>Magister Scientiae - MSc / Current water treatment technologies do not remove many endocrine disruptor compounds (EDCs) such as 17α-ethynylestradiol (EE2) in its entirety, and the amount of these pollutants that continues to enter the aquatic environment through wastewater effluents is still capable of causing harmful health effects. Therefore the development of simpler and more sensitive biosensor system for detection of EE2 must be developed which have high responsiveness, low cost and easy handling. Therefore the aim of this study was to work towards the development of rapid test system of polyaniline-laccase on gold enzyme nanobiosensor (PANI-PSSA/Lac/Glu) for water estrogens. Preliminary studies were first done on the materials used in this study: estrogens, laccase, gold nanoparticles (AuNPs), and electropolymerized PANI-PSSA. Laccase was shown to be active towards EE2 and the enzyme could be stored for over three months. EE2 solution also could be used for over three months. Buffer used in this study was found to be suitable. Phosphoric acid (H3PO4) was a suitable electrolyte than hydrochloric acid (HCl) to be used for the electropolymerization of aniline and was used because it has same ions as the McIlvaine buffer (McIlB) which the post-deposition CVs indicated the formation of electrochemically very stable film. AuNPs were successfully synthesized and its size was identified to be less than 22 nm. McIlB used for testing electrochemical properties of AuNP. CVs of GC/PANI-PSSA and GC/PANIPSSA/ Au showed no difference before and after exposure to aq. EE2 solution, an indication of being re-usable and could also serve as stable immobilising platform in laccase biosensor. When interrogating with electrochemical impedance spectroscopy (EIS), the charge transfer resistance (Rct) of both GC/PANI-PSSA and GC/PANI-PSSA/Lac/Glu showed an average increase by about 2.4% and 21% before and after exposure of EE2, respectively. This shows that the GC/PANI-PSSA/Lac/Glu was a functional EE2 biosensor and showing a positive step towards achieving a re-usable biosensor for EE2 as a model water estrogen. Future work Page | vi will focus on exploring different ways of improving the biosensor’s surface regeneration and its sensitivity to EE2.

The present work is devoted to the study of the nonlinear optical properties of smectic samples containing gold nanoparticles with a rod shape. By using the time-resolved Z-scan technique, we determine the nonlinear refractive and absorptive coefficients at the vicinity of the smectic-A-nematic phase transition. Our results reveal that such coefficients are sensitive to the sample temperature. In particular, we show that the nonlinear refractive index presents a singular behavior close to the transition temperature. Further, we show that a nonlinear optical response may take place at temperatures where the smectic order is well established. We provide a detailed discussion of the effects associated with the introduction gold nanoparticles on the mechanisms behind the optical nonlinearity in liquid-crystal samples. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho é dedicado ao estudo das propriedades ópticas não-lineares de amostras esméticas contendo nanopartículas de ouro com um formato de bastão. Usando a técnica de varredura Z resolvida no tempo, nós determinamos os coeficientes de refração e de absorção não-lineares, nas vizinhanças da transição de fase nemática-esmética-A. Os nossos resultados revelam que esses coeficientes são sensíveis a temperatura da amostra. Em particular, nós mostramos que o índice de refração não-linear apresenta um comportamento singular próximo á temperatura de transição. Além disso,nós mostramos que uma resposta óptica não-linear pode ocorrer em temperaturas onde a ordem esmética está bem estabelecida. Será realizada uma discussão detalhada dos efeitos associados com as nanopartículas de ouro. E uma introdução sobre os mecanismos por trás da não-linearidade óptica em amostras de cristais líquidos esméticos.

Orientadora: Profa. Dra. Iseli Lourenço Nantes / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2015. / A investigação sobre novas rotas de síntese de nanopartículas metálicas tem em um de seus pilares o uso de materiais biológicos como agentes redutores e estabilizadores, valendo-se da capacidade redutora de grupamentos químicos. Sabe-se que a biorredução dos íons metálicos e a estabilização das nanopartículas ocorre por uma combinação de etapas intermediárias no processo de síntese. Nesse sentido, este trabalho tem interesse no estudo mecanístico da ação da cadeia lateral de peptídeos que contém tiol como mediadores da síntese de nanopartículas de ouro (AuNPs) e na influência das condições reacionais no processo de formação das nanopartículas. Utilizamos como agentes redutores alguns peptídeos inspirados no motivo conservado da proteína tioredoxina, que apresenta cisteínas com tiol de baixo pKa devido à vizinhança com resíduos de aminoácidos básicos. Um estudo comparativo foi feito com duas proteínas envolvidas em processos de oxirredução que também contem cisteínas nucleofílicas. As amostras foram caracterizadas por espectroscopia de UV-vis, Raman e dielétrica, difratometria de raios-X, espalhamento dinâmico de luz e microscopia eletrônica de varredura e transmissão. Os resultados indicam que as sequências peptídicas nas quais o grupo tiol é ladeado por aminoácidos básicos tem uma melhor capacidade redutora na síntese das AuNPs em comparação com o mesmo tipo de sequência contendo aminoácidos ácidos. Além disso, esta sistemática revelou que a participação e o tipo de solvente (substituição isotópica) empregados na síntese, além do microambiente reacional e do tipo de especiação dos precursores influenciam drasticamente na capacidade redutora das cisteínas e consequentemente no processo de formação das nanopartículas. / Research on new routes focuses on the use of biological materials as a reducing agent and stabilizer, taking advantage of the reductive capacity of specific chemical groups. It is known that the bioreduction of metal ions and stabilization of the nanoparticles occurs by a combination of intermediate processes in the synthesis process. In this sense, this work is interested in the investigation of detailed mechanisms involving reducing capacity of the side chains of peptides and proteins for the synthesis of metal nanoparticles. In this context, we use as reducing agents of metalic ions some peptides inspired in proteins of high reductive capacity proteins, such as thioredoxin , which has cysteine thiol pKa low due to the proximity of basic amino acids. A comparative study was done with two proteins involved in redox process that also contains nucleophilic cysteine. The samples were characterized by UV-vis, Raman and dielectric spectroscopy, X-ray diffraction, dynamic light scattering and transmission electron microscopy. The results indicate that the peptide sequences in which the thiol group is flanked by basic amino acids has a better reducing capability in the synthesis of AuNPs compared with the same type of sequence containing amino acids. Moreover, this showed that systemic involvement and solvent (isotopic substitution), beyond the reaction microenvironment and type of speciation of precursors employed in the synthesis influence dramatically the reductive capacity of the cysteines and consequently the formation of nanoparticles process.

Orientadora: Profa. Dra. Iseli Lourenço Nantes / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016. / Neste trabalho estudamos as propriedades fotoquimicas e fotofisicas do azul de metileno imobilizado em uma resina cationica chelexR 100. O procedimento de incorporacao consiste em adicionar a resina cationica em solucao de azul de metileno promover a agitacao ate que a resina se torne azul e o meio aquoso transparente, indicando que todo o corante foi adsorvido pela resina. A incorporacao do azul de metileno na resina chelex mantem as moleculas do corante no estado agregado o que favorece o mecanismo fotoquimico tipo I quando o sistema e exposto a irradiacao com luz branca ou vermelha. No mecanismo tipo I as moleculas de azul de metileno passam ao estado triplete por mecanismo de cruzamento intersistema e oxidam seus pares dando origem ao corante cation radical (MB2+¿h) e o corante na forma semi reduzida (MB¿h). A forma semireduzida sofre dismutacao para a forma totalmente reduzida (MBH) que e branca e o seu par inicial (MB+). As formas leuco e semi reduzida sao redutoras e em meio aerado transferem eletrons para o oxigenio molecular que e convertido a ions superoxido, a geracao de grandes quantidades de ions superoxido no interior da resina favorece o processo de dismutacao espontaneo desse radical livre a peroxido de hidrogenio. Em nosso sistema o peroxido de hidrogenio foi identificado por amplex rede pela conversao de HPR a composto II. A geracao de peroxido de hidrogenio nesse sistema se mostrou dependente da concentracao de oxigenio no meio o que torna improvavel que o peroxido de hidrogenio seja resultado da oxidacao da agua pelo MB2+¿h (cation radical). Alem disso, os potenciais redox do par MB2+¿h/MB+ -230 mV nao e favoravel para oxidar agua H2O2 H+ /H2O + OH¿h +320 mV. A capacidade fotoredutora do sistema tambem se mostrou capaz de reduzir ions ouro e prata para a sintese das respectivas nanoparticulas metalicas. Foi caracterizado que esse sistema permite modular forma e tamanho das nanoparticulas com o uso de diferentes razoes de massa de resina/sal metalico. Em determinada razoes de resina sal metalico foi possivel produzir nanoparticulas anisotropicas capazes de aumentar o rendimento quantico de fluorescencia de diferentes fluoroforos e de exacerbar a acao fotodinamica de porfirinas utilizadas como fotossensibilizadores. Para esse ultimo caso o efeito fotodinamico das AuNPs mostrou-se sensivel ao efeito de campo magnetico externo. / We study the photophysical and photochemical properties of methylene blue immobilized on a cationic resin chelexR 100. The adsorption procedure is carried out by shaking a methylene blue solution with a mass of chelexR 100 up to the solution became colorless and resin blue. The incorporation of the methylene blue in the chelex resin stabilizes the dye molecules in the aggregate state which favors the photochemical type I mechanism when the system is exposed to irradiation with white or red light. In type I mechanism the methylene blue molecules are excited to triplet state by intersystem crossing mechanism. A molecules the methylene blue oxidize an adjacent pair to the corresponding the cation radical (MB2+¿h) and is it is converted to the semi reduced form of the dye (MB¿h). The MB¿h molecules undergoes dismutation to the leuco form (MBH) and the ground state form (MB+). The leuco and the semireduced forms are reducing agents that can transfer electrons to molecular oxygen molecules that is in turn converted to superoxide ions. The generation of large quantities of superoxide ions within the resin favors of spontaneous dismutation of hydrogen peroxide and molecular oxygen. In this condition, the generation of hydrogen peroxide was identified by indirectly by AmplexRred kit and directly the conversion of the HPR resting form (Fe3+=O) to the high valence form, compound II (Fe4+=O) The generation of hydrogen peroxide is dependent of molecular oxygen concentration making it unlikely hydrogen peroxide should be significantly produced by the oxidation of water by MB2+¿h (radical cation). Additionally, the redox potentials of the pair MB2+¿h/MB+ -230 mV is not favorable to oxidize water H2O2 H+ /H2O + OH¿h +320 mV. The photoreducing capacity of the system was also able to reduce ions gold and silver for the synthesis of the respective metal nanoparticles. It was characterized in that the system allows modulation of the shape and size of nanoparticles using different of resin dye mass/metal salt ratios. In determined resin dye mass/metal salt ratios it was possible to produce anisotropic nanoparticles bearing the capacity of increasing the fluorescence quantum yields of different fluorophores and exacerbating the photodynamic action of porphyrins used as photosensitizers. For this latter case the photodynamic effect of AuNp's was sensitive to the external magnetic field effect.

Submitted by THIAGO DE MORAIS MARIANO null (thiaguitobatera@gmail.com) on 2016-03-24T18:46:42Z No. of bitstreams: 1 DISSERTAÇÃO-VERSÃO FINAL.pdf: 1116395 bytes, checksum: 647c9edcd2f39b64fa625d689d79f620 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-24T19:59:05Z (GMT) No. of bitstreams: 1 mariano_tm_me_araiq.pdf: 1116395 bytes, checksum: 647c9edcd2f39b64fa625d689d79f620 (MD5) / Made available in DSpace on 2016-03-24T19:59:05Z (GMT). No. of bitstreams: 1 mariano_tm_me_araiq.pdf: 1116395 bytes, checksum: 647c9edcd2f39b64fa625d689d79f620 (MD5) Previous issue date: 2016-03-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O óleo fúsel é o co-produto da destilação do etanol e é formado pela mistura de álcoois superiores (álcoois com mais de 3 carbonos), ésteres, aldeídos, entre outros. O volume de óleo fúsel produzido em média é 2,5 L de óleo fúsel por 1000 L de etanol, sendo utilizado como combustível nas caldeiras das usinas, bem como precursores de ésteres utilizados em indústrias de cosméticos e em fabricação de plásticos. O presente trabalho teve como objetivo desenvolver um sensor eletroquimico (GCE/RGO/AuNP/MIP) baseado em polímeros molecularmente impressos (MIP), utilizando o pirrol (Py) como monômero, contendo nanopartículas de ouro (AuNP) e óxido de grafeno reduzido (RGO) para a determinação do álcool isoamílico, um dos componentes do óleo fusel. Foram realizados estudos eletroquímicos, como estudo de velocidade de varredura, para determinar reversibilidade do sistema e diagnosticar o controle do processo eletródico. Após os estudos eletroquímicos, foram realizadas caracterização morfológica por Microscopia Eletrônica de Varredura com Canhão de Emissão de Eletrons com efeito de campo (MEV-FEG) e caracterização eletroquimica por Espectroscopia de Impedancia Eletroquímica (EIS). Após a caracterização, foi avaliada a performance analítica do sensor GCE/RGO/AuNP/MIP, utilizando um intervalo de concentração de 1,0×10-7 até 1,0×10-4 mol L-1, encontrando um limite de detecção de 8,2×10-8 mol L-1. Foi determinada a concentração de álcool isoamílico em amostra de óleo fúsel pelo método de adição de padrão e o valor encontrado foi de 1,6×10-4 mol L-1. O método foi validado através de ensaio de recuperação, mostrando que o sensor desenvolvido é promissor para a utilização em determinação de álcool isoamílico em óleo fúsel. / The fusel oil is co-product of the distillation of ethanol and is formed by the mixture of higher alcohols (alcohols having more than 3 carbons) esters, aldehydes, etc. The volume of fusel oil produced on average is 2.5 L fusel oil by 1000 L of ethanol, used as fuel in the boilers of the plants, as well as esters of precursors used in the cosmetics and plastics manufacturing. This study aimed to develop an electrochemical sensor (GCE/RGO/AuNP/MIP) based on molecularly imprinted polymers (MIP), using pyrrole (Py) as the monomer, containing gold nanoparticles (AUNP) and reduced graphene oxide (RGO) for determining the isoamyl alcohol, one of fusel oil components. They were conducted electrochemical studies, such as study of scanning speed, to determine system reversibility and diagnose the control of the electrode process. After the electrochemical studies were conducted morphological caractrização by Scanning Electron Microscopy with Electrons Emission Cannon with field effect (SEM-FEG) and electrochemical characterization by spectroscopy Electrochemical Impedance (EIS). After the characterization, the analytical performance of the GCE/RGO/AuNP/MIP sensor was evaluated using a concentration range of 1.0×10-7 to 1.0×10-4 mol L-1, encountering a detection limit 8.2×10-8 mol L-1. Was determined the concentration of isoamyl alcohol in a sample of fusel oil by standard addition method and the value found was 1.6×10-4 mol L-1. The method was validated by recovery test, showing that the sensor is designed promising for use in determining isoamyl alcohol fusel oil.

[pt] Terapia fotodinâmica (PDT) é um tratamento médico baseado na excitação ótica de um fármaco chamado fotossensibilizador. Quando os fotossensibilizadores são expostos a luz em comprimento de onda específico, eles podem produzir espécies reativas, como oxigênio singlete, capazes de matar células próximas ao local irradiado, tais como células cancerígenas. Nanomateriais híbridos formados de nanopartículas metálicas e componentes poliméricos são investigados por seu potencial em aplicações biomédicas devido à sua habilidade de simultaneamente permitir detecção para diagnóstico e terapia (teranóstico). Graças à multifuncionalidade assegurada pelas propriedades plasmônicas das nanopartículas metálicas e atividade terapêutica dos nanotransportadores de drogas, o encapsulamento de nanopartículas de ouro (AuNPs) envolvidas por polímeros biocompatíveis se tornaram um caminho fascinante para testar a terapia fotodinâmica, com a grande vantagem de prevenir efeitos de agregação em condições biológicas. Essa dissertação tem enfoque na estabilização e atividade fotodinâmica de um nanomaterial híbrido constituído de AuNPs sintetizadas em água por ablação a laser pulsado. O copolímero Pluronic F-127 foi utilizado como componente polimérico para estabilizar as nanopartículas. A produção de oxigênio singlete pelos fotossensibilizadores clorina e6 e azul de metileno foi estudada em ausência e em presença das AuNPs, utilizando 1,3-difenilisobenzofurano (DPBF) como sonda molecular. A reação específica de DPBF com oxigênio singlete modifica seu espectro de absorção na faixa visível, permitindo obter taxas de produção da espécie citotóxica. As amostras foram irradiadas com um LED emitindo em 650 nm e os espectros de absorção foram monitorados como função do tempo durante a irradiação. Foram obtidas taxas de fotodegradação dos fotossensibilizadores e rendimento quântico de produção de oxigênio singlete nos diferentes casos. / [en] Photodynamic therapy (PDT) is a medical treatment based on the optical excitation of a drug, called photosensitizer. When photosensitizers are exposed to light of specific wavelength, they can produce reactive species, such as singlet oxygen, capable of killing cells close to the irradiated site, such as cancer cells. Hybrid nanomaterials, comprising metallic nanoparticles and polymeric components, are investigated for their potential in biomedical applications due to their ability to simultaneously allow detection for diagnosis and therapy (theranostic). Thanks to the multi functionality assured by the nanoparticle plasmonic properties and therapeutic activity of the drug nanotransporters, the encapsulation of gold nanoparticles (AuNPs) wrapped by biocompatible polymers has become an attractive way to test photodynamic therapy, with the great advantage of preventing effects of aggregation under biological conditions. This dissertation focuses on the stabilization and photodynamic activity of a hybrid nanomaterial composed of AuNPs synthesized in water by laser ablation. The copolymer Pluronic F-127 was used as a polymeric component to stabilize the nanoparticles. The production of singlet oxygen by the photosensitizers chlorin e6 and methylene blue was studied in the absence and presence of AuNPs using 1,3 diphenylisobenzofuran (DPBF) as a molecular probe. The specific reaction of DPBF with singlet oxygen modifies its absorption spectrum in the visible range and allows to obtain rates of cytotoxic species production. Samples were irradiated with a LED emitting 650 nm radiation and the absorption spectra were monitored as a function of time during irradiation. Rates of photosensitizers degradation and quantum yields of singlet oxygen production were obtained in different cases.

Les aptamères correspondent à de courtes séquences d'oligonucléotides possédant une forte affinité et spécificité envers un ligand (petites molécules organiques, peptides, acides nucléiques, protéines, cellules). Du fait de leurs remarquables propriétés, ils sont utilisés comme alternative aux anticorps dans les dispositifs de type biocapteur/biopuce, notamment pour la détection de petites molécules (PM < 2000 Da). L'imagerie de résonance des plasmons de surface (SPRi) est une technique de détection optique qui a gagné une attention croissante ces dernières années. Elle est basée sur un principe de variation de l'indice de réfraction d'une surface sélective lors de l'interaction sonde/cible. Sa sensibilité est néanmoins limitée aux molécules de poids moléculaire supérieur à 2000 Da. Dans le cadre de ces travaux, nous avons développé une biopuce à aptamères pour à la détection d'une petite molécule, l'adénosine, au moyen de la technique de résonance des plasmons de surface (SPR). Pour cela, deux différentes stratégies ont été développées. La première combine l'utilisation de nanoparticules d'or (AuNPs) pour l'amplification du signal SPRi avec l'ingénierie des séquences d'aptamères. La seconde stratégie est basée sur l'exploitation de la stabilité thermodynamique apportée par l'interaction de la cible (adénosine) avec les séquences d'aptamères. Le dispositif SPR est alors couplé à un système de régulation de température, permettant ainsi d'assurer la dissociation des complexes et d'établir des profils de dénaturation caractéristiques. Nos résultats initient ainsi une nouvelle approche dans la détection de petites molécules par SPRi et ouvrent de nouvelles perspectives de développement des biocapteurs à aptamères. / Aptamers are single-stranded DNA (ssDNA) or RNA molecules capable of binding to target molecules, including proteins, metal ions and drugs. Because of their specific binding abilities and many advantages over antibodies (higher stability, lower cost, easy chemical modification…), they provide a great opportunity to produce sensing surfaces for effective and selective detection of small molecules. Surface Plasmon Resonance imaging (SPRi) has become one of the most widely used label-free method for the study of biorecognition events on sensor surfaces. This technique provides a rapid approach, however, limited by low refractive index changes occurring when small molecules (<2000 Da) are captured on the sensor. Whereas significant reflectivity variation is observed upon the interaction of large molecules like proteins with the sensing interface, for small molecules targets such adenosine, the reflectivity variation is often too small to be detected by SPRi. Thereby, only few studies have been reported so far on SPRi-based biosensor for small molecules detection using aptamers. In this work, we developed two bioassay strategies for the detection of a model small molecule, adenosine, using Surface Plasmon Resonance imaging. The first one combines the SPRi signal enhancement effect induced by gold nanoparticles (AuNPs) with the advantage of using engineered DNA aptamers. The experimental results have demonstrated that the presence of gold nanoparticles and adenosine, which works as a molecular linker between engineered aptamer fragments, can significantly increase the SPRi response. The second strategy is based on the thermodynamics of binding between adenosine and its aptamer. To that end, SPRi technique was coupled with rigorous temperature control and aptamer duplex stability was monitored (affected by target binding) by quantification of melting transitions. Our results initiate a new approach for small molecule detection using SPRi with the aim to validate future prospects for integration in parallelized platform.

A conjugação entre as nanopartículas (NPs) de diferentes materiais, por meio de ligações químicas entre as moléculas orgânicas presentes na superfície das NPs, pode produzir nanoestruturas core-satéllites multifuncionais com potenciais aplicações no campo biomédico. O objetivo deste estudo foi obter nanoestruturas core-satéllites ou conjugadas, com NPs de Fe3O4 e Au, por meio de reações químicas específicas entre moléculas orgânicas presentes nas superfícies das NPs. As NPs de Fe3O4 foram sintetizadas utilizando rotas de decomposição térmica, resultando em NPs com tamanho e forma controlados. O ácido oleico presente na superfície das NPs de Fe3O4, como sintetizadas, foi substituído pelos ligantes, 3-aminopropiltrimetoxisilano (APTMS) ou 3-mercaptopropiltrimetoxisilano (MPTMS). NPs de Au esféricas de 5,7 nm foram sintetizadas pelo método de Brust modificado, e a sua superfície foi modificada usando o ácido mercaptoundecanoico (AMU). A conjugação entre as NPs de Au e Fe3O4 foi realizada por duas vias diferentes. Primeiramente, usando os grupos amina-terminais livres das NPs Fe3O4@APTMS e os grupos carboxilatos das NPs Au@MUA e, depois, com a utilização dos grupos tióis das NPs Fe3O4@MPTMS e as NPs de Au, antes da modificação de superfície. Após a conjugação o comportamento superparamagnético das NPs de Fe3O4 foi preservado, mas a banda plasmon das NPs de Au apresentou um alargamento e um red-shift. Como esperado, a incorporação de materiais não magnéticos nas NPs magnéticas, resultou em uma pequena diminuição na magnetização de saturação em comparação com as NPs como sintetizadas. O alargamento observado na banda plasmon pode ser explicado pela agregação das NPs de Au, no entanto as influências magnéticas não podem ser discutidas. / The conjugation between nanoparticles (NPs) of different materials by using chemical bonds between organic molecules present on NPs surfaces can produce multifunctional core-satellites nanostructures and to provide potential applications in biomedical field. The aim of this study was to obtain core-satellites or conjugated nanostructures with Fe3O4 and Au NPs by specific reactions between organic molecules bonded on NPs surface. The Fe3O4 NPs were synthesized by using thermal decomposition routes leading to size-and shape-controlled NPs. As-synthesized Fe3O4 surface nanoparticles present oleic acid on surface, which was replaced by either (3-aminopropyl)trimethoxysilane (APTMS) or (3-mercaptopropyl)trimethoxylane (MPTMS) ligands. Spherical 5.7 nm Au NPs were synthesized by modified Brust method, and its surface was properly modified by using 11-mercaptoundecanoic acid (MUA). The conjugation between Au and Fe3O4 NPs was performed by two different routes. Firstly, using the free amine-terminal groups from Fe3O4@APTMS and the carboxylates groups from Au@MUA and, secondly, using thiols groups from Fe3O4@MPTMS and as-synthesized naked Au NPs. After conjugation, the superparamagnetic behavior of the Fe3O4 NPs was preserved, but the plasmon band has red-shifted and broadened. As expected the incorporation of non-magnetic materials onto the magnetic NPs, the saturation magnetization presents small decrease compared to as-synthesized NPs. Observed broadening in the plasmonic band can be explained by Au NPs aggregation, but the magnetic influences can not be discussed.

Submitted by Aelson Maciera (aelsoncm@terra.com.br) on 2017-05-19T19:35:37Z No. of bitstreams: 1 DissARLM.pdf: 2999284 bytes, checksum: cb32a2cd7ed71b40fd67f2b5604ce434 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-05-23T19:48:47Z (GMT) No. of bitstreams: 1 DissARLM.pdf: 2999284 bytes, checksum: cb32a2cd7ed71b40fd67f2b5604ce434 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-05-23T19:48:57Z (GMT) No. of bitstreams: 1 DissARLM.pdf: 2999284 bytes, checksum: cb32a2cd7ed71b40fd67f2b5604ce434 (MD5) / Made available in DSpace on 2017-05-23T19:58:53Z (GMT). No. of bitstreams: 1 DissARLM.pdf: 2999284 bytes, checksum: cb32a2cd7ed71b40fd67f2b5604ce434 (MD5) Previous issue date: 2016-03-29 / Outra / The CO preferential oxidation reaction (PROX) is used in the purification of hydrogen streams for various applications. Since the discovery of improved catalytic properties of gold particles, at nanometer range, in the CO oxidation reaction at low temperature, Au catalysts have been the subject of numerous investigations of CO oxidation and PROX. Concerning the heterogeneous catalysis, the catalyst activity is determined by several factors: the nanoparticles size, the metal loading and dispersion, the nature and porosity of the support, and the metal/support interaction. To understand the dependence of the support and the influence of the synthesizing method on the material properties and catalytic performances, gold nanoparticles supported on three different oxides (CeO2, MnO2 and TiO2) were successfully synthesized by the deposition precipitation (DP) method, using urea, and modified polyol (MP) method, using PVP as surfactant and sodium borohydride as reducing agent. Additionally, Au/SiO2 was obtained by the DP method. Characterizations were performed to assess the crystallinity, the metal mass percentage, the reduction temperatures and the respective reducing gas consumptions of pure oxides and supported materials synthesized by both methods. In addition, microscopic pictures were obtained to evaluate the materials morphology and the gold nanoparticles diameter. The Au catalysts synthesized by the DP method presented smaller particle sizes as compared to catalysts obtained by the MP method. Catalytic evaluation of the CO oxidation and PROX reactions were performed using temperature ramp starting at room temperature up to 200 °C. As a comparative parameter, the ratio between the catalyst mass and the gas feed flow remained constant at 1 mg / 1 mL / min for all reactions. The results showed that Au supported on TiO2 prepared by the DP method presented complete CO conversion at room temperature, but with the simultaneous supply of H2, this catalyst tends to oxidize H2, decreasing the CO conversion activity. On the other hand, the Au/CeO2 catalyst prepared by the DP method presented activity up to about 200 °C for PROX and better selectivity towards the CO2 formation. / A reação de oxidação preferencial de CO (PROX) é utilizada na purificação de correntes de hidrogênio para diversas aplicações. Desde a descoberta da melhoria das propriedades catalíticas de partículas de ouro, em escala nanométrica, na reação de oxidação de CO a baixa temperatura, catalisadores de Au têm sido objeto de numerosas investigações em oxidação de CO e de PROX. No que diz respeito a catálise heterogênea, a atividade do catalisador é determinada por vários fatores: o tamanho das nanopartículas, a carga e dispersão metálica, a natureza e a porosidade do suporte, e a interação metal/suporte. Para entender a dependência do suporte e a influência do método de síntese nas propriedades dos materiais e nos desempenhos catalíticos, foram sintetizados com sucesso nanopartículas de ouro suportadas em 3 diferentes óxidos (CeO2, MnO2 e TiO2) pelos métodos de deposição precipitação (DP) com ureia e poliol modificado (PM) utilizando PVP como agente surfactante e borohidreto de sódio como agente redutor. Adionalmente, Au/SiO2 foi obtido pelo método DP. Foram realizadas caracterizações para avaliar a cristalinidade, porcentual mássico de metal, temperaturas de redução e respectivos consumos de gás redutor dos óxidos puros e dos materiais suportados sintetizados por ambos os métodos. Além disso, foram obtidas imagens de microscopia para avaliar a morfologia dos materiais e o diâmetro das nanopartículas de ouro. Os catalisadores de Au sintetizados pelo método DP apresentaram menores tamanhos de partícula, comparados aos catalisadores obtidos pelo método PM. A avaliação catalítica nas reações de oxidação de CO e PROX foram realizadas através de rampa de temperatura, começando pela temperatura ambiente e aquecendo até cerca de 200 ºC. Como parâmetro comparativo, a razão entre a massa de catalisador e a vazão dos gases alimentados manteve-se constante em 1 mg / 1 mL/min em todas as reações. Os resultados mostraram que o catalisador de Au suportado em TiO2 obtido pelo método DP apresentou conversão total de CO em temperatura ambiente, porém com a alimentação simultânea de H2, esse catalisador tende a oxidar o H2, diminuindo a atividade à conversão de CO. Por outro lado, o catalisador de Au/CeO2 preparado pelo método DP apresentou atividade até cerca de 200 ºC na PROX e melhor seletividade à formação de CO2. / PRH-ANP/MCT N° 44

Dans ce travail, les nanoparticles d’or supportées ont été étudiées en raison de leur fort potentiel dans les domaines de la catalyse. Des sphères de silice obtenues par la voie Stöber ont été synthétisées et utilisées comme supports des nanoparticules d’or. Les précurseurs d’or sont des solutions colloïdales possédant des nanoparticules d’or homogènes et de petite taille (environ 3 nm). Les matériaux préparés avec ou sans addition d’un nouvel élément ont été utilisés dans les réactions de l’oxydation du CO et une réaction inédite pour l’or: l’oxydation sélective de l’H2S.Les résultats indiquent que l’utilisation de colloïdes d’or comme précurseurs permet de contrôler la taille et la dispersion avant le dépôt et ceci est facilité par les propriétés optiques des nanoparticules de ce métal. Pour les propriétés catalytiques, outre la dispersion, on confirme très clairement par cette méthode de synthèse que l’interaction Au/Support joue un rôle majeur. L’addition d’un second métal augmente significativement l’activité des matériaux à base d’or. Les particules d’or et de Cu se rassemblent sous les conditions réactionnelles testées. Dans le cas de l’oxydation du CO, de petites quantités d’espèce d’or partiellement oxydée sont générées et forment une glue avec les espèces Cu2+ également formées au cours de la réaction et ceci permet de fixer les nanoparticules sur le support. Dans le cas de l’oxydation sélective de H2S, il a été montré que le système est résistant au soufre, y compris sur une longue durée de test. Les silices Stöber se sont avérées comme des supports catalytiques très intéressants car non poreux et formés de particules de petites tailles, ils sont aptes à exposer les phases actives de l’or aux réactifs, diminuant la pression de surface et facilitant le transfert thermique. Il a également été prouvé que ce matériau peut être mis en compétition avec les matériaux mésoporeux, ces derniers étant jugés indispensables pour obtenir de hautes activités en catalyse hétérogènes jusque là. / Supported gold nanoparticles have been focused on due to their high efficiency in the catalysis field. In this work, Stöber silica consisted by globules were synthesized and used as support for gold nanoparticles. The gold colloids with homogeneous and small nanoparticles (about 3 nm) were applied as gold precursor. The prepared materials with further metal addition were used to active the CO oxidation and another very special reaction- selective oxidation of H2S.The results suggested that by using the gold colloid as precursor the sizes of nanoparticles could be controlled before loading onto silica under the help of its optical properties. The results for catalytic reactions indicated that the interaction between Au-support is another essential factor impacting the activity beyond the size effect. The additions of metal largely enhance the activity of gold materials. The gold and copper (oxide) particles go through reassembling during the reactions. In the CO oxidation, small amounts of partially oxidized gold species were generated and “glued” strongly by the new formed Cu2+ species to the support. While in the selective H2S oxidation, it was found that the material is sulfur-resistant during long time reaction. The Stöber silica is proved to be a very promising support, which is non-porous but beneficial to expose active sites of gold nanoparticles to the reactants, lower the pressure drop, and facilitate the heat transformation. It was proved even can be matched with the well-know mesoporous materials that is claimed to be indispensable for the high activity.