Metal nanostructures exhibit a wide variety of interesting physical and chemical properties, which can be tailored by altering their size, morphology, composition, and environment. Gold and silver nanostructures have received considerable attention for many decades because of their widespread use in applications such as catalysis, photonics, electronics, optoelectronics, information storage, chemical and biological sensing, surface plasmon resonance and surface-enhanced Raman scattering (SERS) detection. This thesis is composed of three main parts about the synthesis, characterization and SERS applications of shape-controlled and surface modified noble metal nanoparticles. The first part is related to a simple synthesis of shape controlled solid gold, hollow gold, silver, gold-silver core-shell, hollow gold-silver double-shell nanoparticles by applying aqueous solution chemistry. Nanoparticles obtained were used for SERS detection of dye molecules like brilliant cresyl blue (BCB) and crystal violet (CV) in aqueous system. v The second part involves the synthesis of surface modified silver nanoparticles for the detection of dopamine (DA) molecules. Determination of a dopamine molecule attached to a iron-nitrilotriaceticacid modified silver (Ag-Fe(NTA)) nanoparticles by using surface-enhanced resonance Raman scattering (SERRS) was achieved. The Ag-Fe (NTA) substrate provided reproducibility and excellent sensitivity. Experimental results showed that DA was detected quickly and accurately without any pretreatment in nM levels with excellent discrimination against ascorbic acid (AA) (which was among the lowest value reported in direct SERS detection of DA). In the third part, a lanthanide series ion (Eu3+) containing silver nanoparticle was prepared for constructing a molecular recognition SERS substrate for the first time. The procedure reported herein, provides a simple way of achieving reproducible and sensitive SERS spectroscopy for organophosphates (OPP) detection. The sensing of the target species was confirmed by the appearance of an intense SERS signal of the methyl phosphonic acid (MPA), a model compound for nonvolatile organophosphate nerve agents, which bound to the surface of the Ag-Eu3+ nanostructure. The simplicity and low cost of the overall process makes this procedure a potential candidate for analytical control processes of nerve agents.

The unique properties of gold nanoparticles make them excellent candidates for applications in electronics, sensing, imaging, and photothermal therapy. Though abundant literature exists for isotropic gold nanoparticles, work on nanoparticles of different shapes has been gaining interest recently. Anisotropic gold nanoparticles, such as nanorods and nanoprisms, have tunable optical properties in the visible and near-infrared regions. Through synthesis and surface modification, the production of various shapes of these gold nanoparticles can be controlled to meet different applications. Two different types of gold nanorods were used in this thesis. The first type was stabilized with cetyltrimethylammonium bromide (CTAB) and had aspect ratios of 3-4 (defined as the nanorod length divided by the diameter). The second type was synthesized using CTAB and benzyldimethylhexadecylammonium chloride (BDAC) in a binary surfactant system which produced aspect ratios greater than 4. The nanorods were characterized with UV-Vis spectroscopy and transmission electron microscopy (TEM). Two types of bowl-shaped macrocyclic compounds called resorcinarenes were used to direct self-assembly of the nanorods. The first type of resorcinarene (R2S) consisted of thiol(SH)-terminated alkyl chains on both rims. The second type (R1S) contained thiol-terminated alkyl chains on only one rim. The monolayer formation of these resorcinarenes on planar gold surfaces was studied and characterized by FTIR spectroscopy. Resorcinarene-mediated assembly of gold nanorods was monitored with UV-Vis spectroscopy, dynamic light scattering (DLS), and TEM. In addition to gold nanorods, gold nanoprisms were synthesized through a kinetically-controlled reduction route in the presence of CTAB. The linking of nanoprisms using resorcinarenes was also explored.

New challenges in nanotechnology arise in the assembly of nanoobjects into three-dimensional superstructures, which may carry synergetic properties and open up new application fields. Within this new class of materials nanostructured, porous functional metals are of great interest since they combine high surface area, gas permeability, electrical conductivity, plasmonic behavior and size-enhanced catalytic reactivity. Even though a large variety of preparation pathways for the fabrication of porous noble metals has already been established, several limitations are still to be addressed by research developments. The new and versatile approach that is presented in this work makes use of a templatefree self-assembly process for the fabrication of highly porous, metallic nanostructures. Thereby, nanochains are formed by the controlled coalescence of noble metal NPs in aqueous media and their interconnection and interpenetration leads to the formation of a self-supported network with macroscopic dimensions. Subsequently, the supercritical drying technique is used to remove the solvent from the pores of the network without causing a collapse of the fragile structure. The resulting highly porous, low-weighted, three-dimensional nanostructured solids are named aerogels. The exceptional properties of these materials originate from the conjunction of the unique properties of nanomaterials magnified by macroscale assembly. Moreover, the combination of different metals may lead to synergetic effects regarding for example their catalytic activity. Therefore, the synthesis of multimetallic gels and the characterization of their structural peculiarities are in the focus of the investigations. In the case of the developed preparation pathways the gelation process starts from preformed, stable colloidal solutions of citrate capped, spherical noble metal (Au, Ag, Pt, Pd) NPs. In order to face various requirements several methods for the initiation of the controlled destabilization and coalescence of the nanosized building blocks were developed and synthesis conditions were optimized, respectively. Multimetallic structures with tunable composition are obtained by mixing different kinds of monometallic NP solutions and performing a joint gel formation. The characterization of the resulting materials by means of electron microscopy reveals the formation of a highly porous network of branched nanochains that provide a polycrystalline nature and diameters in the size range of the initial NPs. Furthermore, synthesis conditions for the spontaneous gel formation of glucose stabilized Au and Pd NPs were investigated. In order to gain a detailed knowledge of the structural properties of bimetallic aerogel structures a versatile set of characterization techniques was applied. A broad pore size distribution dominated by meso- and macropores and remarkably high inner surface areas were concluded from the N2 physisorption isotherms and density measurements. As investigated, a specific thermal treatment could be used to tune the ligament size of Au-Ag aerogels, whereas Au-Pd and Pt-Pd structures provide thermal stability under mild conditions. Further investigations aimed to the enlightenment of the elemental distribution and phase composition within the nanochains of multimetallic gel structures. The different approaches provide complementary and consistent results. Phase analyses based on XRD measurements revealed separated phases of each metal in the case of Ag-Pd and Au-Pd aerogels. They further proved the possibility of temperature induced phase modifications that lead to complete alloying of Au and Pd. In addition, separated domains of Pt and Pd were established from the EXAFS analysis of the corresponding aerogel. STEM EDX high resolution elemental mappings confirmed the separated domains of different metals in the case of Au-Pd and Pt-Pd aerogels. Moreover, a complete interdiffusion and alloy formation of Au and Ag within the corresponding aerogel structure is suggested from STEM EDX results. Finally, the presented investigations further promote the field of metallic aerogels by addressing the challenging issue of processability and device fabrication. Hybrid materials with organic polymers as well as various kinds of coatings on glass substrates and glassy carbon electrodes were prepared whereas the network structure was preserved throughout all processing steps. Moreover, it was illustrated that the NP-based aerogels carry metallic properties as expressed by their low Seebeck coefficients and high electrical conductivities.

Noble metal nanostructures possess unique properties including large near-field enhancement and strong light scattering and absorption due to their plasmon resonance - the collective coherent oscillation of the metal free electrons in resonance with the electromagnetic field of light. The effect of nanostructure size, shape, composition, and environment on the plasmon resonance frequency and plasmonic enhancement is well known. In this thesis, we describe the effect of inter-particle coupling in assembled plasmonic nanostructures on their radiative and non-radiative properties. When metal nanoparticles assemble, plasmon oscillations of neighboring particles couple, resulting in a shift in the plasmon resonance frequency. Our investigation of plasmon coupling in gold nanorods shows that the coupling between the plasmons is "bonding" in nature when the plasmon oscillations are polarized along the inter-particle axis, whereas an "anti-bonding" interaction results when the polarization is perpendicular. We studied the distance-dependence of plasmon coupling using electrodynamic simulations and experimental plasmon resonances of lithographically fabricated gold nanoparticle pairs with systematically varying inter-particle separations. The strength of plasmon bonding, reflected by the fractional plasmon shift, decays near-exponentially with the inter-particle separation (in units of particle size) according to a universal trend independent of the nanoparticle size, shape, metal type, or medium. From the universal scaling model, we obtain a "plasmon ruler equation" which calculates (in good agreement with the experiments of Alivisatos and Liphardt) the inter-particle separation in a gold nanosphere pair from its plasmon resonance shift, making it applicable to the determination of inter-site distances in biological systems. Universal size-scaling is valid also in the metal nanoshell structure, a nanosphere trimer, and pairs of elongated nanoparticles, thus making it a generalized fundamental model, which is useful in optimizing plasmon coupling for achieving tunable plasmon resonances, enhanced plasmonic sensitivities, and large SERS cross-sections. Ultrafast laser pump-probe studies of non-radiative electronic relaxation in coupled metal nanospheres in aggregates and in gold nanospheres conjugated to thiol SAMs are also reported. We also show that the relative contribution of scattering (radiative) to absorption (non-radiative) part of the plasmon relaxation, respectively useful in optical and photothermal applications, can be increased by increasing the nanostructure size.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The catalytic activity of hierarchical hybrid structures, formed by metal nanoparticles, M-NPs (AuNPs and PdNPs), synthesized and stabilized by block copolymers, is reported in this present work. The catalytic activity was investigated by the study of nanoparticle size and chemical nature of the block copolymer overlaying the M-NP. To evaluate the chemical structure effect of the polymer on catalytic properties of the hybrid systems, a series of eight distinct polymers was used: poly(ethylene oxide)113-b-poly(glycerol monomethacrylate)30-b-poly [2-(diisopropylamino)ethyl methacrylate]50 (PEO113-b-PG2MA30-b-PDPA50), poly(ethylene oxide)113-b-poly[2-(diethylamino)ethyl methacrylate]50 (PEO113-b-PDEA50) , poly(2- methacryloyloxyethyl phosphorylcholine)30-b- poly(2-(diisopropylamino) ethyl methacrylate)60 (PMPC30-b-PDPA60), poly(ethylene oxide)100-b-poly(propylene oxide)65-b-poly(ethylene oxide)100 (PEO100-b-PPO65-b-PEO100 or F127), α-carboxylic ω-thiol poly(N-isopropyl acrylamide)137 (HS-PNIPAM137-COOH), poly(4-vinylpyridine)137-b-(ethylene oxide)45 (PEO45-b-P4VP137), poly(N-vinyl caprolactam)94 (PNVCL94) and poly(N-vinyl caprolactam)53 (PNVCL53). The size of M-NPs was determined by dynamic light scattering (DLS) and their morphology was confirmed by transmission electron microscopy (TEM). Subsequently, was tested the catalyst efficiency, by the reduction of p-nitrophenol to p-aminophenol, the catalyst could be regenerated about 6 times, proving that system (AuNPs and PdNPs) as capacity for regeneration and can be an effective catalyst. The PdNPs were tested like catalyst in reactions of Suzuki coupling. / A atividade catalítica de estruturas hierárquicas híbridas formadas por nanopartículas metálicas, M-NPs (AuNPs e PdNPs), sintetizadas e estabilizadas por copolímeros em bloco é relatada neste trabalho. A atividade catalítica foi investigada em função da natureza química do copolímero em bloco que as revestem. Uma série de 08 (oito) polímeros estruturalmente relacionados foi utilizada: poli(óxido de etileno)113-b-poli(metacrilato de 2,3-diidroxipropila)30-b-poli(metacrilato de 2-(diisopropilamino)etila)50 (PEO113-b-PG2MA30-b-PDPA50), Poli(óxido de etileno)113-poli [ metacrilato de 2-(dietilamino)etil]50 (PEO113-b-PDEA50), poli(2-metacriloiloxietil fosforilcolina)30-b-poli[metacrilato de 2-(diisopropilamino)etil]60 (PMPC30-b-PDPA60), poli(óxido de etileno)100-b-poli(óxido de propileno)65-b-poli(óxido de etileno)100 (PEO100-b-PPO55-b-PEO100 ou F127), α-tiol-ω-ácido carboxílico poli(N-isopropil acrilamida)113 (HS-PNIPAM113-COOH), poli(oxido de etileno)137-b- poli(4-vinil piridina)45 (PEO137-b-P4VP43) poli(N-vinil caprolactana)94 (PNVCL94) e poli(N-vinil caprolactana)53 (PNVCL53). O tamanho das M-NPs foi determinado por espalhamento de luz (DLS) e sua morfologia comprovada através de análise de microscopia de transmissão (TEM). Sua eficiência foi posteriormente testada na catálise da redução do p-nitrofenol a p-aminofenol. Comprovou-se, mediante á ciclos reacionais, que ambos os sistemas (AuNPs e PdNPs) apresentaram capacidade de regeneração, sendo regenerado 6 vezes, provando ser um catalisador eficiente. As PdNPs foram testadas em reações de acoplamento de Suzuki.

Para o desenvolvimento dos sensores aqui descritos foram utilizados materiais inovadores considerando relatos atuais da literatura, materiais estes: óxido de grafeno, óxido de grafeno reduzido, nanocompósitos de grafeno e nanopartículas (ródio, antimônio e sílica mesoporosa desordenada), materiais híbridos a base de grafeno e quantum dots de CdTe, além de biossensores incorporando a enzima lacase. Estes materiais foram sintetizados utilizando metodologias específicas e caracterizados por diversas técnicas analíticas como microscopia eletrônica de transmissão de alta resolução, microscopia de força atômica, espectroscopia Raman, difração de raios-X, espectroscopias de UV-Vis e fotoluminescência, e técnicas eletroquímicas. Posteriormente, os materiais foram utilizados para modificação em eletrodos de carbono vítreo e utilizados na determinação de interferentes endócrinos (os hormônios estriol e 17β-estradiol) como sensores eletroquímicos em amostras ambientais e clínicas. Em essência, os eletrodos desenvolvidos apresentaram importantes vantagens, tais como alta sensibilidade, boa reprodutibilidade, simples instrumentação, fácil preparação e procedimentos analíticos rápidos, apresentando baixos limites de detecção, na ordem de picomolar e nanomolar, com baixa taxa de interferência de outras espécies na mesma matriz da amostra. Concluindo assim que as técnicas eletroquímicas podem ser facilmente aplicadas na determinação de interferentes endócrinos em amostras reais. / For the development of the sensors described here innovators materials were used considering current literature reports, these materials: Graphene oxide, reduced graphene oxide, nanocomposites graphene and nanoparticles (rhodium and antimony), hybrid materials of graphene and CdTe quantum dots, and biosensors incorporating the laccase enzyme. These materials were synthesized using specific methodologies and characterized by several analytical techniques such as transmission electron microscopy, high resolution transmission electron microscopy, atomic force microscopy, Raman spectroscopy, X-ray diffraction, UV-Vis and photoluminescence spectroscopy and electrochemical techniques. Subsequently, the materials were used for modification of glassy carbon electrodes to the determination of endocrine disruptors (estriol and 17β-estradiol hormone) as electrochemical sensors for environmental and clinical samples. In essence, developed electrodes showed important advantages such as high sensitivity, good reproducibility, simple instrumentation, easy preparation and quick analytical procedures, with low detection limits in the range of picomolar and nanomolar, low interference rate of other species in same matrix sample. Finally, electrochemical techniques can be easily applied in the determination of endocrine disruptors in real samples.

O presente estudo avaliou a ação in vitro de diferentes nanopartículas de prata (nanoAg) sintetizadas pelo Instituto de Pesquisas Tecnológicas (IPT) e Universidade Federal de São Carlos (IFSC) e controles de sulfadiazina de prata, nitrato de prata e nanoAg comercial Sigma, frente a bactérias e leveduras. Os objetivos do estudo foram avaliar a ação in vitro de NanoAg sintetizadas no Brasil frente a bactérias sensíveis aos antimicrobianos e multirresistentes (MR), incluindo Gram positivos e negativos, além de candidas isoladas de amostras clínicas. Definir as condições de síntese que resultem em nanoAg com melhor efeito antimicrobiano in vitro frente a isolados sensíveis e MR. Foram utilizadas diferentes metodologias tais como agar well diffusion, determinação de concentração inibitória mínima CIM, concentração bactericida mínima (CBM), curva do tempo de morte e inibição da formação de biofilme. Ao todo, foram avaliados 110 isolados, sendo 37 sensíveis aos antimicrobianos, 54 MR, e 19 candidas frente a 29 nanoAg com diferentes características de síntese. Os testes de difusão em meio sólido apresentaram heterogeneidade de resultados frente aos micro-organismos avaliados. Enquanto as informações de CIM50 e CIM90 evidenciaram não existir variações no efeito inibitório frente isolados sensíveis ou resistentes aos antimicrobianos. As curvas do tempo de morte ilustraram a dinâmica de inibição dos compostos de prata e a interferência do sangue nos testes in vitro. A partir dos testes com biofilme foi possível observar efeito inibitório e de descolamento de biofilme previamente formado. Os resultados permitiram concluir a maior eficácia para nanoAg com Citrato e Quitosana, seguido por nitrato de prata, sulfadiazina de prata e PVA. A NanoAg comercial (Sigma, 60 nm) apresentou resultados inferiores ao de nanoAg Citrato, nanoAg Quitosana e nitrato de prata. Estes resultados abrem caminho para novas análises de nanoAg sintetizadas no Brasil em busca de produtos com maior eficácia com ação contra bactérias MR e candidas / The present study evaluated the in vitro action of different silver nanoparticles (nanoAg) synthesized by \"Instituto de Pesquisas Tecnológicas\" (IPT) and \"Universidade Federal de São Carlos\" (IFSC) and silver sulfadiazine, silver nitrate and commercial nanoAg Sigma against bacteria and yeasts. The objectives of the study were to evaluate the in vitro action of NanoAg synthesized in Brazil against antimicrobial susceptible bacteria and multidrug-resistant (MDR), including Gram positive and negative, as well as some candida isolates from clinical source. Define the conditions that result in nanoAg synthesis with best in vitro antimicrobial effect against sensitive isolates and MDR. Different methodologies were used such as agar well diffusion, determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (CBM), the time-kill curve and inhibition of biofilm formation. Altogether 110 isolates were evaluated, being 37 antimicrobial sensitive, 54 MDR, and 19 candidas, against 29 nanoAg with different synthesis. The solid medium diffusion tests showed heterogeneity of results against the evaluated microorganisms. While the information of MIC50 and MIC90 showed no changes in inhibitory effect against sensitive isolates or MDR. The time-kill curve illustrated the dynamics of inhibition of silver compounds and the interference of blood on the in vitro tests. From the tests with biofilm was possible to observe biofilm inhibitory effect and detachment of biofilm previously formed. The conclusion defined to greater effectiveness for nanoAg with Chitosan and Citrate, followed by silver nitrate, silver sulfadiazine and PVA. The commercial NanoAg (Sigma, 60 nm) presented lower performance than nanoAg citrate, nanoAg Chitosan and silver nitrate. These results open the way for new analyses of Brazil synthetized nanoAg with better efficiency against MDR bacterial and candida

Nous avons étudié par spectroscopie pompe-sonde résolue en temps la réponse optique ultrarapide d'agrégats de très petite taille (< 2 nm), pour lesquelles une transition d'un comportement de type solide à un comportement moléculaire est attendue. Les modifications des processus de thermalisation interne (interactions électrons-électrons et électrons phonons) avec la réduction de taille ont été étudiées dans des nanosphères d'argent triées en masse entourées de silice, et dans des échantillons d'or atomiquement définis stabilisées par des surfactants. Ces expériences ont mis en évidence les effets de confinement quantique des états électroniques sur la cinétique électronique. L'étude des vibrations acoustiques de nanoparticules dans le même régime de taille a été effectuée. Les vibrations observées dans les agrégats d'or sont dominées par leur mode de respiration radial avec une période proportionnelle à leur diamètre, an analogie avec les nanoparticules plus grandes. Le mode de respiration observé sur les nanoobjets bimétalliques de type cœur/couronne Pt-Au et Ni-Ag est en accord quantitatif avec les estimations du modèle élastique macroscopique, malgré une épaisseur de couronne monoatomique. La spectroscopie résolue en temps a également été utilisée pour étudier le transfert de chaleur à travers l'interface d'une nanoparticule sphérique. Dans ce but, l'évacuation de la chaleur dans des nanoparticules d'or, nues ou enrobées de silice, en solution colloïdale a été étudiée expérimentalement et modélisée de manière quantitative grâce à la prise en compte de la contribution de l'environnement (échauffement du solvant) au signal optique / We used ultrafast time-resolved pump-probe spectroscopy to experimentally investigate the optical response of small metal nano-objects in the few nanometer range (< 2 nm), where a transition from a small solid behaviour to a molecular one is expected. The modification of the intrinsic thermalization processes (electron-electron and electron-phonon interactions) has been studied both on glass-embedded mass-selected silver samples and chemically synthesized ligand-stabilized atomic-defined gold clusters. Electron gas internal thermalization and cooling with the lattice are shown to be affected by size reduction and the concomitant discretization of electronic states. The acoustic response in the same small size range has been investigated. Vibrations of gold clusters were characterized by a quasi-breathing mode scaling with their size, in analogy with larger nanoparticles. The breathing mode of bimetallic core/shell Pt-Au and Ni-Ag nanospheres appeared to be in good quantitative agreement with predictions of continuous elastic models, despite the monoatomic thickness of the layer shell. The same time-resolved approach was used to investigate heat transfer through the nanoparticles interfaces. In this context, heat evacuation of bare or silica-encapsulated gold

La première synthèse d'un carbène N-hétérocylique borane (NHC-borane) stable a été réalisée en 1993. Pourtant la découverte de leur vaste potentiel en chimie n'a réellement débuté qu'à partir de 2007. Les domaines d'application de ces composés du bore, stables et facile d'accès, s'étendent de la synthèse d'organique (réduction d'imine, hydroboration de liaisons multiples, médiateurs radicalaires) à la chimie organométallique (couplage de Suzuki-Miyaura) en passant par la chimie des polymères (amorceurs ou co-amorceurs de photopolymérisation). L'objectif de ce projet aura été d'étendre l'application des NHC-boranes dans deux différents systèmes de photopolymérisation. Le premier système étudié a permis l'obtention de matériaux acrylates contenant des nanoparticules métalliques à partir d'un seul composé dans un processus monotope. Le second système visait l'amorçage de réactions de polymérisation en émulsion sous irradiation visible. Nous avons utilisé le pouvoir réducteur des NHC-boranes pour former des nanoparticules d'or ou d'argent directement dans des monomères acrylates. Puis, la formation par le NHC-borane de la matrice polymère contenant les nanoparticules est déclenchée par une irradiation UV. L'analyse par HRTEM a mis en évidence des petites nanoparticules (ca. 10 nm) emprisonnées dans la matrice. Cette méthode présente une approche encore plus directe pour obtenir ce type de matériau plutôt que les procédés multi-étapes déjà existants. Le second système étudié utilise pour la première fois un NHC-borane comme co-amorceur de la polymérisation du styrène ou du méthacrylate de méthyle en émulsion sous irradiation visible. Il en résulte des latex stables, composés de particules de tailles moyennes contrôlées formés à partir de quantités de tensioactifs inférieures à celles utilisées dans des systèmes photoamorcés déjà décrits. Ces systèmes amorcés par une irradiation visibles pourraient être intéressants pour réduire les coûts énergétiques des synthèses et éviter la dégradation de composés thermo- ou UV- fragiles / Despite the first synthesis of stable N-heterocyclic carbene (NHC)-boranes occurring as early as 1993, the widespread exploration of their potential in chemistry truly began only in 2007. The versatility of these stable and easily accessible boron compounds has led to their application in organic reactions (imine reduction, multiple bond hydroboration, radical reductions), organometallic reactions (Suzuki- Miyaura cross coupling) and polymerization (initiation or co-initiation of polymerization). The aim of my project was to extend the applicability of NHC-boranes to two different photopolymerization systems. The first aimed to synthesize polymer matrices containing metal nanoparticles in a one pot, one reactant process. The second aimed to perform emulsion polymerizations initiated by visible light. In the first system, the reductive capacity of NHC-boranes was used to generate gold or silver nanoparticles directly in acrylate monomers. Then, the initiating ability of NHC-boranes was triggered by UV light to form the polymer matrix containing embedded nanoparticles. Characterization by HRTEM showed small nanoparticles (ca. 10 nm) successfully contained within the matrix. This method represents a more straightforward approach than obtaining such materials through the multistep processes already reported in literature. In the second system, NHC-boranes were employed for the first time as co-initiators in visible light initiated emulsion polymerization styrene and methyl methacrylate. Stable latexes were generated with controllable particle sizes at lower surfactant concentrations than those used in related light-initiated systems. Such visible light-triggered initiation systems are interesting for reducing energy consumption and avoiding degradation of heat- or UV-sensitive materials

L'épuisement progressif des matières premières d'origine fossile et la nécessité de réduire les émissions de gaz à effets de serre ont conduit la communauté scientifique à rechercher de nouveaux matériaux dont la production ne dépendra pas de ressources non renouvelables. Dans un autre temps ces matériaux pourront déjà être introduits sur le marché afin de substituer des produits déjà existant qui proviennent de matières premières fossiles. Par exemple, l'acide 2,5-furandicarboxylique (FDCA) obtenu par valorisation de la biomasse lignocellulosique est un potentiel substituant de l'acide téréphtalique actuellement utilisé pour la production de polyesters. En effet, le FDCA peut être obtenu par oxydation sélective du 5-hydroxyméthylfurfural (HMF) synthétisé à partir de la biomasse lignocellulosique. Ainsi, ce travail de thèse peut être défini par deux problématiques principales : (1) Le développement de catalyseurs pour l'oxydation de HMF en FDCA sans utiliser de bases inorganiques et (2) Développement de membranes catalytiques de polymères pour la future adaptation du procédé d'oxydation en réacteur à flux continu. Pour ce qui concerne l'oxydation de HMF dans des conditions neutres, une première étude s'est intéressée à la possibilité d'utiliser de l'oxyde de nickel nanométrique comme support pour des nanoparticules. Ensuite, la possibilité d'utiliser des nanoparticules de Pt supportées sur du TiO2 obtenues par décomposition contrôlée de clusters carbonyliques a été étudiée. Ainsi, des membranes de polymère obtenues par électrospinning, contenant les nanoparticules métalliques étudiées précédemment, ont été appliquées comme système catalytique pour l'oxydation du HMF / The depletion of fossil-derived resources and the need to decrease the emission of green-house gases led scientists to look for sustainable materials to replace the already existing fossil-derived ones. For instance, 2,5-furandicarboxylic acid (FDCA) has been pointed out as the bioderived counterpart of terephthalic acid for the synthesis of polyesters. In fact, FDCA could be obtained by means of selective oxidation of 5-hydroxymethylfurfural (HMF), a bio-derived platform molecule produced by glucose hydrolysis. This reaction is known to be catalyzed by supported metal nanoparticle systems in presence of inorganic bases under batch conditions. This work deals with the development of catalytic systems able to perform the base-free HMF oxidation, since the possibility to circumvent base addition leads more sustainable processes. In particular, two different sets of catalytic systems have been studied: mono- and bimetallic Au and Pd nanoparticles on nano-sized NiO, and mono- and bimetallic Pt/Sn systems on titania, prepared via cluster precursor decomposition. Another topic that will be discussed in this thesis focuses on the development of catalytically active polymeric membranes obtained via electrospinning and their application as catalytic system for HMF oxidation either under basic and neutral aqueous conditions. In details, polyacrylonitrile and nylon have been tested as electrospun polymeric matrixes for the embedding of Au-based nanoparticles and Pt clusters