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Previous issue date: 2014-09-17 / This work aims at preparation and morphological and photophysical characterization of
systems consisting of self-assembled structures based on the L-diphenylalanine dipeptide doped
with magnetic and luminescent aditives.
In this way, nanoparticles magnetic particles of maghemite (γ-Fe2O3) were prepared and
used as magnetic additives, while Cadmium Telurium (CD and Te) - based Quantum Dots (QD)
were employed as the luminescent additive. The resulting system was characterized by scanning
electron microscopy and steady-state fluorescence spectroscopy techniques and their properties
were compared tothose presented by the individual components and the intermediate systems.
Also, a study on the interaction forces involved in the self-organization of the dipeptide
was carried out by varying the method of preparation by employing in the preparation, solvents
with distinct physical-chemical properties and by relating conformational differences in the nano
and micro structures obtained in each preparation protocol with the balance of interactions forces
that contribute to the self-assembling phenomenon. Regarding- to that, when self-assembling is
promoted in solvents with distinct polarizabilities (Δf), as obtained by Lippert equation, it is
possible to infer about the forces balance that are predominant. The peculiarities of each structure
obtained were explored by SEM imaging and spectroscopic data. From scanning electron
micrographs, it is observed that self-assembling is governed by interactions between neighboring
aromatic rings, trhough π-stacking interactions and generates, in most cases, tubular structures.
However, in certain protocols, lamellar structures were observed.
When self-assembilng occurs in water, L-diphenylalanine (NT-F-F) nanotube growth
occursfrom a starting site and develops in all directions. The use of additives with distinct
properties acted in self-assebling process, favoring it when the quantum dot is additive or
disfavoring it when the magnetic nanoparticles are the additives. Furthermore, it was observed
that in the system containing both additives in proportions in which aggregates are not observed,
nanotube´s self-asembling and their further association leaded to microtubes.
Structural differences between obtained NT-F-F allow us to infer on the nature of
interactions between the dopants and the NT-F-F. The photophysical behavior analysis revealed
that the fluorescence emission increases due to the nature of interaction between QD and NT-F-F,
to give rise to a charge transfer complex. These results indicate that there may be a conjugation
xxiii
effect favoring luminescent processes from relaxed energy states of the system containing the
magnetic particle and QD as additives, simultaneously. / Este trabalho tem como objetivo a preparação e a caracterização morfológica e fotofísica
de sistemas constituídos de estruturas auto-organizadas baseadas no dipeptídeo L-difenilalanina
contendo como aditivos com propriedades magnéticas nanopartículas partículas magnéticas de
maguemita (γ-Fe2O3) e como aditivo luminescente um Quantum Dot (QD) comercial a base de
Cádmio e Telúrio (Cd e Te). O sistema resultante foi caracterizado morfológica e fotofisicamente
e suas propriedades foram comparadas às apresentadas pelos componentes isolados e pelos
sistemas intermediários. Observou-se que quando a auto-organização é promovida em solventes
com polarizabilidades (Δf) distintas, é possível inferir sobre o balanço de forças que,
predominantemente, atuam sobre a auto-organização. Por meio de imagens de microscopia
eletrônica de varredura, observou-se que, quando auto-organizadas em água, nanotubos de Ldifenilalanina
(NT-F-F) se auto-organizam, partindo de uma região e se desenvolvendo em todas
as direções. A adição de compostos com propriedades distintas influenciou distintamente o
processo de auto-organização, favorecendo-o com o uso do quantum dot como aditivo, ou
desfavorecendo-o, com a adição das nanopartículas magnéticas. No entanto, no sistema contendo
ambos aditivos em proporções em que não são observados agregados, a auto-organização de
nanotubos é favorecida. Ainda, a análise do comportamento fotofísico revelou que a emissão de
fluorescência pode ter sua intensidade aumentada em decorrência da natureza da interação entre
os QD e os NT-F-F, por dar origem a um complexo de transferência de carga. Estes resultados
indicam que pode haver um efeito de conjugação que favorece os processos luminescentes que
partem de estados relaxados de menor energia nos sistemas contendo a partícula magnética e o
QD como aditivos, simultaneamente.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.bc.ufg.br:tede/3954 |
| Date | 17 September 2014 |
| Creators | Dias, Diogo Lopes |
| Contributors | Martins, Tatiana Duque, Martins, Tatiana Duque, Seabra, Amedea Barozzi, Colmati Júnior, Flávio |
| Publisher | Universidade Federal de Goiás, Programa de Pós-graduação em Química (IQ), UFG, Brasil, Instituto de Química - IQ (RG) |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFG, instname:Universidade Federal de Goiás, instacron:UFG |
| Rights | http://creativecommons.org/licenses/by-nc-nd/4.0/, info:eu-repo/semantics/openAccess |
| Relation | 663693921325415158, 600, 600, 600, 7826066743741197278, 1571700325303117195 |
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