Banca de QUALIFICAÇÃO: GRACE KELLY QUARTEIRO GANHARUL

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : GRACE KELLY QUARTEIRO GANHARUL
DATA : 10/12/2019
HORA: 14:00
LOCAL: sala 305, 3º andar, Bloco B, Campus SA da Fundação Universidade Federal do ABC, localizada na Avenida dos Estados, 5001, Santa Terezinha, Santo André, SP
TÍTULO:

SYNTHESIS AND CHARACTERIZATION OF STRUCTURAL, MORPHOLOGICAL, AND OPTICAL PROPERTIES OF SEMICONDUCTOR OXIDES (TiO2 AND CsPbI3) FOR PHOTODEGRADATION APPLICATIONS

PÁGINAS: 50
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
ESPECIALIDADE: Superfícies e Interfaces; Películas e Filamentos
RESUMO:

               Micro and nanostructured semiconductor materials have attracted a lot of attention from the scientific community due to the numerous possibilities of technological applications. Applications involving interaction with electromagnetic radiation such as solar cells, luminescent devices and photodegradation of organic matter are among the most investigated. In this work, a study involving the synthesis of two semiconductor families (TiO₂ and CsPbI₃) and characterization of structural, morphological, optical, and photocatalytic properties was performed.

               The first TiO₂ family was synthesized via microwave assisted hydrothermal method, using as precursors titanium tetraisopropoxide in solution with hydrochloric acid (1) and acetic acid (2). Both syntheses were performed varying the temperature between 120 and 200ºC for ten minutes. X-ray diffraction (XRD) measurements revealed the formation of the rutile (P₄₂ / mnm symmetry group) and anatase (I₄₁ / amd) crystalline structures for synthesis (1) and (2), respectively. Scanning electron microscopy images showed that the rutile phase shows stick morphology with a diameter of 0.14(2) µm and a length ranging from 0.562 to 1.490 µm; Anatase-structured samples formed agglomeration of nanoparticles, as also suggested by XRD measurements. Through UV-visible measurements and using the Tauc plot model, the band gap energies the samples were estimated to be: 2.76(4) eV for the rutile phase and 2.80(3) eV for the anatase phase.

               The second semiconductor family studied was the halide perovskite with chemical formula CsPbI₃. Samples were produced by the solvothermic method using lead iodide, hydroiodic acid, isopropanol and cesium acetate as precursors under stirring at 100 ° C. XRD measurements showed reflections of the intense and narrow Bragg planes belonging to the orthorhombic structure. Scanning electron microscopy images showed the formation of sticks in micrometric scale, with average dimensions of 80(4) µm in length and 2.0(3) µm in diameter. Changing synthesis parameters such as agitation and drying time may result in a reduction in the length and width of the sticks. The band gap energy of 2.70(5) eV was observed.

               The two semiconductor families were used for the photodegradation tests of methylene blue dissolved in methanol using a solar simulator. For 60 minutes exposure to solar radiation, samples with anatase structure degraded 86% of methylene blue; 70% rutile while halide perovskite degradation was 82%. The TiO₂ sample in the anatase phase was heat treated at 400ºC for 2 hours and an increase of approximately 30% in photocatalytic activity was observed. Composites were also produced by mixing both TiO₂ and CsPbI₃ samples. Interestingly, in this case, the photodegradation efficiency of methylene blue reached 96%.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1671688 - ANDRE SARTO POLO
Membro Titular - Examinador(a) Interno ao Programa - 2946001 - ANTONIO ALVARO RANHA NEVES
Membro Titular - Examinador(a) Interno ao Programa - 1957564 - CEDRIC ROCHA LEAO
Membro Titular - Examinador(a) Externo ao Programa - 1762438 - JEAN JACQUES BONVENT
Membro Suplente - Examinador(a) Interno ao Programa - 1544408 - GUSTAVO MARTINI DALPIAN
Membro Suplente - Examinador(a) Interno ao Programa - 2218228 - LUANA SUCUPIRA PEDROZA