O ouro foi considerado um metal pouco interessante do ponto de vista catalítico por muito tempo, devido ao fato de não quimiossorver moléculas como hidrogênio e oxigênio. Entretanto, suas propriedades catalíticas são reveladas quando suas dimensões são reduzidas a poucos nanômetros, particularmente menores do que 10 nm. Assim, nanocatalisadores de ouro vêm recebendo atenção devido as suas excelentes propriedades catalíticas e alta seletividade em reações de oxidação e redução. O presente trabalho descreve a síntese e caracterização de nanopartículas de ouro suportadas e sua aplicação em reações de oxidação de alcoóis para produção de aldeídos, cetonas e ésteres. Para facilitar a separação do catalisador, um suporte magnético composto de magnetita revestida com sílica foi desenvolvido. A síntese das nanopartículas de ouro suportadas foi realizada de duas maneiras: (I) pela impregnação do suporte com espécies aniônicas de ouro seguido de redução e (II) pela impregnação de nanopartículas de ouro pré-sintetizadas. Em todos os casos nanopartículas de ouro na faixa de 5 nm foram obtidas. A etapa de redução do metal impregnado no suporte foi investigada em detalhe através de duas estratégias: a redução térmica e a redução por hidrogênio. Os testes catalíticos para as reações de oxidação de alcoóis mostraram que os catalisadores sintetizados apresentam altas taxas de conversão e seletividade, porém dependentes do método de preparação utilizado / Gold in the bulk form has been regarded to be an uninteresting metal from the point of view of catalysis, as it is chemically inert towards chemisorption of reactive molecules such as oxygen and hydrogen. However, the catalytic properties of gold are revealed when the size is reduced to few nanometers, particularly with dimension less than 10 nm. Therefore, gold nanocatalysts have received great attention due to the excellent catalytic properties and high selectivity in oxidation and reduction reactions. This master thesis describes the synthesis and characterization of supported gold nanoparticles and their application in alcohol oxidation reaction to produce aldehydes, ketones and esters. In order to improve the catalyst separation and recovery, a magnetic support comprised of magnetite coated by silica was developed. The supported gold nanoparticles were synthesized in two different ways: (I) by impregnation of anionic gold species on silica surface followed by metal reduction, and (II) by impregnation of pre-synthesized gold nanoparticles on the support. In all examples supported gold nanoparticles of about 5 nm were obtained. The reduction step (of the metal impreganted on the support) was investigated in detail by two different strategies: thermal reduction and reduction by hydrogen. The synthesized catalysts showed high conversion rates and selectivity in the catalytic reactions of alcohol oxidation, but those are dependent on the preparation method

Les matériaux chiraux peuvent avoir une forte influence sur la propagation de la lumière et ont attiré l'attention de la communauté des nanosciences. Les nanoparticules d'or, matériaux plasmoniques stables ayant une activité dans le visible (400 à 800 nm), sont des objets attrayants en tant que blocs de construction pour la formation de matériaux optiques. Précédemment, nous avons conçu et obtenu des Goldhelices en greffant des nanoparticules d’or sur des nano structures hélicoïdales de silice. Le travail présenté dans cette thèse vise à développer et à organiser les Goldhelices de manière à améliorer, modifier, réduire, voire même éliminer les propriétés chiroptiques. Les détails des nanostructures ainsi que la cinétique de formation de l'auto-assemblage organique utilisé comme support pour la formation de Goldhelices sont étudiés. Des Goldhelices sont ensuit organisées hiérarchiquement à l’aide de trois techniques : la microfluidique, le « dip coating » et le « Grazing Incidence Spraying ». Enfin, l’effet de ces organisations sur les propriétés optiques sont caractérisées par spectroscopies chirales et ellipsométrie. Nous démontrons qu'un tel système peut être utilisé pour la création de polariseur linéaire ou circulaire où une telle polarisation est uniquement dépendant par l'organisation des Goldhelices. / Chiral materials can have strong influence on the propagation of light and have attracted attention in the nano-science community. Gold nanoparticles (GNPs), stable plasmonic materials in the visible range (400-800 nm), are attractive objects as building blocks for optical materials. We have designed and obtained Goldhelices by grafting GNPs on silica nano-helical structures. The work presented in this thesis aims at developing tunable Goldhelices and organizing them in order to enhance, modify, reduce or even eliminate the chiroptical properties. The details of the nanostructures as well as the kinetics of formation of organic self-assembly which is used as templates for the formation of Goldhelices are fully studied. The hierarchical organization of the Goldhelices is investigated by the use of three techniques, the microfluidics, the dip-coating and the grazing incident spraying. Finally, the effect of the organization on their optical properties are characterized by chiral spectroscopies and Mueller matrix polarization ellipsometry. We demonstrate that such a system can be used for the creation of linear or circular polarizer where such polarization is solely tunable by the organization of the Goldhelices.

Separation methods involving a mixture of metals typically include upfront processing that leads to one final product. To lower the waste and ultimately environmental burden, the potential to synthesize multiple functional products from a mixed metal precursor solution is explored. The initial precursor solutions contained varying ratios of gold and copper, gold and nickel, and finally a ternary solution of gold, copper, and nickel. The amount of gold was kept constant, while the amount of copper and/or nickel was sequentially increased. Two separate synthesis processes were tested, the traditional Turkevich method involving trisodium citrate and another chemical reduction method involving sodium borohydride. The particle size and chemical composition of the synthesized particles were characterized using TEM, DLS and ICP-OES. It was determined that gold nanoparticles still formed at a ratio of 1 to 2 gold to copper while using trisodium citrate or sodium borohydride as the reducing agent. The same limiting ratio was observed for the gold to nickel reactions in the presence of either trisodium citrate or sodium borohydride. The ternary mixture limit for gold nanoparticle formation was a molar ratio of 1 to 1 to 1 gold to copper to nickel. The repeatability and stability results for the optimized binary reaction conditions indicate that using sodium borohydride as the reducing agent consistently produces more stable particle suspensions. Quantifying the environmental impact using green chemistry metrics indicate the Turkevich reactions for the optimized reactions have the lower environmental factors.

Radiosensitization is a novel targeted therapy strategy where chemical compounds are being explored to enhance the sensitivity of the tissue to the effects of ionizing radiation. Among the different radiosensitizers alternatives, nanomaterials have shown promising results by enhancing tumor injury through the production of free radicals and reactive oxygen species (ROS). In this work, Gold-supported titania (Au@TiO2) nanocomposites were synthesized through an innovative strategy using X-ray irradiation, and their potential as radiosensitizers was investigated. Radiosensitization of Au@TiO2 nanocomposites was assessed by monitoring the decomposition of Methylene Blue (MB) under X-ray irradiation in the presence of the nanomaterial. Radiosensitization of Au@TiO2 was thoroughly investigated as a function of parameters such as Au loading, TiO2 particle size, nanomaterial concentration, different irradiation voltages, and dose rates. Results showed that the presence of Au@TiO2 increases significantly the absorbed dose, thus enhancing MB decomposition. The mechanism behind Au@TiO2 radiosensitization relies on their interaction with X-rays. TiO2 produces reactive ROS whereas Au leads to the generation of photoelectrons and Auger electrons upon exposure to X-rays. These species lead to an enhanced degradation rate of the dye, a feature that could translate to cancerous cells damage with minimal side effects. The radiosensitization effect of Au@TiO2 nanocomposites was also tested in biological settings using Microcystis Aeruginosa cells. The results showed an increase in cell damage when irradiated in the presence of Au@TiO2 nanocomposites. Au@TiO2 nanocomposites were fabricated using X-ray radiolytic synthesis, a method that diverges from conventional fabrication processes and leads to negligible by-product formation, an important feature for medical and catalytic applications. In this work, Au nanoparticles are supported on TiO2 with a mean particle size of either 6.5 nm or 21.6 nm, using different ligands such as NaOH or urea, and under different absorbed doses to determine the effects of these parameters on the nanomaterials’ characteristics. Overall, Au@TiO2 synthesized by X-rays showed remarkable promise as radiosensitizers, a concept relevant to a number of medical, biological and environmental applications.

The bacterial meningitis caused by Neisseria meningitidis is responsible for considerable morbidity and mortality throughout the world. Given the limitations of existing diagnostic tests and the severity of the illness associated with the disease, there is a clear requirement for a rapid and specific diagnostic assay. This thesis describes the development of nanoparticle based tests for the detection of Neisseria meningitidis specific cell surface markers. As an initial target antigen, a recombinant form of highly conserved outer membrane protein, OMP85 was used. Within the OMP85 protein sequence, a predicted antigenic sequence between residues 720 and 745 was identified and found to be unique to this organism. This amino acid sequence was synthesised as peptide (SR1) with a gly-gly-cysteine spacer sequence at the N-terminus using t-boc chemistry. Also, the major virulence factor, capsular polysaccharide of N. meningitidis serogroup B bacteria was purified. Polyclonal antibodies were raised against purified OMP85 antigen in rabbits and against SR1 peptide and also against formalin inactivated N. meningitidis serogroup B whole cell bacteria in sheep. This panel of different antibodies including the commercial anti-capsular monoclonal antibodies were examined for cross reactivity against a range of closely related Gram negative bacteria. Based on these cross-reactivity studies, a highly specific anti-NM antibody was developed following purification of the anti-SR1 antiserum by immuno-affinity chromatography. Purified OMP85 antigen and anti-OMP85 antibody were successfully conjugated on 13, 30, 40, 50 and 60 nm gold nanoparticles by an electrostatic adsorption method. Coupling of the gold nanoparticles results in a shift of the respective surface plasmon peak toward longer wavelengths (in the range of 600-800 nm) resulting in a change of the colour of the colloidal suspension from red to purple to blue. An attempt was made to develop a rapid diagnostic assay based on gold nanoparticle induced colour shift assay for N. meningitidis by utilising the specific interaction of OMP85 and anti-OMP85 antibody conjugated to gold nanoparticles as a model system. However, this system was not reproducible and is likely to be due to problems with stability of gold nanoparticles during the conjugation process. As an alternative approach, a highly selective quartz crystal microbalance (QCM)-based immunosensor was designed using the same OMP85/anti-OMP85 antibody system. A method was developed using polyvinylidene fluoride (PVDF) coated QCM crystals with protein A for the directional orientation of the antibodies. To further enhance the sensitivity of the test, OMP85-conjugated gold nanoparticles were used as signal amplification probes for the reproducible detection of the target down to 300 ng/mL, corresponding to a five fold increase in sensitivity compared to detection of OMP85 antigen alone. Also, this sensor has successfully been employed to detect whole cell bacteria at a concentration as low as 100 cfu/mL. Thus, in this study using the real-time QCM measurements, a novel strategy has been developed for the sensitive detection of both N. meningitidis bacteria and the protein antigen at very low concentrations, using gold nanoparticles as signal amplification probes.

Injection of a mixture of HAuCl4 and cellulose dissolved in the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride [Bmim]Cl into aqueous NaBH4 leads to colloidal gold nanoparticle/cellulose hybrid precipitates. This process is a model example for a very simple and generic approach towards (noble) metal/cellulose hybrids, which could find applications in sensing, sterile filtration, or as biomaterials.

Development of a simple, specific, sensitive and rapid RNA microchip for detection of Head and Neck Cancer (HNC) mRNA, pathogenic bacteria and dengue virus (DENV) RNA is reported. By use of nucleases and polymerases specific RNAs are selectively labeled and detected without separation, reverse transcription and or polymerase chain reaction. This is accomplished by designing specific Hybrid probes consisting of DNA-2’-O-Me-RNA-DNA regions to target the RNA of interest. Upon hybridization with the target RNA, RNase H digestion is used to remove the 3’- RNA sequences which exposes the template for Klenow extension with reporter molecules such as hapten or fluorophore labels. This novel RNA microchip is fast (ca. 1 h detection time), selective as individual RNAs are detected in a synthetic mixture and total RNA mixtures, specific for single nucleotide polymorphisms (SNPs) discrimination and sensitive up to attomole level for chemiluminescence detection and lower femtomole for gold nanoparticles (AuNPs) and silver staining method. Using chemiluminescence, HNC biomarkers, VCAM1 and IL8 are specifically labeled and detected in the presence of thousands of other mRNAs in cancer cell lines and human colon cancer total RNA without interference. Furthermore, the method is highly specific as shown with DENV SNPs discrimination. Moreover, we report rapid (ca 1hour), selective, specific multi-marker detection of pathogenic mRNAs and HNC mRNAs using AuNPs-silver staining on the RNA microchip. Streptavidin gold nanoparticles technology has a potential in the analysis of specific mRNAs in a wide array of field including infectious diseases diagnosis, viral infections, food safety, gene expression profiling and cancer detection. A simple and rapid NaOH RNA extraction procedure was developed for E. coli total RNA extraction with specific results on the RNA microchip using both chemiluminescence and AuNPs silver staining. This extraction avoids the use of commercial RNA purification kits thus reducing the cost. Furthermore, visual detection on the RNA microchip is simple, does not require electricity or special equipment, and therefore is a good candidate for field diagnostics with minimum resources.

X-ray fluorescence is a well-understood phenomenon in which irradiation of certain materials, such as gold, with x-rays causes the emission of secondary x-rays with characteristic energies. By performing computed tomography using these fluorescence x-rays, the material of interest can be imaged inside an object. Our research group has already demonstrated that x-ray fluorescence computed tomography (XFCT) imaging using a typical 110 kVp microfocus x-ray tube is feasible for a small animal-sized object containing a distribution of a solution of low concentration gold nanoparticles. The primary goal of this thesis work was to study the effect of source x-ray energy spectra on gold fluorescence detection using the XFCT system. A computational approach using the Monte Carlo method was used. First, a computational model was created using the Monte Carlo N-Particle (MCNP) transport code based on the experimental setup of the pre-existing XFCT system. Simulations were run to verify the validity of the MCNP model as an accurate representation of the actual system by means of comparison with experimentally-obtained data. Finally, the model was used for further purely computational work. In the MCNP model, the source spectrum was changed to reflect several theoretical and experimentally obtained options. The effect of these changes on gold fluorescence production was documented and quantified using the signal-to-background ratio and other qualitative measures. The results from this work provided clues on how to improve the detection of fluorescence photons from gold nanoparticle-loaded objects using the XFCT system. This will benefit future research on the development of the XFCT system in the context of making it more feasible for gold nanoparticle-based preclinical molecular imaging applications.

In this study, conjugated monomers containing fluorene units / 2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene (TFT) and 5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine (EFE) were synthesized on the basis of donor-acceptor-donor approach and their electrochemical polymerization were achieved via potential cycling. Optical and electrochemical properties of their corresponding polymers, poly(2-(9,9-dihexyl-2-(thiophen-2-yl)-9H-fluoren-7-yl)thiophene) PTFT, and poly(5-(9,9-dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9H-fluoren-7-yl)-2,3dihydrothieno[3,4b ][1,4] dioxine) PEFE, were investigated and it was found that polymer films exhibited quasi-reversible redox behavior (Epox= 1.10 V for PTFT, Epox = 0.70 V and 1.00 V for PEFE) accompanied with a reversible electrochromic behavior, yellow to dark green for PTFT, yellow to parliament blue for PEFE. Their band gap values (Eg) were found to be 2.36 eV and 2.26 eV for PTFT and PEFE, respectively. Furthermore, gold nanoparticles (AuNP) were prepared and their interaction with polymer films, PTFT and PEFE, were investigated using spectroscopic techniques. The fluorescence properties of the polymers and their composites, prepared by the interaction of AuNP with polymers, were also investigated.

Gold nanoparticles strongly absorb and scatter visible and near infrared light because of the strongly enhanced electric fields at the surface. This provides the potential of designing novel optically active reagents for simultaneous molecular imaging and photothermal cancer therapy. In this thesis, gold nanospheres and nanorods conjugated with anti-epidermal growth factor receptor (anti-EGFR) antibodies that specifically target EGFR on the cell surface are shown to be used for dual diagnostics and therapy. Using micro-absorption spectroscopy and light scattering imaging, cancerous (HOC 313 and HSC 3) and noncancerous cells (HaCat) can be differentiated due to the overexpression of EGFR on the surface of cancer cells. By irradiating the cells with a CW laser, selective photothermal cancer therapy is realized in visible region by using gold nanospheres and in near infrared region by using gold nanorods. The use of nanorods allow for in vivo therapy due to the fact that their absorption is in the near infrared region at which the laser light meets less interference from the tissue absorption. In addition, the catalytic effect of gold nanoparticles on the oxidization of NADH to NAD+ is investigated. The addition of gold nanoparticles is found to quench the NADH fluorescence intensities but has no effect on the fluorescence lifetime. This suggests that the fluorescence quenching is not due to coupling with the excited state, but due to changing the ground state of NADH. The intensity of the 340 nm absorption band of NADH is found to decrease while that of the 260 nm band of NAD+ is found to increase as the concentration of gold nanoparticles increase. This conversion reaction is further supported by nuclear magnetic resonance and mass spectroscopy. The linear relationship between the initial reaction rate of NADH and the concentration of gold nanoparticles strongly supports that NADH is surface catalyzed by the gold nanoparticles. The catalytic property of this important reaction might have important future applications in biological and medical fields.