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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

[en] SYNTHESIS AND CHARACTERIZATION OF FLUORESCENT SILICA NANOPARTICLES WITH POTENTIAL APPLICATION IN TRANSPORT AND ADSORPTION STUDIES IN POROUS MEDIUM / [pt] SÍNTESE E CARACTERIZAÇÃO DE NANOPARTÍCULAS DE SÍLICA FLUORESCENTES COM POTENCIAL APLICAÇÃO EM ESTUDOS DE TRANSPORTE E ADSORÇÃO EM MEIO POROSO

ALESSANDRA PAZINI 31 August 2023 (has links)
[pt] As nanopartículas de sílica (SiNPs) são amplamente utilizadas em diversas áreas e formam nanofluidos com propriedades excepcionais quando suspensas em um fluido base. No entanto, o transporte e a quantificação de SiNPs em meios porosos representam desafios significativos. Para resolver isso, a espectroscopia de fluorescência é uma técnica promissora para essa tarefa. Neste estudo, uma série denanopartículas core-shell fluorescentes à base de sílica (FSiNPs) com núcleos semelhantes, mas diferentes grupos de superfície foram sintetizadas usando os métodos de síntese de Stober e WORM. Essas FSiNPs híbridas foram projetadas e apresentaram o mesmo comportamento coloidal que as SiNPs comerciais amplamente aplicadas na forma de nanofluidos. A presença de grupos amino primários foi confirmada nas FSiNPs positivas, caracterizações posteriorescorroboraram a presença de matéria orgânica confirmando a inserção de moléculas fluorescentes em todas as FSiNPs. Análises comparativas revelaram que o método WORM produziu nanopartículas mais homogêneas tanto no quesito formato quanto na distribuição de tamanho. A análise de adsorção/dessorção de N2 demonstrou semelhanças entre os FSiNPs sintetizados e as SiNPs comerciais, validando sua adequação para experimentos de transporte com foco no comportamento coloidal. Ambas as WORM-FSiNPs foram quantificadas com sucesso no efluente após fluir através da coluna de esferas de vidro. A SiNP contendo grupos de superfície aminopropil mostraram a maior estabilidade e menor adsorção em comparação com aqueles enxertados com grupos silanol. Isso foi atribuído ao efeito de interações atrativas mais fortes entre as NPs e as moléculas do surfactante aniônico. Por fim, foi demonstrado o potencial dessas NPs fluorescentes como marcadores sensíveis para estudos de transporte e adsorção em nanofluidos contendo surfactantes. / [en] Silica nanoparticles (SiNPs) are widely used in various fields, and they form nanofluids with exceptional properties when they are suspended in a base fluid. However, the transport and quantification of SiNPs in porous media pose significant challenges. To address this, fluorescence spectroscopy is a promising technique for this task. In this study, a series of core-shell silica-based fluorescent nanoparticles (FSiNPs) with similar cores but different surface groups were synthesized using the Stober and WORM synthesis methods. These hybrid FSiNPs were designed and presented the same colloidal behavior as commercial SiNPs widely applied in the form of nanofluids. The presence of primary amino groups was confirmed in positive-FSiNPs, and a posterior characterization supported the presence of organic matter in nanoparticles confirming the insertion of fluorescent molecules in all FSiNPs. Comparative analyses revealed that the WORM method produced more homogeneous nanoparticles with consistent form and size distribution. The N2 adsorption/desorption analysis demonstrated similarities between the synthesized FSiNPs and commercial SiNPs, validating their suitability for transport experiments focusing on colloidal behavior. Both WORM-FSiNPs were successfully quantified in the effluent after flowing through the glass bead column. The SiNP-containing aminopropyl surface groups showed the greatest stability and lowest adsorption compared with those grafted with silanol groups. It was attributed to the effect of stronger attractive interactions between the NPs and anionic surfactant molecules. The potential of these fluorescent NPs as sensitive tracers for transport and adsorption studies in nanofluids containing surfactants was demonstrated.

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