Banca de DEFESA: GRACE KELLY QUARTEIRO GANHARUL

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : GRACE KELLY QUARTEIRO GANHARUL
DATA : 07/02/2022
HORA: 14:00
LOCAL: Santo André (remoto)
TÍTULO:

Synthesis and characterization of the physical properties of TiO2 and CsPbI3 semiconductor samples: applications in photodegradation

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 much attention from the scientific community due to their numerous technological applications. Applications involving interaction with electromagnetic radiation such as solar cells, emitting 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 the structural, morphological, optical and photocatalytic properties were carried out. The first family of TiO2 was synthesized via a microwave-assisted hydrothermal method varying the temperature between 120 and 200ºC and the halide perovskite was synthesized by the solvothermal method. Structural, morphological and optical characterizations revealed the formation of two sets of TiO2 with crystal structure rutile (nanorods) and anatase (nanoparticles) with band gap energy of the order of 2.9 eV while CsPbI3 forms microrods with gap energy of 2.7 eV . The two semiconductor families were used for photodegradation tests of methylene blue dissolved in methanol, using a solar simulator. TiO2 samples with anatase crystal structure showed better photocatalytic activity for degradation when compared to other structures. EPR and XPS spectroscopy revealed the presence of self-doping Ti3+ ions in the anatase phase. The creation and increase of these Ti3+ ions are closely related to the high efficiency of photodegradation, increasing the absorption of visible light probably caused by the intermediate energy states induced within the TiO2 gap. Composite formation and fabrication of heterostructures involving these semiconductor samples were carried out to improve the dynamics of charge carriers, which can result in an increase in photocatalytic performance. Thus, composites and heterostructures of TiO2 (anatase) and halide perovskite (CsPbI3) were fabricated and studied. The analysis of photodegradation activity indicated that TiO2/CsPbI3 composites perform much better than heterostructures and pure phases under the same light irradiation conditions. The composite promotes a cooperative degradation mechanism with a kinetic constant of kcomp=91.2, while the heterostructures lead to dye mineralization with khetero = 13.4 x 10-3 min-1. A high rate of photodegradation can be observed in CsPbI3 perovskite even in a solution without the presence of dissolved oxygen, while the heterojunction and the compound promote oxygen-dependent photodegradation. The presence of interstitial structural defects and iodide vacancies in perovskite can act as catalytic centers.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Titular - Examinador(a) Interno ao Programa - 1544408 - GUSTAVO MARTINI DALPIAN
Membro Titular - Examinador(a) Interno ao Programa - 1545089 - DANIEL ZANETTI DE FLORIO
Membro Titular - Examinador(a) Externo à Instituição - VAGNER BERNAL BARBETA - FEI
Membro Titular - Examinador(a) Externo à Instituição - RUBIA FIGUEREDO GOUVEIA - CNPEM
Membro Suplente - Examinador(a) Interno ao Programa - 1671275 - DERVAL DOS SANTOS ROSA
Membro Suplente - Examinador(a) Interno ao Programa - 1957564 - CEDRIC ROCHA LEAO