Caracterização fotofísica e morfológica de estruturas peptídicas contendo composto fluorescente para aplicação ambiental

• Autor(a) principal: Souza, Geovany Albino de
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• dARK ID: ark:/38995/00130000041s3
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/4170
• topic: Cumarina 6; Difenilalanina; Nanotubos; Oxigênio; Coumarin 6; Diphenylalanine; Nanotubes; Oxygen; CIENCIAS EXATAS E DA TERRA::QUIMICA

In this work, we produced a fluorescent system composed of diphenylalanine (FF) nanoestructures containing the (2-benzothiazolyl)-7-dietilaminocoumarin (C6) dye as fluorescent additive. The morphological characteristics of the nanostructures and the influence of the additive on the FF self-organization were studied by scanning electron microscopy. The photophysical properties of the fluorescent system were assessed by photostationary fluorescence spectroscopy. From the morphological analysis, it was observed that the additive favors the FF self-organization, which can be attributed to the influence of the C6 aromatic rings on the π stacking interactions among the FF units. Also, it was observed that the characteristic blue fluorescence of the nanostructures at 400 nm, shifts to 408 nm in the presence of the additive. This is a result of an energy transfer complex that is formed between the FF and the C6, which promotes the fluorescence of the system from relaxed hybrid excited states. The photophysical behavior of the fluorescent system towards different concentrations of a suppressor, the molecular oxygen, was evaluated. Solutions containing the fluorescent additive alone showed poor sensitivity towards oxygen, as expected based on the properties of substituted coumarin derivatives when exposed to oxygen. However, the effect of the interaction between the FF nanostructures and the additive on the coumarin derivative sensitivity towards oxygen quenching was assessed and a remarkable increase of the dye sensitivity was observed. Therefore, we tested the applicability of this newly developed fluorescent system as a sensor for dissolved oxygen (DO) from water samples for potential application in environmental monitoring. The sensitivity and reproducibility of the fluorescent system quenching by DO were carried out in water samples from a tank containing fish specimen. In order to validate the fluorescence quenching measurements in the presence of varying DO concentration with time, the DO measurements were also simultaneously performed by the conventional electroanalytical method. We then observed that the variations in fluorescence intensities of the system agreed with the concentrations of DO measured by the conventional method.