Nanoscale materials usually present strikingly different properties in comparison with their bulk counterparts, such as quantum size effects, surface plasmon resonance (SPR). To explore new properties as well as for novel applications, nanomaterials are being extensively investigated. This project investigates the interactions of electromagnetic fields with nanoscale materials, particularly gold nanoparticles (GNPs), over a wide range of frequency bands, including static field, 261 kHz, 13.56 MHz, 2.45 GHz, millimetre wave, THz, and the visible light. Especially, the efforts have been devoted to the study of heating effect of GNPs in association with potential biomedical applications. To explain the electromagnetic heating of GNPs, dielectric properties of GNP dispersions has been studied from 100 MHz to 20 GHz, as well as in the millimetre wave and THz ranges. The static field induced effects on the size distribution of GNPs has also been examined using ultra-violet spectroscopy and correlated to SPR. It has been revealed that purified GNPs cannot increase the specific absorption rate substantially at whichever frequency points of 261 kHz, 13.56 MHz, or 2.45 GHz. However, a greater temperature rise has been observed in the impurified GNP dispersions compared to deionisedwater, after 10 min RF treatment at 13.56 MHz. The measurements on dielectric properties show that impurified samples have much higher effective conductivity than that of deionised-water, while the conductivity change of purified ones is very small and not detectable within the measurement accuracy. This observation supports that the heating effect of GNP dispersions is mostly contributed by the impurities and disproves that GNPs can increase the specific absorption rate significantly. The magnetic field heating at 261 kHz suggests that GNPs have very weak magnetic properties. It has been found that a static field can change the size distribution of GNPs. Up to 2 THz, it is measured that the dielectric properties of GNP dispersions have no convincing change compared to deionised-water, implying that the electromagnetic heating of GNP below 2 THz may be insignificant. In addition, it is confirmed that GNPs have strong absorption in the visible light range due to SPR.

This thesis reports the effects of incorporating graphite nanoplatelets (GNPs) to epoxy-carbon fibre (CF) laminates to produce multiscale composites. A grade of epoxy resin typical for the application in aerospace engineering, triglycidyl-p-aminophenol (TGPAP), was used in this work cured with 4,4'-diaminodiphenyl sulfone (DDS). To improve the processability of TGPAP, a diluent, the diglycidyl ether of bisphenol F (DGEBF), was added to formulations. Compositions of TGPAP/DGEBF/DDS were optimised using response surface methodology (RSM) with the target response being to obtain high glass transition temperature (Tg) and low resin viscosity. From RSM, the optimum values were obtained at 55.6 wt. % of DGEBF and a stoichiometric ratio of 0.60. Before addition into epoxy, GNPs were treated either covalently using 3-aminopropyltriethoxysilane (APTS) or non-covalently using a commercial surfactant, Triton X-100 (abbreviated as A-GNPs and T-GNPs, respectively). After treatment, XPS analysis showed a new peak at 100 eV for A-GNPs indicating silicon and the C/O ratio increased from 11.0 to 26.2 for T-GNPs relative to unmodified GNPs (U-GNPs), suggesting attachment of the modifier molecules had occurred. Nanocomposites (NCs) were prepared by incorporate GNPs into epoxy using mechanical mixing. Rheological percolation threshold of GNP-epoxy suspensions were determined using oscillatory-shear rheometry as 3.9 wt. % for AR-GNPs, 3.6 wt. % for U-GNPs, 3.2 wt. % for A-GNPs and 3.5 wt. % for T-GNPs, suggesting surface treatment improved dispersion. At 4 wt. % of GNPs, flexural strain of NCs was decreased relative to neat epoxy by 46% for AR-GNPs, 48.6% for U-GNPs, 4.6% for A-GNPs and 30.8% for T-GNPs but flexural moduli showed small increases of 6.1-7.4%. Fracture toughness (K1C) also improved. For example, the K1C increased from 0.80 ± 0.04 MPa.m1/2 for neat epoxy to 1.32 ± 0.01 MPa.m1/2 for NCs containing 6 wt. % of U-GNPs possibly due to the branching of cracks resulting from the embedded GNPs. Due to their mechanical performance, A-GNPs were used to fabricate epoxy/CF/A-GNPs multiscale composites. Multiscale composites showed inferior properties relative to a comparable conventional composite in flexural testing, interlaminar shear strength (ILSS) and interlaminar fracture toughness mode II (G11C) due to weaker bonding at the matrix-CF interface. However, multiscale composites showed ~40% higher capability than conventional composite to absorb energy during impact due to greater interfaces formed by the inclusion of A-GNPs into the system.

Nanomatériaux de silice peuvent être facilement fabriqués, façonné et fonctionnalisés comme plates-formes pour le greffage des nanoparticules pour des applications biomédicales et optiques. Ici, nous utilisons une méthodologie basée sur un modèle de préparer une collection variée de hélicoïdale nanoparticules d'or (PNB) superstructures ayant impartialité contrôlable et mesures structurelles en utilisant PNB que les blocs de construction, et les nanohelices de silice que le modèle. Le matériaux présentent synthétisé bien définir Agencement chiral de PNB suivant l'hélicité de nanohelices de silice, montrant des signaux plasmoniques de dichorism circulaire (CD). D'autres observations ont prouvé ce plasmon CD vient de l'arrangement chiral de PNB et cet effet est très taille, l'échelle et dépend du pH. Nous nous attendons à ce que cette stratégie d'assemblage va découvrir une meilleure vue sur les métamatériaux et de susciter la vue vers "bottom-up" des approches en nanosciences. / Silica nanomaterials can be easily fabricated, fashioned and functionalized as platforms for grafting of nanoparticles for biomedical and optical applications. Herein, we utilize a template-based methodology to prepare a diverse collection of helical gold nanoparticle (GNPs) superstructures having controllable handedness and structural metrics by using GNPs as the building blocks, and the silica nanohelices as the template. The synthesized materials exhibit well-defined chiral arrangement of GNPs following the helicity of silica nanohelices, showing plasmonic circular dichorism (CD) signals. Further observations proved this plasmon CD comes from the chiral arrangement of GNPs and this effect is highly size, scale and pH dependent. We expect that this assembly strategy will discover a better view towards metamaterials and spark the view towards “bottom-up” approaches in nanoscience.

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In comparison with the high-pressure adsorption at room temperature, hydrogen adsorption at cryogenic temperatures can be significantly improved at low pressures, which has great potential for prospective mobile applications. In this study, a differential pressure based manometry system was designed and constructed for fast analysing hydrogen adsorption uptakes of sorbents up to a maximum of 10 wt% at 77 K and up to 11 bar. The safety design of the system in compliance with European ATEX directives (Zone 2) for explosive atmospheres was discussed in detail, together with additional pneumatic systems for remote control of the experiments. A thorough error analysis of related experimental tests was also performed. Common carbon sorbents, including several Norit branded activated carbons and graphene nanoplatelets (GNPs) with various surface areas, were characterised for their pore structures. The structural differences among GPNs of different surface areas were also studied. The hydrogen adsorption isotherms of these sorbents, examined in the newly-built manometry system, were further analysed and discussed with reference to the assessed microstructural properties. The carbonisation processes of plasma carbons from the microwave splitting of methane, and biochars from the pyrolysis of Miscanthus, were intensively studied primarily based on Raman spectroscopy, in conjunction with other characterisation techniques such as XRD, FTIR and XPS, for exploring the formation of graphitic structures and crystallinity under various conditions. Two selected types of carbons, the activated carbon AC Norit GSX with a specific surface areas of 875 m2/g and the graphene nanoplates with a specific surface area of 700 m2/g, were decorated with palladium nanoparticles in different compositions. The growth and distribution of doped palladium particles in the carbon substrates were studied, and their effects on porous properties and microstructures of the sorbents were also reviewed. Hydrogen adsorption tests of the decorated carbons were further conducted and discussed, to explore the potential effects of Pd contents on the adsorption kinetics and hydrogen absolute uptakes.

Ordinary Portland cement (OPC) is the main constituent of concrete works as a principal binder for aggregates and intrinsically transmits the brittleness into concrete through the formation of hydration crystals in the cement microstructure. A number of nano cementitious composites were developed in recent years to offset the brittleness with newly discovered nanomaterials and the most prevalent among those is the graphene oxide (GO). The main objective of this PhD research work is to develop nano graphene cementitious composites (NGCC) using low cost, two dimensional (2D) graphene nanoplatelets (GNPs) and one dimensional (1D) graphited carbon nanofibres (GCNFs) with unique conical surface morphology. The GNPs were sourced synthesised in an environmental friendly way via plasma exfoliation whereas, GCNFs were manufactured through catalytic vapour grown method. The project further investigated the effect of these nanomaterials in regulating the distinctive microstructure of cement matrix leading to enhance its mechanical properties. Three different types of high-performance NGCC namely NGCC-Dot, NGCC-Fnt and NGCC-CNF, are developed by activating pristine GNPs (G-Dot), functionalised GNPs (G-Fnt) and graphited nanofibers (G-CNFs) into the cement matrix respectively. It is found through various characterization and experimental techniques that both GNPs and GCNFs regulated the cement microstructure and influenced the mechanical properties of NGCC uniquely. A remarkable increase in the flexural and the tensile strength of newly developed NGCC has been achieved and that could be attributed to the formation of distinctive microstructure regulated by catalytic activation of these nanomaterials. The shape (1D, 2D) and unique morphology of these nanomaterials played a vital role in the mechanism of crystal formation to regulate the cement microstructure. Based on the observations of test results and comprehensive characterization, the possible mechanisms of crystal formation and development of distinctive microstructure of NGCC has been established which has then proceeded to the development of a physical model for NGCC development.

Orientador: Ian Castro-Gamboa / Resumo: A utilização de produtos naturais pela humanidade, como agentes terapêuticos, é descrita desde primórdios da antiguidade e representam um importante aliado no tratamento de doenças. Com isso a busca por novas ferramentas analíticas mais robustas, com abordagem metabolômica se faz necessária, de forma a otimizar e acelerar a busca por novas moléculas e substâncias com atividade biológica promissora. Nesse contexto, esse trabalho tem como alvo de estudo, os fungos Fusarium solani e Purpureocillium lilacinum isolados da rizosfera de Senna spectabilis. Essas espécies de microrganismos apresentam muitos estudos químicos relatados na literatura, o que influenciou o interesse em realizar os estudos de OSMAC (One Strain Many Compounds). Para, assim, verificar a variação metabólica que acontece com esses fungos em diferentes tipos de cultivo (variando meio de cultura e agitação) incluindo o co-cultivo. Para os extratos obtidos também foram realizados os ensaios biológicos citotóxico e antibacteriano. Foram utilizadas ferramentas analíticas do estado da arte como GC-MS (Cromatografia Gasosa acoplada a Espectrometria de Massas) e LC-MS (Cromatografia Líquida acoplada a Espectrometria de Massas) fazendo uso das ferramentas de bioinformática Molecular Networking (ou Rede Molecular) com a plataforma GNPS (Global Natural Product Social Molecular Networking) e o UNIFI (Sistema de informação científica – Waters Corporation). A espectrometria de massas (MS) foi uma grande aliada que ajudou a d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of natural products by mankind, as therapeutic agents, has been described since ancient times and represents an important ally in the treatment of diseases. Thus, the search for new more robust analytical tools, with a metabolomic approach is necessary, in order to optimize and accelerate the search for new molecules and substances with promising biological activity. In this context, this study is aimed at studying Fusarium solani and Purpureocillium lilacinum fungi isolated from the rhizosphere of Senna spectabilis. These species of microorganisms have many chemical studies reported in the literature, which influenced the interest in carrying out the studies of OSMAC (One Strain Many Compounds). Thus, to verify the metabolic variation that happens with these fungi in different types of cultivation (varying culture medium and agitation) including co-culture. For the extracts obtained, cytotoxic and antibacterial biological tests were also performed. State-of-the-art analytical tools such as GCMS (Gas Chromatography coupled to Mass Spectrometry) and LC-MS (Liquid Chromatography coupled to Mass Spectrometry) were used alongside the bioinformatics tools Molecular Networking with the platform GNPS (Global Natural Product Social Molecular Networking) and UNIFI (Scientific Information System - Waters Corporation). Mass spectrometry (MS) was a great ally that helped to demonstrate the variation of the metabolites profile of these microorganisms in different cultures, in whic... (Complete abstract click electronic access below) / Doutor