<p>Detection of pathogens, toxins, hazardous chemicals, and allergens in the food industry with reliable, sensitive, efficient, and rapid results has increased the demand to develop innovative diagnostic tools. Surface-enhanced Raman spectroscopy (SERS) sensors have demonstrated to detect a wide variety of analytes using nanomaterials like metal nanoparticles. Concerns of synthetic materials that can affect the environment with disposal of sensors have opened the possibility of fabricating SERS sensors with biodegradable materials. Fabrication of electrospun nanofibers from natural polymeric materials such as soy protein isolate can be used as a SERS platform. In the first part of this research, the characteristics of SPI solutions blended with NaOH and polyethylene oxide (PEO) such as PEO Mw, zeta potential and viscosity as well operating parameters such as voltage (15, 20, and 27 kV) were studied to evaluate the best solutions for a nanofibrous SERS platform. Characteristics of electrospun nanofibers, such as surface wettability, fiber diameters, and morphology using SEM, helped determine the most feasible fibers for decoration with noble metal nanoparticles. Fibers fabricated with 12 wt% SPI + 5 wt% PEO (0.1 MDa) + 1 wt% NaOH solution showed the smallest fiber diameter and highest water contact angle measurements. Glutaraldehyde (GLA) was added as a crosslinker to partly increase nanofibers hydrophobicity. These nanofibers were decorated with Au-nanostars and Au@Ag-NPs suspended in 90% butanol and in water. Partly hydrophobic nanofibers decorated with Au-nanostars and Au@Ag-NPs in butanol showed the most feasible results for a SERS platform due to smallest fiber diameter and higher water contact angle. In the second part of this research, decorated SPI nanofibers were evaluated to study its feasibility as a SERS platform for detecting bisphenol A (BPA), a toxic chemical present in food packaging materials. However, SERS spectra were difficult to obtain due to CCD overflow (excessive number of photons) at all laser powers on SPI nanofiber mats. Optimizing other Raman spectroscopy parameters such as the exposure time and the number of averages could enhance the SERS measurements. The fabricated SPI nanofibers in this research showed that hydrophilic and partly hydrophobic nanofibers mats could be used for decoration with metal nanoparticles by suspending the nanoparticles in a hydrophobic solvent. Hydrophilic nanofiber mats with nanoparticles in a hydrophobic solvent open a new strategy for developing another type of SERS platform.</p>

Metal-Organic Frameworks (MOFs) sont constitués de clusters métalliques connectés dans les ligands organiques. L'objectif principal de ma thèse était de caractériser la texture, la structure et la réactivité des MOFs dans le cas de systèmes présentant des défauts, amorphes et composites.La première étude est centrée sur les propriétés de la famille Fe-BTC et ce travail a été réalisé en collaboration avec l'Université d'Utrecht et l'Université d'Oxford. Une étude comparative entre le MIL-100(Fe) et son homologue commercial Basolite F300 (BASF) qui est amorphe ont été évaluées par l’adsorption de méthanol et d'autres techniques de caractérisation. De plus, les deux matériaux ont été testés pour être utilisés comme support pour l'imprégnation des métaux.Dans la deuxième étude, le broyage à la bille est utilisé comme stratégie de modification post-synthèse de MOFs. Le matériau ZIF-8 a été sélectionné de cas car il s'agit d'un MOF disponible dans le commerce (Basolite Z1200) et qui est en train de devenir de référence dans ce domaine. Ce chapitre examiner des propriétés flexibles, de la texture, de la structure, et la réactivité.Les MOFs UiO-66 et MOF-808 sont également analysées. Ces études ont été réalisées en collaboration avec l'Université Technique de Munich. UiO-66 contenant différents défauts d'ingénierie sont examinées. Nous avons démontré que les mesures d’adsorption de vapeur peuvent être un outil précieux pour accéder à la chimie des défauts. Le deuxième système est la série MOF-808 qu’une étude complète est présentée allant des diverses stratégies de synthèse de MOFs défectueux et composites jusqu'à leur propriété d'adsorption et de réactivité / Metal-organic frameworks (MOFs) are a class of porous materials that constructed from metal clusters connected with organic linkers. The main objective of my PhD was to characterize the texture, structure, and reactivity of MOFs materials with a particular focus on defective, amorphous and composite materials. The first study is centered on the properties of the Fe-BTC family and this work was realized in collaboration with Utrecht University and the University of Oxford. A comparative study between crystalline MIL-100(Fe) and its commercial counterpart amorphous Basolite F300 (BASF) were studied by using methanol adsorption to predict the reactivity. Other characterization methods are introduced to investigate both materials which were further tested to be used as supports for metal-impregnation. In the next study, ball-milling was employed as a post-synthesis strategy for MOF modification. This ZIF-8 material was selected since it is commercially available (Basolite Z1200) and is becoming one of the reference materials in this area. Extensive studies including flexibility, textural, structural, as well as reactivity of different milling products is presented. Zirconium-based MOFs (UiO-66 and MOF-808) were also examined in this thesis. These studies were performed in collaboration with TU Munich. UiO-66 series containing engineered defects are first examined. We demonstrated that vapor adsorption measurement is a valuable tool to access the chemistry of the defects. The second studied system is MOF-808 series, where a comprehensive study is presented starting from synthesis strategies of defective and composite MOFs up to adsorption properties and reactivity.

No description available.

<p>The resonance of surface plasmons on metal nanoparticles can be excited at visible wavelengths. The extraordinary enhancement of a variety of optical phenomena in the vicinity of metal nanoparticles has been attributed to the strong fields generated under resonance conditions. As a result, extensive research has been carried out to incorporate the extraordinary optical properties of metal nanoparticles into optical devices and applications, ranging from spectroscopy (e.g, surface enhanced Raman, IR and Fluorescence), optical sensing and imaging, to photovoltaic cells, photonic crystals and optical switches. Particular effort has been directed towards producing stable dispersion of metal nanoparticles within soft dielectric matrices and their subsequent construction into different device geometries.</p> <p>This thesis describes a method to photolytically generate Ag nanoparticles within organosiloxane sols, which can subsequently be photopolymerized in the presence of photoinitiators and therefore, be patterned through a variety of photo-inscription processes. The mechanism of Ag nanoparticle growth and evolution is described in detail followed by the fabrication of periodic metallodielectric gratings through photomask and laser interference lithography. Studies also showed that three different forms of nonlinear light propagation, optical self-trapping, modulation instability and spatial self-phase modulation could be elicited in the Ag nanoparticle-doped systems. Detailed experimental examination of these phenomena elucidated significant differences in their dynamics in the metallodielectric systems compared to non-doped samples. These included variations in the dynamics of self-trapped beams such as the excitation of optical modes, critical thresholds for modulation instability and self-phase modulation. The potential of these nonlinear processes for the self-inscription of 3-D metallodielectric structures including cylindrical multimode waveguides and waveguide lattices has also been studied.</p> / Doctor of Philosophy (PhD)

No / Spheric and anisotropic gold nanoparticles (GNPs) such as rods, stars or nanoprism prepared using hexadecyltrimethyl ammonium bromide (CTAB) as the stabilising agent have received a great deal of interest in the last years. The literature procedures exploited lead to GNPs in aqueous solution. We herein describe a fast, efficient, and cheap method to transfer particles of different shapes from water into toluene solution via ligand exchange (CTAB to dodecanethiol), which was mediated by acetone as a cosolvent. Absorption spectra and TEM-pictures before and after the transfer revealed that the particles survived the transfer intact and without change in shape.

Single-walled carbon nanotubes (SWCNTs) were decorated with metal nanoparticles. Using a complementary analysis with spatially resolved micro-Raman spectroscopy, high resolution transmission electron microscopy, electron diffraction, and tip-enhanced Raman spectroscopy, we show that the SWCNTs form bundles in which smaller diameter SWCNTs are the ones preferentially affected by the presence of Au and Ag nanoparticles. This result is exploited to evaluate the structural organization of SWCNTs with mixed chiralities in bundles, leading us to postulate that smaller diameter SWCNTs surround larger ones. We found that this effect occurs for very distinct scenarios including SWCNTs both in nanometer thin films and in field effect transistor configurations at the wafer-level, suggesting a universal phenomenon for SWCNTs deposited from dispersions. / Einwandige Kohlenstoffnanoröhren (SWCNTs) wurden mit Metallnanopartikeln dekoriert. Nach Anwendung von ortsauflösender Raman-Mikroskopie und -Spektroskopie, Transmissionselektronenmikroskopie, Elektronenbeugung und spitzenverstärkter Ramanspektroskopie wird festgestellt, dass sich aus den SWCNTs fasrige Bündel formen, wobei die analytischen Signaturen der SWCNTs mit kleinerem Durchmesser stärker von der Präsenz der Gold- und Silbernanopartikel beeinflusst werden als die der größeren. Dieses Resultat kann damit erklärt werden, dass in der Struktur solcher Bündel SWCNTs mit kleinerem Durchmesser außen und SWCNTs mit größerem Durchmesser innen zu liegen kommen. Wir konnten diesen Effekt für verschiedene Szenarien nachweisen: i) für SWCNTs in nanometerdünnen ungeordneten Filmen und ii) für SWCNTs, ausgerichtet zwischen Elektroden in der Geometrie eines Feldeffekttransistors. Diese Feststellung legt nahe, dass es sich um ein universelles Phänomen für aus flüssigen Dispersionen abgeschiedene SWCNTs handelt. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Optical trapping of metal nanoparticles investigates phenomena at the interface of plasmonics and optical micromanipulation. This thesis combines ideas of optical properties of metals originating from solid state physics with force mechanism resulting from optical trapping. We explore the influence of the particle plasmon resonance of gold and silver nanospheres on their trapping properties. We aspire to predict the force mechanisms of resonant metal particles with sizes in the Mie regime, beyond the Rayleigh limit. Optical trapping of metal nanoparticles is still considered difficult, yet it provides an excellent tool to investigate their plasmonic properties away from any interface and offers opportunities to investigate interaction processes between light and nanoparticles. Due to their intrinsic plasmon resonance, metal nanoparticles show intriguing optical responses upon interaction with laser light. These differ greatly from the well-known bulk properties of the same material. A given metal nanoparticle may either be attracted or repelled by laser light, only depending on the wavelength of the latter. The optical forces acting on the particle depend directly on its polarisability and scattering cross section. These parameters vary drastically around the plasmon resonance and thus not only change the magnitude but also the direction and entire nature of the acting forces. We distinguish between red-detuned and blue-detuned trapping, that is using a trapping wavelength shorter or longer than the plasmon resonance of the particle. So far optical trapping of metal nanoparticles has focussed on a wavelength regime far from the particle’s resonance in the infrared. We experiment with laser wavelengths close to the plasmon resonance and expand the knowledge of metal nanoparticle trapping available to date. Existing theoretical models are put to the test when we compare these with our real experimental situations.

L'objectif de ce travail est d'étudier une stratégie catalytique originale, consistant à insérer par imprégnation, au sein de la matrice lignocellulosique du bois, un sel métallique de Ni ou Fe, dont les phases catalytiquement actives pour la conversion des goudrons sont générées in-situ au cours de l'étape de pyrolyse. La caractérisation des échantillons de bois imprégné révèle que l'insertion des cations métalliques fait intervenir des mécanismes d'adsorption électrostatique, d'échange ionique et de complexation au sein des hémicelluloses, de la lignine et des microfibrilles de cellulose, assurant un état élevé de dispersion du métal dans la matrice lignocellulosique. L'étude de l'évolution des espèces de Ni au cours de la pyrolyse du bois met en évidence la formation de nanoparticules (NPs) de Ni0 quasi-monocristallines dans la gamme de température 400-500°C, les atomes de carbone jouant le rôle d'agent réducteur. Dans la même gamme de température, les espèces de Fe sont transformées en NPs de FeOx amorphes. Les tests de pyrolyse à 700°C révèlent que le nickel est plus efficace pour augmenter la production de H2 et réduire la formation d'hydrocarbures aromatiques, tandis que le fer est plus performant pour réduire la production totale de goudrons. D'un point de vue mécanistique, la présence des espèces métalliques, très dispersées dans la matrice lignocellulosique, impacte considérablement les mécanismes primaires de pyrolyse. De plus, les réactions secondaires de pyrolyse sont fortement modifiées par la génération in-situ des NPs de Ni0 et de FeOx, considérées comme les phases actives pour les réactions de conversion des goudrons et la réaction du gaz à l'eau. / This exploratory research work aimed at studying an original catalytic strategy for biomass gasification which consists in inserting into the lignocellulosic matrix of wood, by impregnation, a salt of Ni or Fe whose catalytically active phases for tar conversion reactions are generated in-situ during the pyrolysis stage. The characterization of the metal impregnated wood samples reveals that electrostatic adsorption, ion-exchange and metal complexation within hemicelluloses, lignin and cellulose microfibrills are involved in the mechanisms of metal cations insertion, resulting in a very high metal dispersion into the lignocellulosic matrix. The study of the nickel species evolution during wood pyrolysis demonstrates the formation of quasi-monocristalline Ni0 nanoparticles (NPs) in the temperature range 400-500°C, the carbon atoms acting as the reducing agent. In the same temperature range, the Fe species are transformed into amorphous FeOx NPs. The pyrolysis tests performed at 700°C reveal that the nickel catalyst is more efficient for enhancing H2 production and reducing the formation of aromatic hydrocarbons, whereas the iron catalyst exhibits better performances for reducing total tar production. From a mechanistic standpoint, it is suggested that the presence of highly dispersed metal species into the lignocellulosic matrix strongly impacts the mechanisms of primary pyrolysis. Moreover, the secondary pyrolysis reactions are strongly modified by the in-situ generation of Ni0 and FeOx NPs considered as the active phases for tar conversion and water gas shift reactions. Potential interests of the new nanocomposite materials Ni0/C and FeOx/C as obtained are discussed.

Les matériaux nanocomposites poreux organisés présentent de nombreuses propriétés dans le domaine de l’adsorption. Cette étude est portée sur la synthèse de matériaux poreux de grande aire spécifique fonctionnalisés par des nanoparticules métalliques en visant des applications dans le domaine de l’adsorption: en phase liquide et en phase gazeuse.La première application concerne la détection en phase liquide de molécules à de faibles concentrations. Des nanocomposites composés d’une matrice poreuse de silice dans laquelle sont insérées des nanoparticules de métaux nobles (i.e. Ag@SiO2 et Au@SiO2) sont étudiés comme substrats SERS en couplant thermodynamique et spectroscopie Raman. Ce couplage de l’étude de la réponse Raman et de l’étude thermodynamique de l’adsorption a conduit à une meilleure compréhension de l’influence des particules sur le seuil de détection de la molécule. L’influence de plusieurs paramètres sur la réponse Raman de la molécule sonde et sur ses propriétés d’adsorption a aussi été étudiée (la taille des particules, la nature chimique du métal, etc.).La seconde application concerne le stockage d’hydrogène. Des nanocomposites composés de matrices poreuses de silice ou de carbone dans lesquelles sont incorporées des nanoparticules d’un métal de transition (i.e. Ni@SiO2 et Ni@Carbone) sont étudiés comme matériaux de stockage en couplant manométrie et microcalorimétrie d’adsorption. La mise en place d’une méthode de réduction adaptée a constitué une étape importante de ce travail. Ce couplage d’études thermodynamiques de l’adsorption a permis de déterminer les propriétés d’adsorption de l’hydrogène à basse température et basses pressions de ces matériaux. / Nanocomposite organized porous materials present many properties in particular in the field of adsorption. This study was based on the synthesis of porous materials of high specific surface area functionalized with metal nanoparticles focusing in particular on two applications in the field of adsorption: one in the liquid phase and the other one in the gas phase.The first application is the detection of molecules in the liquid phase at low concentrations. Nanocomposites composed of a porous silica matrix in which are inserted noble metal nanoparticles (i.e. Ag@SiO2 and Au@SiO2) are studied as SERS (Surface Enhanced Raman Scattering) substrates by coupling thermodynamics and Raman spectroscopy. The coupling of the Raman response study and the thermodynamics of adsorption study leads to a better understanding of the influence of the particles on the molecule detection threshold. The influence of various parameters on the Raman response of the probe molecule and its adsorption properties were also studied (the particle size, the chemical nature of the metal, etc.)The second application relates to the storage of hydrogen since Nanocomposites composed of porous silica or carbon matrices in which are incorporated transition metal nanoparticles (i.e. Ni@SiO2 and Ni@Carbon) were studied as storage materials by coupling the adsorption manometry and microcalorimetry. The establishment of a suitable reduction method was an important step in this work. This coupling of thermodynamic studies of the adsorption was used to determine the adsorption properties of hydrogen at low temperature and low pressures of these materials.

Dans ce travail, les propriétés des réseaux diffractifs ordonnés de nanoparticules d'or sont étudiées numériquement et expérimentalement. Ces résonances sont beaucoup plus étroites que celles observées dans le cas d'une nanoparticule isolée. D'après les simulations numériques, deux régimes distincts de réponse sont identifiés, l'un correspond à l'anomalie de Rayleigh (RA) l'autre au mode plasmon de réseau 2D (LPM). Dans la partie expérimentale nous avons fabriqué des réseaux de nanoparticules d'or en utilisant la lithographie d'électronique. La transmission spectrale a été mesurée dans le domaine optique pour caractériser ces réseaux. Toutes les caractéristiques essentielles des spectres expérimentaux sont en bon accord avec les simulations numériques. Les distributions du champ électrique pour différents paramètres de réseau sont étudiées pour obtenir le maximum d'augmentation du champ à la surface de la nanoparticule. L'excitation des résonances plasmon dans les réseaux diffractifs de nanoparticules d'or en condition asymétrique de l'indice de réfraction est examinée expérimentalement. L'excitation des modes plasmon à profil spectral étroit dans l'environnement asymétrique a été expérimentalement vérifiée. La possibilité d'accorder la longueur d'onde de ces résonances dans le proche infrarouge en changeant les paramètres structurels des réseaux périodiques en combinant taille et forme des nanoparticules est discutée. Ces résultats sont importants pour les applications telles que les spectroscopies en champ électrique exalté et la détection en biologie ou en chimie. / The properties of ordered diffractive arrays of gold nanoparticles are studied numerically and experimentally. Using numerical simulations I identify, two distinct regimes of lattice response, associated with two-characteristic states of the spectra: Rayleigh anomaly and lattice plasmon mode. In experimental part gold nanoparticle arrays were fabricated using e-beam lithography. Spectroscopic transmission measurements then were carried out to optically characterize these arrays. All the essential features of the experimental spectra were reproduced well by numerical simulations. Electric field distributions for different lattice parameters are studied in order to maximize the enhancement of electric field at the nanoparticle surface. The excitation of plasmon resonances in diffractive arrays of gold nanoparticles placed in asymmetric refractive index environment is examined experimentally. The excitation of the plasmon modes with narrow spectral profile in asymmetric environment was experimentally verified. The ability to tune the wavelength of these resonances in the near infrared range by varying the structural parameters of the periodic arrays in combination with size and geometry of the constituent nanoparticles is discussed. The presented results are of importance for the field enhanced spectroscopy as well as for plasmonic bio and chemical sensing.