Banca de DEFESA: ELIBE SILVA SOUZA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ELIBE SILVA SOUZA
DATE: 19/04/2023
TIME: 08:30
LOCAL: Programa de Pós-Graduação em Ciência de Materiais
TITLE:

Nanocomposites Based on Metalorganic Zinc Networks as Supports for Metallic Nanoparticles: Catalysts for Hydrogen Production and Biocidal Agents

KEY WORDS:

Hydrogen generation. Metal-Organic Framework. AgNPs. AuNPs. CuNPs. Antibacterials.

PAGES: 150
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUMMARY:

Nanotechnology, as an emerging field, is widely used in the areas of clean energy generation and public health, which are current and relevant global problems to be solved. In this sense, metallic nanoparticles (MNPs) have been extensively studied for their magnetic, electronic, optical, antimicrobial and catalytic properties. The manipulation of MNPs to create new materials with specific desired physicochemical properties has shown promise. The combination of MNPs with a porous nanomaterial, such as Metal-Organic Framework (MOF), suppresses the main problem of MNP applications, which is the aggregation resulting from high surface energies. This work presents the synthesis and characterization of nanocomposites based on zinc MOFs, [Zn₂(1,3-bdc)(Bzim)₂] and [Zn(mim)], as support for the incorporation of MNPs (M= Cu, Ag or Au) in order to avoid aggregation and improve properties with respect to their counterparts. For this proof of concept, the Ship in bottle and One-pot methods were used. The synthesized materials were characterized by XRD, SEM, FTIR, ICP-OES, TGA/DTA and BET. MNPs were characterized by absorption spectroscopy in the UVvisible region. The catalytic properties of the synthesized materials were evaluated using the water displacement method, measuring the volume of hydrogen gas generated in the dehydrogenation of the hydrogen storage molecule NH₃BH₃ with the dependence of time, varying temperature and NaOH. Antibacterial properties were evaluated from disc diffusion tests on bacteria against Gram-positive and Gramnegative bacterial strains. The incorporation of MNPs by the methods used did not alter the stability and structural crystalline characteristics of the nanomaterials. The nanocomposites OP:AuNPs@Zn(mim) and OP:AgNPs@Zn(mim) stood out as catalysts for presenting excellent catalytic activities in the hydrolysis of NH₃BH₃, with high rates of hydrogen generation (1979.53 mL min-1 gAu- 1 and 3352.71 mL min-1 gAg- 1) and high efficiency (69.16% and 98.5%). The activation energies were 19.6 kJ.mol- 1 for OP:AuNPs@Zn(mim) and 38.13 kJ.mol-1 for OP:AgNPs@Zn(mim), which are lower than for most of the catalysts containing Au/Ag-MOF used in the hydrolysis of NH₃BH₃ described in the literature. Furthermore, these catalysts showed good stability and reuse, preserving 71.42%, OP:AuNPs@Zn(mim), and 88.23%, OP:AgNPs@Zn(mim), of their initial catalytic activities after five cycles. As biocidal agents, the Zn₂(1,3-bdc) (Bzim)₂ support effectively prevented the aggregation of MNPs and the bactericidal properties of the nanocomposites were enhanced up to thirteen times greater than the nanoparticle without the metalorganic support and up to sixteen times greater than the antibiotic amoxicillin. Therefore, the materials presented here proved to be excellent candidates to produce hydrogen from NH₃BH₃, in particular, OP:AgNPs@Zn(mim), with the combination of a simple synthesis method, low reaction temperature, environmentally friendly solvent, low content of of MNPs, relatively low cost and mild dehydrogenation conditions. From another perspective, the nanocomposites of the Zn₂(1,3-bdc) (Bzim)₂ support with AgNPs and CuNPs showed promise as biocidal agents, being more economical and with a low content of MNPs.

 

COMMITTEE MEMBERS:
Interno - 2457389 - EDUARDO PADRON HERNANDEZ
Interna - 1857515 - GIOVANNIA ARAUJO DE LIMA PEREIRA
Externo à Instituição - JANILSON ALVES FERREIRA
Presidente - 2163324 - JOANNA ELZBIETA KULESZA
Externo à Instituição - LEONIS LOURENÇO DA LUZ - UFPE