the derived curve-fitted parameters such as peak position, Gaussian curve area, amplitude and width were found to be useful for distinguishing different stages of caries. In DR studies, a novel method was established based on DR ratios (R500/R700, R600/R700 and R650/R700) to detect dental caries with improved accuracy. Further the diagnostic accuracy of LIFRS system was evaluated in terms of sensitivity, specificity and area under the ROC curve. On the basis of these results, the LIFRS system was found useful as a valuable adjunct to the clinicians for detecting carious lesions.

Photothermal Investigations on Certain Plasma Polymerized Thin Films and Near IR Overtone Studies of Some Organic Molecules

Photothermal effect refers to heating of a sample due to the absorption of electromagnetic radiation. Photothermal (PT) heat generation which is an example of energy conversion has in general three kinds of applications. 1. PT material probing 2. PT material processing and 3. PT material destruction. The temperatures involved increases from 1-. 3. Of the above three, PT material probing is the most important in making significant contribution to the field of science and technology. Photothermal material characterization relies on high sensitivity detection techniques to monitor the effects caused by PT material heating of a sample. Photothermal method is a powerful high sensitivity non-contact tool used for non-destructive thermal characterization of materials. The high sensitivity of the photothermal methods has led to its application for analysis of low absorbance samples. Laser calorimetry, photothermal radiometry, pyroelectric technique, photoacoustic technique, photothermal beam deflection technique, etc. come under the broad class ofphotothermal techniques. However the choice of a suitable technique depends upon the nature of the sample, purpose of measurement, nature of light source used, etc. The present investigations are done on polymer thin films employing photothermal beam deflection technique, for the successful determination of their thermal diffusivity. Here the sample is excited by a He-Ne laser (A = 6328...\ ) which acts as the pump beam. Due to the refractive index gradient established in the sample surface and in the adjacent coupling medium, another optical beam called probe beam (diode laser, A= 6500A ) when passed through this region experiences a deflection and is detected using a position sensitive detector and its output is fed to a lock-in amplifier from which the amplitude and phase of the deflection can be directly obtained. The amplitude and phase of the signal is suitably analysed for determining the thermal diffusivity.The production of polymer thin film samples has gained considerable attention for the past few years. Plasma polymerization is an inexpensive tool for fabricating organic thin films. It refers to formation of polymeric materials under the influence of plasma, which is generated by some kind of electric discharge. Here plasma of the monomer vapour is generated by employing radio frequency (MHz) techniques. Plasma polymerization technique results in homogeneous, highly adhesive, thermally stable, pinhole free, dielectric, highly branched and cross-linked polymer films. The possible linkage in the formation of the polymers is suggested by comparing the FTIR spectra of the monomer and the polymer.Near IR overtone investigations on some organic molecules using local mode model are also done. Higher vibrational overtones often provide spectral simplification and greater resolution of peaks corresponding to nonequivalent X-H bonds where X is typically C, N or O. Vibrational overtone spectroscopy of molecules containing X-H oscillators is now a well established tool for molecular investigations. Conformational and steric differences between bonds and structural inequivalence ofCH bonds (methyl, aryl, acetylenic, etc.) are resolvable in the higher overtone spectra. The local mode model in which the X-H oscillators are considered to be loosely coupled anharmonic oscillators has been widely used for the interpretation of overtone spectra. If we are exciting a single local oscillator from the vibrational ground state to the vibrational state v, then the transition energy of the local mode overtone is given by .:lE a......v = A v + B v2 • A plot of .:lE / v versus v will yield A, the local mode frequency as the intercept and B, the local mode diagonal anharmonicity as the slope. Here A - B gives the mechanical frequency XI of the oscillator and B = X2 is the anharmonicity of the bond. The local mode parameters XI and X2 vary for non-equivalent X-H bonds and are sensitive to the inter and intra molecular environment of the X-H oscillator.

Synthesis of Bio-Compatible SPION–based Aqueous Ferrofluids and Evaluation of RadioFrequency Power Loss for Magnetic Hyperthermia

Bio-compatible magnetic fluids having high saturation magnetization find immense applications in various biomedical fields. Aqueous ferrofluids of superparamagnetic iron oxide nanoparticles with narrow size distribution, high shelf life and good stability is realized by controlled chemical co-precipitation process. The crystal structure is verified by X-ray diffraction technique. Particle sizes are evaluated by employing Transmission electron microscopy. Room temperature and low-temperature magnetic measurements were carried out with Superconducting Quantum Interference Device. The fluid exhibits good magnetic response even at very high dilution (6.28 mg/cc). This is an advantage for biomedical applications, since only a small amount of iron is to be metabolised by body organs. Magnetic field induced transmission measurements carried out at photon energy of diode laser (670 nm) exhibited excellent linear dichroism. Based on the structural and magnetic measurements, the power loss for the magnetic nanoparticles under study is evaluated over a range of radiofrequencies.

High-Speed Semiconductor Lasers based on Low-Dimensional Active Materials for Optical Telecommunication

The scope of this work is the fundamental growth, tailoring and characterization of self-organized indium arsenide quantum dots (QDs) and their exploitation as active region for diode lasers emitting in the 1.55 µm range. This wavelength regime is especially interesting for long-haul telecommunications as optical fibers made from silica glass have the lowest optical absorption. Molecular Beam Epitaxy is utilized as fabrication technique for the quantum dots and laser structures. The results presented in this thesis depict the first experimental work for which this reactor was used at the University of Kassel. Most research in the field of self-organized quantum dots has been conducted in the InAs/GaAs material system. It can be seen as the model system of self-organized quantum dots, but is not suitable for the targeted emission wavelength. Light emission from this system at 1.55 µm is hard to accomplish. To stay as close as possible to existing processing technology, the In(AlGa)As/InP (100) material system is deployed. Depending on the epitaxial growth technique and growth parameters this system has the drawback of producing a wide range of nano species besides quantum dots. Best known are the elongated quantum dashes (QDash). Such structures are preferentially formed, if InAs is deposited on InP. This is related to the low lattice-mismatch of 3.2 %, which is less than half of the value in the InAs/GaAs system. The task of creating round-shaped and uniform QDs is rendered more complex considering exchange effects of arsenic and phosphorus as well as anisotropic effects on the surface that do not need to be dealt with in the InAs/GaAs case. While QDash structures haven been studied fundamentally as well as in laser structures, they do not represent the theoretical ideal case of a zero-dimensional material. Creating round-shaped quantum dots on the InP(100) substrate remains a challenging task. Details of the self-organization process are still unknown and the formation of the QDs is not fully understood yet. In the course of the experimental work a novel growth concept was discovered and analyzed that eases the fabrication of QDs. It is based on different crystal growth and ad-atom diffusion processes under supply of different modifications of the arsenic atmosphere in the MBE reactor. The reactor is equipped with special valved cracking effusion cells for arsenic and phosphorus. It represents an all-solid source configuration that does not rely on toxic gas supply. The cracking effusion cell are able to create different species of arsenic and phosphorus. This constitutes the basis of the growth concept. With this method round-shaped QD ensembles with superior optical properties and record-low photoluminescence linewidth were achieved. By systematically varying the growth parameters and working out a detailed analysis of the experimental data a range of parameter values, for which the formation of QDs is favored, was found. A qualitative explanation of the formation characteristics based on the surface migration of In ad-atoms is developed. Such tailored QDs are finally implemented as active region in a self-designed diode laser structure. A basic characterization of the static and temperature-dependent properties was carried out. The QD lasers exceed a reference quantum well laser in terms of inversion conditions and temperature-dependent characteristics. Pulsed output powers of several hundred milli watt were measured at room temperature. In particular, the lasers feature a high modal gain that even allowed cw-emission at room temperature of a processed ridge wave guide device as short as 340 µm with output powers of 17 mW. Modulation experiments performed at the Israel Institute of Technology (Technion) showed a complex behavior of the QDs in the laser cavity. Despite the fact that the laser structure is not fully optimized for a high-speed device, data transmission capabilities of 15 Gb/s combined with low noise were achieved. To the best of the author`s knowledge, this renders the lasers the fastest QD devices operating at 1.55 µm. The thesis starts with an introductory chapter that pronounces the advantages of optical fiber communication in general. Chapter 2 will introduce the fundamental knowledge that is necessary to understand the importance of the active region`s dimensions for the performance of a diode laser. The novel growth concept and its experimental analysis are presented in chapter 3. Chapter 4 finally contains the work on diode lasers.

Metallische Nanopartikel auf Quarz

This work presents the developement of an chemically stable and easy to produce in situ sensor for fast and reliable detection of polycyclic aromatic hydrocarbons (PAH) in low nanomolar concentrations. Metallic nanoparticles on dielectric substrates werde used for the rst time with surface enhanced Raman spectroscopy (SERS) in combination with shifted excitation Raman difference spectroscopy (SERDS). The preparation of the metallic nanoparticle ensembles with Volmer-Webergrowth is described first. The nanoparticles are characterized with both, optical spectroscopy and atomic force microscopy. The morphological properties of the nanoparticle ensembles are de ned by the mean axial ratio (a/b) and the mean equivalent radius (R Äq), respectively. The prepared and characterized nanoparticles were then used for intensive Raman spectroscopy measurements. Two sophisticated diode laser systems were used in cooperation with the TU Berlin, to carry out these experiments. The first step was to establish the ideal combination of excitation wavelength of the diode laser and the maximum of the surface plasmon resonance of the nanoparticle ensembles. From these results it was deduced, that for an optimum Raman signal the plasmon resonance maximum of the nanoparticle ensemble has to be red-shifted a few nanometeres in respect to the excitation wavelength. Different PAHs werde detected in concentrations of only 2 and 0.5 nmol/, respectively. Furthermore, the obtained results show an excellent reproducability. In addition the time dependence of the Raman signal intensity was investigated. The results of these measurements show, that only 2 minutes after placing the substrates in the molecular solution, a detectable Raman signal was generated. The maximum Raman signal, i.e. the time in which the molecular adsorption process is finished, was determined to about 10 minutes. In summary it was shown, that the used metallic nanoparticle ensembles are highly usable as substrates for SERS in combination with SERDS to detect PAHs in low nanomolar concentrations.

NIR to visible up-conversion, infrared luminescence, thermoluminescence and defect centres in Y(2)O(3) : Er phosphor

Er(3+) doped Y(2)O(3) phosphor was prepared by the solution combustion method and characterized using powder x-ray diffraction and energy-dispersive analysis of x-ray mapping studies. Room temperature near infrared (NIR) to green up-conversion (UC) emissions in the region 520-580 nm {((2)H(11/2), (4)S(3/2)) -> (4)I(15/2)} and red UC emissions in the region 650-700 nm ((4)F(9/2) -> (4)I(15/2)) of Er(3+) ions have been observed upon direct excitation to the (4)I(11/2) level using similar to 972 nm laser radiation of nanosecond pulses. The possible mechanisms for the UC processes have been discussed on the basis of the energy level scheme, the pump power dependence as well as based on the temporal evolution. The excited state absorption is observed to be the dominant mechanism for the UC process. Y(2)O(3) : Er exhibits one thermally stimulated luminescence (TSL) peak around 367 degrees C. Electron spin resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TSL peak. Room temperature ESR spectrum of irradiated phosphor appears to be a superposition of at least three distinct centres. One of them (centre I) with principal g-values g(parallel to) = 2.0415 and g(perpendicular to) = 2.0056 is identified as O(2)(-) centre while centre II with an isotropic g-factor 2.0096 is assigned to an F(+)-centre (singly ionized oxygen vacancy). Centre III is also assigned to an F(+)-centre with a small g-factor anisotropy (g(parallel to) = 1.974 and g(perpendicular to) = 1.967). Additional defect centres are observed during thermal annealing experiments and one of them appearing around 330 degrees C grows with the annealing temperature. This centre (assigned to an F(+)-centre) seems to originate from an F-centre (oxygen vacancy with two electrons) and the F-centre appears to correlate with the observed TSL peak in Y2O3 : Er phosphor. The trap depth for this peak has been determined to be 0.97 eV from TSL data.

Influência da laserterapia na proliferação de células-tronco do ligamento periodontal humano

Low level laser irradiation (LLLI) has been used in Dentistry to promote wound healing and tissue regeneration. The literature shows a positive effect of LLLI on cell proliferation, but little is known about their effectiveness in promoting stem cells proliferation. The aim of this study was to evaluate the effect of LLLI on the proliferative rate of human periodontal ligament stem cells. Extracts of periodontal ligament were isolated from two third molars removed by surgical and/or orthodontic indication. After enzymatic digestion, the cells were grown in α-MEM culture medium supplemented with antibiotics and 15% fetal bovine serum. On the third subculture, the cells were irradiated with a InGaAlP-diode laser, using two different energy densities (0,5J/cm 2 - 16 seconds and 1,0J/cm² - 33 seconds), with wavelength of 660nm and output power of 30mW. A new irradiation, using the same parameters, was performed 48h after the first. A control group (non irradiated) was kept under the same experimental culture conditions. The Trypan blue exclusion test and the mitochondrial activity of the cells measured by MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] essay were performed to assess the cell proliferation in the intervals of 0, 24, 48 e 72 h after irradiation. The data of cell counts were submitted to nonparametrical statistical tests (Kruskal-Wallis and Mann-Whitney), considering a confidence interval of 95%. DAPI (4 -6-Diamidino-2-phenylindole) staining of the cells was performed at 72h interval to evaluate possible nuclear morphological changes induced by LLLI. The results of this study show that the energy density of 1,0 J/cm² promoted greater cell proliferation compared to the other groups (control and 0,5 J/cm²) at intervals of 48 and 72h. The mitochondrial activity measured by MTT essay showed similar results to the Trypan blue cell counting test. The group irradiated with 1,0J/cm² exhibited a significantly higher MTT activity in the intervals of 48 and 72h, when compared to the group irradiated with 0,5J/cm². No nuclear morphological change was observed in the cells from the three groups studied. It is concluded that LLLI has stimulatory effects on the proliferation of human periodontal ligament stem cells. Therefore, the use of laser irradiation in this cell type may be important to promote future advances in periodontal regeneration

Efeitos da laserterapia na atividade biológica de células de carcinoma epidermóide de língua humano

The low level laser therapy (LLLT) has shown to be effective in promoting the proliferation of different cells in vitro, including keratinocytes, osteoblasts, endothelial cells and stem cells. It has been speculated that the biostimulatory effect of LLLT could cause undesirable enhancement of tumor growth in neoplastic diseases, since the malignant cells are more susceptible to proliferative stimuli. Within this context, this study evaluated the effect of LLLT on epidermoid carcinoma of the tongue cell line (SCC25) proliferation and invasion. Cultured cells were irradiated with an InGaAIP diode laser, 660nm, 30mW using two energy densities (0.5J/cm2 and 1.0J/cm2). Proliferative activity was assessed through trypan blue staining method and through cell cycle analysis using flow cytometry. The invasive potential was measured through cell invasion assay using matrigel. Cyclin D1, E-cadherin, -catenin and MMP-9 expressions were analyzed by immunofluorescence and flow cytometry and related to the investigated biological activities. Proliferation curve demonstrated that SCC25 irradiated with 1.0J/cm2 had the highest proliferative rate when compared to the control group and the group irradiated with 0.5J/cm2 (p<0.05). LLLT affected cell cycle distribution and energy density of 1.0 J/cm2 promoted a higher percentage of cells in S/G2/M phases, with statistically significant differences at 24h interval (p<0.05). LLLT, mainly with 1.0J/cm2, revealed significantly higher potential for invasion and influenced the expression of cyclin D1, E-cadherin, -catenin and MMP-9, promoting the malignant phenotype. In conclusion, our results indicate that LLLT has an important stimulatory effect on proliferation and invasion of SCC25 cells, likely due to altered expression of proteins associated with these processes