Les travaux de cette thèse ont porté sur les micro-bolomètres (détecteurs infrarouges non refroidis) qui fonctionnent selon le principe suivant : le rayonnement infrarouge incident provoque l’échauffement d’une membrane suspendue dont la résistivité électrique dépend de la température. Deux voies ont été explorées pour les améliorer, grâce aux nanotechnologies. D’une part, les propriétés optiques et électroniques (transport et bruit) des films de nanotube de carbone ont été étudiées afin d’évaluer le potentiel de ce nouveau matériau comme thermistor. Pour ce faire des procédés technologiques en salle blanche, des caractérisations et des modèles théoriques ont été mis au point. Après avoir obtenu les figures de mérite adaptées, cette étude a conclu au manque de potentiel de ce matériau pour une application aux micro-bolomètres. D’autre part, nous avons étudié des résonateurs sub-longueur d’onde basés sur des cavités métal-isolant-métal permettant d’obtenir des absorbants totaux, et omnidirectionnels. Un modèle analytique permettant de les décrire et de les concevoir rapidement a été mis au point. La combinaison de ces résonateurs à l’échelle sub-longueur d’onde a permis de mettre en évidence un phénomène de tri de photon et la possibilité de concevoir des absorbants large bande. Nous avons ainsi proposé (et breveté) l’utilisation de ces antennes comme absorbants pour les micro-bolomètres. En effet leur capacité à focaliser le champ dans des volumes sub-longueur d’onde permet d’introduire une rupture conceptuelle pour la conception de bolomètres à hautes performances. / This work was focused on bolometers (uncooled infrared sensors), which are based on the following principle: the incoming infrared radiation is absorbed by a self-standing membrane whose resistivity depends on temperature. In order to improve their design and performances, we explored two solutions based on nanotechnologies. On the one hand, optical and electronic (transport and noise) properties of carbon nanotube films have been investigated in order to evaluate the potential of this new material as a thermistor. Clean room processes, characterization benches and theoretical models have been developed. The obtained figures of merit allow to concluding on the lack of potential for applications in uncooled infrared sensors. On the second hand, subwavelength resonators based on metal-insulator-metal cavities, have been investigated and exhibit perfect, tunable and omni-directional absorption. An analytical model allowing a fast study and design of these resonators has been developed. Photon sorting and wideband absorption have been demonstrated thanks to the combination of these resonators at the sub-wavelength scale. We have thus proposed (and patented) the use of such “antennas” as micro-bolometer’s absorber. Indeed their capacity to focalize the incoming radiation at a subwavelength scale paves the way to the conception of high performance micro-bolometers.

L’une des tendances naturelle des technologies photovoltaïque est la réduction systématique de l’épaisseur des cellules solaires, que cela soit pour des raisons de coûts, d’économie d’éléments rares ou toxiques ou encore pour limiter les recombinaisons. Jusqu’à présent, les technologies couche minces cristallines (GaAs) et poly-crystallines (CIGS) trouvent des optimum d’efficacité de conversion pour des épaisseurs aux alentours de 1 ou 2 microns. Typiquement, cette gamme d’épaisseur ne nécessite pas de nouvelles solutions de piégeages optiques comme cela est le cas pour la filière silicium amorphe. Cependant, si l’on veut réduire ces épaisseurs d’un facteur 10 voire même 100 afin de s’orienter vers les nouveaux concepts de collections et conversions (GaAs ou GaSb) ou encore de réduire l’utilisation d’indium (CIGS), de nouveaux besoin en matière d’absorption efficace de la lumière sont nécessaires pour ces technologies. Ce manuscrit de thèse se concentre sur la conception, la simulation et la réalisation de solutions nanophotoniques nouvelles pour de futures cellules solaires cristallines ultrafines.Dans un premier temps, nous nous sommes engagé dans une approche en rupture avec la conception habituelle des cellules solaires pour piéger la lumière dans une cellule ultrafine (≤100 nm de matériaux couche-mince (GaAs, GaSb et CIGS). Nous proposons un réseau métallique nanostructuré placé en face avant de la cellule reportée sur un miroir métallique afin d'obtenir une absorption très élevée et multi-résonante, indépendante de l’angle d’incidence et de la polarisation. Une analyse numérique approfondie des mécanismes résonants en jeu a été menée ainsi que la fabrication et la caractérisation optique de démonstrateurs. Les résultats de cette étude sont motivants pour des travaux futurs sur les dispositifs ultrafins, mettant en jeu de nouveaux concepts de collection (transport balistique) ou de conversion (cellules solaires à porteurs chauds).Dans un deuxième temps, nous avons étudié la possibilité d’intégrer à court terme un contact arrière nanostructuré en or à des cellules solaires fines (200-400 nm) en CIGS afin d’augmenter potentiellement le courant de court-circuit et la tension de circuit ouvert. Nous avons proposé un procédé innovant pour réaliser cette structure et ce piégeage optique, jusqu’à lors inédits pour les cellules en CIGS. Etude numérique, fabrications de démonstrateurs et premières caractérisations de cellules solaires ultrafines sont présentés. / One of the natural tendencies of photovoltaic technologies is the systematic reduction of the thickness of the solar cells in order to reduce the cost, to save rare or toxic elements or to limit recombination. So far, crystalline thin-film (GaAs) and poly-crystalline (CIGS) technology are reaching optimum conversion efficiency for thicknesses around 1 or 2 microns. Typically, this thickness range does not require new solutions of optical trappings as it is the case for amorphous silicon. However, if we want to reduce these thicknesses by a factor of 10 or even 100 to study new concepts of collections and conversions (GaAs or GaSb) or reduce the use of indium (CIGS), new needs for efficient light absorption are necessary for these technologies. This manuscript is focused on the design, simulation and realization of innovative nanophotonic solutions for future ultra-thin crystalline solar cells.As a first step, we were engaged in an approach at odds with the usual design of solar cells to trap light in a ultra-thin (≤100 nm) layer of material (GaAs, GaSb and CIGS). We propose an array of metal nanostructure placed in front of the cell, transferred on a metal mirror in order to obtain a high, multi-resonant absorption independent of the angle of incidence and polarization. Numerical analysis of the resonant mechanisms involved was conducted as well as the fabrication and optical characterization of demonstrators. The results of this study are motivating for future work on the ultra-thin devices, involving new concepts of collection (ballistic transport) or conversion (hot carrier solar cells).On the other hand, we studied the possibility of integrating a rear gold nanostructured back contact (200-400 nm) in thin CIGS solar cells to potentially increase the current of short circuit and open circuit voltage. We have proposed an innovative process to achieve this structure and the optical trapping for CIGS solar cells. Numerical study, manufacture of demonstrators and first measurements are presented.

Les nanoparticules de métaux nobles possèdent des propriétés optiques étonnantes. Sous l’effet de la lumière, elles sont capables de résonner pour générer des plasmons de surface localisés. Ces plasmons absorbent ou diffusent la lumière aux longueurs d’ondes de ces résonnances et sont fortement dépendants de la forme, de la taille et de l’environnement des nanoparticules. Dans ce manuscrit, elles sont impliquées dans la conception de matériaux furtifs à des fins militaires.Des nanoparticules d’argent de formes contrôlées ont été associées à un polymère pour élaborer de nouveaux matériaux hybrides déposables par voie liquide sous la forme de couches minces.Un absorbeur quasi-parfait (98,8%) sur une gamme étroite de longueur d’onde a été obtenu en maintenant une très bonne dispersion des nanoparticules dans la couche, alors qu’un absorbeur large bande efficace (~90%) sur toute la gamme spectrale du visible a été réalisé en provoquant l’agrégation des nanoparticules. Une étude qualitative par microscopie et spectroscopie sur la densité et l’organisation des nanoparticules au sein de la couche mince a mis en évidence la présence de couplages plasmoniques de natures et d’intensités différentes en fonction de l’espacement entre les cubes. Il a été montré que les propriétés optiques mesurées étaient indépendantes de la nature du substrat utilisé, mais aussi indépendantes de l’angle de la lumière incidente sur une large gamme angulaire. Enfin, des systèmes multicouches déposés par voie liquide ont été explorés afin d’étendre l’absorption des couches jusqu’au proche infrarouge par l’ajout de matériaux tel que le l’oxyde de tungstène. / Nanoparticles of noble metals have unexpected optical properties. Under the effect of light, they are able to resonate, generating localized surface plasmon resonances that are used in many applications. These plasmons absorb and scatter the light at the wavelengths of these resonances and are highly dependent on the shape, the size and the environment of the nanoparticles. In this thesis, they are applied for the design of stealth materials for military purposes. For this, controlled shapes of silver nanoparticles were blended within a polymer to develop new hybrid materials that are solution-processed as thin layers. A quasi-perfect absorber (98,8%) in a precise range of wavelengths has been obtained by maintaining well-dispersed nanoparticles in the layer, while an effective broadband absorber (~90%) over the entire visible range has been achieved by triggering the aggregation of the nanoparticles. Microscopy and spectroscopy qualitative studies performed on the density and organization of the nanoparticles within the thin layers revealed the presence of plasmonic couplings of different natures and intensities as a function of the spacing between the cubes. It has been shown that the optical properties measured are independent of the nature of the substrates used and independent of the angle of the incident light on a wide angular range. Finally, solution-processing of multilayers systems was explored to extend the absorption of the layers to the near infrared by the addition of other materials such as tungsten oxide.

Targeting of key events in viral infection pathways creates opportunities for virus disease prevention and therapy. Nanoparticles with well-defined surfaces are promising tools for the direct visualization of biological processes and for interrogating virus behavior that is usually determined by the synergistic interplay of multiple factors and involves various transient signaling steps. Smart nanoparticles mimicking enveloped viral particles are thus developed and tested in this work with the aim to de-couple key steps in human immune-deficiency virus HIV-1 trans-infection with an engineerable viral model system. Uni-lamellar liposomes resemble biological lipid bilayer membrane structures with tunable particle size, surface charge, and composition. Pretreatment with ganglioside-GM3-containing liposomes inhibited the binding of HIV-1 by dendritic cells, indicating an essential role for GM3 in virus binding. To equip the liposome based model systems with strong non bleaching optical properties, the membranes were in the next step assembled around noble metal nanoparticle core. Noble metal nanoparticles with a size of 20nm-100nm have extraordinarily large scattering cross-sections and enable prolonged tracking of even individual particles with high temporal and spatial resolutions. The plasmon resonance peak of near-field coupled gold nanoparticles red-shifts within decreasing interparticle separation. The distance dependent optical properties of noble metal nanoparticles were utilized for characterizing clustering levels of breast cancer cell marker protein CD24 and CD44 on immortalized cancer cell lines. These encouraging results supported the choice of gold nanoparticles as core for multi-modal artificial virus nanoparticles. Artificial virus nanoparticles combine the biological versatility of a self-assembled membrane with the unique optical properties of a nanoparticle core. We developed these hybrid materials specifically for the purpose of elucidating key steps of the glycoprotein independent binding and uptake of HIV-1 during trans-infection. Systematic validation experiments revealed that GM3 containing artificial virus nanoparticles (AVNs) recapitulate the initial capture and uptake of viruses by sialoadhesin CD169 presenting cells. The AVNs also reproduced the tendency of the virus to re-distribute into confined cluster spots in cell peripheral areas. Upon contact formation between T cell and DC, the AVNs developed a polarized distribution in which they enriched at the interface between DC and CD4+ T cells. The multimodality of the AVNs was instrumental in determining the detailed location and kinetics of the nanoparticles during the trans-infection process, proving the AVN system to be a unique model system to address key mechanistic questions in the infection pathway of enveloped virus particles.

Multifunctional plasmonic nanoparticles have shown extraordinary potential for near infrared photothermal and triggered-therapeutic release treatments of solid tumors. However, the accumulation rate of the nanoparticles in the target tissue, which depends on their capacity to escape the immune system, and the ability to efficiently and accurately track these particles in vivo are still limited. To address these challenges, we have created two different systems. The first one is a multifunctional nanocarrier in which PEG-coated gold nanorods were grouped into natural cell membrane vesicles from lung cancer cell membranes (A549) and loaded with β-lap (CM-β-lap-PEG-AuNRs). Our goal was to develop specific multifunctional systems for cancer treatment by using the antigens and the unique properties of the cancer cell membrane combined with photothermal properties of AuNRs and anticancer activity of β-lap. The results confirmed the assembly of PEG-AuNRs inside the vesicles and the irradiation with NIR laser led to disruption of the vesicles and release of the PEG-AuNRs and β-Lap. In vitro studies revealed an enhanced and synergic cytotoxicity against A549 cancer cells, which can be attributed to the specific cytotoxicity of β-Lap combined with heat generated by laser irradiation of the AuNRs. No cytotoxicity was observed in absence of laser irradiation. In the second system, MRI-active Au nanomatryoshkas were developed. These are Au core-silica layer-Au shell nanoparticles, where Gd(III) ions are encapsulated within the silica layer between the inner core and outer Au layer of the nanoparticle (Gd-NM). This theranostic nanoparticle retains its strong near infrared optical absorption properties, essential for in vivo photothermal cancer therapy, while simultaneously providing increased T1 contrast in MR imaging by concentrating Gd(III) within the nanoparticle. Measurements of Gd-NM revealed a substantially enhanced T1 relaxivity (r1 ~ 17 mM-1 s-1) even at 4.7 T, surpassing conventional Gd(III)-DOTA chelating agents (r1 ~ 4 mM-1 s-1) currently in clinical use. The observed relaxivities are consistent with Solomon-Bloembergen-Morgan (SBM) theory, describing the longer-range interactions between the Gd(III) and protons outside the nanoparticle. These novel multifunctional systems open the door for the development of more efficient nanoplatforms for diagnosis and treatment of cancer. / Nanopartículas plasmônicas multifuncionais têm revelado elevado potencial para fototermia na região (NIR) do infravermelho e liberação controlada de fármacos para o tratamento de tumores sólidos. No entanto, a taxa de acumulação das nanoparticulas no tecido alvo, que depende da capacidade delas de escapar do sistema imunológico, e a habilidade de rastrear de maneira efetiva essas partículas in vivo ainda são limitadas. Para superar essas barreiras, dois sistemas diferentes foram desenvolvidos. O primeiro corresponde a um nanocarreador multifunctional, onde nanobastões de ouro funcionalizados com PEG foram agrupados dentro de vesículas de membranas de células naturais originarias de células cancerígenas de pulmão (A549) conjugadas com β-Lap (CM-β-lap-PEG-AuNRs). Nosso principal objetivo foi desenvolver um sistema multifuncional especifico para tratamento de câncer utilizando os antígenos e propriedades únicas da membrana das células cancerígenas combinados com as propriedades fototérmicas dos AuNRs e a atividade anticancerígena da β-Lap. Os resultados confirmaram o agrupamento dos PEG-AuNRs dentro das CM e irradiação com o laser no NIR levou ao rompimento das vesículas e liberação dos AuNRs e β-Lap. Estudos in vitro revelaram uma elevada e sinérgica citotoxicidade contra células A549, que pode ser atribuída a combinação da especifica toxicidade da β-Lap com o calor gerado pelos AuNRs por meio da irradiação com laser. Nenhuma citotoxicidade significativa foi observada na ausência de irradiação com laser. No segundo sistema, nanomatryoshkas de Au ativas em MRI foram desenvolvidas. Elas consistem em um núcleo de Au, uma camada intersticial de sílica, onde os íons de Gd(III) são encapsulados, e uma camada externa de Au (Gd-NM). Esta nanopartícula teranóstica mantém as propriedades de elevada absorção óptica no NIR, enquanto simultaneamente fornece um elevado contraste T1 em imagem por ressonância magnética por meio da concentração dos íons de Gd(III) dentro da nanoparticula. Medidas de Gd-NM revelaram uma relaxividade elevada (r1 ~ 17 mM-1 s-1 ) a 4,7 T, superando os convencionais agentes quelantes de Gd(III)-DOTA (r1 ~ 4 mM-1 s-1) utilizados clinicamente. As relaxividades observadas são consistentes com a teoria Solomon-Bloembergen-Morgan (SBM), descrevendo as interações de longo alcance entre Gd(III) e prótons de H fora da partícula. Os novos sistemas multifuncionais desenvolvidos abrem oportunidades para o desenvolvimento de nanoplataformas mais eficientes para o diagnóstico e tratamento de câncer.

Smart nanomaterials can selectively respond to a stimulus and consequently be activated in specific conditions, as a result of their interaction with electromagnetic radiation, biomolecules, pH change, etc. These nanomaterials can be produced through distinct routes and be used in artificial skin, drug delivery, and other biomedical applications. In this thesis, two smart nanosystems were developed, viz., i) nanocapsules formed by aniline (A) and chitosan (CS) (A-CS) containing silver nanoparticles (AgNPs), with an average size of 78 ± 19 nm, and ii) polycaprolactone (PCL) nanofibers, fabricated by the electrospinning technique containing AgNP into their bulk, with a diameter of 417 ± 14 nm. A novel system, based on the incorporation of the as-prepared nanocapsules onto the surface of PCL nanofibers containing AgNps (antibacterial mats), was also developed. The methodology employed avoids the direct contact of silver nanoparticles with the host and optimizes its release to the surrounding environment. The AgNPs release was triggered by exposing the nanocapsules to light at 405 nm. Consequently, the electronic energy vibration resulting from the interaction of the irradiation with the surface plasmon band (SPR) of AgNps, breaking the hydrogen bonds of the nanocapsules and releasing of AgNPs at a time of 150 s. To understand the perturbation of AgNps-Nanocapsules against bacteria, membrane models using Langmuir technique with the phospholipids 1,2-dipalmitoyl-sn-glycero-3-phospho-(1\'-rac-glycerol) (DPPG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) were employed, which are the main components of cell membrane of Escherichia coli (E. coli). The results suggest that DPPG has more influence on the incorporation of the nanoparticles on the cell membrane. The antibacterial properties of the nanofibers/nanomaterials mats towards E. coli and Staphylococcus aureus (S. aureus) were investigated using the Agar diffusion test for 8 samples. The experiments revealed that the samples based on nanofibers/nanocapsules and irradiation presented a radius of inhibition of 2.58 ± 0.28 mm for S. aureus and 1.78 ± 0.49 mm for E. coli. This nanosystem showed to be highly interesting for biomedical applications. / Nanomateriais inteligentes podem responder seletivamente a um estímulo e consequentemente ser ativados em condições específicas, como resultado da sua interação com a radiação eletromagnética, mudança do pH, campo magnético, etc. Esses materiais podem ser produzidos através de distintas rotas e utilizados em aplicações como pele artificial, liberação de fármacos, e outras aplicações biomédicas. Nessa tese, dois nanossistemas inteligentes foram desenvolvidos, a saber: i) nanocápsulas formadas por anilina (A) e quitosana (CS) (A-CS) contendo nanopartículas de prata (AgNps), com um tamanho médio de 78 ± 19 nm, e ii) nanofibras de policaprolactona (PCL), fabricadas pela técnica de eletrofiação contendo AgNps em seu interior, com diâmetro de 417 ± 14 nm. Um terceiro sistema foi desenvolvido, baseado na incorporação das nanocápsulas na superfície das nanofibras de PCL contendo AgNps (manta antibacteriana). A metodologia utilizada evita o contato direto das nanopartículas de prata com o hospedeiro e otimiza sua liberação no meio ambiente. As AgNps liberadas foram acionadas pela exposição das nanocápsulas à um fonte de luz em 405 nm. Consequentemente, a vibração da energia eletrônica resultante da interação da irradiação com a banda plasmônica de superfície (SPR) das AgNps, quebra as ligações de hidrogênio da nanocápsula e libera as AgNps no meio em um tempo de 150 s. Para entender a perturbação das AgNps-nanocapsulas contra as bactérias, modelos de membrana foram usados através da técnica de Langmuir com os fosfolipídios 1,2-dipalmitoil-sn-glicero-3- fosfo-(1\'-rac-glicerol) (DPPG) and 1,2-dimiristoil-sn-glicero-3-fosfoetanolamina (DMPE), que são os principais componentes da membrana celular de Escherichia coli (E. coli). Os resultados sugerem que DPPG tem mais influência na incorporação das nanopartículas na membrana celular. As propriedades antibacterianas das mantas de nanofibras/nanomateriais contra E. coli e Staphylococus aureus (S. aureus) foram investigadas usando o teste de difusão Agar em 8 grupos, o qual revelou que o grupo contendo a nanofibra/nanocapsula e irradiação apresentou um raio de inibição de 2.58 ± 0.28 mm para S. aureus e 1.78 ± 0.49 mm para E. coli. Este nanossistema mostrou ser altamente interessante para aplicações biomédicas.

Os metais nobres são admirados desde as culturas mais antigas por sua capacidade de refletir a luz. Com os desenvolvimentos na área da nanotecnologia se pode entender um pouco mais sobre a interação entre a luz e estes metais. Devido a esta interação foi criada a Plasmônica e a partir dela começaram os estudos acerca dos plasmons de superfície (SP). Estes estudos vêm gerando inúmeros desenvolvimentos nas pesquisas de gravação magneto-ótica, microscopia, detectores moleculares biológicos entre outras. Como os SPs são ondas evanescentes, eles precisam ser observados em campo próximo. Com o intuito de observar e compreender a propagação destes SPs foi utilizado um microscópio ótico de varredura em campo próximo (SNOM). Para isto, o SNOM foi adaptado para operar em modo de transmissão. A sonda do SNOM serviu de coletora de luz para que a partir de imagens óticas em amostras de Ag e Au pudéssemos caracterizar a propagação destes SPs na superfície do material e também a sua dependência com a distância de detecção. Os resultados mostraram que a propagação do SP é maior que 70m e a intensidade do SP na superfície do metal depende fortemente da rugosidade da amostra e de possíveis defeitos. Foi possível ainda estimar a que distância a partir da superfície da amostra, em que o SP decai para 1/e. Este resultado está de acordo com o esperado teoricamente, que prevê para a distância de propagação do SP, o valor de 420nm. Através do SP ainda foi possível analisar defeitos existentes na amostra. E pelas imagens topográficas do SNOM também foi possível observar os grãos de Ag e Au da amostra. Em posse destes resultados pudemos concluir que o SNOM é uma ótima ferramenta para a análise dos plasmons de superfície. / The noble metals are largely admired since ancient cultures because of its capability to reflect light. With the development of nanotechnology it is possible now to understand the interaction between these metals and light. Due to this strong interaction, the Plasmonic area was created and the studies on Surface Plasmons(SP) started. These studies are responsible for important new developments in magneto-optical recording, new optical microscopy apparatus, molecular biological sensors, among others. As SPs are evanescent waves, they need to be observed in near-field optics. For the observation and study of the propagation of these SPs a scanning near-field optical microscope (SNOM) was used. The SNOMs probe was used in collection mode so that we could characterize the propagation of SPs in the material surface and the dependence with the distance of detection in air, for thin films of Ag and Au. The results showed that the propagation of the SP inside the metallic film is beyon 70m. And the SPs intensity in the metal surface is strongly dependent on the roughness of the sample. It was also possible to estimate the distance from the samples surface the SP decay to 1/e. Our measurements agree to the theoretical calculation of 420nm for this distance. The SP made it possible to analyze existing defects on the sample. Furthermore, with the SNOM topographical images it was also possible to observe the grains of the policrystalline Ag and Au samples. From these results we could conclude that the SNOM is a very useful tool for the analysis of surface plasmons in thin films.

Nanomateriais baseados em paládio (Pd) desempenham um papel central em catálise. Como suas prorpiedades catalíticas dependem de seus diversos parâmetros físico e químicos, a sua síntese controlada tem grande apelo com contexto do controle e otimização de performances. Nesse trabalho desenvolvemos metodologias simples, versáteis e ambientalmente amigáveis para a preparação de nanoestruturas de Pd com tamanho e forma controlada, seguida pelo seu uso como materiais de partida para a preparação de estruturas bimetálicas contendo ouro (Au) e platina (Pt). Espeficificamente, focamos em nanopartícuals (NPs) de Pd na forma de moitas, prisma e cubo côncavos. Com respeito aos materiais bimetálicos, desenvolvemos estruturas do tipo core-shell, tadpoles, e partículas de Au e Pt decoradas sobre as NPs de Pd. Seguda da síntese, estudamos a performance catalítica dos materiais obtidos frente a hidrogenação do p-nitrofenol (p-NPh) e a oxidação do p-aminotiofenol (PATP) mediada pela ressonância plasmônica de superfície (SPR). Nossos resultados mostraram que as atividades foram dependentes dos parâmetros físicos e químicos que definem as nanoestruturas e que materiais controlados tem desempenho superior ao material comercial. Acreditamos que os resultados desenvolvidos nessa tese contribuem para os mecanismos que governam a síntese controlada de NPs baseadas em Pd, Au e Pt, que pode servir como base para a descoberta de nanomateriais com maior complexidade estrutural e composicional visando aplicações em catálise e plasmônica. / Palladium-based (Pd) nanomaterials play a central role in catalysis. As the catalytic properties of thse materials depend on its various physical and chemical parameters, its controlled synthesis has great appeal in order to control and optimize performances. In this work, we developed facile, versatile and environmentally friendly methodologies for the preparation of Pd nanostructures of controlled sizes and shapes, followed by their use as starting materials for the preparation of bimetallic structures containing gold (Au) and platinum (Pt). Specifically, we focused on Pd nanoparticles (NPs) in the form of bushes, prisms and concave cubes. With respect to bimetallic materials, we have developed core-shell structures, tadpoles, and Au and Pt particles decorated on the Pd NPs. Following their synthestic development, we studied the catalytic performance of the obtained materials towards the hydrogenation of p-nitrophenol (p-NP) and the oxidation of p-aminothiophenol (PATP) mediated by surface plasmon resonance (SPR) excitation. Our results showed that the activities were dependent on the physical and chemical parameters that define the nanostructures and that controlled materials performed better than the commercial conterpart. Overall, we believe that the results developed in this thesis contribute to the mechanisms governing the controlled synthesis of NPs based on Pd, Au and Pt, which can serve as a basis for the discovery of nanomaterials with greater structural and compositional complexity for catalytic and plasmonic applications.

Na presente tese de doutorado, foram exploradas possibilidades para a aplicação de nanopartículas (NPs) metálicas plasmônicas (fenômenos ópticos intensificados) em processos de fotocatálise e em células solares de Si. Estratégias foram exploradas para a imobilização das NPs plasmônicas em TiO2 Degussa P25 (mistura anatase:rutila 4:1) para captação da radiação eletromagnética UV/visível e somente visível em processos fotocatalíticos; e de NPs de Cu em células solares de Si para processos de fotoconversão, contribuindo com a compreensão dos fenômenos de intensificação local de energia mediados pelas NPs, o qual ainda está em debate no cenário científico. Compósitos de P25+NPs Ag de diferentes arquiteturas (fios, esferas e fotorreduzidas), de P25+NPs Ag recoberta com uma camada de SiO2 e de P25+NPs Au foram desenvolvidos. A caracterização dos materiais foi realizada por meio de técnicas de espectroscopia UV-VIS, IR e Raman, área superficial, DRX e de microscopia eletrônica de varredura e de transmissão. Os efeitos das propriedades plasmônicas dessas nanopartículas foram avaliados na eficiência de fotodegradação de três corantes (alizarina vermelha S, vermelho do Congo e fenossafranina) e de fenol. Todos os materiais plasmônicos apresentaram bom desempenho catalítico, aumentando consideravelmente a velocidade e a porcentagem de fotodegradação sob radiação UV/visível, mas principalmente sob radiação visível (onde a fotodegradação catalisada por P25 é limitada). A comparação entre a fotodegradação de fenol pelo compósito P25+NPs Ag esferas e P25+NPs Ag@SiO2 permitiu concluir que a transferência de carga não é o fenômeno que governa o aumento da eficiência catalítica em comparação à fotodegradação catalisada por P25. O fenômeno de intensificação de radiação eletromagnética localizada por meio de LSPR foi observado também em células solares de silício de primeira geração (wafer) contendo NPs de Cu imobilizadas em sua superfície. Aumentos na densidade de corrente de curto-circuito de cerca de 8 % na região acima de 750 nm e de até 16% na potência destas células solares foram observados. / In this thesis, we explored possibilities for the application of metallic plasmonic nanoparticles (NPs) resulting in intensified optical phenomena processes in photocatalysis and Si solar cell. Different strategies were explored for the immobilization of plasmonic NPs on TiO2 Degussa P25 (mixture anatase: rutile 4:1) to capture electromagnetic radiation UV / visible and visible only in photocatalytic processes; and Cu NPs in Si solar cell for photoconversion processes, contributing with the understanding of the phenomena related to the localized ressonance energy mediated by NPs, which is still under debate in the scientific field. Composites of P25+Ag NPs of various architectures (wires, spheres and photoreduced) P25+Ag NPs coated with a layer of SiO2 and P25+Au NPs were developed. The material characterization was performed by means of UV-VIS, IR and Raman spectroscopies, BET surface area, XRD and scanning and transmission electron microscopy. The effects of plasmonic nanoparticles properties were evaluated in the photodegradation efficiency of three textile dyes (Alizarin Red S, Congo red and phenosafranine) and phenol. All plasmonic materials showed good catalytic performance, greatly increasing the kinetic and percentage of photodegradation under UV/visible, but mostly under visible light (where the photodegradation catalyzed by P25 is limited). The comparison between the photodegradation of phenol by P25+Ag sphere NPs and P25+Ag@SiO2 composite showed that the charge transfer is not the phenomenon that governs the increase in catalytic efficiency when compared to the photodegradation catalyzed by P25. The phenomenon of near field intensification through LSPR was also observed in first generation Si solar cells (wafer) containing Cu NPs immobilized on its surface. Increases in the short-circuit current density of about 8% in the region above 750 nm and up to 16% in the power of these solar cells were observed.

In the last few decades, the nanoscale fabrication of metallic structures has demonstrated promising applications in security (e.g. cryptography), photochemistry (e.g. plasmonassisted photo-chemistry), decoration (e.g. colouring), biocompatibility of implants and more. To fabricate such subwavelength nanostructures, we typically resort to the use of several nanolithography techniques that are lengthy and incompatible with large-scale production on complex substrates. For this purpose, we invented an innovative technique for the fast fabrication of nanostructures via the use of a picosecond laser. We used this technique to produce colourful coins for the Royal Canadian Mint which were presented at the World Money Fair in Germany in 2015 as a world rst. To ensure the long-term survival of these plasmonic colours, a new dual-layer passivation technique was conceived based on a atomic deposition process, to meet the commercialisation requirements of our industrial partner. A new burst colouring technology was also invented that allows for the creation of more visually appealing colours. These laser burst colours were also shown to have a high sensing potential and an overall better visual response to the application of the passivation layer.