Banca de QUALIFICAÇÃO: HELDER MOREIRA BRAGA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : HELDER MOREIRA BRAGA
DATA : 13/08/2019
HORA: 15:00
LOCAL: Santo André
TÍTULO:

Synthesis and physical properties of nanostructured semiconductor oxides decorated with quantum dots of perovskites CsPb(Br, I)₃

PÁGINAS: 20
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Física
SUBÁREA: Física da Matéria Condensada
ESPECIALIDADE: Prop. Óticas e Espectrosc. da Mat. Condens; Outras Inter. da Mat. com Rad. e Part.
RESUMO:

Nanostructures of traditional semiconducting transition metal oxides exhibit interesting and important physical properties for technological applications. On the other hand, semiconductors with a perovskite-type structure of halide (Cl, Br, I) synthesized in the form of Quantum Dots (QDs), have shown high efficiency in both solar cells and light emitting devices. In this work, nanostructures of transition metal oxides, Fe₂O₃, NiO and ZnO were obtained through the thermal oxidation process by using metal microwires and microfoils (Fe, Ni, Zn) as precursor materials. Scanning Electron Microscopy (SEM) revealed the formation of nanostructures with different morphologies on the surface of the microwires/microfoils, such as nanowires, nanoparticles, and nanofoils for the studied oxides. X-ray diffraction confirmed the hexagonal, cubic, cubic, and rhombohedral crystalline phases for ZnO, NiO, Fe₂O₃ (hematite), and Fe₃O₄ (magnetite), respectively. On the other hand, colloidal solution with halide QDs, CsPbX₃, where X = Br, I, with perovskite structure, was obtained by the hot injection and supersaturated recrystallization methods at room temperature. Photoluminescence measurements indicated a very pronounced and narrow emission peak at 517 nm and 700 nm for the CsPbBr₃ and CsPbI₃ QD samples, respectively. The results of UV-Vis absorption spectroscopy corroborate with the emission results of the QDs. The band gap energy obtained using the emission peak was 2.30(2) eV and 1.70(2) eV for the QDs of CsPbBr₃ and CsPbI₃, respectively. Afterwards, the nanostructures of ZnO, Fe₂O₃ and NiO were decorated with the QDs in order to obtain local nanoheteroestructures on the surface of the microwires/microfoils. Structural and morphological characterizations confirmed that the QDs were deposited on the surface of the oxides. SEM images also show that on the surface of the oxides were nanocrystals formed in the form of cubes, rods and spheres.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1544408 - GUSTAVO MARTINI DALPIAN
Membro Titular - Examinador(a) Interno ao Programa - 1600858 - HERCULANO DA SILVA MARTINHO
Membro Titular - Examinador(a) Externo ao Programa - 3066318 - JULIAN ANDRES MUNEVAR CAGIGAS
Membro Suplente - Examinador(a) Interno ao Programa - 1545447 - MARCOS ROBERTO DA ROCHA GESUALDI