Les nanocristaux d'AgInS2-ZnS sont des candidats prometteurs pour le développement de nano-luminophores non-toxiques et performants. Grâce à leur taille et à leur forte absorption, ces nano-luminophores permettent l'exploitation d'effets nano-optiques pouvant augmenter leur efficacité à l'absorption ou à l'émission. Ce document présente, dans un premier temps, une méthode d'analyse qui couple la mesure du rendement quantique à celle du temps de vie de luminescence et permet l'étude des contributions radiatives et non-radiatives des différents mécanismes de luminescence des nanocristaux d'AgInS2-ZnS. En modifiant la taille, la chimie de surface et la structure du cœur de ces nanocristaux, nous construisons un modèle global expliquant le rôle de leur composition et soulignant l'importance de leur surface. De nouvelles stratégies sont identifiées pour optimiser ces nanomatériaux. Leur application conjointe permet d'envisager des rendements quantiques proches de 90%. Dans un second temps, une méthode de simulation numérique générale a été développée pour prédire l'effet produit par le couplage nano-optique entre une particule plasmonique et un luminophore. Cette méthode a été appliquée au cas des structures cœur/coquille/coquille (métal/isolant/AgInS2-ZnS) et les configurations optimales du système ont été déterminées. Une nanostructure particulièrement performante permettant de combiner les effets du couplage à l'absorption et à l'émission a été identifiée. Une méthode de synthèse de ces nanostructures est développée. Les résultats expérimentaux obtenus sont en accord à la fois avec la compréhension de la fluorescence des nanocristaux d'AgInS2-ZnS et la prédiction obtenue par simulation. / AgInS2-ZnS nanocrystals are promising materials for the development of non-toxic, highly efficient nano-phosphors. Their size and strong absorption allow them to exploit nano-optical effects potentially enhancing both their absorption and emission processes. This work presents a method combining quantum yield measurements with time resolved emission spectroscopy allowing for the study of both radiative and non-radiative properties of each recombination pathways. Modifying the size, surface chemistry, and core structure of the nanocrystals, we construct a global model explaining the role of their composition and emphasizing the critical aspect of their surface. New strategies are identified to increase the internal quantum yield of these materials. Combining these approaches, it is now possible to expect 90% efficiencies. In a second step, a simulation method was developed to predict the nano-optical effects induced by a plasmonic nanostructure on a given phosphor. We applied this method on core/shell/shell (metal/insulator/AgInS2-ZnS) nanostructures and theoretically determined optimal configurations of the system. A particularly efficient nanostructure achieving coupling on both absorbed and emitted light is identified. Hybrid plasmonic nanostructures are synthesized. Their performances are in accordance with both our understanding of the fluorescence mechanisms of AgInS2-ZnS nanocrystals and the predictions made via simulation.

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.

Neste trabalho estudamos as propriedades estruturais, energéticas e eletrônicas das nanopartículas puras de prata (Ag) e de ouro (Au) e estruturas do tipo core-shell com número total de átomos variando de 147 à 923, no formato cubo-octaédrico. Estudamos também a adsorção da molécula de metanotiol (SCH4) sobre os sítios de coordenação dessas nanoestruturas, analisando, entre outros aspectos, os efeitos da interação de van de Waals. Para tanto, foram feitos cálculos teóricos de primeiros princípios dentro da Teoria do Funcional da Densidade (DFT) usando a Aproximação do Gradiente Generalizado (GGA) e Pseudopotenciais Ultrassuaves (USPP). Concluímos que as maiores nanopartículas puras e core-shell apresentam uma superfície mais esférica e suas energias de formação tendem às energias das superfícies [001] e [111] e dos bulks de Ag e de Au. Uma única camada de shell de ouro ou de prata na core-shell já determina praticamente o comportamento energético e as propriedades da nanopartícula. A inclusão da interação de van de Waals nos cálculos uniformiza, de certa forma, os padrões de deslocamento atômico das superfícies das nanopartículas e o comportamento energético das core-shell, sem entretanto alterar o perfil das densidades de estado. A adsorção da molécula de metanotiol nas nanopartículas puras de Ag e de Au e suas core-shell foi analisada verificando-se que ela praticamente não perturba os estados eletrônicos das nanopartículas e que sua estrutura molecular é preservada. Nas nanopartículas maiores verifica-se um único padrão de adsorção independente do número de camadas de shell nas estruturas core-shell. / In this work we study the structural, energetic and electronic properties of the pure nanoparticles of silver (Ag) and gold (Au) and their core-shell with total number of atoms ranging from 147 to 923 in cube-octahedral shape. We also investigated the adsorption of the methanethiol molecule (SCH4) in the coordination sites of these nanoparticles, analyzing, among other things, the influence of dispersion(van der Waals) interactions. Our simulations are performed using first principles theoretical calculations within of the Density Functional Theory (DFT) framework, described in terms of the Generalized Gradient Approximation (GGA), and by using Ultra-Soft Pseudo-potentials (USPP). We conclude that the largest pure nanoparticles and core-shell have a more spherical surface and their formation energies tend to formation energies of bare surfaces [001] and [111] and bulks of Ag and Au. A single layer of gold or silver shell already determines the properties and energetic behavior of the nanoparticles. The inclusion of van der Waals\' dispersion interaction in the calculations makes uniform, in certain way, the atomic displacement patterns surfaces of the nanoparticles and energetic behavior of core-shell, without change the form of the density of states. The adsorption of methanethiol molecule on the surface of the Ag and Au pure nanoparticles and their core-shell was analyzed and we verified that it almost does not disturb the electronic states of the nanoparticles and their molecular structure is preserved. In the largest nanoparticles we checking only one pattern of adsorption independent of the number of layers shell in the core-shell.

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

Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2016-10-27T16:02:50Z No. of bitstreams: 2 Dissertação - Paula Daiany Gonçalves Silva - 2016.pdf: 5020325 bytes, checksum: 7a70eccab776cc3598c1f6236a35273d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2016-11-07T13:53:03Z (GMT) No. of bitstreams: 2 Dissertação - Paula Daiany Gonçalves Silva - 2016.pdf: 5020325 bytes, checksum: 7a70eccab776cc3598c1f6236a35273d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2016-11-07T13:53:03Z (GMT). No. of bitstreams: 2 Dissertação - Paula Daiany Gonçalves Silva - 2016.pdf: 5020325 bytes, checksum: 7a70eccab776cc3598c1f6236a35273d (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-03-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Since the early 90's researchers have investigated the combination of nanocomposites comprised of multilayers, which have better efficiency than their corresponding individual particles, may present in certain cases, new properties. The resulting structure is called a core-shell. In this study, were synthesized ZrO2:Y 3+ coated with TiO2, obtaining nanocomposites ZrO2:Y 3+ @TiO2 with a thickness of 10, 20 and 50% shell. The photoluminescent property (FL) of the nanocomposites was studied. Such interest is due to the fact that the order/disorder structural at the interface of the core-shell type systems may be possible recombination processes responsible for the photoluminescence emission of these materials. Nanoparticles of the core and the shell were obtained by the Method of Polymeric Precursors. The samples were characterized by X-ray diffraction (XRD) to identify the formation of the nanocomposite and evaluate the structural order in the synthesized materials. The core was obtained with tetragonal structure and the shell with anatase structure. From the diffractograms have been carried out calculations of the crystallite size and lattice parameters. The characterization by Transmission Electron Microscopy (TEM), it was not possible to differentiate the core of the shell by the images, since both are structurally ordered, requiring analysis by Energy Dispersive X-ray (EDX), which was verified the presence of Zr and Ti elements that comprise the core-shell nanocomposite. The FL emission results were explained as a function of the shell thickness, as well as the effect of calcination temperature on the order-disorder structural material. To evaluate the performance of the FL issuing nanocomposites were calculated chromaticity coordinates, based on the FL emission spectra. / Desde o início da década de 90 pesquisadores vêm investigando a combinação de nanocompósitos constituídos por multicamadas, os quais apresentam melhor eficiência do que suas partículas individuais correspondentes, podendo apresentar em alguns casos, novas propriedades. A estrutura obtida é denominada core shell. No presente trabalho, foram sintetizados ZrO2:Y 3+ recobertos com TiO2, obtendo nanocompósitos ZrO2:Y 3+ @TiO2 com espessura de 10, 20 e 50% de shell. Foi estudada a propriedade fotoluminescente (FL) dos nanocompósitos. Tal interesse deve-se ao fato de que a ordem/desordem estrutural na interface dos sistemas do tipo core-shell pode ser possibilitar processos de recombinação responsáveis pela emissão fotoluminescente destes materiais. As nanopartículas do core e do shell foram obtidos pelo Método dos Precursores Poliméricos. As amostras foram caracterizadas por difração de Raios X (DRX) a fim de se identificar a formação do nanocompósito e avaliar a ordem estrutural nos materiais sintetizados. O core foi obtido com estrutura tetragonal e o shell com estrutura anatase. A partir dos difratogramas foram realizados cálculos do tamanho de cristalito e parâmetros de rede. Na caracterização por Microscopia Eletrônica de Transmissão (MET), não foi possível diferenciar o core do shell pelas imagens, uma vez que ambos encontram-se estruturalmente ordenados, sendo necessária a análise por Energia Dispersiva de Raios X (EDX), na qual verificou-se a presença dos elementos Zr e Ti que compõem o nanocompósito core-shell. Os resultados de emissão FL foram explicados em função da espessura do shell, bem como pelo efeito da temperatura de calcinação na ordem-desordem estrutural do material. Para avaliar o desempenho da emissão FL dos nanocompósitos foram calculadas as coordenadas de cromaticidade, baseado nos espectros de emissão FL.

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