Les dispersions de nanoparticules magnétiques (NPs) dans les solvants polaires sont utilisées dans de nombreuses applications dans des domaines variés, du biomédical à l'environnement ou à l'énergie. Aussi appelés ferrofluides (FFs), ces systèmes sont des dispersions de ferrites spinelle magnétiques pouvant être stabilisées par des répulsions électrostatiques. Cela nécessite une bonne compréhension de l'interface NPs/solvant porteur, qui contrôle les interactions entre NPs, la nanostructure et de nombreuses autres propriétés. Nous étudions ici en milieu aqueux la réactivité électrochimique de particules c¿ur/couronne de type MFe2O4@ Fe2O3 (M = Fe,Co,Mn,Cu,Zn), espèces électroactives non conventionnelles. La voltammétrie à signaux carrés et la coulométrie à potentiel contrôlé permettent d'étudier la coquille de maghémite ( Fe2O3), dont le rôle est la protection de l'oxyde mixte du c¿ur en milieu acide. D'autre part, un nouveau procédé d'élaboration de dispersions dans les solvants polaires, testé dans l'eau, est appliqué au diméthylsulfoxide (DMSO). A partir du point de charge nulle des NPs, un ajout connu d'acide ou de base permet de contrôler la charge des NPs, la nature des contreions et la quantité d'électrolyte libre. Des dispersions stabilisées par des répulsions électrostatiques sont obtenues dans le DMSO. La diffusion de rayons X aux petits angles et la diffusion dynamique de la lumière sont utilisées pour comprendre la nanostructure et quantifier les interactions entre particules. De forts effets spécifiques liés aux ions sont mis en évidence ainsi que le rôle de l'interface solide liquide, en particulier sur les propriétés de thermodiffusion. / Dispersions of magnetic nanoparticles (NPs) in polar solvents have been inspiring many applications, to cite a few, biomedical, industrial and thermoelectrical ones. Also called ferrofluids (FFs), they are usually colloidal dispersions of magnetic spinel ferrite NPs, which can be stabilized thanks to electrostatic repulsion. A good understanding of the interface between NPs and the carrier solvent is thus a key point, which governs the interparticle interactions, the nanostructure and many other applicative properties. We study here the electrochemical reactivity of core-shell ferrite MFe2O4@ Fe2O3 (M=Fe,Co,Mn,Cu,Zn) NPs in aqueous medium. Square-wave voltammetry and potential controlled coulometry techniques are used on these non-conventional electroactive systems in order to evidence the shell of maghemite ( Fe2O3), the main function of which is to ensure the thermodynamical stability of NPs in acidic medium. We also present a new process for the elaboration of maghemite based FF in polar solvents, tested in water and applied to dimethyl sulfoxide (DMSO). Departing from the point of zero charge, the NPs are charged in a controlled way by adding acid or base, which enables us to better control the charge and the counter-ions nature, as well as the amount of free electrolyte in the dispersion. Stable dispersions are obtained thanks to electrostatic repulsion, also in DMSO. Small Angle X-ray scattering and Dynamic Light Scattering are used to understand the nanostructure and quantify the interparticle interactions. Specific ionic effects are evidenced as well as the strong influence of the solid/liquid interface on the migration of the NPs in a thermal gradient.

Les suspensions de particules colloidales dans des fluides newtoniens sont utilisées dans un grand nombre de secteurs pour leurs propriétés complexes. Ces dernières proviennent de l’interaction entre les forces hydrodynamiques et les forces physico-chimiques interparticulaires. Malgré de nombreuses études dédiées aux comportements des suspensions colloïdales le lien entre propriétés macroscopiques et forces d’interactions est toujours source de discussions. L’objectif de ce travail est de comprendre et caractériser, aux différentes échelles, et à l’aide de différentes techniques expérimentales, le lien entre la floculation des suspensions et quelques grandeurs rhéologiques (module élastique et contrainte seuil) caractérisant leur comportement macroscopique.La diversité chimique, en taille et en forme des constituants des pâtes cimentaires ainsi que la réactivité du système rendant l’étude trop délicate, des suspensions modèles sont utilisées (particules de silice sphériques et broyés en suspension dans de l’eau).Les suspensions colloïdales formulées sont thixotropes, l’évolution des propriétés rhéologiques en fonction du temps est analysée.Pour les deux types de suspensions, on observe que la contrainte seuil et le module élastique augmentent avec la fraction volumique en particules, la force ionique et le temps de repos.Ces deux grandeurs dépendent de la microstructure des suspensions mais décrivent deux réponses distinctes du matériau suite à l’application d’une sollicitation mécanique. Bien que ces grandeurs soient pilotées par la microstructure du matériau il n’y a pas d’évidence qu’elles soient liées l’une à l’autre. Cependant toutes les données G’=f(Tc) se placent sur une courbe unique pour un type de particule et une taille donnée. Ce résultat confirme que le module élastique peut être utilisé comme un paramètre de structuration caractérisant l’influence de la floculation sur la contrainte seuil. De plus nous nous sommes intéressés à l’impact de la taille des particules sur la réponse rhéologique du matériau. Nous observons que la contrainte seuil est proportionnelle à l’inverse de la taille des particules au carré et le module élastique à l’inverse de la taille des particules. Les modèles présents dans la littérature ne prédisent pas la même normalisation par la taille, cela suggère que les interactions interparticulaires contrôlant le comportement macroscopique ne sont pas encore totalement comprises.L’observation des suspensions au repos par microscopie confocale ne révèle pas de réorganisation structurelle dans le temps. Ainsi la thixotropie des suspensions s’explique probablement par l’existence de nano-organisations structurelles. Cependant des différences de structures sont mises en évidence pour des suspensions de formulations éloignées. Une structure primaire dépendant de l’intensité des interactions et de la fraction volumique se forme de manière instantanée une fois que le précisaillement est arrêté. Il s’en suit une évolution des propriétés rhéologiques avec le temps de repos qui est attribuée à des réarrangements très localisés non visibles par microscopie / Suspensions of colloidal particles suspended in a Newtonian fluid are encountered in many fields of daily life or industrial sectors. Complex behavior of colloidal suspensions comes from the interplay between hydrodynamical and several physico-chemical interactions between the particles. Even if a lot of works have been devoted to these topics, the complex relationships between the interparticle forces and the suspension's overall macroscopic behavior are far from being fully understood. This work aims to understand and characterize, at different scales, and through several techniques, the link between the flocculation state and some rheological properties (elastic modulus and yield stress) of colloidal suspensions.As in real system diversity in sizes, shapes, chemical constituents combined with chemical reaction make the system hard to control we work with model suspensions (spherical and crushed silica particles suspended in water).The suspensions being highly thixotropic, we characterize the evolution of their rheological properties (elastic modulus: G’ and yield stress: τc) with time.We observe for both materials that yield stress and elastic modulus increase with volume fraction, ionic strength and resting time.The two quantities G’ and τc depend on the microstructure ie the floculation state but are linked to two different kinds of response when a mechanical loading is apply to the system. Of course, both quantities depend on the flocculation state of the system but there is not clear evidence that these two quantities must be linked one to the other. However all the data G’=f (τc) collapse onto a simple curve for a given type and a given size of particle. This result proves that elastic shear modulus can be used as a “structural parameter” to account for the influence of flocculation on the yield stress.Moreover we focus on the effect of particle size on the measured properties and we observe that the yield stress scales with the inverse of the squared particle size and the elastic modulus with the inverse of particle size. The models existing in literature do not predict this scaling which would suggest that the interactions controlling macroscopic behaviour are still not fully understood.The observations performed with cofocal microscopy do not reveal any structural organisations when suspensions are left at rest. Then thixotropy of suspensions is assumed to be linked to nano scale change in microstructure. But different microstructure are observed regarding the suspension formulation. A primary microstructure is instantaneously formed once preshear is stopped depending on the intensity of interactions and volume fraction. After that the evolution of rheometric quantities with resting time are attributed to very local rearrangement not detectable with microscopy

The work presented in this thesis reports the use of a series of novel thiobiuret metal complexes [M(SON(CNiPr2)2)n] (M = Cu, Ni, Fe, Zn, Cd or In; n = 2 or 3) for the first time as single source precursors for the colloidal synthesis of metal sulfide nanoparticles. Other single source precursor(s) were also used for the synthesis of CdSe, CdS, CdSe/CdS core/shell, CdSeS alloys and Cu2-xS nanoparticles in microfluidic reactors. Thermolysis experiments of [Cu(SON(CNiPr2)2)2] using only oleylamine produced Cu7S4 nanoparticles as a mixture of monoclinic and orthorhombic phases. Pure orthorhombic Cu7S4 nanoparticles were obtained when a solution of precursor in octadecene was injected into hot oleylamine whereas, Cu1.94S nanoparticles were obtained when a solution of the precursor in oleylamine was injected into hot dodecanethiol. The thermolysis of [Ni(SON(CNiPr2)2)2] gave Ni3S4 in all cases except when precursor solution in oleylamine was injected into hot octadecene which produced NiS nanoparticles. The thermolysis of [Fe(SON(CNiPr2)2)3] in oleylamine/oleylamine produced Fe7S8 nanoparticles but other combinations, in most cases, gave amorphous material. Thermolysis of [Zn(SON(CNiPr2)2)2] in oleylamine produced spherical ZnS nanoparticles. Particles with size smaller than 4.3 nm had a cubic phase, whereas the particles with size larger than 4.3 nm had a hexagonal crystal structure as suggested by the selected area electron diffraction. Powder X-Ray diffraction showed that the CdS nanoparticles obtained from the thermolysis of [Cd(SON(CNiPr2)2)2] in oleylamine were cubic under all reaction conditions except when dodecanethiol was used as an injection solvent which produced hexagonal CdS. β-In2S3 were synthesized from the thermolysis of [In(SON(CNiPr2)2)3]. Transmission electron microscopy showed that the copper, nickel and iron sulfide nanoparticles had various morphologies such as spherical, hexagonal disks, trigonal disks, rods or wires; depending on the reaction temperature, concentration of the precursor, the growth time and the solvent/capping agent combination. The zinc and cadmium sulfide nanoparticles were mostly spherical whereas the indium sulfide nanoparticles were produced in the form of ultra-thin (< 1.0 nm) nanorods or nanowires. ZnxCd1-xS and CuInS2 nanoparticles were synthesised from the 1,1,5,5-tetra-iso-propyl-4-thiobiureto complexes of Zn, Cd and Cu, In, respectively. Powder X-Ray diffraction showed that the obtained ZnxCd1-xS nanoparticles are cubic under all reaction conditions. The ZnxCd1-xS nanoparticles had an average diameter between 3.5 to 6.4 nm as shown by transmission electron microscopy. The optical properties of the ZnxCd1-xS nanoparticles were highly dependent on the ZnS to CdS precursor ratio and the solvents/capping agents. Chalcopyrite (tetragonal), wurtzite (hexagonal) or a mixture of both CuInS2 nanoparticles were obtained depending on the reaction conditions. TEM showed that the CuInS2 nanoparticles could be synthesised with different morphologies (spherical, hexagonal, trigonal or cone). Luminescent CuInS2 nanoparticles were obtained only in the absence of oleylamine. [Cd(S2CNMenHex)2], [Cd(Se2P(iPr)2)2] and [Cu(SON(CNiPr2)2)2] were used as single source precursor(s) for the synthesis of CdS, CdSe, CdSe/CdS core/shell, CdSeS alloys and Cu2-xS in microfludic reactor. The CdS nanoparticles were in size range of 5.0 to 8.0 nm whereas the CdSe nanoparticles were ultra small (ca. 2 nm) with blue luminescence. The CdSe/CdS core/shell and the CdSeS alloys were bluish green or green luminescent depending on their size. The copper sulfide nanoparticles were found to be monoclinic Cu7S4 or monoclinic Cu7S4 with minor impurities of rhombohedral Cu9S5 depending on the reaction conditions.

Ce mémoire a été préparé dans le cadre du projet européen ERUDESP. Il décrit en détail les études qui ont été réalisées dans ce travail. Un bioréacteur sous forme d’une cellule bioélectrochimique à flux a été développé dans le but de servir pour la bioélectrosynthèse enantiopure. Le mémoire est consacré au design de cellules, screenings de différents médiateurs, au test de différentes réactions électroorganiques et électroenzymatiques à la fois dans une cellule électrochimique classique et dans une cellule électrochimique à flux. Un thème central de ce mémoire représente la synthèse d’électrodes macroporeuses tri-dimensionnelles. Grâce à cela, la surface active de l’électrode est augmentée de manière significative. Pour la préparation de ces électrodes une approche de template a été suivie. Des particules de polystyrène monodisperses ont été synthétisées de différentes manières et sont utilisées pour la synthèse des cristaux colloïdaux qui constituent les templates. Comme procédure de préparation contrôlée de ces templates, la technique de Langmuir-Blodgett et la méthode d’évaporation contrôlée, suivi par l’électrodéposition des métaux et des oxydes métalliques sont appliquées. Les diamètres des pores des matériaux macroporeux résultants sont parfaitement contrôlables par le diamètre des particules utilisées. La méthode de Langmuir-Blodgett a été étendue et appliquée pour la première fois à l’utilisation de particules de polystyrène. Le dépôt est réalisé dans les interstices des cristaux colloïdaux préparés préalablement, suivi par la dissolution des particules. De plus, des électrodes poreuses avec une grande surface de 6 x 6 cm2 ont été préparées. Les matériaux obtenus montrent une très bonne interconnéctivité avec une porosité ouverte et une surface active fortement augmentée ce qui se traduit électrochimiquement en une augmentation significative de la puissance du signal. Les matériaux poreux représentent un bénéfice non-seulement pour la (bio)électrosynthèse mais aussi dans le cadre de la (bio)électroanalyse. Dans ce mémoire, d’électrodes poreuses d’oxyde de ruthénium pour l’oxydation direct de NADH avec une surtension significativement améliorée ont été élaborée. La méthode de l’agrandissement de la surface est également appliquée et une meilleure densité de courant a été obtenue. Basé sur le projet ERUDESP, les méthodes apprises pour créer des électrodes poreuses à base de cristaux colloïdales ont dans la suite aussi été appliquées à d’autres domaines d’investigation. L’évolution méthodique de la technique de Langmuir-Blodgett a été utilisée pour le développement d’un système d’électrode renouvelable. Dans ce système, la surface peut être renouvelée sur commande par application d’un potentiel fixe (effet click).Les électrodes de l’oxyde de ruthénium ont non seulement été étudié dans le cadre du projet ERUDESP, mais la miniaturisation de ce matériau poreux et stable sous forme de microélectrodes a permis d’étudier une application comme capteur pH chimiquement et mécaniquement stable avec un meilleur ratio signal sur bruit. Dans ce cas le bruit thermique est diminué grâce à la porosité de l’électrode. Grâce à la technicité acquise par rapport à la synthèse des microélectrodes poreuses, des microélectrodes implantables pour les prothèses de main ont été aussi modifiées avec une couche macroporeuse pour augmenter la surface active et diminuer l’impédance de transition.Nous avons également exploré des couches multicatalyseurs macroporeuses de platine et nickel pour effectuer la génération d’hydrogène in-situ et l’hydrogénation simultanée dans un seul système catalytique.Comme dernière possibilité pour une structuration de surface contrôlée, des îlots de platine d’une étendue nanométrique furent examinées et biofonctionnalisées, ce qui résulte également en une augmentation significatif de la densité de courant. / The present work has been prepared within the framework of the European project ERUDESP and describes the research that has been carried out during this work. A bioreactor as a bioelectrochemical flow-cell was designed and realized with the goal to serve for enantiopure bioelectrosynthesis. The work deals with the cell design and screening of different mediators in a batch-cell and multi-cells, the development of different electroorganic and electroenzymatic reactions in an electrochemical batch- and flow-cell. With respect to the flow-cell, the upscaling of electrochemical reactions was carried out in the present work not only for electroorganic but also for electroenzymatic reactions with regard to the final application. A main focus of the present work represents the synthesis of three-dimensional macroporous electrodes in order to increase significantly the active surface. These macroporous structures were obtained by using the template approach. For the preparation of the templates monodisperse polystyrene particles were synthesized in different ways, and then used for the preparation of colloidal crystals serving as templates. As controlled assembly procedures, the Langmuir-Blodgett technique and the controlled evaporation method with subsequent electrodeposition of metals and metal oxides were chosen. With the present process the pore diameter could be exactly controlled by the diameter of the used particles. The approach of the Langmuir-Blodgett technique has been extended and optimized. For the first time, the Langmuir-Blodgett technique could be used with polystyrene particles. The deposition took place in the interspaces of the prepared colloidal crystals and is followed by the dissolving of the particles. Furthermore, the size of the porous electrodes could be upscaled (6 x 6 cm2). The obtained materials showed a very good interconnectivity with an open porosity and a highly increased active surface, which led to an increased electrochemical signal. The prepared porous materials represent a great benefit not only for (bio)electrosynthesis but also in the field of (bio)electroanalysis. In the framework of this work, the use of porous ruthenium oxide electrodes for direct oxidation of NADH with a significantly improved overvoltage was studied. Also in this context the increase of the surface led to an improved current density. Based on the ERUDESP project, the studied techniques for preparing porous electrodes with colloidal crystals were used for further scientific studies. The new variant of the Langmuir-Blodgett technique has also been used for the elaboration of a renewable electrode system where the surface can be simply renewed by applying a positive potential to the porous multilayers (click effect). The porous ruthenium oxide electrodes have not only been studied with respect to the ERUDESP project, but it was also possible to miniaturize this stable porous material as microelectrodes and use them as chemically and mechanically stable pH sensor with an improved signal to noise ratio. In this case the thermal noise decreased due to the porosity of the electrode. Due to the acquired expertise in the field of the preparation of porous microelectrodes, implantable microelectrodes for hand prosthesis were modified with a porous layer on the surface for increasing the active surface and decreasing their impedance.In addition, macroporous multicatalyst layers of platinum and nickel were synthesized for the simultaneous in-situ generation of hydrogen and hydrogenation reaction in the same catalyst system.As a final example for controlled surface structuring, nanoscale platinum islands were in detail examined and biofunctionalized. This led also to a significant increase of the current density.

Les nanocristaux colloïdaux synthétisés par voie chimique sont des sources prometteuses de lumière non-Classique à température ambiante. Ce travail est consacré à l'étude des propriétés optiques d'un type particulier de nanocristaux colloïdaux, appelé coeur-Bâtonnet, dans lequel un noyau de Seleniure de Cadmium (CdSe) sphérique est entouré d'une coquille de Sulfure de Cadmium (CdS) de forme cylindrique. En étudiant des particules de type coeur-Bâtonnet à température ambiante avec un microscope confocal, une caractérisation complète des propriétés optiques de ces émetteurs est réalisée. Nous étudions d'abord la statistique de clignotement de ces émetteurs. Nous montrons que les émetteurs coeur-Bâtonnet avec des coquilles épaisses se caractérisent par un clignotement réduit sur des échelles de temps courts, inférieurs à quelques millisecondes. Ensuite, une caractérisation détaillée de la statistique de photons des émetteurs coeur-Bâtonnet tenant compte du phénomène de clignotement est réalisée. La polarisation de l'émission est également étudié. Nous montrons que la polarisation d'émission peut être controlée en changeant la géométrie de la structure.Enfin, nous présentons également des expériences de couplage de ces émetteurs avec des dispositifs photoniques. Nous montrons la possibilité d'exciter un émetteur coeur-Bâtonnet en utilisant un nanofil d'oxyde de Zinc (ZnO). Nous montrons aussi que nous sommes en mesure d'orienter efficacement des nanoémetteurs uniques en utilisant la formation controlée de défauts dans des cristaux liquides. / Wet-Chemically synthesized colloidal nanocrystals are promising room temperature non-Classical light sources. This work is devoted to the study of the optical properties of a particular type of colloidal nanocrystals, called dot-In-Rods, in which a spherical Cadmium Selenide (CdSe) core is surrounded by a rod-Like Cadmium Sulfide (CdS) shell. By studying single dot-In-Rods at room-Temperature with a confocal microscope, a complete characterization of the optical, and especially quantum optical, properties of dot-In-Rods is provided for several geometrical parameters. We first study the blinking statistics of such emitters. We show that dot-In-Rods with thick shells are characterized by a reduced blinking that happens on fast timescales, typically on millisecond timescales. We then go on with a detailed characterization of the photon statistics of dot-In-Rods. A complete description of the photon statistics taking into account the blinking process is realized. The polarization of the emission is also investigated. We show that the emission polarization can be tuned by engineering the geometry. Finally, we also present experiments where we couple dot-In-Rods with various photonic devices. We demonstrate the possibility of excitation of a single emitter using a Zinc Oxyde (ZnO) nanowire. Using defects in liquid crystals, we also show that we are able to efficiently orientate single nanoemitters.

Le sélénium (Se) est un élément chalcogène avec un domaine de concentration étroit entre essentialité et toxicité. La toxicité est principalement liée à la spéciation chimique du Se qui évolue en fonction des conditions redox du milieu. Les formes oxyanioniques de Se, le sélénite (Se [IV], SeO32-) et le séléniate (Se [VI], SeO42-), sont solubles dans l'eau, biodisponibles et toxiques. En revanche, le sélénium élémentaire, Se(0), est insoluble et moins toxique. Néanmoins, les nanoparticules du Se(0) sont potentiellement dangereuses pour certains groupes des mollusques (comme les bivalves) et aussi pour les poissons. En outre, lorsque le Se(0) est rejeté dans les écosystèmes aquatiques, sa ré-oxydation jusqu'au sélénite et séléniate peut se produire. Le sélénium élémentaire d'origine biogénique Se(0) a été produit par la réduction de SeO42- dans des conditions anaérobies en utilisant un inoculum microbien mixte (boues granulaires) et par la réduction de SeO32- dans des conditions aérobies en utilisant une culture bactérienne pure (une nouvelle souche de Pseudomonas moraviensis identifiée et caractérisée pour la première fois dans cette thèse). Les deux types de Se(0) ont montré une forte stabilité colloïdale dans l'écart de pH variant de 2 à 12. La stabilité colloïdale est due à la charge négative (-15 mV à -30 mV) de la couche de biopolymère qui entoure Se(0) et à la taille nanométrique des particules de Se(0). La taille des particules de Se(0) produite par la boue anaérobie granulaire se situait entre 50 et 300 nm, avec une taille moyenne de 166 nm. A l'inverse, les nanoparticules de Se(0) produites par Pseudomonas moraviensis stanleyae sont caractérisées par un diamètre plus faible (~ 100 nm).Compte tenu des risques pour l'environnement engendrés par le relargage du Se(0) biogénique, des mesures appropriées doivent être mises en œuvre pour la séparation solide-liquide en utilisant une technologie efficace. Le potentiel de séparation solide-liquide de Se(0) généré a été évaluée par centrifugation, filtration, coagulation-floculation et électrocoagulation. Alors que toutes les approches présentent des rendements de séparation de Se(0) variables, l'électrocoagulation en utilisant des électrodes sacrificielles de fer a montré l'efficacité d'élimination le plus élevée (97%) / Selenium (Se) is a chalcogen element with a narrow window between essentiality and toxicity. The toxicity is mainly related to the chemical speciation that Se undergoes under changing redox conditions. Se oxyanions, namely selenite (Se[IV], SeO32-) and selenate (Se[VI], SeO42-), are water-soluble, bioavailable and toxic. In contrast, elemental selenium, Se(0), is solid and less toxic. Nevertheless, Se(0) nanoparticles are potentially harmful as particulate Se(0) has been reported to be bioavailable to filter feeding mollusks (e.g. bivalves) and fish. Furthermore, Se(0) is prone to re-oxidation to toxic SeO32- and SeO42- when discharged into aquatic ecosystems. Biogenic Se(0) under investigation was produced by the reduction of Na2SeO4 under anaerobic conditions using a mixed bacterial inoculum (anaerobic granular sludge) and through the reduction of Na2SeO3 under aerobic conditions using a pure microbial culture (Pseudomonas moraviensis stanleyae, a novel strain identified and characterized for the first time herein). Both types of Se(0) showed strong colloidal stability within the 2-12 pH range. The colloidal stability is caused by the negatively charged (-15 mV to -30 mV) biopolymer layer covering biogenic Se(0) particles and by their nanometer size. The particle size of Se(0) produced by anaerobic granular sludge ranged between 50 and 300 nm, with an average size of 166 nm. Conversely, the Se(0) particles produced by Pseudomonas moraviensis stanleyae are characterized by a lower diameter (~ 100 nm).The solid-liquid separation potential of Se(0) was assessed by centrifugation, filtration, coagulation-flocculation and electrocoagulation. While all approaches can bring about Se(0) removal from suspension with various degrees of success, electrocoagulation using iron sacrificial electrodes showed the highest removal efficiency (97%). Because biogenic Se(0) is harmful to the environment, appropriate measures must be implemented for the solid-liquid separation using an efficient technology

Tissue response to PNIPAM and HPC nanoparticles has been studied by implantation method. The results suggest that both PNIAPM and HPC nanoparticles possess good biocompatibility and they may serve as a good carrier for the applications of controlled delivery. Rheological properties of dispersions of IPN microgels composed of PNIPAM and PAAc have been studied. It is found that the IPN microgel dispersion can undergo a sol-gel transition at temperature above 33°C. In vivo drug release experiments suggest that the gelation procedure creates a diffusion barrier and thus leads to slow release. An emulsion method has been used to grow columnar crystals by mixing PNIPAM microgel dispersions with organic solvents. Effect of both temperature and microgel concentration on formation of columnar crystals has been studied. PNIPAM-co-NMA microgels have been used for the fabrication of crystalline hydrogel films by self-crosslinking microgels. The hydrogel film exhibits an iridescent. The thermally responsive properties and mechanical properties of this film have been studied. Melting temperature (Tm) of colloidal crystals self-assembled with PNIPAM-co-AAc microgels has been investigated as a function of pH, salt concentration and microgel concentration. It is revealed that Tm increases as pH value increases; Tm decreases with increase of salt concentration; Tm increases as microgel concentration increases. Phase behavior of PNIPAM-co-HEAc microgel dispersions has been investigated. It is observed that these microgel dispersions exhibit liquid, crystal, and glass phase. As microgel size increases, crystal phase shifts to low concentration range. As temperature increases, crystal phase shifts to high concentration ranges. These colloidal crystals can be stabilized by NaOH-induced gelation. Effect of NaOH concentration on formation of physical gelation has been investigated.

Orientadores: Francisco das Chagas Marques, Carlos Lenz César / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-29T22:06:44Z (GMT). No. of bitstreams: 1 VillegasBorrero_NelsonFabian_M.pdf: 7427305 bytes, checksum: 95d120bd4cca81a54f7e8af57dfd2ab5 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho foram fabricadas nanopartículas metálicas de prata (NPsM de Ag) em soluções coloidais usando a técnica de ablação à laser. Parâmetros como o comprimento de onda do laser, energia do pulso e a taxa de repetição afetam a distribuição de tamanho das NPsM. Assim, neste trabalho estudamos a influência destes parâmetros sobre o tamanho das NPsM de Ag. Para isto foi feita uma montagem experimantal na qual um alvo de prata é imerso em um líquido e irradiado por um pulso de laser de Nd:YAG para criar soluções coloidais. Foi encontrada uma variação dos picos de absorção entre = 394nm e = 405nm. Segundo a previsão da teoria de Gustav Mie, as variações nos picos tem a ver com a variação na distribuição de tamanhos. Para comprovar estes resultados foi feita uma estimativa do tamanho médio das NPsM de Ag usando a análise de imagens tomadas com o Microscópio Eletrônico de Varredura (MEV) e a técnica de Espalhamento Dinâmico da Luz (DLS). O espectro experimental e a teoria de Gustav Mie (simulação feita usando o software mathematica) encontram-se em concordância. As NPsM produzidas foram usadas para medir o efeito de aumento no sinal Raman em superfícies (SERS) encontrando-se que o sinal do espalhamento Raman de corantes usados em diferentes pesquisas (Rodâmina B e N719) aumenta com o uso das NPsM / Abstract: In this work we fabricated silver nanoparticles (Ag NPs) in colloidal solutions with specific sizes. Parameters like laser wavelength, pulse energy and pulse repetition rate affect the distribution of NPs size. In this work we studied the influence of these parameters on the size of Ag NPs. For that purpose we mount a set-up in which a silver target was immersed in liquid and irradiated by Nd:YAG pulsed laser to create different colloids. We found that the absorption peak of these colloids lays between 394nm and 405nm. We estimated a mean size of Ag NPs from images taken by Scanning Electron Microscope (SEM) and Dynamic Ligth Scattering (DLS). The calculated absorption spectra and simulation through Gustav Mie theory (Simulated in Matthemathica software) were in good agreement. The produced NPs were used in Enhacement Raman Spectroscopy (SERS) measurements, finding that the signal of Rhodamina B and N719 Dyes increases using these NPsM / Mestrado / Física / Mestre em Física / 1247650/2013 / CAPES

Doenças invasivas causadas por S. pneumoniae provocam cerca de 1,5 milhões de mortes anuais de crianças no mundo. Testes imunocromatográficos rápidos (dipsticks) são alternativa a métodos diagnósticos tradicionais, devido à fácil execução e baixo custo. Neste estudo foram desenvolvidos dipsticks para diagnóstico de S. pneumoniae utilizando: anticorpos de captura - monoclonais anti-pneumolisina recombinante (Ply) - AcMs D9-43 e E10-24, reativos contra 21 sorotipos prevalentes de S. pneumoniae; anticorpos de detecção (conjugados com diferentes partículas coloidais coloridas - corante têxtil, microesferas e nanopartículas de ouro) - Igs anti-Ply e anti-vacina pneumocócica celular (em desenvolvimento no Instituto Butantan) (anti-WCPV). Dipsticks com anti-Ply ou anti-WCPV conjugados com ouro ou microesferas coloidais detectaram a bactéria em todos os sorotipos prevalentes avaliados, entre 104 e 105 UFC/ml e pneumolisina nativa, em sobrenadantes de cultivo de S. pneumoniae, até uma concentração estimada 19,3 ng/ml e 9.7 ng/ml, respectivamente. Os resultados foram visualizados em aproximadamente 10 min. / Invasive diseases caused by S. pneumoniae are responsible for about 1.5 million child deaths per year worldwide. Rapid Immunochromatographic tests (dipsticks) are alternative to traditional diagnostic methods due to easy execution and low cost. In this study, dipsticks have been developed for diagnosis of S. pneumoniae using: capture antibodies - monoclonal anti- recombinant pneumolysin (Ply), MAbs D9 -43 and E10 - 24, reactive against 21 prevalent serotypes of S. pneumoniae; detection antibodies (conjugated with different colored colloidal particles - textile dye; microspheres and gold nanoparticles) - anti-Ply and anti whole cell pneumococcal vaccine (in developing in the Butantan Institute) (anti- WCPV). Dipsticks with anti-Ply or anti-WCPV conjugated with colloidal gold or microspheres detected the bacterium in all the evaluated prevalent serotypes, between 104 e 105 CFU/ml, and native pneumolysin in culture supernatants of S. pneumoniae to an estimated concentration 19.3 ng/ml and 9.7 ng/ml, respectively. The results could be visualized in around 10 min.

abstract: Satisfying the ever-increasing demand for electricity while maintaining sustainability and eco-friendliness has become a key challenge for humanity. Around 70% of energy is rejected as heat from different sectors. Thermoelectric energy harvesting has immense potential to convert this heat into electricity in an environmentally friendly manner. However, low efficiency and high manufacturing costs inhibit the widespread application of thermoelectric devices. In this work, an inexpensive solution processing technique and a nanostructuring approach are utilized to create thermoelectric materials. Specifically, the solution-state and solid-state structure of a lead selenide (PbSe) precursor is characterized by different spectroscopic techniques. This precursor has shown promise for preparing thermoelectric lead selenide telluride (PbSexTe1-x) thin films. The precursor was prepared by reacting lead and diphenyl diselenide in different solvents. The characterization reveals the formation of a solvated lead(II) phenylselenolate complex which deepens the understanding of the formation of these precursors. Further, using slightly different chemistry, a low-temperature tin(II) selenide (SnSe) precursor was synthesized and identified as tin(IV) methylselenolate. The low transformation temperature makes it compatible with colloidal PbSe nanocrystals. The colloidal PbSe nanocrystals were chemically treated with a SnSe precursor and subjected to mild annealing to form conductive nanocomposites. Finally, the room temperature thermoelectric characterization of solution-processed PbSexTe1-x thin films is presented. This is followed by a setup development for temperature-dependent measurements and preliminary temperature-dependent measurements on PbSexTe1-x thin films. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2020