Banca de DEFESA: ANA KARINA PEREIRA LEITE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA KARINA PEREIRA LEITE
DATA : 20/02/2019
HORA: 09:30
LOCAL: Auditório do NUPPRAR
TÍTULO:

Mixed LOFs and derived materials with photoluminescent and magnetic properties: Synthesis to Application

PALAVRAS-CHAVES:

Mixed LOFs, magnetic composites, photoluminescence, selective adsorption, sensor.

PÁGINAS: 90
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Compostos Organo-Metálicos
RESUMO:

LOFs (Lanthanide-Organic Frameworks) have stood out as an important class of functional materials. These materials present interesting optical and magnetic properties, which are directly related to the presence of lanthanide ions connected by organic ligands giving rise to a hybrid crystalline network. More recently, these properties have been extended by combining with other types of materials of interest, or in other words by the formation of composites or derived materials. Among the vast possibilities, the combination of porous and / or luminescent materials with magnetite, which presents interesting magnetic properties, has been considered as promising for the sensing and the selective adsorption of organic chemical compounds besides other possibilities. The aim of this work was to synthesize and characterize LOF and Fe3O4 LOFs and nanocomposites, evaluating their photoluminescent properties and their potential as chemical sensors for heavy metals and organic compounds, as well as the selective adsorption of dyes. The results were distributed in the format of articles in three different chapters. In the first one, a study on thermal hydrous synthesis of mixed LOFs based on Tb3 + doped La3 + and the morphological control of the particles via modification of total reagent concentration and / or addition of acetic acid to the reaction medium is reported. The samples prepared in this study were characterized by XRD, IR, TG, MEV and photoluminescence spectroscopy. The results of XRD indicated that instead of the La3 + ion coordinate to the isophthalic ligand, initially chosen ligand, it was coordinated to the formate ion, unexpectedly formed by the hydrolysis of DMF. The crystallized samples are isoreticular with a structure already reported in the literature and of formula [Ce (HCOO) 3]. Note also the presence of a second phase for higher total concentrations of reagents. The results of IV show the displacement of the stretch related to the carbonyl group of the ion format. The Tb3 + ion was incorporated into the structure giving green luminescence. The morphology of the powders changed from micro-stems to agglomerates of small flower-like particles when the concentration of acetic acid was increased. In a second study a mixed Euf + doped Gd3 + -based LOF and 1,3,5-H3BTC ligand was synthesized by the solvothermal method. The sample (Gd, Eu) -LOF was characterized by XRD, IR, TG and photoluminescence spectroscopy. The characterization by XRD suggests the crystallization of an isoestructure of LOF [Gd (btc) (H2O)] (DMF) (H2O) 0.5, while the result of IV confirms the deprotonation of the carboxyl group of the ligand and its coordination to the ion Gd3 +. The Eu3 + ion is present in the structure, since it has a red luminescence characteristic of europium. At the moment, tests related to the application of this material as photoluminescent sensor for metals and organic compounds are underway. In the third part of the work, the preparation of nanocomposites (Gd, Eu) -LOF-Fe3O4 was carried out. In a typical procedure, Fe3O4 nanoparticles were previously prepared and dispersed in the precursor solution of LOF. The nanocomposite was obtained under solvothermic conditions. the samples were characterized by XRD, IR, TG and photoluminescence spectroscopy. The XRD data confirmed the formation of the isoreticular structure [Gd (btc) (H2O)] (DMF) (H2O) 0.5, whereas no diffraction peaks characteristic of magnetite were observed. However, the nanocomposite formed has magnetic properties characteristic of Fe3O4. This can be evidenced by the easy magnetic separation performed when recovering the prepared material. The analysis of IV confirmed the deprotonation of the carboxyl group of the binder and its coordination to the Gd3 + ion, also a 560 cm-1 band related to the Fe-O stretch of the magnetite. In addition, the composite also showed red luminescence characteristic of the europium ion. The selective adsorption tests of the dyes (cationic and anionic) using the composite and the LOF will be analyzed by two techniques UV-vis and 13C NMR, in order to compare the results of the two materials and the techniques. Parameters such as concentration, adsorption time, reusability and regeneration capacity of the composite and LOF will also be evaluated.

MEMBROS DA BANCA:
Presidente - 1754300 - BRAULIO SILVA BARROS
Interna - 349770 - DULCE MARIA DE ARAUJO MELO
Externo à Instituição - JARLEY FAGNER SILVA DO NASCIMENTO - IFRN
Externa à Instituição - JOANNA ELZBIETA KULESZA - UFPE
Interna - 1805556 - LUCIENE DA SILVA SANTOS
Externa ao Programa - 1979301 - RENATA MARTINS BRAGA