Banca de DEFESA: JARLEY FAGNER SILVA DO NASCIMENTO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : JARLEY FAGNER SILVA DO NASCIMENTO
DATA : 25/08/2017
HORA: 15:00
LOCAL: Sala 3F1
TÍTULO:

SYNTHESIS AND PHOTOPHYSICAL PROPERTIES OF MIXED LOFs

PALAVRAS-CHAVES:

LOFs; antenna effect; photoluminescence; tunable luminescence.

PÁGINAS: 104
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Compostos Organo-Metálicos
RESUMO:

In this work was synthesized a series of new metal-organic frameworks containing lanthanide ions (LOFs) by solvothermal method at 180 ⁰C, using as the organic component terephthalic acid (1,4-H₂BDC). Initially, three matrices containing gadolinium doped with 5 mol% Eu³⁺ ions were prepared (Eu/Gd-1,4-BDC-MOFs). This stage was focused vary the time of synthesis (3, 5 and 7 days) to understand the influence of this parameter on the morphological and luminescent properties of the framework. Subsequently, matrices with different Eu³⁺ molar percentages (1, 3, 5, 7 and 9%) were synthesized with the intention to determine the limiting dopant concentration, as well as to investigate the effect of such percentage variation on the structures and photophysical properties of the LOFs. Finally, a matrix co-doped with 2.5 mol% of Tb³⁺ and Eu³⁺ (Gd/Tb/Eu-1,4-BDC-MOF), was prepared to study whether the ligand was able to act as an antenna for both metal centers, verifying the possibility of the material exhibiting photoluminescent tuning dependent on the excitation wavelength. The samples in powder form, were characterized by X-ray Diffraction (PXRD), Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR), Scanning Electronic Microscopy (SEM), Thermogravimetric Analysis (TGA) and Photoluminescence (PL). Based on the analyzes of DXRP, FTIR and PL, it was identified that materials containing up to 7 mol% of europium ions presented a single-phase. In addition, it was observed from the excitation and emission spectra that an effective intramolecular energy transfer occurred between the ligand and the Eu³⁺ levels, generating characteristic red luminescence of this ion. These samples emission spectra exhibited characteristic emission lines of the Eu³⁺ ion ascribed to the ⁵D₀ → ⁷F₀, ⁷F₁, ⁷F₂,⁷F₃ and ⁷F₄ transitions. The co-doped sample presented efficient tuning-color resulting from the transfer of energy between Tb³⁺ → Eu³⁺. The materials described, incorporate functionalities (luminescence and magnetism), originating from the luminescent ions Eu³⁺ and Tb³⁺, and paramagnetic Gd³⁺ ions, respectively. These are promising for various optical applications.

MEMBROS DA BANCA:
Presidente - 1754300 - BRAULIO SILVA BARROS
Interno - 349770 - DULCE MARIA DE ARAUJO MELO
Externo ao Programa - 1802888 - FABIANA VILLELA DA MOTTA
Externo à Instituição - INGRID TAVORA WEBER - UnB
Externo à Instituição - JOANNA ELZBIETA KULESZA - UFPE
Externo à Instituição - ÉRICO DE MOURA NETO - IFRN