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Doctoral Thesis
DOI
10.11606/T.75.2009.tde-26082009-104202
Document
Author
Full name
Ana Paula Garcia Ferreira
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2009
Supervisor
Committee
Gehlen, Marcelo Henrique (President)
Tiera, Márcio José
Gallas, Márcia Russman
Rossi, Liane Marcia
Varanda, Laudemir Carlos
Title in Portuguese
Preparação e estudo fotofísico de nanopartículas de sílica marcadas com compostos fluorescentes
Keywords in Portuguese
fluorescência
nanopartículas de sílica
polímeros
Abstract in Portuguese
Foi estudado o comportamento fotofísico da 9-aminoacridina (9AA) e derivados, safranina O, auramina e 9-vinilantraceno, em partículas de sílica. Inicialmente, partículas de sílica obtidas comercialmente foram modificadas e marcadas com corantes acridínicos, porém sua morfologia tornou inviável o estudo fotofísico, devido à sua irregularidade. Foram preparadas nanoesferas de sílica, pelo método de Stöber, com diâmetro médio de 50 nm, que apresentaram altos sinais de fluorescência. Além disso, para evitar a dessorção dos marcadores nas nanopartículas em suspensão, foram preparadas nanopartículas do tipo cascacaroço, contendo um núcleo rico em marcador, protegido por uma casca de sílica. Estas nanopartículas, com diâmetro médio de 125 nm, mostraram-se excelentes matrizes para o estudo dos corantes, retardando sua difusão para o solvente. Foram ainda preparadas nanopartículas contendo poli(metacrilato de metila) marcado com derivado acridínico. A interação entre grupos silanol na superfície e o grupo N-H do marcador bloqueou o processo de transferência de carga intramolecular, característico do corante. Por fim, foram preparadas nanopartículas marcadas com 9-aminoacridina e safranina O. Na presença de safranina O, o tempo de vida de fluorescência referente à desativação do cromóforo acridina passou de 12,2 ns para 9,71 ns, indicando processos de transferência de energia e supressão de fluorescência, no interior das partículas.
Title in English
Preparation and photophysical study of silica nanoparticles grafted with fluorescent compounds
Keywords in English
fluorescence
polymers
silica nanoparticles
Abstract in English
Photophysical behavior of 9-aminoacridine (9AA) and derivatives, safranine O, auramine and 9-vinylanthracene was investigated, in silica particles. Firstly, commercial silica was modified and grafted with acridinic dyes; however, photophysical studies became unviable, due to its morphology. Silica nanospheres were prepared by Stöber method, with mean diameter of 50 nm, presenting high fluorescence emission. Moreover, in order to avoid de desorption of dyes from particles in suspension, systems containing a dye reach nucleus protected by silica shells were prepared (core-shell nanoparticles). The core-shell nanospheres, with mean diameter of 125 nm, are excellent matrixes for fluorescence studies, since it retards dye diffusion to the solvent. It was also prepared nanoparticles containing poly(methylmethacrylate) grafted with 9AA derivative. Interaction between silica silanol groups and dye N-H groups broke the intramolecular charge transfer, a characteristic process occurring in this dye. Finally, nanoparticles grafted with 9AA and safranine O were prepared. In the presence of safranine, fluorescence lifetime related to the deactivation of the chromophore acridine reduced from 12.2 ns to 9.71 ns, suggesting energy transfer and fluorescence quenching processes within the particles.
 
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AnaPaulGarcia.pdf (3.52 Mbytes)
Publishing Date
2009-08-26
 
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