Recentemente, a dopagem de semicondutores (envolvendo compostos II-VI, IV-VI, III-V, e do grupo-IV) com espécies magnéticas tem sido extensivamente investigada em função do seu potencial em spintrônica. Neste contexto, semicondutores magnéticos baseados no Si e no Ge são atraentes devido à sua compatibilidade com a indústria de semicondutores existente. Entretanto, a solubilidade das espécies magnéticas nestes materiais em forma cristalina é muito baixa e, consequentemente, sua atividade magnética é limitada. Este não é o caso para o silício amorfo (a-Si) e o germânio amorfo (a-Ge), que podem conter elementos magnéticos além do limite de solubilidade de seus análogos cristalinos, e apresentar propriedades magnéticas notáveis. Motivado por estes fatos, este trabalho apresenta uma investigação abrangente de filmes finos de Si e Ge contendo diferentes quantidades de Mn e Co, trazendo informações úteis no entendimento das propriedades desta classe de materiais. As amostras foram preparadas por co-sputtering, e possuíram concentrações de Mn na faixa de ~ 0.1-24 at.%, e de Co na faixa de ~ 1-10 at.%. Após a deposição, os filmes foram submetidos a tratamentos térmicos cumulativos até 900 oC, e foram investigados por: espectroscopia de energia dispersiva de raios-x (EDS); espalhamento Raman; difração de raios-x; transmissão óptica; microscopias eletrônica de varredura (SEM), de força atômica (AFM) e de força magnética (MFM); magnetometria SQUID; método de van der Pauw; etc. Para fins comparativos, amostras puras também foram preparadas, tratadas e caracterizadas de forma similar. Os presentes resultados indicam que os átomos de Mn e Co foram incorporados de forma efetiva e homogênea nas matrizes amorfas. Além disso, os filmes sem tratamento (puros ou contendo impurezas) são essencialmente amorfos. Ao contrário, tratamentos em altas temperaturas induzem a cristalização das amostras, e alterações em suas demais características, dependentes da introdução de dopantes. Desta forma: suas propriedades estruturais, ópticas, morfológicas, elétricas, e magnéticas, são notadamente afetadas pela inserção de Mn e Co, e pela temperatura de tratamento térmico. Estas observações foram sistematicamente investigadas e serão apresentadas e discutidas em detalhe. / Along the last few years, the doping of semiconductors (either II-VI, IV-VI, III-V, and group-IV compounds) with magnetic species have been extensively studied due to their potential applications in spintronics. Among them, Si- and Ge-based magnetic semiconductors are very attractive because of their total compatibility with the well-established current semiconductor technology. In the crystalline form, however, these materials exhibit a low solubility limit to magnetic species and, consequently, limited magnetic activity. This is not the case for amorphous (a-)Si and a-Ge, which can contain magnetic elements beyond the solubility limit of their crystalline counterparts, and present improved magnetic properties. Motivated by these facts, this work contains a comprehensive investigation of Si and Ge thin films containing different amounts of Mn and Co, providing useful information concerning the properties of this class of materials. The samples were prepared by co-sputtering, rendering Mn concentrations in the ~ 0.1-24 at.% range, and Co contents in the ~ 1-10 at.% range. After deposition, the films were submitted to isochronal thermal annealing treatments up to 900 oC and investigated by: energy dispersive x-ray spectrometry (EDS); Raman scattering spectroscopy; x-ray diffraction; optical transmission measurements; scanning electron (SEM), atomic force (AFM) and magnetic force (MFM) microscopy techniques; SQUID magnetometry; van der Pauw technique; etc. For comparison purposes, pure samples were also prepared, annealed and characterized in a similar way. The present experimental results indicate that the Mn and Co atoms were effectively and homogenously incorporated into the amorphous hosts. Moreover, the as-deposited films (either pure or doped) are essentially amorphous. On the contrary, thermal annealing at increasing temperatures induces the crystallization of the samples, and changes in their further characteristics, that are dependent of the doping. In this way: their structural, optical, morphological, electrical, and magnetic properties, etc., are notably affected by the insertion of Mn and Co, and by the temperature of thermal annealing. These experimental observations were systematically studied and will be presented and discussed in detail.

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No. of bitstreams: 1 alinelucianofilgueiras.pdf: 4846834 bytes, checksum: f046903a257bca51b49b36d371931270 (MD5) Previous issue date: 2017-03-24 / Nesta tese investigou-se as interações químicas dos antimicrobianos tinidazol, metronidazol, aztreonam, rifampicina e tetraciclina (TC) adsorvidos sobre superfícies metálicas de nanopartículas de ouro (AuNP) ou prata (AgNP) através das técnicas espectroscópicas de espalhamento Raman intensificado por superfície (SERS), de espalhamento Raman ressonante intensificado por superfície (SERRS) e de absorção no ultravioleta, visível e infravermelho próximo (UV-VIS-NIR). Também foram investigadas, a citotoxidade das AgNP, quitosana (QUIT), TC e das combinações AgNP com quitosana (AgNP+QUIT), e AgNP com QUIT e TC (AgNP+QUIT+TC) frente a células de fibroblastos bovinos. Foram obtidas as imagens de microscopia eletrônica de transmissão (TEM) das bactérias K.pneumoniae e S. aureus na ausência e presença das AgNP. Diferentes rotas sintéticas de AuNP e AgNP foram propostas, com o objetivo de se aprimorar as possíveis aplicações dessas sínteses. As AgNP devem ser pequenas para aplicações em experimentos biológicos e devem estar em ressonância com as radiações excitantes de comprimento de onda em 532, 633 ou 1064 nm quando forem utilizadas nos experimentos SERS. Os espectros SERS dos adsorbatos estudados foram obtidos na ausência e na presença dos modificadores de superfície 2-mercaptoetanol, polivinil álcool (PVA) ou íons cloreto. A presença destes modificadores superficiais permitiu monitorar os mecanismos de adsorção, que levaram a padrões espectrais SERS distintos. A análise dos espectros SERS da rifampicina foi baseada nas modificações observadas na estrutura eletrônica do grupo cromóforo, enquanto que para o tinidazol, metronidazol e aztreonam as diferenças nos padrões espectrais foram devidas a proximidade do sítio de adsorção do analito em relação à superfície metálica. A atribuição vibracional dos espectros Raman e SERS foi baseada em cálculos teóricos obtidos da teoria do funcional de densidade (DFT) das moléculas isoladas ou interagindo com átomos de metal. Este trabalho foi realizado em parceria com o Prof. Dr. Diego Paschoal da Universidade Federal do Rio de Janeiro e com o Prof. Dr. Hélio Ferreira dos Santos da Universidade Federal de Juiz de Fora. As imagens TEM das bactérias K. pneumoniae e S.aureus obtidas na ausência e presença das AgNP+QUIT foram realizadas em colaboração com o Dr. Celso Sant’Ana e o aluno Mateus Eugênio do Instituto Nacional de Metrologia, Qualidade e Tecnologia. Os ensaios de citotoxicidade das diferentes combinações de AgNP frente as células de fibroblastos bovinos foram realizados através do ensaio colorimétrico com brometo de 3, (-4,5-dimetiltiazol-2-il)-2,5-difeniltetrazolium (MTT). Este trabalho foi realizado em colaboração com a Profa. Dra. Michele Munk da Universidade Federal de Juiz de Fora. / In this thesis were investigated the chemical interaction of the antimicrobians tinidazole, metronidazole, aztreonam, rifampicin and tetracycline adsorbed on metallic surfaces of gold (AuNP) or silver nanoparticles (AgNP) by using the spectroscopic techniques surface enhanced Raman scattering (SERS), surface enhanced resonance Raman scattering (SERRS) and absorption in ultraviolet, visible and near infrared regions (UV-VIS-NIR). The cytotoxic effects of silver nanoparticles, chitosan (QUIT), tetracycline (TC) and its combinations AgNP with chitosan (AgNP+QUIT), and AgNP with QUIT and TC (AgNP+QUIT+TC) against bovine fibroblast cells were also investigated. The images using transmission electron microscopy (TEM) were obtained from the bacteria K.pneumoniae and S. aureus in the absence and presence of AgNP +QUIT. Different AuNP and AgNP were synthesized, with the aim of improving the possible applications of these syntheses. These have to be small in the biological experiments and should be in resonance with laser lines at 532, 633 or 1064 nm when used in the SERS experiments. The SERS spectra of the studied adsorbates were obtained in the absence and presence of the surfaces modifiers 2-mercaptoethanol, chloride ions or polyvinyl alcohol (PVA). The presence of these surfaces modifiers allowed monitoring adsorption mechanisms, which led to distinct SERS spectral patterns. The analyses of the SERS spectra of rifampicin were based on the observed changes in the electronic structure of the chromophore group, while for the tinidazole, metronidazole and aztreonam the differences in the spectral patterns were due to the proximity of anchor site of the analyte in relation to the metallic surface. The vibrational assignments of the Raman and SERS spectra were based on theoretical calculations obtained from density functional theory (DFT) of the isolated molecules or in interaction with metallic atoms. The DFT studies were made in collaboration with the Prof.Dr.Diego Paschoal from Universidade Federal do Rio de Janeiro and Prof.Dr Hélio Ferreira dos Santos from Universidade Federal de Juiz de Fora. The TEM images of K. pneumoniae and S.aureus bacteria obtained in the absence and in the presence of AgNP+QUIT were made in collaboration with the researcher Celso Sant’Ana and its student Mateus Eugênio from Instituto Nacional de Metrologia, Qualidade e Tecnologia. The cytotoxicity assays of the different combination of AgNP and chitosan and tetracycline against bovine fibroblast cells were made though colorimetric assay using MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The biological assay were made in collaboration with the Prof.Dr. Michele Munk and its students Leonara Fayer and Rafaella Zanetti from Universidade Federal de Juiz de Fora.

Ce mémoire présente les travaux effectués sur le développement d'une source optique servant à des applications d'imagerie biomédicale en général et de diffusion Raman cohérente en particulier. En effet la diffusion de ces dernières est freinée par le verrou technologique que constitue la nécessité de deux impulsions synchronisées et décalées en longueur d’onde. La praticité et les possibilités de conversions de fréquences offertes par l’optique non-linéaire fibrée sont ainsi utilisées pour adresser ce verrou technologique. Tout d’abord, une source simplement réglable en longueur d’onde est générée par l’effet d’auto-décalage en fréquence optique d'un soliton par effet Raman. Une étude des principaux paramètres de fibre aboutit à des décalages de 320 à plus de 500 nm, permettant une imagerie des résonances d’intérêt (≈ 1000-4000 cm-1). Deux applications de ce décalage sont présentées. Ensuite, l’autre impulsion voit sa largeur spectrale réduite de 70 à 10 cm-1 par compression spectrale, qui consiste en un "regroupement non-linéaire de fréquences sans pertes", afin de bénéficier de la résolution spectrale nécessaire. Enfin, la source développée est validée par l’acquisition de spectres CARS de différents échantillons de référence, pour différentes résonances (850 à 1750 cm-1). Une extension de la source à d'autres types d'imagerie est proposée, ainsi qu'une architecture de source quasiment entièrement fibrée exploitant les principes développés au cours de cette thèse / This manuscript presents the work done concerning the development of a light source used for biomedical imaging and more particularly for coherent Raman scattering imaging. In fact an efficient broadcasting of these ones is hampered by the need of two synchronized and wavelength shifted pulses. As so, the handiness and frequency conversion capabilities of nonlinear fiber optics are used to circumvent this technological lock. First of all, an easy wavelength tunable source is set by the use of the self-shifting in optical frequency of a soliton. A study of the main fiber parameters lead to shifts of 320 to more than 500 nm which allows interesting molecular resonances imaging (≈ 1000-4000 cm-1). Two applications of this shift are also reported. Then, the second pulse sees its spectral width reduced from 70 to 10 cm-1 by spectral compression, which consists in a "loss-less frequency regrouping", in order to obtain a proper spectral resolution. Finally, the developed source is validated by acquiring CARS spectra of different reference solvents and for different resonances (850 to 1750 cm-1). An evolution of this source to allow other imaging techniques is proposed, as well as a quasi-all-fibered source exploiting the principles addressed during this thesis work

This thesis focuses on the investigation and development of an integrated optical biosensor based on enhanced Raman techniques that will provide label-free detection of biomolecules. This is achieved by using hollow core photonic crystal fibers (HC-PCF), nanoparticles, or both. HC-PCF is a unique type of optical fiber, with continuous ‘channels’ of air (typically) running the entire length. The channels serve to confine electromagnetic waves in the core of the fiber, and tailor its transmission properties. Using HC-PCF as a biosensor requires development of a robust technique to fill hollow-core photonic crystal fibers. Though several groups have reported selective filling of HC-PCF’s core, the processes are cumbersome and limit the choice of liquid to avoid multimode behavior. In my Master’s thesis, I presented a simple technique to non-selectively fill all the HC-PCF channels with samples. The non-selective filling preserves the photonic bandgap property of the fiber, and yields an extremely strong interaction of light and the sample that produces considerable enhancement of the Raman signal from the analyte. Up to now, non-selective filling was accomplished through capillary action and it delivered a Raman signal enhancement of approximately 30-fold, which is not sensitive enough to detect biomolecules at the clinical level. Moreover, there were issues of reliability and reproducibility, due to evaporation, filling and coupling light into the fiber. The objective of this PhD research was to overcome these problems by developing a robust optical fiber platform based on Raman spectroscopy that can be used in a clinical setting. I initially focused on heparin, an important blood anti-coagulant that requires precise monitoring and control in patients undergoing cardiac surgery or dialysis. Since the Raman spectra of heparin-serum mixtures exhibits Raman peaks of heparin with poor signal-to-noise ratios, I concentrated on enhancing the heparin Raman signal and filtering out the spectral background of the serum to improve detection sensitivity. Reaching maximum enhancement of the Raman signal required a strong interaction of light and analyte, which can be achieved by using hollow core photonic crystal fiber as I had used in my Master’s research. Using a small piece of HC-PCF I was able to reach an enhancement in the heparin Raman signal of greater than 90-fold. With this degree of enhancement, I was able to successfully detect and monitor heparin in serum at clinical levels, something that had never been accomplished previously. After developing HC-PCF as a Raman signal enhancer, I focused on making the HC-PCF sensor robust, reliable and reusable. This was achieved by integrating the HC-PCF with a differential pressure system that allowed effective filling, draining and refilling of the samples in an HC-PCF, under identical optical conditions. To demonstrate the device’s detection capabilities, various concentrations of aqueous ethanol and isopropanol, followed by different concentrations of heparin and adenosine in serum, were successfully monitored. To further improve the sensitivity of the HC-PCF based Raman sensor, I incorporated surface enhanced Raman scattering (SERS), by introducing nanoparticles into the HC-PCF fibers. The research focused on determining the optimal volume and size of silver nanoparticles to achieve maximum enhancement of the Raman signal in the HC-PCF. The HC-PCF enhanced the Raman signal of Rhodamine 6G (R6G) approximately 90-fold. In addition, the optimal size and volume of AgNP enhanced the Raman signal of R6G approximately 40-fold, leading to a total enhancement of approximately 4,000 in HC-PCF. This was then used to demonstrate the application of a SERS based HC-PCF sensing platform in monitoring adenosine (a clinically important molecule), as well as malignant cells such as leukemia. Finally, I used hollow core crystal fibers to significantly enhance the efficiency of two-photon photochemistry. Although two-photon photochemical reactions are difficult to achieve with a small volume, I accomplished it by using a novel platform of HC-PCF to efficiently execute the two-photon induced photodecarbonylation reaction of cyclopropenone 1, and its conversion to the corresponding acetylene. The simple optical design configuration involved coupling an 800-nm tsunami laser to a short piece of HC-PCF filled with the sample. This allowed me to increase the efficiency of two-photon induced photochemistry by 80-fold, compared to a conventional spectrophotometer cuvette. Thus, this work leads to the use of HC-PCFs to more effectively study two-photon induced photochemistry processes, which was limited due to the difficulty of detecting photochemical events with a small excitation volume.

Nous avons développé une méthodologie basée sur phénomène de mélange à quatre ondre polarimétrique « Four wave Mixing FWM » et son équivalen résonant la diffusion Raman cohérente anti-Stokes (CARS, Coherent Anti-Stokes Raman Scattering) polarimétrique et réalisé des mesures sur des systèmes cristallins, simili biologiques : les membranes cellulaires connues sous le nom de « Multilamellar Vesicles MLV » et des échantillons de biologiques : la myeline, et ce, en variant les polarisations des lasers excitateurs, Pompe et Stokes. Le signal anti-Stokes émis est ensuite analysé afin d’en extraire les ordres 2 et 4 de la fonction de distribution angulaire des molécules actives constituant l’échantillon. Pour cela, plusieurs approches sont explorées telles que des algorithmes d’optimisation ou par décomposition en série de fourrier du signal polarimétrique. Ces multiples approches en traitement du signal permettent d’obtenir de manière rapide les coefficients des fonctions de distribution angulaire recherchées, et ainsi d’avoir des informations sur la symétrie des échantillons imagés, allant jusqu’à l’observation d’une symétrie d’ordre 4. La capacité de la microscopie non linéaire résolue en polarisation à sonder des ordres moléculaires est clairement démontrée et ainsi son intérêt dans l’étude de la relation entre la structure et la fonction de systèmes biologiques. / The capacity to quantify molecular orientational order in tissues is of a great interest since pathologies (skin lesion, neurodegenerative diseases, etc) can induce strong modifications in proteins’ organization. While numerous studies have been undertaken using polarization resolved second order nonlinear optical microscopy which is only specific to non-centrosymmetric organizations, higher order effects have been less explored. Four-wave mixing (FWM) microscopy and its resonant counterpart coherent anti-Stokes Raman scattering (CARS) can be of a great utility as label free diagnosis tools benefiting from less constraining symmetry rules. In this work, we implement incident polarizations tuning in FWM and CARS microscopy to probe molecular order, using a generic method to read-out symmetry information.Fourier analysis of the polarization-resolved FWM/CARS signal processed with an analytical model provides a fast and direct determination of the symmetry orders of the distribution function of the probed molecules. This method does not require a priori knowledge of the organization structure and provides quantitatively its second and fourth order symmetries. We applied this technique on different systems, from crystalline to less organized (multilamellar vesicles and proteins aggregates). We show that this new approach brings additional and more refined information on supra-molecular structures in complex media.

Selected methods of Raman spectroscopy, like surface-enhanced Raman spectroscopy and single molecule Raman spectroscopy, are described in this diploma work. The basis of two methods for numerical modelling of optical properties of micro- and nanoparticles are prefaced. The methods are Discrete Dipole Approximation and Finite Difference Time Domain. Micro- and nanoparticles are used in surface enhanced Raman spectroscopy and other nanospectroscopic methods. Further, the main instrumentation needed for Raman spectroscopy is described. The first part of experimental section of this work is numerical modelling of photonic nanojet that occures behind dielectric microparticles. This phenomenon leads to a new technique of confocal microscopy with Raman spectra measuring. The second experimental section contains results of Raman spectra measurement with beta-carotene and surface-enhanced Raman spectra of beta-carotene in silver-sol solution.

Les diagnostics lasers ont prouvé leur potentiel pour l'analyse des écoulements et des phénomènes de combustion par la mesure de champs de vitesses, de concentration d'espèces et de température. La diffusion Raman spontanée (DRS) est une des rares méthodes permettant de mesurer la température et la concentration de manière in-situ avec la possibilité de sonder plusieurs espèces simultanément. L'analyse des flammes turbulentes par DRS est difficile en raison de la nécessité de mesures mono-coup avec de fortes résolutions spatiales et temporelles et de la présence de lumière parasite. L'originalité de notre nouveau dispositif de mesure réside dans l'utilisation d'un obturateur électro-optique à base de cellule de Pockels (OCP), permettant d'éliminer les lumières non polarisées de fond de flamme, compatible avec une mesure 1D. Une réduction significative de l'émission de flamme et une amélioration du rapport signal sur bruit des espèces Raman actives ont été obtenues. La capacité de la DRS en tant que méthode de thermométrie mono-coup a été testée avec succès dans le cas d'une flamme de prémélange et de diffusion laminaire fuligineuse. L'écart relatif entre les températures moyennes mesurées dans les gaz brûlés et celles données par la modélisation de flamme est inférieur à 1 %. L'analyse de la thermométrie Raman à basse température a montré qu'une meilleure précision était obtenue avec la modélisation de 02 comparée à celle N2. Par la suite, le potentiel de la DRS à fournir des mesures simultanées de concentrations instantanées de N2, 02 et CO dans les flammes a été validé. Une évaluation des performances de différents détecteurs CCD accompagnés de l'OCP a également été réalisée. Les résultats obtenus avec la BI-CCD et la BI-EMCCD pour la température, le gradient de température et la forte densité sont en bon accord avec les calculs laminaires 1D de flamme adiabatique fournis par COSILAB. La BI-EMCCD a montré qu'elle est le détecteur le plus sensible pour la détection des espèces à faibles concentrations comme le CO. Enfin, des mesures par DRS ont été obtenues dans une flamme-jet de diffusion turbulente, en présence des suies illustrant le potentiel de cette technique pour construire une base de données importante pour la modélisation numérique des flammes / Laser diagnostics have been proven to be an indispensable tool to analyze the flow and combustion phenomena by allowing non-intrusive measurements of the velocity field, concentration and temperature. Spontaneous Raman Scattering (SRS) is one of the few methods providing simultaneously in-situ temperature and multi-species concentrations. Measurement in turbulent flames by SRS is still challenging due to the emission background and the requirement of single-shot measurements with high spatial and temporal resolutions. The originality of the present approach consists in use of a large aperture Pockels cell based electro-optical shutter (PCS), that allows removing unpolarised background flame emission and compatible with a 1D measurement. A significant reduction of flame emission was observed and consequently signal to noise ratio was enhanced. The ability of SRS in terms of thermometric single-shot method was demonstrated successfully in premixed laminar flames and sooty laminar diffusion flames. The measured temperature in burnt gases and those calculated by adiabatic flame modelling was within 1 %. Thermometric Raman analysis for low temperatures demonstrates the reliability of measurements, with a better accuracy for 02 compared to N2. Subsequently, the ability of SRS technique to simultaneously measure instantaneous concentrations of N2, 02 and CO was demonstrated. The ability to measure single-shot scalar values accurately is assessed by comparing different CCD detectors with the PCS. The results obtained from the BI-CCD and the BI-EMCCD concerning temperature, temperature gradient and high density were in good agreement with the COSILAB calculation for 1D laminar adiabatic flame. The BI-EMCCD observed to be the most sensitive in detecting low concentration elements like CO. Finally, SRS technique was applied to a turbulent sooting jet flame, illustrating the potentiel of this technique to build an important database for flame modelling

L’étude expérimentale des processus physico-chimiques de la combustion nécessite de disposer de diagnostics non-intrusifs. Le présent manuscrit reporte le développement du diagnostic laser de mesure de température DRASC (Diffusion Raman anti-Stokes Cohérente) en régime d’impulsions laser femtoseconde pour lequel la configuration à sonde à dérive de fréquence (CPP) a permis d’effectuer des mesures instantanées de température à 1kHz. Un travail à la fois théorique, numérique et expérimental a permis d’extraire la température des spectres DRASC instantanés acquis dans des mélanges air/argon (300-600K) et en flamme prémélangée CH4/Air avec une précision de l’ordre de 1% à 2100 K. La validité de ces résultats est obtenues par des confrontations numérique/expérimental pour différentes grandeurs d’influence. Cette étude permettra dans un proche futur d’appliquer le diagnostic DRASC fs CPP dans des flammes turbulentes représentatives d’écoulements réels observés en combustion aéronautique. / The experimental study of the physico-chemical processes of combustion requires the use of non-intrusive diagnostics. This manuscript reports the development of the CARS (Coherent Anti-Stokes Raman Scattering)) laser diagnostic in the femtosecond pulse regime for which the Chirped Pulse Probe (CPP) configuration enabled instantaneous measurements of temperature at 1kHz. A theoretical, numerical and experimental study allowed highlighting the possibility to measure temperature from the data processing of instantaneous DRASC spectra acquired in air/argon mixtures (300-600K) and in premixed flame CH4/Air with an accuracy of 1% at 2100 K. Validity of these results was obtained from numerical/experimental confrontations for different scalar parameters configurations. This study would enable in the near future the application of the CPP fs CARS diagnostic in turbulent flames representative of real flows observed in aeronautical combustion.

Les progrès technologiques des dispositifs expérimentaux ainsi que les récentes avancées pour la simulation des spectres Raman à haute température rendent aujourd’hui possible la mise en oeuvre d’une technique de mesures multi-espèces de température et de concentration uniquement fondée sur l’ajustement des spectres mono-coups de diffusion Raman spontanée collectés au sein des flammes turbulentes. Dans cette étude, cette stratégie de post-traitement, associée à une chaîne de mesure spécifique, est développée selon plusieurs axes pour permettre l’extension des mesures à des cas de flammes ordinairement hostiles aux mesures classiques Rayleigh/Raman résolues par inversion matricielle ou par méthode hybride. Dans une flamme diphasique d’éthanol, une thermométrie fondée sur l’ajustement des spectres de N2 a été mise en place afin de s’affranchir des contraintes liées à la diffusion de Mie des gouttes. L’intégration d’une thermométrie Raman à partir du spectre du méthane ainsi que d’une procédure de minimisation de l’émission de C2 dans le post-traitement des spectres ont permis la réalisation de cartographies multi-scalaires (température et toutes espèces majoritaires) dans toute la zone de recirculation d’une flamme turbulente légèrement fuligineuse générée par un brûleur bluff-body. Une thermométrie fondée sur la minimisation du spectre Raman de CO2 a également été développée et éprouvée au cours d’une campagne de mesures dans une installation d’échelle semi-industrielle reproduisant les conditions d’oxycombustion des cycles de turbines à gaz dans l’objectif de la capture et de la séquestration du CO2. / Recent progress in experimental devices and simulation of high-temperature Raman spectra enable the implementation of a spectral fitting method to solve single-shot Spontaneous Raman Scattering spectra collected in turbulent flames. In this study, this post-processing method, associated to a specific experimental set-up, has been developed to extend measurements to several cases of non-Raman friendly flames where matrix inversion or hybrid methods are usually limited. In a two-phase flame, N2 Raman thermometry has been used to overcome issues from Mie scattering of droplets. The implementation of a CH4 Raman thermometry and a minimization procedure of C2 emission in the data post-processing allowed the achievement of multi-scalar cartographies (temperature and all major species) throughout the recirculation zone of a slightly sooting turbulent flame stabilized on a bluff-body burner. A thermometry based on the minimization of CO2 Raman spectrum has also been developed and tested during a measurement campaign in a semi-industrial scale installation designed for the study of oxyfuel gas turbine cycle in the aim of carbon capture and sequestration.

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.