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 NANOCOMPOSITES WITH ADSORPTIVE, PHOTOLUMINESCENT AND MAGNETIC PROPERTIES: FROM SYNTHESIS TO APPLICATION
PALAVRAS-CHAVES:
Mixed LOFs, magnetic composites, photoluminescence, selective adsorption, luminescent sensor
PÁGINAS: 90
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Compostos Organo-Metálicos
RESUMO:
The LOFs (Lanthanide-Organic Frameworks) have emerged 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 binders in a hybrid crystal 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. In this work, mixed LOFs and Fe3O4/LOF nanocomposites were synthesized by solvothermic and hydro(solvo)thermal methods using lanthanide ions (La3+, Tb3+, Gd3+, Eu3+) and polytopic organic binders. The samples were characterized by XRD, IR, TG, MEV, photoluminescence spectroscopy and evaluated as chemical sensors for metals (Pb3+,Cd3 + and Li3+), as well as the selective adsorption of organic dyes. The results suggest that the use of a growth promoter, acetic acid, used to control the particle morphology, promoted the formation of an unexpected structure, where the lanthanide ions (La3+ and Tb3+) are coordinated to formate ions in a network three-dimensional, rather than isophthalic linker, as expected. Formate ions were formed from the hydrolysis of the solvent used, dimethylformamide (DMF). The crystallized samples are isoreticular with a structure already reported in the literature and of formula [Ce(HCOO)3]n. The IR spectra exhibited 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 powders changed from micro stems to agglomerates of small flower-like particles when the concentration of acetic acid was increased. LOFs prepared with the lanthanide ions (Gd3+ and Eu3+) and the binder precursor, 1,3,5-benzene tricarboxylic acid (BTC). The results of XRD confirmed the crystallization of an isoestructure of LOF [Gd(BTC)(H2O)](DMF)(H2O)0.5, while IV results suggest the deprotonation of the carboxyl group of the ligand and its coordination to the ion Gd3+. The red luminescence of the compound when excited in the ultraviolet region confirmed the incorporation of Eu3+ ions. Nanocomposites (Gd, Eu) -LOF/ Fe3O4 were prepared under solvothermic conditions. The results of XRD confirmed the formation of the mixed LOF at the same time that characteristic diffraction peaks of the magnetite were observed, which was also confirmed by the magnetic characteristic of the obtained samples. The analysis of IV confirmed the deprotonation of the carboxyl group of the ligand and its coordination to the Gd3+ ion, also a 560 cm-1 band was observed regarding the Fe-O stretch of the magnetite. In addition, the composite also showed red luminescence characteristic of the europium ion. The results of the tests as a chemical sensor showed that the LOF presents a satisfactory result for the Pb3+ ion. Selective adsorption tests of the dyes using the composite and LOF show that the composite adsorbs more methylene blue (98%) than methyl orange (35%) at a concentration of 70mg/L for a time of 2h.
MEMBROS DA BANCA:
Presidente - 1754300 - BRAULIO SILVA BARROS
Interna - 349770 - DULCE MARIA DE ARAUJO MELO
Interna - 1805556 - LUCIENE DA SILVA SANTOS
Externa ao Programa - 1979301 - RENATA MARTINS BRAGA
Externo à Instituição - JARLEY FAGNER SILVA DO NASCIMENTO - IFRN
Externa à Instituição - JOANNA ELZBIETA KULESZA - UFPE