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In this thesis, the morphology and size of the gold and silver nanoparticles obtained by laser ablation were investigated, with different reconfiguration methods. In the case of gold, the target was ablated with a pulsed Nd: YAG laser, (1064 nm, 37.48 mJ/p, 10 Hz, for 10 minutes), the absorption spectra show a single maximum absorption at 521 nm characteristic of the gold spherical nanoparticles. The PLI technique was applied to the colloids with laser pulses of 532 nm wavelength, 25.8 mJ of energy for 6 minutes. Dynamic light scattering (DLS) analysis showed that the NpsAu with PLI were 21 nm in diameter also, it was verified that the amplitude of the photoacoustic signal is directly and proportionally related to the concentration of NpsAu in the colloid evidencing that the greater The photoacoustic response is higher. For the case of silver, the target was ablated with a pulsed Nd: YAG laser (1064 nm, 10 ns, 15.7 mJ/p). The application of the focused PLI to the colloids with energy of 8.7 mJ/p and 1064 nm wavelength, showed that the NpsAg can change their spherical shape and size from approximately 10 to 15 nm in diameter to triangular with rounded corners of Approximately 48 nm sideways, which have been observed by scanning electron microscopy (SEM). In addition, the seed sowing method was used to study the morphology of NpsAg colloids whose characterization shows prismatic forms, pentagons and hexagons, these new configurations are shown by STEM images. From the research it was concluded that the focused PLI technique applied to colloids with NpsAg presents new morphologies. In the case of gold a change in size was found. RESUMEN En la presente tesis se investigó el cambio de morfología y tamaño de las nanopartículas de oro y plata obtenidos por ablación láser, con diferentes métodos de reconfiguración. En el caso del oro, el blanco fue ablacionado con un láser pulsado de Nd: YAG, (1064 nm, 37.48 mJ/p, 10 Hz, durante 10 minutos), los espectros de absorción presentan un solo máximo de absorción a 521 nm característica de las nanopartículas esféricas de oro. Se aplicó la técnica PLI a los coloides con pulsos láser de 532 nm de longitud de onda, 25.8 mJ de energía durante 6 minutos. El análisis por dispersión dinámica de la luz (DLS) mostró que las NpsAu con PLI fueron de 21 nm de diámetro además, se comprobó que la amplitud de la señal fotoacústica está relacionada directa y proporcionalmente con la concentración de NpsAu en el coloide evidenciando que a mayor concentración la respuesta fotoacústica es mayor. Para el caso de la plata, el blanco fue ablacionado con un láser pulsado de Nd: YAG (1064 nm, 10 ns, 15.7 mJ/p). La aplicación de la PLI focalizada a los coloides con energía de 8.7 mJ/p y 1064 nm de longitud de onda, mostraron que las NpsAg pueden cambiar su forma y tamaño, de esféricas de aproximadamente 10 a 15 nm de diámetro a triangulares con esquinas redondeadas de aproximadamente 48 nm de lado, que han sido observados por microscopia electrónica de barrido (SEM). Adicionalmente se utilizó el método de sembrado de semilla para estudiar la morfología de los coloides con NpsAg cuya caracterización muestran formas prismáticas, pentágonas y hexágonos, estas nuevas configuraciones son mostradas por las imágenes de STEM. De la investigación se concluyó que la técnica PLI focalizada aplicada a los coloides con NpsAg presenta nuevas morfologías. En el caso del oro se encontró un cambio de tamaño. Tesis

Tese (doutorado)—Universidade de Brasília, Instituto de Física, 2006. Nessa tese foram investigadas as propriedades magnéticas e fotoacústicas de nanopartículas de maghemita dispersas em microesfera de BSA (bovine serum albumine), nanopartículas de ferrita de cobalto dispersas em microesfera de PLA (polylactic acid), nanopartículas de ferrita de cobalto peptizadas na forma de fluido magnético iônico e nanopartículas de magnetita coberta com dextrana e DMSA (dimercaptosuccinic acid) e peptizadas na forma de fluido magnético biocompatível. Foram realizadas medidas de microscopia eletrônica de transmissão (MET) e medidas de difração de raios-X para obtenção das micrografias, difratogramas, diâmetros médios e polidispersão das nanopartículas investigadas. Medidas Mössbauer permitiram a caracterização da fase magnética dos nanocompósitos (maghemita em BSA e ferrita de cobalto em PLA). Medidas de fotoacústica foram realizadas e analisadas em termos de três bandas (L, S e C). Medidas de susceptibilidade dinâmica foram realizadas na faixa de freqüência de 2 a 80 MHz, em temperatura ambiente e de nitrogênio líquido. Finalmente, a técnica de ressonância magnética foi empregada na investigação das propriedades magnéticas das amostras. As medidas de ressonância magnética foram realizadas em um espectrômetro comercial Bruker ESP-300 operando em banda-X (9,6 GHz), permitindo a investigação das amostras em função da temperatura (100 a 300K) e concentração das nanopartículas. As dependências do campo de ressonância e largura de linha de ressonância com a temperatura foram analisadas usando a aproximação proposta por Morais e colaboradores [98, 110, 112]. __________________________________________________________________________________________ ABSTRACT In this thesis the magnetic and photoacoustic properties of maghemite nanoparticles dispersed in BSA (bovine serum albumine) microsphere, cobalt ferrite nanoparticles dispersed in PLA (polylactic acid) microsphere, cobalt ferrite nanoparticles peptized as ionic magnetic fluid and magnetite nanoparticles surface-coated with dextran and DMSA (dimercaptosuccinic acid) and peptized as biocompatible magnetic fluids were investigated. Transmission electron microscopy and X-ray diffraction measurements were performed in order to obtain the micrographs, diffractograms, average diameter and polydispersity of the investigated nanoparticles. Mössbauer measurements allowed characterization of the nanocomposites magnetic phase (maghemite in BSA and cobalt ferrite in PLA). Photoacoustic measurements were performed and analyzed in terms of three bands (L, S, and C). Dynamic susceptibility measurements were performed in the frequency range of 2 to 80 MHz, at room temperature and liquid nitrogen temperature. Finally, the magnetic resonance technique was employed in the investigation of the magnetic properties of the samples. Magnetic resonance measurements were carried out in a commercial Bruker ESP-300 spectrometer operating in the X-band (9.6 GHz), allowing investigation of the samples as a function of the temperature (100 to 300K) and nanoparticle concentration. The temperature dependence of both resonance field and resonance linewidth were analyzed within the approximation proposed by Morais and coworkers [98, 110, 112].