Des couches fonctionnelles hybrides organiques/inorganiques ont été générées à une interface solide/liquide à l’aide d’une nouvelle technique de fabrication ascendante (bottomup) dénommée Croissance de Couche à partir d’une Surface (Surface Grown Layers - SgL)grâce à une modulation très fine de l’interaction électrostatique entre nano-objets decharges opposés en fonction de la force ionique de la dispersion aqueuse. Différents nanoparticules/tubes à la fois cationiques et anioniques et très stables vis-à-vis d’un environnement fortement salin ont été développés. La complexation électrostatique entre ces nanomatériaux a été étudiée en solution et près d’une interface au travers du concept de “transition de dessalage”. Dans un deuxième temps la croissance de couches hybrides à partird’un substrat a été étudiée en comparant l’approche SgL et la méthode classique d’adsorption séquentielle couche par couche (Layer by layer - LbL). Des expériences préliminaires ont montré le potentiel de cette approche dans le développement de substrats fonctionnels. / In this manuscript, one-step bottom-up fabrication of “smart organic-inorganic hybridfunctional layers” at a liquid/solid interface were fabricated via a novel surfacefunctionalization pathway termed as “Surface Grown Hybrid Functional Layers” or SgLthrough fine tuning of electrostatic interaction between “highly stable” and oppositelycharged nanomaterials as a function of ionic strength of the dispersion. Cationic and anionicnanomaterials based on different hybrid nanoparticles/nanotubes that are very stable towardshigh saline environment have been formulated. The electrostatic complexation between theseoppositely charged nanomaterials has been studied in bulk and at an interface through theconcept of “desalting transition” pathway. In a second step, the growth of functional hybridlayers directly from a substrate via the novel SgL approach was then compared with theconventional Layer-by-Layer approach (LbL). Finally the preliminary experiments haveshown the potential applications of generated functional surfaces.

This thesis reports on the chemical vapour deposition (CVD) growth of carbon nanostructures (mainly carbon nanotubes (CNTs)) on perovskite oxide surfaces with the aid of various catalysts. Two types of perovskite oxide, single crystal SrTiO3 (001) and polycrystalline BaSrTiO₃, have been used as catalyst supports (in metal-catalyst-involved CVD routes) or as catalysts (via metal-catalyst-free CVD routes) for the growth of carbon nanostructures. In metal-catalyst-involved cases, SrTiO₃ (001) single crystal has been proven, for the first time, to serve as a substrate for the growth of CNTs. Fe and Ni catalysts can be tailored in a controllable manner on SrTiO3 (001) surfaces prior to the CNT synthesis, forming truncated pyramid shaped nanocrystals with uniform size distributions. The growth of vertically aligned CNT carpets was realised with the aid of Fe on SrTiO₃ (001) surfaces, and it was further found that the CNTs grow via a base growth model. Furthermore, it is possible to grow helical carbon nanostructures on BaSrTiO3 substrates by introducing a Sn catalyst into the system. The synthesised helical carbon nanostructures follow a tip growth mode, where the structural and chemical aspects of catalyst particles gave rise to a wide range of carbon morphologies. CNTs were also grown on single crystal SrTiO₃ (001) and polycrystalline BaSrTiO3 substrates via metal-catalyst-free routes. The surface-roughness-tailored growth of CNTs was surprisingly achieved on a series of engineered SrTiO₃ (001) surfaces, where a correlation between the surface roughness/morphology of the substrates and the relevant catalytic activity was revealed. The growth of CNTs arises because the catalyst fabrication methods lead to the formation of SrTiO₃ asperities with nanoscale curvatures, over which the CNTs are generated throughout a lift-off process. Facet-selective growth of CNTs was observed on polycrystalline BaSrTiO₃ surfaces, where BaSrTiO₃ (110) facets lead to the growth of CNTs on them, whereas the (001) facets result in no growth at all. This observation was further analysed in the content of the adsorption and diffusion of carbon species on distinct BaSrTiO₃ facets, before reaching the conclusion that the formation of CNTs occurs through a metal-free, stack-up process driven by the assembly of the carbon fragments.

Progress has been made in using human serum albumin nanoparticles (HSAPs) as carrier systems for targeted treatment of cancer. Human serum albumin (HSA), the most abundant human blood protein, can form HSAPs via a desolvation and crosslinking method, with the size of the HSAPs having crucial importance for drug loading and in vivo performance. Gold nanoparticles have also gained medicinal attention due to their ability to absorb near-infrared (NIR) light. These relatively non-toxic particles offer combinational therapy via imaging and photothermal therapy (PPTT) capabilities. A desolvation and crosslinking approach was employed to encapsulate gold nanoparticles (AuNPs), hollow gold nanoshells (AuNSs), and gold nanorods (AuNRs), into efficiently sized HSAPs for future tumor heat ablation via PPTT. The AuNR-HSAPs, AuNP-HSAPs and AuNS-HSAPs had average particle diameters of 222 ± 5, 195 ± 9 and 156 ± 15, respectively. We simultaneously encapsulated AuNRs and the anticancer drug paclitaxel (PAC), forming PAC-AuNR-HSAPs with overall average particle size of 299 ± 6 nm. Loading of paclitaxel into PAC-AuNR-HSAPs reached 3μg PAC/mg HSA. PAC-AuNR-HSAPs experienced photothermal heating of 46 ˚C after 15 minutes of NIR laser exposure; the temperature necessary to cause severe cellular hyperthermia. There was a burst release of paclitaxel up to 188 ng caused by the irradiation session, followed by a temporal drug release. AuNR-HSAPs were tested for ablation of renal cell carcinoma using NIR irradiation in vitro. Particles created with the same amount of AuNRs, but varying HSA (1, 5 or 20 mg) showed overall particle size diameters 409 ± 224, 294 ± 83 and 167 ± 4 nm, respectively. Increasing HSAPs causes more toxicity under non-irradiated treatment conditions: AuNR-HSAPs with 20 mg versus 5 mg HSA caused cell viability of 64.5% versus 87%, respectively. All AuNR-HSAPs batches experienced photothermal heating above 42 ˚C. Coumarin-6, was used to visualize the cellular uptake of AuNR-HSAPs via fluorescence microscopy. Finally, camptothecin (CPT) an antineoplastic agent and BACPT (7-butyl-10-aminocamptothecin) were loaded into HSAPs to combat their aqueous insolubility. BACPT-HSAPs loaded up to 5.25 micrograms BACPT/ mg of HSA. CPT encapsulation could not be determined. BACPT-HSAPs and CPT-HSAPs showed cytotoxicity to human sarcoma cells in vitro.

Ce travail met en évidence le potentiel que la technologie des plasmas présente dans l’élaboration, en une seule étape, des catalyseurs de la synthèse Fischer-Tropsch (SFT), alors que les méthodes habituelles ou conventionnelles comme l’imprégnation et la précipitation sont des voies de production multi-étapes du matériau catalytique. Les nouveaux catalyseurs ont été mis en œuvre à partir d’espèces monométalliques ayant comme support le carbone (Fe/C, Co/C) pour développer des bimétalliques (Co-Fe), des ternaires (Mo-Co-Fe, Ni-Co-Fe) qui ont été ensuite formulés avec la présence de promoteurs (Au/Ni-Co-Fe). Du fait que la préparation par plasma thermique de ces catalyseurs nanométriques supportés par le carbone soit relativement récente, cela permet d’envisager des perspectives d’applications avec des retombées industrielles, car les hautes températures caractéristiques des plasmas permettent de générer des carbures de fer (Fe3C, Fe5C2) très importants dans le processus catalytique de SFT. Des efforts de quantification de toutes les phases de carbures ont été effectués à l’aide de la diffraction des rayons X (DRX), tandis que l’analyse quantitative à l’aide du Rietveld (AQR) n’a été que partiellement concluante à cause de la taille nanométrique des matériaux étudiés qui est en dessous des limites de détection instrumental. Avec des aires spécifiques de BET comprises entre 35 et 93 m2.g-1, les catalyseurs sont typiques de matériaux poreux et présentent ainsi un avantage pour la SFT car les transformations réactionnelles ne sont pas limitées par les phénomènes de transfert de masse. La microscopie électronique à transmission (MET) et la microscopie électronique à balayage (MEB) couplées avec la Spectroscopie à rayons X à dispersion d'énergie (EDX) et la cartographie des rayons X (cartographie X) ont montré une grande dispersion des particules métalliques dans la matrice de carbone, indiquant ainsi l’absence d’agglomération sur les échantillons frais et post réactionnels. Les caractérisations par la spectroscopie Raman et la Spectroscopie photoélectronique par rayon X (XPS) ont mis en évidence un support de catalyseur essentiellement graphitique. Les analyses par la spectroscopie d’absorption des rayons X (SAX), par la spectroscopie de structure près du front d’absorption des rayons X (XANES) ont confirmé que le catalyseur Co/C obtenu par plasma contenait des carbures (Co3C) qui n’ont pu être révélés par XPS. Le test catalytique initial a été effectué en réacteur à lit fixe à 503 K (230°C), sous une pression de 3 MPa avec une vitesse volumique spatiale (VVH) de 6 000 〖cm〗^3 〖.h〗^(-1).g^(-1), pour une durée de 24 heures. Par la suite, les tests ont été performés dans un réacteur triphasique agité continu (3-φ-CSTSR) opérant de façon isotherme pendant 24 heures à des températures de 493–533 K (220–260°C), sous 2 MPa et à VVH = 3 600 〖 cm〗^3 〖.h〗^(-1).g^(-1). Tous les catalyseurs étudiés ont été actifs pour la SFT, produisant des fractions de gasoline (essence) et de diesel mais avec des sélectivités qui dépendaient de la proportion de métal présent dans le catalyseur et des conditions réactionnelles. À 493 K, le catalyseur le plus actif a été Co/C, obtenu par plasma, avec 40% de conversion qui contraste avec les 32% du meilleur catalyseur commercial Fe/C. Ces performances ont été comparées avec celles d’autres catalyseurs synthétisés par plasma Fe/C (25% de conversion) et 80%Co-20%Fe/C (10%), tandis que 50%Co-50%Fe/C, 30%Co-70%Fe/C n’ont montré aucune activité. Le catalyseur Co/C a été aussi le plus sélectif pour la formation de gasoline; mais à 533 K il a généré des quantités excessives de CH4 (46%) et CO2 (19%); ce qui a conduit à l’idée de synthétiser des bimétalliques Co-Fe/C qui ont permis d’abaisser la sélectivité en CH4 ou CO2 en dessous de 10%, pour une conversion de CO dépassant 40%. De même, les catalyseurs contenant du Ni (Ni-Co-Fe/C) ont été plus actifs avec des conversions de CO dépassant 50% avec des sélectivités en gasoline (38%) plus élevées qu’en diesel (20%). Ce catalyseur bimétallique a aussi favorisé la formation importante de CH4 (23%) et de CO2 (14%) beaucoup plus que dans le cas du solide Co-Fe/C. Globalement, le catalyseur bimétallique Co-Fe et sa variante acidifiée (exemple Mo-Co-Fe) ont été plus sélectifs en diesel (~ 55%). L’influence du prétraitement a été examinée et, selon la composition des catalyseurs, ceux qui ont été initialement réduits par CO avaient montré une amélioration de la sélectivité en diesel (50–67%); ces performances se sont avérées meilleures par rapport à celles des solides initialement réduits par H2 (45–55%). En outre, les catalyseurs aux concentrations élevées en cobalt, ainsi que ceux prétraités sous hydrogène ont généré plus d’eau que ceux prétraités ou réduits par CO. La présence d’atomes d’or comme promoteur dans le catalyseur Ni-Co-Fe/C (Au/Ni-Co-Fe/C) a non seulement ralenti l’activité de Ni-Co-Fe/C, mais aussi a diminué sa capacité à former l’eau, bien que n’ayant eu aucun impact significatif sur la sélectivité en composés hydrocarbonés. / Abstract : This work reveals the potential plasma technology presents in producing highly active catalysts for Fischer-Tropsch synthesis (FTS), while simultaneously contracting catalyst production into a single step, which is a certain departure from the traditional multi-step methods such as impregnation or precipitation. Novel catalysts proposed were carbon-based, developed from single metal (Fe/C, Co/C) to bimetallic (Co-Fe), ternary (Mo-Co-Fe, Ni-Co-Fe) and then the promoted Au/Ni-Co-Fe formulations. Since the preparation of nanometric carbon-supported catalysts by plasma is a relatively new phenomenon, it offers the Fischer-Tropsch catalysis prospects of future commercial applications, because of the high temperatures that are achieved in plasma create Fe carbides (Fe3C, Fe5C2), which are assumed to account for Fe-based FTS catalysis. An attempt to fully quantify the carbide phases in the samples by X-ray diffraction (XRD) and Rietveld Quantitative Analysis (RQA) was only partially successful due to the nanometric nature of the materials existing below the instrument’s detection limits. With BET specific surface areas of 35–93 m2.g-1, the catalysts were found to be non-porous, a characteristic that is advantageous because Fischer-Tropsch reaction would operate away from mass transfer limitations. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDX) and X-ray mapping indicated high dispersion of the metal moieties in the carbon matrix, with no signs of nanoparticle agglomeration both in the fresh and used samples. Raman and X-ray Photoelectron Spectroscopy (XPS) characterized the support as highly graphitic, mixed with amorphous carbon arising from substantial defects in the graphite. Evidence from X-ray Absorption Spectroscopy (XAS) using X-ray Absorption Near Edge Structure (XANES) analysis confirmed that plasma synthesized Co/C catalyst contained some carbides (Co3C), which went undetected by XPS. Initial catalyst testing was performed in the fixed-bed reactor at 503 K (230C), 3 MPa pressure, and gas hourly space velocity (GHSV) of 6 000 〖cm〗^3 〖.h〗^(-1).g^(-1) of catalyst for 24 h. Elaborate tests were further executed in a 3-phase continuously stirred-tank slurry reactor (3-φ-CSTSR) isothermally operated between 493–533 K (220–260°C) at 2 MPa pressure, and GHSV = 3 600 〖cm〗^3 〖.h〗^(-1).g^(-1) of catalyst, for 24 h. It was observed that all catalysts were active for FTS, producing both gasoline and diesel fractions, but selectivity depended on the amount of metal in the catalyst or the reaction conditions. The most active catalyst at 493 K was the plasma-synthesized Co/C that showed 40% CO conversion, which was benchmarked against the commercial Fe/C at 32%. This performance was compared to the plasma-synthesized Fe/C (25% CO conversion) and 80%Co-20%Fe/C (10% CO conversion), while both the 50%Co-50%Fe/C and 30%Co-70%Fe/C were inactive. The plasma-synthesized Co/C was also more selective towards the gasoline fraction, but at 533 K it generated excessive CH4 (46%) and CO2 (19%) prompting the development of the Co-Fe/C bimetallics, which exhibited less than 10% selectivity towards CH4 or CO2 at over 40% CO conversion. Similarly, Ni-containing catalysts (Ni-Co-Fe/C) were relatively more active than the bimetallics, exhibiting over 50% CO conversion with higher selectivity towards the gasoline fraction (38%) than towards diesel (20%). The Ni-Co-Fe/C catalysts also produced excessive CH4 (23%) and CO2 (14%), than the Co-Fe/C bimetallics. Overall, the Co-Fe bimetallics and the acidified Co-Fe catalyst (i.e. Mo-Co-Fe/C) were more selective towards diesel formation (~55%). When the effect of pre-treatment medium was investigated, depending on catalyst composition, the CO-reduced catalysts showed enhanced selectivity for diesel fraction (50–67%) than catalysts reduced in H2 (45–55%). In addition, it was observed that catalysts containing high concentration of Co as well as those reduced in H2 generated more H2O than those reduced in CO, and the presence of Au (that is, in Ni-Co-Fe/C) not only depressed the Ni-Co-Fe/C catalyst activity, but it also lowered its capacity to form H2O, although it had no significant impact on the catalyst’s hydrocarbon selectivity.

Nesta tese de doutorado foram desenvolvidos e caracterizados nanomateriais eletroativos, explorando estratégias de estabilização e os efeitos sinérgicos em nanomateriais multifuncionais baseados em alfa-hidróxido de níquel, com potencial aplicação nas mais essências e urgentes áreas de atuação científica e tecnológicas, como por exemplo na conversão e armazenamento de energia, e sensores amperométricos. Nesse sentido, foram desenvolvidos nanopartículas (NPs) de alfa-hidróxidos de níquel (α-Ni(OH)2) estabilizados pela formação de nanocompósitos com óxido de grafeno (GO), denominados de α-Ni(OH)2@GO. Analogamente, foram preparados NPs de sais de hidróxido duplo de níquel e cobalto (α- NiCo(OH)2), estabilizados pela incorporação cátions Co2+ na estrutura do α-Ni(OH)2, e o correspondente nanocompósito com óxido de grafeno reduzido (rGO) denominado de α- NiCo(OH)2@rGO. De modo geral, os nanocompósitos exibiram alta capacidade de carga em elevadas densidades de corrente, alta capacidade de retenção de carga e elevada estabilidade como consequência da interação sinergística de seus componentes, com potencial aplicação em dispositivos de armazenamento de energia de alto desempenho, como por exemplo em supercapacitores híbridos. Por outro lado, um dos principais desafios no campo da conversão de energia, concentra-se no desenvolvimento de eletrocatalisadores eficientes e robustos para impulsionar a cinética intrinsecamente lenta da reação de evolução de oxigênio (OER), que envolve etapas de transferência de elétrons acopladas a de prótons. Para isso, foram preparados nanocompósitos ternários baseados em NPs de αNi(OH)2 de diferentes tamanhos, octacarboxiftalocianina de ferro (FeOCPc) e rGO (α-NiFeOCPc@rGO). As NPs de α- Ni@rGO-K maiores e mais cristalinas e seus respectivos nanocompósitos mostraram propriedades eletrocatalíticas superiores para a OER quando comparados com os respectivos derivados de α-Ni(OH)2-Na, indicando a relevância do tamanho do nanocristal de α-Ni(OH)2 na estrutura do nanocompósito e consequente efeitos sinérgicos nas propriedades eletroquímicas e eletrocatalíticas dos nanocompósitos ternários. Além disso, foram desenvolvidos eletrodos modificados com NPs de hidróxido duplo lamelar de NiCe (α-NiCe) como sensores de alta sensibilidade, e de fundamental importância para detecção e quantificação de prednisona, uma droga proibida pelo Comitê Olímpico Internacional (COI). Em resumo, a incorporação de 20% em mols de íons Ce(III/IV) em nanopartículas de α- Ni(OH)2 aumentou a estabilidade deste material na fase alfa, conferindo melhores propriedades eletrocatalíticas responsáveis pela rápida oxidação da prednisona e de seus subprodutos de degradação, permitindo a preparação de sensores amperométricos com elevada sensibilidade e baixo limite de detecção (LOD) em comparação aos eletrodos modificados já reportando na literatura. Em suma, as estratégias no design de nanomateriais foram exploradas com sucesso para gerar novos nanomateriais e nanocompósitos com propriedades eletrocatalíticas e de armazenamento de carga aprimoradas, com potencial de aplicação em sensores e supercapacitores híbridos. / In this doctoral thesis, nanomaterials design strategies were explored in order to improve the stability of alpha-nickel hydroxide nanoparticles while developing synergistic effects, generating multifunctional electrochemically active nanomaterials and nanocomposites with potential application in amperometric sensors and energy conversion and storage devices. In this context, the α-Ni(OH)2 NPs were stabilized by generating double hydroxide salts, by interaction with octacarboxyphthalocyanine molecules and graphene oxide (GO) generating hybrid and nanocomposite materials, for example α-Ni(OH)2@GO. Nickel hydroxide NPs was stabilized by incorporation of Co2+ cation to produce α-NixCoy(OH)2 double hydroxide salts and the corresponding nanocomposite with reduced graphene oxide (rGO) designated - NiCo(OH)2@rGO. In this way, nanocomposites with potential application in high performance energy storage devices such as hybrid supercapacitors were produced, since exhibited large charge capacities at high current densities and great stability as a consequence of the synergistic interaction of their componentes. One of the main challenges in the field of energy conversion, the development of efficient and robust electrocatalysts to boost the intrinsically slow multielectronic multiprotonic transfer kinetics of the oxygen evolution reaction (OER) was also addressed using ternary nanocomposites based on α-Ni(OH)2 NPs, iron octacarboxyphthalocyanine (FeOCPc) and rGO (α-NiFeOCPc@rGO). The more crystalline - Ni@rGO-K NPs and their respective nanocomposites showed superior electrocatalytic properties when compared to the respective α-Ni(OH)2-Na derivatives, indicating the relevance of the α-Ni(OH)2 nanocrystal size and synergistic effects on their electrochemical and electrocatalytic properties. In addition, amperometric sensors based on NiCe layered doublehydroxide NPs (α-NiCe) were developed for determination of prednisone, a drug forbidden by the International Olympic Committee (IOC). The incorporation of 20 m% of Ce3+/4+ ions in α- Ni(OH)2 nanoparticles increased its stability in the alpha phase, conferring improved electrocatalytic properties responsible for the rapid oxidation of prednisone and its degradation byproducts, responsible for the higher sensitivity and lower detection limits (LOD) than similar devices reported in the literature. In short, nanomaterials design strategies were successfully explored to generated new nanomaterials and nanocomposites with enhanced electrocatalytic and charge storage properties with potential application in sensors and hybrid supercapacitors.

Atualmente, os estudos envolvendo nanomateriais como aditivos em propantes são o foco das companhias e universidades norte-americanas para o desenvolvimento de propantes que possam sofrer alterações químicas e mecânicas dentro do reservatório ou para permitir a rastreabilidade e direcionamento. Este trabalho apresenta um desenvolvimento de grânulos de metacaulim capazes de incorporar nanomateriais em sua estrutura. O método adotado para sua produção foi a mistura intensiva da matéria-prima (MP) com nanomateriais dispersados e adicionados em resina para revestimento. A rota de produção tem potencial para produzir grânulos com grau de K&S variando entre 0,7 e 0,9 tanto para esfericidade como para o arredondamento. Os ensaios de resistência ao esmagamento resultaram em valores entre 3 K e 4 K (x 1.000 psi) para algumas das amostras sinterizadas a 1.300 ºC. As análises de MEV comprovam a incorporação dos nanomateriais de carbono, na estrutura interna dos propantes. / Today, studies on nanomaterials that are used as additives in proppants are the focus of North America\'s companies and universities in order to develop either proppants that can suffer mechanical and chemical changes inside the reservoir or that enable their traceability and direction. This work presents a development on the microspheres of metakaolin\'s capacity to incorporate nanomaterials to their structure. The production route has the potential to produce K & S grade microspheres ranging from 0.7 to 0.9 for both sphericity and rounding. Crush strength tests resulted in values between 3 K and 4 K (x 1,000 psi) for some of the samples sintered at 1300 °C. The SEM analyzes prove the integration of carbon nanomaterials into the proppant structures.

Radionuclide liquid wastes generated from nuclear facilities can affect humans and the environment, thus substantial attention for their safe management has been received worldwide. Treatment of radionuclide liquid wastes is an important step in its management. In the present work, new composite nanomaterials, graphene oxide base nanomaterial (GO) are developed for treatment purpose. Graphene oxide (GO), one of the most graphene derivatives, its unique properties, such as chemical stability, hydrophilicity, large surface area and functional groups, make them able to form strong chemical bonds with radionuclides. GO was successfully synthesized via Hummers method, characterized by Raman spectroscopy, X-Ray Diffraction (XRD), UV/Vis Spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) and applied as an adsorbent in removal of the metallic long-lived radionuclide 68Ge from of aqueous solution The method used for evaluation of nanomaterials retention properties was sorption experiment, being based on contact of solid material with tracer solution under defined boundary conditions (solid/solution ratio, solution composition etc.). Two sorption experimental methods were used in this study. Firstly, an aqueous solution of 68Ge radionuclide solution mixed with GO solution, the solution was filtered using syringe filter membrane unit and the aliquot was quantified by gamma spectrometry. Secondly, the 68Ge radionuclide was mixed with GO solid powder, suspension rotated in a mechanical shaker, centrifuged, an aliquot of 1.0 ml sample taken for gamma spectroscopy and the supernatant was put in an oven to dry overnight for characterization analysis. The results obtained from experiments were the evaluated, using sorption percentage equation and showed that the GO had much low sorption capacity for the pre-concentration of radionuclides from aqueous solutions. The function of the pH, the ionic strength and the reduction of GO will be investigated for future studies for the improvement of the research results. / Physics / M. Sc. (Physics)

The ability to convert photons into mechanical motion is of significant importance for many energy conversion and reconfigurable technologies. Establishing an optical-mechanical interface has been attempted since 1881; nevertheless, only few materials exist that can convert photons of different wavelengths into mechanical motion that is large enough for practical import. Recently, various nanomaterials including nanoparticles, nanowires, carbon nanotubes, and graphene have been used as photo-thermal agents in different polymer systems and triggered using near infrared (NIR) light for photo-thermal actuation. In general, most photomechanical actuators based on sp bonded carbon namely nanotube and graphene are triggered mainly using near infra-red light and they do not exhibit wavelength selectivity. Layered transition metal dichalcogenides (TMDs) provide intriguing opportunities to develop low cost, light and wavelength tunable stimuli responsive systems that are not possible with their conventional macroscopic counterparts. Compared to graphene, which is just a layer of carbon atoms and has no bandgap, TMDs are stacks of triple layers with transition metal layer between two chalcogen layers and they also possess an intrinsic bandgap. While the atoms within the layers are chemically bonded using covalent bonds, the triple layers can be mechanically/chemically exfoliated due to weak van der Waals bonding between the layers. Due to the large optical absorption in these materials, they are already being exploited for photocatalytic, photoluminescence, photo-transistors, and solar cell applications. The large breaking strength together with large band gap and strong light- matter interaction in these materials have resulted in plethora of investigation on electronic, optical and magnetic properties of such layered ultra-thin semiconductors. This dissertation will go in depth in the synthesis, characterization, development, and application of two- dimensional (2D) nanomaterials, with an emphasis on TMDs and molybdenum disulfide (MoS2), when used as photo-thermal agents in photoactuation technologies. It will present a new class of photo-thermal actuators based on TMDs and hyperelastic elastomers with large opto-mechanical energy conversion, and investigate the layer-dependent optoelectronics and light-matter interaction in these nanomaterials and nanocomposites. Different attributes of semiconductive nanoparticles will be studied through different applications, and the possibility of globally/locally engineering the bandgap of such nanomaterials, along with its consequent effect on optomechanical properties of photo thermal actuators will be investigated. Using liquid phase exfoliation in deionized water, inks based on 2D- materials will be developed, and inkjet printing of 2D materials will be utilized as an efficient method for fast fabrication of functional devices based on nanomaterials, such as paper-graphene-based photo actuators. The scalability, simplicity, biocompatibility, and fast fabrication characteristics of the inkjet printing of 2D materials along with its applicability to a variety of substrates such as plastics and papers can potentially be implemented to fabricate high-performance devices with countless applications in soft robotics, wearable technologies, flexible electronics and optoelectronics, bio- sensing, photovoltaics, artificial skins/muscles, transparent displays and photo-detectors.

O desenvolvimento da nanociência e nanotecnologia promoveu uma nova fronteira no estudo da matéria, permitindo que materiais já conhecidos tivessem suas propriedades redescobertas ao serem manipulados em nível molecular. Vários materiais vêm apresentando relevância na nanociência e nanotecnologia, como os nanotubos de carbono (CNTs), nanopartículas (NPs) e óxido de grafeno, uma vez que os CNTs e óxido de grafeno são dotados de propriedades mecânicas, térmicas e elétricas que os tornam apropriados para o desenvolvimento e a aplicação em dispositivos, especialmente na área biotecnológica e de sensores. Diversas áreas se beneficiam com o uso da tecnologia em nanopartículas (NPs), por exemplo: alimentícia, médica, agronegócio, cosmética, etc. Uma possível perspectiva na utilização desses nanomateriais em sistemas biológicos torna muito interessante investigar como tais materiais interagem em nível molecular com modelos de membranas celulares e com células. Esta tese tem como objetivos: i) investigar detalhadamente a interação entre nanopartículas (Fe3O4/Dextran; Fe3O4/PDAC; PDAC; Dextran) e nanotubos de carbono com modelos de membranas celulares; e ii) desenvolver nanofibras poliméricas pela técnica de electrospinning para ser utilizada com óxido de grafeno como modelos mimetizados (scaffolds) para a diferenciação de células-tronco neurais. Os filmes ultrafinos foram fabricados utilizando as técnicas de Langmuir e Langmuir-Blodgett. Esses nanomateriais foram avaliados através da técnica de Espectroscopia vibracional por Geração de Soma de Frequências. A espectroscopia SFG é sensível a interfaces. Nanofibras de Poli(ε-Caprolactone) foram fabricadas pela técnica de electrospinning. Scaffolds com óxido de grafeno/Nanofibras de Poli(ε-Caprolactone) foram desenvolvidos como suportes sólidos para a diferenciação de células-tronco neurais de rato. Óxido de grafeno em diferentes concentrações foi incorporado nas nanofibras poliméricas. Os modelos deste sistema foram investigados por imagens de Microscopia Eletrônica de Varredura. Os resultados mostraram que a carga eletrostática de cada fosfolipídio utilizado pode influenciar nas interações com os nanomateriais (nanopartículas ou nanotubos de carbono), podendo resultar em uma desestruturação no modelo de membrana celular. Scaffolds contendo nanofibras de Poli(ε-Caprolactone) com óxido de grafeno representaram um eficiente modelo mimetizado para a interação/diferenciação de células-tronco neurais de rato conforme revelado por imagens de Microscopia Eletrônica de Varredura. Estas imagens mostraram que o sistema de nanofibras de Poli(ε-Caprolactone) com 1,0 mg/mL de óxido de grafeno foram ideais para a diferenciação de oligodendrócitos em células-tronco neurais de rato. / The development of nanoscience and nanotechnology promoted a new frontier on the study of matter, allowing conventional materials to exhibit novel or improved properties. Several materials show relevance in nanoscience and nanotechnology, such as carbon nanotubes (CNTs), nanoparticles (NPs) and graphene oxide. CNTs and graphene oxide, for example, exhibit unique mechanical, thermal and electrical properties, which make them appropriate to the development and application in devices, especially in biotechnology and sensors areas. Many areas are benefited from the use of nanoparticles (NPs), such as food, medical, agrobusiness, cosmetic etc. The perspective regarding the use of nanomaterials in biological systems requires the understanding on how these materials interact at the molecular level with cell membrane models and with cells. The objectives of this thesis are: i) to investigate the interaction between nanoparticles (Fe3O4/Dextran; Fe3O4/PDAC; PDAC; Dextran) and carbon nanotubes with cell membrane models; and ii) to develop polymeric nanofibers via electrospinning technique, to be used with graphene oxide as mimic models (scaffolds) in the differentiation of neural stem cells. The cell membrane models were manufactured using Langmuir and Langmuir-Blodgett techniques. These nanomaterials were evaluated through Sum Frequency Vibrational Spectrosocopy (SFG). Poly(ε-Caprolactone) nanofibers were manufactured by electrospinning technique. Scaffolds with graphene oxide/Poly(ε-Caprolactone) were developed as solid supports for differentiation of rats neural stem cells. This biosystem was investigated via Scanning Electron Microscopy and biochemical essays. The results showed that the charge of each phospholipid influenced the interactions with the nanomaterials (nanoparticles or carbon nanotubes), in some cases, resulting in a disruption of the cell membrane model. Scaffolds with Poly(ε-Caprolactone) nanofibers obtained via electrospinning with graphene oxide represented an efficient mimic model for interaction/differentiation of neural stem cells as shown via Scanning Electron Microscopy. The images revealed that the PCL nanofibers system with 1.0 mg/mL of graphene oxide were ideal to the differentiation of oligodendrocytes in neural stem cells.

Cellulose Nanocrystals have been used in a wide range of applications including cement composites as a strength enhancer. This work analyses the use of CNC from several sources and production methods, and their effects on rheology and hydration of pastes made using different cement types with different compositions. Cement Types I/II and V were used to prepare pastes with different water to cement ratios (w/c) and measure the changes in rheology upon CNC addition. The presence of tricalcium aluminate (cement chemistry denotes as C3A) made a difference in the magnitude of CNC effects. At dosages under 0.5vol% to dry cement, CNC reduced the yield stress up to 50% the control value. Pastes with more C¡A reduced yield stress over a wider range of CNC dosages. CNC also increased yield stress of pastes with dosages above 0.5%, twice the control value for pastes with high C3A content at 1.5% CNC and up to 20 times for pastes without C3A at the same dosage.<br>All the CNCs used were characterized in length, aspect ratio, and zeta potential to identify a definitive factor that governs the effect in the rheology of cement pastes. However, no definitive evidence was found that any of these characteristics dominated the measured effects.<br>The CNC dosage at which the maximum yield stress reduction occurred increased with the amount of water used in the paste preparation, which provides evidence of the dominance of the water to cement ratio in the rheological impact of CNC.<br>14<br>Isothermal calorimetry showed that CNC cause concerning retardation effects in cement hydration. CNC slurries were then tested for sugars and other carbohydrates that could cause the aforementioned effect, then slurries were filtered, and impurities were detected in the filtrate, these impurities were quantified and characterized, however, the retardation appeared to be unaffected by the amount of the species detected, suggesting that the crystal chemistry, which is a consequence of the production method, is responsible of this retardation.<br>This work explores the benefits and drawbacks of the use of CNC in cement composites by individually approaching rheology and heat of hydration on a range of physical and chemical tests to build a better understanding of the observed effects.<br>Understanding the effect of CNCs on cement paste rheology can provide insights for future work of CNCs applications in cement composites.