Banca de DEFESA: JOSE LUCAS DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOSE LUCAS DA SILVA
DATE: 27/02/2026
TIME: 13:30
LOCAL: Auditório da UAF
TITLE:

Synthesis of Iron Oxide Nanoparticles with Mandacaru via Green Coprecipitation

KEY WORDS:

nanoparticles, iron oxides, green synthesis, mandacaru.

PAGES: 123
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUBÁREA: Física da Matéria Condensada
SUMMARY:

Green synthesis methods have become increasingly common in the production of nanoparticles (NPs) due to the ability of organic compounds to control the nucleation rate of particles, allowing for controlled sizes and morphologies, as well as adapting traditional synthesis processes to make them less harmful to the environment. This work proposed the use of an adapted coprecipitation method for the green synthesis of NPs, employing the pulp of the mandacaru fruit (Cereus jamacaru) as a reducing and controlling agent in the synthesis of iron oxides. The objective of this work is to identify the magnetic, structural, and optical effects in the studied systems resulting from the addition of mandacaru fruit pulp to the synthesis process. For comparison purposes, a control sample without the addition of the extract was prepared under the same experimental conditions. Both samples were calcined at 350, 450, 550, and 650 °C. The results indicate the formation of goethite (α-FeO(OH)) after drying in the sample synthesized by the green route, coupled with a nanometric particle size ranging from 21 to 34 nm and the occurrence of direct hematite (α-Fe2O3) formation after calcination. In contrast, the iron oxide nanoparticles synthesized without the pulp exhibit two distinct prominent phases from 350 °C to 450 °C, corresponding to hematite (α-Fe2O3) and maghemite (γ-Fe2O3), as well as larger sizes ranging from 26 to 38 nm. The samples synthesized with the addition of mandacaru pulp exhibit predominantly antiferromagnetic behavior, which in turn also presents ferromagnetism originating from the particle surface, while the control sample exhibits ferrimagnetic behavior up to 450 °C and antiferromagnetic behavior from 550 °C onwards. The green route also allowed modulation of the band gap (Eg) for a significant increase in the width between the valence and conduction bands. Vibrational modes characteristic of hematite became sharper and narrower with calcination, in addition to exhibiting band characteristics for harmonic crystals. The work concludes that coprecipitation assisted by mandacaru pulp is an efficient route for obtaining nanocrystalline hematite with magnetic and optical properties susceptible to control. This strategy is promising for applications in visible photocatalysis, sensors, and pollutant adsorption/removal systems, and should be followed by applied tests for technological validation.

COMMITTEE MEMBERS:
Presidente - 2341246 - KENNEDY LEITE AGRA
Externo ao Programa - 1702795 - RENILTON CORREIA DA COSTA - UFCGExterna à Instituição - KAROLINE OLIVEIRA MOURA - UFPB