No presente trabalho foi avaliada a capacidade de síntese de nanopartículas de cobre pelo fungo filamentoso Hypocrea lixii. Para tanto, o cultivo do fungo foi otimizado em função da concentração celular e do aspecto das hifas. Verificou-se que o cultivo realizado com inóculo de suspensão de esporos congelados em meio contendo extrato de malte forneceu concentração celular de 10g/L consistentemente, além de um aspecto sem aglomerados de células. A capacidade de biossorção de íons cobre (II) da biomassa não viável do fungo Hypocrea lixii foi avaliada, utilizando-se isotermas de biossorção. Verificou-se que o valor máximo de remoção calculado através do modelo de Langmuir é de 17,4mg/g, que foi considerado condizente com o valor reportado na literatura para o mesmo fungo. Para a síntese de partículas, inicialmente foram utilizadas biomassa viável e não viável do fungo. Após análise de microscopia eletrônica de transmissão (MET) constatou-se a formação de nanopartículas de diâmetro médio de 15nm no interior e na parede das células para a biomassa não viável. Para a biomassa viável verificou-se a formação de partículas apenas no exterior das células, com diâmetro médio de 30nm. Foi investigado o uso de extratos de suspensão de biomassa viável e não viável, obtidos através do contato das biomassas com água deionizada por 24 horas. Análises de microscopia eletrônica para esses extratos indicaram a formação de partículas de diâmetro médio de 12nm, para o extrato de biomassa viável, e de 10nm para o extrato de biomassa não viável. Um método de obtenção de extrato através de centrifugação de células não viáveis também foi investigado para a síntese de nanopartículas. Análises de microscopia eletrônica de transmissão confirmaram a formação de nanopartículas de diâmetro médio igual a 13nm. Foi realizada análise de EDS (energy dispersive X-ray spectroscopy) nas partículas obtidas em amostras de extrato proveniente de centrifugação de células não viáveis e verificou-se que são compostas apenas de cobre, confirmando a capacidade de síntese de nanopartículas metálicas. Outras técnicas de caracterização como difração de raios-X (DRX), espectroscopia de infravermelho (FT-IR) e espectrofotometria (UV-Vis) foram realizadas, porém não forneceram resultados conclusivos. Como forma de verificar os compostos que poderiam estar envolvidos na síntese das partículas através dos diferentes extratos, foram realizadas análises de espectrometria de massas (MALDI-TOF) e cromatografia gasosa. Através dessas análises foi possível verificar que os compostos que interagem com os íons cobre (II) são aminoácidos, ácidos graxos e açúcares. Apenas no extrato de centrifugação de células não viáveis foi possível verificar a presença de compostos com peso molecular na faixa entre 4kDa e 20kDa, compatível com proteínas. Uma vez confirmada a capacidade de síntese através de diferentes métodos, foi realizado um delineamento de experimentos central rotacional completo como forma de investigar a influência dos parâmetros pH e temperatura no diâmetro das partículas formadas com o extrato de centrifugação de células não viáveis. O diâmetro das partículas sintetizadas em cada ensaio foi medido através de análise de espalhamento de luz dinâmico (DLS). Através dos resultados, um modelo de segundo grau foi calculado utilizando-se o software Minitab® e verificou-se que tanto o pH quanto a temperatura não possuem contribuição significativa no tamanho das partículas sintetizadas. Além disso, observou-se que os diâmetros obtidos para os ensaios foram consideravelmente maiores que o obtido através das análises de microscopia eletrônica de transmissão (MET). Considerou-se que essa observação é resultado da presença de ligantes que atuam como estabilizadores das partículas e que contribuem para o aumento virtual do diâmetro medido. Esses ligantes podem ser compostos presentes no extrato e que não aparecem nas análises de microscopia por falta de contraste. Além disso, a análise de DLS é uma medida indireta de diâmetro e são necessárias outras análises para confirmar os resultados obtidos. Através dos resultados obtidos no presente trabalho, houve confirmação da capacidade de síntese de nanopartículas de cobre do fungo Hypocrea lixii e apresentação de metodologias promissoras que podem, após mais estudos, tornar-se um processo industrial. / In this work, the synthesis of copper nanoparticles using fungus Hypocrea lixii was evaluated. Therefore, the culture of the fungus was optimized in terms of cell concentration and hyphae qualitative aspect. It was found that cultures inoculated through frozen spore suspensions and using nutrient rich medium containing malt extract reached cell concentrations of 10g/L consistently, in addition to an aggregates-free hyphae aspect. The biossorption of copper (II) ions using non-viable biomass of Hypocrea lixii was measured, and sorption isotherms were constructed. It was found that the maximum removal calculated using the Langmuir model was 17,4mg/g, which was considered consistent with the value previously reported for this fungus. For the nanoparticle synthesis, the viable and non-viable biomasses of the fungus were initially used. Transmission electron microscopy (TEM) analysis demonstrated the formation of nanoparticles of 15nm of mean diameter inside the cells and in the cell wall for the non-viable biomass. For the viable biomass the particles obtained had 30nm of mean diameter and were located exclusively outside the cells. The use of viable and non-viable biomass suspension extracts was also investigated. The extracts were obtained after contact with double deionized water for 24 hours. Transmission electron microscopy (TEM) analysis showed the formation of particles with mean diameter of 12nm, for the viable biomass extract, and 10nm for the non-viable biomass extract. A method of obtaining cell extracts through centrifugation was also evaluated for the synthesis of copper nanoparticles. Transmission electron microscopy (TEM) analysis confirmed the formation of nanoparticles with mean diameter of 13nm. Energy dispersive X-ray spectroscopy (EDS) was performed on the particles found in samples of the centrifuged cells extract and they were found to be composed of copper only, endorsing the ability of synthesis for this extract. Other characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and spectrophotometry (UV-Vis) were performed but the results were inconclusive. In order to define which compounds present in the cell extracts could be involved in the synthesis reaction, mass spectrometry (MALDI-TOF) and gas chromatography analyses were performed for the different extracts produced. Through the results of those analyses it was seen that the compounds that interact with the copper (II) ions are amino acids and sugars. Only for the centrifuged cells extract it was possible to confirm the presence of compounds with molecular weights between 4kDa and 20kDa, compatible with proteins. Having confirmed the ability of the fungus of synthesizing copper nanoparticles through different methods, a central rotational composite design of experiments was established as a way of assessing the influence of the pH and temperature on the diameter of the particles formed using the centrifuged cells extract. The diameter of the particles was measured using dynamic light scattering (DLS). Through the results, a second order model was calculated using the software Minitab® and it was found that neither the pH nor the temperature had significant contributions to the size of the particles. Moreover, the diameter found for the experiments were considerably larger than the observed through transmission electron microscopy. It was considered that this observation was a result of the presence of ligands that act as stabilizers for the particles and that contribute to a virtual increase of the diameter measured. These ligands are compounds present in the extract and that are not shown in electron microscopy due to the lack of contrast. Furthermore, the DLS analysis is an indirect measurement of the diameter and other analyses are needed to confirm the results obtained. Through the results found in this work, there was a confirmation of the ability of the fungus Hypocrea lixii to synthesize copper nanoparticles. Promising methodologies were proposed that might, after further studies, become an industrial process.

No presente trabalho foi avaliada a capacidade de síntese de nanopartículas de cobre pelo fungo filamentoso Hypocrea lixii. Para tanto, o cultivo do fungo foi otimizado em função da concentração celular e do aspecto das hifas. Verificou-se que o cultivo realizado com inóculo de suspensão de esporos congelados em meio contendo extrato de malte forneceu concentração celular de 10g/L consistentemente, além de um aspecto sem aglomerados de células. A capacidade de biossorção de íons cobre (II) da biomassa não viável do fungo Hypocrea lixii foi avaliada, utilizando-se isotermas de biossorção. Verificou-se que o valor máximo de remoção calculado através do modelo de Langmuir é de 17,4mg/g, que foi considerado condizente com o valor reportado na literatura para o mesmo fungo. Para a síntese de partículas, inicialmente foram utilizadas biomassa viável e não viável do fungo. Após análise de microscopia eletrônica de transmissão (MET) constatou-se a formação de nanopartículas de diâmetro médio de 15nm no interior e na parede das células para a biomassa não viável. Para a biomassa viável verificou-se a formação de partículas apenas no exterior das células, com diâmetro médio de 30nm. Foi investigado o uso de extratos de suspensão de biomassa viável e não viável, obtidos através do contato das biomassas com água deionizada por 24 horas. Análises de microscopia eletrônica para esses extratos indicaram a formação de partículas de diâmetro médio de 12nm, para o extrato de biomassa viável, e de 10nm para o extrato de biomassa não viável. Um método de obtenção de extrato através de centrifugação de células não viáveis também foi investigado para a síntese de nanopartículas. Análises de microscopia eletrônica de transmissão confirmaram a formação de nanopartículas de diâmetro médio igual a 13nm. Foi realizada análise de EDS (energy dispersive X-ray spectroscopy) nas partículas obtidas em amostras de extrato proveniente de centrifugação de células não viáveis e verificou-se que são compostas apenas de cobre, confirmando a capacidade de síntese de nanopartículas metálicas. Outras técnicas de caracterização como difração de raios-X (DRX), espectroscopia de infravermelho (FT-IR) e espectrofotometria (UV-Vis) foram realizadas, porém não forneceram resultados conclusivos. Como forma de verificar os compostos que poderiam estar envolvidos na síntese das partículas através dos diferentes extratos, foram realizadas análises de espectrometria de massas (MALDI-TOF) e cromatografia gasosa. Através dessas análises foi possível verificar que os compostos que interagem com os íons cobre (II) são aminoácidos, ácidos graxos e açúcares. Apenas no extrato de centrifugação de células não viáveis foi possível verificar a presença de compostos com peso molecular na faixa entre 4kDa e 20kDa, compatível com proteínas. Uma vez confirmada a capacidade de síntese através de diferentes métodos, foi realizado um delineamento de experimentos central rotacional completo como forma de investigar a influência dos parâmetros pH e temperatura no diâmetro das partículas formadas com o extrato de centrifugação de células não viáveis. O diâmetro das partículas sintetizadas em cada ensaio foi medido através de análise de espalhamento de luz dinâmico (DLS). Através dos resultados, um modelo de segundo grau foi calculado utilizando-se o software Minitab® e verificou-se que tanto o pH quanto a temperatura não possuem contribuição significativa no tamanho das partículas sintetizadas. Além disso, observou-se que os diâmetros obtidos para os ensaios foram consideravelmente maiores que o obtido através das análises de microscopia eletrônica de transmissão (MET). Considerou-se que essa observação é resultado da presença de ligantes que atuam como estabilizadores das partículas e que contribuem para o aumento virtual do diâmetro medido. Esses ligantes podem ser compostos presentes no extrato e que não aparecem nas análises de microscopia por falta de contraste. Além disso, a análise de DLS é uma medida indireta de diâmetro e são necessárias outras análises para confirmar os resultados obtidos. Através dos resultados obtidos no presente trabalho, houve confirmação da capacidade de síntese de nanopartículas de cobre do fungo Hypocrea lixii e apresentação de metodologias promissoras que podem, após mais estudos, tornar-se um processo industrial. / In this work, the synthesis of copper nanoparticles using fungus Hypocrea lixii was evaluated. Therefore, the culture of the fungus was optimized in terms of cell concentration and hyphae qualitative aspect. It was found that cultures inoculated through frozen spore suspensions and using nutrient rich medium containing malt extract reached cell concentrations of 10g/L consistently, in addition to an aggregates-free hyphae aspect. The biossorption of copper (II) ions using non-viable biomass of Hypocrea lixii was measured, and sorption isotherms were constructed. It was found that the maximum removal calculated using the Langmuir model was 17,4mg/g, which was considered consistent with the value previously reported for this fungus. For the nanoparticle synthesis, the viable and non-viable biomasses of the fungus were initially used. Transmission electron microscopy (TEM) analysis demonstrated the formation of nanoparticles of 15nm of mean diameter inside the cells and in the cell wall for the non-viable biomass. For the viable biomass the particles obtained had 30nm of mean diameter and were located exclusively outside the cells. The use of viable and non-viable biomass suspension extracts was also investigated. The extracts were obtained after contact with double deionized water for 24 hours. Transmission electron microscopy (TEM) analysis showed the formation of particles with mean diameter of 12nm, for the viable biomass extract, and 10nm for the non-viable biomass extract. A method of obtaining cell extracts through centrifugation was also evaluated for the synthesis of copper nanoparticles. Transmission electron microscopy (TEM) analysis confirmed the formation of nanoparticles with mean diameter of 13nm. Energy dispersive X-ray spectroscopy (EDS) was performed on the particles found in samples of the centrifuged cells extract and they were found to be composed of copper only, endorsing the ability of synthesis for this extract. Other characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and spectrophotometry (UV-Vis) were performed but the results were inconclusive. In order to define which compounds present in the cell extracts could be involved in the synthesis reaction, mass spectrometry (MALDI-TOF) and gas chromatography analyses were performed for the different extracts produced. Through the results of those analyses it was seen that the compounds that interact with the copper (II) ions are amino acids and sugars. Only for the centrifuged cells extract it was possible to confirm the presence of compounds with molecular weights between 4kDa and 20kDa, compatible with proteins. Having confirmed the ability of the fungus of synthesizing copper nanoparticles through different methods, a central rotational composite design of experiments was established as a way of assessing the influence of the pH and temperature on the diameter of the particles formed using the centrifuged cells extract. The diameter of the particles was measured using dynamic light scattering (DLS). Through the results, a second order model was calculated using the software Minitab® and it was found that neither the pH nor the temperature had significant contributions to the size of the particles. Moreover, the diameter found for the experiments were considerably larger than the observed through transmission electron microscopy. It was considered that this observation was a result of the presence of ligands that act as stabilizers for the particles and that contribute to a virtual increase of the diameter measured. These ligands are compounds present in the extract and that are not shown in electron microscopy due to the lack of contrast. Furthermore, the DLS analysis is an indirect measurement of the diameter and other analyses are needed to confirm the results obtained. Through the results found in this work, there was a confirmation of the ability of the fungus Hypocrea lixii to synthesize copper nanoparticles. Promising methodologies were proposed that might, after further studies, become an industrial process.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-06-15T11:35:12Z No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:06:49Z (GMT) No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) / Made available in DSpace on 2018-09-03T16:06:49Z (GMT). No. of bitstreams: 1 tamiresmartinhaomachado.pdf: 4666656 bytes, checksum: b71e71df107c39709c20a42e1c35c2c6 (MD5) Previous issue date: 2018-03-02 / Vidros transparentes do sistema vítreo 0.95TeO2-(0.05-x)Sb2O3–xCuO contendo nanopartículas de cobre foi preparado com sucesso pelo método convencional de fusão – resfriamento dos materiais precursores, utilizando a rota redox do óxido de antimônio. Esta técnica de preparação de vidros permite a produção de nanopartículas metálicas durante a fusão dos materiais, através da reação de oxidação Sb3+ → Sb5+ + 2e-, que permite a redução de íons metálicos. A investigação estrutural foi realizada por calorimetria exploratória diferencial (DSC), difração de raios X (DRX) e espectroscopia Raman. Imagens de microscopia eletrônica de transmissão (TEM) e espectroscopia UV-visível evidenciaram a formação de clusters de nanopartículas de cobre cúbicas, distribuídas aleatoriamente em meio a matriz vítrea. A eficácia dos efeitos plasmônicos das nanopartículas de cobre promoveu a intensificação da fluorescência dos íons érbio. A interação da radiação excitante e amostra levou ao processo de excitação térmica, promovendo o aumento da população de níveis de energia específicos dos íons érbio, com consequente resposta óptica, evidenciada pela estrutura vibrônica presente no espectro de fluorescência dos vidros de teluritos contendo nanopartículas de cobre dopados com íons érbio. Além disso, os efeitos plasmônicos das nanopartículas de cobre na intensificação das emissões no infravermelho e conversão ascendente nos vidros de teluritos co-dopados com íons Yb3+/Ce3+/Er3+ sob excitação em 980 nm também foram investigados. As contribuições dos íons Yb3+ e Ce3+ também foram discutidas. A eficiência da ressonância do plasmon de superfície localizado (LSPR) das nanopartículas de cobre promoveu um melhoramento de cerca de 47% da emissão em 1550 nm dos íons Er3+. Além disso, o tempo de decaimento da transição Er3+: 4I13/2 → 4I15/2 aumentou em cerca de 50% na amostra contendo nanopartículas de cobre. Finalmente, os vidros de teluritos contendo nanopartículas de cobre apresentaram resultados interessantes quando utilizados como substratos para obtenção de espectros Raman intensificados por superfície (espectros SERS), sendo obtidos satisfatoriamente espectros SERS para soluções de 2,2’-bipiridina 1,0 × 10-5 mol.L-1 e do corante azul do Nilo 1,0 × 10-7 mol.L-1. / Transparent 0.95TeO2-(0.05-x)Sb2O3-xCuO glassy system containing copper nanoparticles were successfully prepared by the conventional melt quenching method of starting materials, using the antimony oxide redox route. This technique allows the production of metallic nanoparticles during melting, through the reaction Sb3+ → Sb5++ 2e-, which leads to the reduction of metallic ions. The structural investigation was carried out by differential scanning calorimetry (DSC), X ray diffraction (XRD) and Raman spectroscopy. Transmission electron microscopy image (TEM) and UV-visible spectroscopy evidenced the formation of cubic copper nanoparticles, randomly embedded in the glassy matrix. The effectiveness of the plasmonic effects of the copper nanoparticles provided the enhancement of the fluorescence of the erbium ions. The interaction between excitant radiation and sample led to the thermal excitation, which increased the population of specific energy levels of erbium ions, with consequent optical response into vibronic structure, as can be seen in the erbium-doped tellurite glasses containing copper nanoparticles. Furthermore, the plasmonic effects of the copper nanoparticles on the enhancement of the infrared and upconversion emissions intensities in the Er3+/Yb3+/Ce3+ co-doped transparent tellurite glasses under 980 nm laser diode excitation were investigated. The roles of Yb3+ and Ce3+ as sensitizers are also discussed. The effectiveness of localized surface plasmon resonance (LSPR) of the copper nanoparticles provided an improvement about 47% of the 1550 nm luminescence intensity of the Er3+ ions. Moreover, the lifetime of the Er3+: 4I13/2 → 4I15/2 transition increased around 50 % in the copper nanoparticle containing samples. Finally, the tellurite glasses containing copper nanoparticles showed interesting results as substrates for obtainment of surface enhanced Raman spectra (SERS spectra) and SERS spectra were satisfactorily obtained for 2,2'-bipyridine 1.0 × 10 -5 mol.L-1 and Nile blue dye 1.0 × 10-7 mol.L-1 solutions.

The main goal of this thesis is to deposit metal particles on the surface of 2D nanoplatelets using a controlled cementation process. As a proof of concept, copper (Cu) and Graphene Nanoplatelets (GNP) were chosen as the representative metal and 2D nanoplatelets, respectively. Specific goals of this study include depositing nanometer scale Cu particles on the surface of GNP at a low concentration (approximately 5 vol.%) while maintaining clustering and impurities at a minimum. Parametric studies were done to attain these goals by investigating various metallic reducer types and morphologies, GNP surface activation process, acid volume % and copper (II) sulfate concentrations. Optimal conditions were obtained with Mg ribbon as a reducer, 3 minutes of activation, 1 vol.% of acetic acid and 0.01 M CuSO4. The GNP-Cu powder synthesized in this work is a precursor material to be consolidated via spark plasma sintering (SPS) to make a nacre-like, layered structure for future studies.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22775号 / 工博第4774号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 邑瀬 邦明, 教授 杉村 博之, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

A lo largo del año 2020, hemos sido testigos de una de las pandemias mundiales más grandes de la historia, un virus llamado COVID-19 se ha llevado vidas, sin distinguir raza, sexo, estatus social ni religión. Como consecuencia, hoy en día estamos viviendo la llamada “Nueva normalidad” la cual trae consigo un cambio radical en el consumidor, con un gran impacto en la economía mundial y una acelerada transformación digital. El Perú no ha sido ajeno a esta coyuntura, pues ha sido uno de los países más golpeados de Latinoamérica, con pérdidas irreparables en nuestros indicadores económicos y una población que día a día se encuentra atemorizada de no contagiarse. Por ello, ha nacido una nueva necesidad, y con ello una diversidad de productos que buscan limitar el nivel de contagios, entre ellos el alcohol en gel. Doctor Copper es la marca que representa un producto innovador en el mercado peruano, el cual posee un componente capaz de eliminar el 99.9% de virus y bacterias: Nanopartículas de cobre. Este componente hace que los productos Doctor Copper sean el mejor aliado en la prevención del contagio a través de la desinfección de manos. El presente trabajo, explica el proceso de composición del negocio y las etapas que atraviesa el producto hasta llegar al consumidor final, la composición de la empresa y lo más importante, las estrategias que usaremos para lograr la consolidación de la marca y la participación de mercado. / Throughout 2020, we have witnessed one of the largest global pandemics in history, a virus called COVID-19 has taken lives, without distinguishing race, sex, social status or religion. As a consequence, today we are living the so-called “New normal” which brings with it a radical change in the consumer, with a great impact on the world economy and an accelerated digital transformation. Peru has not been alien to this situation, as it has been one of the hardest hit countries in Latin America, with irreparable losses in our economic indicators and a population that day by day is afraid of not getting infected. That is why a new need has been born, and with it a diversity of products that seek to limit the level of contagion, including gel alcohol. Doctor Copper is the brand that represents an innovative product in the Peruvian market, which has a component capable of eliminating 99.9% of viruses and bacteria: copper nanoparticles. This component makes Doctor Copper products the best ally in the prevention of contagion through hand disinfection. This paper explains the process of composition of the business and the stages that the product goes through until it reaches the final consumer, the composition of the company and, most importantly, the strategies that we will use to achieve the consolidation of the brand and market share. / Trabajo de investigación

Philosophiae Doctor - PhD (Chemistry) / Supercapacitors, also known as ultracapacitors or electrochemical capacitors, are considered one of the most important subjects concerning electricity or energy storage which has proven to be problematic for South Africa. In this work, graphene oxide (GO) was supported with platinum, silver and copper nanoparticles anchored with dodecylbenzenesulphonic acid (DBSA) doped polyaniline (PANI) to form nanocomposites. Their properties were investigated with different characterization techniques. The high resolution transmission electron microscopy (HRTEM) revealed GO's nanosheets to be light, flat, transparent and appeared to be larger than 1.5 ?m in thickness. This was also confirmed by high resolution scanning electron microscopy (HRSEM) with smooth surfaces and wrinkled edges observed with the energy dispersive X-ray analysis (EDX) confirming the presence of the functional groups such as carbon and oxygen. The HRTEM analysis of decorated GO with platinum, silver and copper nanoparticles (NPs) revealed small and uniformly dispersed NPs on the surface of GO with mean particle sizes of 2.3 ± 0.2 nm, 2.6 ± 0.3 nm and 3.5 ± 0.5 nm respectively and the surface of GO showed increasing roughness as observed in HRSEM micrographs. The X-ray fluorescence microscopy (XRF) and EDX confirmed the presence of the nanoparticles on the surface of GO as platinum, silver and copper which appeared in abundance in each spectra. Anchoring the GO with DBSA doped PANI revealed that single GO sheets were embedded into the polymer latex, which caused the DBSA-PANI particles to become adsorbed on their surfaces. This process then appeared as dark regions in the HRTEM images. Morphological studies by HRSEM also supported that single GO sheets were embedded into the polymer latex as composite formation appeared aggregated and as bounded particles with smooth and toothed edges.

Les travaux dans cette thèse ont pour objectif la synthèse de catalyseurs (nanoparticules de cuivre) de taille contrôlée pour la synthèse de nanofils de silicium dans des conditions compatibles CMOS, c'est-à-dire en évitant l'utilisation de l'or comme catalyseur et pour des croissances basse température (<450°C). Les résultats obtenus ont permis de montrer que les techniques de chimie de surface classiquement utilisées pour la préparation de catalyseurs sur des supports 3D (silice, nitrure de titane…) sont directement applicables et transférables sur des supports 2D (wafer de silicium recouvert de films fins de SiO2, SiOx et TiN). Nous avons par exemple pu préparer des nanoparticules de cuivre de taille contrôlée (de 3 nm à 40 nm de diamètre moyen suivant les conditions expérimentales et supports). De plus, les mécanismes de formation des nanoparticules en fonction des propriétés de surface des matériaux étudiés ont été démontrés en combinant diverses techniques d'analyses de surface. La croissance de nanofils de silicium à partir de ces catalyseurs sur substrats 2D a également été réalisée avec succès dans des procédés à basse température. Il a notamment été montré l'existence d'un diamètre minimum critique à partir de laquelle la croissance basse température était possible / The work presented in this PhD thesis aimed at the preparation of copper nanoparticles of controllable size and their utilization as catalysts for the growth of silicon nanowires in a process compatible with standard CMOS technology and at low temperature (< 450°C). The growth of silicon nanowires by Chemical Vapor Deposition (CVD) via the catalytic decomposition of a silicon precursor on metallic nanoparticles at low temperature (Vapor Solid-Solid process) was demonstrated to be possible from an oxidized Cu thin film. However, this process does not allow the control over nanowires diameter, which is controlled by the diameter of the nanoparticle of catalyst. In this PhD is presented a fully bottom-up approach to prepare copper nanoparticles of controllable size directly on a surface without the help of external stabilizer by mean of surface organometallic chemistry. First, the preparation of copper nanoparticles is demonstrated on 3D substrates (silica and titanium nitride nanoparticles), along with the fine comprehension of the formation mechanism of the nanoparticles as a function of the surface properties. Then, this methodology is transferred to planar (2D) substrates typically used in microelectronics (silicon wafers). Surface structure is demonstrated to direct the Cu nanoparticles diameter between 3 to 40 nm. The similarities between the 2D and 3D substrates are discussed. Finally, the activity of the Copper nanoparticles in the growth of Silicon nanowire is presented and it is demonstrated that in our conditions a critical diameter may exist above which the growth occurs

D. Tech. (Department of Biotechnology and Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / The synthesis of Ag and Cu nanoparticles was carried out using the thermal decomposition method in the presence of oleylamine as a capping agent. This method was used because it can produce uniform and monodisperse nanoparticles with controlled size distribution. The nanoparticles synthesized under various conditions were characterized by transmission electron microscopy (TEM), UV/Vis spectroscopy, photoluminescence spectroscopy (PL), and X-ray diffraction (XRD). The effect of precursor concentration on the morphology and size of the nanoparticles was investigated. It was observed that an increase in the precursor concentration resulted in an increase in particle sizes with different morphologies for both Ag and Cu nanoparticles. The increase in particle sizes for Ag nanoparticles was due to Ostwald ripening, while for Cu nanoparticles it was due to agglomeration, as Cu tends to oxidize in the atmosphere, leading to a change in particle size and shape. However, the ability to control and manipulate their physical and chemical properties depends on tuning their size and shape. Therefore, varying the precursor concentration helped in selecting the optimal concentration for this study. The nanoparticles produced were used in another study as fillers or additives for the production of nanofiber composites. The development of nanofibers by electrospinning process has led to potential applications in filtration, tissue engineering scaffolds, drug delivery, wound dressing and etc. The current study is an attempt to fabricate composite nanofibers that can be used as wound dressing material for effective wound healing. The approach involves the blending of two different polymers both being biocompatible and biodegradable were one is a natural polymer and the other is a synthetic polymer. In this study, different weight ratios of CS/PVA blends, Ag/Cu/CS/PVA, Ag/CS/PVA and Cu/CS/PVA composite fibers have been successfully prepared by the electrospinning process. The tip-to-collector distance was kept at 15 cm and the applied voltage was varied from 15 to 25 kV. The effects of the weight ratios applied voltage and the nanoparticles loading on the morphology and diameter of the fibers were investigated. The resultant fibers were characterized using scanning electron microscopy (SEM), XRD, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA) and UV-Vis spectroscopy. The SEM results showed that an increase the amount of chitosan in the CS/PVA blend resulted in a decrease in the fiber diameters while an increase in the voltage from 15 to 25 kV led to a decrease in the fiber diameters. Furthermore, an increase in fiber diameters was observed with irregular morphologies upon addition of Ag/Cu nanoparticles into the blend. The latter changes are perceived to be as a result of an increased conductivity and a higher charge density. The XRD results showed peaks which correspond to Ag in the face centred cubic. Ag peaks are more dominant than Cu peaks in the XRD of the mixed nanoparticles. The FTIR spectra of the Ag/Cu/CS/PVA composite fibers gave almost identical features as the blend. This proves that there was an interaction between CS and PVA polymer due to intermolecular hydrogen bonding. The TGA curves showed no significant effect on the thermal stability of the composite fibers upon addition of different nanoparticles loadings. The absorption spectra of the composite fibers showed an improved optical properties compared to the blend. For Ag and Cu nanoparticles composite fibers it was observed that addition of Ag nanoparticles in the blend resulted in an increase in fiber diameters with uniform morphology whereas for Cu resulted in a decrease in fiber diameters. Both Ag and Cu composite fibers showed an improved optical properties. The effect of CS/PVA, Ag/Cu, Ag, and Cu nanofibers on the selected microorganism (K.pneumoniae, S. aureus, P. aeruginosa, and E.coli) was evaluated using the disk diffusion method. It was observed that Ag/Cu/CS/PVA composite fibers showed greater activity against all microorganisms compared to Ag and Cu composite fibers. The alamar blue and Pierce Lactase dehydrogenase (LDH) assay were used to assess the effect of the blend and the composite fibers on cell viability and cytotoxicity, respectively. The results show that the prepared blend and the composite fibers did not have any toxic effect on human adipose derived stem cells (hADSC). The results also showed that as the concentration of Ag/Cu nanoparticles was increased the viability of the cells also increased after 24 hour incubation. More proliferation was observed in day 1 compared to day 3. The 30/70 blend showed more viable cell compared to the negative control. For Ag and Cu composite fibers the 30/70 CS/PVA blend increased cell proliferation after 3 days with 17% more viable cells compared to the negative control. These results show that the prepared blend with its composite fibers are biocompatible with human (ADSC) and may be suitable for use in biomedical application such as wound dressing.