Ce travail de thèse a pour objectif d'étudier les rôles de la taille, de la composition et de la cinétique de croissance sur la morphologie, la structure, et l'état de mélange de l'argent et du cobalt dans des nanoparticules bimétalliques supportées AgCo. Dans ce but, des mesures in-situ et en temps réel par diffusion des rayons X aux petits et aux grands angles en géométrie d'incidence rasante, et en condition anomale, ont été effectuées au cours de la croissance des nanoparticules AgCo dans des conditions de dépôt simultané ou successif des métaux. Des recuits ont ensuite été réalisés afin d'étudier la stabilité des structures obtenues à température ambiante, et d'observer d'éventuelles transitions activées thermiquement. Pour l'ensemble des modes de dépôt, les nanoparticules (dans une gamme de taille comprise entre 2 et 7nm) présentent une configuration chimique ségrégée. Pour des dépôts successifs de Co puis d'Ag, les nanoparticules sont constituées d'un (ou plusieurs) domaine(s) d'Ag juxtaposé(s) à un domaine de Co, tandis que pour un dépôt d'Ag puis de Co les particules présentent une configuration de type coeur-coquille (Co-Ag). Pour les dépôts simultanés, la configuration cœur-coquille est obtenue à très faible composition en Ag (< ou =20%), au-delà la configuration multidomaines monométalliques est observée. Quelle que soit la configuration initiale, le recuit conduit à une séparation de phase des métaux sous forme de particules Janus et à des réorganisations structurales. / The aim of this work is to study the role of size, composition and growth kinetic conditions on the morphology, the structure and the chemical configuration of AgCo bimetallic supported nanoparticles. Thus, in-situ and in real-time anomalous grazing incidence small and wide angle X-ray scattering measurements were performed during AgCo nanoparticles growth. Two types of growth conditions were studied : simultaneous or successive deposition of the two metals. Samples were also annealed to study the stability of the structures observed at room temperature, and to investigate if structural transitions occur due to thermal activation. For all kind of deposition modes, the nanoparticles (in a size range between 2 and 7 nm) exhibit a segregated chemical configuration. For the deposition of Co followed by Ag deposition, the nanoparticles are constituted of one (or several) Ag domain(s) juxtaposed with a Co domain, whereas for Ag deposition followed by Co deposition, the nanoparticles present a (Co-Ag) core-shell configuration. For simultaneous depositions and Ag poor compositions (< or =20%), the core-shell configuration is obtained. For richer compositions, the multidomain configuration is observed. Whatever the initial configuration, annealing leads to a phase separation of the two metals towards Janus particles and some structural reorganizations occur.

DIAS, Diego Felix. Síntese e caracterizações de nanopartículas de FeCo/(Fe,Co)3O4 com acoplamentos magnéticos sintetizadas pelo método sol-gel proteico. 2015. 84 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2015. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2016-02-05T18:59:30Z No. of bitstreams: 1 2015_dis_dfdias.pdf: 4365302 bytes, checksum: 86e3e995f04f6424f30d8e5ab94293bc (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2016-02-05T18:59:49Z (GMT) No. of bitstreams: 1 2015_dis_dfdias.pdf: 4365302 bytes, checksum: 86e3e995f04f6424f30d8e5ab94293bc (MD5) / Made available in DSpace on 2016-02-05T18:59:49Z (GMT). No. of bitstreams: 1 2015_dis_dfdias.pdf: 4365302 bytes, checksum: 86e3e995f04f6424f30d8e5ab94293bc (MD5) Previous issue date: 2015 / FeCo Nanoparticles coated with (Fe,Co)3O4 (Magnetite doped with cobalt) were synthesized by the chemical route known as Sol-Gel Protein. The synthesized materials were characterized by thermogravimetry (TG), X-Ray Diffraction (XRD), Vibrating Sample Magnetometry (VSM), Mössbauer spectroscopy, Scanning Electronic Miscroscopy (SEM) and Transmission Electronic Microscopy (TEM). The results show that the increase in temperature directly influences the size of the shell (Shell) and increased the ratio of remanent magnetization to the saturation magnetization. The effect of Exchange Spring and Exchange Bias were observed in the hysteresis curves. The Core-Shell structure was formed a non-homogeneous manner, ie not all the magnetite particles were coated. / Nanopartículas de FeCo recobertas com (Fe,Co)3O4 (Magnetita dopadas com cobalto) na estrutura casca caroço (Core-Shell), foram sintetizadas pela rota química conhecida como Sol-Gel Proteica. Os materiais sintetizados foram caracterizados por Termogravimetria (TG), Difração de Raios-X (DRX), Magnetometria de Amostra Vibrante (VSM), Espectroscopia Mössbauer, Microscopia Eletrônica de Varredura (MEV) e Microscopia Eletrônica de Transmissão (MET). Os resultados mostram que o aumento da temperatura de re-oxidação influi diretamente no tamanho da casca (Shell) bem como o aumento da razão entre a magnetização remanente pela magnetização de saturação. O efeito de Exchange Spring e Exchange Bias foram observados nas curvas de histerese. A estrutura Core-Shell foi formada de maneira não homogênea, ou seja, nem todas as partículas foram recobertas pela magnetita.

Ce travail a pour objectif la fabrication, en épitaxie par jets moléculaires, de nanofils coeurcoquilleà base de GaAs et AlGaAs déposés sur des substrats Si(111), en vue de réaliser desréseaux de fils pour de nouvelles cellules solaires, et pour des fils photoniques permettant uneapproche bottom-up d’émetteurs de photons uniques.La première partie de ce travail est une étude systématique des paramètres clés qui contrôlent lacroissance uni-dimensionnelle de fils GaAs élaborés par un mécanisme vapeur-liquide-solideauto-catalysé, à savoir le rapport des flux As/Ga, la température du substrat, et la vitesse decroissance.La seconde partie se concentre sur la croissance et la caractérisation de fils GaAs recouvertsd’une coquille d’alliages AlGaAs (35% Al) afin de s’affranchir des recombinaisons de surface.Ces coquillesde AlGaAs sont fabriquées en conditions riche-As (rapport As/Ga > 10) afin deconsommer les gouttes de catalyseur gallium et de promouvoir une croissance radiale (le taux decroissance maximal axial/radial est égal à 6). Diverses caractérisations optiques sont réalisées àbasse température sur ces ensembles de fils : cathodoluminescence, photoluminescence etspectroscopie résolue en temps. L’intensité de luminescence et la durée de vie des porteursaugmentent fortement avec la présence de la coquille : une épaisseur de 7 nm de cette dernièreest suffisante pour optimiser la passivation des nanofils et supprimer les recombinaisons liéesaux états de surface. Une fine couche extérieure de GaAs est nécessaire pour éviter touteoxydation de la coquille d’alliage AlGaAs.De plus, grâce à des mesures de CL résolues spatialement, les longueurs de diffusion desexcitons dans ces fils ont été obtenues, allant de 0.7 μm à 1.5 μm pour des épaisseurs decoquilles comprises entre 20 et 50 nm. Des valeurs plus petites sont mesurées pour des coquillesplus épaisses, ce qui tend à montrer l’introduction de défauts dans l’alliage qui pourraientlimiter la qualité de l’interface. Le décalage en énergie de l’émission fournit des informationssur la génération de contraintes dans ces fils coeur-coquille et sur le champ piézo-électrique quien découle. / This report focuses on the fabrication of GaAs nanowires and GaAs/AlGaAs core-shellstructures by molecular beam epitaxy, deposited on Si (111) substrates in order to providearrays of wires for innovative solar cells and bottom-up photonic wires for efficient singlephoton emitters.The first part of this work is a systematic study of the key parameters which control the onedimensionalgrowth of bare GaAs NWs with a self-assisted vapor-liquid-solid growth process,namely the As-to-Ga flux ratio, the substrate temperature, and the deposition rate.The second part concentrates on the growth and characterization of GaAs wires covered with ashell of AlGaAs alloy (35 % Al) in order to get rid of the surface recombinations. These shellswere fabricated under As-rich condition with ratio As/Ga >10 in order to consume the Gadropletscompletely and to promote a radial growth. The obtained axial-to-radial growth ratio is6. The optical characterizations on ensemble were carried out at low temperature via thecathodoluminescence (CL), photoluminescence (PL), and time-resolved PL measurements. Theresults show that the lifetime of carriers and luminescence intensity increase significantly withshell coverage. About 7 nm thick shell is enough to optimize the passivation and suppress thesurface state recombination. A thin outer cap of GaAs is required in order to prevent someoxidation of the AlGaAs alloy shell.In addition, the exciton diffusion lengths of these NWs, studied via the spatially resolved CL,are in the range of 0.7 - 1.5 μm for NWs with shell thicknesses between 20 - 50 nm. Thesevalues are smaller for thicker shells due to the defect formation, leading to limit the quality ofcore-shell interface. The shift in optical emission experiments provides the information of thestrain generation of core-shell when we vary the shell thickness. The piezoelectric field wasnoticed in these samples.

La détection et la surveillance des gaz est un enjeu important tant pour la sécurité industrielle que pour la protection de l’environnement et des personnes. Le dihydrogène, prend une place de plus en plus importante en tant que combustible et vecteur énergétique mais il est extrêmement inflammable et explosif dans un large domaine de 4 à 75 % dans l’air. De même, l’ammoniac est très utilisé dans l’industrie comme gaz réfrigérant ou comme élément de base pour la production chimiques d’autres composés. Ce gaz présente des risques sur l’environnement et sur les êtres vivants et peut former des mélanges explosifs avec l’air dans les limites de 15 à 28 % en volume. Les capteurs de gaz permettant d’indiquer la présence et/ou la quantification de ces gaz prennent alors toute leur importance. Dans la continuité de nos nombreux travaux sur les capteurs résistifs à base d’assemblages discontinus de nano-objets, l’objet de ce travail de thèse a été de préparer des capteurs résistifs pour la détection de H2 et NH3. Ces capteurs sont à base d’assemblages 2D de nanoparticules de compositions complexes. Trois types de nanoparticules cœur-coquille ont été synthétisés : Au@ZnO, Au@SnO2 et Au@Ag. Différentes techniques physico-chimiques (UV-Visible/TEM / DRX etc) ont permis de caractériser les particules obtenues. L’étape suivante a consisté à les assembler en monocouches compactes. Les films ont été obtenus par la méthode d’assemblage de Langmuir-Blodgett. Après transfert à la surface d’un substrat en verre supportant des électrodes inter digitées, les performances de détection des capteurs résistifs fabriqués ont été alors évaluées. Les capteurs à base de Au@ZnO et Au@SnO2 ont été testés sous H2, tandis que les capteurs à base de Au@Ag l’ont été sous NH3. Les capteurs fabriqués ont montré des performances attractives de détection de H2 et NH3 dans des gammes de concentration étendues. Une autre contribution importante de ce travail concerne la compréhension des mécanismes de détection. Diverses techniques analytiques, tels que la TPD (Température désorption Programmed) et la TPR (Température de réduction programmée) ont été utilisés pour permettre la discussion des les mécanismes impliqués. / Gas sensing and monitoring are important issues for both industrial safety and protection of the environment and human beings. Dihydrogen, is increasingly used as fuel and energy carrier but it is extremely flammable and explosive in a wide range between 4 and 75% in air.Similarly, ammonia is widely used in industry as a cooling gas or as a reagent for the chemical production of other compounds.This gas presents risks to the environment and to living beings and can form explosive mixtures with air within 15 to 28% by volume.Gas sensors, indicating the presence and /or quantification of these gases, are very important.In continuation of our work on resistive sensors based on discontinuous assembly of nano-objects, the aim of this thesis was to prepare resistive sensors for the detection of H2 and NH3.These sensors are based on 2D assemblies of complex compositions of nanoparticles. Three types of core-shell nanoparticles were synthesized: Au@ZnO, Au@SnO2 and Au@Ag. Different physicochemical techniques (UV-Visible / TEM / DRX etc.) were used to characterize the particles. The next step was to assemble them in compact monolayers. The films were obtained by Langmuir-Blodgett assembling technique. Then, they were transferred to the surface of a glass slide supporting interdigitated electrodes. Sensing performances of the as-fabricated resistive sensor were evaluated.Sensors based on Au@ZnO and Au@SnO2 nanoparticles were tested towards H2, while Au@Ag based sensors were tested under NH3.The sensors showed attractive performances in H2 and NH3 detection within wide concentration ranges. Another important contribution of this work is the understanding of detection mechanisms. Various analytical techniques such as TPD (Temperature Programmed Desorption) and TPR (temperature programmed reduction) were used for the discussion of the mechanisms involved.

Le contrôle et l'optimisation des propriétés d'émission des nanomatériaux peuvent être obtenus par un couplage efficace entre nanoémetteurs et nanostructures permettant d’obtenir une directivité plus élevée, une dynamique d’émission plus rapide. Il est pour cela nécessaire d’obtenir l'accord spectral de l'émetteur avec les modes de nanostructures, le positionnement spatial du nanoémetteur à l'endroit où l'intensité du mode résonant de la nanostructure est maximale, et une orientation du dipôle nanoémetteur parallèle au champ électrique résonant. En plasmonique les résonances larges des modes permettent un accord spectral facile. L’accord spatial est plus difficile, mais des stratégies ont été mises en œuvre avec succès. Le contrôle de l'orientation du dipôle reste lui un défi. En plasmonique, par exemple, une interaction efficace ne peut être obtenue que pour des dipôles orthogonaux à la surface métallique. La détermination de l'orientation du dipôle émetteur est donc cruciale pour les dispositifs plasmoniques tels que les nano-antennes.Dans ma thèse, j'ai contribué au développement d'une méthode polarimétrie visant à analyser le dipôle émetteur d'un nanoémetteur et son orientation. J'ai effectué des expériences et les ai analysées. Le modèle décrit l'émission d'un dipôle proche d'une interface plane dans un large éventail de conditions expérimentales réalistes, en particulier le cas où le nanoémetteur se trouve à proximité d’un film d'or. Dans cette situation, pour des nanocristaux de CdSe/CdS assimilable à deux dipôles orthogonaux dégénérés, l'imagerie défocalisée n'est pas suffisamment sensible pour fournir des informations quantitatives fiables sur l'orientation de l'émetteur. A contrario, la polarimétrie permet de répondre à cette question. Avec le même modèle, le diagramme d'émission correspondant à l'émission dipolaire en champ lointain pour toutes ces conditions expérimentales a été calculé. En combinant la polarimétrie et l’étude des diagrammes de rayonnement, on peut obtenir des informations sur la structure dipolaire et l’orientation des dipôles. J'ai appliqué cette méthode pour étudier les nanoplaquettes semi-conductrices colloïdales de CdSe/CdS avec différentes formes géométriques : plaquettes carrées minces, plaquettes rectangulaires minces et plaquettes cubiques. J'ai établi une relation entre les structures géométriques des plaquettes et la nature et l'orientation de leurs dipôles émetteurs associés. / Control and optimization of nanomaterial emission properties, can be obtained thanks to efficient coupling between nanoemitters and nanostructures for achieving higher directivity, quicker dynamics. The requirements are the spectral tuning of the emitter to the nanostructures modes, the spatial positioning of the nanoemitter at the location of maximum intensity of the resonant nanostructure mode, and a proper orientation of the dipole nanoemitter. In plasmonics, the spectrally broad resonances make the spectral tuning easy. Whereas for spatial tuning, many strategies have been implemented successfully, the control of the dipole orientation remains a challenge. In plasmonics, for example, efficient interaction can only be achieved for dipoles orthogonal to the metallic surface. The determination of the orientation of the emitting dipole is thus very crucial for plasmonic devices such as nanoantennas. In my thesis, I contributed to the development of a polarimetric method aiming at the analysis of a nanoemitter’s emitting dipole and its orientation. I performed experiments and analyzed them. The model I used describes the emission of a dipole close to a plane interface in a wide range of realistic experimental conditions, including a very common case in plasmonics when the nanoemitter lies close a gold film. In this situation for CdSe nanocrystals which can be considered as two orthogonal degenerated emitting dipoles, the more standard defocused imaging method is not sufficiently sensitive to provide reliable quantitative information on the emitter’s orientation. With the same model, I also computed the emission diagram corresponding to the dipolar emission in far field for all these experimental conditions. By analyzing the emission’s polarization together with the emission pattern, I could determine the three-dimensional orientation of an emitting dipole. I applied this method to investigate the dipolar structure and orientation of colloidal semiconducting CdSe/CdS nanoplatelets with different geometries: thin square platelets, thin rectangular platelets, and cubic platelets. I established a relationship between the geometric structures of the platelets and the dimensionality and orientation of their associated emitting dipoles.

Orientador: Italo Odone Mazali / Dissertação ( mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-13T04:18:17Z (GMT). No. of bitstreams: 1 Correa_DeleonNascimento_M.pdf: 2416044 bytes, checksum: 1853938c864df0a03a91908eb0f6353b (MD5) Previous issue date: 2009 / Resumo: Este trabalho reporta o estudo e o desenvolvimento da metodologia de síntese e de caracterização de nanopartículas isoladas e nanopartículas heteroestruturadas caroço@casca (NCC) envolvendo os óxidos semicondutores (TiO2, CeO2 e SnO2) impregnados em suporte poroso funcional (vidro poroso Vycor ¿ PVG). Empregou-se a metodologia de Ciclos de Impregnação-Decomposição (CID) alternados de compostos metalorgânicos, a partir da técnica de decomposição de precursores metalogânicos (MOD). A metodologia CID prosseguiu com a impregnação dos compostos metalorgânicos di-(propóxido)-di-(2-etilhexanoato) de titânio (IV) [Ti(OnPr)2(hex)2], 2-etilhexanoato de cério (III) [Ce(hex)2] e 2-etilhexanoato de estanho (II) [Sn(hex)2] no PVG em condições controladas. Os estudos das curvas de ganho de massa cumulativo em função de cada CID evidenciaram que para 3 CID os sistemas responderam com um ganho cumulativo de massa de 17,5% (PVG/3SnO2), 4,3% (PVG/3CeO2) e 2,5% (PVG/3TiO2) com a concentração inicial dos precursores de partida de 0,75 molL. O efeito de confinamento quântico foi descrito pelo Modelo da Aproximação da Massa Efetiva (MAME), observado experimentalmente na borda de absorção dos espectros de refletância difusa, DRS, e pelo Modelo de Confinamento de Fônons (MCF), no deslocamento dos modos vibracionais nos espectros Raman. O tamanho de cristalito para a amostra PVG/3TiO2 por TEM e Raman/MCF foi de 4,7 e 4,9 nm, respectivamente, mostrando boa aproximação. O sistema PVG/xTiO2 apresentou variações sistemáticas (blue shift) da energia da banda proibida (Eg*) do TiO2 (óxido de titânio anatásio) nos espectros DRS, evidenciando que Eg* é uma função direta do tamanho de partícula (Eg* = f(2r)) e da metodologia CID. O raio de Bohr, aB, descrito na literatura para a aplicabilidade do MAME ao sistema PVG/xTiO2 não reproduziu a função Eg* = f(2r) de acordo com os resultados TEM. A Partir dos espectros Raman e DRS e os dados teóricos MCF, realizou-se a determinação empírica do aB de 6,4 nm para os cristalitos de TiO2 impregnados no PVG, constituindo nova metodologia para determinação do tamanho de cristalito das amostras PVG/xTiO2. A aplicabilidade do MAME ao sistema PVG/xCeO2 não ofereceu sucesso, pois os cristalitos de CeO2 sofrem acoplamento elétrons-fônons sofrendo um red shift da borda de absorção do espectro DRS. A média de tamanho de cristalito obtida por TEM e estimado por espectroscopia Raman e associado ao MCF está em torno de 5,0 nm para amostras de PVG/5CeO2 0,75-1,0 molL do precursor Ce(hex)3. Os resultados obtidos por DRS para o sistema PVG/xSnO2 demonstraram que o efeito de confinamento quântico ocorre apenas para precursores de concentração abaixo de 0,25 molL. A média de tamanho encontrado para as imagens TEM das amostras PVG/1SnO2 0,10 molL e PVG/1SnO2 0,25 molL é de 3,5 e 5,8 nm e a associação DRS/MAME 3,8 e 4,6 nm, respectivamente. Sobre a obtenção das NCC, as amostras PVG/xTiO2@yCeO2 e PVG/xCeO2@TiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) demonstraram mudança da inclinação da reta de ganho de massa cumulativo após a alternância dos precursores Ti(OnPr)2(hex)2 e Ce(hex)3 A partir das estimativas das Eg* para as amostras PVG/3TiO2@xCeO2 (x = 1, 2 e 3) comparadas com as amostras PVG@xCeO2, relacionou-se tais energias com a formação das NCC. A NCC PVG/3TiO2@3CeO2, 0,75 molL apresentou tamanho de cristalito de 6,9 nm, constituindo um caroço de TiO2 de até 4,7 nm (Raman/MCF, TEM e DRS/MAME) e uma casca de CeO2 inseridos pelos 3 CID do precursor de cério (PVG/3CeO2 constitui 4,1 nm pelo MCF) nucleando sobre o caroço PVG/3TiO2 corroborando com os dados descritos pelo ganho de massa cumulativo com a mudança da inclinação da reta. Observou-se que o sistema PVG/5CeO2@3TiO2 constituiu uma borda de absorção em torno 3,23 eV, sendo uma evidência qualitativa do recobrimento e a formação de NCC PVG/5CeO2@3TiO2, pois, se as nanopartículas PVG/5CeO2 não estivessem sido encapadas ver-se-ia uma borda de absorção correspondendo a PVG/5CeO2 em torno de 3,17 eV. O sistema PVG/xCeO2@yTiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) foi estudado por espectroscopia Raman. Os resultados mostraram deslocamentos sistemáticos do modo vibracional Eg do TiO2 dependentes da espessura da casca e a estabilização da banda T2g do CeO2 no caroço. Espectros Raman do sistema PVG/xTiO2@yCeO2 (x = 3, 5 e 7 e y = 3, 5 e 7) demonstraram a formação de bandas muitos deslocadas, quando o CeO2 se encontra na casca / Abstract: This work reports the development of a synthesis and characterization methodology for isolated nanoparticles and core-shell heterostructures nanoparticles (CSN), involving the semiconducting oxides (TiO2, CeO2 and SnO2) impregnated into a functional porous support (porous Vycor glass - PVG). The alternated impregnation¿decomposition cycle (ICD) methodology was applied from metallo-organic precursors by the used metalloorganic decomposition (MOD) technique. The ICD methodology used Ti (IV) di-(n-propoxy)-di-(2-ethylhexanoate) [Ti(OnPr)2(hex)2],.Ce(III) 2- ethylhexanoate [Ce(hex)3] and Sn(II) 2-ethylhexanoate [Sn(hex)2] impregnation into PVG in controlled conditions. The studies of the cumulative mass gain curves as functions of each ICD evidenced that, for 3 ICD, the systems had cumulative mass gains of 17.5% (PVG/3SnO2), 4.3% (PVG/3CeO2) e 2.5% (PVG/3TiO2) with initial precursor concentrations of 0.75 mol L. The quantum size effect was described by the effective mass approximation model (EMAM), observed experimentally in the absorption edge of the diffuse reflectance spectra (DRS), and by the phonon confinement model (PCM), in the vibrational modes of the Raman shift. The PVG/3TiO2 sample crystallite size was determined by TEM and Raman/PCM to be 4.7 and 4.9 nm, respectively, showing a good approach. The PVG/xTiO2 system showed systematic blue shift variations in the band gap energies (Eg*) in DRS spectra, showing that Eg* is a particle size function (Eg* = f(2r)) and ICD methodology. The Bohr radius (aB), described in literature for the EMAM application, did not describe the Eg* = f(2r) function for the PVG/xTiO2 system, in concordance with TEM data. From Raman and DRS spectra associated with PCM data, followed by the empirical aB determination for TiO2 (anatase titanium oxide) crystallites impregnated in PVG found to be 6.4 nm, constituting important methodology for crystallite size determination in PVG/xTiO2 samples. The EMAM on the PVG/xCeO2 system was not successful, the CeO2 crystallites suffers a red-shift in the DRS absorption edge as a result of effects arising from electron¿phonon coupling. The average crystallite size from TEM data and estimated by Raman spectroscopy associated with PCM are found to be around 5.0 nm for PVG/5CeO2 (0.75-1.0 mol L precursor concentration) samples. The DRS results for the PVG/xSnO2 system demonstrates that the quantum size effects occurs only below 0.25 molL precursors concentrations. The PVG/1SnO2 0.10 mol L and PVG/1SnO2 0.25 mol L average size found from TEM images were 3.5 and 5.8 nm, respectively, and the DRS/EMAM showed 3.8 and 4.6 nm, respectively. The PVG/xTiO2@yCeO2 and PVG/xCeO2@TiO2 (x = 3, 5 e 7 and y = 3, 5 e 7) CSN samples demonstrated an inclination change of the cumulative mass gain line with the Ti(OnPr)2(hex)2 and Ce(hex)3 precursor alternation. From the estimated Eg* for the PVG/3TiO2@xCeO2 (x = 1, 2 e 3) samples compared with PVG@xCeO2 samples, it was possible to relate the energies with the CSN formation. The PVG/3TiO2@3CeO2, 0.75 mol L CSN present a particles size of 6.9 nm, constituting a TiO2 core around 4.7 nm (Raman/PCM, TEM and DRS/EMAM) and a CeO2 shell insert from 3 ICD from cerium precursor (PVG/3CeO2 presents 4.12 nm by PCM). The data suggest that the CeO2 shell nucleated around the PVG/3TiO2 core, corroborating with the inclination change of the cumulative mass gain line. It was observed that the PVG/5CeO2@3TiO2 system presents an absorption edge around 3.23 eV. This shows qualitative evidence about the PVG/5CeO2@3TiO2 CSN formation. Therefore, if the PVG/5CeO2 core is not covered, it will show an absorption edge around 3.17 eV. The PVG/xCeO2@yTiO2 (x = 3, 5 e 7 e y = 3, 5 e 7) system was studied by Raman spectroscopy. The results showed systematic shifts in TiO2 A Eg band dependent for the TiO2 shell thickness and the CeO2 T2g band stabilization related to the CeO2 covered in the core. Raman spectra on the PVG/xTiO2@yCeO2 (x = 3, 5 e 7 e y = 3, 5 e 7) system showed a big band shift when CeO2 was in the shell / Mestrado / Quimica Inorganica / Mestre em Química

Orientador: Ítalo Odone Mazali / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T10:30:04Z (GMT). No. of bitstreams: 1 Santos_EliasdeBarros_D.pdf: 21364667 bytes, checksum: 387f64757c1773196fb26d80d6304b52 (MD5) Previous issue date: 2011 / Resumo: Este trabalho de tese é referente à preparação e caracterização de sistemas nanoestruturados na forma de nanopartículas caroço-casca e filmes finos alternados dos óxidos semicondutores: TiO2, MoO3 e WO3. Para tal finalidade foram preparadas nanopartículas monocomponentes individuais dos três óxidos mencionados (PVG/TiO2, PVG/MoO3 e PVG/WO3) e nanopartículas caroço-casca bicomponentes (PVG/TiO2-MoO3, PVG/MoO3-TiO2 e PVG/TiO2-WO3), usando o vidro poroso Vycor® (PVG) como suporte. Também foram preparados filmes finos individuais e alternados de TiO2 e MoO3. Para a síntese das nanopartículas foram feitas impregnações do PVG com soluções precursoras dos compostos di-(propóxido)-di-(2-etilhexanoato) de titânio (IV) em hexano, 2-etilhexanoato de molibdênio (VI) em hexano e do composto di-[hexaquis(m-acetato)triacetato(m3-oxo)tritungstênio(III, III, IV) em água. Foi empregado o procedimento de ciclos de impregnação-decomposição sucessivos, que consiste em repetir, empregando o mesmo suporte poroso, o procedimento de impregnação do composto e sua posterior decomposição térmica. Com este método foi possível controlar o tamanho das nanopartículas, que seguido da alternância dos precursores envolvidos em cada ciclo levou a obtenção de nanopartículas compostas por bicamadas (caroço-casca). Os sistemas de nanopartículas foram caracterizados pelas técnicas de espectroscopia Raman, espectroscopia UV-Vis no modo de refletância difusa, difração de raios X usando radiação síncrotron e microscopia eletrônica de transmissão de alta resolução. As nanopartículas individuais PVG/TiO2, PVG/MoO3 e PVG/WO3 e as nanopartículas caroço-casca PVG/TiO2-MoO3, PVG/MoO3-TiO2 e PVG/TiO2-WO3 exibiram efeitos de confinamento quântico por tamanho. Os resultados de caracterização mostraram que a variação do número de ciclos de impregnação-decomposição permitiu controlar o diâmetro do caroço e a espessura da casca, evidenciando as potencialidades das técnicas de caracterização para tal finalidade. Este resultado mostrou que o método de decomposição de precursores metalorgânicos, aliado ao procedimento de ciclos de impregnação-decomposição, mostrou-se eficiente na obtenção de nanopartículas caroço-casca hierarquicamente organizadas. Os filmes finos de TiO2 e MoO3, individuais e alternados, foram depositados sobre substratos de quartzo a partir de ciclos sucessivos de deposição-decomposição alternados, empregando-se a técnica de dip coating. Os filmes finos foram caracterizados por perfilometria óptica, espectroscopia UV-Vis no modo de refletância difusa, espectroscopia Raman, microscopia Raman Confocal, microscopia de força atômica e microscopia eletrônica de varredura com análise espectroscópica de dispersão de energia. Os filmes finos alternados bicomponentes são formados por uma estrutura bicamada entre os dois óxidos componentes. Apesar da maior dimensão dos filmes finos, escala micrométrica, em comparação com as nanopartículas caroço-casca, escala nanométrica, foi possível identificar por espectroscopia Raman a presença dos dois óxidos mostrando que a camada do componente superior não suprime o sinal Raman do componente inferior / Abstract: This work reports the synthesis and characterization of nanostructured systems - core-shell nanoparticles and alternate thin films - based on the semiconductor oxides: TiO2, MoO3 and WO3. For this purpose, individual monocomponent nanoparticles (PVG/TiO2, PVG/MoO3 and PVG/WO3) and bicomponent core-shell nanoparticles (PVG/TiO2-MoO3, PVG/MoO3-TiO2 and PVG/TiO2-WO3) of the above mentioned oxides using porous Vycor® glass (PVG) as support were synthesized. Also, individual thin films and alternate thin films of TiO2 and MoO3 were prepared. For the nanoparticles synthesis, the procedure used was based on the impregnation of PVG pieces with titanium (IV) di-(n-propoxy)-di-(2-ethylhexanoate) in hexane, molybdenum (VI) 2-ethylhexanoate in hexane, or di-[hexakis(m-acetato)triacetate(m3-oxo)tritungstato of hexakis(m-acetate)triaquo(m3-oxo)tritungsten(III, III, IV) in water, followed by thermal decomposition. This procedure, successively repeated over the same PVG piece, was named impregnation-decomposition cycle. With this method it was possible to control the nanoparticles size, and by alternating the metallo-organic precursors used, it was possible to obtain nanoparticles with core-shell architecture. Nanoparticle-based systems were characterized by Raman and diffuse reflectance UV-Vis spectroscopies, powder X-ray diffraction using synchrotron radiation and high resolution transmission electron microscopy. Individual nanoparticles PVG/TiO2, PVG/MoO3 and PVG/WO3 and the core-shell nanoparticles PVG/TiO2-MoO3, PVG/MoO3-TiO2 and PVG/TiO2-WO3 are under quantum confinement regime. Characterization showed that the change in the impregnation-decomposition cycle number enables one to control the core size and shell thickness, showing the potential characterization for this purpose. This result showed that metallo-organic decomposition method and impregnation-decomposition cycle procedure is efficient to prepare organized hierarchically core-shell nanoparticle. Thin films of individual and alternated TiO2 and MoO3 were prepared by dip coating of the Ti(IV) and Mo(VI) metallo-organic precursors listed above over quartz slides, followed by thermal decomposition. This procedure, successively repeated over the same quartz slide, was named deposition-decomposition cycle. The thin films were characterized by optical profilometry, Raman and diffuse reflectance UV-Vis spectroscopies, confocal Raman microscopy, atomic force microscopy and scanning electron microscopy with energy dispersive spectroscopic analysis. The thin films formed by two-component show bilayered structure between the two oxide components. Despite the differences in dimension between thin films - in micrometer scale - and the supported core-shell nanoparticles - in nanometer scale - Raman spectroscopy was able to identify in both systems the presence of the two oxides, showing that the top layer component does not suppress the Raman signal of the lower component / Doutorado / Quimica Inorganica / Doutor em Ciências

The Electrospray (ES) technique is a promising particle generation method for drug delivery due to its capabilities of producing monodisperse PLGA composite particles with unique configurations and high drug encapsulation efficiency. In the dissertation work, the coaxial dual capillary ES was used to generate drug-loaded core-shell PLGA particles to study the effects of particle filling materials, drug loading locations and particle shell thicknesses on the resultant in vitro release behaviors of the hydrophilic and/ or hydrophobic model drugs. Through release profile characterization of drug-loaded PLGA particles (particle size: 400 nm and 1 μm), it was confirmed that the co-encapsulation of Budesonide (BUD, the hydrophobic small-molecule model drug) and Theophylline (THY, the hydrophilic small-molecule model drug) in the particle cores is the most effective drug loading strategy for extended release of the fixed combined BUD and THY. Particles composed of PLGA fillers with lower molecular weights and with greater shell layer thicknesses could release THY in a well controlled fashion. On the other hand, a slower release rate of Bovine Serum Albumin (BSA, the protein model drug) from PLGA particles with greater shell thickness was also observed. Sequential release of BSA and Paclitaxel (PTX, the hydrophobic small-molecule anti-cancer model drug) was achieved by the 400-nm PLGA (Mw: 7,000-17,000 g/mol, LA/GA: 50/50) particles with potential biopharmaceutical applications in cancer therapy.

Au cours ce travail, nous nous sommes intéressés au design de particules plasmoniques pour le contrôle de l’absorption et de l’émission de lumière. Notre stratégie a été de synthétiser des nanoparticules de type cœur@écorce composées d’un cœur d’or et d’une écorce diélectrique de silice contenant des molécules organiques fluorescentes. Nous avons fait varier la distance entre ces dernières et le cœur afin de moduler l’intensité de leur couplage avec les plasmons du métal et d’ainsi contrôler les propriétés optiques des nanoparticules. Nous nous sommes aussi intéressés à l’assemblage de ces nanoparticules sous la forme de supra-particules ou de réseaux bidimensionnels organisés. L’étude des propriétés optiques de ces nouveaux matériaux a permis de mettre en évidence une forte exaltation de l’intensité de fluorescence des particules cœur@écorce quand celles-ci sont confinées entre deux nappes métalliques, ce qui correspond à un mode de cavité fort. Nous avons également travaillé sur la synthèse de particules composées d’un cœur de silice et soit d’une écorce d’or présentant des patchs « vierges », soit d’une écorce de dioxyde de titane comportant des patchs recouverts de nanoparticules d’or. / During this work, we were interested in the design of plasmonic particles for the control of the absorption and the emission of light. Our strategy was to synthesize core@shell nanoparticles made of a gold core and a silica shell containing fluorescent organic molecules. We have varied the distance between the emitters and the core in order to tune their coupling with the plasmons of gold. We thus tuned the optical properties of the particles. We were also interested in the assembly of these nanoparticles to get supra-particles or organized two-dimensional networks. The study of optical properties of these new materials showed that the exaltation of the fluorescence is maximal when the core@shell particles are confined between two gold boundaries, this situation corresponding to a strong cavity mode. We also worked on the synthesis of particles consisting of a silica core and either a gold shell with bare patches or a titanium dioxide shell with patches covered with gold nanoparticles.

Nos objectifs sont ici de comprendre comment les propriétés magnétiques de nanoparticules (NPs) sont affectées par la diminution de leur taille et par leur composition chimique, et comprendre ce qui régit leur mouvement thermophorétique et l'effet magnéto-calorique. Des ferrofluides composés de NPs de structure cœur-couronne sont synthétisés ici avec un cœur de ferrite de Mn, de Co ou de ferrite mixte Zn-Mn, recouvert d'une couronne de maghémite. Les mesures magnétiques révèlent une composition magnétique mixte conduisant à l'observation d'un exchange bias qui se manifeste par des cycles d'hystérésis décalés à basses températures. Nous comparons ce phénomène dans le cas de NPs à cœur magnétiquement dur (CoFe2O4) et à cœur magnétiquement mou (MnFe2O4). Indépendamment de la nature du cœur, ce champ d'échange augmente jusqu'à un maximum, obtenu quand le champ de refroidissement est de l'ordre de la moitié du champ d'anisotropie. Les propriétés thermophorétiques des dispersions, sondées par diffusion Rayleigh forcée, sont gouvernées par la physico-chimie du colloïde (ligand de surface, contre-ions, interactions entre NPs) indépendamment de la composition chimique et des propriétés magnétiques en champ nul. Le coefficient Soret est ici négatif (NPs thermophiles) et est relié à la compressibilité osmotique donnée par un formalisme de Carnahan-Starling effectif. On modélise la friction en régime dilué par la loi d'Einstein et en régime concentré, à l'approche de la transition vitreuse, par un modèle de Vogel-Fulcher. Les mesures de l’effet magnéto-calorique démontrent une similarité avec les matériaux commerciaux, avec une forte influence de la composition chimique du cœur. / Our objective is to understand how the magnetic properties of nanoparticles (NPs) can be affected by their size reduction and their chemical composition, and also to determine their role on their thermophoretic motion and on the magneto-caloric effect. For this purpose, aqueous ferrofluids are synthesized with core-shell NPs based on a core of Mn-ferrite, Co-ferrite and mixed Zn-Mn ferrites, coated with a maghemite shell. The magnetic measurements evidence a ferrimagnetic core, covered with disordered frozen spins (SGL), driving an exchange bias phenomenon shifting the hysteresis loops, when the system is cooled under a field Hfc. This exchange bias is measured as a function of Hfc, in samples with NPs having either a hard (CoFe2O4) or a soft (MnFe2O4) magnetic core. Whatever the nature of the magnetic core, the exchange bias field grows up to reach a maximum, always found at Hfc of the order of half of the anisotropy field. The thermophoretic properties of the dispersions, probed by Forced Rayleigh Scattering, are ruled by colloidal physico-chemical features (surface ligand, counter ions, interparticle interactions) whatever the chemical composition and the magnetic properties in zero magnetic field. The Soret coefficient is found here negative (thermophilic NPs) and is related to the osmotic compressibility, modeled by an effective Carnahan-Staring formalism. In the dilute regime, the friction follows an Einstein law, while a Vogel-Fulcher formalism describes the concentrated regime, at the approach of the glass transition. The magneto-caloric measurements demonstrate a similarity with commercial materials. They are strongly influenced by the core composition.